Regulatory effect of miR-155 on the proliferation, apoptosis and expression of breast cancer resistance protein

CHEN Shuru; HUANG Yukang; WU Chucheng; CHEN Di; FANG Qin; PENG Weiqiang

Abstract：Objective To explore the regulatory effect of microRNA?155 (miR?155) on the proliferation, apoptosis and ex?pression of breast cancer resistance protein. Methods The real?time quantitative PCR (qRT?PCR) was employed to measure the miR?155 level in MCF?7 cells and human normal breast epithelium cells. The MCF?7 cells were randomly assigned into four groups according to the experiment protocol: control group, blank group, inhibition group (transfection with miR?155 inhibitor) and over?expression group (transfection with miR?155 mimics). The qRT?PCR was used to detect the transfection effect at 24, 48, 72 and 96 h after trans?fection. Methyl thiazolyl tetrazolium (MTT) assay was used to assess the proliferation ability at 24, 48, 72 and 96 h after transfection. The apoptosis rate was evaluated at 24 and 48 h after transfection by PI/ Annexin V double staining with flow cytometry. Western blot?ting was used to measure the expression levels of breast cancer resistance protein (BRCP), P?glycoprotein (P?gp) and multidrug re?sistance associated protein 1 (MRP1) protein. Results There was higher level of miR?155 in MCF?7 cells versus human normal breast epithelium cells (P<0?? 05). Transfection with miR?155 inhibitor or mimics could reduce or increase the level of miR?155 in time de?pendent manner in MCF?7 cells ( P< 0?? 05); In comparison with control group, the rates of proliferation and expression levels of BRCP, P?gp and MRP1 decreased in inhibition group but increased in over?expression group (P<0?? 05). The apoptosis rate increased in inhibition group but decreased in over?expression group(P<0?? 05). Conclusion There is higher level of miR?155 in MCF?7 cells. Down?regulation of miR?155 presents an inhibitory effect on the proliferation and expression of drug resistance related protein along with the induction of apoptosis.