The Effects And Mechanisms Of The Tumor Suppressor Gene EIF4EBP3 On The Growth And Liver Metastasis In Gastric Cancer

Backgroud &Aims:Gastric cancer(GC)is the fifth most frequently diagnosed cancer and the third leading cause of cancer-related death among 36 cancers;over one million new cases of GC were diagnosed in 2018.In China,the incidence and mortality of GC are the second highest among malignant tumors.GC is occult,not easy to be found early,and the prognosis is very poor.Genetic and epigenetic aberrations of tumor-related genes have been thought to play a crucial role in GC development.These discoveries may also identify potential biomarkers and therapeutic targets for tumor diagnosis,treatment and prognosis in patients with GC.Through massive expression profiling,We identified eIF4EBP3 as a new methylated gene in GC.However,the alterations and functions of eIF4EBP3 in GC have not been studied.Methods:The expression of eIF4EBP3 in GC specimens and cells were analysed based on data retrieved from open gene expression array database.eIF4EBP3 methylation was evaluated by MSP PCR and BGS.eIF4EBP3 expression was determined by RT-PCR andimmunohistochemistry.Then,the correlation between expression and clinicopathological features and prognosis of patients were analyzed.The effects of eIF4EBP3 on the growth,migration and cell cycle of tumor cells were tested.The downstream targets of eIF4EBP3 were screened by mass spectrometry,and their correlation and role in the development of gastric cancer were verified.Results:eIF4EBP3 is downregulated in GC tissues and cell lines by promoter hypermethylation.eIF4EBP3 was hypermethylated in most GC cell lineswith silenced(6/7)or reduced expression,also in most of the GC tissues(compared with ANT,p < 0.001).eIF4EBP3 was downregulated in primary GC;eIF4EBP3 protein expression was significantly correlated with TNM stage(p = 0.038)and pathologic differentiation(p =0.009).Moreover,negative eIF4EBP3 expression indicated poor 5-year overall survival rate(p < 0.001).After stratification by TNM stage,eIF4EBP3 high-expression patients in stageI/II had significantly longer survival than patients with low expression(p =0.002).Ectopic eIF4EBP3 expression suppresses GC cell growth,induced cell cycle arrest in G1 phase,inhibited GC cell migrationa/invasion,suppressed subcutaneous and liver metastasis tumor growth in nude mice.The downstream target gene β-catenin was selected by LS-MS/MS.IHC and WB proved the negative correlation.The biotin RNA pulldown assay confirmed that eIF4EBP3 down-regulated the protein level of β-catenin by inhibiting the eIF4E-mediated translation of β-catenin,and then inhibited the proliferation,invasion and liver metastasis through its downstream effector molecules such as CDK1 and Slug.It was found that overexpression of β-catenin reversed the inhibition of eIF4EBP3 on proliferation and migration of GC cells.Conclusions:In present study,we first elucidated that eIF4EBP3 plays a TSG role in GC,and its downregulation in GC patients was caused by DNA hypermethylation at its 5’-promoter region.eIF4EBP3 inhibits the proliferation,migration and liver metastasis of GC cells,by targeting the eIF4E/β-catenin axis.eIF4EBP3 expression may as an independentbiomarker for survival of GC patients.