RESUMO
<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>With 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.</p><p><b>RESULTS</b>Enhanced 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).</p><p><b>CONCLUSION</b>The 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.</p>