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Macrophage-mediated abscopal effects of radiation therapy

ABSTRACT: Radiation therapy is a mainstay of cancer treatment, with more than 50% of all cancer patients receiving radiation during the course of their disease. Tumor irradiation can activate both innate and adaptive immune responses, and these responses can be pro- or anti-tumor growth . These observations have led to the search for antitumor approaches combining radiotherapy and specific immunotherapies, most commonly strategies promoting the systemic activation of T cells. Thus far, however, many cancer patients still suffer from local recurrence and/or untreatable metastatic disease after radiotherapy. Here we combine radiotherapy with activation of macrophage-mediated phagocytosis via blockade of the ?don?t-eat-me? cell surface molecule CD47 in small-cell lung cancer (SCLC), a highly metastatic form of lung cancer for which treatment options remain limited. We found that irradiation of SCLC cells in culture results in the secretion of inflammatory cytokines that results in increased migration and phagocytosis by macrophages. In vivo, CD47 blockade potently enhances the local antitumor effects of radiation therapy in murine and human pre-clinical models of SCLC. Strikingly, CD47 blockade also stimulates abscopal antitumor effects inhibiting the growth of non-irradiated SCLC tumors in mice receiving radiation. Similar abscopal antitumor effects were observed in colon cancer and lymphoma models. Surprisingly, these abscopal effects are completely independent of T cells but require macrophages that migrate into the non-irradiated tumor sites in response to inflammatory signals mediated by radiation and are locally activated by CD47 blockade to eliminate cancer cells. The systemic activation of antitumor macrophages following radiotherapy and CD47 blockade may be particularly important in cancer patients who suffer from metastatic disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE156106 | GEO | 2022/09/29

REPOSITORIES: GEO

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Project description:Radiotherapy has a critical role in the treatment of small cell lung cancer (SCLC). Effectiveness of radiation in SCLC remains limited as resistance results from defects in apoptosis. In the current study, we investigated whether using a Bcl-2/Bcl-XL inhibitor S44563 can enhance radiosensitivity of SCLC cells in vitro and in vivo. In vitro studies confirmed that S44563 induce apoptosis in SCLC cells by inducing hallmarks of apoptosis (cleaved caspase-3, sub-G1 fraction induction and induction of the mitochondrial caspase activation pathway). S44563 markedly enhanced sensitivity of H146 cells and H69 cells to radiation in clonogenic assay. In addition, the combination S44563 and cisplatin-based chemo-radiation showed a dramatic tumor growth delay and increased overall survival in mouse xenograft models. In vitro experiments demonstrated a greater induction of apoptosis (sub-G1 fraction and cleaved caspase-3) with the combination as well as in vivo caspase-3 immunostaining. This positive interaction between S44563 and radiation was greater when S44563 was given after the completion of the radiation, which may be explained by the radiation-induced over expression of anti-apoptotic proteins (Bcl-2 and Bcl-XL) through the NF-?B pathway activation. Taken together, these data underline the critical role of sequence administration of targeted therapies with conventional therapies. SCLC cells which survive to IR highly rely on the induction of anti apoptotic proteins in part through NF- ?B activation for their survival yielding to the concept of 'contextual oncogene addiction' to the Bcl-2/Bcl-XL pathway providing rational for targeting survival pathways to potentiate IR. For transcriptome analysis, 106 cells were seeded in T25 flasks, allowed to growth for 24 h, and then left untreated or treated with 2 Gy radiation. After 24 hours, cells were harvested, lysed for the extraction of RNA, and processed to analyze gene expression.The design of this study consists to 6 hybridizations in dual color with Agilent Human Genome 4x44K (design 014850). The reference is always the untreated condition.

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Macrophage-mediated abscopal effects of radiation therapy

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