Abstract: It has been shown that epigenetic modifications play an important role in tumorigenesis. Among the key chromatin modifying enzymes，chromatin histone acetylation influences gene expression，Balanced by the activities of histone acetyltransferases（HATs） and histone deacetylases（HDACs），determining the acetylation status of histones. With a consequent hypoacetylated state of chromatin that can be strictly correlated with low expression of either tumor suppressor or pro-apoptotic genes. Histone deacetylase inhibitors（HDACi）represent a new and promising class of antitumor drugs that influence gene expression by enhancing acetylation of histones in specific chromatin domains. HDACi have been shown to exert potent anticancer activities inducing cell cycle arrest and apoptosis. Several HDACi are currently under clinical investigation.

Key words: Histone deacetylases, Neoplasms, Apoptosis, Cell differentiation