An immunochemical analysis of multidrug resistance gene product P170 glycoprotein in human breast cancer tissues

e22206 Background: P-glycoprotein (gp170; encoded by the MDR1 gene (also known as PGY1) is a membrane protein capable of exporting a variety of anticancer drugs from cells. MDR1/gp170 expression has been studied in breast cancer, but the prevalence of this expression and its role in breast tumour drug resistance are unclear. To offer more effective and less toxic treatment, selecting therapies requires considering the patient and the clinical and molecular characteristics of the tumour. Our primary goal was to clarify the prevalence and clinical relevance of MDR1/gp170 expression in breast cancer patients in correlation with clinocopathologic features. Methods: In this study the expression of MDR1/gp170 protein has been investigated in a series of 40 human breast carcinomas. The immunoperoxidase antigen detection protocol, was employed using anti-p170 monoclonal antibodies (MoABs), (JSB 1 Monosan). Clinicopathologic findings, grade, and molecular markers (HER2, estrogen receptor (ER)alpha, ER beta, and progesterone receptor were also analyzed. Results: MoAB JSB-1 reacted strongly with the transmembranic antigen epitope. The proportion of breast tumours expressing MDR1/gp170 was 22% in Grade 1, 71% and 45.4% in Grade2 and Grade3 Itumors. There was no correlation with hormone receptor status, lymph node status and ΕΕR-2. Conclusions: The data of MDR-1 product expression by immunohistochemistry in breast cancer might suggest that an overexpression of this protein could constitute a hallmark of potential more aggressive phenotype for this type of neoplasia and a rapid method for pre-screening tumours for a constitutive multidrug resistance in order to orientate the cancer treatment. While the functional relevance of this expression remains to be established, it seems likely that MDR1/gp170 is an independent prognostic factor in breast tumours. No significant financial relationships to disclose.