PTGS2 and colorectal neoplasm: In contrast, Lin and Schumaf reported the protective effect of COX2 rs689466 and rs5273 polymorphisms against colorectal neoplasms (26, 33), and some other studies reported an increased risk of CRC carriers of some COX2 polymorphisms such as rs689466 and rs20417 (31, 32, 35, 43).