| Objective:To determine the expression of MALAT1 gene in gastric cancer based on the public database,to explore the clinical significance of MALAT1 in gastric cancer,and to explore the effects of interfering with its expression level on the proliferation,invasion,migration and EMT process of gastric cancer cell line BGC-823.Methods:To explore the difference of MALAT1 expression between gastric cancer tissue and normal gastric mucosa tissue based on TCGA and GTEx database,and to clarify the relationship between the expression level of MALAT1 in gastric cancer tissue and clinical data of patients.The differential genes were screened and analyzed by GO and KEGG enrichment analysis.MALAT1 coexpression genes were screened by MEM database and analyzed by GO and KEGG enrichment analysis.GEO database and Kaplan-Meier Plotter online analysis tool were used to analyze the relationship between the expression level of MALAT1 and OS in patients with gastric cancer.The expression of MALAT1 in human gastric cancer cell lines MGC80-3,HGC-27,SGC-7901,BGC-823 and human gastric epithelial cell line GES-1 was detected by RT-PCR.Human gastric cancer BGC-823 cells were divided into si-MALAT1 group and negative control group(si-NC group).At the same time,MALAT1 siRNA and negative control siRNA,were transfected into two groups of BGC-823 cells to interfere with the expression of MALAT1 gene.After MALAT1 was interfered by siRNA successfully by RT-PCR technique,the proliferation,migration and invasion ability of the two groups were compared by CCK-8 test,scratch test and Transwell test.Western blotting was used to detect the expression of EMT iconic protein molecules N-cadherin,E-cadherin and vimentin after siRNA was successfully transfected into the two groups.Results:(1)Based on the GTEx database,the expression level of MALAT1 in normal men wasranked from high to low,the top five organs were thyroid(value=9.20),pituitary(value=8.72),prostate(value=8.70),nerve tissue(value=8.50)and bladder(value=8.25),and from low to high,the top five organs were liver(value=5.32),pancreas(value=6.61),skeletal muscle(value=6.69),stomach(value=6.80)and brain(value=6.81).In normal women,the expression level of MALAT1 was ranked from high to low,the top five organs were thyroid(value=9.19),ovary(value=9.12),pituitary(value=8.81),fallopian tube(value=8.72)and nerve tissue(value=8.51),and from low to high,the top five organs were liver(value=5.72),pancreas(value=6.51),bone marrow tissue(value=6.60),stomach(value=6.85)and skeletal muscle(value=6.86).(2)Based on GTEx and TCGA database,2144 differential genes,including 951up-regulated genes and 1193 down-regulated genes,were found in 206 normal gastric mucosal tissue samples and 375 gastric cancer tissue samples(P<0.05).(3)Based on TCGA and GTEx database,the expression of MALAT1 in gastric cancer was significantly increased.In TCGA database,there are 32 pairs of gastric cancer tissues and adjacent normal gastric mucosa tissues(P<0.05).There is no significant difference in the expression level of MALAT1 between gastric cancer tissues and their matched paracancerous tissues(P>0.05).(4)Based on the TCGA database,the expression level of MALAT1 was related to the race of patients with gastric cancer and different in patients of different races.The difference was statistically significant(P<0.05).The expression level of MALAT1 in Central Asian race was significantly higher than that in Caucasian and black race.The expression level of MALAT1 was correlated with T stage of gastric cancer.The expression level of MALAT1 was different in patients with different T stage,and the difference was statistically significant(P<0.05).The expression level of MALAT1 in T3 and T4 gastric cancer patients was significantly higher than that in T1 and T2 gastric cancer patients.The expression level of MALAT1 in gastric cancer patients with different clinicopathological stages was different,and the difference was statistically significant(P<0.05).The expression level of MALAT1 in stage Ⅰwas significantly higher than that in stage Ⅲ and Ⅳ(P<0.05).(5)GO analysis of 2144 differential genes showed that the differential genes weremainly enriched in the classical pathway of complement activation,humoral immune response mediated by circulating immunoglobulin and stimulation signal pathway mediated by Fc receptor.KEGG signal pathway analysis showed that the differential genes were mainly concentrated in cell cycle,ECM-receptor interaction,p53 signal pathway and other signal pathways(P<0.05).MALAT1 was not significantly enriched.(6)Based on MEM database,GO analysis of MALAT1 coexpression genes showed that they mainly play the functions of RNA splicing,nuclear composition,Poly(A)RNA binding,protein binding and so on.The analysis of KEGG signal pathway suggests that co-expressed genes may be involved in the signal pathways regulating stem cell pluripotency,such as mTOR signal pathway,Fox0 signal pathway and so on(P<0.05).(7)Based on Kplan-Meier Plotter Gastric Cancer and GEO databases,the overall survival time of gastric cancer patients with high expression of MALAT1(Cutoff >11770)was significantly lower than that of patients with low expression of Cutoff(Cutoff ≤ 11770)(P<0.05).(8)The relative expression of MALAT1 in MGC80-3,HGC-27,SGC-7901 and BGC-823 gastric cancer cell lines was 1.48±0.07,2.00±0.26,3.48±0.50,4.18±0.20 respectively,which was higher than that of normal gastric mucosa cell line GES-1(P<0.05).(9)The ability of cell proliferation,invasion and migration in si-MALAT1 group was significantly lower than that in si-NC group(P < 0.05).The expression of vimentin and N-cadherin,the landmark molecules of EMT decreased,while the expression of E-cadherin increased,and the difference was statistically significant(P<0.05).Conclusion:(1)The expression of MALAT1 was significantly high in gastric cancer,and it was significantly correlated with race,T stage,clinicopathological stage and poor prognosis of patients.In human,MALAT1 may be related to gene functions and signal pathways such as RNA splicing,nuclear composition,Poly(A)RNA binding,protein binding,signal pathway regulating stem cell pluripotency,mTOR signal pathway,Fox0 signal pathway and so on.(2)Interfering with the expression level of MALAT1 can inhibit the proliferation,invasion,migration and EMT process of gastric cancer cell line BGC-823.(3)MALAT1 may be a potential molecular marker and therapeutic target for diagnosis,treatment and prognosis evaluation of gastric cancer. |
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