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

Progress in Research of Nanotherapeutics for Overcoming Multidrug Resistance in Cancer

Chemotherapy has been widely applied in oncotherapy. However, the development of multidrug resistance (MDR) has diminished the effectiveness of anticancer drugs against tumor cells. Such resistance often results in tumor recurrence, metastasis, and patient death. Fortunately, nanoparticle-based drug delivery systems provide a promising strategy by codelivery of multiple drugs and MDR reversal agents and the skillful, flexible, smart modification of drug targets. Such systems have demonstrated the ability to bypass the ABC transporter biological efflux mechanisms due to drug resistance. Hence, how to deliver drugs and exert potential antitumor effects have been successfully explored, applied, and developed. Furthermore, to overcome multidrug resistance, nanoparticle-based systems have been developed due to their good therapeutic effect, low side effects, and high tumor metastasis inhibition. In view of this, we systematically discuss the molecular mechanisms and therapeutic strategies of MDR from nanotherapeutics. Finally, we summarize intriguing ideas and future trends for further research in overcoming MDR.

Metformin and its potential influence on cell fate decision between apoptosis and senescence in cancer, with a special emphasis on glioblastoma

Despite reaching enormous achievements in therapeutic approaches worldwide, GBM still remains the most incurable malignancy among various cancers. It emphasizes the necessity of adjuvant therapies from the perspectives of both patients and healthcare providers. Therefore, most emerging studies have focused on various complementary and adjuvant therapies. Among them, metabolic therapy has received special attention, and metformin has been considered as a treatment in various types of cancer, including GBM. It is clearly evident that reaching efficient approaches without a comprehensive evaluation of the key mechanisms is not possible. Among the studied mechanisms, one of the more challenging ones is the effect of metformin on apoptosis and senescence. Moreover, metformin is well known as an insulin sensitizer. However, if insulin signaling is facilitated in the tumor microenvironment, it may result in tumor growth. Therefore, to partially resolve some paradoxical issues, we conducted a narrative review of related studies to address the following questions as comprehensively as possible: 1) Does the improvement of cellular insulin function resulting from metformin have detrimental or beneficial effects on GBM cells? 2) If these effects are detrimental to GBM cells, which is more important: apoptosis or senescence? 3) What determines the cellular decision between apoptosis and senescence?

Current findings on the antitumor effects of metformin on esophageal squamous cell carcinoma (Review)

Esophageal squamous cell carcinoma (ESCC) is an intractable type of cancer that requires novel therapeutic modalities, since the therapeutic outcomes are often inadequate, even in response to multidisciplinary treatment. The antitumor effect of metformin, an antidiabetic drug, has been reported in esophageal cancer; however, its effects are diverse. Since various multidisciplinary therapies are used in ESCC, the antitumor effect of metformin is expected to be synergistic in some treatment strategies. The present review summarizes the antitumor effects of metformin and discusses its use in combination with existing therapies. The present study reviewed relevant studies where the molecular targets of metformin (AMPK and inflammatory system signals) were described, followed by the classification and organization of its antitumor effects, and subsequently summarized the current research on its antitumor effects, especially in ESCC. A number of studies have reported that metformin prevents the development of ESCC and exerts its antitumor effects through various pathways. In addition, metformin has been shown to inhibit tumor growth, induce apoptosis, inhibit cancer cell invasion, migration and angiogenesis into the tumor, and decrease tumor malignancy, such as metastasis. Furthermore, it may modulate host tumor immunity in a tumor-suppressive manner and is expected to improve prognosis following treatment for ESCC. Notably, metformin may be beneficial in combination with chemotherapy, such as cisplatin, and radiation. By contrast, it has been shown to potentially induce resistance to 5-fluorouracil. Finally, the effects of metformin in combination with other therapies are discussed in the present study, and perspectives on the potential benefits of metformin for future ESCC treatment are presented. In conclusion, the present review may be useful in improving the understanding of the wide range of antitumor effects of metformin. Although some concerning points remain, using metformin in ESCC treatment could be promising. Notably, more knowledge needs to be accumulated regarding the effects of metformin on ESCC.

Synergistic anticancer effects of doxorubicin and metformin combination therapy: A systematic review

INTRODUCTION

Doxorubicin (DOX) a chemotherapy drug often leads to the development of resistance, in cancer cells after prolonged treatment. Recent studies have suggested that using metformin plus doxorubicin could result in synergic effects. This study focuses on exploring the co-treat treatment of doxorubicin and metformin for various cancers.

METHOD

Following the PRISMA guidelines we conducted a literature search using different databases such as Embase, Scopus, Web of Sciences, PubMed, Science Direct and Google Scholar until July 2023. We selected search terms based on the objectives of this study. After screening a total of 30 articles were included.

RESULTS

The combination of doxorubicin and metformin demonstrated robust anticancer effects, surpassing the outcomes of monotherapy drug treatment. In vitro experiments consistently demonstrated inhibition of cancer cell growth and increased rates of cell death. Animal studies confirmed substantial reductions in tumor growth and improved survival rates, emphasizing the synergistic impact of the combined therapy. The research' discoveries collectively emphasize the capability of the co-treat doxorubicin-metformin as a compelling approach in cancer treatment, highlighting its potential to address medicate resistance and upgrade generally helpful results.

CONCLUSION

The findings of this study show that the combined treatment regimen including doxorubicin and metformin has significant promise in fighting cancer. The observed synergistic effects suggest that this combination therapy could be valuable, in a setting. This study highlights the need for clinical research to validate and enhance the application of the doxorubicin metformin regimen.

Metformin in Esophageal Carcinoma: Exploring Molecular Mechanisms and Therapeutic Insights

Esophageal cancer (EC) remains a formidable malignancy with limited treatment options and high mortality rates, necessitating the exploration of innovative therapeutic avenues. Through a systematic analysis of a multitude of studies, we synthesize the diverse findings related to metformin's influence on EC. This review comprehensively elucidates the intricate metabolic pathways and molecular mechanisms through which metformin may exert its anti-cancer effects. Key focus areas include its impact on insulin signaling, AMP-activated protein kinase (AMPK) activation, and the mTOR pathway, which collectively contribute to its role in mitigating esophageal cancer progression. This review critically examines the body of clinical and preclinical evidence surrounding the potential role of metformin, a widely prescribed anti-diabetic medication, in EC management. Our examination extends to the modulation of inflammation, oxidative stress and angiogenesis, revealing metformin's potential as a metabolic intervention in esophageal cancer pathogenesis. By consolidating epidemiological and clinical data, we assess the evidence that supports metformin's candidacy as an adjuvant therapy for esophageal cancer. By summarizing clinical and preclinical findings, our review aims to enhance our understanding of metformin's role in EC management, potentially improving patient care and outcomes.

Alpha-ketoglutarate supplementation reduces inflammation and thrombosis in type 2 diabetes by suppressing leukocyte and platelet activation

The interplay between platelets and leukocytes contributes to the pathogenesis of inflammation, thrombosis, and cardiovascular diseases (CVDs) in type 2 diabetes (T2D). Our recent studies described alpha-ketoglutarate (αKG), a Krebs cycle intermediate metabolite as an inhibitor to platelets and leukocytes activation by suppressing phosphorylated-Akt (pAkt) through augmentation of prolyl hydroxylase-2 (PHD2). Dietary supplementation with a pharmacological concentration of αKG significantly inhibited lung inflammation in mice with either SARS-CoV-2 infection or exposed to hypoxia treatment. We therefore investigated if αKG supplementation could suppress hyperactivation of these blood cells and reduce thromboinflammatory complications in T2D. Our study describes that dietary supplementation with αKG (8 mg/100 g body wt. daily) for 7 days significantly reduced the activation of platelets and leukocytes (neutrophils and monocytes), and accumulation of IL1β, TNFα, and IL6 in peripheral blood of T2D mice. αKG also reduced the infiltration of platelets and leukocytes, and accumulation of inflammatory cytokines in lungs by suppressing pAkt and pP65 signaling. In a cross-sectional investigation, our study also described the elevated platelet-leukocyte aggregates and pro-inflammatory cytokines in circulation of T2D patients. T2D platelets and leukocytes showed an increased aggregation and thrombus formation in vitro. Interestingly, a pre-incubation of T2D blood samples with octyl αKG significantly suppressed the activation of these blood cells and ameliorated aggregate/thrombus formation in vitro. Thus, suggesting a potential therapeutic role of αKG against inflammation, thrombosis, and CVDs in T2D.

Metformin suppressed tendon injury-induced adhesion via hydrogel-nanoparticle sustained-release system

Tendon adhesion is one of the sequelae of tendon injury and can lead to disability in severe cases. Metformin is a commonly used antidiabetic drug. Some studies had shown that metformin could reduce tendon adhesion as well. Considering the characteristic of low absorption rate and short half-life, we established a sustained-release system, i.e., hydrogel-nanoparticle system to deliver metformin. In vitro, metformin could effectively suppress TGF-β1-induced cell proliferation and accelerate cell apoptosis, according to cell counting kit-8, flow cytometry, and 5-ethynyl-2'-deoxyuridine (EdU) staining studies. In vivo, hydrogel-nanoparticle/metformin system could significantly lower adhesion scores and improve the gliding function of repaired flexor tendons, as well as decrease the expression of fibrotic proteins Col1a1, Col3a1, and α-smooth muscle actin (α-SMA). Histological staining revealed that the inflammation had subsided and that the gap between the tendon and the surrounding tissue was wider in the hydrogel-nanoparticle/metformin treatment group. Finally, we speculated that effect of metformin on reducing tendon adhesion might be achieved by regulating both Smad and MAPK-TGF-β1 signaling pathways. In conclusion, metformin delivered through hydrogel-nanoparticle sustained-release system may be a promising strategy for coping with tendon adhesion.

Decursin inhibits EGFR-ERK1/2 signaling axis in advanced human prostate carcinoma cells

We have shown that decursin, a coumarin compound, induces cell cycle arrest and apoptosis in human prostate cancer cells (PCa); however, its molecular mechanisms are largely unexplored. We studied the mechanisms associated with its anticancer activity in advanced human prostate carcinoma cells. We found that decursin inhibited epidermal growth factor receptor (EGFR) signaling by inhibiting its activating phosphorylation at tyrosine 1068 residue in DU145 and 22Rv1 cells. This inhibition of EGFR was associated with the downregulation of ERK1/2 phosphorylation. Both EGFR and ERK1/2 are known to be deregulated/activated in many human malignancies. Consistent with our earlier study, decursin (25-100 µM) treatment for 24-72 h inhibited DU145 cell proliferation by 49%-87% (p < 0.001) which was associated with strong G1 phase arrest and cell death. It also decreased (p < 0.001) the number of surviving colonies. Decursin moderately increased the expression of Rb-related proteins p107 and p130 but decreased the levels of E2F family transcription factors including E2F-3, E2F-4 and E2F-5. Further, decursin strongly inhibited the growth of androgen-dependent prostate carcinoma 22Rv1 cells from 61% to 79% (p < 0.001) and arrested these cells at G1 phase via induction of cyclin-dependent kinase inhibitor p27/Kip1 and downregulation of CDK2 and CDK4 protein expression. Additionally, EGFR inhibitor erlotinib- and EGF ligand-modulated EGFR activation validated EGFR signaling as a target of decursin-mediated cell growth inhibition and cytotoxicity. Decursin decreased EGF ligand-induced phosphorylation of EGFR (Y-1068) as well as activation of its downstream mediator, ERK1/2. Furthermore, inhibitory targeting of EGFR-ERK1/2 axis by combinatorial treatment of decursin and erlotinib further sensitized DU145 cells for the decursin-induced growth inhibition and cell death. Overall, these findings strongly suggest that anticancer efficacy of decursin against human PCa involves inhibitory targeting of EGFR-ERK1/2 signaling axis, a pathway constitutively active in advanced PCa.

Thyroid gland cancer and insulin resistance: a modern view of the problem

Background. The impact of insulin resistance on the probability of increase in thyroid cancer risk has been drawing a lot of attention of researchers lately. This problem is far from being completely solved. Studying this interrelationship may influence the effectiveness of the treatment of the mentioned widespread pathology. Purpose – to review present literature sources on research of interrelationship between insulin resistance and thyroid cancer, and also possible mechanisms of this relationship. Materials and methods. Literature search was performed manually by the keywords (thyroid cancer, insulin resistance, IGF-1, IGF-2, abdominal obesity, increase in body mass index, metformin), and also literature sources from evidential data bases PubMed, Web of Science were reviewed. Metaanalyses, systematic reviews and cohort studies were also taken into account. 148 literature sources were studied in total. The sources, which had been published within the last 10 years, were preferably selected. Results. Insulin resistance is viewed as an important independent factor of development of numerous malignancies. The carcinogenic activity of insulin resistance is caused by the resistance itself, as well as by the metabolic disorders related to it. It has been established that excessive weight and obesity are to a great extent attributed to more aggressive clinical pathological signs of thyroid cancer. Recent research showed a larger volume of thyroid and higher risk of knot forming in patients with insulin resistance. Thus, thyroid cancer is one of the main factors of thyroid transformation. Therapeutic methods of eliminating metabolic syndrome and associated hormonal diseases for prevention and therapy of oncologic diseases are drawing ever-greater scientific interest. The anti-tumor features of metformin and its capability of retarding carcinogenesis are shown in the studies. Conclusions. The given literature analysis has proved that the problem of treating malignant thyroid tumors and their metastasis is caused not only by morphological, cellular and molecular-biological features of the tumor itself, but also by insufficient knowledge about the interrelationship between insulin resistance, abdominal obesity, increase in body mass index, high-calorie diet and reduction of consumption of polyunsaturated fats, harmful impact of environment with molecular changes, specific for thyroid cancer. It is confirmed by a significant increase in thyroid cancer rate, especially papillary histotype, alongside with an increase in obesity rate. The studying of possibilities of decreasing incidence and mortality rates of oncologic pathology when using medications, which stabilize insulin and contribute to a decrease in degree of hyperinsulinemia, one of which is metformin, generates profound interest

Treat more than heat-New therapeutic implications of Cimicifuga racemosa through AMPK-dependent metabolic effects

BACKGROUND

Cimicifuga racemosa extracts (CRE) have obtained a "well-established use status" in the treatment of postmenopausal (i.e., climacteric) complaints, which predominantly include vasomotor symptoms such as hot flushes and sweating, as well as nervousness, irritability, and metabolic changes. Although characteristic postmenopausal complaints are known for a very long time and the beneficial effects of CRE on climacteric symptoms are well accepted, both the pathophysiology of postmenopausal symptoms and the mechanism of action of CREs are not yet fully understood. In particular, current hypotheses suggest that changes in the α-adrenergic and serotonergic signaling pathways secondary to estrogen depletion are responsible for the development of hot flushes.

PURPOSE

Some of the symptoms associated with menopause cannot be explained by these hypotheses. Therefore, we attempted to extend our classic understanding of menopause by integrating of partly age-related metabolic impairments.

METHODS

A comprehensive literature survey was performed using the PubMed database for articles published through September 2021. The following search terms were used: (cimicifuga OR AMPK) AND (hot flush* OR hot flash* OR menopaus* OR osteoporos* OR cancer OR antioxida* OR cardiovasc*). No limits were set with respect to language, and the references cited in the articles retrieved were used to identify additional publications.

RESULTS

We found that menopause is a manifestation of the general aging process, with specific metabolic changes that aggravate menopausal symptoms, which are accelerated by estrogen depletion and associated neurotransmitter dysregulation. Cimicifuga extracts with their metabolic effects mitigate climacteric symptoms but may also modulate the aging process itself. Central to these effects are effects of CRE on the metabolic key regulator, the AMP-activated protein kinase (AMPK).

CONCLUSIONS

As an extension of this effect dimension, other off-label indications may appear attractive in the sense of repurposing of this herbal treatment.

The role of AMPK-dependent pathways in cellular and molecular mechanisms of metformin: a new perspective for treatment and prevention of diseases

Metformin can suppress gluconeogenesis and reduce blood sugar by activating adenosine monophosphate-activated protein kinase (AMPK) and inducing small heterodimer partner (SHP) expression in the liver cells. The main mechanism of metformin's action is related to its activation of the AMPK enzyme and regulation of the energy balance. AMPK is a heterothermic serine/threonine kinase made of a catalytic alpha subunit and two subunits of beta and a gamma regulator. This enzyme can measure the intracellular ratio of AMP/ATP. If this ratio is high, the amino acid threonine 172 available in its alpha chain would be activated by the phosphorylated liver kinase B1 (LKB1), leading to AMPK activation. Several studies have indicated that apart from its significant role in the reduction of blood glucose level, metformin activates the AMPK enzyme that in turn has various efficient impacts on the regulation of various processes, including controlling inflammatory conditions, altering the differentiation pathway of immune and non-immune cell pathways, and the amelioration of various cancers, liver diseases, inflammatory bowel disease (IBD), kidney diseases, neurological disorders, etc. Metformin's activation of AMPK enables it to control inflammatory conditions, improve oxidative status, regulate the differentiation pathways of various cells, change the pathological process in various diseases, and finally have positive therapeutic effects on them. Due to the activation of AMPK and its role in regulating several subcellular signalling pathways, metformin can be effective in altering the cells' proliferation and differentiation pathways and eventually in the prevention and treatment of certain diseases.

Extracellular DNA Traps: Origin, Function and Implications for Anti-Cancer Therapies

Extracellular DNA may serve as marker in liquid biopsies to determine individual diagnosis and prognosis in cancer patients. Cell death or active release from various cell types, including immune cells can result in the release of DNA into the extracellular milieu. Neutrophils are important components of the innate immune system, controlling pathogens through phagocytosis and/or the release of neutrophil extracellular traps (NETs). NETs also promote tumor progression and metastasis, by modulating angiogenesis, anti-tumor immunity, blood clotting and inflammation and providing a supportive niche for metastasizing cancer cells. Besides neutrophils, other immune cells such as eosinophils, dendritic cells, monocytes/macrophages, mast cells, basophils and lymphocytes can also form extracellular traps (ETs) during cancer progression, indicating possible multiple origins of extracellular DNA in cancer. In this review, we summarize the pathomechanisms of ET formation generated by different cell types, and analyze these processes in the context of cancer. We also critically discuss potential ET-inhibiting agents, which may open new therapeutic strategies for cancer prevention and treatment.

Targeting Breast Cancer and Their Stem Cell Population through AMPK Activation: Novel Insights

Despite some significant advancements, breast cancer has become the most prevalent cancer in the world. One of the main reasons for failure in treatment and metastasis has been attributed to the presence of cancer initiating cells-cancer stem cells. Consequently, research is now being focussed on targeting cancer cells along with their stem cell population. Non-oncology drugs are gaining increasing attention for their potent anticancer activities. Metformin, a drug commonly used to treat type 2 diabetes, is the best example in this regard. It exerts its therapeutic action by activating 5' adenosine monophosphate-activated protein kinase (AMPK). Activated AMPK subsequently phosphorylates and targets several cellular pathways involved in cell growth and proliferation and the maintenance of stem-like properties of cancer stem cells. Therefore, AMPK is emerging as a target of choice for developing effective anticancer drugs. Vanadium compounds are well-known PTP inhibitors and AMPK activators. They find extensive applications in treatment of diabetes and obesity via PTP1B inhibition and AMPK-mediated inhibition of adipogenesis. However, their role in targeting cancer stem cells has not been explored yet. This review is an attempt to establish the applications of insulin mimetic vanadium compounds for the treatment of breast cancer by AMPK activation and PTP1B inhibition pathways.

Dual anticancer role of metformin: an old drug regulating AMPK dependent/independent pathways in metabolic, oncogenic/tumorsuppresing and immunity context

Metformin has been known to treat type 2 diabetes for decades and is widely prescribed antidiabetic drug. Recently, its anticancer potential has also been discovered. Moreover, metformin has low cost thus it has attained profound research interest. Comprehensing the complexity of the molecular regulatory networks in cancer provides a mode for advancement of research in cancer development and treatment. Metformin targets many pathways that play an important role in cancer cell survival outcome. Here, we described anticancer activity of metformin on the AMPK dependent/independent mechanisms regulating metabolism, oncogene/tumor suppressor signaling pathways together with the issue of clinical studies. We also provided brief overwiev about recently described metformin's role in cancer immunity. Insight in these complex molecular networks, will simplify application of metformin in clinical trials and contribute to improvement of anti-cancer therapy.

Metformin inhibits the proliferation of canine mammary gland tumor cells through the AMPK/AKT/mTOR signaling pathway in vitro

As an anti-diabetic drug, metformin has been demonstrated to exhibit antitumor effects. However, the mechanisms involved in decreasing tumor formation, including canine mammary gland tumors (CMGTs), are not well elucidated. The aim of the present study was to evaluate the ability of metformin to induce apoptosis and cell cycle arrest in CMGT cells, as well as identifying the pathways underlying these effects. Cell viability was assessed by Cell Counting Kit-8 analysis following treating with metformin. Subsequently, apoptosis and cell cycle progression were assessed by flow cytometry, and the expression of associated proteins was examined. Expression levels of classical AMP-activated protein kinase (AMPK), protein kinase B (AKT), mechanistic target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) were then investigated using western blot analysis. Metformin inhibited the proliferation of CHMm cells in a concentration-dependent manner. Specifically, metformin induced cell cycle arrest in the G₀/G₁ phases, accompanied by increased expression of p21 and p27, and decreased expression of cyclin D1 and cyclin-dependent kinase 4. Marked levels of apoptosis were observed in CHMm cells alongside the activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase. Also, the level of Bcl-2 was decreased, and that of Bax was increased. The expression of associated signaling molecules revealed that metformin markedly increased the phosphorylation of AMPK in CHMm cells, and decreased the levels of phosphorylated (p-)AKT, p-mTOR and p-4E-BP1, while Compound C reversed these changes. These findings demonstrated that metformin may be a potential therapeutic agent for CMGTs, acting via the AMPK/AKT/mTOR signaling pathway.

Metformin exerts anti-AR-negative prostate cancer activity via AMPK/autophagy signaling pathway

BACKGROUND

Encouraged by the goal of developing an effective treatment strategy for prostate cancer, this study explored the mechanism involved in metformin-mediated inhibition of AR-negative prostate cancer.

METHODS

Cell behaviors of DU145 and PC3 cells were determined by CCK8 test, colony formation experiment and scratch test. Flow cytometry was used to detect cell cycle distribution. Cell autophagy was induced with metformin, and an autophagy inhibitor, 3-MA, was used to assess the level of autophagy. Detection of LC3B by immunofluorescence was conducted to determine autophagy level. Cell proliferation, autophagy and cell cycle were examined by performing Western blot. DU145 and PC3 cell lines were transfected with AMPK siRNA targeting AMPK-α1 and AMPK-α2. Tumor formation experiment was carried out to evaluate the anti-prostate cancer effect of metformin in vivo.

RESULTS

The inhibitory effect of metformin on the proliferation of prostate cancer cell lines was confirmed in this study, and the mechanism of such an effect was related to autophagy and the block of cell cycle at G0/G1 phase. Metformin also induced the activation of AMPK, markedly promoted expression of LC3II, and down-regulated the expression of p62/SQSTM1. Animal experiments showed that the tumor volume of metformin group was smaller, meanwhile, the levels of p-AMPK (Thr172) and LC3B were up-regulated and the Ki-67 level was down-regulated, without abnormalities in biochemical indicators.

CONCLUSION

This study found that autophagy induction might be the mechanism through which metformin suppressed the growth of AR-negative prostate cancer. Moreover, the activation of AMPK/autophagy pathway might be a therapeutically effective for treating AR-negative prostate cancer in the future.

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

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

Metformin and insulin-resistant related diseases: Emphasis on the role of microRNAs

Metformin is one of the most prescribed drugs in type II diabetes (T2DM) which has recently found new applications in the prevention and treatment of various illnesses, from metabolic disorders to cardiovascular and age-related diseases. Metformin improves insulin resistance (IR) by modulating metabolic mechanisms and mitochondrial biogenesis. Alternation of microRNAs (miRs) in the treatment of IR-related illnesses has been observed by metformin therapy. MiRs are small non-coding RNAs that play important roles in RNA silencing, targeting the 3'untranslated region (3'UTR) of most mRNAs and inhibiting the translation of related proteins. As a result, their dysregulation is associated with many diseases. Metformin may alter miRs levels in the treatment of various diseases by AMPK-dependent or AMPK-independent mechanisms. Here, we summarized the therapeutic role of metformin by modifying the aberrant expression of miRs as potential biomarkers or therapeutic targets in diseases in which IR plays a key role.

PARP-1 overexpression does not protect HaCaT cells from DNA damage induced by SiO2 nanoparticles

Nano-SiO₂ is increasingly used in diagnostic and biomedical research because of its ease of production and relatively low cost and which is generally regarded as safe and has been approved for use as a food or animal feed ingredient. Although recent literature reveals that nano-SiO₂ may present toxicity and DNA damage, however, the underlying mechanism remains poorly understood. Since in previous studies, we found that nano-SiO₂ treatment down-regulated the expression of the poly(ADP-ribose) polymerases-1 (PARP-1), a pivotal DNA repair gene, in human HaCaT cells and PAPR-1 knockdown can aggravate DNA damage induced by nano-SiO₂. Therefore, we speculate whether PARP-1 overexpression can protect DNA from damage induced by nano-SiO₂. However, our data demonstrated that overexpression of PARP-1 in HaCaT cells slightly enhanced the cellular proliferation of undamaged cells, when compared with both empty vector control cells and parental cells, but had drastic consequences for cells treated with nano-SiO₂. The PARP-1 overtransfected cells were sensitized to the cytotoxic effects and DNA damage of nano-SiO₂ compared with control parental cells. Meanwhile, flow cytometric analysis of nano-SiO₂ stimulated poly(ADP-ribose) synthesis revealed consistently larger fractions of cells positive for this polymer in the PARP-1 overexpression cells than in control clones. Combining our previous research on PARP-1 knockdown HaCaT cells, we hypothesize that an optimal level of cellular poly(ADP-ribose) accumulation exists for the cellular recovery from DNA damage.

Nuclear Magnetic Resonance-Based Metabolomic Analysis of the Anticancer Effect of Metformin Treatment on Cholangiocarcinoma Cells

Metformin is a widely prescribed anti-diabetes drug with potential utilities for cancer therapies. Several studies have related metformin to the reduced risk of cholangiocarcinoma (CCA), highlighting its potentialities for the treatments of CCA. However, the underlying molecular mechanisms remain elusive. Here, we demonstrated that metformin treatment could inhibit proliferations of the human CCA cell lines Mz-ChA-1 and QBC939 in dose-dependent manners. The NMR-based metabonomic analyses showed distinct discriminations between the metformin-treated (Met) and control (Ctrl) groups of both CCA cells. Characteristic metabolites were identified by a combination of multivariate statistical analysis of 1D ¹H-NMR spectral data and the pair-wise t-test of metabolite levels. We then identified four significantly altered metabolic pathways based on the characteristic metabolites, including glucose metabolism, oxidative stress-related metabolism, energy metabolism, and amino acids metabolism. Comparing CCA cells with normal human umbilical vein endothelial cells (HUVECs), we found that metformin treatment profoundly promoted glycolysis and specifically increased the levels of BCAAs and UDP-GlcNAc, implying the occurrence of autophagy and cell cycle arrest in metformin-treated CAA cells. This work provides a mechanistic understanding of the anticancer effect of metformin treatment on CAA cells, and is beneficial to further developments of metformin as an anticancer drug.

Autophagy mitigates ethanol-induced mitochondrial dysfunction and oxidative stress in esophageal keratinocytes

During alcohol consumption, the esophageal mucosa is directly exposed to high concentrations of ethanol (EtOH). We therefore investigated the response of normal human esophageal epithelial cell lines EPC1, EPC2 and EPC3 to acute EtOH exposure. While these cells were able to tolerate 2% EtOH for 8 h in both three-dimensional organoids and monolayer culture conditions, RNA sequencing suggested that EtOH induced mitochondrial dysfunction. With EtOH treatment, EPC1 and EPC2 cells also demonstrated decreased mitochondrial ATPB protein expression by immunofluorescence and swollen mitochondria lacking intact cristae by transmission electron microscopy. Mitochondrial membrane potential (ΔΨm) was decreased in a subset of EPC1 and EPC2 cells stained with ΔΨm–sensitive dye MitoTracker Deep Red. In EPC2, EtOH decreased ATP level while impairing mitochondrial respiration and electron transportation chain functions, as determined by ATP fluorometric assay, respirometry, and liquid chromatography-mass spectrometry. Additionally, EPC2 cells demonstrated enhanced oxidative stress by flow cytometry for mitochondrial superoxide (MitoSOX), which was antagonized by the mitochondria-specific antioxidant MitoCP. Concurrently, EPC1 and EPC2 cells underwent autophagy following EtOH exposure, as evidenced by flow cytometry for Cyto-ID, which detects autophagic vesicles, and immunoblots demonstrating induction of the lipidated and cleaved form of LC3B and downregulation of SQSTM1/p62. In EPC1 and EPC2, pharmacological inhibition of autophagy flux by chloroquine increased mitochondrial oxidative stress while decreasing cell viability. In EPC2, autophagy induction was coupled with phosphorylation of AMP activated protein kinase (AMPK), a cellular energy sensor responding to low ATP levels, and dephosphorylation of downstream substrates of mechanistic Target of Rapamycin Complex (mTORC)-1 signaling. Pharmacological AMPK activation by AICAR decreased EtOH-induced reduction of ΔΨm and ATP in EPC2. Taken together, acute EtOH exposure leads to mitochondrial dysfunction and oxidative stress in esophageal keratinocytes, where the AMPK-mTORC1 axis may serve as a regulatory mechanism to activate autophagy to provide cytoprotection against EtOH-induced cell injury.

Metformin sensitizes therapeutic agents and improves outcome in pre-clinical and clinical diffuse large B-cell lymphoma

BACKGROUND

The treatment of diffuse large B-cell lymphoma (DLBCL) is limited by the development of resistance to therapy, and there is a need to develop novel therapeutic strategies for relapsed and refractory aggressive lymphoma. Metformin is an oral agent for type 2 diabetes that has been shown to decrease cancer risk and lower mortality in other types of cancer.

METHODS

We performed a retrospective analysis of the RPCCC database looking at patients with DLBCL treated with front-line chemotherapy. We also performed pre-clinical studies looking at the effect of metformin on cell viability, cell number, Ki67, ATP production, apoptosis, ROS production, mitochondrial membrane potential, cell cycle, effect with chemotherapeutic agents, and rituximab. Finally, we studied mouse models to see the anti-tumor effect of metformin.

RESULTS

Among diabetic patients, metformin use was associated with improved progression-free survival (PFS) and overall survival (OS) compared to diabetic patients not on metformin. Our pre-clinical studies showed metformin is itself capable of anti-tumor effects and causes cell cycle arrest in the G1 phase. Metformin induces apoptosis, ROS production, and increased mitochondrial membrane permeability. Metformin exhibited additive/synergistic effects when combined with traditional chemotherapy or rituximab in vitro. In vivo, metformin in combination with rituximab showed improved survival compared with rituximab monotherapy.

CONCLUSIONS

Our retrospective analysis showed that metformin with front-line chemotherapy in diabetic patients resulted in improved PFS and OS. Our pre-clinical studies demonstrate metformin has potential to re-sensitize resistant lymphoma to the chemo-immunotherapy and allow us to develop a hypothesis as to its activity in DLBCL.

Antidiabetic drug metformin affects the developmental competence of cleavage-stage embryos

PURPOSE

Metformin is the most commonly prescribed drug in the management of metabolic disorders such as polycystic ovarian syndrome (PCOS) and gestational diabetes in women of reproductive age. Insulin-sensitizing effect of metformin helps in improving from PCOS features such as hyperandrogenism, anovulation, and infertility. However, its ability to cross placental barrier raises concern about safety of the drug on early embryonic development. In this study, we evaluated the effect of metformin on the ovarian function and embryo development.

METHODS

Adult Swiss albino female mice were administered with metformin (0, 50, 100, and 200 mg/kg body weight) for 4 weeks and assessed for reproductive function and preimplantation embryo development. Further, effect of metformin (0, 10, 25, 50, 100, 250, and 500 μg/mL) exposure to 2-cell-stage embryos was tested under in vitro conditions.

RESULTS

Metformin did not alter the body weight, blood glucose, ovarian weight, and follicular reserve. However, the early embryo development was significantly affected in mice treated with metformin in vivo at highest dose. Moreover, embryos which were exposed to metformin in vitro showed dose-dependent decline in blastocyst rate and hatching rate. Furthermore, at highest concentration of metformin (500 μg/mL), all the embryos were arrested at compaction stage.

CONCLUSION

The study revealed that metformin affects the early embryonic development and raises concern about its use during conception.

Canagliflozin impairs blood reperfusion of ischaemic lower limb partially by inhibiting the retention and paracrine function of bone marrow derived mesenchymal stem cells

Background

Canagliflozin (CANA) administration increases the risk of lower limb amputation in the clinic. The present study aimed to investigate whether and how CANA interferes with the intracellular physiological processes of bone marrow derived mesenchymal stem cells (BM-MSCs) and its contribution to ischaemic lower limb.

Methods

The in vivo blood flow recovery in ischaemic lower limbs following CANA treatment was evaluated. The cellular function of BM-MSCs after CANA treatment were also assessed in vitro. In silico docking analysis and mutant substitution assay were conducted to confirm the interaction of CANA with glutamate dehydrogenase 1 (GDH1).

Findings

Following CANA treatment, attenuated angiogenesis and hampered blood flow recovery in the ischaemic region were detected in diabetic and non-diabetic mice, and inhibition of the proliferation and migration of BM-MSCs were also observed. CANA was involved in mitochondrial respiratory malfunction in BM-MSCs and the inhibition of ATP production, cytochrome c release and vessel endothelial growth factor A (VEGFA) secretion, which may contribute to reductions in the tissue repair capacity of BM-MSCs. The detrimental effects of CANA on MSCs result from the inhibition of GDH1 by CANA (evidenced by in silico docking analysis and H199A-GDH1/N392A-GDH1 mutant substitution).

Interpretation

Our work highlights that the inhibition of GDH1 activity by CANA interferes with the metabolic activity of the mitochondria, and this interference deteriorates the retention of and VEGFA secretion by MSCs.

Funding

National Natural Science Foundation of China, Natural Science Foundation of Zhejiang Province and Wenzhou Science and Technology Bureau Foundation.

Silence of cZNF292 suppresses the growth, migration, and invasion of human esophageal cancer Eca-109 cells via upregulating miR-206

Circular RNA (circRNA) cZNF292 has been previously revealed as a circular oncogenic RNA. This study attempted to illustrate the functions of cZNF292 in human esophageal carcinoma Eca-109 cells. Eca-109 cells were transfected with the short hairpin RNA specific against cZNF292 (sh-cZNF292) and/or miR-206 inhibitor. cZNF292 and miR-206 expression was examined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Cell counting kit-8 and flow cytometry were performed for detecting cell growth including cell viability as well as apoptosis. Various kinds of factors, which are involved in cell development including proliferation, apoptosis, migration, and invasion were determined by western blot analysis. Besides, the activation of AMP-activated protein kinase (AMPK) and PI3K/AKT signaling was measured by western blot analysis. It was found that cZNF292 silencing decreased Eca-109 cell viability and induced apoptosis. In the meantime, cZNF292 silencing inhibited cell migration and invasion. cZNF292 silencing upregulated miR-206 expression. And miR-206 downregulation impaired the suppressive effects of cZNF292 silence toward Eca-109 cell growth, migration, and invasion. cZNF292 silencing activated AMPK signaling and inactivated PI3K/AKT signaling also via regulating miR-206. In conclusion, silencing of cZNF292 abated growth, migration, and invasion of Eca-109 cells by upregulating miR-206, which subsequently modulated AMPK and PI3K/AKT signaling pathways.

Metformin inhibits cell proliferation in SKM-1 cells via AMPK-mediated cell cycle arrest

Metformin, a widely used antidiabetic drug, has previously been demonstrated to exert anti-cancer effects in certain hematological malignancies, but its effects on the transformation of myelodysplastic syndromes to acute myeloid leukemia (AML-MDS) remain unclear. The present study aimed to investigate the effects of metformin on SKM-1 cells (an AML-MDS cell line) and its underlying mechanisms. SKM-1 cells were treated with different concentrations of metformin. Cell proliferation was assayed by CCK-8. Apoptosis and cell cycle phases were detected by flow cytometry, while cell cycle related proteins and AMPK were tested by Western blot. SKM-1 cells were transfected with LV-AMPKα1-RNAi to reduce the expression of AMPK. Metformin inhibited cell proliferation in a dose and time dependent manner by inducing G0/G1 phase arrest rather than apoptosis induction. Metformin promoted the expression of p-AMPK, P53, P21^CIP1 and P27^KIP1, while inhibited the expression of CDK4 and CyclinD1. AMPK knockdown attenuated the effects of metformin on SKM-1 cells. These findings suggested that metformin inhibited proliferation of SKM-1 cells, potentially through an AMPK-mediated cell cycle arrest.

Changing expression profiles of lncRNAs, circRNAs and mRNAs in esophageal squamous carcinoma

Abundant evidence indicates that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) serve important roles in tumorigenesis and tumour progression. However, their diagnostic and treatment value for esophageal squamous carcinoma (ESCC) remains unknown. A microarray (SBC human ceRNA array V1.0) was performed to assess the expression profiles and biological functions of lncRNAs, circRNAs and mRNAs in ESCC and para-cancerous tissues from three patients. Microarray data were validated by reverse transcription-quantitative polymerase chain reaction for a group of genes. A number of lncRNA-microRNAs (miRNA) and circRNA-miRNA-mRNA networks were constructed. Bioinformatics tools, including gene ontology and Kyoto Encyclopedia of Genes and Genomes biological pathway analyses, were used to predict the functions of differentially expressed lncRNAs, circRNAs and potentially co-expressed target genes. The results revealed that compared with the expression levels of para-cancerous tissues, 1,384 lncRNAs, 2,046 circRNAs and 936 mRNAs were frequently altered in ESCC tissues. Co-expression networks of lncRNAs-miRNAs-circRNAs-mRNAs were constructed based on the correlation analyses among the differentially expressed RNAs. Furthermore, using bioinformatics methods, correlation expression networks were constructed that included cis- and trans-regulatory elements. Therefore, these results suggest that lncRNAs and circRNAs may be involved in the pathogenesis and development of ESCC. These findings provide a novel and systematic perspective on the potential function of noncoding RNAs in ESCC.

The chronic effect of amorphous silica nanoparticles and benzo[a]pyrene co-exposure at low dose in human bronchial epithelial BEAS-2B cells

As the main components of fine particulate matter (PM2.5), silica nanoparticles (SiNPs) and benzo[a]pyrene (B[a]P) have attracted increasing attention recently. However, co-exposure to SiNPs and B[a]P causes pulmonary injury by aggravating toxicity via an unknown mechanism. This study aimed at investigating the toxicity caused due to long-term co-exposure to SiNPs and B[a]P on pulmonary systems at low dose using human bronchial epithelial (BEAS-2B) cells. The characterizations of SiNPs and B[a]P were done by transmission electron microscopy (TEM) and zeta potential granulometry. Cytotoxicity is evaluated using cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) activity; oxidative stress, cell cycle and apoptosis were assessed by flow cytometry, and inflammatory factors were detected using a Luminex xMAP system. Results show an obvious inhibition of cell proliferation and a marked increase in the LDH expression in the BEAS-2B cells after long-term co-exposure. Furthermore, long-term co-exposure is the most potent in generating intracellular ROS, thus causing inflammation. Cellular apoptotic rate is enhanced in the co-exposed group at low dose. Moreover, the long-term co-exposure induces significant cell cycle arrest, increasing the proportion of cells at the G2/M phase, while decreasing those at the G0/G1 phase. This study is the first attempt to reveal the severe synergistic and additive toxic effects induced by SiNPs and B[a]P co-exposure for long-term in BEAS-2B cells even at low dose.

Mahanine, A dietary phytochemical, represses mammary tumor burden in rat and inhibits subtype regardless breast cancer progression through suppressing self-renewal of breast cancer stem cells

Mahanine (MH), a carbazole alkaloid isolated from an edible plant (Murraya koenigii), potentially inhibits the growth of altered subtypes of breast cancer cells in vitro and significantly reduced the mammary tumor burden in N-Methyl-N-nitrosourea (MNU) induced rat. The experimental results showed that 20-25 μM of MH for 24 h of treatment was very potent to reduce the cell proliferation through apoptosis with arresting the cells in G₀/G₁ in both ER⁺/p53^WT MCF-7 and triple negative/p53^Mut MDA-MB-231 cells. On the other hand, 10-15 μM of MH exposure to those two cell lines, caused inhibition of mammosphere formation and reduction of CD44^high/CD24^low/epithelial-specific antigen-positive (ESA+) population, which ultimately led to loss of self-renewal ability of breast cancer stem cells. Further, in vivo observation indicated that intraperitoneal injection of MH for four weeks with a dose of 50 mg/kg body weight thrice in a week, significantly (P =  0.03) reduced the mammary tumor weight in MNU induced rat. In conclusion, this study provides the novel insight into the mechanism of MH mediated growth arrest in subtype irrespective breast cancer progression.

Mauritian Endemic Medicinal Plant Extracts Induce G2/M Phase Cell Cycle Arrest and Growth Inhibition of Oesophageal Squamous Cell Carcinoma in Vitro

Terrestrial plants have contributed massively to the development of modern oncologic drugs. Despite the wide acceptance of Mauritian endemic flowering plants in traditional medicine, scientific evidence of their chemotherapeutic potential is lacking. This study aimed to evaluate the in vitro tumor cytotoxicity of leaf extracts from five Mauritian endemic medicinal plants, namely Acalypha integrifolia Willd (Euphorbiaceae), Labourdonnaisia glauca Bojer (Sapotaceae), Dombeya acutangula Cav. subsp. rosea Friedmann (Malvaceae), Gaertnera psychotrioides (DC.) Baker (Rubiaceae), and Eugenia tinifolia Lam (Myrtaceae). The cytotoxicities of the extracts were determined against six human cancer cell lines, including cervical adenocarcinoma, colorectal carcinoma, oesophageal adenocarcinoma, and oesophageal squamous cell carcinoma. The potent extracts were further investigated using cell cycle analysis and reverse phase protein array (RPPA) analysis. The antioxidant properties and polyphenolic profile of the potent extracts were also evaluated. Gas chromatography mass spectrometry (GC-MS) analyses revealed the presence of (+)-catechin and gallocatechin in E. tinifolia and L. glauca, while gallic acid was detected in A. integrifolia. L. glauca, A. integrifolia, and E. tinifolia were highly selective towards human oesophageal squamous cell carcinoma (KYSE-30) cells. L. glauca and E. tinifolia arrested KYSE- 30 cells in the G2/M phase, in a concentration-dependent manner. RPPA analysis indicated that the extracts may partly exert their tumor growth-inhibitory activity by upregulating the intracellular level of 5'AMP-activated kinase (AMPK). The findings highlight the potent antiproliferative activity of three Mauritian endemic leaf extracts against oesophageal squamous cell carcinoma and calls for further investigation into their chemotherapeutic application.

Placenta-specific 9, a putative secretory protein, induces G2/M arrest and inhibits the proliferation of human embryonic hepatic cells

Background: Placenta-specific 9 (Plac9) is a putative secreted protein that was first discovered in the context of embryogenesis. The expression pattern of Plac9 during embryogenesis, together with the results of recent reports, suggest that Plac9 may play a role in the liver development. The present study was conducted to investigate the secretory characteristics of Plac9 and its potential role in liver cell physiology. Methods: Immunofluorescence was employed to identify the subcellular distribution of Plac9. Cellular proliferative activity was analyzed by MTT assay and cell colony formation. The cell cycle distribution of Plac9 was analyzed by flow cytometry, and a functional analysis was performed using L02 cells following their stable infection with a lentivirus over-expressing Plac9. Results:Plac9 is a novel protein that is localized to the cytoplasm and may be secreted through the classic endoplasmic reticulum-Golgi route. The overexpression of Plac9 inhibits cell growth and induces G2/M phase arrest. Conclusion: Our findings reveal a novel role for Plac9 in regulating cell growth.

Synchronized Ratiometric Codelivery of Metformin and Topotecan through Engineered Nanocarrier Facilitates In Vivo Synergistic Precision Levels at Tumor Site

The combination of metabolic modulators with chemotherapy holds vast promise for effective inhibition of tumor progression and invasion. Herein, a ratiometric codelivery platform is developed for metformin (MET), a known metabolic modulator and topotecan (TPT), a chemotherapeutic drug, by engineering lipid bilayer-camouflaged mesoporous silica nanoparticles (LB-MSNs). In an attempt to deliver and maintain high tumor site concentrations of MET and TPT, a novel ion pairing-assisted loading procedure is developed using pamoic acid (PA) as an in situ trapping agent. PA, a hydrophobic counterion, increases the hydrophobicity of MET and TPT and facilitates MSNs with exceptionally high payload capacity (>40 and 32 wt%, respectively) and controlled release profile. Further, the synergy between MET and TPT determined by a modeling approach helps to afford synchronized delivery of both the drugs. Coloaded MET and TPT LB-MSNs present synergistic cytotoxicity against MDA-MB-231/4T1 cells and effectively promote apoptosis via mitochondrial membrane depolarization and cell cycle arrest. Extended pharmacokinetic profiles in preclinical models with fourfold to sevenfold longer circulation half-life and 7.5-100 times higher tumor site concentrations correspond to a significant increase in pharmacodynamic efficacy. Taken together, the developed codelivery approach effectively addresses the challenges in the chemotherapeutic efficacy of MET and TPT collectively.

Efficacy of metformin in mediating cellular uptake and inducing apoptosis activity of doxorubicin

The clinical use of doxorubicin (DOX) is limited due to its systemic side effects and drug resistance. Recent evidence suggests that metformin prevents and controls certain but not all types of cancer. The beneficial use of metformin in combination with some chemotherapeutic agents has been reported. The aim of this study is to investigate the influence of metformin on DOX-induced effects in human prostate DU145 cancer cells and clarify its molecular mechanisms. For this purpose, DU145 cells were treated with DOX or metformin, either alone or in combination with each other. The proliferation of DU145 cells was inhibited by DOX-alone and metformin-alone treatment in a time and dose-dependent manner. Metformin could enhance the cytotoxicity of DOX by increasing DOX cellular uptake and cell cycle arrest at G1/S checkpoint which is associated with the enhancement of p21 protein expression. Moreover, metformin could elevate DOX-induced apoptosis in DU145 cells in a concentration-dependent manner and DOX-induced caspase-3 activity. These findings suggest that the combined treatment of metformin with DOX potentiates the anticancer efficacy of DOX in DU145 cells via inhibiting ABCB1 function, cell cycle arrest at G1/S transition and apoptosis induction.

Blastocyst-Derived Stem Cell Populations under Stress: Impact of Nutrition and Metabolism on Stem Cell Potency Loss and Miscarriage

Data from in vitro and in vivo models suggest that malnutrition and stress trigger adaptive responses, leading to small for gestational age (SGA) blastocysts with fewer cell numbers. These stress responses are initially adaptive, but become maladaptive with increasing stress exposures. The common stress responses of the blastocyst-derived stem cells, pluripotent embryonic and multipotent placental trophoblast stem cells (ESCs and TSCs), are decreased growth and potency, and increased, imbalanced and irreversible differentiation. SGA embryos may fail to produce sufficient antiluteolytic placental hormone to maintain corpus luteum progesterone secretion that provides nutrition at the implantation site. Myriad stress inputs for the stem cells in the embryo can occur in vitro during in vitro fertilization/assisted reproductive technology (IVF/ART) or in vivo. Paradoxically, stresses that diminish stem cell growth lead to a higher level of differentiation simultaneously which further decreases ESC or TSC numbers in an attempt to functionally compensate for fewer cells. In addition, prolonged or strong stress can cause irreversible differentiation. Resultant stem cell depletion is proposed as a cause of miscarriage via a "quiet" death of an ostensibly adaptive response of stem cells instead of a reactive, violent loss of stem cells or their differentiated progenies.

Metformin inhibits the migration and invasion of esophageal squamous cell carcinoma cells by downregulating the protein kinase B signaling pathway

Previous studies have suggested that metformin, a biguanide family member widely used as an oral antidiabetic drug, may inhibit proliferation and induce apoptosis in certain types of cancer cell. However, the molecular mechanisms underlying metformin-associated anticancer effects, and in particular antimetastatic effects, remain to be fully understood. The present study assessed the efficacy of metformin in inhibiting the migration and invasion of the esophageal carcinoma cell line EC109, and evaluated the effect of metformin on the protein kinase B (AKT) signaling pathway. EC109 cells were treated with 0, 5, 10 or 20 mM metformin during the logarithmic growth phase. A Transwell assay and western blot analysis revealed that metformin inhibited the migration and invasion of EC109 cells, nuclear factor-κB activation, matrix metallopeptidase 9 and N-cadherin expression in a phosphorylated-AKT dependent manner. These results suggested that metformin inhibits the migration and invasion of human esophageal carcinoma cells by suppressing AKT phosphorylation and regulating the expression of migration- and invasion-associated genes.

Antitumor effects of metformin are a result of inhibiting nuclear factor kappa B nuclear translocation in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is an intractable digestive organ cancer that has proven difficult to treat despite multidisciplinary therapy, and a new treatment strategy is demanded. Metformin is used for type 2 diabetes mellitus and its antitumor effects have been reported recently. Metformin exerts antitumor effects in various respects, such as inhibiting inflammation, tumor growth and epithelial‐mesenchymal transition (EMT). However, few reports have described the efficacy of metformin on ESCC, and their findings have been controversial. We analyzed the antitumor effects of metformin and clarified its effects on anti‐inflammation, growth suppression and EMT inhibition. Activation of nuclear factor kappa B (NF‐κB), the major transcription factor induced by inflammation, was investigated by immunostaining. We found that localization of NF‐κB in the nucleus was reduced after metformin treatment. This suggests that metformin inhibited the activation of NF‐κB. Metformin inhibited tumor growth and induced apoptosis in ESCC cell lines. Associated with EMT, we examined cell motility by a wound healing assay and the epithelial marker E‐cadherin expression of various ESCC cell lines by western blotting. Metformin inhibited cell motility and induced E‐cadherin expression. In conclusion, metformin showed multiple antitumor effects such as growth suppression, invasion inhibition, and control of EMT by inhibiting NF‐κB localization on ESCC. Further exploration of the marker of treatment efficacy and combination therapy could result in the possibility for novel treatment to use metformin on ESCC.

Pre-clinical effects of metformin and aspirin on the cell lines of different breast cancer subtypes

Background Breast cancer is highly prevalent among women worldwide. It is classified into three main subtypes: estrogen receptor positive (ER+), human epidermal growth factor receptor 2 positive (HER2+), and triple negative breast cancer (TNBC). This study has evaluated the effects of aspirin and metformin, isolated or in a combination, in breast cancer cells of the different subtypes. Methods The breast cancer cell lines MCF-7, MDA-MB-231, and SK-BR-3 were treated with aspirin and/or metformin (0.01 mM - 10 mM); functional in vitro assays were performed. The interactions with the estrogen receptors (ER) were evaluated in silico. Results Metformin (2.5, 5 and 10 mM) altered the morphology and reduced the viability and migration of the ER+ cell line MCF-7, whereas aspirin triggered this effect only at 10 mM. A synergistic effect for the combination of metformin and aspirin (2.5, 5 or 10 mM each) was observed in the TNBC cell subtype MDA-MB-231, according to the evaluation of its viability and colony formation. Partial inhibitory effects were observed for either of the drugs in the HER2+ cell subtype SK-BR-3. The effects of metformin and aspirin partly relied on cyclooxygenase-2 (COX-2) upregulation, without the production of lipoxins. In silico, metformin and aspirin bound to the ERα receptor with the same energy. Conclusion We have provided novel evidence on the mechanisms of action of aspirin and metformin in breast cancer cells, showing favorable outcomes for these drugs in the ER+ and TNBC subtypes.

Metformin pharmacogenomics: a genome-wide association study to identify genetic and epigenetic biomarkers involved in metformin anticancer response using human lymphoblastoid cell lines

Metformin is currently considered as a promising anticancer agent in addition to its anti-diabetic effect. To better individualize metformin therapy and explore novel molecular mechanisms in cancer treatment, we conducted a pharmacogenomic study using 266 lymphoblastoid cell lines (LCLs). Metformin cytotoxicity assay was performed using the MTS assay. Genome-wide association (GWA) analyses were performed in LCLs using 1.3 million SNPs, 485k DNA methylation probes, 54k mRNA expression probe sets, and metformin cytotoxicity (IC50s). Top candidate genes were functionally validated using siRNA screening, followed by MTS assay in breast cancer cell lines. Further study of one top candidate, STUB1, was performed to elucidate the mechanisms by which STUB1 might contribute to metformin action. GWA analyses in LCLs identified 198 mRNA expression probe sets, 12 SNP loci, and 5 DNA methylation loci associated with metformin IC50 with P-values <10−4 or <10−5. Integrated SNP/methylation loci-expression-IC50 analyses found 3 SNP loci or 5 DNA methylation loci associated with metformin IC50 through trans-regulation of expression of 11 or 26 genes with P-value <10−4. Functional validation of top 61 candidate genes in 4 IPA networks indicated down regulation of 14 genes significantly altered metformin sensitivity in two breast cancer cell lines. Mechanistic studies revealed that the E3 ubiquitin ligase, STUB1, could influence metformin response by facilitating proteasome-mediated degradation of cyclin A. GWAS using a genomic data-enriched LCL model system, together with functional and mechanistic studies using cancer cell lines, help us to identify novel genetic and epigenetic biomarkers involved in metformin anticancer response.

Long noncoding RNA MALAT1 promotes malignant development of esophageal squamous cell carcinoma by targeting β-catenin via Ezh2

Evidences have shown that lncRNAs involve in the initiation and progression of various cancers including esophageal squamous cell carcinoma (ESCC). The aberrant expression of lncRNA MALAT1 was investigated in 106 paired ESCC tissues and adjacent non-cancerous tissues by qRT-PCR. Down-regulated MALAT1 and Ezh2 over-expression plasmid were constructed respectively to analyze the expression of β-catenin, Lin28 and Ezh2 genes. We found that the MALAT1 expression level was higher in human ESCC tissues (P=0.0011), which was closely correlated with WHO grade (P=0.0395, P=0.0331), lymph node metastasis (P=0.0213) and prognosis (P=0.0294). Silencing of MALAT1 expression inhibited cell proliferation, migration and tumor sphere formation, while increasing cell apoptosis of esophageal cancer in vitro. Down-regulation of MALAT1 decreased the expression of β-catenin, Lin28 and Ezh2 genes, while over-expressed Ezh2 combined with MALAT1 down-regulation completely reversed the si-MALAT1-mediated repression of β-catenin and Lin28 in esophageal cancer cells. Animal experiments showed that knockdown of MALAT1 decreased tumor formation and improved survival. MALAT1 promotes the initiation and progression of ESCC, suggesting that inhibition of MALAT1 might be a potential target for treatment of ESCC.

Metformin-induced activation of AMPK inhibits the proliferation and migration of human aortic smooth muscle cells through upregulation of p53 and IFI16

The proliferation and migration of vascular smooth muscle cells are significant in the development and progression of atherosclerosis and plaque rupture. Metformin is a widely used antidiabetic drug, which has been reported to inhibit cell growth and migration. The antiproliferative and antimigratory effects of metformin have been attributed to 5′ adenosine monophosphate-activated protein kinase (AMPK) activation. The purpose of the present study was to investigate the effects of metformin on primary human aortic muscle cells (HASMCs) in vitro and to clarify the underlying mechanism. We investigated the effectiveness of metformin in inhibiting the proliferation and migration of HASMCs in vitro using RNA extraction and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), cell number counting, cell viability assay, cell cycle assay and cell migration assay. Through transfection with small interfering (si)RNA targeting p53 and interferon-inducible protein 16 (IFI16), the roles of p53 and IFI16 in these processes were evaluated. The present study demonstrated that p53, IFI16 and AMPK were upregulated in senescent primary HASMCs, which exhibited a decrease in proliferation and migration. In addition, metformin was able to activate p53, IFI16 and AMPK, in order to inhibit proliferation and migration of HASMCs. Furthermore, siRNA-mediated knockdown of p53 and IFI16 attenuated AMPK activation and reversed the suppressive effects of metformin. Notably, in response to metformin, the activation of AMPK was not observed in p53- and IFI16-silenced HASMCs. These results indicated that metformin-induced activation of AMPK suppresses the proliferation and migration of HASMCs by upregulating p53 and IFI16. These findings suggested that metformin may have potential use in the treatment of atherosclerosis.

Disulfiram with or without metformin inhibits oesophageal squamous cell carcinoma in vivo

Oesophageal squamous cell carcinoma (OSCC) is highly prevalent in developing countries but there has been little recent progress into efficacious yet affordable treatment strategies. Drug repurposing is one attractive approach for cancer therapy. Disulfiram (DSF), used to treat alcoholism, inhibits cancer growth and we previously found that DSF perturbs protein degradation/turnover pathways in vitro. This was enhanced by combining DSF with the anti-diabetic drug metformin (Met). Here, we investigated DSF with/without Met, against OSCC in vivo. Nude mice injected subcutaneously with the human OSCC cell line WHCO1, were treated with 30 mg/kg or 50 mg/kg DSF three times per week and with/without Met, for 21 days. DSF and DSF/Met-treated animals had significantly smaller tumours compared to untreated, vehicle and positive control cisplatin-treated groups. This effect for DSF was independent of copper, with no significant accumulation of copper in tumours, together with maintained proteasome activity. However, increases in total ubiquitinated proteins, LC3B-II, LAMP1 and p62 in DSF and DSF/Met groups, indicate that autophagy is inhibited. These findings show that DSF and DSF/Met significantly impede OSCC tumour growth in vivo and offer prospective alternative chemotherapy approaches for OSCC.

Oroxyloside inhibits human glioma progression by suppressing proliferation, metastasis and inducing apoptosis related pathways

Malignant glioma are linked to a high mortality rate. Therefore, it is necessary to explore and develop effective therapeutic strategy. Oroxyloside is a metabolite of oroxylin A. However, its inhibitory effects on cancer are little to be known. In the present study, we investigated the effects of oroxyloside on cell proliferation, migration, and apoptosis in vitro and in vivo in human glioma. The results indicated that oroxyloside significantly suppressed the proliferation of human glioma cells through inducing cell cycle arrest at G0/G1 phase through reducing Cyclin D1 and cyclin-dependent kinase 2 (CDK2) while enhancing p53 and p21 expressions. In addition, the migration of glioma cells was dramatically inhibited by oroxyloside in a dose-dependent manner, which was related to its modulation on extracellular matrix (ECM), as evidenced by up-regulated E-cadherin, and metastasis-associated protein 3 (MTA3), whereas down-regulated N-cadherin, Vimentin, Twist, alpha-smooth muscle actin (α-SMA) and Syndecan-2. Furthermore, oroxyloside treatment markedly induced apoptosis in glioma cells through improving Caspase-9, Caspase-3 and PARP cleavage, accompanied with high release of cytochrome c (Cyto-c) into cytoplasm and subsequently increase of apoptotic protease-activating factor 1 (Apaf-1). In vivo, oroxyloside administration significantly inhibited the glioma cell xenograft tumorigenesis through various signaling pathways, including suppression of Cyclin D1/CDK2 and ECM pathways, as well as potentiation of p53/p21 and Caspases pathways. Together, the findings above illustrated that oroxyloside, for the first time, was used as a promising candidate against human glioma.

Metformin and esophageal cancer risk in Taiwanese patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce esophageal cancer risk. Patients with type 2 diabetes mellitus diagnosed during 1999–2005 were recruited from the reimbursement database of Taiwan's National Health Insurance. Those newly treated with metformin (n = 288013, “ever users of metformin”) or other antidiabetic drugs (n = 16216, “never users of metformin”) were followed until December 31, 2011. Sensitivity analyses were conducted in a matched-pair sample of 16216 never users and 16216 ever users. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. The risk associated with infection of Helicobacter pylori, Epstein-Barr virus, hepatitis B virus and hepatitis C virus was also evaluated. Results showed that the incidence of esophageal cancer in ever and never users was 25.03 and 50.87 per 100,000 person-years, respectively. The overall hazard ratio (95% confidence intervals) of 0.487 (0.347–0.684) suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (< 21.47 months), second (21.47–46.00 months) and third (> 46.00 months) tertile of cumulative duration of metformin use to never users was 1.184 (0.834–1.680), 0.403 (0.276–0.588) and 0.113 (0.071–0.179), respectively. Infection of Helicobacter pylori (but not the other viral infections) significantly increased the risk, which could be ameliorated by metformin. Analyses in the matched sample consistently supported a protective role of metformin. In conclusion, metformin reduces esophageal cancer risk when the cumulative duration is more than approximately 2 years.

Metformin prevents peritendinous fibrosis by inhibiting transforming growth factor-β signaling

Injury-induced peritendinous adhesion is a critical clinical problem that leads to tendon function impairment. Therefore, it is very urgent to explore potential approaches to attenuate peritendinous adhesion formation. Recently, several studies have demonstrated the biological effect of metformin in inhibiting multiple tissue fibrosis. In this study, we performed in vitro and in vivo experiments to examine whether metformin prevents injury-induced peritendinous fibrosis. We found that tendon injury induced severe fibrosis formation in rats. However, orally administered metformin significantly alleviated the fibrosis based on macroscopic and histological evaluation. Peritendinous tissue from metformin-treated rats also showed decreased expression of fibrotic genes including col1a1, col3a1, and α-smooth muscle actin (α-SMA), and inhibition of transforming growth factor (TGF)-β1 signaling. The cell counting kit (CCK)-8, flow cytometry, and 5-ethynyl-2′-deoxyuridine (EdU) staining analyses showed that treatment of NIH/3T3 fibroblasts with metformin significantly inhibited excessive cell proliferation and promoted cell apoptosis. Metformin treatment also inhibited the expression of fibrotic genes and decreased the phosphorylation of smad2/3 and extracellular signal-regulated kinase (ERK) 1/2. Furthermore, blocking AMP-activated protein kinase (AMPK) signaling abolished the inhibitory effect of metformin on fibrosis. Our findings indicate that metformin has a protective role against peritendinous tissue fibrosis and suggest its clinical use could be a promising therapeutic approach.

5-Aminoimidazole-4-carboxamide ribonucleotide prevents fat gain following the cessation of voluntary physical activity

NEW FINDINGS

What is the central question of this study? We investigated whether 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) could prevent acute increases in body fat and changes in omental and subcutaneous adipose tissue following the sudden transition from physical activity to physical inactivity. What is the main finding and its importance? AICAR prevented fat gains following the transition from physical activity to inactivity to levels comparable to rats that remained physically active. AICAR and continuous physical activity produced depot-specific changes in cyclin A1 mRNA and protein that were associated with the prevention of fat gain. These findings suggest that targeting AMP-activated protein kinase signalling could oppose rapid adipose mass growth. The transition from physical activity to inactivity is associated with drastic increases in 'catch-up' fat that in turn foster the development of many obesity-associated maladies. We tested whether 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) treatment would prevent gains in body fat following the sudden transition from a physically active state to an inactive state by locking a voluntary running wheel. Male Wistar rats were either sedentary (SED) or given wheel access for 4 weeks, at which time rats with wheels continued running (RUN), had their wheel locked (WL) or had WL with daily AICAR injection (WL + AICAR) for 1 week. RUN and WL + AICAR prevented gains in body fat compared with SED and WL (P < 0.001). Cyclin A1 mRNA, a marker of cell proliferation, was decreased in omental, but not subcutaneous adipose tissue, in RUN and WL + AICAR compared with SED and WL groups (P < 0.05). Both cyclin A1 mRNA and protein were positively associated with gains in fat mass (P < 0.05). Cyclin A1 mRNA in omental, but not subcutaneous, adipose tissue was negatively correlated with p-AMPK levels (P < 0.05). Differences in fat gain and omental mRNA and protein levels were independent of changes in food intake and in differences in select hypothalamic mRNAs. These findings suggest that AICAR treatment prevents acute gains in adipose tissue following physical inactivity to levels of rats that continuously run, and that together, continuous physical activity and AICAR could, at least initially in these conditions, exert similar inhibitory effects on adipogenesis in a depot-specific manner.

Marketed drugs used for the management of hypercholesterolemia as anticancer armament

The design of novel pharmacologic agents as well as their approval for sale in markets all over the world is a tedious and pricey process. Inevitably, oncologic patients commonly experience unwanted effects of new anticancer drugs, while the acquisition of clinical experience for these drugs is largely based on doctor–patient partnership which is not always effective. The repositioning of marketed non-antineoplastic drugs that hopefully exhibit anticancer properties into the field of oncology is a challenging option that gains ground and attracts preclinical and clinical research in an effort to override all these hindrances and minimize the risk for reduced efficacy and/or personalized toxicity. This review aims to present the anticancer properties of drugs used for the management of hypercholesterolemia. A global view of the antitumorigenicity of all marketed antihypercholesterolemic drugs is of major importance, given that atherosclerosis, which is etiologically linked to hypercholesterolemia, is a leading worldwide cause of morbidity and mortality, while hypercholesterolemia and tumorigenesis are known to be interrelated. In vitro, in vivo and clinical literature data accumulated so far outline the mechanistic basis of the antitumor function of these agents and how they could find application at the clinical setting.