Doxorubicin retention and chemoresistance in human mesothelioma cell lines.

Eight cell lines were established from the pleural effusion of 4 patients with malignant mesothelioma. The most sensitive (FCCMES-4) and the most resistant (FCCMES-2) mesothelioma cell lines had IC50 of 0.66 and 1.85 microM for doxorubicin in clonogenic assays, respectively. In comparison with murine leukemic P388 cells, mesothelioma cell lines were 7.5- to 21-fold more resistant to doxorubicin. Co-incubation with verapamil significantly increased doxorubicin retention in one of the cell lines (FCCMES-2) expressing P-glycoprotein in 16.8% of the cells. These results indicate that doxorubicin resistance may be intrinsic in refractory mesothelioma patients and P-glycoprotein-mediated drug efflux may be involved in resistance of some of the mesotheliomas.