The essential role of YAP O-GlcNAcylation in high-glucose-stimulated liver tumorigenesis

PCK1 attenuates tumor stemness via activating the Hippo signaling pathway in hepatocellular carcinoma

Liver cancer stem cells were found to rely on glycolysis as the preferred metabolic program. Phosphoenolpyruvate carboxylase 1 (PCK1), a gluconeogenic metabolic enzyme, is down-regulated in hepatocellular carcinoma and is closely related to poor prognosis. The oncogenesis and progression of tumors are closely related to cancer stem cells. It is not completely clear whether the PCK1 deficiency increases the stemness of hepatoma cells and promotes the oncogenesis of hepatocellular carcinoma. Herein, the results showed that PCK1 inhibited the self-renewal property of hepatoma cells, reduced the mRNA level of cancer stem cell markers, and inhibited tumorigenesis. Moreover, PCK1 increased the sensitivity of hepatocellular carcinoma cells to sorafenib. Furthermore, we found that PCK1 activated the Hippo pathway by enhancing the phosphorylation of YAP and inhibiting its nuclear translocation. Verteporfin reduced the stemness of hepatoma cells and promoted the pro-apoptotic effect of sorafenib. Thus, combined treatment with verteporfin and sorafenib may be a potential anti-tumor strategy in hepatocellular carcinoma.

O-GlcNAcylation controls pro-fibrotic transcriptional regulatory signaling in myofibroblasts

Tissue injury causes activation of mesenchymal lineage cells into wound-repairing myofibroblasts (MFs), whose uncontrolled activity ultimately leads to fibrosis. Although this process is triggered by deep metabolic and transcriptional reprogramming, functional links between these two key events are not yet understood. Here, we report that the metabolic sensor post-translational modification O-linked β-D-N-acetylglucosaminylation (O-GlcNAcylation) is increased and required for myofibroblastic activation. Inhibition of protein O-GlcNAcylation impairs archetypal myofibloblast cellular activities including extracellular matrix gene expression and collagen secretion/deposition as defined in vitro and using ex vivo and in vivo murine liver injury models. Mechanistically, a multi-omics approach combining proteomic, epigenomic, and transcriptomic data mining revealed that O-GlcNAcylation controls the MF transcriptional program by targeting the transcription factors Basonuclin 2 (BNC2) and TEA domain transcription factor 4 (TEAD4) together with the Yes-associated protein 1 (YAP1) co-activator. Indeed, inhibition of protein O-GlcNAcylation impedes their stability leading to decreased functionality of the BNC2/TEAD4/YAP1 complex towards promoting activation of the MF transcriptional regulatory landscape. We found that this involves O-GlcNAcylation of BNC2 at Thr455 and Ser490 and of TEAD4 at Ser69 and Ser99. Altogether, this study unravels protein O-GlcNAcylation as a key determinant of myofibroblastic activation and identifies its inhibition as an avenue to intervene with fibrogenic processes.

A review on decoding the roles of YAP/TAZ signaling pathway in cardiovascular diseases: Bridging molecular mechanisms to therapeutic insights

Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) serve as transcriptional co-activators that dynamically shuttle between the cytoplasm and nucleus, resulting in either the suppression or enhancement of their downstream gene expression. Recent emerging evidence demonstrates that YAP/TAZ is strongly implicated in the pathophysiological processes that contribute to cardiovascular diseases (CVDs). In the cardiovascular system, YAP/TAZ is involved in the orchestration of a range of biological processes such as oxidative stress, inflammation, proliferation, and autophagy. Furthermore, YAP/TAZ has been revealed to be closely associated with the initiation and development of various cardiovascular diseases, including atherosclerosis, pulmonary hypertension, myocardial fibrosis, cardiac hypertrophy, and cardiomyopathy. In this review, we delve into recent studies surrounding YAP and TAZ, along with delineating their roles in contributing to the pathogenesis of CVDs with a link to various physiological processes in the cardiovascular system. Additionally, we highlight the current potential drugs targeting YAP/TAZ for CVDs therapy and discuss their challenges for translational application. Overall, this review may offer novel insights for understanding and treating cardiovascular disorders.

Biological Functions and Potential Therapeutic Significance of O-GlcNAcylation in Hepatic Cellular Stress and Liver Diseases

O-linked-β-D-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation), which is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), is a post-translational modification involved in multiple cellular processes. O-GlcNAcylation of proteins can regulate their biological functions via crosstalk with other post-translational modifications, such as phosphorylation, ubiquitination, acetylation, and methylation. Liver diseases are a major cause of death worldwide; yet, key pathological features of the disease, such as inflammation, fibrosis, steatosis, and tumorigenesis, are not fully understood. The dysregulation of O-GlcNAcylation has been shown to be involved in some severe hepatic cellular stress, viral hepatitis, liver fibrosis, nonalcoholic fatty acid liver disease (NAFLD), malignant progression, and drug resistance of hepatocellular carcinoma (HCC) through multiple molecular signaling pathways. Here, we summarize the emerging link between O-GlcNAcylation and hepatic pathological processes and provide information about the development of therapeutic strategies for liver diseases.

Regulation of myocardial glucose metabolism by YAP/TAZ signaling

The heart utilizes glucose and its metabolites as both energy sources and building blocks for cardiac growth and survival under both physiological and pathophysiological conditions. YAP/TAZ, transcriptional co-activators of the Hippo pathway, are key regulators of cell proliferation, survival, and metabolism in many cell types. Increasing lines of evidence suggest that the Hippo-YAP/TAZ signaling pathway is involved in the regulation of both physiological and pathophysiological processes in the heart. In particular, YAP/TAZ play a critical role in mediating aerobic glycolysis, the Warburg effect, in cardiomyocytes. Here, we summarize what is currently known about YAP/TAZ signaling in the heart by focusing on the regulation of glucose metabolism and its functional significance.

The Hippo signaling pathway in development and regeneration

The Hippo signaling pathway is a central growth control mechanism in multicellular organisms. By integrating diverse mechanical, biochemical, and stress cues, the Hippo pathway orchestrates proliferation, survival, differentiation, and mechanics of cells, which in turn regulate organ development, homeostasis, and regeneration. A deep understanding of the regulation and function of the Hippo pathway therefore holds great promise for developing novel therapeutics in regenerative medicine. Here, we provide updates on the molecular organization of the mammalian Hippo signaling network, review the regulatory signals and functional outputs of the pathway, and discuss the roles of Hippo signaling in development and regeneration.

The alanyl-tRNA synthetase AARS1 moonlights as a lactyltransferase to promote YAP signaling in gastric cancer

Lactylation has been recently identified as a new type of posttranslational modification occurring widely on lysine residues of both histone and nonhistone proteins. The acetyltransferase p300 is thought to mediate protein lactylation, yet the cellular concentration of the proposed lactyl-donor, lactyl-coenzyme A, is about 1,000 times lower than that of acetyl-CoA, raising the question of whether p300 is a genuine lactyltransferase. Here, we report that alanyl-tRNA synthetase 1 (AARS1) moonlights as a bona fide lactyltransferase that directly uses lactate and ATP to catalyze protein lactylation. Among the candidate substrates, we focused on the Hippo pathway, which has a well-established role in tumorigenesis. Specifically, AARS1 was found to sense intracellular lactate and translocate into the nucleus to lactylate and activate the YAP-TEAD complex; and AARS1 itself was identified as a Hippo target gene that forms a positive-feedback loop with YAP-TEAD to promote gastric cancer (GC) cell proliferation. Consistently, the expression of AARS1 was found to be upregulated in GC, and elevated AARS1 expression was found to be associated with poor prognosis for patients with GC. Collectively, this work found AARS1 with lactyltransferase activity in vitro and in vivo and revealed how the metabolite lactate is translated into a signal of cell proliferation.

GALNT2 targeted by miR-139-5p promotes proliferation of clear cell renal cell carcinoma via inhibition of LATS2 activation

Polypeptide N-Acetylgalactosaminyltransferase (GALNTs) are critical enzymes that initiate mucin type-O glycosylation, and are closely associated with the occurrence and development of multiple cancers. However, the significance of GALNT2 in clear cell renal cell carcinoma (ccRCC) progression remains largely undetermined. Based on public multi-omics analysis, GALNT2 was strongly elevated in ccRCC versus adjoining nontumor tissues, and it displayed a relationship with poor overall survival (OS) of ccRCC patients. In addition, GALNT2 over-expression accelerated proliferation of renal cancer cell (RCC) lines. In contrast, GALNT2 knockdown using shRNAs suppressed cell proliferation, and this was rescued by LATS2 knockdown. Similarly, GALNT2 deficiency enhanced p-LATS2/LATS2 expression. LATS2 is activated by phosphorylation (p-LATS2) and, in turn, phosphorylate the downstream substrate protein YAP. Phosphorylated YAP (p-YAP) stimulated its degradation and cytoplasmic retention, as it was unable to translocate to the nucleus. This resulted in reduced cell proliferation. Subsequently, we explored the upstream miRNAs of GALNT2. Using dual luciferase reporter assay, we revealed that miR-139-5p interacted with the 3' UTR of GALNT2. Low miR-139-5p expression was associated with worse ccRCC patient outcome. Based on our experiments, miR-139-5p overexpression inhibited RCC proliferation, and this phenotype was rescued by GALNT2 overexpression. Given these evidences, the miR-139-5p-GALNT2-LATS2 axis is critical for RCC proliferation, and it is an excellent candidate for a new therapeutic target in ccRCC.

Protein O-GlcNAcylation: The sweet hub in liver metabolic flexibility from a (patho)physiological perspective

O-GlcNAcylation is a dynamic, reversible and atypical O-glycosylation that regulates various cellular physiological processes via conformation, stabilisation, localisation, chaperone interaction or activity of target proteins. The O-GlcNAcylation cycle is precisely controlled by collaboration between O-GlcNAc transferase and O-GlcNAcase. Uridine-diphosphate-N-acetylglucosamine, the sole donor of O-GlcNAcylation produced by the hexosamine biosynthesis pathway, is controlled by the input of glucose, glutamine, acetyl coenzyme A and uridine triphosphate, making it a sensor of the fluctuation of molecules, making O-GlcNAcylation a pivotal nutrient sensor for the metabolism of carbohydrates, amino acids, lipids and nucleotides. O-GlcNAcylation, particularly prevalent in liver, is the core hub for controlling systemic glucose homeostasis due to its nutritional sensitivity and precise spatiotemporal regulation of insulin signal transduction. The pathology of various liver diseases has highlighted hepatic metabolic disorder and dysfunction, and abnormal O-GlcNAcylation also plays a specific pathological role in these processes. Therefore, this review describes the unique features of O-GlcNAcylation and its dynamic homeostasis maintenance. Additionally, it explains the underlying nutritional sensitivity of O-GlcNAcylation and discusses its mechanism of spatiotemporal modulation of insulin signal transduction and liver metabolic homeostasis during the fasting and feeding cycle. This review emphasises the pathophysiological implications of O-GlcNAcylation in nonalcoholic fatty liver disease, nonalcoholic steatohepatitis and hepatic fibrosis, and focuses on the adverse effects of hyper O-GlcNAcylation on liver cancer progression and metabolic reprogramming.

The glucocorticoid receptor as a master regulator of the Müller cell response to diabetic conditions in mice

Diabetic retinopathy (DR) is considered a primarily microvascular complication of diabetes. Müller glia cells are at the centre of the retinal neurovascular unit and play a critical role in DR. We therefore investigated Müller cell-specific signalling pathways that are altered in DR to identify novel targets for gene therapy. Using a multi-omics approach on purified Müller cells from diabetic db/db mice, we found the mRNA and protein expression of the glucocorticoid receptor (GR) to be significantly decreased, while its target gene cluster was down-regulated. Further, oPOSSUM TF analysis and ATAC- sequencing identified the GR as a master regulator of Müller cell response to diabetic conditions. Cortisol not only increased GR phosphorylation. It also induced changes in the expression of known GR target genes in retinal explants. Finally, retinal functionality was improved by AAV-mediated overexpression of GR in Müller cells. Our study demonstrates an important role of the glial GR in DR and implies that therapeutic approaches targeting this signalling pathway should be aimed at increasing GR expression rather than the addition of more ligand.

Androgen-repressed lncRNA LINC01126 drives castration-resistant prostate cancer by regulating the switch between O-GlcNAcylation and phosphorylation of androgen receptor

BACKGROUND

Prostate cancer (PCa) initially shows satisfactory response to therapies targeting the androgen receptor (AR). However, progression to a castration-resistant stage indicates poor prognosis in PCa patients. AR signalling still plays a central role in most castration-resistant prostate cancers (CRPC). Therefore, unveiling the mechanisms of AR reactivation under androgen-deprived conditions is imperative to discover novel therapeutic targets for CRPC.

METHODS

Using an integrative analysis of the transcriptomics of three independent PCa cohorts and a published landscape of AR-regulated long non-coding RNA (lncRNA), lncRNA LINC01126 was selected as a candidate gene that could drive CRPC progression for further study. Quantitative reverse transcription polymerase chain reaction, in situ hybridisation (ISH) and fluorescent ISH were performed to detect LINC01126 in PCa tissues and cells. The functional role and mechanism of LINC01126 were further investigated using in vitro and in vivo gain and loss of function assays.

RESULTS

LINC01126, identified as an AR-repressed lncRNA, was significantly upregulated after AR-targeted therapies. In addition, we found that LINC01126 was upregulated in CRPC and was associated with poor prognosis. We also proved that LINC01126 stabilised AR protein and enhanced AR nuclear translocation and transactivation by promoting the transition from O-GlcNAcylation at threonine 80 to phosphorylation at serine 81 (S81) within the AR protein. Mechanism analysis revealed that LINC01126 facilitates the interaction of CDK9 with AR and impedes the binding of O-linked N-acetylglucosamine (O-GlcNAc) transferase to AR. Consequently, LINC01126 expression was sufficient to activate AR signalling without androgen. LINC01126 overexpression increased, whereas LINC01126 knockdown decreased castration resistance traits in PCa cells in vitro and in vivo. Furthermore, our data showed that LINC01126-targeting antisense oligonucleotides (ASO) substantially inhibited CRPC cells in vitro.

CONCLUSIONS

Our research expands the functions of AR-regulated lncRNA in sustaining androgen-independent AR activity and promoting CRPC progression and reveals that LINC01126 may be a new therapeutic target for PCa.

Endothelial YAP Mediates Hyperglycemia-Induced Platelet Hyperactivity and Arterial Thrombosis

BACKGROUND

Hyperglycemia-a symptom that characterizes diabetes-is highly associated with atherothrombotic complications. However, the underlying mechanism by which hyperglycemia fuels platelet activation and arterial thrombus formation is still not fully understood.

METHODS

The profiles of polyunsaturated fatty acid metabolites in the plasma of patients with diabetes and healthy controls were determined with targeted metabolomics. FeCl3-induced carotid injury model was used to assess arterial thrombus formation in mice with endothelial cell (EC)-specific YAP (yes-associated protein) deletion or overexpression. Flow cytometry and clot retraction assay were used to evaluate platelet activation. RNA sequencing and multiple biochemical analyses were conducted to unravel the underlying mechanism.

RESULTS

The plasma PGE2 (prostaglandin E2) concentration was elevated in patients with diabetes with thrombotic complications and positively correlated with platelet activation. The PGE2 synthetases COX-2 (cyclooxygenase-2) and mPGES-1 (microsomal prostaglandin E synthase-1) were found to be highly expressed in ECs but not in other type of vessel cells in arteries from both patients with diabetes and hyperglycemic mice, compared with nondiabetic individuals and control mice, respectively. A combination of RNA sequencing and ingenuity pathway analyses indicated the involvement of YAP signaling. EC-specific deletion of YAP limited platelet activation and arterial thrombosis in hyperglycemic mice, whereas EC-specific overexpression of YAP in mice mimicked the prothrombotic state of diabetes, without affecting hemostasis. Mechanistically, we found that hyperglycemia/high glucose-induced endothelial YAP nuclear translocation and subsequently transcriptional expression of COX-2 and mPGES-1 contributed to the elevation of PGE2 and platelet activation. Blockade of EP3 (prostaglandin E receptor 3) activation by oral administration of DG-041 reversed the hyperactivity of platelets and delayed thrombus formation in both EC-specific YAP-overexpressing and hyperglycemic mice.

CONCLUSIONS

Collectively, our data suggest that hyperglycemia-induced endothelial YAP activation aggravates platelet activation and arterial thrombus formation via PGE2/EP3 signaling. Targeting EP3 with DG-041 might be therapeutic for diabetes-related thrombosis.

Control of stem cell renewal and fate by YAP and TAZ

Complex physiological processes control whether stem cells self-renew, differentiate or remain quiescent. Two decades of research have placed the Hippo pathway, a highly conserved kinase signalling cascade, and its downstream molecular effectors YAP and TAZ at the nexus of this decision. YAP and TAZ translate complex biological cues acting on stem cells - from mechanical forces to cellular metabolism - into genome-wide effects to mediate stem cell functions. While aberrant YAP/TAZ activity drives stem cell dysfunction in ageing, tumorigenesis and disease, therapeutic targeting of Hippo signalling and YAP/TAZ can boost stem cell activity to enhance regeneration. In this Review, we discuss how YAP/TAZ control the self-renewal, fate and plasticity of stem cells in different contexts, how dysregulation of YAP/TAZ in stem cells leads to disease, and how therapeutic modalities targeting YAP/TAZ may benefit regenerative medicine and cancer therapy.

O-GlcNAcylation Regulates Centrosome Behavior and Cell Polarity to Reduce Pulmonary Fibrosis and Maintain the Epithelial Phenotype

O-GlcNAcylation functions as a cellular nutrient and stress sensor and participates in almost all cellular processes. However, it remains unclear whether O-GlcNAcylation plays a role in the establishment and maintenance of cell polarity, because mice lacking O-GlcNAc transferase (OGT) are embryonically lethal. Here, a mild Ogt knockout mouse model is constructed and the important role of O-GlcNAcylation in establishing and maintaining cell polarity is demonstrated. Ogt knockout leads to severe pulmonary fibrosis and dramatically promotes epithelial-to-mesenchymal transition. Mechanistic studies reveal that OGT interacts with pericentriolar material 1 (PCM1) and centrosomal protein 131 (CEP131), components of centriolar satellites required for anchoring microtubules to the centrosome. These data further show that O-GlcNAcylation of PCM1 and CEP131 promotes their centrosomal localization through phase separation. Decrease in O-GlcNAcylation prevents PCM1 and CEP131 from localizing to the centrosome, instead dispersing these proteins throughout the cell and impairing the microtubule-centrosome interaction to disrupt centrosome positioning and cell polarity. These findings identify a previously unrecognized role for protein O-GlcNAcylation in establishing and maintaining cell polarity with important implications for the pathogenesis of pulmonary fibrosis.

The essential role of O-GlcNAcylation in hepatic differentiation

BACKGROUND

O-GlcNAcylation is a post-translational modification catalyzed by the enzyme O-GlcNAc transferase, which transfers a single N-acetylglucosamine sugar from UDP-GlcNAc to the protein on serine and threonine residues on proteins. Another enzyme, O-GlcNAcase (OGA), removes this modification. O-GlcNAcylation plays an important role in pathophysiology. Here, we report that O-GlcNAcylation is essential for hepatocyte differentiation, and chronic loss results in fibrosis and HCC.

METHODS

Single-cell RNA-sequencing (RNA-seq) was used to investigate hepatocyte differentiation in hepatocyte-specific O-GlcNAc transferase-knockout (OGT-KO) mice with decreased hepatic O-GlcNAcylation and in O-GlcNAcase-KO mice with increased O-GlcNAcylation in hepatocytes. Patients HCC samples and the diethylnitrosamine-induced HCC model were used to investigate the effect of modulation of O-GlcNAcylation on the development of liver cancer.

RESULTS

Loss of hepatic O-GlcNAcylation resulted in disruption of liver zonation. Periportal hepatocytes were the most affected by loss of differentiation, characterized by dysregulation of glycogen storage and glucose production. O-GlcNAc transferase-KO mice exacerbated diethylnitrosamine-induced HCC development with increased inflammation, fibrosis, and YAP signaling. Consistently, O-GlcNAcase -KO mice with increased hepatic O-GlcNAcylation inhibited diethylnitrosamine-induced HCC. A progressive loss of O-GlcNAcylation was observed in patients with HCC.

CONCLUSIONS

Our study shows that O-GlcNAcylation is a critical regulator of hepatic differentiation, and loss of O-GlcNAcylation promotes hepatocarcinogenesis. These data highlight increasing O-GlcNAcylation as a potential therapy in chronic liver diseases, including HCC.

Targeting Hippo signaling in cancer: novel perspectives and therapeutic potential

As highly conserved among diverse species, Hippo signaling pathway regulates various biological processes, including development, cell proliferation, stem cell function, tissue regeneration, homeostasis, and organ size. Studies in the last two decades have provided a good framework for how these fundamental functions of Hippo signaling are tightly regulated by a network with numerous intracellular and extracellular factors. The Hippo signaling pathway, when dysregulated, may lead to a wide variety of diseases, especially cancer. There is growing evidence demonstrating that dysregulated Hippo signaling is closely associated with tumorigenesis, cancer cell invasion, and migration, as well as drug resistance. Therefore, the Hippo pathway is considered an appealing therapeutic target for the treatment of cancer. Promising novel agents targeting the Hippo signaling pathway for cancers have recently emerged. These novel agents have shown antitumor activity in multiple cancer models and demonstrated therapeutic potential for cancer treatment. However, the detailed molecular basis of the Hippo signaling-driven tumor biology remains undefined. Our review summarizes current advances in understanding the mechanisms by which Hippo signaling drives tumorigenesis and confers drug resistance. We also propose strategies for future preclinical and clinical development to target this pathway.

Silencing GMPPB Inhibits the Proliferation and Invasion of GBM via Hippo/MMP3 Pathways

Glioblastoma multiforme (GBM) is a highly aggressive malignancy and represents the most common brain tumor in adults. To better understand its biology for new and effective therapies, we examined the role of GDP-mannose pyrophosphorylase B (GMPPB), a key unit of the GDP-mannose pyrophosphorylase (GDP-MP) that catalyzes the formation of GDP-mannose. Impaired GMPPB function will reduce the amount of GDP-mannose available for O-mannosylation. Abnormal O-mannosylation of alpha dystroglycan (α-DG) has been reported to be involved in cancer metastasis and arenavirus entry. Here, we found that GMPPB is highly expressed in a panel of GBM cell lines and clinical samples and that expression of GMPPB is positively correlated with the WHO grade of gliomas. Additionally, expression of GMPPB was negatively correlated with the prognosis of GBM patients. We demonstrate that silencing GMPPB inhibits the proliferation, migration, and invasion of GBM cells both in vitro and in vivo and that overexpression of GMPPB exhibits the opposite effects. Consequently, targeting GMPPB in GBM cells results in impaired GBM tumor growth and invasion. Finally, we identify that the Hippo/MMP3 axis is essential for GMPPB-promoted GBM aggressiveness. These findings indicate that GMPPB represents a potential novel target for GBM treatment.

LPCAT3 Is Transcriptionally Regulated by YAP/ZEB/EP300 and Collaborates with ACSL4 and YAP to Determine Ferroptosis Sensitivity

Aims: Lipid peroxidation occurring in lung adenocarcinoma (LUAD) cells leads to ferroptosis. Lysophosphatidylcholine acyl-transferase 3 (LPCAT3) plays a key role in providing raw materials for lipid peroxidation by promoting esterification of polyunsaturated fatty acids to phospholipids. Whether LPCAT3 determines ferroptosis sensitivity and the mechanism by which its expression is regulated in LUAD has not been reported. Results: LPCAT3 and acyl-coenzyme A (CoA) synthetase long-chain family member (ACSL)4 levels were positively associated with ferroptosis sensitivity in LUAD cell lines. Overexpression of LPCAT3 and ACSL4 sensitized LUAD cells to ferroptosis, while LPCAT3 and ACSL4 knockout showed the opposite effect. Zinc-finger E-box-binding (ZEB) was shown to directly bind the LPCAT3 promoter to stimulate its transcription in a Yes-associated protein (YAP)-dependent manner. An interaction between YAP and ZEB was also observed. E1A-binding protein p300 (EP300) simultaneously bound with YAP and ZEB, and induced H3K27Ac for LPCAT3 transcription. This mechanism was verified in primary LUAD cell and xenograft models. The ACSL4, LPCAT3, and YAP combination can jointly determine LUAD ferroptosis sensitivity. Innovation: The binding site of ZEB exists in the -1600 to -1401 nt region of LPCAT3 promoter, which promotes LPCAT3 transcription after ZEB binding. ZEB and YAP bind, and the ZEB zinc-finger cluster domain and YAP WW domain are crucial for their binding. EP300 may bind with YAP via its Bromo domain and with ZEB via its CBP/p300-HAT domain. In addition, the combination of ACSL4, LPCAT3, and YAP to determine ferroptosis sensitivity of LUAD cells is better than prostaglandin-endoperoxide synthase 2 (PTGS2), transferrin receptor (TFRC), or NADPH oxidase 1 (NOX1). Conclusion: LPCAT3 transcription is regulated by YAP, ZEB, and EP300. LUAD ferroptosis sensitivity can be determined by the combination of ACSL4, LPCAT3, and YAP. Antioxid. Redox Signal. 39, 491-511.

Identification of a diketopiperazine-based O-GlcNAc transferase inhibitor sensitizing hepatocellular carcinoma to CDK9 inhibition

O-GlcNAcylation (O-linked β-N-acetylglucosaminylation) is an important post-translational and metabolic process in cells that is implicated in a wide range of physiological processes. O-GlcNAc transferase (OGT) is ubiquitously present in cells and is the only enzyme that catalyses the transfer of O-GlcNAc to nucleocytoplasmic proteins. Aberrant glycosylation by OGT has been linked to a variety of diseases including cancer, neurodegenerative disorders and diabetes. Previously, we and others demonstrated that O-GlcNAcylation is notably elevated in hepatocellular carcinoma (HCC). The overexpression of O-GlcNAcylation promotes cancer progression and metastasis. Here, we report the identification of HLY838, a novel diketopiperazine-based OGT inhibitor with the ability to induce a global decrease in cellular O-GlcNAc. HLY838 enhances the in vitro and in vivo anti-HCC activity of CDK9 inhibitor by downregulating c-Myc and downstream E2F1 expression. Mechanistically, c-Myc is regulated by the CDK9 at the transcript level, and stabilized by OGT at the protein level. This work therefore demonstrates that HLY838 potentiates the antitumor responses of CDK9 inhibitor, providing an experimental rationale for developing OGT inhibitor as a sensitizing agent in cancer therapeutics.

O‑GlcNAcylation mediates endometrial cancer progression by regulating the Hippo‑YAP pathway

The incidence of endometrial cancer (EC) is rapidly increasing worldwide. The majority of endometrial cancers are diagnosed at an early stage and are associated with a good prognosis; however, patients with advanced‑stage EC have a poor prognosis and present with invasive metastasis. The mechanisms responsible for the invasion and metastasis of endometrial cancer remain unknown. Here, the present study aimed to examine the effects of O‑GlcNAcylation on the malignancy of EC and its association with Yes‑associated protein (YAP). It was found that the expression of O‑GlcNAc transferase (OGT) and O‑GlcNAcylation were increased in EC tissues; the decrease in O‑GlcNAcylation levels was found to lead to the decreased proliferation, migration and invasion of EC cells. Mass spectrometric analysis revealed that OGT knockdown reduced the O‑GlcNAcylation of YAP. Furthermore, it was found that the reduction in the O‑GlcNAcylation of YAP promoted its phosphorylation, which in turn inhibited the access of YAP to the nucleus and downstream target gene activation, demonstrating that the level of O‑GlcNAcylation affects the development of EC. On the whole, the findings of the present study indicate that YAP is a key molecule linking the O‑GlcNAcylation and Hippo pathways, which together regulate the progression of EC.

YAP/TAZ: Molecular pathway and disease therapy

The Yes-associated protein and its transcriptional coactivator with PDZ-binding motif (YAP/TAZ) are two homologous transcriptional coactivators that lie at the center of a key regulatory network of Hippo, Wnt, GPCR, estrogen, mechanical, and metabolism signaling. YAP/TAZ influences the expressions of downstream genes and proteins as well as enzyme activity in metabolic cycles, cell proliferation, inflammatory factor expression, and the transdifferentiation of fibroblasts into myofibroblasts. YAP/TAZ can also be regulated through epigenetic regulation and posttranslational modifications. Consequently, the regulatory function of these mechanisms implicates YAP/TAZ in the pathogenesis of metabolism-related diseases, atherosclerosis, fibrosis, and the delicate equilibrium between cancer progression and organ regeneration. As such, there arises a pressing need for thorough investigation of YAP/TAZ in clinical settings. In this paper, we aim to elucidate the signaling pathways that regulate YAP/TAZ and explore the mechanisms of YAP/TAZ-induce diseases and their potential therapeutic interventions. Furthermore, we summarize the current clinical studies investigating treatments targeting YAP/TAZ. We also address the limitations of existing research on YAP/TAZ and propose future directions for research. In conclusion, this review aims to provide fresh insights into the signaling mediated by YAP/TAZ and identify potential therapeutic targets to present innovative solutions to overcome the challenges associated with YAP/TAZ.

The association between alcohol consumption and the risk of hepatocellular carcinoma according to glycemic status in Korea: A nationwide population-based study

BACKGROUND

Alcohol and diabetes are known risk factors for hepatocellular carcinoma (HCC); however, it is unclear whether the association between alcohol consumption and HCC risk differs by fasting serum glucose level and diabetes. We investigated the dose-response relationship between alcohol consumption and the risk of HCC according to glycemic status.

METHODS AND FINDINGS

This population-based observational cohort study included patients who underwent general health checkups in 2009 using the Korean National Health Insurance Service Database. The primary outcome was HCC incidence, and Cox proportional hazard regression analysis was performed to estimate the relationship between alcohol consumption and HCC risk according to glycemic status. A total of 34,321 patients newly diagnosed with HCC were observed in the median follow-up period of 8.3 years. In the multivariable model, we adjusted for age, sex, smoking, regular exercise, income, hypertension, dyslipidemia, and body mass index. Mild-to-moderate alcohol consumption increased the risk of HCC in all glycemic statuses (normoglycemia: hazard ratio [HR], 1.06; 95% confidence interval [CI], 1.02 to 1.10; prediabetes: HR, 1.19; 95% CI, 1.14 to 1.24; and diabetes: HR, 2.02; 95% CI, 1.93 to 2.11) compared to normoglycemic nondrinking. Heavy alcohol consumption also increased the risk of HCC in all glycemic statuses (normoglycemia: HR, 1.39; 95% CI, 1.32 to 1.46; prediabetes: HR, 1.67; 95% CI, 1.58 to 1.77; and diabetes: HR, 3.29; 95% CI, 3.11 to 3.49) compared to normoglycemic nondrinking. Since alcohol consumption information in this study was based on a self-administered questionnaire, there may be a possibility of underestimation. Although we excluded patients with a history of viral hepatitis using diagnosis codes, we could not obtain information on hepatitis B or hepatitis C serum markers.

CONCLUSIONS

Both mild-to-moderate and heavy alcohol consumption was associated with an increased risk of HCC in all glycemic statuses. The increased risk of HCC according to alcohol consumption was the highest in the diabetes group, suggesting that more intensive alcohol abstinence is required for patients with diabetes.

Protein glycosylation alterations in hepatocellular carcinoma: function and clinical implications

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death worldwide. Understanding the cancer mechanisms provides novel diagnostic, prognostic, and therapeutic markers for the management of HCC disease. In addition to genomic and epigenomic regulation, post-translational modification exerts a profound influence on protein functions and plays a critical role in regulating various biological processes. Protein glycosylation is one of the most common and complex post-translational modifications of newly synthesized proteins and acts as an important regulatory mechanism that is implicated in fundamental molecular and cell biology processes. Recent studies in glycobiology suggest that aberrant protein glycosylation in hepatocytes contributes to the malignant transformation to HCC by modulating a wide range of pro-tumorigenic signaling pathways. The dysregulated protein glycosylation regulates cancer growth, metastasis, stemness, immune evasion, and therapy resistance, and is regarded as a hallmark of HCC. Changes in protein glycosylation could serve as potential diagnostic, prognostic, and therapeutic factors in HCC. In this review, we summarize the functional importance, molecular mechanism, and clinical application of protein glycosylation alterations in HCC.

Emerging field: O-GlcNAcylation in ferroptosis

In 2012, researchers proposed a non-apoptotic, iron-dependent form of cell death caused by lipid peroxidation called ferroptosis. During the past decade, a comprehensive understanding of ferroptosis has emerged. Ferroptosis is closely associated with the tumor microenvironment, cancer, immunity, aging, and tissue damage. Its mechanism is precisely regulated at the epigenetic, transcriptional, and post-translational levels. O-GlcNAc modification (O-GlcNAcylation) is one of the post-translational modifications of proteins. Cells can modulate cell survival in response to stress stimuli, including apoptosis, necrosis, and autophagy, through adaptive regulation by O-GlcNAcylation. However, the function and mechanism of these modifications in regulating ferroptosis are only beginning to be understood. Here, we review the relevant literature within the last 5 years and present the current understanding of the regulatory function of O-GlcNAcylation in ferroptosis and the potential mechanisms that may be involved, including antioxidant defense system-controlled reactive oxygen species biology, iron metabolism, and membrane lipid peroxidation metabolism. In addition to these three areas of ferroptosis research, we examine how changes in the morphology and function of subcellular organelles (e.g., mitochondria and endoplasmic reticulum) involved in O-GlcNAcylation may trigger and amplify ferroptosis. We have dissected the role of O-GlcNAcylation in regulating ferroptosis and hope that our introduction will provide a general framework for those interested in this field.

Signaling pathways in cancer metabolism: mechanisms and therapeutic targets

A wide spectrum of metabolites (mainly, the three major nutrients and their derivatives) can be sensed by specific sensors, then trigger a series of signal transduction pathways and affect the expression levels of genes in epigenetics, which is called metabolite sensing. Life body regulates metabolism, immunity, and inflammation by metabolite sensing, coordinating the pathophysiology of the host to achieve balance with the external environment. Metabolic reprogramming in cancers cause different phenotypic characteristics of cancer cell from normal cell, including cell proliferation, migration, invasion, angiogenesis, etc. Metabolic disorders in cancer cells further create a microenvironment including many kinds of oncometabolites that are conducive to the growth of cancer, thus forming a vicious circle. At the same time, exogenous metabolites can also affect the biological behavior of tumors. Here, we discuss the metabolite sensing mechanisms of the three major nutrients and their derivatives, as well as their abnormalities in the development of various cancers, and discuss the potential therapeutic targets based on metabolite-sensing signaling pathways to prevent the progression of cancer.

Hyperactivation of YAP/TAZ Drives Alterations in Mesangial Cells through Stabilization of N-Myc in Diabetic Nephropathy

SIGNIFICANCE STATEMENT

Mesangial cells (MCs) in the kidney are essential to maintaining glomerular integrity, and their impairment leads to major glomerular diseases including diabetic nephropathy (DN). Although high blood glucose elicits abnormal alterations in MCs, the underlying mechanism is poorly understood. We show that YAP/TAZ are increased in MCs of patients with DN and two animal models of DN. High glucose directly induces activation of YAP/TAZ through the canonical Hippo pathway in cultured MCs. Hyperactivation of YAP/TAZ in mouse MCs recapitulates the hallmarks of DN. Activated YAP/TAZ bind and stabilize N-Myc, one of the Myc family. N-Myc stabilization leads to aberrant enhancement of its transcriptional activity and to MC impairments. Our findings shed light on how high blood glucose in diabetes mellitus leads to DN and support a rationale that lowering blood glucose in diabetes mellitus could delay DN pathogenesis.

BACKGROUND

Mesangial cells (MCs) in the kidney are central to maintaining glomerular integrity, and their impairment leads to major glomerular diseases, including diabetic nephropathy (DN). Although high blood glucose elicits abnormal alterations in MCs, the underlying molecular mechanism is poorly understood.

METHODS

Immunolocalization of YAP/TAZ and pathological features of PDGFRβ + MCs were analyzed in the glomeruli of patients with DN, in Zucker diabetic fatty rats, and in Lats1/2i ΔPβ mice. RiboTag bulk-RNA sequencing and transcriptomic analysis of gene expression profiles of the isolated MCs from control and Lats1/2iΔPβ mice were performed. Immunoprecipitation analysis and protein stability of N-Myc were performed by the standard protocols.

RESULTS

YAP and TAZ, the final effectors of the Hippo pathway, are highly increased in MCs of patients with DN and in Zucker diabetic fatty rats. Moreover, high glucose directly induces activation of YAP/TAZ through the canonical Hippo pathway in cultured MCs. Hyperactivation of YAP/TAZ in mouse model MCs recapitulates the hallmarks of DN, including excessive proliferation of MCs and extracellular matrix deposition, endothelial cell impairment, glomerular sclerosis, albuminuria, and reduced glomerular filtration rate. Mechanistically, activated YAP/TAZ bind and stabilize N-Myc protein, one of the Myc family of oncogenes. N-Myc stabilization leads to aberrant enhancement of its transcriptional activity and eventually to MC impairments and DN pathogenesis.

CONCLUSIONS

Our findings shed light on how high blood glucose in diabetes mellitus leads to DN and support a rationale that lowering blood glucose in diabetes mellitus could delay DN pathogenesis.

Statins improve endothelial function via suppression of epigenetic-driven EndMT

The pleiotropic benefits of statins in cardiovascular diseases that are independent of their lipid-lowering effects have been well documented, but the underlying mechanisms remain elusive. Here we show that simvastatin significantly improves human induced pluripotent stem cell-derived endothelial cell functions in both baseline and diabetic conditions by reducing chromatin accessibility at transcriptional enhanced associate domain elements and ultimately at endothelial-to-mesenchymal transition (EndMT)-regulating genes in a yes-associated protein (YAP)-dependent manner. Inhibition of geranylgeranyltransferase (GGTase) I, a mevalonate pathway intermediate, repressed YAP nuclear translocation and YAP activity via RhoA signaling antagonism. We further identified a previously undescribed SOX9 enhancer downstream of statin-YAP signaling that promotes the EndMT process. Thus, inhibition of any component of the GGTase-RhoA-YAP-SRY box transcription factor 9 (SOX9) signaling axis was shown to rescue EndMT-associated endothelial dysfunction both in vitro and in vivo, especially under diabetic conditions. Overall, our study reveals an epigenetic modulatory role for simvastatin in repressing EndMT to confer protection against endothelial dysfunction.

The Ubiquitin-Proteasome System in Tumor Metabolism

Metabolic reprogramming, which is considered a hallmark of cancer, can maintain the homeostasis of the tumor environment and promote the proliferation, survival, and metastasis of cancer cells. For instance, increased glucose uptake and high glucose consumption, known as the "Warburg effect," play an essential part in tumor metabolic reprogramming. In addition, fatty acids are harnessed to satisfy the increased requirement for the phospholipid components of biological membranes and energy. Moreover, the anabolism/catabolism of amino acids, such as glutamine, cystine, and serine, provides nitrogen donors for biosynthesis processes, development of the tumor inflammatory environment, and signal transduction. The ubiquitin-proteasome system (UPS) has been widely reported to be involved in various cellular biological activities. A potential role of UPS in the metabolic regulation of tumor cells has also been reported, but the specific regulatory mechanism has not been elucidated. Here, we review the role of ubiquitination and deubiquitination modification on major metabolic enzymes and important signaling pathways in tumor metabolism to inspire new strategies for the clinical treatment of cancer.

Hyperglycemia Alters O-GlcNAcylation Patterns of Hepatocytes in Mice Treated With Hepatoxic Carcinogen

BACKGROUND/AIM

Diabetes mellitus (DM) is an established risk for hepatocellular carcinoma (HCC), with unclarified mechanisms. This study investigated the effects of hyperglycemia on O-GlcNacylation in hepatocytes and its associations with hepatocarcinogenesis.

MATERIALS AND METHODS

Mouse and human HCC cell lines were used in an in vitro model of hyperglycemia. Western blotting was used to determine the effects of high glucose on O-GlcNacylation in HCC cells. Twenty 4-week-old C3H/HeNJcl mice were randomized into four groups: non-DM control, non-DM plus diethylnitrosamine (DEN), DM, and DM plus DEN. DM was induced using intraperitoneal injection of a single high dose of streptozotocin. DEN was used to induce HCC. All mice were euthanized at week 16 after DM induction, and the liver tissues were histologically examined using hematoxylin and eosin, and immunohistochemistry.

RESULTS

High glucose increased O-GlcNacylated proteins in mouse and human HCC cell lines compared with those cultured at normal glucose concentration. Mice with hyperglycemia or DEN treatment had increased O-GlcNacylated proteins in hepatocytes. No gross tumors were evident at the end of the experiment but hepatic morbidity was observed. Mice with hyperglycemia and DEN treatment showed greater histological morbidity in their livers, i.e. increased nuclear size, hepatocellular swelling and sinusoidal dilatation, compared with mice in the DM group or treated with DEN alone.

CONCLUSION

Hyperglycemia increased O-GlcNAcylation in both in vitro and animal models. Increased O-GlcNAcylated proteins may be associated with hepatic histological morbidities which then promote HCC development in carcinogen-induced tumorigenesis.

The Essential Role of O-GlcNAcylation in Hepatic Differentiation

Background & Aims

O-GlcNAcylation is a post-translational modification catalyzed by the enzyme O-GlcNAc transferase (OGT), which transfers a single N-acetylglucosamine sugar from UDP-GlcNAc to the protein on serine and threonine residues on proteins. Another enzyme, O-GlcNAcase (OGA), removes this modification. O-GlcNAcylation plays an important role in pathophysiology. Here, we report that O-GlcNAcylation is essential for hepatocyte differentiation, and chronic loss results in fibrosis and hepatocellular carcinoma.

Methods

Single-cell RNA-sequencing was used to investigate hepatocyte differentiation in hepatocyte-specific OGT-KO mice with increased hepatic O-GlcNAcylation and in OGA-KO mice with decreased O-GlcNAcylation in hepatocytes. HCC patient samples and the DEN-induced hepatocellular carcinoma (HCC) model were used to investigate the effect of modulation of O-GlcNAcylation on the development of liver cancer.

Results

Loss of hepatic O-GlcNAcylation resulted in disruption of liver zonation. Periportal hepatocytes were the most affected by loss of differentiation characterized by dysregulation of glycogen storage and glucose production. OGT-KO mice exacerbated DEN-induced HCC development with increased inflammation, fibrosis, and YAP signaling. Consistently, OGA-KO mice with increased hepatic O-GlcNAcylation inhibited DEN-induced HCC. A progressive loss of O-GlcNAcylation was observed in HCC patients.

Conclusions

Our study shows that O-GlcNAcylation is a critical regulator of hepatic differentiation, and loss of O-GlcNAcylation promotes hepatocarcinogenesis. These data highlight increasing O-GlcNAcylation as a potential therapy in chronic liver diseases, including HCC.

Dysregulation of hexosamine biosynthetic pathway wiring metabolic signaling circuits in cancer

Metabolite sensing, a fundamental biological process, plays a key role in metabolic signaling circuit rewiring. Hexosamine biosynthetic pathway (HBP) is a glucose metabolic pathway essential for the synthesis of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), which senses key nutrients and integrally maintains cellular homeostasis. UDP-GlcNAc dynamically regulates protein N-glycosylation and O-linked-N-acetylglucosamine modification (O-GlcNAcylation). Dysregulated HBP flux leads to abnormal protein glycosylation, and contributes to cancer development and progression by affecting protein function and cellular signaling. Furthermore, O-GlcNAcylation regulates cellular signaling pathways, and its alteration is linked to various cancer characteristics. Additionally, recent findings have suggested a close association between HBP stimulation and cancer stemness; an elevated HBP flux promotes cancer cell conversion to cancer stem cells and enhances chemotherapy resistance via downstream signal activation. In this review, we highlight the prominent roles of HBP in metabolic signaling and summarize the recent advances in HBP and its downstream signaling, relevant to cancer.

Dihydroartemisinin inhibited the Warburg effect through YAP1/SLC2A1 pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) was the third most common cause of cancer death. But it has only limited therapeutic options, aggressive nature, and very low overall survival. Dihydroartemisinin (DHA), an anti-malarial drug approved by the Food and Drug Administration (FDA), inhibited cell growth in HCC. The Warburg effect was one of the ten new hallmarks of cancer. Solute carrier family 2 member 1 (SLC2A1) was a crucial carrier for glucose to enter target cells in the Warburg effect. Yes-associated transcriptional regulator 1 (YAP1), an effector molecule of the hippo pathway, played a crucial role in promoting the development of HCC. This study sought to determine the role of DHA in the SLC2A1 mediated Warburg effect in HCC. In this study, DHA inhibited the Warburg effect and SLC2A1 in HepG2215 cells and mice with liver tumors in situ. Meanwhile, DHA inhibited YAP1 expression by inhibiting YAP1 promoter binding protein GA binding protein transcription factor subunit beta 1 (GABPB1) and cAMP responsive element binding protein 1 (CREB1). Further, YAP1 knockdown/knockout reduced the Warburg effect and SLC2A1 expression by shYAP1-HepG2215 cells and Yap1^LKO mice with liver tumors. Taken together, our data indicated that YAP1 knockdown/knockout reduced the SLC2A1 mediated Warburg effect by shYAP1-HepG2215 cells and Yap1^LKO mice with liver tumors induced by DEN/TCPOBOP. DHA, as a potential YAP1 inhibitor, suppressed the SLC2A1 mediated Warburg effect in HCC.

YAP 5-methylcytosine modification increases its mRNA stability and promotes the transcription of exosome secretion-related genes in lung adenocarcinoma

YAP is a transcriptional co-activator with critical roles in tumorigenesis. However, its upstream regulatory mechanism, especially how its mRNA stability is regulated, remains to be further studied. Here, we validated that YAP expression was higher in lung adenocarcinoma (LUAD) tissues compared to adjacent normal tissues, and found that YAP m⁵C modification occurred in its 328-331 3' UTR region under the promotion NSUN2 and ALYREF, and increased the stability of YAP mRNA. This m⁵C modification also inhibited miR-582-3p binding and m⁶A modification in the nearby region. In addition, YAP m⁵C modification enhanced the exosome secretion effect, which was caused by two YAP-dependent transcription factors, Mycn and SOX10, and then stimulating the transcription of seven downstream exosome-promoting genes. Furthermore, we found that YAP m⁵C modification and its exosome-secretion-promoting function contributed to the malignant phenotype and AZD9291 (a third-generation EGFR-TKI) resistance of LUAD cells. Collectively, YAP is promoted by its m⁵C modification, and blocking YAP m⁵C modification will be helpful for future LUAD treatment.

O-GlcNAcylation: an important post-translational modification and a potential therapeutic target for cancer therapy

O-linked β-d-N-acetylglucosamine (O-GlcNAc) is an important post-translational modification of serine or threonine residues on thousands of proteins in the nucleus and cytoplasm of all animals and plants. In eukaryotes, only two conserved enzymes are involved in this process. O-GlcNAc transferase is responsible for adding O-GlcNAc to proteins, while O-GlcNAcase is responsible for removing it. Aberrant O-GlcNAcylation is associated with a variety of human diseases, such as diabetes, cancer, neurodegenerative diseases, and cardiovascular diseases. Numerous studies have confirmed that O-GlcNAcylation is involved in the occurrence and progression of cancers in multiple systems throughout the body. It is also involved in regulating multiple cancer hallmarks, such as metabolic reprogramming, proliferation, invasion, metastasis, and angiogenesis. In this review, we first describe the process of O-GlcNAcylation and the structure and function of O-GlcNAc cycling enzymes. In addition, we detail the occurrence of O-GlcNAc in various cancers and the role it plays. Finally, we discuss the potential of O-GlcNAc as a promising biomarker and novel therapeutic target for cancer diagnosis, treatment, and prognosis.

Posttranslational modifications in diabetes: Mechanisms and functions

As one of the most widespread chronic diseases, diabetes and its accompanying complications affect approximately one tenth of individuals worldwide and represent a growing cause of morbidity and mortality. Accumulating evidence has proven that the process of diabetes is complex and interactive, involving various cellular responses and signaling cascades by posttranslational modifications (PTMs). Therefore, understanding the mechanisms and functions of PTMs in regulatory networks has fundamental importance for understanding the prediction, onset, diagnosis, progression, and treatment of diabetes. In this review, we offer a holistic summary and illustration of the crosstalk between PTMs and diabetes, including both types 1 and 2. Meanwhile, we discuss the potential use of PTMs in diabetes treatment and provide a prospective direction for deeply understanding the metabolic diseases.

Metabolite-derived protein modifications modulating oncogenic signaling

Malignant growth is defined by multiple aberrant cellular features, including metabolic rewiring, inactivation of tumor suppressors and the activation of oncogenes. Even though these features have been described as separate hallmarks, many studies have shown an extensive mutual regulatory relationship amongst them. On one hand, the change in expression or activity of tumor suppressors and oncogenes has extensive direct and indirect effects on cellular metabolism, activating metabolic pathways required for malignant growth. On the other hand, the tumor microenvironment and tumor intrinsic metabolic alterations result in changes in intracellular metabolite levels, which directly modulate the protein modification of oncogenes and tumor suppressors at both epigenetic and post-translational levels. In this mini-review, we summarize the crosstalk between tumor suppressors/oncogenes and metabolism-induced protein modifications at both levels and explore the impact of metabolic (micro)environments in shaping these.

The O-GlcNAcylation and its promotion to hepatocellular carcinoma

O-GlcNAcylation is a posttranslational modification that attaches O-linked β-N-acetylglucosamine (O-GlcNAc) to the serine and threonine residues of proteins. Such a glycosylation would alter the activities, stabilities, and interactions of target proteins that are functional in a wide range of biological processes and diseases. Accumulating evidence indicates that O-GlcNAcylation is tightly associated with hepatocellular carcinoma (HCC) in its onset, growth, invasion and metastasis, drug resistance, and stemness. Here we summarize the discoveries of the role of O-GlcNAcylation in HCC and its function mechanism, aiming to deepen our understanding of HCC pathology, generate more biomarkers for its diagnosis and prognosis, and offer novel molecular targets for its treatment.

ISGylation of EMD promotes its interaction with PDHA to inhibit aerobic oxidation in lung adenocarcinoma

Abnormal nuclear structure caused by dysregulation of skeletal proteins is a common phenomenon in tumour cells. However, how skeletal proteins promote tumorigenesis remains uncovered. Here, we revealed the mechanism by which skeletal protein Emerin (EMD) promoted glucose metabolism to induce lung adenocarcinoma (LUAD). Firstly, we identified that EMD was highly expressed and promoted the malignant phenotypes in LUAD. The high expression of EMD might be due to its low level of ubiquitination. Additionally, the ISGylation at lysine 37 of EMD inhibited lysine 36 ubiquitination and upregulated EMD stability. We further explored that EMD could inhibit aerobic oxidation and stimulate glycolysis. Mechanistically, via its β‐catenin interaction domain, EMD bound with PDHA, stimulated serine 293 and 300 phosphorylation and inhibited PDHA expression, facilitated glycolysis of glucose that should enter the aerobic oxidation pathway, and EMD ISGylation was essential for EMD‐PDHA interaction. In clinical LUAD specimens, EMD was negatively associated with PDHA, while positively associated with EMD ISGylation, tumour stage and diameter. In LUAD with higher glucose level, EMD expression and ISGylation were higher. Collectively, EMD was a stimulator for LUAD by inhibiting aerobic oxidation via interacting with PDHA. Restricting cancer‐promoting role of EMD might be helpful for LUAD treatment.

Reciprocal regulation of actin filaments and cellular metabolism

For cells to adhere, migrate and proliferate, remodeling of the actin cytoskeleton is required. This process consumes a large amount of ATP while having an intimate connection with cellular metabolism. Signaling pathways that regulate energy homeostasis can also affect actin dynamics, whereas a variety of actin binding proteins directly or indirectly interact with the anabolic and catabolic regulators in cells. Here, we discuss the inter-regulation between actin filaments and cellular metabolism, reviewing recent discoveries on key metabolic enzymes that respond to actin remodeling as well as historical findings on metabolic stress-induced cytoskeletal reorganization. We also address emerging techniques that would benefit the study of cytoskeletal dynamics and cellular metabolism in high spatial-temporal resolution.

The role and potential mechanism of O-Glycosylation in gastrointestinal tumors

Glycosylation is a critical post-translational modification (PTM) that affects the function of proteins and regulates cell signaling, thereby regulating various biological processes. Protein oxygen-N-acetylglucosamine (O-GlcNAc) glycosylation modifications are glycochemical modifications that occur within cells in the signal transduction and are frequently found in the cytoplasm and nucleus. Due to the rapid and reversible addition and removal, O-GlcNAc modifications are able to reversibly compete with certain phosphorylation modifications, immediately regulate the activity of proteins, and participate in kinds of cellular metabolic and signal transduction pathways, playing a pivotal role in the regulation of tumors, diabetes, and other diseases. This article provided a brief overview of O-GlcNAc glycosylation modification, introduced its role in altering the progression and immune response regulation of gastrointestinal tumors, and discussed its potential use as a marker of tumor neogenesis.

Targeting O-GlcNAcylation to overcome resistance to anti-cancer therapies

In cancer cells, metabolic reprogramming is associated with an alteration of the O-GlcNAcylation homeostasis. This post-translational modification (PTM) that attaches O-GlcNAc moiety to intracellular proteins is dynamically and finely regulated by the O-GlcNAc Transferase (OGT) and the O-GlcNAcase (OGA). It is now established that O-GlcNAcylation participates in many features of cancer cells including a high rate of cell growth, invasion, and metastasis but little is known about its impact on the response to therapies. The purpose of this review is to highlight the role of O-GlcNAc protein modification in cancer resistance to therapies. We summarize the current knowledge about the crosstalk between O-GlcNAcylation and molecular mechanisms underlying tumor sensitivity/resistance to targeted therapies, chemotherapies, immunotherapy, and radiotherapy. We also discuss potential benefits and strategies of targeting O-GlcNAcylation to overcome cancer resistance.

O-GlcNAcylation of ZEB1 facilitated mesenchymal pancreatic cancer cell ferroptosis

Background: Mesenchymal cancer cells, resistant to the traditional regulated cell death, are exquisitely vulnerable to ferroptosis. However, the underlying mechanism has been rarely studied. While glycolipid metabolism rewiring is a critical determination of both cancer cell mesenchymal phenotype and cell death resistance, we are interested in the underlying cross talk between glycolipid metabolism and mesenchymal cancer cell ferroptosis sensitivity. Methods: CCK-8, western blot and clone forming assay were used to access the effect of glucose on mesenchymal cancer cell ferroptosis susceptibility and O-GlcNAcylation level. GEPIA database, shRNA knockdown and various pharmacological inhibitors were used to analyze the relationship between O-GlcNAcylation and mesenchymal cancer cell ferroptosis in vitro and in vivo. A series of experiments were conducted to investigate the underlying mechanisms of glucose induced ZEB1 O-GlcNAcylation on mesenchymal cancer cell ferroptosis susceptibility. Results: Mesenchymal pancreatic cancer cells O-GlcNAcylation level and ferroptosis cell death was significantly increased under high glucose condition in vitro and in vivo. O-GlcNAcylation of ZEB1, rather than other transcription factors, was involved in this process. Mechanistically, glucose triggered ZEB1 O-GlcNAcylation at Ser555 site enhanced its stabilization and nuclear translocation, induced lipogenesis associated genes, FASN and FADS2, transcription activity, which ultimately resulted in lipid peroxidation dependent mesenchymal pancreatic cancer cell ferroptosis. Conclusions: These results identify a novel role of glycolipid metabolism and O-GlcNAcylation in mesenchymal cancer cells ferroptosis susceptibility, which broaden the molecular mechanism of ferroptosis and suggested a potential clinical therapeutic strategy for refractory tumors.

Roles of Yes-associated protein and transcriptional coactivator with PDZ-binding motif in non-neoplastic liver diseases

The prevalence of liver disease has been increasing worldwide. Moreover, the burden of end-stage liver disease, including cirrhosis and liver cancer, is high because of high mortality and suboptimal treatment. The pathological process of liver disease includes steatosis, hepatocyte death, and fibrosis, which ultimately lead to cirrhosis and liver cancer. Clinical and preclinical evidence indicates that non-neoplastic liver diseases, particularly cirrhosis, are major risk factors for liver cancer, although the mechanism underlying this association remains unclear. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional activators that regulate organ size and cancer development. YAP and TAZ play important roles in liver development, regeneration, and homeostasis. Abnormal YAP and TAZ levels have also been implicated in non-neoplastic liver diseases (e.g., non-alcoholic fatty liver disease, alcoholic liver disease, liver injury, and liver fibrosis). Here, we review recent findings on the roles of YAP and TAZ in non-neoplastic liver diseases and discuss directions for future research. This review provides a basis for the study of non-neoplastic liver diseases.

O-GlcNAcylation: An Emerging Protein Modification Regulating the Hippo Pathway

Simple Summary

The contact point between the Hippo pathway, which serves as a central hub for various external environments, and O-GlcNAcylation, which is a non-canonical glycosylation process acting as a dynamic regulator in various signal transduction pathways, has recently been identified. This review aims to summarize the function of O-GlcNAcylation as an intrinsic and extrinsic regulator of the Hippo pathway.

Abstract

The balance between cellular proliferation and apoptosis and the regulation of cell differentiation must be established to maintain tissue homeostasis. These cellular responses involve the kinase cascade-mediated Hippo pathway as a crucial regulator. Hence, Hippo pathway dysregulation is implicated in diverse diseases, including cancer. O-GlcNAcylation is a non-canonical glycosylation that affects multiple signaling pathways through its interplay with phosphorylation in the nucleus and cytoplasm. An abnormal increase in the O-GlcNAcylation levels in various cancer cells is a potent factor in Hippo pathway dysregulation. Intriguingly, Hippo pathway dysregulation also disrupts O-GlcNAc homeostasis, leading to a persistent elevation of O-GlcNAcylation levels, which is potentially pathogenic in several diseases. Therefore, O-GlcNAcylation is gaining attention as a protein modification that regulates the Hippo pathway. This review presents a framework on how O-GlcNAcylation regulates the Hippo pathway and forms a self-perpetuating cycle with it. The pathological significance of this self-perpetuating cycle and clinical strategies for targeting O-GlcNAcylation that causes Hippo pathway dysregulation are also discussed.

Liver Metastatic Breast Cancer: Epidemiology, Dietary Interventions, and Related Metabolism

The median overall survival of patients with metastatic breast cancer is only 2-3 years, and for patients with untreated liver metastasis, it is as short as 4-8 months. Improving the survival of women with breast cancer requires more effective anti-cancer strategies, especially for metastatic disease. Nutrients can influence tumor microenvironments, and cancer metabolism can be manipulated via a dietary modification to enhance anti-cancer strategies. Yet, there are no standard evidence-based recommendations for diet therapies before or during cancer treatment, and few studies provide definitive data that certain diets can mediate tumor progression or therapeutic effectiveness in human cancer. This review focuses on metastatic breast cancer, in particular liver metastatic forms, and recent studies on the impact of diets on disease progression and treatment.

The role of YAP1 in liver cancer stem cells: proven and potential mechanisms

YAP1 (Yes-associated protein 1) is one of the principal factors that mediates oncogenesis by acting as a driver of gene expression. It has been confirmed to play an important role in organ volume control, stem cell function, tissue regeneration, tumorigenesis and tumor metastasis. Recent research findings show that YAP1 is correlated with the stemness of liver cancer stem cells, and liver cancer stem cells are closely associated with YAP1-induced tumor initiation and progression. This article reviews the advancements made in research on the mechanisms by which YAP1 promotes liver cancer stem cells and discusses some potential mechanisms that require further study.

Regulation of Hippo signaling by metabolic pathways in cancer

Hippo signaling is known to maintain balance between cell proliferation and apoptosis via tight regulation of factors, such as metabolic cues, cell-cell contact, and mechanical cues. Cells directly recognize glucose, lipids, and other metabolic cues and integrate multiple signaling pathways, including Hippo signaling, to adjust their proliferation and apoptosis depending on nutrient conditions. Therefore, the dysregulation of the Hippo signaling pathway can promote tumor initiation and progression. Alteration in metabolic cues is considered a major factor affecting the risk of cancer formation and progression. It has recently been shown that the dysregulation of the Hippo signaling pathway, through diverse routes activated by metabolic cues, can lead to cancer with a poor prognosis. In addition, unique crosstalk between metabolic pathways and Hippo signaling pathways can inhibit the effect of anticancer drugs and promote drug resistance. In this review, we describe an integrated perspective of the relationship between the Hippo signaling pathway and metabolic signals in the context of cancer. We also characterize the mechanisms involved in changes in metabolism that are linked to the Hippo signaling pathway in the cancer microenvironment and propose several novel targets for anticancer drug treatment.

YAP1 activation and Hippo pathway signaling in the pathogenesis and treatment of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA), the second most common primary liver cancer, is a highly lethal epithelial cell malignancy exhibiting features of cholangiocyte differentiation. iCCAs can potentially develop from multiple cell types of origin within liver, including immature or mature cholangiocytes, hepatic stem cells/progenitor cells, and from transdifferentiation of hepatocytes. Understanding the molecular mechanisms and genetic drivers that diversely drive specific cell lineage pathways leading to iCCA has important biological and clinical implications. In this context, activation of the YAP1-TEAD dependent transcription, driven by Hippo-dependent or -independent diverse mechanisms that lead to the stabilization of YAP1 is crucially important to biliary fate commitment in hepatobiliary cancer. In preclinical models, YAP1 activation in hepatocytes or cholangiocytes is sufficient to drive their malignant transformation into iCCA. Moreover, nuclear YAP1/TAZ is highly prevalent in human iCCA irrespective of the varied etiology, and significantly correlates with poor prognosis in iCCA patients. Based on the ubiquitous expression and diverse physiologic roles for YAP1/TAZ in the liver, recent studies have further revealed distinct functions of active YAP1/TAZ in regulating tumor metabolism, as well as the tumor immune microenvironment. In the current review, we discuss our current understanding of the various roles of the Hippo-YAP1 signaling in iCCA pathogenesis, with a specific focus on the roles played by the Hippo-YAP1 pathway in modulating biliary commitment and oncogenicity, iCCA metabolism, and immune microenvironment. We also discuss the therapeutic potential of targeting the YAP1/TAZ-TEAD transcriptional machinery in iCCA, its current limitations, and what future studies are needed to facilitate clinical translation.

Context-dependent transcriptional regulations of YAP/TAZ in cancer

As the downstream effectors of Hippo pathway, YAP/TAZ are identified to participate in organ growth, regeneration and tumorigenesis. However, owing to lack of a DNA-binding domain, YAP/TAZ usually act as coactivators and cooperate with other transcription factors or partners to mediate their transcriptional outputs. In this article, we first present an overview of the core components and the upstream regulators of Hippo-YAP/TAZ signaling in mammals, and then systematically summarize the identified transcription factors or partners that are responsible for the downstream transcriptional output of YAP/TAZ in various cancers.

YAP Targets the TGFβ Pathway to Mediate High-Fat/High-Sucrose Diet-Induced Arterial Stiffness

BACKGROUND

Metabolic syndrome is related to cardiovascular diseases, which is attributed in part, to arterial stiffness; however, the mechanisms remain unclear. The present study aimed to investigate the molecular mechanisms of metabolic syndrome-induced arterial stiffness and to identify new therapeutic targets.

METHODS

Arterial stiffness was induced by high-fat/high-sucrose diet in mice, which was quantified by Doppler ultrasound. Four-dimensional label-free quantitative proteomic analysis, affinity purification and mass spectrometry, and immunoprecipitation and GST pull-down experiments were performed to explore the mechanism of YAP (Yes-associated protein)-mediated TGF (transforming growth factor) β pathway activation.

RESULTS

YAP protein was upregulated in the aortic tunica media of mice fed a high-fat/high-sucrose diet for 2 weeks and precedes arterial stiffness. Smooth muscle cell-specific YAP knockdown attenuated high-fat/high-sucrose diet-induced arterial stiffness and activation of TGFβ-Smad2/3 signaling pathway in arteries. By contrast, Myh11Cre^ERT2-Yap^Tg mice exhibited exacerbated high-fat/high-sucrose diet-induced arterial stiffness and enhanced TGFβ-activated Smad2/3 phosphorylation in arteries. PPM1B (protein phosphatase, Mg²⁺/Mn²⁺-dependent 1B) was identified as a YAP-bound phosphatase that translocates into the nucleus to dephosphorylate Smads in response to TGFβ. This process was inhibited by YAP through removal of the K63-linked ubiquitin chain of PPM1B at K326.

CONCLUSIONS

This study provides a new mechanism by which smooth muscle cell YAP regulates the TGFβ pathway and a potential therapeutic target in metabolic syndrome-associated arterial stiffness.