Emerging role of ubiquitin-specific protease 14 in oncogenesis and development of tumor: Therapeutic implication

USP14 deficiency inhibits neointima formation following vascular injury via degradation of Skp2 protein

Ubiquitin-proteasome system (UPS) is involved in vascular smooth muscle cell (VSMC) proliferation. Deubiquitinating enzymes (DUBs) have an essential role in the UPS-regulated stability of the substrate; however, the function of DUBs in intimal hyperplasia remains unclear. We screened DUBs to identify a protein responsible for regulating VSMC proliferation and identified USP14 protein that mediates cancer development, inflammation, and foam cell formation. USP14 promotes human aortic smooth muscle cell and A7r5 cell growth in vitro, and its inhibition or deficiency decreases the intimal area in the mice carotid artery ligation model. In addition, USP14 stabilizes Skp2 expression by decreasing its degradation, while Skp2 overexpression rescues USP14 loss-induced issues. The current findings suggested an essential role of USP14 in the pathology of vascular remodeling, deeming it a promising target for arterial restenosis therapy.

Ubiquitin-specific protease 14 targets PFKL-mediated glycolysis to promote the proliferation and migration of oral squamous cell carcinoma

Aberrant upregulation of the ubiquitin-specific protease 14 (USP14) has been found in some malignant tumors, including oral squamous cell carcinoma (OSCC). In this study, we further demonstrated that aberrantly overexpressed USP14 was also closely related to adverse clinicopathological features and poor prognosis in patients with OSCC, so we hypothesized that USP14 might act as a tumor-promoting factor during the progression of OSCC. Notably, we originally proved that USP14 is a deubiquitinating enzyme for phosphofructokinase-1 liver type (PFKL), a key rate-limiting enzyme involved in the glycolytic pathway. USP14 interacts with PFKL and enhances its stability through deubiquitination in OSCC cells, which in turn enhances PFKL-mediated glycolytic metabolism and ultimately promote cellular proliferation, migration, and tumorigenesis. In this work, we have also demonstrated for the first time that USP14 is a critical regulator of glycolysis in OSCC and verified a novel mechanism whereby it is involved in tumor metastasis and growth. Collectively, our findings provide novel insights into the tumor-promoting role of USP14 and establish mechanistic foundations for USP14-targeting therapies.

Comprehensive analysis of the role of ubiquitin-specific peptidases in colorectal cancer: A systematic review

BACKGROUND

Colorectal cancer (CRC) is the third most frequent and the second most fatal cancer. The search for more effective drugs to treat this disease is ongoing. A better understanding of the mechanisms of CRC development and progression may reveal new therapeutic strategies. Ubiquitin-specific peptidases (USPs), the largest group of the deubiquitinase protein family, have long been implicated in various cancers. There have been numerous studies on the role of USPs in CRC; however, a comprehensive view of this role is lacking.

AIM

To provide a systematic review of the studies investigating the roles and functions of USPs in CRC.

METHODS

We systematically queried the MEDLINE (via PubMed), Scopus, and Web of Science databases.

RESULTS

Our study highlights the pivotal role of various USPs in several processes implicated in CRC: Regulation of the cell cycle, apoptosis, cancer stemness, epithelial-mesenchymal transition, metastasis, DNA repair, and drug resistance. The findings of this study suggest that USPs have great potential as drug targets and noninvasive biomarkers in CRC. The dysregulation of USPs in CRC contributes to drug resistance through multiple mechanisms.

CONCLUSION

Targeting specific USPs involved in drug resistance pathways could provide a novel therapeutic strategy for overcoming resistance to current treatment regimens in CRC.

Proliferation and migration of ML1 follicular thyroid cancer cells are inhibited by IU1 targeting USP14: role of proteasome and autophagy flux

USP14 is a deubiquitinating enzyme involved in protein degradation by interacting with the proteasome and removal of poly-ubiquitin chains on target proteins. USP14 can influence cellular processes such as cell survival, DNA repair, ER stress, endocytosis, and the inflammatory response. USP14 further plays a role in tumor growth, and the inhibition of USP14 by compounds such as IU1 may affect cancer cell migration and invasion. Here we have studied the mechanisms for the action of IU1 in ML1 follicular thyroid cancer cells, comparing them with control, primary thyroid cells. Treatment with IU1 reduced proliferation of ML1 cells in a concentration-dependent manner, and more prominently than in control cells. IU1 decreased basal migration of ML1 cells, and after stimulation of cells with the bioactive compound, sphingosine-1-phosphate. The sphingosine-1-phosphate receptor 3 was increased in ML1 cells as compared with control thyroid cells, but this was not influenced by IU1. Further studies on the mechanism, revealed that IU1 enhanced the proteasome activity as well as LC3B-dependent autophagy flux in ML1 cells with an opposite effect on control thyroid cells. This indicates that IU1 elicits a cell-type dependent autophagy response, increasing it in ML1 cancer cells. The IU1-mediated stimulation of autophagy and proteasomes can likely contribute to the reduced cell proliferation and migration observed in ML1 cells. The precise set of proteins affected by IU1 in ML1 thyroid and other cancer cells warrant further investigations.

USP14 inhibition regulates tumorigenesis by inducing apoptosis in gastric cancer

Deubiquitinases (DUBs) are an essential component of the ubiquitin-proteasome system (UPS). They trim ubiquitin from substrate proteins, thereby preventing them from degradation, and modulate different cellular processes. Ubiquitin-specific protease 14 (USP14) is a DUB that has mainly been studied for its role in tumorigenesis in several cancers. In the present study, we found that the protein levels of USP14 were remarkably higher in gastric cancer tissues than in the adjacent normal tissues. We also demonstrated that the inhibition of USP14 activity using IU1 (an USP14 inhibitor) or the inhibition of USP14 expression using USP14-specific siRNA markedly reduced the viability of gastric cancer cells and suppressed their migratory and invasive abilities. The reduction in gastric cancer cell proliferation due to the inhibition of USP14 activity was a result of the increase in the degree of apoptosis, as evidenced by the increased expression levels of cleaved caspase-3 and cleaved PARP. Furthermore, an experiment using the USP14 inhibitor IU1 revealed that the inhibition of USP14 activity suppressed 5-fluorouracil (5-FU) resistance in GC cells. Collectively, these findings indicate that USP14 plays critical roles in gastric cancer progression and suggest its potential to serve as a novel therapeutic target for gastric cancer treatment. [BMB Reports 2023; 56(8): 451-456].

USP14 inhibition regulates tumorigenesis by inducing apoptosis in gastric cancer

Deubiquitinases (DUBs) are an essential component of the ubiquitin-proteasome system (UPS). They trim ubiquitin from substrate proteins, thereby preventing them from degradation, and modulate different cellular processes. Ubiquitin-specific protease 14 (USP14) is a DUB that has mainly been studied for its role in tumorigenesis in several cancers. In the present study, we found that the protein levels of USP14 were remarkably higher in gastric cancer tissues than in the adjacent normal tissues. We also demonstrated that the inhibition of USP14 activity using IU1 (an USP14 inhibitor) or the inhibition of USP14 expression using USP14-specific siRNA markedly reduced the viability of gastric cancer cells and suppressed their migratory and invasive abilities. The reduction in gastric cancer cell proliferation due to the inhibition of USP14 activity was a result of the increase in the degree of apoptosis, as evidenced by the increased expression levels of cleaved caspase-3 and cleaved PARP. Furthermore, an experiment using the USP14 inhibitor IU1 revealed that the inhibition of USP14 activity suppressed 5-fluorouracil (5-FU) resistance in GC cells. Collectively, these findings indicate that USP14 plays critical roles in gastric cancer progression and suggest its potential to serve as a novel therapeutic target for gastric cancer treatment. [BMB Reports 2023; 56(8): 451-456].

USP14 promotes pyroptosis of human annulus fibrosus cells derived from patients with intervertebral disc degeneration through deubiquitination of NLRP3

Intervertebral disc degeneration (IVDD) is a general disorder that results in low back pain and disability among many affected individuals. However, the current treatments for IVDD are limited to relieving the symptoms but do not solve the fundamental issue. In this study, the role of USP14 in mediating the activation of the NLRP3 inflammasome and the pyroptosis of AF cells from IVDD patients is determined in vitro, and gain- and loss-of-function assays of USP14 and the NLRP3 inflammasome are conducted. Pyroptosis of AF cells is detected by flow cytometry. The inflammatory cytokines (IL-1β and IL-18) and protein levels of NLRP3, active Caspase-1, Aggrecan, MMP3 and ADAMTS-5 are determined by ELISA and western blot analysis, respectively. The correlation between USP14 and NLRP3 is measured by coimmunoprecipitation and ubiquitination analysis. Upregulation of USP14 is accompanied by increased level of the NLRP3 inflammasome in AF cells from IVDD patients; furthermore, a positive correlation between them is observed. USP14 knockdown inhibits pyroptosis in AF cells by inducing ubiquitination of NLRP3, while overexpression of USP14 has the opposite effect, which is inhibited by the NLRP3 inflammasome inhibitor INF39. USP14 exerts its positive regulatory effect on AF cell pyroptosis by modulating the NLRP3/Caspase-1/IL-1β and IL-18 signaling axes.

Roles and Mechanisms of Deubiquitinases (DUBs) in Breast Cancer Progression and Targeted Drug Discovery

Deubiquitinase (DUB) is an essential component in the ubiquitin—proteasome system (UPS) by removing ubiquitin chains from substrates, thus modulating the expression, activity, and localization of many proteins that contribute to tumor development and progression. DUBs have emerged as promising prognostic indicators and drug targets. DUBs have shown significant roles in regulating breast cancer growth, metastasis, resistance to current therapies, and several canonical oncogenic signaling pathways. In addition, specific DUB inhibitors have been identified and are expected to benefit breast cancer patients in the future. Here, we review current knowledge about the effects and molecular mechanisms of DUBs in breast cancer, providing novel insight into treatments of breast cancer-targeting DUBs.

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.

A New Twist in Protein Kinase B/Akt Signaling: Role of Altered Cancer Cell Metabolism in Akt-Mediated Therapy Resistance

Cancer resistance to chemotherapy, radiotherapy and molecular-targeted agents is a major obstacle to successful cancer therapy. Herein, aberrant activation of the phosphatidyl-inositol-3-kinase (PI3K)/protein kinase B (Akt) pathway is one of the most frequently deregulated pathways in cancer cells and has been associated with multiple aspects of therapy resistance. These include, for example, survival under stress conditions, apoptosis resistance, activation of the cellular response to DNA damage and repair of radiation-induced or chemotherapy-induced DNA damage, particularly DNA double strand breaks (DSB). One further important, yet not much investigated aspect of Akt-dependent signaling is the regulation of cell metabolism. In fact, many Akt target proteins are part of or involved in the regulation of metabolic pathways. Furthermore, recent studies revealed the importance of certain metabolites for protection against therapy-induced cell stress and the repair of therapy-induced DNA damage. Thus far, the likely interaction between deregulated activation of Akt, altered cancer metabolism and therapy resistance is not yet well understood. The present review describes the documented interactions between Akt, its target proteins and cancer cell metabolism, focusing on antioxidant defense and DSB repair. Furthermore, the review highlights potential connections between deregulated Akt, cancer cell metabolism and therapy resistance of cancer cells through altered DSB repair and discusses potential resulting therapeutic implications.

Inhibition of USP14 induces ER stress-mediated autophagy without apoptosis in lung cancer cell line A549

Non-small cell lung cancer is the most common type of lung cancer, accounting for more than 80% of this tumor. Ubiquitin-specific protease (USP) 14 is one of the 100 deubiquitinating enzymes that is overexpressed in lung cancer and has been validated as a therapeutic target. The aim of this study is to determine whether the accumulation of ubiquitinated proteins results in endoplasmic reticulum (ER) stress-mediated autophagy. To inhibit USP-14, A549 lung cancer cells were treated with USP-14 siRNA and IU1-47 (20 μM). The protein level, mRNA expression, and cell cycle analysis were evaluated using Western blot, real-time PCR, and flow cytometry, respectively. We found that treating A549 cells with USP14 inhibitors significantly reduced the proliferation rate and induced cell cycle arrest at G2/M phase. We also found that USP14 inhibitors did not induce apoptosis but actually induced autophagy through accumulation of ubiquitinated proteins/ER stress/unfolded protein response (UPR) axis. Moreover, we have for the first time demonstrated that the USP14 inhibition induces ER stress-mediated autophagy in A549 cells by activation of c-Jun N-terminal kinase 1 (JNK1). In conclusion, the current investigation represents a new mechanism by which inhibition of USP14 triggers autophagy via ER stress-mediated UPR in A549 cells.

Deubiquitination Reactions on the Proteasome for Proteasome Versatility

The 26S proteasome, a master player in proteolysis, is the most complex and meticulously contextured protease in eukaryotic cells. While capable of hosting thousands of discrete substrates due to the selective recognition of ubiquitin tags, this protease complex is also dynamically checked through diverse regulatory mechanisms. The proteasome's versatility ensures precise control over active proteolysis, yet prevents runaway or futile degradation of many essential cellular proteins. Among the multi-layered processes regulating the proteasome's proteolysis, deubiquitination reactions are prominent because they not only recycle ubiquitins, but also impose a critical checkpoint for substrate degradation on the proteasome. Of note, three distinct classes of deubiquitinating enzymes-USP14, RPN11, and UCH37-are associated with the 19S subunits of the human proteasome. Recent biochemical and structural studies suggest that these enzymes exert dynamic influence over proteasome output with limited redundancy, and at times act in opposition. Such distinct activities occur spatially on the proteasome, temporally through substrate processing, and differentially for ubiquitin topology. Therefore, deubiquitinating enzymes on the proteasome may fine-tune the degradation depending on various cellular contexts and for dynamic proteolysis outcomes. Given that the proteasome is among the most important drug targets, the biology of proteasome-associated deubiquitination should be further elucidated for its potential targeting in human diseases.