PTGS2 and neoplasm: Although the precise mechanisms by which NSAIDs, and COX-2 selective inhibitors in particular, modulate tumour growth have not been elucidated, it appears that cell cycle arrest and apoptosis may play a critical role (Chang and Weng, 2001; Grosch et al, 2001; Cheng et al, 2002; Joe et al, 2002; Kundu et al, 2002; Toyoshima et al, 2002).