Low-dose radiation treatment enhances systemic antitumor immune responses by overcoming the inhibitory stroma

Brown B, Chan TA, Chand D, Constanzo J, Demaria S, I. Gabrilovich D, Golden E, Godkin A, Guha C, P. Gupta G, Hasan A, G. Herrera F, Kaufman H, Li D, A. Melcher A, McDonald S, Merghoub T, Monjazeb AM, Paris S, Pitroda S, Sadanandam A, Schaue D, Santambrogio L, Szapary P, Sage J, W. Welsh J, Wilkins A, H. Young K, Wennerberg E, Zitvogel L, Galluzzi L, Deutsch E, C. Formenti S. Updates on radiotherapy-immunotherapy combinations: Proceedings of 8th Annual ImmunoRad Conference

The annual ImmunoRad Conference has established itself as a recurrent occasion to explore the possibility of combining radiation therapy (RT) and immunotherapy (IT) for clinical cancer management. Bringing together a number of preclinical and clinical leaders in the fields of radiation oncology, immuno-oncology and IT, this annual event fosters indeed essential conversations and fruitful exchanges on how to address existing challenges to expand the therapeutic value of RT-IT combinations. The 8th edition of the ImmunoRad Conference, which has been held in October 2024 at the Weill Cornell Medical College of New York City, highlighted exciting preclinical and clinical advances at the interface between RT and IT, setting the stage for extra progress toward extended benefits for patients with an increasing variety of tumor types. Here, we critically summarize the lines of investigation that have been discussed at the occasion of the 8th Annual ImmunoRad Conference.

Consolidative radiotherapy in oligometastatic and oligoprogressive NSCLC: A systematic review

Consolidative radiation is increasingly regarded as an effective treatment for oligometastatic and oligoprogressive non-small cell lung cancer (NSCLC). This systematic review examines the clinical evidence on the significance of consolidative radiation in improving outcomes in NSCLC, including progression-free survival and overall survival. Innovations in radiotherapy, including stereotactic body radiotherapy and intensity-modulated radiotherapy, have enhanced the accuracy and effectiveness of local control in oligometastatic disease. This paper analyzes the integration of consolidative radiotherapy with systemic agents, including immunotherapy and targeted therapy, along with the application of biomarkers such circulating tumor DNA for patient selection. Our findings indicate that consolidative radiotherapy could benefit some patients with controlled oligometastatic NSCLC following systemic therapy, emphasizing the importance of proper patient selection. Additional research is necessary to optimize treatment combinations and develop biomarkers for better patient stratification in consolidative radiotherapy.

Radiosensitization Strategies for Hepatocellular Carcinoma: Mechanisms, Therapeutic Advances, and Clinical Perspectives

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide, with treatment efficacy limited by late-stage diagnosis, frequent recurrence, and therapeutic resistance. Radiotherapy is a key local treatment for HCC; however, its efficacy is frequently limited by intrinsic tumor radioresistance. This review discusses strategies to improve the therapeutic response of HCC to radiotherapy. Targeting DNA repair mechanisms can block tumor cells from recovering after radiation-induced damage, whereas modulating cell cycle arrest and programmed cell death pathways (e.g., apoptosis, autophagy) diminishes their survival capacity. Furthermore, remodeling the tumor microenvironment-through hypoxia alleviation, metabolic reprogramming, oxidative stress regulation, and immune activation-may potentiate radiotherapy efficacy. Technological advances, such as stereotactic body radiotherapy and nanomaterial-based approaches, have also improved the precision and effectiveness of radiotherapy. Clinically, combining radiotherapy with systemic therapies (e.g., immune checkpoint inhibitors and antiangiogenic agents) has demonstrated preliminary promise in enhancing treatment outcomes. However, translating preclinical findings into clinical practice remains challenging due to tumor heterogeneity, normal tissue toxicity, and the lack of predictive biomarkers for treatment selection. Future research should focus on integrating molecular profiling with multimodal therapies to enable personalized radiosensitization and bridge the gap between mechanistic insights and clinical outcomes.

Neoadjuvant with low-dose radiotherapy, tislelizumab, albumin-bound paclitaxel, and cisplatin for resectable locally advanced head and neck squamous cell carcinoma: phase II single-arm trial

Although pathological complete response (pCR) and major pathological response (MPR) rates of neoadjuvant immunotherapy combined with chemotherapy in head and neck squamous cell carcinoma (HNSCC) trials remain suboptimal, emerging evidence highlights the synergistic potential of combining low-dose radiotherapy with immunotherapy to promote the efficacy of immunotherapy. This phase II, open-label, single-arm, multicenter trial (NCT05343325) enrolled 28 patients with untreated stage III-IVB HNSCC (NeoRTPC02). Patients received neoadjuvant low-dose radiotherapy, the programmed death-1 (PD-1) inhibitor tislelizumab, albumin-bound paclitaxel, and cisplatin for two cycles, followed by radical resection ~4 weeks after treatment completion. The primary endpoint, pCR rate, was achieved in 14 of 23 patients (60.9%; 23/28, 82.1% of the total cohort underwent surgery). Secondary endpoints included MPR rate (21.7%, 5/23), R0 resection rate (100%), and objective response rate (64.3%; 18/28). Treatment-related adverse events were manageable, with grade 3 or 4 treatment-related adverse events occurring in 10 (35.7%) patients. No surgical delays were observed. Single-cell RNA sequencing revealed remodeling of the HNSCC tumor microenvironment, which may correlate with improved clinical outcomes. This trial met the pre-specified primary endpoint, demonstrating a high pCR rate with promising efficacy and manageable toxicity in locally advanced HNSCC.

Whole-body CT scanning radiation improves the immune microenvironment of tumor tissues to enhance the antitumor effect of ICI

OBJECTIVE

The effect of frequent whole-body CT scans during immune checkpoint inhibitor (ICI) therapy on patients' anti-tumor immunity.

METHODS

We conducted a retrospective clinical study aimed to investigate the correlation between the frequency of CT scans during immune checkpoint inhibitor (ICI) therapy and the duration of remission (DOR) of ICI therapy in patients with stage IV non-small cell lung cancer (NSCLC). We constructed a hormonal mouse model and administered immune checkpoint inhibitor (ICI) therapy to mice, and radiated five whole-body CT scans to mice during ICI therapy to observe whether frequent whole-body CT scans had an effect on the antitumor effect of immunotherapy in mice.

RESULTS

The more frequent CT scans during patients' immune checkpoint inhibitor (ICI) treatment the longer the duration of remission (DOR) of ICI treatment. In a mouse model we observed that the addition of whole-body CT scanning radiation had a tendency to inhibit tumor growth in mice compared with the anti-PD-1 group alone.Frequent CT scanning radiation during the application of immune checkpoint inhibitor PD-1 increased the proportion of infiltrating CD8 + T cells in tumor tissues and significantly increased the proportion of IFNγ-secreting CD8 + T cells, and single-cell sequencing of the results also revealed that IFNγ and killing-related genes were significantly upregulated in tumor-infiltrating CD8T cells.

CONCLUSION

To our knowledge this is the first study on the effect of CT scan radiation on ICI.Our findings suggest that multiple CT scans during immune checkpoint inhibitor (ICI) treatment did not promote tumor progression, but instead a trend toward delayed tumor progression was observed.

The Radiosurgery Society Working Groups on GRID, LATTICE, Microbeam, and FLASH Radiotherapies: Advancements Symposium and Subsequent Progress Made

PURPOSE

Since the inaugural workshop "Understanding High-Dose, Ultra-High Dose Rate and Spatially Fractionated Radiotherapy." hosted by the National Cancer Institute and sponsored by the Radiosurgery Society (RSS), growing collaborations and investigations have ensued among experts, practitioners, and researchers. The RSS GRID, LATTICE, Microbeam and FLASH (GLMF) Working Groups were formed as a framework for these efforts and have focused on advancing the understanding of the biology, technical/physical parameters, trial design, and clinical practice of these new radiation therapy modalities.

METHODS AND MATERIALS

In view of the steadily increasing clinical interest in Spatially Fractionated Radiotherapy (SFRT) and FLASH, a full-day symposium entitled "Advancements in GRID, LATTICE, and FLASH Radiotherapy Symposium" was established in 2022 that immediately preceded the RSS scientific meeting. This well-attended symposium focused on clinical, technical, and physics approaches for SFRT, and closely examining relevant radiobiological underpinnings. Practical clinical trial development was a highlighted discussion. An additional section reviewed proton therapy and other particle-based techniques for the delivery of GRID and LATTICE therapy. A treatment planning and delivery tutorial for GRID, LATTICE, and proton GRID/LATTICE was directed toward the real-world considerations for the development of new clinical GRID or LATTICE programs. An overall similar approach was applied to the discussion of FLASH. This report summarizes the content of the first GLMF Symposium and related work of the RSS GLMF Working Groups in the field of heterogeneous and ultrahigh dose rate irradiation, over approximately 2 years.

RESULTS

The GLMF Working Groups have continued to expand in membership and attendance, and several resultant trial concepts, research efforts, academic discussions, and peer-reviewed publications have followed as the number of institutions and practitioners using SFRT and FLASH continues to grow.

CONCLUSIONS

The GLMF Working Groups and the RSS continue to demonstrate excellent progress in proliferating use of and improving understanding of SFRT and ultrahigh dose rate radiation therapy techniques.

MHC-I-Driven Antitumor Immunity Counterbalances Low Absorbed Doses of Radiopharmaceutical Therapy

Preclinical and clinical studies increasingly show that the immune response plays a major role in radiotherapy. Here, we investigated the role of major histocompatibility complex class I (MHC-I) molecules recognized by cytotoxic CD8+ T cells in the response to radiopharmaceutical therapy (RPT). Methods: Two murine melanoma cell lines that express low and high MHC-I levels (B16F10 and B16K1, respectively) were grafted in syngeneic or athymic and nude mice, and the response to a single injection of [225Ac]Ac-DOTA-TA99 monoclonal antibodies (9.25 or 18.5 kBq) was assessed and related to dosimetry. For clinical relevance, MHC-I expression was determined in samples from patients with well-differentiated, iodine-avid metastatic thyroid cancer and well-differentiated grade 2 mid-gut neuroendocrine tumors. Results: RPT efficacy was enhanced by T-cell presence and MHC-I expression. In mice harboring B16F10 and B16K1 melanoma tumors, RPT showed a stronger antitumor effect in C57BL/6J (immunocompetent) animals than in athymic and nude (immunodeficient) animals, suggesting a crucial role of T-cell-mediated immune responses. Moreover, the response to irradiation was the same in B16K1 MHC-Ihigh tumors with a low absorbed dose of α-RPT and in B16F10 MHC-Ilow tumors with a 4 times higher absorbed dose. These results indicate that CD8+ T cells can counterbalance low tumor irradiation. Conversely, delivering high absorbed doses leads to side effects and seems to prevent immune system activation, thereby not taking advantage of these mechanisms. Our results also indicate that MHC-I can be used as a predictive biomarker of RPT response in lesions receiving low absorbed doses and that RPT treatment regimens should be reconsidered in the function of the MHC-I expression level. Conclusion: This study shows that MHC-I expression can predict RPT immunostimulatory effects. This is relevant in metastatic disease where lesions in the same patient can receive very low or very high absorbed doses.

Brachytherapy: Perspectives for combined treatments with immunotherapy

Combining brachytherapy with immunotherapies, particularly immune checkpoint inhibitors (ICIs), is a promising approach for potentiating both local control of the tumor and fully exploiting the synergies between pharmaceutic immunomodulation and radiotherapy. Compared to other radiotherapy techniques, BT has a potential to better spare lymphatic drainage areas and gut microbiota, thus reducing the immunosuppressive effects of radiation therapy. In addition, it delivers a broad range of doses due to inherent dose inhomogeneity within the implanted volume. This variability increases the probability that immune infiltrates would be activated, particularly since the optimal dose for immune activation is not yet firmly established. Even if preclinical models show that radiotherapy can stimulate immune responses, it can also induce toxic effects on immune effectors and combination trials show conflicting outcomes. There is a need for refining radiation modalities to enhance immune potentiation. The dosimetric specificities of BT may offer various advantages and should be explored further. Scarce clinical data on combining brachytherapy with ICIs in advanced cancer suggest potential benefits, with case reports of complete local responses and abscopal effects. However, validation requires a large number of patients in randomized clinical trials for which ideal design is discussed. In parallel with ongoing clinical developments, there is a need to refine preclinical models in order to better analyze the specific biological effects involved in BT, in light of immunomodulatory systemic treatments.

Stimulator of Interferon Genes Agonist Synergistically Amplifies Programmed Cell Death Protein-1 Blockade and Radiation-Induced Systemic Antitumor Responses via Tumor Microenvironment Enrichment

PURPOSE

The effectiveness of immune checkpoint inhibitors in solid tumors is limited and heavily dependent on the tumor microenvironment (TME). Radiation therapy (RT) reshapes the TME, promoting T cell infiltration. We explored the combined antitumor effects of the stimulator of interferon genes (STING) agonist with low-dose RT and immunotherapy.

METHODS AND MATERIALS

Tumor cell lines (PRM-SCLC, MC38, and LL2) were treated with the STING agonist diABZI (0.001-10 µM) to assess cytotoxicity. The mRNA expression levels of chemokines and cytokines in tumor cells were quantitatively analyzed in conjunction with RT to assess immune activation. Flow cytometry assessed bone marrow-derived dendritic cell and macrophage maturation. Subcutaneous tumor-bearing mouse models (PRM-SCLC, MC38, LL2) were used to monitor tumor volume, body weight, and survival. Tumor samples were collected for flow cytometry, immunofluorescence, immunohistochemistry, and transcriptome sequencing. Bilateral tumor models assessed the abscopal effect, with tumor and tumor-draining lymph node samples collected.

RESULTS

The STING agonist diABZI did not directly inhibit tumor cell proliferation at tested concentrations. However, when combined with RT, diABZI significantly upregulated chemokines and IFN-β mRNA levels in tumor cells, while mitigating the RT-induced rise in TGF-β levels. In vitro, bone marrow-derived dendritic cells and macrophages treated with STING agonist + RT showed increased maturation. In tumor-bearing mice, the STING agonist enhanced the efficacy of RT, chemotherapy, and immunotherapy. Adding STING agonist to low-dose RT + αPD-1 activated tumor-infiltrating CD45+, CD8+, CD4+ T cells, natural killer cells, and dendritic cells, and promoted M1 macrophage polarization. Transcriptome analysis showed enhanced antigen presentation and T cell activation. In bilateral tumor models, triple therapy reduced both primary and distant tumor volumes, with increased T cell infiltration and a higher presence of TCF1+ PD-1+ TSL cells in tumor-draining lymph nodes.

CONCLUSIONS

STING agonist boosts immune activation and cell recruitment in the TME, enhancing immunotherapy response. It also amplifies the abscopal effect of RT, promoting systemic antitumor immunity with clinical translational potential.

Radiation from frequent whole-body CT scans induces systemic immunosuppression and immune activation of tumor tissue

OBJECTIVE

This study aims to elucidate the impact of repeated whole-body computed tomography (CT) scans on systemic immunity, the tumor immune microenvironment, and tumor control. This inquiry was prompted by clinical observations indicating a decrease in the levels of IFN-β and IFN-γ in patients' blood following whole-body CT scans.

METHODS

A Lewis lung carcinoma (LLC) mouse model was established and divided into two groups: a control group and a group subjected to multiple whole-body CT scanning radiation (WBCTSs). The study monitored tumor growth trends across both groups and employed a comprehensive set of analytical techniques-including enzyme-linked immunosorbent assay (ELISA), flow cytometry analysis, immunohistochemistry, RNA sequencing, and single-cell sequencing-to assess differences in cytokine profiles (IFN-β and IFN-γ), proportions of key immune cells, and gene expression variations between the groups.

RESULTS

Repeated CT scan radiation does not promote tumor progression. In tumor tissues subjected to multiple CT scans, an increase in the proportion of CD8+ T cells, elevated interferon levels, and up-regulation of genes associated with killing in CD8+ T cells and genes associated with Ifnb in macrophages were observed. In contrast, radiation from multiple whole-body CT scans resulted in a decrease in the proportion of CD8+ T cells in the blood and spleen, a decrease in serum interferon levels, and down-regulation of killing-related genes in CD8+ T cells.

CONCLUSION

Our results suggest that repeated whole-body CT scanning radiation induces systemic immunosuppression and immune activation in tumor tissues. Multiple repeated CT scans do not promote tumor progression.

DNA-PKcs Dysfunction Enhances the Antitumor Activity of Radioimmunotherapy by Activating the cGAS-STING Pathway in HNSCC

Introduction

Combining radiotherapy (RT) with immunotherapy for head and neck squamous cell carcinoma (HNSCC) has limited effectiveness due to the DNA damage repair (DDR) pathway activated by ionizing radiation. DNA-PK, encoded by the PRKDC gene, plays a key role in this repair. The potential improvement of radioimmunotherapy by inhibiting the DDR pathway is still unclear.

Methods

The effectiveness of different treatments on tumor growth and survival was tested using the C3H/HeN mouse tumor model. Flow cytometry analyzed treatment-induced immunophenotypic changes. In vitro, Western blot and PCR confirmed the impact of combining immunotherapy with RT on the cGAS-STING pathway after DNA-PKcs dysfunction.

Results

The combination of a DNA-PK inhibitor (NU7441), radiation therapy, and a PD-1 checkpoint inhibitor showed improved antitumor effects and extended survival in mice. Adding NU7441 into the RT and immunotherapy regimen increased CD8+ T cell infiltration. PRKDC alterations or DNA-PKcs dysfunction increased IR-induced DNA breaks, activating the cGAS-STING pathway and boosting the anti-tumor immune response.

Conclusion

These findings suggest that targeting the DDR pathway may represent a promising therapeutic strategy and biomarker to improve the efficacy of radioimmunotherapy in HNSCC.

Preventive effects of low-dose radiation and hypofractionated radiation plus anti-programmed cell death protein 1 on lung metastasis in breast cancer

Background

Previous experiments have demonstrated that hypofractionated radiation therapy (HFRT), low-dose radiation therapy (LDRT), and combined anti-programmed cell death protein 1 (αPD-1) can enhance the abscopal effect. Combined with the phenomenon of low prognosis in patients with breast cancer lung metastasis, our study establishes a mouse model and changes the irradiation regimen of LDRT to explore its preventive effect on breast cancer lung metastasis.

Methods

The breast cancer subcutaneous graft tumor model was developed. Two-lung prophylactic LDRT was performed prior to the onset of lung metastases, in combination with HFRT (8 Gy, 3f), and αPD-1 (200 μg, 4f) therapy. We watched and documented the tumor volume, survival duration, and number of lung metastases. Furthermore, after labeling the corresponding cells using markers, we detected immune-related cell infiltration by immunohistochemistry and flow cytometry, such as T cells. We also determined the expression of cytokines (IFN-γ and TNF-α) by enzyme-linked immunosorbent assay.

Result

The triple therapy (HFRT+LDRT+αPD-1) resulted in tumor shrinkage and prolonged survival in mice, with median survival extending from 35 to 52 days. The most notable decrease in the quantity of advanced lung metastatic nodules in breast cancer was observed with the triple therapy (HFRT+LDRT+αPD-1) (p < 0.05). Furthermore, according to immunohistochemistry and flow cytometry, the triple treatment (HFRT+LDRT+αPD-1) showed the greatest expression of CD8+ T cells. Additionally, the ratio of CD8+/CD4+ T cells was considerably greater than that of the groups (p < 0.0001). Triple therapy (HFRT+LDRT+αPD-1) increased the recruitment of DCs cells, promoted IFN-γ and TNF-α expression, and curbed the aggregation of MDSCs cells (p < 0.05).

Conclusion

Prophylactic LDRT to the lungs, based on HFRT and αPD-1, can enhance anti-tumor efficacy and prevent advanced lung metastases from breast cancer. The process involves boosting the recruitment of DCs and CD8+ T cells, preventing MDSC cell aggregation, and lessening the tumor microenvironment's immunosuppressive effects.

Radiotherapy as salvage therapy and an adjunct to immunotherapy: exploring local and abscopal mechanisms to overcome immunotherapy resistance: a narrative review

Background and Objective

Immune checkpoint inhibitors (ICIs) have ushered in a new era of therapies and play a significant role in the clinical treatment of a variety of tumors. However, immune resistance has increasingly created a bottleneck in treatment, making the question of how to overcome drug resistance an urgent issue to address. In this article, the mechanism of drug resistance is briefly described with a focus on how radiotherapy (RT) acts on the immune system to reverse immunotherapy failure. Combinations of existing treatment modalities need to be optimized to overcome resistance problems. Research has shown that some RT modalities reverse immune resistance or enhance efficacy when used in combination, which shows some value for immune resistance and is worthy of in-depth research.

Methods

In this review, we searched the literature published from 2000 to 2023 surrounding immunotherapy, RT and cancer.

Key Content and Findings

Based on the immune effects and immunosuppressive effects induced by RT, this review examined the preclinical rationales of RT and its clinical results. The findings indicate that RT might provide a novel regimen for patients with locally advanced tumors, especially oligometastatic tumors.

Conclusions

Salvage therapy with RT after immunotherapy resistance is the focus of current research. Other strategies, such as multidrug combination therapies, have made preliminary progress in preclinical experiments. Further research on the roles of different RT doses, fractionation regimens, and other treatment sequences in salvage therapy need to be conducted in the future. The optimal site and timing of low-dose radiotherapy are also undetermined, and prospective studies are need to determine the best regimen for optimizing patient treatment.

Case report: Low-dose radiation reverses pembrolizumab resistance in melanoma

Immunotherapy has been the mainstay of the initial systemic treatment for metastatic melanoma regardless of the tumor's genetic mutation status (Atkins et al., 2022). It is known to offer long-term overall and treatment-free survival benefits, also with generally tolerable side effect profiles. However, upon disease progression on first- and second-line immunotherapy, further systemic treatment options are limited especially for cases without actionable molecular alterations. With emerging evidence suggesting that radiotherapy can enhance the efficacy of immunotherapy via various mechanisms, together with its potential abscopal effect, the possibility of overcoming immunotherapy resistance with radiotherapy is theoretically sound. We report a case of metastatic melanoma which demonstrated a reversal of immunotherapy resistance after the addition of low-dose radiotherapy to progressive tumor. Complete metabolic remission is achieved with durable response observed.

Bacterial membrane-modified cerium oxide nanoboosters enhance systemic antitumor effects of radiotherapy in metastatic triple-negative breast cancer

BACKGROUND

Radiotherapy plays an important role in the treatment of triple-negative breast cancer, yet its ability to trigger systemic responses against distant tumors remains limited.

RESULTS

To address this challenge, we developed a biomimetic nanobooster by incorporating cerium oxide (CeO2) nanoparticles with bacterial outer membrane vesicles (OMVs), termed CeO2@OMV. This innovative strategy overcomes the limitations of conventional radiotherapy by enhancing antigen release and improving immune cell infiltration, thereby amplifying its effectiveness in combating both primary and metastatic tumors. The biocompatibility, antitumor effects, bystander and immunomodulatory impacts of the nanoboosters were assessed by comprehensive in vitro assays and in vivo breast cancer models. Our results demonstrated that CeO2@OMVs can selectively inhibit cancer cells while protecting normal tissue upon irradiation. Additionally, the nanoboosters induced immunogenic cell death, enhanced macrophage polarization, and suppressed the growth of bystander tumors. In vivo studies demonstrated that CeO2@OMVs, when combined with radiotherapy, significantly improved local tumor control and triggered systemic immune responses, leading to substantial inhibition of both primary and distant tumors, effectively preventing new metastases.

CONCLUSIONS

In conclusion, our CeO2@OMV nanoboosters offer a promising therapeutic strategy against metastatic breast cancer, providing a novel tool to achieve radiation-induced abscopal effects.

Identification of TUBB3 as an immunotherapy target in lung cancer by genome wide in vivo CRISPR screening

Recent development of immune checkpoint inhibitors has revolutionized cancer immunotherapy. Although these drugs show dramatic effects on a subset of cancer patients, many other tumors are non-responsive and the pathological mechanism of the resistance is largely unknown. To identify genes underlying anti-PD-1 immunotherapy resistance using a systematic approach, we performed an in vivo genome wide CRISPR screening in lung cancer cells. We integrated our results with multi-omics clinical data and performed both in vitro and in vivo assays to evaluate the role of the top candidate in regulating cytotoxic T cell killing. We identified TUBB3 as a potential target to overcome the resistance and enhance the efficacy of anti-PD-1 immunotherapy. TUBB3 expression is upregulated in lung cancer patients, and its higher expression correlates with poorer patients' survival. We found that TUBB3 expression was significantly elevated in the non-responders compared to responders in our patient cohort that received immunotherapies. Importantly, the results of our preclinical experiments showed that inhibition of TUBB3 with a small molecule inhibitor synergized with anti-PD-1 treatment and enhanced tumor cell killing by cytotoxic T cells. Consistently, anti-PD-1 resistant cells showed significantly higher expression of TUBB3; however, TUBB3 inhibition rendered the resistant cells more susceptible to T cell killing. Mechanistic studies revealed that blocking TUBB3 suppressed the expression of PD-L1 through the EMT-related SNAI1 gene. Our results provide a rationale for a novel combination therapy consisting of the TUBB3 inhibition and anti-PD-1 immunotherapy for lung cancer.

Enhancing immunotherapy efficacy with synergistic low-dose radiation in metastatic melanoma: current insights and prospects

Recent advances in oncology research have highlighted the promising synergy between low-dose radiation therapy (LDRT) and immunotherapies, with growing evidence highlighting the unique benefits of the combination. LDRT has emerged as a potent tool for stimulating the immune system, triggering systemic antitumor effects by remodeling the tumor microenvironment. Notably, LDRT demonstrates remarkable efficacy even in challenging metastatic sites such as the liver (uveal) and brain (cutaneous), particularly in advanced melanoma stages. The increasing interest in utilizing LDRT for secondary metastatic sites of uveal, mucosal, or cutaneous melanomas underscores its potential efficacy in combination with various immunotherapies. This comprehensive review traverses the journey from laboratory research to clinical applications, elucidating LDRT's immunomodulatory role on the tumor immune microenvironment (TIME) and systemic immune responses. We meticulously examine the preclinical evidence and ongoing clinical trials, throwing light on the promising prospects of LDRT as a complementary therapy in melanoma treatment. Furthermore, we explore the challenges associated with LDRT's integration into combination therapies, addressing crucial factors such as optimal dosage, fractionation, treatment frequency, and synergy with other pharmacological agents. Considering its low toxicity profile, LDRT presents a compelling case for application across multiple lesions, augmenting the antitumor immune response in poly-metastatic disease scenarios. The convergence of LDRT with other disciplines holds immense potential for developing novel radiotherapy-combined modalities, paving the way for more effective and personalized treatment strategies in melanoma and beyond. Moreover, the dose-related toxicities of immunotherapies may be reduced by synergistic amplification of antitumor efficacy with LDRT.

The characteristics of the tumor immune microenvironment in colorectal cancer with different MSI status and current therapeutic strategies

Colorectal cancer (CRC) remains a significant cause of cancer-related mortality worldwide. Despite advancements in surgery, chemotherapy, and radiotherapy, the effectiveness of these conventional treatments is limited, particularly in advanced cases. Therefore, transition to novel treatment is urgently needed. Immunotherapy, especially immune checkpoint inhibitors (ICIs), has shown promise in improving outcomes for CRC patients. Notably, patients with deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) tumors often benefit from ICIs, while the majority of CRC cases, which exhibit proficient mismatch repair (pMMR) or microsatellite-stable (MSS) status, generally show resistance to this approach. It is assumed that the MSI phenotype cause some changes in the tumor microenvironment (TME), thus triggering antitumor immunity and leading to response to immunotherapy. Understanding these differences in the TME relative to MSI status is essential for developing more effective therapeutic strategies. This review provides an overview of the TME components in CRC and explores current approaches aimed at enhancing ICI efficacy in MSS CRC.

New insight in immunotherapy and combine therapy in colorectal cancer

The advent of immune checkpoint inhibitors (ICIs) in colorectal cancer (CRC) treatment marks a major breakthrough. These therapies have proven safer and more effective than traditional radiotherapy and targeted treatments. Immunotherapies like pembrolizumab, nivolumab, and ipilimumab have pioneered new treatment avenues, potentially improving patient outcomes and quality of life. Additionally, advances in immunotherapy have prompted detailed research into CRC therapies, especially those integrating ICIs with conventional treatments, providing new hope for patients and shaping future research and practice. This review delves into the mechanisms of various ICIs and evaluates their therapeutic potential when combined with radiotherapy, chemotherapy, and targeted therapies in clinical settings. It also sheds light on the current application and research involving ICIs in CRC treatment.

Fractionated low-dose radiotherapy primes the tumor microenvironment for immunotherapy in a murine mesothelioma model

Combination immune checkpoint inhibitors (nivolumab and ipilimumab) are currently a first-line treatment for mesothelioma; however, not all patients respond. The efficacy of treatment is influenced by the tumor microenvironment. Murine mesothelioma tumors were irritated with various radiotherapy doses. Radiotherapy induced vasculature changes were monitored by power Doppler and photoacoustic ultrasound and analyzed via mixed-effects models. Tissue staining was used to investigate the immune cell infiltrate of tumors. The optimal radiotherapy schedule was combined with immune checkpoint inhibitors, and the survival of mice was analyzed. Using low-dose, low-fraction radiotherapy allowed favorable modification of the murine mesothelioma tumor microenvironment. Irradiating tumors with 2 Gy × 5 fractions significantly improved blood flow and reduced hypoxia, consequently increasing the presence of CD8+ and regulatory T cells in the tumor. Understanding the transient nature of these changes is crucial for optimizing the timing of therapeutic delivery. The combination of radiotherapy with dual immunotherapy (anti-PD-1 plus anti-CTLA-4) proved highly curative when administered concurrently. A diminishing rate of cures was noted with an increasing delay between radiotherapy and subsequent immunotherapy. Concurrent low-dose, low-fraction radiotherapy emerges as a translatable approach for improving the efficacy of immune checkpoint inhibitors in patients.

Immunogenicity of cell death and cancer immunotherapy with immune checkpoint inhibitors

While immunotherapy with immune checkpoint inhibitors (ICIs) has revolutionized the clinical management of various malignancies, a large fraction of patients are refractory to ICIs employed as standalone therapeutics, necessitating the development of combinatorial treatment strategies. Immunogenic cell death (ICD) inducers have attracted considerable interest as combinatorial partners for ICIs, at least in part owing to their ability to initiate a tumor-targeting adaptive immune response. However, compared with either approach alone, combinatorial regimens involving ICD inducers and ICIs have not always shown superior clinical activity. Here, we discuss accumulating evidence on the therapeutic interactions between ICD inducers and immunotherapy with ICIs in oncological settings, identify key factors that may explain discrepancies between preclinical and clinical findings, and propose strategies that address existing challenges to increase the efficacy of these combinations in patients with cancer.

Extracellular vesicles role in radio(nuclide)therapy

Conventional radiation therapy can restore the ability of cells to undergo immunogenic cell death. Recent preclinical studies suggest that targeted radionuclide therapy, which delivers radiation to tumors at a continuous low dose rate, also stimulates the immune system and offers a promising approach for overcoming resistance to immune checkpoint inhibitors. In this context, we examined the growing body of preclinical and clinical findings showing that the immune system can be activated by the release of extracellular vesicles from irradiated cells, contributing to the antitumor immunity.

Immunotherapy for ovarian cancer: towards a tailored immunophenotype-based approach

Despite documented evidence that ovarian cancer cells express immune-checkpoint molecules, such as PD-1 and PD-L1, and of a positive correlation between the presence of tumour-infiltrating lymphocytes and favourable overall survival outcomes in patients with this tumour type, the results of trials testing immune-checkpoint inhibitors (ICIs) in these patients thus far have been disappointing. The lack of response to ICIs can be attributed to tumour heterogeneity as well as inherent or acquired resistance associated with the tumour microenvironment (TME). Understanding tumour immunobiology, discovering biomarkers for patient selection and establishing optimal treatment combinations remains the hope but also a key challenge for the future application of immunotherapy in ovarian cancer. In this Review, we summarize results from trials testing ICIs in patients with ovarian cancer. We propose the implementation of a systematic CD8+ T cell-based immunophenotypic classification of this malignancy, followed by discussions of the preclinical data providing the basis to treat such immunophenotypes with combination immunotherapies. We posit that the integration of an accurate TME immunophenotype characterization with genetic data can enable the design of tailored therapeutic approaches and improve patient recruitment in clinical trials. Lastly, we propose a roadmap incorporating tissue-based profiling to guide future trials testing adoptive cell therapy approaches and assess novel immunotherapy combinations while promoting collaborative research.

Non-homogenous intratumor ionizing radiation doses synergize with PD1 and CXCR2 blockade

The efficacy and side effects of radiotherapy (RT) depend on parameters like dose and the volume of irradiated tissue. RT induces modulations of the tumor immune microenvironment (TIME) that are dependent on the dose. Low dose RT (LDRT, i.e., single doses of 0.5-2 Gy) has been shown to promote immune infiltration into the tumor. Here we hypothesize that partial tumor irradiation combining the immunostimulatory/non-lethal properties of LDRT with cell killing/shrinkage properties of high dose RT (HDRT) within the same tumor mass could enhance anti-tumor responses when combined with immunomodulators. In models of colorectal and breast cancer in immunocompetent female mice, partial irradiation (PI) with millimetric precision to deliver LDRT (2 Gy) and HDRT (16 Gy) within the same tumor induces substantial tumor control when combined with anti-PD1. Using flow cytometry, cytokine profiling and single-cell RNA sequencing, we identify a crosstalk between the TIME of the differentially irradiated tumor volumes. PI reshapes tumor-infiltrating CD8+ T cells into more cytotoxic and interferon-activated phenotypes but also increases the infiltration of pro-tumor neutrophils driven by CXCR2. The combination of the CXCR2 antagonist SB225002 with PD1 blockade and PI improves tumor control and mouse survival. Our results suggest a strategy to reduce RT toxicity and improve the therapeutic index of RT and immune checkpoint combinations.

Preclinical study and phase II trial of adapting low-dose radiotherapy to immunotherapy in small cell lung cancer

BACKGROUND

Immune checkpoint inhibitors (ICIs) provide modest but unsatisfactory benefits for extensive-stage small cell lung cancer (ES-SCLC). Developing strategies for treating ES-SCLC is critical.

METHODS

We preliminarily explored the outcomes of salvage low-dose radiotherapy (LDRT) plus ICI on refractory SCLC patients. Next, we evaluated the combinational efficacy in murine SCLC. The tumor immune microenvironment (TIME) was analyzed for mechanistic study. Subsequently, we conducted a multicenter, prospective phase II trial that administered concurrent thoracic LDRT plus chemoimmunotherapy to treatment-naive ES-SCLC patients (MATCH trial, NCT04622228). The primary endpoint was confirmed objective response rate (ORR), and the key secondary endpoints included progression-free survival (PFS) and safety.

FINDINGS

Fifteen refractory SCLC patients treated with LDRT plus ICI were retrospectively reviewed. The ORR was 73.3% (95% confidence interval [CI], 44.9-92.2). We identified a specific dose of LDRT (15 Gy/5 fractions) that exhibited growth retardation and improved survival in murine SCLC when combined with ICIs. This combination recruited a special T cell population, TCF1+ PD-1+ CD8+ stem-like T cells, from tumor-draining lymph nodes into the TIME. The MATCH trial showed a confirmed ORR of 87.5% (95% CI, 75.9-94.8). The median PFS was 6.9 months (95% CI, 5.4-9.3).

CONCLUSIONS

These findings verified that LDRT plus chemoimmunotherapy was safe, feasible, and effective for ES-SCLC, warranting further investigation.

FUNDING

This research was funded by West China Hospital (no. ZYJC21003), the National Natural Science Foundation of China (no. 82073336), and the MATCH trial was fully funded by Roche (China) Holding Ltd. (RCHL) and Shanghai Roche Pharmaceuticals Ltd. (SRPL).

Enhanced tumor control and survival in preclinical models with adoptive cell therapy preceded by low-dose radiotherapy

Introduction

Effective infiltration of chimeric antigen receptor T (CAR-T) cells into solid tumors is critical for achieving a robust antitumor response and improving therapeutic outcomes. While CAR-T cell therapies have succeeded in hematologic malignancies, their efficacy in solid tumors remains limited due to poor tumor penetration and an immunosuppressive tumor microenvironment. This study aimed to evaluate the potential of low-dose radiotherapy (LDRT) administered before T-cell therapy to enhance the antitumor effect by promoting CAR-T cell infiltration. We hypothesized that combining LDRT with T-cell therapy would improve tumor control and survival compared to either treatment alone.

Methods

We investigated this hypothesis using two NSG mouse models bearing GSU or CAPAN-2 solid tumors. The mice were treated with engineered CAR-T cells targeting guanyl cyclase-C (GCC) or mesothelin as monotherapy or in combination with LDRT. Additionally, we extended this approach to a C57BL/6 mouse model implanted with MC38-gp100+ cells, followed by adoptive transfer of pmel+ T cells before and after LDRT. Tumor growth and survival outcomes were monitored in all models. Furthermore, we employed atomic force microscopy (AFM) in a small cohort to assess the effects of radiotherapy on tumor stiffness and plasticity, exploring the role of tumor nanomechanics as a potential biomarker for treatment efficacy.

Results

Our results demonstrated enhanced tumor control and prolonged survival in mice treated with LDRT followed by T-cell therapy across all models. The combination of LDRT with CAR-T or pmel+ T-cell therapy led to superior tumor suppression and survival compared to monotherapy, highlighting the synergistic impact of the combined approach. Additionally, AFM analysis revealed significant changes in tumor stiffness and plasticity in response to LDRT, suggesting that the nanomechanical properties of the tumor may be predictive of therapeutic response.

Discussion

The findings of this study highlight the transformative potential of incorporating LDRT as a precursor to adoptive T-cell therapy in solid tumors. By promoting CAR-T and pmel+ T-cell infiltration into the tumor microenvironment, LDRT enhanced tumor control and improved survival outcomes, offering a promising strategy to overcome the challenges associated with CAR-T therapy in solid tumors. Additionally, the changes in tumor nanomechanics observed through AFM suggest that tumor stiffness and plasticity could be biomarkers for predicting treatment outcomes. These results support further investigation into the clinical application of this combined approach to improve the efficacy of cell-based therapies in patients with solid tumors.

Superior antitumor immune response achieved with proton over photon immunoradiotherapy is amplified by the nanoradioenhancer NBTXR3

Recent findings suggest that immunoradiotherapy (IRT), combining photon radiotherapy (XRT) or proton radiotherapy (PRT) with immune checkpoint blockade, can enhance systemic tumor control. However, the comparative efficacy of XRT and PRT in IRT remains understudied. To address this, we compared outcomes between XRT + αPD1 and PRT + αPD1 in murine αPD1-resistant lung cancer (344SQR). We also assessed the impact of the nanoparticle radioenhancer NBTXR3 on both XRT + αPD1 and PRT + αPD1 for tumor control and examined the tumor immune microenvironment using single-cell RNA sequencing (scRNAseq). Additionally, mice cured by NBTXR3 + PRT + αPD1 were rechallenged with three lung cancer cell lines to evaluate memory antitumor immunity. PRT + αPD1 showed superior local tumor control and abscopal effects compared to XRT + αPD1. NBTXR3 + PRT + αPD1 significantly outperformed NBTXR3 + XRT + αPD1 in tumor control, promoting greater infiltration of antitumor lymphocytes into irradiated tumors. Unirradiated tumors treated with NBTXR3 + PRT + αPD1 had more NKT cells, CD4 T cells, and B cells, with fewer Tregs, than those treated with NBTXR3 + XRT + αPD1. NBTXR3 + PRT + αPD1 also stimulated higher expression of IFN-γ, GzmB, and Nkg7 in lymphocytes, reduced the TGF-β pathway, and increased tumor necrosis factor alpha expression compared to NBTXR3 + XRT + αPD1. Moreover, NBTXR3 + PRT + αPD1 resulted in greater M1 macrophage polarization in both irradiated and unirradiated tumors. Mice achieving remission through NBTXR3 + PRT + αPD1 exhibited a robust memory immune response, effectively inhibiting growth of subsequent tumors from three distinct lung cancer cell lines. Proton IRT combined with NBTXR3 offers enhanced tumor control and survival rates over photon-based treatments in managing αPD1-resistant lung cancer, indicating its potential as a potent systemic therapy.

Immune modulation of the liver metastatic colorectal cancer microenvironment via the oral CAPOX-mediated cGAS-STING pathway

We evaluated modulation of the immunosuppressive tumor microenvironment in both local and liver metastatic colorectal cancer (LMCC), focusing on tumor-associated macrophages, which are the predominant immunosuppressive cells in LMCC. We developed an orally administered metronomic chemotherapy regimen, oral CAPOX. This regimen combines capecitabine and a nano-micelle encapsulated, lysine-linked deoxycholate and oxaliplatin complex (OPt/LDC-NM). The treatment effectively modulated immune cells within the tumor microenvironment by activating the cGAS-STING pathway and inducing immunogenic cell death. This therapy modulated immune cells more effectively than did capecitabine monotherapy, the current standard maintenance chemotherapy for colorectal cancer. The macrophage-modifying effect of oral CAPOX was mediated via the cGAS-STING pathway. This is a newly identified mode of immune cell activation induced by metronomic chemotherapy. Moreover, oral CAPOX synergized with anti-PD-1 antibody (αPD-1) to enhance the T-cell-mediated antitumor immune response. In the CT26. CL25 subcutaneous model, combination therapy achieved a 91 % complete response rate with a confirmed memory effect against the tumor. This combination also altered the immunosuppressive tumor microenvironment in LMCC, which αPD-1 monotherapy could not achieve. Oral CAPOX and αPD-1 combination therapy outperformed the maximum tolerated dose for treating LMCC, suggesting metronomic therapy as a promising strategy.

Prospects of Synergy: Local Interventions and CAR T Cell Therapy in Solid Tumors

Chimeric antigen receptor T cell therapy has been established in the treatment of various B cell malignancies. However, translating this therapeutic effect to treat solid tumors has been challenging because of their inter-tumoral as well as intratumoral heterogeneity and immunosuppressive microenvironment. Local interventions, such as surgery, radiotherapy, local ablation, and locoregional drug delivery, can enhance chimeric antigen receptor T cell therapy in solid tumors by improving tumor infiltration and reducing systemic toxicities. Additionally, ablation and radiotherapy have proven to (re-)activate systemic immune responses via abscopal effects and reprogram the tumor microenvironment on a physical, cellular, and chemical level. This review highlights the potential synergy of the combined approaches to overcome barriers of chimeric antigen receptor T cell therapy and summarizes recent studies that may pave the way for new treatment regimens.

Strategies for overcoming tumour resistance to immunotherapy: harnessing the power of radiation therapy

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; yet their efficacy remains variable across patients. This review delves into the intricate interplay of tumour characteristics contributing to resistance against ICI therapy and suggests that combining with radiotherapy holds promise. Radiation, known for its ability to trigger immunogenic cell death and foster an in situ vaccination effect, may counteract these resistance mechanisms, enhancing ICI response and patient outcomes. However, particularly when delivered at high-dose, it may trigger immunosuppressive mechanism and consequent side-effects. Notably, low-dose radiotherapy (LDRT), with its capacity for tumour reprogramming and reduced side effects, offers the potential for widespread application. Preclinical and clinical studies have shown encouraging results in this regard.

Integrative Approaches in Non-Small Cell Lung Cancer Management: The Role of Radiotherapy

Treatment guidelines for non-small cell lung cancer (NSCLC) vary by several factors including pathological stage, patient candidacy, and goal of treatment. With many therapeutics and even more combinations available in the NSCLC clinician's toolkit, a multitude of questions remain unanswered vis-a-vis treatment optimization. While some studies have begun exploring the interplay among the many pillars of NSCLC treatment-surgical resection, radiotherapy, chemotherapy, and immunotherapy-the vast number of combinations and permutations of different therapy modalities in addition to the modulation of each constituent therapy leaves much to be desired in a field that is otherwise rapidly evolving. Given NSCLC's high incidence and lethality, the experimentation of synergistic benefits that combinatorial treatment may confer presents a ripe target for advancement and increased understanding without the cost and burden of novel drug development. This review introduces, synthesizes, and compares prominent NSCLC therapies, placing emphasis on the interplay among types of therapies and the synergistic benefits some combinatorial therapies have demonstrated over the past several years.

The future of cancer treatment: combining radiotherapy with immunotherapy

Radiotherapy (RT) and immunotherapy (IT) are the powerful tools for cancer treatment which act through the stimulation of immune response, and evidence suggest that combinatorial actions of these therapies may augment each other's beneficial effect through complex synergistic mechanisms. These molecular strategies are designed to target rapidly dividing cancer cells by either directly or indirectly inducing DNA damage. However, when cells detect DNA damage, they activate a range of signalling pathways known as the DNA damage response (DDR) to repair. Strategies are being developed to interfere with the DDR pathways in cancer cells to ensure their damage-induced degeneration. The stability of a cell's genetic material is largely dependent on the efficacy of DNA repair and therefore, an in-depth understanding of DNA damages and repair mechanism(s) in cancer cells is important to develop a promising therapeutic strategies for ensuring the efficacy of damage-induced tumor cell death. In recent years, a wide range of small molecule drugs have been developed which are currently being employed to combat the DNA repair deficiencies associated with tumor cells. Sequential or concurrent use of these two modalities significantly enhances the anti-tumor response, however with a concurrent probability of increased incidence of symptomatic adverse effects. With advent of newer IT agents, and administration of higher doses of radiation per fraction, such effects are more difficult to predict owing to the paucity of randomized trial data. It is well established that anti cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4), anti- Programmed cell death protein 1(PD-1), anti-Programmed cell death one ligand 1 (PD-L1) can be safely administered with RT and many studies have demonstrated survival benefit with such combination for patients with metastatic malignancy. However, the biology of radioimmunotherapy (RT/IT) is still an open area where research need to be focused to determine optimum dosage specially the interaction of the RT/IT pathways to determine optimum dosing schedule. In the current article we have summarised the possible intracellular immunological events that might be triggered when RT and IT modalities are combined with the DDR antagonists and highlighted present clinical practices, outcome, and toxicity profile of this novel treatment strategy.

Spatially Fractionated Radiotherapy in the Era of Immunotherapy

Spatially fractionated radiotherapy (SFRT) includes historical grid therapy approaches but more recently encompasses the controlled introduction of one or more cold dose regions using intensity modulation delivery techniques. The driving hypothesis behind SFRT is that it may allow for an increased immune response that is otherwise suppressed by radiation effects. With both two- and three-dimensional SFRT approaches, SFRT dose distributions typically include multiple dose cold spots or valleys. Despite its unconventional methods, reported clinical experience shows that SFRT can sometimes induce marked tumor regressions, even in patients with large hypoxic tumors. Preclinical models using extreme dose distributions (i.e., half-sparing) have been shown to nevertheless result in full tumor eradications, a more robust immune response, and systemic anti-tumor immunity. SFRT takes advantage of the complementary immunomodulatory features of low- and high-dose radiotherapy to integrate the delivery of both into a single target. Clinical trials using three-dimensional SFRT (i.e., lattice-like dose distributions) have reported both promising tumor and toxicity results, and ongoing clinical trials are investigating synergy between SFRT and immunotherapies.

Altered cancer metabolism and implications for next-generation CAR T-cell therapies

This review critically examines the evolving landscape of chimeric antigen receptor (CAR) T-cell therapy in treating solid tumors, with a particular focus on the metabolic challenges within the tumor microenvironment. CAR T-cell therapy has demonstrated remarkable success in hematologic malignancies, yet its efficacy in solid tumors remains limited. A significant barrier is the hostile milieu of the tumor microenvironment, which impairs CAR T-cell survival and function. This review delves into the metabolic adaptations of cancer cells and their impact on immune cells, highlighting the competition for nutrients and the accumulation of immunosuppressive metabolites. It also explores emerging strategies to enhance CAR T-cell metabolic fitness and persistence, including genetic engineering and metabolic reprogramming. An integrated approach, combining metabolic interventions with CAR T-cell therapy, has the potential to overcome these constraints and improve therapeutic outcomes in solid tumors.

Combining immunotherapy and radiation therapy in gastrointestinal cancers: A review

INTRODUCTION AND PURPOSE

With a significant global impact, treatment of gastrointestinal (GI) cancers still presents with challenges, despite current multimodality approaches in advanced stages. Clinical trials are expanding for checkpoint inhibition (ICI) combined with radiation therapy (RT). This review intends to offer a comprehensive image of the current data regarding the effectiveness of this association, and to reflect on possible directions to further optimize the results.

RESULTS

Several early phase studies demonstrated encouraging potential. However, translating preclinical outcomes to clinical settings proves challenging, especially in immunologically "cold" environments. GI cancers exhibit heterogeneity, requiring tailored approaches based on disease stage and patient characteristics. Current results, though promising, lack the power of evidence to influence the general practice.

CONCLUSIONS

Finding biomarkers for identifying or converting resistant cancers is essential for maximizing responses, moreover in this context strategic RT parameters need to be carefully considered. Our review emphasizes the significance of having a thorough grasp of how immunology, tumour biology, and treatment settings interact in order to propose novel research avenues and efficient GI cancer therapy.

Optimizing GRID and Lattice Spatially Fractionated Radiation Therapy: Innovative Strategies for Radioresistant and Bulky Tumor Management

Treating radioresistant and bulky tumors is challenging due to their inherent resistance to standard therapies and their large size. GRID and lattice spatially fractionated radiation therapy (simply referred to GRID RT and LRT) offer promising techniques to tackle these issues. Both approaches deliver radiation in a grid-like or lattice pattern, creating high-dose peaks surrounded by low-dose valleys. This pattern enables the destruction of significant portions of the tumor while sparing healthy tissue. GRID RT uses a 2-dimensional pattern of high-dose peaks (15-20 Gy), while LRT delivers a three-dimensional array of high-dose vertices (10-20 Gy) spaced 2-5 cm apart. These techniques are beneficial for treating a variety of cancers, including soft tissue sarcomas, osteosarcomas, renal cell carcinoma, melanoma, gastrointestinal stromal tumors (GISTs), pancreatic cancer, glioblastoma, and hepatocellular carcinoma. The specific grid and lattice patterns must be carefully tailored for each cancer type to maximize the peak-to-valley dose ratio while protecting critical organs and minimizing collateral damage. For gynecologic cancers, the treatment plan should align with the international consensus guidelines, incorporating concurrent chemotherapy for optimal outcomes. Despite the challenges of precise dosimetry and patient selection, GRID RT and LRT can be cost-effective using existing radiation equipment, including particle therapy systems, to deliver targeted high-dose radiation peaks. This phased approach of partial high-dose induction radiation therapy with standard fractionated radiation therapy maximizes immune modulation and tumor control while reducing toxicity. Comprehensive treatment plans using these advanced techniques offer a valuable framework for radiation oncologists, ensuring safe and effective delivery of therapy for radioresistant and bulky tumors. Further clinical trials data and standardized guidelines will refine these strategies, helping expand access to innovative cancer treatments.

Analysis of tumor microenvironment alterations in partially responsive rectal cancer patients treated with neoadjuvant chemoradiotherapy

PURPOSE

Achieving a pathologic complete response (pCR) after neoadjuvant chemoradiotherapy (NCRT) remains a challenge for most patients with rectal cancer. Exploring the potential of combining NCRT with immunotherapy or targeted therapy for those achieving a partial response (PR) offers a promising avenue to enhance treatment efficacy. This study investigated the impact of NCRT on the tumor microenvironment in locally advanced rectal cancer (LARC) patients who exhibited a PR.

METHODS

This was a retrospective, observational study. Five patients demonstrating a PR after neoadjuvant treatment for LARC were enrolled in the study. Biopsy samples before treatment and resected specimens after treatment were stained with a panel of 26 antibodies targeting various immune and tumor-related markers, each labeled with distinct metal tags. The labeled samples were then analyzed using the Hyperion imaging system.

RESULTS

Heterogeneity within the tumor microenvironment was observed both before and after NCRT. Notably, tumor-associated macrophages, CD4 + T cells, CD8 + T cells, CD56 + natural killer cells, tumor-associated neutrophils, cytokeratin, and E-cadherin exhibited slight increase in abundance within the tumor microenvironment following treatment (change ratios = 0.78, 0.2, 0.27, 0.32, 0.17, 0.46, 0.32, respectively). Conversely, the number of CD14 + monocytes, CD19 + B cells, CD45 + CD4 + T cells, collagen I, α-smooth muscle actin, vimentin, and β-catenin proteins displayed significant decreases post-treatment (change ratios = 1.73, 1.92, 1.52, 1.25, 1.52, 1.12, 2.66, respectively). Meanwhile, Foxp3 + regulatory cells demonstrated no significant change (change ratio = 0.001).

CONCLUSIONS

NCRT has diverse effects on various components of the tumor microenvironment in LARC patients who achieve a PR after treatment. Leveraging combination therapies may optimize treatment outcomes in this patient population.

Hierarchical cluster analysis and nonlinear mixed-effects modelling for candidate biomarker detection in preclinical models of cancer

BACKGROUND

Preclinical models of cancer can be of translational benefit when assessing how different biomarkers are regulated in response to particular treatments. Detection of molecular biomarkers in preclinical models of cancer is difficult due inter-animal variability in responses, combined with limited accessibility of longitudinal data.

METHODS

Nonlinear mixed-effects modelling (NLME) was used to analyse tumour growth data based on expected tumour growth rates observed 7 days after initial doses (DD7) of Radiotherapy (RT) and Combination of RT with DNA Damage Response Inhibitors (DDRi). Cox regression was performed to confirm an association between DD7 and survival. Hierarchical Cluster Analysis (HCA) was then used to identify candidate biomarkers impacting responses to RT and RT/DDRi and these were validated using NLME.

RESULTS

Cox regression confirmed significant associations between DD7 and survival. HCA of RT treated samples, combined with NLME confirmed significant associations between DD7 and Cluster specific CD8+ Ki67 MFI, as well as DD7 and cluster specific Natural Killer cell density in RT treated mice.

CONCLUSION

Application of NLME, as well as HCA of candidate biomarkers may provide additional avenues to assess the effect of RT in MC38 syngeneic tumour models. Additional studies would need to be conducted to confirm association between DD7 and biomarkers in RT/DDRi treated mice.

Technical feasibility of novel immunostimulatory low-dose radiation for polymetastatic disease with CBCT-based online adaptive and conventional approaches

PURPOSE

A workflow/planning strategy delivering low-dose radiation therapy (LDRT) (1 Gy) to all polymetastatic diseases using conventional planning/delivery (Raystation/Halcyon = "conventional") and the AI-based Ethos online adaptive RT (oART) platform is developed/evaluated.

METHODS

Using retrospective data for ten polymetastatic non-small cell lung cancer patients (5-52 lesions each) with PET/CTs, gross tumor volumes (GTVs) were delineated using PET standardized-uptake-value (SUV) thresholding. A 1 cm uniform expansion of GTVs to account for setup/contour uncertainty and organ motion-generated planning target volumes (PTVs). Dose optimization/calculation used the diagnostic CT from PET/CT. Dosimetric objectives were: Dmin,0.03cc ≥ 95% (acceptable variation (Δ) ≥ 90%), V100% ≥ 95% (Δ ≥ 90%), and D0.03cc ≤ 120% (Δ ≤ 125%). Additionally, online adaptation was simulated. When available, subsequent diagnostic CT was used to represent on-treatment CBCT. Otherwise, the CT from PET/CT used for initial planning was deformed to simulate clinically representative changes.

RESULTS

All initial plans generated, both for Raystation and Ethos, achieved clinical goals within acceptable variation. For all patients, Dmin,0.03cc ≥ 95%, V100% ≥ 95%, and D0.03cc ≤ 120% goals were achieved for 84.8%/99.5%, 97.7%/98.7%, 97.4%/92.3%, in conventional/Ethos plans, respectively. The ratio of 50% isodose volume to PTV volume (R50%), maximum dose at 2 cm from PTV (D2cm), and the ratio of the 100% isodose volume to PTV volume (conformity index) in Raystation/Ethos plans were 7.9/5.9; 102.3%/88.44%; and 0.99/1.01, respectively. In Ethos, online adapted plans maintained PTV coverage whereas scheduled plans often resulted in geographic misses due to changes in tumor size, patient position, and body habitus. The average total duration of the oART workflow was 26:15 (min:sec) ranging from 6:43 to 57:30. The duration of each oART workflow step as a function of a number of targets showed a low correlation coefficient for influencer generation and editing (R2 = 0.04 and 0.02, respectively) and high correlation coefficient for target generation, target editing and plan generation (R2 = 0.68, 0.63 and 0.69, respectively).

CONCLUSIONS

This study demonstrates feasibility of conventional planning/treatment with Raystation/Halcyon and highlights efficiency gains when utilizing semi-automated planning/online-adaptive treatment with Ethos for immunostimulatory LDRT conformally delivered to all sites of polymetastatic disease.

Strategies to reprogram anti-inflammatory macrophages towards pro-inflammatory macrophages to support cancer immunotherapies

Tumor-associated myeloid cells, including macrophages and myeloid-derived suppressor cells, can be highly prevalent in solid tumors and play a significant role in the development of the tumor. Therefore, myeloid cells are being considered potential targets for cancer immunotherapies. In this review, we focused on strategies aimed at targeting tumor-associated macrophages (TAMs). Most strategies were studied preclinically but we also included a limited number of clinical studies based on these strategies. We describe possible underlying mechanisms and discuss future challenges and prospects.

CDK4/6 inhibitor abemaciclib combined with low-dose radiotherapy enhances the anti-tumor immune response to PD-1 blockade by inflaming the tumor microenvironment in Rb-deficient small cell lung cancer

Background

Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have shown significant activity against several solid tumors by reducing the phosphorylation of the canonical CDK4/6 substrate retinoblastoma (Rb) protein, while the anti-tumor effect of CDK4/6 inhibitors on Rb-deficient tumors is not clear. Most small cell lung cancers (SCLCs) are Rb-deficient and show very modest response to immune checkpoint blockade (ICB) despite recent advances in the use of immunotherapy. Here, we aimed to investigate the direct effect of CDK4/6 inhibition on SCLC cells and determine its efficacy in combination therapy for SCLC.

Methods

The immediate impact of CDK4/6 inhibitor abemaciclib on cell cycle, cell viability and apoptosis in four SCLC cell lines was initially checked. To explore the effect of abemaciclib on double-strand DNA (ds-DNA) damage induction and the combination impact of abemaciclib coupled with radiotherapy (RT), western blot, immunofluorescence (IF) and quantitative real-time polymerase chain reaction (qRT-PCR) were performed. An Rb-deficient immunocompetent murine SCLC model was established to evaluate efficacy of abemaciclib in combination therapy. Histological staining, flow cytometry analysis and RNA sequencing were performed to analyze alteration of infiltrating immune cells in tumor microenvironment (TME).

Results

Here, we demonstrated that abemaciclib induced increased ds-DNA damage in Rb-deficient SCLC cells. Combination of abemaciclib and RT induced more cytosolic ds-DNA, and activated the STING pathway synergistically. We further showed that combining low doses of abemaciclib with low-dose RT (LDRT) plus anti-programmed cell death protein-1 (anti-PD-1) antibody substantially potentiated CD8+ T cell infiltration and significantly inhibited tumor growth and prolonged survival in an Rb-deficient immunocompetent murine SCLC model.

Conclusions

Our results define previously uncertain DNA damage-inducing properties of CDK4/6 inhibitor abemaciclib in Rb-deficient SCLCs, and demonstrate that low doses of abemaciclib combined with LDRT inflame the TME and enhance the efficacy of anti-PD-1 immunotherapy in SCLC model, which represents a potential novel therapeutic strategy for SCLC.

Low-dose radiotherapy synergizes with iRGD-antiCD3-modified T cells by facilitating T cell infiltration

BACKGROUND AND PURPOSE

Poor penetration of transferred T cells represents a critical factor impeding the development of adoptive cell therapy in solid tumors. We demonstrated that iRGD-antiCD3 modification promoted both T cell infiltration and activation in our previous work. Interest in low-dose radiotherapy has recently been renewed due to its immuno-stimulatory effects including T cell recruitment. This study aims to explore the synergistic effects between low-dose radiotherapy and iRGD-antiCD3-modified T cells.

MATERIALS AND METHODS

Flow cytometry was performed to assess the expression of iRGD receptors and chemokines. T cell infiltration was evaluated by immunohistofluorescence and in vivo real-time fluorescence imaging and antitumor effects were investigated by in vivo bioluminescence imaging in the gastric cancer peritoneal metastasis mouse model.

RESULTS

We found that 2 Gy irradiation upregulated the expression of all three iRGD receptors and T-cell chemokines. The addition of 2 Gy low-dose irradiation boosted the accumulation and penetration of iRGD-antiCD3-modified T cells in peritoneal tumor nodules. Combining 2 Gy low-dose irradiation with iRGD-antiCD3-modified T cells significantly inhibited tumor growth and prolonged survival in the peritoneal metastasis mouse model with a favorable safety profile.

CONCLUSION

Altogether, we demonstrated that low-dose radiotherapy could improve the antitumor potency of iRGD-antiCD3-modified T cells by promoting T cell infiltration, providing a rationale for exploring low-dose radiotherapy in combination of other adoptive T cell therapies in solid tumors.

Low-dose radiation therapy mobilizes antitumor immunity: New findings and future perspectives

Radiotherapy has unique immunostimulatory and immunosuppressive effects. Although high-dose radiotherapy has been found to have systemic antitumor effects, clinically significant abscopal effects were uncommon on the basis of irradiating single lesion. Low-dose radiation therapy (LDRT) emerges as a novel approach to enhance the antitumor immune response due to its role as a leverage to reshape the tumor immune microenvironment (TIME). In this article, from bench to bedside, we reviewed the possible immunomodulatory role of LDRT on TIME and systemic tumor immune environment, and outlined preclinical evidence and clinical application. We also discussed the current challenges when LDRT is used as a combination therapy, including the optimal dose, fraction, frequency, and combination of drugs. The advantage of low toxicity makes LDRT potential to be applied in multiple lesions to amplify antitumor immune response in polymetastatic disease, and its intersection with other disciplines might also make it a direction for radiotherapy-combined modalities.

The Next Chapter in Immunotherapy and Radiation Combination Therapy: Cancer-Specific Perspectives

Immunotherapeutic agents have revolutionized cancer treatment over the past decade. However, most patients fail to respond to immunotherapy alone. A growing body of preclinical studies highlights the potential for synergy between radiation therapy and immunotherapy, but the outcomes of clinical studies have been mixed. This review summarizes the current state of immunotherapy and radiation combination therapy across cancers, highlighting existing challenges and promising areas for future investigation.

Immunotherapy and Radiotherapy Combinations for Sarcoma

Sarcomas are a heterogeneous group of bone and soft tissue tumors. Survival outcomes for advanced (unresectable or metastatic) disease remain poor, so therapeutic improvements are needed. Radiotherapy plays an integral role in the neoadjuvant and adjuvant treatment of localized disease as well as in the treatment of metastatic disease. Combining radiotherapy with immunotherapy to potentiate immunotherapy has been used in a variety of cancers other than sarcoma, and there is opportunity to further investigate combining immunotherapy with radiotherapy to try to improve outcomes in sarcoma. In this review, we describe the diversity of the tumor immune microenvironments for sarcomas and describe the immunomodulatory effects of radiotherapy. We discuss studies on the timing of radiotherapy relative to immunotherapy and studies on the radiotherapy dose and fractionation regimen to be used in combination with immunotherapy. We describe the impact of radiotherapy on the tumor immune microenvironment. We review completed and ongoing clinical trials combining radiotherapy with immunotherapy for sarcoma and propose future directions for studies combining immunotherapy with radiotherapy in the treatment of sarcoma.

Global research landscape and trends of cancer radiotherapy plus immunotherapy: A bibliometric analysis

The aim of this study was to present current research trends on the synergistic use of radiotherapy and immunotherapy (IRT) for cancer treatment. On March 1, 2023, we conducted a literature search for IRT papers using the Web of Science database. We extracted information and constructed two databases - the Core Database (CD) with 864 papers and Generalized Database (GD) with 6344 papers. A bibliometric analysis was performed to provide insights into the research landscape, to identify emerging trends and highly cited papers and journals in the field of IRT. The CD contained 864 papers that were collectively cited 31,818 times. Prominent journals in this area included the New England Journal of Medicine, Lancet Oncology, and the Journal of Clinical Oncology. Corresponding authors from the USA contributed the most publications. In recent years, lung cancer, melanoma, stereotactic radiotherapy, immune checkpoint inhibitors, and the tumor microenvironment emerged as hot research areas. This bibliometric analysis presented quantitative insights into research concerning IRT and proposed potential avenues for further exploration. Moreover, researchers can use our findings to select appropriate journals for publication or identify prospective collaborators. In summary, this bibliometric analysis provides a comprehensive overview of the historical progression and recent advancements in IRT research that may serve as inspiration for future investigations.

Fluorescence and immune-cell infiltration of nonneoplastic, postbrachytherapy brain tissue in 5-ALA-guided resection of recurrent anaplastic meningioma: illustrative case

BACKGROUND

5-Aminolevulinic acid (5-ALA) fluorescence-guided surgery is a well-established technique for resecting high-grade gliomas. However, its application in meningiomas, especially those previously treated with radiation therapy, remains under investigation.

OBSERVATIONS

A 48-year-old female with recurrent anaplastic meningioma, World Health Organization grade 3, underwent a right-sided craniotomy using off-label 5-ALA as a surgical adjunct. The patient had previously undergone brachytherapy seed implantation (20 × cesium 131) for tumor management. During the surgery, a large fluorescent tumor mass adjacent to the brachytherapy-treated area was resected, and the prior brachytherapy seeds were removed. Interestingly, the surrounding brain tissue in the irradiated area showed robust 5-ALA fluorescence. Pathological examination confirmed that the fluorescent brain tissue was nonneoplastic and associated with lymphocyte and macrophage infiltration.

LESSONS

This case report presents unique 5-ALA fluorescence in nonneoplastic tissue following brachytherapy, which was found during the resection of recurrent anaplastic meningioma. This phenomenon may reflect an intricate interplay among radiation therapy, immune cells, the tumor microenvironment, and 5-ALA metabolism. Given that false-positive findings in fluorescence-guided surgery can lead to unnecessary tissue resection and increased surgical morbidity, further research is warranted to elucidate the mechanisms underlying this phenomenon and its implications for meningioma surgery.

Immune modulatory roles of radioimmunotherapy: biological principles and clinical prospects

Radiation therapy (RT) not only can directly kill tumor cells by causing DNA double-strand break, but also exerts anti-tumor effects through modulating local and systemic immune responses. The immunomodulatory effects of RT are generally considered as a double-edged sword. On the one hand, RT effectively enhances the immunogenicity of tumor cells, triggers type I interferon response, induces immunogenic cell death to activate immune cell function, increases the release of proinflammatory factors, and reshapes the tumor immune microenvironment, thereby positively promoting anti-tumor immune responses. On the other hand, RT stimulates tumor cells to express immunosuppressive cytokines, upregulates the function of inhibitory immune cells, leads to lymphocytopenia and depletion of immune effector cells, and thus negatively suppresses immune responses. Nonetheless, it is notable that RT has promising abscopal effects and may achieve potent synergistic effects, especially when combined with immunotherapy in the daily clinical practice. This systematic review will provide a comprehensive profile of the latest research progress with respect to the immunomodulatory effects of RT, as well as the abscopal effect of radioimmunotherapy combinations, from the perspective of biological basis and clinical practice.

PROTAC Prodrug-Integrated Nanosensitizer for Potentiating Radiation Therapy of Cancer

Radiation therapy (RT) is one of the primary options for clinical cancer therapy, in particular advanced head and neck squamous cell carcinoma (HNSCC). Herein, the crucial role of bromodomain-containing protein 4 (BRD4)-RAD51 associated protein 1 (RAD51AP1) axis in sensitizing RT of HNSCC is revealed. A versatile nanosensitizer (RPB7H) is thus innovatively engineered by integrating a PROteolysis TArgeting Chimeras (PROTAC) prodrug (BPA771) and hafnium dioxide (HfO2 ) nanoparticles to downregulate BRD4-RAD51AP1 pathway and sensitize HNSCC tumor to RT. Upon intravenous administration, the RPB7H nanoparticles selectively accumulate at the tumor tissue and internalize into tumor cells by recognizing neuropilin-1 overexpressed in the tumor mass. HfO2 nanoparticles enhance RT effectiveness by amplifying X-ray deposition, intensifying DNA damage, and boosting oxidative stress. Meanwhile, BPA771 can be activated by RT-induced H2 O2 secretion to degrade BRD4 and inactivate RAD51AP1, thus impeding RT-induced DNA damage repair. This versatile nanosensitizer, combined with X-ray irradiation, effectively regresses HNSCC tumor growth in a mouse model. The findings introduce a PROTAC prodrug-based radiosensitization strategy by targeting the BRD4-RAD51AP1 axis, may offer a promising avenue to augment RT and more effective HNSCC therapy.