USP44 Promotes the Tumorigenesis of Prostate Cancer Cells through EZH2 Protein Stabilization

Detection of differentially methylated CpGs between tumour and adjacent benign cells in diagnostic prostate cancer samples

Differentially methylated CpG sites (dmCpGs) that distinguish prostate tumour from adjacent benign tissue could aid in the diagnosis and prognosis of prostate cancer. Previously, the identification of such dmCpGs has only been undertaken in radical prostatectomy (RP) samples and not primary diagnostic tumour samples (needle biopsy or transurethral resection of the prostate). We interrogated an Australian dataset comprising 125 tumour and 43 adjacent histologically benign diagnostic tissue samples, including 41 paired samples, using the Infinium Human Methylation450 BeadChip. Regression analyses of paired tumour and adjacent benign samples identified 2,386 significant dmCpGs (Bonferroni p < 0.01; delta-β ≥ 40%), with LASSO regression selecting 16 dmCpGs that distinguished tumour samples in the full Australian diagnostic dataset (AUC = 0.99). Results were validated in independent North American (npaired = 19; AUC = 0.87) and The Cancer Genome Atlas (TCGA; npaired = 50; AUC = 0.94) RP datasets. Two of the 16 dmCpGs were in genes that were significantly down-regulated in Australian tumour samples (Bonferroni p < 0.01; GSTM2 and PRKCB). Ten additional dmCpGs distinguished low (n = 34) and high Gleason (n = 88) score tumours in the diagnostic Australian dataset (AUC = 0.95), but these performed poorly when applied to the RP datasets (North American: AUC = 0.66; TCGA: AUC = 0.62). The DNA methylation marks identified here could augment and improve current diagnostic tests and/or form the basis of future prognostic tests.

Aberrated PSMA1 expression associated with clinicopathological features and prognosis in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is a globally prevalent cancer with significant mortality rates. OSCC a predominant subtype of head and neck squamous cell carcinoma (HNSCC), poses a substantial health burden. Despite advancements in diagnosis and therapy, OSCC prognosis remains poor. The 26S proteasome, a cellular protein degradation complex, is associated with cancer, including PSMA1, a proteasomal subunit, which is upregulated in various cancers. We analyzed PSMA1 expression using TCGA data, validated it in OSCC samples using real-time PCR, and explored its role through various databases. Tumor and adjacent normal tissues from OSCC patients were examined, and PSMA1 expression was analyzed. Survival analysis assessed the impact of PSMA1 on patient outcomes, while immune infiltration was examined using the TIMER database. GeneMANIA, STRING, and Metascape were utilized for gene interaction and pathway analysis. PSMA1 was significantly upregulated in OSCC and HNSCC. Its overexpression correlated with advanced clinicopathological features and poorer prognosis in HNSCC patients. PSMA1 expression is also related to immune cell infiltration. Gene interaction analysis revealed PSMA1 involvement in proteolysis regulation, suggesting its potential as a therapeutic target. PSMA1 upregulation in HNSCC association with adverse clinicopathological features and prognosis underscores its potential significance. Further research is warranted to elucidate its molecular mechanisms and therapeutic potential in OSCC management.

RNA-binding protein NOVA1 promotes acute T-lymphocyte leukemia progression by stabilizing USP44 mRNA

Acute T-lymphocyte leukemia (T-ALL) is a malignant tumor disease. RNA-binding protein neotumor ventral antigen-1 (NOVA1) is highly expressed in bone marrow mononuclear cells of T-ALL patients, while the role of NOVA1 in T-ALL progression remains unknown. The gain- and loss-of-function studies for NOVA1 were performed in Jurkat and CCRF-CEM cells. NOVA1 overexpression promoted cell proliferation and cell cycle progression. NOVA1 knockdown increased the apoptosis rate of T-ALL cells. Ubiquitin-specific protease 44 (USP44), a nuclear protein with deubiquitinase catalytic activity, has been reported to play an oncogene role in human T-cell leukemia. USP44 expression was positively associated with NOVA1, and RNA immunoprecipitation assay verified the binding of NOVA1 to the mRNA of USP44. USP44 knockdown partially abolished NOVA1-induced cell proliferation and inhibition of apoptosis. The in vivo xenograft experiment was performed by injection of T-ALL tumor cells into the tail vein of NOD/SCID mice. The knockdown of NOVA1 had lower tumorigenicity. NOVA1 knockdown alleviated pathological changes in lung and spleen tissues, and increased the overall survival period and the weight of T-ALL mice. Thus, NOVA1 acts as an accelerator in T-ALL, and its function might be achieved by binding to and stabilizing USP44 mRNA.

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.

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.

Ubiquitin specific peptidases and prostate cancer

Protein ubiquitination is an important post-translational modification mechanism, which regulates protein stability and activity. The ubiquitination of proteins can be reversed by deubiquitinating enzymes (DUBs). Ubiquitin-specific proteases (USPs), the largest DUB subfamily, can regulate cellular functions by removing ubiquitin(s) from the target proteins. Prostate cancer (PCa) is the second leading type of cancer and the most common cause of cancer-related deaths in men worldwide. Numerous studies have demonstrated that the development of PCa is highly correlated with USPs. The expression of USPs is either high or low in PCa cells, thereby regulating the downstream signaling pathways and causing the development or suppression of PCa. This review summarized the functional roles of USPs in the development PCa and explored their potential applications as therapeutic targets for PCa.

PSMA1 mediates tumor progression and poor prognosis of gastric carcinoma by deubiquitinating and stabilizing TAZ

The deubiquitinating enzyme family in tumor progression play important role in intracellular protein degradation. The proteasome subunit alpha type 1 (PSMA1) has been reported to act as an oncogene in several human cancers. The present study aimed to reveal the functional significance of PSMA1 in gastric cancer (GC) progression and the underlying mechanisms. The expression of PSMA1 in human GC samples and GC cell lines was examined by western blot analysis, real-time PCR, immunohistochemistry (IHC), and in vitro ubiquitination assays and established a xenograft mouse model. We found that PSMA1 was upregulated in GC and promoted proliferation, migration and invasion in GC cells. Herein, we report transcriptional co-activator with PDZ-binding motif (TAZ) was a downstream gene of PSMA1. Mechanistically, PSMA1 directly interacted with and stabilized TAZ via deubiquitination in GC. Furthermore, we found that TAZ was the essential mediator of PSMA1-modulated oncogenic activity in vitro and in vivo. Examination of clinical samples confirmed that elevated mediators of PSMA1, concomitant with increased TAZ abundance, correlate with human GC progression. These data suggested that PSMA1 promotes GC progression and proliferation by deubiquitinating TAZ. PSMA1 promotes GC progression and proliferation regarding PSMA1-mediated deubiquitinating enzyme activity and suggest potential therapeutic targets for GC management.

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.

Role of ubiquitin specific proteases in the immune microenvironment of prostate cancer: A new direction

Regulation of ubiquitination is associated with multiple processes of tumorigenesis and development, including regulation of the tumor immune microenvironment. Deubiquitinating enzymes (DUBs) can remove ubiquitin chains from substrates, thereby stabilizing target proteins and altering and remodeling biological processes. During tumorigenesis, deubiquitination-altered biological processes are closely related to tumor metabolism, stemness, and the immune microenvironment. Recently, tumor microenvironment (TME) modulation strategies have attracted considerable attention in cancer immunotherapy. Targeting immunosuppressive mechanisms in the TME has revolutionized cancer therapy. Prostate cancer (PC) is one of the most common cancers and the second most common cause of cancer-related death in men worldwide. While immune checkpoint inhibition has produced meaningful therapeutic effects in many cancer types, clinical trials of anti-CTLA4 or anti-PD1 have not shown a clear advantage in PC patients. TME affects PC progression and also enables tumor cell immune evasion by activating the PD-1/PD-L1 axis. Over the past few decades, an increasing number of studies have demonstrated that deubiquitination in PC immune microenvironment may modulate the host immune system’s response to the tumor. As the largest and most diverse group of DUBs, ubiquitin-specific proteases (USPs) play an important role in regulating T cell development and function. According to current studies, USPs exhibit a high expression signature in PC and may promote tumorigenesis. Elevated expression of USPs often indicates poor tumor prognosis, suggesting that USPs are expected to develop as the markers of tumor prognosis and even potential drug targets for anti-tumor therapy. Herein, we first summarized recent advances of USPs in PC and focused on the relationship between USPs and immunity. Additionally, we clarified the resistance mechanisms of USPs to targeted drugs in PC. Finally, we reviewed the major achievement of targeting USPs in cancers.

Inhibition of the deubiquitinating enzyme USP47 as a novel targeted therapy for hematologic malignancies expressing mutant EZH2

Activating mutations in EZH2, the catalytic component of PRC2, promote cell proliferation, tumorigenesis, and metastasis through enzymatic or non-enzymatic activity. The EZH2-Y641 gain-of-function mutation is one of the most significant in diffuse large B-cell lymphoma (DLBCL). Although EZH2 kinase inhibitors, such as EPZ-6438, provide clinical benefit, certain cancer cells are resistant to the enzymatic inhibition of EZH2 because of the inability to functionally target mutant EZH2, or because of cells' dependence on the non-histone methyltransferase activity of EZH2. Consequently, destroying mutant EZH2 protein may be more effective in targeting EZH2 mutant cancers that are dependent on the non-catalytic activity of EZH2. Here, using extensive selectivity profiling, combined with genetic and animal model studies, we identified USP47 as a novel regulator of mutant EZH2. Inhibition of USP47 would be anticipated to block the function of mutated EZH2 through induction of EZH2 degradation by promoting its ubiquitination. Moreover, targeting of USP47 leads to death of mutant EZH2-positive cells in vitro and in vivo. Taken together, we propose targeting USP47 with a small molecule inhibitor as a novel potential therapy for DLBCL and other hematologic malignancies characterized by mutant EZH2 expression.

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.

USP44 Promoter Methylation in Plasma Cell-Free DNA in Prostate Cancer

Simple Summary

Liquid biopsy provides real-time monitoring of tumor evolution and response to therapy through analysis of circulating tumor cells (CTCs) and plasma-circulating tumor DNA (ctDNA). USP44 is a member of family proteins deubiquitinases, and plays an important role in cell growth; however, its accurate role in other cellular networks is under research. In this study, we examined for the first time USP44 promoter methylation in plasma cell-free DNA (cfDNA) of patients with prostate cancer (early stage n = 32, metastatic n = 39) and 10 healthy donors (HD). USP44 promoter methylation was detected in plasma cell-free DNA by a newly developed highly specific and sensitive real-time MSP method. We report for the first time that detection of USP44 promoter methylation in plasma cell free DNA provides significant prognostic information in metastatic prostate cancer.

Abstract

Liquid biopsy provides real-time monitoring of tumor evolution and response to therapy through analysis of circulating tumor cells (CTCs) and plasma-circulating tumor DNA (ctDNA). USP44 is a critical gene which plays an important role in cell proliferation; however, its accurate role in other cellular networks is under research. USP44 promoter methylation has been so far reported in colorectal neoplasia and metastatic breast cancer. In this study, we examined for the first time USP44 promoter methylation in plasma cell-free DNA (cfDNA) of patients with prostate cancer (early stage n = 32, metastatic n = 39) and 10 healthy donors (HD). USP44 promoter methylation was detected in plasma cell-free DNA by a newly developed highly specific and sensitive real-time MSP method. Our findings indicate that USP44 promoter is methylated in plasma cell-free DNA of metastatic prostate cancer patients and that detection of USP44 promoter methylation is significantly associated with overall survival (OS) (p = 0.008). We report for the first time that detection of USP44 promoter methylation in plasma cell free DNA provides significant prognostic information in metastatic prostate cancer.

Lack of intrafollicular memory CD4 + T cells is predictive of early clinical failure in newly diagnosed follicular lymphoma

Despite a characteristic indolent course, a substantial subset of follicular lymphoma (FL) patients has an early relapse with a poor outcome. Cells in the microenvironment may be a key contributor to treatment failure. We used a discovery and validation study design to identify microenvironmental determinants of early failure and then integrated these results into the FLIPI. In total, 496 newly diagnosed FL grade 1-3 A patients who were prospectively enrolled into the MER cohort from 2002 to 2012 were evaluated. Tissue microarrays were stained for CD4, CD8, FOXP3, CD32b, CD14, CD68, CD70, SIRP-α, TIM3, PD-1, and PD-L1. Early failure was defined as failing to achieve event-free survival at 24 months (EFS24) in immunochemotherapy-treated patients and EFS12 in all others. CyTOF and CODEX analysis were performed to characterize intratumoral immunophenotypes. Lack of intrafollicular CD4 expression was the only predictor of early failure that replicated with a pooled OR 2.37 (95%CI 1.48-3.79). We next developed a bio-clinical risk model (BioFLIPI), where lack of CD4 intrafollicular expression moved patients up one FLIPI risk group, adding a new fourth high-risk group. Compared with BioFLIPI score of 1, patients with a score of 2 (OR 2.17; 95% CI 1.08-4.69), 3 (OR 3.53; 95% CI 1.78-7.54), and 4 (OR 8.92; 95% CI 4.00-21.1) had increasing risk of early failure. The favorable intrafollicular CD4 T cells were identified as activated central memory T cells, whose prognostic value was independent from genetic features. In conclusion, lack of intrafollicular CD4 expression predicts early failure in FL and combined with FLIPI improves identification of high-risk patients; however, independent validation is warranted.

Regulation of Cancer Metabolism by Deubiquitinating Enzymes: The Warburg Effect

Cancer is a disorder of cell growth and proliferation, characterized by different metabolic pathways within normal cells. The Warburg effect is a major metabolic process in cancer cells that affects the cellular responses, such as proliferation and apoptosis. Various signaling factors down/upregulate factors of the glycolysis pathway in cancer cells, and these signaling factors are ubiquitinated/deubiquitinated via the ubiquitin-proteasome system (UPS). Depending on the target protein, DUBs act as both an oncoprotein and a tumor suppressor. Since the degradation of tumor suppressors and stabilization of oncoproteins by either negative regulation by E3 ligases or positive regulation of DUBs, respectively, promote tumorigenesis, it is necessary to suppress these DUBs by applying appropriate inhibitors or small molecules. Therefore, we propose that the DUBs and their inhibitors related to the Warburg effect are potential anticancer targets.

USP16 regulates castration-resistant prostate cancer cell proliferation by deubiquitinating and stablizing c-Myc

Background

c-Myc, a well-established oncogene, plays an important role in the initiation and progression of various cancers, including prostate cancer. However, its mechanism in cancer cell remains largely unknown and whether there exist a deubiquitinase targeting c-Myc also remains elusive.

Methods

Bioinformatic analysis and shRNA screening methods were used to identify potential deubiquitinases that correlate with c-Myc gene signature. Cell proliferation and viability were measured by Cell-Counting-Kit 8 and colony formation assays. A mouse xenograft model of PC3 cells was established to confirm the function of USP16 in vivo. The interaction between USP16 and c-Myc protein was assessed by co-immunoprecipitation and protein co-localization assays. Immunohistochemistry staining was performed to detect the expression of USP16, Ki67, and c-Myc in xenograft tissues and clinical tumour tissues. Furthermore, the correlation between USP16 and c-Myc was confirmed by RNA sequencing.

Results

Functional analyses identified USP16, known as a deubiquitinase, was strongly correlated with the c-Myc gene signature. Depletion of USP16 was shown to significantly suppress the growth of PCa cells both in vitro and in vivo. Co-immunoprecipitation and ubiquitination assays confirmed that USP16 served as a novel deubiquitinase of c-Myc and overexpression of c-Myc significantly rescued the effects of USP16 disruption. Immunohistochemistry staining and RNA-seq tactics were further used to confirm the positive correlation between USP16 and c-Myc expression. Expression of USP16 in human PCa tissues was higher than that seen in normal prostate tissues and its high expression was found associated with poor prognosis.

Conclusions

USP16 serves as a novel deubiquitinase of c-Myc. Downregulation of USP16 markedly suppressed PCa cell growth both in vitro and in vivo. USP16 regulates PCa cell proliferation by deubiquitinating and stabilizing c-Myc, making it a potential therapeutic candidate for the treatment of PCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01843-8.

Pathogenic mechanisms and the potential clinical value of circFoxo3 in cancers

Circular RNAs (circRNAs) are covalently closed circular structures that can function in various physiological and pathological processes by acting as microRNA (miRNA) sponges, RNA-binding protein (RBP) sponges, mRNA transcriptional regulators, and protein translational templates. circFoxo3 is one of the most studied circRNAs and is generated from the tumor suppressor gene Foxo3. Increasing studies have demonstrated the multiple functions of circFoxo3 in the pathogenesis of different cancer types. circFoxo3 plays important roles in cancer development mainly by binding to various miRNAs. The diagnostic potential of circFoxo3 has been revealed in several cancers. Some research results have been found to contradict the results of other studies, and this may be due to insufficient sample sizes and inconsistencies in the experimental and nomenclature methods. In this review, we systematically summarize current knowledge about the biogenesis and functions of circRNAs, elucidate the roles of circFoxo3 in different cancers, and explore the clinical applications of circFoxo3.

The deubiquitinase USP44 promotes Treg function during inflammation by preventing FOXP3 degradation

The transcription factor forkhead box P3 (FOXP3) is essential for the development of regulatory T cells (Tregs) and their function in immune homeostasis. Previous studies have shown that in natural Tregs (nTregs), FOXP3 can be regulated by polyubiquitination and deubiquitination. However, the molecular players active in this pathway, especially those modulating FOXP3 by deubiquitination in the distinct induced Treg (iTreg) lineage, remain unclear. Here, we identify the ubiquitin-specific peptidase 44 (USP44) as a novel deubiquitinase for FOXP3. USP44 interacts with and stabilizes FOXP3 by removing K48-linked ubiquitin modifications. Notably, TGF-β induces USP44 expression during iTreg differentiation. USP44 co-operates with USP7 to stabilize and deubiquitinate FOXP3. Tregs genetically lacking USP44 are less effective than their wild-type counterparts, both in vitro and in multiple in vivo models of inflammatory disease and cancer. These findings suggest that USP44 plays an important role in the post-translational regulation of Treg function and is thus a potential therapeutic target for tolerance-breaking anti-cancer immunotherapy.

USP7 deubiquitinates and stabilizes EZH2 in prostate cancer cells

Regulation of target proteins by the ubiquitin-proteasome system (UPS) is common in a wide range of cellular events, including transcriptional regulation, cell cycle progression, differentiation, and tumorigenesis. Ubiquitin-specific protease 7 (USP7) has been implicated in tumor development and metastasis in various malignancies through the regulation of target protein stability. In this study, we found that the enhancer of zeste homolog 2 (EZH2), which catalyzes the methylation at lysine 27 of histone H3, is a target of USP7 and is stabilized by USP7-mediated deubiquitination. In prostate cancer cells, the transcriptional repression function of EZH2 was inhibited by USP7-knockdown. Furthermore, ectopic introduction of EZH2 restored the cell migration, invasion, and sphere-forming potential of prostate cancer cells, which had been decreased by USP7-knockdown. Moreover, combined treatment with the USP7-specific inhibitor P5091 and EZH2 inhibitors, such as GSK126, EPZ6438, and DZNep, induced synergistic inhibitory effects on cell migration, invasion, and sphere-forming potential in prostate cancer cells. Collectively, our findings revealed that the promotion of the malignancy-associated characteristics of prostate cancer cells by USP7 was in part due to EZH2 stabilization. Thus, we suggest that simultaneous treatment with a USP7 inhibitor and an EZH2 inhibitor could be a rational strategy for treating EZH2-dependent cancers.

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.

Ubiquitin-specific protease-44 inhibits the proliferation and migration of cells via inhibition of JNK pathway in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is the most common form of adult kidney cancer. Ubiquitin-specific protease (USP)44 has been reported to be involved in various cancers. We investigated the function, role and molecular mechanism of USP44 in ccRCC.

Methods

Data obtained from the Cancer Genome Atlas Data Portal and Gene Expression Omnibus database were analyzed to uncover the clinical relevance of USP44 expression and tumor development. USP44 function in the proliferation and migration of tumor cells was assessed by cellular and molecular analyses using ccRCC lines (786-O cells and Caki-1 cells).

Results

USP44 showed low expression in ccRCC cancer tissues compared with that in normal tissue. USP44 expression was negatively correlated with tumor stage, tumor grade, and patient survival. USP44 overexpression inhibited the proliferation and migration of 786-O cells and Caki-1 cells significantly. USP44 overexpression also prohibited cell proliferation by upregulating expression of P21, downregulating cyclin-D1 expression, and inhibiting cell migration by downregulating expression of matrix metalloproteinase (MMP)2 and MMP9. USP44 knockdown enhanced the proliferation and migration of 786-O cells and Caki-1 cells. USP44 function in inhibiting the proliferation and migration of 786-O cells and Caki-1 cells was associated with phosphorylation of Jun N-terminal kinase (JNK).

Conclusion

USP44 may be a marker in predicting ccRCC progression. Inhibition by USP44 of the proliferation and migration of 786-O cells and Caki-1 cells is dependent upon the JNK pathway.

The role of ubiquitin-specific peptidases in cancer progression

Protein ubiquitination is an important mechanism for regulating the activity and levels of proteins under physiological conditions. Loss of regulation by protein ubiquitination leads to various diseases, such as cancer. Two types of enzymes, namely, E1/E2/E3 ligases and deubiquitinases, are responsible for controlling protein ubiquitination. The ubiquitin-specific peptidases (USPs) are the main members of the deubiquitinase family. Many studies have addressed the roles of USPs in various diseases. An increasing number of studies have indicated that USPs are critical for cancer progression, and some USPs have been used as targets to develop inhibitors for cancer prevention. Herein we collect and organize most of the recent studies on the roles of USPs in cancer progression and discuss the development of USP inhibitors for cancer therapy in the future.