MicroRNA-34 suppresses proliferation of human ovarian cancer cells by triggering autophagy and apoptosis and inhibits cell invasion by targeting Notch 1.

Ovarian cancer is one the prevalent cancers in women and is responsible for 5% of all the cancer related mortalities in women. Owing to late diagnosis, frequent relapses, side effects of chemotherapy, development of drug resistance, there is pressing need to screen out novel and effective treatment options. Accumulating evidences suggest that miRNAs may prove essential therapeutic targets for the treatment of cancer. This study was designed to investigate the role and therapeutic potential of miR-34 in ovarian cancer. It was found that miR-34 is significantly downregulated in ovarian cancer cell lines. Overexpression of miR-34 causes significant decrease in the proliferation of OVACAR-3 ovarian cancer cells via activation of apoptosis and autophagy. The miR-34 overexpression was concomitant with upsurge of apoptosis related proteins (Bax) and the autophagy associated protein (LC3 II and p62). TargetScan analysis showed Notch 1 to be the main target of miR-34 in OVACAR-3 cells which was further validated by luciferase reporter assay. The qRT-PCR results showed Notch 1 to be 3.2-4.1 fold higher in the ovarian cancer cell lines relative to the non-cancerous cells. Nonetheless, miR-34 overexpression in OVACAR-3 cells resulted in the post-transcriptional suppression of Notch 1 expression. Silencing of Notch 1 also caused inhibition of OVACAR-3 cell proliferation via induction of apoptosis and autophagy. Overexpression of Notch 1 could partially rescue the effects of miR-34 overexpression on the proliferation of OVACAR-3 cells. Moreover, overexpression of miR-34 causes significant inhibition of the invasion of the OVACAR-3 cells. The findings of the present study indicate the tumor suppressive role of miR-34 in ovarian cancer and may therefore prove to be a potential therapeutic target.