Cyclooxygenase 2 (COX2) expression is associated with poor outcome in ER-negative, but not ER-positive, breast cancer.

Inflammation and hormonal signalling induce cyclooxygenase 2 (COX2) expression in solid tumours. COX2 expression is linked to neovascularization and tumour growth. HER2 modulates colorectal cancer COX2 expression. We investigated interactions between COX2 and HER1-4 in breast cancer. COX2 expression was localized to epithelial cells with 21.2% of cases expressing higher levels than normal epithelium. Elevated COX2 expression was not associated with size, grade, high Nottingham prognostic index (NPI) or oestrogen receptor (ER) negativity. No association was observed between COX2 and HER1-4 expression. High COX2 expression was associated with reduced disease-free survival (P = 0.03) and disease-related survival in ER-negative (P = 0.046) but not ER-positive disease (P = 0.835). HER1, 2, 3 and 4 are not associated with high breast tumour COX2 expression. COX2 is frequently expressed in breast carcinoma cells and adjacent epithelium. COX2 may be an important factor in promoting tumour progression in ER-negative tumours and a potential drug target in breast tumours.