Research progress on linear ubiquitin chain assembly complex and OTU deubiquitinase with linear linkage specificity in tumor / 药学实践杂志

Linear ubiquitination is an important post-translational modification that has been discovered in recent years. The linear ubiquitin chain is formed by the linkage of glycine residue of one ubiquitin protein to the methionine residue of another ubiquitin. This process is regulated by the linear ubiquitin chain assembly complex (LUBAC) and the OTU deubiquitinase with linear linkage specificity (OTULIN). Linear ubiquitination is involved in various biological processes, including immune response, inflammation, and cell apoptosis. Recent studies have shown that linear ubiquitination is closely related to the occurrence, development, and drug resistance of tumors by affecting signaling pathways such as NF-κB and Wnt/β-catenin. The research progress on the function of LUBAC and OTULIN in tumors was reviewed in this paper.

Deubiquitinating enzyme MINDY1 is an independent risk factor for the maintenance of stemness and poor prognosis in liver cancer cells / 中华肝脏病杂志

Objective: To explore the key deubiquitinating enzymes that maintain the stemness of liver cancer stem cells and provide new ideas for targeted liver cancer therapy. Methods: The high-throughput CRISPR screening technology was used to screen the deubiquitinating enzymes that maintain the stemness of liver cancer stem cells. RT-qPCR and Western blot were used to analyze gene expression levels. Stemness of liver cancer cells was detected by spheroid-formation and soft agar colony formation assays. Tumor growth in nude mice was detected by subcutaneous tumor-bearing experiments. Bioinformatics and clinical samples were examined for the clinical significance of target genes. Results: MINDY1 was highly expressed in liver cancer stem cells. The expression of stem markers, the self-renewal ability of cells, and the growth of transplanted tumors were significantly reduced and inhibited after knocking out MINDY1, and its mechanism of action may be related to the regulation of the Wnt signaling pathway. The expression level of MINDY1 was higher in liver cancer tissues than that in adjacent tumors, which was closely related to tumor progression, and its high expression was an independent risk factor for a poor prognosis of liver cancer. Conclusion: The deubiquitinating enzyme MINDY1 promotes stemness in liver cancer cells and is one of the independent predictors of poor prognosis in liver cancer.

Deubiquitinase JOSD2 Promotes the Survival and Metastasis of Hepatoma Cells / 中国生物化学与分子生物学报

Ubiquitination is a reversible post-translational modification that regulates protein stability and plays a function in numerous signaling pathways. Deubiquitinases play important roles in the regulation of the occurrence and development of different cancers. In this study, we analyzed the survival and prognosis of liver cancer patients according to the expression levels of 63 deubiquitinases. Results discovered that JOSD2 expression in tumor was significantly higher than that in the adjacent tissue (P<0. 0001) and was negatively associated with overall survival of patients (P < 0. 05). JOSD2 is a deubiquitinase from MJD sub-family. Other members of this sub-family were not correlated with liver cancer. The pathways related to cell proliferation were significantly enriched (FDR < 0. 05) in a differential gene function enrichment analysis of JOSD2 high-expressing samples in TCGA data. In hepatoma cell lines, we demonstrated that the overexpression of JOSD2 significantly enhances cell survival, migration and invasion. In conclusion, this study found that JOSD2 is highly expressed in liver cancer (P = 0. 041), and that patients with high-expressed JOSD2 have significantly shorter overall survival. Furthermore, overexpression of JOSD2 can promote the survival and metastasis of hepatoma cells (P < 0. 01), which suggests that JOSD2 might promote the survival and metastasis of hepatocellular carcinoma.

The Role of Deubiquitinases in Tumor Epithelial-mesenchymal Transition / 中国生物化学与分子生物学报

Tumor invasion and metastasis are the main reasons for the tumor deterioration and the cause of poor prognosis of patients. In recent years a vast amount of research has been reported that epithelial-mesenchymal transition (EMT) in cancer cells plays a critical role in tumor metastasis. Moreover, EMT is also closely related to tumor stemness, tumor drug resistance and other tumor malignant behaviors. Therefore, effective suppression of EMT has been investigated as potential therapeutic strategy for the treatment of tumor. One of the main functions of the deubiquitinating enzymes (DUBs) is to maintain the dynamic balance of intracellular protein levels via removing conjugated ubiquitin from target proteins, which in turn avoids degradation of target proteins through the ubiquitin protease pathway. DUBs are a class of proteins responsible for regulating protein ubiquitination modification, which abnormal expression or alterations of enzyme activity often results in the initiation of many diseases, including a variety of cancers. Numerous studies have found that some DUBs are unbalanced in the process of tumor invasion and metastasis, and play important roles in the process of tumor metastasis. EMT refers to the dynamic cellular process of transforming epithelial cells to mesenchymal cells, which involves changes in the expression levels of various molecular markers, such as EMT-related transcription factors (Snial1, Slug, ZEB1 etc.), and cell surface proteins (E-cadherin, N-cadherin etc.). Generally, these associated proteins are unstable and easily degraded, meanwhile the occurrence of the EMT process involves the regulation of protein stability. DUBs, as a class of enzymes that maintain protein stability, play important roles in regulating the stability of EMT-related proteins. The occurrence of EMT is also inseparable from the abnormal activation of many signaling pathways in cells such as TGF-β and Wnt pathways. DUBs mediate the activation of these pathways to indirectly regulate the occurrence and development of EMT. DUBs can directly or indirectly affect the progress of EMT by regulating EMT-related molecules or signaling pathways. Therefore, targeting DUBs to inhibit tumor invasion and metastasis will provide new methods and programs for tumor treatment. This review mainly discusses the important roles of DUBs in the EMT process to elucidate that DUBs play critical roles in regulating EMT-related molecules and signal pathways, and may serve as potential therapeutic targets for cancers.

Deubiquitinase JOSD2 stabilizes YAP/TAZ to promote cholangiocarcinoma progression

Cholangiocarcinoma (CCA) has emerged as an intractable cancer with scanty therapeutic regimens. The aberrant activation of Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) are reported to be common in CCA patients. However, the underpinning mechanism remains poorly understood. Deubiquitinase (DUB) is regarded as a main orchestrator in maintaining protein homeostasis. Here, we identified Josephin domain-containing protein 2 (JOSD2) as an essential DUB of YAP/TAZ that sustained the protein level through cleavage of polyubiquitin chains in a deubiquitinase activity-dependent manner. The depletion of JOSD2 promoted YAP/TAZ proteasomal degradation and significantly impeded CCA proliferation

Research advances on deubiquitinating enzymes involved in the development of hepatocellular carcinoma / 中国肿瘤临床

The ubiquitin-proteasome pathway is the primary regulator of intracellular protein degradation. In recent years, it has been found that multiple members of the deubiquitinating enzyme family play an important role in the development of liver cancer. The deubiquitinating enzymes remove ubiquitin chains of substrate proteins to maintain their stability; thus, they affect tumor progression via maintaining the stability of proteins involved in cell apoptosis, autophagy, cell cycle regulation, and DNA damage. Some small molecule inhibitors can exert an anti-tumor effect by inhibiting the activity of deubiquitinating enzymes. Here, we have reviewed research regarding deubiquitinating enzymes and their small molecule inhibitors in order to provide a new theoretical foundation for exploring novel and effective therapeutic targets for liver cancer.

How are MCPIP1 and cytokines mutually regulated in cancer-related immunity?

Cytokines are secreted by various cell types and act as critical mediators in many physiological processes, including immune response and tumor progression. Cytokines production is precisely and timely regulated by multiple mechanisms at different levels, ranging from transcriptional to post-transcriptional and posttranslational processes. Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), a potent immunosuppressive protein, was first described as a transcription factor in monocytes treated with monocyte chemoattractant protein-1 (MCP-1) and subsequently found to possess intrinsic RNase and deubiquitinase activities. MCPIP1 tightly regulates cytokines expression via various functions. Furthermore, cytokines such as interleukin 1 beta (IL-1B) and MCP-1 and inflammatory cytokines inducer lipopolysaccharide (LPS) strongly induce MCPIP1 expression. Mutually regulated MCPIP1 and cytokines form a complicated network in the tumor environment. In this review, we summarize how MCPIP1 and cytokines reciprocally interact and elucidate the effect of the network formed by these components in cancer-related immunity with aim of exploring potential clinical benefits of their mutual regulation.

The deubiquitinase USP38 affects cellular functions through interacting with LSD1

BACKGROUND: Deubiquitination is a posttranslational protein modification prevalent in mammalian cells. Deubiquitinases regulate the functions of the target protein by removing its ubiquitin chain. In this study, the effects of the deubiquitinase USP38's functions on the LSD1 protein and on cell physiology were investigated. MATERIALS AND METHODS: Western blotting, real-time quantitative PCR, immunoprecipitation, denaturing immunoprecipitation and luciferase reporter assays were used to analyze the protein stability, protein interactions and changes in the ubiquitin chain. Cell proliferation assays, colony formation assays, drug treatments and western blotting were used to explore the functions of USP38 in cells. RESULTS: The deubiquitinase USP38 stabilizes protein LSD1 in cells by binding LSD1 and cleaving its ubiquitin chain to prevent the degradation of LSD1 by the intracellular proteasome. USP38 enhances the ability of LSD1 to activate signaling pathways and hence promotes cellular abilities of proliferation and colony formation through interacting with LSD1. Furthermore, USP38 enhances the drug tolerance of human colon cancer cells. CONCLUSIONS: USP38 is an LSD1-specific deubiquitinase that affects cellular physiology through interacting with LSD1.

Deubiquitinases as pivotal regulators of T cell functions / 医学前沿

T cells efficiently respond to foreign antigens to mediate immune responses against infections but are tolerant to self-tissues. Defect in T cell activation is associated with severe immune deficiencies, whereas aberrant T cell activation contributes to the pathogenesis of diverse autoimmune and inflammatory diseases. An emerging mechanism that regulates T cell activation and tolerance is ubiquitination, a reversible process of protein modification that is counter-regulated by ubiquitinating enzymes and deubiquitinases (DUBs). DUBs are isopeptidases that cleave polyubiquitin chains and remove ubiquitin from target proteins, thereby controlling the magnitude and duration of ubiquitin signaling. It is now well recognized that DUBs are crucial regulators of T cell responses and serve as potential therapeutic targets for manipulating immune responses in the treatment of immunological disorders and cancer. This review will discuss the recent progresses regarding the functions of DUBs in T cells.

Immunohistochemical analysis of OTUB1 in 90 cases of ovarian mucinous tumors / 中国癌症杂志

Background and purpose:The ovarian mucinous tumor is one of the major subtypes of the ovari-an epithelial cancer. Ubiquitination is one of the main post-translational modifications, which has proven to be involved in tumorigenicity. Deubiquitinase is the protein enzyme that could reverse the process of ubiquitination to affect the initiation and progression of malignancies. This study aimed to analyze the expression and clinical application of deubiquitinase OTUB1 (OTU deubiquitinase, ubiquitin aldehyde binding 1) in ovarian primary mucinous tumors. Methods:This study collected 90 cases of ovarian primary mucinous tumors during 2010-2015 in Obstetrics and Gynecology Hospital of Fudan University, and then collected the clinicopathological information and performed the immunochemistry.Results:Fourteen out of 90 cases were ovarian primary mucinous cystadenoma, 17 were borderline mucinous tumor (intestinal type and intraepithelial carcinoma), and 59 were ovarian primary mucinous carcinoma. The expression rate and intensity of OTUB1 were much higher in malignant cases than those in benign ones (P<0.05). The expression rate and intensity of OTUB1 were much higher in cases with mucinous intraepithelial carcinoma than those in cases with intestinal type borderline mucinous tumor (P<0.05). The expression rate and intensity of OTUB1 increased with the advance of FIGO staging (P<0.05). The expression rate and intensity of OTUB1 were much higher in cases with involved fallopian tubes than those in cases without involved fallopian tubes (P<0.05). The expression rate and intensity of OTUB1were much higher in cases with involved uterus and omentum than those in cases with-out involvement (P<0.05). The expression rate and intensity of OTUB1were much higher in cases with lymph node metastasis than those in cases without involvement (P<0.05).Conclusion:There is significant difference in OTUB1 expression between ovarian primary mucinous carcinoma and benign mucinous cystadenoma. It is highly correlated to FIGO staging and invasion and metastasis of tumor. OTUB1 could be used in differential diagnosis and in monitoring the tumor initiation and progression in ovarian mucinous carcinoma.