Emerging Roles of Ubiquitin-Specific Protease 25 in Diseases

USP25 attenuates anti-GBM nephritis in mice by negative feedback regulation of Th17 cell differentiation

PURPOSE

This study aimed to elucidate the role of USP25 in a mouse model of anti-glomerular basement membrane glomerulonephritis (anti-GBM GN).

METHODS

USP25-deficient anti-GBM GN mice were generated, and their nephritis progression was monitored. Naïve CD4+ T cells were isolated from spleen lymphocytes and stimulated to differentiate into Th1, Th2, and Th17 cells. This approach was used to investigate the impact of USP25 on CD4+ T lymphocyte differentiation in vitro. Furthermore, changes in USP25 expression were monitored during Th17 differentiation, both in vivo and in vitro.

RESULTS

USP25-/- mice with anti-GBM GN exhibited accelerated renal function deterioration, increased infiltration of Th1 and Th17 cells, and elevated RORγt transcription. In vitro experiments demonstrated that USP25-/- CD4+ T lymphocytes had a higher proportion for Th17 cell differentiation and exhibited higher RORγt levels upon stimulation. Wild-type mice with anti-GBM GN showed higher USP25 levels compared to healthy mice, and a positive correlation was observed between USP25 levels and Th17 cell counts. Similar trends were observed in vitro.

CONCLUSION

USP25 plays a crucial role in mitigating renal histopathological and functional damage during anti-GBM GN in mice. This protective effect is primarily attributed to USP25's ability to inhibit the differentiation of naïve CD4+ T cells into Th17 cells. The underlying mechanism may involve the downregulation of RORγt. Additionally, during increased inflammatory responses or Th17 cell differentiation, USP25 expression is activated, forming a negative feedback regulatory loop that attenuates immune activation.

MicroRNA biomarkers as next-generation diagnostic tools for neurodegenerative diseases: a comprehensive review

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells-all indicative of disease progression-before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer's disease, Parkinson's disease, Multiple sclerosis, Huntington's disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or de-ubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies.

The Emerging Role of Deubiquitinases in Radiosensitivity

Radiation therapy is a primary treatment for cancer, but radioresistance remains a significant challenge in improving efficacy and reducing toxicity. Accumulating evidence suggests that deubiquitinases (DUBs) play a crucial role in regulating cell sensitivity to ionizing radiation. Traditional small-molecule DUB inhibitors have demonstrated radiosensitization effects, and novel deubiquitinase-targeting chimeras (DUBTACs) provide a promising strategy for radiosensitizer development by harnessing the ubiquitin-proteasome system. This review highlights the mechanisms by which DUBs regulate radiosensitivity, including DNA damage repair, the cell cycle, cell death, and hypoxia. Progress on DUB inhibitors and DUBTACs is summarized, and their potential radiosensitization effects are discussed. Developing drugs targeting DUBs appears to be a promising alternative approach to overcoming radioresistance, warranting further research into their mechanisms.

The role of deubiquitinases in cardiac disease

Deubiquitinases are a group of proteins that identify and digest monoubiquitin chains or polyubiquitin chains attached to substrate proteins, preventing the substrate protein from being degraded by the ubiquitin-proteasome system. Deubiquitinases regulate cellular autophagy, metabolism and oxidative stress by acting on different substrate proteins. Recent studies have revealed that deubiquitinases act as a critical regulator in various cardiac diseases, and control the onset and progression of cardiac disease through a board range of mechanism. This review summarizes the function of different deubiquitinases in cardiac disease, including cardiac hypertrophy, myocardial infarction and diabetes mellitus-related cardiac disease. Besides, this review briefly recapitulates the role of deubiquitinases modulators in cardiac disease, providing the potential therapeutic targets in the future.

Expression of USP25 associates with fibrosis, inflammation and metabolism changes in IgG4-related disease

IgG4-related disease (IgG4-RD) has complex clinical manifestations ranging from fibrosis and inflammation to deregulated metabolism. The molecular mechanisms underpinning these phenotypes are unclear. In this study, by using IgG4-RD patient peripheral blood mononuclear cells (PBMCs), IgG4-RD cell lines and Usp25 knockout mice, we show that ubiquitin-specific protease 25 (USP25) engages in multiple pathways to regulate fibrotic and inflammatory pathways that are characteristic to IgG4-RD. Reduced USP25 expression in IgG4-RD leads to increased SMAD3 activation, which contributes to fibrosis and induces inflammation through the IL-1β inflammatory axis. Mechanistically, USP25 prevents ubiquitination of RAC1, thus, downregulation of USP25 leads to ubiquitination and degradation of RAC1. Decreased RAC1 levels result in reduced aldolase A release from the actin cytoskeleton, which then lowers glycolysis. The expression of LYN, a component of the B cell receptor signalosome is also reduced in USP25-deficient B cells, which might result in B cell activation deficiency. Altogether, our results indicate a potential anti-inflammatory and anti-fibrotic role for USP25 and make USP25 a promising diagnostic marker and potential therapeutic target in IgG4-RD.

A New Modulator of Neuroinflammation in Diabetic Retinopathy: USP25

Diabetic retinopathy (DR) is a diabetes-associated complication that poses a threat to vision, distinguished by persistent and mild inflammation of the retinal microvasculature. The activation of microglia plays a crucial role in driving this pathological progression. Previous investigations have demonstrated that ubiquitin-specific peptidase 25 (USP25), a deubiquitinating enzyme, is involved in the regulation of immune cell activity. Nevertheless, the precise mechanisms through which USP25 contributes to the development of DR remain incompletely elucidated. Firstly, we have demonstrated the potential mechanism by which ROCKs can facilitate microglial activation and augment the synthesis of inflammatory mediators through the modulation of NF-κB signaling pathways in a high-glucose milieu. Furthermore, our study has provided novel insights by demonstrating that the regulatory role of USP25 in the secretion of proinflammatory factors is mediated through the involvement of ROCK in modulating the expression of NF-κB and facilitating the nuclear translocation of the phosphatase NF-κB. This regulatory mechanism plays a crucial role in modulating the activation of microglial cells within a high-glycemic environment. Hence, USP25 emerges as a pivotal determinant for the inflammatory activation of microglial cells, and its inhibition exhibits a dual effect of promoting retinal neuron survival while suppressing the inflammatory response in the retina. In conclusion, the promotion of diabetic retinopathy (DR) progression by USP25 is attributed to its facilitation of microglial activation induced by high glucose levels, a process mediated by the ROCK pathway. These findings highlight the importance of considering USP25 as a potential therapeutic target for the management of diabetic neuroinflammation.

Modified activities of macrophages' deubiquitinating enzymes after Francisella infection

Francisella tularensis influences several host molecular/signaling pathways during infection. Ubiquitination and deubiquitination are among the most important regulatory mechanisms and respectively occur through attachment or removal of the ubiquitin molecule. The process is necessary not only to mark molecules for degradation, but also, for example, to the activation of signaling pathways leading to pro-inflammatory host response. Many intracellular pathogens, including Francisella tularensis, have evolved mechanisms of modifying such host immune responses to escape degradation. Here, we describe that F. tularensis interferes with the host's ubiquitination system. We show increased total activity of deubiquitinating enzymes (DUBs) in human macrophages after infection, while confirm reduced enzymatic activities of two specific DUBs (USP10 and UCH-L5), and demonstrate increased activity of USP25. We further reveal the enrichment of these three enzymes in exosomes derived from F. tularensis-infected cells. The obtained results show the regulatory effect on ubiquitination mechanism in macrophages during F. tularensis infection.

USP25 promotes hepatocellular carcinoma progression by interacting with TRIM21 via the Wnt/β-catenin signaling pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The ubiquitin-specific peptidase 25 (USP25) protein has been reported to participate in the development of several cancers. However, few studies have reported its association with HCC. In this study, we aimed to investigate the function and mechanism of USP25 in the progression of HCC.

METHODS

We analyzed USP25 protein expression in HCC based on The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) database cohorts. Then, we constructed USP25-overexpressing and USP25-knockdown HepG2, MHCC97H, and L-O2 cells. We detected the biological function of USP25 by performing a series of assays, such as Cell Counting Kit-8 (CCK-8), colony formation, transwell, and wound healing assays. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) analyses were performed to detect the interaction between USP25 and the Wnt/β-catenin signaling pathway. The relationship between USP25 and tripartite motif-containing 21 (TRIM21) was assessed through mass spectrometry and co-immunoprecipitation (Co-IP) analysis. Finally, we constructed a mouse liver cancer model with the USP25 gene deletion to verify in vivo role of USP25.

RESULTS

USP25 was highly expressed in HCC tissue and HCC cell lines. Importantly, high expression of USP25 in tissues was closely related to a poor prognosis. USP25 knockdown markedly reduced the proliferation, migration, and invasion of HepG2 and MHCC97H cells, whereas USP25 overexpression led to the opposite effects. In addition, we demonstrated that USP25 interacts with TRIM21 to regulate the expression of proteins related to epithelial-mesenchymal transition (EMT; E-cadherin, N-cadherin, and Snail) and the Wnt/β-catenin pathway (β-catenin, Adenomatous polyposis coli, Axin2 and Glycogen synthase kinase 3 beta) and those of their downstream proteins (C-myc and Cyclin D1). Finally, we verified that knocking out USP25 inhibited tumor growth and distant metastasis in vivo .

CONCLUSIONS

In summary, our data showed that USP25 was overexpressed in HCC. USP25 promoted the proliferation, migration, invasion, and EMT of HCC cells by interacting with TRIM21 to activate the β-catenin signaling pathway.

Valosin containing protein (VCP): initiator, modifier, and potential drug target for neurodegenerative diseases

The AAA+ ATPase valosin containing protein (VCP) is essential for cell and organ homeostasis, especially in cells of the nervous system. As part of a large network, VCP collaborates with many cofactors to ensure proteostasis under normal, stress, and disease conditions. A large number of mutations have revealed the importance of VCP for human health. In particular, VCP facilitates the dismantling of protein aggregates and the removal of dysfunctional organelles. These are critical events to prevent malfunction of the brain and other parts of the nervous system. In line with this idea, VCP mutants are linked to the onset and progression of neurodegeneration and other diseases. The intricate molecular mechanisms that connect VCP mutations to distinct brain pathologies continue to be uncovered. Emerging evidence supports the model that VCP controls cellular functions on multiple levels and in a cell type specific fashion. Accordingly, VCP mutants derail cellular homeostasis through several mechanisms that can instigate disease. Our review focuses on the association between VCP malfunction and neurodegeneration. We discuss the latest insights in the field, emphasize open questions, and speculate on the potential of VCP as a drug target for some of the most devastating forms of neurodegeneration.

USP25 inhibits renal fibrosis by regulating TGFβ-SMAD signaling pathway in Ang II-induced hypertensive mice

Renal fibrosis is a crucial pathological feature of hypertensive renal disease (HRD). In-depth analysis of the pathogenesis of fibrosis is of great significance for the development of new drugs for the treatment of HRD. USP25 is a deubiquitinase that can regulate the progression of many diseases, but its function in the kidney remains unclear. We found that USP25 was significantly increased in human and mice HRD kidney tissues. In the HRD model induced by Ang II, USP25^-/- mice showed significant aggravation of renal dysfunction and fibrosis compared with the control mice. Consistently, AAV9-mediated overexpression of USP25 significantly improved renal dysfunction and fibrosis. Mechanistically, USP25 inhibited the TGF-β pathway by reducing SMAD4 K63-linked polyubiquitination, thereby suppressing SMAD2 nuclear translocation. In conclusion, this study demonstrates for the first time that the deubiquitinase USP25 plays an important regulatory role in HRD.

Regulation of USP25 by SP1 Associates with Amyloidogenesis

BACKGROUND

Trisomy 21, an extra copy of human chromosome 21 (HSA21), causes most Down's syndrome (DS) cases. Individuals with DS inevitably develop Alzheimer's disease (AD) neuropathological phenotypes after middle age including amyloid plaques and tau neurofibrillary tangles. Ubiquitin Specific Peptidase 25 (USP25), encoding by USP25 gene located on HSA21, is a deubiquitinating enzyme, which plays an important role in both DS and AD pathogenesis. However, the regulation of USP25 remains unclear.

OBJECTIVE

We aimed to determine the regulation of USP25 by specificity protein 1 (SP1) in neuronal cells and its potential role in amyloidogenesis.

METHODS

The transcription start site and promoter activity was identified by SMART-RACE and Dual-luciferase assay. Functional SP1-responsive elements were examined by EMSA. USP25 expression was examined by RT-PCR and immunoblotting. Student's t-test or one-way ANOVA were applied or statistical analysis.

RESULTS

The transcription start site of human USP25 gene was identified. Three functional SP1 responsive elements in human USP25 gene were revealed. SP1 promotes USP25 transcription and subsequent USP25 protein expression, while SP1 inhibition significantly reduces USP25 expression in both non-neuronal and neuronal cells. Moreover, SP1 inhibition dramatically reduces amyloidogenesis.

CONCLUSION

We demonstrates that transcription factor SP1 regulates USP25 gene expression, which associates with amyloidogenesis. It suggests that SP1 signaling may play an important role in USP25 regulation and contribute to USP25-mediated DS and AD pathogenesis.

Estimating the causal effects of genetically predicted plasma proteome on heart failure

Background

Heart Failure (HF) is the end-stage cardiovascular syndrome with poor prognosis. Proteomics holds great promise in the discovery of novel biomarkers and therapeutic targets for HF. The aim of this study is to investigate the causal effects of genetically predicted plasma proteome on HF using the Mendelian randomization (MR) approach.

Methods

Summary-level data for the plasma proteome (3,301 healthy individuals) and HF (47,309 cases; 930,014 controls) were extracted from genome-wide association studies (GWASs) of European descent. MR associations were obtained using the inverse variance-weighted (IVW) method, sensitivity analyses, and multivariable MR analyses.

Results

Using single-nucleotide polymorphisms as instrumental variables, 1-SD increase in MET level was associated with an approximately 10% decreased risk of HF (odds ratio [OR]: 0.92; 95% confidence interval [CI]: 0.89 to 0.95; p = 1.42 × 10^-6), whereas increases in the levels of CD209 (OR: 1.04; 95% CI: 1.02-1.06; p = 6.67 × 10^-6) and USP25 (OR: 1.06; 95% CI: 1.03-1.08; p = 7.83 × 10^-6) were associated with an increased risk of HF. The causal associations were robust in sensitivity analyses, and no evidence of pleiotropy was observed.

Conclusion

The study findings suggest that the hepatocyte growth factor/c-MET signaling pathway, dendritic cells-mediated immune processes, and ubiquitin-proteasome system pathway are involved in the pathogenesis of HF. Moreover, the identified proteins have potential to uncover novel therapies for cardiovascular diseases.

CG4968 positively regulates the immune deficiency pathway by targeting Imd protein in Drosophila

Drosophila melanogaster relies solely on innate immunity to defend against various microbial pathogens. Although it is well-known that the adaptor protein Imd undergoes K63-linked ubiquitination to activate the downstream signaling cascades, its involvement with K48-linked ubiquitination and what is responsible for controlling this modification remain largely unknown. In this study, we explored the immunological function of CG4968, which encodes a typical ovarian tumour-associated protease (OTU)-type deubiquitinase (Dub) in flies. Our in vitro and vivo evidence demonstrated that CG4968 plays a positive role in governing the immune deficiency (IMD), but not the Toll innate immune response in an OTU domain-dependent manner. Mechanistically, we found that CG4968 is associated with Imd to restrict its K48-linked ubiquitination, thereby contributing to its turnover. Collectively, our study uncovered a novel regulatory mechanism involving the K48-linked ubiquitination of Imd in Drosophila innate immunity.

USP25 UPREGULATION BOOSTS GSDMD -MEDIATED PYROPTOSIS OF ACINAR CELLS IN ACUTE PANCREATITIS

ABSTRACT

Acute pancreatitis (AP) is an inflammation-associated disorder in the digestive system. Ubiquitin-specific peptidase 25 ( USP25 ) can modulate inflammation in diseases. This study expounded on the role of USP25 in pyroptosis of acinar cells in AP. Acinar cells were treated with lipopolysaccharide (LPS) and caerulein (CRE) to induce AP. Afterward, the expression patterns of USP25 , microRNA (miR)-10a-5p, and Krüppel-like factor 4 ( KLF4 ) in acinar cells were examined. Then, acinar cell viability and levels of NLR family pyrin-domain containing 3 (NLRP3), cleaved caspase-1, cleaved N -terminal gasdermin D ( GSDMD - N ), interleukin (IL)-1β, and IL-18 were determined. We observed that USP25 was highly expressed in AP models, and silencing USP25 increased cell viability and inhibited pyroptosis of AP acinar cells. The bindings of USP25 to KLF4 and miR-10a-5p to KLF4 and the GSDMD 3'UTR sequence were validated. We found that USP25 binding to KLF4 inhibited ubiquitination degradation of KLF4 , KLF4 transcriptionally decreased miR-10a-5p expression, and miR-10a-5p targeted GSDMD expression. Finally, rescue experiments proved that KLF4 overexpression or miR-10a-5p suppression enhanced pyroptosis of AP acinar cells. Overall, USP25 stabilized KLF4 expression through deubiquitination, limited miR-10a-5p expression, and increased GSDMD expression, finally promoting pyroptosis of acinar cells in AP.

USP25 Deficiency Exacerbates Acute Pancreatitis via Up-Regulating TBK1-NF-κB Signaling in Macrophages

BACKGROUND & AIMS

Severe acute pancreatitis can easily lead to systemic inflammatory response syndrome and death. Macrophages are known to be involved in the pathophysiology of acute pancreatitis (AP), and macrophage activation correlates with disease severity. In this study, we examined the role of ubiquitin-specific protease 25, a deubiquitinating enzyme and known regulator of macrophages, in the pathogenesis of AP.

METHODS

We used L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP in Usp25^-/- mice and wild-type mice. We also generated bone marrow Usp25^-/- chimeric mice and initiated L-arginine-mediated AP. Primary acinar cells and bone marrow-derived macrophages were isolated from wild-type and Usp25^-/- mice to dissect molecular mechanisms.

RESULTS

Our results show that Usp25 deficiency exacerbates pancreatic and lung injury, neutrophil and macrophage infiltration, and systemic inflammatory responses in L-arginine, cerulein, and choline-deficient ethionine-supplemented diet-induced models of AP. Bone marrow Usp25^-/- chimeric mice challenged with L-arginine show that Usp25 deficiency in macrophages exaggerates AP by up-regulating the TANK-binding kinase 1 (TBK1)-nuclear factor-κB (NF-κB) signaling pathway. Similarly, in vitro data confirm that Usp25 deficiency enhances the TBK1-NF-κB pathway, leading to increased expression of inflammatory cytokines in bone marrow-derived macrophages.

CONCLUSIONS

Usp25 deficiency in macrophages enhances TBK1-NF-κB signaling, and the induction of inflammatory chemokines and type I interferon-related genes exacerbates pancreatic and lung injury in AP.

USP49 mediates tumor progression and poor prognosis through a YAP1-dependent feedback loop in gastric cancer

The importance of the Hippo-Yes-associated protein 1 (YAP1) pathway in gastric carcinogenesis and metastasis has attracted considerable research attention; however, the regulatory network of YAP1 in gastric cancer (GC) is not completely understood. In this study, ubiquitin-specific peptidase 49 (USP49) was identified as a novel deubiquitinase of YAP1, knockdown of USP49 inhibited the proliferation, metastasis, chemoresistance, and peritoneal metastasis of GC cells. Overexpression of USP49 showed opposing biological effects. Moreover, USP49 was transcriptionally activated by the YAP1/TEAD4 complex, which formed a positive feedback loop with YAP1 to promote the malignant progression of GC cells. Finally, we collected tissue samples and clinical follow-up information from 482 GC patients. The results showed that USP49 expression was high in GC cells and positively correlated with the expression of YAP1 and its target genes, connective tissue growth factor (CTGF) and cysteine-rich angiogenic inducer 61 (CYR61). Survival and Cox regression analysis showed that high USP49 expression was associated with poor prognosis and was an independent prognostic factor. Moreover, patients with high USP49 and YAP1 expression had extremely short overall survival. The findings of this study reveal that the aberrant activation of the USP49/YAP1 positive feedback loop plays a critical role in the malignant progression of GC, thus providing potential novel prognostic factors and therapeutic targets for GC.

Ubiquitin-like processing of TUG proteins as a mechanism to regulate glucose uptake and energy metabolism in fat and muscle

In response to insulin stimulation, fat and muscle cells mobilize GLUT4 glucose transporters to the cell surface to enhance glucose uptake. Ubiquitin-like processing of TUG (Aspscr1, UBXD9) proteins is a central mechanism to regulate this process. Here, recent advances in this area are reviewed. The data support a model in which intact TUG traps insulin-responsive "GLUT4 storage vesicles" at the Golgi matrix by binding vesicle cargoes with its N-terminus and matrix proteins with its C-terminus. Insulin stimulation liberates these vesicles by triggering endoproteolytic cleavage of TUG, mediated by the Usp25m protease. Cleavage occurs in fat and muscle cells, but not in fibroblasts or other cell types. Proteolytic processing of intact TUG generates TUGUL, a ubiquitin-like protein modifier, as the N-terminal cleavage product. In adipocytes, TUGUL modifies a single protein, the KIF5B kinesin motor, which carries GLUT4 and other vesicle cargoes to the cell surface. In muscle, this or another motor may be modified. After cleavage of intact TUG, the TUG C-terminal product is extracted from the Golgi matrix by the p97 (VCP) ATPase. In both muscle and fat, this cleavage product enters the nucleus, binds PPARγ and PGC-1α, and regulates gene expression to promote fatty acid oxidation and thermogenesis. The stability of the TUG C-terminal product is regulated by an Ate1 arginyltransferase-dependent N-degron pathway, which may create a feedback mechanism to control oxidative metabolism. Although it is now clear that TUG processing coordinates glucose uptake with other aspects of physiology and metabolism, many questions remain about how this pathway is regulated and how it is altered in metabolic disease in humans.

ALDH1A3 Segregated Expression and Nucleus-Associated Proteasomal Degradation Are Common Traits of Glioblastoma Stem Cells

Aldehyde dehydrogenase 1 isoforms A1 and A3 have been implicated as functional biomarkers associated with distinct molecular subtypes of glioblastoma and glioblastoma stem cells. However, the exact roles of these isoforms in different types of glioma cells remain unclear. The purpose of this study was to dissect the association of A1 or A3 isoforms with stem and non-stem glioblastoma cells. This study has undertaken a systematic characterization of A1 and A3 proteins in glioblastoma tissues and a panel of glioblastoma stem cells using immunocytochemical and immunofluorescence staining, Western blot and the subcellular fractionation methodology. Our main findings are (i) human GSCs express uniformly ALDH1A3 but not the ALDH1A1 isoform whereas non-stem glioma cells comparably express both isoforms; (ii) there is an abundance of ALDH1A3 peptides that prevail over the full-length form in glioblastoma stem cells but not in non-stem glioma cells; (iii) full-length ALDH1A3 and ALDH1A3 peptides are spatially segregated within the cell; and (vi) the abundance of full-length ALDH1A3 and ALDH1A3 peptides is sensitive to MG132-mediated proteasomal inhibition. Our study further supports the association of ALDH1A3 with glioblastoma stem cells and provide evidence for the regulation of ALDH1A3 activities at the level of protein turnover.

USP28: Oncogene or Tumor Suppressor? A Unifying Paradigm for Squamous Cell Carcinoma

Squamous cell carcinomas are therapeutically challenging tumor entities. Low response rates to radiotherapy and chemotherapy are commonly observed in squamous patients and, accordingly, the mortality rate is relatively high compared to other tumor entities. Recently, targeting USP28 has been emerged as a potential alternative to improve the therapeutic response and clinical outcomes of squamous patients. USP28 is a catalytically active deubiquitinase that governs a plethora of biological processes, including cellular proliferation, DNA damage repair, apoptosis and oncogenesis. In squamous cell carcinoma, USP28 is strongly expressed and stabilizes the essential squamous transcription factor ΔNp63, together with important oncogenic factors, such as NOTCH1, c-MYC and c-JUN. It is presumed that USP28 is an oncoprotein; however, recent data suggest that the deubiquitinase also has an antineoplastic effect regulating important tumor suppressor proteins, such as p53 and CHK2. In this review, we discuss: (1) The emerging role of USP28 in cancer. (2) The complexity and mutational landscape of squamous tumors. (3) The genetic alterations and cellular pathways that determine the function of USP28 in squamous cancer. (4) The development and current state of novel USP28 inhibitors.