PFN2 Regulates Palmitic Acid Metabolism Through PI3K/FABP5/AKT Axis And Promotes EMT In Lung Cancer

Background:Lung cancer is one of the most deadly cancers in the world,and most lung cancer belong to non-small cell lung cancer(NSCLC).Since the early symptoms of lung cancer are not obvious and there is a lack of effective early screening means,most patients are already in the middle to late stage when they are detected,thus the prognosis of lung cancer patients is currently poor.As lung cancer research continues to advance,people have increasingly realized the key role of lipid metabolism reprogramming in the development of lung cancer and explored the corresponding mechanisms.Several studies have found that increased fatty acid uptake,synthesis,oxidative utilization,and storage in cancer cells in a variety of tumors promote malignant progression.However,studies on the reprogramming of lipid metabolism in lung cancer are still insufficient,and studies on the biological processes and molecular mechanisms of lipid metabolism in lung cancer may provide theoretical support for the diagnosis of early lung cancer and the prognosis of lung cancer patients.FABP5(Fatty acid-binding protein 5),a member of the fatty acid-binding protein family,is involved in the cellular uptake and transport of fatty acids and is also required for the ab initio synthesis of fatty acids,and regulates the expression of enzymes involved in this pathway(including FASN and SCD1)by targeting fatty acids to specific metabolic pathways to redirect fatty acids to complex lipid synthesis.In addition,the function of FABP5 is required for tumor cell cycle,migration,and in vivo growth.TCGA database analysis revealed that FABP5 is highly expressed in NSCLC and its differential expression correlates with tumor size,grade,metastasis,and TNM stage of NSCLC.PFN2(Profilin,pro-fibrillin 2)is an actin-binding protein that is mainly involved in constituting the cytoskeleton and regulating actin polymerization.In recent years,the important role played by PFN2 in the progression of some cancers has been gradually attracting attention and research.Our group performed immunoprecipitation and mass spectrometry analysis for PFN2 in advance to search for proteins which PFN2 potentially interacts.In the mass spectrometry results,we focused on the FABP5 molecule.The results of immunoprecipitation then demonstrated that PFN2 could bind to FABP5,so we speculated that PFN2 might affect the biological process of NSCLC through FABP5.Thus,this experiment investigated the effect of PFN2 on lipid metabolism in NSCLC at the cellular level as well as at the animal level,and the results may provide new therapeutic targets for lipid metabolism in NSCLC.Methods:Firstly,we analyzed the expression of FABP5 and PFN2 in lung cancer cells and their relationship with prognosis by TCGA database.We screened for PFN2 expression in lung cancer and its correlation with prognosis,and screened for high expression of PFN2 and its binding molecule FABP5 in the histological results of clinical samples.after that,we performed PFN2 knockdown in NSCLC cell line A549 and explored that PFN2 knockdown could have an effect on EMT-related molecule expression as well as phenotype in NSCLC,and The changes of FABP5 expression level after PFN2 knockdown were explored by Western Blot assay.On this basis,the phenotypes of lipid metabolism affected by PFN2 were explored,and the intracellular neutral lipid content and lipid metabolism-related molecules [e.g.CD36(cluster of differentiation 36,leukocyte differentiation antigen 36): mediates lipid uptake;FASN(Fatty Acid Synthase).regulates fatty acid synthesis;HSL(hormone-sensitive lipase): regulates lipolysis] were examined.Next,we examined the differences in medium and long chain fatty acids in A549 cells after PFN2 knockdown by metabolomics and explored the mechanisms.Results:We derived elevated expression of FABP5 and PFN2 in lung cancer through TCGA database analysis and correlated with poor prognosis.We also explored the effect of PFN2 knockdown on the biological function of lung cancer cells and discovered the binding of PFN2 to FABP5,and subsequently demonstrated that PFN2 knockdown affected the expression of lipid metabolism-related proteins such as CD36,FASN,and HSL while affecting the expression of FABP5 in lung cancer cells,thus promoting the reprogramming of lipid metabolism in lung cancer cells.It was found that palmitate catabolic utilization was significantly reduced in lung cancer cells after PFN2 knockdown,resulting in intracellular lipid accumulation,which in turn affected lung cancer cell proliferation and apoptosis.In this study,the relationship between PFN2 expression and FABP5,lipid levels and lipid metabolism-related molecules in lung cancer was first determined by exploring the relationship between PFN2 and lipid metabolism reprogramming in lung cancer.Conclusions:1.PFN2 is associated with EMT in lung cancer2.PFN2 promotes EMT in lung cancer by reprogramming palmitic acid metabolism.3.PFN2 regulates palmitate metabolism in lung cancer through PI3K/FABP5/AKT axis.