Histone deacetylase inhibitor is a novel class of histone deacetylase targeted anti-cancer drug, which takes excellent effects on anti-proliferation, pro-apoptosis, pro-differentiation, cell cycle arrest, anti-angiogenesis and so on. Histone deacetylase inhibitor plays an important role in the development of anticancer drug with its unique anti-tumor mechanism. Among the histone deacetylase inhibitors, the cyclopeptide histone deacetylase inhibitor with the most complicated structure has good antagonism on various types of solid tumors and hematologic cancer. In this review, the structural features of the metal binding region, the surface recognition region and the linker region of natural and synthetic cyclic peptide histone deacetylase inhibitors are summarized, and the inhibitory activity and anti-tumor proliferative activity of various inhibitors are described. Modification of different structure domains can make inhibitors with high efficiency and specificity on different tumor cells. We expect to find the structure rule of the high efficient and low toxic targeted peptide inhibitors through structure-activity relationships, providing new sights for investigation of anti-cancer drugs.

Contents
1 Introduction
2 Histone deacetylase inhibitors and classification
3 Cyclopeptide histone deacetylase inhibitors
3.1 Cyclopeptide histone deacetylase inhibitors containing ketone
3.2 Cyclopeptide histone deacetylase inhibitors containing hydroxamic acid
3.3 Cyclopeptide histone deacetylase inhibitors containing sulfur
3.4 Cyclopeptide histone deacetylase inhibitors containing carboxylic acid or amide
3.5 Other histone deacetylase inhibitors
4 Conclusion