Design,Synthesis And Activity Study Of Histone Deacetylase Inhibitors Based On Chidamide Analogues

Recently,with the development of research on the pathogenesis of tumor,more andmore evidences have revealed that chromatin epigenetic modification plays a crucial role in tumor development,wherein acetylation of histones is particularly important.Histone deacetylases(HDACs)are a class of Zn2+ proteases,responsible for regulating the acetylation state of histone.It has been revealed that hyper-activation or abnormal expression of HDACs is often associated with malignancy and poor prognosis of cancers.Accordingly,Histone deacetylase inhibitors(HDACIs)developed for HDACs inhibition can recover or increase the level of histone acetylation and restart the expression of tumor suppressor genes via inhibiting HDACs,exhibiting significant anticancer potential.Due to their high selectivity and specificity against tumor cells,HDACIs have been considered as promising anticancer drugs.The highly selective Chidamide(CS055)was selected as lead compound to design HDACIs.Basing on structure-activity relationship of similar drugs,this study modified the structure of CS055: substituting the pyridine group in surface recognition domain with phenyl,tert-butyl or methyl etc;introducing hydrophobic group in linker domain to improve the hydrophobicity;keeping N-(2-aminophenyl)benzamide and 4’-fluorine atom of Zn2+binding domain to enhance the interaction of compounds with HDACs.First of all,three series of compounds were designed and analysed by computer software autodock4.2.Then,thirteen of them were synthesized according to the results of docking.All target compounds have been verified by HR-MS,1H NMR and13 C NMR.Secondly,the HDACs-inhibitory activity of the new compounds was measured using the HDACs fluorimetric enzymatic activity assay kits.The results showed that the majority of these compounds exhibited good inhibitory activity on HDACs and HDAC2,and the inhibitory activity on HDAC6 was poor.Besides,compound A18 exhibited the highest inhibitory activity,and the IC50 values on HDACs and HDAC2 were 0.043 μM and 0.091 μM,respectively.Whereafter,the anti-proliferation activity of all new compounds was assessed against hepatoma cell Hep G2,hepatoma cell SMMC-7721,breast cancer cell MCF-7,breast cancer cell MDA-MB-231 and histiocytic lymphoma cell U937,chronic myelogenous leukemia cell K562,acute promyelocytic leukemia cell HL60.The results indicated that the anti-proliferation activity of compounds on solid tumor cells was better than hematologicaltumor cells,the inhibitory effect of compounds on hepatoma cell SMMC-7721 was stronger than Hep G2;the inhibitory effect on breast cancer cell MCF-7 was higher than MDA-MB-231;overall,the inhibitory effect of compounds on hepatoma cells was better than breast cancer cells.All of these results indicated that the target compounds had selectivity to tumor cells.The results of further experiment on hepatoma cell SMMC-7721 showed that the inhibitory effect of compound A18(IC50=17.38 μM)was higher than positive control Chidamide(IC50=19.79 μM).Finally,more accurate molecular docking was used to study the interaction between target compounds and HDAC2,HDAC6.The docking results and the enzyme activity inhibition results were basically identical.The structure-activity relationship of compounds demonstated that introducing phenyl in linker domain of compounds was beneficial to enhance the hydrophobic interaction between the linker domain and the active pocket of enzymes.