Design And Synthesis Of Small Molecular Inhibitors Of Histone Deacetylase

Epigenetic modification of gene expression is closely related with cancer. Histone modification draw attention as one of the major epigenetic modification at the end of histone tails either through acetylation, methylation, phosphorylation, ubiquitination and so on. Histone modification is regulated by two mutually antagonistic enzymes, histone acetyl transferase (HAT) and histone deacetylase (HDAC). HDAC are responsible for removing acetyl group from N-acetylated lysine residues which enhance the binding between DNA and histone and lead chromatin condensation and transcriptional repression. High expression of HDACs will lead to balance disorder which causing cancer. HDACs are new targets for finding drugs. Most of histone deacetylases Inhibitors (HDACIs) have common structural characteristics:zinc binding group, linker and surface recognition group. Search new inhibitors which have high selectivity and high activity through designing the separated three parts.Based on the structural features of SAHA, FK228and reported inhibitors, two series of inhibitors were designed. The first series of derivatives are based on2-aminoheptanoic acid which introduced hydrophobic group in the amino-terminal and carboxy-terminal as surface recognition group,5methylene as linker, thioester as zinc binding group. The second series of derivatives are use nitrobenzene as zinc binding group. In this research, more than300kinds of HDACIs were designed and screened by Autodock4.2and13kinds of compounds were synthesized by means of solution phase synthesis method. All the synthesized compounds were detected by HPLC, ESI-MS,1H NMR and13C NMR.All synthesized target compounds were evaluated on enzyme inhibition and cancer cell growth inhibition.12C1(IC50=0.045μM) and12C2(IC50=0.092μM) exhibited more potent HDAC inhibition relative to the others. It is founded that2-amino-4-phenylthiazole as a terminal cap group of the inhibitors can improve the activity significantly. The HDAC1and HDAC6inhibition activity of compounds showed similar trend as HDACs.In the anti-proliferative experiment, the selectivity of target compounds for HeLa is higher than MCF-7(breast cancer) and SMMC-7721(hepatic carcinoma). Compound12C1(IC50=40.3μM) is better than TSA (IC50=48.5μM) in HeLa antiproliferative experiment. To compare the level of anti-proliferative activity and the level of enzyme inhibition, the first series of compounds exhibit higher improvement than TSA. Probability that the thioester could be hydrolyzed into thiols in vivo can enhance the combination which may result in good activity. The other compounds due to the lipophilic penetration causes inhibition activity lose.From the analysis of bingding energy, the more number of rotatable bonds of compounds and much electrostatic energy do not conducive the interaction of complexes. The binding energy of HDAC2complexes and HDAC4complexes have same distribution trend. In the HDAC2docking experiments, the number of hydrogen bonds between12C1and HDAC2are more than others and only the N atom of12C1with2-amino-4-phenyl-thiazole as the surface involved in hydrogen bonding. In the HDAC4docking experiments, the hydroxamic acid groups of TSA formed more hydrogen bonding than thioacetyl which is consistent with vitro enzyme inhibitory activity. The sulfhydryl groups have strong enzyme interaction than thioacetyl therefore thioacetyl hydrolyzed intro cell will increase the interaction with enzyme, which is in line with the vitro antiproliferative activity test.