In vitro and in vivo antitumoral action of metformin on hepatocellular carcinoma

Molecular interactions between metformin and D-limonene inhibit proliferation and promote apoptosis in breast and liver cancer cells

BACKGROUND

Cancer is a fatal disease that severely affects humans. Designing new anticancer strategies and understanding the mechanism of action of anticancer agents is imperative.

HYPOTHESIS/PURPOSE

In this study, we evaluated the utility of metformin and D-limonene, alone or in combination, as potential anticancer therapeutics using the human liver and breast cancer cell lines HepG2 and MCF-7.

STUDY DESIGN

An integrated systems pharmacology approach is presented for illustrating the molecular interactions between metformin and D-limonene.

METHODS

We applied a systems-based analysis to introduce a drug-target-pathway network that clarifies different mechanisms of treatment. The combination treatment of metformin and D-limonene induced apoptosis in both cell lines compared with single drug treatments, as indicated by flow cytometric and gene expression analysis.

RESULTS

The mRNA expression of Bax and P53 genes were significantly upregulated while Bcl-2, iNOS, and Cox-2 were significantly downregulated in all treatment groups compared with normal cells. The percentages of late apoptotic HepG2 and MCF-7 cells were higher in all treatment groups, particularly in the combination treatment group. Calculations for the combination index (CI) revealed a synergistic effect between both drugs for HepG2 cells (CI = 0.14) and MCF-7 cells (CI = 0.22).

CONCLUSION

Our data show that metformin, D-limonene, and their combinations exerted significant antitumor effects on the cancer cell lines by inducing apoptosis and modulating the expression of apoptotic genes.

Metformin Reduces Tumor Growth in a Murine Flank Schwannoma Model

HYPOTHESIS

Metformin and aspirin reduce vestibular schwannoma (VS) growth.

BACKGROUND

There have been reported associations between patients with VS prescribed metformin and decreased tumor volumetric growth. Aspirin has also been associated with decreased VS growth in animal studies.

METHODS

Rat schwannoma cell lines were grown and implanted into 50 athymic nude mice. Tumors were grown to 5 mm, and then mice were injected with either low- or high-dose metformin, aspirin, or saline daily. Tumors were measured until 14 days elapsed or mice demonstrated symptoms such as ulceration, inability to walk, or passed away.

RESULTS

There were no significant differences in day 0 tumor sizes between the control and the treatment groups ( p = 0.73). In the low-dose, but not high-dose groups, day 7 volumes were significantly different for both metformin ( p = 0.04) and aspirin ( p = 0.02) compared with placebo. Mean tumor growth rates were 126.6 ± 65.6 mm 3 /day for saline compared with 73.7 ± 29.5 mm 3 /day for low-dose metformin ( p = 0.03) and 68.7 ± 34.8 mm 3 /day for low-dose aspirin ( p = 0.016). There were no significant differences in tumor sizes ( p = 0.59) or growth rates ( p = 0.75) between low-dose metformin and aspirin groups. Low-dose groups had treatment stopped at 14 days, with continued monitoring demonstrating significant increases in tumor growth off treatment for both aspirin ( p = 0.006) and metformin ( p = 0.048).

CONCLUSIONS

Metformin treatment significantly reduced VS growth to a similar level as aspirin. Furthermore, when removing both metformin and aspirin treatment, tumor growth significantly increased.

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.

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.

Enhanced oral permeability of Trans-Resveratrol using nanocochleates for boosting anticancer efficacy; in-vitro and ex-vivo appraisal

Hepatocellular carcinoma (HCC) is a prevalent liver cancer representing the fourth most lethal cancer worldwide. Trans-Resveratrol (T-R) possesses a promising anticancer activity against HCC. However, it suffers from poor bioavailability because of the low solubility, chemical instability, and hepatic metabolism. Herein, we developed T-R-loaded nanocochleates using a simple trapping method. Nanocarriers were optimized using a comprehensive in-vitro characterization toolset and evaluated for the anticancer activity against HepG2 cell line. T-R-loaded nanocochleates demonstrated monodispersed cylinders (163.27 ± 2.68 nm and 0.25 ± 0.011 PDI) and -46.6 mV ζ-potential. They exhibited a controlled biphasic pattern with minimal burst followed by sustained release for 72 h. Significant enhancements of Caco-2 transport and ex-vivo intestinal permeation over liposomes, with 1.8 and 2.1-folds respectively, were observed. Nanocochleates showed significant reduction of 24 h IC₅₀ values compared to liposomes and free T-R. Moreover, an efficient knockdown of anti-apoptotic (Bcl-2) and cancer stemness (NANOG) genes was demonstrated. To the best of our knowledge, we are the first to develop T-R loaded nanocochleates and scrutinize its potential in suppressing NANOG expression, 2-folds lower, compared to free T-R. According to these auspicious outcomes, nanocochleates represent a promising nanoplatform to enhance T-R oral permeability and augment its anticancer efficacy in the treatment of HCC.

Postnatal metformin treatment alters rat Sertoli cell proliferation and daily sperm production

BACKGROUND

The direct correlation between Sertoli cell number and sperm production capacity highlights the importance of deciphering external factors that modify Sertoli cell proliferation. A growing body of evidence in vitro suggests that metformin, the main pharmacological agent for type 2 diabetes treatment in children, exerts anti-proliferative effects on Sertoli cells.

OBJECTIVE

The aims of this study were to investigate the effect of metformin administration during postnatal period on Sertoli cell proliferation and on cell cycle regulators expression and to analyze the impact of this treatment on the sperm production capacity in adulthood.

MATERIALS AND METHODS

Sprague Dawley rat pups were randomly divided into two groups: MET (receiving daily 200 mg/kg metformin, from Pnd3 to Pnd7 inclusive) and control (receiving vehicle). BrdU incorporation was measured to assess proliferation. Gene expression analyses were performed in Sertoli cells isolated from animals of both groups. Daily sperm production and sperm parameters were measured in adult male rats (Pnd90) that received neonatal treatment.

RESULTS

MET group exhibited a significant decrease in BrdU incorporation in Sertoli cells. Concordantly, MET group showed a reduction in cyclin D1 and E2 expression and an increase in p21 expression in Sertoli cells. In addition, metformin-treated animals displayed lower values of daily sperm production on Pnd90.

DISCUSSION AND CONCLUSION

These results suggest that metformin treatment may lead to a decrease in Sertoli cell proliferation, a concomitant altered expression of cell cycle regulators and ultimately, a reduction in daily sperm production in adult animals.

Metformin suppresses Nrf2-mediated chemoresistance in hepatocellular carcinoma cells by increasing glycolysis

The diabetes drug metformin has recently been shown to possess anti-cancer properties when used with other chemotherapeutic drugs. However, detailed mechanisms by which metformin improves cancer treatment are poorly understood. Here we provide evidence in HepG2 hepatocellular carcinoma cells that metformin sensitizes cisplatin-resistant HepG2 cells (HepG2/DDP) through increasing cellular glycolysis and suppressing Nrf2-dependent transcription. We show that metformin increases glucose uptake and enhances glucose metabolism through glycolytic pathway, resulting in elevated concentrations of intracellular NADPH and lactate. Consistently, high glucose medium suppresses Nrf2-dependent transcription and sensitizes HepG2/DDP cells to cisplatin. Elevated glycolysis was required for metformin to regulate Nrf2-dependent transcription and cisplatin sensitivity, as inhibition of glycolysis with 2-Deoxy-D-glucose (2-DG) significantly mitigates the beneficial effect of metformin. Together, our study has revealed an important biological process and gene transcriptional program underlying the beneficial effect of metformin on reducing chemo-resistance in HepG2 cells and provided new information on improving chemotherapy of liver cancers.

Brain somatic mutations in MTOR reveal translational dysregulations underlying intractable focal epilepsy

Brain somatic mutations confer genomic diversity in the human brain and cause neurodevelopmental disorders. Recently, brain somatic activating mutations in MTOR have been identified as a major etiology of intractable epilepsy in patients with cortical malformations. However, the molecular genetic mechanism of how brain somatic mutations in MTOR cause intractable epilepsy has remained elusive. In this study, translational profiling of intractable epilepsy mouse models with brain somatic mutations and genome-edited cells revealed a novel translational dysregulation mechanism and mTOR activation-sensitive targets mediated by human MTOR mutations that lead to intractable epilepsy with cortical malformation. These mTOR targets were found to be regulated by novel mTOR-responsive 5'-UTR motifs, distinct from known mTOR inhibition-sensitive targets regulated by 5' terminal oligopyrimidine motifs. Novel mTOR target genes were validated in patient brain tissues, and the mTOR downstream effector eIF4E was identified as a new therapeutic target in intractable epilepsy via pharmacological or genetic inhibition. We show that metformin, an FDA-approved eIF4E inhibitor, suppresses intractable epilepsy. Altogether, the present study describes translational dysregulation resulting from brain somatic mutations in MTOR, as well as the pathogenesis and potential therapeutic targets of intractable epilepsy.

Mitochondrial metabolic reprogramming: An important player in liver cancer progression

Mitochondria are known as essential biosynthetic, bioenergetic and signaling organelles, and play a critical role in cell differentiation, proliferation, and death. Nowadays, cancer is emergingly considered as a mitochondrial metabolic disease. Mitochondria also play an essential role in liver carcinogenesis. Liver cells are highly regenerative and require high energy. For that reason, a large number of mitochondria are present and functional in liver cells. Abnormalities in mitochondrial metabolism in human liver are known to be one of the carcinogenic factors. Interestingly, immune checkpoints regulate mitochondrial metabolic energetics of the tumor, the tumor microenvironment, as well as the tumor-specific immune response. This regulation forms a positive loop between the metabolic reprogramming of both cancer cells and immune cells. In this review, we discuss the evidence and mechanisms that mitochondria interplay with immune checkpoints to influence different steps of oncogenesis, as well as the potential of mitochondria as therapeutic targets for liver cancer therapy.

Drug Repurposing for Retinoblastoma: Recent Advances

Retinoblastoma is the intraocular malignancy that occurs during early childhood. The current standard of care includes chemotherapy followed by focal consolidative therapies, and enucleation. Unfortunately, these are associated with many side and late effects. New drugs and/or drug combinations need to be developed for safe and effective treatment. This compelling need stimulated efforts to explore drug repurposing for retinoblastoma. While conventional drug development is a lengthy and expensive process, drug repurposing is a faster, alternate approach, where an existing drug, not meant for treating cancer, can be repurposed to treat retinoblastoma. The present article reviews various attempts to test drugs approved for different purposes such as calcium channels blockers, non-steroidal antiinflammatory drugs, cardenolides, antidiabetic, antibiotics and antimalarial for treating retinoblastoma. It also discusses other promising candidates that could be explored for repurposing for retinoblastoma.

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.

Effect of adriamycin combined with metformin on biological function of human tongue cancer SSC-15 cells

The effect of adriamycin (ADM) combined with metformin (MET) on the biological function of human tongue cancer SSC-15 cells was investigated. SCC-15 cells (ATCC^® CRL-1623) were cultured in vitro. The close concentration of the median lethal dose (LD50) of ADM was 0.05 mg/l and the LD50 of MET was 10 mmol/l after 48 h of intervention. They were used for drug combination experiments. Cells without drug treatment were used as the control group, cells treated with ADM alone, MET alone and their drug combination (ADM+MET) as the experimental groups. CCK-8 was used to detect the cell survival rate, and flow cytometry to detect the apoptosis rate in each group, Transwell chamber to detect the invasion ability in vitro of cells and scratch-healing experiment to observe the migration ability of the cells. The survival rate of tongue cancer SCC-15 cells gradually decreased with the increase in ADM and MET concentrations and in intervention time (P<0.05). The apoptosis rate in the ADM, MET and ADM+MET groups was significantly higher than that in the control group (P<0.05). The apoptosis rate in the ADM+MET group was higher than that in the ADM and MET groups (P<0.05). The invasion and migration ability of cells in the ADM and MET groups were higher than those in the ADM+MET group (P<0.05). The cell membrane number and the migration rate of cells in the ADM+MET group were significantly lower than those in the ADM and MET groups (P<0.05). Both MET and ADM inhibit the growth, invasion and migration of tongue cancer SSC-15 cells, and induce their apoptosis. Thus, ADM and MET in combination is more effective than ADM alone and MET alone in inhibiting the growth, invasion and migration of tongue cancer cells as well as in inducing their apoptosis.

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.

Treatment with metformin is associated with a prolonged survival in patients with hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most lethal cancers. Nutrition- and life style-associated risk factors are increasingly prevalent. Metformin, the mainstay of type 2 diabetes mellitus (T2DM)-treatment, reduces the risk of hepatocarcinogenesis. However, its influence on the prognosis of patients with HCC has not been investigated on a large scale, yet.

METHODS

Five thousand and ninety-three patients treated for HCC between 2000 and 2016 at three referral centres were included in this retrospective multicentre study. The aim of this study was to assess whether treatment with metformin for T2DM is associated with a prolonged overall survival (OS) in patients diagnosed with HCC.

RESULTS

Among 5093 patients with HCC, 1917 patients (37.6%) were diagnosed with T2DM, of which 338 (17.6%) received treatment with metformin. Compared to diabetic patients not treated with metformin, patients on metformin had a significantly better hepatic function (Child-Pugh-Score A: 69.2% vs 47.4%, P < 0.001) and underwent significantly more often tumour resection (22.1% vs 16.5%, P = 0.024). Patients on metformin had a significantly longer median OS (mOS) compared to diabetic patients not treated with metformin (22 vs 15 months, P = 0.019). The prolongation of survival was most significant in patients treated with surgery. Using a propensity score match (PSM), patients were adjusted for hepatic function and initial therapy. In the matched cohorts, mOS remained significantly longer in metformin-treated patients (22 vs 16 months, P = 0.021). Co-treatment of metformin and sorafenib was associated with a survival disadvantage.

CONCLUSION

Treatment with metformin was associated with an improved survival in patients with T2DM and HCC. This effect was most pronounced in patients at potentially curative tumour stages.

Anti-proliferative and anti-apoptotic potential effects of epigallocatechin-3-gallate and/or metformin on hepatocellular carcinoma cells: in vitro study

The effects of epigallocatechin-3-gallate (EGCG) and metformin single treatment have been tested against hepatocellular carcinoma (HCC). This study aimed to assess the combination effects of EGCG and metformin on proliferation and apoptosis of HepG2cells and identified new potential molecular targets. The effect of EGCG and metformin against cell proliferation in HepG2 was determined using MTT assay. Reverse transcription polymerase chain reaction was applied to examine the gene expression of cyclin D1, lncRNA-AF085935, caspase-3, survivin and VEGF. The level of protein expression of glypican-3 was assessed by western blot. In HepG2 cells, EGCG and metformin combination treatment exhibited high significant effect against tumor proliferation. It significantly reduced cyclin D1, lncRNA-AF085935, glypican-3 and promoted apoptosis through increasing caspase3 and decreasing survivin compared to control cells. Moreover, EGCG and metformin treated cells showed decreased expression levels of VEGF. Our study provided new insights of the anticarcinogenic effects of EGCG and metformin on HCC through their effects on glypican-3 and lncRNA-AF085935.

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 counteracts the effects of FSH on rat Sertoli cell proliferation

Metformin (MET) is one of the most widely used anti-hyperglycemic agents for treating patients with type 2 diabetes and it has started to be used in pediatric population at ages when Sertoli cells are still proliferating. It is well known that follicle-stimulating hormone (FSH) is the major Sertoli cell mitogen. The aim of the study is to investigate a possible effect of MET, which has been shown to have anti-proliferative properties, on FSH regulation of postnatal Sertoli cell proliferation and on the molecular mechanisms involved in this regulation. The present study was performed in eight-day-old rat Sertoli cell cultures. The results obtained show that MET in the presence of FSH increases phosphorylated acetyl-CoA carboxylase and decreases phosphorylated p70S6K levels. Moreover, we show that MET decreases FSH-stimulated Sertoli cell proliferation, and this decrease is accompanied by a reduction in FSH-stimulated Ccnd1 and Ccnd2 expression and an increase in cell cycle inhibitor p21Cip expression. Altogether, these results suggest that MET can, at least in part, counteract the effect of FSH on postnatal Sertoli cell proliferation.

Anti-tumoral effects of exercise on hepatocellular carcinoma growth

Regular physical exercise has many beneficial effects, including antitumor properties, and is associated with a reduced risk of developing hepatocellular carcinoma (HCC). Less is known about the impact of exercise on HCC growth and progression. Here, we investigated the effects of exercise on HCC progression and assessed whether any beneficial effects would be evident under sorafenib treatment and could be mimicked by metformin. American Cancer Institute rats with orthotopic syngeneic HCC derived from Morris Hepatoma‐3924A cells were randomly assigned to exercise (Exe) and sedentary groups, or sorafenib±Exe groups or sorafenib±metformin groups. The Exe groups ran on a motorized treadmill for 60 minutes/day, 5 days/week for 4 weeks. Tumor viable area was decreased by exercise, while cell proliferation and vascular density were reduced. Exercise increased the expression of phosphatase and tensin homolog deleted from chromosome 10 and increased the phosphorylation of adenosine monophosphate‐activated protein kinase, while the phosphorylation of protein kinase B, S6 ribosomal protein, and signal transducer and activator of transcription 3 were decreased. Transcriptomic analysis suggested major effects of exercise were on nontumoral liver rather than tumor tissue. Exercise demonstrated similar effects when combined with sorafenib. Moreover, similar effects were observed in the group treated with sorafenib+metformin, revealing an exercise‐mimicking effect of metformin. Conclusion: Exercise attenuates HCC progression associated with alterations in key signaling pathways, cellular proliferation, tumor vascularization, and necrosis. These beneficial effects are maintained when combined with sorafenib and can be mimicked by metformin. (Hepatology Communications 2018;2:607‐620)

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.

Metformin use improves survival of diabetic liver cancer patients: systematic review and meta-analysis

Metformin has garnered considerable interest as a chemo-preventive and chemo-therapeutic agent given the increased risk of liver cancer among diabetic patients. This work was performed to illustrate the association between metformin use and survival of diabetic liver cancer patients. We conducted a comprehensive literature search of PubMed, Web of Science, Embase, BIOSIS Previews, Cochrane Library from inception to 12 May 2016. Meta-analyses were performed using Stata (version 12.0), with hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) as effect measures. Eleven cohort studies involving 3452 liver cancer patients fulfilled the inclusion criteria. Meta-analyses showed that metformin use was associated with better survival (HR = 0.59; 95% CI, 0.42-0.83; p = 0.002) of liver cancer patients, and the beneficial effect persisted (HR = 0.64; 95% CI, 0.42-0.97; p = 0.035) when the population was restricted to diabetic liver cancer patients. After adjusting for age, etiology, index of tumor severity and treatment of liver cancer, the association between metformin use and better survival of liver cancer patients was stable, pooled HR ranged from 0.47 to 0.57. The results indicated that metformin use improved survival of diabetic liver cancer patients. However, the results should be interpreted with caution given the possibility of residual confounding. Further prospective studies are still needed to confirm the prognostic benefit of metformin use.

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.

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.

Metformin requires 4E-BPs to induce apoptosis and repress translation of Mcl-1 in hepatocellular carcinoma cells

Metformin inhibits the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, which is frequently upregulated in hepatocellular carcinoma (HCC). Metformin has also been shown to induce apoptosis in this cancer. Here, we investigate whether metformin-induced apoptosis in HCC is mediated by the downstream mTORC1 effectors eukaryotic initiation factor 4E and (eIF4E)-binding proteins (4E-BPs). Further, we ask whether changes in 4E-BPs activity during metformin treatment negatively regulate translation of the anti-apoptotic myeloid cell leukemia 1 (Mcl-1) mRNA. A genetic HCC mouse model was employed to assess the ability of metformin to reduce tumor formation, induce apoptosis, and control 4E-BP1 activation and Mcl-1 protein expression. In parallel, the HCC cell line Huh7 was transduced with scrambled shRNA (control) or shRNAs targeting 4E-BP1 and 4E-BP2 (4E-BP knock-down (KD)) to measure differences in mRNA translation, apoptosis, and Mcl-1 protein expression after metformin treatment. In addition, immunohistochemical staining of eIF4E and 4E-BP1 protein levels was addressed in a HCC patient tissue microarray. We found that metformin decreased HCC tumor burden, and tumor tissues showed elevated apoptosis with reduced Mcl-1 and phosphorylated 4E-BP1 protein levels. In control but not 4E-BP KD Huh7 cells, metformin induced apoptosis and repressed Mcl-1 mRNA translation and protein levels. Immunostaining of HCC patient tumor tissues revealed a varying ratio of eIF4E/4E-BP1 expression. Our results propose that metformin induces apoptosis in mouse and cellular models of HCC through activation of 4E-BPs, thus tumors with elevated expression of 4E-BPs may display improved clinical chemopreventive benefit of metformin.

Metformin enhances anti-tumor effect of L-type amino acid transporter 1 (LAT1) inhibitor

BACKGROUND

In many cancer cells, L-type amino acid transporter 1 (LAT1) transports neutral amino acids with bulky side chain, which activate mammalian target of rapamycin (mTOR) to cause cell proliferation. An anti-diabetic drug, metformin, has been shown to activate AMP-activated protein kinase (AMPK), which leads to inhibition of mTOR. LAT1 inhibition in combination with metformin could result in more prominent suppression of mTOR activity.

PURPOSE

Anti-proliferative effect of a newly developed LAT1 specific inhibitor JPH203 in combination with metformin is evaluated in 2 head and neck cancer cell lines, Ca9-22 and HEp-2 cells and in nude mice inoculated with Ca9-22 cells.

RESULTS AND DISCUSSION

By MTT assay, 0.5 mM metformin inhibited proliferation of Ca9-22 cells to 70% of control. In the presence of 100 μM JPH203, proliferation of Ca9-22 cells was inhibited to 60% of control. By combining these 2 drugs, proliferation of Ca9-22 was significantly inhibited to 40% of control. However, this regimen was not very effective against HEp-2 cells. This combination also suppressed in vivo growth of Ca9-22 cells in a xenotransplant model. A combination of anti-LAT1 drug with metformin may be an effective anti-proliferative therapy for certain subsets of cancers.

Molecular targets of metformin antitumor action

Epidemiological studies have shown that metformin, a first line therapeutic agent for diabetes mellitus, reduced the risk of developing various malignancies. Several preclinical studies established some possible mechanisms of its anticancer effects. The primary effect of metformin action is a decrease in cell energy status, which activates AMP-activated kinase (AMPK), a cellular metabolic sensor. This event is followed by a decrease in serum concentrations of insulin and insulin growth factor I (IGF-I), the potent mitogens for cancer cells. In addition to the indirect mode of action, metformin may exhibit direct inhibitory effect on cancer cells by targeting mammalian target of rapamycin (mTOR) signaling and anabolic processes. This review gathers information on mechanisms of metformin antitumor activity, with special attention given to the impact of this antidiabetic drug on insulin/PI3K/mTOR and AMPK signaling. Furthermore, the factors required for this novel activity of metformin are discussed.

Metformin inhibits the prometastatic effect of sorafenib in hepatocellular carcinoma by upregulating the expression of TIP30

We previously found that a low dose of sorafenib had a prometastatic effect on hepatocellular carcinoma (HCC), which was caused by downregulation of TIP30 expression. More recently, metformin has been shown to have potential as a preventive and therapeutic agent for different cancers, including HCC. This study evaluated whether the combination of sorafenib and metformin is sufficient to revert the expression of TIP30, thereby simultaneously reducing lung metastasis and improving survival. Our data show that the combination of sorafenib and metformin inhibits proliferation and invasion in vitro, prolongs median survival, and reduces lung metastasis of HCC in vivo. This effect is closely associated with the upregulation of TIP30, partly through activating AMP‐activated protein kinase. Thioredoxin, a prometastasis factor, is negatively regulated by TIP30 and plays an essential role during the process of HCC metastasis. Overall, our results suggest that metformin might be a potent enhancer for the treatment of HCC by using sorafenib.

Metformin inhibits early stage diethylnitrosamine‑induced hepatocarcinogenesis in rats

Antitumor effects of metformin have recently emerged despite its original use for type II diabetes. In the present study, the effects of metformin on the development and recurrence of hepatocellular carcinoma (HCC) were investigated using the diethylnitrosamine (DEN)‑induced rat model of HCC. Tumor foci were characterized by gross examination and by histopathological characteristics, including proliferation, hepatic progenitor cell content and the expression of hepatocarcinoma‑specific molecular markers. Potential target molecules of metformin were investigated to determine the molecular mechanism underlying the inhibitory effects of metformin on chemically induced liver tumorigenesis. The antitumor effects of metformin were increased by the reduction of surface nodules and decreased the incidence of altered hepatocellular foci, hepatocellular adenoma and carcinoma. Also, decreased expression levels of glutathione S‑transferase placental form, proliferating cell nuclear antigen and cytokeratin 8 described the inhibitory effects of metformin on HCC. In the present study, Wistar rats receiving treatment with DEN were administered metformin for 16 weeks. In addition, metformin suppressed liver tumorigenesis via an AMPK‑dependent pathway. These results suggested that metformin has promising effects on the early stage of HCC in rats. Therefore, metformin may be used for the prevention of HCC recurrence following primary chemotherapy for HCC and/or for high‑risk patients, including chronic hepatitis and cirrhosis.

Metformin and cancer: Between the bioenergetic disturbances and the antifolate activity

For decades, metformin has been the first-line drug for the treatment of type II diabetes mellitus, and it thus is the most widely prescribed antihyperglycemic drug. Retrospective studies associate the use of metformin with a reduction in cancer incidence and cancer-related death. However, despite extensive research about the molecular effects of metformin in cancer cells, its mode of action remains controversial. In this review, we summarize the current molecular evidence in an effort to elucidate metformin's mode of action against cancer cells. Some authors describe that metformin acts directly on mitochondria, inhibiting complex I and restricting the cell's ability to cope with energetic stress. Furthermore, as the drug interrupts the tricarboxylic acid cycle, metformin-induced alteration of mitochondrial function leads to a compensatory increase in lactate and glycolytic ATP. It has also been reported that cell cycle arrest, autophagy, apoptosis and cell death induction is mediated by the activation of AMPK and Redd1 proteins, thus inhibiting the mTOR pathway. Additionally, unbiased metabolomics studies have provided strong evidence to support that metformin alters the methionine and folate cycles, with a concomitant decrease in nucleotide synthesis. Indeed, purines such as thymidine or hypoxanthine restore the proliferation of tumor cells treated with metformin in vitro. Consequently, some authors prefer to refer to metformin as an "antimetabolite drug" rather than a "mitochondrial toxin". Finally, we also review the current controversy concerning the relationship between the experimental conditions of in vitro-reported effects and the plasma concentrations achieved by chronic treatment with metformin.

Systematic review: Preventive and therapeutic applications of metformin in liver disease

Metformin, a biguanide derivative, is the most commonly prescribed medication in the treatment of type 2 diabetes mellitus. More recently, the use of metformin has shown potential as a preventive and therapeutic agent for a broad spectrum of conditions, including liver disease and hepatic malignancies. In this systematic review, we critically analyze the literature behind the potential use of metformin across the spectrum of liver disease and malignancies. The PubMed and Ovid MEDLINE databases were searched from 2000 to March 2015, using a combination of relevant text words and MeSH terms: metformin and mammalian target of rapamycin, hepatitis B virus (HBV), hepatitis B virus (HCV), non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC) or cholangiocarcinoma. The search results were evaluated for pertinence to the issue of metformin in liver disease as well as for quality of study design. Metformin has a number of biochemical effects that would suggest a benefit in treating chronic liver diseases, particularly in the context of insulin resistance and inflammation. However, the literature thus far does not support any independent therapeutic role in NAFLD or HCV. Nonetheless, there is Level III evidence for a chemopreventive role in patients with diabetes and chronic liver disease, with decreased incidence of HCC and cholangiocarcinoma. The use of metformin seems to be safe in patients with cirrhosis, and provides a survival benefit. Once hepatic malignancies are already established, metformin does not offer any therapeutic potential. In conclusion, there is insufficient evidence to recommend use of metformin in the adjunctive treatment of chronic liver diseases, including NAFLD and HCV. However, there is good evidence for a chemopreventive role against HCC among patients with diabetes and chronic liver disease, and metformin should be continued in patients even with cirrhosis to provide this benefit.

Anti-tumor effects of metformin in animal models of hepatocellular carcinoma: a systematic review and meta-analysis

BACKGROUND

Several studies have reported that metformin can reduce the risk of hepatocellular carcinoma (HCC) in diabetes patients. However, the direct anti-HCC effects of metformin have hardly been studied in patients, but have been extensively investigated in animal models of HCC. We therefore performed a systematic review and meta-analysis of animal studies evaluating the effects of metformin on HCC.

METHODS

We collected the relevant studies by searching EMBASE, Medline (OvidSP), Web of Science, Scopus, PubMed Publisher, and Google Scholar. Studies were included according to the following inclusion criteria: HCC, animal study, and metformin intervention. Study quality was assessed using SYRCLE's risk of bias tool. A meta-analysis was performed for the outcome measures: tumor growth (tumor volume, weight and size), tumor number and incidence.

RESULTS

The search resulted in 573 references, of which 13 could be included in the review and 12 included in the meta-analysis. The study characteristics of the included studies varied considerably. Two studies used rats, while the others used mice. Only one study used female animals, nine used male, and three studies didn't mention the gender of animals in their experiments. The quality of the included studies was low to moderate based on the assessment of their risk of bias. The meta-analysis showed that metformin significantly inhibited the growth of HCC tumour (SMD -2.20[-2.96,-1.43]; n=16), but no significant effect on the number of tumors (SMD-1.05[-2.13,0.03]; n=5) or the incidence of HCC was observed (RR 0.62[0.33,1.16]; n=6). To investigate the potential sources of significant heterogeneities found in outcome of tumor growth (I2=81%), subgroup analyses of scales of growth measures and of types of animal models used were performed.

CONCLUSION

Metformin appears to have a direct anti-HCC effect in animal models. Although the intrinsic limitations of animal studies, this systematic review could provide an important reference for future preclinical animal trials of good quality and clinical development.

Metformin decreases IL-22 secretion to suppress tumor growth in an orthotopic mouse model of hepatocellular carcinoma

Epidemiological, preclinical and cellular studies in the last 5 years have shown that metformin exerts anti-tumoral properties, but its mode of action in cancer remains unclear. Here, we investigated the effects of metformin on a mouse hepatocellular carcinoma (HCC) model and tumor-associated T cell immune responses. Oral metformin administration led to a significant reduction of tumor growth, which was accompanied by decreased interleukin-22 (IL-22). Meanwhile, IL-22-induced STAT3 phosphorylation and upregulation of downstream genes Bcl-2 and cyclin D1 were inhibited by metformin. At the cellular level, metformin attenuated Th1- and Th17-derived IL-22 production. Furthermore, metformin inhibited de novo generation of Th1 and Th17 cells from naive CD4(+) cells. These observations were further supported by the fact that metformin treatment inhibited CD3/CD28-induced IFN-γ and IL-17A expression along with the transcription factors that drive their expression (T-bet [Th1] and ROR-γt [Th17], respectively). The effects of metformin on T cell differentiation were mediated by downregulated STAT3 and STAT4 phosphorylation via the AMP-activated kinase-mammalian target of rapamycin complex 1 pathway. Notably, metformin led to a reduction in glucose transporter Glut1 expression, resulting in less glucose uptake, which is critical to regulate CD4(+) T cell fate. Taken together, these findings provide evidence for the growth-inhibitory and immune-modulatory effects of metformin in HCC and thus, broaden our understanding about the action of metformin in liver cancer treatment.

DEPTOR-related mTOR suppression is involved in metformin's anti-cancer action in human liver cancer cells

Metformin, one of the most commonly used drugs for patients with type 2 diabetes, recently has received much attention regarding its anti-cancer action. It is thought that the suppression of mTOR signaling is involved in metformin's anti-cancer action. Although liver cancer is one of the most responsive types of cancer for reduction of incidence by metformin, the molecular mechanism of the suppression of mTOR in liver remains unknown. In this study, we investigated the mechanism of the suppressing effect of metformin on mTOR signaling and cell proliferation using human liver cancer cells. Metformin suppressed phosphorylation of p70-S6 kinase, and ribosome protein S6, downstream targets of mTOR, and suppressed cell proliferation. We found that DEPTOR, an endogenous substrate of mTOR suppression, is involved in the suppressing effect of metformin on mTOR signaling and cell proliferation in human liver cancer cells. Metformin increases the protein levels of DEPTOR, intensifies binding to mTOR, and exerts a suppressing effect on mTOR signaling. This increasing effect of DEPTOR by metformin is regulated by the proteasome degradation system; the suppressing effect of metformin on mTOR signaling and cell proliferation is in a DEPTOR-dependent manner. Furthermore, metformin exerts a suppressing effect on proteasome activity, DEPTOR-related mTOR signaling, and cell proliferation in an AMPK-dependent manner. We conclude that DEPTOR-related mTOR suppression is involved in metformin's anti-cancer action in liver, and could be a novel target for anti-cancer therapy.

Livin is associated with the invasive and oncogenic phenotypes of human hepatocellular carcinoma cells

AIM

Livin, a member of the inhibitors of apoptosis proteins, is expressed in variable cancers, and its expression is considered a poor prognostic marker. The aims of this study were to observe the effect of Livin on the behaviors of hepatocellular carcinoma (HCC) cells and to evaluate its expression in HCC tissues and its relation to prognosis.

METHODS

The biological effects of Livin on tumor cell behavior were investigated using siRNA in HepG2 and Chang cells. Migration, invasion and proliferation assays were performed. Flow cytometric analyses and western blotting were used to evaluate the impact of Livin on apoptosis and the cell cycle. In addition, western blotting and immunohistochemistry were used to investigate Livin expression in HCC tissues.

RESULTS

Livin knockdown suppressed tumor cell migration, invasion and proliferation in HCC cells, and increased the proportion of apoptotic cells as compared with scrambled siRNA-transfected HCC cells. Furthermore, Livin knockdown resulted in the activation of caspases and increased apoptosis. In addition, Livin knockdown modulated cell cycle regulatory protein levels such as decrease of cyclins and cyclin-dependent kinase (CDK) level, and increase of CDK inhibitor (CDKI) level in HCC cells. The Livin protein level was significantly elevated in HCC tissues as compared with normal hepatic tissues. However, Livin expression was not found to be associated with clinicopathological parameters, which included patient survival.

CONCLUSION

These results suggest that Livin is associated with invasive and oncogenic phenotypes of human HCC cells.

Metformin Induced AMPK Activation, G0/G1 Phase Cell Cycle Arrest and the Inhibition of Growth of Esophageal Squamous Cell Carcinomas In Vitro and In Vivo

Esophageal squamous cell carcinomas (ESCC) have become a severe threat to health and the current treatments for ESCC are frequently not effective. Recent epidemiological studies suggest that the anti-hyperglycemic agent metformin may reduce the risk of developing cancer, including ESCC, among diabetic patients. However, the antitumor effects of metformin on ESCC and the mechanisms underlying its cell cycle regulation remain elusive. The findings reported herein show that the anti-proliferative action of metformin on ESCC cell lines is partially mediated by AMPK. Moreover, we observed that metformin induced G0/G1 phase arrest accompanied by the up-regulation of p21CIP1 and p27KIP1. In vivo experiments further showed that metformin inhibited tumor growth in a ESCC xenograft model. Most importantly, the up-regulation of AMPK, p53, p21CIP1, p27KIP1 and the down-regulation of cyclinD1 are involved in the anti-tumor action of metformin in vivo. In conclusion, metformin inhibits the growth of ESCC cells both in cell cultures and in an animal model. AMPK, p53, p21CIP1, p27KIP1 and cyclinD1 are involved in the inhibition of tumor growth that is induced by metformin and cell cycle arrest in ESCC. These findings indicate that metformin has the potential for use in the treatment of ESCC.

Effects of metformin on retinoblastoma growth in vitro and in vivo

Recent studies suggest that the anti-diabetic drug metformin may reduce the risk of cancer and have anti-proliferative effects for some but not all cancers. In this study, we examined the effects of metformin on human retinoblastoma cell proliferation in vitro and in vivo. Two different human retinoblastoma cell lines (Y79, WERI) were treated with metformin in vitro and xenografts of Y79 cells were established in nu/nu immune-deficient mice and used to assess the effects of pharmacological levels of metformin in vivo. Metformin inhibited proliferation of the retinoblastoma cells in vitro. Similar to other studies, high concentrations of metformin (mM) blocked the cell cycle in G0‑G1, indicated by a strong decrease of G1 cyclins, especially cyclin D, cyclin-dependent kinases (4 and 6), and flow cytometry assessment of the cell cycle. This was associated with activation of AMPK, inhibition of the mTOR pathways and autophagy marker LC3B. However, metformin failed to suppress growth of xenografted tumors of Y79 human retinoblastoma cells in nu/nu mice, even when treated with a maximally tolerated dose level achieved in human patients. In conclusion, suprapharmacological levels (mM) of metformin, well above those tolerated in vivo, inhibited the proliferation of retinoblastoma cells in vitro. However, physiological levels of metformin, such as seen in the clinical setting, did not affect the growth of retinoblastoma cells in vitro or in vivo. This suggests that the potential beneficial effects of metformin seen in epidemiological studies may be limited to specific tumor types or be related to indirect effects/mechanisms not observed under acute laboratory conditions.

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

Metformin is a commonly used oral anti-hyperglycemic agent of the biguanide family. Recent studies suggest that metformin may reduce cancer risk and improve prognosis. However, the antitumor mechanism of metformin in several types of cancers, including hepatocellular carcinoma (HCC), has not been elucidated. The goal of the present study was to evaluate the effects of metformin on HCC cell proliferation in vitro and in vivo, and to study microRNAs (miRNAs) associated with the antitumor effect of metformin in vitro. We used the cell lines Alex, HLE and Huh7, and normal hepatocytes to study the effects of metformin on human HCC cells. In an in vivo study, athymic nude mice bearing xenograft tumors were treated with metformin or left untreated. Tumor growth was recorded after 4 weeks, and the expression of cell cycle-related proteins was determined. Metformin inhibited the proliferation of Alex, HLE and Huh7 cells in vitro and in vivo. Metformin blocked the cell cycle in G0/G1 in vitro and in vivo. This blockade was accompanied by a strong decrease of G1 cyclins, especially cyclin D1, cyclin E and cyclin-dependent kinase 4 (Cdk4). In addition, microRNA (miRNA) expression was markedly altered by the treatment with metformin in vitro and in vivo. In addition, various miRNAs induced by metformin also may contribute to the suppression of tumor growth. Our results demonstrate that metformin inhibits the growth of HCC, possibly by inducing G1 cell cycle arrest through the alteration of microRNAs.

Low and high linear energy transfer radiation sensitization of HCC cells by metformin

The purpose of this study was to investigate the efficacy of metformin as a radiosensitizer for use in combination therapy for human hepatocellular carcinoma (HCC). Three human HCC cell lines (Huh7, HepG2, Hep3B) and a normal human hepatocyte cell line were treated with metformin alone or with radiation followed by metformin. In vitro tests were evaluated by clonogenic survival assay, FACS analysis, western blotting, immunofluorescence and comet assay. Metformin significantly enhanced radiation efficacy under high and low Linear Energy Transfer (LET) radiation conditions in vitro. In combination with radiation, metformin abrogated G2/M arrest and increased the cell population in the sub-G1 phase and the ROS level, ultimately increasing HCC cellular apoptosis. Metformin inhibits the repair of DNA damage caused by radiation. The radiosensitizing effects of metformin are much higher in neutron (high LET)-irradiated cell lines than in γ (low LET)-irradiated cell lines. Metformin only had a moderate effect in normal hepatocytes. Metformin enhances the radiosensitivity of HCC, suggesting it may have clinical utility in combination cancer treatment with high-LET radiation.

New molecules and old drugs as emerging approaches to selectively target human glioblastoma cancer stem cells

Despite relevant progress obtained by multimodal treatment, glioblastoma (GBM), the most aggressive primary brain tumor, is still incurable. The most encouraging advancement of GBM drug research derives from the identification of cancer stem cells (CSCs), since these cells appear to represent the determinants of resistance to current standard therapies. The goal of most ongoing studies is to identify drugs able to affect CSCs biology, either inducing selective toxicity or differentiating this tumor cell population into nontumorigenic cells. Moreover, the therapeutic approach for GBM could be improved interfering with chemo- or radioresistance mechanisms, microenvironment signals, and the neoangiogenic process. During the last years, molecular targeted compounds such as sorafenib and old drugs, like metformin, displayed interesting efficacy in preclinical studies towards several tumors, including GBM, preferentially affecting CSC viability. In this review, the latest experimental results, controversies, and prospective application concerning these promising anticancer drugs will be discussed.

AMP-activated protein kinase suppresses the in vitro and in vivo proliferation of hepatocellular carcinoma

AMP-activated protein kinase (AMPK) is a central metabolic sensor and plays an important role in regulating glucose, lipid and cholesterol metabolism. Therefore, AMPK is a key therapeutic target in diabetes. Recent pilot studies have suggested that diabetes drugs may reduce the risk of cancer by affecting the AMPK pathway. However, the association between AMPK and the proliferation of hepatocellular carcinoma (HCC) is unknown. In this study, we investigated the relationship between AMPK activity and the proliferation of HCC in cell lines, nude mice and human clinic samples. We first investigated the relationship between AMPK activity and cell proliferation in two HCC cell lines, PLC/PRF/5 and HepG2, by two AMPK activators, 5-aminoimidazole-4-carboxamide-1-h-D-ribofuranoside (AICAR) and metformain. AICAR and metformin treatment significantly inhibited the proliferation of HCC cells and induced cell cycle arrest at G1-S checkpoint. We then observed that metformin abrogated the growth of HCC xenografts in nude mice. The clinical pathology of AMPK activity in HCC, including cell proliferation, differential grade, tumor size and microvessel density, was studied by using 30 clinical tissue samples. In HCC tissue samples, phosphorylated AMPK was expressed mainly in cytoplasm. AMPK activity decreased significantly in HCC in comparison with paracancerous liver tissues (P<0.05). AMPK activity was negatively correlated with the level of Ki-67 (a marker of cell proliferation), differential degradation and tumor size (P<0.05), but not with microvessel density, hemorrhage or necrosis in HCC. Our findings suggest that AMPK activity inhibits the proliferation of HCC and AMPK might be an effective target for prevention and treatment of HCC.

Metformin selectively targets tumor-initiating cells in ErbB2-overexpressing breast cancer models

Metformin is an oral biguanide used for type II diabetes. Epidemiologic studies suggest a link between metformin use and reduced risk of breast and other types of cancers. ErbB2-expressing breast cancer is a subgroup of tumors with poor prognosis. Previous studies demonstrated that metformin is a potent inhibitor of ErbB2-overexpressing breast cancer cells; metformin treatment extends the life span and impedes mammary tumor development in ErbB2 transgenic mice in vivo. However, the mechanisms of metformin associated antitumor activity, especially in prevention models, remain unclear. We report here for the first time that systemic administration of metformin selectively inhibits CD61(high)/CD49f(high) subpopulation, a group of tumor-initiating cells (TIC) of mouse mammary tumor virus (MMTV)-ErbB2 mammary tumors, in preneoplastic mammary glands. Metformin also inhibited CD61(high)/CD49f(high) subpopulation in MMTV-ErbB2 tumor-derived cells, which was correlated with their compromised tumor initiation/development in a syngeneic tumor graft model. Molecular analysis indicated that metformin induced downregulation of ErbB2 and EGFR expression and inhibited the phosphorylation of ErbB family members, insulin-like growth factor-1R, AKT, mTOR, and STAT3 in vivo. In vitro data indicate that low doses of metformin inhibited the self-renewal/proliferation of cancer stem cells (CSC)/TICs in ErbB2-overexpressing breast cancer cells. We further demonstrated that the expression and activation of ErbB2 were preferentially increased in CSC/TIC-enriched tumorsphere cells, which promoted their self-renewal/proliferation and rendered them more sensitive to metformin. Our results, especially the in vivo data, provide fundamental support for developing metformin-mediated preventive strategies targeting ErbB2-associated carcinogenesis.

Metformin suppresses hepatocellular carcinoma cell growth through induction of cell cycle G1/G0 phase arrest and p21CIP and p27KIP expression and downregulation of cyclin D1 in vitro and in vivo

Metformin is used as a first-line therapy for type 2 diabetes, with reports of its usefulness for the prevention and control of several types of cancers. This study investigated the effects of metformin on hepatocellular carcinoma (HCC). The human HCC cell lines HepG2 and PLC/PRF/5 were cultured and treated with metformin or 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), an activator of adenosine monophosphate (AMP)-activated protein kinase. Changes in cell viability and cell cycle distribution were evaluated by MTT and flow cytometry, respectively. Apoptosis was assessed by fluorescent-dye staining. An HCC model was established in 6- to 8-week-old BALB/c-nu mice by subcutaneous injection of PLC/PRF/5 cells. After 1 week, mice were treated intragastrically with metformin or vehicle. Tumor xenograft tissues were examined using immunohistochemistry for evaluation of the the expression of cyclin D1, p21CIP and p27KIP. HCC cells and tissues from the in vitro and in vivo experiments, respectively, were subjected to protein extraction and western blotting. We found that metformin treatment reduced HCC cell viability in a dose-dependent manner similar to AICAR treatment. In addition, metformin treatment induced HCC cell cycle arrest at G1/G0 phase and apoptosis. Intragastric treatment of the mouse PLC/PRF/5 cell xenograft model with metformin showed that metformin not only blocked tumor progression, but also reduced tumor morbidity. Treatment with metformin upregulated the expression of p21CIP and p27KIP, but downregulated cyclin D1 levels, both in vitro and in vivo. Metformin treatment also upregulated the expression of phosphorylated AMPK protein in xenograft tissues. These findings indicate that metformin warrants further evaluation as a novel therapeutic and preventive strategy against HCC.

Low concentration of metformin induces a p53-dependent senescence in hepatoma cells via activation of the AMPK pathway

The induction of senescence for cancer treatment has provoked considerable interest recently. Metformin, a first-line drug for diabetes mellitus type 2, appears to be associated with a lower risk and improved outcomes in hepatocellular carcinoma (HCC). The mechanism involved in function of metformin in HCC is poorly understood. We show that low doses of metformin induced hepatoma cell senescence characterized by accumulation of senescence-associated β-galactosidase activity (SA-β-gal) and the senescence marker Dec1, whereas the higher doses initiated apoptotic cell death. Metformin-induced senescence was accompanied by enhanced phosphorylation levels of AMP-activated protein kinase (AMPK) and its downstream target acetyl-CoA carboxylase (ACC). The expression of acetylated p53 at Lys382 (Ac-p53) and p21 was also increased, while phosphorylation of p53 at Ser15 (p-p53), p53, p16 and pRB was rarely altered after metformin treatment. Moreover, inhibition of AMPK decreased p-AMPK, p-ACC, Ac-p53 and p21 expression, diminished SA-β-gal staining and restored hepatoma cell proliferation. In addition, p53 siRNA transfection attenuated metformin-induced SA-β-gal staining. Intriguingly, co-expression of SIRT1 and p53 dramatically reduced the levels of Ac-p53, however, low doses of metformin treatment partially reversed the effect of SIRT1 on p53 acetylation and elevated SA-β-gal activity. These observations indicate that activation of the AMPK pathway promotes senescence in hepatoma cells exposed to low concentrations of metformin in a p53-dependent manner. Further, low doses of metformin may have the potential to be used as an adjuvant to HCC therapy.

The mTOR pathway in hepatic malignancies

The mechanistic/mammalian target of rapamycin (mTOR) pathway plays a critical role in cellular metabolism, growth, and proliferation and has been evaluated as a target for therapy in various malignancies. The mTOR pathway is a major tumor-initiating pathway in hepatocellular carcinoma, with up-regulation seen in up to 50% of tumors. Metformin, which represses mTOR signaling by activating adenosine monophosphate-activated protein kinase, has been shown to decrease liver carcinogenesis in population studies. mTOR inhibitors such as everolimus have been evaluated as adjunctive chemotherapy with some success, although efficacy has been limited by the lack of complete mTOR pathway inhibition. The active site mTOR inhibitors hold greater promise, given that they offer complete mTOR suppression. There is also evidence of mTOR pathway activation in cholangiocarcinoma, although its biological significance in initiating and promoting tumor progression remains ambiguous. This review provides an overview of the complex biochemistry behind the mTOR pathway and its role in carcinogenesis, especially as it pertains to hepatic malignancies.

Metformin, a diabetes drug, eliminates tumor-initiating hepatocellular carcinoma cells

Metformin has been widely used as an oral drug for diabetes mellitus for approximately 60 years. Interestingly, recent reports showed that metformin exhibited an anti-tumor action in a wide range of malignancies including hepatocellular carcinoma (HCC). In the present study, we investigated its impact on tumor-initiating HCC cells. Metformin suppressed cell growth and induced apoptosis in a dose-dependent manner. Flow cytometric analysis showed that metformin treatment markedly reduced the number of tumor-initiating epithelial cell adhesion molecule (EpCAM)⁺ HCC cells. Non-adherent sphere formation assays of EpCAM⁺ cells showed that metformin impaired not only their sphere-forming ability, but also their self-renewal capability. Consistent with this, immunostaining of spheres revealed that metformin significantly decreased the number of component cells positive for hepatic stem cell markers such as EpCAM and α-fetoprotein. In a xenograft transplantation model using non-obese diabetic/severe combined immunodeficient mice, metformin and/or sorafenib treatment suppressed the growth of tumors derived from transplanted HCC cells. Notably, the administration of metformin but not sorafenib decreased the number of EpCAM⁺ cells and impaired their self-renewal capability. As reported, metformin activated AMP-activated protein kinase (AMPK) through phosphorylation; however its inhibitory effect on the mammalian target of rapamycin (mTOR) pathway did not necessarily correlate with its anti-tumor activity toward EpCAM⁺ tumor-initiating HCC cells. These results indicate that metformin is a promising therapeutic agent for the elimination of tumor-initiating HCC cells and suggest as-yet-unknown functions other than its inhibitory effect on the AMPK/mTOR pathway.

Metformin and cancer

Type 2 diabetes mellitus is a rising cause of cardiovascular morbidity and mortality. A number of studies have also identified diabetic patients as having increased risk for the development of cancer. Metformin is a widely prescribed antidiabetic drug with an established efficacy coupled with a favorable safety profile and low cost. An increasing number of studies have associated metformin treatment with a decrease of cancer risk. Moreover, metformin has also been associated with improved outcomes in cancer patients. These possible pleiotropic effects of metformin may establish metformin as a cancer prevention and treatment option. However, any favorable effects of metformin on cancer are not always corroborated by clinical trials. Larger studies are expected to better investigate the possible antineoplastic effects of metformin.