MRP expression of testicular cancers and its clinical relevance

Background: The expression of a multidrug resistance associated protein (MR P) has been investigated in a variety of human tumors. However, there is a lack of data regarding its expression in germ cell testicular armors (GCTTs ). Patients and Methods: MRP expression was examined by immunohistochemistr y (IHC) using mouse monoclonal antibody (MRPm6) against human MRP in 56 tes tis cancer specimens, This antigen was also correlated with the histology, metastatic behavior, clinical stage and tumor suppressor protein p53 immuno staining of GCTTs. Results: All testis tumors, regardless of their histolog y, metastatic status and clinical stage gave positive signals. MRP was posi tive not only in the cytoplasm but, very interestingly, in the nuclei. Conc lusion: Our results suggested that ala GCTTs express high levels of MRP pro tein with no relation to any of clinicopathological variables investigated here. Since germ cell tumors are very sensitive to chemotherapy, the role o f MRP as mediator of drug resistance seems unconvincing in this malignancy. MRP is located in the cytoplasm and the nuclei of tumor cells and may be i nvolved in transportation and/or redistribution certain substrates from the nucleus to the cytoplasm.