The review, led by Kexun Li, Zilong Qian and Jie Mao with senior authors Yongtao Han and Xuefeng Leng, synthesises evidence across the major gastrointestinal malignancies: gastric and esophageal cancers, colorectal cancer, pancreatic ductal adenocarcinoma, hepatocellular carcinoma and biliary tract cancers. Its central claim is that the tumour secretome, the full complement of proteins released by tumour cells, stromal cells and immune cells into the extracellular space, functions as a dynamic signalling layer that determines whether immune cells are recruited to the tumour, whether they penetrate it, whether they function once they arrive, and whether they exhaust themselves in the struggle. When checkpoint blockade releases the brakes on T cells, the success of that manoeuvre depends on the state of the road ahead, and the secretome largely builds that road.

The authors catalogue an imposing roster of recurrent suppressive circuits. Transforming growth factor beta, long implicated in immune exclusion and fibroblast activation, appears across nearly every gastrointestinal tumour type as a driver of stromal barriers that physically wall off cytotoxic lymphocytes. Vascular endothelial growth factor, best known for promoting the chaotic, leaky vasculature of tumours, also actively repels T-cell infiltration and fosters immunosuppressive myeloid cells. The chemokine CXCL12, acting through its receptor CXCR4, excludes T cells from tumour nests in pancreatic and colorectal cancers, while CXCL8, also known as interleukin-8, signalling through CXCR1 and CXCR2, attracts neutrophils and suppresses T-cell function. The CCL2-CCR2 axis recruits inflammatory monocytes that can differentiate into tumour-promoting macrophages, and the CSF1-CSF1R pathway sustains those macrophages in a suppressive, pro-tumour state.

Beyond these canonical axes, the review highlights a second tier of secreted mediators whose roles have crystallised more recently. Interleukin-6 family cytokines drive chronic inflammatory programmes that blunt antitumour immunity and correlate with poor outcomes. SPP1, the gene encoding osteopontin, marks a distinctive population of tumour-associated macrophages and fibroblasts that sculpt an immunosuppressive niche. Periostin, secreted largely by cancer-associated fibroblasts, reinforces extracellular matrix barriers and promotes metastatic colonisation. Galectins, a family of beta-galactoside-binding lectins, can directly induce T-cell apoptosis and dysfunction. DKK1, a Wnt pathway antagonist, contributes to immune exclusion and stemness. Macrophage migration inhibitory factor, or MIF, sustains inflammatory suppression, while components of the complement cascade, traditionally viewed as blood-borne effectors of innate immunity, have been co-opted by tumours to remodel the microenvironment in their favour. Finally, soluble forms of PD-L1 and PD-L1 carried on extracellular vesicles circulate through the bloodstream, potentially mopping up therapeutic antibodies and dampening T-cell activity far from the tumour itself.

Against this suppressive chorus, the review sets out the secretome signatures of immune-permissive tumours. The chemokines CXCL9, CXCL10 and CXCL11, signalling through the receptor CXCR3, recruit effector T cells expressing that receptor, and their abundance consistently correlates with T-cell infiltration and responsiveness to checkpoint blockade. Even more striking is CXCL13, the chemokine that draws B cells and organises tertiary lymphoid structures, ectopic lymph-node-like aggregates that form within tumour tissue. Tumours rich in tertiary lymphoid structures, particularly in colorectal and gastric cancer, respond to immunotherapy at markedly higher rates, and CXCL13-associated signalling appears to be a key driver of their formation. The secretome, in other words, is not uniformly hostile; it can be reprogrammed toward a state that amplifies the effect of checkpoint inhibitors once stromal and myeloid barriers are relieved.

To bring analytical order to this complexity, the authors organise the suppressive and permissive circuits into four overlapping functional modules. The myeloid-enriched module encompasses the chemokines and colony-stimulating factors that flood tumours with suppressive macrophages, monocytes and granulocytes. The fibroblast-driven exclusion module centres on TGF-beta, periostin and matrix-remodelling signals that build physical and biochemical barriers to immune infiltration. The angiogenic-immunosuppressive module couples VEGF-driven vascular dysfunction to myeloid suppression and hypoxia. The immune-permissive module, by contrast, comprises the CXCR3 ligand axis and CXCL13-driven tertiary lymphoid structure programmes that characterise tumours primed for immunotherapy response. This modular framework allows clinicians and researchers to describe a tumour’s secretome state not as an undifferentiated list of molecules but as a pattern of dominant biological programmes with distinct therapeutic implications.

Perhaps the review’s most consequential methodological contribution is its insistence on a four-level evidence hierarchy that separates clinical validation from mechanistic inference. Many secreted proteins have been convincingly shown in cell culture and animal models to suppress or promote antitumour immunity, yet only a subset has been validated as predictive or prognostic biomarkers in large clinical cohorts, and fewer still have been targeted successfully in combination trials. TGF-beta, for example, has mechanistic support at every level, and signatures of TGF-beta-driven fibroblast activity have been shown to predict poor checkpoint response in multiple cancer types, yet TGF-beta inhibitors have delivered mixed results in the clinic, suggesting that timing, context and combination partners matter enormously. The hierarchy is designed to prevent over-interpretation of preclinical enthusiasm and to guide rational prioritisation of which secretome targets should advance toward biomarker-guided trials.

Equally important is the review’s argument that protein abundance alone is biologically meaningless without context. The same chemokine can recruit antitumour T cells or immunosuppressive myeloid cells depending on which receptor-bearing cells are present. The same cytokine can promote or restrain immunity depending on its spatial distribution within the tumour, whether it is produced by malignant epithelium, fibroblasts or infiltrating immune cells, and whether it is measured before treatment, during therapy or at the moment of acquired resistance. Metastatic sites differ from primary tumours in their secretome programmes, and host physiology, including liver function, microbiome composition and systemic inflammation, modulates the interpretation of circulating protein signals. A clinically useful secretome biomarker must therefore integrate cellular source, spatial localisation, receptor context, temporal dynamics and linkage to actionable immune-state transitions, a demand that far exceeds what a single blood test or immunohistochemical stain can deliver.

This contextual complexity helps explain why genomic biomarkers such as microsatellite instability and tumour mutational burden, while genuinely predictive in defined settings, leave most gastrointestinal cancer patients without a reliable answer. A colorectal tumour with high mutational burden may nonetheless be saturated with CXCL12-expressing fibroblasts and CSF1-dependent macrophages that render even reinvigorated T cells ineffective. A pancreatic cancer with modest genomic immunogenicity may be so thoroughly walled off by TGF-beta-driven stroma that no quantity of checkpoint blockade can achieve meaningful infiltration. Conversely, a gastric tumour with abundant tertiary lymphoid structures and a CXCL9-rich chemokine milieu may respond even with intermediate genomic predictors. The secretome is the layer at which these competing influences are integrated and expressed.

The therapeutic implications are substantial. Combination strategies already in clinical testing, including TGF-beta inhibition, CSF1R blockade, CXCR4 antagonism, VEGF pathway targeting and IL-6 pathway suppression, can be understood as attempts to dismantle specific suppressive modules and convert tumours from an excluded or suppressive secretome state into a permissive one. The review suggests that the rational design of such combinations should be guided by modular secretome profiling of individual tumours, with the goal of matching each patient to the barrier-removing strategy most likely to unmask checkpoint activity. Biomarker development, the authors argue, should focus on identifying actionable immune-state transitions, moments at which a tumour’s secretome programme is poised to flip from suppression to permissiveness, and on capturing that transition with spatially resolved, temporally informed measurements. As single-cell and spatial transcriptomic technologies mature and become clinically deployable, the prospect of reading a tumour’s secreted protein circuitry and intervening accordingly moves from aspiration toward practice. For the majority of gastrointestinal cancer patients who today derive little benefit from immunotherapy, that shift may ultimately determine whether the immunotherapy revolution reaches them at all.

Subject of Research: Secreted protein signalling circuits in the gastrointestinal tumour microenvironment that determine immunotherapy response and resistance

Article Title: Secreted protein circuits in the gastrointestinal tumour microenvironment: determinants of immunotherapy response and resistance

Article References: Li, K., Qian, Z., Mao, J., Han, Y., & Leng, X. (2026). Secreted protein circuits in the gastrointestinal tumour microenvironment: determinants of immunotherapy response and resistance. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08945-x

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08945-x

Keywords: gastrointestinal cancer, tumour microenvironment, secretome, immune checkpoint blockade, TGF-beta, VEGF, chemokines, tertiary lymphoid structures, cancer-associated fibroblasts, tumour-associated macrophages, immunotherapy resistance, biomarkers

The investigation began with a computational analysis of publicly available transcriptomic and clinical data from widely used prostate cancer cohorts. The researchers sought to identify genes whose expression patterns could reliably predict patient outcomes, a longstanding goal in the field of precision oncology. Using differential expression analysis to pinpoint genes that behaved differently between tumor and healthy tissue, the team then applied LASSO-Cox regression, a statistical technique that penalizes overly complex models to prevent overfitting and select only the most robust predictors. The result was a compact three-gene prognostic signature consisting of MECR, HVCN1, and NGFR. What makes this finding particularly striking is the model’s performance: the three-gene combination independently predicted patient survival and outperformed conventional clinicopathological variables such as stage, grade, and prostate-specific antigen levels, which clinicians have relied upon for decades. In clinical practice, this kind of molecular signature could eventually help stratify patients at diagnosis, identifying those who need intensified surveillance or more aggressive intervention even when traditional indicators appear reassuring.

Of the three genes in the signature, MECR emerged as the standout. Short for mitochondrial enoyl-CoA reductase, MECR encodes an enzyme embedded in the fatty acid synthesis machinery of mitochondria, and it was the only member of the trio whose elevated expression was associated with poor prognosis. This connection to lipid metabolism is scientifically significant because cancer cells are notorious for rewiring their metabolic programs to support rapid proliferation. Fatty acid synthesis, in particular, provides building blocks for membranes, energy storage, and signaling molecules that tumors need as they grow and spread. The observation that a mitochondrial enzyme in this pathway correlates with worse outcomes in prostate cancer suggested to the researchers that MECR might not merely be a biomarker but an active participant in the disease process.

To test this hypothesis, the team turned to functional experiments in prostate cancer cell lines. When they reduced MECR expression, the cancer cells lost several of their malignant advantages. Proliferation slowed, migration—the cellular behavior that underpins metastasis—was impaired, and the cells showed increased apoptosis-related nuclear morphological changes, meaning they displayed the characteristic structural hallmarks of programmed cell death. These results indicate that MECR helps prostate cancer cells resist apoptosis, the built-in suicide program that healthy organisms use to eliminate damaged or dangerous cells. Tumors that evade apoptosis are notoriously difficult to treat with chemotherapy and radiation, both of which work in part by triggering this death pathway. A gene that suppresses apoptosis therefore represents an attractive therapeutic target, because inhibiting it could potentially re-sensitize tumors to existing treatments.

The mechanistic story deepened when the researchers probed how MECR exerts its effects. Their experiments revealed that MECR regulates the activity of the PI3K/AKT pathway, one of the most frequently activated signaling cascades in human cancer. This pathway functions as a master switch for cell survival, growth, and metabolism; when constitutively active, it drives uncontrolled proliferation and protects cells from dying. By modulating PI3K/AKT signaling, MECR appears to sit upstream of processes that are central to tumor maintenance. Beyond this canonical cancer pathway, the team also found evidence that MECR influences immune-related cellular mechanisms, hinting that the gene’s impact extended beyond the tumor cell itself and into the surrounding microenvironment—the complex ecosystem of immune cells, fibroblasts, blood vessels, and signaling molecules that envelops every tumor.

That hint was put to a rigorous test using immunocompetent syngeneic tumor models, laboratory systems in which tumors are grown in mice with fully functioning immune systems. This experimental design is critical because many cancer studies rely on immunodeficient mice, which cannot reveal how a tumor interacts with the immune system. When the researchers knocked down MECR in these models, tumor progression was significantly inhibited. Crucially, the suppressed tumors showed increased activation of CD8-positive T cells, the cytotoxic “killer” cells of the adaptive immune system that are responsible for recognizing and destroying cancer cells. This finding positioned MECR not just as a metabolic driver but as a potential architect of immune evasion, reshaping the tumor microenvironment in ways that keep the most potent anti-cancer immune warriors in check.

To confirm that CD8-positive T cells were genuinely responsible for the antitumor effect, the researchers performed an elegant depletion experiment. When they eliminated CD8-positive T cells from the mice, the antitumor benefits of MECR silencing were partially rescued—in other words, tumors grew more effectively again when the killer T cells were absent. This experiment demonstrated that CD8-mediated immunity is a key contributor to the therapeutic effect of suppressing MECR, cementing the link between this metabolic enzyme and the immune response against prostate cancer. The implication is profound: targeting MECR could simultaneously deprive tumors of a metabolic advantage and unleash the immune system against them, a dual mechanism that mirrors the goals of modern combination immunotherapy.

The broader context of this work touches one of the most pressing challenges in prostate cancer treatment. While immune checkpoint inhibitors have revolutionized the treatment of many cancers, prostate cancer has proven remarkably resistant to these therapies, in part because prostate tumors typically foster an immunologically “cold” microenvironment with few active T cells. Understanding how individual metabolic genes remodel this microenvironment could reveal why prostate cancers exclude or suppress immune cells and point to strategies for reversing that process. The authors of the new study frame their findings as a contribution to understanding immune evasion and the therapeutic resistance that flows from it. By integrating tumor-intrinsic mechanisms—proliferation, migration, apoptosis resistance—with immune-associated remodeling, the study offers a more holistic view of how prostate cancer progresses than approaches that examine tumor cells in isolation.

There are also translational implications for prognostic modeling. A three-gene signature that outperforms standard clinical variables would be relatively straightforward to implement in pathology laboratories using routine molecular techniques such as quantitative PCR or RNA sequencing. If validated in prospective clinical cohorts, the MECR-HVCN1-NGFR signature could help clinicians identify patients whose apparent low-risk disease nonetheless carries molecular features of aggressiveness, guiding decisions about active surveillance versus active treatment. Meanwhile, MECR itself, as the sole poor-prognosis gene in the panel and a mechanistically validated driver, stands out as a candidate for drug development. Small molecules targeting mitochondrial fatty acid synthesis enzymes are an emerging area of cancer pharmacology, and this study provides preclinical evidence that such an approach could pay dividends in prostate cancer specifically.

The study was approved by the Ethics Committee of Nanjing Medical University, conducted in accordance with the Declaration of Helsinki with written informed consent from all human participants, and animal experiments complied with institutional ethical regulations and ARRIVE guidelines. The research team, spanning the Affiliated Huaian No. 1 People’s Hospital of Nanjing Medical University, the Affiliated Suzhou Hospital of Nanjing Medical University, and the Second Affiliated Hospital of Soochow University, published the work as an open-access article, making the data freely available to researchers worldwide. As with all preclinical research, the path from laboratory finding to clinical application will require further validation, including studies in larger patient cohorts and the development of pharmacological tools to inhibit MECR in humans. But the convergence of prognostic value, mechanistic clarity, and immune relevance in a single gene is rare in cancer research, and it is precisely this convergence that makes MECR a target worth watching. If future studies confirm these findings, suppressing MECR could become a strategy that attacks prostate cancer on two fronts at once—starving the tumor of its metabolic advantages while stripping away the defenses it uses to hide from the immune system.

Immune checkpoint inhibitors have transformed treatment for several advanced cancers by releasing molecular brakes that prevent T cells from attacking malignant cells. Anti-PD-1 drugs work by blocking the interaction between PD-1 on T cells and its ligands on tumor or immune cells, allowing exhausted T cells to regain some of their cytotoxic activity. However, colorectal cancer remains a particularly difficult setting for immunotherapy. Only a subset of tumors responds effectively, and many patients who initially benefit eventually develop acquired resistance. The new findings suggest that chronic inflammation may help explain why this resistance develops, by changing not only the immune cells surrounding a tumor but also the internal regulatory machinery of the cancer cells themselves.

The study, published in Nature Communications, was led by Assistant Professor Takumi Itoh of the Department of Therapy Development and Innovation for Immune Disorders and Cancers at Juntendo University’s Graduate School of Medicine. The researchers examined human colorectal cancer samples using single-cell RNA sequencing and broader transcriptomic analyses, then tested their observations in human IL-26 transgenic mice and inflammation-induced mouse models. These approaches were combined with immunofluorescence imaging, chromatin immunoprecipitation sequencing, co-immunoprecipitation experiments, and targeted interventions directed against IL-26, STAT1, BRD4, CXCL chemokines, the chemokine receptor CXCR2, and neutrophils. Together, the experiments followed the mechanism from cytokine production by immune cells to epigenetic changes inside tumor cells and, ultimately, altered responses to immunotherapy.

The researchers found that IL-26-producing CD8-positive type 17 T cells accumulated in colorectal tumors that had become resistant to anti-PD-1 treatment. Type 17 T cells are associated with inflammatory immune responses and can produce cytokines that influence both neighboring immune cells and tissue cells. In this case, IL-26 behaved in an unusual way. Rather than acting solely through receptors at the cell surface, the cytokine was detected inside the nuclei of tumor cells. There, it interacted with signal transducer and activator of transcription 1, known as STAT1, a transcriptional regulator that can move into the nucleus after cytokine signaling and bind regulatory regions of DNA. The findings indicate that IL-26 helped assemble a transcriptional complex involving STAT1, nuclear factor kappa B, and bromodomain-containing protein 4, or BRD4.

BRD4 is an epigenetic reader: it recognizes acetylated histones, the proteins around which DNA is wrapped, and helps recruit machinery that activates gene transcription. By engaging BRD4, inflammatory signaling can produce changes in gene activity without changing the DNA sequence itself. The Juntendo team’s experiments showed that the IL-26–STAT1 interaction promoted BRD4-associated regulatory activity at regions controlling genes for several C-X-C motif chemokines, including CXCL1, CXCL2, CXCL3, and CXCL7. These molecules are powerful chemoattractants. Their expression increased by several thousand-fold in some experimental settings, indicating that the pathway could convert a relatively localized inflammatory signal into a large-scale remodeling of the tumor microenvironment.

The consequences were particularly significant for neutrophils. Chemokines such as CXCL1 and CXCL2 can recruit neutrophils through CXCR2, a receptor expressed on these cells. Although neutrophils are essential components of normal host defense, tumors can manipulate them into immunosuppressive states. Within the colorectal tumor models examined in the study, the influx of neutrophils was associated with weakened antitumor CD8-positive T-cell activity. These neutrophils helped create conditions in which cancer-directed T cells were less effective, even when PD-1 signaling was pharmacologically blocked. The result was a feedback loop in which inflammation promoted chemokine production, chemokines recruited suppressive neutrophils, and the altered immune environment allowed the tumor to evade immune destruction.

The researchers then tested whether disrupting different components of this pathway could restore treatment sensitivity. Blocking IL-26 reduced the inflammatory program in tumor cells. Inhibiting BRD4 interfered with the epigenetic machinery responsible for maintaining increased chemokine transcription. Targeting CXCR2 limited neutrophil recruitment, while direct depletion or inhibition of neutrophils reduced their suppressive influence within the tumor. In preclinical models, these interventions improved antitumor immune responses and enhanced the activity of anti-PD-1 therapy. The results point to the IL-26–STAT1–BRD4 axis as a possible therapeutic vulnerability, although the experiments do not yet establish that the approach is safe or effective in human patients.

The findings also broaden the understanding of how inflammatory cytokines can influence cancer biology. Cytokines are often described as soluble messengers that bind receptors and activate signaling cascades, but IL-26 appears capable of exerting a more direct influence on the tumor-cell nucleus. By coupling immune-derived signaling to epigenetic regulation, it may give cancer cells the ability to reshape the immune landscape around them. Dr. Itoh described IL-26 as a rare cytokine capable of inducing epigenetic changes in cancer cells and emphasized that the resulting increase in CXCL chemokines was strong enough to substantially alter the tumor microenvironment. This mechanism offers a molecular explanation for how chronic inflammation can become an active participant in immunotherapy resistance rather than merely a background feature of the disease.

The study raises the possibility of combining anti-PD-1 drugs with therapies directed against IL-26, BRD4, CXCR2, or neutrophil-mediated suppression. Such combinations could be especially relevant for patients whose tumors contain high levels of IL-26-producing type 17 T cells or show evidence of CXCL-driven neutrophil infiltration. Before clinical applications can be considered, researchers will need to determine how common this pathway is across colorectal cancer subtypes and other malignancies, whether IL-26 activity can be measured reliably in patients, and how broadly its blockade can be applied without disrupting protective immune functions. The study also includes potential conflicts of interest: several researchers are inventors and patent holders of a humanized anti-IL-26 antibody, while some authors hold relationships with a company connected to the technology. Even with these considerations, the work provides a detailed preclinical framework for understanding how inflammation, epigenetic remodeling, and immune escape can converge to undermine cancer immunotherapy.

By revealing that IL-26 can drive a STAT1- and BRD4-dependent transcriptional program in colorectal cancer cells, the researchers have identified a previously unrecognized connection between immune signaling and cancer-cell epigenetics. The pathway does not simply suppress T cells directly; it changes the tumor’s chemical environment, recruits neutrophils, and helps establish resistance to immune checkpoint blockade. If future studies confirm the mechanism in patients, blocking IL-26-driven reprogramming could become part of a new generation of combination strategies designed to make resistant tumors visible and vulnerable to the immune system again.

Subject of Research: Animals

Article Title: IL-26-driven epigenetic remodeling promotes immune evasion in colorectal cancer

Web References: https://doi.org/10.1038/s41467-026-75754-7

References: Takumi Itoh, Ryo Hatano, Yuta Hasegawa, Nao Hosokawa, Kazuyoshi Takeda, Ayako Yamamoto, Yoshiya Horimoto, Jinghui Yu, Hayato Nakamura, Harumi Saeki, Shogo Ehata, Shuji Matsuoka, Haruna Otsuka, Hiroshi Ohtsu, Michio Tomura, Nam H. Dang, Yutaro Kaneko, Kei Ohnuma, and Chikao Morimoto. “IL-26-driven epigenetic remodeling promotes immune evasion in colorectal cancer.” Nature Communications. DOI: 10.1038/s41467-026-75754-7

Image Credits: Dr. Takumi Itoh, Juntendo University, Japan

Keywords: IL-26, colorectal cancer, cancer immunology, immunotherapy resistance, anti-PD-1 therapy, epigenetic remodeling, STAT1, BRD4, CXCL chemokines, neutrophils, tumor microenvironment, cancer research

In OPTIM, patients first receive nivolumab, an immune checkpoint inhibitor that blocks PD-1 signaling and helps reactivate exhausted T cells. Participants who later show progression are not simply discontinued; instead, they enter a randomized phase that assigns one of two subsequent approaches. One arm uses nivolumab-ipilimumab, pairing PD-1 blockade with CTLA-4 inhibition to potentially broaden and intensify antitumor immune responses.

The alternative strategy tests docetaxel, a chemotherapy agent widely used in head and neck cancers. By comparing an immunotherapy intensification route against a conventional cytotoxic option after initial nivolumab failure, the trial aims to identify which sequence is more effective in real-world progression scenarios. This “therapeutic after progression” concept is particularly relevant because many patients initially respond to PD-1 inhibitors only to develop resistance.

Investigators emphasize that sequencing matters: tumors that escape PD-1 blockade may still remain susceptible to immune re-education through combination checkpoint inhibition, or alternatively may respond better to cytotoxic mechanisms that can reduce tumor burden and modify the tumor microenvironment. The study’s randomized design is intended to reduce bias and provide clearer evidence than retrospective treatment comparisons.

Although Phase II trials are not definitive for practice-changing guidance, OPTIM is expected to generate important signals about response rates, progression patterns, and clinical benefit under different post-nivolumab pathways. If the immunotherapy intensification strategy performs well, it could support broader use of combination regimens at progression rather than switching immediately to chemotherapy.

Overall, the trial reflects a growing shift in oncology toward rational sequencing—using biomarkers of clinical behavior, such as progression after first-line immunotherapy, to guide the next line. For patients with advanced head and neck cancer, where options can narrow after relapse, OPTIM offers a structured test of two plausible escape-response strategies.

Subject of Research: Recurrent/metastatic squamous cell carcinoma of the head and neck; sequential immunotherapy after progression

Article Title: OPTIM: a randomized phase II trial of nivolumab followed by nivolumab-ipilimumab or docetaxel at progression in recurrent/metastatic squamous cell carcinoma of the head and neck (OPTIM; AIO-KHT-0117).

Article References: Grünwald, V., Alt, J., Tometten, M. et al. OPTIM: a randomized phase II trial of nivolumab followed by nivolumab-ipilimumab or docetaxel at progression in recurrent/metastatic squamous cell carcinoma of the head and neck (OPTIM; AIO-KHT-0117). Br J Cancer (2026). https://doi.org/10.1038/s41416-026-03558-z

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03558-z

Keywords:

Melanoma represents a particularly aggressive skin cancer subtype with a notorious ability to evade immune surveillance. While immunotherapy has revolutionized treatment paradigms by harnessing the body’s immune defenses, many tumors evolve mechanisms to subvert immune attack, rendering therapy ineffective. The study focuses on elucidating the molecular underpinnings of immune evasion, with DHHC3 emerging as a critical player influencing melanoma’s immunological landscape.

DHHC3 functions as a palmitoyltransferase, an enzyme catalyzing the attachment of palmitoyl groups to target proteins, thus affecting their localization, stability, and function. Additionally, DHHC3 is known to moderate oxidative stress by maintaining cellular redox homeostasis. Prior studies hinted at correlations between elevated DHHC3 expression and poor clinical outcomes across several cancer types, prompting investigation into its specific role within melanoma microenvironments.

Utilizing CRISPR-Cas9 gene editing, the team ablated DHHC3 expression in the murine B16F10 melanoma cell line, creating a model to observe resultant cellular and immunological changes. Loss of DHHC3 induced pronounced oxidative stress within tumor cells, evidenced by an upregulation of TXNIP, a potent mediator of reactive oxygen species. This heightened oxidative stress triggered senescence-associated pathways, marked by increased expression of classical senescence markers, indicating that DHHC3 ablation compromises tumor cell homeostasis.

Crucially, when these DHHC3-deficient melanoma cells were implanted into immunocompetent mice, tumor growth was substantially diminished compared to controls. Interestingly, this growth suppression was absent in immunodeficient mice lacking functional immune systems, pointing toward an immune-dependent mechanism underlying the observed tumor inhibition. The results suggest that DHHC3 enables melanoma cells to escape immune recognition, and its loss reinvigorates host anti-tumor immunity.

Immune profiling of the tumor microenvironment revealed significant shifts in immune cell populations following DHHC3 knockout. Tumors exhibited marked infiltration by natural killer (NK) cells, M1-polarized macrophages associated with pro-inflammatory and anti-tumor functions, as well as CD4+ and CD8+ T lymphocytes, all instrumental in orchestrating effective immune responses against malignancies. Conversely, populations of immunosuppressive M2 macrophages and myeloid-derived suppressor cells (MDSCs), which typically promote tumor progression, were reduced.

Despite these profound changes in primary tumor growth dynamics, pulmonary metastases did not show significant differences between DHHC3-expressing and knockout conditions in either immunocompetent or immunodeficient mice. Additionally, melanoma cell proliferation rates measured under traditional culture conditions remained unchanged, underscoring that DHHC3’s impact is not due to intrinsic growth alterations but rather through modulating immune interactions in vivo.

The researchers propose a model whereby increased oxidative stress and cellular senescence triggered by DHHC3 deficiency elicit a senescence-associated secretory phenotype (SASP). This SASP acts as a molecular beacon, recruiting and activating anti-tumor immune effector cells into the tumor microenvironment, enhancing immune-mediated tumor clearance. Such a mechanism highlights the dual role of DHHC3 in both cellular homeostasis and immune regulation within melanoma.

These findings illuminate DHHC3 as a multifunctional regulator that melanoma cells exploit to evade immune surveillance, thereby facilitating tumor survival and expansion. Targeting DHHC3 enzymatic activity or its downstream signaling pathways may represent an innovative therapeutic avenue to bolster anti-melanoma immunity, particularly in tumors refractory to existing immunotherapies.

Beyond its immediate implications for melanoma treatment, the study also provides valuable insight into the intricate crosstalk between oxidative stress, cellular senescence, and immune modulation. It sets the stage for future investigations aimed at exploiting metabolic and immunological vulnerabilities in cancer.

In conclusion, the research narrates a compelling story positioning DHHC3 as a central node linking tumor-intrinsic oxidative regulation to extrinsic immune environment alterations. The strategic targeting of DHHC3 could enhance the efficacy of immunotherapeutic regimens and mitigate immune escape, offering renewed hope for melanoma patients facing poor prognoses.

This study stands as a testament to the power of combining advanced gene editing techniques with robust in vivo models to unravel cancer’s evasive tactics, paving the way for next-generation immunomodulatory therapies.

Subject of Research: Cells
Article Title: DHHC3 interferes with antitumor immunity in melanoma cells
News Publication Date: June 8, 2026
Web References: https://doi.org/10.18632/oncotarget.28880
Image Credits: Copyright: © 2026 Sharma et al. (Distributed under CC BY 4.0 license)
Keywords: cancer, oxidative stress, DHHC3, anti-cancer immunity, palmitoylation, melanoma

Immunotherapy represents a transformative strategy in oncology, aiming to empower the patient’s immune system to recognize and eradicate cancer cells. However, despite remarkable successes, a significant subset of patients exhibits resistance or suboptimal responses. The Karolinska team sought to decipher the cellular dynamics that contribute to these varied outcomes, centering their investigations on neutrophils within two distinct murine cancer models: melanoma and breast carcinoma. These granulocytes, although frontline defenders against pathogens, exhibit complex, often paradoxical, behavior in malignancies.

By employing genetically engineered mice completely lacking neutrophils, researchers created a fundamental contrast with normal counterparts possessing intact neutrophil populations. Remarkably, the absence of neutrophils was associated with amplified effectiveness of multiple immunotherapeutic modalities. Tumor volumes decreased more significantly, paralleled by an influx and heightened activation of cytotoxic T lymphocytes (CTLs) within the tumor niche. This phenomenon underscores a previously underappreciated suppressive influence neutrophils exert over the adaptive immune response prompted by therapy.

Delving deeper, the study elucidates a sophisticated feedback mechanism involving neutrophils and tumor signaling pathways. Following the initiation of immunotherapy, neutrophils themselves undergo a phenotypic modulation wherein they begin expressing programmed death-ligand 1 (PD-L1). PD-L1 is a critical immune checkpoint molecule that suppresses T cell-mediated tumor clearance by binding to PD-1 receptors on T cells, thereby attenuating their cytotoxic functions. This induction of PD-L1 expression on neutrophils is driven by interferon-gamma (IFN-γ), a type II interferon secreted by activated immune cells within the tumor milieu.

Crucially, when the research team selectively ablated PD-L1 or disrupted the IFN-γ receptor specifically on neutrophils, immunotherapeutic efficacy was restored to greater degrees. This compelling evidence demonstrates that the tumor microenvironment dynamically instructs neutrophils to adopt immune checkpoint properties that blunt T cell activity. Such findings challenge the prevailing conception of neutrophils as mere innate immune effectors and highlight their role as modulators of adaptive immune resistance in cancer.

The implications of this discovery are far-reaching. It establishes that the neutrophil response to cancer immunotherapy is not a static trait but is governed by extrinsic signals within the tumor’s immunological landscape. Consequently, therapeutic strategies that target neutrophil-mediated inhibition hold promise to synergize with existing immunotherapies, potentially overcoming resistance and refining treatment responses. This conceptual pivot points toward the development of combination therapies integrating immune checkpoint blockade with interventions designed to neutralize neutrophil-driven suppression.

Moreover, the translational relevance of the study is underscored by observations from human tumor samples. Analysis of specimens from lung cancer patients undergoing immunotherapy revealed similar neutrophil PD-L1 expression patterns, hinting that the interplay observed in murine models reflects conserved phenomena in human malignancies. This cross-species validation bolsters the clinical significance of targeting neutrophil-mediated pathways to augment immunotherapy outcomes.

These insights also invite a broader reconsideration of the tumor microenvironment’s composition and the intricate crosstalk among immune cell subsets. Neutrophils, once relegated to simple categorizations of pro-inflammatory or anti-inflammatory cells, are now appreciated as plastic entities capable of both promoting and suppressing tumor progression, contingent upon microenvironmental cues. The dynamic induction of inhibitory molecules such as PD-L1 represents a striking example of how tumors can hijack immune cells to construct barriers against eradication.

The study was the result of an international collaboration, bringing together expertise from institutions across Sweden, the United States, Germany, and China. Supported by funding from major agencies including the National Institutes of Health, the Swedish Cancer Society, and the Swedish Foundation for Strategic Research, the comprehensive nature of the research reflects a global commitment to advancing cancer immunology. Importantly, the investigators have declared no conflicts of interest, adding credibility to their groundbreaking conclusions.

In practical terms, these findings suggest that future cancer treatment regimens may need to incorporate strategies that either deplete neutrophils or inhibit their PD-L1 induction to unleash maximal T cell function. Such approaches could involve novel pharmacological inhibitors, antibody-based therapies against neutrophil-expressed PD-L1, or modulation of IFN-γ signaling pathways. The goal is to dismantle the immunosuppressive barricades within tumors that limit the curative potential of current immunotherapies.

Ultimately, this research deepens our understanding of the immune landscape in cancer and highlights the nuanced roles played by different leukocyte populations. It emphasizes the importance of a systems biology approach to cancer therapy, where combinatorial treatments targeting multiple cellular and molecular mechanisms stand a better chance of success. As immunotherapy continues to revolutionize cancer care, dissecting the multifaceted interactions within the tumor milieu remains paramount for overcoming resistance and achieving durable remissions.

The Karolinska Institutet study encapsulates a pivotal moment in cancer immunology—recognizing neutrophils not just as effectors but also as modulators of immune evasion. Such nuanced insights will undoubtedly steer the field towards more sophisticated, rationally designed therapies, paving the way for improved patient outcomes in the battle against cancer.

Subject of Research: Neutrophil regulation in cancer immunotherapy through type II interferon signaling.

Article Title: Neutrophil regulation of immunotherapy for cancer is controlled by type II interferon

News Publication Date: 15 June 2026

Web References: https://doi.org/10.1016/j.immuni.2026.05.014

References: Shengduo Pei, Yueyun Pan, Heng Liang, Li Lei, Qirong Lin, Jiarui Mi, Jeffrey V Ravetch, Oliver Soehnlein, Mikael C.I. Karlsson, Immunity, 15 June 2026.

Keywords: Cancer, Immunotherapy, Neutrophils, PD-L1, Interferon-gamma, Tumor microenvironment, T cells, Immune checkpoints, Immunosuppression, Leukocytes, Granulocytes, Tumor resistance

At the core of this discovery lies the behavior of mitochondria under stress. Upon depolarization—a condition indicating a loss of mitochondrial membrane potential—CD8⁺ T cells ramp up proteasome activity, the cellular machinery responsible for degrading proteins. Intriguingly, this process selectively targets mitochondrial hemoproteins. Their breakdown results in the liberation of regulatory heme, a molecule traditionally considered merely as a metabolic byproduct rather than a signaling entity. This reframing of regulatory heme heralds a paradigm shift in our understanding of intracellular communication pathways governing immune cell fate.

Rather than lingering inertly within the cytoplasm, the freed regulatory heme embarks on a journey to the nucleus of the T cell, where it executes a critical role. Here, heme binds to the transcription factor Bach2, inducing its destabilization. Bach2 normally acts as a repressor of Blimp1, a master regulator of terminal exhaustion in T cells. The degradation of Bach2 effectively lifts this repression, triggering the upregulation of Blimp1. This shift decisively locks T cells into an exhausted, dysfunctional state and erodes their stem-like properties critical for sustained immune responses.

Deciphering this cellular circuitry required delving deep into the molecular players orchestrating these changes. The researchers identified the E3 ubiquitin ligase CBLB as a pivotal driver in tagging mitochondrial proteins for proteasomal degradation. This selective ubiquitination marks hemoproteins for breakdown, fueling the excess heme pool. Meanwhile, PGRMC2 was characterized as the chaperone responsible for escorting regulatory heme into the nucleus, facilitating its interaction with Bach2. Together, these molecules form an elegant metabolic signaling switch bridging mitochondrial status to transcriptional fate decisions.

Professor Ho emphasizes the significance of this discovery: “We uncovered a metabolic signaling switch that converts mitochondrial stress into a permanent transcriptional decision. This pathway explains how energy failure becomes immune failure.” His team has further demonstrated that this molecular axis is not merely descriptive but clinically actionable. Through transient, low-dose administration of the proteasome inhibitor bortezomib during CAR-T cell manufacture, proteasome-driven heme signaling can be attenuated. This intervention downregulates exhaustion-associated gene programs, promoting durable epigenetic reprogramming toward a stem-like, memory phenotype that correlates with enhanced T cell persistence.

The clinical relevance of these findings is underscored by patient data from individuals with B-cell acute lymphoblastic leukemia (B-ALL). CAR-T cells exhibiting elevated proteasome activity were associated with poorer therapeutic outcomes, highlighting the prognostic and potentially therapeutic value of targeting this heme signaling pathway. As first author Y. Xu notes, “Our previous work identified mitochondrial damage as the cause of T cell failure, and this study reveals the molecular switch behind it and how to turn exhaustion off. Identifying regulatory heme as a signaling mediator was unexpected and provides a tangible avenue for intervention.”

Collectively, these discoveries redefine T cell exhaustion not simply as a consequence of chronic antigen exposure but as an active outcome of dysregulated metabolic signaling cascades. The integration of proteostasis, mitochondrial health, and nuclear transcription factor modulation represents a sophisticated cellular strategy regulating immune cell fate under stress conditions. Such insights into fundamental T cell biology are poised to reshape approaches to adoptive cell therapies, including CAR-T cells, where durability and functional persistence remain major clinical challenges.

This study bridges metabolic biology and immuno-oncology, presenting a seamless mechanism whereby proteasome-guided heme signaling irrevocably imprints exhaustion programs onto T cells. Therapeutic modulation of this axis opens new frontiers in optimizing CAR-T cell manufacturing protocols and designing combination therapies to circumvent immune failure. By targeting early molecular events linking energy deprivation to transcriptional reprogramming, future interventions could dramatically enhance the longevity and efficacy of engineered immune cells deployed against cancer.

The international collaborative effort spearheaded by Professor Ho and Y. Xu involved researchers from institutions spanning Switzerland, China, Taiwan, the United Kingdom, and the United States, underscoring the global commitment to unraveling immune dysfunction in cancer. Their work received robust support from prestigious funding agencies including the Swiss National Science Foundation and the Cancer Research Institute. Such multidisciplinary and multinational endeavors exemplify the power of converging expertise to solve complex biomedical puzzles.

In summary, the revelation of regulatory heme as a pivotal signaling molecule in T cell exhaustion heralds a new chapter in understanding how metabolic stress translates into irreversible immune cell fate decisions. This metabolic-transcriptional crosstalk mediated by proteasome activity, CBLB, and PGRMC2 not only elucidates fundamental mechanisms of immune dysfunction but also offers a promising therapeutic switch. Attenuating this pathway could revolutionize adoptive immunotherapies and pave the way toward more durable cancer treatments, finally turning the tide in the battle against T cell exhaustion.

Subject of Research:
T cell exhaustion and metabolic signaling pathways in cancer immunotherapy

Article Title:
Proteasome-guided haem signalling axis contributes to T cell exhaustion

News Publication Date:
18-Mar-2026

Web References:
http://dx.doi.org/10.1038/s41586-026-10250-y

Image Credits:
Ho Lab, 2025

Keywords:
Cancer, T lymphocytes, Mitochondria, Proteasomes, Transcription factors, Immunotherapy, Hemoproteins, Regulatory heme, CAR-T cells, Proteasome activity, Immune exhaustion, Metabolic signaling

Immune checkpoint blockade therapies targeting the PD-1/PD-L1 axis have revolutionized cancer treatment over the past decade by reinvigorating exhausted T cells to attack tumor cells. However, therapeutic outcomes have been limited by the frequent emergence of resistance, often attributed to extrinsic factors such as immunosuppressive tumor microenvironments or loss of antigen presentation machinery. The discovery that PD-L1 itself intrinsically undermines antigen presentation refines this landscape by implicating PD-L1 as a direct regulator of β2m stability and MHC-I expression on tumor and antigen-presenting cells.

β2m plays a pivotal role as a non-polymorphic component of MHC-I, necessary for the proper folding, assembly, and surface expression of the antigen-presenting complex that flags intracellular peptides to CD8+ T cells. By mediating ubiquitin-dependent degradation of β2m, PD-L1 effectively impairs MHC-I surface levels, blunting tumor antigen presentation, thereby diminishing tumor visibility to cytotoxic T lymphocytes. This novel mechanism enables tumor cells to evade immune surveillance more insidiously than previously understood, through intrinsic modulation of their antigen presentation apparatus rather than solely through external checkpoints.

Functional assays in the study demonstrated that interfering with PD-L1’s E3 ubiquitin ligase activity or disrupting its interaction with β2m reverses this degradation pathway. Restoration of β2m levels led to enhanced MHC-I surface expression and improved recognition by CD8+ T cells, substantially increasing tumor cell susceptibility to destruction. These findings carry profound therapeutic implications, particularly for cancers characterized by low baseline β2m expression, which exhibit marked resistance to existing PD-1/PD-L1 blockade therapies.

The discovery also elucidates why certain tumors are refractory to immune checkpoint blockade despite PD-L1 expression and presence of tumor-infiltrating lymphocytes. A tumor intrinsically orchestrating MHC-I downregulation via PD-L1’s ligase function effectively handicaps T cell mediated immune recognition from within. This newly identified “intrinsic resistance” mechanism expands the conceptual framework beyond the previously understood extrinsic suppressive factors such as regulatory T cells, myeloid-derived suppressor cells, or hostile cytokine milieus.

From a molecular perspective, the revelation that PD-L1 is endowed with E3 ubiquitin ligase activity is unexpected as PD-L1 has long been described as a type I transmembrane protein primarily acting as a ligand for PD-1 receptor, inhibiting T cell activation. The study’s biochemical analyses detailed how PD-L1 forms part of a ubiquitin ligase complex, targeting β2m for mono- and polyubiquitylation, an essential step marking proteins for proteasomal degradation. This challenges the canonical view and positions PD-L1 as both a checkpoint ligand and an intracellular enzyme directly modulating immune evasion mechanisms.

This research invites reassessment of current therapeutic strategies. For example, PD-L1 inhibitors designed primarily to block receptor-ligand interactions may be insufficient if PD-L1’s enzymatic activity persists. Therefore, developing next-generation inhibitors that abrogate PD-L1’s E3 ligase function or block its binding site for β2m could dramatically improve treatment efficacy. Such strategies could restore antigen presentation capacity and potentiate T cell-mediated immunity in resistant tumor types.

Moreover, the study suggests a potential biomarker for predicting patient response to PD-1/PD-L1 blockade: measuring β2m abundance or detecting PD-L1 ligase activity in tumors. Cancers with high PD-L1 ligase activity and concomitant β2m degradation may require combinatorial or alternative immunotherapeutic regimens. This opens new avenues for personalized medicine approaches targeting both extracellular and intracellular immune evasion pathways.

The interplay between PD-L1 and β2m described also raises intriguing questions about tumor evolution under immune pressure. Tumors may acquire or select for heightened PD-L1 ligase activity to survive in hostile immune environments. Understanding this selective force could inform strategies to forestall resistance or pre-emptively target tumors before extensive immune escape evolves.

In essence, this study refines the immune evasion narrative by attributing a multifaceted role to PD-L1, not simply as a ligand transmitting negative signals to T cells, but as an active participant reshaping antigen presentation landscapes. It reinforces the concept that tumor cells exploit both external immunosuppressive signals and intrinsic molecular machinery to avoid immune destruction.

The clinical relevance is underscored by the finding that targeting PD-L1’s E3 ligase function sensitizes tumor cells to PD-L1 blockade, overcoming a significant hurdle in immunotherapy. This provides a rationale for therapeutic innovation aimed at dual inhibition of PD-L1’s receptor engagement and its enzymatic degradation of β2m, enhancing anti-tumor immunity.

Future research could delineate whether this mechanism extends to other cancers beyond those studied and how it interacts with additional immune evasion tactics. It also prompts examination of whether β2m degradation by PD-L1 occurs in antigen-presenting cells beyond tumor cells, potentially influencing broader immune contexts.

Overall, Zhao and colleagues provide compelling evidence of a hitherto unrecognized function of PD-L1, broadening the molecular understanding of immune escape and resistance in cancer. This advancement stands to invigorate immunotherapy research and foster development of more effective, durable treatment strategies.

By redefining the boundaries of tumor immune evasion, this discovery heralds prospective breakthroughs in overcoming resistance mechanisms that have long stymied the promises of immune checkpoint blockade. Its impact will likely resonate across oncology, immunology, and therapeutic development in the years to come.

Subject of Research: Tumor immune evasion mechanisms involving PD-L1-mediated β2-microglobulin ubiquitylation and degradation

Article Title: Tumor PD-L1 induces β2m ubiquitylation and degradation for cancer cell immune evasion

Article References:
Zhao, Q., Li, C., Zhang, M. et al. Tumor PD-L1 induces β2m ubiquitylation and degradation for cancer cell immune evasion. Cell Res (2026). https://doi.org/10.1038/s41422-025-01205-5

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41422-025-01205-5

The study, recently published in the prestigious journal Nature, provides robust evidence that the interaction between cancer cells and tumor-associated nerves plays a significant role in shaping the tumor microenvironment. Specifically, the cancerous cells infiltrate and degrade the protective myelin sheath surrounding these nerves. Damage to the nerve fibers leads to the release of inflammatory mediators such as interleukin-6 (IL-6) and type 1 interferons, which initially may trigger tissue repair mechanisms but eventually contribute to creating an immunosuppressive milieu that blunts anti-tumor immune responses.

Anti-PD-1 immunotherapy, which has revolutionized treatment for several cancers by unleashing T-cell mediated immune attack on malignant cells, faces a significant clinical challenge: many patients do not respond or develop resistance over time. The findings of this study shine a light on a previously unappreciated resistance pathway—nerve injury-induced inflammation—that actively suppresses immune activity within the tumor. By altering nerve integrity, tumors can effectively modulate immune surveillance and escape eradication.

Kenneth Tsai, M.D., Ph.D., co-corresponding author and co-director of the Donald A. Adam Melanoma and Skin Cancer Center of Excellence at Moffitt Cancer Center, stated that their team’s findings emphasize the direct influence of nerve injury on immune cell behavior within tumors. “Our research illustrates that nerve injury is not simply collateral damage from tumor growth, but rather a functional driver that remodels the immune landscape, facilitating immune evasion. The exciting part of our work is demonstrating that this process is reversible, opening the door to potential interventions,” Dr. Tsai explained.

Utilizing patient-derived samples and preclinical models encompassing a variety of cancer types—including cutaneous squamous cell carcinoma, melanoma, gastric cancer, and pancreatic cancer—the research team dissected the cellular dynamics at play. They observed that nerve damage induced by cancer cells triggers a complex inflammatory response, which, although initially reparative, transitions into a chronic suppressive state that dampens immune cell infiltration and activation.

To intervene in this detrimental feedback loop, the researchers explored multiple therapeutic strategies designed to restore immune sensitivity. They discovered that resistance to anti-PD-1 therapy could be mitigated by either surgically removing pain-transmitting nerves, pharmacologically blocking neuronal injury signaling pathways, or employing combination therapies that target both the PD-1 axis and the IL-6-mediated inflammatory pathways. These approaches successfully reversed tumor-induced immune resistance in preclinical settings, underscoring their translational potential.

This research highlights a critical and previously underexplored role for the nervous system in cancer progression and therapeutic resistance. Traditionally, oncology has focused primarily on the direct interactions between cancer cells and immune cells, but this study underscores that nerve-cancer cross talk can profoundly shape immunological outcomes. Targeting nerve injury-related signals could, therefore, become an innovative strategy to enhance responses to current immunotherapies.

Moreover, the study lays groundwork for future investigations into the molecular mechanisms by which nerve damage alters immune signaling within the tumor microenvironment. Key inflammatory mediators like IL-6 and type 1 interferons may become biomarkers for identifying patients likely to exhibit resistance due to nerve involvement. This stratification could guide personalized treatment regimens incorporating nerve-targeted therapies.

Clinically, targeting nerve injury pathways has compelling implications, especially for cancers characterized by perineural invasion—a phenomenon where tumors grow along nerves, commonly linked to poor prognosis and reduced treatment efficacy. By neutralizing the immune-suppressive signaling that arises from nerve damage, oncologists may improve therapeutic outcomes and extend patient survival.

Dr. Tsai further emphasized, “Understanding the bidirectional crosstalk between nerves and cancer cells reveals new vulnerabilities we can exploit therapeutically. Our discovery encourages an integrative perspective that combines neural biology and immunology to combat tumor immune evasion.”

The study was rigorously funded by the National Institutes of Health, underscoring its significance and potential impact on cancer research and treatment paradigms. As nerve-targeted therapy development advances, combination treatments involving immune checkpoint inhibitors and nerve injury signaling blockers could enter clinical trials, offering hope to patients who currently face limited options due to immune resistance.

In conclusion, this pioneering work broadens the conceptual framework of tumor immunology by incorporating the nervous system as a key player in cancer progression and resistance mechanisms. It challenges existing paradigms and paves the way for innovative, multi-modal treatment strategies that could transform patient outcomes in the era of precision oncology.

Subject of Research: People

Article Title: Cancer-induced nerve injury promotes resistance to anti-PD-1 therapy

News Publication Date: 20-Aug-2025

Web References:
https://www.nature.com/articles/s41586-025-09370-8

References:
Tsai, K., et al. (2025). Cancer-induced nerve injury promotes resistance to anti-PD-1 therapy. Nature. DOI: 10.1038/s41586-025-09370-8

Keywords: Immunotherapy

The report, published in Nature on 22 January 2025, is already creating a stir among immunologists and cancer specialists. The idea sounds fantastical at first blush: how could something as large and complex as a mitochondrion be uprooted from a tumor cell and end up inside a T cell, the specialized immune cell type that forms a vital line of defense against tumors? In earlier dogma, mitochondria were thought to remain strictly in their cell of origin, passed only from mother to child. Yet in the past decade, careful in vitro research has demonstrated that cancer cells can sometimes hijack or exchange mitochondria with other cell types, albeit under conditions many considered artificial or extreme. Now, with human data in hand, this new paper ups the ante: real tumors from cancer patients appear to deposit defective mitochondria into tumor-infiltrating lymphocytes (TILs), a process that can leave the T cells less capable of mounting an effective attack on malignant cells.

The implications are numerous, not least for a rising wave of immunotherapies designed to harness T cells against cancer. Should it become clearer that T cells are being undermined by receiving “diseased” mitochondria, then TIL treatments or chimeric antigen receptor T (CAR T) cell therapies might need an extra step that checks the metabolic health of these immune cells. Equally, drug developers might try to engineer small molecules or antibodies that block the mitochondria-transferring mechanism. At the same time, scientists who study basic cell biology are busy grappling with fundamental questions of how these organelles physically pass from one cell to another. Does the tumor form tiny nanotubes that shuttle mitochondria outward? Do T cells phagocytose small blebs that contain entire mitochondria? The exact route remains to be pinned down, though preliminary evidence suggests multiple pathways may be possible depending on microenvironmental cues.

Curiously, cancer’s ability to manipulate the metabolic infrastructure of T cells aligns well with known observations about T cell exhaustion. T cell exhaustion is a well-documented phenomenon in which T cells, after chronic exposure to antigens—for instance, in prolonged infections or in tumors that keep reappearing—lose their capacity to secrete effective cytotoxic factors, to proliferate, or to ramp up normal immune functions. Though many triggers for T cell exhaustion have been proposed, the new findings hint that one mechanism might be the infiltration of broken mitochondria that degrade T cell function from the inside. Mitochondria are best known as the energy powerhouses of the cell; but they’re also integral to vital processes such as apoptosis (programmed cell death) and signaling pathways that coordinate cell division and immune activation. If the mitochondria are defective—say, carrying significant DNA mutations or dysfunctional electron transport chain proteins—they could rob the T cell of crucial metabolic flexibility. They might even produce high levels of reactive oxygen species (ROS) that hamper cell viability. In essence, the T cell is stuck with the oncogenic equivalent of a Trojan horse, left to handle a substandard organelle that strains its entire metabolic operation.

No less intriguing is how the researchers behind this study reached their conclusions. To start, they examined small numbers of participants with cancer, carefully sequencing the mitochondrial DNA (mtDNA) from each person’s tumor cells. Then they sequenced mtDNA from the TILs that had infiltrated those same tumors. In three individuals, they found identical or overlapping mtDNA mutations in the TILs and the tumor cells—a telltale sign that the TILs had ended up hosting mitochondria derived from the cancer. While a cohort of three is small, it’s enough to raise a red flag, especially given that non-tumor tissues from the same individuals did not display these suspicious mutations. That is one line of evidence.

A second line emerged from experiments in which the scientists engineered cancer cells to express fluorescently tagged mitochondria. When they mixed these labeled cancer cells with TILs, the T cells soon began glowing under the microscope, indicating they had taken in the fluorescent mitochondria. After a few days, some T cells contained so many of the cancer’s mitochondria that their original, “native” mitochondria had all but disappeared in comparison. The T cells with the most tumor-derived mitochondria turned out to be the least functional in terms of cellular division, ability to produce immune effector molecules, or capacity to kill tumor cells. The phenomenon was so pronounced that these TILs seemed close to apoptosis, the end-of-line cell death program.

The immediate question that leaps out is: how widespread is this transfer in the real human body, beyond the conditions in which T cells and cancer cells are grown side by side in vitro? That’s the puzzle. The in vivo evidence from actual tumors is tantalizing but still limited. The researchers found matching mtDNA in a few people, but it will take larger cohorts to show how often and in which types of cancers this phenomenon emerges. Some tumors may rely heavily on this mechanism; others may rarely if ever engage in it. Another question is: do all TILs accept these mitochondria, or only some subtypes, such as those that are already partially dysfunctional? The complexity is immense, and no one expects quick answers.

Some immunologists, upon hearing of these data, have compared the concept to “metabolic sabotage.” Typically, to sustain their hyperactive growth, tumor cells keep a tight leash on how they use or manipulate their own mitochondria. Mitochondria can also be harnessed to generate building blocks for biomass or to manage oxidative stress. If those mitochondria harbor unexpected or harmful mutations, one might guess the tumor cell would rid itself of them. Yet how exactly the tumor cell decides to expel or degrade its defective organelles is unclear. The simplest route would be to break them down in situ, possibly with autophagy. But perhaps there’s an advantage to shipping them out to TILs. If indeed the tumor can quietly hamper the T cells by giving them broken mitochondria, that’s a neat double win: the cancer spares itself the metabolic burden of dealing with worthless or toxic organelles, and at the same time demoralizes its immune adversaries. It’s reminiscent of a cunning battlefield tactic: “We rid ourselves of these failing resources, and in doing so, we sabotage the enemy’s camp.”

Skeptics nonetheless caution that many extraordinary claims in cell biology have crumbled when confronted by deeper investigation. This concept of cross-cellular mitochondrial transfer has been building for about a decade, but for a while, it was considered a curiosity limited to a few lab-based scenarios. Now, more refined imaging tools, single-cell sequencing, and advanced molecular barcoding are revealing that these organelle “swaps” may be more common than ever suspected. A fundamental shift is underway in how we think about the boundaries between cells. For example, it was once believed that each cell in the body—except for sperm and egg—held a fixed set of organelles that it never parted with. But from nanotube-mediated exchanges to microvesicle release, cells can often share or trade mitochondria and other cargo. The new cancer data cast mitochondria as a pawn in a microenvironment teeming with malicious cross-talk.

The ramifications extend to TIL-based immunotherapies, a rising star among next-generation cancer treatments. TIL therapy typically involves harvesting T cells that have infiltrated a tumor, expanding them into large numbers ex vivo, and then reinfusing them back into the patient in hopes they will track down and destroy malignant cells. Early clinical trials with TIL therapy have produced remarkable responses in certain cancers, such as advanced melanoma, leading regulatory bodies like the FDA to approve the first TIL-based product last year. But many participants do not experience a lasting remission, presumably because T cells eventually become exhausted or suppressed. Mitochondrial sabotage might be an element in that exhaustion. If so, a possible solution might be to “rescue” TILs in the lab, screening them for defective organelles or recharging them with healthy mitochondria before sending them back into the bloodstream. Indeed, one biotech firm (IMEL Biotherapeutics) is investigating ways to “power up” TILs by equipping them with robust mitochondria, possibly gleaned from alternative sources or from an engineered line. The concept is reminiscent of giving T cells a metabolic facelift, so they remain more lethal to tumors. But it’s early days yet, with no guarantee of success.

Another possible angle lies in blocking the path of those mitochondria from tumor to T cell altogether. For instance, if the cancer is using nanotubes or exosomes to pass defective mitochondria along, an inhibitor that intercepts that process might shield T cells from sabotage. We’d still need to ensure that this blockade does not inadvertently disrupt beneficial mitochondrial exchanges that might exist in healthy tissues. As with all targeted therapies, specificity will be key.

Outside the sphere of oncology, some researchers are now pondering whether other diseases might exploit similar organelle shuttling. Could certain viral infections hamper immune function by transferring diseased mitochondria as well? Could autoimmune disorders be influenced by reciprocal organelle traffic between healthy and inflamed tissues? The new findings push us to revisit many open questions. Because mitochondria have historically been overshadowed by the nucleus in many genetics discussions, we rarely examine the full range of mtDNA in a large array of cell types. That may soon change. Another point the authors highlight is that analyzing the fine structure of mitochondrial DNA in both tumor cells and T cells is relatively easy with current sequencing technologies. If more labs replicate the result that T cells harbor the tumor’s mutated mtDNA, the link would become nearly indisputable.

Still, the present evidence is derived from a fairly small number of participants. Critics want to see broader investigations across multiple cancer types—lung, breast, pancreatic, and others—and at different disease stages. It could be that in some very advanced cancers, the sabotage is rampant, but in early-stage cancers, maybe it’s less so. Or the extent of sabotage might correlate with the degree of T cell exhaustion clinically observed. The magnitude of these questions demands bigger cohorts, ideally with single-cell resolution so we can watch the infiltration in near real-time. If feasible, intravital imaging or advanced 3D tumor slice culture might directly catch the tumor cells in the act, transferring lumps of mitochondria through microscopic protrusions.

Meanwhile, the broad interest in mitochondrial biology is surging. After decades of focusing primarily on nuclear genes, the field is belatedly recognizing how crucial mitochondria can be in shaping cell fate, intercellular signaling, and immunity. That extends from cancer research to metabolic diseases, from neurodegenerative disorders to aging. Mitochondria, after all, are the eukaryotic cell’s original endosymbiont, thought to have evolved from free-living bacteria that merged with an ancestral host cell. Perhaps it should not be surprising that cells still retain some capacity to transfer mitochondria, at least under stress. But it is surprising to see that in humans, tumors might co-opt that capacity for malignant advantage.

For immuno-oncologists, the next logical step is to test TILs from a more substantial number of patients. If, for instance, a fraction of TILs are heavily loaded with tumor-derived mitochondria, one might want to separate out those TILs from the population and see if the rest remain more potent. Another question is whether TILs with healthy mitochondria can rescue or “fix” the defective mitochondria in neighbors. That might be overly optimistic, but it’s worth exploring. If an in vitro system or a mouse model can demonstrate that blocking or reversing mitochondrial exchange profoundly affects tumor clearance, that would be a strong impetus to develop an anti-transfer drug.

Down the line, the new biology of mitochondrial transfer might also demand a thorough rethinking of the many ways we manipulate T cells. For instance, in CAR T therapy, T cells are genetically engineered to recognize specific tumor antigens, grown in large numbers, and delivered back to the patient. If the tumor can still sabotage these engineered T cells by flooding them with broken mitochondria, then no matter how well the receptor is designed, the T cells could become metabolically compromised. That might help explain certain CAR T failures or relapses. Conversely, if scientists incorporate some safeguard—like a gene that confers T cells with the ability to degrade or reject foreign mitochondria—this sabotage might be circumvented entirely.

It is also important to note that some immunologists suspect that tumor-derived mitochondria might not be purely detrimental. Perhaps in some contexts, the T cells can adapt or break down the defective organelles and glean something beneficial. The body is replete with complexities, and not every cellular interchange is uniformly harmful. For now, the data from the new study clearly point to negative consequences, at least for TIL function. But additional research might discover nuance—maybe what is harmful in advanced disease states is neutral or even helpful in earlier contexts. The interplay of metabolic signals is rarely black and white.

Scientists, including those not involved in the project, emphasize caution as they process the excitement. While the result is widely described as “crazy” or “science fiction” on first hearing, the reality is that biology continually surprises us. Ten or fifteen years ago, the concept that entire organelles could hop between cells was borderline heretical. Today it feels less like heresy and more like a new frontier. This underscores how quickly entire paradigms can shift once more powerful observational and sequencing tools become available.

For the biomedical community, the next challenge is harnessing these insights in a clinically relevant fashion. One of the authors, for example, wants to investigate whether new TIL-based therapies fail when tumor mitochondria infiltration is especially high. Another sees a chance to develop selective “mitophagy enhancers,” small molecules that help T cells degrade foreign mitochondria faster. Or perhaps scientists can refine the process of TIL expansion ex vivo to confirm that these cells are free of suspicious mitochondria, resulting in a more potent therapy for direct infusion back into the patient. Any or all of these solutions might eventually appear in the pipeline, altering how we approach immune-based treatments.

Moreover, the principle could extend beyond oncology. If T cells are susceptible to organelle infiltration, other key immune cells, such as macrophages, B cells, or dendritic cells, might be equally vulnerable under certain conditions. And it may not just be cancer cells that do the infiltrating—infectious pathogens, or even dying or senescent cells, might transfer mitochondria as part of disease pathogenesis. A broader reexamination of defective mitochondrial trafficking in chronic illnesses such as autoimmunity or persistent infections might yield breakthroughs. If so, the study’s impact will echo far beyond tumor immunology.

For now, the immediate takeaway is that the relationship between cancer cells and T cells is even more cunning than we supposed. Not only can tumors shape their microenvironment with immunosuppressive cytokines or manipulate checkpoint pathways (like PD-1 or CTLA-4), but they can also physically pass broken-down mitochondria to hamper T cell metabolism. A war is fought not just with ephemeral signals or simple resource deprivation, but with strategic distribution of “toxic cargo.” If further validated, we may soon be talking about the “mitochondrial dimension” of immune evasion, ranking it alongside the best-known tricks that tumors use to survive.

That prospect stirs many new questions. Are certain tumor types—like lung adenocarcinoma or triple-negative breast cancer—more adept at this sabotage? Do metastatic cells or advanced-stage tumors rely on it heavily? Does preventing or reversing this infiltration have synergy with existing immunotherapies, such as checkpoint inhibitors? And does the presence of defective mitochondria inside T cells correlate with a poor prognosis, thereby serving as a biomarker for how well a patient might respond to immunotherapy? Each question invites new experiments that can rapidly be performed using carefully prepared patient samples and standardized detection methods.

The biggest takeaway for many is the exciting possibility that we have glimpsed a hidden layer of metabolic cross-talk that helps malignant cells endure. In the grand scheme of cancer immunobiology, this might prove to be one of those unexpected discoveries that reshapes an entire subfield. If so, the present study could mark the start of a new line of treatment approaches, offering a fresh vantage point on the never-ending standoff between cancer and the immune system. And if we can find ways to prevent or mitigate the TIL sabotage, the ultimate beneficiary might be every patient who turns to immunotherapy in their battle against cancer.

Subject of Research: The phenomenon of mitochondria transfer from cancer cells to immune cells
Article Title : Cancer Cells ‘Poison’ the Immune System with Tainted Mitochondria
News Publication Date : 22 January 2025
Article Doi References : https://doi.org/10.1038/d41586-025-00176-2
Image Credits : Scienmag
Keywords : Cancer Immunology, TIL Exhaustion, Mitochondrial Transfer, Tumor Evasion, T Cell Biology