IMMUNOCHEMICAL DETECTION OF THE MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN MRP IN HUMAN MULTIDRUG-RESISTANT TUMOR-CELLS BY MONOCLONAL-ANTIBODIES

We have generated rat and murine monoclonal. antibodies against multid rug resistance-associated protein (MRP), a M(r) 180,000-195,000 membra ne glycoprotein involved in a non-P-glycoprotein multidrug resistance of human tumor cells. The antibodies were raised against two different segments of MRP and found to be suitable for protein blot analyses, i mmunohistochemical and cytochemical studies, as well as flow cytometry of permeabilized cells. The antibodies do not cross-react with the hu man P-glycoproteins. Immunocytochemistry using MRP-overexpressing tumo r cells of different histogenetic origins showed that MRP is predomina ntly located in the plasma membrane. Immunoelectron microscopy confirm ed the plasma membrane location of MRP. The MRP antibodies provide a s ensitive and specific tool for studies on MRP-mediated multidrug resis tance.