HOTAIR Induces EMT By Regulating Histone Modification In Gastric Cancer

In China,the incidence and mortality of cancer has been increasing and become one of the most important diseases that affect public health.Gastric cancer represents one of the most aggressive and deadly tumors in the world.The latest data shows that gastric cancer remains the second morbidity in China,which is a highly invasive and aggressive malignancy.The main treatments for advanced gastric cancer is chemotherapy and molecularly targeted therapy,however,the treatment effect is not optimistic.Therefore,it is crucial for exploring a biomarker to indicate metastasis of gastric cancer.To explore the effect of long non coding RNA HOTAIR on the development of gastric cancer,we used vivo experiment and vitro experiment.Vitro experiments were used to detect the cancer cells migration and proliferation,including transwell experiment,migration experiment and cloning experiments.The results revealed that inhibition of HOTAIR decreased gastric cancer cells invasion,migration and proliferation.In vivo experiment,we established a subcutaneous gastric carcinoma model using MGC-80 cells with Lenti-NC and Lenti-HOTAIR si treatment.We detected the tumor volume,weight of mice to verify that HOTAIR is an oncogene to promote the progression of gastric carcinoma.We explored the molecular mechanisms of by which the HOTAIR regulate histone modification in different cell lines.In SGC-7901 and MGC-803 gastric cancer cells,BEL-7402 hepatocarcinoma cells and U87 VIII glioma cell,the levels of H3K4 me1/2/3 and H3K27 ac were increased,and those of H3K4 ac and H3K27me1/2/3 were decreased following treatment with Lenti-HOTAIR si.Previous study had showed that HOTAIR recruited PRC2 complex(SUNZ12,EZH2,EED)to affect histone H3 lysine 27 methylation.We sought to identify the histone modifying enzymes that could be involved in H3K27 methylation and acetylation affected by HOTAIR.The results demostrated that HOTAIR targeted methylase EZH2 to the sites of H3K27.However,acetyltransferases CBP was considered as an important role in histone H3K27 ac without the existence of SUZ12.Therefores we showed that the loss of PRC2 activity induced by HOTAIR depletion results in a global decrease in H3K27 methylation and a large increase in H3K27 acetylation.Since the EMT is characterized by increased cell migration and invasiveness,we evaluated the effect of HOTAIR on gastric cancer cell-EMT processes.The expression of the epithelial marker E-cadherin(CDH1)was higher in HOTAIR knockdown cells compared to the control cells.By contrast,the mesenchymal markers,including N-cadherin,snail,slug,twist and ?-catenin,were decreased in the HOTAIR knockdown cells.To study the underlying mechanism by which E-cadherin transcription was suppressed by HOTAIR-mediated H3K27 methylation and acetylation,we performed chromatin immunoprecipitation(Ch IP)coupled with quantitative PCR analysis(ChIP-qPCR)to detect specific binding to the promoter of E-cadherin(CDH1).Gene Brownser showed that both H3K27me3 and H3K27 ac were enriched in the promoter region of the CDH1 gene.The results showed that HOTAIR silencing decreased the binding of H3K27me3 to the E-cadherin promoter and induced a strong recruitment of H3K27 ac to the E-cadherin binding site at the promoter of E-cadherin in gastric cancer cells.In conclusion,we validated that HOTAIR is a critical factor during carcinogenesis and progression in gastric cancer.Next,we explored the relationship between HOTAIR and histone modification.Additionally,the relationship between PRC2 complex and H3K27me3/ac needs deeper exploration.In a word,HOTAIR promotes the EMT of gastric cancer by a switch between the acetylation and the trimethylation of H3K27 that correlates with the transcriptional activation of E-cadherin,indicates a new sights of target therapy in gastric cancer.