Multidrug resistance-associated protein (MRP) gene expression in human lung cancer.

Multidrug resistance-associated protein (MRP) is a 190 kD transmembrane protein and a potentially important drug-transporter protein in human cancers. While the MRP gene is expressed in normal cells and tissues, the expression in solid tumors is not sufficiently determined. MRP and mdr1 mRNA expressions were examined in normal lung parenchyma and in tumor tissues from six small cell lung cancer (SCLC) patients who had received preoperative chemotherapy and eleven nonsmall cell lung cancer (NSCLC) patients. The reverse transcriptase polymerase chain reaction was used. Normal lung tissues and all SCLCs expressed abundant levels of MRP mRNA, while the NSCLCs expressed a wide range of levels from low to high. Most tumor tissues coexpressed both MRP and mdr1, but the levels of mdrl expression was low except in two SCLCs and one NSCLC. MRP is more likely than mdr1 to be one of the clinical multidrug resistance mechanisms found in lung cancer.