Characterization of multidrug-resistant MOVP-3 cells. The newly generated VP16-resistant MOVP-3 cell line was analyzed for MDR-1 gene expression (A) and MDR-1 protein expression on the cell surface (B). MDR-1 gene expression was determined by RT-PCR analysis on total RNA isolated from MOVP-3 and Molt-3 cells, respectively (A). Expression of GAPDH was used as a control for the integrity of the cDNA. MDR-1 protein expression on MOVP-3 cells was determined by FACS analysis using 1 μg UIC2 primary antibody per 10⁶ cells and compared with Molt-3 parental cells (B). The gene expression of other resistance mechanisms was determined by RT-PCR (C). Results obtained with Molt-3 cells (top) were compared with MOVP-3 cells (bottom). Lane 1 indicates 100-bp marker; 2, GAPDH; 3, MDR-1; 4, MRP; 5, LRP; 6, bax; 7, Topo I; 8, Topo IIα; 9, Topo IIβ; and 10, 100-bp marker.