Alpha-Enolase (ENO1) Correlates with Invasiveness of Cutaneous Melanoma—An In Vitro and a Clinical Study

Circular RNA PIP5K1A Promotes Glucose and Lipid Metabolism Disorders and Inflammation in Type 2 Diabetes Mellitus

Disorders of glucose and lipid metabolism are an important cause of type 2 diabetes mellitus (T2DM). Identifying the molecular mechanism of metabolic disorders is key to the treatment of T2DM. The study was to investigate the effect of circRNA PIP5K1A (circPIP5K1A) on glucose and lipid metabolism and inflammation in T2DM rats. A T2DM rat model was established, and then the T2DM rats were injected with lentiviral vectors that interfere with circPIP5K1A, miR-552-3p, or ENO1 expression. Fasting blood glucose (FBG) and fasting insulin (FINS) levels of rats were detected by an automatic analyzer and insulin detection kit, and HOMA-IR was calculated. Lipid metabolism was assessed by measuring serum levels of TG, TC, LDL-C, leptin, and resistin. Serum levels of inflammatory factors (TNF-α and IL-6) were detected by ELISA. The pathological conditions of pancreatic tissue were observed by HE staining. circPIP5K1A, miR-552-3p and ENO1 levels were recorded. The experimental results showed that circPIP5K1A and ENO1 were up-regulated, and miR-552-3p was down-regulated in T2DM rats. Down-regulating circPIP5K1A or up-regulating miR-552-3p reduced blood glucose and lipid levels, inhibited inflammation, and improved pancreatic histopathological changes in T2DM rats. In addition, up-regulating ENO1 rescued the ameliorating effects of down-regulated circPIP5K1A on T2DM rats. In general, downregulating circPIP5K1A improves insulin resistance and lipid metabolism disorders and inhibits inflammation by targeting miR-552-3p to mediate ENO1 expression.

Role of ENO1 and its targeted therapy in tumors

ENO1, also called 2-phospho-D-glycerate hydrolase in cellular glycolysis, is an enzyme that converts 2-phosphoglycerate to phosphoenolpyruvate and plays an important role in the Warburg effect. In various tumors, ENO1 overexpression correlates with poor prognosis. ENO1 is a multifunctional oncoprotein that, when located on the cell surface, acts as a "moonlighting protein" to promote tumor invasion and metastasis. When located intracellularly, ENO1 facilitates glycolysis to dysregulate cellular energy and sustain tumor proliferation. Additionally, it promotes tumor progression by activating oncogenic signaling pathways. ENO1 is a tumor biomarker and represents a promising target for tumor therapy. This review summarizes recent advances from 2020 to 2024 in understanding the relationship between ENO1 and tumors and explores the latest targeted therapeutic strategies involving ENO1.

The regulatory roles and clinical significance of glycolysis in tumor

Metabolic reprogramming has been demonstrated to have a significant impact on the biological behaviors of tumor cells, among which glycolysis is an important form. Recent research has revealed that the heightened glycolysis levels, the abnormal expression of glycolytic enzymes, and the accumulation of glycolytic products could regulate the growth, proliferation, invasion, and metastasis of tumor cells and provide a favorable microenvironment for tumor development and progression. Based on the distinctive glycolytic characteristics of tumor cells, novel imaging tests have been developed to evaluate tumor proliferation and metastasis. In addition, glycolytic enzymes have been found to serve as promising biomarkers in tumor, which could provide assistance in the early diagnosis and prognostic assessment of tumor patients. Numerous glycolytic enzymes have been identified as potential therapeutic targets for tumor treatment, and various small molecule inhibitors targeting glycolytic enzymes have been developed to inhibit tumor development and some of them are already applied in the clinic. In this review, we systematically summarized recent advances of the regulatory roles of glycolysis in tumor progression and highlighted the potential clinical significance of glycolytic enzymes and products as novel biomarkers and therapeutic targets in tumor treatment.

Tumour-specific phosphorylation of serine 419 drives alpha-enolase (ENO1) nuclear export in triple negative breast cancer progression

BACKGROUND

The glycolytic enzyme alpha-enolase is a known biomarker of many cancers and involved in tumorigenic functions unrelated to its key role in glycolysis. Here, we show that expression of alpha-enolase correlates with subcellular localisation and tumorigenic status in the MCF10 triple negative breast cancer isogenic tumour progression model, where non-tumour cells show diffuse nucleocytoplasmic localisation of alpha-enolase, whereas tumorigenic cells show a predominantly cytoplasmic localisation. Alpha-enolase nucleocytoplasmic localisation may be regulated by tumour cell-specific phosphorylation at S419, previously reported in pancreatic cancer.

RESULTS

Here we show ENO1 phosphorylation can also be observed in triple negative breast cancer patient samples and MCF10 tumour progression cell models. Furthermore, prevention of alpha-enolase-S419 phosphorylation by point mutation or a casein kinase-1 specific inhibitor D4476, induced tumour-specific nuclear accumulation of alpha-enolase, implicating S419 phosphorylation and casein kinase-1 in regulating subcellular localisation in tumour cell-specific fashion. Strikingly, alpha-enolase nuclear accumulation was induced in tumour cells by treatment with the specific exportin-1-mediated nuclear export inhibitor Leptomycin B. This suggests that S419 phosphorylation in tumour cells regulates alpha-enolase subcellular localisation by inducing its exportin-1-mediated nuclear export. Finally, as a first step to analyse the functional consequences of increased cytoplasmic alpha-enolase in tumour cells, we determined the alpha-enolase interactome in the absence/presence of D4476 treatment, with results suggesting clear differences with respect to interaction with cytoskeleton regulating proteins.

CONCLUSIONS

The results suggest for the first time that tumour-specific S419 phosphorylation may contribute integrally to alpha-enolase cytoplasmic localisation, to facilitate alpha-enolase's role in modulating cytoskeletal organisation in triple negative breast cancer. This new information may be used for development of triple negative breast cancer specific therapeutics that target alpha-enolase.

Extracellular Vesicles-Based Cell-Cell Communication in Melanoma: New Perspectives in Diagnostics and Therapy

Extracellular vesicles (EVs) are a heterogeneous group of cell-secreted particles that carry cargo of functional biomolecules crucial for cell-to-cell communication with both physiological and pathophysiological consequences. In this review, we focus on evidence demonstrating that the EV-mediated crosstalk between melanoma cells within tumor, between melanoma cells and immune and stromal cells, promotes immune evasion and influences all steps of melanoma development from local progression, pre-metastatic niche formation, to metastatic colonization of distant organs. We also discuss the role of EVs in the development of resistance to immunotherapy and therapy with BRAF^V600/MEK inhibitors, and shortly summarize the recent advances on the potential applications of EVs in melanoma diagnostics and therapy.

The Long and the Short of It: NEAT1 and Cancer Cell Metabolism

Simple Summary

Altered metabolism is a hallmark of most cancers. The way that cancer cells regulate their energy production to fuel constant proliferation has been of interest with the hope that it may be exploited therapeutically. The long noncoding RNA, NEAT1, is often dysregulated in tumours. NEAT1 RNA can be transcribed as two isoforms with different lengths, with each variant responsible for different functions. This review explores how the isoforms contribute to cancer metabolism.

Abstract

The long noncoding RNA NEAT1 is known to be heavily dysregulated in many cancers. A single exon gene produces two isoforms, NEAT1_1 and NEAT1_2, through alternative 3′-end processing. As the longer isoform, NEAT1_2 is an essential scaffold for nuclear paraspeckle formation. It was previously thought that the short NEAT1_1 isoform only exists to keep the NEAT1 locus active for rapid paraspeckle formation. However, a recent glycolysis-enhancing function for NEAT1_1, contributing to cancer cell proliferation and the Warburg effect, has been demonstrated. Previous studies have mainly focused on quantifying total NEAT1 and NEAT1_2 expression levels. However, in light of the NEAT1_1 role in cancer cell metabolism, the contribution from specific NEAT1 isoforms is no longer clear. Here, the roles of NEAT1_1 and NEAT1_2 in metabolism and cancer progression are discussed.