Downregulation of BCL2 by miRNAs augments drug induced apoptosis: Combined computational and experimental approach

Abstract

A number of anti-cancer strategies aim at targeting the mitochondrial apoptotic machinery to induce tumour cell death. Mitochondria play a key role as death amplifiers by releasing apoptogenic factors from the mitochondrial inter-membrane space into the cytosol. BCL2 proteins are known for their ability to regulate both mitochondrial physiology and cell death and their deregulated expression often renders cancer cells insensitive to apoptosis inducing anticancer drugs. Recently a few microRNAs, the novel class of gene regulators, have been identified to regulate expressions of some members of BCL2 family. In the present study we have combined computational and experimental approaches to identify miRNAs which can regulate the anti-apoptotic protein BCL2. Here we report that miR-195, miR-24-2 and miR-365-2 act as negative regulators of BCL2 through direct binding to their respective binding sites in the 3′ UTR of human BCL2 gene. Ectopic expression of miR-195, miR-24-2 and miR-365-2 individually led to significant reduction of BCL2 protein levels. Additionally, we found that over expression of these miRNAs induced dissipation of mitochondrial membrane potential and release of cytochrome c from mitochondria into the cytosol. Furthermore, we demonstrated that over expression of these miRNAs not only caused an increase in apoptosis but also augmented the apoptotic effect of etoposide in breast cancer MCF7 cells. This data not only shows the apoptotic nature of miR-195, miR-24-2 and miR-365-2 but also highlights the therapeutic potential of these miRNAs.