Radiation therapy-induced remodeling of the tumor immune microenvironment.

The tumor immune microenvironment is a determinant of response to cancer immunotherapy and, in many cases, is prognostic for patient survival independently of the type of treatment. Radiation therapy is used in most cancer patients for its direct cytotoxic effects on malignant cells but there is increasing evidence that it also reprograms the tumor immune microenvironment. In this review we discuss the main mechanisms whereby the local inflammatory reaction induced by radiation can reset the cross-talk between the tumor and the immune system. The outcome reflects the balance between immunostimulatory signals that lead to increased tumor antigen presentation and effector T cell activation, and immunosuppressive signals that hinder radiation-induced tumor rejection. The emerging role of small extracellular vesicles (exosomes) in this process will be discussed. Overall, preclinical and early clinical findings support the hypothesis that radiation has the potential to generate an immune-permissive tumor microenvironment. An improved understanding of the pathways involved will enable the design of more effective combinations of radiation and immunotherapy, based on a rationale integration of radiation with other interventions.

Live Imaging to Quantify Cellular Radiosensitivity in Patient-Derived Tumor Organoids.

Radiation therapy (RT) is one of the mainstays of modern clinical cancer management. However, not all cancer types are equally sensitive to irradiation, often (but not always) because of differences in the ability of malignant cells to repair oxidative DNA damage as elicited by ionizing rays. Clonogenic assays have been employed for decades to assess the sensitivity of cultured cancer cells to ionizing irradiation, largely because irradiated cancer cells often die in a delayed manner that is difficult to quantify with short-term flow cytometry- or microscopy-assisted techniques. Unfortunately, clonogenic assays cannot be employed as such for more complex tumor models, such as patient-derived tumor organoids (PDTOs). Indeed, irradiating established PDTOs may not necessarily abrogate their growth as multicellular units, unless their stem-like compartment is completely eradicated. Moreover, irradiating PDTO-derived single-cell suspensions may not properly recapitulate the sensitivity of malignant cells to RT in the context of established PDTOs. Here, we detail an adaptation of conventional clonogenic assays that involves exposure of established PDTOs to ionizing radiation, followed by single-cell dissociation, replating in suitable culture conditions and live imaging. Non-irradiated (control) PDTO-derived stem-like cells reform growing PDTOs with a PDTO-specific efficiency, which is negatively influenced by irradiation in a dose-dependent manner. In these conditions, PDTO-forming efficiency and growth rate can be quantified as a measure of radiosensitivity on time-lapse images collected until control PDTOs achieve a predefined space occupancy.

[Support in addictology: hydrotherapy]. / Accompagnement en addictologie: une pratique de l'hydrothérapie.

Hydrotherapy is a corporal mediation treatment used with patients with addictions by the Mayenne centre for addiction support therapy and prevention. A demonstration of the benefit of hydrotherapy for these patients through a patient's case.

CD40 agonism improves anti-tumor T cell priming induced by the combination of radiation therapy plus CTLA4 inhibition and enhances tumor response.

Radiation therapy (RT) combined with CTLA4 blockers converts immunosuppressed (cold) mouse triple negative breast cancers (TNBCs) into immune infiltrated (hot) lesions. We have recently shown that targeting the myeloid compartment to improve dendritic cell activation is required for most TNBC-bearing mice to achieve superior therapeutic responses to RT plus CTLA4 inhibitors.

Immunotherapy targeting different immune compartments in combination with radiation therapy induces regression of resistant tumors.

Radiation therapy (RT) increases tumor response to CTLA-4 inhibition (CTLA4i) in mice and in some patients, yet deep responses are rare. To identify rational combinations of immunotherapy to improve responses we use models of triple negative breast cancer highly resistant to immunotherapy in female mice. We find that CTLA4i promotes the expansion of CD4+ T helper cells, whereas RT enhances T cell clonality and enriches for CD8+ T cells with an exhausted phenotype. Combination therapy decreases regulatory CD4+ T cells and increases effector memory, early activation and precursor exhausted CD8+ T cells. A combined gene signature comprising these three CD8+ T cell clusters is associated with survival in patients. Here we show that targeting additional immune checkpoints expressed by intratumoral T cells, including PD1, is not effective, whereas CD40 agonist therapy recruits resistant tumors into responding to the combination of RT and CTLA4i, indicating the need to target different immune compartments.

hnRNP-A1 binds to the IRES of MELOE-1 antigen to promote MELOE-1 translation in stressed melanoma cells.

The major challenge in antigen-specific immunotherapy of cancer is to select the most relevant tumor antigens to target. To this aim, understanding their mode of expression by tumor cells is critical. We previously identified a melanoma-specific antigen, melanoma-overexpressed antigen 1 (MELOE-1)-coded for by a long noncoding RNA-whose internal ribosomal entry sequence (IRES)-dependent translation is restricted to tumor cells. This restricted expression is associated with the presence of a broad-specific T-cell repertoire that is involved in tumor immunosurveillance in melanoma patients. In the present work, we explored the translation control of MELOE-1 and provide evidence that heterogeneous nuclear ribonucleoprotein A1 (hnRNP-A1) binds to the MELOE-1 IRES and acts as an IRES trans-activating factor (ITAF) to promote the translation of MELOE-1 in melanoma cells. In addition, we showed that endoplasmic reticulum (ER) stress induced by thapsigargin, which promotes hnRNP-A1 cytoplasmic translocation, enhances MELOE-1 translation and recognition of melanoma cells by a MELOE-1-specific T-cell clone. These findings suggest that pharmacological stimulation of stress pathways may enhance the efficacy of immunotherapies targeting stress-induced tumor antigens such as MELOE-1.

Radiotherapy-exposed CD8+ and CD4+ neoantigens enhance tumor control.

Neoantigens generated by somatic nonsynonymous mutations are key targets of tumor-specific T cells, but only a small number of mutations predicted to be immunogenic are presented by MHC molecules on cancer cells. Vaccination studies in mice and patients have shown that the majority of neoepitopes that elicit T cell responses fail to induce significant antitumor activity, for incompletely understood reasons. We report that radiotherapy upregulates the expression of genes containing immunogenic mutations in a poorly immunogenic mouse model of triple-negative breast cancer. Vaccination with neoepitopes encoded by these genes elicited CD8+ and CD4+ T cells that, whereas ineffective in preventing tumor growth, improved the therapeutic efficacy of radiotherapy. Mechanistically, neoantigen-specific CD8+ T cells preferentially killed irradiated tumor cells. Neoantigen-specific CD4+ T cells were required for the therapeutic efficacy of vaccination and acted by producing Th1 cytokines, killing irradiated tumor cells, and promoting epitope spread. Such a cytotoxic activity relied on the ability of radiation to upregulate class II MHC molecules as well as the death receptors FAS/CD95 and DR5 on the surface of tumor cells. These results provide proof-of-principle evidence that radiotherapy works in concert with neoantigen vaccination to improve tumor control.

Atherosclerosis associated with pericardial effusion in a central bearded dragon (Pogona vitticeps).

Atherosclerosis is a common disease in pet birds, particularly in psittacines, and is frequently found when performing postmortem examinations on adult and old dogs, in which it is mainly associated with endocrine diseases, such as hypothyroidism and diabetes mellitus. However, atherosclerosis is poorly documented in reptiles and consequently poorly understood. In the current case report, atherosclerosis and pericardial effusion were diagnosed in a 2-year-old male central bearded dragon (Pogona vitticeps) based on ultrasound visualization, necropsy, and histologic examination.

IL15 synergizes with radiotherapy to reprogram the tumor immune contexture through a dendritic cell connection.

IL15 is a key cytokine for the activation and survival of anti-tumor effectors CD8+ T and NK cells. Recently published preclinical studies demonstrate that the therapeutic activity of IL15 requires conventional dendritic cells type 1 (cDC1). Radiotherapy cooperates with IL15 by enhancing cDC1 tumor infiltration via interferon type 1 activation.

Radiotherapy Cooperates with IL15 to Induce Antitumor Immune Responses.

Focal radiotherapy can promote cross-presentation of tumor antigens to T cells, but by itself, it is insufficient to induce therapeutically effective T-cell responses. The common gamma-chain cytokine IL15 promotes and sustains the proliferation and effector function of CD8+ T cells but has limited activity against poorly immunogenic tumors that do not elicit significant spontaneous T-cell responses. Here, we show that radiotherapy and subcutaneous IL15 had complementary effects and induced CD8+ T-cell-mediated tumor regression and long-term protective memory responses in two mouse carcinoma models unresponsive to IL15 alone. Mechanistically, radiotherapy-induced IFN type I production and Batf3-dependent conventional dendritic cells type 1 (cDC1) were required for priming of tumor-specific CD8+ T cells and for the therapeutic effect of the combination. IL15 cooperated with radiotherapy to activate and recruit cDC1s to the tumor. IL15 alone and in complex with a hybrid molecule containing the IL15α receptor have been tested in early-phase clinical trials in patients with cancer and demonstrated good tolerability, especially when given subcutaneously. Expansion of natural killer (NK) cells and CD8+ T cells was noted, without clear clinical activity, suggesting further testing of IL15 as a component of a combinatorial treatment with other agents. Our results provide the rationale for testing combinations of IL15 with radiotherapy in the clinic.

Cancer vaccines: designing artificial synthetic long peptides to improve presentation of class I and class II T cell epitopes by dendritic cells.

There is now a consensus that efficient peptide vaccination against cancer requires that peptides should (i) be exclusively presented by professional APC and (ii) stimulate both CD4 and CD8-specific T cell responses. To this aim, in recent trials, patients were vaccinated with pools of synthetic long peptides (SLP) (15-30 aa long) composed of a potential class I epitope(s) elongated at both ends with native antigen sequences to also provide a potential class II epitope(s). Using MELOE-1 as a model antigen, we present an alternative strategy consisting in linking selected class I and class II epitopes with an artificial cathepsin-sensitive linker to improve epitope processing and presentation by DC. We provide evidence that some linker sequences used in our artificial SLPs (aSLPs) could increase up to 100-fold the cross-presentation of class I epitopes to CD8-specific T cell clones when compared to cross-presentation of the corresponding native long peptide. Presentation of class II epitopes were only slightly increased. We confirmed this increased cross-presentation after in vitro stimulation of PBMC from healthy donors with aSLP and assessment of CD8-specific responses and also in vivo following aSLP vaccination of HLA*A0201/HLA-DRB0101 transgenic mice. Finally, we provide some evidence that vaccination with aSLP could inhibit the growth of transplanted tumors in mice. Our data thus support the use of such aSLPs in future cancer vaccination trials to improve anti-tumor CD8 T cell responses and therapeutic efficacy.

Immunotherapies in transplantation and cancer: 22nd NAT meeting/2nd NAT LabEx IGO joint meeting; 1-2 June 2017, Nantes, France.

This 22nd edition of the Nantes Actualités Transplantation annual meeting was co-organized for the second time with the LabEx Immuno-Graft Oncology network. This international meeting was held on 1 and 2 June 2017 in Nantes (western France). The topic of this 2-day meeting was 'Immunotherapies in transplantation and cancer'. This meeting brought together 17 international invited speakers, young researchers and 220 attendees mainly from Europe and North America. It was a unique opportunity to bring together the pioneers and leading immunologists in the fields of transplantation and cancer, focusing on shared mechanisms that control immune responses in organ or bone marrow transplantation and in cancer.

IRES-dependent translation of the long non coding RNA meloe in melanoma cells produces the most immunogenic MELOE antigens.

MELOE-1 and MELOE-2, two highly specific melanoma antigens involved in T cell immunosurveillance are produced by IRES-dependent translation of the long « non coding ¼ and polycistronic RNA, meloe. In the present study, we document the expression of an additional ORF, MELOE-3, located in the 5' region of meloe. Data from in vitro translation experiments and transfection of melanoma cells with bicistronic vectors documented that MELOE-3 is exclusively translated by the classical cap-dependent pathway. Using a sensitive tandem mass spectrometry technique, we detected the presence of MELOE-3 in total lysates of both melanoma cells and normal melanocytes. This contrasts with our previous observation of the melanoma-restricted expression of MELOE-1 and MELOE-2. Furthermore, in vitro stimulation of PBMC from 6 healthy donors with overlapping peptides from MELOE-1 or MELOE-3 revealed a very scarce MELOE-3 specific T cell repertoire as compared to the abundant repertoire observed against MELOE-1. The poor immunogenicity of MELOE-3 and its expression in melanocytes is consistent with an immune tolerance towards a physiologically expressed protein. In contrast, melanoma-restricted expression of IRES-dependent MELOE-1 may explain its high immunogenicity. In conclusion, within the MELOE family, IRES-dependent antigens represent the best T cell targets for immunotherapy of melanoma.

The melanoma antigens MELOE-1 and MELOE-2 are translated from a bona fide polycistronic mRNA containing functional IRES sequences.

Our previous studies on melanoma antigens identified two new polypeptides, named MELOE-1 and MELOE-2, that are involved in immunosurveillance. Intriguingly, these antigens are coded by distinct open reading frames (ORF) of the meloe mRNA which is significantly expressed only in the melanocytic lineage. In addition, MELOE-1 and -2 specific T cell clones recognized melanoma cells but very poorly normal melanocytes suggesting differential translation of meloe in normal vs tumor cells. This prompted us to elucidate the mechanisms of translation of these antigens in melanoma cells. We first demonstrated that no splicing event or cryptic promoter could generate shorter meloe transcripts containing only one of the two ORFs. Triggering meloe RNA degradation with a siRNA close to the ORF coding for MELOE-2 abrogated expression of both MELOE-1 and MELOE-2, thus confirming that the two ORFs are always associated. Next we showed, in a bicistronic reporter system, that IRES activities could be detected upstream of MELOE-1 and MELOE-2 and finally confirmed their translation from full length meloe cDNA in melanoma cells with eGFP constructs. In conclusion, meloe is a polycistronic mRNA that generates both MELOE-1 and MELOE-2 antigens through IRES-dependent translation in melanoma cells and that may explain their tumor specificity.