Effect of the anti-diabetic drug metformin in hepatocellular carcinoma in vitro and in vivo

Restricting Colorectal Cancer Cell Metabolism with Metformin: An Integrated Transcriptomics Study

BACKGROUND

Metformin is a first-line therapy for type 2 diabetes as it disrupts cellular metabolism. Despite the association between metformin and lower cancer incidence, the anti-tumour activity of the drug in colorectal cancer (CRC) is incompletely understood. This study identifies underlying molecular mechanisms by which metformin slows colorectal cancer cell proliferation by investigating metformin-associated microRNA (miRNA) and target gene pairs implicated in signalling pathways.

METHODS

The present study analysed changes in miRNAs and the coding transcriptome in CRC cells treated with a sublethal dose of metformin, followed by the contextual validation of potential miRNA-target gene pairs.

RESULTS

Analyses of small RNA and transcriptome sequencing data revealed 104 miRNAs and 1221 mRNAs to be differentially expressed in CRC cells treated with metformin for 72 h. Interaction networks between differentially expressed miRNAs and putative target mRNAs were identified. Differentially expressed genes were mainly implicated in metabolism and signalling processes, such as the PI3K-Akt and MAPK/ERK pathways. Further validation of potential miRNA-target mRNA pairs revealed that metformin induced miR-2110 and miR-132-3p to target PIK3R3 and, consequently, regulate CRC cell proliferation, cell cycle progression and the PI3K-Akt signalling pathway. Metformin also induced miR-222-3p and miR-589-3p, which directly target STMN1 to inhibit CRC cell proliferation and cell cycle progression.

CONCLUSIONS

This study identified novel changes in the coding transcriptome and small non-coding RNAs associated with metformin treatment of CRC cells. Integration of these datasets highlighted underlying mechanisms by which metformin impedes cell proliferation in CRC. Importantly, it identified the post-transcriptional regulation of specific genes that impact both metabolism and cell proliferation.

Metformin and the Liver: Unlocking the Full Therapeutic Potential

Metformin is a highly effective medication for managing type 2 diabetes mellitus. Recent studies have shown that it has significant therapeutic benefits in various organ systems, particularly the liver. Although the effects of metformin on metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis are still being debated, it has positive effects on cirrhosis and anti-tumoral properties, which can help prevent the development of hepatocellular carcinoma. Furthermore, it has been proven to improve insulin resistance and dyslipidaemia, commonly associated with liver diseases. While more studies are needed to fully determine the safety and effectiveness of metformin use in liver diseases, the results are highly promising. Indeed, metformin has a terrific potential for extending its full therapeutic properties beyond its traditional use in managing diabetes.

Mechanistic Insights about Sorafenib-, Valproic Acid- and Metformin-Induced Cell Death in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is among the main causes of death by cancer worldwide, representing about 80-90% of all liver cancers. Treatments available for advanced HCC include atezolizumab, bevacizumab, sorafenib, among others. Atezolizumab and bevacizumab are immunological options recently incorporated into first-line treatments, along with sorafenib, for which great treatment achievements have been reached. However, sorafenib resistance is developed in most patients, and therapeutical combinations targeting cancer hallmark mechanisms and intracellular signaling have been proposed. In this review, we compiled evidence of the mechanisms of cell death caused by sorafenib administered alone or in combination with valproic acid and metformin and discussed them from a molecular perspective.

Metformin: update on mechanisms of action on liver diseases

Substantial attention has been paid to the various effects of metformin on liver diseases; the liver is the targeted organ where metformin exerts its antihyperglycemic properties. In non-alcoholic fatty liver disease (NAFLD), studies have shown that metformin affects the ATP/AMP ratio to activate AMPK, subsequently governing lipid metabolism. The latest research showed that low-dose metformin targets the lysosomal AMPK pathway to decrease hepatic triglyceride levels through the PEN2-ATP6AP1 axis in an AMP-independent manner. Metformin regulates caspase-3, eukaryotic initiation factor-2a (eIF2a), and insulin receptor substrate-1 (IRS-1) in palmitate-exposed HepG2 cells, alleviating endoplasmic reticulum (ER) stress. Recent observations highlighted the critical association with intestinal flora, as confirmed by the finding that metformin decreased the relative abundance of Bacteroides fragilis while increasing Akkermansia muciniphila and Bifidobacterium bifidum. The suppression of intestinal farnesoid X receptor (FXR) and the elevation of short-chain fatty acids resulted in the upregulation of tight junction protein and the alleviation of hepatic inflammation induced by lipopolysaccharide (LPS). Additionally, metformin delayed the progression of cirrhosis by regulating the activation and proliferation of hepatic stellate cells (HSCs) via the TGF-β1/Smad3 and succinate-GPR91 pathways. In hepatocellular carcinoma (HCC), metformin impeded the cell cycle and enhanced the curative effect of antitumor medications. Moreover, metformin protects against chemical-induced and drug-induced liver injury (DILI) against hepatotoxic drugs. These findings suggest that metformin may have pharmacological efficacy against liver diseases.

Metformin and cancer hallmarks: shedding new lights on therapeutic repurposing

Metformin is a well-known anti-diabetic drug that has been repurposed for several emerging applications, including as an anti-cancer agent. It boasts the distinct advantages of an excellent safety and tolerability profile and high cost-effectiveness at less than one US dollar per daily dose. Epidemiological evidence reveals that metformin reduces the risk of cancer and decreases cancer-related mortality in patients with diabetes; however, the exact mechanisms are not well understood. Energy metabolism may be central to the mechanism of action. Based on altering whole-body energy metabolism or cellular state, metformin's modes of action can be divided into two broad, non-mutually exclusive categories: "direct effects", which induce a direct effect on cancer cells, independent of blood glucose and insulin levels, and "indirect effects" that arise from systemic metabolic changes depending on blood glucose and insulin levels. In this review, we summarize an updated account of the current knowledge on metformin antitumor action, elaborate on the underlying mechanisms in terms of the hallmarks of cancer, and propose potential applications for repurposing metformin for cancer therapeutics.

The Emerging Role of Metformin in the Treatment of Hepatocellular Carcinoma: Is There Any Value in Repurposing Metformin for HCC Immunotherapy?

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. There has been significant progress in understanding the risk factors and epidemiology of HCC during the last few decades, resulting in efficient preventative, diagnostic and treatment strategies. Type 2 diabetes mellitus (T2DM) has been demonstrated to be a major risk factor for developing HCC. Metformin is a widely used hypoglycemic agent for patients with T2DM and has been shown to play a potentially beneficial role in improving the survival of patients with HCC. Experimental and clinical studies evaluating the outcomes of metformin as an antineoplastic drug in the setting of HCC were reviewed. Pre-clinical evidence suggests that metformin may enhance the antitumor effects of immune checkpoint inhibitors (ICIs) and reverse the effector T cells' exhaustion. However, there is still limited clinical evidence regarding the efficacy of metformin in combination with ICIs for the treatment of HCC. We appraised and analyzed in vitro and animal studies that aimed to elucidate the mechanisms of action of metformin, as well as clinical studies that assessed its impact on the survival of HCC patients.

Metformin Induces a Caspase 3-Unrelated Apoptosis in Human Colorectal Cancer Cell Lines HCT116 and SW620

Purpose

To study the effects of metformin on the proliferation and growth of human colorectal cancer cell lines HCT116 and SW620.

Materials and Methods

The antiproliferative effect of metformin was assayed using an MTS reagent and its ability to inhibit colony formation was demonstrated using a clonogenic assay. Flow cytometry using YO-PRO-1/PI was performed to examine the effects of metformin on apoptosis and cell death of HCT116 and SW620. Caspase 3 activities were measured in caspase-3 activity tests using a caspase-3 activity kit. Furthermore, Western blots were performed with anti-PARP1, anti-caspase 3, and anti-cleaved caspase 3 to confirm whether caspase activation was present or not.

Results

Both MTS proliferation assays and clonogenic assays showed that metformin inhibited the proliferation and growth of HCT116 and SW620 cells in a concentration-dependent manner. Flow cytometric analysis identified early apoptosis and metformin-induced cell death in both cell lines. However, caspase 3 activity could not be detected. Cleavage of both PARP1 and pro-caspase 3 was not observed in the Western blot, confirming the absence of caspase 3 activations.

Conclusion

This present study suggests a caspase 3-unrelated apoptosis mechanism of metformin-induced cell death in human colorectal cancer cell lines HCT116 and SW620.

Antitumor Effects and Mechanisms of Metabolic Syndrome Medications on Hepatocellular Carcinoma

Liver cancer has a high incidence and mortality rate worldwide, with hepatocellular carcinoma (HCC) being the most common histological type. With the decrease in the number of newly infected patients and the spread of antiviral therapy, hepatitis virus-negative chronic liver diseases including steatohepatitis are increasingly accounting for a large proportion of HCC, and an important clinical characteristic is the high prevalence of metabolic syndrome including hypertension, type 2 diabetes (T2D), dyslipidemia, and obesity. Since patients with steatohepatitis are less likely to undergo surveillance for early detection of HCC, they may be diagnosed at an advanced stage and have worse prognosis. Therefore, treatment strategies for patients with HCC caused by steatohepatitis, especially in advanced stages, become increasingly important. Further, hypertension, T2D, and dyslipidemia may occur as side effects during systemic treatment, and there will be increasing opportunities to prescribe metabolic syndrome medications, not only for originally comorbid diseases, but also for adverse events during HCC treatment. Interestingly, epidemiological studies have shown that patients taking some metabolic syndrome medications are less likely to develop various types of cancers, including HCC. Basic studies have also shown that these drugs have direct antitumor effects on HCC. In particular, angiotensin II receptor blockers (a drug group for treating hypertension), biguanides (a drug group for treating T2D), and statins (a drug group for treating dyslipidemia) have shown to elucidate antitumor effects against HCC. In this review, we focus on the antitumor effects of metabolic syndrome medications on HCC and their mechanisms based on recent literature. New therapeutic agents are also increasingly being reported. Analysis of the antitumor effects of metabolic syndrome medications on HCC and their mechanisms will be doubly beneficial for HCC patients with metabolic syndrome, and the use of these medications may be a potential strategy against HCC.

Metformin and vitamin D modulate adipose-derived stem cell differentiation towards the beige phenotype

Adipose-derived stem cells (ADSCs) represent an ideal stem cell population for regenerative medicine. ADSC adipogenic differentiation is controlled by the activation of a specific transcriptional program, including epigenetic factors and key adipogenic genes. Under certain conditioned media, ADSCs can differentiate into several phenotypes. We previously demonstrated that bioactive molecules could counteract lipid accumulation and regulate adipogenesis, acting on inflammation and vitamin D metabolism. In the present paper, we aimed at evaluating the effect of metformin and vitamin D in targeting ADSC differentiation towards an intermediate phenotype, as beige adipocytes. We exposed ADSCs to different conditioned media and then we evaluated the levels of expression of main markers of adipogenesis, aP2, LPL and ACOT2. We also analysed the gene and protein expression of thermogenic UCP1 protein, and the expression of PARP1 and the beige specific marker TMEM26. Our results showed a novel effect of metformin and vitamin D not only in inhibiting adipogenesis, but also in inducing a specific ‘brown-like’ phenotype. These findings pave the way for their possible application in the control of de novo lipogenesis useful for the prevention of obesity and its related metabolic disorders.

Multi-omics subtyping of hepatocellular carcinoma patients using a Bayesian network mixture model

Comprehensive molecular characterization of cancer subtypes is essential for predicting clinical outcomes and searching for personalized treatments. We present bnClustOmics, a statistical model and computational tool for multi-omics unsupervised clustering, which serves a dual purpose: Clustering patient samples based on a Bayesian network mixture model and learning the networks of omics variables representing these clusters. The discovered networks encode interactions among all omics variables and provide a molecular characterization of each patient subgroup. We conducted simulation studies that demonstrated the advantages of our approach compared to other clustering methods in the case where the generative model is a mixture of Bayesian networks. We applied bnClustOmics to a hepatocellular carcinoma (HCC) dataset comprising genome (mutation and copy number), transcriptome, proteome, and phosphoproteome data. We identified three main HCC subtypes together with molecular characteristics, some of which are associated with survival even when adjusting for the clinical stage. Cluster-specific networks shed light on the links between genotypes and molecular phenotypes of samples within their respective clusters and suggest targets for personalized treatments.

Metformin Enhances the Anti-Cancer Efficacy of Sorafenib via Suppressing MAPK/ERK/Stat3 Axis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) incidence, as well as related mortality, has been steadily increasing in the USA and across the globe, partly due to the lack of effective therapeutic options for advanced HCC. Though sorafenib is considered standard-of-care for advanced HCC, it only improves median survival by a few months when compared to placebo. Sorafenib is also associated with several unpleasant side effects that often lead to early abatement of therapy. Here, we investigate whether a combination regimen including low-dose sorafenib and a non-toxic dose of anti-diabetic drug metformin can achieve effective inhibition of HCC. Indeed, combining metformin with low-dose sorafenib inhibited growth, proliferation, migration, and invasion potential of HCC cells. We observed a 5.3- and 1.9-fold increase in sub-G1 population in the combination treatment compared to sorafenib alone. We found that the combination of metformin enhanced the efficacy of sorafenib and inhibited the MAPK/ERK/Stat3 axis. Our in vivo studies corroborated the in vitro findings, and mice harboring HepG2-derived tumors showed effective tumor reduction upon treatment with low-dose sorafenib and metformin combination. This work sheds light on a therapeutic strategy aiming to augment sorafenib efficacy or dose-de-escalation that may prove beneficial in circumventing sorafenib resistance as well as minimizing related side effects.

In Vitro and In Ovo Evaluation of the Potential Hepatoprotective Effect of Metformin

Background and Objectives: Metformin is currently the leading drug of choice for treating type 2 diabetes mellitus, being one of the most widely used drugs worldwide. The beneficial effects of Metformin, however, extend far beyond the reduction of blood glucose. Therefore, this study aimed to evaluate Metformin's effects both in vitro and in ovo. Materials and Methods: Metformin has been tested in five different concentrations in human hepatocytes -HepaRG, in terms of cell viability, morphology, structure and number of nuclei and mitochondria, as well as the effect on cell migration. Through the application of HET-CAM, the biocompatibility and potential anti-irritant, as well as protective effects on the vascular plexus were also assessed. Results: According to the results obtained, Metformin increases cell viability without causing morphological changes to cells, mitochondria, or nuclei. Metformin displayed an anti-irritant activity rather than causing irritation at the level of the vascular plexus. Conclusions: In conclusion, Metformin enhances cell viability and proliferation and, has a protective effect on the vascular plexus. Nonetheless, more studies are required to clarify the mechanism of hepatoprotective effect of metformin.

miR1908-5p regulates energy homeostasis in hepatocyte models

We previously identified genomic variants that are quantitative trait loci for circulating miR-1908-5p and then showed this microRNA to causally associate with plasma levels of LDL-C, fasting blood glucose and HbA1c. The link to LDL-C was subsequently validated and clarified by the identification of a miR1908-5p-TGFB-LDLR regulatory axis. Here, we continue our investigations on miR1908-5p function by leveraging human primary hepatocytes and HuH-7 hepatoma models. Expression of miR1908-5p was shown to be sensitive to glucose and agents affecting glucose metabolism. Transcriptome-wide changes in primary hepatocytes and HuH-7 cells treated with a miR1908-5p mimic were investigated by enrichment approaches to identify targeted transcripts and cognate pathways. Significant pathways included autophagy and increased mitochondrial function. Reduced activation and/or levels of several key energy and metabolic regulators (AKT, mTOR, ME1, G6PD, AMPK and LKB) were subsequently confirmed in mimic treated HuH-7 cells. These effects were associated with reduced NADPH to NADP+ ratio in HuH-7 cells. LKB1 was validated as a direct target of miR1908-5p, the reintroduction of which was however insufficient to compensate for the impact of the miR1908-5p mimic on AMPK and ACC1. These findings implicate miR1908-5p in metabolic and energy regulation in hepatocyte models via multiple, independent, pathways.

In-vitro and in-vivo investigation of amygdalin, metformin, and combination of both against doxorubicin on hepatocellular carcinoma

AIM

Hepatocellular carcinoma (HCC) is a potentially life-threatening cancer. In the current study, anti-HCC efficacy of amygdalin, or metformin alone or in combination in comparison to doxorubicin was studied.

MAIN METHODS

Both in-vitro and in-vivo based models. HepG-2 and Huh-7 cell lines as established in-vitro model for HCC were treated with different concentrations of indicated drugs to evaluate the cytotoxicity and determine IC₅₀ for 24, 48 and 72 h. Moreover, the effect of different treatments on apoptosis and cell cycle using flow cytometric analysis were studied. Hepatocellular carcinoma induced in rats by diethyl-nitrosamine and carbon tetrachloride was established, to further investigate the efficacy of indicated drugs. Aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase were measured by spectrophotometer, alpha-fetoprotein, cytochrome-c, caspase-3 and malondialdehyde were measured by ELISA, and liver biopsies were also evaluated histopathologically.

KEY FINDINGS

In-vitro results showed that the combination has a promising effect when compared to amygdalin or metformin alone as it is more cytotoxic and have higher ability for induction of apoptosis and arresting cell cycle. In-vivo doxorubicin has a good effect for treating HCC. Also, the combination showed a promising prognostic effect depending on the cytotoxic activity and tumor marker when compared to amygdalin or metformin alone.

SIGNIFICANCE

Based on the current data, it was hypothesized that amygdalin and metformin especially when used in combination will be a promising approach with low side effects for enhancement of HCC.

miR-10a-5p Inhibits the Differentiation of Goat Intramuscular Preadipocytes by Targeting KLF8 in Goats

Intramuscular fat contributes to the improvement of meat quality of goats. MicroRNAs (miRNAs) have been reported to regulate adipocyte differentiation and maturation. The aim of our study was to clarify whether miR-10a-5p regulates goat intramuscular preadipocyte (GIPC) differentiation and its direct downstream signaling pathway. GIPCs were isolated from longissimus dorsi, whose miR-10a-5p level was measured at different time point of differentiation induction. Adipogenic differentiation of the GIPCs was evaluated by Oil Red O and BODIPY staining, and the expression changes of adipogenic genes like ACC, ATGL, CEBPβ, PPARγ, etc. Related mechanisms were verified by qPCR, a bioinformatic analysis, a dual-luciferase reporter assay, overexpression, and siRNA transfection. Oil Red O and BODIPY staining both with adipogenic gene detection showed that miR-10a-5p suppressed the accumulation of lipid droplets in GIPCs and inhibited its differentiation. The dual-luciferase reporter assay experiment revealed that miR-10a-5p regulates GIPC differentiation by directly binding to KLF8 3’UTR to regulate its expression. Thus, the results indicated that miR-10a-5p inhibits GIPC differentiation by targeting KLF8 and supply a new target for fat deposition and meat quality improvement.

Metformin and Gastrointestinal Cancer Development in Newly Diagnosed Type 2 Diabetes: A Population-Based Study in Korea

INTRODUCTION

Clinical studies have produced conflicting results on the effects of metformin on gastrointestinal cancer development. We aimed to investigate the association between metformin use and stomach, colon, liver, and pancreatic cancer development among patients with newly diagnosed, drug-naïve type 2 diabetes.

METHODS

This retrospective study evaluated propensity score-matched patients with newly diagnosed type 2 diabetes from the Korean National Health Insurance Service database. Metformin users were categorized into tertiles according to the cumulative dose or duration of metformin treatment, and the risks of gastrointestinal cancers were compared.

RESULTS

Metformin users had reduced risks of developing stomach cancer (hazard ratio [HR]: 0.841, 95% confidence interval [CI]: 0.797-0.887), colon cancer (HR: 0.865, 95% CI: 0.822-0.91), and liver cancer (HR: 0.709, 95% CI: 0.675-0.746; P < 0.001). However, metformin users did not have a reduced overall risk of pancreatic cancer (HR: 1.335, 95% CI: 1.209-1.475; P < 0.001). The risks tended to decrease at higher cumulative doses and durations of metformin use, with significantly reduced risks of all 4 cancers at the highest cumulative dose (≥1,200,000 mg) and the longest duration (≥2,000 days) of metformin use.

DISCUSSION

This population-based data suggest that metformin could be associated with reductions in the risks of stomach, colon, and liver cancers, as well a reduced risk of pancreatic cancer in some subgroups. Metformin has benefit as a first-line treatment for type 2 diabetes mellitus. A further role in cancer risk reduction could be studied in controlled trials.

Drug-Drug Interaction between Metformin and Sorafenib Alters Antitumor Effect in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is one of the leading causes of cancer-related deaths worldwide. The multitarget inhibitor sorafenib is a first-line treatment of patients with advanced unresectable HCC. Recent clinical studies have evidenced that patients treated with sorafenib together with the antidiabetic drug metformin have a survival disadvantage compared with patients receiving sorafenib only. Here, we examined whether a clinically relevant dose of metformin (50 mg/kg per day) could influence the antitumoral effects of sorafenib (15 mg/kg per day) in a subcutaneous xenograft model of human HCC growth using two different sequences of administration, i.e., concomitant versus sequential dosing regimens. We observed that the administration of metformin 6 hours prior to sorafenib was significantly less effective in inhibiting tumor growth (15.4% tumor growth inhibition) than concomitant administration of the two drugs (59.5% tumor growth inhibition). In vitro experiments confirmed that pretreatment of different human HCC cell lines with metformin reduced the effects of sorafenib on cell viability, proliferation, and signaling. Transcriptomic analysis confirmed significant differences between xenografted tumors obtained under the concomitant and the sequential dosing regimens. Taken together, these observations call into question the benefit of parallel use of metformin and sorafenib in patients with advanced HCC and diabetes, as the interaction between the two drugs could ultimately compromise patient survival. SIGNIFICANCE STATEMENT: When drugs are administered sequentially, metformin alters the antitumor effect of sorafenib, the reference treatment for advanced hepatocellular carcinoma, in a preclinical murine xenograft model of liver cancer progression as well as in hepatic cancer cell lines. Defective activation of the AMP-activated protein kinase pathway as well as major transcriptomic changes are associated with the loss of the antitumor effect. These results echo recent clinical work reporting a poorer prognosis for patients with liver cancer who were cotreated with metformin and sorafenib.

Anticancer potential of metformin: focusing on gastrointestinal cancers

Gastrointestinal cancers are one of the most common types of cancer that have high annual mortality; therefore, identification and introduction of safe drugs in the control and prevention of these cancers are of particular importance. Metformin, a lipophilic biguanide, is the most commonly prescribed agent for type 2 diabetes management. In addition to its great effects on lowering the blood glucose concentrations, the anti-cancer properties of this drug have been reported in many types of cancers such as gastrointestinal cancers. Hence the effects of this agent as a safe drug on the reduction of gastrointestinal cancer risk and suppression of these types of cancers have been studied in different clinical trials. Furthermore, the proposed mechanisms of metformin in preventing the growth of these cancers have been investigated in several studies. In this review, we discuss recent advances in elucidating the molecular mechanisms that are relevant for metformin use in gastrointestinal cancer treatment.

Metformin: The next angiogenesis panacea?

Angiogenesis, the development of new blood vessels from existing ones, is a critical process in wound healing and skeletal muscle hypertrophy. It also leads to pathological conditions such as retinopathy and tumor genesis. Metformin, the first-line treatment for type 2 diabetic mellitus, has a specific regulatory effect on the process of angiogenesis. Anti-angiogenesis can inhibit the occurrence and metastasis of tumors and alleviate patients’ symptoms with polycystic ovary syndrome. Moreover, promoting angiogenesis effect can accelerate wound healing and promote stroke recovery and limb ischemia reconstruction. This review reorganizes metformin in angiogenesis, and the underlying mechanism in alleviating disease to bring some inspiration to relevant researchers.

Mechanisms Underlying Hepatocellular Carcinoma Progression in Patients with Type 2 Diabetes

Hepatocellular carcinoma (HCC) ranks third in cancer-related deaths from solid tumors worldwide. The incidence of type 2 diabetes mellitus (T2DM) has increased worldwide in conjunction with the expansion of the Western lifestyle. Furthermore, patients with T2DM have been documented to have an increased risk of HCC, as well as bile tract cancer. Growing evidence shows that T2DM is a strong additive metabolic risk factor for HCC, but how diabetes affects the incidence of HCC requires additional investigation. In this review, we discuss the underlying mechanisms of HCC in patients with T2DM. Topics covered include abnormal glucose and lipid metabolism, hyperinsulinemia, and insulin resistance; the effect of activated platelets; hub gene expression associated with HCC; inflammation and signaling pathways; miRNAs; altered gut microbiota and immunomodulation. The evidence suggests that reducing obesity, diabetes, and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis through efficient measures of prevention may lead to decreased rates of T2DM-related HCC.

MicroRNAs in the Pathogenesis of Hepatocellular Carcinoma: A Review

Simple Summary

Hepatocellular carcinoma (HCC) is one of the most frequently occurring cancers, and the prognosis for late-stage HCC remains poor. A better understanding of the pathogenesis of HCC is expected to improve outcomes. MicroRNAs (miRNAs) are small, noncoding, single-stranded RNAs that regulate the expression of various target genes, including those in cancer-associated genomic regions or fragile sites in various human cancers. We summarize the central roles of miRNAs in the pathogenesis of HCC and discuss their potential utility as valuable biomarkers and new therapeutic agents for HCC.

Abstract

Hepatocellular carcinoma (HCC) is the seventh most frequent cancer and the fourth leading cause of cancer mortality worldwide. Despite substantial advances in therapeutic strategies, the prognosis of late-stage HCC remains dismal because of the high recurrence rate. A better understanding of the etiology of HCC is therefore necessary to improve outcomes. MicroRNAs (miRNAs) are small, endogenous, noncoding, single-stranded RNAs that modulate the expression of their target genes at the posttranscriptional and translational levels. Aberrant expression of miRNAs has frequently been detected in cancer-associated genomic regions or fragile sites in various human cancers and has been observed in both HCC cells and tissues. The precise patterns of aberrant miRNA expression differ depending on disease etiology, including various causes of hepatocarcinogenesis, such as viral hepatitis, alcoholic liver disease, or nonalcoholic steatohepatitis. However, little is known about the underlying mechanisms and the association of miRNAs with the pathogenesis of HCC of various etiologies. In the present review, we summarize the key mechanisms of miRNAs in the pathogenesis of HCC and emphasize their potential utility as valuable diagnostic and prognostic biomarkers, as well as innovative therapeutic targets, in HCC diagnosis and treatment.

Anti-diabetic drug metformin inhibits cell proliferation and tumor growth in gallbladder cancer via G0/G1 cell cycle arrest

Gallbladder cancer is the most common biliary tract cancer with poor prognosis and wide variation in incidence rates worldwide, being very high in some countries in Latin America and Asia. Treatment of type 2 diabetes with metformin causes a reduction in the incidence of cancer. Till date, there are no reports on the anti-tumor effects of metformin in gall bladder cancer. Therefore, this study evaluated the effects of metformin on the proliferation of human gallbladder adenocarcinoma cells in vitro and in vivo, as well as explored the microRNAs associated with the anti-tumor effects of metformin. Metformin inhibited the proliferation in gallbladder adenocarcinoma cell lines NOZ, TGBC14TKB, and TGBC24TKB, and blocked the G0 to G1 transition in the cell cycle. This was accompanied by strong reduction in the expression of G1 cyclins, especially cyclin D1 and its catalytic subunits including cyclin-dependent kinase 4, and in retinoblastoma protein phosphorylation. In addition, metformin reduced the phosphorylation of receptor tyrosine kinases, especially Tie-2, ALK, PYK, EphA4, and EphA10, as well as angiogenesis-related proteins, including RANTES, TGF-β, and TIMP-1. Moreover, metformin also markedly altered microRNA expression profile leading to an anti-tumor effect. Treatment of athymic nude mice bearing xenograft tumors with metformin inhibited tumor growth. These results suggest that metformin may be used clinically for the treatment of gallbladder adenocarcinoma.

A CRISPR knockout negative screen reveals synergy between CDKs inhibitor and metformin in the treatment of human cancer in vitro and in vivo

Laboratory research and pharmacoepidemiology provide support for metformin as a potential antitumor agent. However, the lack of a clear understanding of the indications of metformin limits its efficacy. Here, we performed a genome-wide CRISPR knockout negative screen to identify potential targets that might synergize with metformin. Next-generation sequencing of pooled genomic DNAs isolated from surviving cells after 18 days of metformin treatment (T18) compared to those of the untreated cells at day 0 (T0) yielded candidate genes. Knockdown of a group of cyclin-dependent kinases (CDKs), including CDK1, CDK4, and CDK6, confirmed the results of the screen. Combination treatment of the CDKs inhibitor abemaciclib with metformin profoundly inhibited tumor viability in vitro and in vivo. Although cell cycle parameters were not further altered under the combination treatment, investigation of the metabolome revealed significant changes in cell metabolism, especially with regard to fatty acid oxidation, the tricarboxylic acid cycle and aspartate metabolism. Such changes appeared to be mediated through inhibition of the mTOR pathway. Collectively, our study suggests that the combination of CDKs inhibitor with metformin could be recognized as a potential therapy in future clinical applications.

Anticancer mechanisms of metformin: A review of the current evidence

Metformin, a US Food and Drug Administration-approved "star" drug used for diabetes mellitus type 2, has become a topic of increasing interest to researchers due to its anti-neoplastic effects. Growing evidence has demonstrated that metformin may be a promising chemotherapeutic agent, and several clinical trials of metformin use in cancer treatment are ongoing. However, the anti-neoplastic effects of metformin and its underlying mechanisms have not been fully elucidated. In this review, we present the newest findings on the anticancer activities of metformin, and highlight its diverse anticancer mechanisms. Several clinical trials, as well as the limitations of the current evidence are also demonstrated. This review explores the crucial roles of metformin and provides supporting evidence for the repurposing of metformin as a treatment of cancer.

Regorafenib and ginsenoside combination therapy: inhibition of HepG2 cell growth through modulating survivin and caspase-3 gene expression

BACKGROUND

This work aimed to investigate the inhibitory effect of regorafenib in combination with ginsenoside on the growth of HepG2 liver cancer cells.

METHODS

HepG2 liver cancer cells were divided into blank control group, regorafenib single-drug group, ginsenoside single-drug group, and regorafenib/ginsenoside combination group. Cells in the regorafenib single-drug group were treated with regorafenib at 0.25 mg/L, 0.5 mg/L, and 1 mg/L, respectively, while cells in the ginsenoside single-drug group were treated with ginsenoside at 5.0 mg/L, 10.0 mg/L, and 20.0 mg/L, respectively. HepG2 cell proliferation, expression of survivin mRNA, and the apoptotic effector caspase-3 in HepG2 liver cancer cells were assessed.

RESULTS

An inhibitory effect on the growth of HepG2 liver cancer cells was observed for both the single-drug therapies and the combination therapy. The synergistic inhibitory effect presented by the combination therapy was dependent on the gradient concentration and treatment time. RT-qPCR results showed that both regorafenib and ginsenoside significantly reduced the expression of survivin mRNA in HepG2 liver cancer cells and the expression level of survivin mRNA in the regorafenib/ginsenoside combination group was much lower than those in the regorafenib single-drug group and ginsenoside single-drug group. The two drugs demonstrated synergistic inhibitory effect when used in combination.

CONCLUSIONS

The findings in this study offered a theoretical insight into clinical use of regorafenib and ginsenoside for treatment of liver cancer.

Kinetic modelling of quantitative proteome data predicts metabolic reprogramming of liver cancer

Background

Metabolic alterations can serve as targets for diagnosis and cancer therapy. Due to the highly complex regulation of cellular metabolism, definite identification of metabolic pathway alterations remains challenging and requires sophisticated experimentation.

Methods

We applied a comprehensive kinetic model of the central carbon metabolism (CCM) to characterise metabolic reprogramming in murine liver cancer.

Results

We show that relative differences of protein abundances of metabolic enzymes obtained by mass spectrometry can be used to assess their maximal velocity values. Model simulations predicted tumour-specific alterations of various components of the CCM, a selected number of which were subsequently verified by in vitro and in vivo experiments. Furthermore, we demonstrate the ability of the kinetic model to identify metabolic pathways whose inhibition results in selective tumour cell killing.

Conclusions

Our systems biology approach establishes that combining cellular experimentation with computer simulations of physiology-based metabolic models enables a comprehensive understanding of deregulated energetics in cancer. We propose that modelling proteomics data from human HCC with our approach will enable an individualised metabolic profiling of tumours and predictions of the efficacy of drug therapies targeting specific metabolic pathways.

Nutraceuticals and "Repurposed" Drugs of Phytochemical Origin in Prevention and Interception of Chronic Degenerative Diseases and Cancer

BACKGROUND

Chronic, degenerative diseases are often characterized by inflammation and aberrant angiogenesis. For these pathologies, including rheumatoid arthritis, cardiovascular and autoimmune diseases, cancer, diabetes, and obesity, current therapies have limited efficacy.

OBJECTIVES

The validation of novel (chemo)preventive and interceptive approaches, and the use of new or repurposed agents, alone or in combination with registered drugs, are urgently required.

RESULTS

Phytochemicals (triterpenoids, flavonoids, retinoids) and their derivatives, nonsteroidal anti-inflammatory drugs (aspirin) as well as biguanides (metformin and phenformin) originally developed from phytochemical backbones, are multi-target agents showing antiangiogenic and anti-anti-inflammatory proprieties. Many of them target AMPK and metabolic pathways such as the mTOR axis. We summarize the beneficial effects of several compounds in conferring protection and supporting therapy, and as a paradigm, we present data on terpenoids & biquanides on beer hop xanthohumol and hydroxytryrosol from olive mill waste waters.

CONCLUSIONS

These molecules could be employed for combinatorial chemoprevention and interception approaches or chemoprevention/therapy regimens for cancer and other chronic complex diseases.

The Role of AMP-Activated Protein Kinase as a Potential Target of Treatment of Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) is the fifth most frequent cancer worldwide with a very high recurrence rate and very dismal prognosis. Diagnosis and treatment in HCC remain difficult, and the identification of new therapeutic targets is necessary for a better outcome of HCC treatment. AMP-Activated Protein Kinase (AMPK) is an essential intracellular energy sensor that plays multiple roles in cellular physiology and the pathological development of chronic diseases. Recent studies have highlighted the important regulation of AMPK in HCC. This review aims to comprehensively and critically summarize the role of AMPK in HCC. Methods: Original studies were retrieved from NCBI database with keywords including AMPK and HCC, which were analyzed with extensive reading. Results: Dysregulation of the kinase activity and expression of AMPK was observed in HCC, which was correlated with survival of the patients. Loss of AMPK in HCC cells may proceed cell cycle progression, proliferation, survival, migration, and invasion through different oncogenic molecules and pathways. Conclusions: We identified several AMPK activators which may possess potential anti-HCC function, and discussed the clinical perspective on the use of AMPK activators for HCC therapy.

Metformin and glucose starvation decrease the migratory ability of hepatocellular carcinoma cells: targeting AMPK activation to control migration

Hepatocellular carcinoma (HCC) is a highly metastatic cancer with very poor prognosis. AMP activated kinase (AMPK) constitutes a candidate to inhibit HCC progression. First, AMPK is downregulated in HCC. Second, glucose starvation induces apoptosis in HCC cells via AMPK. Correspondingly, metformin activates AMPK and inhibits HCC cell proliferation. Nevertheless, the effect of AMPK activation on HCC cell invasiveness remains elusive. Here, migration/invasion was studied in HCC cells exposed to metformin and glucose starvation. Cell viability, proliferation and differentiation, as well as AMPK and PKA activation were analyzed. In addition, invasiveness in mutants of the AMPKα activation loop was assessed. Metformin decreased cell migration, invasion and epithelial-mesenchymal transition, and interference with AMPKα expression avoided metformin actions. Those antitumor effects were potentiated by glucose deprivation. Metformin activated AMPK at the same time that inhibited PKA, and both effects were enhanced by glucose starvation. Given that AMPKα(S173) phosphorylation by PKA decreases AMPK activation, we hypothesized that the reduction of PKA inhibitory effect by metformin could explain the increased antitumor effects observed. Supporting this, in AMPK activating conditions, cell migration/invasion was further impaired in AMPKα(S173C) mutant cells. Metformin emerges as a strong inhibitor of migration/invasion in HCC cells, and glucose restriction potentiates this effect.

Metformin delays AKT/c-Met-driven hepatocarcinogenesis by regulating signaling pathways for de novo lipogenesis and ATP generation

Hepatocellular carcinoma (HCC) is a lethal malignancy with few effective options for therapeutic treatment in its advanced stages. Metformin, a first-line oral agent used in the treatment of type 2 diabetes, exhibits efficacy in metabolic reprogramming fueling changes in cell growth and proliferation for multiple cancer types, including HCC. However, the molecular mechanism by which metformin delays hepatocarcinogenesis in individuals with hepatic steatosis remains rare. Here, we investigate the preventive efficacy of metformin in a rapid AKT/c-Met-triggered HCC mouse model featuring excessive levels of steatosis. Hematoxylin and eosin staining, Oil Red O staining and immunoblotting were applied for mechanistic investigations. Pharmacological and biochemical strategies were employed to illuminate molecular evidence for HCC cell lines. The results show that metformin obstructs the malignant transformation of hepatocytes in AKT/c-Met mice. Mechanistically, metformin reduces the expression of phospho-ERK (Thr202/Tyr204) and two forms of proto-oncogenes, Cyclin D1 and c-Myc, in AKT/c-Met mice. Moreover, metformin ameliorates FASN-mediated aberrant lipogenesis and HK2/PKM2-driven ATP generation in vivo. Furthermore, metformin represses the expression of FASN and HK-2 by targeting c-Myc in an AMPK-dependent manner in vitro. In addition, metformin is effective at inhibiting PKM2 expression in the presence of an AMPK inhibitor compound C, suggesting that its functioning in PKM2 is AMPK-independent. Our study experimentally validates a novel molecular mechanism by which metformin alleviates enhanced lipogenesis and high energy metabolism during hepatocarcinogenesis, indicating that metformin may serve as an agent for the prevention of HCC in patients with nonalcoholic fatty liver diseases.

Metformin Counteracts HCC Progression and Metastasis Enhancing KLF6/p21 Expression and Downregulating the IGF Axis

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is the common tumor of the liver. Unfortunately, most HCC seem to be resistant to conventional chemotherapy and radiotherapy. The poor efficacy of antitumor agents is also due, at least in part, to the inefficient drug delivery and metabolism exerted by the steatotic/cirrhotic liver that hosts the tumor. Thus, novel approaches in chemotherapy may be needed to improve the survival rate in patients with HCC. Metformin (METF) has been found to lower HCC risk; however, the mechanisms by which METF performs its anticancer activity are not completely elucidated. Previous studies have showed METF action on growth inhibition in the liver in a dose/time-dependent manner and its antitumor role by targeting multiple pathways. We investigated molecular effects of METF in an in vitro human hepatoma model (HepG2), studying cell cycle regulators, tumorigenesis markers, and insulin-like growth factor (IGF) axis regulation.

MATERIALS AND METHODS

HepG2 cells were treated with METF (400 μM) for 24, 48, and 72 hours. METF action on cell cycle progression and cellular pathways involved in metabolism regulation was evaluated by gene expression analysis, immunofluorescence, and Western blot assay.

RESULTS

By assessing HepG2 cell viability, METF significantly decreased growth cell capacity raising KLF6/p21 protein content. Moreover, METF ameliorated the cancer microenvironment reducing cellular lipid drop accumulation and promoting AMPK activity. The overexpression of IGF-II molecule and the IGF-I receptor that plays a main role in HCC progression was counteracted by METF. Furthermore, the protein content of HCC principal tumor markers, CK19 and OPN, linked to the metastasis process was significantly reduced by METF stimulus.

CONCLUSION

Our data show that METF could suppress HepG2 proliferation, through induction of cell cycle arrest at the G0/G1 phase. In addition, METF effect on the cancer microenvironment and on the IGF axis leads to the development of new METF therapeutic use in HCC treatment.

Metformin induces miR-378 to downregulate the CDK1, leading to suppression of cell proliferation in hepatocellular carcinoma

Metformin is one of the extensively and most commonly used oral antihyperglycemic agents, but it has been shown to exert antineoplastic effects in many cancer cells. Recent studies have confirmed that metformin has an antitumor effect on hepatocellular carcinoma (HCC). However, the molecular mechanism underlying this effect needs to be further studied.

Epigenetic effects of metformin: From molecular mechanisms to clinical implications

There is a growing body of evidence that links epigenetic modifications to type 2 diabetes. Researchers have more recently investigated effects of commonly used medications, including those prescribed for diabetes, on epigenetic processes. This work reviews the influence of the widely used antidiabetic drug metformin on epigenomics, microRNA levels and subsequent gene expression, and potential clinical implications. Metformin may influence the activity of numerous epigenetic modifying enzymes, mostly by modulating the activation of AMP-activated protein kinase (AMPK). Activated AMPK can phosphorylate numerous substrates, including epigenetic enzymes such as histone acetyltransferases (HATs), class II histone deacetylases (HDACs) and DNA methyltransferases (DNMTs), usually resulting in their inhibition; however, HAT1 activity may be increased. Metformin has also been reported to decrease expression of multiple histone methyltransferases, to increase the activity of the class III HDAC SIRT1 and to decrease the influence of DNMT inhibitors. There is evidence that these alterations influence the epigenome and gene expression, and may contribute to the antidiabetic properties of metformin and, potentially, may protect against cancer, cardiovascular disease, cognitive decline and aging. The expression levels of numerous microRNAs are also reportedly influenced by metformin treatment and may confer antidiabetic and anticancer activities. However, as the reported effects of metformin on epigenetic enzymes act to both increase and decrease histone acetylation, histone and DNA methylation, and gene expression, a significant degree of uncertainty exists concerning the overall effect of metformin on the epigenome, on gene expression, and on the subsequent effect on the health of metformin users.

Investigating Effect of Rapamycin and Metformin on Angiogenesis in Hepatocellular Carcinoma Cell Line

Purpose: Human hepatocellular carcinoma is one of the most common causes of death in the world. Metformin and rapamycin may decrease the expression of VEGF protein and subsequently angiogenesis. The purpose of this study was to evaluate the effect of these two drugs on expression of VEGF protein and the cell proliferation in the hepatocellular carcinoma cell line (ATCC HB-8065).

Methods: HepG2 was cultured in RPMI-1640 medium at 37°C for 48h as a pre-culture and then treated by different concentrations of metformin (0, 5, 10 and 20 mM) and rapamycin (0, 5, 10 and 20 nM) at different times (12, 24 and 48 h). Cell viability was assessed by the MTT assay. Total RNA was extracted by the Trizol reagent and VEGF gene expression was analyzed by quantitative real-time PCR and was calculated by 2^–ΔCt method. The VEGF protein level was determined by Elisa assay. Finally, Apoptosis index was calculated by DAPI staining.

Results: Metformin and rapamycin significantly decrease cancer cells viability (p<0.05). Rapamycin but not metformin decreases VEGF gene expression in HepG2 cells. Metformin and rapamycin significantly induce cell apoptosis in hepatocellular carcinoma (HCC) cells.

Conclusion: Metformin and rapamycin have an anti-tumor effect on HCC. According to our data rapamycin might have an anti-angiogenesis effect via inhibition of VEGF expression. Our results provide an insight into future clinical strategies to improve chemotherapy outcomes in HCC.

Gelidium elegans Extract Ameliorates Type 2 Diabetes via Regulation of MAPK and PI3K/Akt Signaling

Gelidium elegans, a red alga native to the Asia Pacific region, contains biologically active polyphenols. We conducted a molecular biological study of the anti-diabetic effect of Gelidium elegans extract (GEE) in C57BL/KsJ-db/db mice. Mice that had been administered GEE had significantly lower body mass, water consumption, and fasting blood glucose than db/db controls. Moreover, hemoglobin A1c (HbA1c), an indicator of the glycemic status of people with diabetes, was significantly lower in mice that had been administered GEE. We also found that 200 mg/kg/day GEE upregulates the insulin signaling pathway by activating insulin receptor substrate-1 (IRS-1) and phosphoinositide 3-kinase (PI3K), and increasing the expression of glucose transporter type 4 (GLUT4). In parallel, mitogen-activated protein kinase (MAPK) activity was lower in GEE-treated groups. In summary, these findings indicate that GEE regulates glucose metabolism by activating the insulin signaling pathway and downregulating the MAPK signaling pathway.

Metformin synergistically enhances antitumor activity of cisplatin in gallbladder cancer via the PI3K/AKT/ERK pathway

Metformin (Met) is a widely used antidiabetic drug and has demonstrated interesting anticancer effects in various cancer models, alone or in combination with chemotherapeutic drugs. The aim of the present study is to investigate the synergistic effect of Met with cisplatin (Cis) on the tumor growth inhibition of gallbladder cancer cells (GBC-SD and SGC-996) and explore the underlying mechanism. Cells were treated with Met and/or Cis and subjected to cell viability, colony formation, apoptosis, cell cycle, western blotting, xenograft tumorigenicity assay and immunohistochemistry. The results demonstrated that Met and Cis inhibited the proliferation of gallbladder cancer cells, and combination treatment with Met and Cis resulted in a combination index < 1, indicating a synergistic effect. Co-treatment with Met and Cis caused G0/G1 phase arrest by upregulating P21, P27 and downregulating CyclinD1, and induced apoptosis through decreasing the expression of p-PI3K, p-AKT, and p-ERK. In addition, pretreatment with a specific AKT activator (IGF-1) significantly neutralized the pro-apoptotic activity of Met + Cis, suggesting the key role of AKT in this process. More importantly, in nude mice model, Met and Cis in combination displayed more efficient inhibition of tumor weight and volume in the SGC-996 xenograft mouse model than Met or Cis alone. Immunohistochemistry analysis suggests the combinations greatly suppressed tumor proliferation, which is consistent with our in vitro results. In conclusion, our findings indicate that the combination therapy with Met and Cis exerted synergistic antitumor effects in gallbladder cancer cells through PI3K/AKT/ERK pathway, and combination treatment with Met and Cis would be a promising therapeutic strategy for gallbladder cancer patients.

Galectin‑9 ameliorates fulminant liver injury

Fulminant hepatitis is a severe liver disease resulting in hepatocyte necrosis. Galectin-9 (Gal-9) is a tandem-repeat-type galectin that has been evaluated as a potential therapeutic agent for various diseases that regulate the host immune system. Concanavalin A (ConA) injection into mice results in serious, immune-mediated liver injury similar to human viral, autoimmune and fulminant hepatitis. The present study investigated the effects of Gal-9 treatment on fulminant hepatitis in vivo and the effect on the expression of microRNAs (miRNAs), in order to identify specific miRNAs associated with the immune effects of Gal-9. A ConA-induced mouse hepatitis model was used to investigate the effects of Gal-9 treatment on overall survival rates, liver enzymes, histopathology and miRNA expression levels. Histological analyses, TUNEL assay, immunohistochemistry and miRNA expression characterization, were used to investigate the degree of necrosis, fibrosis, apoptosis and infiltration of neutrophils and macrophages. Overall survival rates following ConA administration were significantly higher in Gal-9-treated mice compared with control mice treated with ConA + PBS. Histological examination revealed that Gal-9 attenuated hepatocellular damage, reduced local neutrophil infiltration and prevented the local accumulation of macrophages and liver cell apoptosis in ConA-treated mice. In addition, various miRNAs induced by Gal-9 may contribute to its anti-apoptotic, anti-inflammatory and pro-proliferative effects on hepatocytes. The results of the present study demonstrate that Gal-9 may be a candidate therapeutic target for the treatment of fulminant hepatitis.

Role of VEGF in metformin induced apoptosis of HepG2 cells

AIM

To investigate the molecular mechanism of metformin induced apoptosis of HepG2 cells.

METHODS

HepG2 cells were treated with different concentrations (0-20 mmol/L) of metformin (MET) for 24 h or 10 mmol/L MET for different times (0-48 h), and the effect of MET on cell proliferation was measured by MTT assay. Annexin V-FITC/PI flow cytometry was used to determine the apoptosis rate. RT-PCR was used to analyze the expression of vascular endothelial growth factor (VEGF) in HepG2 cells treated with MET.

RESULTS

MET had an obvious inhibitory effect on HepG2 cell proliferation. After treatment with 0, 5, 10, 15, and 20 mmol/L MET for 24 h, the relative cell viability rates of HepG2 cells were 100%, 80.56% ± 0.72%, 71.06% ± 0.70%, 64.73% ± 0.35%, and 54.73% ± 0.40%, respectively, showing a dose-dependent manner. After treatment with 10 mmol/L MET for 0, 12, 24, 36, and 48 h, the relative cell viability rates of HepG2 cells were 100%, 83.40% ± 0.70%, 69.86% ± 0.45%, 60.40% ± 0.88%, and 50.70% ± 0.45%, respectively, showing a time-dependent manner. Annexin V-FITC/PI flow cytometry revealed that the apoptosis rates of HepG2 cell were increased after treatment with 0, 5, 10, 15, and 20 mmol/L MET for 24 h, and the apoptosis rates were 2.78% ± 0.68%, 9.33% ± 0.22%, 17.13% ± 0.10%, 21.61% ± 0.20%, and 25.26% ± 1.09%, respectively, showing a dose-dependent manner. The apoptosis rates of HepG2 cells were increased after treatment with 10 mmol/L for 0, 12, 24, 36, 48 h, and the apoptosis rates were 2.05% ± 0.04%, 8.10% ± 0.08%, 16.53% ± 0.93%, 20.95% ± 0.16%, and 25.65% ± 0.44%, showing a time-dependent manner. The expression of VEGF decreased after treatment with different concentrations of MET for 24 h or 10 mmol/L MET for different times, showing a dose- and time-dependent manner.

CONCLUSION

MET can inhibit HepG2 cell proliferation via inducing apoptosis, which may involve the expression of VEGF.

Association between metformin and the risk of gastric cancer in patients with type 2 diabetes mellitus: a meta-analysis of cohort studies

Objectives

The objective of this study was to evaluate the association between metformin therapy and the incidence of gastric cancer (GC) in patients with type 2 diabetes mellitus (T2DM).

Methods

We systemically searched the following databases for studies published between the databases’ dates of inception and Nov. 2016: PubMed, Embase, the Cochrane Library, the Web of Science, and the China National Knowledge Infrastructure (CNKI). Hazard ratios (HR)and corresponding 95% confidence intervals (CIs) for the association between metformin therapy and the incidence of GC in patients with T2DM were the outcome measures assessed in this study. STATA 12.0 (Stata Corporation, College Station, Texas, USA) was used to conduct the statistical analysis.

Results

A total of seven cohort studies including 591,077 patients met all the criteria for inclusion in the analysis. Our data showed that metformin therapy was associated with a significantly lower incidence of GC in patients with T2DM than other types of therapy (HR=0.763, 95% CI: 0.642˜0.905). Subgroup analysis showed that patients living in Taiwan benefitted more from metformin therapy than patients living in any other region, as metformin significantly decreased the risk of GC in patients living in Taiwan but did not significantly decrease the risk of GC in patients living in other regions (HR=0.514, 95% CI: 0.384-0.688). The results of the present analysis support the idea that metformin facilitates reductions in the risk of T2DM-related GC.

Conclusions

The risk of GC among patients with T2DM is lower in patients receiving metformin therapy than in patients not receiving metformin therapy.

Metformin promotes apoptosis in hepatocellular carcinoma through the CEBPD-induced autophagy pathway

Metformin, as an AMP-activated protein kinase (AMPK) activator, can activate autophagy. A study showed that metformin decreased the risk of hepatocellular carcinoma (HCC) in diabetic patients. However, the detailed mechanism in the metformin-mediated anticancer effect remains an open question. Transcription factor CCAAT/enhancer-binding protein delta (CEBPD) has been suggested to serve as a tumor suppressor and is responsive to multiple anticancer drugs in HCC. In this study, we found that CEBPD and autophagy are involved in metformin-induced cell apoptosis in Huh7 cells. The underlying mechanisms in this process included a reduction in Src-mediated CEBPD protein degradation and an increase in CEBPD-regulated LC3B and ATG3 gene transcription under metformin treatment. We also found that AMPK is involved in metformin-induced CEBPD expression. Combined treatment with metformin and rapamycin can enhance autophagic cell death through the AMPK-dependent and AMPK-independent pathway, respectively. Taken together, we provide a new insight and therapeutic approach by targeting autophagy in the treatment of HCC.

Strong antineoplastic effects of metformin in preclinical models of liver carcinogenesis

Studies suggest that metformin, widely used for treating Type 2 diabetes, possesses innate antineoplastic properties. For metabolic syndrome patients with hepatocellular carcinoma (HCC), metformin may provide antitumoral effects. We evaluated the impact of metformin on tumour growth and visceral fat composition using relevant preclinical models of metabolic syndrome. Studies were performed in three hepatoma cell lines, in HepG2 xenograft mice fed with standard chow (SC) diet, 60% high-fat diet (HFD) or 30% fructose diet (FR), and an ex vivo model of human cultured HCC slices. Visceral fatty acid composition was analysed by magnetic resonance imaging (MRI). Metformin had a dose-dependent inhibitory effect on cell proliferation and apoptosis in vitro through the deregulation of mTOR/AMPK, AKT and extracellular signal regulated kinase (ERK) signalling pathways. Tumour engraftment rates were higher in HFD mice than SC mice (hepatic: 79% compared with 25%, P=0.02) and FR mice (subcutaneous: 86% compared with 50%, P=0.04). Subcutaneous tumour volume was increased in HFD mice (+64% compared with FR and SC, P=0.03). Metformin significantly decreased subcutaneous tumour growth via cell-cycle block and mammalian target of rapamycin (mTOR) pathway inhibition, and also induced hypoxia and decreased angiogenesis. In ex vivo tumour slices, metformin treatment led to increased necrosis, decreased cyclin D1 and increased carbonic anhydrase-9 (CA-9). Metformin caused qualitative changes in visceral fat composition of HFD mice, with decreased proportions of polyunsaturated fatty acids (14.6% ± 2.3% compared with 17.9% ± 3.0%, P=0.04). The potent antitumoral effects of metformin in multiple preclinical models implicating several molecular mechanisms provide a strong rationale for clinical trials including combination studies in HCC patients.

Metformin potentiates the anticancer activities of gemcitabine and cisplatin against cholangiocarcinoma cells in vitro and in vivo

Metformin, an oral biguanide drug used to treat type 2 diabetes, has displayed anticancer activities in several types of cancer cells. The combination of gemcitabine and cisplatin is the standard chemotherapy regimen for cholangiocarcinoma, but its benefit is limited. The present study aimed to investigate whether metformin could enhance the activities of gemcitabine and cisplatin against cholangiocarcinoma, and the underlying mechanisms. Metformin inhibited the proliferation of human cholangiocarcinoma RBE and HCCC-9810 cells and induced cell cycle arrest at the G0/G1 phase by increasing the activation of AMP-activated protein kinase (AMPK) pathways. Metformin upregulated the expression of p21Waf1 and p27kip1, and downregulated the expression of cyclin D1, a key protein required for cell cycle progression. The combination of gemcitabine and cisplatin inhibited the proliferation and induced the apoptosis of human cholangiocarcinoma cells by inducing the phosphorylation of AMPK, downregulating cyclin D1, and activating caspase-3. Administration of metformin enhanced the efficacy of gemcitabine and cisplatin to suppress the growth of cholangiocarcinoma tumors established in experimental models by inhibiting cell proliferation and inducing cell apoptosis through their effects on AMPK, cyclin D1 and caspase-3. Given that metformin has been used to treat type 2 diabetes patients for over half a century due to its superior safety profile, the results presented here indicate that metformin may be a potent agent for enhancing the efficacy of gemcitabine and cisplatin in the treatment of cholangiocarcinoma.

Metformin-suppressed differentiation of human visceral preadipocytes: Involvement of microRNAs

Visceral adipose tissue contributes to the pathophysiology of metabolic syndrome. Metformin has been reported to suppress lipogenesis in a murine preadipocyte cell line. However, the effect of metformin on the differentiation of human visceral adipose tissue remains unknown. MicroRNAs (miRNAs or miRs) have been suggested as therapeutic targets because of their involvement in the differentiation and maturation of fatty cells. The aim of this study was to determine whether metformin suppresses the differentiation of human preadipocytes and to identify miRNAs associated with the regulation of lipid metabolism. Human visceral preadipocytes (HPrAD-vis) were preincubated in growth media and then cultured with differentiation media containing metformin for 1 or 2 weeks. Adipogenic differentiation of the cells was assessed by Oil Red O staining, and soluble adiponectin in the culture media was measured using an enzyme-linked immunosorbent assay. Cell proliferation was assessed using a WST-8 assay, and the gene and protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT-enhancer-binding protein α (C/EBPα) was determined by RT-qPCR and western blot analysis, respectively. miRNAs were profiled using human miRNA Oligo chips after total RNA was extracted and labeled. Oil Red O staining showed that metformin suppressed the accumulation of lipid droplets in HPrAD-vis cells. The adiponectin concentration in the culture media was also decreased in metformin-treated cells. The WST-8 assay revealed no effect on proliferation or growth inhibition following metformin treatment, although metformin suppressed the expression of PPARγ and C/EBPα. miRNA profiling further revealed differences between the metformin-treated group and control HPrAD-vis cells. Thus, the findings of the present study demonstrated that metformin suppressed the differentiation of human preadipocytes in vitro and altered the miRNA profile of these cells. Thus, the miRNAs whose expression levels were altered by metformin may contribute to the observed suppression of HPrAD-vis cell differentiation.

Diabetes mellitus and metformin in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death worldwide. Diabetes mellitus, a risk factor for cancer, is also globally endemic. The clinical link between these two diseases has been the subject of investigation for a century, and diabetes mellitus has been established as a risk factor for HCC. Accordingly, metformin, a first-line oral anti-diabetic, was first proposed as a candidate anti-cancer agent in 2005 in a cohort study in Scotland. Several subsequent large cohort studies and randomized controlled trials have not demonstrated significant efficacy for metformin in suppressing HCC incidence and mortality in diabetic patients; however, two recent randomized controlled trials have reported positive data for the tumor-preventive potential of metformin in non-diabetic subjects. The search for biological links between cancer and diabetes has revealed intracellular pathways that are shared by cancer and diabetes. The signal transduction mechanisms by which metformin suppresses carcinogenesis in cell lines or xenograft tissues and improves chemoresistance in cancer stem cells have also been elucidated. This review addresses the clinical and biological links between HCC and diabetes mellitus and the anti-cancer activity of metformin in clinical studies and basic experiments.

Metformin induces apoptosis of human hepatocellular carcinoma HepG2 cells by activating an AMPK/p53/miR-23a/FOXA1 pathway

The antidiabetic drug metformin has been shown to possess antitumor functions in many types of cancers. Although studies have revealed its beneficial effects on the prognosis of hepatocellular carcinoma (HCC), the detailed molecular mechanism underlying this event remains largely unknown. In this work, we showed that miR-23a was significantly induced upon metformin treatment; inhibition of miR-23a abrogated the proapoptotic effect of metformin in HepG2 cells. We next established forkhead box protein A1 (FOXA1) as the functional target of miR-23a, and silencing FOXA1 mimicked the effect of metformin. Moreover, the phosphorylation of AMP-activated protein kinase (AMPK) and the expression of p53 were increased upon metformin treatment, and the inhibition of p53 abrogated the induction of miR-23a by metformin, suggesting that AMPK/p53 signaling axis is responsible for the induction of miR-23a by metformin. In summary, we unraveled a novel AMPK/p53/miR-23a/FOXA1 axis in the regulation of apoptosis in HCC, and the application of metformin could, therefore, be effective in the treatment of HCC.

Metformin induces apoptosis by microRNA-26a-mediated downregulation of myeloid cell leukaemia-1 in human oral cancer cells

In recent years, population-based studies and retrospective analyses of clinical studies have shown that metformin treatment is associated with reduced cancer incidence and a decrease in cancer‑associated mortality. However, its mechanism of action remains to be fully understood. The present study demonstrates the effects of metformin on KB human oral cancer cells and explores the role of myeloid cell leukaemia‑1 (Mcl‑1) in metformin‑induced mitochondria‑dependent cellular apoptosis. It was demonstrated that metformin exposure caused significant suppression of KB cell proliferation and induced cell death. Furthermore, metformin induced apoptosis through the downregulation of Mcl‑1 in KB human oral cancer cells, and the overexpression of Mcl‑1 in metformin‑treated KB cells significantly increased cell viability. Consistently, Bax and Bim were upregulated in metformin‑treated cells. The results also reveal that microRNA (miR)‑26a expression was markedly increased by metformin. Subsequent to enforced miR‑26a expression in KB cells using miR‑26a mimics, cell viability and the level of Mcl‑1 decreased. These results suggest that the anti‑proliferative effects of metformin in KB cells may result partly from induction of apoptosis by miR-26a-induced downregulation of Mcl-1.

Metformin inhibits prostate cancer cell proliferation, migration, and tumor growth through upregulation of PEDF expression

Metformin has been reported to inhibit the growth of various types of cancers, including prostate cancer. Yet the mode of anti-cancer action of metformin and the underlying mechanisms remain not fully elucidated. We hypothesized that the antitumorigenic effects of metformin are mediated through upregulation of pigment epithelium-derived factor (PEDF) expression in prostate cancer cells. In this report, metformin treatment significantly inhibited the proliferation and colony formation of prostate cancer cells, in a dose- and time-dependent manner. Meanwhile, Metformin markedly suppressed migration and invasion and induced apoptosis of both LNCaP and PC3 cancer cells. Metformin also reduced PC3 tumor growth in BALB/c nude mice in vivo. Furthermore, metformin treatment was associated with higher PEDF expression in both prostate cancer cells and tumor tissue. Taken together, metformin inhibits prostate cancer cell proliferation, migration, invasion and tumor growth, and these activities are mediated by upregulation of PEDF expression. These findings provide a novel insight into the molecular functions of metformin as an anticancer agent.