| Background:Gastric cancer ranks fourth in incidence and third in mortality among all cancers worldwide.Nearly one million people are diagnosed with gastric cancer every year worldwide,among which of 88%are in developing countries and more than 50%in East Asia,especially in China,Korea and Japan.To date,surgery have remained the only curative option in the treatment of gastric cancers,and for metastasis,chemotherapy have shown only a modest benefit with an average survival of approximately ten months.Therefore,a more effective therapies and molecular targeted agents are in demanded for gastric cancer treatment.Valproic acid,a commonly used drug for treating epilepsy and bipolar disorders,has emerged as a promising agent for cancer treatment in recent years.VPA has been identified as a potent selective histone deacetylase inhibitor,which induces cellular differentiation,growth arrest,and apoptosis in gliomas and other types of cancers.Increasing evidences suggested that VPA affect oncogenesis in both solid and hematologic malignancies.However,the effect of VPA treatment in gastric cancers and the related mechanisms still remains unknown.Objectives:To investigate the therapeutic potential of VPA against gastric adenocarcinoma,and explore the related mechanisms.Materials and methods:Gastric cancer cell lines AGS,MKN-28,MKN-74,SGC-7901 proliferation treated by VPA was detected by MTT.Colony formation and Western blot assays were used to screen for the proliferation attenuating effects of VPA on gastric cancer cells AGS and SGC-7901.Annexin-V/PI double staining flow cytometry and hoechst staining assays were used to detect the apoptosis of AGS and SGC-7901 cells after the treatment with VPA.Western blot assays were performed to analyse the activation of caspases and apoptosis-related protein expression.Immunofluorescence,acridine orange staining,western blot and electron microscopy assays were performed to analyse the autophagy-inducing effect of the drug treatment and autophagy-related protein expression.To investigate the mechanisms underlying the inhibition of cell growth by VPA,western blot assays were performed to detect the expression of PI3K/AKT/mTOR signaling pathway in AGS and SGC-7901 cells treated by VPA.Results:The MTT assays showed that the inhibition of cell growth in gastric cancer cells AGS,MKN-28,MKN-74,SGC-7901 were dependent on the dose of VPA.AGS and SGC-7901 cells exhibited the most sensitivity towards VPA in growth inhibition.Colony formation and western blot assays were observed the anti-proliferative potential of VPA on gastric cancer cells.Hoechst33342 staining showed that more frequency chromatin fragmentation and condensation in AGS and SGC-7901 cells exposed to concomitant treatment compared with the control group.Flow cytometry results of VPA-treated gastric cancer cells confirmed the augment of apoptosis.Western blot results showed that VPA could activate caspase-3,caspase-8,caspase-9 and induce apoptosis.Acridine orange staining and electron microscopy experiment indicated that the VPA treatment of the gastric cancer cells was sufficient to instigate an autophagic response.Western blot and immunofluorescence staining showed that the conversion rates of LC3-? to LC3-?,as well as the expression Beclin-1 protein,increased in the VPA-treated gastric cancer cells.As to the mechanisms,increased expression of PTEN and decreased p-AKT,p-S6,p-mTOR and p-4EBP1 expressions were observed in AGS and SGC-7901 cells after VPA treatment.Conclusions:1.VPA inhibits the proliferation of gastric adenocarcinoma cells via the modulation of apoptosis and autophagy.2.VPA contributes to its cytotoxicity against gastric adenocarcinoma involving the inhibition of PI3K/AKT/mTOR signaling pathway. |
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