Abstract
PURPOSE: Aromatase catalyzes the conversion of androgens to estrogens; its high expression in breast cancers may be responsible for the local high levels of estrogen and may promote tumor growth and progression; however, the clinical importance of aromatase remains unclear and needs to be further researched. METHODS: By immunochemistry, we detected aromatase, MMP2 and MMP9 immunoreactivity in 244 axillary lymph node negative breast cancers. RESULTS: Aromatase immunoreactivity was positively associated with co-expression of MMP2 and MMP9 (MMP2/9) in the estrogen receptor and/or progestin receptor- (ER/PR) positive patients (P < 0.05), but not in the ER and PR negative patients (P > 0.05); aromatase status positively associated with tumor size in the postmenopausal patients (P < 0.05) but not in the premenopausal patients (P > 0.05). The proportional hazards assumption was violated for aromatase status (global test, P < 0.05), and aromatase was an unfavorable prognostic factor for disease-free survival (DFS) (P = 0.04) in multivariate analysis of time-dependent non-proportional Cox regression. In the ER/PR-positive patients, positive aromatase staining was significantly associated with decreased overall survival (OS) (P = 0.04), but there was no such association in the ER and PR negative patients (P > 0.05). CONCLUSIONS: Our study suggested that local estrogen production by aromatase plays important roles in the growth and invasiveness of breast cancer; tumor aromatase status may be indicative of breast cancer prognosis in some patients.