Functional Analysis of O-GlcNAcylation in Cancer Metastasis

O-GlcNAcylation of CSNK2A1 by OGT is Involved in the Progression of Colorectal Cancer

Colorectal cancer (CRC) metastasis is challenging for improved clinical outcomes. The casein kinase 2 alpha 1 (CSNK2A1) is an oncogene involved in several cancers. This study aimed to investigate the influence of CSNK2A1 on CRC progression and the related molecular mechanism. The CSNK2A1 levels were predicted using bioinformatic analysis and were measured using quantitative real-time polymerase chain reaction (qRT-PCR). Cell phenotypes were analyzed using cell-counting kit-8, colony formation, transwell assay, and western blot. Tumor growth was evaluated in a tumor-bearing mouse model in vivo. Similarly, O-GlcNAc modification of CSNK2A1 was assessed by immunoprecipitation, western blot, and immunofluorescence. Results indicated that CSNK2A1 was upregulated in CRC and was related to poor prognosis. Interference with CSNK2A1 suppressed CRC cell proliferation, migration, invasion, and epithelial-mesenchymal transition, inhibiting tumor growth. Moreover, OGT promoted the glycosylation modification of CSNK2A1, enhanced its protein stability, and reversed tumor progression when CSNK2A1 was knocked down. The CSNK2A1 might also affect CRC progression via the PI3K/AKT pathway. In conclusion, the OGT-O-GlcNAcylation-CSNK2A1 axis accelerated the malignant advancement of CRC, suggesting potential CRC therapeutic targets.

Senegenin suppresses hepatocellular carcinoma by regulating O-GlcNAcylation

BACKGROUND

Based on current knowledge, hepatocellular carcinoma (HCC) is a condition with numerous etiologies and risk factors. However, the pathogenesis of HCC remains unclear.

AIM

To investigate the roles of senegenin and O-GlcNAcylation in the growth and metastasis of HCC.

METHODS

The levels of O-linked N-acetylglucosamine transferase (OGT) and O-GlcNAcylation in HCC cells and tissues were detected using western blot analysis. The effects of senegenin and O-GlcNAcylation on the proliferation of HCC cells were investigated in vitro using cell counting kit-8 and clonogenic assays. The potential effects of senegenin and O-GlcNAcylation on HCC metastasis were examined using the transwell migration assay. O-GlcNAcylation levels were altered via drug treatment and lentiviral infection, and western blot analysis was used to detect proteins involved in various pathways.

RESULTS

Western blot analysis revealed that OGT and O-GlcNAcylation levels were significantly elevated in HCC tissues and cells. O-GlcNAcylation levels in HCC cells were significantly altered by drug treatment and lentiviral infection. An increase in the glycosylation level was linked to enhanced proliferation, invasiveness, clonogenicity, and metastatic potential of cancer cells. O-GlcNAcylation induced by senegenin was found to slow the proliferation and migration of HCC cells. The levels of proteins involved in nuclear factor-kappa B (NF-κB) and c-Jun N-terminal kinase (JNK) pathways, which are associated with endoplasmic reticulum stress, were altered.

CONCLUSION

Senegenin lowers O-GlcNAcylation levels, decreases OGT expression, and inhibits cancer cell growth and metastasis by regulating proteins involved in NF-κB and JNK pathways.

O-GlcNAcylation of MITF regulates its activity and CDK4/6 inhibitor resistance in breast cancer

Cyclin-dependent kinases 4 and 6 (CDK4/6) play a pivotal role in cell cycle and cancer development. Targeting CDK4/6 has demonstrated promising effects against breast cancer. However, resistance to CDK4/6 inhibitors (CDK4/6i), such as palbociclib, remains a substantial challenge in clinical settings. Using high-throughput combinatorial drug screening and genomic sequencing, we find that the microphthalmia-associated transcription factor (MITF) is activated via O-GlcNAcylation by O-GlcNAc transferase (OGT) in palbociclib-resistant breast cancer cells and tumors. Mechanistically, O-GlcNAcylation of MITF at Serine 49 enhances its interaction with importin α/β, thus promoting its translocation to nuclei, where it suppresses palbociclib-induced senescence. Inhibition of MITF or its O-GlcNAcylation re-sensitizes resistant cells to palbociclib. Moreover, clinical studies confirm the activation of MITF in tumors from patients who are palbociclib-resistant or undergoing palbociclib treatment. Collectively, our studies shed light on the mechanism regulating palbociclib resistance and present clinical evidence for developing therapeutic approaches to treat CDK4/6i-resistant breast cancer patients.

Glycosylation editing: an innovative therapeutic opportunity in precision oncology

Cancer is still one of the most arduous challenges in the human society, even though humans have found many ways to try to conquer it. With our incremental understandings on the impact of sugar on human health, the clinical relevance of glycosylation has attracted our attention. The fact that altered glycosylation profiles reflect and define different health statuses provide novel opportunities for cancer diagnosis and therapeutics. By reviewing the mechanisms and critical enzymes involved in protein, lipid and glycosylation, as well as current use of glycosylation for cancer diagnosis and therapeutics, we identify the pivotal connection between glycosylation and cellular redox status and, correspondingly, propose the use of redox modulatory tools such as cold atmospheric plasma (CAP) in cancer control via glycosylation editing. This paper interrogates the clinical relevance of glycosylation on cancer and has the promise to provide new ideas for laboratory practice of cold atmospheric plasma (CAP) and precision oncology therapy.

The role of O-GlcNAcylation in bone metabolic diseases

O-GlcNAcylation, as a post-translational modification, can modulate cellular activities such as kinase activity, transcription-translation, protein degradation, and insulin signaling by affecting the function of the protein substrate, including cellular localization of proteins, protein stability, and protein/protein interactions. Accumulating evidence suggests that dysregulation of O-GlcNAcylation is associated with disease progression such as cancer, neurodegeneration, and diabetes. Recent studies suggest that O-GlcNAcylation is also involved in the regulation of osteoblast, osteoclast and chondrocyte differentiation, which is closely related to the initiation and development of bone metabolic diseases such as osteoporosis, arthritis and osteosarcoma. However, the potential mechanisms by which O-GlcNAcylation regulates bone metabolism are not fully understood. In this paper, the literature related to the regulation of bone metabolism by O-GlcNAcylation was summarized to provide new potential therapeutic strategies for the treatment of orthopedic diseases such as arthritis and osteoporosis.

Antitumor efficacy of a sequence-specific DNA-targeted γPNA-based c-Myc inhibitor

Targeting oncogenes at the genomic DNA level can open new avenues for precision medicine. Significant efforts are ongoing to target oncogenes using RNA-targeted and protein-targeted platforms, but no progress has been made to target genomic DNA for cancer therapy. Here, we introduce a gamma peptide nucleic acid (γPNA)-based genomic DNA-targeted platform to silence oncogenes in vivo. γPNAs efficiently invade the mixed sequences of genomic DNA with high affinity and specificity. As a proof of concept, we establish that γPNA can inhibit c-Myc transcription in multiple cell lines. We evaluate the in vivo efficacy and safety of genomic DNA targeting in three pre-clinical models. We also establish that anti-transcription γPNA in combination with histone deacetylase inhibitors and chemotherapeutic drugs results in robust antitumor activity in cell-line- and patient-derived xenografts. Overall, this strategy offers a unique therapeutic platform to target genomic DNA to inhibit oncogenes for cancer therapy.

Emerging trends in post-translational modification: Shedding light on Glioblastoma multiforme

Recent multi-omics studies, including proteomics, transcriptomics, genomics, and metabolomics have revealed the critical role of post-translational modifications (PTMs) in the progression and pathogenesis of Glioblastoma multiforme (GBM). Further, PTMs alter the oncogenic signaling events and offer a novel avenue in GBM therapeutics research through PTM enzymes as potential biomarkers for drug targeting. In addition, PTMs are critical regulators of chromatin architecture, gene expression, and tumor microenvironment (TME), that play a crucial function in tumorigenesis. Moreover, the implementation of artificial intelligence and machine learning algorithms enhances GBM therapeutics research through the identification of novel PTM enzymes and residues. Herein, we briefly explain the mechanism of protein modifications in GBM etiology, and in altering the biologics of GBM cells through chromatin remodeling, modulation of the TME, and signaling pathways. In addition, we highlighted the importance of PTM enzymes as therapeutic biomarkers and the role of artificial intelligence and machine learning in protein PTM prediction.

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.

O-GlcNAcylation of MITF regulates its activity and CDK4/6 inhibitor resistance in breast cancer

Cyclin-dependent kinases 4 and 6 (CDK4/6) play a pivotal role in cell cycle and cancer development. Targeting CDK4/6 has demonstrated promising effects against breast cancer. However, resistance to CDK4/6 inhibitors (CDK4/6i), such as palbociclib, remains a substantial challenge in clinical settings. Using high-throughput combinatorial drug screening and genomic sequencing, we found that the microphthalmia-associated transcription factor (MITF) is activated via O-GlcNAcylation by O-GlcNAc transferase (OGT) in palbociclib-resistant breast cancer cells and tumors; O-GlcNAcylation of MITF at Serine 49 enhanced its interaction with importin α/β, thus promoting its translocation to nuclei, where it suppressed palbociclib-induced senescence; inhibition of MITF or its O-GlcNAcylation re-sensitized resistant cells to palbociclib. Remarkably, clinical studies confirmed the activation of MITF in tumors from patients who are palbociclib-resistant or undergoing palbociclib treatment. Collectively, our studies shed light on a novel mechanism regulating palbociclib-resistance, and present clinical evidence for developing therapeutic approaches to treat CDK4/6i-resistant breast cancer patients.

Skin Cancer Microenvironment: What We Can Learn from Skin Aging?

Aging is a natural intrinsic process associated with the loss of fibrous tissue, a slower cell turnover, and a reduction in immune system competence. In the skin, the continuous exposition of environmental factors superimposes extrinsic damage, mainly due to ultraviolet radiation causing photoaging. Although not usually considered a pathogenic event, photoaging affects cutaneous biology, increasing the risk of skin carcinogenesis. At the cellular level, aging is typified by the rise of senescence cells a condition characterized by reduced or absent capacity to proliferate and aberrant hyper-secretory activity. Senescence has a double-edged sword in cancer biology given that senescence prevents the uncontrolled proliferation of damaged cells and favors their clearance by paracrine secretion. Nevertheless, the cumulative insults and the poor clearance of injured cells in the elderly increase cancer incidence. However, there are not conclusive data proving that aged skin represents a permissive milieu for tumor onset. On the other hand, tumor cells are capable of activating resident fibroblasts onto a pro-tumorigenic phenotype resembling those of senescent fibroblasts suggesting that aged fibroblasts might facilitate cancer progression. This review discusses changes that occur during aging that can prime neoplasm or increase the aggressiveness of melanoma and non-melanoma skin cancer.

Advances in protein glycosylation and its role in tissue repair and regeneration

After tissue damage, a series of molecular and cellular events are initiated to promote tissue repair and regeneration to restore its original structure and function. These events include inter-cell communication, cell proliferation, cell migration, extracellular matrix differentiation, and other critical biological processes. Glycosylation is the crucial conservative and universal post-translational modification in all eukaryotic cells [1], with influential roles in intercellular recognition, regulation, signaling, immune response, cellular transformation, and disease development. Studies have shown that abnormally glycosylation of proteins is a well-recognized feature of cancer cells, and specific glycan structures are considered markers of tumor development. There are many studies on gene expression and regulation during tissue repair and regeneration. Still, there needs to be more knowledge of complex carbohydrates' effects on tissue repair and regeneration, such as glycosylation. Here, we present a review of studies investigating protein glycosylation in the tissue repair and regeneration process.

The multi-omics analysis identifies a novel cuproptosis-anoikis-related gene signature in prognosis and immune infiltration characterization of lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD) has emerged as one of the most aggressive lethal cancers. Anoikis serves as programmed apoptosis initiated by the detachment of cells from the extracel-lular matrix. Cuproptosis is distinct from traditional cell death modalities. The above two modes are both closely related to tumor progression, prognosis, and treatment. However, whether they have synergistic effects in LUAD deserves further investigation.

Methods

The anoikis-related prognostic genes (ANRGs) co-expressed with cuproptosis-associated genes (CAGs) were screened using correlation analysis, analysis of variance, least absolute shrinkage, and selection operator (LASSO), and COX regression followed by functional analysis, and then LUAD risk score model was constructed. Using consensus clustering, the relationship between different subtypes and clinicopathological features, immune infiltration characteristics, and somatic mutations was analyzed. A nomogram was developed by incorporating clinical information, which provided a prediction of the survival of patients. Finally, a comprehensive analysis of ANRGs was performed and verified by the HPA database.

Results

A total of 27 ANRGs associated with cuproptosis were obtained. On this basis, three distinct ANRGs subtypes were identified, and the differences between clinical prognosis and immune infiltration were observed. A risk score model has been constructed by incorporating seven ANRGs signatures (EIF2AK3, IKZF3, ITGAV, OGT, PLK1, TRAF2, XRCC5). A highly reliable nomogram was developed to help formulate treatment strategies based on risk score and the clinicopathological features of LUAD. The seven-gene signature was turned out to be strongly linked to immune cells and validated in single-cell data. Immunohistochemistry proved that all of them are highly expressed in LUAD tissues.

Conclusion

This study reveals the potential relationship between cuproptosis-related ANRGs and clinicopathological features, tumor microenvironment (TME), and mutation characteristics, which can be applied for predicting the prognosis of LUAD and help develop individualized treatment strategies.

OGT controls mammalian cell viability by regulating the proteasome/mTOR/ mitochondrial axis

O-GlcNAc transferase (OGT) modifies serine and threonine residues on nuclear and cytosolic proteins with O-linked N-acetylglucosamine (GlcNAc). OGT is essential for mammalian cell viability, but the underlying mechanisms are still enigmatic. We performed a genome-wide CRISPR-Cas9 screen in mouse embryonic stem cells (mESCs) to identify candidates whose depletion rescued the block in cell proliferation induced by OGT deficiency. We show that the block in cell proliferation in OGT-deficient cells stems from mitochondrial dysfunction secondary to mTOR (mechanistic target of rapamycin) hyperactivation. In normal cells, OGT maintains low mTOR activity and mitochondrial fitness through suppression of proteasome activity; in the absence of OGT, increased proteasome activity results in increased steady-state amino acid levels, which in turn promote mTOR lysosomal translocation and activation, and increased oxidative phosphorylation. mTOR activation in OGT-deficient mESCs was confirmed by an independent phospho-proteomic screen. Our study highlights a unique series of events whereby OGT regulates the proteasome/ mTOR/ mitochondrial axis in a manner that maintains homeostasis of intracellular amino acid levels, mitochondrial fitness, and cell viability. A similar mechanism operates in CD8⁺ T cells, indicating its generality across mammalian cell types. Manipulating OGT activity may have therapeutic potential in diseases in which this signaling pathway is impaired.

KIAA1199 promotes oxaliplatin resistance and epithelial mesenchymal transition of colorectal cancer via protein O-GlcNAcylation

Oxaliplatin is a commonly used platinum drug for colorectal cancer (CRC). However, the treatment of CRC by oxaliplatin usually fails because of drug resistance, which results in a huge challenge in the therapy of CRC. Elucidation of molecular mechanisms may help to overcome oxaliplatin resistance of CRC. In our study, we revealed that KIAA1199 can promote oxaliplatin resistance of CRC. Mechanistically, KIAA1199 prevents oxaliplatin mediated apoptosis via up-regulated PARP1 derived from reduced endoplasmic reticulum stress induced by protein O-GlcNAcylation. In the meantime, KIAA1199 can also trigger epithelial mesenchymal transition by stabilizing SNAI1 protein via O-GlcNAcylation. Therefore, KIAA1199 has great potential to be a novel biomarker, therapeutic target for oxaliplatin resistance and metastasis of CRC.

Recent advances in the use of legume lectins for the diagnosis and treatment of breast cancer

Poor lifestyle choices and genetic predisposition are factors that increase the number of cancer cases, one example being breast cancer, the third most diagnosed type of malignancy. Currently, there is a demand for the development of new strategies to ensure early detection and treatment options that could contribute to the complete remission of breast tumors, which could lead to increased overall survival rates. In this context, the glycans observed at the surface of cancer cells are presented as efficient tumor cell markers. These carbohydrate structures can be recognized by lectins which can act as decoders of the glycocode. The application of plant lectins as tools for diagnosis/treatment of breast cancer encompasses the detection and sorting of glycans found in healthy and malignant cells. Here, we present an overview of the most recent studies in this field, demonstrating the potential of lectins as: mapping agents to detect differentially expressed glycans in breast cancer, as histochemistry/cytochemistry analysis agents, in lectin arrays, immobilized in chromatographic matrices, in drug delivery, and as biosensing agents. In addition, we describe lectins that present antiproliferative effects by themselves and/or in conjunction with other drugs in a synergistic effect.

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.

O-GlcNAcylation promotes cerebellum development and medulloblastoma oncogenesis via SHH signaling

Cerebellar development relies on a precise coordination of metabolic signaling, epigenetic signaling, and transcriptional regulation. Here, we reveal that O-GlcNAc transferase (OGT) regulates cerebellar neurogenesis and medulloblastoma growth via a Sonic hedgehog (Shh)-Smo-Gli2 pathway. We identified Gli2 as a substrate of OGT, and unveiled cross-talk between O-GlcNAc and epigenetic signaling as a means to regulate Gli2 transcriptional activity. Moreover, genetic ablation or chemical inhibition of OGT significantly suppresses tumor progression and increases survival in a mouse model of Shh subgroup medulloblastoma. Taken together, the data in our study provide a line of inquiry to decipher the signaling mechanisms underlying cerebellar development, and highlights a potential target to investigate related pathologies, such as medulloblastoma.

Sonic hedgehog (Shh) signaling plays a critical role in regulating cerebellum development by maintaining the physiological proliferation of granule neuron precursors (GNPs), and its dysregulation leads to the oncogenesis of medulloblastoma. O-GlcNAcylation (O-GlcNAc) of proteins is an emerging regulator of brain function that maintains normal development and neuronal circuitry. Here, we demonstrate that O-GlcNAc transferase (OGT) in GNPs mediate the cerebellum development, and the progression of the Shh subgroup of medulloblastoma. Specifically, OGT regulates the neurogenesis of GNPs by activating the Shh signaling pathway via O-GlcNAcylation at S355 of GLI family zinc finger 2 (Gli2), which in turn promotes its deacetylation and transcriptional activity via dissociation from p300, a histone acetyltransferases. Inhibition of OGT via genetic ablation or chemical inhibition improves survival in a medulloblastoma mouse model. These data uncover a critical role for O-GlcNAc signaling in cerebellar development, and pinpoint a potential therapeutic target for Shh-associated medulloblastoma.

O-GlcNAc tranferase regulates p21 protein levels and cell proliferation through the FoxM1-Skp2 axis in a p53-independent manner

The protein product of the CDKN1A gene, p21, has been extensively characterized as a negative regulator of the cell cycle. Nevertheless, it is clear that p21 has manifold complex and context-dependent roles that can be either tumor suppressive or oncogenic. Most well studied as a transcriptional target of the p53 tumor suppressor protein, there are other means by which p21 levels can be regulated. In this study, we show that pharmacological inhibition or siRNA-mediated reduction of O-GlcNAc transferase (OGT), the enzyme responsible for glycosylation of intracellular proteins, increases expression of p21 in both p53-dependent and p53-independent manners in nontransformed and cancer cells. In cells harboring WT p53, we demonstrate that inhibition of OGT leads to p53-mediated transactivation of CDKN1A, while in cells that do not express p53, inhibiting OGT leads to increased p21 protein stabilization. p21 is normally degraded by the ubiquitin-proteasome system following ubiquitination by, among others, the E3 ligase Skp-Cullin-F-box complex; however, in this case, we show that blocking OGT causes impairment of the Skp-Cullin-F-box ubiquitin complex as a result of disruption of the FoxM1 transcription factor–mediated induction of Skp2 expression. In either setting, we conclude that p21 levels induced by OGT inhibition correlate with cell cycle arrest and decreased cancer cell proliferation.

Targeted Inhibition of O-Linked β-N-Acetylglucosamine Transferase as a Promising Therapeutic Strategy to Restore Chemosensitivity and Attenuate Aggressive Tumor Traits in Chemoresistant Urothelial Carcinoma of the Bladder

Acquisition of acquired chemoresistance during treatment cycles in urothelial carcinoma of the bladder (UCB) is the major cause of death through enhancing the risk of cancer progression and metastasis. Elevated glucose flux through the abnormal upregulation of O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) controls key signaling and metabolic pathways regulating diverse cancer cell phenotypes. This study showed that OGT expression levels in two human UCB cell models with acquired resistance to gemcitabine and paclitaxel were significantly upregulated compared with those in parental cells. Reducing hyper-O-GlcNAcylation by OGT knockdown (KD) markedly facilitated chemosensitivity to the corresponding chemotherapeutics in both cells, and combination treatment with OGT-KD showed more severe growth defects in chemoresistant sublines. We subsequently verified the suppressive effects of OGT-KD monotherapy on cell migration/invasion in vitro and xenograft tumor growth in vivo in chemoresistant UCB cells. Transcriptome analysis of these cells revealed 97 upregulated genes, which were enriched in multiple oncogenic pathways. Our final choice of suspected OGT glycosylation substrate was VCAN, S1PR3, PDGFRB, and PRKCG, the knockdown of which induced cell growth defects. These findings demonstrate the vital role of dysregulated OGT activity and hyper-O-GlcNAcylation in modulating treatment failure and tumor aggression in chemoresistant UCB.

Protein post-translational modifications in the regulation of cancer hallmarks

Posttranslational modifications (PTMs) of proteins, the major mechanism of protein function regulation, play important roles in regulating a variety of cellular physiological and pathological processes. Although the classical PTMs, such as phosphorylation, acetylation, ubiquitination and methylation, have been well studied, the emergence of many new modifications, such as succinylation, hydroxybutyrylation, and lactylation, introduces a new layer to protein regulation, leaving much more to be explored and wide application prospects. In this review, we will provide a broad overview of the significant roles of PTMs in regulating human cancer hallmarks through selecting a diverse set of examples, and update the current advances in the therapeutic implications of these PTMs in human cancer.

O-GlcNAcylation and Its Role in Cancer-Associated Inflammation

Cancer cells, as well as surrounding stromal and inflammatory cells, form an inflammatory tumor microenvironment (TME) to promote all stages of carcinogenesis. As an emerging post-translational modification (PTM) of serine and threonine residues of proteins, O-linked-N-Acetylglucosaminylation (O-GlcNAcylation) regulates diverse cancer-relevant processes, such as signal transduction, transcription, cell division, metabolism and cytoskeletal regulation. Recent studies suggest that O-GlcNAcylation regulates the development, maturation and functions of immune cells. However, the role of protein O-GlcNAcylation in cancer-associated inflammation has been less explored. This review summarizes the current understanding of the influence of protein O-GlcNAcylation on cancer-associated inflammation and the mechanisms whereby O-GlcNAc-mediated inflammation regulates tumor progression. This will provide a theoretical basis for further development of anti-cancer therapies.

Ogt Demonstrated Conspicuous Clinical Significance in Cancers, from Pan-Cancer to Small-Cell Lung Cancer

The clinical progression of small-cell lung cancer (SCLC) remains pessimistic. The aim of the present study was to promote the understanding of the clinical significance and mechanism of O-linked N-acetylglucosamine (GlcNAc) transferase (OGT) in SCLC. Wilcoxon tests, standardized mean difference (SMD), and Kruskal–Wallis tests were utilized to compare OGT level differences among the experimental and control groups. The univariate Cox regression analysis, Kaplan–Meier curves, and receiver operating characteristic curves were applied to determine OGT's clinical relevance in cancers. The Spearman correlation analysis and enrichment analysis were utilized to explore the underlying mechanisms of OGT in cancers. For the first time in the field, we provide an overview of OGT in 32 cancers using a large number of samples (n = 21,196), determining distinct OGT expression in 25 cancers and its prognosis effects in 12 cancers. Furthermore, using 950 samples from multiple sources, upregulated OGT was found in both mRNA and protein levels in SCLC (SMD = 0.93, 95% CI [0.24, 1.63]). Higher OGT levels represented a more unfavorable disease-free interval for SCLC patients (p < 0.001). The research also identified OGT expression as a potential marker for SCLC prediction (sensitivity = 0.79, specificity = 0.86, and AUC = 0.88). The high expression of OGT in SCLC may result from the positive regulation of two transcription factors—DEK and XRN2. We primarily investigated the underlying mechanisms of OGT in SCLC. Herein, based on the analyses from pan-cancer to SCLC, OGT demonstrated conspicuous clinical significance. OGT may be an underlying biomarker for the treatment and identification of some cancers, including SCLC.

O-GlcNAcylation regulation of cellular signaling in cancer

O-GlcNAcylation is a post-translational modification occurring on serine/threonine residues of nuclear and cytoplasmic proteins, mediated by the enzymes OGT and OGA which catalyze the addition or removal of the UDP-GlcNAc moieties, respectively. Structural changes brought by this modification lead to alternations of protein stability, protein-protein interactions, and phosphorylation. Importantly, O-GlcNAcylation is a nutrient sensor by coupling nutrient sensing with cellular signaling. Elevated levels of OGT and O-GlcNAc have been reported in a variety of cancers and has been linked to regulation of multiple cancer signaling pathways. In this review, we discuss the most recent findings on the role of O-GlcNAcylation as a metabolic sensor in signaling pathways and immune response in cancer.

Role and Function of O-GlcNAcylation in Cancer

Simple Summary

Despite the rapid advancement in immunotherapy and targeted agents, many patients diagnosed with cancer have poor prognosis with dismal overall survival. One of the key hallmarks of cancer is the ability of cancer cells to reprogram their energy metabolism. O-GlcNAcylation is an emerging potential mechanism for cancer cells to induce proliferation and progression of tumor cells and resistance to chemotherapy. This review summarizes the mechanism behind O-GlcNAcylation and discusses the role of O-GlcNAcylation, including its function with receptor tyrosine kinase and chemo-resistance in cancer, and immune response to cancer and as a prognostic factor. Further pre-clinical studies on O-GlcNAcylation are warranted to assess the clinical efficacy of agents targeting O-GlcNAcylation.

Abstract

Cancer cells are able to reprogram their glucose metabolism and retain energy via glycolysis even under aerobic conditions. They activate the hexosamine biosynthetic pathway (HBP), and the complex interplay of O-linked N-acetylglucosaminylation (O-GlcNAcylation) via deprivation of nutrients or increase in cellular stress results in the proliferation, progression, and metastasis of cancer cells. Notably, cancer is one of the emerging diseases associated with O-GlcNAcylation. In this review, we summarize studies that delineate the role of O-GlcNAcylation in cancer, including its modulation in metastasis, function with receptor tyrosine kinases, and resistance to chemotherapeutic agents, such as cisplatin. In addition, we discuss the function of O-GlcNAcylation in eliciting immune responses associated with immune surveillance in the tumor microenvironment. O-GlcNAcylation is increasingly accepted as one of the key players involved in the activation and differentiation of T cells and macrophages. Finally, we discuss the prognostic role of O-GlcNAcylation and potential therapeutic agents such as O-linked β-N-acetylglucosamine-transferase inhibitors, which may help overcome the resistance mechanism associated with the reprogramming of glucose metabolism.

MiRNA-424-5p Suppresses Proliferation, Migration, and Invasion of Clear Cell Renal Cell Carcinoma and Attenuates Expression of O-GlcNAc-Transferase

Simple Summary

The identification of biomarkers that predict the metastatic potential of tumors is a current area of interest in cancer research. A previous study from our laboratory identified numerous microRNA (miRNA) biomarkers that are differentially expressed in pathologic stage I clear cell renal cell carcinoma (ccRCC) tumors that progress to metastatic disease. This study investigated the role of aberrant expression of one of these miRNA, miR-424-5p, and one of its associated protein targets, O-GlcNAc-transferase (OGT). We examined the influence of miR-424-5p and OGT expression on the proliferation, migration, and invasion of ccRCC cells, and confirmed the direct interaction between miR-424-5p and OGT. These findings suggest that the decrease in miR-424-5p expression observed in these small renal masses leads to an increase in OGT, which facilitates metastasis.

Abstract

MicroRNAs (miRNAs) are non-coding post-transcriptional regulators of gene expression that are dysregulated in clear cell renal cell carcinoma (ccRCC) and play an important role in tumor progression. Our prior work identified a subset of miRNAs in pT1 ccRCC tumors, including miR-424-5p, that are associated with an aggressive phenotype. We investigate the impact of this dysregulated miRNA and its protein target O-GlcNAc-transferase (OGT) to better understand the mechanisms behind aggressive stage I ccRCC. The ccRCC cell lines 786-O and Caki-1 were used to assess the impact of miR-424-5p and OGT. Cells were transfected with pre-miR-424-5p, a lentiviral anti-OGT shRNA, or were treated with the demethylating agent 5-Aza-2′-deoxycytidine. Cell proliferation was measured via MT cell viability assay. Cell migration and invasion were analyzed using Transwell assays. The expression of miR-424-5p was determined through qRT-PCR, while OGT protein expression was evaluated through Western blotting. The interaction between miR-424-5p and OGT was confirmed via luciferase reporter assay. The transfection of ccRCC cells with pre-miR-424-5p or anti-OGT shRNA significantly inhibited cell proliferation, migration, and OGT expression, while miR-424-5p also attenuated cell invasion. Addition of the demethylating agent significantly reduced cell proliferation, migration, invasion, and OGT expression, while significantly increasing the expression of miR-424-5p. Altogether, these findings suggest that epigenetic downregulation of miR-424-5p, which in turn augments OGT expression, contributes to the creation of aggressive forms of stage I ccRCC.

Hexosamine Biosynthetic Pathway-Derived O-GlcNAcylation Is Critical for RANKL-Mediated Osteoclast Differentiation

O-linked-N-acetylglucosaminylation (O-GlcNAcylation) performed by O-GlcNAc transferase (OGT) is a nutrient-responsive post-translational modification (PTM) via the hexosamine biosynthetic pathway (HBP). Various transcription factors (TFs) are O-GlcNAcylated, affecting their activities and significantly contributing to cellular processes ranging from survival to cellular differentiation. Given the pleiotropic functions of O-GlcNAc modification, it has been studied in various fields; however, the role of O-GlcNAcylation during osteoclast differentiation remains to be explored. Kinetic transcriptome analysis during receptor activator of nuclear factor-kappaB (NF-κB) ligand (RANKL)-mediated osteoclast differentiation revealed that the nexus of major nutrient metabolism, HBP was critical for this process. We observed that the critical genes related to HBP activation, including Nagk, Gfpt1, and Ogt, were upregulated, while the global O-GlcNAcylation was increased concomitantly during osteoclast differentiation. The O-GlcNAcylation inhibition by the small-molecule inhibitor OSMI-1 reduced osteoclast differentiation in vitro and in vivo by disrupting the translocation of NF-κB p65 and nuclear factor of activated T cells c1 (NFATc1) into the nucleus by controlling their PTM O-GlcNAcylation. Furthermore, OSMI-1 had a synergistic effect with bone target therapy on osteoclastogenesis. Lastly, knocking down Ogt with shRNA (shOgt) mimicked OSMI-1’s effect on osteoclastogenesis. Targeting O-GlcNAcylation during osteoclast differentiation may be a valuable therapeutic approach for osteoclast-activated bone diseases.