Prostaglandin E2 regulates tumor angiogenesis in prostate cancer

In cancer management, the cyclooxygenase (COX)-targeted approach has shown great promise in anticancer therapeutics. However, the use of COX-2 inhibitors has side effects and health hazards; thus, targeting its major metabolite prostaglandin E-2 (PGE(2))-mediated signaling pathway might be a rational approach for the next generation of cancer management. Recent studies on several in vitro and in vivo models have revealed that elevated expression of COX-2 correlates with prostate tumor growth and angiogenesis. In this study, we have shown the in-depth molecular mechanism and the PGE(2) activation of the epidermal growth factor receptor and beta 3 integrin through E prostanoid 2 (EP2)-mediated and EP4-mediated pathways, which lead to activator protein-1 (AP-1) activation. Moreover, PGE(2) also induces activating transcription factor-4 (ATF-4) activation and stimulates crosstalk between ATF-4 and AP-1, which is unidirectional toward AP-1, which leads to the increased expressions of urokinase-type plasminogen activator and vascular endothelial growth factor and, eventually, regulates prostate tumor cell motility. In vivo Matrigel angiogenesis assay data revealed that PGE(2) induces angiogenesis through EP2 and EP4. Human prostate cancer specimen analysis also supported our in vitro and in vivo studies. Our data suggest that targeting PGE2 signaling pathway (i.e., blocking EP2 and EP4 receptors) might be a rational therapeutic approach for overcoming the side effects of COX-2 inhibitors and that this might be a novel strategy for the next generation of prostate cancer management.