USP44 suppresses proliferation and enhances apoptosis in colorectal cancer cells by inactivating the Wnt/β-catenin pathway via Axin1 deubiquitination

UBE2N promotes cell viability and glycolysis by promoting Axin1 ubiquitination in prostate cancer cells

BACKGROUND

Ubiquitin-conjugating enzyme E2 N (UBE2N) is recognized in the progression of some cancers; however, little research has been conducted to describe its role in prostate cancer. The purpose of this paper is to explore the function and mechanism of UBE2N in prostate cancer cells.

METHODS

UBE2N expression was detected in Cancer Genome Atlas Prostate Adenocarcinoma (TCGA-PRAD) data, prostate cancer tissue microarrays, and prostate cancer cell lines, respectively. UBE2N knockdown or overexpression was used to analyze its role in cell viability and glycolysis of prostate cancer cells and tumor growth. XAV939 or Axin1 overexpression was co-treated with UBE2N overexpression to detect the involvement of the Wnt/β-catenin signaling and Axin1 in the UBE2N function. UBE2N interacting with Axin1 was analyzed by co-immunoprecipitation assay.

RESULTS

UBE2N was upregulated in prostate cancer and the UBE2N-high expression correlated with the poor prognosis of prostate cancer. UBE2N knockdown inhibited cell viability and glycolysis in prostate cancer cells and restricted tumor formation in tumor-bearing mice. Wnt/β-catenin inhibition and Axin1 overexpression reversed the promoting viability and glycolysis function of UBE2N. UBE2N promoted Axin1 ubiquitination and decreased Axin1 protein level.

New insights in ubiquitin-dependent Wnt receptor regulation in tumorigenesis

Wnt signaling plays a crucial role in embryonic development and homeostasis maintenance. Delicate and sensitive fine-tuning of Wnt signaling based on the proper timings and positions is required to balance cell proliferation and differentiation and maintain individual health. Therefore, homeostasis is broken by tissue hypoplasia or tumor formation once Wnt signal dysregulation disturbs the balance of cell proliferation. The well-known regulatory mechanism of Wnt signaling is the molecular reaction associated with the cytoplasmic accumulation of effector β-catenin. In addition to β-catenin, most Wnt effector proteins are also regulated by ubiquitin-dependent modification, both qualitatively and quantitatively. This review will explain the regulation of the whole Wnt signal in four regulatory phases, as well as the different ubiquitin ligases and the function of deubiquitinating enzymes in each phase. Along with the recent results, the mechanism by which RNF43 negatively regulates the surface expression of Wnt receptors, which has recently been well understood, will be detailed. Many RNF43 mutations have been identified in pancreatic and gastrointestinal cancers and examined for their functional alteration in Wnt signaling. Several mutations facilitate or activate the Wnt signal, reversing the RNF43 tumor suppressor function into an oncogene. RNF43 may simultaneously play different roles in classical multistep tumorigenesis, as both wild-type and mutant RNF43 suppress the p53 pathway. We hope that the knowledge obtained from further research in RNF43 will be applied to cancer treatment in the future despite the fully unclear function of RNF43.

Role of protein degradation systems in colorectal cancer

Protein degradation is essential for maintaining protein homeostasis. The ubiquitin‒proteasome system (UPS) and autophagy-lysosome system are the two primary pathways responsible for protein degradation and directly related to cell survival. In malignant tumors, the UPS plays a critical role in managing the excessive protein load caused by cancer cells hyperproliferation. In this review, we provide a comprehensive overview of the dual roles played by the UPS and autolysosome system in colorectal cancer (CRC), elucidating their impact on the initiation and progression of this disease while also highlighting their compensatory relationship. Simultaneously targeting both protein degradation pathways offers new promise for enhancing treatment efficacy against CRC. Additionally, apoptosis is closely linked to ubiquitination and autophagy, and caspases degrade proteins. A thorough comprehension of the interplay between various protein degradation pathways is highly important for clarifying the mechanism underlying the onset and progression of CRC.

The scaffold protein AXIN1: gene ontology, signal network, and physiological function

AXIN1, has been initially identified as a prominent antagonist within the WNT/β-catenin signaling pathway, and subsequently unveiled its integral involvement across a diverse spectrum of signaling cascades. These encompass the WNT/β-catenin, Hippo, TGFβ, AMPK, mTOR, MAPK, and antioxidant signaling pathways. The versatile engagement of AXIN1 underscores its pivotal role in the modulation of developmental biological signaling, maintenance of metabolic homeostasis, and coordination of cellular stress responses. The multifaceted functionalities of AXIN1 render it as a compelling candidate for targeted intervention in the realms of degenerative pathologies, systemic metabolic disorders, cancer therapeutics, and anti-aging strategies. This review provides an intricate exploration of the mechanisms governing mammalian AXIN1 gene expression and protein turnover since its initial discovery, while also elucidating its significance in the regulation of signaling pathways, tissue development, and carcinogenesis. Furthermore, we have introduced the innovative concept of the AXIN1-Associated Phosphokinase Complex (AAPC), where the scaffold protein AXIN1 assumes a pivotal role in orchestrating site-specific phosphorylation modifications through interactions with various phosphokinases and their respective substrates.

Comprehensive analysis of the role of ubiquitin-specific peptidases in colorectal cancer: A systematic review

BACKGROUND

Colorectal cancer (CRC) is the third most frequent and the second most fatal cancer. The search for more effective drugs to treat this disease is ongoing. A better understanding of the mechanisms of CRC development and progression may reveal new therapeutic strategies. Ubiquitin-specific peptidases (USPs), the largest group of the deubiquitinase protein family, have long been implicated in various cancers. There have been numerous studies on the role of USPs in CRC; however, a comprehensive view of this role is lacking.

AIM

To provide a systematic review of the studies investigating the roles and functions of USPs in CRC.

METHODS

We systematically queried the MEDLINE (via PubMed), Scopus, and Web of Science databases.

RESULTS

Our study highlights the pivotal role of various USPs in several processes implicated in CRC: Regulation of the cell cycle, apoptosis, cancer stemness, epithelial-mesenchymal transition, metastasis, DNA repair, and drug resistance. The findings of this study suggest that USPs have great potential as drug targets and noninvasive biomarkers in CRC. The dysregulation of USPs in CRC contributes to drug resistance through multiple mechanisms.

CONCLUSION

Targeting specific USPs involved in drug resistance pathways could provide a novel therapeutic strategy for overcoming resistance to current treatment regimens in CRC.

The deubiquitinating enzyme USP44 suppresses hepatocellular carcinoma progression by inhibiting Hedgehog signaling and PDL1 expression

Hepatocellular carcinoma (HCC) is one of the deadliest malignancies in the world. Research into the key genes that maintain the malignant behavior of cancer cells is crucial for the treatment of HCC. Here, we identified ubiquitin-specific peptidase 44 (USP44), a member of the deubiquitinase family, as a novel regulator of HCC progression. The tumor suppressive function of USP44 was evaluated in a series of in vitro and in vivo experiments. Through quantitative proteomics examination, we demonstrated that USP44 inhibits HCC PDL1 expression by downregulating the Hedgehog (Hh) signaling pathway. Mechanistically, we found that USP44 directly interacts with Itch, an E3 ligase involved in Hh signaling, and promotes the deubiquitination and stabilization of Itch. These events result in the proteasomal degradation of Gli1 and subsequent inactivation of Hh signaling, which ultimately suppresses PDL1 expression and the progression of HCC. Furthermore, the HCC tissue microarray was analyzed by immunohistochemistry to evaluate the pathological relevance of the USP44/Itch/Gli1/PDL1 axis. Finally, the Gli1 inhibitor GANT61 was found to act in synergy with anti-PDL1 therapy. Overall, USP44 can act as a suppressive gene in HCC by modulating Hh signaling, and co-inhibition of Gli1 and PDL1 might be an effective novel combination strategy for treating HCC patients.

Analysis of mRNA m6A modification and mRNA expression profiles in middle ear cholesteatoma

Introduction: Middle ear cholesteatoma is characterized by the hyperproliferation of keratinocytes. In recent decades, N6-methyladenosine (m6A) modification has been shown to play an essential role in the pathogenesis of many proliferative diseases. However, neither the m6A modification profile nor its potential role in the pathogenesis of middle ear cholesteatoma has currently been investigated. Therefore, this study aimed to explore m6A modification patterns in middle ear cholesteatoma. Materials and methods: An m6A mRNA epitranscriptomic microarray analysis was performed to analyze m6A modification patterns in middle ear cholesteatoma tissue (n = 5) and normal post-auricular skin samples (n = 5). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the potential biological functions and signaling pathways underlying the pathogenesis of middle ear cholesteatoma. Subsequently, m6A modification levels were verified by methylated RNA immunoprecipitation-qPCR (MeRIP-qPCR) in middle ear cholesteatoma tissue and normal skin samples, respectively. Results: A total of 6,865 distinctive m6A-modified mRNAs were identified, including 4,620 hypermethylated and 2,245 hypomethylated mRNAs, as well as 9,162 differentially expressed mRNAs, including 4,891 upregulated and 4,271 downregulated mRNAs, in the middle ear cholesteatoma group relative to the normal skin group. An association analysis between methylation and gene expression demonstrated that expression of 1,926 hypermethylated mRNAs was upregulated, while expression of 2,187 hypomethylated mRNAs and 38 hypermethylated mRNAs was downregulated. Moreover, GO analysis suggested that differentially methylated mRNAs might influence cellular processes and biological behaviors, such as cell differentiation, biosynthetic processes, regulation of molecular functions, and keratinization. KEGG pathway analysis demonstrated that the hypermethylated transcripts were involved in 26 pathways, including the Hippo signaling pathway, the p53 signaling pathway, and the inflammatory mediator regulation of transient receptor potential (TRP) channels, while the hypomethylated transcripts were involved in 13 pathways, including bacterial invasion of epithelial cells, steroid biosynthesis, and the Hippo signaling pathway. Conclusion: Our study presents m6A modification patterns in middle ear cholesteatoma, which may exert regulatory roles in middle ear cholesteatoma. The present study provides directions for mRNA m6A modification-based research on the epigenetic etiology and pathogenesis of middle ear cholesteatoma.

Integrated network findings reveal ubiquitin-specific protease 44 overexpression suppresses tumorigenicity of liver cancer

Hepatocellular carcinoma (HCC) is the sixth most common cancer and third leading cause of cancer-related deaths worldwide. HCC is a multistep disease marked by various signaling alterations. A better understanding of the new molecular drivers of HCC could therefore provide an opportunity to develop effective diagnostic and therapeutic targets. Ubiquitin-specific protease 44 (USP44), a member of the cysteine protease family, has been reported to play a role in many cancer types. However, its contribution to HCC development remains unknown. In the present study, we observed suppression of USP44 expression in HCC tissue. Clinicopathologic analysis further showed that low USP44 expression correlated with poorer survival and a later tumor stage in HCC, suggesting that USP44 could be a predictor of poor prognosis in patients with HCC. Gain-of-function analysis in vitro demonstrated the importance of USP44 in HCC cell growth and G₀/G₁ cell cycle arrest. To investigate the downstream targets of USP44 and the molecular mechanisms underlying its regulation of cell proliferation in HCC, we conducted a comparative transcriptomic analysis and identified a cluster of proliferation-related genes, including CCND2, CCNG2, and SMC3. Ingenuity Pathway Analysis further delineated the gene networks controlled by USP44 through the regulation of membrane proteins and receptors, enzymes, transcriptional factors, and cyclins involved in the control of cell proliferation, metastasis, and apoptosis in HCC. To summarize, our results highlight, for the first time, the tumor-suppression role of USP44 in HCC and suggest a new prognostic biomarker in this disease.

Targeted therapy based on ubiquitin-specific proteases, signalling pathways and E3 ligases in non-small-cell lung cancer

Lung cancer is one of the most common malignant tumours worldwide, with the highest mortality rate. Approximately 1.6 million deaths owing to lung cancer are reported annually; of which, 85% of deaths occur owing to non-small-cell lung cancer (NSCLC). At present, the conventional treatment methods for NSCLC include radiotherapy, chemotherapy, targeted therapy and surgery. However, drug resistance and tumour invasion or metastasis often lead to treatment failure. The ubiquitin–proteasome pathway (UPP) plays an important role in the occurrence and development of tumours. Upregulation or inhibition of proteins or enzymes involved in UPP can promote or inhibit the occurrence and development of tumours, respectively. As regulators of UPP, ubiquitin-specific proteases (USPs) primarily inhibit the degradation of target proteins by proteasomes through deubiquitination and hence play a carcinogenic or anticancer role. This review focuses on the role of USPs in the occurrence and development of NSCLC and the potential of corresponding targeted drugs, PROTACs and small-molecule inhibitors in the treatment of NSCLC.

LSM12 facilitates the progression of colorectal cancer by activating the WNT/CTNNB1 signaling pathway

Aberrant activation of the WNT signaling pathway is a joint event in colorectal cancer (CRC), but the molecular mechanism is still unclear. Recently, RNA-splicing factor LSM12 (like-Sm protein 12) is highly expressed in CRC tissues. This study aimed to verify whether LSM12 is involved in regulating CRC progression via regulating the WNT signaling pathway. Here, we found that LSM12 is highly expressed in CRC patient-derived tissues and cells. LSM12 is involved in the proliferation, invasion, and apoptosis of CRC cells, similar to the function of WNT signaling in CRC. Furthermore, protein interaction simulation and biochemical experiments proved that LSM12 directly binds to CTNNB1 (also known as β-Catenin) and regulates its protein stability to affect the CTTNB1-LEF1-TCF1 transcriptional complex formation and the associated WNT downstream signaling pathway. LSM12 depletion in CRC cells decreased the in vivo tumor growth through repression of cancer cell growth and acceleration of cancer cell apoptosis. Taken together, we suggest that the high expression of LSM12 is a novel factor leading to aberrant WNT signaling activation, and that strategies targeting this molecular mechanism may contribute to developing a new therapeutic method for CRC.

Wnt3a is a promising target in colorectal cancer

Most colorectal cancers (CRC) are associated with activated Wnt signaling, making it the fourth most prevalent type of cancer globally. To function properly, the Wnt signaling pathway requires secreted glycoproteins known as Wnt ligands (Wnts). Humans have 19 Wnts, which suggest a complicated signaling and biological process, and we still know little about their functions in developing CRC. This review aims to describe the canonical Wnt signaling in CRC, particularly the Wnt3a expression pattern, and their association with the angiogenesis and progression of CRC. This review also sheds light on the inhibition of Wnt3a signaling in CRC. Despite some obstacles, a thorough understanding of Wnts is essential for effectively managing CRC.

Insight into the physiological and pathological roles of USP44, a potential tumor target (Review)

Ubiquitin-specific peptidase 44 (USP44) is a member of the ubiquitin-specific proteases (USPs) family and its functions in various biological processes have been gradually elucidated in recent years. USP44 targets multiple downstream factors and regulates multiple mechanisms through its deubiquitination activity. Ubiquitination is, in essence, a process in which a single ubiquitin molecule or a multiubiquitin chain binds to a substrate protein to form an isopeptide bond. Deubiquitination is the catalyzing of the isopeptide bonds between ubiquitin and substrate proteins through deubiquitylating enzymes. These two processes serve an important role in the regulation of the expression, conformation, localization and function of substrate proteins by regulating their binding to ubiquitin. Based on existing research, this paper summarized the current state of knowledge about USP44. The physiological roles of USP44 in various cellular events and its pathophysiological roles in different cancer types are evaluated and the therapeutic potential of USP44 for cancer treatment is evaluated.

Targeting UBR5 in hepatocellular carcinoma cells and precise treatment via echinacoside nanodelivery

Background

Hepatocellular carcinoma (HCC) is among the most common and malignant cancers with no effective therapeutic approaches. Echinacoside (ECH), a phenylethanoid glycoside isolated from Chinese herbal medicine, Cistanche salsa, can inhibit HCC progression; however, poor absorption and low bioavailability limit its biological applications.

Methods

To improve ECH sensitivity to HepG2 cells, we developed a mesoporous silica nanoparticle (MSN)-based drug delivery system to deliver ECH to HepG2 cells via galactose (GAL) and poly(ethylene glycol) diglycidyl ether (PEGDE) conjugation (ECH@Au@MSN-PEGDE-GAL, or ECH@AMPG). Gain- and loss-of-function assays were conducted to assess the effects of UBR5 on HCC cell apoptosis and glycolysis. Moreover, the interactions among intermediate products were also investigated to elucidate the mechanisms by which UBR5 functions.

Results

The present study showed that ubiquitin protein ligase E3 component N-recognin 5 (UBR5) acted as an oncogene in HCC tissues and that its expression was inhibited by ECH. AMPG showed a high drug loading property and a slow and sustained release pattern over time. Moreover, owing to the valid drug accumulation, ECH@AMPG promoted apoptosis and inhibited glycolysis of HepG2 cells in vitro. In vivo experiments demonstrated that AMPG also enhanced the antitumor effects of ECH in HepG2 cell-bearing mice.

Conclusions

Our results indicated the clinical significance of UBR5 as a therapeutic target. On the basis of the nontoxic and high drug-loading capabilities of AMPG, ECH@AMPG presented better effects on HCC cells compared with free ECH, indicating its potential for the chemotherapy of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00394-w.

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.

Wnt signaling in colorectal cancer: pathogenic role and therapeutic target

Background

The Wnt signaling pathway is a complex network of protein interactions that functions most commonly in embryonic development and cancer, but is also involved in normal physiological processes in adults. The canonical Wnt signaling pathway regulates cell pluripotency and determines the differentiation fate of cells during development. The canonical Wnt signaling pathway (also known as the Wnt/β-catenin signaling pathway) is a recognized driver of colon cancer and one of the most representative signaling pathways. As a functional effector molecule of Wnt signaling, the modification and degradation of β-catenin are key events in the Wnt signaling pathway and the development and progression of colon cancer. Therefore, the Wnt signaling pathway plays an important role in the pathogenesis of diseases, especially the pathogenesis of colorectal cancer (CRC).

Objective

Inhibit the Wnt signaling pathway to explore the therapeutic targets of colorectal cancer.

Methods

Based on studying the Wnt pathway, master the biochemical processes related to the Wnt pathway, and analyze the relevant targets when drugs or inhibitors act on the Wnt pathway, to clarify the medication ideas of drugs or inhibitors for the treatment of diseases, especially colorectal cancer.

Results

Wnt signaling pathways include: Wnt/β-catenin or canonical Wnt signaling pathway, planar cell polarity (Wnt-PCP) pathway and Wnt-Ca²⁺ signaling pathway. The Wnt signaling pathway is closely related to cancer cell proliferation, stemness, apoptosis, autophagy, metabolism, inflammation and immunization, microenvironment, resistance, ion channel, heterogeneity, EMT/migration/invasion/metastasis. Drugs/phytochemicals and molecular preparations for the Wnt pathway of CRC treatment have now been developed. Wnt inhibitors are also commonly used clinically for the treatment of CRC.

Conclusion

The development of drugs/phytochemicals and molecular inhibitors targeting the Wnt pathway can effectively treat colorectal cancer clinically.

Potential mechanism of oral baicalin treating psoriasis via suppressing Wnt signaling pathway and inhibiting Th17/IL-17 axis by activating PPARγ

Psoriasis (PSO), an immune-mediated chronic inflammatory skin disease, has seriously affected the quality of patients' life. It is urgent to find effective medicines with lower costs and less side effects. Baicalin (HQG) is the main bioactive substance from Scutellaria baicalensis with effects of anti-inflammation and immunoregulation. Herein, we explored the effect of oral HQG treating PSO and its potential mechanism. Firstly, network pharmacology was used to predict that HQG may act on Estrogen, TNF-alpha (tumor necrosis factor, TNF), interleukin-17 (IL-17) signaling pathways and Th17 cell differentiation, especially the key targets including TNF, Proto-oncogene tyrosine-protein kinase Src, Peroxisome proliferator-activated receptor gamma and Matrix metalloproteinase-9. Imiquimod (IMQ)-induced mice were then used to study the effects of HQG treating PSO. HQG could significantly ameliorate the skin lesions, decrease the level of inflammatory factors and inhibit Th1/Th17 cell differentiation in IMQ-induced mice. Finally, transcriptome analysis of skin lesions integrated with the prediction of network pharmacology further demonstrated that the potential mechanism may be associated with suppressing Wnt signaling pathway and inhibiting Th17/IL-17 axis by activating PPARγ. In conclusion, this study suggested that HQG may be a promising agent for further studies in the search for therapeutic strategies to treat PSO in the future.

USP20 regulates the stability of EMT transcription factor SOX4 and influences colorectal cancer metastasis

BACKGROUND

Colorectal cancer (CRC) is a familiar malignancy accompanied by higher morbidity and mortality. The deubiquitination enzyme USP20 has been discovered to be one key factor in several cancers progression. SOX4 is a critical transcription factor to regulate the expression of various genes, and participates into the occurrence and progression of cancers. In this study, it was aimed to illustrate the role of USP20 and the regulatory relationship between USP20 and SOX4 in CRC.

METHODS

The protein expressions of USP20, SOX4, E-cadherin, N-cadherin, Snail and slug were tested through western blot. The cell proliferation ability was verified through CCK-8 assay. The migration and invasion abilities were detected through Transwell assay. The mRNA expression of SOX4 was confirmed through RT-qPCR. The interaction between USP20 and SOX4 was notarized through Co-IP assay.

RESULT

Our study demonstrated that USP20 displayed higher expression, and facilitated CRC progression through regulating cell proliferation, migration, invasion and EMT process markers. USP20 was found to modulate SOX4 protein expression. Next, it was verified that USP20 regulated SOX4 degradation through deubiquitination. Finally, through rescue assays, we revealed that USP20 mediated SOX4 expression to accelerate CRC progression.

CONCLUSIONS

In this study, USP20 regulated the stability of EMT transcription factor SOX4 and aggravated colorectal cancer metastasis. This finding might highlight the function of USP20 in the treatment of CRC.

The E3 Ubiquitin Ligase TRIM11 Facilitates Gastric Cancer Progression by Activating the Wnt/β-Catenin Pathway via Destabilizing Axin1 Protein

Background

Aberrant expression of tripartite motif 11 (TRIM11) and the Wnt/β-catenin pathway are essential for facilitating tumorigenesis and progression in multiple types of cancer.

Aim

To investigate the molecular changes linking the dysregulation of TRIM11 and Wnt/β-catenin pathway activation in gastric cancer (GC) progression.

Methods

The expression levels of TRIM11 were detected in GC tissues and cells by immunohistochemistry and western blotting. The role of TRIM11 in the growth, proliferation, and invasion of gastric cancer cells was observed by a series of cell functional experiments and further verified in vivo. Co-immunoprecipitation (Co-IP), immunofluorescence, cycloheximide, and western blotting assays and other experiments were conducted to explore the mechanisms of TRIM11 underlying the regulation of the Wnt/β-catenin pathway. For further verification, rescue experiments were performed by cotransfection of TRIM11 and Axin1 siRNA in GC cells.

Results

Using Co-IP assays, we identified TRIM11 as a potent binding partner of Axin1 in GC cells. Elevated TRIM11 levels were significantly correlated with unfavorable clinical outcomes and poor survival in patients with GC. In addition, TRIM11 promoted the cell proliferation and invasion capacities of GC cells in vitro and tumor growth in vivo. Mechanistic investigations revealed that TRIM11 destabilized Axin1 protein by interacting with Axin1, thus inducing the activation of the Wnt/β-catenin pathway. Moreover, we found that the oncogenic effects of TRIM11 on GC cells were partly mediated by suppression of Axin1. Furthermore, the protein expression of TRIM11 and Axin1 was negatively correlated in GC tissues.

Conclusion

Collectively, our findings not only establish a pivotal TRIM11-Axin1-β-catenin axis in driving GC progression but also indicate that TRIM11 serves as a valuable therapeutic target for the treatment of GC patients.

Therapeutic strategies targeting Wnt/β‑catenin signaling for colorectal cancer (Review)

Colorectal cancer (CRC) is one of the most common carcinomas. Although great progress has been made in recent years, CRC survival remains unsatisfactory due to high metastasis and recurrence. Understanding the underlying molecular mechanisms of CRC tumorigenesis and metastasis has become increasingly important. Recently, aberrant Wnt/β‑catenin signaling has been reported to be strongly associated with CRC tumorigenesis, metastasis and recurrence. Therefore, the Wnt/β‑catenin signaling pathway has potential value as a therapeutic target for CRC. In the present review, the dysregulation of this pathway in CRC and the promoting or suppressing function of therapeutic targets on CRC were explored. In addition, the interaction between this pathway and epithelial‑mesenchymal transition (EMT), cell stemness, mutations, metastasis‑related genes and tumor angiogenesis in CRC cells were also investigated. Numerous studies on this pathway may help identify the potential diagnostic and prognostic markers and therapeutic targets for CRC.

USP44 accelerates the growth of T-cell acute lymphoblastic leukemia through interacting with WDR5 and repressing its ubiquitination

T-cell acute lymphoblastic leukemia (T-ALL) is a common hematologic malignancy. Based on the data from GSE66638 and GSE141140, T-ALL patients depicted a higher USP44 level. However, its role in T-ALL is still unclear. In the present study, we investigated the role of USP44 in T-ALL growth. USP44 overexpression elevated the proliferation of CCRF-CEM cells, while USP44 knockdown suppressed the proliferation of Jurkat and MOLT-4 cells. In addition, USP44 accelerated the cell cycle progression, with boosted cyclinD and PCNA levels. However, USP44 knockdown induced apoptosis in Jurkat and MOLT-4 cells, with an upheaval among cleaved caspase-3 and PARP levels. Mechanistically, USP44 co-localized and interacted with WDR5, leading to the repression of its ubiquitination and degradation. Interestingly, WDR5 overexpression abolished the apoptosis induced by USP44 knockdown. Consistently, the in vivo study revealed that USP44 knockdown restricted the leukemic engraftments in the bone marrow and spleens and reduced the infiltration of T-ALL cells in the livers and lungs. In conclusion, this study indicated that USP44 enhanced the growth of T-ALL through interacting with WDR5 and repressing its ubiquitination. This study highlights the potential use of USP44 as a therapeutic target of T-ALL.

Ubiquitin-Specific Proteases: Players in Cancer Cellular Processes

Ubiquitination represents a post-translational modification (PTM) essential for the maintenance of cellular homeostasis. Ubiquitination is involved in the regulation of protein function, localization and turnover through the attachment of a ubiquitin molecule(s) to a target protein. Ubiquitination can be reversed through the action of deubiquitinating enzymes (DUBs). The DUB enzymes have the ability to remove the mono- or poly-ubiquitination signals and are involved in the maturation, recycling, editing and rearrangement of ubiquitin(s). Ubiquitin-specific proteases (USPs) are the biggest family of DUBs, responsible for numerous cellular functions through interactions with different cellular targets. Over the past few years, several studies have focused on the role of USPs in carcinogenesis, which has led to an increasing development of therapies based on USP inhibitors. In this review, we intend to describe different cellular functions, such as the cell cycle, DNA damage repair, chromatin remodeling and several signaling pathways, in which USPs are involved in the development or progression of cancer. In addition, we describe existing therapies that target the inhibition of USPs.

Progress in research of deubiquitination enzymes in colorectal cancer

Dubiquitinating enzymes include six subfamilies, which are widely distributed in various cells of the body. They play an important role in many processes, such as regulating the degradation of protein, and are involved in cell growth and proliferation, immune regulation, nerve function, tumor development, and molecular signaling pathways. Colorectal cancer, as one of the five malignant tumors with the highest morbidity and mortality, is a serious threat to human health. More and more studies have reported that the deubiquitination enzyme family plays an important role in the occurrence and development of colorectal cancer. Here, we review the recent progress in the research of deubiquitination enzymes in colorectal cancer.

Deubiquitinating Enzyme-Mediated Signaling Networks in Cancer Stem Cells

Cancer stem cells (CSCs) have both the capacity for self-renewal and the potential to differentiate and contribute to multiple tumor properties, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Thus, CSCs are considered to be promising therapeutic targets for cancer therapy. The function of CSCs can be regulated by ubiquitination and deubiquitination of proteins related to the specific stemness of the cells executing various stem cell fate choices. To regulate the balance between ubiquitination and deubiquitination processes, the disassembly of ubiquitin chains from specific substrates by deubiquitinating enzymes (DUBs) is crucial. Several key developmental and signaling pathways have been shown to play essential roles in this regulation. Growing evidence suggests that overactive or abnormal signaling within and among these pathways may contribute to the survival of CSCs. These signaling pathways have been experimentally shown to mediate various stem cell properties, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation. In this review, we focus on the DUBs involved in CSCs signaling pathways, which are vital in regulating their stem-cell fate determination.

Overexpression of UBE2M through Wnt/β-Catenin signaling is associated with poor prognosis and chemotherapy resistance in colorectal cancer

Background

The expression of ubiquitin-conjugating enzyme E2 M (UBE2M) is elevated in colorectal carcinoma (CRC). However, the underlying mechanisms and effects of UBE2M on the prognosis and drug resistance in CRC have not been investigated.

Methods

CRC specimens and adjacent normal tissues were collected from 74 patients. The expression of UBE2M was measured by quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry. Multivariable cox regression analysis was used to analyze the risk factors for overall survival in clinical CRC patients. Human colorectal cancer cell lines HCT116 and SW480 were transfected with specific UBE2M small interfering ribonucleic acid (siRNA) or plasmid to either suppress or increase the expression of UBE2M for in vitro experiments. Also, chemotherapy-resistant HCT116 and SW480 cells were established by being treated with increasingly higher concentrations of fluorouracil (5-FU) or oxaliplatin. XAV-939 was used as a wingless/integrated-beta-catenin (Wnt/β-catenin) signaling inhibitor.

Results

According to quantitative real-time PCR and immunohistochemistry, the expression of UBE2M was elevated in CRC tissues compared to normal tissues. Based on cox regression analysis, the overexpression of UBE2M was a risk factor for overall survival of CRC patients. The expression of UBE2M was notably high in 5-FU- and oxaliplatin-resistant cells in in vitro experiments. Also, cells transfected with specific UBE2M siRNA or plasmid induced lower resistance to 5-FU and higher resistance to oxaliplatin. Finally, the expression of β-catenin was correlated with the expression of UBE2M in transfected cells and treatment with XAV939 decreased the degree of drug resistance in chemotherapy-resistant HCT116 cells.

Conclusions

Overexpression of UBE2M in CRC specimens contributes to a decreased overall survival of patients and mediates 5-FU and oxaliplatin resistance in CRC cells via the Wnt/β-catenin signaling pathway.

Regulation of Wnt Signaling through Ubiquitination and Deubiquitination in Cancers

The Wnt signaling pathway plays important roles in embryonic development, homeostatic processes, cell differentiation, cell polarity, cell proliferation, and cell migration via the β-catenin binding of Wnt target genes. Dysregulation of Wnt signaling is associated with various diseases such as cancer, aging, Alzheimer’s disease, metabolic disease, and pigmentation disorders. Numerous studies entailing the Wnt signaling pathway have been conducted for various cancers. Diverse signaling factors mediate the up- or down-regulation of Wnt signaling through post-translational modifications (PTMs), and aberrant regulation is associated with several different malignancies in humans. Of the numerous PTMs involved, most Wnt signaling factors are regulated by ubiquitination and deubiquitination. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and usually induces proteasomal degradation of Wnt signaling factors such as β-catenin, Axin, GSK3, and Dvl. Conversely, deubiquitination induced by the deubiquitinating enzymes (DUBs) detaches the ubiquitins and modulates the stability of signaling factors. In this review, we discuss the effects of ubiquitination and deubiquitination on the Wnt signaling pathway, and the inhibitors of DUBs that can be applied for cancer therapeutic strategies.

USP44 suppresses proliferation and enhances apoptosis in colorectal cancer cells by inactivating the Wnt/β-catenin pathway via Axin1 deubiquitination

Colorectal cancer (CRC) is the leading cause of cancer death, and its 5-year survival rate remains unsatisfactory. Recent studies have revealed that ubiquitin-specific protease 44 (USP44) is a cancer suppressor or oncogene depending on the type of neoplasm. However, its role in CRC remains unclear. Here, we found that the USP44 expression level was markedly decreased in CRC, and USP44 overexpression inhibited proliferation while enhancing apoptosis in CRC cells, suggesting that USP44 is a cancer suppressor in CRC. We then investigated if USP44 functioned through regulating the Wnt/β-catenin pathway. We found that USP44 overexpression increased the Axin1 protein while decreasing β-catenin, c-myc, and cyclin D1 proteins, suggesting that USP44 inhibited the activation of the Wnt/β-catenin pathway. Moreover, we found that two Wnt/β-catenin activators, LiCl and SKL2001, both attenuated oeUSP44-mediated proliferation and apoptosis in CRC cells. Collectively, these data points indicated that USP44 inhibited proliferation while promoting apoptosis in CRC cells by inhibiting the Wnt/β-catenin pathway. Interestingly, we observed that USP44 overexpression did not affect the Axin1 mRNA level. Further study uncovered that USP44 interacted with Axin1 and reduced the ubiquitination of Axin1. Furthermore, Axin1 knock-down abolished the effects of oeUSP44 on proliferation, apoptosis, and Wnt/β-catenin activity in CRC cells. Taken together, this study demonstrates that USP44 inhibits proliferation while enhancing apoptosis in CRC cells by inactivating the Wnt/β-catenin pathway via Axin1 deubiquitination. USP44 is a cancer suppressor in CRC and a potential target for CRC therapy.