Relationship between the expression of cyclooxygenase 2 and MDR1/P-glycoprotein in invasive breast cancers and their prognostic significance

Immunohistochemical reactions were performed using monoclonal antibodies against COX-2 and MDR1/P-gp on samples originating from 104 cases of primary invasive breast cancer.COX-2-positive cases were shown to demonstrate higher expression of MDR1/P-gp (P < 0.0001). The studies also demonstrate that COX-2 expression was typical for cases of a higher grade (P = 0.01), a shorter overall survival time (P < 0.0001) and a shorter progression-free time (P < 0.0001). In the case of MDR1/P-gp, its higher expression characterised cases of a higher grade (P < 0001), with lymph node involvement (P < 0001), and shorter overall survival (P < 0.0001) and progression-free time (P < 0.0001).Our studies confirmed the unfavourable prognostic significance of COX-2 and MDR1/P-gp. We also document a relationship between COX-2 and MDR1/P-gp, which suggests that COX-2 inhibitors should be investigated in trials as a treatment supplementary to chemotherapy of breast cancers.Breast cancer is the most common malignant tumour of females in the western world [1]. The incidence of breast cancer remains high, and its clinical courses are highly variable. It is of general importance to predict the biology of the tumour and, thus, the course of the disease in the individual patient to ensure adequate therapy and patient surveillance [2]. The principal therapeutic approach in breast cancer involves surgery. In advanced cases supplementary therapy is needed, involving pharmacotherapy and/or radiotherapy. Among the pharmacological means, tamoxifen used to be applied most frequently, as well as various chemotherapeutic regimes, including CMF (cyclophosphamide, methothrexate and 5-fluorouracil), anthracyclines and paclitaxel [3,4]. The main reason for therapeutic failure in cases of invasive breast cancers involves resistance to anti-estrogenic treatment and to chemotherapy [5,6]. Identification of the factors that characterise the resistant cases would permit immediate treatment of the patients with alt