Deubiquitylase OTUD3 Stabilizes GRP78 And Promotes Lung Tumorigenesis

Global cancer surveys have shown that lung cancer is one of the leading causes of cancer deaths and new cancer cases in recent years.Lung cancer includes small cell lung cancer(SCLC)and non-small cell lung cancer(NSCLC).NSCLC occupies 85% of the new lung cancer cases and is further divided into three categories including adenocarcinoma(ADC),squamous cell carcinoma(SCC)and large cell carcinoma through histopathological heterogeneity.Multiple studies have demonstrated that activating mutations and ectopic expression of receptor tyrosine kinases and RAS pathway members,including KRAS,EGFR,BRAF and HER2,would contribute to NSCLC.Protein ubiquitylation is a dynamic multifaceted post-translational modification and participates in the pathogenesis of various cancers through regulating the stability or activity of certain critical proteins.Recently,accumulative evidence has established the critical role of ubiquitylation in cancer pathogenesis and revealed the great therapeutic potential of targeting ubiquitylation in multiple cancers.Like other post-translational modifications,ubiquitylation also could be reversed by peptidases termed deubiquitylase or deubiquitylating enzymes(DUBs),which could cleave and remove the ubiquitin chains from substrate proteins.In the human proteome,there are about 100 DUBs consisting of six families: UCHs?USPs?OTUs?Josephins?JAMMs? MCPIP.Recently,we identified the OTU(ovarian tumour protease)family member OTUD3(OTU domain-containing protein 3)is a potential tumour suppressor gene in breast cancer and OTUD3 protein directly interacts with PTEN(phosphatase and tension homologue deleted in chromosome 10)and stabiilizes PTEN protein to suppress PI3K/AKT signaling transduction.OTUD3 transgenic mice exhibit higher levels of the PTEN protein and are less prone to tumorigenesis.Reduction of OTUD3 expression,concomitant with decreased PTEN abundance,correlates with human breast cancer progression.So far,current studies showed OTUD3 as a potent DUB for PTEN and then a tumour suppressor in breast cancer;however,the comprehensive understandings of the role of OTUD3 in human cancers are still limited.Although we already know OTUD3 is a tumor suppressor gene in breast cancer,and unexpectedly we also found OTUD3 play a promoting role in the lung cancer and promotes tumorigenesis of the lung adenocarcinoma through deubiquitylating and stabilizing GRP78 with our initial research,but the physiological function of OTUD3 in vivo is not entirely clear,the mechanism of the OTUD3 in different tumors is not thorough,in order to further explore OTUD3 physiological and pathological functions in vivo and the detailed mechanism of promoting tumorigenesis in lung cancer,we made a more in-depth and comprehensive study.After our further research,the current data obtained are as follows:(1)The KrasG12D-driven lung adenocarcinoma model of KrasLSL-G12D/WT/OTUD3 KO and KrasLSL-G12D/WT/OTUD3 TG was established.We found that compared with KrasLSL-G12D/WT/ OTUD3 WT mice,KrasLSL-G12D/WT/OTUD3 KO mice show increased resistance to the tumorigenesis of lung cancer and result in a markedly prolonged survival,while KrasLSL-G12D/WT/OTUD3 TG mice show decreased resistance to the tumorigenesis of lung cancer and result in poorer overall survival.(2)Further tissue microarray analysis in a variety of other tumors showed that the expression levels of OTUD3 were decreased,concomitant with reduction of PTEN abundance,in human breast cancer,hepatocellular cancer,colon cancer and cervical cancer.Strikingly,OTUD3 was upregulated in human lung adenocarcinoma cancer.(3)For the different substrates of OTUD3 in a variety of other tumors.We revealed that GRP78 is a specific substrate of OTUD3 in lung cancer cells.We found that overexpression of OTUD3 did not alter the stability or ubiquitylation level of GRP78 in MCF7 cells and HeLa cells The interaction between OTUD3 and GRP78 was hardly detected in MCF7 cells and Hela cells.The interaction between OTUD3 and PTEN was hardly detected in lung cancer H1299 cells.(4)OTUD3 and GRP78 shown a close correlation between in human lung cancer tissues.Elevated OTUD3 expression increased GRP78 protein level in the lung tissue of OTUD3 TG mice,whereas OTUD3 knockout decreased GRP78 expression in the mouse lung tissue.(5)We orthotopically transplant a mouse lung cancer cell line in OTUD3 WT /OTUD3 KO and OTUD3 TG mice to assess tumor development.We found that OTUD3 knockout mice show significantly slower tumor growth than wild-type mice and OTUD3 TG mice show significantly faster tumor growth than wild-type mice in lung tissue.It is suggested that OTUD3 may promote the development of lung cancer through the microenvironment between stromal cells in lung tissue.Collectively,these findings elucidate an unexpected proto-oncogenic role of OTUD3 in lung cancer and indicate that deubiquitylase can elicit tumour suppressor or oncogene activities in a cell-and tissue-dependent context.These results also broaden the understanding of physiological tumor-associated function of OTUD3 in multiple types of human cancer.