The Fuction And Mechmism Of MALAT-1 In The Invasion And Metastasis Of Gastric Cancer

BackgroundGastric cancer is one of the quite common malignant tumor around the world.In recent years,with the constantly advance in medical diagnosis and treatment technology,the combination of chemotherapy,radiotherapy and surgery treatment,the life of the patients with gastric cancer and the quality of life has improved,but the overall lower survival rate still make people feel dissatisfactory.One of the reasons is the lack of early molecular marker,so that gastric cancer was found at advanced stage with lymph node metastasis and distant metastasis.Invasion and metastasis are the dominant factor of survival and prognosis in patients with gastric cancer.A growing body of evidence shows that many long non-coding RNA play an important role in gastric cancer development(including the invasion and metastasis).LncRNA is a type of high-profile non-coding RNA in recent years,its length is more than 200 nt,can regulate gene expression at multiple levels(epigenetic level,transcriptional level and post-transcriptional level).Mammalian metastasis-associated lung adenocarcinoma transcript 1(MALAT-1)is a long noncoding RNA with a length of more than 8,000 nt,located in 11q13 and the nuclear speckle.Since its discovery in 2003,MALAT-1 has been confirmed that it expressed in various types of cancer,and correlated with proliferation,apoptosis,invasion and metastasis of cancer.However,its research are rarely reported in gastric cancer.Objective1.To investigate the expression patterns of MALAT-1 in gastric cancer cells and tissues;2.To explore the role of MALAT-1 in the invasion and metastasis of gastric cancer and potential molecular mechanisms.Methods1.To detect the expression level of MALAT-1 in GC cell lines(SGC7901,MKN45,BGC823,AGS)and high and low metastasis potential GC cell lines(SGC7901M,SGC7901NM)with qRT-PCR.2.To detect the expression level of MALAT-1 in 20 cases of GC tissues(relative to pericarcinomatous tissues)with qRT-PCR.3.To stably downregulate MALAT-1 expression in GC cell lines SGC7901 M and AGS by constructing si RNA lentivirus;to test the influence of dowregulation of MALAT-1expression on the migration and invasion ability of GC cell lines SGC7901 M and AGS by in vitro and in vivo experiments,such as wound-healing assays,transwell assays,high content assays and the nude mouse tail intravenous injection assays and so on.4.To test the expression of EMT-related markers E-cadherin and Vimentin after stably downregulation of MALAT-1 expression through qRT-PCR,WB experiment and cell immunofluorescence,so as to verify whether MALAT-1 promotes the invasion and metastasis of GC by promoting the occurrence of EMT,in order to provide new ideas for clinical prevention and treatment of GC.Results1.The qRT-PCR results showed that MALAT-1 was upregulated in GC cell lines SGC7901,MKN45,BGC823,AGS,with the most significant upregulation of AGS(relative to immortalized gastric epithelial cell line GES);the expression of MALAT-1 was higher in the high metastasis potential GC cell line SGC7901 M than the low metastasis potential GC cell line SGC7901 NM.2.The qRT-PCR results showed that the expression level of MALAT-1 in GC tissues was significantly higher than its expression in the pericarcinomatous tissues.3.After downregulating MALAT-1 expression in SGC7901M and AGS,compared with the control group,we confirmed that the migration and invasion ability of SGC7901M and AGS reduced significantly through wound-healing assays,transwell assays,high content assays and the nude mouse tail intravenous injection assays.4.After downregulating MALAT-1 expression in SGC7901M and AGS,the results of qRT-PCR showed that the m RNA expression of E-cadherin increased and the m RNA expression of Vimentin reduced;the results of WB experiment and cell immunofluorescence showed that protein expression of E-cadherin increased obviously and protein expression of Vimentin significantly reduced,suggesting that MALAT-1mediated the invasion and metastasis of GC cells involving in EMT.Conclusions1.LncRNA MALAT-1 is one of the key molecules which influences the invasion and metastasis of GC.2.LncRNA MALAT-1 may partly promote the invasion and metastasis of GC cells by regulating EMT.