Molecular Mechanism Of Deubiquitinase DUB3 Regulating The Proliferation Of Non-small Cell Lung Cancer Via Stabilizing Cyclin A

Lung cancer is the malignant tumor with the highest morbidity and mortality in the world.According to the latest global cancer statistics,there were 1.82 million new cases of lung cancer and 1.59 million deaths in 2018.The pathological types of lung cancer mainly include small cell lung cancer and non-small cell lung cancer(NSCLC).The non-small cell lung cancer accounts for 75% ~ 80% of the total number,which includes squamous cell carcinoma,adenocarcinoma and large cell undifferentiated carcinoma.Because of its rapid deterioration process and poor sensitivity to radiotherapy and chemotherapy,the prognosis of NSCLC is extremely poor.The 5-year survival rate for NSCLC is only 15.9%.Despite the continuous improvement in the means of treatments in the past decades,the 5-year survival rate has not improved significantly.Therefore,the further study of the pathogenesis of NSCLC and the search for meaningful molecular targets are of great significance for the timely diagnosis and treatment of NSCLC.DUB3 is an important member of the deubiquitinating enzyme family,which stabilizes its substrates through deubiquitination.Numerous studies show that DUB3 plays an important role in cell inflammation,cell growth and proliferation,signal transduction and DNA damage repair.The overexpression of DUB3 protein has been found in various cancer tissues and cell lines,which promote malignant phenotypes of cancer cells by regulating cell cycle,cell invasion and migration.Previous studies show that DUB3 can promote cell proliferation by affecting cell cycle from G1 to S phase transition in NSCLC.However,the underlying molecular mechanism of DUB3 in NSCLC is largely unknown.Cyclin A,a member of the cell cycle protein family,plays an important role in cell cycle progression.On the one hand,cyclin A can promote G1 / S transformation by interacting with and activating CDK2.In addition,it also participates in G2 / M transition by binding to and activating CDK1.Growing evidences show that cyclin A protein is strictly regulated at the level of transcription and post-transcription.Overexpression of cyclin A has been found in various tumors,which is closely related to cell proliferation.To identify the underlying molecular mechanism of DUB3 in NSCLC,we analyzed a series of cell cycle associated proteins and found that DUB3 influenced cyclin A levels.The overexpression of DUB3 protein in NSCLC cells increased cyclin A levels,while the knockdown of DUB3 decreased cyclin A levels.To clarify the molecular mechanism of DUB3-mediated cyclin A regulation,we performed a series of experiments including co-immunoprecipitation,point mutation,ubiquitination and half-life analysis.These results demonstrated that DUB3 stabilized cyclin A by removing the polyubiquitin chains conjugated onto cyclin A.Furthermore,we revealed that DUB3 regulated cell cycle progression by stabilizing cyclin A,because ablation of DUB3 arrests cell cycle from G0/G1 to S phase and the resulting effect can be rescued by introducing cyclin A into NSCLC cells.Functionally,we found that the effect of DUB3 on cyclin A mediates proliferation of NSCLC cells.Moreover,a significant correlation between DUB3 abundance and cyclin A expression levels were also found in NSCLC samples.In conclusion,this study revealed that DUB3 regulated the cell cycle process via stabilizing cyclin A for proliferation of NSCLC cells,implicating DUB3 as a promising target for NSCLC diagnosis and treatment.