The modern immunotherapy era began with high-dose interleukin-2, which demonstrated that immune activation could produce long-lasting tumor regression in a small proportion of patients with metastatic melanoma and renal cell carcinoma. The arrival of antibodies against CTLA-4, followed by inhibitors of the PD-1 and PD-L1 pathways, transformed that early proof of concept into a central pillar of cancer treatment. These drugs work by interrupting inhibitory signals that restrain T cells. CTLA-4 blockade mainly enhances T-cell priming in lymphoid tissues, while PD-1 or PD-L1 inhibition can restore the function of exhausted T cells within the tumor microenvironment. The results have included unprecedented survival improvements and long-term remission for some people with melanoma, non-small cell lung cancer, kidney cancer, and other malignancies. Yet the benefits remain uneven, and many tumors either never respond or eventually evolve around immune attack.

One of the most important newer targets is LAG-3, an inhibitory receptor found on activated T cells, regulatory T cells, B cells, and natural killer cells. LAG-3 can bind major histocompatibility complex class II molecules and suppress T-cell receptor signaling, proliferation, and production of immune-stimulating cytokines such as interleukin-2 and interferon-gamma. Its expression is particularly prominent in exhausted T cells, suggesting that it may help maintain a dysfunctional immune state inside tumors. The first approved LAG-3-directed therapy, relatlimab, is used with the PD-1 inhibitor nivolumab in advanced or metastatic melanoma. In the RELATIVITY-047 trial, the combination extended median progression-free survival to 10.1 months, compared with 4.6 months for nivolumab alone, and increased the objective response rate from 32.6 percent to 43.1 percent. Severe treatment-related adverse events occurred in 18.9 percent of patients receiving the combination, versus 9.7 percent with nivolumab alone—higher, but generally less frequent than with CTLA-4 and PD-1 combinations.

The LAG-3 story also illustrates why the next generation of immunotherapy will not be a simple succession of universal replacements for older drugs. Relatlimab has shown limited activity in patients whose disease has already progressed on checkpoint inhibitors, with an objective response rate of about 12 percent in one reported setting. Established PD-1 resistance often reflects multiple biological failures, including defective antigen presentation, exclusion of T cells from tumors, altered interferon signaling, and the emergence of immune-suppressive cell populations. Blocking one additional checkpoint may therefore be insufficient once resistance is entrenched. Still, the nivolumab-relatlimab combination has generated interest in earlier disease. Studies in melanoma have reported encouraging pathological responses before surgery, including a 57 percent pathological complete response rate in one neoadjuvant cohort and an 80 percent four-year event-free rate. Other LAG-3 strategies include fianlimab, the immune-activating fusion protein eftilagimod alpha, and bispecific antibodies designed to target both PD-1 and LAG-3 in a single molecule.

Perhaps the most powerful shift is the expansion of immunotherapy beyond the organ where a cancer began. Tissue-agnostic treatment relies on biological features shared across different tumor types, particularly defective DNA mismatch repair and high microsatellite instability. Mismatch repair proteins normally correct small copying errors made during DNA replication. When this system fails, tumors accumulate insertions, deletions, and other mutations, producing abnormal proteins known as neoantigens. These neoantigens can make cancer cells more visible to T cells, increasing the likelihood that PD-1 blockade will work. Deficient mismatch repair can result from inherited mutations associated with Lynch syndrome or from acquired epigenetic silencing, such as methylation of the MLH1 promoter. Clinicians can identify the phenotype using immunohistochemistry, polymerase chain reaction, or next-generation sequencing, allowing treatment decisions to be based on tumor biology rather than anatomical origin.

Tumor mutational burden, which measures the number of somatic mutations per megabase of tumor DNA, offers a related but less reliable signal. The underlying theory is straightforward: more mutations should create more potential neoantigens and therefore more targets for immune recognition. Clinical studies have indeed associated higher mutational burden with improved responses in diseases such as lung cancer and melanoma. However, not every mutation produces an antigen, and not every antigen is displayed effectively by a tumor cell. Measurements also vary between sequencing platforms, differ between tissue and blood samples, and can be distorted by tumor heterogeneity. As a result, mutational burden has not proved consistently dependable as a standalone predictor. A particularly striking subgroup is formed by tumors carrying pathogenic POLE proofreading mutations. These cancers can be ultramutated, densely infiltrated by lymphocytes, and exceptionally responsive to immunotherapy, even when their microscopic appearance suggests aggressive disease.

The clinical consequences of these biomarkers are becoming visible in major trials. In the KEYNOTE-158 study, pembrolizumab produced a response rate of approximately 29 percent in tumors classified as having high mutational burden, compared with 6 percent in tumors without that designation. Responses in mismatch repair-deficient or microsatellite-instability-high cancers were often remarkably durable. In advanced colorectal cancer, the phase 3 KEYNOTE-177 trial showed that first-line pembrolizumab produced a median overall survival of 77.5 months, compared with 36.7 months for chemotherapy, with five-year survival rates of 54.8 percent and 44.2 percent, respectively. The CheckMate-8HW trial further indicated that combining nivolumab with ipilimumab could outperform chemotherapy and nivolumab alone in selected patients, producing a two-year progression-free survival of 72 percent versus 14 percent with chemotherapy. In locally advanced mismatch repair-deficient rectal cancer, neoadjuvant dostarlimab has produced an especially dramatic signal: all 41 patients reported in one study achieved a clinical complete response and entered a watch-and-wait program without immediate surgery or chemoradiotherapy.

That result points toward one of the most provocative possibilities in oncology: replacing automatically scheduled surgery with response-adapted care. The concept is not yet established broadly, and longer follow-up plus prospective randomized evidence remain essential. Nevertheless, highly immunogenic tumors may eventually be managed by treating first, measuring the depth of response, and reserving surgery for residual or recurrent disease. Similar discussions are emerging in melanoma, head and neck cancer, and lung cancer. The approach would represent a profound change in the traditional sequence of cancer care, potentially preserving organs and reducing the complications of major operations. It also raises demanding technical questions. A clinical complete response does not always mean every malignant cell has disappeared, and microscopic residual disease may be difficult to detect with imaging or endoscopy. Future trials will need sensitive molecular monitoring, carefully defined retreatment strategies, and long-term surveillance to determine which patients can safely avoid surgery.

Checkpoint inhibitors are also being combined with established treatments to reshape the tumor environment before immune cells arrive. Chemotherapy can kill cancer cells and release tumor antigens, effectively providing raw material for immune priming. Antiangiogenic drugs can alter abnormal tumor blood vessels, reduce immune suppression, and improve T-cell access. In unresectable liver cancer, atezolizumab plus bevacizumab and the durvalumab-tremelimumab regimen have improved outcomes compared with the former standard, sorafenib. Median overall survival has reached roughly 16.4 to 19.2 months with atezolizumab and bevacizumab, compared with 13.4 to 13.8 months with sorafenib. The choice between regimens can depend on bleeding risk and the safety of vascular endothelial growth factor inhibition. In extensive-stage small-cell lung cancer, adding atezolizumab or durvalumab to platinum-etoposide chemotherapy has delivered the first major advance in decades, extending survival beyond the short-lived responses traditionally produced by chemotherapy alone.

The next wave reaches beyond soluble antibodies and conventional drug combinations. Bispecific antibodies and T-cell engagers can bind a tumor-associated molecule with one arm and a T-cell receptor component with the other, physically bringing immune cells into contact with malignant cells. Antibody-drug conjugates attach potent cytotoxic payloads to tumor-targeting antibodies, concentrating chemotherapy-like activity near cancer cells while potentially limiting exposure elsewhere. Adoptive cell therapies are being adapted for solid tumors through tumor-infiltrating lymphocytes, chimeric antigen receptors, and engineered T-cell receptors. TIL therapy uses a polyclonal population of tumor-reactive lymphocytes expanded from a patient’s own tumor, while CAR and TCR technologies genetically reprogram T cells to recognize selected targets. Engineered cytokines seek to preserve the immune-stimulating effects of interleukin therapies without reproducing their severe systemic toxicity. Personalized vaccines, particularly those directed against patient-specific neoantigens, aim to initiate or strengthen an immune response tailored to the mutations carried by an individual tumor.

Together, these advances reveal an emerging strategy rather than a single miracle treatment. The future of solid-tumor immunotherapy will depend on matching the right immune mechanism to the right biological context, deciding when combinations are more valuable than sequential treatment, and identifying resistance before tumors become clinically obvious. Immune-related toxicities—including pneumonitis, myocarditis, neurological complications, and permanent endocrine damage—remain a major concern as treatment moves into earlier-stage disease, where many patients may already be cured by surgery or other therapies. People with active brain metastases, poor performance status, or a need for corticosteroids have also been underrepresented in pivotal trials. The field is therefore converging on precision immuno-oncology: biomarker testing, response-adapted treatment, engineered molecules, cellular products, and increasingly individualized vaccines. If researchers can make immune attacks more selective and resistance more predictable, therapies once effective only for a minority could become durable, organ-preserving treatments across a much broader range of solid cancers.

The approach, described in a study published in Science Advances, is called SHIFTERS. Rather than searching for a naturally occurring antigen that appears exclusively on cancer cells, the system is designed to make tumor cells display one. Its target is CD19, a surface protein already recognized by many clinically developed CAR-T cells. CD19 is normally associated with B cells and is not broadly displayed by solid tumors. SHIFTERS uses a genetic program, combined with the low-oxygen environment characteristic of many tumors and externally applied focused ultrasound, to prompt selected cancer cells to temporarily present CD19 on their surfaces.

The system is built around a two-signal logic gate. The first signal is hypoxia, or low oxygen concentration, a hallmark of rapidly growing solid tumors. As malignant tissue expands, its blood vessels often fail to deliver enough oxygen, creating oxygen-deprived regions within the tumor mass. SHIFTERS is engineered to respond to molecular conditions associated with this hypoxic environment. The second signal is supplied by a physician through focused ultrasound. Because ultrasound can be directed toward tissue beneath the skin without an incision, it provides a spatial control mechanism: the genetic circuit is intended to become active only where tumor biology and the physician’s acoustic instruction coincide.

When both conditions are present, the engineered program activates CD19 production at the tumor-cell surface. This converts previously invisible cancer cells into temporary beacons for CAR-T cells. The T cells do not need to recognize the original biology of the tumor, which may vary widely among patients and cancer types. Instead, they use their existing CD19-specific receptor to identify the primed cells, form an immunological synapse and release cytotoxic molecules such as perforin and granzymes. These molecules damage the target cell and initiate its death. According to the USC team, the induced marker can remain detectable for approximately one week, creating a treatment window during which the location and timing of immune-cell activation can be controlled.

That design addresses a fundamental difficulty in solid-tumor immunotherapy. Blood cancers often carry relatively uniform surface markers that can be targeted throughout the malignant cell population. Solid tumors, by contrast, develop from normal tissues and frequently share many molecular features with healthy cells. Even when a candidate antigen is abundant in a tumor, it may also appear in essential organs, raising the risk of dangerous off-target damage. Tumors are also heterogeneous: different regions, and sometimes different cells within the same tumor, may carry different mutations and surface proteins. A temporary, externally controlled marker could offer a way to separate target recognition from the tumor’s naturally inconsistent antigen landscape.

The researchers evaluated SHIFTERS through a series of preclinical experiments. They first studied the system in cultured cancer cells, where they could measure genetic activation, CD19 display and CAR-T-mediated killing under controlled oxygen and ultrasound conditions. They then moved to three-dimensional tumor models, which reproduce some of the physical barriers found in actual tumors, including dense cellular organization and limited diffusion. Finally, they tested the strategy in animal models carrying human brain and liver tumors. Across these stages, the team reported that ultrasound treatment increased CD19 expression and enabled CAR-T cells to attack tumor tissue more effectively than they did without the priming step.

In animal experiments, tumors exposed to the ultrasound-guided system shrank substantially, while tumors that did not receive the same activation continued to grow. The findings do not yet establish that SHIFTERS will work in patients, but they suggest that the approach can translate a physical treatment signal into a molecular recognition signal. Focused ultrasound is already used in medicine for several purposes, including imaging and selected therapeutic applications, although the acoustic parameters and safety requirements for this system would need to be carefully defined for each tumor type and anatomical location. Treating a brain tumor, for example, introduces additional challenges because the skull can distort and weaken ultrasound waves, while liver and pancreatic tumors may move with respiration.

One of the study’s most notable observations was that not every cancer cell needed to display CD19 for the treatment to produce a broader antitumor response. The team reported that activating the marker on roughly 10% to 25% of tumor cells was sufficient to drive substantial killing in laboratory models. These CD19-positive cells appeared to act as “training centers” or initiating targets for the immune response. After recognizing and destroying them, CAR-T cells and other immune mechanisms may contribute to wider damage across neighboring cancer cells, including cells that never displayed the engineered marker. This effect could be especially important in heterogeneous tumors, where reaching every malignant cell with a genetic therapy may be unrealistic.

The researchers describe this phenomenon as a form of bystander or collateral immune killing, although its exact biological basis will require further investigation. Direct CAR-T recognition of CD19-positive cells may release inflammatory signals, alter the tumor microenvironment and expose additional tumor antigens to the immune system. Dying cancer cells can also release intracellular proteins that are processed and presented to other immune cells, potentially broadening the response beyond the synthetic CD19 target. Whether this amplification remains effective in the immunosuppressive environment of human solid tumors is unknown. Many such tumors contain regulatory immune cells, abnormal blood vessels, fibrotic tissue and metabolic conditions that can restrict T-cell entry and function.

Delivery is currently the largest practical obstacle. SHIFTERS requires tumor cells to receive genetic instructions encoding the hypoxia- and ultrasound-responsive program, and those instructions must reach enough of the tumor without spreading dangerously to healthy tissue. The USC team is comparing lipid nanoparticles with modified viral vectors. Lipid nanoparticles can carry nucleic acids without using a replicating virus and have become important in several biomedical applications, but their distribution and persistence in solid tumors can be uneven. Viral vectors may deliver genes more efficiently to certain cells, yet they introduce additional questions involving immune reactions, dose control, manufacturing and the possibility of unintended expression outside the treatment zone.

The study was conducted in animals and has not yet been tested in people. Before clinical trials could begin, investigators would need to establish reliable delivery, determine how long CD19 expression lasts, define safe ultrasound intensities and evaluate the risk of activating CAR-T cells in healthy tissue. They would also need to study whether repeated treatment is possible, how the therapy behaves in tumors with different oxygen patterns and whether engineered cells can penetrate the tumor at clinically meaningful levels. The work was funded in part by the National Institutes of Health. The authors disclosed that Yi Wang is a scientific co-founder and consultant of Cell E&G Inc. and Acoustic Cell Therapy Inc., while the other authors reported no competing interests.

Despite these limitations, SHIFTERS represents a shift in the way researchers are approaching the antigen problem. Instead of waiting for solid tumors to reveal a perfect natural marker, the strategy seeks to install a temporary one under the direction of tumor physiology and focused ultrasound. Peter Yingxiao Wang, who led the work at USC, said the broader goal is to “rewire” both the tumor and the T cell so they can recognize and destroy one another more effectively. The technology remains years from clinical use and will require larger animal studies, improved delivery systems and rigorous safety testing. But if those hurdles can be overcome, an ultrasound-controlled, temporary antigen could give CAR-T therapy a new route into cancers that have so far remained largely beyond its reach.

Subject of Research: Animals

Article Title: Ultrasound priming gated by solid tumor hallmarks to guide CAR-T therapy

News Publication Date: 10-Jun-2026

Web References: https://www.science.org/doi/10.1126/sciadv.aed0666; https://viterbischool.usc.edu/; https://www.cancer.gov/about-cancer/treatment/research/car-t-cells

References: Science Advances, DOI: 10.1126/sciadv.aed0666

Keywords

CAR-T cell therapy, solid tumors, cancer immunotherapy, focused ultrasound, SHIFTERS, CD19, hypoxia, genetic engineering, glioblastoma, liver cancer, tumor targeting, immune-cell therapy

NK cells are an integral component of the innate immune system, known for their ability to recognize and destroy malignant cells. Their unique mode of action allows them to target tumor cells without the necessity of prior sensitization. This characteristic makes NK cells an invaluable tool in oncology, particularly for patients with solid tumors that often evade traditional immune responses. The study highlights the multifaceted approach researchers are taking to exploit NK cells in clinical settings, emphasizing their adaptability and effectiveness against various tumor types.

The analysis reveals a significant uptick in clinical trials involving NK cell therapies from 2005 onwards. This surge aligns with a broader trend in immunotherapy where researchers have begun to understand and harness the complexities of the immune response. The study catalogs numerous ongoing trials aimed at different solid tumor types, ranging from breast cancer and colorectal cancer to more aggressive variants such as pancreatic and lung cancers. By mapping these trials, the authors underscore the growing recognition of NK cell therapies as a viable option for patients who have exhausted conventional treatment options.

One of the critical points raised in the article is the diversity of approaches taken in NK cell therapies. Some trials focus on enhancing the cytotoxic capabilities of NK cells through genetic modifications, while others investigate the synergistic effects of combining NK cell infusions with other treatment modalities, including checkpoint inhibitors and monoclonal antibodies. This multidimensional approach is vital, as it not only optimizes the therapeutic potential of NK cells but also addresses the complexities of the tumor microenvironment that often restricts the efficacy of immune therapies.

The authors also address the geographical spread of these clinical trials, providing insights into which regions are at the forefront of NK cell research. The United States emerges as a significant hub for NK cell therapy investigations, reflecting the country’s robust investment in cancer research and innovative therapeutic modalities. However, countries in Europe and Asia are also contributing to the growing body of clinical data, fostering a collaborative international landscape that is crucial in advancing NK cell therapies.

In addition to mapping the clinical landscape, the study emphasizes the importance of rigorous data collection and analysis to determine the effectiveness of NK cell therapies. The authors call for more comprehensive reporting standards in clinical trials to ensure that findings are robust and reproducible. By standardizing data collection and reporting protocols, researchers can better compare results across different studies, thereby accelerating the pace of discovery and implementation of effective NK cell therapies.

Moreover, the article touches on the challenges inherent in translating promising preclinical findings into successful clinical outcomes. Many NK cell therapies face obstacles, including the heterogeneous nature of solid tumors and the immunosuppressive environments in which they thrive. The authors advocate for research focused on understanding these challenges, which will ultimately be critical for improving the efficacy of NK cell therapies in real-world clinical settings.

Another intriguing aspect of the study is the potential for combination therapies that integrate NK cell therapies with other innovative treatments. The authors present a compelling argument for exploring how NK cells can complement established treatments such as chemotherapy and radiation, thus creating a more holistic approach to cancer care. These combinations could serve to amplify the immune response and overcome tumor resistance mechanisms, providing new hope for patients facing aggressive forms of cancer.

The anticipated outcomes of NK cell therapy trials, as presented in the study, are poised to significantly impact clinical practice in oncology. If successful, these therapies could offer new treatment paradigms that improve survival rates and quality of life for patients with solid tumors. The urgency of the findings calls for a continued investment in research efforts, not only to bolster the understanding of NK cell biology but also to streamline the translation of this knowledge into impactful therapies.

As the landscape of NK cell therapies continues to evolve, the study serves as a vital reference point for researchers, clinicians, and policymakers alike. By providing a comprehensive analysis of ongoing clinical trials and their geographical distribution, Wei et al. contribute to the growing body of literature advocating for NK cell therapy as a transformative force in cancer treatment. The authors’ findings emphasize the need for collaborative efforts across disciplines to optimize and implement NK cell therapies effectively.

With ongoing research and clinical trials, the future of NK cell therapies appears promising. As the scientific community gathers more data, refined approaches and innovative methodologies will likely emerge, further solidifying NK cells as a cornerstone of immunotherapeutic strategies against solid tumors. By leveraging insights from the extensive analysis conducted in this study, researchers can pave the way for future breakthroughs that will enhance the landscape of cancer treatment and improve patient outcomes across the globe.

As this exciting field of research progresses, it remains crucial for all stakeholders—researchers, clinicians, and patients—to stay engaged with developments in NK cell therapies. The broader implications of these therapies extend beyond individual treatment success; they represent a fundamental shift in our understanding of cancer and its interactions with the immune system. The insights gleaned from ongoing clinical trials will inform future clinical practices, potentially setting a new standard of care in oncology that prioritizes immune-based therapies, thereby fundamentally changing the trajectory of cancer treatment for years to come.

In conclusion, the comprehensive mapping of NK cell therapy trials presents a fertile ground for continued exploration and innovation. As researchers, institutions, and healthcare providers work collaboratively, there is hope that NK cell therapies will soon become a staple in the armamentarium against solid tumors, delivering effective solutions where traditional therapies have faltered.

Subject of Research: NK cell therapies for solid tumors

Article Title: Mapping the global clinical landscape of NK cell therapies for solid tumors: an analysis based on the ClinicalTrials.gov for the 2005–2024 period.

Article References:

Wei, W., Wu, X., Wang, L. et al. Mapping the global clinical landscape of NK cell therapies for solid tumors: an analysis based on the ClinicalTrials.gov for the 2005–2024 period.
J Cancer Res Clin Oncol 151, 277 (2025). https://doi.org/10.1007/s00432-025-06329-0

Image Credits: AI Generated

DOI: 10.1007/s00432-025-06329-0

Keywords: NK cell therapy, solid tumors, immunotherapy, ClinicalTrials.gov, cancer treatment.