Abstract 1650: Whole-genome RNAi screen identified BCAS1 as a novel modifier of non-small cell lung carcinoma radioresistance

Abstract Introduction: Despite optimal chemotherapy, radiotherapy and/or surgery, non-small cell lung carcinoma (NSCLC) remains the leading cause of cancer-related death in the United States. Therefore, there is a need for agents, such as radiosensitizers, that can improve the efficacy of current therapies. Using a whole-genome shRNA screen, we sought to identify and characterize novel gene products that may be involved in NSCLC radioresistance. We hypothesize that these proteins may represent novel targets for NSCLC radiosensitization. Materials and Methods: A whole-genome pooled retroviral shRNA screen was performed using the Hannon-Elledge library of 74,705 distinct shRNAs directed against over 18,000 genes, to identify gene knockdowns that showed cytotoxicity only in cells treated with fractionated radiation given daily Monday-Friday. To confirm targets identified in the whole-genome screen, we treated A549 and NCI-H460 NSCLC cells with siRNAs targeted against the genes of interest and assessed cell viability following irradiation using the CellTiter-Glo assay and clonogenic survival assays. Results: We identified six novel genes (BCAS1, c7orf24, CDC45L, KIAA0101, TCN1 and TNC) whose knockdown sensitized NSCLC cells to radiation. Of the six genes, siRNA knockdown of BCAS1 showed the most consistent increases in sensitivity to ionizing radiation. Analysis of cell viability following radiation revealed that BCAS1 knockdown resulted in a 50% additional decrease in cell viability in A549 and NCI-H460 cells following 8 and 4 Gy of ionizing radiation, respectively. We confirmed these results by clonogenic survival assays. To assess for tumor-specific expression in NSCLC, we compared expression data between matched normal tissue and NSCLC biopsy samples and found that BCAS1 is substantially more highly expressed in tumor tissues. Examination of affinity capture-mass spectroscopy data suggested that BCAS1 interacts with RUVBL2, a RuvB-like AAA ATPase, which has known functions in DNA damage and repair. Conclusions: BCAS1 emerged from a whole-genome RNAi screen as a potential target for improving the efficacy of radiotherapy in NSCLC. We demonstrated that BCAS1 is overexpressed in tumor tissues compared to normal lung, and that its knockdown consistently sensitizes NSCLC cell lines to radiation, validating the screen hit. Ongoing work suggests that BCAS1 may modulate DNA damage repair. Further studies to understand the mechanism by which BCAS1 is involved in radioresistance are necessary. Citation Format: Colin O’Leary, Peter Deraska, Alan D’Andrea, David Kozono. Whole-genome RNAi screen identified BCAS1 as a novel modifier of non-small cell lung carcinoma radioresistance. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1650.