Lysine acetylation of histones is one of the major epigenetic regulators of 
chromatin conformation and gene expression. The dynamic nature of histone 
acetylation is determined by the counterbalancing activity of histone 
acetyltransferase and histone deacetylase (HDAC) enzymes. Acetylation of 
histones is generally associated with open and transcriptionally active 
chromatin, whereas the activity of HDACs leads to histone deacetylation, 
condensation of chromatin, and inhibition of transcription. Aberrant silencing 
of tumor suppressors and other genes has been found in different types of 
cancer. Abnormal activity of HDACs has been implicated in tumorigenesis and 
therefore considerable effort has been put into the development of HDAC 
inhibitors as a means of modifying histone acetylation status and reexpressing 
aberrantly silenced tumor suppressor genes. This has led to the generation of a 
number of structurally diverse compounds that can effectively inhibit HDAC 
activity, thus altering chromatin structure in cancer cells. This unit discusses 
the methods and recent technological developments with respect to the studies of 
HDAC inhibition in cancer.