ELL2 Expression Is Downregulated In Gastric Cancer Tissues And Overexpression Of ELL2 Inhibits Proliferation,migration And Invasion Of Gastric Cancer Cells

Background and purpose Gastric cancer(GC)is considered one of the world’s most common prevalent malignancies,ranking fifth(5.6%)among the 36 cancers worldwide,respectively.In our country,GC is the second most commonly diagnosed cancer and also the second leading cause of tumor mortality.The usual lack of specific signs in early GC,coupled with the lack of widespread gastroscopy,leads to a low detection rate,and most patients have missed the best opportunity for surgery by the time they are first seen.In addition,the overall prognosis of GC remains poor due to high morbidity,metastasis,and mortality.Therefore,it is necessary to explore the mechanism of GC development and explore new therapeutic targets.Recent studies have shown that the elongation factor for RNA polymerase II 2(ELL2)can be bound and stabilized by RB,and that simultaneous knockdown of ELL2 and RB enhances the proliferation of prostate cancer cells.Besides,ELL2 regulates RNA processing in plasma cells.Currently,no studies on ELL2 have been reported in GC.In this study,we examined the variation of ELL2 expression in GC and its connection with prognosis as well as its influences on GC cell function to probe the mechanism of its role in GC.Methods(1)Relevant datasets from GEO,GTEx,and TCGA databases were processed using R language software(version 4.0.0)to analyze ELL2 expression in pan-and gastric cancer,and validated using clinical GC samples.(2)Kaplan-Meier database to analyze the relationship between ELL2 expression and OS of gastric cancer patients.Differentially expressed genes associated with ELL2 in the STAD dataset were identified using the Linked Omics database,and the 200 differentially expressed genes that were positively associated were subjected to GO functional analysis.GSEA software analyzed the enrichment of pathways in the high and low expression groups of ELL2 in the STAD dataset.(3)The relationship between ELL2 expression and immune cell infiltration was analyzed using R software and TIMER database,and the relationship between ELL2 and infiltration of 24 immune cell subpopulations was further validated using the ss GSEA method.Subsequently,the expression levels of ELL2 were analyzed for correlation with immune checkpoints as well as immune cell surface markers.(4)Knockdown and overexpression treatments of ELL2 gene in AGS and HGC cell lines were performed using si RNA and overexpression plasmids and detected using Western bloting and q RT-PCR.Finally,CCK-8 and Transwell assays were used to detect the changes in proliferation,migration and invasion ability of gastric cancer cells after knockdown or overexpression treatment.Results(1)Several databases and clinical gastric cancer samples show that ELL2 expression is decreased in gastric cancer compared to normal tissue.(2)Kaplan-Meier website analyzed that the lower the expression of ELL2,the worse the prognosis of GC patients.The GO function analysis of the differential genes was mainly enriched in "positive regulation of MAPK cascade","regulation of epithelial cell proliferation","epithelial cell migration" and other functions.The enrichment analysis of GSEA was mainly in "JAK-STAT signaling pathway","cancer signaling pathway","T cell receptor signaling pathway" and other pathways.(3)The analysis of immune cell infiltrations revealed that the expression of ELL2 was positively correlated with the degree of infiltration of B,CD8+ T,CD4+ T cells,and with immune checkpoints such as PD-1 and immune cell markers such as CD79 A and CD8 A.(4)Western bloting and q RT-PCR assays of the gastric cancer cell lines AGS/HGC after si RNA/overexpression plasmid treatment,respectively,suggested downregulation/upregulation of ELL2 expression.Functional assays of knockdown and overexpression cell lines revealed that their proliferation,migration and invasion abilities were promoted/inhibited.ConclusionThis study demonstrates that ELL2 expression is lowered in GC and positively associates with diverse immune cell infiltration.Overexpression of ELL2 gene can suppress the proliferation,migration and invasion of GC cells.It may act as a fresh target for the therapy of GC.