The treatment of CRC patients with selective COX2 inhibitors should be less effective, because increased COX2 expression is present in the earlier phase of colorectal carcinogenesis (Eberhart et al, 1994; Yona and Arber, 2006), but the exact molecular biological reasons in the background of this phenomenon are not clarified yet. The gene discussed is PTGS2; the disease is colorectal carcinoma.