miR-449a, a novel tumor suppressor, is deregulated in various malignancies, including prostate cancer. Overexpression of miR-449a induces cell cycle arrest, apoptosis, and senescence, but its role in response to ionizing radiation and underlying molecular mechanism are still unknown. Here, we report that miR-449a enhances radiation-induced G2/M phase arrest and apoptosis through modulating pRb/E2F1 and sensitizes prostate cancer cells to X-ray radiation. In wild-type Rb PC-3 cells, overexpression of miR-449a enhances radiation-induced G2/M arrest and apoptosis and promotes the sensitivity to X-ray radiation. While mutant Rb DU-145 cells are resistant to the X-ray radiation despite in the presence of miR-449a. The cell cycle distribution of DU-145 cells is not significantly altered by miR-449a in the response to ionizing radiation. Furthermore, elevated miR-449a downregulates cell cycle regulator CDC25A and oncogene HDAC1. By targeting genes involved in controlling pRb/E2F1 activity, miR-449a regulates cell cycle progression and apoptosis and consequently enhances the radiosensitivity of PC-3 cells. Thus, miR-449a, as a miRNA component of the Rb pathway, promotes the radiosensitivity of PC-3 cells through regulating pRb/E2F1.
Keywords: Apoptosis; G2/M arrest; Prostate cancer; Radiosensitivity; miR-449a; pRb/E2F1.