The Ubiquitin-Specific Peptidase USP18 Promotes Lipolysis, Fatty Acid Oxidation, and Lung Cancer Growth

USP18 Is Associated with PD-L1 Antitumor Immunity and Improved Prognosis in Colorectal Cancer

BACKGROUND

Compared with conventional chemotherapy and targeted therapy, immunotherapy has improved the treatment outlook for a variety of solid tumors, including lung cancer, colorectal cancer (CRC), and melanoma. However, it is effective only in certain patients, necessitating the search for alternative strategies to targeted immunotherapy. The deubiquitinating enzyme USP18 is known to play an important role in various aspects of the immune response, but its role in tumor immunity in CRC remains unclear.

METHODS

In this study, multiple online datasets were used to systematically analyze the expression, prognosis, and immunomodulatory role of USP18 in CRC. The effect of USP18 on CRC was assessed via shRNA-mediated knockdown of USP18 expression in combination with CCK-8 and colony formation assays. Finally, molecular docking analysis of USP18/ISG15 and programmed death-ligand 1 (PD-L1) was performed via HDOCK, and an ELISA was used to verify the potential of USP18 to regulate PD-L1.

RESULTS

Our study revealed that USP18 expression was significantly elevated in CRC patients and closely related to clinicopathological characteristics. The experimental data indicated that silencing USP18 significantly promoted the proliferation and population-dependent growth of CRC cells. In addition, high USP18 expression was positively correlated with the CRC survival rate and closely associated with tumor-infiltrating CD8+ T cells and natural killer (NK) cells. Interestingly, USP18 was correlated with the expression of various chemokines and immune checkpoint genes. The results of molecular docking simulations suggest that USP18 may act as a novel regulator of PD-L1 and that its deficiency may potentiate the antitumor immune response to PD-L1 blockade immunotherapy in CRC.

CONCLUSIONS

In summary, USP18 shows great promise for research and clinical application as a potential target for CRC immunotherapy.

MiR-4769-3p suppresses adipogenesis in systemic sclerosis by negatively regulating the USP18/VDAC2 pathway

Systemic sclerosis (SSc) is an autoimmune disease affecting multiple tissues. The underlying causes and mechanisms of subcutaneous adipose tissue (SAT) loss in SSc remain unclear. Recent studies have highlighted the role of microRNAs in adipogenesis. Our study found that miR-4769-3p was upregulated in SSc patients and its silencing promoted SAT recovery in bleomycin-induced SSc mice, suggesting that miR-4769-3p might affect adipogenesis in SSc. Manipulating miR-4769-3p expression in 3T3-L1 cells revealed that its inhibition enhanced adipogenesis, while its overexpression weakened it. Further investigations showed that miR-4769-3p bound to 3'UTR of ubiquitin-specific protease-18 (USP18), inhibiting its expression, while USP18 interacted with voltage-dependent anion channel-2 (VDAC2), both of which were reduced in SSc. Silencing either USP18 or VDAC2 attenuated adipogenesis. Notably, USP18 inhibited VDAC2 ubiquitination and degradation, whereas miR-4769-3p reversed the VDAC2-induced elevation of adipogenesis, suggesting that miR-4769-3p inhibited adipogenesis by negatively regulating the USP18/VDAC2 pathway, providing a potential therapeutic target for SSc.

Role of ubiquitination in the occurrence and development of osteoporosis (Review)

The ubiquitin (Ub)‑proteasome system (UPS) plays a pivotal role in maintaining protein homeostasis and function to modulate various cellular processes including skeletal cell differentiation and bone homeostasis. The Ub ligase E3 promotes the transfer of Ub to the target protein, especially transcription factors, to regulate the proliferation, differentiation and survival of bone cells, as well as bone formation. In turn, the deubiquitinating enzyme removes Ub from modified substrate proteins to orchestrate bone remodeling. As a result of abnormal regulation of ubiquitination, bone cell differentiation exhibits disorder and then bone homeostasis is affected, consequently leading to osteoporosis. The present review discussed the role and mechanism of UPS in bone remodeling. However, the specific mechanism of UPS in the process of bone remodeling is still not fully understood and further research is required. The study of the mechanism of action of UPS can provide new ideas and methods for the prevention and treatment of osteoporosis. In addition, the most commonly used osteoporosis drugs that target ubiquitination processes in the clinic are discussed in the current review.

The CRL3KCTD10 ubiquitin ligase-USP18 axis coordinately regulates cystine uptake and ferroptosis by modulating SLC7A11

SLC7A11 is a cystine transporter and ferroptosis inhibitor. How the stability of SLC7A11 is coordinately regulated in response to environmental cystine by which E3 ligase and deubiquitylase (DUB) remains elusive. Here, we report that neddylation inhibitor MLN4924 increases cystine uptake by causing SLC7A11 accumulation, via inactivating Cullin-RING ligase-3 (CRL-3). We identified KCTD10 as the substrate-recognizing subunit of CRL-3 for SLC7A11 ubiquitylation, and USP18 as SLC7A11 deubiquitylase. Upon cystine deprivation, the protein levels of KCTD10 or USP18 are decreased or increased, respectively, contributing to SLC7A11 accumulation. By destabilizing or stabilizing SLC7A11, KCTD10, or USP18 inversely regulates the cystine uptake and ferroptosis. Biologically, MLN4924 combination with SLC7A11 inhibitor Imidazole Ketone Erastin (IKE) enhanced suppression of tumor growth. In human breast tumor tissues, SLC7A11 levels were negatively or positively correlated with KCTD10 or USP18, respectively. Collectively, our study defines how SLC7A11 and ferroptosis is coordinately regulated by the CRL3KCTD10/E3-USP18/DUB axis, and provides a sound rationale of drug combination to enhance anticancer efficacy.

Energy metabolism as the hub of advanced non-small cell lung cancer management: a comprehensive view in the framework of predictive, preventive, and personalized medicine

Energy metabolism is a hub of governing all processes at cellular and organismal levels such as, on one hand, reparable vs. irreparable cell damage, cell fate (proliferation, survival, apoptosis, malignant transformation etc.), and, on the other hand, carcinogenesis, tumor development, progression and metastazing versus anti-cancer protection and cure. The orchestrator is the mitochondria who produce, store and invest energy, conduct intracellular and systemically relevant signals decisive for internal and environmental stress adaptation, and coordinate corresponding processes at cellular and organismal levels. Consequently, the quality of mitochondrial health and homeostasis is a reliable target for health risk assessment at the stage of reversible damage to the health followed by cost-effective personalized protection against health-to-disease transition as well as for targeted protection against the disease progression (secondary care of cancer patients against growing primary tumors and metastatic disease). The energy reprogramming of non-small cell lung cancer (NSCLC) attracts particular attention as clinically relevant and instrumental for the paradigm change from reactive medical services to predictive, preventive and personalized medicine (3PM). This article provides a detailed overview towards mechanisms and biological pathways involving metabolic reprogramming (MR) with respect to inhibiting the synthesis of biomolecules and blocking common NSCLC metabolic pathways as anti-NSCLC therapeutic strategies. For instance, mitophagy recycles macromolecules to yield mitochondrial substrates for energy homeostasis and nucleotide synthesis. Histone modification and DNA methylation can predict the onset of diseases, and plasma C7 analysis is an efficient medical service potentially resulting in an optimized healthcare economy in corresponding areas. The MEMP scoring provides the guidance for immunotherapy, prognostic assessment, and anti-cancer drug development. Metabolite sensing mechanisms of nutrients and their derivatives are potential MR-related therapy in NSCLC. Moreover, miR-495-3p reprogramming of sphingolipid rheostat by targeting Sphk1, 22/FOXM1 axis regulation, and A2 receptor antagonist are highly promising therapy strategies. TFEB as a biomarker in predicting immune checkpoint blockade and redox-related lncRNA prognostic signature (redox-LPS) are considered reliable predictive approaches. Finally, exemplified in this article metabolic phenotyping is instrumental for innovative population screening, health risk assessment, predictive multi-level diagnostics, targeted prevention, and treatment algorithms tailored to personalized patient profiles-all are essential pillars in the paradigm change from reactive medical services to 3PM approach in overall management of lung cancers. This article highlights the 3PM relevant innovation focused on energy metabolism as the hub to advance NSCLC management benefiting vulnerable subpopulations, affected patients, and healthcare at large.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00357-5.

Lipid metabolism reprogramming in head and neck cancer

Lipid metabolism reprogramming is one of the most prominent metabolic anomalies in cancer, wherein cancer cells undergo dysregulation of lipid metabolism to acquire adequate energy, cell membrane building blocks, as well as signaling molecules essential for cell proliferation, survival, invasion, and metastasis. These adaptations enable cancer cells to effectively respond to challenges posed by the tumor microenvironment, leading to cancer therapy resistance and poor cancer prognosis. Head and neck cancer, ranking as the seventh most prevalent cancer, exhibits numerous abnormalities in lipid metabolism. Nevertheless, the precise role of lipid metabolic rewiring in head and neck cancer remains unclear. In line with the LIPID MAPS Lipid Classification System and cancer risk factors, the present review delves into the dysregulated molecules and pathways participating in the process of lipid uptake, biosynthesis, transportation, and catabolism. We also present an overview of the latest advancements in understanding alterations in lipid metabolism and how they intersect with the carcinogenesis, development, treatment, and prognosis of head and neck cancer. By shedding light on the significance of metabolic therapy, we aspire to improve the overall prognosis and treatment outcomes of head and neck cancer patients.

RNF152 Suppresses Fatty Acid Oxidation and Metastasis of Lung Adenocarcinoma by Inhibiting IRAK1-Mediated AKR1B10 Expression

Lung adenocarcinoma (LUAD) is a common subtype of primary lung cancer. Fatty acid oxidation plays a key role in LUAD development by providing energy for tumor cells. This study aimed to identify the role of ring finger protein 152 (RNF152) in LUAD. RNF152 was down-regulated in LUAD, and low RNF152 expression correlated with a poor prognosis in LUAD patients. RNF152 overexpression inhibited the proliferation and malignant phenotype of LUAD cells, whereas RNF152 knockdown exerted an opposite effect. Tumor cells overexpressing RNF152 showed less fatty acid oxidation compared with control cells, whereas RNF152 knockdown induced fatty acid uptake and oxidation. Further analysis revealed the binding reaction between RNF152 and interleukin-1 receptor-associated kinase 1 (IRAK1). RNF152 reduced the stability of IRAK1 in LUAD cells by promoting its ubiquitination. RNF152-overexpressed tumor cells exhibited a significantly lower level of Aldo-Keto reductase family 1 member 10 (AKR1B10), whereas up-regulation of IRAK1 restored the expression of AKR1B10 in RNF152-overexpressed cells. Furthermore, up-regulation of IRAK1 eliminated the antitumor effect of RNF152 in LUAD cells. Mouse xenograft models confirmed the inhibitory effect of RNF152 on the tumorigenesis and metastasis of LUAD. Taken together, RNF152 played a tumor suppressive role in LUAD by promoting IRAK1 ubiquitination and IRAK1-mediated down-regulation of AKR1B10, thereby reversing the malignant phenotype of LUAD.

Tumor-promoting action of ubiquitin protease 43 in gastric cancer progression through deubiquitination and stabilization of stress-inducible phosphoprotein 1

Gastric cancer (GC) is the 5th most common cancer over the world. Ubiquitin protease 43 (UBP43) is a multifunctional protein with deubiquitinase activities. Abnormal expression of UBP43 has been reported in numerous types of malignancies. Bioinformatic analysis was performed to identify the differentially expressed genes (Fold change ≥2 or ≤ -2 and p < 0.01) in GC from the datasets downloaded from Gene Expression Omnibus and Gene Expression Profiling Interactive Analysis databases, which showed that UBP43 and stress-inducible phosphoprotein 1 (STIP1) were up-regulated in both datasets. Online databases displayed the binding of UBP43 to STIP1 and the positive correlation between the two proteins. This study aims to explore: the role of UBP43 in cell proliferation and apoptosis in GC; the relationship between UBP43 and STIP1; and whether UBP43 exerts its function via STIP1 in GC. Knockdown/overexpression stable GC cell lines were generated by transducing lentivirus carrying coding sequence/short hairpin RNA of UBP43 and puromycin selection. GC patients with higher expressions of UBP43 had poor prognosis. Loss-/gain-of-function experiments revealed that pro-proliferative and anti-apoptotic abilities of UBP43 in GC cells and xenografts. UBP43 could interact with STIP1, inhibit its ubiquitination, and promote its protein stability, thereby enhancing STIP1 expression. Moreover, STIP1 knockdown reversed the pro-proliferative ability of UBP43 in GC cells. Our study uncovers that the pro-proliferative role of UBP43 in GC development is STIP1-dependent and indicates that UBP43 may act as a potent therapeutic target in GC treatment.

USP18 enhances the resistance of BRAF-mutated melanoma cells to vemurafenib by stabilizing cGAS expression to induce cell autophagy

This study aims to discern the possible molecular mechanism of the effect of ubiquitin-specific peptidase 18 (USP18) on the resistance to BRAF inhibitor vemurafenib in BRAF V600E mutant melanoma by regulating cyclic GMP-AMP synthase (cGAS). The cancer tissues of BRAF V600E mutant melanoma patients before and after vemurafenib treatment were collected, in which the protein expression of USP18 and cGAS was determined. A BRAF V600E mutant human melanoma cell line (A2058R) resistant to vemurafenib was constructed with its viability, apoptosis, and autophagy detected following overexpression and depletion assays of USP18 and cGAS. Xenografted tumors were transplanted into nude mice for in vivo validation. Bioinformatics analysis showed that the expression of cGAS was positively correlated with USP18 in melanoma, and USP18 was highly expressed in melanoma. The expression of cGAS and USP18 was up-regulated in cancer tissues of vemurafenib-resistant patients with BRAF V600E mutant melanoma. Knockdown of cGAS inhibited the resistance to vemurafenib in A2058R cells and the protective autophagy induced by vemurafenib in vitro. USP18 could deubiquitinate cGAS to promote its protein stability. In vivo experimentations confirmed that USP18 promoted vemurafenib-induced protective autophagy by stabilizing cGAS protein, which promoted resistance to vemurafenib in BRAF V600E mutant melanoma cells. Collectively, USP18 stabilizes cGAS protein expression through deubiquitination and induces autophagy of melanoma cells, thereby promoting the resistance to vemurafenib in BRAF V600E mutant melanoma.

USP18 regulates the malignant phenotypes of glioblastoma stem cells

Glioblastoma (GBM) is the most malignant primary brain tumor. The 5-year survival rate of the patients is poor, and they are prone to relapse and the treatment is limited. Therefore, the search for biological targets is one of the key measures for the treatment and prognosis of GBM. Ubiquitin-specific peptidase 18 (USP18) plays a regulatory role in tumorigenesis. In this study, we found that USP18 was up-regulated in GBM, promoted the growth and proliferation of glioblastoma stem cells (GSCs), affected the epithelial-mesenchymal transition (EMT), and was associated with poor clinical prognosis of patients. Finally, our findings reveal a critical role for USP18 in GBM malignancy, targeting USP18 may open new avenues for GBM treatment.

UBP43 promotes epithelial ovarian carcinogenesis via activation of β-catenin signaling pathway

Dysregulation of the deubiquitinating protease, UBP43, has been implicated in many human diseases, including cancer. Here, we evaluated the functional significance and mechanism of action of UBP43 in epithelial ovarian cancer. We found that UBP43 was significantly upregulated in the tumor tissues of patients with epithelial ovarian cancer. Similar results were observed in OVCAR-3, Caov-3, TOV-112D, A2780, and SK-OV-3 cells. Furthermore, in vitro functional assays of A2780 and TOV-112D cells demonstrated that UBP43 overexpression promoted cell proliferation, migration, and invasion. Upregulation of UBP43 might result in epithelial-mesenchymal transition by inducing the nuclear transport of β-catenin, which was accompanied by enhanced N-cadherin but decreased E-cadherin expression. These malignant phenotypes were reversed by UBP43 silencing. Further investigation revealed that the knockdown of UBP43 inhibited cell proliferation by inducing a cell cycle arrest at the G2/M phase. The oncogenic characteristics of UBP43 were validated in a subcutaneous xenograft mouse model. In vivo, tumor growth was delayed in the UBP43-silenced group but accelerated after UBP43 overexpression. Finally, we demonstrated that β-catenin is a key protein in the UBP43-mediated malignant development of epithelial ovarian cancer. Specifically, overexpression of UBP43 decreased the ubiquitination degradation of β-catenin and enhanced its protein stability. Also, we observed that the downstream genes of beta-catenin such as cyclin D1, MMP2, and MMP9 were upregulated due to UBP43 overexpression. Thus, we concluded that UBP43 promoted epithelial ovarian cancer tumorigenesis and metastasis through activation of the β-catenin pathway, suggesting that UBP43 may be a potential therapeutic target for this intractable disease.

The Functional Roles of ISG15/ISGylation in Cancer

The protein ISG15 encoded by interferon-stimulated gene (ISG) 15 is the first identified member of the ubiquitin-like protein family and exists in the form of monomers and conjugated complexes. Like ubiquitin, ISG15 can mediate an ubiquitin-like modification by covalently modifying other proteins, known as ISGylation. There is growing evidence showing that both the free and conjugated ISG15 are involved in multiple key cellular processes, including autophagy, exosome secretion, DNA repair, immune regulation, and cancer occurrence and progression. In this review, we aim to further clarify the function of ISG15 and ISGylation in cancer, demonstrate the important relationship between ISG15/ISGylation and cancer, and emphasize new insights into the different roles of ISG15/ISGylation in cancer progression. This review may contribute to therapeutic intervention in cancer. However, due to the limitations of current research, the regulation of ISG15/ISGylation on cancer progression is not completely clear, thus further comprehensive and sufficient correlation studies are still needed.

HCC: RNA-Sequencing in Cirrhosis

Hepatocellular carcinoma (HCC) ranks the most common types of cancer worldwide. As the fourth leading cause of cancer-related deaths, its prognosis remains poor. Most patients developed HCC on the basis of chronic liver disease. Cirrhosis is an important precancerous lesion for HCC. However, the molecular mechanisms in HCC development are still unclear. To explore the changes at the level of transcriptome in this process, we performed RNA-sequencing on cirrhosis, HCC and paracancerous tissues. Continuously changing mRNA was identified using Mfuzz cluster analysis, then their functions were explored by enrichment analyses. Data of cirrhotic HCC patients were obtained from TCGA, and a fatty acid metabolism (FAM)-related prognostic signature was then established. The performance and immunity relevance of the signature were verified in internal and external datasets. Finally, we validated the expression and function of ADH1C by experiments. As a result, 2012 differently expressed mRNA were identified by RNA-sequencing and bioinformatics analyses. Fatty acid metabolism was identified as a critical pathway by enrichment analyses of the DEGs. A FAM-related prognostic model and nomogram based on it were efficient in predicting the prognosis of cirrhotic HCC patients, as patients with higher risk scores had shorter survival time. Risk scores calculated by the signature were then proved to be associated with a tumor immune environment. ADH1C were downregulated in HCC, while silence of ADH1C could significantly promote proliferation and motility of the HCC cell line.

USPs in Pancreatic Ductal Adenocarcinoma: A Comprehensive Bioinformatic Analysis of Expression, Prognostic Significance, and Immune Infiltration

Pancreatic ductal adenocarcinoma (PDAC), as an intractable malignancy, still causes an extremely high mortality worldwide. The ubiquitin-specific protease (USP) family constitutes the major part of deubiquitinating enzymes (DUBs) which has been reported to be involved in initiation and progression of various malignancies via the function of deubiquitination. However, the biological function and clinical values of USPs in PDAC have not been comprehensively elucidated. In this study, Gene Expression Profiling Interactive Analysis (GEPIA), Gene Expression Omnibus (GEO) datasets, UALCAN database, and the Human Protein Atlas (HPA) online tool were used to analyze the expression level and the relationship between USP expression and clinicopathological features in PDAC. Survival module of HPA and Kaplan-Meier plotter (KMP) databases was recruited to explore the prognostic value of USPs. Tumor Immune Estimation Resource (TIMER) online tool and KMP databases were utilized to elucidate tumor immune infiltration and immune-related survival of USPs. CBioPortal online tool was used to identify the gene mutation level of USPs in PDAC. Both cBioPortal and LinkedOmics were used to confirm the potential biological functions of USPs in PDAC. Our study showed that USP10, USP14, USP18, USP32, USP33, and USP39 (termed as six-USPs) expressions were significantly elevated in tumor tissues. The high expression of the four USPs (USP10, USP14, USP18, and USP39) indicated a poor prognosis. A significant relationship was indicated between the expression of six-USPs and clinicopathological features. Also, the expression of six-USPs was related to promoter methylation level. Moreover, more than 40% genetic alterations and mutations were discovered in six-USPs. Furthermore, the six-USP expression was correlated with immune infiltration and immune-related prognosis. The functional analysis found that the six-USPs were involved in various biological processes and signaling pathways, such as nucleocytoplasmic transport, choline metabolism in cancer, cell cycle, ErbB signaling pathway, RIG-I-like receptor signaling pathway, TGF-β signaling pathway, and TNF signaling pathway. In conclusion, the results showed that six-USPs are potential prognostic biomarkers and can be recruited as possible therapeutic targets of PDAC.

A pan-cancer analysis of thioredoxin-interacting protein as an immunological and prognostic biomarker

Background

The critical role of thioredoxin-interacting protein (TXNIP) in cellular sulfhydryl redox homeostasis and inflammasome activation is already widely known, however, no pan-cancer analysis is currently available.

Methods

We thus first explored the potential roles of TXNIP across thirty-three tumors mainly based on The Cancer Genome Atlas and Gene Expression Omnibus datasets.

Results

TXNIP is lowly expressed in most cancers, and distinct associations exist between TXNIP expression and the prognosis of tumor patients. TXNIP expression was associated with tumor mutational burden, microsatellite instability, mismatch repair genes, tumor infiltrating immune cell abundance as well as cancer-associated fibroblasts. Moreover, ubiquitin mediated proteolysis, protein post-translational modification and other related pathways were involved in the functional mechanisms of TXNIP.

Conclusions

Our first pan-cancer study comprehensively revealed the carcinostatic role of TXNIP across different tumors. And this molecule may be considered as a potential immunological and prognostic biomarker.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02639-2.

Cuproptosis-related gene FDX1 expression correlates with the prognosis and tumor immune microenvironment in clear cell renal cell carcinoma

Background

Cuproptosis, a newly discovered form of cell death, is regulated by protein lipoylation and is related to mitochondrial metabolism. However, further research is needed to determine how the cuproptosis-related gene ferredoxin 1 (FDX1) affects the tumor immune response and its prognostic significance in clear cell renal cell carcinoma (ccRCC).

Methods

The Cancer Genome Atlas was used to screen for FDX1 gene expression in ccRCC and healthy tissue samples. The results were validated using the Gene Expression Omnibus and the Human Protein Atlas. Multivariable analysis and Kaplan-Meier survival curves were used to examine the relationship between FDX1 gene expression, clinicopathological parameters, and overall survival (OS). The protein network containing FDX1 gene interaction was constructed using the online Search Tool for the Retrieval of Interacting Genes/Proteins. The relationship between FDX1 gene expression and immune cell infiltration in ccRCC was examined using Gene Ontology, gene set enrichment analysis (GSEA), and a single-sample GSEA. Using the Gene Expression Profiling Interactive Analysis and Tumor Immune Estimation Resource databases, we investigated the relationship between FDX1 gene expression, the degree of immune cell infiltration, and the corresponding gene marker sets.

Results

ccRCC samples had significantly (p < 0.05) lower FDX1 gene expression levels than normal tissue samples. Lower FDX1 gene expression levels were strongly associated with higher cancer grades and more advanced tumor-node-metastasis stages. The findings of multivariate and univariate analyses illustrated that the OS in ccRCC patients with low FDX1 expression is shorter than in patients with high FDX1 expression (p < 0.05). Ferredoxin reductase and CYP11A1 are key proteins interacting with the FDX1 gene, and ccRCC with an FDX1 enzyme defect was associated with a low number of invading immune cells and their corresponding marker.

Conclusion

In ccRCC, decreased FDX1 expression was linked to disease progression, an unfavorable prognosis, and dysregulated immune cell infiltration.

Recent Advances on the Role of ATGL in Cancer

The hypoxic state of the tumor microenvironment leads to reprogramming lipid metabolism in tumor cells. Adipose triglyceride lipase, also known as patatin-like phospholipase= domain-containing protein 2 and Adipose triglyceride lipase (ATGL), as an essential lipid metabolism-regulating enzyme in cells, is regulated accordingly under hypoxia induction. However, studies revealed that ATGL exhibits both tumor-promoting and tumor-suppressing effects, which depend on the cancer cell type and the site of tumorigenesis. For example, elevated ATGL expression in breast cancer is accompanied by enhanced fatty acid oxidation (FAO), enhancing cancer cells’ metastatic ability. In prostate cancer, on the other hand, tumor activity tends to be negatively correlated with ATGL expression. This review outlined the regulation of ATGL-mediated lipid metabolism pathways in tumor cells, emphasizing the Hypoxia-inducible factors 1 (HIF-1)/Hypoxia-inducible lipid droplet-associated (HIG-2)/ATGL axis, peroxisome proliferator-activated receptor (PPAR)/G0/G1 switch gene 2 (G0S2)/ATGL axis, and fat-specific protein 27 (FSP-27)/Early growth response protein 1 (EGR-1)/ATGL axis. In the light of recent research on different cancer types, the role of ATGL on tumorigenesis, tumor proliferation, and tumor metastasis was systemically reviewed.

USP18 reduces paclitaxol sensitivity of triple-negative breast cancer via autophagy

Paclitaxol is a first-line treatment for triple-negative breast cancer (TNBC). The molecular mechanisms underlying paclitaxol resistance in TNBC remain largely unclear. In this study, differential expressed genes (DEGs) between TNBC cells and paclitaxol-resistant (taxol-R) TNBC cells were screened by bioinformatics analysis. Among these DEGs, USP18 mRNA expression was significantly increased in taxol-R TNBC cells. USP18 overexpression reduced paclitaxol sensitivity by decreasing paclitaxol-induced apoptosis and cell cycle arrest in TNBC cells. In contrast, USP18 knockdown increased paclitaxol mediated anticancer activity in taxol-R TNBC cells in vitro and in vivo. Mechanistically, USP18 induced autophagy, an important pathway in chemotherapy resistance. The autophagy inhibitor leupeptin could effectively reverse the effect of USP18 on paclitaxol resistance phenotype. These findings suggested that USP18 may be a promising target for overcoming paclitaxol resistance in TNBC.

The emerging role of deubiquitylating enzymes as therapeutic targets in cancer metabolism

Cancer cells must rewire cellular metabolism to satisfy the unbridled proliferation, and metabolic reprogramming provides not only the advantage for cancer cell proliferation but also new targets for cancer treatment. However, the plasticity of the metabolic pathways makes them very difficult to target. Deubiquitylating enzymes (DUBs) are proteases that cleave ubiquitin from the substrate proteins and process ubiquitin precursors. While the molecular mechanisms are not fully understood, many DUBs have been shown to be involved in tumorigenesis and progression via controlling the dysregulated cancer metabolism, and consequently recognized as potential drug targets for cancer treatment. In this article, we summarized the significant progress in understanding the key roles of DUBs in cancer cell metabolic rewiring and the opportunities for the application of DUBs inhibitors in cancer treatment, intending to provide potential implications for both research purpose and clinical applications.

USP18 promotes tumor metastasis in esophageal squamous cell carcinomas via deubiquitinating ZEB1

The dysregulation of deubiquitinating enzymes (DUBs), which regulate the stability of most cellular proteins, have been implicated in many human diseases, including cancers. Ubiquitin-specific protease 18 (USP18), a member of the DUBs family, functions as a potential tumour promoter in various cancers. However, the biological function and clinical significance of USP18 in esophageal squamous cell carcinomas (ESCC) are still unclear. Here, we found that ESCC tumors had higher USP18 expression compared with that of normal esophageal epithelial tissues, and high USP18 level was significantly correlated with malignant phenotype and shorter survival in patients with ESCC. In functional experiments, USP18 knockdown significantly inhibited ESCC invasion and metastasis in vitro. Consistently, a xenograft assay showed that knockdown of USP18 in ESCC cell suppressed their dissemination to lung tissue in vivo. Furthermore, we showed that USP18 promoted ESCC cell metastasis by inducing ZEB1 mediated epithelial-mesenchymal transition (EMT). Importantly, our results demonstrated that the oncogenic effect of USP18 in ESCC is partially dependent on ZEB1 enhancement. Mechanistic investigations revealed that USP18 directly bound ZEB1 and decreased its ubiquitination to enhance the protein stability of ZEB1 in ESCC cells. Overall, our data highlighted an essential role of USP18 in ESCC metastasis, suggesting that it could be a potential diagnostic and therapeutic target for ESCC.

Downregulated Expression of USP18 Is Associated with a Higher Recurrence Risk of Papillary Thyroid Carcinoma

As a member of the deubiquitinating protease family, ubiquitin specific peptidase 18 (USP18) is well acknowledged for its roles in stabilizing downstream protein substrates and inhibiting type I interferon signaling. USP18 has been reported to exert distinct roles in different cancer types. However, its expression and function in papillary thyroid carcinoma (PTC) remain unknown. Here we collected 156 PTC patients and retrospectively retrieved their clinicopathological characteristics as well as their survival data. Among them, USP18 was hypoexpressed in 47 PTC samples (30.1%) and significantly correlated with oncogenic characteristics. According to univariate and multivariate analyses, low USP18 can act as an independent prognostic indicator for unfavorable progression-free survival of PTC patients. Ectopic overexpression and knockdown assays indicated that USP18 can negatively regulate the proliferation of PTC cell lines. The anti-tumor effect of USP18 was finally validated by xenografts results from nude mice. Taken together, PTC patients with low level of USP18 have worse survival compared to those possess high USP18 expression. Downregulated USP18 may be involved in the proliferation of PTC, and USP18 expression can serve as an independent survival predictor.

FDX1 can Impact the Prognosis and Mediate the Metabolism of Lung Adenocarcinoma

Background: Lung cancer has emerged as one of the most common cancers in recent years. The mitochondrial electron transport chain (ETC) is closely connected with metabolic pathways and inflammatory response. However, the influence of ETC-associated genes on the tumor immune response and the pathogenesis of lung cancer is not clear and needs further exploration.

Methods: The RNA-sequencing transcriptome and clinical characteristic data of LUAD were downloaded from the Cancer Genome Atlas (TCGA) database. The LASSO algorithm was used to build the risk signature, and the prediction model was evaluated by the survival analysis and receiver operating characteristic curve. We explored the function of FDX1 through flow cytometry, molecular biological methods, and liquid chromatography–tandem mass spectrometry/mass spectrometry (LC–MS/MS).

Results: 12 genes (FDX1, FDX2, LOXL2, ASPH, GLRX2, ALDH2, CYCS, AKR1A1, MAOB, RDH16, CYBB, and CYB5A) were selected to build the risk signature, and the risk score was calculated with the coefficients from the LASSO algorithm. The 1-year, 3-year, and 5-year area under the curve (AUC) of ROC curves of the dataset were 0.7, 0.674, and 0.692, respectively. Univariate Cox analysis and multivariate Cox regression analysis indicated that the risk signature is an independent risk factor for LUAD patients. Among these genes, we focused on the FDX1 gene, and we found that knockdown of FDX1 neither inhibited tumor cell growth nor did it induce apoptosis or abnormal cell cycle distribution. But FDX1 could promote the ATP production. Furthermore, our study showed that FDX1 was closely related to the glucose metabolism, fatty acid oxidation, and amino acid metabolism.

Conclusion: Collectively, this study provides new clues about carcinogenesis induced by ETC-associated genes in LUAD and paves the way for finding potential targets of LUAD.