OBJECTIVETo investigate the expression of COX-2 and BCL-2 in transitional mucosa adjacent to rectal carcinoma, and to determine whether precursor event exists in the transitional mucosa.

METHODSMucin histochemical method (HID/AB) was used to determine the distal mucosa 2 cm away from rectal carcinoma in 54 patients with rectal cancer. Immunohistochemical method was employed to detect the expression of BCL-2 and COX-2 in the rectal cancer specimen, transitional mucosa (TM), non-transitional mucosa (NTM), and 20 cases of normal rectal mucosa. Student's t-test and Chi-square test were preformed.

RESULTSNineteen patients with positive TM were found. COX-2 expression was identified in 81.5% of cancer tissue, 21.1% of TM, 17.1% of NTM, and 10.0% in normal mucosa. BCL-2 protein was found in 77.8% of cancer tissue, 21.1% of TM, 22.9% of NTM, and 5.0% of normal mucosa. The expressions of COX-2 and BCL-2 in TM were significantly different from tumor tissue[(0.737±0.895) versus (3.519±1.998), and (0.632±0.955) versus (2.833±1.756), all P<0.01]. However, there were no significant differences between TM and NTM or normal mucosa.

CONCLUSIONSExpressions of COX-2 and BCL-2 are non-specific in the transitional mucosa at the distal rectum. Evidence is not available in TM being precursor lesion.