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Figure 5. Panobinostat, but not vorinostat, upregulates HDAC6 expression. (A) RMPI-8226 and Kas6 were treated with 50 nM vorinostat or panobinostat for 12 h before harvesting for total RNA, and HDAC6 expression was measured by RT-PCR. Expression of HDAC6 in RMPI-8226 and Kas6 cells treated with vorinostat or panobinostat was normalized to vehicle-treated RPMI-8226wt and Kas6wt, respectively. (B, C) RMPI-8226 and Kas6 were treated with 50 nM vorinostat or panobinostat for 12 h before harvesting for protein, and HDAC6 expression was measured by immunoblotting. Results were quantified by scanning for band density and plotted. Patient sample (peripheral blood) derived from a phase I/II newly diagnosed multiple myeloma clinical trial before and after the first cycle treatment was harvested (Clinicaltrials.gov, number NCT01440582), and HDAC6 expression in PBMC was measured by immunoblotting, and quantitative results were plotted next to immunoblotting. (D) SUDHL4 and Daudi cells were treated with 50 nM vorinostat or panobinostat for 12 h before harvest for total RNA or protein. HDAC6 mRNA expression was measured by RT-PCR. Expression of HDAC6 in cells treated with vorinostat or panobinostat was normalized to vehicle control. HDAC6 expression was measured by immunoblotting. Results were quantified by scanning for band density and plotted. ^*P < 0.05. HDAC: Histone deacetylase.