PTGS2 and neoplasm: In a recent study conducted in animal model with knock out cPLA2, COX-1, COX-2, and mPGES-1 have exhibited suppression in tumor development, while rat model will knock out PGD synthase resulted in proliferation of tumor cells (Takaku et al., 2000; Tiano et al., 2002; Kawamori et al., 2005).