Discrete mechanisms of mTOR and cell cycle regulation by AMPK agonists independent of AMPK. Proc Natl Acad Sci U S A. 2014;111:E435-E444. [PMID: 24474794 DOI: 10.1073/pnas.1311121111]

Molecular pathways and therapeutic targets linked to triple-negative breast cancer (TNBC)

Cancer is a group of diseases characterized by uncontrolled cellular growth, abnormal morphology, and altered proliferation. Cancerous cells lose their ability to act as anchors, allowing them to spread throughout the body and infiltrate nearby cells, tissues, and organs. If these cells are not identified and treated promptly, they will likely spread. Around 70% of female breast cancers are caused by a mutation in the BRCA gene, specifically BRCA1. The absence of progesterone, oestrogen and HER2 receptors (human epidermal growth factor) distinguishes the TNBC subtype of breast cancer. There were approximately 6,85,000 deaths worldwide and 2.3 million new breast cancer cases in women in 2020. Breast cancer is the most common cancer globally, affecting 7.8 million people at the end of 2020. Compared to other cancer types, breast cancer causes more women to lose disability-adjusted life years (DALYs). Worldwide, women can develop breast cancer at any age after puberty, but rates increase with age. The maintenance of mammary stem cell stemness is disrupted in TNBC, governed by signalling cascades controlling healthy mammary gland growth and development. Interpreting these essential cascades may facilitate an in-depth understanding of TNBC cancer and the search for an appropriate therapeutic target. Its treatment remains challenging because it lacks specific receptors, which renders hormone therapy and medications ineffective. In addition to radiotherapy, numerous recognized chemotherapeutic medicines are available as inhibitors of signalling pathways, while others are currently undergoing clinical trials. This article summarizes the vital druggable targets, therapeutic approaches, and strategies associated with TNBC.

Molecular mechanisms of action of metformin: latest advances and therapeutic implications

Metformin is among the most widely used antidiabetic drugs. Studies over the past few years have identified multiple novel molecular targets and pathways that metformin acts on to exert its beneficial effects in treating type 2 diabetes as well as other disorders involving dysregulated inflammation and redox homeostasis. In this mini-review, we discuss the latest cutting-edge research discoveries on novel molecular targets of metformin in glycemic control, cardiovascular protection, cancer intervention, anti-inflammation, antiaging, and weight control. Identification of these novel targets and pathways not only deepens our understanding of the molecular mechanisms by which metformin exerts diverse beneficial biological effects, but also provides opportunities for developing new mechanistically based drugs for human diseases.

Modulation of AMPK Significantly Alters Uveal Melanoma Tumor Cell Viability

INTRODUCTION

Uveal melanoma (UM) responds poorly to targeted therapies or immune checkpoint inhibitors. Adenosine monophosphate-activated protein kinase (AMPK) is a pivotal serine/threonine protein kinase that coordinates vital processes such as cell growth. Targeting AMPK pathway, which represents a critical mechanism mediating the survival of UM cells, may prove to be a novel treatment strategy for UM. We aimed to demonstrate the effects of AMPK modulation on UM cells.

METHODS

In silico analyses were performed to compare UM and normal melanocyte cells via Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Set Enrichment Analysis (GSEA). The effects of AMPK modulation on cell viability and proliferation in UM cell lines with different molecular profiles (i.e., 92-1, MP46, OMM2.5, and Mel270) were investigated via XTT cell viability and proliferation assays after treating the cells with varying concentrations of A-769662 (AMPK activator) or dorsomorphin (AMPK inhibitor).

RESULTS

KEGG/GSEA studies demonstrated that genes implicated in the AMPK signaling pathway were differentially regulated in UM. Gene sets comprising genes involved in AMPK signaling and genes involved in energy-dependent regulation of mammalian target of rapamycin by liver kinase B1-AMPK were downregulated in UM. We observed gradual decreases in the numbers of viable UM cells as the concentration of A-769662 treatment increased. All UM cells demonstrated statistically significant decreases in cell viability when treated with 200 µm A-769662. Moreover, the effects of AMPK inhibition on UM cells were potent, since low doses of dorsomorphin treatment resulted in significant decreases in viabilities of UM cells. The half maximal inhibitory concentration (IC50) values confirmed the potency of dorsomorphin treatment against UM in vitro.

CONCLUSION

AMPK may act like a friend or a foe in cancer depending on the context. As such, the current study contributes to the literature in determining the effects of therapeutic strategies targeting AMPK in several UM cells. We propose a new perspective in the treatment of UM. Targeting AMPK pathway may open up new avenues in developing novel therapeutic approaches to improve overall survival in UM.

Advances in the mechanism of action of metformin in pituitary tumors

Pituitary tumors are common intracranial tumors, but when faced with drug-resistant or aggressive tumors, existing medical measures may not provide good control, leading to progression and deterioration. Metformin, a traditional hypoglycemic drug, has recently been discovered to have multiple functions including antitumor effects. There have been studies on the mechanism of metformin for the treatment of pituitary tumors, but it is uncertain whether it will provide new adjuvant or alternative therapies for the treatment of these tumors. We analyzed the potential mechanisms of action of metformin with respect to the inhibition of pituitary tumor growth and hormone secretion by reviewing the available literature.

Efficacy and safety of metformin plus low-dose temozolomide in patients with recurrent or refractory glioblastoma: a randomized, prospective, multicenter, double-blind, controlled, phase 2 trial (KNOG-1501 study)

PURPOSE

Glioblastoma (GBM) has a poor prognosis after standard treatment. Recently, metformin has been shown to have an antitumor effect on glioma cells. We performed the first randomized prospective phase II clinical trial to investigate the clinical efficacy and safety of metformin in patients with recurrent or refractory GBM treated with low-dose temozolomide.

METHODS

Included patients were randomly assigned to a control group [placebo plus low-dose temozolomide (50 mg/m², daily)] or an experimental group [metformin (1000 mg, 1500 mg, and 2000 mg per day during the 1st, 2nd, and 3rd week until disease progression, respectively) plus low-dose temozolomide]. The primary endpoint was progression-free survival (PFS). Secondary endpoints were overall survival (OS), disease control rate, overall response rate, health-related quality of life, and safety.

RESULTS

Among the 92 patients screened, 81 were randomly assigned to the control group (43 patients) or the experimental group (38 patients). Although the control group showed a longer median PFS, the difference between the two groups was not statistically significant (2.66 versus 2.3 months, p = 0.679). The median OS was 17.22 months (95% CI 12.19-21.68 months) in the experimental group and 7.69 months (95% CI 5.16-22.67 months) in the control group, showing no significant difference by the log-rank test (HR: 0.78; 95% CI 0.39-1.58; p = 0.473). The overall response rate and disease control rate were 9.3% and 46.5% in the control group and 5.3% and 47.4% in the experimental group, respectively.

CONCLUSIONS

Although the metformin plus temozolomide regimen was well tolerated, it did not confer a clinical benefit in patients with recurrent or refractory GBM. Trial registration NCT03243851, registered August 4, 2017.

Endocannabinoids are potential inhibitors of glioblastoma multiforme proliferation

Globally, it is evident that glioblastoma multiforme (GBM) is an aggressive malignant cancer with a high mortality rate and no effective treatment options. Glioblastoma is classified as the stage-four progression of a glioma tumor, and its diagnosis results in a shortened life expectancy. Treatment options for GBM include chemotherapy, immunotherapy, surgical intervention, and conventional pharmacotherapy; however, at best, they extend the patient's life by a maximum of 5 years. GBMs are considered incurable due to their high recurrence rate, despite various aggressive therapeutic approaches which can have many serious adverse effects. Ceramides, classified as endocannabinoids, offer a promising novel therapeutic approach for GBM. Endocannabinoids may enhance the apoptosis of GBM cells but have no effect on normal healthy neural cells. Cannabinoids promote atypical protein kinase C, deactivate fatty acid amide hydrolase enzymes, and activate transient receptor potential vanilloid 1 (TRPV1) and TRPV2 to induce pro-apoptotic signaling pathways without increasing endogenous cannabinoids. In previous in vivo studies, endocannabinoids, chemically classified as amide formations of oleic and palmitic acids, have been shown to increase the pro-apoptotic activity of human cancer cells and inhibit cell migration and angiogenesis. This review focuses on the biological synthesis and pharmacology of endogenous cannabinoids for the enhancement of cancer cell apoptosis, which have potential as a novel therapy for GBM. Please cite this article as: Duzan A, Reinken D, McGomery TL, Ferencz N, Plummer JM, Basti MM. Endocannabinoids are potential inhibitors of glioblastoma multiforme proliferation. J Integr Med. 2023; Epub ahead of print.

Promoter methylation levels of RASSF1 and ATIC genes are associated with lung cancer in Iranian patients

OBJECTIVES

Epigenetic alterations like methylation of tumor suppressor genes or oncogenes, in respiratory epithelium have been associated with lung cancer. Hypermethylation of genes promoter is an epigenetic event, and is responsible to tumor suppressor genes inactivation as well as oncogenes activation. This study aimed to assess the role of methylation status in promoter of RASSF1 and ATIC genes their potential implication in the pathogenesis of lung tumor in Iranian patients.

METHODS

In this study, we collected 100 tissue samples (50 lung cancer tissues and 50 adjacent non-cancerous lung tissues) from Iranian lung cancer patients. The genomic DNA was extracted, and methylation status of both RASSF1 and ATIC genes was investigated by methylation-sensitive high-resolution melting (MS-HRM) assay technique and Real-Time PCR. Cancer Genome Atlas (TCGA) dataset was also analyzed for further validation of the gene's methylation.

RESULTS

Methylation of RASSF1 gene promoter was significantly higher in lung tumor tissues. However, promoter methylation levels of ATIC gene was significantly lower in lung tumor tissues. These results were additionally confirmed by TCGA analysis. Promoter methylation of both RASSF1 and ATIC genes was significantly associated with lymph node metastasis, and clinical stage of lung cancer. The receiver operating characteristic (ROC) curve analysis indicated a high accuracy of promoter methylation in these genes as a diagnostic biomarker for lung cancer.

CONCLUSIONS

Methylation levels of both RASSF1 and ATIC genes promoters were associated with lung cancer pathogenesis in Iranian population, and may be a suitable biomarker for diagnosis and prognosis of lung cancer in early stage of tumorigenesis.

The participation of non-canonical autophagic proteins in the autophagy process and their potential as therapeutic targets

INTRODUCTION

Autophagy is a conserved catabolic process that helps recycle intracellular components to maintain homeostasis. The completion of autophagy requires the synergistic effect of multiple canonical autophagic proteins. Defects in autophagy machinery have been reported to promote diseases, rendering autophagy a bone fide health-modifying agent. However, the clinical implication of canonical pan-autophagic activators or inhibitors has often led to undesirable side effects, making it urgent to find a safer autophagy-related therapeutic target. The discovery of non-canonical autophagic proteins has been found to specifically affect the development of diseases without causing a universal impact on autophagy and has shed light on finding a safer way to utilize autophagy in the therapeutic context.

AREAS COVERED

This review summarizes recently discovered non-canonical autophagic proteins, how these proteins influence autophagy, and their potential therapeutic role in the disease due to their interaction with autophagy.

EXPERT OPINION

Several therapies have been studied thus far and continued research is needed to identify the potential that non-canonical autophagic proteins have for treating certain diseases. In the meantime, continue to uncover new non-canonical autophagic proteins and examine which are likely to have therapeutic implications.

Standardization and validation of novel ex-vivo method for mitochondrial bioenergetics using mitochondrial modulators

Mitochondria is an essential organelle; it produces 95% of the adenine triphosphate (ATP) of cells, their dysfunction is related to the pathogenesis of multiple diseases, such as diabetes mellitus, cardiovascular and neurological disorders. Various pharmacologic agents are known to target mitochondrial function. Moreover, the toxic side effects of multiple drugs used to treat diseases are related to the impairment of mitochondrial function. Thus, there is a need to develop a method to evaluate the effect of pharmacologic agents for their potential and side effects to identify effective mitochondrial-modulating agents. Therefore, the objective of this study was to develop and validate an ex-vivo method for studying the effect of pharmacologic agents on mitochondrial function and rescue of dysfunction. Dimethyl sulfoxide (DMSO) concentrations that drugs were soluble in and maintained mitochondrial function were determined. Metformin (MET) is a known mitochondrial complex-1 inhibitor tested for its ability to compromise mitochondrion function. Coenzyme Q10 (Q10) and Resveratrol (RSV), which are known to enhance mitochondrial function, were added alone and dose-dependent, tested for the ability to rescue metformin-induced mitochondrial dysfunction. Ex-vivo liver and brain mitochondrial function was assessed using an oxytherm Clark-type oxygen electrode. DMSO was found to be toxic above 10% and drugs insoluble below 5%. The addition of 0.5 mg/ml MET decreased liver and brain mitochondrial respiratory control rate (RCR). At the same time, Q10 improved RCR in normal mitochondria and a concentration-dependent manner in MET-induced dysfunctional mitochondria. RSV was added in the last step of the experiment to confirm that compromised function is due to MET. Hence this method can be used to screen pharmacological agents for their potential therapeutics or toxic effect on mitochondria.

Metformin in therapeutic applications in human diseases: its mechanism of action and clinical study

Metformin, a biguanide drug, is the most commonly used first-line medication for type 2 diabetes mellites due to its outstanding glucose-lowering ability. After oral administration of 1 g, metformin peaked plasma concentration of approximately 20-30 μM in 3 h, and then it mainly accumulated in the gastrointestinal tract, liver and kidney. Substantial studies have indicated that metformin exerts its beneficial or deleterious effect by multiple mechanisms, apart from AMPK-dependent mechanism, also including several AMPK-independent mechanisms, such as restoring of redox balance, affecting mitochondrial function, modulating gut microbiome and regulating several other signals, such as FBP1, PP2A, FGF21, SIRT1 and mTOR. On the basis of these multiple mechanisms, researchers tried to repurpose this old drug and further explored the possible indications and adverse effects of metformin. Through investigating with clinical studies, researchers concluded that in addition to decreasing cardiovascular events and anti-obesity, metformin is also beneficial for neurodegenerative disease, polycystic ovary syndrome, aging, cancer and COVID-19, however, it also induces some adverse effects, such as gastrointestinal complaints, lactic acidosis, vitamin B12 deficiency, neurodegenerative disease and offspring impairment. Of note, the dose of metformin used in most studies is much higher than its clinically relevant dose, which may cast doubt on the actual effects of metformin on these disease in the clinic. This review summarizes these research developments on the mechanism of action and clinical evidence of metformin and discusses its therapeutic potential and clinical safety.

Brain pharmacokinetics and metabolism of the AMP-activated protein kinase selective inhibitor SBI-0206965, an investigational agent for the treatment of glioblastoma

PURPOSE

Emerging evidence suggests that 5' Adenosine Monophosphate-Activated Protein Kinase (AMPK), a key regulator of cellular bioenergetics, is a novel target for the treatment of glioblastoma (GBM), a lethal brain tumor. SBI-0206965, an aminopyrimidine derivative, is a potent AMPK inhibitor being investigated for the treatment of GBM. Here we characterized the systemic and brain pharmacokinetics (PK) and hepatic metabolism of SBI-0206965.

METHODS

We performed intracerebral microdialysis to determine brain partitioning of SBI-0206965 in jugular vein cannulated rats. We assessed systemic PK of SBI-0206965 in rats and C57BL/6 mice following oral administration. Employing human, mouse, and rat liver microsomes we characterized the metabolism of SBI-0206965.

RESULTS

SBI-0206965 is quickly absorbed, achieving plasma and brain extracellular fluid (ECF) peak levels within 0.25 - 0.65 h. Based on the ratio of C_max and AUC in brain ECF to plasma (corrected for protein binding), brain partitioning is ~ 0.6-0.9 in rats. However, the compound has a short elimination half-life (1-2 h) and low relative oral bioavailability (~ 0.15). The estimated in-vitro hepatic intrinsic clearance of SBI-0206965 in mouse, rat and human was 325, 76 and 68 mL/min/kg, respectively. SBI-0206965 metabolites included desmethylated products, and the metabolism was strongly inhibited by ketoconazole, a CYP3A inhibitor.

CONCLUSION

SBI-0206965 has adequate brain permeability but low relative oral bioavailability which may be due to rapid hepatic metabolism, likely catalyzed by CYP3A enzymes. Our observations will facilitate further development of SBI-0206965, and/or other structurally related molecules, for the treatment of GBM and other brain tumors.

A Novel Classification Model for Lower-Grade Glioma Patients Based on Pyroptosis-Related Genes

Recent studies demonstrated that pyroptosis plays a crucial role in shaping the tumor-immune microenvironment. However, the influence of pyroptosis on lower-grade glioma regarding immunotherapy and targeted therapy is still unknown. This study analyzed the variations of 33 pyroptosis-related genes in lower-grade glioma and normal tissues. Our study found considerable genetic and expression alterations in heterogeneity among lower-grade gliomas and normal brain tissues. There are two pyroptosis phenotypes in lower-grade glioma, and they exhibited differences in cell infiltration characteristics and clinical characters. Then, a PyroScore model using the lasso-cox method was constructed to measure the level of pyroptosis in each patient. PyroScore can refine the lower-grade glioma patients with a stratified prognosis and a distinct tumor immune microenvironment. Pyscore may also be an effective factor in predicting potential therapeutic benefits. In silico analysis showed that patients with a lower PyroScore are expected to be more sensitive to targeted therapy and immunotherapy. These findings may enhance our understanding of pyroptosis in lower-grade glioma and might help optimize risk stratification for the survival and personalized management of lower-grade glioma patients.

Regulation and role of CAMKK2 in prostate cancer

In 2011, CAMKK2, the gene encoding calcium/calmodulin-dependent kinase kinase 2 (CAMKK2), was demonstrated to be a direct target of the androgen receptor and a driver of prostate cancer progression. Results from multiple independent studies have confirmed these findings and demonstrated the potential role of CAMKK2 as a clinical biomarker and therapeutic target in advanced prostate cancer using a variety of preclinical models. Drug development efforts targeting CAMKK2 have begun accordingly. CAMKK2 regulation can vary across disease stages, which might have important implications in the use of CAMKK2 as a biomarker. Moreover, new non-cell-autonomous roles for CAMKK2 that could affect tumorigenesis, metastasis and possible comorbidities linked to disease and treatment have emerged and could present novel treatment opportunities for prostate cancer.

Effects of Metformin Combined With Antifolates on HepG2 Cell Metabolism and Cellular Proliferation

Hepatocellular carcinoma (HCC), one of the most prevalent types of cancers worldwide, continues to maintain high levels of resistance to standard therapy. As clinical data revealed poor response rates, the need for developing new methods has increased to improve the overall wellbeing of patients with HCC. Furthermore, a growing body of evidence shows that cancer metabolic changes are a key feature of many types of human malignancies. Metabolic reprogramming refers to cancer cells’ ability to change their metabolism in order to meet the increased energy demand caused by continuous growth, rapid proliferation, and other neoplastic cell characteristics. For these reasons, metabolic pathways may become new therapeutic and chemopreventive targets. The aim of this study was to investigate the metabolic alterations associated with metformin (MET), an anti-diabetic agent when combined with two antifolate drugs: trimethoprim (TMP) or methotrexate (MTX), and how metabolic changes within the cancer cell may be used to increase cellular death. In this study, single drugs and combinations were investigated using in vitro assays including cytotoxicity assay (MTT), RT-qPCR, annexin V/PI apoptosis assay, scratch wound assay and Seahorse XF analysis, on a human HCC cell line, HepG2. The cytotoxicity assay showed that the IC₅₀ of MET as single therapy was 44.08 mM that was reduced to 22.73 mM and 29.29 mM when combined with TMP and MTX, respectively. The co-treatment of both drugs increased p53 and Bax apoptotic markers, while decreased the anti-apoptotic marker; Bcl-2. Both combinations increased the percentage of apoptotic cells and halted cancer cell migration when compared to MET alone. Furthermore, both combinations decreased the MET-induced increase in glycolysis, while also inducing mitochondrial damage, altering cancer cell bioenergetics. These findings provide an exciting insight into the anti-proliferative and apoptotic effects of MET and anti-folates on HepG2 cells, and how in combination, may potentially combat the aggressiveness of HCC.

Impact of Variants in the ATIC and ARID5B Genes on Therapeutic Failure with Imatinib in Patients with Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm derived from the balanced reciprocal translocation of chromosomes 9 and 22 t (9q34 and 22q11), which leads to the formation of the Philadelphia chromosome and fusion of the BCR-ABL genes. The first-line treatment for CML is imatinib, a tyrosine kinase inhibitor that acts on the BCR-ABL protein. However, even though it is a target-specific drug, about 25% of patients do not respond to this treatment. The resistance mechanisms involved in this process have been investigated and studies have shown that germinal alterations can influence this mechanism. The aim of this work was to investigate 32 polymorphisms in 24 genes of carcinogenic pathway to verify the influence of these genetic variants on the response to treatment with imatinib. Our results demonstrated that individuals with the recessive GG genotype for the rs2372536 variant in the ATIC gene are approximately three times more likely to experience treatment failure with imatinib (p = 0.045, HR = 2.726, 95% CI = 0.9986–7.441), as well as individuals with the TT genotype for the rs10821936 variant in the ARID5B gene, who also have a higher risk for treatment failure with imatinib over time (p = 0.02, HR = 0.4053, IC 95% = 0.1802–0.911). In conclusion, we show that variants in the ATIC and ARIDB5 gene, never screened in previous studies, could potentially influence the therapeutic response to imatinib in patients treated for CML.

Type 2 Diabetes Mellitus and Cancer: Epidemiology, Physiopathology and Prevention

Individuals with type 2 diabetes mellitus are at greater risk of developing cancer and of dying from it. Both diseases are age-related, contributing to the impact of population aging on the long-term sustainability of health care systems in European Union countries. The purpose of this narrative review was to describe, from epidemiological, pathophysiological and preventive perspectives, the links between type 2 diabetes mellitus and the most prevalent cancers in these patients. Multiple metabolic abnormalities that may occur in type 2 diabetes mellitus, particularly obesity, could explain the increased cancer risk. In addition, the effectiveness of drugs commonly used to treat type 2 diabetes mellitus (e.g., metformin and thiazolidinediones) has been broadly evaluated in cancer prevention. Thus, a better understanding of the links between type 2 diabetes mellitus and cancer will help to identify the contributing factors and the pathophysiological pathways and to design personalized preventive strategies. The final goal is to facilitate healthy aging and the prevention of cancer and other diseases related with type 2 diabetes mellitus, which are among the main sources of disability and death in the European Union and worldwide.

Adaptation of AMPK-mTOR-signal pathways and lipid metabolism in response to low- and high-level rapeseed meal diet in Chinese perch (Siniperca chuatsi)

It is well known that carnivorous fish cannot use plant-proteins efficiently. They affect lipid metabolism of fish and cause serious problems to fish health. The reasons for this deficiency of fish metabolism are not known well. Chinese perch, a carnivorous fish, can accept artificial diet after domestication and is also considered as a novel model of fish for nutrition studies. Therefore, the aim of this study was to explore the effect of fish meal replacement by low- or high-rapeseed meal on lipid and glucose metabolism of Chinese perch. Three experimental diets were formulated with 0, 10%, and 30% rapeseed meal, named as Control, RSL, and RSH groups, respectively. After 8-weeks of the feeding trial, the inhibition of growth and fat deposition were observed in Chinese perch fed with rapeseed meal diets compared to the control group. Fish fed with RSL diets showed decreased food intake, serum low density lipoprotein (LDL), phosphorylated Grb10 (P < 0.05), inhibited fatty acid (FA) transport (lipoprotein lipase (LPL)), and glycerol synthesis (phosphoenol pyruvate carboxykinase (PEPCK)) in the liver. In addition, fish fed with RSL diets were also inhibited FA synthesis (fatty acid synthase (FAS), sterol regulatory element binding protein 1 (SREBP1), and Acetyl-CoA carboxylase (ACC1)), lipid uptake (hepatic lipase (HL)), β-oxidation (carnitine palmitoyltransferase I (CPT1)), and glycerol synthesis (PEPCK) in the visceral adipose tissue. Fish fed with RSH diets showed phosphorylated AMPK, inhibited FA synthesis (SREBP1, ACC1, and FAS), while enhanced lipolysis (hormone-sensitive lipase (HSL)), and then reduced Acetyl-CoA pool. In turn, β-oxidation (peroxisome proliferator-activated receptor-a (PPARα) and CPT1) was inhibited, while glycolysis (glucose-6-phosphatase (G6PD) and pyruvate carboxylase (PC)) were enhanced, consequently the lipid accumulation was decreased in the liver. Fish were also inhibited lipid uptake (LPL), that caused inhibiting of FA synthesis (SREBP1), β-oxidation (CPT1), glycerol synthesis (PEPCK), and in turn improved lipolysis (HSL) in the visceral adipose tissue. Our study suggested that both RSL and RSH diets decreased lipid accumulation in Chinese perch; however, the mechanism of lipid metabolism was different. Fish accepted less diet in RSL group, which inhibited lipid metabolism in the liver and in the visceral adipose tissues, while fish in RSH group activated AMPK pathway, inhibited FA synthesis, and enhanced lipolysis, which reduced Acetyl-CoA pool in the liver. Subsequently, lipid uptake and metabolism were inhibited in the visceral adipose tissue of RSH fish.

AMPK in the brain: its roles in glucose and neural metabolism

The adenosine monophosphate-activated protein kinase (AMPK) is an integrative metabolic sensor that maintains energy balance at the cellular level and plays an important role in orchestrating intertissue metabolic signaling. AMPK regulates cell survival, metabolism, and cellular homeostasis basally as well as in response to various metabolic stresses. Studies so far show that the AMPK pathway is associated with neurodegeneration and CNS pathology, but the mechanisms involved remain unclear. AMPK dysregulation has been reported in neurodegenerative diseases such as amyotrophic lateral sclerosis, multiple sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and other neuropathies. AMPK activation appears to be both neuroprotective and pro-apoptotic, possibly dependent upon neural cell types, the nature of insults, and the intensity and duration of AMPK activation. While embryonic brain development in AMPK null mice appears to proceed normally without any overt structural abnormalities, our recent study confirmed the full impact of AMPK loss in the postnatal and aging brain. Our studies revealed that Ampk deletion in neurons increased basal neuronal excitability and reduced latency to seizure upon stimulation. Three major pathways, glycolysis, pentose phosphate shunt, and glycogen turnover, contribute to utilization of glucose in the brain. AMPK's regulation of aerobic glycolysis in astrocytic metabolism warrants further deliberation, particularly glycogen turnover and shuttling of glucose- and glycogen-derived lactate from astrocytes to neurons during activation. In this minireview, we focus on recent advances in AMPK and energy-sensing in the brain.

Biguanides drugs: Past success stories and promising future for drug discovery

Biguanides have attracted much attention a century ago and showed resurgent interest in recent years after a long period of dormancy. They constitute an important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases. Therapeutic indications of biguanides include antidiabetic, antimalarial, antiviral, antiplaque, and bactericidal applications. This review presents an extensive overview of the biological activity of biguanides and different mechanisms of action of currently marketed biguanide-containing drugs, as well as their pharmacological properties when applicable. We highlight the recent developments in research on biguanide compounds, with a primary focus on studies on metformin in the field of oncology. We aim to provide a critical overview of all main bioactive biguanide compounds and discuss future perspectives for the design of new drugs based on the biguanide fragment.

One-Carbon Metabolism Associated Vulnerabilities in Glioblastoma: A Review

Simple Summary

Glioblastoma tumours are the most malignant and common type of central nervous system tumours. Despite aggressive treatment measures, disease recurrence in patients with glioblastoma is inevitable and survival rates remain low. Glioblastoma cells, like other cancer cells, can leverage metabolic pathways to increase their rate of proliferation, maintain self-renewal, and develop treatment resistance. Furthermore, many of the metabolic strategies employed by cancer cells are similar to those employed by stem cells in order to maintain self-renewal and proliferation. One-carbon metabolism and de novo purine synthesis are metabolic pathways that are essential for biosynthesis of macromolecules and have been found to be essential for tumourigenesis. In this review, we summarize the evidence showing the significance of 1-C-mediated de novo purine synthesis in glioblastoma cell proliferation and tumourigenesis, as well as evidence suggesting the effectiveness of targeting this metabolic pathway as a therapeutic modality.

Abstract

Altered cell metabolism is a hallmark of cancer cell biology, and the adaptive metabolic strategies of cancer cells have been of recent interest to many groups. Metabolic reprogramming has been identified as a critical step in glial cell transformation, and the use of antimetabolites against glioblastoma has been investigated. One-carbon (1-C) metabolism and its associated biosynthetic pathways, particularly purine nucleotide synthesis, are critical for rapid proliferation and are altered in many cancers. Purine metabolism has also been identified as essential for glioma tumourigenesis. Additionally, alterations of 1-C-mediated purine synthesis have been identified as commonly present in brain tumour initiating cells (BTICs) and could serve as a phenotypic marker of cells responsible for tumour recurrence. Further research is required to elucidate mechanisms through which metabolic vulnerabilities may arise in BTICs and potential ways to therapeutically target these metabolic processes. This review aims to summarize the role of 1-C metabolism-associated vulnerabilities in glioblastoma tumourigenesis and progression and investigate the therapeutic potential of targeting this pathway in conjunction with other treatment strategies.

AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAr) has been one of the most commonly used pharmacological modulators of AMPK activity. The majority of early studies on the role of AMPK, both in the physiological regulation of metabolism and in cancer pathogenesis, were based solely on the use of AICAr as an AMPK-activator. Even with more complex models of AMPK downregulation and knockout being introduced, AICAr remained a regular starting point for many studies focusing on AMPK biology. However, there is an increasing number of studies showing that numerous AICAr effects, previously attributed to AMPK activation, are in fact AMPK-independent. This review aims to give an overview of the present knowledge on AMPK-dependent and AMPK-independent effects of AICAr on metabolism, hypoxia, exercise, nucleotide synthesis, and cancer, calling for caution in the interpretation of AICAr-based studies in the context of understanding AMPK signaling pathway.

AICAr, a Widely Used AMPK Activator with Important AMPK-Independent Effects: A Systematic Review

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAr) has been one of the most commonly used pharmacological modulators of AMPK activity. The majority of early studies on the role of AMPK, both in the physiological regulation of metabolism and in cancer pathogenesis, were based solely on the use of AICAr as an AMPK-activator. Even with more complex models of AMPK downregulation and knockout being introduced, AICAr remained a regular starting point for many studies focusing on AMPK biology. However, there is an increasing number of studies showing that numerous AICAr effects, previously attributed to AMPK activation, are in fact AMPK-independent. This review aims to give an overview of the present knowledge on AMPK-dependent and AMPK-independent effects of AICAr on metabolism, hypoxia, exercise, nucleotide synthesis, and cancer, calling for caution in the interpretation of AICAr-based studies in the context of understanding AMPK signaling pathway.

How far along are we in revealing the connection between metformin and colorectal cancer?

Colorectal cancer (CRC) is among the most prevalent cancers worldwide, and its prevention and reduction of incidence is imperative. The presence of diabetes has been associated with a 30% increased risk of CRC, likely through the mechanism of hyperinsulinemia, which promotes tumorigenesis via the insulin receptor in the epithelium or by insulin-like growth factor pathways, inflammation, or adipokines, inducing cancer cell proliferation and cancer spread. Metformin, the first-line agent in treating type 2 diabetes, has a chemopreventive role in CRC development. Additionally, preclinical studies suggest synergistic effects of metformin with oxaliplatin in inhibiting in vitro models of colon cancer. Although preclinical studies on the post diagnostic use of metformin were promising and suggested its synergistic effects with chemotherapy, the data on the possible effects of metformin after surgery and other CRC treatment in the clinical setting are less conclusive, and randomized controlled trials are still lacking.

AICAR and compound C negatively modulate HCC-induced primary human hepatic stellate cell activation in vitro

Tumor stroma and microenvironment have been shown to affect hepatocellular carcinoma (HCC) growth, with activated hepatic stellate cells (HSC) as a major contributor in this process. Recent evidence suggests that the energy sensor adenosine monophosphate-activated kinase (AMPK) may mediate a series of essential processes during carcinogenesis and HCC progression. Here, we investigated the effect of different HCC cell lines with known TP53 or CTNBB1 mutations on primary human HSC activation, proliferation, and AMPK activation. We show that conditioned media obtained from multiple HCC cell lines differently modulate human hepatic stellate cell (hHSC) proliferation and hHSC AMPK activity in a paracrine manner. Pharmacological treatment of hHSC with AICAR and Compound C inhibited the HCC-induced proliferation/activation of hHSC through AMPK-dependent and AMPK-independent mechanisms, which was further confirmed using mouse embryonic fibroblasts (MEFs) deficient of both catalytic AMPKα isoforms (AMPK^α1/α2-/-) and wild type (wt) MEF. Both compounds induced S-phase cell-cycle arrest and, in addition, AICAR inhibited the mTORC1 pathway by inhibiting phosphorylation of 4E-BP1 and S6 in hHSC and wt MEF. Data mining of the Cancer Genome Atlas (TCGA) and the Liver Cancer (LICA-FR) showed that AMPKα1 (PRKAA1) and AMPKα2 (PRKAA2) expression differed depending on the mutation (TP53 or CTNNB1), tumor grading, and G1-G6 classification, reflecting the heterogeneity in human HCC. Overall, we provide evidence that AMPK modulating pharmacological agents negatively modulate HCC-induced hHSC activation and may therefore provide a novel approach to target the mutual, tumor-promoting interactions between hHSC and HCC.NEW & NOTEWORTHY HCC is marked by genetic heterogeneity and activated hepatic stellate cells (HSC) are considered key players during HCC development. The paracrine effect of different HCC cell lines on the activation of primary hHSC was accompanied by differential AMPK activation depending on the HCC line used. Pharmacological treatment inhibited the HCC-induced hHSC activation through AMPK-dependent and AMPK-independent mechanisms. This heterogenic effect on HCC-induced AMPK activation was confirmed by data mining TCGA and LICA-FR databases.

Identification and Validation of a Prognostic Model Based on Three Autophagy-Related Genes in Hepatocellular Carcinoma

Background

Accumulating studies have demonstrated that autophagy plays an important role in hepatocellular carcinoma (HCC). We aimed to construct a prognostic model based on autophagy-related genes (ARGs) to predict the survival of HCC patients.

Methods

Differentially expressed ARGs were identified based on the expression data from The Cancer Genome Atlas and ARGs of the Human Autophagy Database. Univariate Cox regression analysis was used to identify the prognosis-related ARGs. Multivariate Cox regression analysis was performed to construct the prognostic model. Receiver operating characteristic (ROC), Kaplan-Meier curve, and multivariate Cox regression analyses were performed to test the prognostic value of the model. The prognostic value of the model was further confirmed by an independent data cohort obtained from the International Cancer Genome Consortium (ICGC) database.

Results

A total of 34 prognosis-related ARGs were selected from 62 differentially expressed ARGs identified in HCC compared with noncancer tissues. After analysis, a novel prognostic model based on ARGs (PRKCD, BIRC5, and ATIC) was constructed. The risk score divided patients into high- or low-risk groups, which had significantly different survival rates. Multivariate Cox analysis indicated that the risk score was an independent risk factor for survival of HCC after adjusting for other conventional clinical parameters. ROC analysis showed that the predictive value of this model was better than that of other conventional clinical parameters. Moreover, the prognostic value of the model was further confirmed in an independent cohort from ICGC patients.

Conclusion

The prognosis-related ARGs could provide new perspectives on HCC, and the model should be helpful for predicting the prognosis of HCC patients.

Metformin Reduces Histone H3K4me3 at the Promoter Regions of Positive Cell Cycle Regulatory Genes in Lung Cancer Cells

Simple Summary

To understand the effect of metformin on epigenetic regulation, we analyzed histone H3 methylation, DNA methylation, and chromatin accessibility in lung cancer cells. Metformin showed little effect on DNA methylation or chromatin accessibility but significantly reduced H3K4me3 levels at the promoters of positive cell cycle regulatory genes. Metformin downregulated H3K4 methyltransferase MLL2 expression and knockdown of MLL2 resulted in suppression of H3K4me3 expression and lung cancer cell proliferation. We further evaluated the clinicopathological significance of MLL2 in tumor and matched normal tissues from 42 non-small cell lung cancer patients. MLL2 overexpression was significantly associated with poor recurrence-free survival in lung adenocarcinoma. Our study facilitates the understanding of the effect of metformin on the regulation of histone H3K4me3 at promoter regions of cell cycle regulatory genes in lung cancer cells, and MLL2 may be a potential therapeutic target for lung cancer therapy.

Abstract

This study aimed at understanding the effect of metformin on histone H3 methylation, DNA methylation, and chromatin accessibility in lung cancer cells. Metformin significantly reduced H3K4me3 level at the promoters of positive cell cycle regulatory genes such as CCNB2, CDK1, CDK6, and E2F8. Eighty-eight genes involved in cell cycle showed reduced H3K4me3 levels in response to metformin, and 27% of them showed mRNA downregulation. Metformin suppressed the expression of H3K4 methyltransferases MLL1, MLL2, and WDR82. The siRNA-mediated knockdown of MLL2 significantly downregulated global H3K4me3 level and inhibited lung cancer cell proliferation. MLL2 overexpression was found in 14 (33%) of 42 NSCLC patients, and a Cox proportional hazards analysis showed that recurrence-free survival of lung adenocarcinoma patients with MLL2 overexpression was approximately 1.32 (95% CI = 1.08–4.72; p = 0.02) times poorer than in those without it. Metformin showed little effect on DNA methylation and chromatin accessibility at the promoter regions of cell cycle regulatory genes. The present study suggests that metformin reduces H3K4me3 levels at the promoters of positive cell cycle regulatory genes through MLL2 downregulation in lung cancer cells. Additionally, MLL2 may be a potential therapeutic target for reducing the recurrence of lung adenocarcinoma.

Targeting reduced mitochondrial DNA quantity as a therapeutic approach in pediatric high-grade gliomas

Background

Despite increased understanding of the genetic events underlying pediatric high-grade gliomas (pHGGs), therapeutic progress is static, with poor understanding of nongenomic drivers. We therefore investigated the role of alterations in mitochondrial function and developed an effective combination therapy against pHGGs.

Methods

Mitochondrial DNA (mtDNA) copy number was measured in a cohort of 60 pHGGs. The implication of mtDNA alteration in pHGG tumorigenesis was studied and followed by an efficacy investigation using patient-derived cultures and orthotopic xenografts.

Results

Average mtDNA content was significantly lower in tumors versus normal brains. Decreasing mtDNA copy number in normal human astrocytes led to a markedly increased tumorigenicity in vivo. Depletion of mtDNA in pHGG cells promoted cell migration and invasion and therapeutic resistance. Shifting glucose metabolism from glycolysis to mitochondrial oxidation with the adenosine monophosphate–activated protein kinase activator AICAR (5-aminoimidazole-4-carboxamide ribonucleotide) or the pyruvate dehydrogenase kinase inhibitor dichloroacetate (DCA) significantly inhibited pHGG viability. Using DCA to shift glucose metabolism to mitochondrial oxidation and then metformin to simultaneously target mitochondrial function disrupted energy homeostasis of tumor cells, increasing DNA damage and apoptosis. The triple combination with radiation therapy, DCA and metformin led to a more potent therapeutic effect in vitro and in vivo.

Conclusions

Our results suggest metabolic alterations as an onco-requisite factor of pHGG tumorigenesis. Targeting reduced mtDNA quantity represents a promising therapeutic strategy for pHGG.

Beyond the Warburg Effect: Oxidative and Glycolytic Phenotypes Coexist within the Metabolic Heterogeneity of Glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor, with a median survival at diagnosis of 16-20 months. Metabolism represents a new attractive therapeutic target; however, due to high intratumoral heterogeneity, the application of metabolic drugs in GBM is challenging. We characterized the basal bioenergetic metabolism and antiproliferative potential of metformin (MF), dichloroacetate (DCA), sodium oxamate (SOD) and diazo-5-oxo-L-norleucine (DON) in three distinct glioma stem cells (GSCs) (GBM18, GBM27, GBM38), as well as U87MG. GBM27, a highly oxidative cell line, was the most resistant to all treatments, except DON. GBM18 and GBM38, Warburg-like GSCs, were sensitive to MF and DCA, respectively. Resistance to DON was not correlated with basal metabolic phenotypes. In combinatory experiments, radiomimetic bleomycin exhibited therapeutically relevant synergistic effects with MF, DCA and DON in GBM27 and DON in all other cell lines. MF and DCA shifted the metabolism of treated cells towards glycolysis or oxidation, respectively. DON consistently decreased total ATP production. Our study highlights the need for a better characterization of GBM from a metabolic perspective. Metabolic therapy should focus on both glycolytic and oxidative subpopulations of GSCs.

Topsentinol L Trisulfate, a Marine Natural Product That Targets Basal-like and Claudin-Low Breast Cancers

Patients diagnosed with basal-like breast cancer suffer from poor prognosis and limited treatment options. There is an urgent need to identify new targets that can benefit patients with basal-like and claudin-low (BL-CL) breast cancers. We screened fractions from our Marine Invertebrate Compound Library (MICL) to identify compounds that specifically target BL-CL breast cancers. We identified a previously unreported trisulfated sterol, i.e., topsentinol L trisulfate (TLT), which exhibited increased efficacy against BL-CL breast cancers relative to luminal/HER2+ breast cancer. Biochemical investigation of the effects of TLT on BL-CL cell lines revealed its ability to inhibit activation of AMP-activated protein kinase (AMPK) and checkpoint kinase 1 (CHK1) and to promote activation of p38. The importance of targeting AMPK and CHK1 in BL-CL cell lines was validated by treating a panel of breast cancer cell lines with known small molecule inhibitors of AMPK (dorsomorphin) and CHK1 (Ly2603618) and recording the increased effectiveness against BL-CL breast cancers as compared with luminal/HER2+ breast cancer. Finally, we generated a drug response gene-expression signature and projected it against a human tumor panel of 12 different cancer types to identify other cancer types sensitive to the compound. The TLT sensitivity gene-expression signature identified breast and bladder cancer as the most sensitive to TLT, while glioblastoma multiforme was the least sensitive.

O-GlcNAcylation in Hyperglycemic Pregnancies: Impact on Placental Function

The dynamic cycling of N-acetylglucosamine, termed as O-GlcNAcylation, is a post-translational modification of proteins and is involved in the regulation of fundamental cellular processes. It is controlled by two essential enzymes, O-GlcNAc transferase and O-GlcNAcase. O-GlcNAcylation serves as a modulator in placental tissue; furthermore, increased levels of protein O-GlcNAcylation have been observed in women with hyperglycemia during pregnancy, which may affect the short-and long-term development of offspring. In this review, we focus on the impact of O-GlcNAcylation on placental functions in hyperglycemia-associated pregnancies. We discuss the following topics: effect of O-GlcNAcylation on placental development and its association with hyperglycemia; maternal-fetal nutrition transport, particularly glucose transport, via the mammalian target of rapamycin and AMP-activated protein kinase pathways; and the two-sided regulatory effect of O-GlcNAcylation on inflammation. As O-GlcNAcylation in the placental tissues of pregnant women with hyperglycemia influences near- and long-term development of offspring, research in this field has significant therapeutic relevance.

Human de novo purine biosynthesis

The focus of this review is the human de novo purine biosynthetic pathway. The pathway enzymes are enumerated, as well as the reactions they catalyze and their physical properties. Early literature evidence suggested that they might assemble into a multi-enzyme complex called a metabolon. The finding that fluorescently-tagged chimeras of the pathway enzymes form discrete puncta, now called purinosomes, is further elaborated in this review to include: a discussion of their assembly; the role of ancillary proteins; their locus at the microtubule/mitochondria interface; the elucidation that at endogenous levels, purinosomes function to channel intermediates from phosphoribosyl pyrophosphate to AMP and GMP; and the evidence for the purinosomes to exist as a protein condensate. The review concludes with a consideration of probable signaling pathways that might promote the assembly and disassembly of the purinosome, in particular the identification of candidate kinases given the extensive phosphorylation of the enzymes. These collective findings substantiate our current view of the de novo purine biosynthetic metabolon whose properties will be representative of how other metabolic pathways might be organized for their function.

5-aminoimidazole-4-carboxamide ribonucleoside induces differentiation in a subset of primary acute myeloid leukemia blasts

Background

All-trans retinoic acid (ATRA)-based treatment of acute promyelocytic leukemia (APL) is the most successful pharmacological treatment of acute myeloid leukemia (AML). Recent development of inhibitors of mutated isocitrate dehydrogenase and dihydroorotate dehydrogenase (DHODH) has revived interest in differentiation therapy of non-APL AML. Our previous studies demonstrated that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAr) induced differentiation of monocytic cell lines by activating the ATR/Chk1 via pyrimidine depletion. In the present study, the effects of AICAr on the viability and differentiation of primary AML blasts isolated from bone marrow of patients with non-APL AML were tested and compared with the effects of DHODH inhibitor brequinar and ATRA.

Methods

Bone marrow samples were obtained from 35 patients and leukemia blasts were cultured ex vivo. The cell viability was assessed by MTT assay and AML cell differentiation was determined by flow cytometry and morphological analyses. RNA sequencing and partial data analysis were conducted using ClusterProfiler package. Statistical analysis was performed using GraphPad Prism 6.0.

Results

AICAr is capable of triggering differentiation in samples of bone marrow blasts cultured ex vivo that were resistant to ATRA. AICAr-induced differentiation correlates with proliferation and sensitivity to DHODH inhibition. RNA-seq data obtained in primary AML blasts confirmed that AICAr treatment induced downregulation of pyrimidine metabolism pathways together with an upregulation of gene set involved in hematopoietic cell lineage.

Conclusion

AICAr induces differentiation in a subset of primary non-APL AML blasts, and these effects correlate with sensitivity to a well-known, potent DHODH inhibitor.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12885-020-07533-6.

Mitochondrial Metabolism in PDAC: From Better Knowledge to New Targeting Strategies

Cancer cells reprogram their metabolism to meet bioenergetics and biosynthetic demands. The first observation of metabolic reprogramming in cancer cells was made a century ago (“Warburg effect” or aerobic glycolysis), leading to the classical view that cancer metabolism relies on a glycolytic phenotype. There is now accumulating evidence that most cancers also rely on mitochondria to satisfy their metabolic needs. Indeed, the current view of cancer metabolism places mitochondria as key actors in all facets of cancer progression. Importantly, mitochondrial metabolism has become a very promising target in cancer therapy, including for refractory cancers such as Pancreatic Ductal AdenoCarcinoma (PDAC). In particular, mitochondrial oxidative phosphorylation (OXPHOS) is an important target in cancer therapy. Other therapeutic strategies include the targeting of glutamine and fatty acids metabolism, as well as the inhibition of the TriCarboxylic Acid (TCA) cycle intermediates. A better knowledge of how pancreatic cancer cells regulate mitochondrial metabolism will allow the identification of metabolic vulnerabilities and thus novel and more efficient therapeutic options for the benefit of each patient.

Benefits of Metformin in Attenuating the Hallmarks of Aging

Biological aging involves an interplay of conserved and targetable molecular mechanisms, summarized as the hallmarks of aging. Metformin, a biguanide that combats age-related disorders and improves health span, is the first drug to be tested for its age-targeting effects in the large clinical trial-TAME (targeting aging by metformin). This review focuses on metformin's mechanisms in attenuating hallmarks of aging and their interconnectivity, by improving nutrient sensing, enhancing autophagy and intercellular communication, protecting against macromolecular damage, delaying stem cell aging, modulating mitochondrial function, regulating transcription, and lowering telomere attrition and senescence. These characteristics make metformin an attractive gerotherapeutic to translate to human trials.

Transcriptomic landscape profiling of metformin-treated healthy mice: Implication for potential hypertension risk when prophylactically used

Recently, the first-line anti-diabetic drug metformin shows versatile protective effects against several diseases and is potentially prescribed to healthy individual for prophylactic use against ageing or other pathophysiological processes. However, for healthy individuals, it remains unclear what effects metformin treatment will induce on their bodies. A systematic profiling of the molecular landscape of metformin treatment is expected to provide crucial implications for this issue. Here, we delineated the first transcriptomic landscape induced by metformin in 10 tissues (aorta, brown adipose, brain, eye, heart, liver, kidney, skeletal muscle, stomach and testis) of healthy mice by using RNA-sequencing technique. A comprehensive computational analysis was performed. The overrepresentation of cardiovascular disease-related gene sets, positive correlation with hypertension-related transcriptomic signatures and the associations of drugs with hypertensive side effect together indicate that although metformin does exert various beneficial effects, it would also increase the risk of hypertension in healthy mice. This prediction was experimentally validated by an independent animal experiments. Together, this study provided important resource necessary for investigating metformin's beneficial/deleterious effects on various healthy tissues, when it is potentially prescribed to healthy individual for prophylactic use.

Phenformin inhibits proliferation, invasion, and angiogenesis of cholangiocarcinoma cells via AMPK-mTOR and HIF-1A pathways

Phenformin (Phen), a potent activator of AMPK, is effective against some resistant cancers. This study evaluated the inhibition of proliferation, migration, invasion, and angiogenesis by Phen in aggressive cancer cells and investigated the underlying mechanism of the inhibition. Cholangiocarcinoma (CCA) KKU-156 and KKU-452 cells were used in this study. The results showed that Phen suppressed cell proliferation and induced apoptosis in both cells. Phen suppressed migration and invasion of cancer cells in wound healing and transwell chamber assays, respectively. The effects were associated with depletions of glutathione (GSH) and decreased glutathione redox ratio which represents cellular redox state. The redox stress was linked with the loss of mitochondrial transmembrane potential, as evaluated by JC-1 assay. The effect of Phen on angiogenesis was performed using HUVEC cultured cells. Phen alone did not affect tube formation of HUVEC cells. However, conditioned media from CCA cell cultures treated with Phen suppressed the tube-like structure formation. The antitumor effect of Phen was associated with AMPK activation and suppression of mTOR phosphorylation, HIF-1A, and VEGF protein expression. In conclusion, Phen inhibits cell proliferation, migration, invasion, and angiogenesis probably through AMPK-mTOR and HIF-1A-VEGF pathways. Phen may be repurposed as chemoprevention of cancer.

Repurposed drug candidates for antituberculosis therapy

Antibiotics have been a key part of clinical treatments for more than 70 years. Long-term use of antimicrobial treatments has led to the development of severe bacterial resistance, which has become increasingly serious due to antibiotic abuse, resulting in the treatment of bacterial infections becoming challenging. The repurposing of approved drugs presents a promising strategy to address current bottlenecks in the development of novel antibacterial agents. Drug repurposing is a cost-effective emerging strategy, which aims to treat resistant infectious diseases by identifying known drugs with predicted efficacy for diseases other than the target disease. This strategy has potential in the treatment of tuberculosis (TB), particularly drug-resistant TB. In recent years, a panel of drugs approved for clinical use or clinical trials, such as linezolid, vancomycin and celecoxib, have been found to have anti-TB activities. However, the utility of drug repurposing is limited by the number of candidate compounds and their low activities. The low activities of repurposed drugs have slowed the development of a drug-repurposing strategy for anti-TB drugs. The present review discusses progress in the discovery of new anti-TB agents through drug repurposing since 2014. We also discuss the challenges faced and analyze the innovative ways that are being used to overcome these difficulties. This review may provide a useful guide for researchers in the field of drug repurposing.

Evaluation of the effects of metformin administration on morphine tolerance in mice

Opioids are used in clinical practice to relieve moderate to severe pain. Prolonged use of opioids can lead to a situation of analgesic tolerance and dependence. Several mechanisms are involved in the tolerance to analgesic opioids, including desensitization or internalization of the opioid receptor, elevation of cAMP levels, microglial activation and neuroinflammation, elevation of spinal mTOR activity and change in the expression of some proteins involved in tolerance, such as nNOS. Activation of the AMPK pathway inhibits mTOR and p38 MAPK ameliorating neuroinflammation and tolerance induced by morphine. Metformin, a potent antidiabetic agent, can also activate AMPK. Morphine tolerance was induced in mice by intraperitoneal administration three times daily at 08:00, 11.00 and 16.00 h of 50, 50 and 75 mg/kg morphine, respectively during four days. On the fifth day mice received a single injection of morphine 50 mg/kg. To evaluate the effects of metformin in development of morphine-induced analgesic tolerance a group of mice received metformin (10 mg/kg) 45 min before each morphine administration. Tail flick and hot plate tests were performed to estimate analgesic latency on days 1, 3 and 5. At five days, the animals were sacrificed, the brain dissected and nitrite levels determined. Chronic metformin administration significantly increased the analgesic latency on days 3 and 5 compared to the morphine group in hot plate test and in tail flick test. Chronic and acute metformin administration significantly decreased nitric oxide level compare to morphine group. The present results revealed that metformin attenuated analgesic tolerance induced by repeated intraperitoneal injections of morphine in mice.

Metformin as Potential Therapy for High-Grade Glioma

Metformin (MET), 1,1-dimethylbiguanide hydrochloride, is a biguanide drug used as the first-line medication in the treatment of type 2 diabetes. The recent years have brought many observations showing metformin in its new role. The drug, commonly used in the therapy of diabetes, may also find application in the therapy of a vast variety of tumors. Its effectiveness has been demonstrated in colon, breast, prostate, pancreatic cancer, leukemia, melanoma, lung and endometrial carcinoma, as well as in gliomas. This is especially important in light of the poor options offered to patients in the case of high-grade gliomas, which include glioblastoma (GBM). A thorough understanding of the mechanism of action of metformin can make it possible to discover new drugs that could be used in neoplasm therapy.

Regulation of autophagy and apoptosis by Dp44mT-mediated activation of AMPK in pancreatic cancer cells

Upon activation, the 5'-adenosine monophosphate-activated protein kinase (AMPK) increases catabolism, while inhibiting anabolism. The anti-cancer agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), activates AMPK in multiple tumor cell-types (Biochim. Biophys Acta 2016;1863:2916-2933). This acts as an initial cell "rescue response" after iron-depletion mediated by Dp44mT. Considering Dp44mT-mediated AMPK activation, the role of AMPK on Dp44mT cytotoxicity was examined. Dp44mT increased the p-AMPK/AMPK ratio in multiple tumor cell-types over short (24 h) and longer (72 h) incubations. Notably, Dp44mT was more effective in inhibiting tumor cell proliferation after AMPK silencing, potentially due to the loss of AMPK-mediated metabolic plasticity that protects cells against Dp44mT cytotoxicity. The silencing of AMPK-increased cellular cholesterol and stabilized lysosomes against Dp44mT-mediated lysosomal membrane permeabilization. This was substantiated by studies demonstrating that the cholesterol-depleting agent, methyl-β-cyclodextrin (MβCD), restores Dp44mT-mediated lysosomal membrane permeabilization in AMPK silenced cells. The increased levels of cholesterol after AMPK silencing were independent of the ability of AMPK to inhibit the rate-limiting step of cholesterol synthesis via the inactivating phosphorylation of 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) at Ser872. In fact, Dp44mT did not increase phosphorylation of HMGCR at (Ser872), but decreased total HMGCR expression similarly in both the presence or absence of AMPK silencing. Dp44mT was demonstrated to increase autophagic initiation after AMPK silencing via an AMPK- and Beclin-1-independent mechanism. Further, there was increased cleaved caspase 3 and cleaved PARP after incubation of AMPK silenced cells with Dp44mT. Overall, AMPK silencing promotes Dp44mT anti-proliferative activity, suggesting a role for AMPK in rescuing its cytotoxicity by inhibiting autophagy and also apoptosis.

mTORC1 directly inhibits AMPK to promote cell proliferation under nutrient stress

Central to cellular metabolism and cell proliferation are highly conserved signalling pathways controlled by mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK)^1,2, dysregulation of which are implicated in pathogenesis of major human diseases such as cancer and type 2 diabetes. AMPK pathways leading to reduced cell proliferation are well established and, in part, act through inhibition of TOR complex-1 (TORC1) activity. Here we demonstrate reciprocal regulation, specifically that TORC1 directly down-regulates AMPK signalling by phosphorylating the evolutionarily conserved residue Ser367 in the fission yeast AMPK catalytic subunit Ssp2, and AMPK α1Ser347/α2Ser345 in the mammalian homologs, which is associated with reduced phosphorylation of activation loop Thr172. Genetic or pharmacological inhibition of TORC1 signalling led to AMPK activation in the absence of increased AMP:ATP ratios; under nutrient stress conditions this was associated with growth limitation in both yeast and human cell cultures. Our findings reveal fundamental, bi-directional regulation between two major metabolic signalling networks and uncover new opportunity for cancer treatment strategies aimed at suppressing cell proliferation in the nutrient-poor tumor microenvironment.

Diabetes and Cancer: Cancer Should Be Screened in Routine Diabetes Assessment

Cancer incidence appears to be increased in both type 1 and type 2 diabetes mellitus (DM). DM represents a risk factor for cancer, particularly hepatocellular, hepatobiliary, pancreas, breast, ovarian, endometrial, and gastrointestinal cancers. In addition, there is evidence showing that DM is associated with increased cancer mortality. Common risk factors such as age, obesity, physical inactivity and smoking may contribute to increased cancer risk in patients with DM. Although the mechanistic process that may link diabetes to cancer is not completely understood yet, biological mechanisms linking DM and cancer are hyperglycemia, hyperinsulinemia, increased bioactivity of insulin-like growth factor 1, oxidative stress, dysregulations of sex hormones, and chronic inflammation. However, cancer screening rate is significantly lower in people with DM than that in people without diabetes. Evidence from previous studies suggests that some medications used to treat DM are associated with either increased or reduced risk of cancer. However, there is no strong evidence supporting the association between the use of anti-hyperglycemic medication and specific cancer. In conclusion, all patients with DM should be undergo recommended age- and sex appropriate cancer screenings to promote primary prevention and early detection. Furthermore, cancer should be screened in routine diabetes assessment.

Relevance of Translation Initiation in Diffuse Glioma Biology and its Therapeutic Potential

Cancer cells are continually exposed to environmental stressors forcing them to adapt their protein production to survive. The translational machinery can be recruited by malignant cells to synthesize proteins required to promote their survival, even in times of high physiological and pathological stress. This phenomenon has been described in several cancers including in gliomas. Abnormal regulation of translation has encouraged the development of new therapeutics targeting the protein synthesis pathway. This approach could be meaningful for glioma given the fact that the median survival following diagnosis of the highest grade of glioma remains short despite current therapy. The identification of new targets for the development of novel therapeutics is therefore needed in order to improve this devastating overall survival rate. This review discusses current literature on translation in gliomas with a focus on the initiation step covering both the cap-dependent and cap-independent modes of initiation. The different translation initiation protagonists will be described in normal conditions and then in gliomas. In addition, their gene expression in gliomas will systematically be examined using two freely available datasets. Finally, we will discuss different pathways regulating translation initiation and current drugs targeting the translational machinery and their potential for the treatment of gliomas.

Metformin as Anti-Aging Therapy: Is It for Everyone?

Metformin is the most widely prescribed oral hypoglycemic medication for type 2 diabetes worldwide. Metformin also retards aging in model organisms and reduces the incidence of aging-related diseases such as neurodegenerative disease and cancer in humans. In spite of its widespread use, the mechanisms by which metformin exerts favorable effects on aging remain largely unknown. Further, not all individuals prescribed metformin derive the same benefit and some develop side effects. Before metformin finds its way to mainstay therapy for anti-aging, a more granular understanding of the effects of the drug in humans is needed. This review provides an overview of recent findings from metformin studies in aging and longevity and discusses the use of metformin to combat aging and aging-related diseases.

Intersections and Clinical Translations of Diabetes Mellitus with Cancer Promotion, Progression and Prognosis

The association between cancer and dysglycemia has been well documented. It is underappreciated, however, that sustained dysglycemia could potentially be a catalyst toward a pro-cancer physiologic milieu and/or increase the burden of cancer. Hyperglycemia, hyperinsulinemia and energy metabolism at large impact a cascade of growth pathways, epi/genetic modifications, and mitochondrial changes that could feasibly link to tumor processes. Oxidative stress is a recurring motif in cell dysfunction: in diabetes, oxidative stress and reactive oxygen species (ROS) feature prominently in the damage and demise of pancreatic beta cells, as well as cell damage contributing to diabetes-related complications. Oxidative stress may be one intersection at which metabolic and oncogenic processes cross paths with deleterious results in the development of precancer, cancer, and cancer progression. This would augur for tight glucose control. Regrettably, some medical societies have recently relaxed hemoglobin A1c targets. A framework for the hyperglycemic state is presented that helps account and translate the full scope of effects of dysglycemia to ultimately improve clinical best practices.

The ribonucleoside AICAr induces differentiation of myeloid leukemia by activating the ATR/Chk1 via pyrimidine depletion

Metabolic pathways play important roles in proliferation and differentiation of malignant cells. 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAr), a precursor in purine biosynthesis and a well-established activator of AMP-activated protein kinase (AMPK), induces widespread metabolic alterations and is commonly used for dissecting the role of metabolism in cancer. We have previously reported that AICAr promotes differentiation and inhibits proliferation of myeloid leukemia cells. Here, using metabolic assays, immunoblotting, flow cytometry analyses, and siRNA-mediated gene silencing in leukemia cell lines, we show that AICAr-mediated differentiation was independent of the known metabolic effects of AMPK, including glucose consumption, but instead depends on the activation of the DNA damage–associated enzyme checkpoint kinase 1 (Chk1) induced by pyrimidine depletion. LC/MS/MS metabolomics analysis revealed that AICAr increases orotate levels and decreases uridine monophosphate (UMP) levels, consistent with inhibition of UMP synthesis at a step downstream of dihydroorotate dehydrogenase (DHODH). AICAr and the DHODH inhibitor brequinar had similar effects on differentiation markers and S-phase arrest, and genetic or pharmacological Chk1 inactivation abrogated both of these effects. Our results delineate an AMPK-independent effect of AICAr on myeloid leukemia differentiation that involves perturbation of pyrimidine biosynthesis and activation of the DNA damage response network.

Effect of metformin on cell proliferation, apoptosis, migration and invasion in A172 glioma cells and its mechanisms

The purpose of the present study was to determine the effects of metformin on the inhibition of proliferation, apoptosis, invasion and migration of A172 human glioma cells in vitro and determine the underlying mechanism. The effects of metformin at different concentrations (0, 0.1, 1 and 10 mmol/l) on the inhibition of A172 cell proliferation were detected using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay. Cell apoptosis was detected by flow cytometry. Caspase‑3 activity was analyzed by spectrophotometry. The invasion and migration of cells were detected by Transwell assays. The levels of Bcl‑2‑associated X protein (Bax), B‑cell lymphoma 2 (Bcl‑2), AMP‑activated protein kinase (AMPK), phosphorylated‑(p)AMPK and mechanistic target of rapamycin (mTOR) protein expression were detected by western blot analysis, and changes in the malondialdehyde (MDA) content and activity of superoxide dismutase (SOD) were determined. Compared with the control group, metformin significantly increased the inhibition of proliferation and apoptosis, and significantly reduced the invasion and migration of A172 cells in dose‑ and time‑dependent manners (P<0.05). In addition, compared with the control group, metformin significantly enhanced the activity of caspase‑3, increased the expression of AMPK/pAMPK/Bax proteins and reduced the expression of mTOR/Bcl‑2 proteins (P<0.05). Metformin increased the MDA content and reduced the activity of SOD in a dose‑dependent manner (P<0.05). Metformin may inhibit glioma cell proliferation, migration and invasion, and promote its apoptosis; the effects may be associated with the AMPK/mTOR signaling pathway and oxidative stress.

AMPK mediates inhibition of electrolyte transport and NKCC1 activity by reactive oxygen species

Reactive oxygen species such as H₂O₂ are believed to play a prominent role in the injury and loss of transport function that affect the intestinal epithelium in inflammatory conditions such as inflammatory bowel diseases. Defects in intestinal epithelial ion transport regulation contribute to dysbiosis and inflammatory phenotypes. We previously showed that H₂O₂ inhibits Ca²⁺-dependent Cl^- secretion across intestinal epithelial cells (IECs) via a phosphatidylinositol 3-kinase (PI3K)- and extracellular signal-regulated kinase (ERK)-dependent mechanism that occurs, at least in part, through inhibition of the basolateral Na⁺-K⁺-2Cl^- cotransporter NKCC1. NKCC1 governs Cl^- entry into crypt IECs and thus plays a critical role in maintaining the driving force for Cl^- secretion. Electrolyte transport consumes large amounts of cellular energy, and direct pharmacological activation of the cellular energy sensor AMP-activated protein kinase (AMPK) has been shown to inhibit a number of ion transport proteins. Here, we show that H₂O₂ activates AMPK in human IEC lines and ex vivo human colon. Moreover, we demonstrate that the inhibitory effect of H₂O₂ on Ca²⁺-dependent Cl^- secretion and NKCC1 activity is AMPK-dependent. This inhibitory effect is associated with a physical interaction between AMPK and NKCC1, as well as increased phosphorylation (Thr^212,217) of NKCC1, without causing NKCC1 internalization. These data identify a key role for AMPK-NKCC1 interaction as a point of convergence for suppression of colonic epithelial ion transport by inflammatory reactive oxygen species.NEW & NOTEWORTHY H₂O₂ inhibition of intestinal epithelial Ca²⁺-dependent Cl^- secretion involves recruitment of AMP-activated protein kinase (AMPK) downstream of ERK and phosphatidylinositol 3-kinase signaling pathways, physical interaction of AMPK with the Na⁺-K⁺-2Cl^- cotransporter NKCC1, and AMPK-dependent suppression of NKCC1-mediated electrolyte influx without causing NKCC1 internalization. It is intriguing that, in human intestinal epithelial cell lines and human colon, H₂O₂ activation of AMPK increased phosphorylation of NKCC1 residues required for promoting, not inhibiting, NKCC1 activity. These data identify an elevated complexity of AMPK regulation of NKCC1 in the setting of an inflammatory stimulus.

The Role of AMPK/mTOR Modulators in the Therapy of Acute Myeloid Leukemia

Differentiation therapy of acute promyelocytic leukemia with all-trans retinoic acid represents the most successful pharmacological therapy of acute myeloid leukemia (AML). Numerous studies demonstrate that drugs that inhibit mechanistic target of rapamycin (mTOR) and activate AMP-kinase (AMPK) have beneficial effects in promoting differentiation and blocking proliferation of AML. Most of these drugs are already in use for other purposes; rapalogs as immunosuppressants, biguanides as oral antidiabetics, and 5-amino-4-imidazolecarboxamide ribonucleoside (AICAr, acadesine) as an exercise mimetic. Although most of these pharmacological modulators have been widely used for decades, their mechanism of action is only partially understood. In this review, we summarize the role of AMPK and mTOR in hematological malignancies and discuss the possible role of pharmacological modulators in proliferation and differentiation of leukemia cells.