OBJECTIVETo study the expression of the cyclooxygenase-2 (COX-2) gene in breast cancer in contrast to that of normal breast tissues or benign breast tumors and its significance in the carcinogenesis and development of breast cancer.

METHODSWith reference to the expression of the beta-actin gene, the expression of COX-2 mRNA was examined in cancerous tissues and adjacent normal breast tissue from 30 patients and benign breast tumors from 15 patients by reverse transcription-polymerase chain reaction (RT-PCR). Quantitation of relative band densities was performed using densitometry-scanning software. Estrogen receptors of 30 breast cancers were investigated by immunohistochemistry.

RESULTSEnhanced expression of COX-2 was observed in ninety percent of cancers tissue with a range of 0.05 - 0.91 (median 0.53). Rare cases showed significant COX-2 expression in normal breast tissues with a range of 0 - 0.09 (median 0). In part of benign breast tumors, COX-2 expressions were obviously elevated with a range of 0 - 0.68 (median 0.07). The difference of expression of COX-2 mRNA among breast cancers, normal breast tissues, mastopathy or fibroadenomas was significant (rank-sum test, P < 0.05) and the difference of that between estrogen receptor negative and positive was also observed (rank-sum test, P < 0.01).

CONCLUSIONThe level of expression of COX-2 mRNA is obviously higher in breast cancer tissue than in normal breast tissue, mastopathy or fibroadenomas. The expression of COX-2 in hormone-dependent breast cancer is higher than that in hormone-independent breast cancer. The overexpression of COX-2 may play a crucial role in the carcinogenesis and development of cancer in patients with breast carcinoma.