miR-150 Promotes Human Breast Cancer Growth and Malignant Behavior by Targeting the Pro-Apoptotic Purinergic P2X7 Receptor

The P2X(7) receptor regulates cell growth through mediation of apoptosis. Low level expression of P2X(7) has been linked to cancer development because tumor cells harboring a defective P2X(7) mechanism can escape P2X(7) pro-apoptotic control. microRNAs (miRNAs) function as negative regulators of post-transcriptional gene expression, playing major roles in cellular differentiation, proliferation, and metastasis. In this study, we found that miR-150 was over-expressed in breast cancer cell lines and tissues. In these breast cancer cell lines, blocking the action of miR-150 with inhibitors leads to cell death, while ectopic expression of the miR-150 results in increased cell proliferation. We deploy a microRNA sponge strategy to inhibit miR-150 in vitro, and the result demonstrates that the 39-untranslated region (3'UTR) of P2X(7) receptor contains a highly conserved miR-150-binding motif and its direct interaction with miR-150 down-regulates endogenous P2X(7) protein levels. Furthermore, our findings demonstrate that miR-150 over-expression promotes growth, clonogenicity and reduces apoptosis in breast cancer cells. Meanwhile, these findings can be decapitated in nude mice with breast cancer xenografts. Finally, these observations strengthen our working hypothesis that up-regulation of miR-150 in breast cancer is inversely associated with P2X(7) receptor expression level. Together, these findings establish miR-150 as a novel regulator of P2X(7) and a potential therapeutic target for breast cancer.