In this study, we want to study: 1) whether miR-21 regulates hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) expression; 2) whether miR-21 regulates tumor angiogenesis in prostate cancer cells; 3) the signaling molecules and pathways that are regulated by miR-21 for mediating HIF-1 and VEGF expression; and 4) whether HIF-1 is the miR-21 target for regulating tumor angiogenesis. The gene discussed is HIF1A; the disease is prostate cancer.