The Research Of Mechanisms On The Inhibitory Effect Of A Novel Selective HDAC6 Inhibitor On The Growth Of Gastric Cancer

Gastric cancer is the second most deadly cancer in China and widely distributed around the world.Routine treatments include surgery,radiotherapy,and chemotherapy.Postoperative prognosis is related to many factors including pathological stage and grading,so chemotherapy plays an important role in the treatment of gastric cancer.But because there are differences between individual patients,there are more and more applications of targeted drugs.Epigenetic modifications are related to the occurrence and development of cancer.The acetylation modifications regulated by histone acetyltransferases(HATs)and histone deacetylases(HDACs)have been deeply studied.SAHA is one of the widely used HDAC inhibitors.It is a multi-target deacetylase inhibitor and can inhibit a variety of deacetylases(HDAC1,HDAC2,HDAC3,HDAC6,HDAC8).But SAHA has side effects such as fatigue,nausea,and toxicity to the heart.The previous research indicates that modification of cap structure of SAHA could reduce the targeting and side effects of the compound,so new HDAC inhibitors with specific targets are one of the approaches in the treatment of cancer.In our previous work,OBHS-SAHA compounds were designed and synthesized based on the newly compound OBHS and SAHA.The effect of anti-cancer and enzyme inhibition of compounds was tested.According to the following principles,we gradually screened out 24h(renamed TC24)from four compounds(21a,22,23f,24h)as a follow experimental compound:1.Modification method of SAHA:21a and 22 are synthesized by docking SAHA with the sulfonate group of OBHS,23f and 24h are synthesized by docking SAHA with the phenolic hydroxyl group of OBHS;2.The activity of HDACs inhibition of OBHS-SAHA:22 and 24h are HDAC6 inhibitors,21a and 23f are HDAC1 inhibitors;3.The side effect of OBHS-SAHA:all four compounds have no obvious cytoxin effect on gastric normal GES-1 cells;4.The anti-proliferative activity of the compounds on the gastric cancer cell:22 and 24h suppressed the proliferation of human gastric cancer cells,but 24h is the complete HDAC6 inhibitor.TC24 can increase the acetylation of a-tubulin in gastric cancer cell lines but has no effect on the acetylation of H3.Molecular docking experiments also confirmed that TC24 could directly combine the binding pocket of HDAC6 by chelates with Zn2+ and hydrogen bonds,but we could not find models of TC24-HDAC1.HDAC6 has a larger catalytic activity pocket than HDAC1,so TC24 with a larger cap structure can bind to HDAC6 and more efficiently block the catalytic activity pocket of HDAC6.The experiment further demonstrated the specific inhibition of HDAC6 by TC24.HDAC6 is a member of class ? of HDACs and participates in many physiological processes such as autophagy,apoptosis and cell migration in cancer,but some research showed that the tolerance to the loss of HDAC6 in animals and cells.Therefore,HDAC6 selective inhibitors have received more and more attention.Further experiments showed that TC24 inhibited proliferation,cell migration,the formation of clones of gastric cancer cells.In addition,TC24 can induce G2/M cell cycle arrest,cell apoptosis and loss of mitochondrial membrane potential in gastric cancer cells.Meanwhile,the G2/M checkpoint proteins cyclin B1,cdc2 and pro-survival protein Bcl-2 were decreased.The pro-apoptosis protein Bax and cleaved-PARP were increased.On the other hand,TC24 also can down-regulate HIF-1? and VEGF through CREB and may participate in the inhibition of angiogenesis.When using MKN28,which with a lower expression of HDAC6,as a control,we further found that TC24 only inhibited cell proliferation at high concentrations,and had no effect on the formation of MKN28 clones.Also,the ability of induced apoptosis was weaker.In conclusion,our work demonstrated that TC24 is a selective inhibitor of HDAC6 and showed significant anti-proliferative effects on gastric cancer cells and had no side effects on gastric epithelial cells.The anti-proliferative activity of TC24 may be related to the inhibition of angiogenesis,inducing cell cycle arrest and apoptosis.TC24 can be used as a potential drug and this work has also helped the synthesis of other related compounds.