The purpose of this study is to investigate the role of carbonic anhydrase IX (CAIX) expression in predicting the response to epirubicin and disease-free survival (DFS) in breast cancer patients enrolled in a single institution trial of primary anthracycline and tamoxifen therapy. CAIX expression was assessed in 183 patients with T2–4 N0–1 breast cancer enrolled in a randomized trial comparing four cycles of single agent epirubicin versus epirubicin + tamoxifen as primary systemic treatment. All patients received postoperatively four cycles of the four weekly i.v. cyclophosphamide, methotrexate, 5-fluorouracil regimen. Patients with estrogen receptor (ER)-positive primary tumors received 5 years of adjuvant tamoxifen. Pretreatment, p53 (P = 0.007), c-erbB2 (P < 0.01), and Ki67 (P = 0.02) were directly associated with CAIX expression, while bcl2 (P < 0.000) and ER (P = 0.000) and progesterone receptor (PgR; P < 0.01) were inversely correlated. In multivariate analysis, only high p53 and low bcl2 were independently associated with CAIX positivity. CAIX immunostaining was significantly associated with poor outcome for DFS (P < 0.002) and overall survival (P = 0.001). In multivariate analysis, a significant interaction was found between CAIX and markers of hormone sensitivity, bcl2 (P = 0.01), ER (P = 0.02), PgR (P = 0.02), and lymph node involvement (P = 0.04), in predicting DFS. Presently, there are few clinical markers of resistance to tamoxifen treatment in ER-positive tumors. CAIX expression in breast cancer patients shows a negative predictive role of treatment efficacy in ER-positive patients on the adjuvant tamoxifen after primary chemo-endocrine therapy. Studies investigating the effects of pH on tamoxifen uptake and the effects of therapy with CA inhibitors are planned.
Plasmatic exosomes from prostate cancer patients show increased carbonic anhydrase IX expression and activity and low pH