Ubiquitin-Specific Protease 10: A New Target in Tumor Immune Escape

Abstract

Tumor immune escape is a major challenge in cancer treatment, and targeted immune escape therapy has become a key strategy for cancer treatment. As an important deubiquitinating enzyme, ubiquitin-specific protease 10 (USP10) participates in the process of tumor development by adjusting the balance between ubiquitination and deubiquitination of substrate proteins. Recently, USP10 has been shown to be closely related to tumor immune escape, where it serves to reduce the immunogenicity of tumor cells by stabilizing immune checkpoints and promotes tumor immune escape. In this review, we focus on the structural and functional characteristics of USP10 and elaborate on the biological function of USP10 in the occurrence and development of tumors, as well as its role in immune escape, including the regulation of immune checkpoints and the effect on immune cells in the immune microenvironment. It is possible to improve the efficacy of traditional cancer therapies by appropriately regulating the expression of USP10. The aim of this review is to provide a reference for further understanding the mechanism of tumor immune escape and the development of new tumor treatment methods.

Background

Ubiquitination is a reversible process in which deubiquitinating enzymes (DUBs) specifically hydrolyze small ubiquitin molecules from target proteins or precursor proteins by hydrolyzing peptide bonds, isopeptide bonds, or ester bonds at the carboxy-terminal of ubiquitin to protect target proteins from ubiquitin–proteasome degradation.^1,2 Ubiquitin-specific proteases are the largest subfamily of DUBs, comprising approximately 56 members; these enzymes are characterized by a catalytic core that is associated with ubiquitin binding (Figure 1).^3,4 USPs are involved in various intracellular life activities and are also closely related to human diseases, such as tumors and inflammation.^5,6 USP10, a member of the USP family, is a cysteine protease that is widely distributed in human tissues and has enormous significance in diverse cellular processes and various human diseases. ⁷ Studies have shown that USP10 acts as an anti-stress molecule in oxidative stress, viral infection, heat shock, and other stressful environments.^8,9 In terms of metabolism, USP10 regulates lipid formation, lactic acid production, and glycolysis gene expression. ¹⁰

Figure 1.

Schematic representation of the domain architectures of human USPs. The red arrow points to the specific structural composition of USP10

Tumor immune escape is a process by which tumor cells evade the recognition and attack of the immune system through a variety of mechanisms, which enables tumors to continue to grow and metastasize in the body. The mechanism of tumor immune escape is complex, involving changes in the characteristics of tumor cells, immunosuppression of the tumor microenvironment, and dysfunction of the host immune system. ¹¹ Among the many molecular mechanisms that affect tumor immune escape, the role of DUBs has gradually attracted attention.^12,13 As an important member of the DUB family, USP10 plays a key role in the process of tumor immune escape by deubiquitinating substrate proteins to regulate their stability, localization, and function.^14,15 An in-depth study of the mechanism of USP10 in tumor immune escape is crucial to elucidate the pathogenesis of tumors and develop new treatment strategies.

Biological Function of USP10

USP10, also known as UBPO, is located on chromosome 16q24.1 and contains 18 exons. ¹⁶ It comprises 798 amino acids with a relative molecular weight of 93 kDa. ¹⁷ Figure 1 shows the molecular structure of USP10 (red arrow). USP10 mainly consists of an Ataxin-2 C domain and a USP domain. ⁷ Ataxin-2 is a polyglutamine protein involved in biological processes such as RNA metabolism and cytoskeletal recombination. ¹⁸ The USP domain has a modified catalytic site on it and participates in the deubiquitination of various proteins. ¹⁹ USP10 is mainly located in the cytoplasm. It deubiquitinates various proteins in the cytoplasm, thereby regulating cell proliferation, cell cycle, cell apoptosis, autophagy, DNA damage repair, and other important physiological processes (Table 1). ⁵⁷ Based on its unique structural characteristics, the active pocket and amino acid segment of the catalytic domain of USP have become key targets for the design of small molecular inhibitors.

Table 1.

Role and Biological Function of USP10 in Various Types of Cancer

Role of USP10	Mechanism	Types	REF
Proliferation and metastasis	Suppression of USP10 accelerated the degradation of HDAC7 and weakened NSCLC growth	Non–small cell lung cancer	20
Proliferation and metastasis	USP10 inhibited YAP1 ubiquitination and degradation to promote Cyr61 expression, which induced immune escape and promoted the growth and metastasis of PAAD	Pancreatic adenocarcinoma	21
Proliferation, migration, and invasion	Loss of USP10 could restore the G3BP1-induced proliferation, migration, and invasion of ovarian cancer cells	Ovarian cancer	22
Proliferation and migration	USP10 could induce PCNA deubiquitination to promote hepatocellular carcinoma cell proliferation and migration	Hepatocellular carcinoma	23
Proliferation, migration, and cell cycle	USP10 was involved in vascular remodeling by directly promoting VSMC proliferation and migration via stabilization of Skp2 protein expression	Vascular smooth muscle cell	24
Proliferation	USP10 activated PTEN by preventing its K63-linked polyubiquitination mediated by TRIM25 and suppressed the Akt/mammalian target of the rapamycin signaling pathway, thereby inhibiting NSCLC proliferation	Non–small cell lung cancer	25
Proliferation and metastasis	NLRP7 deubiquitination by USP10 promotes tumor progression and tumor-associated macrophage polarization in colorectal cancer	Colorectal cancer	26
Proliferation	USP10 promoted the proliferation of hepatocellular carcinoma by deubiquitinating and stabilizing YAP/TAZ	Hepatocellular carcinoma	27
Metastasis	USP10 promoted hepatocellular carcinoma metastasis through deubiquitinating and stabilizing Smad4 protein	Hepatocellular carcinoma	28
Proliferation and cell cycle	Inhibition of USP10 suppressed the proliferation of chronic myeloid leukemia cells, which depended on the SKP2 status	Chronic myeloid leukemia	29
Proliferation, cell cycle, and apoptosis	Spautin-1(USP10 inhibitor) inhibited prostate cancer progression by inhibiting the EGFR pathway	Prostate cancer	30
Proliferation	TRAF4 promoted fibroblast proliferation in keloids by destabilizing p53 via interacting with USP10	Fibroblast	31
Proliferation	USP10 regulated MSI2 stability via deubiquitination and promoted tumor proliferation in colon cancer	Colon cancer	32
Proliferation, migration, and apoptosis	USP10 promoted proliferation and migration and inhibited the apoptosis of endometrial stromal cells in endometriosis by activating the Raf-1/MEK/ERK pathway	Endometrial stromal	33
Proliferation	Oncogene-induced senescence mediated by c-Myc requires USP10-dependent deubiquitination and stabilization of p14ARF	Foreskin fibroblasts, fetal lung	34
Proliferation	USP10 promoted cell survival and growth, dependent on G3BP2-mediated signaling	Prostate cancer	35
Proliferation	USP10 inhibited lung cancer cell growth and invasion by upregulating PTEN	Lung cancer	36
Proliferation and cell cycle	USP10 antagonized c-Myc transcriptional activation through sirtuin-6 (SIRT6) stabilization to suppress tumor formation	Colon cancer	37
Proliferation and cell cycle	USP10 was closely connected with RBM15 alterations, and cell cycles were regulated by it	Pancreatic adenocarcinoma	38
Cell cycle	USP10 directly interacted with EIF4G1, while acting as a negative regulator for EIF4G1-mediated functions	Lung cancer	39
Apoptosis and cell cycle	Suppression of the USP10/CCND1 axis induced glioblastoma cell apoptosis	Glioblastoma	40
Apoptosis and fibrosis	FSTL1 treatment ameliorated cardiac dysfunction in MI with co-existent T2DM, possibly through the inhibition of myocardial fibrosis and apoptosis by upregulating USP10/Notch1 signaling	Myocardium	41
Apoptosis	USP10 inhibited the dopamine-induced reactive oxygen species−dependent apoptosis of neuronal cells by stimulating the antioxidant Nrf2 activity	Parkinson’s disease	42
Apoptosis	USP10 abated LPS-induced renal tubular epithelial cell injury and apoptosis	Renal tubular epithelial	43
Apoptosis	FoxO4 negatively modulated USP10 transcription to aggravate the apoptosis via blocking the Hippo/YAP pathway	Cardiomyocyte	44
Apoptosis	USP10 inhibitor (Wu-5) enhanced acute myeloid leukemia (AML) cell death via inhibiting FLT3 and AMPK pathways	Acute myeloid leukemia	45
Apoptosis	USP10 suppressed inflammation and apoptosis through the inhibition of TAK1 signaling	Cerebral ischemia	46
Apoptosis	CNYP granule promoted apoptosis and inhibited inflammation in endometrial stromal cells by inhibiting USP10	Endometriosis	47
Apoptosis	USP10 inhibited apoptosis of long-term hematopoietic stem cells	Hematopoietic stem cells	48
Apoptosis	USP10 inhibited stress-induced ROS production and apoptosis in HTLV-1-infected T cells	Leukemia	8
Autophagy	USP10 promoted autophagy-related pathways and molecules and increased the synthesis of autophagosomes in NASH	Nonalcoholic steatohepatitis	49
Autophagy	USP10 predicted the prognosis of patients with osteosarcoma	Osteosarcoma	50
Autophagy	USP10 deubiquitinated LC3B to increase LC3B levels and autophagic activity	Human cell	51
Autophagy	The mammalian ortholog of yeast ATG6 (Beclin1) controlled the p53 levels by regulating the deubiquitination activity of USP10	Human cell	17
DNA damage repair	DnaK bound to USP10, reducing p53 stability and anticancer functions	Various types of cancer	52,53
DNA damage	USP10 deubiquitinated and stabilized MutS Homolog 2 to regulate cellular sensitivity to DNA damage	Lung cancer	54
DNA damage	USP10 led to persistent recruitment of mono-ubiquitinated PCNA and polymerase-η to nuclear foci, causing an increase in mutation frequency	HeLa cells	55
DNA damage	USP10 regulated p53 localization and stability by deubiquitinating p53	Clear cell carcinomas	56

The Role of USP10 in Cell Proliferation and Apoptosis

As an important tumor suppressor protein, p53 inhibits cell proliferation and tumor formation by promoting cell apoptosis.^58,59 In normal cells, p53 is ubiquitinated by interaction with the E3 ligase murine double minute 2 in the nucleus, then exported from the nucleus to the cytoplasm, and finally degraded by the proteasome, thereby promoting apoptosis.^56,60–62 Continuous degradation keeps the p53 protein at a low level.

Studies have shown that USP10 deubiquitinates and stabilizes p53 in the cytoplasm, enhances the function of p53, and enables p53 to re-enter the nucleus. ⁶³ In the case of DNA damage and ataxia-telangiectasia mutant (ATM) activation, USP10 is phosphorylated and accumulates in the nucleus. ⁵⁶ Moreover, USP10 knockout has been shown to inhibit colon cancer cell apoptosis by promoting wild-type p53 degradation. ⁵⁶ In addition, previous research has shown that USP10 knockout in HCT116 cells with wild-type p53 increased their proliferation, but USP10 knockout in HCT116 cells with p53 double deletion had no effect on their proliferation. ⁵⁶ USP10 has been found to promote cell proliferation in p53 mutant cells, but the specific molecular mechanism remains unclear. ⁶⁴ Another study revealed that USP10 regulated Musashi-2 (MSI2) stability via deubiquitination and promoted tumor proliferation in colon cancer. ³² These results demonstrate that USP10 stabilized the protein level of p53 in cells by deubiquitination of p53, thus enhancing the anticancer effect of wild-type p53 on cells and achieving the effect of inhibiting cell proliferation and apoptosis (Figure 2A). ⁵⁶ Currently, studies on the effect of USP10 on tumor cell proliferation and apoptosis mostly focus on the p53 protein pathway, which may also be related to the tumor suppressor effect of the p53 protein itself.

Figure 2.

The biological function of USP10. Some mechanistic pathways of USP10 in proliferation and apoptosis (A), cell cycle (B), autophagy (C), and DNA damage repair (D) pathways

The Role of USP10 in Cell Cycle

As a member of the histone deacetylase family, sirtuin-6 (SIRT6) is a tumor suppressor protein encoded by genes localized to telomeres in human cells. SIRT6 controls cellular senescence and telomere structure by deacetylating histone H3 lysine 9 (H3K9). ⁶⁵ Through proteomic analysis of SIRT6, some scholars found that USP10 deubiquitinated and stabilized SIRT6. ⁶⁶ In addition, the overexpression of USP10 or SIRT6 significantly reduced the G2/M and S phases and increased the G0/G1 phase of HCT116 colon cancer cells; the overexpression of USP10 and SIRT6 had a more significant effect on the cell cycle. ⁶⁷ The knockout of USP10 or SIRT6 promoted cell cycle progression by increasing S and G2/M phases, and the effect of the knockout of USP10 and SIRT6 was more obvious. ⁶⁷ The aforementioned information suggested that USP10 and SIRT6 synergistically regulated the cell cycle of colon cancer cells. ⁶⁷ Because SIRT6 performed its anticancer function by inhibiting the transcriptional activity of c-Myc, it regulated tumor cell cycle progression by regulating the expression levels of some key genes.^34,68 Subsequent experiments found that the overexpression of SIRT6 or p53 partially restored the interference of USP10 on the cell cycle, while the co-expression of p53 and SIRT6 completely restored the interference. Therefore, the researchers concluded that USP10 inhibited the cell cycle process by enhancing the SIRT6-and p53-mediated inhibition of c-Myc. ³⁷

A recent study showed that USP10 interacted with CCND1 and prevented the polymerization of its K48- but not K63-connections in glioblastoma U251 and HS683 cells, thereby increasing the stability of CCND1. ⁴⁰ In line with the effect of USP10 on CCND1, the USP10 knockdown of CCND1 resulted in glioblastoma multiforme (GBM) cell cycle arrest in the G1 phase and induced GBM cell apoptosis (Figure 2B). ⁴⁰ Despite its role as a double-edged sword in tumors, USP10 is widely recognized as an oncogene in several settings, driving the malignant progression of tumors by driving cell cycle progression.

The Role of USP10 in Autophagy

Autophagy is a basic metabolic mechanism that degrades unnecessary or abnormal cellular components through lysosomes, before recycling through autophagy. ⁶⁹ Vacuolar sorting protein 34 (Vps34) is an essential component of the PI3 kinase (PI3K) family and the only known PI3K class. Vps34 exists in mammalian cells in the form of complexes, including Vps complex 1 and Vps complex, and plays a central role in autophagosome formation and maturation.^70,71 Both complexes share a core component, Beclin1, which is an essential molecule in the formation of autophagosomes and can mediate the localization of other autophagic proteins to phagophores.^72–74 USP10 and USP13 regulate Vps34 complex–mediated autophagy through Beclin1 deubiquitination. ⁷⁵ However, some experiments have proven that Beclin1 interacts directly with USP13 and only indirectly or instantaneously with USP10. ⁷⁵ Moreover, downregulation of the Vps34 complex or Beclin1 reduced endogenous levels of USP10 and USP13. ⁷⁵ Further experiments revealed that USP13 deubiquitinated USP10, suggesting that Beclin1 and Vps34 also regulate USP10 activity by interacting with USP13, thus affecting autophagy. ⁷⁵ Furthermore, researchers have found that USP10 alleviated hepatic steatosis in patients with nonalcoholic steatohepatitis in an autophagy-dependent manner (Figure 2C). ⁴⁹ In general, USP10 interferes with the autophagy process of tumor cells mainly by regulating the autophagy initiation complex, stabilizing key proteins of autophagy nucleation, and interfering with autophagosome–lysosome fusion, thereby affecting the progression of tumor cells.

The Role of USP10 in DNA Damage Repair

The external environment and internal factors often lead to DNA molecular damage. After damage, certain mechanisms can restore DNA structure and function or improve the survival rate of damaged cells. ⁷⁶ In normal cells, USP10 is mostly located in the cytoplasm, where it deubiquitinates p53, which allows p53 to re-enter the nucleus. ⁷⁷ However, after DNA damage, USP10 is phosphorylated by activated ATM and transferred from the cytoplasm to accumulate in the nucleus, thereby stabilizing p53 in the nucleus. ⁵⁶ Therefore, USP10 is a necessary factor for p53 to participate in DNA damage repair. ⁵⁶ Moreover, USP10 interacts with MutS and deubiquitinates and stabilizes MutS homologous 2 to regulate cell sensitivity to DNA damage (Figure 2D). ⁵⁴ The genomic instability caused by DNA damage repair defects promotes the development of cancer and causes adverse outcomes such as tumor drug resistance. USP10 mediates tumor DNA damage repair through ubiquitination regulation and promotes tumor chemotherapy resistance, which provides a new idea for targeted tumor therapy.

USP10 and Tumor Immune Escape Mechanism

USP10 in Cancer Types

As a specific deubiquitination enzyme, USP10 plays a vital role in cell life activities, with its role in cancer attracting increasing attention in recent years. USP10 is involved in the occurrence and progression of various cancer types and is a potential molecular marker for cancer diagnosis and prognosis prediction (Figure 3). Next, we summarize the specific role and mechanistic pathway of USP10 in some cancers.

Figure 3.

Role and function of USP10 in various cancers

In addition, USP10 inhibits hepatic steatosis, insulin resistance, and inflammation through SIRT6. ⁶⁶ In the context of DNA damage, USP10 inhibits the activation of nuclear factor kappa B (NF-κB) and the production of inflammatory cytokines. ⁷⁸ In addition, as a DUB, USP10 has a crucial role in the development and progression of tumors. For example, USP10 inhibits the growth of cancer cells and tumor development by inhibiting the ubiquitination and protein degradation of p53 and SIRT6.^37,56 USP10 regulates the stability of KLF transcription factor 4 (KLF4) and suppresses lung tumorigenesis. ⁷⁹ The association of USP10 with GTPase-activating protein (SH3 domain)-binding protein 2 inhibits p53 signaling and contributes to poor outcome in prostate cancer. ⁷⁵ USP10 regulates MSI2 stability via deubiquitination and promotes tumor proliferation in colon cancer. ³² Herein, we evaluated USP10 expression in patients with different types of cancer according to the UALCAN Cancer Database. As shown in Figure 4A, esophageal carcinoma (ESCA) and liver hepatocellular carcinoma showed the highest and lowest USP10 expression, respectively. Furthermore, most cancerous tissues exhibit higher expression levels of USP10 than normal tissues. Among them, cholangiocarcinoma, ESCA, GBM, and pancreatic adenocarcinoma differ significantly from normal tissues (P < .05), suggesting that USP10 may be involved in the development of these tumors and that its inhibition may show better efficacy. The expression level of USP10 in DLBC, LAML, and PCPG cells is lower than that in normal tissues, which might be associated with the tumor-suppressor function of USP10 in these tumor types. For these tumors, up-regulating the expression of USP10 may lead to a better prognosis. (Figure 4B). Based on the GEPIA database Survival Analysis, USP10 expression in breast cancer (BRCA) and head and neck squamous cell carcinoma (HNSC) shows an inverse proportional relationship with the overall survival rate. In contrast, in kidney renal clear cell carcinoma (KIRC), USP10 expression is directly proportional to the overall survival rate, and these differences are statistically significant (P < .05) (Figure 4C). Whether USP10 plays a pro- or anti-tumor role is related to its expression level and downstream substrates in different tumors, which needs to be personalized designed in the treatment of tumors.

Figure 4.

The relationship of USP10 with tumors by bioinformatics. (A) The expression level of USP10 in different cancer types. (B) Comparison of USP10 expression between tumor and normal tissues. Blue columns stand for normal tissues. Red columns stand for cancerous tissues. (C) The relationship between USP10 and the overall survival rate of several types of tumors; BRCA, breast cancer; HNSC, head and neck squamous cell carcinoma; KIRC, kidney renal clear cell carcinoma; The data is sourced from the Gene Expression Profiling Interactive Analysis (GEPIA) database

Immune Checkpoint Proteins and USP10

Immune checkpoint proteins play a critical role in tumor immune escape, and USP10 has been found to regulate the expression and stability of multiple immune checkpoint proteins.

Regulation of PD-L1

In tumor cells, USP10 can interact with programmed death ligand 1 (PD-L1) to inhibit its degradation through deubiquitination, thereby upregulating its expression level. In prostate cancer studies, NDR1 hinders the ubiquitination and degradation of PD-L1 by increasing the interaction between USP10 and PD-L1, resulting in the abundant expression of PD-L1 on the surface of tumor cells (Figure 5). After binding to the programmed death receptor 1 (PD-1) on the surface of T cells, PD-L1 inhibits the activation and proliferation of T cells and promotes immune escape of prostate cancer cells. ¹⁴ In a study on esophageal cancer (EC), FOXP4-AS1 was found to stabilize PD-L1 through USP10, reduce PD-L1 ubiquitination, and promote immune escape of EC cells by hindering the function of CD8 + cytotoxic T lymphocytes (CTLs). ¹⁵ USP10 mainly maintains the protein stability of PD-L1 through deubiquitination, ultimately promoting tumor immune escape and influencing the response to immunotherapy. However, the specific molecular mechanism still needs to be further clarified, providing a theoretical basis for improving the efficacy of immunotherapy.

Figure 5.

The mutual regulatory relationship between USP10 and PD-1/PD-L1

Regulation of B7-H4

B7-H4, a coinhibitory B7 family ligand, is a key immune checkpoint that inhibits CD8 T cell activity. B7-H4 mRNA can be detected in multiple normal tissues, but protein levels are barely detectable in normal tissues; the inconsistency between B7-H4 mRNA and protein levels suggests that B7-H4 undergoes post-transcriptional modification. Studies have shown that B7-H4 can be glycosylated or ubiquitinated. ⁸⁰ Zeng et al discovered that in triple-negative breast cancer, USP10 acts as a critical DUB to suppress tumor immunogenicity by inhibiting autocrine motor factor receptor-mediated B7-H4 stabilization, which in turn mediates tumor immune escape by stabilizing protein expression. Inhibition of USP10 expression can reduce the stability of B7-H4, increase tumor immunogenicity, and enhance the ability of immune cells to recognize and kill tumor cells. ⁸¹ Currently, there are relatively few studies on USP10 and B7-H4. The immunotherapy for cold tumors based on these two factors has only been verified in breast cancer research. Further studies are needed to explore how they can overcome immune suppression and treat drug resistance.

Effect of USP10 on Immune Cell Function in the Tumor Microenvironment

The tumor microenvironment is a complex ecosystem of non-malignant components surrounding a tumor cell, including immune cells, stromal cells, and the factors produced and released by them. ⁸² Their functional status is crucial for tumor immune escape, and USP10 plays a regulatory role in it.

Effects on T Cell Function

T cells are involved in coordinating multiple aspects of adaptive immunity throughout life, including immune responses, homeostasis, and the establishment and maintenance of memory. ⁸³ USP10 indirectly affects the function of T cells through the expression of immune checkpoint proteins. USP10 can stabilize immune checkpoint proteins such as PD-L1, prevent their degradation, and promote the exhaustion of CD8 + CTLs while reducing their killing activity against tumor cells. ¹⁵ USP10 may also directly affect T cell differentiation and function through other pathways. Indeed, in some tumor models, aberrant expression of USP10 has been found to lead to an imbalance in T cell subsets, an increase in the proportion of regulatory T cells, and a decrease in the proportion of effector T cells with antitumor activity, thereby promoting tumor immune escape.

Effect on Macrophage Function

Macrophages are the main type of immune cells and play a crucial role in the tumor microenvironment. Macrophages mainly polarize into either the classically activated “M1” type, which promotes antitumor immune responses, or the selectively activated “M2” phenotype, which leads to immunosuppression and tumor development. ⁸⁴ The expression level of USP10 has been shown to correlate with the immunosuppressive M2 polarization of macrophages. Studies in colorectal cancer (CRC) have revealed that USP10 can interact with NLRP7 and catalyze its deubiquitination in CRC cells, which stabilizes NLRP7 and increases its protein level. NLRP3 promotes the secretion of CCL2 by activating the NF-κB signaling pathway, which further promotes the polarization of M2-like tumor macrophages. ²⁶ In addition, several studies have shown that USP10 inhibits YAP1 ubiquitination and degradation, enhances Cyr61 expression, and enhances M2 macrophage polarization in the tumor microenvironment, leading to immune escape and malignant development of pancreatic cancer cells. Knockdown of USP10 has been shown to increase the ubiquitination and degradation of YAP1 in pancreatic cancer cells, increase the proportion of M1-polarized macrophages, and decrease the proportion of M2-polarized macrophages. ⁸⁴ USP10, in different tumors or diseases, exerts its deubiquitination-stabilizing protein function by acting on different protein substrates. USP10 promotes the transformation of macrophages into M2-like cells and plays various roles, including facilitating tumor progression and alleviating disease.

Effect on Other Immune Cell Function

USP10 has also been discovered to exert an influence on other immune cells. For example, USP10 transcriptionally upregulates PD-L1 and galectin-9 (Gal-9) by deubiquitinating YAP1, desensitizing pancreatic ductal adenocarcinoma (PDAC) cells to NK cell-mediated cytotoxicity. ⁸⁵ The high expression of USP10 is also positively associated with neutrophils, dendritic cells, macrophages, etc. ⁸⁶ Currently, research on the impact of USP10 the functions of immune cells primarily focus on T cells and macrophages. Further in-depth studies on the effects of USP10 on other immune cells are needed to enhance the theoretical credibility.

The Current Status of Tumor Treatment Targeting USP10

In view of the key role of USP10 in tumor immune escape, targeting USP10 has become a popular research direction in tumor treatment. USP10 is overexpressed in various tumors and is closely related to a poor prognosis. Functionally, USP10, as an oncogene, can increase the proliferation and metastasis of tumor cells both in vivo and in vitro. ⁸⁷ Some small-molecule inhibitors targeting USP10 have been developed. These inhibitors can specifically inhibit the deubiquitination enzyme activity of USP10 and block its regulatory effect on substrate proteins. USP10 is overexpressed in osteosarcoma and significantly induces autophagy, cell proliferation, and invasion by enhancing ULK1 expression. Treatment with the USP10 inhibitor Spautin-1 inhibits the proliferation of osteosarcoma cells and increases their sensitivity to the chemotherapy drug cisplatin. Studies in an animal xenograft tumor model also revealed that using Spautin-1 to inhibit USP10 can slow tumor growth. ⁸⁸ However, many USP10 inhibitors are still in the research stage and need further optimization and improvement in terms of drug specificity, efficacy, and safety.

Therapeutic Potential of USP10 Inhibitors

It is currently understood that USP10 promotes the growth and progression of some tumors. ⁸⁹ USP10 can be used as a novel drug target for tumor therapy because it is involved in regulating tumor cell proliferation, apoptosis, and migration. As a result, some studies have been performed on USP10 inhibitors (Table 2). ²⁹ The small-molecule inhibitors of USP10 reported in recent years are summarized as follows:

Table 2.

Summary of Inhibitors Targeting USP10

Inhibitor	IC50 (μM)	Formula/weight	Structure	Mechanism	REF
Spautin-1	0.6-0.7	C15H11F2N3 271.26		Spautin-1 is a specific and potent autophagy inhibitor that inhibits USP10 and USP13	90
HBX19818	28.1	C25H28ClN3O 421.96		An inhibitor of deubiquitinase USP10 leads to the dual degradation of spleen tyrosine kinase and FLT3	91
Wu-5	3.7-8.3	C15H13NO7S 351.33		Wu-5 targets USP10 to inhibit downstream FLT3 signaling pathways	45
LY-2	10.87 ± 1.07	C28H26ClN3O3 488.17		LY-2 inhibits the proteasomal degradation of YAP and p53 mediated by USP10	92
F806		C28H38N2O6 498.61		Targeting the USP10-ANLN axis	93
Curcumin		C21H20O6 368.38		Curcumin promotes the expansion of mitochondria by targeting USP10	94
Quercetin		C15H10O7 302.24		Quercetin suppresses USP10 activity to abrogate T-bet upregulation	95

Spautin-1

Specific and potent autophagy interactivator-1 (spautin-1) is the most commonly used small-molecule inhibitor of USP10, which has a strong inhibitory effect on autophagy. Previous research has shown that spautin-1 regulates osteoclast formation by inhibiting autophagy induced by receptor activator for NF-kB and 1α,25-(OH)₂D₃. ⁹⁶ Furthermore, spautin-1 has been shown to alleviate acute pancreatitis in animal models established using the combination of frog skin peptide and lipopolysaccharide by inhibiting pancreatic cell autophagy. ⁹⁷ In tumors, spautin-1 enhances the sensitivity of osteosarcoma and chronic myeloid leukemia to chemotherapeutic agents by inhibiting autophagy. Spautin-1 also decreases cell survival and colony formation in osteosarcoma cells.^98,99 Most importantly, spautin-1 inhibits autophagy by interacting with USP10 and USP13 through the inhibition of Beclin-1 protein expression levels. Spautin-1 suppresses melanoma growth via ROS-mediated DNA damage and exhibits synergy with cisplatin.^100,101 Currently, there have been no reports on the efficacy of spautin-1 in vivo animal studies; thus, spautin-1 is still in preclinical development.

HBX19818

HBX19818 is another USP10 inhibitor. Originally thought to be an inhibitor of USP7, HBX19818 targets USP7 and reduces UV-induced phosphorylation of Chk1 and the levels of the checkpoint mediator Claspin. ¹⁰² Later, Yang et al found that HBX19818 leads to the dual degradation of spleen tyrosine kinase and FMS-like tyrosine kinase 3 (FLT3), resulting in the death of acute myeloid leukemia cells. ¹⁰³

Wu-5

Wu-5 is a little-known USP10 inhibitor. The kinase FLT3 internal tandem duplication (FLT3-ITD) is known to be associated with adverse clinical outcomes in AML. ¹⁰⁴ Wu-5 has been found to induce synergistic cell death in FLT3-ITD-positive cells by reducing FLT3 and AMP-activated protein kinase proteins. ⁴⁵ However, further in-depth research is still needed to explore the specific efficacy and clinical outcomes of Wu-5 in the treatment of human cancers.

LY-2

Dong et al developed the small molecular inhibitor LY-2 via structural optimization of the previously identified USP10 inhibitor D₂. By substituting the 1,2,4-oxadiazole moiety with an amide bond linkage, LY-2 exhibited substantially enhanced binding affinity for USP10 compared to its lead compound D₂. Comprehensive structure-activity relationship (SAR) analyses further validated its potential as a promising therapeutic candidate. Additionally, LY-2 is the first USP10 inhibitor to achieve nanomolar binding affinity. In liver cancer, LY-2 effectively inhibits the proteasomal degradation of downstream proteins YAP and p53 mediated by USP10, thereby leading to the subsequent downregulation of CDK4 in the p53 signaling pathway. ⁹² However, LY-2 has currently only been validated at the cellular level, and its activity in vivo animal models as well as clinical settings remains to be further confirmed.

F806

F806 is a natural macrolide compound isolated from the Chinese actinomycete strain FIM-04-806. It selectively targets the deubiquitinase USP10 and suppresses its catalytic activity, which disrupts the homeostasis of the USP10-Cdh1-ANLN complex, thereby exerting a potent inhibitory effect on cell cycle progression in esophageal squamous cell carcinoma (ESCC) cells. ⁹³ In addition, F806 has been shown to induce ESCC cell apoptosis through blocking the activation of integrin β1. ¹⁰⁵ Furthermore, it exerts anti-ESCC activity by facilitating the internalization of glucose transporter 1 and its subsequent degradation within autolysosomes. ⁹³

Other Inhibitors

Notably, several natural products and their derivatives also exert regulatory effects on USP10 activity. For example, curcumin induces mitochondrial expansion in breast cancer cells through targeting USP10. Specifically, silencing or inhibiting USP10 expression effectively abrogates curcumin-induced upregulation of polyubiquitinated proteins and CHOP, attenuates curcumin-mediated activation of ERK and JNK signaling pathways, and diminishes mitochondrial peroxide production, ultimately mitigating curcumin induced breast cancer cell death in a marked manner. ⁹⁴ Quercetin also exerts a distinct inhibitory effect on USP10. In the context of asthma, USP10 interacts with the transcription factor T-bet and sustains its structural stability via deubiquitination, thereby protecting T-bet from proteasomal degradation. As a key regulator of adaptive immunity, T-bet orchestrates Th1 immune responses by upregulating the expression of Th1-signature cytokines. Importantly, quercetin suppresses USP10 activity to abrogate T-bet upregulation, consequently mitigating asthmatic inflammation. Collectively, quercetin has been proven to be a potential anti-inflammatory drug in autoimmune diseases. ⁹⁵ However, currently the inhibitors of USP10 are only used in preclinical experiments, and there is still a long way to go before they can make a substantive contribution to human diseases.

To date, no new USP10 inhibitors have been reported. With the development of high-throughput proteomics technology, it is possible to screen specific substrates and specific deubiquitination sites of USP10 through various research methods and develop new specific inhibitors, providing new drugs for targeted therapy of tumors.

Conclusion and Prospect

As a member of the ubiquitin-specific protease family, USP10 affects the degradation and stability of substrate proteins by removing the substrate ubiquitin and participates in the whole process of tumor development, ⁹³ including regulating immune checkpoint proteins, regulating the infiltration of specific immune cell subsets, and affecting cell migration and invasion. Thus, USP10 can be used as a potential marker for tumor prognosis. Currently, research on USP10 in tumor immune escape has made some progress, but there remain many problems to be solved. In terms of basic research, it is still necessary to further clarify whether USP10 affects tumor immunity and progression through other pathways, and whether there are other unknown substrate proteins. In terms of clinical application, how to safely and effectively transfer USP10 targeted therapy strategies to cancer treatment remains a major challenge. In the future, it will be important to elucidate the mechanism of USP10 in tumors and conduct more clinical trials to evaluate its efficacy and safety in various tumors and patient populations. Furthermore, future research should explore the potential of a combined treatment approach involving USP10 modulation alongside chemotherapy, radiotherapy, targeted therapy, and immunotherapy. The ultimate goal is to create personalized treatment plans that consider the patient’s specific gene mutations and the unique characteristics of their immune microenvironment.

The Future Direction of Combination Therapy With USP10 Inhibitors

USP10 participates in crucial processes by regulating the stability of substrate proteins, including tumor proliferation, apoptosis, and microenvironment remodeling. Nevertheless, owing to its tumor-type-dependent bidirectionality, the monotherapy of USP10 inhibitors is restricted. Consequently, combination therapy has emerged as the core approach to overcome the bottleneck of USP10 monotherapy and enhance the anti-tumor efficacy. The following focuses on exploring the mechanism and development prospects of the combined application of USP10 inhibitors with immune checkpoint inhibitors and chemotherapy drugs. Research on the relationship between USP10 and immune checkpoint inhibitors has mainly focused on PD-L1 and B7-H4, and the specific mechanism have been comprehensively elaborated in the preceding content.^14,81 The mechanisms underlying the combined application of USP10 inhibitors and chemotherapeutic drugs primarily encompass the following aspects. USP10 promotes tumor resistance to chemotherapy by facilitating DNA damage repair. Inhibiting USP10 can enhance the efficacy of oxaliplatin in the chemotherapy of colorectal cancer.^100,101 USP10 can promote the migration and cisplatin resistance of esophageal squamous cell carcinoma (ESCC) through deubiquitination and stabilization of integrin β1/YAP. Deficiency of USP10 can significantly suppress the migratory ability and chemoresistance of ESCC cells. ¹⁰⁶ In the treatment of thyroid cancer, USP10 plays a unique role. Overexpression of USP10 suppresses the invasion, migration, and epithelial-mesenchymal transition (EMT) characteristics of doxorubicin-resistant (FTC133-DOX) cells, promotes cell apoptosis, and enhances the chemosensitivity of FTC133 cells to DOX treatment. ¹⁰⁷ Targeting USP10 can also generate a synergistic effect with anti-tumor drugs by amplifying the cytotoxicity of chemotherapy and optimizing the response to chemotherapy, thus overcoming drug resistance in tumors. In the future, more efforts should be made to focus on issues such as precise tumor classification and in-depth exploration of mechanisms, so as to promote the combination of USP10 inhibitors in clinical tumor treatment.

Potential Immunomodulatory Function of USP10: Potential Perspectives

Effective immunotherapy currently includes immune checkpoint blocking, chimeric antigen receptor-T cell, and natural killer cell therapy; however, patients with tumors still have low survival rates because most are diagnosed at an advanced stage due to non-specific symptoms and a lack of biomarkers, especially in the early stage of the disease. Thus, finding a valid target for tumors remains an urgent issue. ¹⁰⁸ USP10 affects oncogenic and tumor-suppressor signals, tumor immunogenicity, and immune cells and is involved in pro-tumor responses. Thus, USP10 inhibitors have important implications for the development and application of both epigenetic therapies and cancer immunotherapies, and combinations thereof.

Challenges in USP10 Inhibitors Development for Tumors Therapy

There are currently only a few available USP10 inhibitors, and none of them have entered clinical studies. In addition, USP10 inhibitors in combination with other compounds may be an effective way to treat tumors. However, there is a lack of compound combination therapy and exploration of combination mechanisms. Of course, it is also critical to improve the subtype selectivity of compounds.

In this paper, we have discussed the biological function of USP10 and its key role in tumor progression. Many detailed molecular mechanisms of USP10 in the context of tumorigenesis and development remain unclear. We have also summarized the current knowledge of USP10 inhibitors in treating tumors. USP10 has attracted attention in research on epigenetic regulation of tumor development because of its involvement in the whole progression of many tumors. With the advances in methods such as structural biology and computer-aided drug design, we hope that this review will encourage and accelerate advances in the continuing search for novel USP10 inhibitors for tumor therapy. Additionally, the application of USP10 as a target for tumor diagnosis and targeted therapy in clinical practice is expected in the future.

Appendix.

Abbreviations

PD-1

Programmed Death Receptor 1

PD-L1

Programmed Death Ligand 1

DUBs

Deubiquitinating Enzymes

USP

Ubiquitin-Specific Protease

MDM2

Murine Double Minute 2

ATM

Ataxia-Telangiectasia Mutant

PI3K

PI3 Kinase

SIRT6

Sirtuin-6

MSI2

Musashi-2

ESCA

Esophageal Carcinoma

LIHC

Liver Hepatocellular Carcinoma

CHOL

Cholangiocarcinoma

GBM

Glioblastoma Multiforme

PAAD

Pancreatic Adenocarcinoma

BRCA

Breast Carcinoma

HNSC

Head Neck Squamous Carcinoma

CRC

Colorectal Cancer.

ORCID iD

Xiaojing Li https://orcid.org/0009-0000-2013-9171

Ethical Considerations

This manuscript is a review article and does not involve a research protocol requiring approval by the relevant institutional review board or ethics committee.