PTGS2 and breast carcinoma: Studies with celecoxib, a selective COX-2 inhibitor, in an HER2/neu-induced breast cancer model in transgenic mice have revealed that celecoxib reduced the incidence of mammary tumours and lowered mammary PGE2 levels by 50% (Howe et al, 2002; Lanza-Jacoby et al, 2003).