The Role Of Long Non-coding RNA MALAT1 In Gastric Cancer

Purpose: Gastric cancer(GC)is the most common in China and the third most common cancer worldwide.In China,about 500,000 new cases of gastric cancer occur annually,accounting for nearly half of the global total,and the new patients with gastric cancer are younger.Although some progress has been made in the research of gastric cancer drugs in recent years,they cannot fundamentally improve the prognosis of gastric cancer.Although great progress has been made in treating gastric cancer,surgery is still the only way to cure gastric cancer.However,gastric cancer is characterized by insidious onset,inconspicuous early symptoms and missed diagnosis,easy metastasis and recurrence,and poor prognosis.Therefore,understanding the mechanisms of gastric cancer progression is critical for developing new therapeutic strategies.There is an urgent need for biomarker discovery and new therapeutic targets for early diagnosis.Long noncoding RNAs(lnc RNAs)are a class of noncoding RNAs more than 200 nucleotides in length that can regulate the expression of various genes,are involved in many pathophysiological processes and participate in tumorigenesis and development.Lung adenocarcinoma metastasis-associated transcript 1(MALAT1)is an important member of the lnc RNA family and promotes tumor progression by regulating mi RNAs.MALAT1 can trigger cancer processes by interacting with various cellular molecules such as RNA,DNA,and proteins,thereby affecting several signaling pathways that impact proliferation,migration,apoptosis,invasion,and tumorigenicity.MALAT1 is highly expressed in gastric cancer tissues and cells,but the mechanism of MALAT1 in gastric cancer is not fully understood.Our current work aims to elucidate a new molecular mechanism to reveal the effect of MALAT1 in gastric cancer and provide new targets and ideas for clinical intervention and treatment of gastric cancer.Methods: Gastric cancer tissues and adjacent tissues were examined by lnc RNA chip,and differentially expressed lnc RNAs were determined.In conjunction with functional bioinformatics analysis,MALAT1 was selected as a research target for experimentation.Gastric cancer and adjacent tissues were examined clinically,and RT-q PCR detected the expression differences of lnc RNA MALAT1 and mi R-320 b.The effects of Lnc RNA MALAT1 on biological functions such as gastric cancer cell proliferation was verified in vitro:Different pathological types of gastric cancer cell lines(MGC-803,MKN-45,SGC-7901,HGC-27)were cultured,and RT-q PCR detected the expression differences of Lnc RNA MALAT1 and mi R-320 b.Gastric cancer cells were cultured,and the experimental groups were as follows:(1)si R-NC;(2)si-Lnc RNA MALAT1 1#;(3)si-Lnc RNA MALAT1 2#;(4)p LVNC;(5)p LV-Lnc RNA MALAT1.The difference in Lnc RNA MALAT1 expression was detected by q RT-PCR;MTT drew the cell proliferation curve;the effect of Lnc RNA MALAT1 silencing on cell proliferation was observed by Brd U staining.The apoptosis and cell cycle changes were detected by flow cytometry;cyclin D1 was detected by q RT-PCR,and Western blotting,p21,CDK4,cyclin E2 expression changes,and GAPDH were used as an internal reference.Transwell was used to detect the changes in cell invasion ability;Western blotting was used to detect the expression changes of p-AKT and AKT signaling pathways.Verify that the effect of mi R-320 b on the biological function of gastric cancer cells is related to the AKT signaling pathway:Gastric cancer cells were cultured,and the experimental groups were as follows:(1)inhibitorNC;(2)mi R-320 b inhibitor;(3)mimics-NC;(4)mi R-320 b mimics.q RT-PCR was used to detect the differences in the expression of Lnc RNA MALAT1 and mi R-320b;MTT was used to draw the cell proliferation curve;Brd U staining was used to observe the effect of mi R-320 b on cell proliferation;flow cytometry was used to detect the changes of cell apoptosis and cell cycle;q RT-PCR and Western The expression changes of cyclin D1,p21,CDK4,and Cyclin E2 were detected by blotting with GAPDH as an internal reference;Transwell detected the changes of cell invasion ability;the expression changes of p-AKT and AKT signaling pathways were detected by Western blotting.Verification of the binding relationship between mi R-320 b and Lnc RNA MALAT1 in vitro:The luciferase reporter gene vector of Luc-Lnc RNA MALAT1 was constructed,and the binding of mi R-320 b to Lnc RNA MALAT1 was clarified by the activity of the luciferase reporter gene.Results: Our study showed that the expression of MALAT1 transcript was significantly increased in gastric cancer.The expression level of MALAT1 was increased in MGC803,MKN45,SGC7901,and HGC27 cell lines,while the expression level of mi R-320 b was significantly decreased.This suggests that upregulation of MALAT1 expression may play a key role in gastric cancer progression.However,MALAT1 was significantly downregulated in cells transfected with a MALAT1-specific si RNA plasmid(MALAT1-Homo-1183).Downregulation of MALAT1 significantly increased the apoptosis rate of gastric cancer cells,suggesting that MALAT1 promotes gastric cancer metastasis.In contrast,the relationship between MALAT1 and mi R-320 b and alters the expression of the AKT signaling pathway showed that MALAT1 reduced the expression of mi R-320 b,which was in contrast to that of MALAT1.The Akt-silencing MALAT1 effectively suppressed cell viability and delayed cell cycle transition from G1 to S phase in MGC803 and HGC27 cell lines by knocking down MALAT1.The cell proliferation index(PI)was also decreased by knocking down MALAT1.In cells in which MALAT1 was knocked down,the levels of the cell cycle-dependent proteins cyclin E2,cyclin D1,and CDK4 were decreased,and the level of p21 was significantly increased.These results suggest that downregulation of MALAT1 and overexpression of mi R-320 b reduce p-Akt/Akt phosphorylation,thereby decreasing GC cell growth and survival and increasing the proportion of cells in the G0/G1 phase.Thus,MALAT1 inhibits GC by triggering Akt-dependent apoptosis.Conclusions: MALAT1 is critical for GC development and progression through the mi R-320b/Akt signaling pathway.