Efflux of Hoechst 33342 by MCF7, MCF7-sh-scrambled and MCF7-sh-WISP2 cells.

<p>(<b>A</b>) MCF7, MCF7-sh-scrambled and MCF7-sh-WISP2 cells were exposed to Hoechst 33342 in the presence or absence of Verapamil, a non-specific inhibitor of membrane transporters. Images were obtained by microscopy at 40× magnification. Arrows indicate low staining and arrowheads high staining. The histogram indicates the quantification of low and high Hoechst-stained cells, in presence or absence of Verapamil, expressed as (%) of total counted cells. (<b>B</b>) RNA was isolated from MCF7, MCF7-sh-scrambled and MCF7-sh-WISP2 cells and the expression of selected ABC transporters including ABCG2, ABCC1, ABCC2 and ABCA2 was analyzed by qRT-PCR. Fold induction in mRNA expression was calculated as compared with the corresponding mRNA in MCF7-sh-scrambled cells. Results are the means ± SD of three independent experiments. (<b>C</b>) The side-population (SP) cells were analyzed by Hoechst and flow cytometry. After staining with H33342, in presence or absence of Verapamil, Hoechst Blue and Hoechst Red fluorescence were measured by flow cytometry. Data are representative of three individual analyses. **p<0.01, ***p<0.001.