journal contribution
posted on 2023-03-30, 22:03 authored by Wen-Jun Wang, Si-Pei Wu, Jia-Bin Liu, Yong-Sheng Shi, Xue Huang, Qian-Bing Zhang, Kai-Tai Yao <p>PDF file - 2674K, A, Western blot analysis of c-MYC, CHK1, and CHK2 in vector control and c-MYC+shCHK1/shCHK2 infected PKH26- NPC CNE2 cells. B. EdU proliferation assay of vector control, c-MYC, and c-MYC+shCHK1/CHK2 infected irradiated (8 Gy) PKH26- NPC CNE2 cells. Quantification of the percentages of cells with comet tails following irradiation at different doses. (Data represent the mean�standard deviation (SD); N = 3; *P=0.000; **P=0.064, with a 20 msec exposure time for image acquisition). C. Alkaline comet assay of vector control, c-MYC, and c-MYC+shCHK1/CHK2 infected irradiated (8 Gy) PKH26+NPC CNE2 cells. Quantification of the percentages of cells with comet tails following irradiation at different doses (Data represent the mean�standard deviation (SD); N = 3; *P=0.000; **P=0.102)</p>
History
ARTICLE ABSTRACT
Radiotherapy is the most successful nonsurgical treatment for nasopharyngeal carcinoma (NPC). Despite this, the prognosis remains poor. Although NPCs initially respond well to a full course of radiation, recurrence is frequent. The cancer stem cell (CSC) hypothesis provides a framework for explaining the discrepancy between the response of NPC to therapy and the poor survival rate. In this study, a stem cell-like subpopulation (PKH26+) was identified in NPC cell lines using a label-retention technique. PKH26+ cells were enriched for clonogenicity, sphere formation, side-population cells, and resistance to radiotherapy. Using genomic approaches, we show that the proto-oncogene c-MYC (MYC) regulates radiotolerance through transcriptional activation of CHK1 (CHEK1) and CHK2 (CHEK2) checkpoint kinases through direct binding to the CHK1 and CHK2 promoters. Overexpression of c-MYC in the PKH26+ subpopulation leads to increased expression of CHK1 and CHK2 and subsequent activation of the DNA-damage-checkpoint response, resulting in radioresistance. Furthermore, loss of CHK1 and CHK2 expression reverses radioresistance in PKH26+ (c-MYC high expression) cells in vitro and in vivo. This study elucidates the role of the c-MYC-CHK1/CHK2 axis in regulating DNA-damage-checkpoint responses and stem cell characteristics in the PKH26+ subpopulation. Furthermore, these data reveal a potential therapeutic application in reversal of radioresistance through inhibition of the c-MYC-CHK1/CHK2 pathway. Cancer Res; 73(3); 1219–31. ©2012 AACR.
