A phase I study of the combination of atezolizumab, tiragolumab, and stereotactic body radiation therapy in patients with metastatic multiorgan cancer.

BACKGROUND: Immunotherapy targeting the PD-1/PD-L1 pathway is a standard of care in a number of metastatic malignancies, but less than a fifth of patients are expected to respond to ICIs (Immune Checkpoint Inhibitors). In a clinical trial, combining the anti-TIGIT (T cell immunoreceptor with Ig and ITIM domains) Mab (monoclonal antibody) tiragolumab with atezolizumab improved outcomes in non-small cell lung cancer. In preclinical models, SBRT (Stereotactic Body Radiation Therapy) could increase expression levels of the inhibitory co-receptors TIGIT and PD-L1. We aim to assess the combination of tiragolumab with atezolizumab and SBRT in metastatic, previously treated by ICIs, non-small cell lung cancer, head and neck cancer, bladder cancer, and renal cell cancer. METHODS: This phase I study (ClinicalTrials.gov NCT05259319) will assess the efficacy and safety of the combination of atezolizumab with tiragolumab and stereotactic body radiation therapy in patients with histologically proven metastatic non-small cell lung cancer, renal cell cancer, bladder cancer, and head and neck cancer previously treated. First part: 2 different schedules of SBRT in association with a fixed dose of atezolizumab and tiragolumab will be investigated only with metastatic non-small cell lung cancer patients (cohort 1). The expansion cohorts phase will be a multicentric, open-label study at the recommended scheme of administration and enroll additional patients with metastatic bladder cancer, renal cell cancer, and head and neck cancer (cohort 2, 3 and 4). Patients will be treated until disease progression, unacceptable toxicity, intercurrent conditions that preclude continuation of treatment, or patient refusal in the absence of progression or intolerance. The primary endpoint of the first phase is the safety of the combination in a sequential or concomitant scheme and to determine the expansion cohorts phase recommended scheme of administration. The primary endpoint of phase II is to evaluate the efficacy of tiragolumab + atezolizumab + SBRT in terms of 6-month PFS (Progression-Free Survival). Ancillary analyses will be performed with peripheral and intratumoral immune biomarker assessments. TRIAL REGISTRATION: This study is registered on ClinicalTrials.gov: NCT05259319, since February 28th, 2022.

Cisplatin-based chemoradiation decreases telomerase-specific CD4 TH1 response but increases immune suppressive cells in peripheral blood.

BACKGROUND: The synergistic effect of chemoradiation (CRT) has been previously demonstrated in several cancer types. Here, we investigated the systemic immune effects of CRT in patients with lung or head and neck cancer. MATERIALS AND METHODS: Peripheral blood mononuclear cells were collected at baseline and 1 month after treatment from blood samples of 29 patients treated with cisplatin-based chemoradiotherapy for lung or head and neck cancer. Circulating anti-tumor Th1 response was assessed by the ELISpot assay using a mixture of human leucocyte antigen (HLA) class II restricted peptides derived from telomerase (TERT). Phenotyping of circulating immunosuppressive cells (Treg and MDSC) was performed by flow cytometry. RESULTS: A significant increase of circulating Treg was observed in 60% of patients after CRT The mean rate of Treg was 3.1% versus 4.9% at baseline and after CRT respectively, p = 0.0015). However, there was a no significant increase of MDSC rate after CRT. In contrast, a decrease of tumor-specific Th1 response was documented in 7 out of 10 evaluated patients. We found high frequency of pre-existing tumor-specific Th1 response among patients with objective response after CRT compared to non-responders. CONCLUSION: Cisplatin-based CRT promotes expansion of Treg and decrease of circulating anti-tumor Th1 response in peripheral blood. The balance towards a sustained specific anti-tumor T-cell response appears to be associated with response to CRT.

Clinical and dosimetric study of radiotherapy for glioblastoma: three-dimensional conformal radiotherapy versus intensity-modulated radiotherapy.

BACKGROUND AND PURPOSE: We aimed to compare three-dimensional conformal radiotherapy (3D-CRT) with intensity-modulated radiotherapy (IMRT) for the treatment of glioblastoma. MATERIALS AND METHODS: Retrospective study of 220 patients with glioblastoma, treated with 3D-CRT or IMRT, with or without surgery. Dosimetric parameters as well as clinical and survival data for the two techniques were analyzed and compared. RESULTS: The median conformity index was 1.53 (range 0-2.69) for 3D-CRT and 1.25 (range 0.97-2.01) for IMRT, p < 10-4. The median homogeneity index was 0.10 (range 0.03-0.32) for 3D-CRT and 0.07 (range 0.03-0.18) for IMRT, p < 10-4. There were significantly fewer acute grade 1 and 2 neurological toxicities in the IMRT group especially for edema (1.3 versus 12.4%, p = 0.017), concentration disorders (6.6 versus 19.9%, p = 0.003) and consciousness disorders (2.6 versus 13.2%, p = 0.002) although IMRT patients had a significantly worse pre-treatment neurological status than 3D-CRT patients. Median survival was 16.0 months (range 11.9-17.8) for IMRT and 13.4 months (range 11.7-15.7) for 3D-CRT patients (p = 0.542). CONCLUSION: IMRT improved target conformity and reduced neurological toxicities for patients with glioblastomas.

Characterization of Natural Killer cells infiltrating irradiated murine tumors through flow cytometry.

The radiation-induced immune response is increasingly well documented. However, some aspects remain unclear, notably the role of Natural Killer (NK) cells, a subgroup of innate lymphoid cells involved in the antitumor response, in the response to RT. It therefore seems necessary to better characterize NK cells infiltrating irradiated tumors in order to better understand the mechanisms of action of RT, enabling its subsequent optimization and combination with other immunomodulatory treatments. A key technology for studying intratumoral immune cells is flow cytometry, which can simultaneously quantify and analyze the phenotype of numerous cells. Here, we propose a method for phenotyping intratumoral NK cells through flow cytometry in mice bearing colorectal tumors treated with radiotherapy. This procedure can also be used to study the radiation-induced NK cell response in a wide range of solid tumors.

Targeting two radiation-induced immunosuppressive pathways to improve the efficacy of normofractionated radiation therapy in a preclinical colorectal cancer model.

PURPOSE: We have previously demonstrated in a murine colorectal cancer model that normofractionated RT (normoRT: 18 × 2 Gy) induced MDSC infiltration and PD-L1 expression, while hypofractionated RT (hypoRT: 3 × 8 Gy) induced Treg. Here, we wanted to assess whether the association of normoRT with treatments that target two radiation-induced immunosuppressive pathways (MDSC and PD-L1) could improve tumor control. MATERIALS AND METHODS: Subcutaneous tumors were induced using colon tumor cells (CT26) in immunocompetent mice (BALB/c) and were treated with RT alone (18 × 2 Gy or 3 × 8 Gy), or concomitantly with 5-Fluorouracil (5FU) (10 mg/kg) to deplete MDSC, and/or anti-PD-L1 (10 mg/kg). We assessed the impact of these combinations on tumor growth and immune cells infiltration by flow cytometry. In addition, we performed tumor rechallenge experiments and IFN-γ ELISpots to study the long-term memory response. RESULTS: Even though tumor growth was significantly delayed in the RT + 5FU compared to 5FU and untreated groups (p < .05), there was no significant difference between RT + 5FU (CRT) and RT alone. The rate of MDSC increased significantly 1 week after the end of normoRT (8.09% ± 1.03%, p < .05) and decreased with the addition of 5FU (3.39% ± 0.69%, p < .05). PD-L1 expressing tumor cells were increased after treatment. Adding anti-PD-L1 significantly delayed tumor growth, achieved the highest complete response rate, and induced a long-lasting protective specific anti-tumor immunity. CONCLUSIONS: These results tend to demonstrate the interest of inhibiting two radiation-induced immunosuppressive mechanisms. In patients, the combination of normoRT with 5FU is already the standard of care in locally advanced rectal cancer. Adding an anti-PD-L1 to this treatment could show promising results.

Supramolecular Heterodimer Peptides Assembly for Nanoparticles Functionalization.

Nanoparticle (NP) surface functionalization with proteins, including monoclonal antibodies (mAbs), mAb fragments, and various peptides, has emerged as a promising strategy to enhance tumor targeting specificity and immune cell interaction. However, these methods often rely on complex chemistry and suffer from batch-dependent outcomes, primarily due to limited control over the protein orientation and quantity on NP surfaces. To address these challenges, a novel approach based on the supramolecular assembly of two peptides is presented to create a heterotetramer displaying VHHs on NP surfaces. This approach effectively targets both tumor-associated antigens (TAAs) and immune cell-associated antigens. In vitro experiments showcase its versatility, as various NP types are biofunctionalized, including liposomes, PLGA NPs, and ultrasmall silica-based NPs, and the VHHs targeting of known TAAs (HER2 for breast cancer, CD38 for multiple myeloma), and an immune cell antigen (NKG2D for natural killer (NK) cells) is evaluated. In in vivo studies using a HER2+ breast cancer mouse model, the approach demonstrates enhanced tumor uptake, retention, and penetration compared to the behavior of nontargeted analogs, affirming its potential for diverse applications.

Subcutaneous Administration of a Zwitterionic Chitosan-Based Hydrogel for Controlled Spatiotemporal Release of Monoclonal Antibodies.

Subcutaneous (SC) administration of monoclonal antibodies (mAbs) is a proven strategy for improving therapeutic outcomes and patient compliance. The current FDA-/EMA-approved enzymatic approach, utilizing recombinant human hyaluronidase (rHuPH20) to enhance mAbs SC delivery, involves degrading the extracellular matrix's hyaluronate to increase tissue permeability. However, this method lacks tunable release properties, requiring individual optimization for each mAb. Seeking alternatives, physical polysaccharide hydrogels emerge as promising candidates due to their tunable physicochemical and biodegradability features. Unfortunately, none have demonstrated simultaneous biocompatibility, biodegradability, and controlled release properties for large proteins (≥150 kDa) after SC delivery in clinical settings. Here, a novel two-component hydrogel comprising chitosan and chitosan@DOTAGA is introduced that can be seamlessly mixed with sterile mAbs formulations initially designed for intravenous (IV) administration, repurposing them as novel tunable SC formulations. Validated in mice and nonhuman primates (NHPs) with various mAbs, including trastuzumab and rituximab, the hydrogel exhibited biodegradability and biocompatibility features. Pharmacokinetic studies in both species demonstrated tunable controlled release, surpassing the capabilities of rHuPH20, with comparable parameters to the rHuPH20+mAbs formulation. These findings signify the potential for rapid translation to human applications, opening avenues for the clinical development of this novel SC biosimilar formulation.

Radiation therapy-activated nanoparticle and immunotherapy: The next milestone in oncology?

Radiotherapy (RT) is a fundamental treatment at the locoregional or oligometastatic stages of cancer. In various tumors, RT effects may be optimized using synergistic combinations that enhance tumor response. Innovative strategies have been designed that explore the radiation mechanisms, at the physical, chemical and biological levels, to propose precision RT approaches. They consist in combining RT with immunotherapy to revert radiation immunosuppressive effects or to enhance radiation-induced immune defenses against the tumor to favor immunogenic cell death. Radiotherapy-activated nanoparticles are another innovation. By increasing radiation response in situ, nanoparticles improve tumor control locally, and can trigger systemic immune reactions that may be exploited to improve the systemic efficacy of RT. Strong clinical evidence of improved outcomes is now available for combinations of RT and immunotherapy on one hand and RT and nanoparticles on the other hand. The triple combination of RT, immunotherapy and nanoparticles is promising in terms of tolerance, local and systemic anti-tumor control. Yet, significant challenges remain to unravel the complexity of the multiscale mechanisms underlying response to this combination and their associated parameters. Such parameters include patient characteristics, tumor bulk and histology, radiation technique, energy, dose, fractionation, immunotherapy targets and predictive biomarkers, nanoparticle type, size, delivery (intratumoral/intravenous), distribution. The temporal combination is another critical parameter. The mechanisms of response of the combinatorial approaches are reviewed, with a focus on underlying mechanisms based on preclinical, translational and clinical studies. Opportunities for translation of current understanding into precision RT trials combined with immunotherapy and nanoparticles are also discussed.

Combining radiotherapy and NK cell-based therapies: The time has come.

Natural killer (NK) cells are innate lymphoid cells that play an essential role in the anti-tumor response through immunosurveillance, multiple mechanisms of cytotoxicity and the synthesis of cytokines modulating the immune tumor microenvironment (TME). After the dramatic advances in immunotherapy targeting T cells including the success of checkpoint inhibitors or autologous chimeric antigen receptor (CAR) expressing T cells in clinical practice, NK cells have gained growing interest for the development of new therapies. Although NK cells have shown promising responses in leukemia patients, the effects of NK-targeted therapies are currently limited in the treatment of solid tumors. Thus, radiotherapy could provide a valuable solution to improve treatments targeting NK cells. Indeed, ionizing radiations represent a powerful immuno-modulator that can either induce a pro-inflammatory and anti-tumor TME, or conversely lead to immunosuppression of effector immune cells in favor of tumor growth and therapeutic escape, depending on how it is delivered and tumor models. However, the effects of ionizing radiation on NK cells are only partially understood. Therefore, we review the effects of radiotherapy on the NK cell-mediated anti-tumor response, and propose potential strategies to reinvigorate NK cells by combining radiotherapy with NK cell-targeted therapies.

Novel platform for subcutaneous tumor irradiation in mice.

Preclinical development of cancer treatments including radiotherapy (RT) is now crucial to optimize all the treatment aspects for a better efficacy and to help clinicians to build new clinical trials based on robust results. More and more teams use preclinical irradiators to deliver radiotherapy in a comparable way to clinical treatments (image-based RT, arc therapy, stereotactic body RT…). In daily conditions, users usually need to develop easy to use techniques (for applicator technicians for example), allowing to treat many mice per day with a high level of reproducibility. Besides, the best compromise between a satisfying dose coverage to the tumor and nearby organs at risk sparing has to be ensured. We describe here new a home-made immobilization device to irradiate grafted tumors, as well as the different steps to develop the treatment planning and generate an easy procedure to routinely irradiate subcutaneous tumor model.

Chemotherapy to potentiate the radiation-induced immune response.

Chemoradiation (CRT) is a conventional therapy used in local cancers, especially when they are locally advanced. Studies have shown that CRT induces strong anti-tumor responses involving several immune effects in pre-clinical models and humans. In this review, we have described the various immune effects involved in CRT efficacy. Indeed, effects such as immunological cell death, activation and maturation of antigen-presenting cells, and activation of an adaptive anti-tumor immune response are attributed to CRT. As often described in other therapies, various immunosuppressive mechanisms mediated, in particular, by Treg and myeloid populations may reduce the CRT efficacy. We have therefore discussed the relevance of combining CRT with other therapies to potentiate the CRT-induced anti-tumor effects.

Predicting acute severe toxicity for head and neck squamous cell carcinomas by combining dosimetry with a radiosensitivity biomarker: a pilot study.

OBJECTIVE: Radiotherapy (RT) against head and neck squamous cell carcinomas (HNSCC) may lead to severe toxicity in 30-40% of patients. The normal tissue complication probability (NTCP) models, based on dosimetric data refined the normal tissue dose/volume tolerance guidelines. In parallel, the radiation-induced nucleoshuttling (RIANS) of the Ataxia-Telangiectasia Mutated protein (pATM) is a predictive approach of individual intrinsic radiosensitivity. Here, we combined NTCP with RADIODTECT©, a blood assay derived from the RIANS model, to predict RT toxicity in HNSCC patients. METHODS: RADIODTECT© cutoff values (i.e. 57.8 ng/mL for grade⩾2 toxicity and 46 ng/mL for grade⩾3 toxicity) have been previously assessed. Validation was performed on a prospective cohort of 36 HNSCC patients treated with postoperative RT. Toxicity was graded with the Common Terminology Criteria for Adverse Events (CTCAE) scale and two criteria were considered: grade⩾2 oral mucositis (OM2), grade⩾3 mucositis (OM3) and grade⩾2 dysphagia (DY2), grade⩾3 dysphagia (DY3). pATM quantification was assessed in lymphocytes of HNSCC patients. The discrimination power of the pATM assay was evaluated through the Area Under the Receiver Operator Characteristics Curve (AUC-ROC). Two previously described NTCP models were considered, including the dose to the oral cavity and the mean dose to the parotid glands (OM2 and OM3) and the dose to the oral cavity, to the larynx and the volume of pharyngeal constrictor muscles (DY2 and DY3). RESULTS: Combining NTCP models with RADIODTECT© blood test improved the AUC-ROC. Considering the prediction of mucositis, AUC-ROCNTCP+RADIODTECT©=0.80 was for OM2, and AUC-ROCNTCP+RADIODTECT©=0.78 for OM3. Considering the prediction of acute dysphagia, AUC-ROCNTCP+RADIODTECT©=0.71 for DY2 and for DY3. CONCLUSIONS: Combining NTCP models with a radiosensitivity biomarker might significantly improve the prediction of toxicities for HNSCC patients.

Challenges in glioblastoma research: focus on the tumor microenvironment.

Glioblastoma (GBM) is the most deadly type of malignant brain tumor, despite extensive molecular analyses of GBM cells. In recent years, the tumor microenvironment (TME) has been recognized as an important player and therapeutic target in GBM. However, there is a need for a full and integrated understanding of the different cellular and molecular components involved in the GBM TME and their interactions for the development of more efficient therapies. In this review, we provide a comprehensive report of the GBM TME, which assembles the contributions of physicians and translational researchers working on brain tumor pathology and therapy in France. We propose a holistic view of the subject by delineating the specific features of the GBM TME at the cellular, molecular, and therapeutic levels.

Treatment related factors associated with the risk of breast radio-induced-sarcoma.

BACKGROUND AND PURPOSE: The Radiation Induced Sarcoma (RIS) is a rare but serious adverse event following radiotherapy (RT). Current RT techniques are more precise, but irradiate a larger volume at a low dose. This study aimed to describe radiation characteristics in a large series of patients suffering from RIS. MATERIALS AND METHODS: Patient-representative voxel-based anthropomorphic phantoms were used to reconstruct patient-specific RT fields for 125 patients diagnosed with RIS after primary breast cancer. For each patient, the location of the RIS onset site was determined and transferred onto the phantom as a contour. Using a treatment planning system (TPS), the dose distribution on the RIS in the phantom was calculated. RESULTS: The mean dose (Dmean) received in the area where RIS subsequently developed was 47.8 ± 11.6 Gy. The median dose in the zones where RIS later developed ranged from 11 Gy to 58.8 Gy. The median time from RT to RIS development was 8 years (range 2-32 years). Analysis for predictors of time to radiation-induced sarcoma development highlighted a significant impact of age of patient during the RT whereas in multivariable analysis chemotherapy and hormonotherapy for primary breast cancer were not associated with a significant difference in time to diagnosis of RIS. CONCLUSIONS: This study highlights that the dose received by the tissue in which the RIS developed was almost 47 Gy. These results are encouraging for the use of new RT techniques increasing volumes receiving low doses, without fear of an excess of RIS over the next 10 years.

About the Influence of PEG Spacers on the Cytotoxicity of Titanate Nanotubes-Docetaxel Nanohybrids against a Prostate Cancer Cell Line.

The association between chemotherapeutic drugs and metal oxide nanoparticles has sparked a rapidly growing interest in cancer nanomedicine. The elaboration of new engineered docetaxel (DTX)-nanocarriers based on titanate nanotubes (TiONts) was reported. The idea was to maintain the drug inside cancer cells and avoid multidrug resistance mechanisms, which often limit drug efficacy by decreasing their intracellular concentrations in tumor cells. HS-PEGn-COOH (PEG: polyethylene glycol, n = 3000, 5000, 10,000) was conjugated, in an organic medium by covalent linkages, on TiONts surface. This study aimed to investigate the influence of different PEG derivatives chain lengths on the TiONts colloidal stability, on the PEGn density and conformation, as well as on the DTX biological activity in a prostate cancer model (human PC-3 prostate adenocarcinoma cells). In vitro tests highlighted significant cytotoxicities of the drug after loading DTX on PEGn-modified TiONts (TiONts-PEGn-DTX). Higher grafting densities for shorter PEGylated chains were most favorable on DTX cytotoxicity by promoting both colloidal stability in biological media and cells internalization. This promising strategy involves a better understanding of nanohybrid engineering, particularly on the PEGylated chain length influence, and can thus become a potent tool in nanomedicine to fight against cancer.

Anti-PD-1/Anti-PD-L1 Drugs and Radiation Therapy: Combinations and Optimization Strategies.

Immune checkpoint inhibitors have been associated with long-term complete responses leading to improved overall survival in several cancer types. However, these novel immunotherapies are only effective in a small proportion of patients, and therapeutic resistance represents a major limitation in clinical practice. As with chemotherapy, there is substantial evidence that radiation therapy promotes anti-tumor immune responses that can enhance systemic responses to immune checkpoint inhibitors. In this review, we discuss the main preclinical and clinical evidence on strategies that can lead to an enhanced response to PD-1/PD-L1 blockade in combination with radiation therapy. We focused on central issues in optimizing radiation therapy, such as the optimal dose and fractionation for improving the therapeutic ratio, as well as the impact on immune and clinical responses of dose rate, target volume, lymph nodes irradiation, and type of radiation particle. We explored the addition of a third immunomodulatory agent to the combination such as other checkpoint inhibitors, chemotherapy, and treatment targeting the tumor microenvironment components. The strategies described in this review provide a lead for future clinical trials.

Impact of proton therapy on antitumor immune response.

Radiotherapy delivered using photons induces an immune response that leads to modulation of the tumor microenvironment. Clinical studies are ongoing to evaluate immune checkpoint inhibitors in association with photon radiotherapy. At present, there is no publication on the radio-induced immune response after proton therapy. Balb/c mice bearing subcutaneous CT26 colon tumors were irradiated by a single fraction of 16.4 Gy using a proton beam extracted from a TR24 cyclotron. RNA sequencing analysis was assessed at 3 days post-treatment. Proton therapy immune response was monitored by flow cytometry using several panels (lymphoid, myeloid cells, lymphoid cytokines) at 7 and 14 days post-irradiation. RNA-Seq functional profiling identified a large number of GO categories linked to "immune response" and "interferon signaling". Immunomonitoring evaluation showed induced tumor infiltration by immune cells. This is the first study showing the effect of proton therapy on immune response. These interesting results provide a sound basis to assess the efficacy of a combination of proton therapy and immune checkpoint inhibitors.

Proof of Concept of a Binary Blood Assay for Predicting Radiosensitivity.

Radiation therapy (RT), either alone or in combination with surgery and/or chemotherapy is a keystone of cancers treatment. Early toxicity is common, sometimes leading to discontinuation of treatment. Recent studies stressed the role of the phosphorylated ATM (pATM) protein in RT-toxicity genesis and its ability in predicting individual radiosensitivity (IRS) in fibroblasts. Here we assessed the reliability of the pATM quantification in lymphocytes to predict IRS. A first retrospective study was performed on 150 blood lymphocytes of patients with several cancer types. Patients were divided into 2 groups, according to the grade of experienced toxicity. The global quantity of pATM molecules was assessed by ELISA on lymphocytes to determine the best threshold value. Then, the binary assay was assessed on a validation cohort of 36 patients with head and neck cancers. The quantity of pATM molecules in each sample of the training cohort was found in agreement with the observed Common Terminology Criteria for Adverse Events (CTCAE) grades with an AUC = 0.71 alone and of 0.77 combined to chemotherapy information. In the validation cohort, the same test was conducted with the following performances: sensitivity = 0.84, specificity = 0.54, AUC = 0.70 and 0.72 combined to chemotherapy. This study provides the basis of an easy to perform assay for clinical use.

Chemoradiation triggers antitumor Th1 and tissue resident memory-polarized immune responses to improve immune checkpoint inhibitors therapy.

BACKGROUND: Multiple synergistic combination approaches with cancer drugs are developed to overcome primary resistance to immunotherapy; however, the mechanistic rationale to combine chemoradiotherapy (CRT) with immune checkpoint inhibitors remains elusive. METHODS: This study described the immunological landscape of tumor microenvironment (TME) exposed to CRT. Tumor samples from patients with rectal cancer (n=43) treated with neoadjuvant CRT or radiotherapy were analyzed by nanostring and immunohistochemistry. Studies in mice were performed using three syngeneic tumors (TC1, CT26 and MC38). Tumor-bearing mice were treated either with platinum-based CRT, radiotherapy or chemotherapy. Anti-CTLA-4 and/or anti-Programmed Cell Death Receptor-1 (PD-1) therapy was used in combination with CRT. The therapy-exposed TME was screened by RNA sequencing and flow cytometry and tumor-infiltrating T lymphocyte functionality was evaluated by interferon (IFN)-γ ELIspot and intracellular cytokine staining. RESULTS: Front-to-front comparison analysis revealed the synergistic effect of CRT to establish a highly inflamed and Th1-polarized immune signature in the TME of patients and mice. In both settings, CRT-exposed TMEs were highly enriched in newly-infiltrated tumor-specific CD8+ T cells as well as tissue resident memory CD103+CD8+ T cells. In mice, CD8 T cells were involved in the antitumor response mediated by CRT and were primed by CRT-activated CD103+ dendritic cells. In the three tumor models, we showed that concurrent combination of CRT with a dual CTLA-4 and PD-1 blockade was required to achieve an optimal antitumor effect and to establish a broad and long-lasting protective antitumor T cell immunity. CONCLUSIONS: Our results highlight the ability of CRT to stimulate strong antitumor T-cell-mediated immunity and tissue resident memory T activation in TME, to foster immune checkpoint inhibitors action. These findings have implications in clinic for the design clinical trials combining chemoradiation with immunotherapy.