Tumor Necrosis Factor ? Reduces SNAP29 Dependent Autolysosome Formation To Up-Regulate Prion Protein Expression And Promote Tumor Cell Migration

Tumor necrosis factor ?(TNF?)is an important proinflammatory factor,which plays an important role in the process of immunity,inflammation,cell proliferation,differentiation and apoptosis.It can regulate tumor microenvironment,but the mechanism of inflammation promoting cancer cell migration and metastasis is not completely clear.Therefore,it is of great significance for cancer treatment to explore the mechanism by which inflammation stimulates cancer cell metastasis from the cellular and molecular level.In the first chapter I introduce the research background.I first describe the epidemiology,genetics,and biology of melanoma and lung cancer.Then I elaborate the function of inflammatory factor TNF? and its relationship with the occurrence and development of cancer followed by introducing the two main degradation systems in cells,and finally I focus the structure,function and role of Forkhead box protein P3(FOXP3),Synaptosomal-associated protein 29(SNAP29),prion protein(Pr P)and other related proteins in melanoma and lung cancer.The second chapter is the main focus of the dissertation.In a human melanoma cell line,M2,and a lung carcinoma cell line,A549,TNF? up-regulated Pr P,and promoted tumor cell migration in a Pr P dependent manner.Silencing PRNP abrogated TNF? induced tumor cell migration;this phenotype was reversed when PRNP was reintroduced.However,under TNF? treatment,the transcription level of Pr P did not change,therefore TNF? somehow changed the degradation pathway of Pr P.In M2 and A549 cell lines,the degradation of Pr P was mainly through autophagy.Did TNF? influence the degradation pathway and lead to the increase of Pr P expression? TNF ? treatment increased Microtubule-associated proteins 1A/1B light chain 3B(LC3)and Sequestosome-1(SQSTM1/p62)expression,indicating that the fusion of autophagosome and lysosome was inhibited.The double fluorescent plasmid m Cherry-GFP-LC3 was transfected into tumor cells,and the yellow dots were increased significantly,which is proved this conclusion.TNF? treatment reduced SNAP29 expression,which is essential in the fusion of autophagosomes and lysosomes creating autolysosomes,and causing a reduction in the transcription level.But,when SNAP29 was silenced,cancer cells no longer responded to TNF?.FOXP3 is an important transcription factor,which plays an important role in maintaining the homeostasis of the immune system.FOXP3 being a bona fide transcription factor for SNAP29 was confirmed in a promoter binding assay.Treatment with TNF? activated nuclear factor kappa B(NF-?b)signaling,reduced the expression of FOXP3,and then reducing SNAP29 expression.In conclusion,a reduction in autophagy is the underlying mechanism by which expression of Pr P is up-regulated,and tumor cell migration is enhanced upon TNF? treatment.Disrupting the TNF?-NF-?b-FOXP3-SNAP29 signaling axis may provide a therapeutic approach to mitigate tumor cell migration.The third chapter is the summary and discussion of this paper.TNF? stimulates tumor cells to reduce FOXP3 expression,inhibit Pr P degradation and accelerate tumor cell migration.However,the specific mechanism of FOXP3 regulation by TNF? and the mechanism of Pr P regulating cancer cell migration need to be further explored.