Compensation mechanism after specific HDAC8 inhibition in RT-112, VM-CUB1, SW-1710, 639-V and UM-UC-3 cells. Effects of HDAC8 inhibitor treatment on (A) mRNA and (B) protein expression of the class I histone deacetylases HDAC8, HDAC1, HDAC2 and HDAC3, compared to DMSO solvent control (compound 2, compound 5, compound 6; IC50, 72 h). The mRNA expression values were measured by quantitative RT-PCR analysis and were normalized to TBP as a reference gene. p < 0.05 was regarded as significant and marked as *, whereas p < 0.01 and p < 0.001 were defined as highly significant and marked as ** and ***. The calculated significances of the treated value refer to the DMSO solvent control. Protein expression levels were analyzed by western blotting, and α-tubulin was stained on each blot as a loading control.