Activation Of SREBP-1c Alters Lipogenesis And Promotes Tumor Growth And Metastasis In Gastric Cancer

【Background】Gastric cancer is the fourth most common type of cancer and remains ranking at second leading cause of cancer-related death all over the world.The main strategy therapy of gastric cancer is surgical resection supplemented with adjuvant chemotherapy or chemoradiation which can improve overall survival of patients.Unfortunately,it has been considered as an aggressive disease with a poor prognosis and often diagnosed at an advanced or metastatic stage that continues to play a daunting impact on human health,the median overall survival of advanced or metastatic gastric cancer remains less than 1 year.So,it is urgent to give a continued focus on prevention,early detection and novel therapeutic options research of gastric cancer.Here starting with metabolites and lipids of gastric cancer tissues applying an omic approach,we attended to explore key factors for the development of gastric cancer upstream and investigate new potential targets for gastric cancer therapy.A metabolomics method is widely performed for providing intact information about biological systems,reflecting on the pathophysiological status of many diseases in humans and animals and their corresponding therapies,in which lipidomics is on basis of the lipid metabolic profiles of metabolomics.Lipidomics could identify the key typical lipid as signatures of species and provide a useful tool for the diagnosis and prognosis of disease.The fatty acid metabolism have contributed to the research of the potential pathogenic mechanism of cancer.Some kind of fatty acid such as palmitic acid(PA)was designated specifically reduce malignant hepatocellular carcinoma cell proliferation,impaired cell invasiveness,and suppressed tumor growth both in vitro and in vivo experiments.Oleic acid in omental adipocytes enhanced the invasiveness of gastric cancer cells induced by the activation of the PI3K-Akt signaling pathway.It was also recognized that lipid biosynthesis related enzymes could be one of the important hallmarks of cancer cells,such as stearoyl-Co A desaturase-1(SCD1),it increased monounsaturated fatty acids(MUFA)levels and MUFA administration could rescue migration and invasion defect of colorectal cancer cells induced by SCD1 knockdown.However,it was still confused that how lipogenic pathways are regulated in gastric cancer and the role of fatty acid in promoting gastric cancer.The sterol regulatory element binding protein 1c(SREBP-1c)is a member of sterol regulatory element-binding proteins family,which regulates the expression of genes required for the fatty acid synthesis such as fatty acid synthetase FASN and SCD1.The SREBP-1c is positively associated with many human malignancies,for example,the lipogenesis converged by SREBP-1 is responsible for regulating growth and progression of prostate cancer cells.SREBP-1 is also an independent prognostic marker and promotes invasion and migration in breast cancer.It has been demonstrated that the SREBP-1c was activated and its target genes was also upregulated in human glioblastoma multiforme carrying activating EGFR mutations.However,the function of SREBP-1 and the variation of fatty acid caused by SREBP-1 in human gastric remains to be fully elucidated.Our main aim of this study was to clarify the abnormal metabolic profile of gastric cancer tissues,especially related lipids,and to find out the main regulatory factors in the upstream.In this study,the UPLC-MS/MS-based metabonomics and lipidomics on human gastric cancer tissues and adjacent normal tissues were performed for this purpose.During the differential metabolites and lipids identification,the downregulation of PA in gastric cancer tissues was noticed.Next,we verified the therapeutic effect of PA on gastric cancer cells proliferation,migration and invasion.Moreover,we found the activation of SREBP-1c in gastric cancer and knockdown SREBP-1c inhibited gastric cancer progression.【Research methods】(1)Collected tissue samples of patients with gastric cancer from the Department of Gastrointestinal Surgery,the First Affiliated Hospital of Anhui Medical University,30 gastric cancer tissues and 30 adjacent normal gastric tissues,extracted water and lipid metabolites from each tissue,and detected each sample by UPLC-MS / MS Metabolites,followed by untargeted metabolomics and lipidomics analysis.(2)Western blot(WB)and real-time quantitative PCR(q RT-PCR)were used to screen out gastric cancer cell lines with high expression of SREBP-1c,and then gastric cancer cell lines with low expression of SREBP-1c were constructed.WB,q RTPCR,CCK8,Transwell,plate cloning assay and immunofluorescence(IF)were used to detect the effect of SREBP-1c on proliferation,migration and invasion of gastric cancer cells in vitro.The effects of SREBP-1c expression on epithelialmesenchymal transition(EMT)related proteins N-Cadherin and vimentin were also studied.【Research results】(1)In this study,the UPLC-MS/MS-based metabonomics and lipidomics on human gastric cancer tissues and adjacent normal tissues were performed for this purpose.During the differential metabolites and lipids identification,the downregulation of PA in gastric cancer tissues was noticed.(2)The expression level of SREBP-1c in gastric cancer was significantly higher than that in adjacent normal tissues.We collected gastric cancer tissues and adjacent normal tissues(n=30)from the Department of Gastrointestinal Surgery of the First Affiliated Hospital of Anhui Medical University.The expression of SREBP-1c in human gastric cancer tissues was significantly higher than that in adjacent normal tissues by Western Blot(WB)and real-time quantitative PCR(q RT-PCR)(P<0.05).The m RNA expression level of SREBP-1c in human gastric cancer tissues was significantly higher than that in adjacent normal tissues(P<0.05).Interfering SREBP-1c expression with specific si RNA lentivirus in SGC-7901 and AGS cell lines.WB and q RT-PCR assay showed that the SREBP-1c protein expression level and m RNA gene expression level in the cells were significantly lower than those in the control group after interference(p<0.05).Knockdown of SREBP-1c expression,the results of CCK8 assay showed that the proliferation of human gastric cancer cells was inhibited.Plate cloning experiment showed that the ability of human gastric cancer cells clone formation was decreased.The migration ability of human gastric cancer cells was inhibited by knockdown of SREBP-1c expression in SGC-7901 and AGS cells in Migration assay,and the Invasion assay suggested that interfering SREBP-1c expression inhibited the invasive ability of human gastric cancer cells.Western Blot assay was used to detect the expression of EMT-related markers N-Cadherin and Vimentin protein.It was found that compared with the control group,the expression of N-Cadherin protein and Vimentin protein decreased significantly in SGC-7901 and AGS cells by knockdown of SREBP-1c expression.【Conclusions】(1)SREBP-1c is significantly up-regulated and alters lipogenesis in human gastric cancer.(2)Down-regulating the expression of SREBP-1c inhibits the proliferation,migration,and invasion of gastric cancer cells,which can inhibit the progression of gastric cancer.(3)Down-regulation of SREBP-1c can significantly express the expression of NCadherin and Vimentin proteins.