The review, led by Ying Liu, Linke Bian, and colleagues at Shanghai East Hospital, Tongji University, systematically maps how locoregional ablation reshapes the tumor immune microenvironment and why pairing it with immunotherapy is biologically compelling. The authors are careful, however, to draw a hard line between mechanism and proof: most of the supporting evidence remains preclinical or comes from small, non-randomized studies, and no robust phase III data yet demonstrate a survival benefit for ablation-immunotherapy combinations in liver cancer.

The core concept is immunogenic cell death. Ablation creates a characteristic three-layer injury zone: a central necrotic core, a transitional zone of sublethal stress, and surrounding viable tissue. Dying cells release tumor-associated antigens and damage-associated molecular patterns in a temporally ordered sequence—surface calreticulin acting as an early “eat-me” signal for dendritic cells, secreted ATP recruiting and activating innate immunity through NLRP3 inflammasome signaling, and finally passive release of HMGB1 and heat shock proteins that drive dendritic cell maturation. Together these signals can prime CD8-positive T cells capable of attacking tumor cells far beyond the treated site, the so-called abscopal effect.

But the immune response ablation provokes is self-limiting. Within days, residual tumor cells upregulate PD-L1, exhausted T cells accumulate inhibitory receptors such as Tim-3 and CD244, and regulatory T cells and myeloid-derived suppressor cells flood the ablation margin. Natural killer cell dynamics tell a similar story: while ablation can boost NK-mediated interferon-gamma production, an expansion of immature CD56-positive CD16-negative NK cells one month after radiofrequency ablation predicts recurrence. The result is a window of immune activation that closes before durable memory is established.

The review’s most striking mechanistic finding concerns incomplete ablation, or iRFA—residual tumor surviving in the sublethal transitional zone, a particular risk for tumors of three centimeters or larger or those near major vessels where blood flow dissipates heat. Surviving cells undergo epithelial-mesenchymal transition and angiogenic reprogramming, and, critically, sublethal thermal stress triggers SUMO2-mediated SUMOylation that suppresses type I interferon signaling, impairing dendritic cell maturation and T cell infiltration. Incomplete ablation thus couples residual tumor substrate with active immunosuppression, converting a zone of potential immune priming into one of tolerance. The authors argue that preventing iRFA through better planning and image guidance is a prerequisite for any combination strategy to work.

Not all modalities are immunologically equivalent. Thermal techniques such as radiofrequency and microwave ablation release broad antigen loads but risk heat-induced antigen denaturation. Cryoablation preserves antigens in near-native conformation, favoring uptake by antigen-presenting cells, while irreversible electroporation engages multiple regulated cell death pathways—pyroptosis and necroptosis among them—while preserving vascular and extracellular scaffolds that ease immune cell infiltration. The trade-offs include procedural complexity and, rarely, cryoshock after extensive hepatic treatment.

On the clinical side, the evidence is promising but thin. Adding radiofrequency or microwave ablation to ongoing nivolumab raised the objective response rate from 10 to 24 percent in a prospective cohort of 50 patients. Tremelimumab combined with subtotal ablation produced a median time to progression of 7.4 months with increased intratumoral CD8-positive infiltration in a 32-patient pilot. A phase I/II trial of OK-432-stimulated dendritic cells injected after radiofrequency ablation extended recurrence-free survival from 13.0 to 24.8 months, though overall survival was unchanged. Irreversible electroporation paired with allogeneic NK cell infusion showed feasibility signals in small studies. None of these results, the authors stress, substitutes for randomized validation.

The combination toolbox extends well beyond checkpoint inhibitors. Pattern recognition receptor agonists—CpG oligonucleotides, STING agonists, GM-CSF—can enforce dendritic cell licensing at the ablation site. Oncolytic viruses such as G47Δ, given before ablation so infected cells can replicate, amplified T cell responses in mouse models, though the negative phase III PHOCUS trial of Pexa-Vec in HCC is a sobering reminder that preclinical immune activation does not guarantee clinical survival benefit. Nanobiomaterial platforms add a third layer: hydrogels and nanoparticles that co-localize ablation-released antigens with adjuvants, sustain release over days, or ferry captured tumor debris to draining lymph nodes for concentrated T cell priming.

Timing emerges as a central unresolved question. Immune profiling after irreversible electroporation suggests a systemic innate activation window roughly three to fourteen days after treatment—a plausible interval for starting checkpoint inhibitors or adoptive cell therapy, but one derived from limited kinetic observations rather than prospective schedule comparisons. The review also distinguishes three therapeutic settings with different goals: adjuvant therapy after curative ablation, where the endpoint is recurrence-free survival; cytoreductive ablation during systemic immunotherapy for advanced disease, where progression-free survival and response rates matter; and salvage of incomplete ablation, where complete local eradication must remain the priority and immunotherapy is an investigational adjunct.

The authors’ verdict is measured. Mechanistic understanding has substantially outpaced clinical validation, and reliable predictive biomarkers—tumor immunophenotype, circulating NK cell function, post-ablation ctDNA dynamics, neutrophil-to-lymphocyte ratio—remain unvalidated in this setting. Response assessment needs immune-adapted criteria such as iRECIST to capture pseudoprogression and abscopal regression. Still, the conceptual framework is coherent: ablation as an in situ vaccine, immunotherapy as the amplifier that converts a transient spark into durable systemic memory. Prospective, biomarker-stratified trials with serial immune profiling will determine whether that logic translates into longer lives for liver cancer patients.

Subject of Research: Combining locoregional tumor ablation with immunotherapy to enhance antitumor immunity in hepatocellular carcinoma

Article Title: Synergistic strategies of tumor ablation and immunotherapy in hepatocellular carcinoma: mechanisms, clinical translation, and perspectives

Article References: Liu, Y., Bian, L., Wang, H., Cui, D., Wu, Z., & Zhai, B. (2026). Synergistic strategies of tumor ablation and immunotherapy in hepatocellular carcinoma: mechanisms, clinical translation, and perspectives. Holistic Integrative Oncology, 5(1), Article 82. https://doi.org/10.1007/s44178-026-00303-7

Image Credits: AI Generated

DOI: 10.1007/s44178-026-00303-7

Keywords: hepatocellular carcinoma, tumor ablation, immunotherapy, immunogenic cell death, tumor microenvironment, radiofrequency ablation, cryoablation, irreversible electroporation, immune checkpoint inhibitors, abscopal effect, incomplete ablation, nanobiomaterials

The central idea behind the work is that cancer cells possess cytoprotective machinery that helps them survive stress and evade the immune system. One of the most important of these mechanisms is the unfolded protein response, or UPR, a signaling network that restores protein homeostasis when the endoplasmic reticulum becomes overloaded with misfolded proteins. The researchers hypothesized that if they could intensify and prolong proteostatic stress inside tumor cells without killing them outright, they could disrupt that survival machinery and simultaneously make the tumor more visible to the immune system. LOFU offered an ideal tool for the job. Unlike high-intensity focused ultrasound, or HIFU, which ablates tissue through coagulative necrosis, LOFU induces thermal and mechanical stress in cells while leaving them intact—enough stress to trigger immunogenic changes, but not enough to destroy the tissue.

To test this, the team used their in-house ultrasound platform, called APTx, which combines two coaxially mounted transducers operating at 1.1 megahertz and 250 kilohertz, focused simultaneously on the tumor center for a continuous three-second exposure. They studied three escalating intensities—80, 160, and 240 watts per square centimeter—in mice bearing orthotopic TSA tumors on a BALB/c background and E0771 tumors on a C57BL/6 background. A fine-gauge thermocouple implanted in the tumor core revealed a dose-dependent thermal response: untreated tumors sat at roughly 25 degrees Celsius, and each increase in intensity raised the maximum internal tumor temperature by about 5 degrees, reaching approximately 38 degrees Celsius at the highest setting. That temperature is warm enough to stress cells but far below the threshold for ablation, which is precisely the balance the researchers were seeking.

The molecular readouts confirmed that the acoustic stress was registering inside the tumor cells. Five hours after a single LOFU treatment, the team harvested tumor tissue and used quantitative reverse-transcription PCR to measure the expression of 62 genes associated with the unfolded protein response and 62 genes linked to heat shock proteins. Both gene sets were upregulated in a direct dose-dependent fashion with increasing intensity, and the most pronounced increase—without any tissue ablation—occurred at 240 watts per square centimeter, which became the standard dose for all subsequent experiments. Heatmaps of individual genes showed statistically significant upregulation across key branches of the UPR, including the PERK-ATF4 signaling pathway. Notably, the gene Eif2ak, which encodes PERK, was among those upregulated; PERK phosphorylates eIF2α, attenuating canonical translation and shifting cells toward non-canonical mRNA translation, a process previously linked to the generation of peptides presented on major histocompatibility complex class I molecules.

The stress response also translated into immunogenic cell death signals. Within 24 hours of a three-day LOFU regimen, the researchers observed cytosolic heat shock proteins—specifically BiP, HSP90, and HSP40—translocating to the surface of tumor cells, where they can act as damage-associated molecular patterns that activate dendritic cells and promote cross-presentation of tumor antigens to CD8-positive T cells. Using TSA cells engineered to carry a red fluorescent protein tag on the chromatin protein HMGB1, the team showed that LOFU treatment progressively increased the release of HMGB1 into the culture medium over 72 hours, another hallmark of immunogenic cell death. Interestingly, LOFU alone did not induce surface expression of calreticulin, an eat-me signal that radiation therapy does trigger, which is one reason the researchers chose to combine the two modalities rather than rely on ultrasound alone.

When the team added radiation to the protocol—delivering sub-ablative doses of 8 or 10 gray per fraction via a small-animal radiation platform two to four hours after each LOFU session—the combination produced changes that neither therapy achieved on its own. Radiation increased surface expression of the co-stimulatory molecules CD40 and CD80 on tumor cells, and the LOFU-plus-radiation combination additionally reduced expression of CD47, the do-not-eat-me signal that normally shields tumor cells from phagocytosis. In survival studies, mice receiving the combination therapy lived significantly longer than those receiving radiation alone, and tumor volumes in the combination group were substantially lower than in the radiation monotherapy group at later time points in both the TSA and E0771 models. LOFU monotherapy, by contrast, was less effective at controlling tumors than no treatment at all, underscoring that the ultrasound works best as a priming agent rather than a standalone therapy.

Two experiments pointed decisively to T cells as the mediators of the combination’s benefit. First, the survival advantage seen in wild-type mice disappeared entirely in athymic nude mice, which lack a functional T cell population. Second, in a dual-tumor model in which only the primary tumor was treated, the combination therapy reduced not only the treated tumor but also the untreated secondary tumor on the opposite flank—a systemic abscopal effect that radiation monotherapy failed to produce. Immunophenotyping of tumors ten days after treatment revealed why: while radiation increased the overall percentage of CD8-positive T cells infiltrating both tumor types, it also raised the proportion of regulatory T cells, or Tregs, in TSA tumors, an immunosuppressive population that can blunt the anti-tumor response. Adding LOFU prevented that radiation-induced Treg expansion, resulting in a significantly elevated ratio of CD8-positive T cells to Tregs in the combination group compared with untreated controls in both models. That ratio is clinically meaningful in breast cancer, where a higher CD8-to-FOXP3-positive Treg ratio in the tumor stroma correlates with improved survival.

The team also probed the quality of the T cell response, not just its quantity. Within the effector memory T cell subset—antigen-primed cells marked by CD44-positive, CD62L-negative expression that can position themselves in both lymphoid and peripheral tissues—the combination therapy reduced the percentage of cells expressing FAS in both CD8-positive and CD4-positive populations and increased the percentage of CD8-positive effector memory cells expressing the transcription factor Tbet, a marker of a Th1-biased cytotoxic program. Radiation alone produced some of these changes, but the combination was more effective. Cytokine analysis told a similar story: radiation increased interferon-gamma secretion in both CD8-positive and CD4-positive T cells, and the combination showed a trend toward even greater interferon-gamma production. Curiously, the radiation-induced upregulation of tumor necrosis factor alpha seen in monotherapy was not observed in the combination groups, hinting at a nuanced interplay between the two modalities in shaping the cytokine milieu of the tumor microenvironment.

Perhaps most striking was the evidence that the combination therapy generates a genuinely tumor-specific adaptive immune response. Using tetramer staining to identify T cells recognizing defined tumor-associated antigens, the researchers found that the combination significantly increased the infiltration of anti-gp70 CD8-positive T cells in TSA tumors—gp70 being an overexpressed epitope derived from an endogenous murine leukemia retrovirus—and significantly raised the anti-gp70 CD8-to-Treg ratio above both untreated and radiation-only groups. In E0771 tumors, the combination group showed the highest percentage of anti-p15E CD8-positive T cells, though that trend did not reach statistical significance, possibly because p15E is not an established tumor-associated antigen in that model. The quality of the anti-gp70 cells also improved under the combination, with fewer cells expressing FAS and more expressing Tbet compared with radiation alone.

The authors are careful to note that the combination is not curative: tumors that regressed to non-palpable sizes frequently recurred, echoing the clinical reality that roughly 15 percent of early-stage breast cancer patients experience local recurrence within 15 years. Still, the findings carry significant translational weight. The team showed that LOFU allows a 20 percent reduction in radiation dose while maintaining tumor control comparable to the higher dose alone—a meaningful margin, given that a 20 percent dose reduction could virtually eliminate serious side effects in radiation-sensitive patients. The researchers plan to explore whether adding anti-PD-1 immunotherapy or surgical resection after treatment can convert transient regression into durable control, and to dissect the role of tumor-associated macrophage polarization in the ultrasound-primed microenvironment. For now, the study positions LOFU as a promising non-ablative priming tool that, paired with radiation, turns the tumor itself into something resembling an in-situ vaccine—one that teaches the immune system to recognize and attack cancer both at the treated site and, potentially, far beyond it.

Subject of Research: Low-intensity focused ultrasound combined with radiation therapy enhances antitumor immunity in murine breast cancer models

Article Title: Enhancing tumoricidal effects of radiation therapy with low-intensity focused ultrasound in murine breast cancers

Article References: Schumacher, M. M., Gutierrez Chavez, C., Malachowska, B., Pandey, S., Tchaikovskaya, T., Singh, S., Barry, S., Macedo, R., & Guha, C. (2025). Enhancing tumoricidal effects of radiation therapy with low-intensity focused ultrasound in murine breast cancers. Frontiers in Acoustics, 3, Article 1616297. https://doi.org/10.3389/facou.2025.1616297

Image Credits: AI Generated

DOI: 10.3389/facou.2025.1616297

Keywords: low-intensity focused ultrasound, LOFU, radiation therapy, breast cancer, tumor microenvironment, immunotherapy, CD8-positive T cells, regulatory T cells, unfolded protein response, heat shock proteins, immunogenic cell death, abscopal effect

The obstacle that has defeated photodynamic therapy, or PDT, in pigmented melanoma is fundamentally optical and chemical. PDT relies on photosensitizing drugs that, when illuminated with light of a specific wavelength, generate reactive oxygen species, including excited-state singlet oxygen, that kill tumor cells directly or shut down the blood vessels feeding the tumor. Melanin undermines this at every step: it absorbs and scatters light so effectively that very little reaches deeper tissue, and it chemically neutralizes reactive oxygen species before they can inflict lethal damage. Many melanoma cells also actively pump photosensitizers back out of the cell. In measurements on excised S91 murine melanoma reported in the new study, transmission of 690-nanometer treatment light fell by four orders of magnitude through just 2 millimeters of tissue, and light became undetectable beyond 3 millimeters.

The research team, led by L. Pires and B. C. Wilson of Texas A&M University and the Princess Margaret Cancer Center in Toronto, did not try to blast through this barrier with ever-stronger light. Instead, they paired two photosensitizers already in clinical use: Photodithazine, a chlorin e6 derivative that concentrates in tumor cells, and Visudyne, a liposomal benzoporphyrin formulation that targets the tumor microvasculature. Each drug was illuminated at its own red absorption peak, delivered through an optical fiber, and a topically applied optical clearing agent made of PEG-400 and propanediol was rubbed into tape-stripped skin to reduce light scattering and improve penetration. The protocol was first shown to eradicate thin, pigmented tumors, but in immunodeficient mice the animals still succumbed to metastatic spread.

The decisive change in the new work was testing the identical protocol in mice with intact immune systems, and against tumors deliberately grown to 3 to 4 millimeters thick, several times deeper than any effective light dose could reach. In immunocompetent DBA mice, the treated tumor site became intensely inflamed within hours, ulcerated within days, and healed completely by about three weeks, leaving no trace of tumor. Nineteen of 20 treated mice, 95 percent, survived to the 90-day endpoint without disease. In nude mice lacking T cells, the same treatment produced only superficial damage, and every animal died of tumor overgrowth with a median survival of just 21 days, indistinguishable from untreated controls. The dramatic split between the two groups is, the authors argue, only explicable if the immune system finished what the light started.

How could light that penetrates only the top millimeter of a tumor destroy the entire mass? The answer, according to the study’s mechanistic analysis, is that the photodynamic damage to the superficial layer acts as a biological alarm. Dying cancer cells release damage-associated molecular patterns such as calreticulin, ATP and HMGB1, molecules that alert dendritic cells and other antigen-presenting cells. These cells ingest tumor debris, carry tumor antigens to the draining lymph nodes, and prime cytotoxic CD8-positive T cells that can recognize and kill melanoma cells anywhere in the body, including regions the light never touched. The researchers have named this cascade photodynamic immune stimulation, or PDIS.

The immune signatures measured after treatment were striking in their breadth and speed. Within three to six hours, CD3-positive T cells and CD19-positive B cells flooded into the tumor, while populations of Ly-6G-positive, Ly-6C-positive myeloid cells associated with immunosuppression fell. By 12 hours, immunohistochemistry showed T cells distributed throughout the tumor parenchyma, not merely clustered at the margins. In blood, eosinophils rose sharply while circulating lymphocytes dropped, consistent with migration toward the tumor, and activated CD69-positive T cells increased in both blood and lymph nodes. Plasma levels of inflammatory messengers including IL-2, IL-6, IL-18, ENA-78 and GRO-alpha surged, returning toward baseline by two weeks.

Gene expression profiling of treated tumors revealed a wholesale transcriptional shift, most pronounced at 24 hours. Gene Ontology analysis showed enrichment of pathways governing lymphocyte differentiation, cytokine signaling, leukocyte proliferation and myeloid cell differentiation, while KEGG pathway analysis highlighted IL-17 signaling, chemokine signaling, natural killer cell-mediated cytotoxicity, T-cell and B-cell receptor signaling, Toll-like receptor signaling and pathways of apoptosis and cellular senescence. Most tellingly, T cells in the draining lymph nodes shifted over time from naive and central-memory phenotypes toward effector-memory cells, the population capable of rapid cytotoxic attack on re-encountering tumor antigens, the cellular signature of durable immune memory.

A series of functional experiments made the causal case. When CD8-positive T cells were depleted with antibodies before treatment, five of six mice died of tumor overgrowth within 34 days, collapsing the 95 percent disease-free survival down toward control levels and proving that cytotoxic T cells are the dominant effectors. In adoptive transfer experiments, splenocytes from treated mice mixed with melanoma cells and injected into healthy recipients slowed tumor growth dramatically, without any attack on healthy tissue, indicating tumor-specific memory. In mice bearing tumors on both flanks, treating only one tumor completely eradicated it and significantly delayed growth of the untreated opposite tumor, an abscopal effect that extended median survival from 6 to 15 days. Finally, when mice cured 30 days earlier were injected intravenously with a million melanoma cells, all remained tumor-free, while every control mouse developed bulky lung and peritoneal metastases.

The authors are careful about the limits of the work. All experiments used male mice and a single murine melanoma cell line, so the findings must be validated across genetically diverse models before clinical translation. They also note that the light gradient through pigmented tissue may generate different cell death pathways at different depths, potentially shaping the strength of the immune response, a relationship they are now investigating to optimize dosing. Even so, male mice are known to mount weaker immune responses than females, making the observed effect particularly notable, and the fact that melanin’s barrier could be sidestepped rather than defeated challenges two decades of assumptions in the field.

The clinical possibilities outlined by the team are tantalizing. PDIS could be delivered shortly before surgical resection, exploiting the perioperative window to counter the immune suppression that surgery itself induces and to attack unsuspected micrometastases. Its ability to convert immunologically cold tumors into hot ones suggests rational combination with immune checkpoint inhibitors, preclinical studies of which are planned. The measured immune biomarkers could guide patient selection and real-time monitoring, extending dosimetry beyond drug uptake and light dose to include the tumor’s immune landscape. The same principle may extend to uveal melanoma, where the group’s multiphoton PDT work has already shown lymphocyte activation with partial tumor targeting, and to immunotherapy-resistant cancers such as pancreatic and lung tumors. For a disease whose five-year survival collapses to roughly 30 percent once it metastasizes, a low-toxicity treatment that both destroys the primary tumor and vaccinates the body against recurrence would represent a genuinely new chapter in melanoma care.

Subject of Research: Photodynamic immune stimulation as an immunotherapy strategy for pigmented melanoma

Article Title: Photodynamic immune stimulation eradicates primary pigmented melanoma and induces long-lasting anti-tumor immunity

Article References: Pires, L., Calcada, C., Cerqueira-Rodrigues, B., Fan, Y., George, J. T., McGaha, T., & Wilson, B. C. (2026). Photodynamic immune stimulation eradicates primary pigmented melanoma and induces long-lasting anti-tumor immunity. British Journal of Cancer. https://doi.org/10.1038/s41416-026-03585-w

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03585-w

Keywords: melanoma, photodynamic therapy, immunotherapy, photosensitizers, CD8 T cells, abscopal effect, immune memory, tumor microenvironment, optical clearing, immunogenic cell death, preclinical study, British Journal of Cancer

The review, led by Madeline I. Foo of Johns Hopkins Hospital and Alissa Hendricks-Wenger of Mayo Clinic Florida, together with colleagues including Eli Vlaisavljevich of Virginia Tech, one of the technique’s pioneering engineers, searched PubMed and SCOPUS for studies of histotripsy ablation of parenchymal tissues in vivo. From an initial pool of 1,270 publications identified on June 22, 2026, the team applied strict inclusion criteria: the work had to use histotripsy for in vivo ablation of parenchymal tissue, be peer-reviewed, and have full text available in English. Conference abstracts, preprints, reviews, and studies targeting non-parenchymal structures such as phantoms, abscesses, or thromboses were excluded. The final analysis included 141 studies, of which 114 were pre-clinical and 27 were clinical reports. Most animal work involved healthy tissue in murine or porcine models, while the clinical literature concentrated overwhelmingly on hepatic malignancies, with 25 of the 27 clinical studies focused on the liver. Assuming no overlaps beyond those identified, the clinical experience could encompass a maximum of roughly 607 unique patients, a reminder of how early the human evidence base still is.

The authors performed a formal meta-analysis only on clinical cohort studies of hepatic ablation, synthesizing the remaining findings qualitatively and grading severity with the Society of Interventional Radiology adverse event classification. The pooled numbers tell a broadly reassuring story with important caveats. The screen-failure rate, meaning patients deemed appropriate on clinical criteria who ultimately did not receive treatment, was 49 percent, reflecting how carefully candidates are still being selected. The overall incidence of serious adverse events, grade 3 or higher on the SIR scale, was 6 percent. The two most common serious complications were thrombotic events and acute kidney injury, each with a pooled incidence of roughly 4 to 6 percent. Pain, by contrast, was infrequently and inconsistently reported, but where it was measured, most patients experienced only mild to moderate discomfort with minimal analgesic requirements, and in a canine osteosarcoma limb-sparing trial, treated animals actually improved their weight-bearing on the treated limb over follow-up.

What makes the review particularly valuable is its attention to mechanism-specific risks. Because histotripsy works by mechanical fractionation rather than thermal coagulation, it creates injury patterns that thermal ablation does not. The rapid liquefaction of tissue releases intracellular electrolytes and macromolecules into the circulation, a process that may contribute to local and systemic injury. Cavitation events occur with a probabilistic distribution, which means that even an adequate-appearing treatment can leave viable cells behind, generate debris particles measuring up to 54 micrometers, small enough to act as embolic agents, and theoretically liberate tumor cell clusters that could disseminate. The review also distinguishes injuries along the ultrasound beam path: pre-focal damage between the transducer and the focus, post-focal injury deep to the treatment zone, and unintended effects within the prescribed treatment volume itself.

Some of the most sobering findings come from the pre-clinical literature. Three bowel perforations occurred in a murine study using a custom 1 MHz transducer with high treatment parameters and wide margins that encompassed bowel. In porcine pancreatic ablation with the Edison clinical system, two grade 3 events were reported, including septic peritonitis requiring euthanasia and gastrointestinal obstruction, with poor ultrasound visualization from overlying bowel gas associated with bowel damage in three of nine swine. Pulmonary injury appeared in a porcine study of transcostal hepatic treatment, where four of five subjects showed magnetic resonance evidence of right lower lobe lung injury, though no pneumothoraxes developed. A chronic rodent study found that mice developed alveolar septal rupture and pulmonary hemorrhage because the acoustic channel was long relative to their small bodies, an injury absent when the same protocol was applied to rats, underscoring how body size and acoustic-window geometry shape beam-path risk. Urinary tract studies reported rectoprostatic fistulas and urethral perforation in a canine prostate model, while a porcine ureter study showed only low-grade, reversible urothelial injury.

Clinically, the pattern of serious events differs in instructive ways. Gastrointestinal and pulmonary adverse events have so far appeared only in animals, while vascular injuries, acute kidney injuries, and disease progression have emerged only in humans. Acute kidney injury following hepatic histotripsy has become a recognized systemic complication: in a five-center review of 146 procedures, nine patients developed AKI, including two grade 5 events, and additional cases have surfaced in case reports and the FDA’s MAUDE registry. Vascular complications have included bleeding requiring embolization and transfusion, hepatic pseudoaneurysms within the treatment zone, and hemorrhagic shock, with one death on postoperative day 28 from fulminant hepatic failure in a vascular-injury series. Portal and hepatic vein thrombosis has emerged as one of the most common clinically significant events, with central tumor location and overlapping treatment zones identified as key risk factors, findings that align with pre-clinical work linking thrombosis to cavitation-induced endothelial injury. Notably, three anticoagulated large-animal studies found no significant hemorrhage after hepatic, renal, or prostate treatment, and pre-clinical work suggests prophylactic low-dose heparin can mitigate thrombotic risk without increasing bleeding.

Perhaps the most scientifically provocative section of the review concerns tumor biology. Across 41 publications with at least one week of follow-up, the majority of clinical and all veterinary studies reported stable or progressive systemic disease acutely, which is expected given the advanced stage of most treated patients. But five clinical reports described fourteen patients in whom untreated tumors regressed on follow-up imaging, sometimes with concordant decreases in tumor markers, a phenomenon consistent with the abscopal effect, in which local treatment sparks systemic immune activity against cancer elsewhere. Two pre-clinical studies support the idea that histotripsy can elicit statistically significant systemic tumor inhibition through immune-mediated mechanisms, likely because mechanical fractionation releases tumor antigens in a form the immune system can process. Against this hopeful backdrop stands a single clinical case report of hyperprogression: a patient with recurrent cholangiocarcinoma developed hyperacute, extensive metastatic disease within three months of treatment, with roughly fifty lesions appearing in the retroperitoneum and subcutaneous fat in an atypical pattern. Causality cannot be established from one case, and no animal study showed an acute increase in systemic disease burden compared with controls, but the authors argue it highlights the need for long-term oncologic surveillance and mechanistic investigation.

The review is candid about the limitations of the evidence it synthesizes. Histotripsy data span fewer than two decades, dominated by pre-clinical models with highly variable transducers and acoustic parameters, while clinical data cover only about six years and consist almost entirely of single-arm trials, feasibility studies, case series, and case reports. Multiple publications derive from overlapping cohorts, so the number of papers overrepresents the breadth of independent experience. The predominance of early-adopter centers and investigator-industry collaborations introduces potential publication and reporting bias, and learning-curve effects may inflate apparent adverse event rates while incomplete ascertainment, such as omitting laboratory tests needed to detect kidney injury, may lower them. Strikingly, the review found that pre-clinical studies routinely specified therapeutic parameters such as mechanism, transducer frequency, and acoustic delivery, while clinical studies often did not, with no clear reporting of the Edison system’s acoustic parameters, making it difficult to extrapolate animal safety data to human treatments.

The authors close with practical guidance and a call for rigor. Non-target injury is best minimized through careful patient selection, pretreatment planning, a clear acoustic window, continuous bubble-cloud visualization, respiratory management, precise transducer alignment, and therapy pauses when needed, with particular avoidance of susceptible structures such as lung and bowel. Standardized post-procedure imaging protocols should prospectively evaluate for thrombotic and embolic events, and clinical systems must report their therapeutic parameters in line with the established ablation reporting lexicon. The overall verdict is measured: early data suggest an acceptable acute safety profile in select settings, and most studies reported few adverse events, but the serious exceptions, thromboses, vascular injuries, kidney injuries, and the single hyperprogression case, form a framework for mechanism-specific vigilance. As histotripsy expands beyond subcostal liver targets toward pancreas, kidney, prostate, and extremity tumors, the review’s central message is that open adverse event reporting and rigorous, longer-term follow-up must keep pace with the technology’s undeniable appeal, ensuring that enthusiasm for a genuinely noninvasive cancer therapy is matched by equally rigorous science.

Subject of Research: Safety and adverse events of histotripsy, a cavitation-based focused ultrasound ablation technique, across pre-clinical and clinical studies

Article Title: Understanding histotripsy ablation safety: a systematic review of pre-clinical and clinical adverse events

Article References: Foo, M. I., Uzoukwu, C., Morhard, R., Falk, K. L., Wood, B. J., Frey, G., Ziemlewicz, T. J., Vlaisavljevich, E., Toskich, B. B., & Hendricks-Wenger, A. (2026). Understanding histotripsy ablation safety: a systematic review of pre-clinical and clinical adverse events. CVIR Oncology, 2(1), Article 33. https://doi.org/10.1007/s44343-026-00062-2

Image Credits: AI Generated

DOI: 10.1007/s44343-026-00062-2

Keywords: histotripsy, focused ultrasound, cavitation, tumor ablation, adverse events, liver cancer, thrombosis, acute kidney injury, abscopal effect, systematic review, interventional radiology, patient safety

The central paradox the authors dissect is the abscopal effect, a phenomenon first described in the context of radiation therapy and named from the Greek “ab” and “skopos,” suggesting a target away from the intended one. In rare and notoriously unpredictable cases, destroying a tumor at one site triggers shrinkage of untreated metastases elsewhere in the body, implying that the local treatment somehow activated a systemic immune response capable of hunting cancer cells it had never physically touched. For most of the history of oncology, abscopal responses were little more than a curiosity, reported sporadically and explained hand-wavingly as immune effects. What has changed is the arrival of immune checkpoint inhibitors, drugs such as anti-PD-1 and anti-PD-L1 antibodies that release the molecular brakes keeping T cells exhausted. The review frames the abscopal effect as a model system for understanding systemic immune activation precisely because checkpoint blockade can convert the transient, dampened immunity generated by ablation into something sustained and clonally expansive.

The mechanistic logic of the synergy unfolds in stages that the review maps with unusual clarity. Ablation first acts as an antigen release event: dying tumor cells expose and release proteins that were previously sequestered, along with calreticulin, ATP, and other damage signals that dendritic cells recognize as evidence of an aberrant, dangerous death rather than quiet apoptosis. These dendritic cells engulf the debris, migrate to draining lymph nodes, and present tumor-derived peptides on major histocompatibility molecules to naïve T cells, a process known as immune priming. Some modalities are particularly adept at this. Cryoablation, which freezes cells rather than coagulating them, tends to preserve antigen structure and has been shown in mouse models to trigger type I interferon-dependent antitumor immunity, in part through the cGAS-STING cytosolic DNA sensing pathway. Mechanical high-intensity focused ultrasound and histotripsy generate unique tumor debris that enhances dendritic cell-mediated T cell activation, and irreversible electroporation has been shown to augment checkpoint immunotherapy while promoting tumor antigen-specific tissue-resident memory CD8+ T cells.

Yet priming alone is not enough, and this is where the review is most candid about the immunobiology that separates laboratory promise from clinical reality. The tumor microenvironment into which newly activated T cells must travel is often immunologically hostile, densely infiltrated by regulatory T cells, tumor-associated macrophages skewed toward suppressive phenotypes, and myeloid cells secreting inhibitory cytokines. Even if cytotoxic T lymphocytes are successfully primed against ablation-released antigens, they frequently arrive at distant tumor sites exhausted, their receptors engaged by PD-L1 and related ligands, their metabolism deranged. Immune checkpoint inhibitors address precisely this bottleneck: they do not create tumor-specific T cells but instead preserve and prolong the function of those that ablation has helped to generate. The combination therefore follows a rational division of labor, with ablation supplying antigen and inflammatory context, functioning as an in situ vaccine, while immunotherapy supplies the survival signals that allow the resulting T cell response to expand, persist, traffic, and kill across anatomical compartments. Preclinical studies across multiple solid tumors, including lung cancer, hepatocellular carcinoma, breast cancer, prostate cancer, and melanoma, have shown that this pairing can promote immune priming, increase infiltration of cytotoxic lymphocytes, and produce systemic disease control where either approach alone fails.

Clinical evidence is accumulating, though unevenly, and the review carefully catalogues where the concept has moved from mouse to human. In lung cancer, microwave ablation has been reported to enhance local T cell abundance and strengthen systemic immune responses, and cryoablation combined with PD-1 blockade has produced striking responses in metastatic disease. A window-of-opportunity trial in early-stage breast cancer combined preoperative camrelizumab with microwave ablation, providing a direct look at immune changes in the treated tumor before surgery. In hepatocellular carcinoma, where ablation is already a standard locoregional therapy, combinations with checkpoint inhibitors are being explored intensively, although the review notes that the hepatocellular carcinoma microenvironment is more immunosuppressive than that of colorectal liver metastases, complicating extrapolation between tumor types. Notably, individual case reports describe abscopal responses and even reversal of checkpoint inhibitor resistance following radiofrequency ablation in patients with refractory disease, and retrospective analyses in metastatic lung cancer have documented abscopal phenomena when radiotherapy was added to immunotherapy. These are signals, the authors emphasize, not proof, and the rarity of such responses remains the field’s defining challenge.

Perhaps the most technically interesting section of the review concerns the choice of ablative modality, which turns out to be anything but interchangeable. Radiofrequency ablation and microwave ablation are both thermal techniques that coagulate tissue, but microwave energy heats faster and reaches higher temperatures, producing different cell death kinetics and, evidence suggests, different immune signatures. Cryoablation, by contrast, kills through ice crystal formation and osmotic rupture, leaving antigens and tumor architecture relatively intact and preserving epitopes that might otherwise be denatured. High-intensity focused ultrasound can operate in thermal or purely mechanical modes, and histotripsy, which fractionates tissue with pulsed ultrasound cavitation, generates debris with distinctive immune-stimulating properties. Photothermal and photodynamic therapies, increasingly delivered through engineered nanoparticles, add another layer of programmability, with nanoplatforms now capable of repolarizing tumor-associated macrophages, delivering STING agonists, and creating autologous cancer vaccines from the patient’s own ablated tissue. The immunogenic character of cell death induced at different temperatures, one cited study found, varies measurably in hepatocellular carcinoma cells, meaning that a radiation oncologist’s choice of energy, dose, and timing is, in effect, an immunological design decision.

That decision is complicated by a darker caveat the review does not shy away from: incomplete ablation may backfire. Studies of insufficient thermal ablation have documented increased tumorigenesis at ablation margins, and analyses of hepatocellular carcinoma treated with transarterial chemoembolization plus radiofrequency ablation found that inadequate ablation associated with intrahepatic and extrahepatic metastasis. Hypoxic, inflamed, partially viable tissue at the ablation edge can recruit suppressive myeloid cells and promote angiogenesis, converting a well-intentioned immune-priming event into a pro-tumor insult. This finding sharpens the translational imperative: if ablation is to serve as an in situ vaccine, the ablation must be adequate, the inflammatory context must be productive, and the checkpoint blockade must be present at the right time to rescue the primed T cell response before it collapses into exhaustion or deletion.

Timing, in fact, emerges as one of the most stubborn unresolved variables. Should checkpoint inhibitors be given before ablation, so that T cells are already released from inhibition when antigen floods the system, or after, so that the drugs encounter a maximally primed immune repertoire? Should ablation be complete or deliberately partial, leaving residual antigen-rich tissue as a vaccine substrate? Which lesion should be ablated in a patient with multiple metastases, and does lesion size matter, as one study of liver metastatic melanoma receiving cryoablation plus PD-1 blockade suggests it does? None of these questions has a definitive answer, and the review identifies the absence of biomarker-driven patient stratification as a central obstacle. Candidate biomarkers are proliferating, from PD-L1 expression and interferon-gamma gene signatures to circulating tumor DNA kinetics, T cell receptor clonality, liquid biopsy measurements of minimal residual disease, and radiomics features extracted from imaging. What is lacking is large-scale validation linking any of these to abscopal responses or to outcomes of specific ablation-immunotherapy combinations in defined tumor types.

The translational roadmap the authors sketch is correspondingly ambitious. It calls for mechanistically informed clinical trial designs that treat modality, dose, timing, and immunotherapy schedule as coordinated experimental variables rather than independent choices; for comparative immunology that maps how each energy-based technique shapes antigen release, dendritic cell activation, and T cell trafficking; for integration of nanotechnology, cytokine engineering, and STING agonists to amplify the in situ vaccine effect; and for artificial intelligence-driven multi-omics modeling to predict which patients and which tumors are most likely to respond. The stakes are considerable. Checkpoint inhibitors have transformed outcomes in a subset of cancers but leave the majority of patients with solid tumors without durable benefit, often because their tumors are immunologically cold, devoid of T cells and antigen presentation. Ablation offers a physical means of heating those tumors up, converting individual lesions into antigen depots and inflammatory scaffolds. If the field can convert what is today a rare and unpredictable abscopal event into a reproducible therapeutic strategy, the review concludes, local tumor destruction will have fulfilled a promise far larger than the sum of the tissue it removes: the promise of teaching the immune system, in a single controlled injury, to recognize and eliminate cancer throughout the entire body.

Subject of Research: Mechanisms of abscopal effect and synergy between tumor ablation and immunotherapy in cancer

Article Title: Ablation–immunotherapy synergy in cancer: mechanisms of the abscopal effect, emerging clinical applications, and translational roadmaps for next-generation onco-immunology

Article References: Hama, M. A., Madhat, M. A., Awlqadr, F. H., Mahmood, A. H. A., Abdalla, R. A., Ali, R. K., Kareem, S. H. T., Hama, N. E., Hamalaw, S. R., & AL-Farga, A. M. (2026). Ablation–immunotherapy synergy in cancer: mechanisms of the abscopal effect, emerging clinical applications, and translational roadmaps for next-generation onco-immunology. Medical Oncology, 43(11), Article 313. https://doi.org/10.1007/s12032-026-03396-2

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03396-2

Keywords: abscopal effect, tumor ablation, immunotherapy, immune checkpoint inhibitors, cryoablation, radiofrequency ablation, microwave ablation, high-intensity focused ultrasound, immunogenic cell death, tumor microenvironment, cGAS-STING, in situ vaccination

The core idea behind interventional oncology is deceptively simple: if you can see a tumor clearly under imaging, you can often treat it without opening the body. High-resolution computed tomography, ultrasound, and magnetic resonance imaging allow physicians to navigate instruments to lesions deep within organs, destroying or starving them with millimeter-level precision. What began decades ago with image-guided biopsies, using needles to sample suspicious tissue, has evolved into a therapeutic arsenal of remarkable sophistication. The field’s trajectory, the authors note, illustrates the accelerating pace of innovation in oncology, transforming procedures that once seemed impossible into routine clinical practice.

Among the most consequential of these techniques is trans-arterial embolization, which has reshaped the treatment of liver cancer in particular. Rather than flooding the entire body with chemotherapy, interventionalists thread a catheter through the arterial system until its tip reaches the vessel feeding the tumor. Therapeutic agents are then delivered directly into that blood supply, often combined with particles that block the vessel altogether, cutting off the tumor’s nourishment. The approach delivers a concentrated payload to the malignancy while sparing functional liver tissue, a critical consideration in an organ whose reserve capacity often determines whether a patient can tolerate further treatment.

Equally transformative are percutaneous ablation techniques, in which needles or probes are placed directly into tumors and used to destroy them in situ. Thermal ablation, the most widely used family of methods, kills cancer cells by applying extreme heat through radiofrequency energy or microwaves, or by freezing tissue with cryoablation. These procedures have opened new pathways for patients who might otherwise have been poor candidates for invasive surgery, whether because of tumor location, coexisting illness, or insufficient organ reserve. Crucially, the authors emphasize, such advances have not merely provided alternatives to conventional treatment; they have created entirely new therapeutic possibilities, both for previously untreatable conditions and for combination strategies that make curative approaches achievable for more patients.

Perhaps the most scientifically exciting frontier lies at the intersection of interventional oncology and immunotherapy, the class of drugs that unleashes the body’s own immune defenses against cancer. Recent discoveries have revealed that many interventional procedures do more than physically destroy tumor tissue; they can actively stimulate a systemic immune response. When thermal ablation breaks down tumor cells, it releases tumor antigens, molecular fingerprints that the immune system can recognize and remember. In some patients this triggers a phenomenon known as the abscopal effect, in which the local treatment of one lesion appears to provoke immune-mediated regression of untreated tumors elsewhere in the body. The effect offers tantalizing avenues for combination therapies that pair targeted physical intervention with immunological activation, and research into this synergy is one of the field’s most active areas.

The growing power of interventional oncology is inseparable from its integration into the multidisciplinary machinery of modern cancer care. Interventional oncologists now sit regularly on tumor boards, the committees where medical oncologists, surgical oncologists, radiation oncologists, and other specialists jointly design each patient’s therapeutic strategy. This collaboration has produced more nuanced and personalized treatment sequences. Interventional procedures can be used to downstage tumors, shrinking them so that curative surgery becomes feasible, or to treat residual disease and oligoprogression, the isolated growth of a few lesions after conventional therapy has otherwise controlled the cancer. The ability to interleave treatments in this way has measurably improved outcomes and expanded options for patients who once faced limited choices.

Looking forward, the technological horizon appears remarkably bright. Artificial intelligence and machine learning are enhancing the precision of image-guided procedures, helping clinicians plan trajectories and interpret imaging with increasing accuracy. Robotic systems are extending the reach and steadiness of interventional techniques beyond what human hands alone can achieve, while advanced imaging technologies now provide real-time views of tumor biology and treatment response. Nanotechnology and molecular medicine are opening new frontiers in targeted therapy delivery, promising treatments that are more precise, more effective, and more personalized than ever before. The convergence of these computational, robotic, and biological tools suggests that the next decade of interventional oncology may be even more transformative than its last.

The field’s progress, however, is not without obstacles. Pereira and Helmberger are candid about the challenges ahead: the discipline must continue to strengthen its evidence base through rigorous clinical trials, and quality assurance frameworks need to be standardized across institutions. One concrete response is the International Accreditation System for Interventional Oncology Services, known as IASIOS, which aims to certify that centers performing these procedures meet consistent standards of training, equipment, and patient care. Training programs must also evolve, and the visibility of interventional oncology among medical students and fellows must grow to meet the rising demand for skilled interventionalists. The COVID-19 pandemic, though deeply disruptive, accelerated certain aspects of the field’s development, as supportive and palliative interventions and telemedicine-guided procedures gained prominence when conventional care pathways were strained.

Scholarly publishing has a role to play in sustaining this momentum, and the launch of CVIR Oncology itself reflects the field’s maturation. The journal is designed as a bridge between oncological specialties, welcoming contributions from interventional radiologists, medical and surgical oncologists, radiation oncologists, and basic scientists alike. The editorial logic is that cross-disciplinary dialogue breaks down silos: a surgical oncologist’s insights on post-procedural outcomes can refine interventional techniques, just as an immunologist’s findings can enhance procedural efficacy. By publishing both basic science and clinical research, the journal aims to translate laboratory discoveries into practical therapies, supporting the shift toward personalized medicine. As an open-access publication, it also ensures that practitioners in resource-limited settings can access the same evidence base as those in major academic centers.

Ultimately, the promise of interventional oncology extends beyond its technical achievements to something more human: the quality of patients’ lives. By offering less invasive treatments with fewer complications and shorter recovery times, the field is making cancer therapy more tolerable, benefiting patients and society alike. From primary liver and kidney tumors to metastatic disease, and from palliative symptom control to curative intent, interventional oncology is redefining what is possible across the entire spectrum of malignancy. The story, as its pioneers tell it, is one of continuous innovation and adaptation, and as the field stands on the threshold of new discoveries, its practitioners are confident that it will play an increasingly vital role in a future where cancer treatment is not only more effective, but also more humane.

Subject of Research: The evolution of interventional oncology as a minimally invasive, image-guided fourth pillar of multidisciplinary cancer treatment

Article Title: The evolution of interventional oncology: pioneering a new era in cancer care

Article References: Pereira, P. L., & Helmberger, T. (2025). The evolution of interventional oncology: pioneering a new era in cancer care. CVIR Oncology, 1(1), Article 1. https://doi.org/10.1007/s44343-025-00002-6

Image Credits: AI Generated

DOI: 10.1007/s44343-025-00002-6

Keywords: interventional oncology, interventional radiology, thermal ablation, trans-arterial embolization, immunotherapy, abscopal effect, liver cancer, artificial intelligence, multidisciplinary cancer care, IASIOS accreditation, minimally invasive treatment, CVIR Oncology

The scale of the problem is considerable. Canine oral tumors account for up to 12 percent of all cancers seen in dogs, with melanoma, squamous cell carcinoma, acanthomatous ameloblastoma, and fibrosarcoma representing the most common diagnoses of the oral cavity and pharynx. When these tumors are caught early, wide surgical excision remains the most effective local treatment. But many oral cancers are diagnosed at a locally advanced stage, when complete surgical resection is no longer possible. Radiation and chemotherapy become the fallback options, and while radiation can produce high response rates in tumors such as oral melanoma and squamous cell carcinoma, one-year survival rates for some of the most common oral cancers fall below 50 percent. Novel adjuvant therapies are urgently needed to make those responses last.

The drug at the heart of the study, CB101, is a proprietary hydrogel-based injectable formulation of resiquimod, a molecule known as a toll-like receptor 7/8 agonist. Toll-like receptors sit on the surface or within certain immune cells and act as sentinels for danger signals. In humans, TLR8 is uniquely expressed on myeloid dendritic cells, monocytes, and natural killer cells, making it an attractive lever for pulling the immune system into a fight against cancer. Activating these receptors may disrupt the immunosuppressive microenvironment that tumors build around themselves. Resiquimod itself has never been approved by the FDA, but topical formulations have been tested in human clinical trials for skin diseases and as a vaccine adjuvant, generating an extensive body of toxicology and pharmacology data supporting its safety profile.

The rationale for pairing this immune agonist with radiation rests on a phenomenon called immunogenic cell death. High-dose radiation, such as the 8 Gy per fraction used in some hypofractionated protocols, can kill tumor cells in a way that makes them more visible to the immune system, releasing tumor antigens that dendritic cells can engulf and cross-present to CD8-positive cytotoxic T lymphocytes. Research suggests that doses around 8 Gy per fraction are particularly well suited to synergizing with immunotherapeutics. In principle, this cascade can generate an adaptive, tumor-specific immune response capable of affecting not just the irradiated tumor but also distant, non-irradiated lesions, the so-called abscopal effect. Preliminary mouse data showed that the combination of radiation and CB101 improved local tumor control compared with either treatment alone and elicited such abscopal responses. Injecting the drug directly into the tumor is designed to limit systemic exposure and minimize off-target immune side effects.

Three dogs with histologically confirmed head and neck cancers were prospectively enrolled in the pilot study. Each animal received a baseline CT scan for radiation planning, followed by palliative radiation therapy delivered as four weekly 8 Gy fractions over weeks one through four. CB101 was administered intratumorally at a fixed dose of 10 micrograms in 500 to 1,000 microliters of volume at one-week intervals during weeks two through five, with the first dose given immediately before the second radiation fraction. Treatment planning relied on CT-based software, and dogs were anesthetized and immobilized in vacuum cushions with bite blocks to ensure reproducible setup. A follow-up CT scan at week 12 assessed tumor response, and serial thoracic radiographs at week 24 monitored for distant metastasis. All owners provided informed consent under institutional animal care protocols.

Feasibility proved to be the study’s clearest success. Little to no difficulty occurred during the intratumoral injections, and leakage of the formulation was negligible. Tumors arising from or containing bone were more challenging to infuse; one dog with mandibular fibrosarcoma required both intratumoral and peritumoral administration because of the density of the tumor and its proximity to the normal mandible. Injections were generally performed under general anesthesia for patient comfort, and no pain was noted after the procedure. The volume of each injection was chosen based on the expected ability of the hydrogel to diffuse into the tumor and surrounding tissue, guided by physical examination, CT evidence of bone infiltration, and three-dimensional tumor measurements.

Safety outcomes were equally encouraging. Toxicity was graded using the Veterinary Cooperative Oncology Group criteria and a veterinary radiation morbidity scoring scheme. Only one adverse event was attributable to CB101 itself: a case of grade 1, mild pain during a fourth injection performed under light sedation rather than general anesthesia. Every other adverse event documented was an expected side effect of palliative radiation, and no dog experienced toxicity higher than grade II. One dog developed grade I skin and mucosal toxicity along with grade II ocular toxicity requiring eye drops and antibiotics, an outcome anticipated from the radiation dose distribution, which included a large portion of the left eye. Another dog experienced no toxicity at all.

Tumor responses varied, as expected in such a small and histologically diverse cohort. The dog with oronasal squamous cell carcinoma showed a partial response at week 12 but developed distant progressive disease, first in lymph nodes and then in the lungs, between weeks 12 and 24, and was euthanized 198 days after enrollment. The dog with oral melanoma experienced local progression at week 12 and pulmonary metastasis by week 24, surviving 254 days. The dog with oral fibrosarcoma had stable disease at the week 12 scan, with eventual progression outside the radiation field at week 26 and a survival time of 371 days. All three dogs were free of distant metastases when treatment began.

Intriguingly, serum cytokine analysis revealed negligible changes in the immune signaling molecules the team measured, including TNF-alpha, IL-6, IL-15, interferon-alpha, IL-1 beta, and IL-12p40. The researchers suspect the sampling schedule missed any transient cytokine peaks, which could be expected within hours to three days after dosing rather than a full week later. The absence of clinical signs of cytokine release suggests the weekly 10 microgram dose was well tolerated but may have fallen below a therapeutic threshold. The starting dose was chosen conservatively because a human trial using 12.5 micrograms intralesionally had reportedly triggered cytokine storm and hypotension in some patients. Other veterinary researchers have used far higher resiquimod doses, with a University of Kansas group treating dogs with cutaneous mast cell tumors using doses ranging from 0.07 to 1.36 milligrams and observing one complete response and three partial responses among six dogs.

The Penn team acknowledges several confounders, including the use of NSAIDs in two of the three dogs, which could have either blunted the innate immune response or improved outcomes through COX-2 inhibition, and antimicrobial treatment in one dog, which in human melanoma patients has been associated with worse survival on immunotherapy. Future studies, the authors say, should standardize these medications, sample blood at multiple early time points after injection, and consider analyzing tumor tissue to capture local immune effects within the microenvironment. A dose escalation study appears warranted, and the researchers envision eventually combining TLR agonists with checkpoint inhibitors, an approach that could shift immunologically cold tumors toward hot ones. As academic and industry groups work toward commercializing canine checkpoint inhibitors, this modest pilot study in three dogs may mark the first step of a translational path that runs from the veterinary clinic to human oncology and back again.

Subject of Research: Combining intratumoral resiquimod immunotherapy with hypofractionated radiation therapy in canine head and neck cancer

Article Title: Preliminary evaluation of the safety and feasibility of toll-like receptor ligand CB101 combined with hypofractionated radiation therapy in canine head and neck cancer: a pilot study

Article References: Ghanian, A., DiBona, J., Duda, L., Xu, X., Lukens, J. N., Pearce, T., Ehrhardt, M., Rook, A., Durham, A., Maity, A., & Flesner, B. (2025). Preliminary evaluation of the safety and feasibility of toll-like receptor ligand CB101 combined with hypofractionated radiation therapy in canine head and neck cancer: a pilot study. Veterinary Oncology, 2(1), Article 18. https://doi.org/10.1186/s44356-025-00031-6

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00031-6

Keywords: canine cancer, head and neck cancer, radiation therapy, resiquimod, CB101, toll-like receptors, immunotherapy, intratumoral injection, veterinary oncology, dendritic cells, abscopal effect, pilot study

A team led by Min Deng of the State Key Laboratory of Molecular Oncology at the Cancer Hospital of the Chinese Academy of Medical Sciences, working with Zhenkun Lou of the Mayo Clinic and Bin Chen of Anhui University, has identified a tumor-intrinsic checkpoint that operates specifically in human cancer cells and is essentially absent from the murine models on which most radioimmunotherapy research is built. The circuit centers on three proteins: the farnesoid X receptor, or FXR, a nuclear receptor best known for its role in bile acid metabolism; TRIM22, an E3 ubiquitin ligase of the tripartite motif family; and STAT1, the transcription factor that sits at the heart of interferon signaling. In human tumor cells, the researchers found, radiation inadvertently activates this axis, and the result is a molecular strangulation of the very interferon program that radiation is supposed to unleash.

The mechanistic story begins with protein stability. The team showed that ionizing radiation stabilizes FXR in human cancer cells through the action of ubiquitin-specific peptidase 7, or USP7, a deubiquitinating enzyme that removes the ubiquitin tags that would otherwise mark FXR for proteasomal destruction. Once stabilized, FXR translocates its transcriptional activity toward a specific target: the gene encoding TRIM22. TRIM22, in turn, selectively binds STAT1 and catalyzes the attachment of K48-linked polyubiquitin chains, the canonical signal for degradation by the 26S proteasome. With STAT1 levels falling, the downstream interferon-stimulated gene program, the battery of ISGs that coordinates antigen presentation, T-cell recruitment, and inflammatory amplification, is extinguished precisely when radiation has done its work and the immune system should be mobilizing.

What makes this discovery particularly striking is its species specificity. When the researchers compared human and murine cancer cells, they found that mouse tumor cells simply lack a TRIM22 family member capable of destabilizing STAT1 in this way. Radiation therefore produces robust, sustained STAT1-dependent interferon signaling in mouse tumors, while the same insult in human cells is blunted by the FXR-TRIM22 circuit. This single proteostatic difference offers a mechanistic explanation for one of the most persistent frustrations in translational radiation oncology: the repeated failure of dramatic preclinical abscopal effects to translate into consistent clinical benefit. Decades of combination trials pairing radiation with immune checkpoint inhibitors have been designed around mouse data that, it now appears, were structurally incapable of revealing this human brake.

The consequences of dismantling the brake were demonstrated through genetic and pharmacologic means. When the team disrupted FXR or TRIM22 in human cancer cells, STAT1 was preserved, type I interferon signaling was amplified, and the irradiated tumor cells became markedly better at activating CD8-positive T cells. These effects were tested in peripheral blood mononuclear cell-humanized mouse models, which carry functional human immune components and human tumor cells, providing a far more faithful platform than conventional murine systems. In these humanized settings, loss of the FXR-TRIM22 axis enhanced abscopal tumor control, meaning that untreated tumors at distant sites regressed as the systemic immune response gathered strength, a phenomenon that has long been the holy grail of radiation-immunology research.

The pharmacologic arm of the study is where the work acquires its most immediate clinical resonance. Ursodeoxycholic acid, or UDCA, is a bile acid that has been used clinically for decades, primarily to treat cholestatic liver diseases and primary biliary cholangitis, with a long and well-characterized safety record. Prior work, including studies in morbidly obese patients, had suggested that UDCA exerts antagonistic effects on FXR signaling. The team reasoned that a safe, approved drug capable of dampening FXR might suppress the radiation-induced TRIM22 response and thereby preserve STAT1. That is exactly what they observed: UDCA treatment suppressed radiation-induced TRIM22 expression in human tumor cells, restored STAT1 protein levels and interferon-stimulated gene signaling, and potentiated the antitumor effects of radiotherapy in humanized models.

Crucially, the benefits extended to combination therapy. When UDCA was paired with radiotherapy and an anti-PD-1 immune checkpoint antibody in humanized mice, the triple combination produced superior tumor control without overt toxicity. This is a significant point, because the tolerability profile of UDCA is exceptionally well understood from its long hepatology track record, and any strategy that could enhance radioimmunotherapy using an already-approved, orally available drug would face a far shorter path to clinical testing than a purpose-built inhibitor of a novel target. The authors also note that the ubiquitin-proteasome machinery involved, including the E3 ligase TRIM22, belongs to target classes increasingly considered druggable in modern oncology, offering additional avenues if dedicated FXR or TRIM22 inhibitors are developed.

The study also contributes to a broader rethinking of how radiation and immunity interact in human tumors. It has long been appreciated that type I interferon signaling is a double-edged sword in cancer, with chronic or dysregulated interferon sometimes promoting immune escape, but the acute interferon burst following DNA damage is widely regarded as essential for effective antitumor immunity. By showing that a human-specific proteostatic checkpoint throttles that burst at the level of STAT1 stability, the work reframes the problem of radiation resistance: the issue is not that human tumors fail to sense DNA damage through cGAS-STING, but that a downstream transcriptional regulator is actively degraded before it can broadcast the alarm. Intervening at the level of protein stability, rather than at pathway activation, may therefore be the more effective strategy in patients.

Caveats remain, as they always do at this stage of translation. The evidence for the FXR-TRIM22-STAT1 axis and the efficacy of UDCA comes from cell lines and humanized mouse models, not yet from clinical trials, and the precise dosing, timing, and patient selection needed to deploy UDCA alongside radiation and checkpoint blockade in humans remain to be established. The authors declare no competing interests, and the RNA-sequencing data underpinning the transcriptional analyses have been deposited in public repositories for independent scrutiny. Still, the conceptual payoff is immediate: a human-biased mechanism that has been hiding in plain sight, masked by the very mouse models used to study it, now has a name, a circuit diagram, and a candidate drug. If the findings hold in patients, a decades-old bile acid could become an unexpected partner for radiation in the fight against cancer.

Subject of Research: A human-biased FXR-TRIM22-STAT1 immune checkpoint that limits radiation-induced antitumor immunity and its pharmacologic modulation by ursodeoxycholic acid

Article Title: Ursodeoxycholic acid enhances cancer radioimmunotherapy by releasing a human-biased FXR-TRIM22-STAT1 immune brake

Article References: Li, X., Jiang, P., Yin, H., Huo, Z., Xu, X., Nowsheen, S., Aziz, K., Zheng, S., Sun, N., Chen, B., Lou, Z., & Deng, M. (2026). Ursodeoxycholic acid enhances cancer radioimmunotherapy by releasing a human-biased FXR-TRIM22-STAT1 immune brake. Cell Research. https://doi.org/10.1038/s41422-026-01293-x

Image Credits: AI Generated

DOI: 10.1038/s41422-026-01293-x

Keywords: radiotherapy, radioimmunotherapy, FXR, TRIM22, STAT1, ursodeoxycholic acid, type I interferon, cGAS-STING, abscopal effect, CD8 T cells, ubiquitination, cancer immunotherapy

Plasmids are circular pieces of DNA that can be engineered to carry therapeutic genes into cells. Unlike viral vectors, which have dominated gene therapy because of their efficiency at transferring genetic material, plasmids are comparatively simple to manufacture, can carry larger payloads, and tend to raise fewer safety concerns related to insertional mutagenesis or uncontrolled viral replication. Their principal limitation has always been delivery: naked DNA does not readily cross cell membranes, and achieving clinically meaningful levels of gene expression inside tumors without a viral carrier has proven challenging. The new research addresses this obstacle by pairing an optimized plasmid combination with an intratumoral delivery approach, injecting the therapeutic construct directly into accessible lesions so that high local concentrations of the encoded proteins are produced precisely where they are needed most.

The therapeutic logic behind intratumoral plasmid delivery rests on a concept that has reshaped modern cancer immunotherapy: the idea that a tumor can be converted from a site of immune evasion into the equivalent of an in situ vaccine. When immune-stimulating genes are expressed inside a tumor, dying cancer cells release tumor antigens together with danger signals, and dendritic cells that traffic through the injected lesion can capture these antigens and carry them to draining lymph nodes. There, T cells are primed against the specific mutations and proteins of that patient’s cancer. Because melanoma is among the most mutationally dense of all human tumors, it presents a rich array of neoantigens, making it a particularly suitable candidate for this kind of localized priming strategy. Once activated, T cells can circulate through the bloodstream and attack metastatic deposits far removed from the injection site, a systemic effect commonly described as an abscopal response.

The combination described in the study was designed so that each plasmid component contributes a complementary function to this immunological cascade. One element is intended to drive the production of immune-activating cytokines within the tumor microenvironment, counteracting the immunosuppressive conditions that melanomas establish through regulatory T cells, suppressive macrophages, and inhibitory signaling pathways. Additional plasmids support antigen presentation and local inflammation, ensuring that the tumor becomes visible to the immune system rather than remaining immunologically silent. By encoding several factors simultaneously on separate but co-delivered plasmids, the approach avoids the cargo-size constraints that limit many viral vectors and allows the relative composition of the mixture to be tuned, something that fixed viral constructs cannot easily achieve.

Technically, the delivery of plasmid DNA into cells in vivo is typically enhanced by electroporation, a process in which short electrical pulses are applied to the injected tissue to transiently permeabilize cell membranes, allowing DNA to enter. Intratumoral electroporation has been explored in multiple clinical trials of cancer gene therapy, and its safety profile has been well characterized: the procedure is minimally invasive, can be performed under local anesthesia for accessible lesions, and confines gene expression largely to the treated tissue. This spatial restriction is an important safety feature, because it limits systemic exposure to cytokines that, when delivered as recombinant proteins throughout the body, can cause severe toxicity. The authors of the new work built on this established foundation, refining both the genetic composition of the plasmid cocktail and the parameters of its administration to maximize expression levels and antitumor activity.

The reported outcome, high levels of metastatic melanoma regression, is significant for several reasons. First, regression extended beyond the directly injected lesions, indicating that the treatment did more than destroy the cells physically contacted by the needle. This systemic component is the essential requirement for any therapy intended to control metastatic disease, in which tumor deposits are scattered across the skin, lymph nodes, lungs, liver, brain, and other organs. Second, the magnitude of the response suggests that the plasmid combination achieved biologically meaningful expression levels, overcoming the historical weakness of non-viral delivery. Third, the strategy is modular: because plasmids are cheap and quick to produce under good manufacturing practice conditions, alternative gene combinations could in principle be swapped in for different tumor types or to overcome resistance mechanisms as they emerge.

The implications for combination therapy are particularly noteworthy. Current standards of care for advanced melanoma include anti-PD-1 antibodies, sometimes combined with anti-CTLA-4 blockade, and BRAF plus MEK inhibitors for patients whose tumors carry BRAF V600 mutations. Each of these approaches eventually encounters resistance. An intratumoral plasmid therapy that generates local inflammation and broad neoantigen-specific T cell priming could act synergistically with checkpoint inhibitors, which function by releasing the brakes on T cells that have already been activated. In this sense, plasmid-based intratumoral treatment addresses the ignition problem, priming and expanding antitumor immunity, while checkpoint blockade addresses the brake problem, sustaining that immunity once it exists. Clinical trials testing such rational combinations are a natural next step for the field, and the preclinical findings reported here provide the mechanistic justification for pursuing them.

Safety and manufacturability considerations also weigh in favor of the plasmid approach. DNA plasmids are non-infectious, do not integrate efficiently into the genome, and can be produced at scale in bacterial fermentation at costs far below those of engineered viral vectors or personalized neoantigen vaccines. For patients, intratumoral administration means that only lesions reachable by injection can be treated directly, which is a limitation for visceral disease, although the demonstrated abscopal effect means that even a single injected lesion can, in principle, drive immunity against distant deposits. The procedure also allows repeated dosing, since DNA expression is transient by design, and transient expression of potent immunostimulatory molecules is generally safer than continuous systemic exposure.

The study adds momentum to a broader revival of interest in non-viral gene delivery, a field currently energized by the success of lipid nanoparticles in RNA therapeutics. Plasmid DNA and RNA-based approaches differ in important ways, with plasmids offering nuclear delivery and potentially longer expression, and the present work demonstrates that, with the right construct design and delivery conditions, non-viral DNA can reach the expression levels required for robust therapeutic activity in cancer. For metastatic melanoma patients whose disease has stopped responding to approved immunotherapies, and for the clinicians caring for them, the prospect of a simple, reproducible, and manufacturable intratumoral treatment that recruits the immune system against the full antigenic breadth of their own tumor represents a meaningful and cautiously encouraging advance. Continued preclinical validation and, ultimately, controlled clinical testing will determine how this novel plasmid combination fits into the evolving treatment landscape of advanced melanoma.

Subject of Research: Intratumoral plasmid gene delivery for the treatment of metastatic melanoma

Article Title: Intratumor delivery of a novel plasmid combination induces high levels of metastatic melanoma regression

Article References: Heller, L. C., Singh, J. S., Synowiec, J. C., Jaroszeski, M. J., Otten, A., & Heller, R. (2026). Intratumor delivery of a novel plasmid combination induces high levels of metastatic melanoma regression. Gene Therapy. https://doi.org/10.1038/s41434-026-00644-y

Image Credits: AI Generated

DOI: 10.1038/s41434-026-00644-y

Keywords: metastatic melanoma, plasmid DNA, intratumoral delivery, gene therapy, cancer immunotherapy, non-viral vectors, electroporation, antitumor immunity, abscopal effect, checkpoint inhibitors, tumor microenvironment, melanoma regression

The review, conducted by researchers at Shiraz University of Medical Sciences, Tehran University of Medical Sciences and University College London, followed the PRISMA 2020 guidelines and searched PubMed, Scopus, Web of Science and Embase for studies published up to September 2025. The team’s protocol was prospectively registered in the PROSPERO database. From the initial search, twenty-four preclinical studies met the inclusion criteria: animal models in which investigators assessed distant tumor regression or systemic immune activation following PDT, whether delivered alone or in combination with other therapies.

The findings were strikingly consistent. Across the included studies, PDT reliably produced local tumor regression and activated the immune system, with the molecular fingerprints of immunogenic cell death clearly visible. Dying tumor cells released damage-associated molecular patterns, exposed calreticulin on their surfaces, and recruited cytotoxic CD8-positive T lymphocytes into the tumor microenvironment. These are the same hallmarks that immunologists look for when a cell death event is capable of training the adaptive immune system to recognize and attack cancer, rather than simply clearing debris.

The abscopal effect itself, named from ‘ab’ meaning away and ‘scopal’ meaning target, has historically been a rare and unpredictable curiosity in radiation oncology. When it occurs, a localized treatment appears to prime immune cells that then travel through the circulation and attack tumors that were never irradiated. For decades, clinicians reported it only sporadically, and its rarity made it difficult to study. The new review suggests that PDT may offer a more controllable way to induce this systemic response, because the therapy’s oxidative burst can be tuned by adjusting drug dose, light intensity, timing and photosensitizer chemistry.

Crucially, the strongest abscopal responses emerged when PDT was paired with immune checkpoint blockade, specifically antibodies targeting programmed cell death protein-1, or PD-1, and its ligand PD-L1. Checkpoint inhibitors release the molecular brakes that tumors place on T cells, and the review’s authors found that combining them with PDT’s immune-priming effect produced clear distant tumor regression in several animal studies. Adjuvants, substances that boost immune signaling, also amplified the systemic response when co-administered with the light treatment. This synergy makes mechanistic sense: PDT floods the tumor with antigens and danger signals, while checkpoint blockade ensures the newly activated T cells are not silenced as they circulate.

The systemic nature of the immune activation was confirmed at the molecular level. Multiple studies reported upregulation of key inflammatory cytokines, including interleukin-6, interferon-gamma and tumor necrosis factor-alpha, in the circulation of treated animals. These signaling molecules are characteristic of a robust, body-wide immune response rather than a purely local inflammatory reaction. Interferon-gamma in particular is central to antitumor immunity, enhancing antigen presentation and directly inhibiting tumor cell proliferation, while tumor necrosis factor-alpha contributes to vascular disruption within tumors and supports cytotoxic lymphocyte function.

What distinguishes PDT from radiotherapy, its closest conceptual rival for abscopal induction, is the nature of the cell death it provokes. Reactive oxygen species generated by the photosensitizer can trigger immunogenic apoptosis and necrosis while preserving tumor antigen integrity, and PDT can also damage tumor vasculature and reprogram the immunosuppressive tumor microenvironment. The review notes that immune reprogramming, the shift of a tumor from a cold, T-cell-excluded state to a hot, inflamed state, appears to be a key mechanism by which PDT converts a local treatment into a systemic one. By depleting suppressive myeloid cells and regulatory T cells and promoting dendritic cell maturation, PDT can create the conditions under which newly primed T cells can function effectively.

The authors are careful to frame their conclusions as preclinical, with early clinical studies offering preliminary support but not definitive proof. Animal models of cancer frequently overstate immune effects that later fail to translate into human trials, and the twenty-four studies included in the review varied in photosensitizer, tumor model, light dosing and combination regimens, making direct comparison difficult. The review nonetheless argues that the consistency of the immune activation signals across models, and the reproducibility of abscopal responses when PDT is combined with checkpoint blockade, justify moving the field toward carefully designed clinical evaluation. Optimizing treatment parameters, the authors suggest, may allow PDT to evolve from a local, cytotoxic treatment into a genuine systemic cancer immunotherapy.

The implications for patients with metastatic disease are considerable. If a clinician could illuminate a single accessible lesion and thereby vaccinate the patient’s immune system against their own tumor, the strategy could complement existing immunotherapies rather than replace them. Combination trials pairing PDT with PD-1 or PD-L1 inhibitors are the most obvious next step, and the review’s systematic synthesis of preclinical evidence provides a roadmap for which parameters, photosensitizers and adjuvant strategies appear most promising. Questions remain about the durability of the induced immunity, the risk of immune-related adverse events, and whether human tumors, which are more heterogeneous than laboratory models, will respond as predictably.

For now, the review stands as the most comprehensive preclinical assessment to date of PDT’s ability to reach beyond the beam of light that delivers it. It documents a therapy long thought of as surgically precise quietly revealing a second identity: an immune catalyst capable of sending signals far beyond the treated site. As the authors conclude, with optimized parameters and rational combinations with immunotherapy, photodynamic therapy may develop from a local cytotoxic tool into a systemic weapon against cancer, one that turns a single illuminated tumor into the trigger for a body-wide immune campaign.

Subject of Research: Systematic review of preclinical evidence that photodynamic therapy induces immunogenic cell death and abscopal, systemic antitumor immune responses

Article Title: Immunogenic and systemic antitumor responses induced by photodynamic therapy: a systematic review of the abscopal effect

Article References: Faghani-Eskandarkolaei, P., Zareei-khooshab, V., Mansouri-Bidekani, R., Heli, H., Abdollahi, M., Haghighi, H., Zahraie, N., & Sattarahmady, N. (2026). Immunogenic and systemic antitumor responses induced by photodynamic therapy: a systematic review of the abscopal effect. Cancer Cell International. https://doi.org/10.1186/s12935-026-04455-4

Image Credits: AI Generated

DOI: 10.1186/s12935-026-04455-4

Keywords: photodynamic therapy, abscopal effect, immunogenic cell death, reactive oxygen species, immune checkpoint blockade, CD8-positive T lymphocytes, calreticulin, damage-associated molecular patterns, cytokines, tumor microenvironment, cancer immunotherapy, metastatic cancer