Targeting the USP7/RRM2 axis drives senescence and sensitizes melanoma cells to HDAC/LSD1 inhibitors

SQSTM1/p62 Orchestrates Skin Aging via USP7 Degradation

Skin aging is a complex process driven by intrinsic genetic factors and extrinsic environmental influences. In this study, sequestosome1 (SQSTM1/p62) was identified as a key regulator of senescence, the senescence-associated secretory phenotype (SASP), and skin aging. Notably, p62 expression is reduced in senescent cells and aging skin of both humans and mice. The depletion of p62 in the epidermis was found to be positively associated with accelerated aging and the initiation of SASP. Mechanistically, p62 inhibits the accumulation of ubiquitin-specific protease 7 (USP7) during senescence induction by orchestrating its degradation through specific binding interactions. In particular, the Tyr-67 residue within the PB1 domain or Gln-418 within the UBA domain of p62 forms a hydrogen bond with Ala-993 in the Ubl5 domain of USP7. Mutations in either Tyr-67 or Gln-418 of p62, or Ala-993 of USP7, resulted in the induction of cellular senescence, highlighting the critical role of these molecular interactions in the regulation of aging processes.

Splicing factor SF3B4 acts as a switch in cancer cell senescence by regulating p21 mRNA stability

SF3B4, a splicing factor known to regulate mRNA expression and function, is upregulated in various cancers. Despite its potential significance, the mechanisms through which SF3B4 regulates nonsense-mediated mRNA decay (NMD) and cancer cell senescence remain poorly understood. This study explores the underlying mechanisms by which SF3B4 modulates mRNA stability through the NMD pathway and elucidates its role in switching cancer cells between growth and senescence. We demonstrate that SF3B4 deficiency leads to decreased cancer cell proliferation, increased senescence-associated β-galactosidase (SA-β-Gal) activity, p53-independent upregulation of p21 expression, and ultimate induction of cell senescence. We further show that SF3B4 recruits essential NMD factors, including UPF1, MAGOH, and RNPS1, which facilitate mRNA decay of the crucial senescence regulator, p21. Conversely, SF3B4 depletion results in the dissociation of these factors from the 3'UTR of p21 mRNA, thereby enhancing its stability. Collectively, our results suggest that SF3B4 critically regulates p21 expression at the post-transcriptional level, providing insights into the novel role of SF3B4 in regulating p21 mRNA stability, interacting with key NMD factors, and modulating cancer cell senescence.

Selective USP7 Inhibition Synergizes with MEK1/2 Inhibitor to Enhance Immune Responses and Potentiate Anti-PD-1 Therapy in NRAS-Mutant Melanoma

Targeted therapy for NRAS-mutant melanoma remains an unmet clinical need. We found that inhibiting USP7 with the selective ubiquitin-specific protease 7 inhibitor (USP7i) FT671 inhibited cell proliferation in NRAS-mutant melanoma cell lines. In addition, we identified and validated that knockout of TP53BP1, TP53, or CDKN1A conferred resistance to FT671, suggesting that the activation of a functional p53 signaling pathway is essential for the efficacy of USP7i. In Nras-mutant melanoma isograft models, FT671 treatment delayed tumor growth. Moreover, the combinatorial treatment with FT671 and MAPK/(extracellular signal-regulated kinase) kinase 1/2 inhibitor was synergistic and induced pyroptosis in vitro. In immunocompetent mice, the combined treatment profoundly suppressed tumor growth, prolonged survival, and enhanced intratumoral immune cell infiltration, particularly increasing the ratios of CD8+ T cells and mature dendritic cells, indicative of activated antitumor immunity. Notably, the triple combination of USP7i, MAPK/(extracellular signal-regulated kinase) kinase 1/2 inhibitor, and anti-PD-1 antibody resulted in durable tumor regression, with effects persisting beyond 80 days after treatment cessation. These findings establish USP7i + MAPK (extracellular signal-regulated kinase) kinase 1/2 inhibitor as a promising strategy for targeting NRAS, an 'undruggable' mutation in melanoma, and provide a strong rationale for the clinical development of USP7i plus MAPK (extracellular signal-regulated kinase) kinase 1/2 inhibitor as an adjuvant therapy to enhance anti-PD-1 immunotherapy in patients with NRAS-mutant melanoma.

Osalmid sensitizes clear cell renal cell carcinoma to navitoclax through a STAT3/BCL-XL pathway

Clear cell renal cell carcinoma (ccRCC) is a common and lethal urinary malignancy characterized by its resistance to apoptosis. Despite the emerging treatment options available for ccRCC, only a small proportion of patients achieve long-term survival benefits. Previous studies have demonstrated that inducing tumor cell senescence, followed by treatment using senolytics, represents a potential strategy for triggering tumor cell apoptosis. However, it remains unclear whether this strategy is suitable for the treatment of ccRCC. Using the whole-genome CRISPR screening database Dependency Map portal (DepMap), we identified ribonucleotide reductase family member 2 (RRM2), which catalyzes the conversion of ribonucleotides to deoxyribonucleotides (dNTPs), as an essential targetable gene for ccRCC. Herein, we report that the combination of the choleretic drug osalmid targeting RRM2 and the senolytic compound navitoclax targeting BCL-XL represents a novel therapeutic approach for ccRCC. Furthermore, we have validated this approach across a panel of human ccRCC cells with different genetic backgrounds and multiple preclinical models, including cell line-derived xenografts (CDX), patient-derived xenografts (PDX), and patient-derived organoids (PDO). Mechanistically, osalmid-mediated inhibition of dNTPs generation induces cellular senescence in ccRCC, concomitant with STAT3 activation and upregulation of BCL-XL, thus rendering these cells vulnerable to navitoclax, which targets the BCL-2 protein family.

USP7 V517F mutation as a mechanism of inhibitor resistance

Anticipating and addressing resistance is essential for maximizing the potential of an oncology target and effectively addressing clinical needs. In this study, we aimed to proactively outline the resistance mechanisms of USP7 inhibitors. We discovered a key treatment-emergent heterozygous mutation (V517F) in USP7 in the binding pocket of compounds as the primary cause of resistance to the USP7 inhibitor USP7-797. Our structural analysis, supported by AlphaFold2 predictions, indicates that the V517F mutation altered the conformation of the compound binding pocket, causing steric hindrance and reducing the affinity between USP7 and its inhibitors. Consistent with these predictions, the affinity between V517F mutant and USP7 inhibitors was found to reduce significantly. Conversely, substitutions at position V517 with smaller side chains, such as V517G, V517A, and V517I, do not significantly impact binding affinity. In contrast, replacement with the bulkier side chain V517Y leads to reduced binding affinity and diminished inhibitor efficacy. Furthermore, the engineered cell lines harboring the V517F mutation exhibited substantial resistance to USP7 inhibition. These data provide rationales for patient selection and the development of next-generation USP7 inhibitors designed to overcome treatment-emergent mutations.

Involvement of the ubiquitin-proteasome system in the regulation of the tumor microenvironment and progression

The tumor microenvironment is a complex environment comprising tumor cells, non-tumor cells, and other critical non-cellular components. Some studies about tumor microenvironment have recently achieved remarkable progress in tumor treatment. As a substantial part of post-translational protein modification, ubiquitination is a crucial player in maintaining protein stability in cell signaling, cell growth, and a series of cellular life activities, which are also essential for regulating tumor cells or other non-tumor cells in the tumor microenvironment. This review focuses on the role and function of ubiquitination and deubiquitination modification in the tumor microenvironment while discussing the prospect of developing inhibitors targeting ubiquity-related enzymes, thereby providing ideas for future research in cancer therapy.

Unveiling the complexity of cellular senescence in cancers: From mechanism to therapeutic opportunities

Cellular senescence is characterized by a sustained and irreversible cessation of cell proliferation in response to diverse environmental stimuli. However, senescent cells exhibit strong metabolic activity and release a range of cytokines and inflammatory mediators into the tumor microenvironment, collectively referred to as the senescence‐associated secretory phenotype (SASP). In recent years, to develop new therapies for cancers, researchers have conducted extensive studies on the mechanism of cancer cell senescence and revealed that induction of cancer cell senescence could effectively suppress cancer progression. However, it has been documented that cellular senescence not only inhibits cancer initiation but also contributes significantly to cancer progression in some cases. Hence, it is imperative to comprehend the correlation between cellular senescence and tumorigenesis, and discuss the potential utilization of cellular senescence mechanisms to suppress cancer progression, which lays a theoretical foundation for new drugs to treat cancers. In this review, we first provide an overview of the discovery of cellular senescence and its key milestone events. Meanwhile, this review examines the major stimulus for the induction of senescence, and provides an overview of the categorization of cellular senescence. Subsequently, an examination of the primary regulatory mechanisms of cellular senescence is discussed, followed by a summary of the control of the SASP expression and its dual biological roles in cancers. Additionally, we also provide an overview of common biomarkers utilized in the identification of cellular senescence. Finally, this review investigates the efficacy of the “One‐Two punch” sequential treatment approach for cancers, and examines the emerging challenges of this novel approach.

Creation of an innovative diagnostic framework for hepatocellular carcinoma employing bioinformatics techniques focused on senescence-related and pyroptosis-related genes

BACKGROUND

Liver hepatocellular carcinoma (LIHC) continues to pose a major global health concern and is characterized by elevated mortality rates and a lack of effective therapies. This study aimed to explore differential gene expression linked to cellular senescence and pyroptosis in LIHC and to develop a prognostic risk model for use in clinical settings.

METHODS

We acquired datasets from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). DESeq2 was used to identify differentially expressed genes associated with cell senescence and pyrodeath. The least absolute shrinkage and selection operator (LASSO) regression model was developed using cellular senescence- and pyroptosis-related differentially expressed genes (CSR&PRDEGs), and its predictive performance was evaluated with Kaplan-Meier survival analysis and time-dependent receiver operating characteristic (ROC) curves. We also performed various functional analyses of the genes. These findings were validated by real-time fluorescence quantitative polymerase chain reaction (PCR).

RESULTS

Using bioinformatics analysis, we developed a prognostic risk framework incorporating six critical genes: ANXA2, APOA1, EZH2, IGF2BP3, SQSTM1, and TNFRSF11B.The model demonstrated a statistically significant difference in overall survival between the high-risk and low-risk groups (p < 0.05). Additionally, real-time fluorescence quantitative PCR confirmed that genes ANXA2, APOA1, EZH2, IGF2BP3, SQSTM1, and TNFRSF11B were significantly overexpressed in the peripheral blood of patients with LIHC in comparison to normal volunteers, thereby validating the prognostic risk model's accuracy.

CONCLUSIONS

This study systematically elucidated the functions of genes associated with senescence and pyroptosis in LIHC cells. The constructed prognostic risk model serves to guide the development of personalized treatment plans, enhance patient management via risk stratification, facilitate the identification of high-risk patients, intensify monitoring or implement proactive interventions, thereby providing a novel perspective for the diagnosis and treatment of LIHC.

Ubiquitin-Specific Protease Inhibitors for Cancer Therapy: Recent Advances and Future Prospects

Cancer management has traditionally depended on chemotherapy as the mainstay of treatment; however, recent advancements in targeted therapies and immunotherapies have offered new options. Ubiquitin-specific proteases (USPs) have emerged as promising therapeutic targets in cancer treatment due to their crucial roles in regulating protein homeostasis and various essential cellular processes. This review covers the following: (1) the structural and functional characteristics of USPs, highlighting their involvement in key cancer-related pathways, and (2) the discovery, chemical structures, mechanisms of action, and potential clinical implications of USP inhibitors in cancer therapy. Particular attention is given to the role of USP inhibitors in enhancing cancer immunotherapy, e.g., modulation of the tumor microenvironment, effect on regulatory T cell function, and influence on immune checkpoint pathways. Furthermore, this review summarizes the current progress and challenges of clinical trials involving USP inhibitors as cancer therapy. We also discuss the complexities of achieving target selectivity, the ongoing efforts to develop more specific and potent USP inhibitors, and the potential of USP inhibitors to overcome drug resistance and synergize with existing cancer treatments. We finally provide a perspective on future directions in targeting USPs, including the potential for personalized medicine based on specific gene mutations, underscoring their significant potential for enhancing cancer treatment. By elucidating their mechanisms of action, clinical progress, and potential future applications, we hope that this review could serve as a useful resource for both basic scientists and clinicians in the field of cancer therapeutics.

Histone deacetylases in the regulation of cell death and survival mechanisms in resistant BRAF-mutant cancers

Small-molecule BRAF inhibitors (e.g., vemurafenib and dabrafenib) and MEK (MAPK/ERK) kinases inhibitors (e.g., trametinib) have distinctly improved the survival of patients suffering from BRAF-mutant cancers such as melanomas. However, the emergence of resistance to BRAF and MEK inhibitor-based melanoma therapy, as well as the reduced sensitivity of other BRAF-mutant cancers such as CRC, poses a considerable clinical problem. For instance, the reactivation of MAPK/ERK signaling hampering cell death induction mechanisms was responsible for BRAF inhibitor resistance, which can be correlated with distinct post-translational and epigenetic processes. Histone deacetylases (HDACs) are prominent epigenetic drug targets and some HDAC inhibitors have already been clinically approved for the therapy of various blood cancers. In addition, several HDACs were identified, which also play a crucial role in the drug resistance of BRAF-mutant cancers. Consequently, inhibition of HDACs was described as a promising approach to overcome resistance. This review summarizes the influence of HDACs (Zn2+-dependent HDACs and NAD+-dependent sirtuins) on BRAF-mutant cancers and BRAF inhibitor resistance based on upregulated survival mechanisms and the prevention of tumor cell death. Moreover, it outlines reasonable HDAC-based strategies to circumvent BRAF-associated resistance mechanisms based on downregulated cell death mechanisms.

USP7 facilitates deubiquitination of LRRC42 in colorectal cancer to accelerate tumorigenesis and augment Wnt/β-catenin signaling

Colorectal cancer is a prevalent malignancy with an increasing incidence worldwide. Leucine-rich repeat-containing protein 42 (LRRC42) is known to be dysregulated in tumor tissues, yet its role in colorectal cancer remains largely unexplored. Herein, the function of LRRC42 in colorectal cancer was investigated using clinical samples, cellular experiments, animal models, and multiple omics techniques. The results demonstrated that LRRC42 was highly expressed in colorectal cancer tissues and was associated with poor clinical outcomes. Silencing LRRC42 suppressed cell proliferation, induced G0/G1 phase arrest, and promoted apoptosis by reducing Bcl2 expression while elevating the expression of Bax, cleaved PARP and cleaved caspase 3. Conversely, LRRC42 overexpression exhibited the opposite effects. Consistent findings were observed in vivo. Additionally, ubiquitin specific peptidase 7 was identified as a potential LRRC42-interacting protein through immunoprecipitation-mass spectrometry, with ubiquitin specific peptidase 7 stabilizing LRRC42 expression by promoting its deubiquitination. Notably, LRRC42 overexpression partially reversed the effects of ubiquitin specific peptidase 7 silencing on tumor cell proliferation and apoptosis. mRNA sequencing analysis revealed that differentially expressed genes in LRRC42 overexpressing cells were linked to Wnt signaling pathway, suggesting that LRRC42 overexpression may activate this pathway. Furthermore, LRRC42 was proved to elevate the levels of ki67, cyclin D1 and WNT3, while reducing the level of p-β-catenin. These findings suggest that LRRC42 perhaps serve as a potential oncogenic factor in colorectal cancer, regulated by ubiquitin specific peptidase 7 and capable of activating Wnt/β-catenin signaling pathway.

Ubiquitin-specific protease 7 maintains c-Myc stability to support pancreatic cancer glycolysis and tumor growth

BACKGROUND

The typical pathological feature of pancreatic ductal adenocarcinoma (PDAC) is a significant increase in stromal reaction, leading to a hypoxic and poorly vascularized tumor microenvironment. Tumor cells undergo metabolic reprogramming, such as the Warburg effect, yet the underlying mechanisms are not fully understood.

METHODS

Interference and overexpression experiments were conducted to analyze the in vivo and in vitro effects of USP7 on the growth and glycolysis of tumor cells. Small-molecule inhibitors of USP7 and transgenic mouse models of PDAC were employed to assess the consequences of targeting USP7 in PDAC. The molecular mechanism underlying USP7-induced c-Myc stabilization was determined by RNA sequencing, co-IP and western blot analyses.

RESULTS

USP7 is abnormally overexpressed in PDAC and predicts a poor prognosis. Hypoxia and extracellular matrix stiffness can induce USP7 expression in PDAC cells. Genetic silencing of USP7 inhibits the glycolytic phenotypes in PDAC cells, while its overexpression has the opposite effect, as demonstrated by glucose uptake, lactate production, and extracellular acidification rate. Importantly, USP7 promotes PDAC tumor growth in a glycolysis-dependent manner. The small-molecule inhibitor P5091 targeting USP7 effectively suppresses the Warburg effect and cell growth in PDAC. In a transgenic mouse model of PDAC, named KPC, P5091 effectively blocks tumor progression. Mechanistically, USP7 interacts with c-Myc, enhancing its stability and expression, which in turn upregulates expression of glycolysis-related genes.

CONCLUSIONS

This study sheds light on the molecular mechanisms underlying the Warburg effect in PDAC and unveils USP7 as a potential therapeutic target for improving PDAC treatment.

Exploring the impact of deubiquitination on melanoma prognosis through single-cell RNA sequencing

Background

Cutaneous melanoma, characterized by the malignant proliferation of melanocytes, exhibits high invasiveness and metastatic potential. Thus, identifying novel prognostic biomarkers and therapeutic targets is essential.

Methods

We utilized single-cell RNA sequencing data (GSE215120) from the Gene Expression Omnibus (GEO) database, preprocessing it with the Seurat package. Dimensionality reduction and clustering were executed through Principal Component Analysis (PCA) and Uniform Manifold Approximation and Projection (UMAP). Cell types were annotated based on known marker genes, and the AUCell algorithm assessed the enrichment of deubiquitination-related genes. Cells were categorized into DUB_high and DUB_low groups based on AUCell scores, followed by differential expression analysis. Importantly, we constructed a robust prognostic model utilizing various genes, which was evaluated in the TCGA cohort and an external validation cohort.

Results

Our prognostic model, developed using Random Survival Forest (RSF) and Ridge Regression methods, demonstrated excellent predictive performance, evidenced by high C-index and AUC values across multiple cohorts. Furthermore, analyses of immune cell infiltration and tumor microenvironment scores revealed significant differences in immune cell distribution and microenvironment characteristics between high-risk and low-risk groups. Functional experiments indicated that TBC1D16 significantly impacts the migration and proliferation of melanoma cells.

Conclusion

This study highlights the critical role of deubiquitination in melanoma and presents a novel prognostic model that effectively stratifies patient risk. The model's strong predictive ability enhances clinical decision-making and provides a framework for future studies on the therapeutic potential of deubiquitination mechanisms in melanoma progression. Further validation and exploration of this model's applicability in clinical settings are warranted.

The Role and Mechanism of Deubiquitinase USP7 in Tumor-Associated Inflammation

Deubiquitinating enzymes are a class of proteases that remove ubiquitin tags from proteins, thereby controlling protein stability and function. Tumor inflammation arises from interactions between tumor cells and their microenvironment, which trigger an inflammatory response. The deubiquitinating enzyme USP7 plays a central role in this process. Research suggests that USP7 may modulate various signaling pathways related to inflammatory responses through its deubiquitinating activity, thereby influencing tumor development and progression, including regulating T cell immune activity, improving macrophage anti-tumor activity, and regulating NF-κB signal pathways. Overall, describing the role and mechanism of USP7 in the tumor inflammatory response is of great importance for elucidating the regulatory mechanism of tumor inflammation and developing new therapeutic strategies. This article mainly reviews the structure, function, role, and mechanism of USP7 in the tumor inflammation response.

Epigenetics-targeted drugs: current paradigms and future challenges

Epigenetics governs a chromatin state regulatory system through five key mechanisms: DNA modification, histone modification, RNA modification, chromatin remodeling, and non-coding RNA regulation. These mechanisms and their associated enzymes convey genetic information independently of DNA base sequences, playing essential roles in organismal development and homeostasis. Conversely, disruptions in epigenetic landscapes critically influence the pathogenesis of various human diseases. This understanding has laid a robust theoretical groundwork for developing drugs that target epigenetics-modifying enzymes in pathological conditions. Over the past two decades, a growing array of small molecule drugs targeting epigenetic enzymes such as DNA methyltransferase, histone deacetylase, isocitrate dehydrogenase, and enhancer of zeste homolog 2, have been thoroughly investigated and implemented as therapeutic options, particularly in oncology. Additionally, numerous epigenetics-targeted drugs are undergoing clinical trials, offering promising prospects for clinical benefits. This review delineates the roles of epigenetics in physiological and pathological contexts and underscores pioneering studies on the discovery and clinical implementation of epigenetics-targeted drugs. These include inhibitors, agonists, degraders, and multitarget agents, aiming to identify practical challenges and promising avenues for future research. Ultimately, this review aims to deepen the understanding of epigenetics-oriented therapeutic strategies and their further application in clinical settings.

Complex Inhibitory Activity of Pentacyclic Triterpenoids against Cutaneous Melanoma In Vitro and In Vivo: A Literature Review and Reconstruction of Their Melanoma-Related Protein Interactome

Pentacyclic triterpenoids (PTs) are a class of plant metabolites with a wide range of pharmacological activities, including strong antitumor potential against skin malignancies. By acting on multiple signaling pathways that control key cellular processes, PTs are able to exert complex effects on melanoma progression in vitro and in vivo. In this review, we have analyzed the works published in the past decade and devoted to the effects of PTs, both natural and semisynthetic, on cutaneous melanoma pathogenesis, including not only their direct action on melanoma cells but also their influence on the tumor microenvironment and abberant melanogenesis, often associated with melanoma aggressiveness. Special attention will be paid to the molecular basis of the pronounced antimelanoma potency of PTs, including a detailed consideration of the pathways sensitive to PTs in melanoma cells, as well as the reconstruction of the melanoma-related protein interactome of PTs using a network pharmacology approach based on previously published experimentally verified protein targets of PTs. The information collected on the primary targets of PTs was compiled in the Protein Interactome of PTs (PIPTs) database, freely available at http://www.pipts-db.ru/, which can be used to further optimize the mechanistic studies of PTs in the context of melanoma and other malignancies. By summarizing recent research findings, this review provides valuable information to scientists working in the fields related to the evaluation of melanoma pathogenesis and development of PTs-based drug candidates.

USP7 alleviates neuronal inflammation and apoptosis in spinal cord injury via deubiquitinating NRF1/KLF7 axis

BACKGROUND

Ubiquitin-specific protease 7 (USP7) has been found to be associated with motor function recovery after spinal cord injury (SCI). Therefore, its role and mechanism in SCI process need further exploration.

METHODS

SCI rat models were established via performing laminectomy at the T9-T11 spinal vertebrae and cutting spinal cord tissues. SCI cell models were constructed by inducing PC12 cells with lipopolysaccharide (LPS). The protein levels of USP7, nuclear respiratory factor 1 (NRF1), Krüppel-like factor 7 (KLF7) and apoptosis-related markers were detected by western blot. Cell viability and apoptosis were tested by cell counting kit-8 assay and flow cytometry. The contents of inflammatory factors were examined using ELISA. The interaction between NRF1 and USP7 or KLF7 was analyzed by co-immunoprecipitation assay, chromatin immunoprecipitation assay and dual-luciferase reporter assay, respectively.

RESULTS

USP7 was downregulated in SCI rat models and LPS-induced PC12 cells. Overexpressed USP7 promoted viability, while repressed apoptosis and inflammation in LPS-induced PC12 cells. USP7 could stabilize NRF1 protein expression via deubiquitination, and NRF1 knockdown reversed the protective effect of USP7 against LPS-induced PC12 cell injury. NRF1 is bound to KLF7 promoter to enhance its transcription. NRF1 overexpression inhibited LPS-induced PC12 cell inflammation and apoptosis via increasing KLF7 expression.

CONCLUSION

USP7 alleviated inflammation and apoptosis in LPS-induced PC12 cells via NRF1/KLF7 axis, indicating that targeting of USP7/NRF1/KLF7 axis might be a promising treatment strategy for SCI.

Regorafenib promotes antitumor progression in melanoma by reducing RRM2

Melanoma is a malignant tumor with a terrible prognosis. Although so many therapies are used for melanoma, the overall survival rate is still poor globally. Novel therapies are still required. In our study, the role and potential mechanism of regorafenib in melanoma are explored. Regorafenib has the ability to limit the growth, invasion, and metastasis of melanoma cells but to upregulate apoptosis-prompting markers (cleaved-PARP and Bax). RRM2 is identified to be the downstream target of regorafenib by RNA sequencing. In addition, we discovered that RRM2 inhibition and regorafenib have comparable effects on melanoma cells. Rescue experiments showed that RRM2 is crucial in regulating regorafenib's anti-melanoma progression. Moreover, ERK/E2F3 signaling influences regorafenib's ability to suppress melanoma cell growth. Ultimately, regorafenib significantly inhibits tumor growth in vivo. In conclusion, our finding demonstrated that regorafenib promotes antitumor progression in melanoma by reducing RRM2.

LncOCMRL1 promotes oral squamous cell carcinoma growth and metastasis via the RRM2/EMT pathway

BACKGROUND

Long noncoding RNAs (lncRNAs) are widely involved in cancer development and progression, but the functions of most lncRNAs have not yet been elucidated. Metastasis is the main factor restricting the therapeutic outcomes of various cancer types, including oral squamous cell carcinoma (OSCC). Therefore, exploring the key lncRNAs that regulate OSCC metastasis and elucidating their molecular mechanisms will facilitate the development of new strategies for effective OSCC therapy.

METHODS

We analyzed the lncRNA expression profiles of tumor tissues from OSCC patients with and without cervical lymph node metastasis, and OSCC cell lines. We revealed high expression of oral squamous cell carcinoma metastasis-related lncRNA 1 (lncOCMRL1) in OSCC patient tumor tissues with lymph node metastasis and highly metastatic OSCC cell lines. The effects of lncOCMRL1 knockdown on the invasion, migration and proliferation abilities of OSCC cells were explored through qRT-PCR, Transwell, colony formation, and cell proliferation experiments. The mechanism by which lncOCMRL1 promotes OSCC metastasis and proliferation was explored through RNA pull-down, silver staining, mass spectrometry, RIP, and WB experiments. To increase its translational potential, we developed a reduction-responsive nanodelivery system to deliver siRNA for antitumor therapy.

RESULTS

We determined that lncOCMRL1 is highly expressed in OSCC metastatic tumor tissues and cells. Functional studies have shown that high lncOCMRL1 expression can promote the growth and metastasis of OSCC cells both in vivo and in vitro. Mechanistically, lncOCMRL1 could induce epithelial-mesenchymal transition (EMT) via the suppression of RRM2 ubiquitination and thereby promote the proliferation, invasion, and migration of OSCC cells. We further constructed reduction-responsive nanoparticles (NPs) for the systemic delivery of siRNAs targeting lncOCMRL1 and demonstrated their high efficacy in silencing lncOCMRL1 expression in vivo and significantly inhibited OSCC tumor growth and metastasis.

CONCLUSIONS

Our results suggest that lncOCMRL1 is a reliable target for blocking lymph node metastasis in OSCC.

USP7 promotes cardiometabolic disorders and mitochondrial homeostasis dysfunction in diabetic mice via stabilizing PGC1β

Diabetic cardiomyopathy (DCM) is a major complication of diabetes and is characterized by left ventricular dysfunction. Currently, there is a lack of effective treatments for DCM. Ubiquitin-specific protease 7 (USP7) plays a key role in various diseases. However, whether USP7 is involved in DCM has not been established. In this study, we demonstrated that USP7 was upregulated in diabetic mouse hearts and NMCMs co-treated with HG+PA or H9c2 cells treated with PA. Abnormalities in diabetic heart morphology and function were reversed by USP7 silencing through conditional gene knockout or chemical inhibition. Proteomic analysis coupled with biochemical validation confirmed that PCG1β was one of the direct protein substrates of USP7 and aggravated myocardial damage through coactivation of the PPARα signaling pathway. USP7 silencing restored the expression of fatty acid metabolism-related proteins and restored mitochondrial homeostasis by inhibiting mitochondrial fission and promoting fusion events. Similar effects were also observed in vitro. Our data demonstrated that USP7 promoted cardiometabolic metabolism disorders and mitochondrial homeostasis dysfunction via stabilizing PCG1β and suggested that silencing USP7 may be a therapeutic strategy for DCM.

The potential role of CMC1 as an immunometabolic checkpoint in T cell immunity

T cell immunity is critical for human defensive immune response. Exploring the key molecules during the process provides new targets for T cell-based immunotherapies. CMC1 is a mitochondrial electron transport chain (ETC) complex IV chaperon protein. By establishing in-vitro cell culture system and Cmc1 gene knock out mice, we evaluated the role of CMC1 in T cell activation and differentiation. The B16-OVA tumor model was used to test the possibility of targeting CMC1 for improving T cell anti-tumor immunity. We identified CMC1 as a positive regulator in CD8+T cells activation and terminal differentiation. Meanwhile, we found that CMC1 increasingly expressed in exhausted T (Tex) cells. Genetic lost of Cmc1 inhibits the development of CD8+T cell exhaustion in mice. Instead, deletion of Cmc1 in T cells prompts cells to differentiate into metabolically and functionally quiescent cells with increased memory-like features and tolerance to cell death upon repetitive or prolonged T cell receptor (TCR) stimulation. Further, the in-vitro mechanistic study revealed that environmental lactate enhances CMC1 expression by inducing USP7, mediated stabilization and de-ubiquitination of CMC1 protein, in which a mechanism we propose here that the lactate-enriched tumor microenvironment (TME) drives CD8+TILs dysfunction through CMC1 regulatory effects on T cells. Taken together, our study unraveled the novel role of CMC1 as a T cell regulator and its possibility to be utilized for anti-tumor immunotherapy.

A comprehensive analysis of ribonucleotide reductase subunit M2 for carcinogenesis in pan-cancer

BACKGROUND

Although there is evidence that ribonucleotide reductase subunit M2 (RRM2) is associated with numerous cancers, pan-cancer analysis has seldom been conducted. This study aimed to explore the potential carcinogenesis of RRM2 in pan-cancer using datasets from The Cancer Genome Atlas (TCGA).

METHODS

Data from the UCSC Xena database were analyzed to investigate the differential expression of RRM2 across multiple cancer types. Clinical data such as age, race, sex, tumor stage, and status were acquired to analyze the influence of RRM2 on the clinical characteristics of the patients. The role of RRM2 in the onset and progression of multiple cancers has been examined in terms of genetic changes at the molecular level, including tumor mutational burden (TMB), microsatellite instability (MSI), biological pathway changes, and the immune microenvironment.

RESULTS

RRM2 was highly expressed in most cancers, and there was an obvious correlation between RRM2 expression and patient prognosis. RRM2 expression is associated with the infiltration of diverse immune and endothelial cells, immune checkpoints, tumor mutational burden (TMB), and microsatellite instability (MSI). Moreover, the cell cycle is involved in the functional mechanisms of RRM2.

CONCLUSIONS

Our pan-cancer study provides a comprehensive understanding of the carcinogenesis of RRM2 in various tumors.

TRIM22 induces cellular senescence by targeting PHLPP2 in hepatocellular carcinoma

The ubiquitin-proteasome system is a vital protein degradation system that is involved in various cellular processes, such as cell cycle progression, apoptosis, and differentiation. Dysregulation of this system has been implicated in numerous diseases, including cancer, vascular disease, and neurodegenerative disorders. Induction of cellular senescence in hepatocellular carcinoma (HCC) is a potential anticancer strategy, but the precise role of the ubiquitin-proteasome system in cellular senescence remains unclear. In this study, we show that the E3 ubiquitin ligase, TRIM22, plays a critical role in the cellular senescence of HCC cells. TRIM22 expression is transcriptionally upregulated by p53 in HCC cells experiencing ionizing radiation (IR)-induced senescence. Overexpression of TRIM22 triggers cellular senescence by targeting the AKT phosphatase, PHLPP2. Mechanistically, the SPRY domain of TRIM22 directly associates with the C-terminal domain of PHLPP2, which contains phosphorylation sites that are subject to IKKβ-mediated phosphorylation. The TRIM22-mediated PHLPP2 degradation leads to activation of AKT-p53-p21 signaling, ultimately resulting in cellular senescence. In both human HCC databases and patient specimens, the levels of TRIM22 and PHLPP2 show inverse correlations at the mRNA and protein levels. Collectively, our findings reveal that TRIM22 regulates cancer cell senescence by modulating the proteasomal degradation of PHLPP2 in HCC cells, suggesting that TRIM22 could potentially serve as a therapeutic target for treating cancer.

TMP269, a small molecule inhibitor of class IIa HDAC, suppresses RABV replication in vitro

TMP269, a small molecular inhibitor of IIa histone deacetylase, plays a vital role in cancer therapeutic. However, the effect of TMP269 on the regulation of viral replication has not been studied. In the present study, we found that TMP269 treatment significantly inhibited RABV replication at concentrations without significant cytotoxicity in a dose-dependent manner. In addition, TMP269 can reduce the viral titers and protein levels of RABV at an early stage in the viral life cycle. RNA sequencing data revealed that immune-related pathways and autophagy-related genes were significantly downregulated after RABV infection treated with TMP269. Further exploration shows that autophagy enhances RABV replication in HEK-293T cells, while TMP269 can inhibit autophagy to decrease RABV replication. Together, these results provide a novel treatment strategy for rabies.

Deubiquitinating enzyme JOSD2 affects susceptibility of non-small cell lung carcinoma cells to anti-cancer drugs through DNA damage repair

OBJECTIVES

To investigate the effects and mechanisms of deubiquitinating enzyme Josephin domain containing 2 (JOSD2) on susceptibility of non-small cell lung carcinoma (NSCLC) cells to anti-cancer drugs.

METHODS

The transcriptome expression and clinical data of NSCLC were downloaded from the Gene Expression Omnibus. Principal component analysis and limma analysis were used to investigate the deubiquitinating enzymes up-regulated in NSCLC tissues. Kaplan-Meier analysis was used to investigate the relationship between the expression of deubiquitinating enzymes and overall survival of NSCLC patients. Gene ontology enrichment and gene set enrichment analysis (GSEA) were used to analyze the activation of signaling pathways in NSCLC patients with high expression of JOSD2. Gene set variation analysis and Pearson correlation were used to investigate the correlation between JOSD2 expression levels and DNA damage response (DDR) pathway. Western blotting was performed to examine the expression levels of JOSD2 and proteins associated with the DDR pathway. Immunofluorescence was used to detect the localization of JOSD2. Sulforhodamine B staining was used to examine the sensitivity of JOSD2-knock-down NSCLC cells to DNA damaging drugs.

RESULTS

Compared with adjacent tissues, the expression level of JOSD2 was significantly up-regulated in NSCLC tissues (P<0.05), and was significantly correlated with the prognosis in NSCLC patients (P<0.05). Compared with the tissues with low expression of JOSD2, the DDR-related pathways were significantly upregulated in NSCLC tissues with high expression of JOSD2 (all P<0.05). In addition, the expression of JOSD2 was positively correlated with the activation of DDR-related pathways (all P<0.01). Compared with the control group, overexpression of JOSD2 significantly promoted the DDR in NSCLC cells. In addition, DNA damaging agents significantly increase the nuclear localization of JOSD2, whereas depletion of JOSD2 significantly enhanced the sensitivity of NSCLC cells to DNA damaging agents (all P<0.05).

CONCLUSIONS

Deubiquitinating enzyme JOSD2 may regulate the malignant progression of NSCLC by promoting DNA damage repair pathway, and depletion of JOSD2 significantly enhances the sensitivity of NSCLC cells to DNA damaging agents.

Post-translational modifications of histones: Mechanisms, biological functions, and therapeutic targets

Histones are DNA-binding basic proteins found in chromosomes. After the histone translation, its amino tail undergoes various modifications, such as methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, and lactylation, which together constitute the "histone code." The relationship between their combination and biological function can be used as an important epigenetic marker. Methylation and demethylation of the same histone residue, acetylation and deacetylation, phosphorylation and dephosphorylation, and even methylation and acetylation between different histone residues cooperate or antagonize with each other, forming a complex network. Histone-modifying enzymes, which cause numerous histone codes, have become a hot topic in the research on cancer therapeutic targets. Therefore, a thorough understanding of the role of histone post-translational modifications (PTMs) in cell life activities is very important for preventing and treating human diseases. In this review, several most thoroughly studied and newly discovered histone PTMs are introduced. Furthermore, we focus on the histone-modifying enzymes with carcinogenic potential, their abnormal modification sites in various tumors, and multiple essential molecular regulation mechanism. Finally, we summarize the missing areas of the current research and point out the direction of future research. We hope to provide a comprehensive understanding and promote further research in this field.

USP7 - a crucial regulator of cancer hallmarks

Over the course of three decades of study, the deubiquitinase Herpesvirus associated Ubiquitin-Specific Protease/Ubiquitin-Specific Protease 7 (HAUSP/USP7) has gradually come to be recognized as a crucially important molecule in cellular physiology. The fact that USP7 is overexpressed in a number of cancers, including breast, prostate, colorectal, and lung cancers, supports the idea that USP7 is also an important regulator of tumorigenesis. In this review, we discuss USP7's function in relation to the cancer hallmarks described by Hanahan and Weinberg. This post-translational modifier can support increased proliferation, block unfavorable growth signals, stop cell death, and support an unstable cellular genome by manipulating key players in the pertinent signalling circuit. It is interesting to note that USP7 also aids in the stabilization of molecules that support angiogenesis and metastasis. Targeting USP7 has now emerged as a crucial component of USP7 research because pharmacological inhibition of USP7 supports p53-mediated cell cycle arrest and apoptosis. Efficacious USP7 inhibition is currently being investigated in both synthetic and natural compounds, but issues with selectivity and a lack of co-crystal structure have hindered USP7 inhibition from being tested in clinical settings. Moreover, the development of new, more effective USP7 inhibitors and their encouraging implications by numerous groups give us a glimmer of hope for USP7-targeting medications as effective substitutes for hazardous cancer chemotherapeutics.