MiR-338-3p Inhibits Skin Inflammation And Lung Cancer Progression By Regulating AKT Signaling Pathway

An increasing number of research suggests that chronic inflammation can lead to tumors.In this process,microRNAs(miRNAs)play a significant role in the regulation of the signaling pathways related to these two diseases.miRNAs are short non-coding RNAs and can inhibit translation or promote degradation of a target mRNA by binding to its 3'-UTR thus regulating cell proliferation,differentiation,migration,growth,apoptosis and other behaviors.AKT signaling pathway is a very important intracellular signal transduction pathway in mammals and this pathway is closely related to the process of cell transformation,proliferation,mobility and metabolism,as well as the occurrence and development of various diseases.Therefore,exploring the relationship between miRNAs and PI3K/AKT signaling pathway,and their roles in the process of inflammation and tumor development will be of great value to elucidate the mechanism of inflammation and tumorigenesis.In this study,miR-338-3p(a member of the miR-338 family located on intron 17 of the apoptosis associated tyrosine kinase)was used to investigate the regulatory mechanism of the development of acne(an inflammatory model)and lung cancer(a tumor model).In addition,the relationship between miR-338-3p and PI3K/AKT signaling pathway was also studied.The research contents are as follows:1.An in vitro inflammatory model(acne)was established by the induction of TNF-a.In this model,TNF-a can promote the formation of lipid droplets in sebaceous cells(related to the development of acne).After transfection of miR-338-3p,the cells were analysed by flow cytometry and TLC experiment.Results showed that miR-338-3p could inhibit the formation of lipid droplets induced by TNF-a.A significant decrease in phosphorylation levels of different AKT sites(Ser473,Thr308)in the PI3K/AKT signaling pathway was observed using immunofluorescence experiments.However,recovering the activity of PI3K/AKT can reverse the amount of lipoprotein induced by miR-338-3p-treated TNF-a,indicating that miR-338-3p can inhibit the signal transduction of PI3K/AKT in sebaceous cells.After that,specific inhibitors of PI3K and AKT were employed to block their activity and subsequently the production of fat induced by TNF-a was measured.It was found that the fat content was significantly reduced,which to some extent indicated that PI3K/AKT signaling pathway was involved in the regulation of inflammatory response,and the down-regulation of PI3K/AKT activity would reduce the generation of fat,thereby inhibiting the inflammatory response.We also found that transfection of siRNA against PREX2a,a potential target of miR-338-3p,could significantly reduced the phosphorylation of AKT at Ser473 and Thr308 in cells,while the overexpression of PREX2a reversed the miR-3 3 8-3p-mediated inhibition of both AKT phosphorylation at these sites and lipogenesis by,indicating that PREX2a was involved in the regulation of PI3K/AKT signaling pathway.In addition,miR-338-3p showed significant inhibition of sebaceous gland lipogenesis from Tg-huTNFa mice.Based on these results,we concluded that miR-338-3p can inhibit the formation of fat by down-regulating the expression of PREX2a and blocking AKT signaling,thus inhibiting the inflammatory response.2.The content of the second part was mainly about the role and mechanism of miR-338-3p in the invasion of lung cancer cells(A549).First,it was observed that the proliferation of A549 cells was increased and the apoptosis was promoted after the transfection of miR-338-3p.The transwell test confirmed that miR-338-3p significantly reduced the invasion of A549 cells.The results of gene chip analysis showed that miR-338-3p could lead to up-regulation of 216 genes and down-regulation of 147 genes in A549 cells,and these affected genes were enriched in various signal pathways,including AKT and ?-catenin signaling pathways.Results of immunofluorescence staining and western blotting showed that miR-338-3p could down-regulate phosphorylation of AKT(at Ser473 and Thr308)and ?-catenin(at Ser552)in cells,leading to the inhibitiob of AKT/?-catenin signaling pathway.In addition,miR-338-3p significantly inhibited the development of primary tumors in KrasG12D mice.Therefore,miR-338-3p mainly inhibits the invasion of lung cancer cells by down-regulating AKT/?-catenin signal transduction.