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Abrogation of USP7 decreased PD-L1 expression in GC cells. (A) USP7 and PD-L1 expression in eight gastric cell lines. (B) PD-L1 expression in MFC and MGC-803 cells treated with Almac4 (5 mmol/L) for the indicated times. The values were normalized on PD-L1 expression in control samples. (C) PD-L1 expression in MGC-803 and MFC cells when USP7 was knocked down. The values were normalized on the PD-L1 expression in control samples. (D) PD-L1 expression in BGC-823, MGC-803, SGC-7901 and MFC cells in the presence of different concentrations of Almac4 for 4 days. The values were normalized on the PD-L1 expression in control samples. (E) FACS analysis for cell surface PD-L1 expression in MGC-803 USP7 KD cells or MGC-803, SGC-7901 and MFC cells treated with Almac4 (5 mmol/L). Data are shown as mean AE SD (n Z 3), n.s., not significant; *P < 0.05, **P < 0.01, ***P < 0.001. P values were calculated using two-tailed t-test statistical analysis.
Source publication
Targeting immune checkpoints such as programmed cell death protein 1 (PD-1) and programmed death ligand-1 (PD-L1) have been approved for treating melanoma, gastric cancer (GC) and bladder cancer with clinical benefit. Nevertheless, many patients failed to respond to anti-PD-1/PD-L1 treatment, so it is necessary to seek an alternative strategy for t...
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... there may be inter-regulation between USP7 and PD-L1. As PD-L1 is a transmembrane protein and USP7 distributes from nucleus to the cytoplasm as a deubiquitinase, USP7 was supposed as an upstream regulator of PD-L1. To study the regulation of USP7 on PD-L1, expressions of USP7 and PD-L1 were evaluated in eight gastric cell lines. As shown in Fig. 2A, USP7 was ubiquitously expressed in all tested cell lines and six GC cell lines express high amount of USP7 comparing with the cell line of normal gastric epithelium or GES-1. In addition, BGC-823, MGC-803, NCI-N87 and SGC-7901 cells lines expressed higher level of PD-L1 than other GC cell lines, while PD-L1 was absent in MKN45 cells. Among ...
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... than other GC cell lines, while PD-L1 was absent in MKN45 cells. Among these cell lines, MGC-803 cell line was chosen to explore the effect of endogenous USP7 on regulating PD-L1 expression due to its high expression of PD-L1 and USP7. Firstly, USP7 inhibitor Almac4 29 was applied to MGC-803 and mouse gastric cancer cell MFC. As indicated in Fig. 2B, when cells were treated with Almac4 to inhibit USP7 activity, expression of PD-L1 was decreased in both of the two cell lines in a timedependent manner (Fig. 2B). Moreover, to further verify these results, USP7 was knocked down in MGC-803 and MFC cell lines, and PD-L1 expression was significantly reduced compared to control cells ...
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... on regulating PD-L1 expression due to its high expression of PD-L1 and USP7. Firstly, USP7 inhibitor Almac4 29 was applied to MGC-803 and mouse gastric cancer cell MFC. As indicated in Fig. 2B, when cells were treated with Almac4 to inhibit USP7 activity, expression of PD-L1 was decreased in both of the two cell lines in a timedependent manner (Fig. 2B). Moreover, to further verify these results, USP7 was knocked down in MGC-803 and MFC cell lines, and PD-L1 expression was significantly reduced compared to control cells (Fig. 2C). Subsequently, BGC-823, MGC-803 and SGC-7901 cells were incubated with Almac4, and results in Fig. 2D suggest that Almac4 treatment decreased the total ...
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... in Fig. 2B, when cells were treated with Almac4 to inhibit USP7 activity, expression of PD-L1 was decreased in both of the two cell lines in a timedependent manner (Fig. 2B). Moreover, to further verify these results, USP7 was knocked down in MGC-803 and MFC cell lines, and PD-L1 expression was significantly reduced compared to control cells (Fig. 2C). Subsequently, BGC-823, MGC-803 and SGC-7901 cells were incubated with Almac4, and results in Fig. 2D suggest that Almac4 treatment decreased the total amount of PD-L1 in all these three cell lines in a dose-dependent way. Moreover, treatment of MFC with Almac4 also dramatically decreased mPD-L1 expression either (Fig. 2D). As PD-L1 ...
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... in both of the two cell lines in a timedependent manner (Fig. 2B). Moreover, to further verify these results, USP7 was knocked down in MGC-803 and MFC cell lines, and PD-L1 expression was significantly reduced compared to control cells (Fig. 2C). Subsequently, BGC-823, MGC-803 and SGC-7901 cells were incubated with Almac4, and results in Fig. 2D suggest that Almac4 treatment decreased the total amount of PD-L1 in all these three cell lines in a dose-dependent way. Moreover, treatment of MFC with Almac4 also dramatically decreased mPD-L1 expression either (Fig. 2D). As PD-L1 on membrane of cancer cells exhibits immunosuppressive effect through binding to PD-1 on activated T ...
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... to control cells (Fig. 2C). Subsequently, BGC-823, MGC-803 and SGC-7901 cells were incubated with Almac4, and results in Fig. 2D suggest that Almac4 treatment decreased the total amount of PD-L1 in all these three cell lines in a dose-dependent way. Moreover, treatment of MFC with Almac4 also dramatically decreased mPD-L1 expression either (Fig. 2D). As PD-L1 on membrane of cancer cells exhibits immunosuppressive effect through binding to PD-1 on activated T cells 38 , whether USP7 positively regulates membrane PD-L1 remains unclear. Results in Fig. 2E reveal that the amount of membrane PD-L1 was lower than that in parental cells for MGC-803 cells when USP7 was abrogated ...
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... these three cell lines in a dose-dependent way. Moreover, treatment of MFC with Almac4 also dramatically decreased mPD-L1 expression either (Fig. 2D). As PD-L1 on membrane of cancer cells exhibits immunosuppressive effect through binding to PD-1 on activated T cells 38 , whether USP7 positively regulates membrane PD-L1 remains unclear. Results in Fig. 2E reveal that the amount of membrane PD-L1 was lower than that in parental cells for MGC-803 cells when USP7 was abrogated genetically or pharmacologically in the presence of Almac4, respectively (Fig. 2E). Likewise, in the presence of Almac4, amount of membrane of PD-L1 was decreased in SGC-7901 and MFC cells (Fig. 2E). Meanwhile, in ...
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... effect through binding to PD-1 on activated T cells 38 , whether USP7 positively regulates membrane PD-L1 remains unclear. Results in Fig. 2E reveal that the amount of membrane PD-L1 was lower than that in parental cells for MGC-803 cells when USP7 was abrogated genetically or pharmacologically in the presence of Almac4, respectively (Fig. 2E). Likewise, in the presence of Almac4, amount of membrane of PD-L1 was decreased in SGC-7901 and MFC cells (Fig. 2E). Meanwhile, in the presence of P5091, another USP7 inhibitor, amount of membrane of PD-L1 also decreased in MGC-803 and BGC-823 cells (Supporting Information Fig. S2). All these results indicate that USP7 abrogation can ...
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... remains unclear. Results in Fig. 2E reveal that the amount of membrane PD-L1 was lower than that in parental cells for MGC-803 cells when USP7 was abrogated genetically or pharmacologically in the presence of Almac4, respectively (Fig. 2E). Likewise, in the presence of Almac4, amount of membrane of PD-L1 was decreased in SGC-7901 and MFC cells (Fig. 2E). Meanwhile, in the presence of P5091, another USP7 inhibitor, amount of membrane of PD-L1 also decreased in MGC-803 and BGC-823 cells (Supporting Information Fig. S2). All these results indicate that USP7 abrogation can decrease the expression level of PD-L1 in GC ...
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... in the presence of Almac4, amount of membrane of PD-L1 was decreased in SGC-7901 and MFC cells (Fig. 2E). Meanwhile, in the presence of P5091, another USP7 inhibitor, amount of membrane of PD-L1 also decreased in MGC-803 and BGC-823 cells (Supporting Information Fig. S2). All these results indicate that USP7 abrogation can decrease the expression level of PD-L1 in GC cells. ...
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... which patient may be benefit from PD-1/PD-L1 targeting therapy 56 , findings of new drug or combinational therapy approaches that modulate the tumor microenvironment to promote antitumor immunity are in urgent 6,57 . In this study, abrogation of USP7 reduced the expression of PD-L1 in a dose-and timedependent manner in GC cells and results in Fig. 2B show that it took 48 h to decrease expression of PD-L1. We supposed that USP7 may stabilize PD-L1 in an indirect manner although USP7 can interact with PD-L1 directly. These results demonstrate that abrogation of USP7 increased PD-L1 polyubiquitinaion, decreased the PD-1/PD-L1 interaction and sensitized gastric cancer cells to T ...
Citations
... Additionally, USP7 inhibitors reduced cell growth by stabilizing p53 in gastric cancer. USP7 inhibitors not only hinder the cell proliferation but also reduce PD-L1 levels, thereby boosting the anti-tumor immune response (113). USP7 reprogrammed tumor-associated macrophages and modulates antitumor immune response in lung cancer. ...
Immunotherapy has been developed, which harnesses and enhances the innate powers of the immune system to fight disease, particularly cancer. PD-1 (programmed death-1) and PD-L1 (programmed death ligand-1) are key components in the regulation of the immune system, particularly in the context of cancer immunotherapy. PD-1 and PD-L1 are regulated by PTMs, including phosphorylation, ubiquitination, deubiquitination, acetylation, palmitoylation and glycosylation. PROTACs (Proteolysis Targeting Chimeras) are a type of new drug design technology. They are specifically engineered molecules that target specific proteins within a cell for degradation. PROTACs have been designed and demonstrated their inhibitory activity against the PD-1/PD-L1 pathway, and showed their ability to degrade PD-1/PD-L1 proteins. In this review, we describe how PROTACs target PD-1 and PD-L1 proteins to improve the efficacy of immunotherapy. PROTACs could be a novel strategy to combine with radiotherapy, chemotherapy and immunotherapy for cancer patients.
... Its involvement in numerous substrates linked to cancer progression renders it a potential therapeutic target [89]. Recent studies have highlighted the positive association between USP7 expression and PD-L1 protein levels in gliomas and gastric cancer [90,91]. ...
... Similarly, USP7 directly interacts with PD-L1 in GC, enhancing its stability and affecting cancer cell proliferation. Silencing USP7 leads to decreased PD-L1 expression and increased T-cell-mediated cancer cell destruction [91]. These findings indicate the potential of USP7 inhibition in cancer treatment, particularly in strategies targeting the PD-L1/PD-1 pathway. ...
... This results in improved breakdown of PD-L1 and an increase in T-cell-killing activity. Additionally, the emergence of novel therapeutic strategies, including small-molecule inhibitors that focus on blocking PD-L1 deubiquitination, particularly those targeting USPs [91,94,97,117], and the use of proteolysis-targeting chimeras (PROTACs) and the development of antibody-based PROTACs (AbTACs) designed to control PD-L1 ubiquitination [118][119][120][121], marks a significant transformation in cancer therapy approaches (Table 3). These strategies could offer a dual advantage: directly modulating PD-L1 levels and function and potentially circumventing resistance mechanisms that have been a significant hurdle in cancer immunotherapy. ...
Programmed death ligand 1 (PD-L1) plays a pivotal role in cancer immune evasion and is a critical target for cancer immunotherapy. This review focuses on the regulation of PD-L1 through the dynamic processes of ubiquitination and deubiquitination, which are crucial for its stability and function. Here, we explored the intricate mechanisms involving various E3 ubiquitin ligases and deubiquitinating enzymes (DUBs) that modulate PD-L1 expression in cancer cells. Specific ligases are discussed in detail, highlighting their roles in tagging PD-L1 for degradation. Furthermore, we discuss the actions of DUBs that stabilize PD-L1 by removing ubiquitin chains. The interplay of these enzymes not only dictates PD-L1 levels but also influences cancer progression and patient response to immunotherapies. Furthermore, we discuss the therapeutic implications of targeting these regulatory pathways and propose novel strategies to enhance the efficacy of PD-L1/PD-1-based therapies. Our review underscores the complexity of PD-L1 regulation and its significant impact on the tumor microenvironment and immunotherapy outcomes.
... colon cancer and B16-F10 melanoma cancer cells ( Supplementary Fig. 9c−e). At least five DUBs were reported to stabilize PD-L1 in different cancers, including USP7, USP9X, USP22, CSN5 and OTUB1 23,[37][38][39][40] . Although USP7, USP22 and OTUB1 played a certain role in the regulation of PD-L1 in NCI-H358 cells and USP22 slightly regulated PD-L1 abundance in SK-MES-1 cells, we found that OTUB2 had the most significant impact on the regulation of PD-L1 both in NCI-H358 and SK-MES-1 lung cancer cells ( Fig. 3g and Supplementary Fig. 10a−g). ...
... In fact, PD-L1 protein stability is maintained at multiple levels of complex regulation, including specific E3 ligases, DUBs, proteases, glycosylases and regulators of the proteasome and lysosomes 48 . Previous studies demonstrated that USP7, USP9X and USP22 stabilize PD-L1 in gastric cancer, oral squamous cell carcinoma or liver cancer, respectively [38][39][40] . The regulation of PD-L1 degradation by CSN5 or OTUB1 is mainly found in breast cancer 23,37 . ...
PD-1 is a co-inhibitory receptor expressed by CD8⁺ T cells which limits their cytotoxicity. PD-L1 expression on cancer cells contributes to immune evasion by cancers, thus, understanding the mechanisms that regulate PD-L1 protein levels in cancers is important. Here we identify tumor-cell-expressed otubain-2 (OTUB2) as a negative regulator of antitumor immunity, acting through the PD-1/PD-L1 axis in various human cancers. Mechanistically, OTUB2 directly interacts with PD-L1 to disrupt the ubiquitination and degradation of PD-L1 in the endoplasmic reticulum. Genetic deletion of OTUB2 markedly decreases the expression of PD-L1 proteins on the tumor cell surface, resulting in increased tumor cell sensitivity to CD8⁺ T-cell-mediated cytotoxicity. To underscore relevance in human patients, we observe a significant correlation between OTUB2 expression and PD-L1 abundance in human non-small cell lung cancer. An inhibitor of OTUB2, interfering with its deubiquitinase activity without disrupting the OTUB2-PD-L1 interaction, successfully reduces PD-L1 expression in tumor cells and suppressed tumor growth. Together, these results reveal the roles of OTUB2 in PD-L1 regulation and tumor evasion and lays down the proof of principle for OTUB2 targeting as therapeutic strategy for cancer treatment.
... Furthermore, USP7 inhibitors have also shown the capability to promote the degradation of PD-L1 in gastric cancer cells, leading to enhanced antitumor immune responses. 103 This involvement of USP7 in cancer immunotherapy further supports the notion that USP7 inhibitors could be of great benefit in the treatment of cancer. ...
The ubiquitin‐proteasome system assumes a critical role in numerous cellular processes, and among its components, deubiquitinases (DUBs) have emerged as essential regulators. With roughly 100 DUBs encoded within the human genome, these enzymes can be categorized into two main types: cysteine protease DUBs and metalloproteinase DUBs, based on the catalytic mechanism of the active site. DUBs exert significant influence over specific substrates implicated in cancer progression, establishing them as closely associated with various malignancies, including breast carcinoma, prostate cancer, and chronic myeloid leukemia. Consequently, the targeted inhibition of DUBs presents an enticing therapeutic strategy for cancer treatment. Here, we delve into the functional roles of DUBs in different cancer types and provide a thorough overview of the anticancer properties exhibited by DUB inhibitors. This knowledge will propel the development and clinical application of DUB inhibitors, opening promising avenues for tumor treatment.
... In several types of cancer, such as gastric tumors, overexpression of USP7 has been observed, and its expression levels exhibit a positive relevance to PD-L1 expression [60]. Hence USP7 may assist in stabilizing PD-L1 protein levels, potentially playing a role in tumor immune evasion. ...
... More important, USP7 inhibition was capable of potentiating the efficacy exhibited by the adenovirus-based tumor vaccine and the anti-PD-1 monoclonal antibody therapy in mice with TC1 lung tumor [57]. Almac4 as another critical USP7 inhibitor, has been demonstrated to decrease tumor cell membrane PD-L1 levels, to attenuate the interaction between PD-L1 and PD-1, then making GC cells more sensitive to cytotoxicity mediated by T cells [60] (Fig. 1C). ...
... Inhibiting these USP members sensitizes tumor cells to immunosurveillance and enhances anti-PD-L1/ anti-PD-1 therapy efficacy. The typical USP inhibitors, such as P5091 and WP1130, have been reported to promote anti-PD-1/PD-L1 therapeutic efficacy through significantly inhibiting the deubiquitination of PD-L1 [60,164]. However, such regulatory and therapeutic effects are not unique, and opposite results have been found. ...
Tumors have evolved in various mechanisms to evade the immune system, hindering the antitumor immune response and facilitating tumor progression. Immunotherapy has become a potential treatment strategy specific to different cancer types by utilizing multifarious molecular mechanisms to enhance the immune response against tumors. Among these mechanisms, the ubiquitin–proteasome system (UPS) is a significant non-lysosomal pathway specific to protein degradation, regulated by deubiquitinating enzymes (DUBs) that counterbalance ubiquitin signaling. Ubiquitin-specific proteases (USPs), the largest DUB family with the strongest variety, play critical roles in modulating immune cell function, regulating immune response, and participating in antigen processing and presentation during tumor progression. According to recent studies, the expressions of some USP family members in tumor cells are involved in tumor immune escape and immune microenvironment. This review explores the potential of targeting USPs as a new approach for cancer immunotherapy, highlighting recent basic and preclinical studies investigating the applications of USP inhibitors. By providing insights into the structure and function of USPs in cancer immunity, this review aims at assisting in developing new therapeutic approaches for enhancing the immunotherapy efficacy.
... More recently, it was reported that ectopic expression of USP51 was able to induce chemoresistant phenotypes, such as DNA damage response, in certain cancer cells [60]. In addition, another deubiquitinase ubiquitin specific peptidase 7 (USP7) had been identified to regulate PD-L1 protein stabilization in gastric cancer [61]. Targeting USP7 with its small molecule inhibitors sensitized cancer cells to T cell-induced destruction by diminishing cell surface PD-L1 content while decreasing its association with PD-1. ...
Background:
Programmed death ligand 1 (PD-L1) has been demonstrated to facilitate tumor progression and therapeutic resistance in an immune-independent manner. Nevertheless, the function and underlying signaling network(s) of cancer cell-intrinsic PD-L1 action remain largely unknown. Herein, we sought to better understand how ubiquitin-specific peptidase 51 (USP51)/PD-L1/integrin beta-1 (ITGB1) signaling performs a cell-intrinsic role in mediating chemotherapeutic resistance in non-small cell lung cancer (NSCLC).
Methods:
Western blotting and flow cytometry were employed for PD-L1 detection in NSCLC cell lines. Coimmunoprecipitation and pulldown analyses, protein deubiquitination assay, tissue microarray, bioinformatic analysis and molecular biology methods were then used to determine the significance of PD-L1 in NSCLC chemoresistance and associated signaling pathways in several different cell lines, mouse models and patient tissue samples. Ubiquitin-7-amido-4-methylcoumarin (Ub-AMC)-based deubiquitinase activity, cellular thermal shift and surface plasmon resonance (SPR) analyses were performed to investigate the activity of USP51 inhibitors.
Results:
We provided evidence that cancer cell-intrinsic PD-L1 conferred the development of chemoresistance by directly binding to its membrane-bound receptor ITGB1 in NSCLC. At the molecular level, PD-L1/ITGB1 interaction subsequently activated the nuclear factor-kappa B (NF-κB) axis to elicit poor response to chemotherapy. We further determined USP51 as a bona fide deubiquitinase that targeted the deubiquitination and stabilization of the PD-L1 protein in chemoresistant NSCLC cells. Clinically, we found a significant direct relationship between the USP51, PD-L1 and ITGB1 contents in NSCLC patients with chemoresistant potency. The elevated USP51, PD-L1 and ITGB1 levels were strongly associated with worse patient prognosis. Of note, we identified that a flavonoid compound dihydromyricetin (DHM) acted as a potential USP51 inhibitor and rendered NSCLC cells more sensitive to chemotherapy by targeting USP51-dependent PD-L1 ubiquitination and degradation in vitro and in vivo.
Conclusions:
Together, our results demonstrated that the USP51/PD-L1/ITGB1 network potentially contributes to the malignant progression and therapeutic resistance in NSCLC. This knowledge is beneficial to the future design of advanced cancer therapy.
... Similarly, USP7 expression is upregulated and positively associated with PD-L1 in gastric cancer. Silencing USP7 decreases PD-L1 expression on cell surfaces, and augments the T cell-mediated killing of cancer cells (19). However, the regulatory relationship between USP7 and PD-L1 appears to be context-dependent. ...
Immune evasion is essential for carcinogenesis and cancer progression. Programmed death-ligand 1 (PD-L1), a critical immune checkpoint molecule, interacts with programmed death receptor-1 (PD-1) on immune cells to suppress anti-tumor immune responses. In the past decade, antibodies targeting PD-1/PD-L1 have tremendously altered cancer treatment paradigms. Post-translational modifications have been reported as key regulators of PD-L1 expression. Among these modifications, ubiquitination and deubiquitination are reversible processes that dynamically control protein degradation and stabilization. Deubiquitinating enzymes (DUBs) are responsible for deubiquitination and have emerged as crucial players in tumor growth, progression, and immune evasion. Recently, studies have highlighted the participation of DUBs in deubiquitinating PD-L1 and modulating its expression. Here, we review the recent developments in deubiquitination modifications of PD-L1 and focus on the underlying mechanisms and effects on anti-tumor immunity.
... One study revealed that PD-L1 expression was positively associated with USP7 levels in gastric cancer patients. USP7 directly bound to PD-L1 and stabilize it (129). Abrogation of USP7 impaired the interaction between PD-1 and PD-L1, leading to sensitization of cancer cells to T cell killing in cancer cells and in mice. ...
... Abrogation of USP7 impaired the interaction between PD-1 and PD-L1, leading to sensitization of cancer cells to T cell killing in cancer cells and in mice. In addition, inhibition of USP7 by its inhibitor reduced cell proliferation due to p53 stabilization in gastric cancer cells (129). Hence, USP7 suppression by its inhibitors not only blocked gastric tumor cell proliferation but also inhibit the expression of PD-L1 to improve anti-cancer immune response in gastric cancer (129). ...
... In addition, inhibition of USP7 by its inhibitor reduced cell proliferation due to p53 stabilization in gastric cancer cells (129). Hence, USP7 suppression by its inhibitors not only blocked gastric tumor cell proliferation but also inhibit the expression of PD-L1 to improve anti-cancer immune response in gastric cancer (129). It is required to explore whether USP7 inhibitors could enhance the immune response of bladder cancer. ...
Bladder cancer is one of the common malignant urothelial tumors. Post-translational modification (PTMs), including ubiquitination, acetylation, methylation, and phosphorylation, have been revealed to participate in bladder cancer initiation and progression. Ubiquitination is the common PTM, which is conducted by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin-protein ligase. E3 ubiquitin ligases play a key role in bladder oncogenesis and progression and drug resistance in bladder cancer. Therefore, in this review, we summarize current knowledge regarding the functions of E3 ubiquitin ligases in bladder cancer development. Moreover, we provide the evidence of E3 ubiquitin ligases in regulation of immunotherapy in bladder cancer. Furthermore, we mention the multiple compounds that target E3 ubiquitin ligases to improve the therapy efficacy of bladder cancer. We hope our review can stimulate researchers and clinicians to investigate whether and how targeting E3 ubiquitin ligases acts a novel strategy for bladder cancer therapy.
... USP7 has received extensive attention and been the subject of much research in recent due to its role in the pathogenesis and progression of various diseases (such as tumors and inflammation) [26][27][28]. Previous studies have clearly shown that USP7 plays an important role in the regulation of bone remodeling [29]. ...
Background:
Abnormal osteoclast and osteoblast differentiation is an essential pathological process in osteoporosis. As an important deubiquitinase enzyme, ubiquitin-specific peptidase 7 (USP7) participates in various disease processes through posttranslational modification. However, the mechanism by which USP7 regulates osteoporosis remains unknown. Herein, we aimed to investigate whether USP7 regulates abnormal osteoclast differentiation in osteoporosis.
Methods:
The gene expression profiles of blood monocytes were preprocessed to analyze the differential expression of USP genes. CD14+ peripheral blood mononuclear cells (PBMCs) were isolated from whole blood collected from osteoporosis patients (OPs) and healthy donors (HDs), and the expression pattern of USP7 during the differentiation of CD14+ PBMCs into osteoclasts was detected by western blotting. The role of USP7 in the osteoclast differentiation of PBMCs treated with USP7 siRNA or exogenous rUSP7 was further investigated by the F-actin assay, TRAP staining and western blotting. Moreover, the interaction between high-mobility group protein 1 (HMGB1) and USP7 was investigated by coimmunoprecipitation, and the regulation of the USP7-HMGB1 axis in osteoclast differentiation was further verified. Osteoporosis in ovariectomized (OVX) mice was then studied using the USP7-specific inhibitor P5091 to identify the role of USP7 in osteoporosis.
Results:
The bioinformatic analyses and CD14+ PBMCs from osteoporosis patients confirmed that the upregulation of USP7 was associated with osteoporosis. USP7 positively regulates the osteoclast differentiation of CD14+ PBMCs in vitro. Mechanistically, USP7 promoted osteoclast formation by binding to and deubiquitination of HMGB1. In vivo, P5091 effectively attenuates bone loss in OVX mice.
Conclusion:
We demonstrate that USP7 promotes the differentiation of CD14+ PBMCs into osteoclasts via HMGB1 deubiquitination and that inhibition of USP7 effectively attenuates bone loss in osteoporosis in vivo.The translational potential of this article:The study reveals novel insights into the role of USP7 in the progression of osteoporosis and provides a new therapeutic target for the treatment of osteoporosis.
... It is worth noting how DUBs reversely regulate PD-L1 polyubiquitination. Among them, USP9X, CSN5, USP22 and USP7 are responsible for the deubiquitination and stabilization of PD-L1 in tumor cells [98][99][100][101]. As a mechanism by which TNF-α inhibits T-cell surveillance, the TNF-α-activated transcription factor p65 mediates the transcriptional activation of CSN5, thereby inhibiting the ubiquitination and proteolysis of PD-L1 [99]. ...
Tumor development relies on a complex and aberrant tissue environment in which cancer cells receive the necessary nutrients for growth, survive through immune escape, and acquire mesenchymal properties that mediate invasion and metastasis. Stromal cells and soluble mediators in the tumor microenvironment (TME) exhibit characteristic anti-inflammatory and protumorigenic activities. Ubiquitination, which is an essential and reversible posttranscriptional modification, plays a vital role in modulating the stability, activity and localization of modified proteins through an enzymatic cascade. This review was motivated by accumulating evidence that a series of E3 ligases and deubiquitinases (DUBs) finely target multiple signaling pathways, transcription factors and key enzymes to govern the functions of almost all components of the TME. In this review, we systematically summarize the key substrate proteins involved in the formation of the TME and the E3 ligases and DUBs that recognize these proteins. In addition, several promising techniques for targeted protein degradation by hijacking the intracellular E3 ubiquitin-ligase machinery are introduced.
