Downregulation of miR-4772-3p promotes enhanced regulatory T cell capacity in malignant pleural effusion by elevating Helios levels

Background:Malignant pleural effusion(MPE)is a complicated condition of patients with advanced tumors.Further dissecting the microenvironment of infiltrated immune cells and malignant cells are warranted to understand the immune-evasion mechanisms of tumor development and progression.Methods:The possible involvement of microRNAs(miRNAs)in malignant pleural fluid was investigated using small RNA sequencing.Regulatory T cell(Treg)markers(CD4,CD25,forkhead box P3),and Helios(also known as IKAROS Family Zinc Finger 2[IKZF2])were detected using flow cytometry.The expression levels of IKZF2 and miR-4772-3p were measured using quantitative real-time reverse transcription polymerase chain reaction.The interaction between miR-4772-3p and Helios was determined using dual-luciferase reporter assays.The effects of miR-4772-3p on Helios expression were evaluated using an in vitro system.Correlation assays between miR-4772-3p and functional molecules of Tregs were performed.Results:Compared with non-malignant controls,patients with non-small cell lung cancer had an increased Tregs frequency with Helios expression in the MPE and peripheral blood mononuclear cells.The verified downregulation of miR-4772-3p was inversely related to the Helios*Tregs frequency and Helios expression in the MPE.Overexpression of miR-4772-3p could inhib让Helios expression in in vitro experiments.However,ectopic expression of Helios in induced Tregs reversed the effects induced by miR-4772-3p overexpression.Additionally,miR-4772-3p could regulate Helios expression by directly targeting IKZF2 mRNA.Conclusion:Downregulation of miR-4772-3p,by targeting Helios,contributes to enhanced Tregs activities in the MPE microenvironment.