DHHC protein family targets different subsets of glioma stem cells in specific niches

Ubiquitin E3 ligases assisted technologies in protein degradation: Sharing pathways in neurodegenerative disorders and cancer

E3 ligases, essential components of the ubiquitin-proteasome-mediated protein degradation system, play a critical role in cellular regulation. By covalently attaching ubiquitin (Ub) molecules to target proteins, these ligases mark them for degradation, influencing various bioprocesses. With over 600 E3 ligases identified, there is a growing realization of their potential as therapeutic candidates for addressing proteinopathies in cancer and neurodegenerative disorders (NDDs). Recent research has highlighted the need to delve deeper into the intricate roles of E3 ligases as nexus points in the pathogenesis of both cancer and NDDs. Their dysregulation is emerging as a common thread linking these seemingly disparate diseases, necessitating a comprehensive understanding of their molecular intricacies. Herein, we have discussed (i) the fundamental mechanisms through which different types of E3 ligases actively participate in selective protein degradation in cancer and NDDs, followed by an examination of common E3 ligases playing pivotal roles in both situations, emphasising common players. Moving to, (ii) the functional domains and motifs of E3 ligases involved in ubiquitination, we have explored their interactions with specific substrates in NDDs and cancer. Additionally, (iii) we have explored techniques like PROTAC, molecular glues, and other state-of-the-art methods for hijacking neurotoxic and oncoproteins. Lastly, (iv) we have provided insights into ongoing clinical trials, offering a glimpse into the evolving landscape of E3-based therapeutics for cancer and NDDs. Unravelling the intricate network of E3 ligase-mediated regulation holds the key to unlocking targeted therapies that address the specific molecular signatures of individual patients, heralding a new era in personalized medicines.

The role of s-palmitoylation in neurological diseases: implication for zDHHC family

S-palmitoylation is a reversible posttranslational modification, and the palmitoylation reaction in human-derived cells is mediated by the zDHHC family, which is composed of S-acyltransferase enzymes that possess the DHHC (Asp-His-His-Cys) structural domain. zDHHC proteins form an autoacylation intermediate, which then attaches the fatty acid to cysteine a residue in the target protein. zDHHC proteins sublocalize in different neuronal structures and exert dif-ferential effects on neurons. In humans, many zDHHC proteins are closely related to human neu-rological disor-ders. This review focuses on a variety of neurological disorders, such as AD (Alz-heimer's disease), HD (Huntington's disease), SCZ (schizophrenia), XLID (X-linked intellectual disability), attention deficit hyperactivity disorder and glioma. In this paper, we will discuss and summarize the research progress regarding the role of zDHHC proteins in these neu-rological disorders.

Identification and prognostic biomarkers among ZDHHC4/12/18/24, and APT2 in lung adenocarcinoma

S-palmitoylases and S-depalmitoylases are differentially expressed in various cancers and several malignant tumors and show a strong prognostic ability. Notwithstanding, the potential clinical impact of S-palmitoylases and S-depalmitoylases, particularly in the prognosis and progression of lung adenocarcinoma (LUAD), has not been clarified. Expression levels of S-palmitoylases and S-depalmitoylases in LUAD were investigated using TCGA. GEPIA was used to evaluate the mRNA levels of S-palmitoylases and S-depalmitoylases at different pathological stages. Metascape was used to investigate the biological significance of S-palmitoylases and S-depalmitoylases. The Kaplan-Meier plotter was used to analyze the prognostic value of S-palmitoylases and S-depalmitoylases. CBioportal was used to analyze gene alterations in S-palmitoylases and S-depalmitoylases. UALCAN was used to examine DNA promoter methylation levels of S-palmitoylases and S-depalmitoylases. Finally, we investigated the relationship between S-palmitoylases, S-depalmitoylases, and tumor-infiltrating immune cells using TIMER. Correlations with immune checkpoint-related genes were determined using the R packages reshape2, ggpubr, ggplot2, and corrplot. PCR was also performed to assess the degree of ZDHHC4/12/18/24 and APT2 transcript expression in lung adenocarcinoma and adjacent normal lung tissues. HPA was utilized to investigate protein levels of S-palmitoylases and S-depalmitoylases in LUAD and normal lung tissue. Our study found that ZDHHC2/3/4/5/6/7/9/12/13/16/18/20/21/23/24, APT1/2, PPT1, LYPLAL1, ABHD4/10/11/12/13 and ABHD17C mRNA expression was significantly upregulated in LUAD, whereas ZDHHC1/8/11/11B/14/15/17/19/22, ABHD6/16A and ABHD17A mRNA expression was significantly downregulated. The functions of the differentially expressed S-palmitoylases and S-depalmitoylases were mainly associated with protein-cysteine S-palmitoyltransferase and protein-cysteine S-acyltransferase activities. Patients with high expression of ZDHHC4/12/18/24, APT2, ABHD4, ABHD11 and ABHD12 had a shorter overall survival. Infiltration of six immune cells (B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells) was closely associated with the expression of ZDHHC4/12/18/24 and APT2. ZDHHC4/12/18/24 and APT2 positively correlated with the immune checkpoint-related gene CD276. We assessed the mRNA levels of ZDHHC4/12/18/24 and APT2 using qRT-PCR and found increased expression of ZDHHC4/12/18/24 in LUAD compared with healty control lung tissues. ZDHHC4/12/18/24, and APT2 are potential prognostic biomarkers of LUAD. Their expression levels could be related to the tumor microenvironment in LUAD.

Targeting EZH2 regulates the biological characteristics of glioma stem cells via the Notch1 pathway

Glioma is the most common malignant brain tumor, and its behavior is closely related to the presence of glioma stem cells (GSCs). We found that the enhancer of zeste homolog 2 (EZH2) is highly expressed in glioma and that its expression is correlated with the prognosis of glioblastoma multiforme (GBM) in two databases: The Cancer Genome Atlas and the Chinese Glioma Genome Atlas. Additionally, EZH2 is known to regulate the stemness-associated gene expression, proliferation, and invasion ability of GSCs, which may be achieved through the activation of the STAT3 and Notch1 pathways. Furthermore, we demonstrated the effect of the EZH2-specific inhibitor GSK126 on GSCs; these results not only corroborate our hypothesis, but also provide a potential novel treatment approach for glioma.

Diverse Roles of Protein Palmitoylation in Cancer Progression, Immunity, Stemness, and Beyond

Protein S-palmitoylation, a type of post-translational modification, refers to the reversible process of attachment of a fatty acyl chain-a 16-carbon palmitate acid-to the specific cysteine residues on target proteins. By adding the lipid chain to proteins, it increases the hydrophobicity of proteins and modulates protein stability, interaction with effector proteins, subcellular localization, and membrane trafficking. Palmitoylation is catalyzed by a group of zinc finger DHHC-containing proteins (ZDHHCs), whereas depalmitoylation is catalyzed by a family of acyl-protein thioesterases. Increasing numbers of oncoproteins and tumor suppressors have been identified to be palmitoylated, and palmitoylation is essential for their functions. Understanding how palmitoylation influences the function of individual proteins, the physiological roles of palmitoylation, and how dysregulated palmitoylation leads to pathological consequences are important drivers of current research in this research field. Further, due to the critical roles in modifying functions of oncoproteins and tumor suppressors, targeting palmitoylation has been used as a candidate therapeutic strategy for cancer treatment. Here, based on recent literatures, we discuss the progress of investigating roles of palmitoylation in regulating cancer progression, immune responses against cancer, and cancer stem cell properties.

ZDHHC11B is decreased in lung adenocarcinoma and inhibits tumorigenesis via regulating epithelial-mesenchymal transition

PURPOSE

The role and mechanism of zinc finger DHHC protein 11B (ZDHHC11B) in lung adenocarcinoma (LUAD) remain unclear. We, thus, analyzed the expression pattern, biological function, and potential mechanism of ZDHHC11B in LUAD.

METHODS

The expression level and prognostic value of ZDHHC11B were evaluated based on The Cancer Genome Atlas (TCGA) database and further confirmed in LUAD tissues and cells. The effect of ZDHHC11B on the malignant biological progression of LUAD was evaluated in vitro and in vivo. Gene set enrichment analysis (GSEA) and western blot were used to explore the molecular mechanisms of ZDHHC11B.

RESULTS

In vitro, ZDHHC11B inhibited the proliferation, migration, and invasion of LUAD cells and induced the apoptosis of LUAD cells. In addition, ZDHHC11B inhibited the growth of tumors in nude mice. GSEA revealed that ZDHHC11B expression is positively correlated with epithelial-mesenchymal transition (EMT). Western blot analysis demonstrated that molecular markers of EMT were inhibited under ZDHHC11B overexpression conditions.

CONCLUSIONS

Our findings indicated that ZDHHC11B plays a significant role in inhibiting tumorigenesis via EMT. In addition, ZDHHC11B may be a candidate molecular target for LUAD treatment.

Super-enhancer-driven lncRNA LIMD1-AS1 activated by CDK7 promotes glioma progression

Long non-coding RNAs (lncRNAs) are tissue-specific expression patterns and dysregulated in cancer. How they are regulated still needs to be determined. We aimed to investigate the functions of glioma-specific lncRNA LIMD1-AS1 activated by super-enhancer (SE) and identify the potential mechanisms. In this paper, we identified a SE-driven lncRNA, LIMD1-AS1, which is expressed at significantly higher levels in glioma than in normal brain tissue. High LIMD1-AS1 levels were significantly associated with a shorter survival time of glioma patients. LIMD1-AS1 overexpression significantly enhanced glioma cells proliferation, colony formation, migration, and invasion, whereas LIMD1-AS1 knockdown inhibited their proliferation, colony formation, migration, and invasion, and the xenograft tumor growth of glioma cells in vivo. Mechanically, inhibition of CDK7 significantly attenuates MED1 recruitment to the super-enhancer of LIMD1-AS1 and then decreases the expression of LIMD1-AS1. Most importantly, LIMD1-AS1 could directly bind to HSPA5, leading to the activation of interferon signaling. Our findings support the idea that CDK7 mediated-epigenetically activation of LIMD1-AS1 plays a crucial role in glioma progression and provides a promising therapeutic approach for patients with glioma.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

ZDHHC15 promotes glioma malignancy and acts as a novel prognostic biomarker for patients with glioma

BACKGROUND

Glioma is the most common and aggressive tumor in the adult brain. Recent studies have indicated that Zinc finger DHHC-type palmitoyltransferases (ZDHHCs) play vital roles in regulating the progression of glioma. ZDHHC15, a member of the ZDHHCs family, participates in various physiological activities in the brain. However, the biological functions and related mechanisms of ZDHHC15 in glioma remain poorly understood.

METHODS

Data from multiple glioma-associated datasets were used to investigate the expression profiles and potential biological functions of ZDHHC15 in glioma. Expression of ZDHHC15 and its association with clinicopathological characteristics in glioma were validated by quantitative reverse transcription PCR (RT-qPCR) and immunohistochemical experiments. GO enrichment analysis, KEGG analysis, GSEA analysis, CCK-8, EdU, transwell, and western blotting assays were performed to confirm the functions and mechanism of ZDHHC15 in glioma. Moreover, we performed Kaplan-Meier analysis and Cox progression analysis to explore the prognostic significance of ZDHHC15 in glioma patients.

RESULTS

ZDHHC15 expression was significantly up-regulated in glioma and positively associated with malignant phenotypes. Results from the GO and KEGG enrichment analysis revealed that ZDHHC15 was involved in regulating cell cycle and migration. Knockdown of ZDHHC15 inhibited glioma cell proliferation and migration, while overexpression of ZDHHC15 presented opposite effects on glioma cells. Besides, results from GSEA analysis suggested that ZDHHC15 was enriched in STAT3 signaling pathway. Knockdown or overexpression of ZDHHC15 indeed affected the activation of STAT3 signaling pathway. Additionally, we identified ZDHHC15 as an independent prognostic biomarker in glioma, and higher expression of ZDHHC15 predicted a poorer prognosis in glioma patients.

CONCLUSION

Our findings suggest that ZDHHC15 promotes glioma malignancy and can serve as a novel prognostic biomarker for glioma patients. Targeting ZDHHC15 may be a promising therapeutic strategy for glioma.

Loss of p53 Concurrent with RAS and TERT Activation Induces Glioma Formation

There is an ongoing debate regarding whether gliomas originate due to functional or genetic changes in neural stem cells (NSCs). Genetic engineering has made it possible to use NSCs to establish glioma models with the pathological features of human tumors. Here, we found that RAS, TERT, and p53 mutations or abnormal expression were associated with the occurrence of glioma in the mouse tumor transplantation model. Moreover, EZH2 palmitoylation mediated by ZDHHC5 played a significant role in this malignant transformation. EZH2 palmitoylation activates H3K27me3, which in turn decreases miR-1275, increases glial fibrillary acidic protein (GFAP) expression, and weakens the binding of DNA methyltransferase 3A (DNMT3A) to the OCT4 promoter region. Thus, these findings are significant because RAS, TERT, and p53 oncogenes in human neural stem cells are conducive to a fully malignant and rapid transformation, suggesting that gene changes and specific combinations of susceptible cell types are important factors in determining the occurrence of gliomas.

Identification of the miRNA-mRNA regulatory network associated with radiosensitivity in esophageal cancer based on integrative analysis of the TCGA and GEO data

BACKGROUND

The current study set out to identify the miRNA-mRNA regulatory networks that influence the radiosensitivity in esophageal cancer based on the The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases.

METHODS

Firstly, esophageal cancer-related miRNA-seq and mRNA-seq data were retrieved from the TCGA database, and the mRNA dataset of esophageal cancer radiotherapy was downloaded from the GEO database to analyze the differential expressed miRNAs (DEmiRNAs) and mRNAs (DEmRNAs) in radiosensitive and radioresistant samples, followed by the construction of the miRNA-mRNA regulatory network and Gene Ontology and KEGG enrichment analysis. Additionally, a prognostic risk model was constructed, and its accuracy was evaluated by means of receiver operating characteristic analysis.

RESULTS

A total of 125 DEmiRNAs and 42 DEmRNAs were closely related to the radiosensitivity in patients with esophageal cancer. Based on 47 miRNA-mRNA interactions, including 21 miRNAs and 21 mRNAs, the miRNA-mRNA regulatory network was constructed. The prognostic risk model based on 2 miRNAs (miR-132-3p and miR-576-5p) and 4 mRNAs (CAND1, ZDHHC23, AHR, and MTMR4) could accurately predict the prognosis of esophageal cancer patients. Finally, it was verified that miR-132-3p/CAND1/ZDHHC23 and miR-576-5p/AHR could affect the radiosensitivity in esophageal cancer.

CONCLUSION

Our study demonstrated that miR-132-3p/CAND1/ZDHHC23 and miR-576-5p/AHR were critical molecular pathways related to the radiosensitivity of esophageal cancer.

Novel peripheral blood diagnostic biomarkers screened by machine learning algorithms in ankylosing spondylitis

Background: Ankylosing spondylitis (AS) is a chronic inflammatory disorder of unknown etiology that is hard to diagnose early. Therefore, it is imperative to explore novel biomarkers that may contribute to the easy and early diagnosis of AS. Methods: Common differentially expressed genes between normal people and AS patients in GSE73754 and GSE25101 were screened by machine learning algorithms. A diagnostic model was established by the hub genes that were screened. Then, the model was validated in several data sets. Results: IL2RB and ZDHHC18 were screened using machine learning algorithms and established as a diagnostic model. Nomograms suggested that the higher the expression of ZDHHC18, the higher was the risk of AS, while the reverse was true for IL2RB in vivo. C-indexes of the model were no less than 0.84 in the validation sets. Calibration analyses suggested high prediction accuracy of the model in training and validation cohorts. The area under the curve (AUC) values of the model in GSE73754, GSE25101, GSE18781, and GSE11886 were 0.86, 0.84, 0.85, and 0.89, respectively. The decision curve analyses suggested a high net benefit offered by the model. Functional analyses of the differentially expressed genes indicated that they were mainly clustered in immune response-related processes. Immune microenvironment analyses revealed that the neutrophils were expanded and activated in AS while some T cells were decreased. Conclusion: IL2RB and ZDHHC18 are potential blood biomarkers of AS, which might be used for the early diagnosis of AS and serve as a supplement to the existing diagnostic methods. Our study deepens the insight into the pathogenesis of AS.

Palmitoylation of MDH2 by ZDHHC18 activates mitochondrial respiration and accelerates ovarian cancer growth

Epithelial ovarian cancer (EOC) exhibits strong dependency on the tricarboxylic acid (TCA) cycle and oxidative phosphorylation to fuel anabolic process. Here, we show that malate dehydrogenase 2 (MDH2), a key enzyme of the TCA cycle, is palmitoylated at cysteine 138 (C138) residue, resulting in increased activity of MDH2. We next identify that ZDHHC18 acts as a palmitoyltransferase of MDH2. Glutamine deprivation enhances MDH2 palmitoylation by increasing the binding between ZDHHC18 and MDH2. MDH2 silencing represses mitochondrial respiration as well as ovarian cancer cell proliferation both in vitro and in vivo. Intriguingly, re-expression of wild-type MDH2, but not its palmitoylation-deficient C138S mutant, sustains mitochondrial respiration and restores the growth as well as clonogenic capability of ovarian cancer cells. Notably, MDH2 palmitoylation level is elevated in clinical cancer samples from patients with high-grade serous ovarian cancer. These observations suggest that MDH2 palmitoylation catalyzed by ZDHHC18 sustains mitochondrial respiration and promotes the malignancy of ovarian cancer, yielding possibilities of targeting ZDHHC18-mediated MDH2 palmitoylation in the treatment of EOC.

Dynamic Expression of Palmitoylation Regulators across Human Organ Development and Cancers Based on Bioinformatics

Protein palmitoylation is a reversible modification process that links palmitate to cysteine residues via a reversible thioester bond. Palmitoylation exerts an important role in human organ development and tumor progression. However, a comprehensive landscape regarding the dynamic expression of palmitoylation regulators in human organ development remains unclear. In this study, we analyzed the dynamic expression of palmitoylation regulators in seven organ development and eight cancer types based on bioinformatics. We found that the expression levels of most palmitoylation regulators were altered after birth. In particular, ZDHHC7/20/21 exhibited converse expression patterns in multiple cancer types. Survival analysis showed that the poor prognosis in patients with kidney renal clear carcinoma (KIRC) is related to low expression of ZDHHC7/20/21, and a high expression of ZDHHC7/20/21 is related to worse survival in patients with liver hepatocellular carcinoma (LIHC). Furthermore, we found that the expression of ZDHHC7 is associated with infiltration levels of some types of immune cells in the tumor microenvironment (TME), and we explored the relationship between ZDHHC7 expression and immune checkpoint (ICP) genes across 33 cancer types. In addition, gene set enrichment analysis (GSEA) results indicated that ZDHHC7 might regulate different genes to mediate the same pathway in different organs. In summary, the comprehensive analysis of palmitoylation regulators reveals their functions in human organ development and cancer, which may provide new insights for developing new tumor markers.

Current knowledge of protein palmitoylation in gliomas

Malignant tumor cells can obtain proliferative benefits from deviant metabolic networks. Emerging evidence suggests that lipid metabolism are dramatically altered in gliomas and excessive fatty acd accumulation is detrimentally correlated with the prognosis of glioma patients. Glioma cells possess remarkably high levels of free fatty acids, which, in turn, enhance post-translational modifications (e.g. palmitoylation). Our and other groups found that palmitoylational modification is essential for remaining intracellular homeostasis and cell survival. Disrupting the balance between palmitoylation and depalmitoylation affects glioma cell viability, apoptosis, invasion, self-renew and pyroptosis. In this review, we focused on summarizing roles and relevant mechanisms of protein palmitoylational modification in gliomas.

Propofol enhances stem-like properties of glioma via GABAAR-dependent Src modulation of ZDHHC5-EZH2 palmitoylation mechanism

Background

Propofol is a commonly used anesthetic. However, its effects on glioma growth and recurrence remain largely unknown.

Methods

The effect of propofol on glioma growth was demonstrated by a series of in vitro and in vivo experiments (spheroidal formation assay, western blotting, and xenograft model). The acyl-biotin exchange method and liquid chromatography-mass spectrometry assays identified palmitoylation proteins mediated by the domain containing the Asp-His-His-Cys family. Western blotting, co-immunoprecipitation, quantitative real-time polymerase chain reaction, co-immunoprecipitation, chromatin immunoprecipitation, and luciferase reporter assays were used to explore the mechanisms of the γ-aminobutyric acid receptor (GABA_AR)/Src/ZDHHC5/EZH2 signaling axis in the effects of propofol on glioma stem cells (GSCs).

Results

We found that treatment with a standard dose of propofol promoted glioma growth in nude mice compared with control or low-dose propofol. Propofol-treated GSCs also led to larger tumor growth in nude mice than did vector-treated tumors. Mechanistically, propofol enhances the stem-like properties of gliomas through GABA_AR to increase Src expression, thereby enhancing the palmitoylation of ZDHHC5-mediated EZH2 and Oct4 expression.

Conclusion

These results demonstrate that propofol may promote glioma growth through the GABA_AR-Src-ZDHHC5-EZH2 mechanism and are helpful in guiding the clinical use of propofol to obtain a better patient prognosis after the surgical resection of tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03087-5.

Oct4A palmitoylation modulates tumorigenicity and stemness in human glioblastoma cells

BACKGROUND

Glioblastoma multiforme and other solid malignancies are heterogeneous, containing subpopulations of tumor cells that exhibit stem characteristics. Oct4, also known as POU5F1, is a key transcription factor in the self-renewal, proliferation, and differentiation of stem cells. Although it has been detected in advanced gliomas, the biological function of Oct4, and transcriptional machinery maintained by the stemness of Oct4 protein-mediated glioma stem cells (GSC), has not been fully determined.

METHODS

The expression of Oct4 variants was evaluated in brain cancer cell lines, and in brain tumor tissues, by quantitative real-time PCR, western blotting, and immunohistochemical analysis. The palmitoylation level of Oct4A was determined by the acyl-biotin exchange method, and the effects of palmitoylation Oct4A on GSCs were investigated by a series of in vitro (neuro-sphere formation assay, double immunofluorescence, pharmacological treatment, luciferase assay, and coimmunoprecipitation) and in vivo (xenograft model) experiments.

RESULTS

Here, we report that all three variants of Oct4 are expressed in different types of cerebral cancer, while Oct4A is important for maintaining tumorigenicity in GSCs. Palmitoylation mediated by ZDHHC17 was indispensable for preserving Oct4A from lysosome degradation to maintain its protein stability. Oct4A palmitoylation also helped to integrate Sox4 and Oct4A in the SOX2 enhancement subregion to maintain the stem performance of GSCs. We also designed Oct4A palmitoylation competitive inhibitors, inhibiting the self-renewal ability and tumorigenicity of GSCs.

CONCLUSIONS

These findings indicate that Oct4A acts on the tumorigenic activity of glioblastoma, and Oct4A palmitoylation is a candidate therapeutic target.

Palmitoyl transferases act as potential regulators of tumor-infiltrating immune cells and glioma progression

High immune-cell infiltration in glioblastomas (GBMs) leads to immunotherapy resistance. Emerging evidence has shown that zinc finger Asp-His-His-Cyc-type (ZDHHC) palmitoyl transferases participate in regulating tumor progression and the immune microenvironment. In the present study, a large cohort of patients with gliomas from The Cancer Genome Atlas (TCGA) and Rembrandt databases was included to perform omics analysis of ZDHHCs in gliomas. CCK-8, flow cytometry, quantitative real-time PCR, western blotting, and transwell assays were performed to determine the effects of ZDHHC inhibition on glioma cells and microglia. We found that five (ZDHHC11, ZDHHC12, ZDHHC15, ZDHHC22, and ZDHHC23) out of 23 ZDHHCs were aberrantly expressed in gliomas and might play their roles through the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway. Further results indicated that inhibition of ZDHHCs with 2-bromopalmitate (2-BP) suppressed glioma-cell viability and autophagy, as well as promoted apoptosis. Targeting ZDHHCs also promoted the sensitivity of glioma cells to temozolomide (TMZ) chemotherapy. In addition, the inhibition of ZDHHCs weakened the migratory ability of microglia induced by glioma cells in vitro and in vivo. Taken together, our findings suggest that the inhibition of ZDHHCs suppresses glioma-cell viability and microglial infiltration. Targeting ZDHHCs may be promising for glioma treatments.

Zinc finger Asp-His-His-Cys palmitoyl -acyltransferase 19 accelerates tumor progression through wnt/β-catenin pathway and is upregulated by miR-940 in osteosarcoma

Osteosarcoma (OS) is the most frequent malignant primary bone tumor in children and young adults. Zinc finger Asp-His-His-Cys palmitoyl-acyltransferase 19 (ZDHHC19) is a key enzyme in protein palmitoylation and plays crucial roles in tumor progression. However, its expression profile and biological function in OS have been unclear. In the present study, the expression level of ZDHHC19 in OS cell lines was determined by qRT-PCR and Western blot. The effect of ZDHHC19 in cell growth, invasion and migration was analyzed by CCK8, EDU, transwell, wound healing assay in vitro, and xenograft tumor model in vivo. In addition, bioinformatics analysis was used to explore the potential mechanism of ZDHHC19 in OS. Furthermore, the luciferase reporter assay was conducted to determine the direct binding between miR-940 and ZDHHC19. We discovered that ZDHHC19 was overexpressed in OS cells compared with the normal cells. The functional investigation demonstrated that ZDHHC19 silencing could inhibit proliferation, invasion and migration of OS in vitro and suppress tumorigenicity and lung metastasis in a xenograft model in vivo. Mechanistically, we identified that ZDHHC19 was a direct target of miR-940 and forced ZDHHC19 expressions partially rescue the suppression of proliferation, migration and invasion induced by miR-940. Moreover, bioinformatics analysis combined with validation experiments revealed that activating wnt/β-catenin pathway contributed to the pro-oncogenic effect induced by ZDHHC19. Furthermore, rescue experiments further verified that miR-940/ZDHHC19 axis regulated wnt/β-catenin pathway. Overall, these findings indicated that miR-940/ZDHHC19 axis played a significant role in OS progression and might be considered as a novel target for OS treatment.Abbreviations: OS, osteosarcoma; miRNAs, microRNAs; 3'-UTR, 3'- untranslated region; TARGET, Therapeutically Applicable Research To Generate Effective Treatments; qRT-PCR, quantitative real-time PCR; IHC, Immunohistochemistry; GSVA, Gene Set Variation Analysis; GSEA, Gene Set Enrichment Analysis; KEGG, Kyoto Encyclopedia of Genes and Genomes.

Identification of a 3-gene signature based on differentially expressed invasion genes related to cancer molecular subtypes to predict the prognosis of osteosarcoma patients

Invasion is a critical pathway leading to tumor metastasis. This study constructed an invasion-related polygenic signature to predict osteosarcoma prognosis. We initially determined two molecular subtypes of osteosarcoma, Cluster1 (C1) and Cluster2 (C2).. A 3 invasive-gene signature was established by univariate Cox analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis of the differentially expressed genes (DEGs) between the two subtypes, and was validated in internal and two external data sets (GSE21257 and GSE39058). Patients were divided into high- and low-risk groups by their signature, and the prognosis of osteosarcoma patients in the high-risk group was poor. Based on the time-independent receiver operating characteristic (ROC) curve, the area under the curve (AUC) for 1-year and 2-year OS were higher than 0.75 in internal and external cohorts. This signature also showed a high accuracy and independence in predicting osteosarcoma prognosis and a higher AUC in predicting 1-year osteosarcoma survival than other four existing models. In a word, a 3 invasive gene-based signature was developed, showing a high performance in predicting osteosarcoma prognosis. This signature could facilitate clinical prognostic analysis of osteosarcoma.

RNF144A deficiency promotes PD-L1 protein stabilization and carcinogen-induced bladder tumorigenesis

RNF144A is a DNA damage-induced E3 ubiquitin ligase that targets proteins involved in genome instability for degradation, e.g., DNA-PKcs and BMI1. RNF144A is frequently mutated or epigenetically silenced in cancer, providing the rationale to evaluate RNF144A loss of function in tumorigenesis. Here we report that RNF144A-deficient mice are more prone to the development of bladder tumors upon carcinogen exposure. In addition to DNA-PKcs and BMI1, we identify the immune checkpoint protein PD-L1 as a novel degradation target of RNF144A, since these proteins are expressed at higher levels in Rnf144a KO tumors. RNF144A interacts with PD-L1 in the plasma membrane and intracellular vesicles and promotes poly-ubiquitination and degradation of PD-L1. Therefore, Rnf144a KO stabilizes PD-L1 and leads to a reduction of tumor-infiltrating CD8⁺ T cell populations in the BBN-induced bladder tumors. The bladder tumors developed in WT and Rnf144a KO mice primarily express CK5 and CK14, markers of basal cancer subtype, as expected in BBN-induced bladder tumors. Intriguingly, the Rnf144a KO tumors also express GATA3, a marker for the luminal subtype, suggesting that RNF144A loss of function promotes features of cellular differentiation. Such differentiation features in Rnf144a KO tumors likely result from a decrease of EGFR expression, consistent with the reported role of RNF144A in maintaining EGFR expression. In summary, for the first time our study demonstrates the in vivo tumor suppressor activity of RNF144A upon carcinogenic insult. Loss of RNF144A promotes the expression of DNA-PKcs, BMI1 and PD-L1, likely contributing to the carcinogen-induced bladder tumorigenesis.

Heterogeneity of subsets in glioblastoma mediated by Smad3 palmitoylation

Glioblastoma (GBM) is the most common and deadly of the primary intracranial tumors and is comprised of subsets that show plasticity and marked heterogeneity, contributing to the lack of success in genomic profiling to guide development of precision medicine for these tumors. In this study, a mutation in isocitrate dehydrogenase 1 was found to suppress the transforming growth factor-beta signaling pathway and E2F4 interacted with Smad3 to inhibit expression of mesenchymal markers. However, palmitoylation of Smad3 mediated by palmitoyltransferase ZDHHC19 promoted activation of the transforming growth factor-beta signaling pathway, and its interaction with EP300 promoted expression of mesenchymal markers in the mesenchymal subtype of GBM. Smad3 and hypoxia-inducible factor 1-alpha may be important molecular targets for treatment of glioma because they appear to coordinate the basic aspects of cancer stem cell biology.

Super-enhancer-associated TMEM44-AS1 aggravated glioma progression by forming a positive feedback loop with Myc

Background

Long non-coding RNAs (lncRNAs) have been considered as one type of gene expression regulator for cancer development, but it is not clear how these are regulated. This study aimed to identify a specific lncRNA that promotes glioma progression.

Methods

RNA sequencing (RNA-seq) and quantitative real-time PCR were performed to screen differentially expressed genes. CCK-8, transwell migration, invasion assays, and a mouse xenograft model were performed to determine the functions of TMEM44-AS1. Co-IP, ChIP, Dual-luciferase reporter assays, RNA pulldown, and RNA immunoprecipitation assays were performed to study the molecular mechanism of TMEM44-AS1 and the downstream target.

Results

We identified a novel lncRNA TMEM44-AS1, which was aberrantly expressed in glioma tissues, and that increased TMEM44-AS1 expression was correlated with malignant progression and poor survival for patients with glioma. Expression of TMEM44-AS1 increased the proliferation, colony formation, migration, and invasion of glioma cells. Knockdown of TMEM44-AS1 in glioma cells reduced cell proliferation, colony formation, migration and invasion, and tumor growth in a nude mouse xenograft model. Mechanistically, TMEM44-AS1 is directly bound to the SerpinB3, and sequentially activated Myc and EGR1/IL-6 signaling; Myc transcriptionally induced TMEM44-AS1 and directly bound to the promoter and super-enhancer of TMEM44-AS1, thus forming a positive feedback loop with TMEM44-AS. Further studies demonstrated that Myc interacts with MED1 regulates the super-enhancer of TMEM44-AS1. More importantly, a novel small-molecule Myc inhibitor, Myci975, alleviated TMEM44-AS1-promoted the growth of glioma cells.

Conclusions

Our study implicates a crucial role of the TMEM44-AS1-Myc axis in glioma progression and provides a possible anti-glioma therapeutic agent.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02129-9.

Potential Role of S-Palmitoylation in Cancer Stem Cells of Lung Adenocarcinoma

S-palmitoylation, catalyzed by a family of 23 zinc finger Asp-His-His-Cys (DHHC) domain-containing (ZDHHC) protein acyltransferases localized on the cell membrane. However, stemness genes modulated by ZDHHCs in lung adenocarcinoma (LUAD) remain to be defined. Previously, we have constructed a network of cancer stem cell genes, including INCENP, based on mRNA stemness indices (mRNAsi) of LUAD. INCENP has the function of a chromosomal passenger complex locating to centromeres, which is performed by the conserved region of its N-terminal domain. INCENP protein with a deletion of the first non-conserved 26 amino acid sequence failed to target centromeres. However, the exact function of the deleted sequence has not been elucidated. To identify novel cancer stem cell-relevant palmitoylated proteins and responsible ZDHHC enzymes in LUAD, we analyzed multi-omics data obtained from the database of The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Clinical Proteomic Tumor Analysis Consortium (CPTAC), and the Human Protein Atlas (HPA). ZDHHC5 is distinguished from the ZDHHC family for being up-regulated in mRNA and protein levels and associated with malignant prognosis. ZDHHC5 was positively associated with INCENP, and the correlation score increased with LUAD stages. CSS-Palm results showed Cys¹⁵ was the S-palmitoylation site of INCENP. Interestingly, Cys¹⁵ locates in the 1-26 aa sequence of INCENP, and is a conserved site across species. As INCENP is a nuclear protein, we predicted that the nuclear localization signal of ZDHHC5 was specific to the importin αβ pathway, and the result of immunofluorescence proves that ZDHHC5 is located in the nucleoplasm, in addition to the plasma membrane. Therefore, our study indicates the S-palmitoylation of INCENP mediated by ZDHHC5 as a potential mechanism of S-palmitoylation to modulate CSCs in LUAD.

Fn14-targeted BiTE and CAR-T cells demonstrate potent preclinical activity against glioblastoma

T cell-engaging therapies involving bispecific T cell engager (BiTE) and chimeric antigen receptor T (CAR-T) cells have achieved great success in the treatment of hematological tumors. However, the paucity of ideal cell surface molecules that can be targeted on glioblastoma (GBM) partially reduces the immunotherapeutic efficacy. Recently, high expression of Fn14 has been reported in several solid tumors, so the strategy of exploiting this specific antigen for GBM immunotherapy is worth studying. Consequently, we constructed Fn14× CD3 BiTE and Fn14-specific CAR-T cells and investigated their cytotoxic activity against GBM in vitro and in vivo. First, expression of Fn14 was confirmed in glioma tissues and GBM cells. Then, we designed Fn14-specific BiTE and CAR-T cells and tested their cytotoxicity in GBM cell cultures and mouse models of GBM. Fn14 was highly expressed in GBM tissues and cell lines, while it was undetectable in normal brain samples. Fn14× CD3 BiTE, Fn14 CAR-T cells and Fn14 CAR-T/IL-15 cells were antigen-specific and highly cytotoxic, showing good antitumor activity in vitro and causing significant regression of established solid tumors in xenograft models. However, the xenografts treated with Fn14 CAR-T cells regrew, whereas xenografts treated with Fn14 CAR-T/IL-15 cells did not. IL-15 engineering augmented the antitumor activity of Fn14 CAR-T cells and resulted in significant antitumor effects similar to those of Fn14× CD3 BiTE. Our results suggest that Fn14 is an appropriate target for GBM. Anti-Fn14 BiTE and Fn14-specific CAR-T/IL-15 cells may be exciting immunotherapeutic options for malignant brain cancer.

Inhibitors of DHHC family proteins

Protein S-acylation is a prevalent post-translational protein lipidation that is dynamically regulated by 'writer' protein S-acyltransferases and 'eraser' acylprotein thioesterases. The protein S-acyltransferases comprise 23 aspartate-histidine-histidine-cysteine (DHHC)-containing proteins, which transfer fatty acid acyl groups from acyl-coenzyme A onto protein substrates. DHHC proteins are increasingly recognized as critical regulators of S-acylation-mediated cellular processes and pathology. As our understanding of the importance and breadth of DHHC-mediated biology and pathology expands, so too does the need for chemical inhibitors of this class of proteins. In this review, we discuss the challenges and progress in DHHC inhibitor development, focusing on 2-bromopalmitate, the most commonly used inhibitor in the field, and N-cyanomethyl-N-myracrylamide, a new broad-spectrum DHHC inhibitor. We believe that current and ongoing advances in structure elucidation, mechanistic interrogation, and novel inhibitor design around DHHC proteins will spark innovative strategies to modulate these critical proteins in living systems.

Plasticity of Cancer Stem Cell: Origin and Role in Disease Progression and Therapy Resistance

In embryonic development and throughout life, there are some cells can exhibit phenotypic plasticity. Phenotypic plasticity is the ability of cells to differentiate into multiple lineages. In normal development, plasticity is highly regulated whereas cancer cells re-activate this dynamic ability for their own progression. The re-activation of these mechanisms enables cancer cells to acquire a cancer stem cell (CSC) phenotype- a subpopulation of cells with increased ability to survive in a hostile environment and resist therapeutic insults. There are several contributors fuel CSC plasticity in different stages of disease progression such as a complex network of tumour stroma, epidermal microenvironment and different sub-compartments within tumour. These factors play a key role in the transformation of tumour cells from a stable condition to a progressive state. In addition, flexibility in the metabolic state of CSCs helps in disease progression. Moreover, epigenetic changes such as chromatin, DNA methylation could stimulate the phenotypic change of CSCs. Development of resistance to therapy due to highly plastic behaviour of CSCs is a major cause of treatment failure in cancers. However, recent studies explored that plasticity can also expose the weaknesses in CSCs, thereby could be utilized for future therapeutic development. Therefore, in this review, we discuss how cancer cells acquire the plasticity, especially the role of the normal developmental process, tumour microenvironment, and epigenetic changes in the development of plasticity. We further highlight the therapeutic resistance property of CSCs attributed by plasticity. Also, outline some potential therapeutic options against plasticity of CSCs. Graphical Abstract .

The adaptive transition of glioblastoma stem cells and its implications on treatments

Glioblastoma is the most malignant tumor occurring in the human central nervous system with overall median survival time <14.6 months. Current treatments such as chemotherapy and radiotherapy cannot reach an optimal remission since tumor resistance to therapy remains a challenge. Glioblastoma stem cells are considered to be responsible for tumor resistance in treating glioblastoma. Previous studies reported two subtypes, proneural and mesenchymal, of glioblastoma stem cells manifesting different sensitivity to radiotherapy or chemotherapy. Mesenchymal glioblastoma stem cells, as well as tumor cells generate from which, showed resistance to radiochemotherapies. Besides, two metabolic patterns, glutamine or glucose dependent, of mesenchymal glioblastoma stem cells also manifested different sensitivity to radiochemotherapies. Glutamine dependent mesenchymal glioblastoma stem cells are more sensitive to radiotherapy than glucose-dependent ones. Therefore, the transition between proneural and mesenchymal subtypes, or between glutamine-dependent and glucose-dependent, might lead to tumor resistance to radiochemotherapies. Moreover, neural stem cells were also hypothesized to participate in glioblastoma stem cells mediated tumor resistance to radiochemotherapies. In this review, we summarized the basic characteristics, adaptive transition and implications of glioblastoma stem cells in glioblastoma therapy.

Local anesthetics impair the growth and self-renewal of glioblastoma stem cells by inhibiting ZDHHC15-mediated GP130 palmitoylation

BACKGROUND

A large number of preclinical studies have shown that local anesthetics have a direct inhibitory effect on tumor biological activities, including cell survival, proliferation, migration, and invasion. There are few studies on the role of local anesthetics in cancer stem cells. This study aimed to determine the possible role of local anesthetics in glioblastoma stem cell (GSC) self-renewal and the underlying molecular mechanisms.

METHODS

The effects of local anesthetics in GSCs were investigated through in vitro and in vivo assays (i.e., Cell Counting Kit 8, spheroidal formation assay, double immunofluorescence, western blot, and xenograft model). The acyl-biotin exchange method (ABE) assay was identified proteins that are S-acylated by zinc finger Asp-His-His-Cys-type palmitoyltransferase 15 (ZDHHC15). Western blot, co-immunoprecipitation, and liquid chromatograph mass spectrometer-mass spectrometry assays were used to explore the mechanisms of ZDHHC15 in effects of local anesthetics in GSCs.

RESULTS

In this study, we identified a novel mechanism through which local anesthetics can damage the malignant phenotype of glioma. We found that local anesthetics prilocaine, lidocaine, procaine, and ropivacaine can impair the survival and self-renewal of GSCs, especially the classic glioblastoma subtype. These findings suggest that local anesthetics may weaken ZDHHC15 transcripts and decrease GP130 palmitoylation levels and membrane localization, thus inhibiting the activation of IL-6/STAT3 signaling.

CONCLUSIONS

In conclusion, our work emphasizes that ZDHHC15 is a candidate therapeutic target, and local anesthetics are potential therapeutic options for glioblastoma.

The role of E3 ubiquitin ligases in the development and progression of glioblastoma

Despite recent advances in our understanding of the disease, glioblastoma (GB) continues to have limited treatment options and carries a dismal prognosis for patients. Efforts to stratify this heterogeneous malignancy using molecular classifiers identified frequent alterations in targetable proteins belonging to several pathways including the receptor tyrosine kinase (RTK) and mitogen-activated protein kinase (MAPK) signalling pathways. However, these findings have failed to improve clinical outcomes for patients. In almost all cases, GB becomes refractory to standard-of-care therapy, and recent evidence suggests that disease recurrence may be associated with a subpopulation of cells known as glioma stem cells (GSCs). Therefore, there remains a significant unmet need for novel therapeutic strategies. E3 ubiquitin ligases are a family of >700 proteins that conjugate ubiquitin to target proteins, resulting in an array of cellular responses, including DNA repair, pro-survival signalling and protein degradation. Ubiquitin modifications on target proteins are diverse, ranging from mono-ubiquitination through to the formation of polyubiquitin chains and mixed chains. The specificity in substrate tagging and chain elongation is dictated by E3 ubiquitin ligases, which have essential regulatory roles in multiple aspects of brain cancer pathogenesis. In this review, we begin by briefly summarising the histological and molecular classification of GB. We comprehensively describe the roles of E3 ubiquitin ligases in RTK and MAPK, as well as other, commonly altered, oncogenic and tumour suppressive signalling pathways in GB. We also describe the role of E3 ligases in maintaining glioma stem cell populations and their function in promoting resistance to ionizing radiation (IR) and chemotherapy. Finally, we consider how our knowledge of E3 ligase biology may be used for future therapeutic interventions in GB, including the use of blood-brain barrier permeable proteolysis targeting chimeras (PROTACs).

Protein S-Palmitoylation and Lung Diseases

S-palmitoylation of protein is a posttranslational, reversible lipid modification; it was catalyzed by a family of 23 mammalian palmitoyl acyltransferases in humans. S-palmitoylation can impact protein function by regulating protein sorting, secretion, trafficking, stability, and protein interaction. Thus, S-palmitoylation plays a crucial role in many human diseases including mental illness and cancers. In this chapter, we systematically reviewed the influence of S-palmitoylation on protein performance, the characteristics of S-palmitoylation regulating protein function, and the role of S-palmitoylation in pulmonary inflammation and pulmonary hypertension and summed up the treatment strategies of S-palmitoylation-related diseases and the research status of targeted S-palmitoylation agonists/inhibitors. In conclusion, we highlighted the potential role of S-palmitoylation and depalmitoylation in the treatment of human diseases.

Clinical implication of cellular vaccine in glioma: current advances and future prospects

Gliomas, especially glioblastomas, represent one of the most aggressive and difficult-to-treat human brain tumors. In the last few decades, clinical immunotherapy has been developed and has provided exceptional achievements in checkpoint inhibitors and vaccines for cancer treatment. Immunization with cellular vaccines has the advantage of containing specific antigens and acceptable safety to potentially improve cancer therapy. Based on T cells, dendritic cells (DC), tumor cells and natural killer cells, the safety and feasibility of cellular vaccines have been validated in clinical trials for glioma treatment. For TAA engineered T cells, therapy mainly uses chimeric antigen receptors (IL13Rα2, EGFRvIII and HER2) and DNA methylation-induced technology (CT antigen) to activate the immune response. Autologous dendritic cells/tumor antigen vaccine (ADCTA) pulsed with tumor lysate and peptides elicit antigen-specific and cytotoxic T cell responses in patients with malignant gliomas, while its pro-survival effect is biased. Vaccinations using autologous tumor cells modified with TAAs or fusion with fibroblast cells are characterized by both effective humoral and cell-mediated immunity. Even though few therapeutic effects have been observed, most of this therapy showed safety and feasibility, asking for larger cohort studies and better guidelines to optimize cellular vaccine efficiency in anti-glioma therapy.

Dual inhibition of Src and PLK1 regulate stemness and induce apoptosis through Notch1-SOX2 signaling in EGFRvIII positive glioma stem cells (GSCs)

Glioma stem cells (GSCs) have been implicated in the promotion of malignant progression. Epidermal growth factor receptor variant (EGFRv) has been associated with glioma "stemness". However, the molecular mechanism is not clear. In this study, we were committed to investigate the role of EGFRv in GSCs and presented a new therapeutic target in EGFRvIII positive GSCs. The results showed that EGFRvIII could induce the expression of p-Src and PLK1, and both could induce the Notch1-SOX2 signaling pathway to promote self-renewal and tumor progression of GSCs. Mechanistically, both p-Src and PLK1 can induce Notch1, and the intracellular domain of Notch1 (NICD) can directly bind to SOX2, thereby promoting the maintenance of glioma stem cells. Furthermore, Saracatinib (Src inhibition) and BI2536 (PLK1 inhibition) diminished GSC self-renewal in vitro, and combining the two inhibitors increased survival of orthotopic tumor-bearing mice. Taken together, these data indicate that p-Src and PLK1 contribute to cancer stemness in EGFRvIII-positive GSCs by driving Notch1-SOX2 signaling, a finding that has important clinical implications.

MiR-146b-5p suppresses the malignancy of GSC/MSC fusion cells by targeting SMARCA5

Recent studies have confirmed that both cancer-associated bone marrow mesenchymal stem cells (BM-MSCs, MSCs) and glioma stem-like cells (GSCs) contribute to malignant progression of gliomas through their mutual interactions within the tumor microenvironment. However, the exact ways and relevant mechanisms involved in the actions of GSCs and MSCs within the glioma microenvironment are not fully understood. Using a dual-color fluorescence tracing model, our studies revealed that GSCs are able to spontaneously fuse with MSCs, yielding GSC/MSC fusion cells, which exhibited markedly enhanced proliferation and invasiveness. MiR-146b-5p was downregulated in the GSC/MSC fusion cells, and its overexpression suppressed proliferation, migration and invasion by the fusion cells. SMARCA5, which is highly expressed in high-grade gliomas, was a direct downstream target of miR-146b-5p in the GSC/MSC fusion cells. miR-146b-5p inhibited SMARCA5 expression and inactivated a TGF-β pathway, thereby decreasing GSC/MSC fusion cell proliferation, migration and invasion. Collectively, these findings demonstrate that miR-146b-5p suppresses the malignant phenotype of GSC/MSC fusion cells in the glioma microenvironment by targeting a SMARCA5-regulated TGF-β pathway.

Protein Palmitoylation Regulates Cell Survival by Modulating XBP1 Activity in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) almost invariably acquires an invasive phenotype, resulting in limited therapeutic options. Protein palmitoylation markedly affects tumorigenesis and malignant progression in GBM. The role of protein palmitoylation in GBM, however, has not been systematically reported. This study aimed to investigate the effect of protein palmitoylation on GBM cell survival and the cell cycle. In this study, most palmitoyltransferases were upregulated in GBM and its cell lines, and protein palmitoylation participated in signaling pathways controlling cell survival and the GBM cell cycle. Inhibition of protein palmitoylation with substrate-analog inhibitors, that is, 2-bromopalmitate, cerulenin, and tunicamycin, induced G₂ cell cycle arrest and cell death in GBM cells through enhanced endoplasmic reticulum (ER) stress. These effects are primarily attributed to the palmitoylation inhibitors activating pro-apoptotic pathways and ER stress signals. Further analysis revealed was the accumulation of SUMOylated XBP1 (X-box binding protein 1) and its transcriptional repression, along with a reduction in XBP1 palmitoylation. Taken together, the present results indicate that protein palmitoylation plays an important role in the survival of GBM cells, further providing a potential therapeutic strategy for GBM.

RBR E3 ubiquitin ligases in tumorigenesis

RING-in-between-RING (RBR) E3 ligases are one class of E3 ligases that is characterized by the unique RING-HECT hybrid mechanism to function with E2s to transfer ubiquitin to target proteins for degradation. Emerging evidence has demonstrated that RBR E3 ligases play essential roles in neurodegenerative diseases, infection, inflammation and cancer. Accumulated evidence has revealed that RBR E3 ligases exert their biological functions in various types of cancers by modulating the degradation of tumor promoters or suppressors. Hence, we summarize the differential functions of RBR E3 ligases in a variety of human cancers. In general, ARIH1, RNF14, RNF31, RNF144B, RNF216, and RBCK1 exhibit primarily oncogenic roles, whereas ARIH2, PARC and PARK2 mainly have tumor suppressive functions. Moreover, the underlying mechanisms by which different RBR E3 ligases are involved in tumorigenesis and progression are also described. We discuss the further investigation is required to comprehensively understand the critical role of RBR E3 ligases in carcinogenesis. We hope our review can stimulate the researchers to deeper explore the mechanism of RBR E3 ligases-mediated carcinogenesis and to develop useful inhibitors of these oncogenic E3 ligases for cancer therapy.