USP40 Regulates Cisplatin Resistance In Non-small Cell Lung Cancer Through STING

Background: Under normal circumstances,DNA is mainly found in the nucleus and mitochondria.When the invasion of foreign pathogens or DNA damage induced by external factors leads to the entry of nuclear DNA into the cytoplasm,aptamer c GAS or STING will further recognize and bind the cytoplasmic DNA,induce the expression of immune-stimulating genes and type I interferon,and activate T cells to link adaptive immunity.Sting-based pathways play a key role in host anti-tumor immune response.Therefore,targeting STING can provide a new therapeutic strategy.Ubiquitination is one of the major post-translational modifications of proteins and plays an important role in regulating protein function.STING,as an important connector protein,is regulated by various types of ubiquitination modifications.Deubiquitination enzymes mainly regulate the function and fate of proteins by removing ubiquitin chains on substrates.The study of STING deubiquitination enzymes is helpful to regulate its stability and function.Chemotherapeutic resistance is a common phenomenon in clinical treatment,which leads to a decrease in the efficacy of drug therapy.There is increasing evidence that the ubiquitination-proteasome system is associated with chemotherapy resistance,so deubiquitinase can be an effective target for chemotherapy resistance.Objective: To screen the deubiquitination enzyme regulating STING,determine the effects of STING and its deubiquitination enzyme on nonsmall cell lung cancer,and study the effect of deubiquitination enzyme USP40 on chemotherapy sensitivity of non-small cell lung cancer,so as to provide a new perspective for clinical tumor chemotherapy resistance.Methods: We used the expression of STING in the database to analyze the survival prognosis of patients with non-small cell lung cancer.In vitro biological function experiments verified the role of STING in NSCLC.Western Blotting screened USP40,a deubiquitination enzyme that regulated STING protein levels,and constructed cell lines with overexpression and knockdown USP40 to explore its effects on cell proliferation,clonal formation and migration.The effect of USP40 on the growth of non-small cell lung cancer cells was further investigated by subcutaneous tumor-forming experiment in nude mice.In addition,a series of experiments including q PCR,Western Blotting,CCK8 and Transwell were conducted to further investigate the role of USP40 in chemotherapy sensitivity of NSCLC.Results: TCGA database showed that the expression levels of USP40 and STING were decreased in non-small cell lung cancer tissues,and the expression levels were positively correlated with patient survival.Biological function experiments demonstrated that the high expression of USP40 and STING could inhibit the proliferation,clonal formation and migration of NSCLC cells.In addition,in vivo subcutaneous tumorigenesis in nude mice demonstrated that low expression of USP40 accelerated tumor cell cycle progression.In vitro experiments also proved that USP40 interacted with STING and played a deubiquitination enzyme activity.By removing STING’s K48-related ubiquitination chain,the protein level of STING was stabilized.Finally,we found that the high expression of USP40 can improve the resistance of NSCLC to chemotherapeutic drugs.Conclusion: USP40 and STING both play the role of tumor suppressor genes in non-small cell lung cancer and prolong the survival of patients.USP40 inhibited the progression of NSCLC by up-regulating STING expression;USP40 inhibits chemotherapy resistance in non-small cell lung cancer.