Metformin in cancer

A simple, quantitative method for spectroscopic detection of metformin using gold nanoclusters

We synthesized bovine serum albumin (BSA)-stabilized gold nanoclusters (BSA-GNCs) and confirmed their ultra-small size using HRTEM (High-resolution Transmission Electron Microscope) and DLS (Dynamic Light Scattering). The fluorescence intensity of BSA-GNCs is "turned off" in the presence of Cu(II) metal ions. The resulting Cu(II)-mediated BSA-GNCs were utilized to detect metformin, a drug used to control diabetes. Metformin binds to and displaces Cu(II) ions from the BSA on the surface of the nanoclusters, which turns on the fluorescence of the nanoclusters. The interactions between the protein-stabilized nanoclusters were investigated in the absence and presence of Cu(II) using circular dichroism (CD) and Fourier-transform infrared spectroscopy (FTIR). Cu(II)-quenched BSA-GNCs had an extremely high sensitivity to detect metformin, with a low limit of detection (LOD) of 0.068 μM and a dynamic range of limit of quantification (LOQ = 10/3 LOD) of 0.22 to 11 μM. The ability of this novel "turn-on" nanosensor to detect metformin in human serum and urine samples was confirmed: the percentage recovery in fluorescence for spiked analyte ranged from 96.00-98.50% and 92.60-96.62% in human serum and urine samples, respectively. Thus, BSA-GNCs provide a valid, sensitive, specific fluorometric methodology for the detection of metformin in biomedical applications.

Time course and dose effect of metformin on weight in patients with different disease states

OBJECTIVES

The present study was to quantitate and compare the efficacy of metformin on weight in different disease states using model-based meta-analysis (MBMA).

METHODS

Randomized controlled trials (RCT) of metformin effects on weight in different disease states were collected by searching the public databases. The change rate of weight from baseline was selected as the efficacy indicator.

RESULTS

A total 21 RCTs containing 1885 patients including patients with type 2 diabetes mellitus, patients with antipsychotic induced weight gain, patients with obesity, were included into the present study. After deducting placebo effect, the maximal effect (E_max) of metformin on weight in patients with type 2 diabetes mellitus, patients with antipsychotic induced weight gain, patients with obesity were -6.86%, -8.82%, and -4.14%, respectively. The treatment duration to reach half of the maximal effect (ET₅₀) were 107, 45.5, and 15.1 weeks, respectively. Within the metformin dose range from 21 RCTs, no significant dose-response relationship was observed. However, the time-course relationship is obvious for efficacy of metformin on weight.

CONCLUSIONS

The present study firstly provided quantitative information for metformin effects on weight in different disease states, including patients with type 2 diabetes mellitus, patients with antipsychotic induced weight gain, patients with obesity.

Metformin Increases the Chemosensitivity of Pancreatic Cancer Cells to Gemcitabine by Reversing EMT Through Regulation DNA Methylation of miR-663

Background

Pancreatic cancer is a devastating malignancy with poor prognosis. Metformin, a classic anti-diabetes drug, seems to improve survival of pancreatic cancer patients in some studies.

Methods

Cell counting kit-8 assay was used to detect the BxPC-3 and MIAPaCa-2 cell viability after treatment with gemcitabine only or with different concentrations of metformin. The methylation state and expression level of miR-663 were detected by methylation analysis and RT-PCR. Dual-luciferase reporter gene analysis, Western blot and RT-PCR were used to confirm the target of miR-663. Moreover, xenograft experiment was also performed to validate the role of metformin in chemosensitivity in vivo.

Results

We found that metformin increased the chemosensitivity of pancreatic cancer cells to gemcitabine, and epithelial-mesenchymal transition (EMT) progress caused by gemcitabine was suppressed by metformin. We further explored the possible molecular mechanisms and it was demonstrated that CpG islands of miR-663 were hypomethylated and relative expression level of miR-663 was up-regulated after treatment of metformin. miR-663, an important cancer suppressor miRNA, was confirmed to increase the chemosensitivity of pancreatic cancer cells by reversing EMT directly targeted TGF-β1. Moreover, we identified that metformin increased the chemosensitivity through up-regulating expression of miR-663.

Conclusion

We demonstrated that metformin increased the chemosensitivity of pancreatic cancer cells to gemcitabine by reversing EMT through regulation DNA methylation of miR-663.

Role of metformin in various pathologies: state-of-the-art microcapsules for improving its pharmacokinetics

Metformin was originally derived from a botanical ancestry and became the most prescribed, first-line therapy for Type 2 diabetes in most countries. In the last century, metformin was discovered twice for its antiglycemic properties in addition to its antimalarial and anti-influenza effects. Metformin exhibits flip-flop pharmacokinetics with limited oral bioavailability. This review outlines metformin pharmacokinetics, pharmacodynamics and recent advances in polymeric particulate delivery systems as a potential tool to target metformin delivery to specific tissues/organs. This interesting biguanide is being rediscovered this century for multiple clinical indications as anticancer, anti-aging, anti-inflammatory, anti-Alzheimer's and much more. Microparticulate delivery systems of metformin may improve its oral bioavailability and optimize the therapeutic goals expected.

The Synergistic Effect of an ATP-Competitive Inhibitor of mTOR and Metformin on Pancreatic Tumor Growth

BACKGROUND

The mechanistic target of rapamycin complex 1 (mTORC1) is a nutrient-sensing pathway and a key regulator of amino acid and glucose metabolism. Dysregulation of the mTOR pathways is implicated in the pathogenesis of metabolic syndrome, obesity, type 2 diabetes, and pancreatic cancer.

OBJECTIVES

We investigated the impact of inhibition of mTORC1/mTORC2 and synergism with metformin on pancreatic tumor growth and metabolomics.

METHODS

Cell lines derived from pancreatic tumors of the KPC (KrasG12D/+; p53R172H/+; Pdx1-Cre) transgenic mice model were implanted into the pancreas of C57BL/6 albino mice (n = 10/group). Two weeks later, the mice were injected intraperitoneally with daily doses of 1) Torin 2 (mTORC1/mTORC2 inhibitor) at a high concentration (TH), 2) Torin 2 at a low concentration (TL), 3) metformin at a low concentration (ML), 4) a combination of Torin 2 and metformin at low concentrations (TLML), or 5) DMSO vehicle (control) for 12 d. Tissues and blood samples were collected for targeted xenometabolomics analysis, drug concentration, and cell signaling.

RESULTS

Metabolomic analysis of the control and treated plasma samples showed differential metabolite profiles. Phenylalanine was significantly elevated in the TLML group compared with the control (+426%, P = 0.0004), whereas uracil was significantly lower (-38%, P = 0.009). The combination treatment reduced tumor growth in the orthotopic mouse model. TLML significantly decreased pancreatic tumor volume (498 ± 104 mm3; 37%; P < 0.0004) compared with control (1326 ± 134 mm3; 100%), ML (853 ± 67 mm3; 64%), TL (745 ± 167 mm3; 54%), and TH (665 ± 182 mm3; 50%) (ANOVA and post hoc tests). TLML significantly decreased tumor weights (0.66 ± 0.08 g; 52%) compared with the control (1.28 ± 0.19 g; 100%) (P < 0.002).

CONCLUSIONS

The combination of mTOR dual inhibition by Torin 2 and metformin is associated with an altered metabolomic profile and a significant reduction in pancreatic tumor burden compared with single-agent therapy, and it is better tolerated.

Effects of metformin on adipose-derived stromal cell (ADSC) - Breast cancer cell lines interaction

AIMS

Metformin is a clinical drug administered to patients to treat type 2 diabetes mellitus that was found to be associated with a lower risk of occurrence of cancer and cancer-related death. The present study investigated the effects of metformin on human adipose-derived stromal cells (ADSC) - breast cancer cell line interactions.

MAIN METHODS

ADSCs grown from lipoaspirates were tested for growth-stimulating and migration-controlling activity on breast cancer cell lines after pretreatment with metformin. Furthermore, secreted proteins of ADSCs, phosphorylation of intracellular proteins and the effect of metformin on adipocytic differentiation of ADSCs were assayed.

KEY FINDINGS

Compared to breast cancer cell lines (4.0 ± 3.5% reduction of proliferation), 2 mM metformin significantly inhibited the proliferation of ADSC lines (19.2 ± 8.4% reduction of proliferation). This effect on ADSCs seems to be mediated by altered phosphorylation of GSK-3, CREB and PRAS40. Furthermore, treatment with metformin abolished the induction of differentiation of three ADSC lines to adipocytes. 1 and 2 mM metformin significantly impaired the migration of breast cancer cell lines MDA-MB-231 and MDA-MB-436 in scratch assays.

SIGNIFICANCE

Metformin showed low direct inhibitory effects on breast cancer cell lines at physiological concentrations but exerted a significant retardation of the growth and the adipocytic differentiation of ADSCs. Thus, the anticancer activity of metformin in breast cancer at physiological drug concentrations seems to be mediated by an indirect mechanism that lowers the supportive activity of ADSCs.

Therapeutic effect of metformin in the treatment of endometrial cancer

The present review aims at reviewing the role of metformin in the treatment of endometrial cancer (EC). According to the literature, excessive estrogen levels and insulin resistance are established risk factors of EC. As a traditional insulin sensitizer and newly discovered anticancer agent, metformin directly and indirectly inhibits the development of EC. The direct mechanisms of metformin include inhibition of the LKB1-AMP-activated protein kinase-mTOR, PI3K-Akt and insulin-like growth factor 1-related signaling pathways, which reduces the proliferation and promotes the apoptosis of EC cells. In the indirect mechanism, metformin increases the insulin sensitivity of body tissues and decreases circulating insulin levels. Decreased levels of insulin increase the blood levels of sex hormone binding globulin, which leads to reductions in circulating estrogen and androgens. The aforementioned findings suggest that metformin serves an important role in the treatment of EC. Increased understanding of the mechanism of metformin in EC may provide novel insights into the treatment of this malignancy.

Neoadjuvant metformin added to conventional chemotherapy synergizes anti-proliferative effects in ovarian cancer

Background

Ovarian cancer is the leading cause of cancer-related death among women. Complete cytoreductive surgery followed by platinum-taxene chemotherapy has been the gold standard for a long time. Various compounds have been assessed in an attempt to combine them with conventional chemotherapy to improve survival rates or even overcome chemoresistance. Many studies have shown that an antidiabetic drug, metformin, has cytotoxic activity in different cancer models. However, the synergism of metformin as a neoadjuvant formula plus chemotherapy in clinical trials and basic studies remains unclear for ovarian cancer.

Methods

We applied two clinical databases to survey metformin use and ovarian cancer survival rate. The Cancer Genome Atlas dataset, an L1000 microarray with Gene Set Enrichment Analysis (GSEA) analysis, Western blot analysis and an animal model were used to study the activity of the AKT/mTOR pathway in response to the synergistic effects of neoadjuvant metformin combined with chemotherapy.

Results

We found that ovarian cancer patients treated with metformin had significantly longer overall survival than patients treated without metformin. The protein profile induced by low- concentration metformin in ovarian cancer predominantly involved the AKT/mTOR pathway. In combination with chemotherapy, the neoadjuvant metformin protocol showed beneficial synergistic effects in vitro and in vivo.

Conclusions

This study shows that neoadjuvant metformin at clinically relevant dosages is efficacious in treating ovarian cancer, and the results can be used to guide clinical trials.

Molecular mechanism for metformin to enhance pro-apoptotic effect of sorafenib in HepG2 cells

BACKGROUND

Prolonging the survival time of patients with advanced liver cancer is a major clinical challenge. Sorafenib (Sor) is the only targeted drug for the treatment of advanced liver cancer, but drug resistance has become a problem.

AIM

To explore the effect and molecular mechanism of metformin (Met) in enhancing pro-apoptotic effect of Sor in HepG2 cells.

METHODS

MTT assay was used to evaluate the anti-proliferation effects of Met and Sor, alone or in combination. Flow cytometry was employed to analyze cell cycle and cell apoptosis. The expression of Caspase-3, Bax, AMPK, P53, and mTORC1 was evaluated by Western blot.

RESULTS

MTT assay showed that both Met and Sor decreased HepG2 cells viability, and Met combined with Sor had a synergistic inhibitory effect. The relative cell viability rates of the control group, Met group, Sor group, and combination group were 100%, 79.96% ± 4.41%, 85.33% ± 1.00%, and 68.60% ± 4.02%, respectively. Flow cytometry showed that both Met and Sor induced HepG2 cell apoptosis, and Met combined with Sor had a synergistic effect. The apoptosis rates of the control group, Met group, Sor group, and combination group were 4.47% ± 1.93%, 13.73% ± 1.18%, 9.50% ± 0.20%, and 29.03% ± 0.35%, respectively. Western blot analysis showed that both Met and Sor increased the expression of Caspase-3, Bax, P53, and AMPK and decreased the expression of mTORC1.

CONCLUSION

Met can enhance the pro-apoptotic effect of Sor in HepG2 cells.

Drug Repositioning of the α1-Adrenergic Receptor Antagonist Naftopidil: A Potential New Anti-Cancer Drug?

Failure of conventional treatments is often observed in cancer management and this requires the development of alternative therapeutic strategies. However, new drug development is known to be a high-failure process because of the possibility of a lower efficacy than expected for the drug or appearance of non-manageable side effects. Another way to find alternative therapeutic drugs consists in identifying new applications for drugs already approved for a particular disease: a concept named "drug repurposing". In this context, several studies demonstrated the potential anti-tumour activity exerted by α1-adrenergic receptor antagonists and notably renewed interest for naftopidil as an anti-cancer drug. Naftopidil is used for benign prostatic hyperplasia management in Japan and a retrospective study brought out a reduced incidence of prostate cancer in patients that had been prescribed this drug. Further studies showed that naftopidil exerted anti-proliferative and cytotoxic effects on prostate cancer as well as several other cancer types in vitro, as well as ex vivo and in vivo. Moreover, naftopidil was demonstrated to modulate the expression of Bcl-2 family pro-apoptotic members which could be used to sensitise cancer cells to targeting therapies and to overcome resistance of cancer cells to apoptosis. For most of these anti-cancer effects, the molecular pathway is either not fully deciphered or shown to involve α1-adrenergic receptor-independent pathway, suggesting off target transduction signals. In order to improve its efficacy, naftopidil analogues were designed and shown to be effective in several studies. Thereby, naftopidil appears to display anti-cancer properties on different cancer types and could be considered as a candidate for drug repurposing although its anti-cancerous activities need to be studied more deeply in prospective randomized clinical trials.

Lipids and cancer: Emerging roles in pathogenesis, diagnosis and therapeutic intervention

With the advent of effective tools to study lipids, including mass spectrometry-based lipidomics, lipids are emerging as central players in cancer biology. Lipids function as essential building blocks for membranes, serve as fuel to drive energy-demanding processes and play a key role as signaling molecules and as regulators of numerous cellular functions. Not unexpectedly, cancer cells, as well as other cell types in the tumor microenvironment, exploit various ways to acquire lipids and extensively rewire their metabolism as part of a plastic and context-dependent metabolic reprogramming that is driven by both oncogenic and environmental cues. The resulting changes in the fate and composition of lipids help cancer cells to thrive in a changing microenvironment by supporting key oncogenic functions and cancer hallmarks, including cellular energetics, promoting feedforward oncogenic signaling, resisting oxidative and other stresses, regulating intercellular communication and immune responses. Supported by the close connection between altered lipid metabolism and the pathogenic process, specific lipid profiles are emerging as unique disease biomarkers, with diagnostic, prognostic and predictive potential. Multiple preclinical studies illustrate the translational promise of exploiting lipid metabolism in cancer, and critically, have shown context dependent actionable vulnerabilities that can be rationally targeted, particularly in combinatorial approaches. Moreover, lipids themselves can be used as membrane disrupting agents or as key components of nanocarriers of various therapeutics. With a number of preclinical compounds and strategies that are approaching clinical trials, we are at the doorstep of exploiting a hitherto underappreciated hallmark of cancer and promising target in the oncologist's strategy to combat cancer.

Redox Imbalances in Ageing and Metabolic Alterations: Implications in Cancer and Cardiac Diseases. An Overview from the Working Group of Cardiotoxicity and Cardioprotection of the Italian Society of Cardiology (SIC)

Metabolic syndrome (MetS) is a well established risk factor for cardiovascular (CV) diseases. In addition, several studies indicate that MetS correlates with the increased risk of cancer in adults. The mechanisms linking MetS and cancer are not fully understood. Several risk factors involved in MetS are also cancer risk factors, such as the consumption of high calorie-food or high fat intake, low fibre intake, and sedentary lifestyle. Other common aspects of both cancer and MetS are oxidative stress and inflammation. In addition, some anticancer treatments can induce cardiotoxicity, including, for instance, left ventricular (LV) dysfunction and heart failure (HF), endothelial dysfunction and hypertension. In this review, we analyse several aspects of MetS, cancer and cardiotoxicity from anticancer drugs. In particular, we focus on oxidative stress in ageing, cancer and CV diseases, and we analyse the connections among CV risk factors, cancer and cardiotoxicity from anticancer drugs.

The effect of metformin on esophageal cancer risk in patients with type 2 diabetes mellitus: a systematic review and meta‑analysis

OBJECTIVE

Recently, numerous studies have yielded inconsistent results regarding the effect of metformin on esophageal cancer risk in type 2 diabetes mellitus patients. The purpose of this study is to systematically assess this effect using meta-analysis.

METHODS

We searched clinical studies on metformin and esophageal cancer risk in PubMed, Embase, and the Cochrane Library. After literature screening, a series of meta-analyses were conducted using RevMan 5.3 software. The pooled hazard ratio (HR) and the corresponding 95% confidence interval (CI) were used as the effect size.

RESULTS

Five eligible studies (four cohort studies and one case-control study) were included for our meta-analysis using a random-effect model. The analysis showed that metformin could not reduce esophageal cancer risk in type 2 diabetes mellitus patients (HR 0.88, 95% CI 0.60-1.28, P > 0.05). Subgroup analyses by geographic location showed that metformin significantly reduced esophageal cancer risk in Asian patients with type 2 diabetes mellitus (HR 0.59, 95% CI 0.39-0.91, P = 0.02), without heterogeneity between studies (P = 0.80 and I² = 0%).

CONCLUSIONS

Overall, our systematic review and meta-analysis demonstrate that metformin does not reduce esophageal cancer risk in type 2 diabetes mellitus patients. However, a significant reduction in esophageal cancer risk in Asian populations remains to be clarified.

Metformin's Modulatory Effects on miRNAs Function in Cancer Stem Cells-A Systematic Review

Cancer stem cells (CSCs) have been reported in various hematopoietic and solid tumors, therefore, are considered to promote cancer progression, metastasis, recurrence and drug resistance. However, regulation of CSCs at the molecular level is not fully understood. microRNAs (miRNAs) have been identified as key regulators of CSCs by modulating their major functions: self-renewal capacity, invasion, migration and proliferation. Various studies suggest that metformin, an anti-diabetic drug, has an anti-tumor activity but its precise mechanism of action has not been understood. The present article was written in accordance to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We systematically reviewed evidence for metformin’s ability to eradicate CSCs through modulating the expression of miRNAs in various solid tumors. PubMed and MEDLINE were searched from January 1990 to January 2020 for in vitro studies. Two authors independently selected and reviewed articles according to predefined eligibility criteria and assessed risk of bias of included studies. Four papers met the inclusion criteria and presented low risk bias. All of the included studies reported a suppression of CSCs’ major function after metformin dosage. Moreover, it was showed that metformin anti-tumor mechanism of action is based on regulation of miRNAs expression. Metformin inhibited cell survival, clonogenicity, wound-healing capacity, sphere formation and promotes chemosensitivity of tumor cells. Due to the small number of publications, aforementioned evidences are limited but may be consider as background for clinical studies.

Noncoding SNPs associated with increased GDF15 levels located in a metformin-activated enhancer region upstream of GDF15

Aim: GDF15 levels are a biomarker for metformin use. We performed the functional annotation of noncoding genome-wide association study (GWAS) SNPs for GDF15 levels and the Genotype-Tissue Expression (GTEx)-expression quantitative trait loci (eQTLs) for GDF15 expression within metformin-activated enhancers around GDF15. Materials & methods: These enhancers were identified using chromatin immunoprecipitation followed by sequencing data for active (H3K27ac) and silenced (H3K27me3) histone marks on human hepatocytes treated with metformin, Encyclopedia of DNA Elements data and cis-regulatory elements assignment tools. Results: The GWAS lead SNP rs888663, the SNP rs62122429 associated with GDF15 levels in the Outcome Reduction with Initial Glargine Intervention trial, and the GTEx-expression quantitative trait locus rs4808791 for GDF15 expression in whole blood are located in a metformin-activated enhancer upstream of GDF15 and tightly linked in Europeans and East Asians. Conclusion: Noncoding variation within a metformin-activated enhancer may increase GDF15 expression and help to predict GDF15 levels.

Metformin, an AMPK Activator, Inhibits Activation of FLSs but Promotes HAPLN1 Secretion

AMP-activated protein kinase (AMPK) is essential for maintaining energy balance and has a crucial role in various inflammatory pathways. In this study, AMPK levels positively correlated with many inflammatory indexes in rheumatoid arthritis (RA) patients, especially in the affected synovium. In RA sera, a positive correlation between phosphorylated (p-)AMPK-α1 levels and DAS28 (disease activity score 28) activity (r = 0.270, p < 0.0001) was found. Similarly, a positive correlation was observed between AMPK-α1 and tumor necrosis factor α (TNF-α) levels (r = 0.460, p = 0.0002). Differentially expressed genes between osteoarthritis (OA) and RA synovium from NCBI GEO profiles and our RNA sequencing data suggested activation of metabolic pathways specific to RA-fibroblast-like synoviocytes (FLSs). AMPK-α1 was highly expressed in the synovium of RA but not OA patients. An AMPK activator, metformin, inhibited FLS proliferation at higher but not lower concentrations, whereas the inhibitor dorsomorphin promoted the proliferation of RA-FLSs. Interestingly, both metformin and dorsomorphin inhibited the migration of RA-FLSs. After metformin treatment, expression of interleukin 6 (IL-6), TNF-α, and IL-1β were significantly downregulated in RA-FLSs; however, increased expression of p-AMPK-α1, protein kinase A (PKA)-α1, and HAPLN1 (hyaluronan and proteoglycan link protein 1) was observed. Increased levels of HAPLN1 in RA-FLSs by an AMPK activator could potentially be beneficial in protecting the joints. Hence, our results demonstrate the potential of an AMPK activator as a therapeutic for RA.

Methotrexate elicits pro-respiratory and anti-growth effects by promoting AMPK signaling

One-carbon metabolism fuels the high demand of cancer cells for nucleotides and other building blocks needed for increased proliferation. Although inhibitors of this pathway are widely used to treat many cancers, their global impact on anabolic and catabolic processes remains unclear. Using a combination of real-time bioenergetics assays and metabolomics approaches, we investigated the global effects of methotrexate on cellular metabolism. We show that methotrexate treatment increases the intracellular concentration of the metabolite AICAR, resulting in AMPK activation. Methotrexate-induced AMPK activation leads to decreased one-carbon metabolism gene expression and cellular proliferation as well as increased global bioenergetic capacity. The anti-proliferative and pro-respiratory effects of methotrexate are AMPK-dependent, as cells with reduced AMPK activity are less affected by methotrexate treatment. Conversely, the combination of methotrexate with the AMPK activator, phenformin, potentiates its anti-proliferative activity in cancer cells. These data highlight a reciprocal effect of methotrexate on anabolic and catabolic processes and implicate AMPK activation as a metabolic determinant of methotrexate response.

Diabetes: an Overview for Clinical Oncologists

Diabetes and cancer are common conditions highly prevalent in the general population. The co-existence of diabetes and cancer in a patient is therefore not unexpected. Diabetes increases the risk of mortality from cancer and morbidity from the treatment of cancer. Furthermore, many cancer chemotherapeutic regimens increase glucose levels, especially those involving glucocorticoids. Many clinical oncologists will deal with patients with diabetes in their clinical work, and some working knowledge of diabetes diagnosis and management is helpful when managing such patients. This overview aims to summarise the clinical diagnosis and management of diabetes, review the potential links between diabetes and cancer, and provide some practical guidance on the management of hyperglycaemia in patients undergoing cancer therapy.

Metformin revert insulin-induced oxaliplatin resistance by activating mitochondrial apoptosis pathway in human colon cancer HCT116 cells

BACKGROUND

Several studies have suggested that drug resistance in colon cancer patients with diabetes may be associated with long-term insulin administration, which in turn decreases the survival rate. Metformin is a commonly used drug to treat diabetes but has been recently demonstrated to have a potential therapeutic effect on colon cancer. This study aimed to elucidate the underlying mechanism by which metformin reverts insulin-induced oxaliplatin resistance in human colon cancer HCT116 cells.

METHODS

Two colon cancer cell lines (HCT116 and LoVo) were used to verify whether the expression of insulin receptor substrate 1 (IRS-1) could impact the half maximal inhibitory concentration (IC50) of oxaliplatin after chronic insulin treatment. The IC50 of oxaliplatin in both cell lines was measured to identify metformin sensitization to oxaliplatin. The adenosine monophosphate-activated protein kinase (AMPK) inhibitor, namely AMPK small interfering RNA, was used to block AMPK activation to identify critical proteins in the AMPK/Erk signaling pathway. Bcl-2 is a vital antiapoptotic protein involved in the mitochondrial apoptosis pathway. Finally, immunofluorescence and electron microscopy were performed to investigate how metformin affects the ultrastructural integrity of mitochondria.

RESULTS

The IC50 of oxaliplatin in HCT116 cells was noticeably increased. After the cells were treated with metformin, oxaliplatin resistance was reversed. According to the results of the western blotting assay of vital proteins involved in the classical apoptosis pathway, cleaved caspase-9 was noticeably upregulated, suggesting that the mitochondrial apoptosis pathway was activated. These results were verified by imaging of mitochondria using electron microscopy. The AMPK/Erk signaling pathway experiments revealed that the upregulation of Bcl-2 induced by insulin through Erk phosphorylation was inhibited by metformin and that such inhibition could be mitigated by the inhibition of AMPK.

CONCLUSIONS

Insulin-induced oxaliplatin resistance was reversed by metformin-mediated AMPK activation. Accordingly, metformin is likely to sensitize patients with diabetes to chemotherapeutic drugs used to treat colon cancer.

Metabolic Heterogeneity of Cancer Cells: An Interplay between HIF-1, GLUTs, and AMPK

It has been long recognized that cancer cells reprogram their metabolism under hypoxia conditions due to a shift from oxidative phosphorylation (OXPHOS) to glycolysis in order to meet elevated requirements in energy and nutrients for proliferation, migration, and survival. However, data accumulated over recent years has increasingly provided evidence that cancer cells can revert from glycolysis to OXPHOS and maintain both reprogrammed and oxidative metabolism, even in the same tumor. This phenomenon, denoted as cancer cell metabolic plasticity or hybrid metabolism, depends on a tumor micro-environment that is highly heterogeneous and influenced by an intensity of vasculature and blood flow, oxygen concentration, and nutrient and energy supply, and requires regulatory interplay between multiple oncogenes, transcription factors, growth factors, and reactive oxygen species (ROS), among others. Hypoxia-inducible factor-1 (HIF-1) and AMP-activated protein kinase (AMPK) represent key modulators of a switch between reprogrammed and oxidative metabolism. The present review focuses on cross-talks between HIF-1, glucose transporters (GLUTs), and AMPK with other regulatory proteins including oncogenes such as c-Myc, p53, and KRAS; growth factor-initiated protein kinase B (PKB)/Akt, phosphatydyl-3-kinase (PI3K), and mTOR signaling pathways; and tumor suppressors such as liver kinase B1 (LKB1) and TSC1 in controlling cancer cell metabolism. The multiple switches between metabolic pathways can underlie chemo-resistance to conventional anti-cancer therapy and should be taken into account in choosing molecular targets to discover novel anti-cancer drugs.

The Relationship Between Prostate Cancer and Metformin Consumption: A Systematic Review and Meta-analysis Study

INTRODUCTION

Prostate cancer is the most common malignant cancer in men worldwide and after lung cancer, it is the second leading cause of cancer mortality in men. The purpose of this study was to investigate the relationship between prostate cancer and metformin consumption in men.

METHODS

The current study is a systematic and meta-analysis review based on the PRISMA statement. To access the studies of domestic and foreign databases, Iran Medex, SID, Magiran, Iran Doc, Medlib, ProQuest, Science Direct, PubMed, Scopus, Web of Science and the Google Scholar search engine were searched during the 2009- 2018 period for related keywords. In order to evaluate the heterogeneity of the studies, Q test and I2 indicator were used. The data were analyzed using the STATA 15.1 software.

RESULTS

In 11 studies with a sample size of 877058, the odds ratio of metformin consumption for reducing prostate cancer was estimated at 0.89 (95%CI: 0.67-1.17). Meta-regression also showed there was no significant relationship between the odds ratio and the publication year of the study. However, there was a significant relationship between the odds ratio and the number of research samples.

CONCLUSION

Using metformin in men reduces the risk of prostate cancer but it is not statistically significant.

NF-κB and mitochondria cross paths in cancer: mitochondrial metabolism and beyond

NF-κB plays a pivotal role in oncogenesis. This transcription factor is best known for promoting cancer cell survival and tumour-driving inflammation. However, several lines of evidence support a crucial role for NF-κB in governing energy homeostasis and mediating cancer metabolic reprogramming. Mitochondria are central players in many metabolic processes altered in cancer. Beyond their bioenergetic activity, several facets of mitochondria biology, including mitochondrial dynamics and oxidative stress, promote and sustain malignant transformation. Recent reports revealed an intimate connection between NF-κB pathway and the oncogenic mitochondrial functions. NF-κB can impact mitochondrial respiration and mitochondrial dynamics, and, reciprocally, mitochondria can sense stress signals and convert them into cell biological responses leading to NF-κB activation. In this review we discuss their emerging reciprocal regulation and the significance of this interplay for anticancer therapy.

Occurrence, toxic effects and removal of metformin in the aquatic environments in the world: Recent trends and perspectives

Metformin (MET) is the most common drug used to treat type 2 diabetes, but also it is used as an anticancer agent and as a treatment for polycystic ovary syndrome. This drug is not metabolized in the human body, and may enter into the environment through different pathways. In wastewater treatments plants (WWTPs), this contaminant is mainly transformed to guanylurea (GUA). However, three further transformation products (TPs): (a) 2,4- diamino-1,3,5-triazine, 4-DAT; (b) 2-amino-4-methylamino-1,3,5-triazine, 2,4-AMT; and (c) methylbiguanide, MBG; have also been associated with its metabolism. MET, GUA and MBG have been found in WWTPs influents, effluents and surface waters. Furthermore, MET and GUA bioaccumulate in edible plants species, fish and mussels potentially contaminating the human food web. MET is also a potential endocrine disruptor in fish. Phytoremediation, adsorption and biodegradation have shown a high removal efficiency of MET, in laboratory. Nonetheless, these removal methods had less efficiency when tried in WWTPs. Therefore, MET and its TPs are a threat to the human being as well as to our environment. This review comprehensively discuss the (1) pathways of MET to the environment and its life-cycle, (2) occurrence of MET and its transformation products (3) removal, (4) toxic effects and (5) future trends and perspectives of possible methods of elimination in water in order to provide potential options for managing these contaminants.

Metformin-repressed miR-381-YAP-snail axis activity disrupts NSCLC growth and metastasis

BACKGROUND

Recent evidence indicates that metformin inhibits mammalian cancer growth and metastasis through the regulation of microRNAs. Metformin regulates miR-381 stability, which plays a vital role in tumor progression. Moreover, increased YAP expression and activity induce non-small cell lung cancer (NSCLC) tumor growth and metastasis. However, the molecular mechanism underpinning how metformin-induced upregulation of miR-381 directly targets YAP or its interactions with the epithelial-mesenchymal transition (EMT) marker protein Snail in NSCLC is still unknown.

METHODS

Levels of RNA and protein were analyzed using qPCR, western blotting and immunofluorescence staining. Cellular proliferation was detected using a CCK8 assay. Cell migration and invasion were analyzed using wound healing and transwell assays. Promoter activity and transcription were investigated using the luciferase reporter assay. Chromatin immunoprecipitation was used to detect the binding of YAP to the promoter of Snail. The interaction between miR-381 and the 3'UTR of YAP mRNA was analyzed using the MS2 expression system and co-immunoprecipitation with biotin.

RESULTS

We observed that miR-381 expression is negatively correlated with YAP expression and plays an opposite role to YAP in the regulation of cellular proliferation, invasion, migration, and EMT of NSCLC cells. The miR-381 function as a tumor suppressor was significantly downregulated in lung cancer tissue specimens and cell lines, which decreased the expression of its direct target YAP. In addition, metformin decreased cell growth, migration, invasion, and EMT via up-regulation of miR-381. Moreover, YAP, which functions as a co-transcription factor, enhanced NSCLC progression and metastasis by upregulation of Snail. Snail knockdown downregulated the mesenchymal marker vimentin and upregulated the epithelial marker E-cadherin in lung cancer cells. Furthermore, miR-381, YAP, and Snail constitute the miR-381-YAP-Snail signal axis, which is repressed by metformin, and enhances cancer cell invasiveness by directly regulating EMT.

CONCLUSIONS

Metformin-induced repression of miR-381-YAP-Snail axis activity disrupts NSCLC growth and metastasis. Thus, we believe that the miR-381-YAP-Snail signal axis may be a suitable diagnostic marker and a potential therapeutic target for lung cancer.

The Association between Metformin and Survival of Head and Neck Cancer: A Systematic Review and Meta-Analysis of 7 Retrospective Cohort Studies

BACKGROUND

Metformin has been associated with improved survival outcomes in various malignancies. However, observational studies in head and neck cancer are inconsistent.

OBJECTIVE

The study aimed to summarize and quantify the relationship between metformin use and the survival of head and neck cancer.

METHODS

A meta-analysis based on cohort studies was systematically conducted (published up to Jan 18, 2020), identified from PubMed, Embase, Web of Science, Cochrane Library, Google Scholar, and Scopus databases. Summary hazard ratios (HR) and 95% confidence intervals (CI) were calculated using a random-effects model.

RESULTS

Seven retrospective cohort studies including 3,285 head and neck cancer patients were included. The association between the use of metformin and cancer survival was not statistically significant: summarized HR of 0.89 (95% CI 0.66-1.18, P=0.413, I2=64.0%) for overall survival, summarized HR of 0.65 (95% CI 0.31-1.35, P=0.246, I2=60.3%) for disease-free survival, and summarized HR of 0.69 (95% CI 0.40-1.20, P=0.191, I2=73.1%) for disease-specific survival.

CONCLUSION

In this meta-analysis of 7 retrospective cohort studies, there was not a statistically significant association between the use of metformin and better survival for head and neck cancer. However, the analysis may have been underpowered. More studies of prospective designs with larger sample sizes are needed to investigate the effect of metformin on the survival of head and neck cancer.

Metformin reverses the drug resistance of cisplatin in irradiated CNE-1 human nasopharyngeal carcinoma cells through PECAM-1 mediated MRPs down-regulation

Objective: To explore a way to reverse the drug resistance for irradiated CNE-1 human nasopharyngeal carcinoma cells and try to develop a new high efficacy with low toxicity therapeutic approach. Methods: 300 Gy irradiated the CNE-1 human nasopharyngeal carcinoma cells, and then treated with single-agent cisplatin or metformin, or combination of both drugs. MTT assay and FCM were applied to detect cell viability and apoptosis. Western blot and RT-PCR were used to characterize the protein and mRNA expression after various drug administrations. Results: The results presented single-agent metformin was capable of arresting the tumor growth and inducing apoptosis in irradiated CNE-1 cells and also demonstrated a synergy effect with cisplatin. Furthermore, metformin down-regulates the PECAM-1 expression, which could regulate Multi-drug Resistance-associate Proteins (MRPs) expression leading to cisplatin resistance of irradiated CNE-1 cells. A pan-MRP inhibitor, probenecid, can resecure cisplatin resistance leading by radiation. Conclusions: Metformin, due to its independent effects on PECAM-1, had a unique anti-proliferative effect on irradiated CNE-1 cells. It would be a new therapeutic option to conquer cisplatin resistance for advanced NPC patients after radiotherapy.

The Role of Adipokines in Breast Cancer: Current Evidence and Perspectives

PURPOSE

The current review shows evidence for the role of adipokines in breast cancer (BC) pathogenesis summarizing the mechanisms underlying the association between adipokines and breast malignancy. Special emphasis is given also on intriguing insights into the relationship between obesity and BC as well as on the role of novel adipokines in BC development.

RECENT FINDINGS

Recent evidence has underscored the role of the triad of obesity, insulin resistance, and adipokines in postmenopausal BC. Adipokines exert independent and joint effects on activation of major intracellular signal networks implicated in BC cell proliferation, growth, survival, invasion, and metastasis, particularly in the context of obesity, considered a systemic endocrine dysfunction characterized by chronic inflammation. To date, more than 10 adipokines have been linked to BC, and this catalog is continuously increasing. The majority of circulating adipokines, such as leptin, resistin, visfatin, apelin, lipocalin 2, osteopontin, and oncostatin M, is elevated in BC, while some adipokines such as adiponectin and irisin (adipo-myokine) are generally decreased in BC and considered protective against breast carcinogenesis. Further evidence from basic and translational research is necessary to delineate the ontological role of adipokines and their interplay in BC pathogenesis. More large-scale clinical and longitudinal studies are awaited to assess their clinical utility in BC prognosis and follow-up. Finally, novel more effective and safer adipokine-centered therapeutic strategies could pave the way for targeted oncotherapy.

Influence of pre-operative oral carbohydrate loading vs. standard fasting on tumor proliferation and clinical outcome in breast cancer patients ─ a randomized trial

Background

Conflicting results have been reported on the influence of carbohydrates in breast cancer.

Objective

To determine the influence of pre-operative per-oral carbohydrate load on proliferation in breast tumors.

Design

Randomized controlled trial.

Setting

University hospital with primary and secondary care functions in South-West Norway.

Patients

Sixty-one patients with operable breast cancer from a population-based cohort.

Intervention

Per-oral carbohydrate load (preOp™) 18 and 2–4 h before surgery (n = 26) or standard pre-operative fasting with free consumption of tap water (n = 35).

Measurements

The primary outcome was post-operative tumor proliferation measured by the mitotic activity index (MAI). The secondary outcomes were changes in the levels of serum insulin, insulin-c-peptide, glucose, IGF-1, and IGFBP3; patients’ well-being, and clinical outcome over a median follow-up of 88 months (range 33–97 months).

Results

In the estrogen receptor (ER) positive subgroup (n = 50), high proliferation (MAI ≥ 10) occurred more often in the carbohydrate group (CH) than in the fasting group (p = 0.038). The CH group was more frequently progesterone receptor (PR) negative (p = 0.014). The CH group had a significant increase in insulin (+ 24.31 mIE/L, 95% CI 15.34 mIE/L to 33.27 mIE/L) and insulin c-peptide (+ 1.39 nM, 95% CI 1.03 nM to 1.77 nM), but reduced IGFBP3 levels (− 0.26 nM; 95% CI − 0.46 nM to − 0.051 nM) compared to the fasting group. CH-intervention ER-positive patients had poorer relapse-free survival (73%) than the fasting group (100%; p = 0.012; HR = 9.3, 95% CI, 1.1 to 77.7). In the ER-positive patients, only tumor size (p = 0.021; HR = 6.07, 95% CI 1.31 to 28.03) and the CH/fasting subgrouping (p = 0.040; HR = 9.30, 95% CI 1.11 to 77.82) had independent prognostic value. The adverse clinical outcome of carbohydrate loading occurred only in T2 patients with relapse-free survival of 100% in the fasting group vs. 33% in the CH group (p = 0.015; HR = inf). The CH group reported less pain on days 5 and 6 than the control group (p <  0.001) but otherwise exhibited no factors related to well-being.

Limitation

Only applicable to T2 tumors in patients with ER-positive breast cancer.

Conclusions

Pre-operative carbohydrate load increases proliferation and PR-negativity in ER-positive patients and worsens clinical outcome in ER-positive T2 patients.

Trial registration

CliniTrials.gov; NCT03886389. Retrospectively registered March 22, 2019.

Cetylpyridinium chloride is a potent AMP-activated kinase (AMPK) inducer and has therapeutic potential in cancer

AMP-activated protein kinase (AMPK) is a eukaryotic energy sensor and protector from mitochondrial/energetic stress that is also a therapeutic target for cancer and metabolic disease. Metformin is an AMPK inducer that has been used in cancer therapeutic trials. Through screening we isolated cetylpyridinium chloride (CPC), a drug known to dose-dependently inhibit mitochondrial complex 1, as a potent and dose-dependent AMPK stimulator. Mitochondrial biogenesis and bioenergetics changes have also been implicated in glioblastoma, which is the most aggressive form of brain tumors. Cetylpyridinium chloride has been administered in humans as a safe drug-disinfectant for several decades, and we report here that under in vitro conditions, cetylpyridinium chloride kills glioblastoma cells in a dose dependent manner at a higher efficacy compared to current standard of care drug, temozolomide.

The Impact of Comorbidities on the Pharmacological Management of Type 2 Diabetes Mellitus

Diabetes mellitus affects over 20% of people aged > 65 years. With the population of older people living with diabetes growing, the condition may be only one of a number of significant comorbidities that increases the complexity of their care, reduces functional status and inhibits their ability to self-care. Coexisting comorbidities may compete for the attention of the patient and their healthcare team, and therapies to manage comorbidities may adversely affect a person's diabetes. The presence of renal or liver disease reduces the types of antihyperglycemic therapies available for use. As a result, insulin and sulfonylurea-based therapies may have to be used, but with caution. There may be a growing role for sodium-glucose co-transporter 2 (SGLT-2) inhibitors in diabetic renal disease and for glucagon-like peptide (GLP)-1 therapy in renal and liver disease (nonalcoholic steatohepatitis). Cancer treatments pose considerable challenges in glucose therapy, especially the use of cyclical chemotherapy or glucocorticoids, and cyclical antihyperglycemic regimens may be required. Clinical trials of glucose lowering show reductions in microvascular and, to a lesser extent, cardiovascular complications of diabetes, but these benefits take many years to accrue, and evidence specifically in older people is lacking. Guidelines recognize that clinicians managing patients with type 2 diabetes mellitus need to be mindful of comorbidity, particularly the risks of hypoglycemia, and ensure that patient-centered therapeutic management of diabetes is offered. Targets for glucose control need to be carefully considered in the context of comorbidity, life expectancy, quality of life, and patient wishes and expectations. This review discusses the role of chronic kidney disease, chronic liver disease, cancer, severe mental illness, ischemic heart disease, and frailty as comorbidities in the therapeutic management of hyperglycemia in patients with type 2 diabetes mellitus.

Anticancer activity of metformin: a systematic review of the literature

Background

The anticancer activity of metformin has been confirmed against several cancer types in vitro and in vivo. However, the underlying mechanisms of metformin in the treatment of cancer are not fully understood. This systematic review aims to discuss the possible anticancer mechanism of action of metformin.

Method

A search through different databases was conducted, including Medline and EMBASE.

Results

A total of 96 articles were identified of which 56 were removed for duplication and 24 were excluded after reviewing the title and abstract. A total of 12 research articles were included that describe different antiproliferative mechanisms that may contribute to the antineoplastic effects of metformin.

Conclusion

This analysis discussed the potential anticancer activity of metformin and highlighted the importance of AMPK as a potential target for anticancer therapy.

Challenges in the management of people with diabetes and cancer

Although micro- and macrovascular complications of diabetes are the most important cause of mortality and morbidity in people with diabetes, it is increasingly recognized that diabetes increases the risk of developing cancer. Diabetes and cancer commonly co-exist, and outcomes in people with both conditions are poorer than in those who have cancer but no diabetes. There is no randomized trial evidence that treating hyperglycaemia in people with cancer improves outcomes, but therapeutic nihilism should be avoided, and a personalized approach to managing hyperglycaemia in people with cancer is needed. This review aims to outline the link between diabetes therapies and cancer, and discuss the reasons why glucose should be actively managed people with both. In addition, we discuss clinical challenges in the management of hyperglycaemia in cancer, specifically in relation to glucocorticoids, enteral feeding and end-of-life care.

Metformin reduces risk of benign nodular goiter in patients with type 2 diabetes mellitus

Background Whether metformin might affect the risk of benign nodular goiter in patients with type 2 diabetes mellitus has not been investigated. Methods Patients with new-onset type 2 diabetes mellitus during 1999-2005 were enrolled from Taiwan's National Health Insurance database. Analyses were conducted in a propensity score matched-pairs of 20,048 ever users and 20,048 never users of metformin. The patients were followed until December 31, 2011, for the incidence of benign nodular goiter. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using the propensity score. Results Among the never users and ever users of metformin, 392 and 221 cases were diagnosed of benign nodular goiter during follow-up, with incidence of 457.88 and 242.45 per 100,000 person-years, respectively. The overall hazard ratio for ever versus never users was 0.527 (95% confidence interval: 0.447-0.621). When cumulative duration of metformin therapy was divided into tertiles, the hazard ratios for the first (<25.3 months), second (25.3-57.3 months) and third (>57.3 months) tertiles were 0.815 (0.643-1.034), 0.648 (0.517-0.812) and 0.255 (0.187-0.348), respectively. Sensitivity analyses estimating the overall hazard ratios for patients enrolled in each specific year from 1999 to 2005 consistently showed a lower risk of benign nodular goiter among users of metformin. Conclusion Metformin use is associated with a lower risk of benign nodular goiter in patients with type 2 diabetes mellitus.

Impact of metformin use on the outcomes of newly diagnosed diffuse large B-cell lymphoma and follicular lymphoma

The diabetes mellitus (DM) drug metformin targets mechanistic/mammalian target of rapamycin and inhibits lymphoma growth in vitro. We investigated whether metformin affected outcomes of newly diagnosed diffuse large B-cell (DLBCL, n = 869) and follicular lymphoma (FL, n = 895) patients enrolled in the Mayo component of the Molecular Epidemiology Resource cohort study between 2002 and 2015. Hazard ratios (HR) and 95% confidence intervals (CIs) adjusted for age, sex, body mass index, prognostic index and treatment were used to estimate the association of metformin exposure (No DM/No metformin; DM/No metformin; DM/Metformin) with event-free (EFS), lymphoma-specific (LSS) and overall (OS) survival. Compared to No DM/No metformin DLBCL patients, there was no association of DM/Metformin (n = 48; HR = 1·05, 95% CI 0·59-1·89) or DM/No metformin(n = 54; HR = 1·41, 95% CI 0·88-2·26) with EFS; results were similar for LSS and OS. Compared to No DM/No metformin FL patients, there was no association of DM/Metformin (n = 37; HR = 1·16, 95% CI 0·71-1·89) or DM/No metformin (n = 19; HR = 1·16, 95% CI 0·66-2·04) with EFS; results were similar for LSS. However, DM/Metformin was associated with inferior OS (HR = 2·17; 95% CI 1·19-3·95) compared to No DM/No metformin. In conclusion, we found no evidence that metformin use was associated with improved outcomes in newly diagnosed DLBCL and FL.

Wastewater analysis reveals spatial pattern in consumption of anti-diabetes drug metformin in China

Metformin has been widely used as an oral drug for the treatment of diabetes mellitus. However, its consumption can be influenced by many economic and social factors. In this study, we investigated the spatial consumption pattern of metformin in China through wastewater-based epidemiology (WBE) approach. Influent wastewater samples were collected from 21 wastewater treatment plants (WWTPs) in 19 cities of the northeast China. A method using solid-phase extraction combined with N-Methyl-bis (trifluoroacetamide) derivatization for GC-MS detection was applied for metformin analysis. In 21 days, metformin showed high stability in wastewater at 24 °C and -20 °C. The mean concentrations of metformin in all WWTPs ranged from 2.42 μg L^-1 to 53.6 μg L^-1. The consumption of metformin was 0.66-15.6 mg d^-1 capita^-1 with the mean value of 5.54 ± 4.28 mg d^-1 capita^-1. The prevalence of metformin ranged from 0.09% to 2.10% with an average of 0.74%. Both the consumption and prevalence of metformin displays significant spatial variations in northeast China. A statistical correlation analysis indicated that the consumption of metformin increases with the decrease of per capita disposable income of urban residents. To further predict the use of metformin in China, we developed a regress model and depicted a consumption map. The annual consumption of urban residents in Chinese provinces range from 1085-63,828 kg yr^-1 with mean value of 25,347 kg yr^-1, which would provide a certain reference value for public health care and diabetes control.

Glioblastoma Stem-Like Cells, Metabolic Strategy to Kill a Challenging Target

Over the years, substantial evidence has definitively confirmed the existence of cancer stem-like cells within tumors such as Glioblastoma (GBM). The importance of Glioblastoma stem-like cells (GSCs) in tumor progression and relapse clearly highlights that cancer eradication requires killing of GSCs that are intrinsically resistant to conventional therapies as well as eradication of the non-GSCs cells since GSCs emergence relies on a dynamic process. The past decade of research highlights that metabolism is a significant player in tumor progression and actually might orchestrate it. The growing interest in cancer metabolism reprogrammation can lead to innovative approaches exploiting metabolic vulnerabilities of cancer cells. These approaches are challenging since they require overcoming the compensatory and adaptive responses of GSCs. In this review, we will summarize the current knowledge on GSCs with a particular focus on their metabolic complexity. We will also discuss potential approaches targeting GSCs metabolism to potentially improve clinical care.

Obesity and cancer risk: Emerging biological mechanisms and perspectives

Continuously rising trends in obesity-related malignancies render this disease spectrum a public health priority. Worldwide, the burden of cancer attributable to obesity, expressed as population attributable fraction, is 11.9% in men and 13.1% in women. There is convincing evidence that excess body weight is associated with an increased risk for cancer of at least 13 anatomic sites, including endometrial, esophageal, renal and pancreatic adenocarcinomas; hepatocellular carcinoma; gastric cardia cancer; meningioma; multiple myeloma; colorectal, postmenopausal breast, ovarian, gallbladder and thyroid cancers. We first synopsize current epidemiologic evidence; the obesity paradox in cancer risk and mortality; the role of weight gain and weight loss in the modulation of cancer risk; reliable somatometric indicators for obesity and cancer research; and gender differences in obesity related cancers. We critically summarize emerging biological mechanisms linking obesity to cancer encompassing insulin resistance and abnormalities of the IGF-I system and signaling; sex hormones biosynthesis and pathway; subclinical chronic low-grade inflammation and oxidative stress; alterations in adipokine pathophysiology; factors deriving from ectopic fat deposition; microenvironment and cellular perturbations including vascular perturbations, epithelial-mesenchymal transition, endoplasmic reticulum stress and migrating adipose progenitor cells; disruption of circadian rhythms; dietary nutrients; factors with potential significance such as the altered intestinal microbiome; and mechanic factors in obesity and cancer. Future perspectives regarding prevention, diagnosis and therapeutics are discussed. The aim of this review is to investigate how the interplay of these main potential mechanisms and risk factors, exerts their effects on target tissues provoking them to acquire a cancerous phenotype.

Metformin triggers the intrinsic apoptotic response in human AGS gastric adenocarcinoma cells by activating AMPK and suppressing mTOR/AKT signaling

Metformin is commonly used to treat patients with type 2 diabetes and is associated with a decreased risk of cancer. Previous studies have demonstrated that metformin can act alone or in synergy with certain anticancer agents to achieve anti-neoplastic effects on various types of tumors via adenosine monophosphate-activated protein kinase (AMPK) signaling. However, the role of metformin in AMPK-mediated apoptosis of human gastric cancer cells is poorly understood. In the current study, metformin exhibited a potent anti-proliferative effect and induced apoptotic characteristics in human AGS gastric adenocarcinoma cells, as demonstrated by MTT assay, morphological observation method, terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase-3/7 assay kits. Western blot analysis demonstrated that treatment with metformin increased the phosphorylation of AMPK, and decreased the phosphorylation of AKT, mTOR and p70S6k. Compound C (an AMPK inhibitor) suppressed AMPK phosphorylation and significantly abrogated the effects of metformin on AGS cell viability. Metformin also reduced the phosphorylation of mitogen-activated protein kinases (ERK, JNK and p38). Additionally, metformin significantly increased the cellular ROS level and included loss of mitochondrial membrane potential (ΔΨm). Metformin altered apoptosis-associated signaling to downregulate the BAD phosphorylation and Bcl-2, pro-caspase-9, pro-caspase-3 and pro-caspase-7 expression, and to upregulate BAD, cytochrome c, and Apaf-1 proteins levels in AGS cells. Furthermore, z-VAD-fmk (a pan-caspase inhibitor) was used to assess mitochondria-mediated caspase-dependent apoptosis in metformin-treated AGS cells. The findings demonstrated that metformin induced AMPK-mediated apoptosis, making it appealing for development as a novel anticancer drug for the treating gastric cancer.

High Glucose Represses the Anti-Proliferative and Pro-Apoptotic Effect of Metformin in Triple Negative Breast Cancer Cells

Metformin, the most widely prescribed anti-diabetic drug, is shown to possess anti-cancer potential in treatment of cancers, including breast cancer; decreases breast cancer risk; and improves overall survival. However, reports suggest that higher glucose concentrations may negatively impact the anti-cancer efficacy of metformin. Therefore, we examined the anti-cancer potential of metformin in triple-negative breast cancer cells (TNBCs) exposed to different glucose (25 mM, 5.5 mM and zero glucose/glucose-starved) conditions. Our data indicates that a high glucose (25 mM) concentration (mimicking diabetes) significantly abrogated the effect of metformin on cell proliferation, cell death and cell cycle arrest in addition to loss of efficacy in inhibition of the mTOR pathway, a key metabolic pathway in TNBC cells. The mTOR pathway is activated in TNBCs compared to other subtypes of breast cancer, regulates the synthesis of proteins that are critical for the growth and survival of cancer cells and its activation is correlated to poor outcomes among TNBC patients, while also contributing to metastatic progression and development of resistance to chemotherapy/radiotherapy. Our studies were performed in two different types of TNBCs, MDA-MB-231 cells (mesenchymal stem cell-like (MSL)) and MDA-MB-468 (basal like-1 (BL-1)). Interestingly, lower concentrations of metformin (50, 100, 250, and 500 μM) significantly increased cell proliferation in 25 mM glucose exposed MDA-MB-231 cells, an effect which was not observed in MDA-MB-468 cells, indicating that the effective concentration of metformin when used as anti-cancer drug in TNBCs may have to be determined based on cell type and blood glucose concentration. Our data indicates that metformin treatment was most effective under zero glucose/glucose-starved conditions in MDA-MB-468 with a significant increase in the apoptotic population (62.3 ± 1.5%; p-value < 0.01). Under 5.5 mM glucose conditions in both MDA-MB-231 and MDA-MB-468 cells our data showed reduced viability of 73.56 ± 2.53%; p-value < 0.05 and 70.49 ± 1.68%; p-value < 0.001, respectively, along with a significant increase in apoptotic populations of both cell types. Furthermore, metformin (2 mM) inhibited the mTOR pathway and its downstream components under zero glucose/glucose-starved conditions indicating that using metformin in combination with agents that inhibit the glycolytic pathway should be more beneficial for the treatment of triple-negative breast cancers in diabetic individuals.

Role of Mitochondria in the Mechanism(s) of Action of Metformin

Metformin is a drug from the biguanide family that is used for decades as the first-line therapeutic choice for the treatment of type 2 diabetes. Despite its worldwide democratization, owing to its clinical efficacy, high safety profile and cheap cost, the exact mechanism(s) of action of this anti-hyperglycemic molecule with pleiotropic properties still remains to be fully elucidated. The concept that metformin would exert some of its actions though modulation of the mitochondrial bioenergetics was initially forged in the 50s but undeniably revived at the beginning of the twenty-first century when it was shown to induce a weak but specific inhibition of the mitochondrial respiratory-chain complex 1. Furthermore, metformin has been reported to reduce generation of reactive oxygen species at the complex 1 and to prevent mitochondrial-mediated apoptosis, suggesting that it can protect against oxidative stress-induced cell death. Nevertheless, despite some recent progress and the demonstration of its key role in the inhibition of hepatic gluconeogenesis, the exact nature of the mitochondrial interaction between the drug and the complex 1 is still poorly characterized. Recent studies reported that metformin may also have anti-neoplastic properties by inhibiting cancer cell growth and proliferation, at least partly through its mitochondrial action. As such, many trials are currently conducted for exploring the repositioning of metformin as a potential drug for cancer therapy. In this mini-review, we discuss both historical and more recent findings on the central role played by the interaction between metformin and the mitochondria in its cellular mechanism of action.

Classic and Novel Adipocytokines at the Intersection of Obesity and Cancer: Diagnostic and Therapeutic Strategies

PURPOSE OF REVIEW

In this review, we investigate the role of classic and novel adipocytokines in cancer pathogenesis synopsizing the mechanisms underlying the association between adipocytokines and malignancy. Special emphasis is given on novel adipocytokines as new evidence is emerging regarding their entanglement in neoplastic development.

RECENT FINDINGS

Recent data have emphasized the role of the triad of overweight/obesity, insulin resistance and adipocytokines in cancer. In the setting of obesity, classic and novel adipocytokines present independent and joint effects on activation of major intracellular signaling pathways implicated in cell proliferation, expansion, survival, adhesion, invasion, and metastasis. Until now, more than 15 adipocytokines have been associated with cancer, and this list continues to expand. While the plethora of circulating pro-inflammatory adipocytokines, such as leptin, resistin, extracellular nicotinamide phosphoribosyl transferase, and chemerin are elevated in malignancies, some adipocytokines such as adiponectin and omentin-1 are generally decreased in cancers and are considered protective against carcinogenesis. Elucidating the intertwining of inflammation, cellular bioenergetics, and adiposopathy is significant for the development of preventive, diagnostic, and therapeutic strategies against cancer. Novel more effective and safe adipocytokine-centered therapeutic interventions may pave the way for targeted oncotherapy.

Targeting mitochondria in cancer: current concepts and immunotherapy approaches

An essential advantage during eukaryotic cell evolution was the acquisition of a network of mitochondria as a source of energy for cell metabolism and contrary to conventional wisdom, functional mitochondria are essential for the cancer cell. Multiple aspects of mitochondrial biology beyond bioenergetics support transformation including mitochondrial biogenesis, fission and fusion dynamics, cell death susceptibility, oxidative stress regulation, metabolism, and signaling. In cancer, the metabolism of cells is reprogrammed for energy generation from oxidative phosphorylation to aerobic glycolysis and impacts cancer mitochondrial function. Furthermore cancer cells can also modulate energy metabolism within the cancer microenvironment including immune cells and induce "metabolic anergy" of antitumor immune response. Classical approaches targeting the mitochondria of cancer cells usually aim at inducing changing energy metabolism or directly affecting functions of mitochondrial antiapoptotic proteins but most of such approaches miss the required specificity of action and carry important side effects. Several types of cancers harbor somatic mitochondrial DNA mutations and specific immune response to mutated mitochondrial proteins has been observed. An attractive alternative way to target the mitochondria in cancer cells is the induction of an adaptive immune response against mutated mitochondrial proteins. Here, we review the cancer cell-intrinsic and cell-extrinsic mechanisms through which mitochondria influence all steps of oncogenesis, with a focus on the therapeutic potential of targeting mitochondrial DNA mutations or Tumor Associated Mitochondria Antigens using the immune system.

Metformin synergistically enhances the antitumor activity of the third-generation EGFR-TKI CO-1686 in lung cancer cells through suppressing NF-κB signaling

PURPOSE

Third-generation irreversible epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), rociletinib (CO-1686), is great efficacy against EGFR-mutated patients bearing the T790M resistance mutation. However, acquired resistance may emerge. There is a need to characterize acquired resistance mechanism(s) and to devise ways to overcome CO-1686 resistance.

EXPERIMENTAL DESIGN

MTT assay, ki67 incorporation assay, transwell assay and TUNEL assay were employed to analyze the effects of metformin to reverse CO-1686 resistance in vitro. The NF-κB activity was measured by the antibody of p50, p65, p-IKBɑ, and p-IKKɑ/β. Western blotting was used to analyze the proteins in cells.

RESULTS

We have established CO-1686-resistant cell lines of PC-9GRCOR and H1975COR from two parental cell lines of PC-9GR and H1975 by long-term exposure to increasing doses of CO-1686. Compared with the parental cells, PC-9GRCOR cells and H1975COR cells showed 90-folds and 20-folds higher resistance to CO-1686, respectively. Critically, we showed that the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling molecular proteins subunits of p50, p65 and its inhibitor proteins of IKBɑ, IKKɑ/β in phosphorylation levels in resistant cells were higher than parental cells. Accordingly, inhibition of NF-κB activity used TPCA-1 effective in decreasing viability and inducing apoptosis of resistant cells. Moreover, metformin overcame the acquired resistance to CO-1686 by reducing cell proliferation and invasion. Metformin combined with CO-1686 synergistically inhibited the p-IKBɑ, p-IKKɑ/β, p50, and p65.

CONCLUSIONS

NF-κB signaling activation induced acquired resistance to CO-1686. Metformin sensitized resistant cells to CO-1686 via inhibiting NF-κB signaling.

Metformin Clinical Trial in HPV+ and HPV- Head and Neck Squamous Cell Carcinoma: Impact on Cancer Cell Apoptosis and Immune Infiltrate

Background: Metformin, an oral anti-hyperglycemic drug which inhibits mitochondrial complex I and oxidative phosphorylation has been reported to correlate with improved outcomes in head and neck squamous cell carcinoma (HNSCC) and other cancers. This effect is postulated to occur through disruption of tumor-driven metabolic and immune dysregulation in the tumor microenvironment (TME). We report new findings on the impact of metformin on the tumor and immune elements of the TME from a clinical trial of metformin in HNSCC.

Methods: Human papilloma virus—(HPV–) tobacco+ mucosal HNSCC samples (n = 12) were compared to HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples (n = 17) from patients enrolled in a clinical trial. Apoptosis in tumor samples pre- and post-treatment with metformin was compared by deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Metastatic lymph nodes with extra-capsular extension (ECE) in metformin-treated patients (n = 7) were compared to archival lymph node samples with ECE (n = 11) for differences in immune markers quantified by digital image analysis using co-localization and nuclear algorithms (PD-L1, FoxP3, CD163, CD8).

Results: HPV–, tobacco + HNSCC (mean Δ 13.7/high power field) specimens had a significantly higher increase in apoptosis compared to HPV+ OPSCC specimens (mean Δ 5.7/high power field) (p < 0.001). Analysis of the stroma at the invasive front in ECE nodal specimens from both HPV—HNSCC and HPV+ OPSCC metformin treated specimens showed increased CD8+ effector T cell infiltrate (mean 22.8%) compared to archival specimens (mean 10.7%) (p = 0.006). Similarly, metformin treated specimens showed an increased FoxP3+ regulatory T cell infiltrate (mean 9%) compared to non-treated archival specimens (mean 5%) (p = 0.019).

Conclusions: This study presents novel data demonstrating that metformin differentially impacts HNSCC subtypes with greater apoptosis in HPV—HNSCC compared to HPV+ OPSCC. Moreover, we present the first in vivo human evidence that metformin may also trigger increased CD8+ Teff and FoxP3+ Tregs in the TME, suggesting an immunomodulatory effect in HNSCC. Further research is necessary to assess the effect of metformin on the TME of HNSCC.

Antidiabetic Biguanides Radiosensitize Hypoxic Colorectal Cancer Cells Through a Decrease in Oxygen Consumption

Background and Purpose: The anti-diabetic biguanide drugs metformin and phenformin exhibit antitumor activity in various models. However, their radiomodulatory effect under hypoxic conditions, particularly for phenformin, is largely unknown. This study therefore examines whether metformin and phenformin as mitochondrial complex I blockades could overcome hypoxic radioresistance through inhibition of oxygen consumption.

Materials and Methods: A panel of colorectal cancer cells (HCT116, DLD-1, HT29, SW480, and CT26) was exposed to metformin or phenformin for 16 h at indicated concentrations. Afterward, cell viability was measured by MTT and colony formation assays. Apoptosis and reactive oxygen species (ROS) were detected by flow cytometry. Phosphorylation of AMP-activated protein kinase (AMPK) was examined by western blot. Mitochondria complexes activity and oxygen consumption rate (OCR) were measured by seahorse analyzer. The radiosensitivity of tumor cells was assessed by colony formation assay under aerobic and hypoxic conditions. The in vitro findings were further validated in colorectal CT26 tumor model.

Results: Metformin and phenformin inhibited mitochondrial complex I activity and subsequently reduced OCR in a dose-dependent manner starting at 3 mM and 30 μM, respectively. As a result, the hypoxic radioresistance of tumor cells was counteracted by metformin and phenformin with an enhancement ratio about 2 at 9 mM and 100 μM, respectively. Regarding intrinsic radioresistance, both of them did not exhibit any effect although there was an increase of phosphorylation of AMPK and ROS production. In tumor-bearing mice, metformin or phenformin alone did not show any anti-tumor effect. While in combination with radiation, both of them substantially delayed tumor growth and enhanced radioresponse, respectively, by 1.3 and 1.5-fold.

Conclusion: Our results demonstrate that metformin and phenformin overcome hypoxic radioresistance through inhibition of mitochondrial respiration, and provide a rationale to explore metformin and phenformin as hypoxic radiosensitizers.

Challenges and perspectives in the treatment of diabetes associated breast cancer

Type 2 diabetes mellitus is one of the most common chronic disease worldwide and affects all cross-sections of the society including children, women, youth and adults. Scientific evidence has linked diabetes to higher incidence, accelerated progression and increased aggressiveness of different cancers. Among the different forms of cancer, research has reinforced a link between diabetes and the risk of breast cancer. Some studies have specifically linked diabetes to the highly aggressive, triple negative breast cancers (TNBCs) which do not respond to conventional hormonal/HER2 targeted interventions, have chances of early recurrence, metastasize, tend to be more invasive in nature and develop drug resistance. Commonly used anti-diabetic drugs, such as metformin, have recently gained importance in the treatment of breast cancer due to their proposed anti-cancer properties. Here we discuss the link between diabetes and breast cancer, the metabolic disturbances in diabetes that support the development of breast cancer, the challenges involved and future perspective and directions. We link the three main metabolic disturbances (dyslipidemia, hyperinsulinemia and hyperglycemia) that occur in diabetes to potential aberrant molecular pathways that may lead to the development of an oncogenic phenotype of the breast tissue, thereby leading to acceleration of cell growth, proliferation, migration, inflammation, angiogenesis, EMT and metastasis and inhibition of apoptosis in breast cancer cells. Furthermore, managing diabetes and treating cancer using a combination of anti-diabetic and classical anti-cancer drugs should prove to be more efficient in the treatment diabetes associated cancers.