Significance of c-kit and COX-2 expression in breast tissue

Background : The proto-oncogene c-kit encodes a transmembrane tyrosine kinase growth factor receptor. Studies have shown that c-kit is highly expressed in normal breast epithelium, but expression is decreased in primary breast cancer. Cyclooxygenase-2 (COX-2) is an inducible enzyme that converts arachidonic acid to prostaglandins. Expression of COX-2 has been reported in malignant tumors including breast cancer. We evaluated the expression of c-kit and COX-2 in benign and malignant lesions of the breast to assess the roles of these proteins in cancer initiation and progression. Methods : We characterized 20 benign lesions, 20 intraductal carcinomas and 70 invasive breast carcinomas. Immunohistochemical staining for c-kit and COX-2 was performed. Results : Expression of c-kit was detected in 75% of the benign breast lesions, 40% of the intraductal carcinomas and 10% of the invasive carcinomas. COX-2 expression was observed in 80% of the benign lesions, 70% of the intraductal carcinomas and 52% of the invasive carcinomas. Expression of c-kit was significantly correlated with tumor size (p=0.02). COX-2 expression was significantly correlated with negative expression of estrogen receptor and progesterone receptor (p=0.02, p=0.04), Her-2/neu expression (p=0.008) and the high proliferation index (p=0.0002). Conclusions : Our results suggest that c-kit and COX-2 might be involved in malignant transformation of the mammary epithelium and tumor progression. It is suggested that c-kit and COX-2 can be used as predictive markers and therapeutic targets.