HDAC2 and urinary bladder cancer: With respect to HDAC4, and using bladder cancer tissue arrays coupled to an immunohistochemical protocol, the frequency of HDAC4-positive tissues (but not of HDAC2-positive ones) was significantly higher in the tumor than normal specimens, with the HDAC4 protein levels (in contrast to HDAC1 and 2 ones) being also elevated in a certain collection of bladder cancer cell lines [165,173].