[Over-expression of circNR4A1/Hsa-circ-0026352 inhibits proliferation and induces apoptosis in MCF-7 cells]

Objective To investigate the expression of circNR4A1/Hsa-circ-0026352 in breast tumor tissue, peripheral blood, cell lines and its effect on the proliferation and apoptosis of MCF-7 breast cancer cells. Methods Using circRNA microarray, different expression of human circRNAs was found out between the breast cancer tissues and adjacent normal tissues. The expression of circNR4A1 in breast cancer tissues, peripheral blood and breast cancer cell lines including MCF-7, HCC-1937, MDA-MB-231, T-47D and MCF-10A were detected by quantitative real-time PCR (qRT-PCR). Circular RNA interactome software and KEGG software were used to predict its target miRNA and bio-function. The circNR4A1 over-expression vector was constructed and transfected into MCF-7 cells. The effect of circNR4A1 on the proliferation of MCF-7 cells was detected by CCK-8 assay and clone formation assay. The cell apoptosis and cell cycle distribution were analyzed by flow cytometry and Hoechst 33258 stainning. The qRT-PCR was performed to detect the mRNA expression levels of MEK/ERK signal pathway genes (K-RAS, MEK, ERK) and apoptosis-related genes (Bcl2, BAX, BAD, caspase-3). Western blotting was used to detect the expression of MEK, ERK, Bcl2, BAD and caspase-3 proteins. Results The expression of circNR4A1(Hsa-circ-0026352) was lower in breast cancer tissues, peripheral blood and breast cancer cell lines than in adjacent normal tissues, healthy individuals' peripheral blood and human breast epithelial cells. Over-expression of circNR4A1 in MCF-7 cells inhibited the cell proliferation, promoted cell apoptosis and blocked the cell cycle in G1/S phase. The mRNA and protein expression of MEK, ERK, Bcl2 were significantly depressed, while the expression of BAD, caspase-3 were enhanced in the MCF-7 cells over-expressing circNR4A1. Conclusion The expression of circNR4A1/Hsa-circ-0026352 is lower in breast cancer tissues, peripheral blood and breast cancer cells. Over-expression of circNR4A1 can inhibit cell proliferation and induce cell apoptosis in MCF-7 cells.