1. Genome-wide RNAi Screening Identifies RFC4 as a Factor That Mediates Radioresistance in Colorectal Cancer by Facilitating Nonhomologous End Joining Repair
- Author
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Zhen Hai Lu, Meng Jie Yang, Gao Yuan Wang, Jianhong Peng, Zi Yang Wang, Wenlin Huang, Yuan Meng, Ranyi Liu, Qi Hua Peng, Xue Cen Wang, Xin Yue, Rong Xin Zhang, Ting Yu Liu, Li Yuan Le, and Zhizhong Pan
- Subjects
Male ,0301 basic medicine ,Cancer Research ,DNA End-Joining Repair ,Ku80 ,DNA Repair ,DNA repair ,DNA damage ,Colorectal cancer ,Mice, Nude ,Apoptosis ,Radiation Tolerance ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Radioresistance ,Biomarkers, Tumor ,Tumor Cells, Cultured ,medicine ,Animals ,Humans ,RNA, Small Interfering ,Replication Protein C ,Ku Autoantigen ,Cell Proliferation ,Mice, Inbred BALB C ,Ku70 ,Genome, Human ,business.industry ,Cancer ,Chemoradiotherapy, Adjuvant ,Middle Aged ,Prognosis ,medicine.disease ,Xenograft Model Antitumor Assays ,Neoadjuvant Therapy ,High-Throughput Screening Assays ,Gene Expression Regulation, Neoplastic ,Survival Rate ,030104 developmental biology ,Oncology ,030220 oncology & carcinogenesis ,Cancer research ,Female ,RNA Interference ,Colorectal Neoplasms ,business ,Chemoradiotherapy - Abstract
Purpose: Neoadjuvant chemoradiotherapy (neoCRT) is a standard treatment for locally advanced rectal cancer (LARC); however, resistance to chemoradiotherapy is one of the main obstacles to improving treatment outcomes. The goal of this study was to identify factors involved in the radioresistance of colorectal cancer and to clarify the underlying mechanisms. Experimental Design: A genome-wide RNAi screen was used to search for candidate radioresistance genes. After RFC4 knockdown or overexpression, colorectal cancer cells exposed to X-rays both in vitro and in a mouse model were assayed for DNA damage, cytotoxicity, and apoptosis. Moreover, the regulatory effects and mechanisms of RFC4 in DNA repair were investigated in vitro. Finally, the relationships between RFC4 expression and clinical parameters and outcomes were investigated in 145 patients with LARC receiving neoCRT. Results: RFC4, NCAPH, SYNE3, LDLRAD2, NHP2, and FICD were identified as potential candidate radioresistance genes. RFC4 protected colorectal cancer cells from X-ray–induced DNA damage and apoptosis in vitro and in vivo. Mechanistically, RFC4 promoted nonhomologous end joining (NHEJ)-mediated DNA repair by interacting with Ku70/Ku80 but did not affect homologous recombination–mediated repair. Higher RFC4 expression in cancer tissue was associated with weaker tumor regression and poorer prognosis in patients with LARC treated with neoCRT, which likely resulted from the effect of RFC4 on radioresistance, not chemoresistance. Conclusions: RFC4 was identified as a radioresistance factor that promotes NHEJ-mediated DNA repair in colorectal cancer cells. In addition, the expression level of RFC4 predicted radiotherapy responsiveness and the outcome of neoadjuvant radiotherapy in patients with LARC.
- Published
- 2019