Compensation mechanism after HDAC8 knockdown in RT-112, VM-CUB1, SW-1710, 639-V and UM-UC-3 cells. Effects of siRNA mediated HDAC8 knockdown on (A) mRNA and (B) protein expression levels of the class I histone deacetylase HDAC8, HDAC1, HDAC2 and HDAC3 (72 h) in comparison to untreated and irrelevant control. 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 ***. Protein expression levels were analyzed by western blotting, and α-tubulin was stained on each blot as a loading control.