Artemis (DCLRE1C) Acts as a Target to Enhance Radiotherapy Response in Triple-Negative Breast Cancer

Lack of canonical biomarkers and strategies to target radioresistance contribute to poor patient outcomes in triple-negative breast cancer (TNBC). Identifying and targeting novel radioresistance genes will benefit in enhancing radiotherapy response and treatment outcome in TNBC patients. A genome-wide CRISPR screen was performed to identify radioresistance genes in the MDA-MB-231 TNBC cell line. An in vitro clonogenic assay was used to assess antipro-liferative effects of Artemis knockout or pharmacologic inhibition of Artemis, either alone or in combination with RT. Tumor doubling time and animal survival were assessed using an in vivo xenograft model. RNA-Seq analysis was performed to identify genes and pathways deregulated under Artemis knockout conditions, both alone and in combina-tion with RT. Cellular senescence was evaluated using a -galactosidase assay. Our CRISPR screen identified Artemis as a top hit in RT-treated MDA-MB-231 cells, whose depletion led to radiosensitization in TNBC. Artemis knockout significantly reduced cell proliferation and enhanced the antiproliferative effects of RT in vitro. Compared to mice bearing control MDA-MB-231 xenografts, Artemis knockout exhibited prolonged survival that was further enhanced with RT. Bulk RNA-Sequencing indicated that the antipro-liferative and radiosensitization effects of Artemis depletion were mediated by activation of cellular senescence which was confirmed with a -galactosidase assay. Taken together, our results highlight the critical role of Artemis in TNBC cell proliferation and response to radiation. Our findings identify Artemis as a potential biomarker in-dicative of sensitivity to radiation and a putative target that could be inhibited to enhance the efficacy of RT in TNBC.