Prostate-specific oncogene OTUD6A promotes prostatic tumorigenesis via deubiquitinating and stabilizing c-Myc

DLGAP5 enhances bladder cancer chemoresistance by regulating glycolysis through MYC stabilization

Rationale: Bladder cancer (BLCA), one of the most lethal urological tumors, exhibits high rates of recurrence and chemoresistance, particularly to gemcitabine (GEM). Understanding the mechanisms of GEM resistance is crucial for improving therapeutic outcomes. Our study investigates the role of DLGAP5 in promoting GEM resistance through modulation of glycolysis and MYC protein stability in BLCA cells. Methods: We utilized various BLCA cell lines and clinical tissue samples to analyze the impact of DLGAP5 on GEM resistance. Through biochemical assays, protein interaction studies, and gene expression analyses, we examined how DLGAP5 interacts with USP11 and MYC, assessed the effects on MYC deubiquitination and stability. The influence of these interactions on glycolytic activity and GEM resistance was also evaluated via mouse subcutaneous xenograft model and spontaneous BLCA model. Results: Our findings indicate that DLGAP5 enhances GEM resistance by stabilizing MYC protein via deubiquitination, a process mediated by USP11. DLGAP5 was found to facilitate the interaction between USP11 and MYC, promoting MYC-driven transcription of DLGAP5 itself, thereby creating a positive feedback loop. This loop leads to sustained MYC accumulation and increased glycolytic activity, contributing to GEM resistance in BLCA cells. Conclusion: The study highlights the critical role of DLGAP5 in regulating MYC protein stability and suggests that disrupting the DLGAP5-USP11-MYC axis may provide a novel therapeutic approach to overcome GEM resistance in BLCA. DLGAP5 represents a potential target for therapeutic intervention aimed at mitigating chemoresistance in bladder cancer BLCA.

Unveiling the molecular profile of a prostate carcinoma: implications for personalized medicine

BACKGROUND

Prostate cancer is the most common diagnosed tumor and the fifth cancer related death among men in Europe. Although several genetic alterations such as ERG-TMPRSS2 fusion, MYC amplification, PTEN deletion and mutations in p53 and BRCA2 genes play a key role in the pathogenesis of prostate cancer, specific gene alteration signature that could distinguish indolent from aggressive prostate cancer or may aid in patient stratification for prognosis and/or clinical management of patients with prostate cancer is still missing. Therefore, here, by a multi-omics approach we describe a prostate cancer carrying the fusion of TMPRSS2 with ERG gene and deletion of 16q chromosome arm.

RESULTS

We have observed deletion of KDM6A gene, which may represent an additional genomic alteration to be considered for patient stratification. The cancer hallmarks gene signatures highlight intriguing molecular aspects that characterize the biology of this tumor by both a high hypoxia and immune infiltration scores. Moreover, our analysis showed a slight increase in the Tumoral Mutational Burden, as well as an over-expression of the immune checkpoints. The omics profiling integrating hypoxia, ROS and the anti-cancer immune response, optimizes therapeutic strategies and advances personalized care for prostate cancer patients.

CONCLUSION

The here data reported can lay the foundation for predicting a poor prognosis for the studied prostate cancer, as well as the possibility of targeted therapies based on the modulation of hypoxia, ROS, and the anti-cancer immune response.

Deubiquitinases as novel therapeutic targets for diseases

Deubiquitinating enzymes (DUBs) regulate substrate ubiquitination by removing ubiquitin or cleaving within ubiquitin chains, thereby maintaining cellular homeostasis. Approximately 100 DUBs in humans counteract E3 ubiquitin ligases, finely balancing ubiquitination and deubiquitination processes to maintain cellular proteostasis and respond to various stimuli and stresses. Given their role in modulating ubiquitination levels of various substrates, DUBs are increasingly linked to human health and disease. Here, we review the DUB family, highlighting their distinctive structural characteristics and chain-type specificities. We show that DUB family members regulate key signaling pathways, such as NF-κB, PI3K/Akt/mTOR, and MAPK, and play crucial roles in tumorigenesis and other diseases (neurodegenerative disorders, cardiovascular diseases, inflammatory disorders, and developmental diseases), making them promising therapeutic targets Our review also discusses the challenges in developing DUB inhibitors and underscores the critical role of the DUBs in cellular signaling and cancer. This comprehensive analysis enhances our understanding of the complex biological functions of the DUBs and underscores their therapeutic potential.

PROTAC as a novel anti-cancer strategy by targeting aging-related signaling

Aging and cancer share common cellular hallmarks, including cellular senescence, genomic instability, and abnormal cell death and proliferation, highlighting potential areas for therapeutic interventions. Recent advancements in targeted protein degradation technologies, notably Proteolysis-Targeting Chimeras (PROTACs), offer a promising approach to address these shared pathways. PROTACs leverage the ubiquitin-proteasome system to specifically degrade pathogenic proteins involved in cancer and aging, thus offering potential solutions to key oncogenic drivers and aging-related cellular dysfunction. This abstract summarizes the recent progress of PROTACs in targeting critical proteins implicated in both cancer progression and aging, and explores future perspectives in integrating these technologies for more effective cancer treatments.

Therapeutic importance and diagnostic function of circRNAs in urological cancers: from metastasis to drug resistance

Circular RNAs (circRNAs) are a member of non-coding RNAs with no ability in encoding proteins and their aberrant dysregulation is observed in cancers. Their closed-loop structure has increased their stability, and they are reliable biomarkers for cancer diagnosis. Urological cancers have been responsible for high mortality and morbidity worldwide, and developing new strategies in their treatment, especially based on gene therapy, is of importance since these malignant diseases do not respond to conventional therapies. In the current review, three important aims are followed. At the first step, the role of circRNAs in increasing or decreasing the progression of urological cancers is discussed, and the double-edged sword function of them is also highlighted. At the second step, the interaction of circRNAs with molecular targets responsible for urological cancer progression is discussed, and their impact on molecular processes such as apoptosis, autophagy, EMT, and MMPs is highlighted. Finally, the use of circRNAs as biomarkers in the diagnosis and prognosis of urological cancer patients is discussed to translate current findings in the clinic for better treatment of patients. Furthermore, since circRNAs can be transferred to tumor via exosomes and the interactions in tumor microenvironment provided by exosomes such as between macrophages and cancer cells is of importance in cancer progression, a separate section has been devoted to the role of exosomal circRNAs in urological tumors.

Implications of c-Myc in the pathogenesis and treatment efficacy of urological cancers

Urological cancers, including prostate, bladder, and renal cancers, are significant causes of death and negatively impact the quality of life for patients. The development and progression of these cancers are linked to the dysregulation of molecular pathways. c-Myc, recognized as an oncogene, exhibits abnormal levels in various types of tumors, and current evidence supports the therapeutic targeting of c-Myc in cancer treatment. This review aims to elucidate the role of c-Myc in driving the progression of urological cancers. c-Myc functions to enhance tumorigenesis and has been documented to increase growth and metastasis in prostate, bladder, and renal cancers. Furthermore, the dysregulation of c-Myc can result in a diminished response to therapy in these cancers. Non-coding RNAs, β-catenin, and XIAP are among the regulators of c-Myc in urological cancers. Targeting and suppressing c-Myc therapeutically for the treatment of these cancers has been explored. Additionally, the expression level of c-Myc may serve as a prognostic factor in clinical settings.

OTUD6A orchestrates complex modulation of TEAD4-mediated transcriptional programs

TEAD transcription factors play a central role in the Hippo signaling pathway. In this study, we focused on transcriptional enhancer factor TEF-3 (TEAD4), exploring its regulation by the deubiquitinase OTU domain-containing protein 6A (OTUD6A). We identified OTUD6A as a TEAD4-interacting deubiquitinase, positively influencing TEAD-driven transcription without altering TEAD4 stability. Structural analyses revealed specific interaction domains: the N-terminal domain of OTUD6A and the YAP-binding domain of TEAD4. Functional assays demonstrated the positive impact of OTUD6A on the transcription of YAP-TEAD target genes. Despite no impact on TEAD4 nuclear localization, OTUD6A selectively modulated nuclear interactions, enhancing YAP-TEAD4 complex formation while suppressing VGLL4 (transcription cofactor vestigial-like protein 4)-TEAD4 interaction. Critically, OTUD6A facilitated YAP-TEAD4 complex binding to target gene promoters. Our study unveils the regulatory landscape of OTUD6A on TEAD4, providing insights into diseases regulated by YAP-TEAD complexes.

Deubiquitination of CDC6 by OTUD6A promotes tumour progression and chemoresistance

BACKGROUND

CDC6 is an oncogenic protein whose expression level fluctuates during the cell cycle. Although several E3 ubiquitin ligases responsible for the ubiquitin-mediated proteolysis of CDC6 have been identified, the deubiquitination pathway for CDC6 has not been investigated.

METHODS

The proteome-wide deubiquitinase (DUB) screening was used to identify the potential regulator of CDC6. Immunofluorescence, protein half-life and deubiquitination assays were performed to determine the protein stability of CDC6. Gain- and loss-of-function experiments were implemented to analyse the impacts of OUTD6A-CDC6 axis on tumour growth and chemosensitivity in vitro. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced conditional Otud6a knockout (CKO) mouse model and tumour xenograft model were performed to analyse the role of OTUD6A-CDC6 axis in vivo. Tissue specimens were used to determine the association between OTUD6A and CDC6.

RESULTS

OTUD6A interacts with, depolyubiquitinates and stabilizes CDC6 by removing K6-, K33-, and K48-linked polyubiquitination. Moreover, OTUD6A promotes cell proliferation and decreases sensitivity to chemotherapy by upregulating CDC6. CKO mice are less prone to BCa tumorigenesis induced by BBN, and knockdown of OTUD6A inhibits tumour progression in vivo. Furthermore, OTUD6A protein level has a positive correlation with CDC6 protein level, and high protein levels of OTUD6A and CDC6 are associated with poor prognosis in patients with bladder cancer.

CONCLUSIONS

We reveal an important yet missing piece of novel DUB governing CDC6 stability. In addition, our findings propose a model for the OTUD6A-CDC6 axis that provides novel insights into cell cycle and chemosensitivity regulation, which may become a potential biomarker and promising drug target for cancer treatment.

Deubiquitinase OTUD6a drives cardiac inflammation and hypertrophy by deubiquitination of STING

BACKGROUND

Cardiac hypertrophy is a crucial pathological characteristic of hypertensive heart disease and subsequent heart failure. Deubiquitinating enzymes (DUBs) have been found to be involved in the regulation of myocardial hypertrophy. OTU Domain-Containing Protein 6a (OTUD6a) is a recently identified DUB. To date, the potential role of OTUD6a in myocardial hypertrophy has not yet been revealed.

METHODS AND RESULTS

We examined the up-regulated level of OTUD6a in mouse or human hypertrophic heart tissues. Then, transverse aortic constriction (TAC)- or angiotensin II (Ang II)- induced ventricular hypertrophy and dysfunction were significantly attenuated in OTUD6a gene knockout mice (OTUD6a-/-). In mechanism, we identified that the Stimulator of Interferon Genes (STING) is a direct substrate protein of OTUD6a via immunoprecipitation assay and mass spectrometry. OTUD6a maintains STING stability via clearing the K48-linked ubiquitin in cardiomyocytes. Subsequently, OTUD6a regulates the STING-downstream NF-κB signaling activation and inflammatory gene expression both in vivo and in vitro. Inhibition of STING blocked OTUD6a overexpression-induced inflammatory and hypertrophic responses in cardiomyocytes.

CONCLUSION

This finding extends our understanding of the detrimental role of OTUD6a in myocardial hypertrophy and identifies STING as a deubiquinating substrate of OTUD6a, indicating that targeting OTUD6a could be a potential strategy for the treatment of cardiac hypertrophy.

Blockade of the deubiquitinating enzyme USP48 degrades oncogenic HMGA2 and inhibits colorectal cancer invasion and metastasis

HMGA2, a pivotal transcription factor, functions as a versatile regulator implicated in the progression of diverse aggressive malignancies. In this study, mass spectrometry was employed to identify ubiquitin-specific proteases that potentially interact with HMGA2, and USP48 was identified as a deubiquitinating enzyme of HMGA2. The enforced expression of USP48 significantly increased HMGA2 protein levels by inhibiting its degradation, while the deprivation of USP48 promoted HMGA2 degradation, thereby suppressing tumor invasion and metastasis. We discovered that USP48 undergoes SUMOylation at lysine 258, which enhances its binding affinity to HMGA2. Through subsequent phenotypic screening of small molecules, we identified DUB-IN-2 as a remarkably potent pharmacological inhibitor of USP48. Interestingly, the small-molecule inhibitor targeting USP48 induces destabilization of HMGA2. Clinically, upregulation of USP48 or HMGA2 in cancerous tissues is indicative of poor prognosis for patients with colorectal cancer (CRC). Collectively, our study not only elucidates the regulatory mechanism of DUBs involved in HMGA2 stability and validates USP48 as a potential therapeutic target for CRC, but also identifies DUB-IN-2 as a potent inhibitor of USP48 and a promising candidate for CRC treatment.

MYC induces CDK4/6 inhibitors resistance by promoting pRB1 degradation

CDK4/6 inhibitors (CDK4/6i) show anticancer activity in certain human malignancies, such as breast cancer. However, their application to other tumor types and intrinsic resistance mechanisms are still unclear. Here, we demonstrate that MYC amplification confers resistance to CDK4/6i in bladder, prostate and breast cancer cells. Mechanistically, MYC binds to the promoter of the E3 ubiquitin ligase KLHL42 and enhances its transcription, leading to RB1 deficiency by inducing both phosphorylated and total pRB1 ubiquitination and degradation. We identify a compound that degrades MYC, A80.2HCl, which induces MYC degradation at nanomolar concentrations, restores pRB1 protein levels and re-establish sensitivity of MYC high-expressing cancer cells to CDK4/6i. The combination of CDK4/6i and A80.2HCl result in marked regression in tumor growth in vivo. Altogether, these results reveal the molecular mechanisms underlying MYC-induced resistance to CDK4/6i and suggest the utilization of the MYC degrading molecule A80.2HCl to potentiate the therapeutic efficacy of CDK4/6i.

OTUD6A in tubular epithelial cells mediates angiotensin II-induced kidney injury by targeting STAT3

Kidney fibrosis is a prominent pathological feature of hypertensive kidney diseases (HKD). Recent studies have highlighted the role of ubiquitinating/deubiquitinating protein modification in kidney pathophysiology. Ovarian tumor domain-containing protein 6 A (OTUD6A) is a deubiquitinating enzyme involved in tumor progression. However, its role in kidney pathophysiology remains elusive. We aimed to investigate the role and underlying mechanism of OTUD6A during kidney fibrosis in HKD. The results revealed higher OTUD6A expression in kidney tissues of nephropathy patients and mice with chronic angiotensin II (Ang II) administration than that from the control ones. OTUD6A was mainly located in tubular epithelial cells. Moreover, OTUD6A deficiency significantly protected mice against Ang II-induced kidney dysfunction and fibrosis. Also, knocking OTUD6A down suppressed Ang II-induced fibrosis in cultured tubular epithelial cells, whereas overexpression of OTUD6A enhanced fibrogenic responses. Mechanistically, OTUD6A bounded to signal transducer and activator of transcription 3 (STAT3) and removed K63-linked-ubiquitin chains to promote STAT3 phosphorylation at tyrosine 705 position and nuclear translocation, which then induced profibrotic gene transcription in epithelial cells. These studies identified STAT3 as a direct substrate of OTUD6A and highlighted the pivotal role of OTUD6A in Ang II-induced kidney injury, indicating OTUD6A as a potential therapeutic target for HKD.NEW & NOTEWORTHY Ovarian tumor domain-containing protein 6 A (OTUD6A) knockout mice are protected against angiotensin II-induced kidney dysfunction and fibrosis. OTUD6A promotes pathological kidney remodeling and dysfunction by deubiquitinating signal transducer and activator of transcription 3 (STAT3). OTUD6A binds to and removes K63-linked-ubiquitin chains of STAT3 to promote its phosphorylation and activation, and subsequently enhances kidney fibrosis.

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

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

Gasdermins and cancers

The identification of gasdermin as the executor of pyroptosis has opened new avenues for the study of this process. Although pyroptosis research has mainly focused on immune cells since it was discovered three decades ago, accumulating evidence suggests that pyroptosis plays crucial roles in many biological processes. One example is the discovery of gasdermin-mediated cancer cell pyroptosis (CCP) which has become an important and frontier field in oncology. Recent studies have shown that CCP induction can heat tumor microenvironment (TME) and thereby elicit the robust anti-tumor immunity to suppress tumor growth. As a newly discovered form of tumor cell death, CCP offers promising opportunities for improving tumor treatment and developing new drugs. Nevertheless, the research on CCP is still in its infancy, and the molecular mechanisms underlying the expression, regulation and activation of gasdermins are not yet fully understood. In this review, we summarize the recent progress of gasdermin research in cancer area, and propose that the anti-tumor effect of immune cell pyroptosis (ICP) and CCP depends on their duration, intensity, and the type of cells undergoing pyroptosis within TME.

The Apoptotic and Anti-Warburg Effects of Brassinin in PC-3 Cells via Reactive Oxygen Species Production and the Inhibition of the c-Myc, SIRT1, and β-Catenin Signaling Axis

Though Brassinin is known to have antiangiogenic, anti-inflammatory, and antitumor effects in colon, prostate, breast, lung, and liver cancers, the underlying antitumor mechanism of Brassinin is not fully understood so far. Hence, in the current study, the apoptotic mechanism of Brassinin was explored in prostate cancer. Herein, Brassinin significantly increased the cytotoxicity and reduced the expressions of pro-Poly ADP-ribose polymerase (PARP), pro-caspase 3, and B-cell lymphoma 2 (Bcl-2) in PC-3 cells compared to DU145 and LNCaP cells. Consistently, Brassinin reduced the number of colonies and increased the sub-G1 population and terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL)-positive cells in the PC-3 cells. Of note, Brassinin suppressed the expressions of pyruvate kinase-M2 (PKM2), glucose transporter 1 (GLUT1), hexokinase 2 (HK2), and lactate dehydrogenase (LDH) as glycolytic proteins in the PC-3 cells. Furthermore, Brassinin significantly reduced the expressions of SIRT1, c-Myc, and β-catenin in the PC-3 cells and also disrupted the binding of SIRT1 with β-catenin, along with a protein-protein interaction (PPI) score of 0.879 and spearman's correlation coefficient of 0.47 being observed between SIRT1 and β-catenin. Of note, Brassinin significantly increased the reactive oxygen species (ROS) generation in the PC-3 cells. Conversely, ROS scavenger NAC reversed the ability of Brassinin to attenuate pro-PARP, pro-Caspase3, SIRT1, and β-catenin in the PC-3 cells. Taken together, these findings support evidence that Brassinin induces apoptosis via the ROS-mediated inhibition of SIRT1, c-Myc, β-catenin, and glycolysis proteins as a potent anticancer candidate.

Deubiquitinase OTUD6A Regulates Innate Immune Response via Targeting UBC13

OTUD6A is a deubiquitinase that plays crucial roles in various human diseases. However, the precise regulatory mechanism of OTUD6A remains unclear. In this study, we found that OTUD6A significantly inhibited the production of type I interferon. Consistently, peritoneal macrophages and bone marrow-derived macrophages from Otud6a-/- mice produced more type I interferon after virus infection compared to cells from WT mice. Otud6a-/-- mice also exhibited increased resistance to lethal HSV-1 and VSV infections, as well as LPS attacks due to decreased inflammatory responses. Mechanistically, mass spectrometry results revealed that UBC13 was an OTUD6A-interacting protein, and the interaction was significantly enhanced after HSV-1 stimulation. Taken together, our findings suggest that OTUD6A plays a crucial role in the innate immune response and may serve as a potential therapeutic target for infectious disease.

E3 ubiquitin ligases and deubiquitinases in bladder cancer tumorigenesis and implications for immunotherapies

With the rapidly increasing incidence of bladder cancer in China and worldwide, great efforts have been made to understand the detailed mechanism of bladder cancer tumorigenesis. Recently, the introduction of immune checkpoint inhibitor-based immunotherapy has changed the treatment strategy for bladder cancer, especially for advanced bladder cancer, and has improved the survival of patients. The ubiquitin-proteasome system, which affects many biological processes, plays an important role in bladder cancer. Several E3 ubiquitin ligases and deubiquitinases target immune checkpoints, either directly or indirectly. In this review, we summarize the recent progress in E3 ubiquitin ligases and deubiquitinases in bladder cancer tumorigenesis and further highlight the implications for bladder cancer immunotherapies.

Deubiquitinase OTUD6A in macrophages promotes intestinal inflammation and colitis via deubiquitination of NLRP3

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract, which has been shown to increase the incidence of colorectal cancer. Recent studies have highlighted the role of ubiquitination, a post-translational modification, in the occurrence and development of colonic inflammation. Ovarian tumor deubiquitinase 6 A (OTUD6A) is a deubiquitinating enzyme, which regulates cell proliferation and tumorigenesis. In this study, we investigated the expression and role of OTUD6A in IBD. Wide-type or Otud6a-/- mice were used to develop dextran sodium sulfate (DSS)- or 2,6,4-trinitrobenzene sulfonic acid (TNBS)-induced colitis model, as well as azoxymethane (AOM)/DSS-induced colitis-associated cancer model. Bone marrow-derived macrophages (BMDMs) were isolated from wild-type and Otud6a-/- mice to dissect molecular mechanisms. Our data show that OTUD6A deficiency attenuated DSS or TNBS-induced colitis, as well as AOM/DSS-induced colitis-related colon cancer in vivo. Bone marrow transplantation experiments further revealed that OTUD6A in myeloid cells was responsible for exacerbation of DSS-induced colitis. Mechanistically, OTUD6A directly bound to NACHT domain of NLRP3 inflammasome and selectively cleaved K48-linked polyubiquitin chains from NLRP3 at K430 and K689 to enhance the stability of NLRP3, leading to increased IL-1β level and inflammation. Taken together, our research identifies a new function of OTUD6A in the pathogenesis of colitis by promoting NLRP3 inflammasome activation, suggesting that OTUD6A could be a potential target for the treatment of IBD.

IGF2BP1-mediated N6-methyladenosine modification promotes intrahepatic cholangiocarcinoma progression

N6-methyladenosine (m6A) RNA methylation and its associated RNA-binding protein insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) are involved in tumor initiation and progression. Here, we explored the biological function and clinical significance of IGF2BP1 in intrahepatic cholangiocarcinoma (iCCA). We found that IGF2BP1 expression was upregulated by H3K27 acetylation enrichment of its promoter, which positively correlated with poor clinicopathological characteristics and survival. Gain- and loss-of-function experiments showed that IGF2BP1 overexpression (knockdown) enhanced (attenuated) iCCA growth and metastasis in vitro and in vivo. Mechanistically, IGF2BP1 not only regulated the c-Myc/p16 axis to promote iCCA growth and inhibit senescence, but also activated the ZIC2/PAK4/AKT/MMP2 axis to induce tumor metastasis. More importantly, BTYNB, a recently identified IGF2BP1 inhibitor, exerted promising anti-tumor efficacy in a patient-derived xenograft (PDX) model, and IGF2BP1 conditional knockout (cKO) reduced the tumor burden. These results demonstrate the crucial role of IGF2BP1 in iCCA progression via m6A-dependent modification, highlighting IGF2BP1 as a potential therapeutic target in iCCA.

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.

Suppression of Cancer Cell Stemness and Drug Resistance via MYC Destabilization by Deubiquitinase USP45 Inhibition with a Natural Small Molecule

Cancer stem cells (CSCs) play significant roles in cancer development, drug resistance and cancer recurrence. In cancer treatments based on the CSC characteristics and inducing factors, MYC is a promising target for therapeutic molecules. Although it has been regarded as an undrugable target, its stability tightly regulated by the ubiquitin-proteasome system offers a new direction for molecule targeting and cancer treatment. Herein we report our discoveries in this research area, and we have found that deubiquitinase USP45 can directly bind with MYC, resulting in its deubiquitination and stabilization. Further, USP45 overexpressing can upregulate MYC, and this overexpressing can significantly enhance cancer development, cancer cell stemness and drug resistance. Interestingly, without enhancing cancer development, MYC silencing with shRNA can only suppress USP45-induced stemness and drug resistance. Moreover, we have identified that USP45 can be specifically bound and inhibited by a natural small molecule (α-mangostin), in turn significantly suppressing USP45-induced stemness and drug resistance. Since USP45 is significantly expressed in cervical tumors, we have discovered that the combination of α-mangostin and doxorubicin can significantly inhibit USP45-induced cervical tumorigenesis in an animal model. In general, on the basis of our USP45 discoveries on its MYC deubiquitination and α-mangostin inhibition, suppressing USP45 has opened a new window for suppressing cancer development, stemness and drug resistance.

Protein degradation: expanding the toolbox to restrain cancer drug resistance

Despite significant progress in clinical management, drug resistance remains a major obstacle. Recent research based on protein degradation to restrain drug resistance has attracted wide attention, and several therapeutic strategies such as inhibition of proteasome with bortezomib and proteolysis-targeting chimeric have been developed. Compared with intervention at the transcriptional level, targeting the degradation process seems to be a more rapid and direct strategy. Proteasomal proteolysis and lysosomal proteolysis are the most critical quality control systems responsible for the degradation of proteins or organelles. Although proteasomal and lysosomal inhibitors (e.g., bortezomib and chloroquine) have achieved certain improvements in some clinical application scenarios, their routine application in practice is still a long way off, which is due to the lack of precise targeting capabilities and inevitable side effects. In-depth studies on the regulatory mechanism of critical protein degradation regulators, including E3 ubiquitin ligases, deubiquitylating enzymes (DUBs), and chaperones, are expected to provide precise clues for developing targeting strategies and reducing side effects. Here, we discuss the underlying mechanisms of protein degradation in regulating drug efflux, drug metabolism, DNA repair, drug target alteration, downstream bypass signaling, sustaining of stemness, and tumor microenvironment remodeling to delineate the functional roles of protein degradation in drug resistance. We also highlight specific E3 ligases, DUBs, and chaperones, discussing possible strategies modulating protein degradation to target cancer drug resistance. A systematic summary of the molecular basis by which protein degradation regulates tumor drug resistance will help facilitate the development of appropriate clinical strategies.

Deubiquitinase OTUD6A promotes breast cancer progression by increasing TopBP1 stability and rendering tumor cells resistant to DNA-damaging therapy

The DNA damage response (DDR) is critical for maintaining cellular homeostasis and genome integrity. Mounting evidence has shown that posttranslational protein modifications play vital roles in the DDR. In this study, we showed that deubiquitinase OTUD6A is involved in the DDR and is important for maintaining genomic stability. Mechanistically, in response to DNA damage, the abundance of OTUD6A was increased; meanwhile, PP2A interacted with OTUD6A and dephosphorylated OTUD6A at sites S70/71/74, which promoted nuclear localization of OTUD6A. Subsequently, OTUD6A was recruited to the damage site, where it interacted with TopBP1 and blocked the interaction between TopBP1 and its ubiquitin E3 ligase UBR5, decreasing K48-linked polyubiquitination and increasing the stability of TopBP1. OTUD6A depletion impaired CHK1 S345 phosphorylation and blocked cell cycle progression under DNA replication stress. Consistently, knockout of OTUD6A rendered mice hypersensitive to irradiation, shortened survival, and inhibited tumor growth by regulating TopBP1 in xenografted nude mice. Moreover, OTUD6A is expressed at high levels in breast cancer, and OTUD6A overexpression promotes cell proliferation, migration and invasion, indicating that dysregulation of OTUD6A expression contributes to genomic instability and is associated with tumor development. In summary, this study demonstrates that OTUD6A plays a critical role in promoting tumor cell resistance to chemoradiotherapy by deubiquitinating and stabilizing TopBP1.

Ovarian tumor deubiquitinase 6A regulates cell proliferation via deubiquitination of nucleolin and caspase‑7

Most proteins maintain protein homeostasis via post‑translational modifications, including the ubiquitin‑proteasome system. Deubiquitinating enzymes (DUBs) have essential intercellular roles, such as responses to DNA damage, proteolysis and apoptosis. Therefore, it is important to understand DUB‑related diseases to identify DUBs that target abnormally regulated proteins in cells. Ovarian tumor deubiquitinase 6A (OTUD6A) was previously reported as a downregulated DUB in HCT116 cells with p53 knockdown. Therefore, it was expected that the relationship between OTUD6A and p53 would affect cell proliferation. In the present study, putative substrates of OTUD6A related to the p53 signaling pathway were identified. Application of liquid chromatography‑tandem mass spectrometry and proteomic analysis led to the identification of nucleolin (known to bind p53) as a binding protein. In addition, immunoprecipitation studies determined that caspase‑7, an apoptotic protein, is associated with p53 signaling and is regulated by OTUD6A. It was further identified that OTUD6A regulates the protein stability of nucleolin, but not caspase‑7. It was also demonstrated that OTUD6A acts as a respective DUB through the deubiquitination of K48‑linked polyubiquitin chain of nucleolin and the K63‑linked polyubiquitin chain of caspase‑7. Furthermore, overexpression of OTUD6A induced cell proliferation via enhancing cell cycle progression of MCF7 cells. Taken together, OTUD6A may be proposed as a target for anticancer therapy.

Silencing circOMA1 Inhibits Osteosarcoma Progression by Sponging miR-1294 to Regulate c-Myc Expression

Background

Several studies have reported that circRNAs have a crucial function in the tumorigenesis of various cancers. However, the expression and function of circOMA1 in osteosarcoma is unknown.

Methods

circOMA1 was identified through bioinformatics analysis. qRT-PCR was used to assess the expressions of circOMA1, miR-1294, and c-Myc in osteosarcoma tissues. Further, we performed functional experiments to explore the biological function of circOMA1 in osteosarcoma. Moreover, a luciferase reporter assay, RNA immunoprecipitation (RIP), and fluorescence in situ hybridisation (FISH) assay were performed to demonstrate the association between circOMA1 and miR-1294.

Results

circOMA1 exhibited considerable upregulation in osteosarcoma tissues compared with adjacent normal tissues. Silencing circOMA1 suppressed osteosarcoma progression in vitro and in vivo. Mechanically, circOMA1 functioned as a sponge of miR-1294 to upregulate c-Myc expression.

Conclusion

circOMA1 played the role of an oncogene in osteosarcoma and promoted osteosarcoma progression by mediating the miR-1294/c-Myc pathway, which might be a new target for treating osteosarcoma.