Many studies have demonstrated that microRNAs (miRNAs) may play vital roles in the development of breast cancer. The aim of this study was to examine the expression levels of miR-497 in human breast cancer and investigate whether its potential roles involved targeting Bcl-2. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to examine the expression levels of miR-497 in 48 breast cancer specimens and six breast cancer cell lines. MTT assay, colony formation assay, and flow cytometry were conducted to explore the potential functions of miR-497 in human MDA-MB-231 breast cancer cells. Correlation analysis and dual-luciferase reporter assay were performed to validate whether Bcl-2 was a direct target of miR-497. The effects of modulating miR-497 on endogenous levels of Bcl-2 were subsequently confirmed via qRT-PCR and western blot. MTT assay, colony formation assay and flow cytometry were used to indicate the roles of endogenous Bcl-2 in breast cancer cells. miR-497 expression levels were significantly decreased in human breast cancer specimens and cell lines (P<0.05). Overexpression of miR-497 in breast cancer cells suppressed cell proliferation and induced apoptosis. Correlation analysis indicated that miR-497 was highly inversely correlated with Bcl-2 protein expression in breast cancer specimens. Dual-luciferase reporter assays confirmed that Bcl-2 was a direct target of miR-497. qRT-PCR and western blot showed that miR-497 negatively regulated Bcl-2 protein expression but had no impact on mRNA expression of Bcl-2. Knockdown of Bcl-2 expression in MDA-MB-231 cells significantly suppressed cell proliferation and promoted apoptosis. Our study suggests that miR-497 may act as a breast cancer suppressor through negative regulation of Bcl-2 protein expression at the posttranscriptional levels. Therefore, targeting miR-497 may provide a novel strategy for the diagnosis and treatment of patients with this lethal disease.
Keywords: Bcl-2; apoptosis; breast cancer; miR-497.