Control of CCND1 ubiquitylation by the catalytic SAGA subunit USP22 is essential for cell cycle progression through G1 in cancer cells.
ABSTRACT: Overexpression of the deubiquitylase ubiquitin-specific peptidase 22 (USP22) is a marker of aggressive cancer phenotypes like metastasis, therapy resistance, and poor survival. Functionally, this overexpression of USP22 actively contributes to tumorigenesis, as USP22 depletion blocks cancer cell cycle progression in vitro, and inhibits tumor progression in animal models of lung, breast, bladder, ovarian, and liver cancer, among others. Current models suggest that USP22 mediates these biological effects via its role in epigenetic regulation as a subunit of the Spt-Ada-Gcn5-acetyltransferase (SAGA) transcriptional cofactor complex. Challenging the dogma, we report here a nontranscriptional role for USP22 via a direct effect on the core cell cycle machinery: that is, the deubiquitylation of the G1 cyclin D1 (CCND1). Deubiquitylation by USP22 protects CCND1 from proteasome-mediated degradation and occurs separately from the canonical phosphorylation/ubiquitylation mechanism previously shown to regulate CCND1 stability. We demonstrate that control of CCND1 is a key mechanism by which USP22 mediates its known role in cell cycle progression. Finally, USP22 and CCND1 levels correlate in patient lung and colorectal cancer samples and our preclinical studies indicate that targeting USP22 in combination with CDK inhibitors may offer an approach for treating cancer patients whose tumors exhibit elevated CCND1.
Project description:Emerging evidence indicates the deubiquitinase USP22 regulates transcriptional activation and modification of target substrates to promote pro-oncogenic phenotypes. Here, <i>in vivo</i> characterization of tumor-associated USP22 upregulation and unbiased interrogation of USP22-regulated functions <i>in vitro</i> demonstrated critical roles for USP22 in prostate cancer. Specifically, clinical datasets validated that USP22 expression is elevated in prostate cancer, and a novel murine model demonstrated a hyperproliferative phenotype with prostate-specific USP22 overexpression. Accordingly, upon overexpression or depletion of USP22, enrichment of cell-cycle and DNA repair pathways was observed in the USP22-sensitive transcriptome and ubiquitylome using prostate cancer models of clinical relevance. Depletion of USP22 sensitized cells to genotoxic insult, and the role of USP22 in response to genotoxic insult was further confirmed using mouse adult fibroblasts from the novel murine model of USP22 expression. As it was hypothesized that USP22 deubiquitylates target substrates to promote protumorigenic phenotypes, analysis of the USP22-sensitive ubiquitylome identified the nucleotide excision repair protein, XPC, as a critical mediator of the USP22-mediated response to genotoxic insult. Thus, XPC undergoes deubiquitylation as a result of USP22 function and promotes USP22-mediated survival to DNA damage. Combined, these findings reveal unexpected functions of USP22 as a driver of protumorigenic phenotypes and have significant implications for the role of USP22 in therapeutic outcomes. SIGNIFICANCE: The studies herein present a novel mouse model of tumor-associated USP22 overexpression and implicate USP22 in modulation of cellular survival and DNA repair, in part through regulation of XPC.
Project description:Although immune checkpoint blockade (ICB) improves clinical outcome in several types of malignancies, pancreatic ductal adenocarcinoma (PDA) remains refractory to this therapy. Preclinical studies have demonstrated that the relative abundance of suppressive myeloid cells versus cytotoxic T cells determines the efficacy of combination immunotherapies, which include ICB. Here, we evaluated the role of the ubiquitin-specific protease 22 (USP22) as a regulator of the immune tumor microenvironment (TME) in PDA. We report that deletion of USP22 in pancreatic tumor cells reduced the infiltration of myeloid cells and promoted the infiltration of T cells and natural killer (NK) cells, leading to an improved response to combination immunotherapy. We also showed that ablation of tumor cell-intrinsic USP22 suppressed metastasis of pancreatic tumor cells in a T-cell-dependent manner. Finally, we provide evidence that USP22 exerted its effects on the immune TME by reshaping the cancer cell transcriptome through its association with the deubiquitylase module of the SAGA/STAGA transcriptional coactivator complex. These results indicated that USP22 regulates immune infiltration and immunotherapy sensitivity in preclinical models of pancreatic cancer.
Project description:<i>Ras</i> mutations are commonly observed in juvenile myelomonocytic leukemia (JMML) and chronic myelomonocytic leukemia (CMML). JMML and CMML transform into acute myeloid leukemia (AML) in about 10% and 50% of patients, respectively. However, how additional events cooperate with Ras to promote this transformation are largely unknown. We show that absence of the ubiquitin-specific peptidase 22 (USP22), a component of the Spt-Ada-GCN5-acetyltransferase chromatin-remodeling complex that is linked to cancer progression, unexpectedly promotes AML transformation in mice expressing oncogenic <i>Kras</i><sup><i>G12D/+</i></sup> USP22 deficiency in <i>Kras</i><sup><i>G12D/+</i></sup> mice resulted in shorter survival compared with control mice. This was due to a block in myeloid cell differentiation leading to the generation of AML. This effect was cell autonomous because mice transplanted with USP22-deficient <i>Kras</i><sup><i>G12D/+</i></sup> cells developed an aggressive disease and died rapidly. The transcriptome profile of USP22-deficient <i>Kras</i><sup><i>G12D/+</i></sup> progenitors resembled leukemic stem cells and was highly correlated with genes associated with poor prognosis in AML. We show that USP22 functions as a PU.1 deubiquitylase by positively regulating its protein stability and promoting the expression of PU.1 target genes. Reconstitution of PU.1 overexpression in USP22-deficient <i>Kras</i><sup><i>G12D/+</i></sup> progenitors rescued their differentiation. Our findings uncovered an unexpected role for USP22 in Ras-induced leukemogenesis and provide further insights into the function of USP22 in carcinogenesis.
Project description:Emerging evidence has shown that GSK3? plays oncogenic roles in multiple tumour types; however, the underlying mechanisms remain largely unknown. Here, we show that nuclear GSK3? is responsible for the accumulation of the histone demethylase KDM1A and critically regulates histone H3K4 methylation during tumorigenesis. GSK3? phosphorylates KDM1A Ser683 upon priming phosphorylation of KDM1A Ser687 by CK1?. Phosphorylation of KDM1A induces its binding with and deubiquitylation by USP22, leading to KDM1A stabilization. GSK3?- and USP22-dependent KDM1A stabilization is required for the demethylation of histone H3K4, thereby repressing BMP2, CDKN1A and GATA6 transcription, which results in cancer stem cell self-renewal and glioblastoma tumorigenesis. In human glioblastoma specimens, KDM1A levels are correlated with nuclear GSK3? and USP22 levels. Furthermore, a GSK3 inhibitor, tideglusib, sensitizes tumour xenografts to chemotherapy in mice via KDM1A downregulation and improves survival. Our findings demonstrate that nuclear GSK3?- and USP22-mediated KDM1A stabilization is essential for glioblastoma tumorigenesis.
Project description:<h4>Purpose</h4>Growing evidence indicates that aberrant expression of microRNAs contributes to tumor development. However, the biological role of microRNA-4490 (miR-4490) in gastric cancer (GC) remains to be clarified.<h4>Methods</h4>To explore the function of miR-4490 in GC, we performed colony formation, EdU incorporation, qRT-PCR, Western blotting, in situ hybridization (ISH), immunohistochemistry (IHC), flow cytometry, ChIP and dual-luciferase reporter assays. In addition, the growth, migration and invasion capacities of GC cells were evaluated.<h4>Results</h4>We found that miR-4490 was significantly downregulated in primary GC samples and in GC-derived cell lines compared with normal controls, and that this expression level was negatively correlated with GC malignancy. Exogenous miR-4490 expression not only reduced cell cycle progression and proliferation, but also significantly inhibited GC cell migration, invasion and epithelial-mesenchymal transition (EMT) in vitro. Mechanistically, we found that miR-4490 directly targets USP22, which mediates inhibition of GC cell proliferation and EMT-induced metastasis in vitro and in vivo. Moreover, we found through luciferase and ChIP assays that transcription factor POU2F1 can directly bind to POU2F1 binding sites within the miR-4490 and USP22 promoters and, by doing so, modulate their transcription. Spearman's correlation analysis revealed a positive correlation between USP22 and POU2F1 expression and negative correlations between miR-4490 and USP22 as well as miR-4490 and POU2F1 expression in primary GC tissues.<h4>Conclusion</h4>Based on our results we conclude that miR-4490 acts as a tumor suppressor, and that the POU2F1/miR-4490/USP22 axis plays an important role in the regulation of growth, invasion and EMT of GC cells.
Project description:Increasing evidence links deregulation of the ubiquitin-specific proteases 22 (USP22) deubitiquitylase to cancer development and progression in a select group of tumor types, but its specificity and underlying mechanisms of action are not well defined. Here we show that USP22 is a critical promoter of lethal tumor phenotypes that acts by modulating nuclear receptor and oncogenic signaling. In multiple xenograft models of human cancer, modeling of tumor-associated USP22 deregulation demonstrated that USP22 controls androgen receptor accumulation and signaling, and that it enhances expression of critical target genes coregulated by androgen receptor and MYC. USP22 not only reprogrammed androgen receptor function, but was sufficient to induce the transition to therapeutic resistance. Notably, in vivo depletion experiments revealed that USP22 is critical to maintain phenotypes associated with end-stage disease. This was a significant finding given clinical evidence that USP22 is highly deregulated in tumors, which have achieved therapeutic resistance. Taken together, our findings define USP22 as a critical effector of tumor progression, which drives lethal phenotypes, rationalizing this enzyme as an appealing therapeutic target to treat advanced disease.
Project description:Glioblastoma (GBM) is the most common and aggressive primary brain tumor with limited therapeutic options, possibly because of the highly tumorigenic subpopulations of stem cell-like cells. Mechanisms that sustain cancer stem cells are crucial to tumor progression. The polycomb group protein BMI1 (BMI1 proto-oncogene, polycomb ring finger) maintains cancer hallmarks including the glioblastoma stem-like cell (GSC) state. Ubiquitin-specific protease 22 (USP22) is highly expressed in and required for the maintenance of cancer stem cells (CSCs). Previously, we observed that forced expressed microRNA-218 in glioblastoma cells led to suppressed BMI1 expression. However, the pathways engaged by USP22 or driving BMI1 accumulation in GSCs remained elusive. Here, we found USP22 to be a novel deubiquitylase of BMI1. USP22 directly deubiquitylates and stabilizes BMI1. USP22 protein levels are elevated in tumor neurosphere. USP22 depletion induces BMI1 destabilization, and results in the inhibition of GSCs self-renewal by regulating a broad range of genes involved in glioma stemness and progression. Xenograft analyses using U87MG cells showed that both USP22 and BMI1 depletion attenuated tumor growth. Clinically, the expression levels of USP22 and BMI1 were positively correlated with those common targets like POSTN, HEY2, or PDGFRA and inversely correlated with ATF3 in human glioblastoma specimens. Taken together, our data reveals that USP22 functions as a novel deubiquitylase of BMI1 and inhibits self-renewal of GSCs by stabilizing BMI1. These findings also indicate that the USP22-BMI1 axis has a critical role in glioma tumorigenesis and that targeting the axis may provide a new therapeutic approach for human glioblastoma.
Project description:Ubiquitin-specific protease 22 (USP22) edits the histone code by deubiquitinating H2A and H2B as part of the mammalian SAGA (Spt-Ada-Gcn5) complex, and is required for transcriptional regulation and normal cell-cycle progression. Here, we show that USP22 affects the expression of p21 by altering far upstream element (FUSE)-binding protein 1 (FBP1) ubiquitination, as ablation of USP22 leads to increased FBP1 ubiquitination and decreased FBP1 protein occupancy at the p21 gene. Surprisingly, increased polyubiquitination of FBP1 does not alter its protein stability, but instead modulates the stable recruitment of FBP1 to target loci. Our results indicate a mechanism by which USP22 regulates cell proliferation and tumorigenesis.
Project description:Renal cell carcinoma (RCC) is one of the commonest urological tumors. The incidence of RCC ranks third among urological tumors, after prostate cancer and bladder tumors. However, the etiology of RCC remains unclear. Ubiquitin-specific protease 22 (USP22), a potential marker of cancer stem cells, is associated with the occurrence and progression of numerous tumors. However, the roles of USP22 in RCC have not yet been investigated. Survivin is a member of the inhibitor of apoptotic protein family involved in RCC progression. The present study first detected the expression of USP22 and survivin in RCC tissues using immunohistochemistry and western blotting. It was revealed that the protein levels of USP22 and survivin in RCC tissues were higher than those in adjacent normal renal tissue. Subsequently, it was demonstrated that USP22 knockdown inhibited the growth of an RCC cell line ACHN and downregulated the protein level of survivin, accompanied by an increased level of cleaved-caspase-3. By contrast, overexpression of USP22 promoted the growth of ACHN cells, upregulated the expression of survivin and decreased the level of cleaved-caspase-3. Notably, the changes in USP22 expression did not affect the SURVIVIN mRNA level. Finally, it was confirmed that USP22 interacted with survivin and stabilized it by downregulating its ubiquitination. The present results indicate that USP22 may regulate survivin via deubiquitination, thereby promoting the proliferation of RCC cells. The results of the current study suggest that USP22 may represent a novel therapeutic target for patients with RCC.
Project description:<i>Usp22</i> overexpression is observed in several human cancers and is correlated with poor patient outcomes. The molecular basis underlying this correlation is not clear. <i>Usp22</i> is the catalytic subunit of the deubiquitylation module in the SAGA histone-modifying complex, which regulates gene transcription. Our previous work demonstrated that the loss of <i>Usp22</i> in mice leads to decreased expression of several components of receptor tyrosine kinase and TGFβ signaling pathways. To determine whether these pathways are upregulated when <i>Usp22</i> is overexpressed, we created a mouse model that expresses high levels of <i>Usp22</i> in all tissues. Phenotypic characterization of these mice revealed over-branching of the mammary glands in females. Transcriptomic analyses indicate the upregulation of key pathways involved in mammary gland branching in mammary epithelial cells derived from the <i>Usp22</i>-overexpressing mice, including estrogen receptor, ERK/MAPK, and TGFβ signaling. However, <i>Usp22</i> overexpression did not lead to increased tumorigenesis in any tissue. Our findings indicate that elevated levels of <i>Usp22</i> are not sufficient to induce tumors, but it may enhance signaling abnormalities associated with oncogenesis.