Fig. 2. P-glycoprotein was not involved in the resistance to UI-152 in A375P/Mdr cells. (A) To determine the effect of verapamil on the resistance to UI-152, increasing concentrations of UI-152 with or without verapamil were added to A375P/Mdr cells. The cell growth rate was measured by the MTT assay. The relative proliferation rate of cells treated with vehicle alone was regarded as 100%. Values represent the mean ± SD of quadruplicate determinants from 1 of 3 representative experiments. (B) Immunofluorescence analysis was performed to detect the expression of MDR proteins (P-glycoprotein) in A375P/Mdr cells. MDR proteins were immunostained with anti-MDR antibody, and subsequently reacted with anti-rabbit IgG-Texas Red, respectively. Nuclei were counterstained with DAPI. Fluorescence was captured by fluorescence microscopy. Red depicts MDR expression; blue depicts DAPI nuclear staining. The results presented are representative of at least 3 independent experiments performed under the conditions described.