Essential Role of NADPH Oxidase-Dependent Reactive Oxygen Species Generation in Regulating MicroRNA-21 Expression and Function in Prostate Cancer

Abstract Aims: Oncogenic microRNAs (miRs) promote tumor growth and invasiveness. One of these, miR-21, contributes to carcinogenesis in prostate and other cancers. In the present study, we tested the hypothesis that NADPH oxidase-dependent reactive oxygen species (ROS) regulate the expression and function of miR-21 and its target proteins, maspin and programmed cell death 4 (PDCD4), in prostate cancer cells. Results: The highly aggressive androgen receptor negative PC-3M-MM2 prostate cancer cells demonstrated high expression of miR-21 and p47phox (an essential subunit of NADPH oxidase). Using loss-of-function strategy, we showed that transfection of PC-3M-MM2 cells with anti-miR-21- and p47phox siRNA (si-p47phox) led to reduced expression of miR-21 with concurrent increase in maspin and PDCD4, and decreased the invasiveness of the cells. Tail-vein injections of anti-miR-21- and si-p47phox-transfected PC-3M-MM2 cells in severe combined immunodeficient mice reduced lung metastases. Clinical samples from pat...