DNA Polymerase Iota Promotes Esophageal Squamous Cell Carcinoma Proliferation Through Erk-OGT-Induced G6PD Overactivation

The crosstalk between glucose metabolism and telomerase regulation in cancer

Accumulated alterations in metabolic control provide energy and anabolic demands for enhanced cancer cell proliferation. Exemplified by the Warburg effect, changes in glucose metabolism during cancer progression are widely recognized as a characteristic of metabolic disorders. Since telomerases are a vital factor in maintaining DNA integrity and stability, any damage threatening telomerases could have a severe impact on DNA and, subsequently, whole-cell homeostasis. However, it remains unclear whether the regulation of glucose metabolism in cancer is connected to the regulation of telomerase. In this review, we present the latest insights into the crosstalk between telomerase function and glucose metabolism in cancer cells. However, at this moment this subject is not well investigated that the association is mostly indirectly regulations and few explicit regulating pathways were identified between telomerase and glucose metabolism. Therefore, the information presented in this review can provide a scientific basis for further research on the detail mechanism and the clinical application of cancer therapy, which could be valuable in improving the effectiveness of chemotherapy.

DNA polymerase iota promotes EMT and metastasis of esophageal squamous cell carcinoma by interacting with USP7 to stabilize HIF-1α

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal cancer types, with a low 5-year survival rate of ~20%. Our prior research has suggested that DNA Polymerase iota (Pol ι), a member of Y-family DNA polymerase, plays a crucial role in the invasion and metastasis of ESCC. However, the underlying mechanism is not well understood. In this study, we utilized ChIP-PCR and luciferase reporter assays to investigate the binding of HIF-1α to the promoter of the Pol ι gene. Transwell, wound healing, and mouse models were employed to assess the impact of Pol ι and HIF-1α on the motility of ESCC cells. Co-immunoprecipitation and Western blot were carried out to explore the interaction between Pol ι and HIF-1α, while qRT-PCR and Western blot were conducted to confirm the regulation of Pol ι and HIF-1α on their downstream targets. Our results demonstrate that HIF-1α activates the transcription of the Pol ι gene in ESCC cells under hypoxic conditions. Furthermore, the knockdown of Pol ι impeded HIF-1α-induced invasion and metastasis. Additionally, we found that Pol ι regulates the expression of genes involved in epithelial-mesenchymal transition (EMT) and initiates EMT through the stabilization of HIF-1α. Mechanistically, Pol ι maintains the protein stability of HIF-1α by recruiting USP7 to mediate the deubiquitination of HIF-1α, with the residues 446-578 of Pol being crucial for the interaction between Pol ι and USP7. Collectively, our findings unveil a novel feedforward molecular axis of HIF-1α- Pol ι -USP7 in ESCC that contributes to ESCC metastasis. Hence, our results present an attractive target for intervention in ESCC.

Growing and dividing: how O-GlcNAcylation leads the way

Cell cycle errors can lead to mutations, chromosomal instability, or death; thus, the precise control of cell cycle progression is essential for viability. The nutrient-sensing posttranslational modification, O-GlcNAc, regulates the cell cycle allowing one central control point directing progression of the cell cycle. O-GlcNAc is a single N-acetylglucosamine sugar modification to intracellular proteins that is dynamically added and removed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. These enzymes act as a rheostat to fine-tune protein function in response to a plethora of stimuli from nutrients to hormones. O-GlcNAc modulates mitogenic growth signaling, senses nutrient flux through the hexosamine biosynthetic pathway, and coordinates with other nutrient-sensing enzymes to progress cells through Gap phase 1 (G1). At the G1/S transition, O-GlcNAc modulates checkpoint control, while in S Phase, O-GlcNAcylation coordinates the replication fork. DNA replication errors activate O-GlcNAcylation to control the function of the tumor-suppressor p53 at Gap Phase 2 (G2). Finally, in mitosis (M phase), O-GlcNAc controls M phase progression and the organization of the mitotic spindle and midbody. Critical for M phase control is the interplay between OGT and OGA with mitotic kinases. Importantly, disruptions in OGT and OGA activity induce M phase defects and aneuploidy. These data point to an essential role for the O-GlcNAc rheostat in regulating cell division. In this review, we highlight O-GlcNAc nutrient sensing regulating G1, O-GlcNAc control of DNA replication and repair, and finally, O-GlcNAc organization of mitotic progression and spindle dynamics.

On a sugar high: Role of O-GlcNAcylation in cancer

Recent advances in the understanding of the molecular mechanisms underlying cancer progression have led to the development of novel therapeutic targeting strategies. Aberrant glycosylation patterns and their implication in cancer have gained increasing attention as potential targets due to the critical role of glycosylation in regulating tumor-specific pathways that contribute to cancer cell survival, proliferation, and progression. A special type of glycosylation that has been gaining momentum in cancer research is the modification of nuclear, cytoplasmic, and mitochondrial proteins, termed O-GlcNAcylation. This protein modification is catalyzed by an enzyme called O-GlcNAc transferase (OGT), which uses the final product of the Hexosamine Biosynthetic Pathway (HBP) to connect altered nutrient availability to changes in cellular signaling that contribute to multiple aspects of tumor progression. Both O-GlcNAc and its enzyme OGT are highly elevated in cancer and fulfill the crucial role in regulating many hallmarks of cancer. In this review, we present and discuss the latest findings elucidating the involvement of OGT and O-GlcNAc in cancer.

Skewing cPLA2α activity toward oxoeicosanoid production promotes neutrophil N2 polarization, wound healing, and the response to sepsis

Uncontrolled inflammation is linked to poor outcomes in sepsis and wound healing, both of which proceed through distinct inflammatory and resolution phases. Eicosanoids are a class of bioactive lipids that recruit neutrophils and other innate immune cells. The interaction of ceramide 1-phosphate (C1P) with the eicosanoid biosynthetic enzyme cytosolic phospholipase A2 (cPLA2) reduces the production of a subtype of eicosanoids called oxoeicosanoids. We investigated the effect of shifting the balance in eicosanoid biosynthesis on neutrophil polarization and function. Knockin mice expressing a cPLA2 mutant lacking the C1P binding site (cPLA2αKI/KI mice) showed enhanced and sustained neutrophil infiltration into wounds and the peritoneum during the inflammatory phase of wound healing and sepsis, respectively. The mice exhibited improved wound healing and reduced susceptibility to sepsis, which was associated with an increase in anti-inflammatory N2-type neutrophils demonstrating proresolution behaviors and a decrease in proinflammatory N1-type neutrophils. The N2 polarization of cPLA2αKI/KI neutrophils resulted from increased oxoeicosanoid biosynthesis and autocrine signaling through the oxoeicosanoid receptor OXER1 and partially depended on OXER1-dependent inhibition of the pentose phosphate pathway (PPP). Thus, C1P binding to cPLA2α suppresses neutrophil N2 polarization, thereby impairing wound healing and the response to sepsis.

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.

Recent findings in the regulation of G6PD and its role in diseases

Glucose-6-phosphate dehydrogenase (G6PD) is the only rate-limiting enzyme in the pentose phosphate pathway (PPP). Rapidly proliferating cells require metabolites from PPP to synthesize ribonucleotides and maintain intracellular redox homeostasis. G6PD expression can be abnormally elevated in a variety of cancers. In addition, G6PD may act as a regulator of viral replication and vascular smooth muscle function. Therefore, G6PD-mediated activation of PPP may promote tumor and non-neoplastic disease progression. Recently, studies have identified post-translational modifications (PTMs) as an important mechanism for regulating G6PD function. Here, we provide a comprehensive review of various PTMs (e.g., phosphorylation, acetylation, glycosylation, ubiquitination, and glutarylation), which are identified in the regulation of G6PD structure, expression and enzymatic activity. In addition, we review signaling pathways that regulate G6PD and evaluate the role of oncogenic signals that lead to the reprogramming of PPP in tumor and non-neoplastic diseases as well as summarize the inhibitors that target G6PD.

O-GlcNAcylation: The Underestimated Emerging Regulators of Skeletal Muscle Physiology

O-GlcNAcylation is a highly dynamic, reversible and atypical glycosylation that regulates the activity, biological function, stability, sublocation and interaction of target proteins. O-GlcNAcylation receives and coordinates different signal inputs as an intracellular integrator similar to the nutrient sensor and stress receptor, which target multiple substrates with spatio-temporal analysis specifically to maintain cellular homeostasis and normal physiological functions. Our review gives a brief description of O-GlcNAcylation and its only two processing enzymes and HBP flux, which will help to better understand its physiological characteristics of sensing nutrition and environmental cues. This nutritional and stress-sensitive properties of O-GlcNAcylation allow it to participate in the precise regulation of skeletal muscle metabolism. This review discusses the mechanism of O-GlcNAcylation to alleviate metabolic disorders and the controversy about the insulin resistance of skeletal muscle. The level of global O-GlcNAcylation is precisely controlled and maintained in the “optimal zone”, and its abnormal changes is a potential factor in the pathogenesis of cancer, neurodegeneration, diabetes and diabetic complications. Although the essential role of O-GlcNAcylation in skeletal muscle physiology has been widely studied and recognized, it still is underestimated and overlooked. This review highlights the latest progress and potential mechanisms of O-GlcNAcylation in the regulation of skeletal muscle contraction and structural properties.

MEK1/2 regulates APOBEC3B and polymerase iota-induced mutagenesis in head and neck cancer cells

Resistance to chemotherapy provides a major challenge in treatment of metastatic cancer. Prolonged exposure to almost any drug regimen leads to the formation of resistant subclones in almost all advanced solid tumors. Tumor heterogeneity because of intrinsic genetic instability is seen as one of the major contributing factors. In this work, we present evidence that genetic instability measured by mutation frequency is induced by treatment with the EGFR inhibitor afatinib or cisplatin in head and neck squamous cancer cells. We find that APOBEC3B and polymerase iota are upregulated, and inhibition of MEK1/2 by U0126 leads to downregulation on the protein level. Costimulation of afatnib and cisplatin with U0126 leads to a significantly lower mutation frequency. These findings may represent a molecular mechanism for dynamically controlling genetic instability during chemotherapy in head and neck squamous cell carcinoma (HNSCC) cancer cells.