Figure 1
Chronic exposure to vorinostat induces resistance to pan-HDACi in the AML-related lymphoma cell line U937. U937-B8 cells were cultured in drug-free media for up to 3 weeks. After 2 days, 1 week and 3 weeks, U937-B8 cells’ sensitivity to vorinostat was evaluated by quantification of cell death after 48 h exposure to the indicated concentration of vorinostat. Cell death was assessed by DNA fragmentation using PI staining and flow cytometry (a). Doubling time was measured by cell counting (b). U937-B8 cells grown without vorinostat for 1 week and their parental cells U937 were treated with the indicated concentrations of vorinostat for 72 h before cell viability was evaluated by Titer-Glo assay (c) or 24 h before relative caspase 3 and 7 activation was evaluated by Caspase 3/7-Glo assay (d). Parental and resistant cells were exposed to the indicated concentrations of LBH589, tubastatin and MGCD0103 for 48 h and cell death was evaluated by DNA fragmentation using PI staining (e). U937 and U937-B8 cells grown in vorinostat and U937-B8 cells grown without vorinostat for 1 week were submitted to western blot analysis using whole-cell extract and the antibody indicated on the right (f). U937-B8 cells grown without vorinostat for 1 week and their parental cells U937 were treated with the indicated concentrations of vorinostat for 18 h, and cell cycle analysis was performed by PI staining and flow cytometry (g)
