PTGS2 and neoplasm: COX-2 derived PGE-2 promotes tumor growth, enhancement of cellular proliferation, promotion of angiogenesis, stimulation of invasion/mobility, suppression of immune responses and inhibition of programmed cell death by binding to four types G protein-coupled receptors termed EP1, EP2, EP3, and EP4 (E-series prostanoid receptors ) [23, 24], that activate different signal transduction pathways.