SNHG17 alters anaerobic glycolysis by resetting phosphorylation modification of PGK1 to foster pro-tumor macrophage formation in pancreatic ductal adenocarcinoma

BACKGROUND

Within the tumor immune microenvironment (TME), tumor-associated macrophages (TAMs) are crucial in modulating polarization states to influence cancer development through metabolic reprogramming. While long non-coding RNAs (lncRNAs) have been shown to play a pivotal role in the progression of various cancers, the underlying mechanisms by which lncRNAs alter M2 polarization through macrophage metabolism remodeling remain unelucidated.

METHODS

RNA sequencing was used to screen for differentially expressed lncRNAs in TAMs and normal tissue-resident macrophages (NTRMs) isolated from pancreatic ductal adenocarcinoma (PDAC) tissues, whilst RT-qPCR and FISH were employed to detect the expression level of SNHG17. Moreover, a series of in vivo and in vitro experiments were conducted to assess the functions of SNHG17 from TAMs in the polarization and glycolysis of M2-like macrophages and in the proliferation and metastasis of pancreatic cancer cells (PCs). Furthermore, Western blotting, RNA pull-down, mass spectrometry, RIP, and dual-luciferase assays were utilized to explore the underlying mechanism through which SNHG17 induces pro-tumor macrophage formation.

RESULTS

SNHG17 was substantially enriched in TAMs and was positively correlated with a worse prognosis in PDAC. Meanwhile, functional assays determined that SNHG17 promoted the malignant progression of PCs by enhancing M2 macrophage polarization and anaerobic glycolysis. Mechanistically, SNHG17 could sponge miR-628-5p to release PGK1 mRNA and concurrently interact with the PGK1 protein, activating the pro-tumorigenic function of PGK1 by enhancing phosphorylation at the T168A site of PGK1 through ERK1/2 recruitment. Lastly, SNHG17 knockdown could reverse the polarization status of macrophages in PDAC.

CONCLUSIONS

The present study illustrated the essential role of SNHG17 and its molecular mechanism in TAMs derived from PDAC, indicating that SNHG17 might be a viable target for PDAC immunotherapy.

Human anaerobic microbiome: a promising and innovative tool in cancer prevention and treatment by targeting pyruvate metabolism

INTRODUCTION

Even in present-day times, cancer is one of the most fatal diseases. People are overwhelmed by pricey chemotherapy, immunotherapy, and other costly cancer therapies in poor and middle-income countries. Cancer cells grow under anaerobic and hypoxic conditions. Pyruvate is the final product of the anaerobic glycolysis pathway, and many cancer cells utilize pyruvate for their growth and development. The anaerobic microbiome produces many anti-cancer substances that can act as anti-tumor agents and are both feasible and of low cost. There are different mechanisms of action of the anaerobic microbiome, such as the production of short-chain fatty acids (SCFAs), and competition for the anaerobic environment includes the metabolic product pyruvate to form lactic acid for energy.

KEY FINDINGS

In this review, we have summarized the role of the metabolic approach of the anaerobic human microbiome in cancer prevention and treatment by interfering with cancer metabolite pyruvate. SCFAs possess decisive outcomes in condoning almost all the hallmarks of cancer and helping the spread of cancer to other body parts. Studies have demonstrated the impact and significance of using SCFA, which results from anaerobic bacteria, as an anti-cancer agent. Anaerobic bacteria-based cancer therapy has become a promising approach to treat cancer using obligate and facultative anaerobic bacteria because of their ability to penetrate and increase in an acidic hypoxic environment.

SIGNIFICANCE

This review attempts to provide the interconnection of cancer metabolism and anaerobic microbiome metabolism with a focus on pyruvate metabolism to understand and design unique anaerobic microbiota-based therapy for cancer patients.

Photodynamic therapy enhances the cytotoxicity of temozolomide against glioblastoma via reprogramming anaerobic glycolysis

The successful application of photodynamic therapy in the treatment of glioma (CNS WHO grade 4) depends in large part to the effect of killing cells in the infiltrating area after tumor had been removed, when combined with radiotherapy, chemotherapy, and targeted drug therapy. The purpose of this study was to investigate the potential mechanism of TMZ's involvement in the glioma's glycolytic metabolic pathway during photodynamic therapy. The low dose of photodynamic therapy treatment on the cell viability of gliomas was investigated by CCK8. Alterations in reactive oxygen species were detected by flow cytometer. The differentially expressed proteins related to glucose transporter 1 (GLUT-1), matrix metalloproteinase-2 (MMP-2)/actively MMP-2 and apoptosis-associated caspase-3/cleaved caspase-3 were evaluated by Western Blot experiment. Additionally, transmission electron microscopy observed apoptosis, necrosis and the changes of the ultrastructure in U251 cells. In addition, antitumor effects in vivo were tested using orthotopic BALB/c mice with the glioma U87 model. The findings showed that low dose PDT affected mitochondrial function by inducing radical oxygen, hindered cellular glucose transport and metabolism, and induced apoptosis. The results also showed that cell viability considerably decreased and increased cell apoptosis under the PDT therapy. The HIF-1/GLUT-1 axis enhanced the cytotoxicity of temozolomide in gliomas as a result of PDT treatment, which was influenced by ROS. As a result, this study presents PDT as a potential therapeutic approach for treating malignant glioma, and enhanced antitumor effect of TMZ by inhibiting glycolytic pathway.

Posttranslational modification of pyruvate kinase type M2 (PKM2): novel regulation of its biological roles to be further discovered

PKM2, pyruvate kinase type M2, has been shown to play a key role in aerobic glycolysis and to regulate the malignant behaviors of cancer cells. Recently, PKM2 has been revealed to hold dual metabolic and nonmetabolic roles. Working as both a pyruvate kinase with catalytic activity and a protein kinase that phosphorylates its substrates, PKM2 stands at the crossroads of glycolysis and tumor growth. Recently, it was revealed that the catalytic activity of PKM2 can be regulated by its posttranslational modification (PTM). Several PTM types, including phosphorylation, methylation, acetylation, oxidation, hydroxylation, succinylation, and glycylation, have been gradually identified on different amino acid residues of the PKM2 coding sequence. In this review, we highlight the recent advancements in understanding PKM2 PTMs and the regulatory roles conferred by PTMs during anaerobic glycolysis in tumors.

Identification of Gliotoxin isolated from marine fungus as a new pyruvate kinase M2 inhibitor

Pyruvate kinase M2 (PKM2) functions as an important rate-limiting enzyme of aerobic glycolysis that is involved in tumor initiation and progression. However, there are few studies on effective PKM2 inhibitors. Gliotoxin is a marine-derived fungal secondary metabolite with multiple biological activities, including immunosuppression, cytotoxicity, and et al. In this study, we found that Gliotoxin directly bound to PKM2 and inhibited its glycolytic activity in a dose-dependent manner accompanied by the decreases in glucose consumption and lactate production in the human glioma cell line U87. Moreover, Gliotoxin suppressed tyrosine kinase activity of PKM2, leading to a dramatic reduction in Stat3 phosphorylation in U87 cells. Furthermore, Gliotoxin suppressed cell viability in U87 cells, and cytotoxicity of Gliotoxin on U87 cells was obviously augmented under hypoxia condition compared to normal condition. Finally, Gliotoxin was demonstrated to induce cell apoptosis of U87 cells and synergize with temozolomide. Our findings identify Gliotoxin as a new PKM2 inhibitor with anti-tumor activity, which lays the foundation for the development of Gliotoxin as a promising anti-tumor drug in the future.

Icariin increases chondrocyte vitality by promoting hypoxia-inducible factor-1α expression and anaerobic glycolysis

BACKGROUND

Articular cartilage is a unique avascular tissue in which chondrocytes are embedded in extracellular matrix (ECM). The decreased ECM resulting from the loss of articular chondrocyte viability leads to degenerative diseases such as osteoarthritis (OA). This study aims to investigate the effect of icariin (ICA) on ECM synthesis and chondrocyte viability.

METHODS

Micromass culture, alcian blue, and Safran O (SO)/fast green staining were used to investigate chondrocyte viability and ECM synthesis in chondrocytes treated with ICA. The expression of hypoxia-inducible factor-1α (HIF-1α), SOX9, and anaerobic glycolysis enzymes were detected by western blot and reverse transcription-quantitative polymerase chain reaction.

RESULTS

ICA, an active flavonoid component of Herba epimedii, was demonstrated to increase chondrocyte viability and ECM synthesis. HIF-1α is a key mediator of chondrocyte response to fluctuations in oxygen availability during cartilage development or damage, and its expression was unregulated by ICA treatment. Meanwhile, ICA treatment increased SOX9 expression, which is a key regulator of ECM synthesis. Furthermore, ICA treatment increased the expression of glucose transporter 1 (GLUT1), glucose-6-phosphate dehydrogenase (G6PD), phosphoglycerate kinase 1 (PGK1), and pyruvate dehydrogenase kinase 1 (PDK1), which contribute to glucose transfer and anaerobic glycolysis.

CONCLUSIONS

The present study revealed that ICA treatment facilitates chondrocyte vitality by promoting HIF-1α expression and anaerobic glycolysis. Therefore, ICA could be a novel clinical treatment for OA.

Effect of the periodic properties of toxic stress on the oscillatory behaviour of glycolysis in yeast-evidence of a toxic effect frequency

Starving and nondividing yeast cells induce changes in the electron donor nicotinamide adenine dinucleotide (NADH) levels in a cyclic and wave-like manner for over 90min. Yeast suspensions were used to examine the toxic effects of contaminants on the cyclic behaviour of metabolite changes during anaerobic glycolysis. The cyclic behaviour NADH levels in yeast cell suspensions starved for 2 to 5h was studied after the addition of 10mM glucose for 5min followed by 10mM KCN to block aerobic glycolysis. The effects of three toxic elements (CuSO₄, silver nanoparticles-nAg, and GdCl₃), known for their potential to alter glycolsysis, on NADH levels over time were examined during the 3-h starvation step. The data were analyzed using spectral analysis (Fourier transformation) to characterize the cyclic behaviour of NADH levels during anaerobic glycolysis. Increasing the starvation time by 3h increased the amplitude of changes in NADH levels with characteristic periods of 3 to 8min. Longer starvation times decreased the amplitude of oscillations during these periods, with the appearance of NADH changes at higher frequencies. Moreover, the amplitude changes in NADH were proportional to the starvation time. Exposure to the above chemicals during the 3-h starvation time led to the formation of higher frequencies with concentration-dependent amplitude changes. In comparison with nAg and Gd³⁺, Cu²⁺ was the most toxic (decreased viability the most) and produce changes at higher frequencies as well. It is noteworthy that each element produced a characteristic change in the frequency profiles, which suggests different mechanisms of action in which the severity of toxicity shifted NADH changes at higher frequencies. In conclusion, the appearance of synchronized oscillations in dense yeast populations following synchronization stress could be induced by starvation and exposure to chemicals. However, synchronicity could be abolished when cells desynchronize as a result of loss of cell viability, which contributes to heterogeneity in yeast populations, translating into NADH changes at higher frequencies. This is the first report on the influence of environmental contaminants on the cyclic or wave-like behaviour of biochemical changes in cells.

Blockage of glycolysis by targeting PFKFB3 alleviates sepsis-related acute lung injury via suppressing inflammation and apoptosis of alveolar epithelial cells

Sepsis-related acute lung injury (ALI) is characterized by excessive lung inflammation and apoptosis of alveolar epithelial cells resulting in acute hypoxemic respiratory failure. Recent studies indicated that anaerobic glycolysis play an important role in sepsis. However, whether inhibition of aerobic glycolysis exhibits beneficial effect on sepsis-induced ALI is not known. In vivo, a cecal ligation and puncture (CLP)-induced ALI mouse model was set up and mice treated with glycolytic inhibitor 3PO after CLP. The mice treated with the 3PO ameliorated the survival rate, histopathological changes, lung inflammation, lactate increased and lung apoptosis of mice with CLP-induced sepsis. In vitro, the exposure of human alveolar epithelial A549 cells to lipopolysaccharide (LPS) resulted in cell apoptosis, inflammatory cytokine production, enhanced glycolytic flux and reactive oxygen species (ROS) increased. While these changes were attenuated by 3PO treatment. Sequentially, treatment of A549 cells with lactate caused cell apoptosis and enhancement of ROS. Pretreatment with N-acetylcysteine (NAC) significantly lowered LPS and lactate-induced the generation of ROS and cell apoptosis in A549 cells. Therefore, these results indicate that anaerobic glycolysis may be an important contributor in cell apoptosis of sepsis-related ALI. Moreover, LPS specifically induces apoptotic insults to A549 cell through lactate-mediated enhancement of ROS.

Hypoxic glucose metabolism in glioblastoma as a potential prognostic factor

PURPOSE

Metabolic activity and hypoxia are both important factors characterizing tumor aggressiveness. Here, we used F-18 fluoromisonidazole (FMISO) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to define metabolically active hypoxic volume, and investigate its clinical significance in relation to progression free survival (PFS) and overall survival (OS) in glioblastoma patients.

EXPERIMENTAL DESIGN

Glioblastoma patients (n = 32) underwent FMISO PET, FDG PET, and magnetic resonance imaging (MRI) before surgical intervention. FDG and FMISO PET images were coregistered with gadolinium-enhanced T1-weighted MR images. Volume of interest (VOI) of gross tumor volume (GTV) was manually created to enclose the entire gadolinium-positive areas. The FMISO tumor-to-normal region ratio (TNR) and FDG TNR were calculated in a voxel-by-voxel manner. For calculating TNR, standardized uptake value (SUV) was divided by averaged SUV of normal references. Contralateral frontal and parietal cortices were used as the reference region for FDG, whereas the cerebellar cortex was used as the reference region for FMISO. FDG-positive was defined as the FDG TNR ≥1.0, and FMISO-positive was defined as FMISO TNR ≥1.3. Hypoxia volume (HV) was defined as the volume of FMISO-positive and metabolic tumor volume in hypoxia (hMTV) was the volume of FMISO/FDG double-positive. The total lesion glycolysis in hypoxia (hTLG) was hMTV × FDG SUVmean. The extent of resection (EOR) involving cytoreduction surgery was volumetric change based on planimetry methods using MRI. These factors were tested for correlation with patient prognosis.

RESULTS

All tumor lesions were FMISO-positive and FDG-positive. Univariate analysis indicated that hMTV, hTLG, and EOR were significantly correlated with PFS (p = 0.007, p = 0.04, and p = 0.01, respectively) and that hMTV, hTLG, and EOR were also significantly correlated with OS (p = 0.0028, p = 0.037, and p = 0.014, respectively). In contrast, none of FDG TNR, FMISO TNR, GTV, HV, patients' age, or Karnofsky performance scale (KPS) was significantly correlated with PSF or OS. The hMTV and hTLG were found to be independent factors affecting PFS and OS on multivariate analysis.

CONCLUSIONS

We introduced hMTV and hTLG using FDG and FMISO PET to define metabolically active hypoxic volume. Univariate and multivariate analyses demonstrated that both hMTV and hTLG are significant predictors for PFS and OS in glioblastoma patients.