Expression of the multidrug resistance-associated protein 1 (MRP1) and the lung resistance-related protein (LRP) in human lung cancer.

Fifty lung cancer samples (41 non-small cell lung cancer-NSCLC and 9 small cell lung cancer-SCLC) were immunohistochemically analyzed for lung resistance-related protein (LRP) and multidrug resistance-associated protein 1 (MRP1) expressions which were then correlated with histopathological subtype of the tumor. To detect these proteins, monoclonal antibodies LRP-56 and MRPm6 were used. NSCLC samples were divided into two groups, adenocarcinomas (17 samples) and squamous cell carcinomas (24 samples). Four categories of LRP and MRP1 quantity were distinguished: +++ = high level--90--100% of positive cells, ++ = lower level--10--90% of positive cells, + = low level--up to 10% of positive cells, - = negative cells--0% of positive cells. Within the NSCLC group the most samples (36/41) had the similar level of LRP and MRP1. Significantly higher expression of both proteins was observed in the adenocarcinomas in comparison with squamous cell carcinomas. The lowest positive staining for LRP and MRP1 proteins has been found in SCLC. It is suggested that our finding can confirm the overall empirical clinical knowledge about much higher chemosensitivity of untreated SCLC comparing to NSCLC.