Ma, WenhuiYu, JiangQi, XiaolongLiang, LiZhang, YanDing, YiLin, XiaoshanLi, GuoxinDing, Yanqing2015-11-032015Ma, Wenhui, Jiang Yu, Xiaolong Qi, Li Liang, Yan Zhang, Yi Ding, Xiaoshan Lin, Guoxin Li, and Yanqing Ding. 2015. “Radiation-induced microrna-622 causes radioresistance in colorectal cancer cells by down-regulating Rb.” Oncotarget 6 (18): 15984-15994.1949-2553http://nrs.harvard.edu/urn-3:HUL.InstRepos:23473913The standard treatment for patients with locally advanced rectal cancer is preoperative 5-fluorouracil-based chemoradiotherapy followed by total mesorectal excision. However, tumor response to standard dose radiation varies. In this study, we found that miR-622 was increased significantly in ionizing radiation-treated colorectal cancer (CRC) cells compared to the cells cultured with irradiated medium, and persisted stably in surviving cells treated with continuous low-dose radiation. Overexpression of miR-622 induced the radioresistance in vitro. In addition, miR-622 inhibited Rb expression by directly targeting RB1-3′UTR. Overexpression of Rb reversed miR-622-induced radioresistance in vitro. In response to ionizing radiation, the Rb-E2F1-P/CAF complex activated proapoptotic genes. Importantly, miR-622 was highly expressed in tumors of rectal cancer patients with non-regression after standard dose radiotherapy. In conclusion, miR-622 overexpressing cells are induced or selected by radiotherapy, causing in turn radioresistance and poor response to further therapy. MiR-622 is a potential biomarker of responders for radiotherapy and a potential therapeutic target.en-USradiosensitivitymicroRNA-622apoptosisRB1RbJournal Article2015-11-03