P-glycoprotein and MRP1 expression in axillary lymph node metastases of breast cancer patients

Background: Only little information on the expression of P-glycoprotein (P- gp) and MRP1 in metastases of breast carcinomas is currently available. The aim of the present study was to investigate the expression of these two pr oteins in axillary lymph node metastases of breast cancer patients. Materia ls and Methods: We determined the expression of P-gp and MRP1 in axillary l ymph node metastases of 63 breast cancer patients and, in 32 patients, comp ared this expression to the expression of corresponding primary tumors. P-g p was detected by means of C219 and Ab-2 monoclonal antibodies, and MRP1 by means of the MRPr1 monoclonal antibody. Results: In lymph node metastases P-g expression was positive, usually at low levels, in 28 (44%) specimens w hilst MRP1 expression was positive in all specimens with low, intermediate and high levels in 3 (5%), 46 (73%) and 14(22%) specimens, respectively. Th e percentage of P-gp expression was slightly lower in lymph nodes than in p rimary tumors while MRP1 expression showed a higher staining intensity in l ymph node metastases of breast cancer patients and that MRP1 expression is more pronounced in lymph node metastases than in corresponding primary tumo rs.