MicroRNA-769-3p於覆氧狀況下調降MCF-7細胞株中NDRG1基因表現並促進細胞凋亡

Abstract

Hypoxia and reoxygenation were characteristic features of solid tumors, which resulted in the complex changes in cellular energy charge, oxidant generating systems, and antioxidant defenses. These changes led to an oxidative stress, tissue damage, and activation of stress-response genes. Although, a protective state would be induced to against reactive oxygen species, little was known about the mechanism of protection. Previously, our lab identified that N-myc downstream-regulated gene 1 (NDRG1) was strongly up-regulated under hypoxia and down-regulated after shifting to reoxygenation. Although, it had well known that NDRG1 played a critical role in tumor adaptation to the fluctuation of oxygen concentrations, the regulatory mechanism of NDRG1 remained elusive. In order to investigate the regulatory mechanism, we focused on the regulation between microRNAs (miRNAs) and NDRG1. In this study, breast cancer MCF-7 cells were cultured under 0.5% oxygen for 24 h followed by 24 h of reoxygenation. Cells were harvested at 0, 1, 12, and 24 h during reoxygenation, and examined the miRNA profile by Nanostring nCounter. Forty-three miRNAs had dramatic changes as compared with 0 h upon reoxygenation, with 63% (n=27) of the miRNAs up-regulated upon reoxygenation. In silico analysis revealed that, four miRNAs could perfectly match with 3'UTR sequences of NDRG1. Especially, miR-769-3p decreased the luciferase activity in the greatest extent and led a significant reduction of NDRG1 protein and mRNA upon reoxygenation. The role of miR-769-3p was investigated by over-expressing miR-769-3p in MCF-7 cells. Upon reoxygenation, miR-769-3p significantly inhibited cell proliferation and induced apoptosis. Our results were the first to reveal that NDRG1 could be regulated by miRNAs, and investigate the functions of miR-769-3p.