A novel 95 kilodalton membrane polypeptide associated with lung cancer drug resistance

A novel 95 kilodalton (kDa) membrane protein has been previously shown to be induced in breast cancer cells made resistant in vitro to adriamycin. We have used antisera raised against the 95 kDa protein to examine a panel of early passage small cell lung cancer cell lines from patients with untreated extensive stage disease. Two lines, demonstrating marked de novo resistance to etoposide, showed expression of the 95 kDa protein by Western blotting. The protein was enriched in detergent-solubilized membrane preparations, and detected by silver staining and immune blotting. The 95 kDa protein is frequently detected in small cell lung cancer cell lines obtained from patients relapsed after chemotherapy, suggesting that it may be selected for by chemotherapy in vivo.