POH1 deubiquitylates and stabilizes E2F1 to promote tumour formation

Recent advances in the development of deubiquitinases inhibitors as antitumor agents

Ubiquitination is a type of post-translational modification that covalently links ubiquitin to a target protein, which plays a critical role in modulating protein activity, stability, and localization. In contrast, this process is reversed by deubiquitinases (DUBs), which remove ubiquitin from ubiquitinated substrates. Dysregulation of DUBs is associated with several human diseases, such as cancer, inflammation, neurodegenerative disorders, and autoimmune diseases. Thus, DUBs have become promising targets for drug development. Although the physiological and pathological effects of DUBs are increasingly well understood, the clinical drug discovery of selective DUB inhibitors has been challenging. Herein, we summarize the structures and functions of main classes of DUBs and discuss the recent progress in developing selective small-molecule DUB inhibitors as antitumor agents.

DLGAP5 triggers proliferation and metastasis of bladder cancer by stabilizing E2F1 via USP11

Bladder cancer (BLCA) is one of the most widespread malignancies worldwide, and displays significant tumor heterogeneity. Understanding the molecular mechanisms exploitable for treating aggressive BLCA represents a crucial objective. Despite the involvement of DLGAP5 in tumors, its precise molecular role in BLCA remains unclear. BLCA tissues exhibit a substantial increase in DLGAP5 expression compared with normal bladder tissues. This heightened DLGAP5 expression positively correlated with the tumor's clinical stage and significantly affected prognosis negatively. Additionally, experiments conducted in vitro and in vivo revealed that alterations in DLGAP5 expression notably influence cell proliferation and migration. Mechanistically, the findings demonstrated that DLGAP5 was a direct binding partner of E2F1 and that DLGAP5 stabilized E2F1 by preventing the ubiquitination of E2F1 through USP11. Furthermore, as a pivotal transcription factor, E2F1 fosters the transcription of DLGAP5, establishing a positive feedback loop between DLGAP5 and E2F1 that accelerates BLCA development. In summary, this study identified DLGAP5 as an oncogene in BLCA. Our research unveils a novel oncogenic mechanism in BLCA and offers a potential target for both diagnosing and treating BLCA.

POH1 induces Smad3 deubiquitination and promotes lung cancer metastasis

Smad3 is the key mediator of TGF-β1-triggered signal transduction and the related biological responses, promoting cell invasion and metastasis in various cancers, including lung cancer. However, the deubiquitinase stabilizing Smad3 remains unknown. In this study, we present a paradigm in which POH1 is identified as a novel deubiquitinase of Smad3 that plays a tumor-promoting role in lung adenocarcinoma (LUAD) by regulating Smad3 stability. POH1 markedly increased Smad3 protein levels and prolonged its half-life. POH1 directly interacted and colocalized with Smad3, leading to the removal of poly-deubiquitination of Smad3. Functionally, POH1 facilitated cell proliferation, migration, and invasion by stabilizing Smad3. Importantly, POH1 also promoted liver metastasis of lung cancer cells. The protein levels of both POH1 and Smad3 were raised in the tumor tissues of patients with LUAD, which predicts poor prognosis. Collectively, we demonstrate that POH1 acts as an oncoprotein by enhancing TGF-β1/Smad3 signaling and TGF-β1-mediated metastasis of lung cancer.

Deubiquitinating enzyme PSMD7 promotes bladder cancer development: Involvement of RAB1A stabilization

BACKGROUND

Proteasome 26S subunit, non-ATPase 7 (PSMD7) is a deubiquitinating enzyme that is involved in the stability of ubiquitinated proteins and participates in the development of multiple types of cancer. The roles of PSMD7 and its potential mechanisms in bladder cancer (BC) remain elusive.

METHODS

In this study, we identified that PSMD7 was overexpressed in BC tissues based on gene expression omnibus (GEO) database and TNMplot web. To investigate the functional role of PSMD7, two BC cell lines, T24 and 5637, were selected. The cells were transfected with vectors containing short hairpin RNAs against PSMD7 or plasmids containing full-length PSMD7 to knockdown or overexpress PSMD7.

RESULTS

Our results revealed that silencing PSMD7 inhibited cell proliferation, cycle progression, migration, invasion, and promoted cell apoptosis, whereas PSMD7 overexpression led to the opposite effects in the BC cells. Mechanically, PSMD7 influenced the protein expression but not the mRNA expression of the Ras-related protein Rab-1 A (RAB1A). PSMD7 combined with RAB1A and negatively regulated its ubiquitination, indicating that PSMD7 enhanced the stability of RAB1A through post-transcriptional modification. Moreover, the rescue experiment demonstrated that RAB1A was an important downstream effector molecule of PSMD7. Besides, the negative regulation of silencing PSMD7 on tumor growth was confirmed in mice.

CONCLUSIONS

Our study substantiated a novel mechanism by which PSMD7 stabilized RAB1A to accelerate the progression of BC.

Silencing TRIM29 Sensitizes Non-small Cell Lung Cancer Cells to Anlotinib by Promoting Apoptosis via Binding RAD50

BACKGROUND

Previous studies have proposed that the transcriptional regulatory factor tripartite motif containing 29 (TRIM29) is involved in carcinogenesis via binding with nucleic acid. TRIM29 is confirmed to be highly expressed when the cancer cells acquire therapy-resistant properties. We noticed that TRIM29 levels were significantly increased in anlotinib-resistant NCIH1975 (NCI-H1975/AR) cells via mining data information from gene expression omnibus (GEO) gene microarray (GSE142031; log2 fold change > 1, p < 0.05).

OBJECTIVE

Our study aimed to investigate the function of TRIM29 on the resistance to anlotinib in non-small cell lung cancer (NSCLC) cells, including NCI-H1975 and A549 cells.

METHODS

Real-time RT-PCR and western blot were used to detect TRIM29 expression in anlotinib- resistant NSCLC (NSCLC/AR) cells. Apoptosis were determined through flow cytometry, acridine orange/ethidium bromide staining as well as western blot. ELISA was used to measure the content of C-X3-C motif chemokine ligand 1. Co-Immunoprecipitation assay was performed to verify the interaction between TRIM29 and RAD50 double-strand break repair protein (RAD50).

RESULTS

TRIM29 expression was shown to be elevated in the cytoplasm and nucleus of NSCLC/ AR cells compared to normal NSCLC cells. Next, we demonstrated that TRIM29 knockdown facilitated apoptosis and enhanced the sensitivity to anlotinib in NSCLC/AR cells. Based on the refined results citing from the database BioGRID, it was proved that TRIM29 interacted with RAD50. Herein, RAD50 overexpression diminished the pro-apoptotic effect induced by silencing TRIM29 in anlotinib-resistant A549 (A549/AR) cells.

CONCLUSION

Finally, we concluded that the increased sensitivity to anlotinib in NSCLC/AR cells was achieved by knocking down TRIM29, besides, the positive effects of TRIM29 knockdown were attributed to the promotion of apoptosis via binding to RAD50 in NSCLC/AR cell nucleus. Therefore, TRIM29 might become a potential target for overcoming anlotinib resistance in NSCLC treatment.

The function and mechanism of PSMD14 in promoting progression and resistance to anlotinib in osteosarcoma

BACKGROUND

Osteosarcoma is a rare bone malignancy that frequently affects adolescents and poses formidable obstacles in its advanced stages. Studies revealed that PSMD14 may be a viable osteosarcoma treatment target. However, PSMD14's function and mechanism in osteosarcoma remain unknown. This study aimed to examine the function and mechanism of PSMD14 in the biological behavior of osteosarcoma and its role in anlotinib resistance.

METHODS

Western blotting, qRT-PCR, and immunohistochemistry (IHC) studies were used to examine PSMD14 levels. The role of PSMD14 in the malignant phenotype of osteosarcoma and its molecular pathway was explored by a series of studies, including Western blotting, cell amplification assay, transwell assay, and tumor growth. Furthermore, a series of in vitro investigations were done to determine the effect of PSMD14 on anlotinib-resistant osteosarcoma cell lines.

RESULTS

PSMD14 expression was elevated in osteosarcoma tissues compared to normal tissues. Overexpression of PSMD14 was associated with osteosarcoma patients' pathological grade and clinical stage, and PSMD14 was an independent poor prognostic factor. PSMD14 knockdown inhibits in vitro cell proliferation, migration, invasion, and in vivo tumor growth. PSMD14 knockdown has the potential to downregulate the PI3K/Akt/mTOR pathway, which was regarded as one of the key mechanisms promoting tumor growth. PSMD14 was likewise overexpressed in anlotinib-resistant OS cell lines, and its knockdown not only reduced the proliferation, migration, and invasion of subline cells and triggered cell apoptosis. Importantly, combination therapy with anlotinib enhanced these effects.

CONCLUSIONS

PSMD14 is substantially expressed in osteosarcoma and may be an independent risk factor associated with poor prognosis. It can promote tumor progression and anlotinib resistance in osteosarcoma and may promote osteosarcoma progression by modulating PI3K/AKT/mTOR signaling pathway.

Ubiquitin ligase enzymes and de-ubiquitinating enzymes regulate innate immunity in the TLR, NLR, RLR, and cGAS-STING pathways

Ubiquitination (or ubiquitylation) and de-ubiquitination, which are both post-translational modifications (PTMs) of proteins, have become a research hotspot in recent years. Some ubiquitinated or de-ubiquitinated signaling proteins have been found to promote or suppress innate immunity through Toll-like receptor (TLR), RIG-like receptor (RIG-I-like receptor, RLR), NOD-like receptor (NLR), and the cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS)-STING pathway. This article aimed to provide a review on the role of ubiquitination and de-ubiquitination, especially ubiquitin ligase enzymes and de-ubiquitinating enzymes, in the above four pathways. We hope that our work can contribute to the research and development of treatment strategies for innate immunity-related diseases such as inflammatory bowel disease.

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Clinical Implication of E2F Transcription Factor 1 in Hepatocellular Carcinoma Tissues

Background: To date, the clinical management of advanced hepatocellular carcinoma (HCC) patients remains challenging and the mechanisms of E2F transcription factor 1 (E2F1) underlying HCC are obscure. Materials and Methods: Our study integrated datasets mined from several public databases to comprehensively understand the deregulated expression status of E2F1. Tissue microarrays and immunohistochemistry staining was used to validate E2F1 expression level. The prognostic value of E2F1 was assessed. In-depth subgroup analyses were implemented to compare the differentially expressed levels of E2F1 in HCC patients with various tumor stages. Functional enrichments were used to address the predominant targets of E2F1 and shedding light on their potential roles in HCC. Results: We confirmed the elevated expression of E2F1 in HCC. Subgroup analyses indicated that elevated E2F1 level was independent of various stages in HCC. E2F1 possessed moderate discriminatory capability in differentiating HCC patients from non-HCC controls. Elevated E2F1 correlated with Asian race, tumor classification, neoplasm histologic grade, eastern cancer oncology group, and plasma AFP levels. Furthermore, high E2F1 correlated with poor survival condition and pooled HR signified E2F1 as a risk factor for HCC. Enrichment analysis of differentially expressed genes, coexpressed genes, and putative targets of E2F1 emphasized the importance of cell cycle pathway, where CCNE1 and CCNA2 served as hub genes. Conclusions: We confirmed the upregulation of E2F1 and explored the prognostic value of E2F1 in HCC patients. Two putative targeted genes (CCNE1 and CCNA2) of E2F1 were identified for their potential roles in regulating cell cycle and promote antiapoptotic activity in HCC patients.

POH1 facilitates pancreatic carcinogenesis through MYC-driven acinar-to-ductal metaplasia and is a potential therapeutic target

Pancreatic acinar cells undergo acinar-to-ductal metaplasia (ADM), a necessary process for pancreatic ductal adenocarcinoma (PDAC) initiation. However, the regulatory role of POH1, a deubiquitinase linked to several types of cancer, in ADM and PDAC is unclear. In this study, we investigated the role of POH1 in ADM and PDAC using murine models. Our findings suggest that pancreatic-specific deletion of Poh1 alleles attenuates ADM and impairs pancreatic carcinogenesis, improving murine survival. Mechanistically, POH1 deubiquitinates and stabilizes the MYC protein, which potentiates ADM and PDAC. Furthermore, POH1 is highly expressed in PDAC samples, and clinical evidence establishes a positive correlation between aberrantly expressed POH1 and poor prognosis in PDAC patients. Targeting POH1 with a specific small-molecule inhibitor significantly reduces pancreatic tumor formation, highlighting POH1 as a promising therapeutic target for PDAC treatment. Overall, POH1-mediated MYC deubiquitination is crucial for ADM and PDAC onset, and targeting POH1 could be an effective strategy for PDAC treatment, offering new avenues for PDAC targeted therapy.

Comprehensive clinicopathological significance and putative transcriptional mechanisms of Forkhead box M1 factor in hepatocellular carcinoma

BACKGROUND

The Forkhead box M1 factor (FOXM1) is a crucial activator for cancer cell proliferation. While FOXM1 has been shown to promote hepatocellular carcinoma (HCC) progression, its transcriptional mechanisms remain incompletely understood.

METHODS

We performed an in-house tissue microarray on 313 HCC and 37 non-HCC tissue samples, followed by immunohistochemical staining. Gene chips and high throughput sequencing data were used to assess FOXM1 expression and prognosis. To identify candidate targets of FOXM1, we comprehensively reanalyzed 41 chromatin immunoprecipitation followed by sequencing (ChIP-seq) data sets. We predicted FOXM1 transcriptional targets in HCC by intersecting candidate FOXM1 targets with HCC overexpressed genes and FOXM1 correlation genes. Enrichment analysis was employed to address the potential mechanisms of FOXM1 underlying HCC. Finally, single-cell RNA sequencing analysis was performed to confirm the transcriptional activity of FOXM1 on its predicted targets.

RESULTS

This study, based on 4235 HCC tissue samples and 3461 non-HCC tissue samples, confirmed the upregulation of FOXM1 in HCC at mRNA and protein levels (standardized mean difference = 1.70 [1.42, 1.98]), making it the largest multi-centered study to do so. Among HCC patients, FOXM1 was increased in Asian and advanced subgroups, and high expression of FOXM1 had a strong ability to differentiate HCC tissue from non-HCC tissue (area under the curve = 0.94, sensitivity = 88.72%, specificity = 87.24%). FOXM1 was also shown to be an independent exposure risk factor for HCC, with a pooled hazard ratio of 2.00 [1.77, 2.26]. The predicted transcriptional targets of FOXM1 in HCC were predominantly enriched in nuclear division, chromosomal region, and catalytic activity acting on DNA. A gene cluster encoding nine transcriptional factors was predicted to be positively regulated by FOXM1, promoting the cell cycle signaling pathway in HCC. Finally, the transcriptional activity of FOXM1 and its targets was supported by single-cell analysis of HCC cells.

CONCLUSIONS

This study not only confirmed the upregulation of FOXM1 in HCC but also identified it as an independent risk factor. Moreover, our findings enriched our understanding of the complex transcriptional mechanisms underlying HCC pathogenesis, with FOXM1 potentially promoting HCC progression by activating other transcription factors within the cell cycle pathway.

Modulation of the ubiquitin-proteasome system by phytochemicals: Therapeutic implications in malignancies with an emphasis on brain tumors

Regarding the multimechanistic nature of cancers, current chemo- or radiotherapies often fail to eradicate disease pathology, and frequent relapses or resistance to therapies occur. Brain malignancies, particularly glioblastomas, are difficult-to-treat cancers due to their highly malignant and multidimensional biology. Unfortunately, patients suffering from malignant tumors often experience poor prognoses and short survival periods. Thus far, significant efforts have been conducted to discover novel and more effective modalities. To that end, modulation of the ubiquitin-proteasome system (UPS) has attracted tremendous interest since it affects the homeostasis of proteins critically engaged in various cell functions, for example, cell metabolism, survival, proliferation, and differentiation. With their safe and multimodal actions, phytochemicals are among the promising therapeutic tools capable of turning the operation of various UPS elements. The present review, along with an updated outline of the role of UPS dysregulation in multiple cancers, provided a detailed discussion on the impact of phytochemicals on the UPS function in malignancies, especially brain tumors.

Six immune-related promising biomarkers may promote hepatocellular carcinoma prognosis: a bioinformatics analysis and experimental validation

Background

Abnormal miRNA and mRNA expression and dysregulated immune microenvironment have been found to frequently induce the progression of hepatocellular carcinoma (HCC) in recent reports. In particular, the immune-related competing endogenous RNAs (ceRNA) mechanism plays a crucial role in HCC progression. However, the underlying mechanisms remain unclear.

Methods

Differentially expressed immune-related genes were obtained from the Immport, GEO, and TCGA databases. The mRNA and protein expression levels in HCC tissues and adjacent normal tissues were confirmed, and we further investigated the methylation levels of these biomarkers to explore their function. Then, the TIMER and TISCH databases were used to assess the relationship between immune infiltration and hub genes. Survival analysis and univariate and multivariate Cox models were used to evaluate the association between hub genes and HCC diagnosis. Hub gene expression was experimentally validated in six HCC cell lines and 15 HCC samples using qRT-PCR and immunohistochemistry. The hub genes were uploaded to DSigDB for drug prediction enrichment analysis.

Results

We identified that patients with abnormal miRNAs (hsa-miR-125b-5p and hsa-miR-21-5p) and their targeted genes (NTF3, PSMD14, CD320, and SORT1) had a worse prognosis. Methylation analysis of miRNA-targeted genes suggested that alteration of methylation levels is also a factor in the induction of tumorigenesis. We also found that the development of HCC progression caused by miRNA-mRNA interactions may be closely correlated with the infiltration of immunocytes. Moreover, the GSEA, GO, and KEGG analysis suggested that several common immune-related biological processes and pathways were related to miRNA-targeted genes. The results of qRT-PCR, immunohistochemistry, and western blotting were consistent with our bioinformatics results, suggesting that abnormal miRNAs and their targeted genes may affect HCC progression.

Conclusions

Briefly, our study systematically describes the mechanisms of miRNA-mRNA interactions in HCC and predicts promising biomarkers that are associated with immune filtration for HCC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-023-02888-9.

Novel insights into the non-canonical roles of PSMD14/POH1/Rpn11 in proteostasis and in the modulation of cancer progression

PSMD14/POH1/Rpn11 plays a crucial role in cellular homeostasis. PSMD14 is a structural subunit of the lid subcomplex of the proteasome 19S regulatory particle with constitutive deubiquitinase activity. Canonically, PSMD14 removes the full ubiquitin chains with K48-linkages by hydrolyzing the isopeptide bond between the substrate and the C-terminus of the first ubiquitin, a crucial step for the entry of substrates into the catalytic barrel of the 20S proteasome and their subsequent degradation, all in context of the 26S proteasome. However, more recent discoveries indicate PSMD14 DUB activity is not only coupled to the translocation of substrates into the core of 20S proteasome. During the assembly of the lid, activity of PSMD14 has been detected in the context of the heterodimer with PSMD7. Additionally, assembly of the lid subcomplex occurs as an independent event of the base subcomplex and 20S proteasome. This feature opens the possibility that the regulatory particle, free lid subcomplex or the heterodimer PSMD14-PSMD7 might play other physiological roles including a positive function on protein stability through deubiquitination. Here we discuss scenarios that could enhance this PSMD14 non-canonical pathway, the potential impact in preventing degradation of substrates by autophagy highlighting the main findings that support this hypothesis. Finally, we discuss why this information should be investigated in biomedicine specifically with focus on cancer progression to design new therapeutic strategies against the lid subcomplex and the heterodimer PSMD14-PSMD7, highlighting PSMD14 as a druggable target for cancer therapy.

Identification of Key Genes and Pathways Associated with Preeclampsia by a WGCNA and an Evolutionary Approach

Preeclampsia (PE) is the serious obstetric-related disease characterized by newly onset hypertension and causes damage to the kidneys, brain, liver, and more. To investigate genes with key roles in PE’s pathogenesis and their contributions, we used a microarray dataset of normotensive and PE patients and conducted a weighted gene co-expression network analysis (WGCNA). Cyan and magenta modules that are highly enriched with differentially expressed genes (DEGs) were revealed. By using the molecular complex detection (MCODE) algorithm, we identified five significant clusters in the cyan module protein–protein interaction (PPI) network and nine significant clusters in the magenta module PPI network. Our analyses indicated that (i) human accelerated region (HAR) genes are enriched in the magenta-associated C6 cluster, and (ii) positive selection (PS) genes are enriched in the cyan-associated C3 and C5 clusters. We propose these enriched HAR and PS genes, i.e., EIF4E, EIF5, EIF3M, DDX17, SRSF11, PSPC1, SUMO1, CAPZA1, PSMD14, and MNAT1, including highly connected hub genes, HNRNPA1, RBMX, PRKDC, and RANBP2, as candidate key genes for PE’s pathogenesis. A further clarification of the functions of these PPI clusters and key enriched genes will contribute to the discovery of diagnostic biomarkers for PE and therapeutic intervention targets.

A cancer stem cell associated gene signature for predicting overall survival of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most prevalent type of primary liver cancer characterized by high mortality and morbidity rate. The lack of effective treatments and the high frequency of recurrence lead to poor prognosis of patients with HCC. Therefore, it is important to develop robust prediction tools for predicting the prognosis of HCC. Recent studies have shown that cancer stem cells (CSC) participate in HCC progression. The aim of this study was to explore the prognostic value of CSC-related genes and establish a prediction model based on data from The Cancer Genome Atlas (TCGA) database. In this study, 475 CSC-related genes were obtained from the Molecular Signature Database and 160 differentially expressed CSC-related genes in HCC patients were identified using the limma R package in the TCGA database. A total of 79 CSC-related genes were found to be associated with overall survival (OS). Using the least absolute shrinkage and selection operator (LASSO) and multivariate Cox regressions, a 3-gene signature (RAB10, TCOF1, and PSMD14) was constructed. Receiver operating characteristic (ROC) curves and Kaplan-Meier survival curves were constructed to test the prediction performance of the signature. Performance of the signature was validated using the International Cancer Genome Consortium (ICGC) dataset. In addition, immune feature and functional enrichment analyses were carried out to explore the underlying mechanisms. Moreover, a co-expression network was constructed using the weighted gene correlation network analysis (WGCNA) method to select genes significantly associated with risk scores in HCC in the TCGA dataset. The SGO2 gene was found to be significantly associated with risk scores of HCC. In vitro experiments revealed that it can promote HCC cell proliferation. Therefore, SGO2 may be a potential therapeutic target for HCC treatment. The constructed nomogram can help clinicians make decisions about HCC treatment.

Emerging Roles of Non-proteolytic Ubiquitination in Tumorigenesis

Ubiquitination is a critical type of protein post-translational modification playing an essential role in many cellular processes. To date, more than eight types of ubiquitination exist, all of which are involved in distinct cellular processes based on their structural differences. Studies have indicated that activation of the ubiquitination pathway is tightly connected with inflammation-related diseases as well as cancer, especially in the non-proteolytic canonical pathway, highlighting the vital roles of ubiquitination in metabolic programming. Studies relating degradable ubiquitination through lys48 or lys11-linked pathways to cellular signaling have been well-characterized. However, emerging evidence shows that non-degradable ubiquitination (linked to lys6, lys27, lys29, lys33, lys63, and Met1) remains to be defined. In this review, we summarize the non-proteolytic ubiquitination involved in tumorigenesis and related signaling pathways, with the aim of providing a reference for future exploration of ubiquitination and the potential targets for cancer therapies.

Deubiquitinases in Cancers: Aspects of Proliferation, Metastasis, and Apoptosis

Simple Summary

This review summarizes the current DUBs findings that correlate with the most common cancers in the world (liver, breast, prostate, colorectal, pancreatic, and lung cancers). The DUBs were further classified by their biological functions in terms of proliferation, metastasis, and apoptosis. The work provides an updated of the current findings, and could be used as a quick guide for researchers to identify target DUBs in cancers.

Abstract

Deubiquitinases (DUBs) deconjugate ubiquitin (UBQ) from ubiquitylated substrates to regulate its activity and stability. They are involved in several cellular functions. In addition to the general biological regulation of normal cells, studies have demonstrated their critical roles in various cancers. In this review, we evaluated and grouped the biological roles of DUBs, including proliferation, metastasis, and apoptosis, in the most common cancers in the world (liver, breast, prostate, colorectal, pancreatic, and lung cancers). The current findings in these cancers are summarized, and the relevant mechanisms and relationship between DUBs and cancers are discussed. In addition to highlighting the importance of DUBs in cancer biology, this study also provides updated information on the roles of DUBs in different types of cancers.

A positive feedback loop of CENPU/E2F6/E2F1 facilitates proliferation and metastasis via ubiquitination of E2F6 in hepatocellular carcinoma

Centromere protein U (CENPU), a centromere-binding protein required for cellular mitosis, has been reported to be closely associated with carcinogenesis in multiple malignancies; however, the role of CENPU in hepatocellular carcinoma (HCC) is still unclear. Herein, we investigated its biological role and molecular mechanism in the development of HCC. High CENPU expression in HCC tissue was observed and correlated positively with a poor prognosis in HCC patients. CENPU knockdown inhibited the proliferation, metastasis, and G1/S transition of HCC cells in vivo and in vitro, while ectopic expression of CENPU exerted the opposite effects. Mechanistically, CENPU physically interacted with E2F6 and promoted its ubiquitin-mediated degradation, thus affecting the transcription level of E2F1 and further accelerating the G1/S transition to promote HCC cell proliferation. E2F1 directly binds to the CENPU promoter and increases the transcription of CENPU, thereby forming a positive regulatory loop. Collectively, our findings indicate a crucial role for CENPU in E2F1-mediated signalling for cell cycle progression and reveal a role for CENPU as a predictive biomarker and therapeutic target for HCC patients.

Structural and Functional Basis of JAMM Deubiquitinating Enzymes in Disease

Deubiquitinating enzymes (DUBs) are a group of proteases that are important for maintaining cell homeostasis by regulating the balance between ubiquitination and deubiquitination. As the only known metalloproteinase family of DUBs, JAB1/MPN/Mov34 metalloenzymes (JAMMs) are specifically associated with tumorigenesis and immunological and inflammatory diseases at multiple levels. The far smaller numbers and distinct catalytic mechanism of JAMMs render them attractive drug targets. Currently, several JAMM inhibitors have been successfully developed and have shown promising therapeutic efficacy. To gain greater insight into JAMMs, in this review, we focus on several key proteins in this family, including AMSH, AMSH-LP, BRCC36, Rpn11, and CSN5, and emphatically discuss their structural basis, diverse functions, catalytic mechanism, and current reported inhibitors targeting JAMMs. These advances set the stage for the exploitation of JAMMs as a target for the treatment of various diseases.

The prognostic role of PSMD14 in head and neck squamous cell carcinoma

PURPOSE

PSMD14 is an essential protein for proteasomal degradation. Inhibition of this protein disrupts homeostasis and inhibits cancer cell viability. Overexpression of PSMD14 was associated with advanced cancer characteristics and a worse prognosis in various carcinomas. This study aimed to analyze PSMD14 copy number variation, mRNA and protein expression in HNSCC, and its role as an independent prognostic biomarker.

METHODS

PSMD14 mRNA expression and copy number variations were analyzed in "The Cancer Genome Atlas (TCGA)" in 510 patients. Protein expression was evaluated using immunohistochemistry in a second cohort including 115 patients. PSMD14 levels were analyzed for correlation with clinicopathological data, overall and disease-free survival.

RESULTS

PSMD14 mRNA expression and copy number variation were high in 44 and 50% of patients, respectively. Protein expression of PSMD14 was high in 56%. In both cohorts, high PSMD14 levels were associated with advanced staging. High PSMD14 mRNA expression was additionally associated with a worse prognosis in univariable analysis. However, after correction for possible confounders, PSMD14 mRNA was not an independent prognostic marker.

CONCLUSION

PSMD14 is commonly expressed in HNSCC patients and associated with advanced stages. High expression of PSMD14 mRNA was associated with a worse outcome. However, this may be a result of the association of PSMD14 with poor prognosticators. Based on our study, further evaluation of PSMD14 as a prognostic marker and potential therapeutic target is warranted.

POH1/Rpn11/PSMD14: a journey from basic research in fission yeast to a prognostic marker and a druggable target in cancer cells

POH1/Rpn11/PSMD14 is a highly conserved protein in eukaryotes from unicellular organisms to human and has a crucial role in cellular homoeostasis. It is a subunit of the regulatory particle of the proteasome, where it acts as an intrinsic deubiquitinase removing polyubiquitin chains from substrate proteins. This function is not only coupled to the translocation of substrates into the core of the proteasome and their subsequent degradation but also, in some instances, to the stabilisation of ubiquitinated proteins through their deubiquitination. POH1 was initially discovered as a functional homologue of the fission yeast gene pad1⁺, which confers drug resistance when overexpressed. In translational studies, expression of POH1 has been found to be increased in several tumour types relative to normal adjacent tissue and to correlate with tumour progression, higher tumour grade, decreased sensitivity to cytotoxic drugs and poor prognosis. Proteasome inhibitors targeting the core particle of the proteasome are highly active in the treatment of myeloma, and recently developed POH1 inhibitors, such as capzimin and thiolutin, have shown promising anticancer activity in cell lines of solid tumours and leukaemia. Here we give an overview of POH1 function in the cell, of its potential role in oncogenesis and of recent progress in developing POH1-targeting drugs.

Mitochondrial micropeptide STMP1 promotes G1/S transition by enhancing mitochondrial complex IV activity

The roles of micropeptides in cell cycle regulation and cancer development remain largely unknown. Here we found that a micropeptide STMP1 (small transmembrane protein 1) was up-regulated in multiple malignancies including hepatocellular carcinoma (HCC), and its high level was associated with short recurrence-free survival of HCC patients. Gain- and loss-of-function analyses revealed that STMP1 accelerated cell proliferation and clonogenicity in vitro and tumor growth in vivo, and silencing STMP1 blocked G1/S transition. Mechanistically, STMP1 promoted the mRNA and protein levels of CCNE2, CDK2 and E2F1. STMP1 was localized in the inner membrane of mitochondria and interacted with mitochondrial complex IV and then enhanced its activity. Moreover, treatment with the mitochondrial complex IV inhibitor tetrathiomolybdate dramatically abrogated the promoting effect of STMP1 on cell proliferation and the expression of cyclin E2, CDK2 and E2F1. These results suggest that STMP1 may promote G1/S transition and cell proliferation by enhancing mitochondrial complex IV activity, which highlight STMP1 as a new regulator of the cell cycle and a potential target for anti-cancer therapy.

Impact of RSUME Actions on Biomolecular Modifications in Physio-Pathological Processes

The small RWD domain-containing protein called RSUME or RWDD3 was cloned from pituitary tumor cells with increasing tumorigenic and angiogenic proficiency. RSUME expression is induced under hypoxia or heat shock and is upregulated, at several pathophysiological stages, in tissues like pituitary, kidney, heart, pancreas, or adrenal gland. To date, several factors with essential roles in endocrine-related cancer appear to be modulated by RWDD3. RSUME regulates, through its post-translational (PTM) modification, pituitary tumor transforming gene (PTTG) protein stability in pituitary tumors. Interestingly, in these tumors, another PTM, the regulation of EGFR levels by USP8, plays a pathogenic role. Furthermore, RSUME suppresses ubiquitin conjugation to hypoxia-inducible factor (HIF) by blocking VHL E3-ubiquitin ligase activity, contributing to the development of von Hippel-Lindau disease. RSUME enhances protein SUMOylation of specific targets involved in inflammation such as IkB and the glucocorticoid receptor. For many of its actions, RSUME associates with regulatory proteins of ubiquitin and SUMO cascades, such as the E2-SUMO conjugase Ubc9 or the E3 ubiquitin ligase VHL. New evidence about RSUME involvement in inflammatory and hypoxic conditions, such as cardiac tissue response to ischemia and neuropathic pain, and its role in several developmental processes, is discussed as well. Given the modulation of PTMs by RSUME in neuroendocrine tumors, we focus on its interactors and its mode of action. Insights into functional implications and molecular mechanisms of RSUME action on biomolecular modifications of key factors of pituitary adenomas and renal cell carcinoma provide renewed information about new targets to treat these pathologies.

Integrative immunogenomic analysis reveals transcriptional and immune-related differences in hepatocellular carcinoma patients with different disease-free survival

A comprehensive investigation of the neoantigen spectrum and immune infiltration in patients with hepatocellular carcinoma (HCC) is lacking. This study aimed to examine the molecular features correlating with better prognoses in HCC patients. 27 paired tumor and normal tissues from 27 HCC patients were collected and performed with whole-exome sequencing. The most frequently mutated gene in 27 HCC patients was TP53 (16/27, 59.26%). Based on the whole median disease-free survival (DFS), all patients were divided into 'long-term' (n = 14, median DFS = 318 weeks) and 'short-term' (n = 13, median DFS = 11 weeks) groups. RNA-seq was performed to compare differentially expressed genes, immune infiltration, and neoantigens. Immunohistochemistry was performed to evaluate the immune infiltration. There were no significant differences in tumor mutation burden, immune score, cytolytic activity score, or neoantigen load between two groups. Compared with the long-term group, significantly increased B lineage (P = 0.0463), myeloid dendritic cells (P = 0.0152), and fibroblast (P = 0.0244) infiltration levels were observed in the short-term group, in which genes involved in ribosome, proteasome, and ECM-receptor interaction pathways were also overexpressed. Additionally, 16 patients with tumor thrombus were explored to identify specific biomarkers for prognosis. We found that patients with tumor thrombus carrying TP53/ARID2 neoantigens had significantly longer DFS. In conclusion, higher B lineage, myeloid dendritic cells, and fibroblast infiltration levels might cause poor prognosis in the short-term group, which also showed higher expression of genes involved in ribosome, proteasome, and ECM-receptor interaction pathways. In patients with tumor thrombus, specific TP53/ARID2 neoantigens may be used as biomarkers toward personalized immunotherapy.

The nociceptin receptor promotes autophagy through NF-kB signaling and is transcriptionally regulated by E2F1 in HCC

Opioids and their receptors are involved in cancer progression. However, the roles of the nociceptin receptor (NOP) and its antagonist (JTC801) in hepatocellular carcinoma (HCC) are poorly understood. The prognostic value of NOP expression was evaluated using tissue microarray and immunohistochemical staining analyses in a human HCC cohort. The biological role and mechanism of NOP in HCC tumor growth were determined in vitro and in vivo. We found that NOP was associated with the clinicopathological features and survival outcomes of HCC patients. NOP overexpression promoted HCC growth in vitro and in vivo. Mechanistically, NOP activated NF-kB signaling to promote autophagy, which inhibited apoptosis, in HCC cells. An inhibitor of autophagy, 3-MA, and an inhibitor of NF-kB, JSH-23, attenuated the function of NOP in HCC. E2F1 was identified as a transcription factor of NOP. The oncogenic role of NOP was positively regulated by E2F1. Furthermore, JTC801, a selective antagonist of NOP, abolished the function of NOP by inhibiting NF-kB signaling and autophagy. Our study demonstrates that NOP is an oncogene in HCC. We provide a potential therapeutic candidate and prognostic predictor for HCC. JTC801 could become a potential drug for HCC therapy.

PSMD14 Targeting Triggers Paraptosis in Breast Cancer Cells by Inducing Proteasome Inhibition and Ca2+ Imbalance

PSMD14, a subunit of the 19S regulatory particles of the 26S proteasome, was recently identified as a potential prognostic marker and therapeutic target in diverse human cancers. Here, we show that the silencing and pharmacological blockade of PSMD14 in MDA-MB 435S breast cancer cells induce paraptosis, a non-apoptotic cell death mode characterized by extensive vacuolation derived from the endoplasmic reticulum (ER) and mitochondria. The PSMD14 inhibitor, capzimin (CZM), inhibits proteasome activity but differs from the 20S proteasome subunit-inhibiting bortezomib (Bz) in that it does not induce aggresome formation or Nrf1 upregulation, which underlie Bz resistance in cancer cells. In addition to proteasome inhibition, the release of Ca²⁺ from the ER into the cytosol critically contributes to CZM-induced paraptosis. Induction of paraptosis by targeting PSMD14 may provide an attractive therapeutic strategy against cancer cells resistant to proteasome inhibitors or pro-apoptotic drugs.

Deubiquitinase PSMD14 promotes ovarian cancer progression by decreasing enzymatic activity of PKM2

Dysregulation of deubiquitination has been reported to contribute to carcinogenesis. However, the function and mechanism of deubiquitinating enzyme 26S proteasome non-ATPase regulatory subunit 14 (PSMD14) in the progression of ovarian cancer (OV), the deadliest gynecological cancer, still remains to be characterized. The present study demonstrated that PSMD14 was overexpressed in OV tissues and its higher levels correlated with a higher International Federation of Gynecology and Obstetrics (FIGO) stage in OV patients. A high level of PSMD14 expression was related to poor survival in OV patients. Knockdown and overexpression experiments elucidated that PSMD14 stimulated OV cell proliferation, invasion, and migration in vitro. Repression of PSMD14 suppressed OV tumor growth in vivo. PSMD14 inhibitor O-phenanthroline (OPA) effectively attenuated malignant behaviors of OV cells in vitro and OV tumor growth in vivo. Mechanistically, we uncovered that PSMD14 was involved in post-translational regulation of pyruvate kinase M2 isoform (PKM2). PSMD14 decreased K63-linked ubiquitination on PKM2, downregulated the ratio of PKM2 tetramers to dimers and monomers, and subsequently diminished pyruvate kinase activity and induced nuclear translocation of PKM2, contributing to aerobic glycolysis in OV cells. Collectively, our findings highlight the potential roles of PSMD14 as a biomarker and therapeutic candidate for OV.

CHPF promotes gastric cancer tumorigenesis through the activation of E2F1

Chondroitin polymerizing factor (CHPF) is an important glycosyltransferase involved in the biosynthesis of chondroitin sulfate. However, the relationship between CHPF and gastric cancer has not been fully investigated. CHPF expression in gastric cancer tissues was detected by immunohistochemistry and correlated with gastric cancer patient prognosis. Cultured gastric cancer cells and human gastric epithelial cell line GES1 were used to investigate the effects of shCHPF and shE2F1 on the development and progression of gastric cancer by MTT, western blotting, flow cytometry analysis of cell apoptosis, colony formation, transwell and gastric cancer xenograft mouse models, in vitro and in vivo. In gastric cancer tissues, CHPF was found to be significantly upregulated, and its expression correlated with tumor infiltration and advanced tumor stage and shorter patient survival in gastric cancer. CHPF may promote gastric cancer development by regulating cell proliferation, colony formation, cell apoptosis and cell migration, while knockdown induced the opposite effects. Moreover, the results from in vivo experiments demonstrated that tumor growth was suppressed by CHPF knockdown. Additionally, E2F1 was identified as a potential downstream target of CHPF in the regulation of gastric cancer, and its knockdown decreased the CHPF-induced promotion of gastric cancer. Mechanistic study revealed that CHPF may regulate E2F1 through affecting UBE2T-mediated E2F1 ubiquitination. This study showed, for the first time, that CHPF is a potential prognostic indicator and tumor promoter in gastric cancer whose function is likely carried out through the regulation of E2F1.

Identification of PSMD14 as a potential novel prognosis biomarker and therapeutic target for osteosarcoma

BACKGROUND

Osteosarcoma is the most common primary bone tumor. The survival rate of osteosarcoma patients has not significantly increased in the past decades. Uncovering the mechanisms of malignancy, progression, and metastasis will shed light on the development of new therapeutic targets and treatment for osteosarcoma.

AIM

The aim of this study is to identify potential osteosarcoma biomarker and/or therapeutic targets by using integrated bioinformatics analysis.

METHODS AND RESULTS

We utilized existing gene expression datasets to identify differential expressed genes (DEGs) that could serve as osteosarcoma biomarkers or even as therapeutic targets. We found 48 DEGs were overlapped in three datasets. Among these 48 DEGs, PSMD14 was on the top of the up-regulated gene list. We further found that higher PSMD14 expression was correlated with higher risk group (younger age group, ≤20.83 years of age), metastasis within 5 years and higher grade of tumor. Higher PSMD14 expression in osteosarcoma had positive correlation with higher infiltration of CD8+ T cells, neutrophils and myeloid dendritic cells. Kaplan-Myer survival data further revealed that higher expression of PSMD14 predicted significantly worse prognosis (p = .013). Gene set enrichment analysis was further performed for the DEGs related to PSMD14 in osteosarcoma. We found that lower PSMD14 expression group had more immune responses such as interferon γ, α responses, inflammation response etc. However, the higher PSMD14 expression group had more cell proliferation-related biological processes, such as G2M checkpoints and Myc targets. Through establishing protein-protein interaction networks using PSMD14 related DEGs, we identified 10 hub genes that were all ribosomal proteins. These hub genes may play roles in osteosarcoma tumorigenesis, progression and/or metastasis.

CONCLUSION

We identified PSMD14 gene as a possible osteosarcoma biomarker, and/or a possible therapeutic target.

Deubiquitination of the repressor E2F6 by USP22 facilitates AKT activation and tumor growth in hepatocellular carcinoma

Dysregulated ubiquitination of tumor-related proteins plays a critical role in tumor development and progression. The deubiquitinase USP22 is aberrantly expressed in certain types of cancer and contributes to aggressive tumor progression. However, the precise mechanism underlying the pro-tumorigenic function of USP22 in hepatocellular carcinoma (HCC) remains unclear. Here, we report that E2F6, a pocket protein-independent transcription repressor, is essential for HCC cell growth, and that its activities are controlled by USP22-mediated deubiquitination. USP22 interacts with and stabilizes E2F6, resulting in the transcriptional repression of phosphatase DUSP1. Moreover, the process involving DUSP1 repression by E2F6 strengthens AKT activation in HCC cells. Therefore, these findings provide mechanistic insights into the USP22-mediated control of oncogenic AKT signaling, emphasizing the importance of USP22-E2F6 regulation in HCC development.

Gypenoside LI arrests the cell cycle of breast cancer in G0/G1 phase by down-regulating E2F1

ETHNOPHARMACOLOGICAL RELEVANCE

Gynostemma pentaphyllum (Thunb.) Makino, a traditional medicine in China, has been widely used for the treatment of various diseases. Gypenoside LI (Gyp LI) is a major constituent from steamed G. pentaphyllum. Previous studies have shown that gypnenoside LI possess inhibitory effect on the growth of many cancer cells. However, its pharmacological effect in breast cancer and the mechanism have not been reported yet.

AIM OF THE STUDY

To investigate the anti-breast cancer activity of gypenoside LI and underlying mechanisms of gypenoside LI in MDA-MB-231 and MCF-7 cells.

MATERIAL/METHODS

The cytotoxicity of gypenoside LI was determined by MTT, colony-formation and three-dimensional spheroid assay. The migration, cell apoptosis and the cell cycle were investigated through cell morphology observation, flow cytometry analysis and key proteins detection. The anticancer mechanisms of gypenoside LI were detected by RNA sequencing (RNA-seq) and Gene Set Enrichment Analysis (GSEA) transcriptome analysis.

RESULTS

Gypenoside LI inhibited cell proliferation, migration, induced cell apoptosis and cell cycle arrest. Gypenoside LI arrested cell cycle at G0/G1 phase by regulating E2F1. It also inhibited tumor proliferation by regulating the expression of ERCC6L. Interestingly, we found that E2F1 siRNA also down-regulated the expression of ERCC6L. Gypenoside LI showed potential anti-breast cancer cells activity, especially on triple-negative breast cancer cells.

CONCLUSIONS

These data indicate that gypenoside LI could inhibit human breast cancer cells through inhibiting proliferation and migration, inducing apoptosis, arresting cell cycle at G0/G1 phase by regulating E2F1. It could be used as potential multi-target chemopreventive agents for cancer.

PSMD7 downregulation suppresses lung cancer progression by regulating the p53 pathway

Lung cancer is the second most common cancer in both men and women. The deubiquitinase PSMD7, as a core component of the 26S proteasome, is critical for the degradation of ubiquitinated proteins in the proteasome. Currently, PSMD7 expression and its roles in the progression of lung cancer remain largely unknown. In this study, we assessed PSMD7 expression and investigated the underlying molecular events by which PSMD7 regulates tumor progression in non-small cell lung cancer (NSCLC). The results showed that PSMD7 is more highly expressed in NSCLC tissues than in adjacent noncancerous tissues. PSMD7 expression was also closely associated with lymph node invasion and the laterality of the tumor in lung adenocarcinoma (LUAD). A high PSMD7 level predicted poor overall survival (OS) and disease-free survival (DFS) in LUAD patients, and PSMD7 knockdown significantly reduced cell proliferation and induced G0/G1-phase cell cycle arrest, cell senescence and apoptosis. PSMD7 knockdown inhibited expression of a set of proteins regulating cell cycle progression. Depletion of PSMD7 increased p53 levels and induced p21 and puma expression in a p53-dependent manner. Importantly, knockdown of PSMD7 markedly inhibited LUAD tumor growth in a xenograft mouse model. Taken together, these findings indicate that PSMD7 may serve as a valuable prognostic indicator and potential therapeutic target in LUAD.

Small-Molecule Inhibitors Targeting Proteasome-Associated Deubiquitinases

The 26S proteasome is the principal protease for regulated intracellular proteolysis. This multi-subunit complex is also pivotal for clearance of harmful proteins that are produced throughout the lifetime of eukaryotes. Recent structural and kinetic studies have revealed a multitude of conformational states of the proteasome in substrate-free and substrate-engaged forms. These conformational transitions demonstrate that proteasome is a highly dynamic machinery during substrate processing that can be also controlled by a number of proteasome-associated factors. Essentially, three distinct family of deubiquitinases–USP14, RPN11, and UCH37–are associated with the 19S regulatory particle of human proteasome. USP14 and UCH37 are capable of editing ubiquitin conjugates during the process of their dynamic engagement into the proteasome prior to the catalytic commitment. In contrast, RPN11-mediated deubiquitination is directly coupled to substrate degradation by sensing the proteasome’s conformational switch into the commitment steps. Therefore, proteasome-bound deubiquitinases are likely to tailor the degradation events in accordance with substrate processing steps and for dynamic proteolysis outcomes. Recent chemical screening efforts have yielded highly selective small-molecule inhibitors for targeting proteasomal deubiquitinases, such as USP14 and RPN11. USP14 inhibitors, IU1 and its progeny, were found to promote the degradation of a subset of substrates probably by overriding USP14-imposed checkpoint on the proteasome. On the other hand, capzimin, a RPN11 inhibitor, stabilized the proteasome substrates and showed the anti-proliferative effects on cancer cells. It is highly conceivable that these specific inhibitors will aid to dissect the role of each deubiquitinase on the proteasome. Moreover, customized targeting of proteasome-associated deubiquitinases may also provide versatile therapeutic strategies for induced or repressed protein degradation depending on proteolytic demand and cellular context.

The PSMD14 inhibitor Thiolutin as a novel therapeutic approach for esophageal squamous cell carcinoma through facilitating SNAIL degradation

Metastasis and chemoresistance are major causes of poor prognosis in patients with esophageal squamous cell carcinoma (ESCC), manipulated by multiple factors including deubiquitinating enzyme (DUB). DUB PSMD14 is reported to be a promising therapeutic target in various cancers. Here, we explored the antitumor activity of Thiolutin (THL), the PSMD14 inhibitor, as a new therapy strategy in ESCC.

Methods: Through 4-NQO-induced murine ESCC model, we investigated the expression of PSMD14 in esophageal tumorigenesis. Ubiquitin-AMC assay was performed to evaluate DUB activity of PSMD14 with THL treatment. The effect of THL on epithelial-to-mesenchymal transition (EMT), invasion, stemness and chemosensitivity was detected by using in vitro and in vivo experiments. Immunoprecipitation and in vivo ubiquitination assay were conducted to examine whether THL could impair the deubiquitination and stability of SNAIL regulated by PSMD14.

Results: Compared with normal esophageal epithelium, PSMD14 was upregulated in 4-NQO-induced murine esophageal epithelium dysplasia and ESCC tissues. THL could significantly weaken DUB activity of PSMD14. Furthermore, the results of in vitro and in vivo assays showed that THL efficiently suppressed motility and stemness and increased sensitivity to cisplatin in ESCC. Mechanically, THL impaired the interaction between PSMD14 and SNAIL, then promoted the ubiquitination and degradation of SNAIL to inhibit EMT which plays a crucial role in ESCC metastasis, stemness and chemosensitivity. TCGA database analysis revealed that high concomitant PSMD14/SNAIL expression predicted shorter overall survival in esophageal cancer.

Conclusion: Our findings demonstrate for the first time that suppression of PSMD14/SNAIL axis by THL could be a novel and promising therapeutic approach for ESCC clinical therapy.

LncRNA Lnc-APUE is Repressed by HNF4α and Promotes G1/S Phase Transition and Tumor Growth by Regulating MiR-20b/E2F1 Axis

Many long noncoding RNAs (lncRNAs) have been annotated, but their functions remain unknown. The authors found a novel lnc-APUE (lncRNA accelerating proliferation by upregulating E2F1) that is upregulated in different cancer types, including hepatocellular carcinoma (HCC), and high lnc-APUE level is associated with short recurrence-free survival (RFS) of HCC patients. Gain- and loss-of-function analyses showed that lnc-APUE accelerated G1/S transition and tumor cell growth in vitro and allows hepatoma xenografts to grow faster in vivo. Mechanistically, lnc-APUE binds to miR-20b and relieves its repression on E2F1 expression, resulting in increased E2F1 level and accelerated G1/S phase transition and cell proliferation. Consistently, lnc-APUE level is positively associated with the expression of E2F1 and its downstream target genes in HCC tissues. Further investigations disclose that hepatocyte nuclear factor 4 alpha (HNF4α) binds to the lnc-APUE promoter, represses lnc-APUE transcription, then diminishes E2F1 expression and cell proliferation. HNF4α expression is reduced in HCC tissues and low HNF4α level is correlated with high lnc-APUE expression. Collectively, a HNF4α/lnc-APUE/miR-20b/E2F1 axis in which HNF4α represses lnc-APUE expression and keeps E2F1 at a low level is identified. In tumor cells, HNF4α downregulation leads to lnc-APUE upregulation, which prevents the inhibition of miR-20b on E2F1 expression and thereby promotes cell cycle progression and tumor growth.

Dysregulation of the Ubiquitin Proteasome System in Human Malignancies: A Window for Therapeutic Intervention

Simple Summary

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. Dysregulation of the UPS results in loss of ability to maintain protein quality through proteolysis, and is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss the mechanisms linking dysregulated UPS to human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

Abstract

The ubiquitin proteasome system (UPS) governs the non-lysosomal degradation of oxidized, damaged, or misfolded proteins in eukaryotic cells. This process is tightly regulated through the activation and transfer of polyubiquitin chains to target proteins which are then recognized and degraded by the 26S proteasome complex. The role of UPS is crucial in regulating protein levels through degradation to maintain fundamental cellular processes such as growth, division, signal transduction, and stress response. Dysregulation of the UPS, resulting in loss of ability to maintain protein quality through proteolysis, is closely related to the development of various malignancies and tumorigenesis. Here, we provide a comprehensive general overview on the regulation and roles of UPS and discuss functional links of dysregulated UPS in human malignancies. Inhibitors developed against components of the UPS, which include U.S. Food and Drug Administration FDA-approved and those currently undergoing clinical trials, are also presented in this review.

The Long Non-coding RNA TMPO-AS1 Promotes Bladder Cancer Growth and Progression via OTUB1-Induced E2F1 Deubiquitination

Background: Increasing evidence indicates that long non-coding RNAs (lncRNAs) play crucial roles in cancer tumorigenesis and progression. TMPO antisense RNA 1 (TMPO-AS1) has been found to be involved in several cancers by acting as a competing endogenous RNA. However, the potential roles of TMPO-AS1 in bladder cancer (BC) and the potential interactions with proteins remain poorly understood.

Methods: The expression of the lncRNA TMPO-AS1 was evaluated via bioinformatic analysis and further validated by quantitative real-time PCR (qRT-PCR). Loss- and gain-of-function assays were performed to determine the biological functions of TMPO-AS1 in BC cell proliferation, migration, and invasion. Moreover, chromatin immunoprecipitation, Western blotting, and fluorescence in situ hybridization, as well as RNA pull-down, RNA immunoprecipitation, and luciferase reporter assays, were conducted to explore the upstream and downstream molecules interacting with TMPO-AS1.

Results: TMPO-AS1 is upregulated in BC. Functional experiments demonstrated that TMPO-AS1 promotes cell proliferation, migration, and invasion in BC and inhibits cell apoptosis in vivo and in vitro. Mechanically, E2F1 is responsible for TMPO-AS1 upregulation. Additionally, TMPO-AS1 facilitates the interaction of E2F1 with OTU domain-containing ubiquitin aldehyde binding 1 (OTUB1), leading to E2F1 deubiquitination and stabilization; therefore, TMPO-AS1 promotes BC malignant phenotypes. Furthermore, rescue experiments showed that TMPO-AS1 promotes BC growth in an E2F1-dependent manner.

Conclusions: Our study is the first to uncover the novel TMPO-AS1/E2F1 positive regulatory loop important for the promotion of BC malignant behaviors. The TMPO-AS1/E2F1 loop should be considered in the quest for new BC therapeutic options.

The E3 Ubiquitin Ligase RNF5 Facilitates SARS-CoV-2 Membrane Protein-Mediated Virion Release

As an enveloped virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains a membrane protein (M) that mediates viral release from cellular membranes. However, the molecular mechanisms of SARS-CoV-2 virion release remain poorly understood. In the present study, we performed RNA interference (RNAi) screening and identified the E3 ligase RNF5, which mediates the ubiquitination of SARS-CoV-2 M at residue K15 to enhance the interaction of the viral envelope protein (E) with M, whereas the deubiquitinating enzyme POH1 negatively regulates this process. The M-E complex ensures the uniform size of viral particles for viral maturation and mediates virion release. Moreover, M traffics from the Golgi apparatus to autophagosomes and uses autophagosomes for virion release, and this process is dependent on RNF5-mediated ubiquitin modification and M-E interaction. These results demonstrate that ubiquitin modification of SARS-CoV-2 M stabilizes the M-E complex and uses autophagosomes for virion release. IMPORTANCE Enveloped virus particles are released from the membranes of host cells, and viral membrane proteins (M) are critical for this process. A better understanding of the molecular mechanisms of SARS-CoV-2 assembly and budding is critical for the development of antiviral therapies. Envelope protein (E) and M of SARS-CoV-2 form complexes to mediate viral assembly and budding. RNF5 was identified to play a role as the E3 ligase, and POH1 was demonstrated to function as the deubiquitinating enzyme of SARS-CoV-2 M. The two components collectively regulate the interaction of M with E to promote viral assembly and budding. Ubiquitinated M uses autophagosomes for viral release. Our findings provide insights into the mechanisms of SARS-CoV-2 assembly and budding, demonstrating the importance of ubiquitination modification and autophagy in viral replication.

The oncogenic role of ubiquitin specific peptidase (USP8) and its signaling pathways targeting for cancer therapeutics

USP8 is a deubiquitinating enzyme in the family of ubiquitin-specific proteases (USPs) which can remove ubiquitin from the substrate and protect the substrate from degradation. The upregulated or mutated USP8 becomes hyperactivated and stabilizes numerous oncogenes or proto-oncogenes leading to cancer progression and survival by activating multiple signaling pathways. Moreover, USP8 inhibition is also important to overcome anticancer drug-resistant. This review is the first study to find, combine, analyze, and represent the multiple oncogenic signaling pathways with their downstream and upstream regulation activated or enhanced by USP8, which will help the researchers to find any therapeutic strategy for drug discovery by inhibiting or suppressing the multi-targeted USP8.

Promoting cell proliferation, cell cycle progression, and glycolysis: Glycometabolism-related genes act as prognostic signatures for prostate cancer

BACKGROUND

The Warburg effect seen in most solid tumors occurs only in the late stages of prostate cancer (PCa). Currently, the management of patients with low-risk localized PCa and patients after radical therapy remains a challenge. Our objective here was to evaluate glycometabolism-related genes as prognostic signatures for PCa.

METHODS

The International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA) databases and glycometabolism-related gene sets were obtained online. Glycometabolic prognostic signatures were identified and validated in a TCGA cohort and tested in an ICGC cohort. We used the gene set enrichment analysis to reveal biological processes associated with the glycometabolism-related signatures. Novel glycometabolism-related genes were selected for verifying their oncogenic phenotypes in vitro.

RESULTS

Two glycometabolic prognostic signatures were applied respectively to construct risk score formulas for PCa. Survival and receiver operating characteristic curve analyses were performed to detect the value of these prognostic signatures. We performed univariate and multivariate Cox regression analyses in the TCGA cohort, demonstrating the independence of the prognostic signatures. Three glycometabolism-related genes were found to be novel PCa-associated genes. These were shown to affect proliferation, cell cycle progression, and glycolysis of DU145 and PC3 cells in different degrees.

CONCLUSION

The present research represents the first glycometabolic and high-throughput investigation on PCa, revealing potential biomarkers and treatment targets. We confirm the vital role of glycometabolism in PCa and provide essential resources for future exploration of metabolism in PCa.

Prognostic Value and Molecular Mechanisms of Proteasome 26S Subunit, Non-ATPase Family Genes for Pancreatic Ductal Adenocarcinoma Patients after Pancreaticoduodenectomy

Objective: Pancreatic cancer (PC) is an extremely malignant tumor with similar morbidity and mortality and lack of an effective treatment. This study explored the prognostic value and molecular mechanisms of proteasome 26S subunit, non-ATPase (PSMD) family genes in pancreatic ductal adenocarcinoma (PDAC).Methods: Survival analyses were performed to elucidate the relationship between prognosis and the level of PSMD expression. ROC curves and nomograms were constructed to predict the prognosis. A bioinformatics analysis was used to explore the co-expression and complex interaction networks of PSMDs. The potential mechanisms were further explored via gene set enrichment analysis (GSEA).Results: We find high levels of PSMD6, PSMD9, PSMD11, and PSMD14 expression were significantly associated with a poorer OS. High PSMD6 and PSMD11 expression was associated with a poorer relapse-free survival (RFS). A risk score model was constructed based on prognosis-related genes. The area under ROC curves (AUC) was 53.3%, 59.3%, and 62.9% for 1-, 2-, 3 years, respectively.Conclusion: GSEA revealed that PSMD6 and PSMD11 play a role in PDAC through various biological processes and signaling pathways, including TP53, CDKN2A, MYC pathway, DNA repair, KRAS, cell cycle checkpoint, NIK, NF-κB signaling pathway, and proteasomes. This study demonstrated that PSMD6 and PSMD11 could serve as a potential prognostic and diagnostic biomarkers for patients with early-stage PDAC after pancreaticoduodenectomy.

Blockade of deubiquitinating enzyme PSMD14 overcomes chemoresistance in head and neck squamous cell carcinoma by antagonizing E2F1/Akt/SOX2-mediated stemness

Increasing evidence reveals a close relationship between deubiquitinating enzymes (DUBs) and cancer progression. In this study, we attempted to identify the roles and mechanisms of critical DUBs in head and neck squamous cell carcinoma (HNSCC).

Methods: Bioinformatics analysis was performed to screen differentially expressed novel DUBs in HNSCC. Immunohistochemistry assay was used to measure the expression of DUB PSMD14 in HNSCC specimens and adjacent normal tissues. The level of PSMD14 in HNSCC tumorigenesis was investigated using a 4-NQO-induced murine HNSCC model. The function of PSMD14 was determined through loss-of-function assays. Chromatin immunoprecipitation, immunoprecipitation and in vivo ubiquitination assay were conducted to explore the potential mechanism of PSMD14. The anti-tumor activity of PSMD14 inhibitor Thiolutin was assessed by in vitro and in vivo experiments.

Results: We identified PSMD14 as one of significantly upregulated DUBs in HNSCC tissues. Aberrant expression of PSMD14 was associated with tumorigenesis and malignant progression of HNSCC and further indicated poor prognosis. The results of in vitro and in vivo experiments demonstrated PSMD14 depletion significantly undermined HNSCC growth, chemoresistance and stemness. Mechanically, PSMD14 inhibited the ubiquitination and degradation of E2F1 to improve the activation of Akt pathway and the transcription of SOX2. Furthermore, PSMD14 inhibitor Thiolutin exhibited a potent anti-tumor effect on HNSCC in vivo and in vitro by impairing DUB activity of PSMD14.

Conclusion: Our findings demonstrate the role and mechanism of PSMD14 in HNSCC, and provide a novel and promising target for diagnosis and clinical therapy of HNSCC.

Ubiquitin-proteasome system (UPS) as a target for anticancer treatment

The ubiquitin-proteasome system (UPS) plays an important role in the cellular processes for protein quality control and homeostasis. Dysregulation of the UPS has been implicated in numerous diseases, including cancer. Indeed, components of UPS are frequently mutated or abnormally expressed in various cancers. Since Bortezomib, a proteasome inhibitor, received FDA approval for the treatment of multiple myeloma and mantle cell lymphoma, increasing numbers of researchers have been seeking drugs targeting the UPS as a cancer therapeutic strategy. Here, we introduce the essential component of UPS, including ubiquitinating enzymes, deubiquitinating enzymes and 26S proteasome, and we summarize their targets and mechanisms that are crucial for tumorigenesis. In addition, we briefly discuss some UPS inhibitors, which are currently in clinical trials as cancer therapeutics.

The Roles of Ubiquitin in Mediating Autophagy

Ubiquitination, the post-translational modification essential for various intracellular processes, is implicated in multiple aspects of autophagy, the major lysosome/vacuole-dependent degradation pathway. The autophagy machinery adopted the structural architecture of ubiquitin and employs two ubiquitin-like protein conjugation systems for autophagosome biogenesis. Ubiquitin chains that are attached as labels to protein aggregates or subcellular organelles confer selectivity, allowing autophagy receptors to simultaneously bind ubiquitinated cargos and autophagy-specific ubiquitin-like modifiers (Atg8-family proteins). Moreover, there is tremendous crosstalk between autophagy and the ubiquitin-proteasome system. Ubiquitination of autophagy-related proteins or regulatory components plays significant roles in the precise control of the autophagy pathway. In this review, we summarize and discuss the molecular mechanisms and functions of ubiquitin and ubiquitination, in the process and regulation of autophagy.

Deubiquitination Reactions on the Proteasome for Proteasome Versatility

The 26S proteasome, a master player in proteolysis, is the most complex and meticulously contextured protease in eukaryotic cells. While capable of hosting thousands of discrete substrates due to the selective recognition of ubiquitin tags, this protease complex is also dynamically checked through diverse regulatory mechanisms. The proteasome's versatility ensures precise control over active proteolysis, yet prevents runaway or futile degradation of many essential cellular proteins. Among the multi-layered processes regulating the proteasome's proteolysis, deubiquitination reactions are prominent because they not only recycle ubiquitins, but also impose a critical checkpoint for substrate degradation on the proteasome. Of note, three distinct classes of deubiquitinating enzymes-USP14, RPN11, and UCH37-are associated with the 19S subunits of the human proteasome. Recent biochemical and structural studies suggest that these enzymes exert dynamic influence over proteasome output with limited redundancy, and at times act in opposition. Such distinct activities occur spatially on the proteasome, temporally through substrate processing, and differentially for ubiquitin topology. Therefore, deubiquitinating enzymes on the proteasome may fine-tune the degradation depending on various cellular contexts and for dynamic proteolysis outcomes. Given that the proteasome is among the most important drug targets, the biology of proteasome-associated deubiquitination should be further elucidated for its potential targeting in human diseases.

The Role of Deubiquitinating Enzymes in Acute Lung Injury and Acute Respiratory Distress Syndrome

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) are characterized by an inflammatory response, alveolar edema, and hypoxemia. ARDS occurs most often in the settings of pneumonia, sepsis, aspiration of gastric contents, or severe trauma. The prevalence of ARDS is approximately 10% in patients of intensive care. There is no effective remedy with mortality high at 30-40%. Most functional proteins are dynamic and stringently governed by ubiquitin proteasomal degradation. Protein ubiquitination is reversible, the covalently attached monoubiquitin or polyubiquitin moieties within the targeted protein can be removed by a group of enzymes called deubiquitinating enzymes (DUBs). Deubiquitination plays an important role in the pathobiology of ALI/ARDS as it regulates proteins critical in engagement of the alveolo-capillary barrier and in the inflammatory response. In this review, we provide an overview of how DUBs emerge in pathogen-induced pulmonary inflammation and related aspects in ALI/ARDS. Better understanding of deubiquitination-relatedsignaling may lead to novel therapeutic approaches by targeting specific elements of the deubiquitination pathways.

ECT2/PSMD14/PTTG1 axis promotes the proliferation of glioma through stabilizing E2F1

BACKGROUND

Epithelial cell transformation sequence 2 (ECT2) is upregulated in glioma and promotes glioma cell proliferation. A preliminary experiment showed a positive correlation between ECT2 and pituitary tumor-transforming gene 1 (PTTG1). The aim of this study was to explore how ECT2 affects PTTG1 to influence the proliferation of glioma cells.

METHODS

The expression of ECT2 in glioma was detected by western blot and reverse transcription PCR. The effect of ECT2 on glioma proliferation was examined using cell proliferation-related assays and in vivo experiments. The effect of ECT2 on the stability of E2F transcription factor 1 (E2F1) and the expression of PTTG1 were examined by western blot, co-immunoprecipitation, and in vivo ubiquitination assays.

RESULTS

ECT2 was upregulated in gliomas and was negatively correlated with prognosis; its downregulation inhibited glioma cell proliferation. Furthermore, ECT2 regulated PTTG1 expression by affecting the stability of E2F1, thereby affecting the glioma cell proliferation. In addition, the deubiquitinating enzyme proteasome 26S subunit, non-ATPase 14 (PSMD14) affected the degradation of E2F1 and regulated the stability of E2F1. Interestingly, ECT2 regulated the expression of PSMD14.

CONCLUSION

In this study, we clarify a new mechanism by which ECT2 regulates the expression of PTTG1 and thus affects the proliferation of glioma cells: ECT2 influences the stability of E2F1 by regulating the expression of the deubiquitinating enzyme PSMD14, thereby affecting the expression of PTTG1. Intensive and extensive understanding of the mechanism of ECT2 in glioma proliferation may provide an opportunity for the development of new molecular therapeutic targets for glioma treatment.

Upregulation of deubiquitinase PSMD14 in lung adenocarcinoma (LUAD) and its prognostic significance

PSMD14 is a 19S-proteasome-associated deubiquitinating enzyme that facilitates protein degradation by the 20S proteasome core particle. Although accumulating evidence indicates that PSMD14 has emerged as a critical oncogenic factor by promoting tumor growth, the expression and function of PSMD14 in non-small cell lung cancer (NSCLC) remain largely unknown. In this study, we assessed PSMD14 expression and correlated it with clinical-pathological features and patient survival in NSCLC. We also determined the roles of PSMD14 in the regulation of lung adenocarcinoma (LUAD) cell growth. The results showed that PSMD14 expression was significantly upregulated in human NSCLC tissues compared with adjacent non-cancerous tissues. The PSMD14 level was associated with tumor size, lymph node invasion, and TNM stage in LUAD patients. Importantly, high PSMD14 expression was associated with poor overall survival (OS) and disease-free survival (DFS) in LUAD patients. Further, knockdown of PSMD14 significantly inhibited cell growth and caused G1 arrest and cellular senescence by increasing p21 stability in LUAD cells. PSMD14 knockdown also promoted cell apoptosis by increasing cleaved caspase-3 levels in H1299 cells. PSMD14 may serve as a potential prognostic marker and therapeutic target for LUAD patients.