Deubiquitinases: Pro-oncogenic Activity and Therapeutic Targeting in Blood Malignancies

OTUB2 silencing promotes ovarian cancer via mitochondrial metabolic reprogramming and can be synthetically targeted by CA9 inhibition

Ovarian cancer is an aggressive gynecological tumor characterized by a high relapse rate and chemoresistance. Ovarian cancer exhibits the cancer hallmark of elevated glycolysis, yet effective strategies targeting cancer cell metabolic reprogramming to overcome therapeutic resistance in ovarian cancer remain elusive. Here, we revealed that epigenetic silencing of Otubain 2 (OTUB2) is a driving force for mitochondrial metabolic reprogramming in ovarian cancer, which promotes tumorigenesis and chemoresistance. Mechanistically, OTUB2 silencing destabilizes sorting nexin 29 pseudogene 2 (SNX29P2), which subsequently prevents hypoxia-inducible factor-1 alpha (HIF-1α) from von Hippel-Lindau tumor suppressor-mediated degradation. Elevated HIF-1α activates the transcription of carbonic anhydrase 9 (CA9) and drives ovarian cancer progression and chemoresistance by promoting glycolysis. Importantly, pharmacological inhibition of CA9 substantially suppressed tumor growth and synergized with carboplatin in the treatment of OTUB2-silenced ovarian cancer. Thus, our study highlights the pivotal role of OTUB2/SNX29P2 in suppressing ovarian cancer development and proposes that targeting CA9-mediated glycolysis is an encouraging strategy for the treatment of ovarian cancer.

Discovery of a Potent Deubiquitinase (DUB) Small-Molecule Activity-Based Probe Enables Broad Spectrum DUB Activity Profiling in Living Cells

Deubiquitinases (DUBs) are a family of >100 proteases that hydrolyze isopeptide bonds linking ubiquitin to protein substrates, often leading to reduced substrate degradation through the ubiquitin proteasome system. Deregulation of DUB activity has been implicated in many diseases, including cancer, neurodegeneration and auto-inflammation, and several have been recognized as attractive targets for therapeutic intervention. Ubiquitin-derived covalent activity-based probes (ABPs) provide a powerful tool for DUB activity profiling, but their large recognition element impedes cellular permeability and presents an unmet need for small molecule ABPs which can account for regulation of DUB activity in intact cells or organisms. Here, through comprehensive chemoproteomic warhead profiling, we identify cyanopyrrolidine (CNPy) probe IMP-2373 (12) as a small molecule pan-DUB ABP to monitor DUB activity in physiologically relevant live cells. Through proteomics and targeted assays, we demonstrate that IMP-2373 quantitatively engages more than 35 DUBs across a range of non-toxic concentrations in diverse cell lines. We further demonstrate its application to quantification of changes in intracellular DUB activity during pharmacological inhibition and during MYC deregulation in a model of B cell lymphoma. IMP-2373 thus offers a complementary tool to ubiquitin ABPs to monitor dynamic DUB activity in the context of disease-relevant phenotypes.

Assessment of MMP14, CAV2, CLU and SPARCL1 expression profiles in endometriosis

Endometriotic cells exhibit a notable degree of invasiveness and some characteristics of tissue remodeling underlying lesion formation. In this regard, do matrix metalloproteinases 14 (MMP14) and other related genes such as SPARC-like protein 1 (SPARCL1), caveolin 2 (CAV2), and clusterin (CLU) exert any significant influence in the processes of endometriosis development and pathophysiology is not apparent. We aim to assess whether these genes could serve as potential diagnostic biomarkers in endometriosis. Microarray-based gene expression analysis was performed on total RNA extracted from endometriotic tissue samples treated with and without gonadotropin-releasing hormone agonist (GnRHa). The GnRHa untreated patients were considered the control group. The validation of genes was performed using quantitative real-time polymerase chain reaction (qRT-PCR). qRT-PCR analysis showed significant downregulation in the expression of MMP14 (p = 0.024), CAV2 (p = 0.017), and upregulation of CLU (p = 0.005) in endometriosis patients treated with GnRHa. SPARCL1 did not show any significant (p = 0.30) change in the expression compared to the control group. These data have the potential to contribute to the comprehension of the molecular pathways implicated in the remodeling of the extracellular matrix, which is a vital step for the physiology of the endometrium. Based on the result, it is concluded that changes in the expression of MMP14, CAV2, and CLU post-treatment imply their role in the pathophysiology of endometriosis and may serve as a potential diagnostic biomarker of endometriosis in response to GnRHa treatment in patients with ovarian endometrioma.

Deubiquitinase inhibitor PR-619 potentiates colon cancer immunotherapy by inducing ferroptosis

A substantial number of colon cancer patients do not benefit from immunotherapy using programmed cell death 1 (PD1) antibodies. Therefore, combination therapy drugs are required to improve the efficacy of colon cancer immunotherapy. Recent studies have shown that deubiquitinases are negative regulators of anti-tumour immunity. In the present study, we investigated the effect of the deubiquitinase inhibitor PR-619 in combination with anti-PD1 for the treatment of colorectal cancer. The results revealed that co-treatment with PR-619 and anti-PD1 significantly inhibited tumour growth in tumour-bearing BALB/c mice compared to monotherapy with a single drug. In addition, PR-619/anti-PD1 combined therapy inhibited cell proliferation, promoted cell apoptosis, induced intratumor infiltration of CD8+ T cells, and enhanced the release of anti-tumour cytokines. Moreover, PR-619 induced ferroptosis in colon cancer cells, thereby inducing the release of damage-associated molecular patterns that triggered anti-tumour immunity. Finally, we discovered that PR-619 could degrade the GPX4 protein, the high expression of which was associated with poor prognosis and blocked CD8+ T cells infiltration in colon cancer. In conclusion, PR-619 may potentiate immunotherapy by inducing ferroptosis, and thereby promoting CD8+ T cells-mediated anti-tumour immunity, providing a potential strategy for colon cancer treatment.

An expanded lexicon for the ubiquitin code

Our understanding of the ubiquitin code has greatly evolved from conventional E1, E2 and E3 enzymes that modify Lys residues on specific substrates with a single type of ubiquitin chain to more complex processes that regulate and mediate ubiquitylation. In this Review, we discuss recently discovered endogenous mechanisms and unprecedented pathways by which pathogens rewrite the ubiquitin code to promote infection. These processes include unconventional ubiquitin modifications involving ester linkages with proteins, lipids and sugars, or ubiquitylation through a phosphoribosyl bridge involving Arg42 of ubiquitin. We also introduce the enzymatic pathways that write and reverse these modifications, such as the papain-like proteases of severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. Furthermore, structural studies have revealed that the ultimate functions of ubiquitin are mediated not simply by straightforward recognition by ubiquitin-binding domains. Instead, elaborate multivalent interactions between ubiquitylated targets or ubiquitin chains and their readers (for example, the proteasome, the MLL1 complex or DOT1L) can elicit conformational changes that regulate protein degradation or transcription. The newly discovered mechanisms provide opportunities for innovative therapeutic interventions for diseases such as cancer and infectious diseases.

Oncogenic deubiquitination controls tyrosine kinase signaling and therapy response in acute lymphoblastic leukemia

Dysregulation of kinase signaling pathways favors tumor cell survival and therapy resistance in cancer. Here, we reveal a posttranslational regulation of kinase signaling and nuclear receptor activity via deubiquitination in T cell acute lymphoblastic leukemia (T-ALL). We observed that the ubiquitin-specific protease 11 (USP11) is highly expressed and associates with poor prognosis in T-ALL. USP11 ablation inhibits leukemia progression in vivo, sparing normal hematopoiesis. USP11 forms a complex with USP7 to deubiquitinate the oncogenic lymphocyte cell-specific protein-tyrosine kinase (LCK) and enhance its activity. Impairment of LCK activity leads to increased glucocorticoid receptor (GR) expression and glucocorticoids sensitivity. Genetic knockout of USP7 improved the antileukemic efficacy of glucocorticoids in vivo. The transcriptional activation of GR target genes is orchestrated by the deubiquitinase activity and mediated via an increase in enhancer-promoter interaction intensity. Our data unveil how dysregulated deubiquitination controls leukemia survival and drug resistance, suggesting previously unidentified therapeutic combinations toward targeting leukemia.

The roles of histone modifications in tumorigenesis and associated inhibitors in cancer therapy

Histone modifications are key factors in chromatin packaging, and are responsible for gene regulation during cell fate determination and development. Abnormal alterations in histone modifications potentially affect the stability of the genome and disrupt gene expression patterns, leading to many diseases, including cancer. In recent years, mounting evidence has shown that various histone modifications altered by aberrantly expressed modifier enzymes contribute to tumor development and metastasis through the induction of epigenetic, transcriptional, and phenotypic changes. In this review, we will discuss the existing histone modifications, both well-studied and rare ones, and their roles in solid tumors and hematopoietic cancers, to identify the molecular pathways involved and investigate targeted therapeutic drugs to reorganize the chromatin and enhance cancer treatment efficiency. Finally, clinical inhibitors of histone modifications are summarized to better understand the developmental stage of cancer therapy in using these drugs to inhibit the histone modification enzymes.

SF3B1 homeostasis is critical for survival and therapeutic response in T cell leukemia

The production of noncanonical mRNA transcripts is associated with cell transformation. Driven by our previous findings on the sensitivity of T cell acute lymphoblastic leukemia (T-ALL) cells to SF3B1 inhibitors, we identified that SF3B1 inhibition blocks T-ALL growth in vivo with no notable associated toxicity. We also revealed protein stabilization of the U2 complex component SF3B1 via deubiquitination. Our studies showed that SF3B1 inhibition perturbs exon skipping, leading to nonsense-mediated decay and diminished levels of DNA damage response-related transcripts, such as the serine/threonine kinase CHEK2, and impaired DNA damage response. We also identified that SF3B1 inhibition leads to a general decrease in R-loop formation. We further demonstrate that clinically used SF3B1 inhibitors synergize with CHEK2 inhibitors and chemotherapeutic drugs to block leukemia growth. Our study provides the proof of principle for posttranslational regulation of splicing components and associated roles and therapeutic implications for the U2 complex in T cell leukemia.

Time-resolved in vivo ubiquitinome profiling by DIA-MS reveals USP7 targets on a proteome-wide scale

Mass spectrometry (MS)-based ubiquitinomics provides system-level understanding of ubiquitin signaling. Here we present a scalable workflow for deep and precise in vivo ubiquitinome profiling, coupling an improved sample preparation protocol with data-independent acquisition (DIA)-MS and neural network-based data processing specifically optimized for ubiquitinomics. Compared to data-dependent acquisition (DDA), our method more than triples identification numbers to 70,000 ubiquitinated peptides in single MS runs, while significantly improving robustness and quantification precision. Upon inhibition of the oncology target USP7, we simultaneously record ubiquitination and consequent changes in abundance of more than 8,000 proteins at high temporal resolution. While ubiquitination of hundreds of proteins increases within minutes of USP7 inhibition, we find that only a small fraction of those are ever degraded, thereby dissecting the scope of USP7 action. Our method enables rapid mode-of-action profiling of candidate drugs targeting DUBs or ubiquitin ligases at high precision and throughput.

Combining improved sample preparation, data-independent acquisition mass spectrometry and deep learning, the authors develop a workflow for more robust and precise quantitative ubiquitinome profiling. They use this method to characterize targets of the deubiquitinase USP7 and effects of USP7 inhibitors.

Deubiquitinases in hematological malignancies

Deubiquitinases (DUBs) are enzymes that control the stability, interactions or localization of most cellular proteins by removing their ubiquitin modification. In recent years, some DUBs, such as USP7, USP9X and USP10, have been identified as promising therapeutic targets in hematological malignancies. Importantly, some potent inhibitors targeting the oncogenic DUBs have been developed, showing promising inhibitory efficacy in preclinical models, and some have even undergone clinical trials. Different DUBs perform distinct function in diverse hematological malignancies, such as oncogenic, tumor suppressor or context-dependent effects. Therefore, exploring the biological roles of DUBs and their downstream effectors will provide new insights and therapeutic targets for the occurrence and development of hematological malignancies. We summarize the DUBs involved in different categories of hematological malignancies including leukemia, multiple myeloma and lymphoma. We also present the recent development of DUB inhibitors and their applications in hematological malignancies. Together, we demonstrate DUBs as potential therapeutic drug targets in hematological malignancies.

Deubiquitinating Enzymes Orchestrate the Cancer Stem Cell-Immunosuppressive Niche Dialogue: New Perspectives and Therapeutic Potential

Cancer stem cells (CSCs) are sparks for igniting tumor recurrence and the instigators of low response to immunotherapy and drug resistance. As one of the important components of tumor microenvironment, the tumor associated immune microenvironment (TAIM) is driving force for the heterogeneity, plasticity and evolution of CSCs. CSCs create the inhibitory TAIM (ITAIM) mainly through four stemness-related signals (SRSs), including Notch-nuclear factor-κB axis, Hedgehog, Wnt and signal transducer and activator of transcription. Ubiquitination and deubiquitination in proteins related to the specific stemness of the CSCs have a profound impact on the regulation of ITAIM. In regulating the balance between ubiquitination and deubiquitination, it is crucial for deubiquitinating enzymes (DUBs) to cleave ubiquitin chains from substrates. Ubiquitin-specific peptidases (USPs) comprise the largest family of DUBs. Growing evidence suggests that they play novel functions in contribution of ITAIM, including regulating tumor immunogenicity, activating stem cell factors, upregulating the SRSs, stabilizing anti-inflammatory receptors, and regulating anti-inflammatory cytokines. These overactive or abnormal signaling may dampen antitumor immune responses. The inhibition of USPs could play a regulatory role in SRSs and reversing ITAIM, and also have great potential in improving immune killing ability against tumor cells, including CSCs. In this review, we focus on the USPs involved in CSCs signaling pathways and regulating ITAIM, which are promising therapeutic targets in antitumor therapy.

USP7 targeting modulates anti-tumor immune response by reprogramming Tumor-associated Macrophages in Lung Cancer

Background: Tumor associated macrophages (TAMs) have strong plasticity and if reprogrammed, can clear tumor cells and regulate the adaptive immune system for cancer immunotherapy. Deubiquitinating enzymes (DUBs), which can remove ubiquitin (Ub) from Ub-modified substrates, have been associated with oncogenic metabolism but are not well-known for regulating TAMs repolarization.

Methods: The expression of DUB related genes in macrophages (MΦs) was detected by reverse transcription-PCR. Flow cytometry and immunofluorescence were used to detect the changes of immune cells in the tumor microenvironment and spleen, including M1 (CD11b⁺F4/80⁺CD86⁺CD206^-), and M2 (CD11b⁺F4/80⁺CD86^-CD206⁺) MΦs, and IFN-γ⁺CD8⁺T cells. A proliferation assay was used to determine the effect of M2 MΦs treated with a USP7 inhibitor on T cell proliferation. Western blotting was used to detect the expression of USP7 and the activation of the MAPK pathway. The TGCA database was used to assess the role of USP7 in the immune microenvironment of human lung adenocarcinoma (LUAD).

Results: 51 DUB genes were screened and USP7 was identified as a highly expressed gene in M2 but not M1 MΦs. Specific silencing of USP7 using siRNA or USP7 inhibitors led to phenotypical and functional changes in M2 MΦs, favoring CD8⁺T cells proliferation in vitro. USP7 inhibitors delayed tumor growth in mice with Lewis lung carcinoma, and promoted tumor infiltration of M1 MΦs and IFN-γ⁺CD8⁺T cells. Depletion of TAMs attenuated these therapeutic effects. USP7 inhibition was shown to mediate MΦs reprogramming by activating the p38 MAPK pathway. Administration of USP7 inhibitors increased the expression of programmed cell death ligand 1 (PD-L1) in tumors, while blocking programmed cell death protein 1 (PD-1) provided an effective anti-tumor response. Clinical databases suggest that high expression of USP7 in LUAD was negatively correlated with innate and adaptive immunity.

Conclusions: Taken together, these results provide evidence to suggest that therapeutic approaches targeting USP7, in combination with immunotherapy, should be considered for lung cancer treatment.

The Role of Deubiquitinating Enzymes in Hematopoiesis and Hematological Malignancies

Hematopoietic stem cells (HSCs) are responsible for the production of blood cells throughout the human lifespan. Single HSCs can give rise to at least eight distinct blood-cell lineages. Together, hematopoiesis, erythropoiesis, and angiogenesis coordinate several biological processes, i.e., cellular interactions during development and proliferation, guided migration, lineage programming, and reprogramming by transcription factors. Any dysregulation of these processes can result in hematological disorders and/or malignancies. Several studies of the molecular mechanisms governing HSC maintenance have demonstrated that protein regulation by the ubiquitin proteasomal pathway is crucial for normal HSC function. Recent studies have shown that reversal of ubiquitination by deubiquitinating enzymes (DUBs) plays an equally important role in hematopoiesis; however, information regarding the biological function of DUBs is limited. In this review, we focus on recent discoveries about the physiological roles of DUBs in hematopoiesis, erythropoiesis, and angiogenesis and discuss the DUBs associated with common hematological disorders and malignancies, which are potential therapeutic drug targets.