The Effect Of MiR-422a On The Metabolism And Malignant Biological Behavior Of Gastric Cancer Cells And Its Mechanism

Aim: Gastric cancer is one of the most common cancer types and the third leading cause of cancer-related death worldwide.Although Helicobacter pylori infection is responsible for gastric neoplastic transformation via inducing chronic gastritis in the early stages of GC initiation,the evolution into an invasive cancer is a multistep process with various modification in cell differentiation,proliferation,and/or survival;the potential mechanism is not fully understood.MicroRNAs(miRNAs),a class of endogenous non-coding small RNAs,repress gene expression by binding to the 3'-untranslated regions(3'-UTR)of their target m RNAs,leading to the degradation or translational suppression.Previous studies have demonstrated that miRNAs are abnormally expressed in numerous cancer types and display tumor promoting or suppressing roles via their interaction with tumor suppressors and oncogenes.Therefore,determining specific miRNAs that contribute to carcinogenesis would be in favor of cancer diagnosis,prognosis and therapy Despite its having been characterized as a tumor suppressor gene for lung cancer and colorectal cancer,the biological functions of miR-422 a and its molecular mechanisms in GC remain unknown.Methods: qRT-PCR analysis was used to measured miR-422 a expression in 60 paired tumor tissues and in corresponding adjacent tissues from GC patients.Lentivirus infection was used to restore miR-422 a expression or suppressed its expression in GC cell lines.Using Edu,colony formation and tranwell assays,we evaluated the effects of miR-422 a on tumor cell proliferation and motility in vitro.A series of animal studies were performed to examine the rolef of miR-422 a in tumor cell proliferation and metastiasis in vivo.To verify the impact of miR-422 a on glycolysis and oxidative phosphorylation,extracellular acidification rates(ECAR)and oxygen consumption rates(OCR)were measured.Five algorithms were applied to investigate putative targets of miR-422 a.Via flow cytometry,we examined the impacts of miR-422 a on ROS production.Via western blotting,we explored which signaling pathway the miR-422 a impacts.Results: We showed that micro RNA-422a(miR-422a)expression was dramatically downregulated in gastric cancer(GC)samples and cell lines compared with normal controls,and that its expression level was inversely related to tumor size and depth of infiltration.Functional studies revealed that the overexpression of miR-422 a in GC tumor cells suppressed cell proliferation and migration,and drove a metabolic shift from aerobic glycolysis to oxidative phosphorylation.Mechanistic analysis suggested that miR-422 a repressed pyruvate dehydrogenase kinase 2(PDK2)to restore activity of the pyruvate dehydrogenase(PDH),the gatekeeping enzyme that catalyzes the decarboxylation of pyruvate to produce acetyl-Co A.Importantly,we further demonstrated that the mir-422a-PDK2 axis also influenced another metabolic pathway,de novo lipogenesis in cancer cells,and that it subsequently affected reactive oxygen species(ROS)and RB phosphorylation levels,ultimately resulting in cell-cycle arrest in G1 phase.Conclusion: The miR-422a-PDK2 axis is an important mediator in metabolic reprogramming and a promising therapeutic target for antitumor treatment.