Effect Of G9a SiRNA On Proliferation Apoptosis And Histone H3k9Methylation In MCG803Cells

Objective: This study was aimed at investigating the involvement of the G9ahistone methyltransferase on the epigenetic change in gastric carcinoma. Weretrospectively analyzed the protein of G9a and mono-methylated histone H3lysine9(H3K9me1), di-methylated histone H3lysine9(H3K9me2) in175case of gastriccarcinoma. by immunohistochemistry. We further study the effects of G9a on cellsbiological changes, histone methylation and acetylation in gastric cancer MGC-803cells line.Methods：The expression of G9a,H3K9me1, and H3K9me2were detected byimmunohistochemistry in gastric cancer, chronic superficial gastritis, atrophic gastritisand moderate to severe atypical hyperplasia tissues. siRNA segments targeting G9agene was transfect into MGC-803cells by lipofectamine2000. The optimal segmentwas screened by RT-PCR and Western blot. Cell growth inhibition was determined byMTT. Cell apoptosis was measured by TUNEL assay.The expression ofBCL-2,pro-Caspase-3,BAX,H3K9me1,H3K9me2,H3K9me3,H3K27me1,H3K27me2and acetylation of H3were detected by Western blot.Results: The expression of G9a and H3K9me2in gastric cancer is87.43%（153/175)and90.28%(158/175), which were significantly higher than that in chronicsuperficial gastritis, atrophic gastritis, moderate to severe atypical hyperplasia tissues(p＜0.05). It is correlated with degree of differentiation,depth of infiltration,lymphatic metastasis and TNM stages in gastric cancer compared to others(p＜0.05).There were no significant differences in the expression of H3K9me1betweengastric cancer and other groups(p>0.05).The optimal sequence of G9a was sense5’-UUCAGUCUCUACUAUGAUUTT-3’，antisense5’-AAUCAUAGUAGAGACUGAATT-3’.G9a siRNA inhibited proliferation of MGC-803cells, and decreasedBCL-2, Procaspase-3and promoted Bax, induced cell apoptosis. G9a siRNAdownregulated H3K9me1,H3K9me2and H3K27me1, H3K27me2,there were no noeffect on H3K9me3and H3acetylation.Conclusions:High expression of G9a and H3K9me2is in gastric cancer.Theycorrelate with degree of differentiation, depth of infiltration, and lymphatic invasions, Tumor, Node,Metastasis stages,suggesting that G9a and H3K9me2may play a role inthe pathogenesis gastric cancer occurrence,development， infiltration andmetastasis.Depletion of G9a gene could inhibit the cell proliferation in gastric cancer,initiate apoptosis program, and induce tumor cell apoptosis. Further study found thatDepletion of G9a gene modulate H3K9and H3K27methylation, dowregulateH3K9me1, H3K9me2, and H3K27me1, H3K27me2, It might cause chromosomeconformation change and kill the tumor cells. G9a gene might be an anti-cancertarget.