Anti-tumor activity of metformin: from metabolic and epigenetic perspectives

Targeting the Epigenetic Marks in Type 2 Diabetes Mellitus: Will Epigenetic Therapy Be a Valuable Adjunct to Pharmacotherapy?

Although genetic, environmental, and lifestyle factors largely contribute to type 2 diabetes mellitus (T2DM) risk, the role of epigenetics in its pathogenesis is now well established. The epigenetic mechanisms in T2DM mainly consist of DNA methylation, histone modifications and regulation by noncoding RNAs (ncRNAs). For instance, DNA methylation at CpG islands in the promoter regions of specific genes encoding insulin signaling and glucose metabolism suppresses these genes. Modulating the enzyme mediators of these epigenetic marks aims to restore standard gene expression patterns and improve glycemic control. In targeting these epigenetic marks, using epigenetic drugs such as DNA methyltransferase (DNAMT), histone deacetylase (HDAC) and histone acetyltransferase (HAT) inhibitors has led to variable success in humans and experimental murine models. Specifically, the United States' Food and Drug Administration (US FDA) has approved DNAMT inhibitors like 5-azacytidine and 5-aza-2'-deoxycytidine for use in diabetic retinopathy: a T2DM microvascular complication. These DNAMT inhibitors block the genes for methylation of mitochondrial superoxide dismutase 2 (SOD2) and matrix metallopeptidase 9 (MMP-9): the epigenetic marks in diabetic retinopathy. Traditional pharmacotherapy with metformin also have epigenetic effects in T2DM and positively alter disease outcomes when combined with epigenetic drugs like DNAMT and HDAC inhibitors, raising the prospect of using epigenetic therapy as a valuable adjunct to pharmacotherapy. However, introducing small interfering RNAs (siRNAs) in cells to silence specific target genes remains in the exploratory phase. Future research should focus on regulating gene expression in T2DM using long noncoding RNA (lncRNA) molecules, another type of ncRNA. This review discusses the epigenetics of T2DM and that of its macro- and microvascular complications, and the potential benefits of combining epigenetic therapy with pharmacotherapy for optimal results.

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.

Activation of AMPK inhibits cervical cancer growth by hyperacetylation of H3K9 through PCAF

BACKGROUND

Dysregulation in histone acetylation, a significant epigenetic alteration closely associated with major pathologies including cancer, promotes tumorigenesis, inactivating tumor-suppressor genes and activating oncogenic pathways. AMP-activated protein kinase (AMPK) is a cellular energy sensor that regulates a multitude of biological processes. Although a number of studies have identified the mechanisms by which AMPK regulates cancer growth, the underlying epigenetic mechanisms remain unknown.

METHODS

The impact of metformin, an AMPK activator, on cervical cancer was evaluated through assessments of cell viability, tumor xenograft model, pan-acetylation analysis, and the role of the AMPK-PCAF-H3K9ac signaling pathway. Using label-free quantitative acetylproteomics and chromatin immunoprecipitation-sequencing (ChIP) technology, the activation of AMPK-induced H3K9 acetylation was further investigated.

RESULTS

In this study, we found that metformin, acting as an AMPK agonist, activates AMPK, thereby inhibiting the proliferation of cervical cancer both in vitro and in vivo. Mechanistically, AMPK activation induces H3K9 acetylation at epigenetic level, leading to chromatin remodeling in cervical cancer. This also enhances the binding of H3K9ac to the promoter regions of multiple tumor suppressor genes, thereby promoting their transcriptional activation. Furthermore, the absence of PCAF renders AMPK activation incapable of inducing H3K9 acetylation.

CONCLUSIONS

In conclusion, our findings demonstrate that AMPK mediates the inhibition of cervical cancer growth through PCAF-dependent H3K9 acetylation. This discovery not only facilitates the clinical application of metformin but also underscores the essential role of PCAF in AMPK activation-induced H3K9 hyperacetylation.

Repurposing of atorvastatin and metformin denotes their individual and combined antiproliferative effects in non-small cell lung cancer

BACKGROUND

Due to the limited success in the treatment of lung adenocarcinomas, new treatment protocols are urgently needed to increase the curability rate and the survival of lung cancer patients.

OBJECTIVES

Although statins, like atorvastatin (Ator), and metformin (Met) are widely accepted as hypolipidemic and hypoglycemic drugs, respectively, there are many predictions about their enhancing antitumor effect when they are combined with traditional chemotherapeutics.

METHODS

The individual and combined antiproliferative potential of Ator and Met was tested by MTT-assay in non-small cell lung cancer (NSCLC) A549 cell line, compared to the corresponding effect of Gemcitabine (Gem) with implication on the mechanisms of action.

RESULTS

Initially, both drugs demonstrated concentration-dependent cytotoxicity in A549 cells. Also, their combination index (CI) indicated their synergistic effect at equi-IC50 concentration (CI = 0.00984). Moreover, Ator and/or Met-treated cells revealed disrupted patterns of SOD, CAT, GSH, MDA, and TAC, developed apoptosis, and larger fractions of the cell population were arrested in G0/G1 phase, particularly in cells dually-treated both Ator and Met. These observations were accompanied by downregulation in the expression of iNOS, HO-1, and the angiogenic marker VEGF, meanwhile, an altered expression of MAPK and AMPK was observed.

CONCLUSION

Conclusively, these data suggest that repurposing of Ator and Met demonstrates their individual and combined antiproliferative effect in non-small cell lung cancer and they may adopt a similar mechanism of action.

An effective treatment approach of liposomally encapsulated metformin in colon cancer

Metformin is a drug that is widely used in the treatment of type-2 diabetes and its anticarcinogenic effect has been detected in many studies since the 2000s. Metformin has a short half-life and poor biocompatibility, which limits the activity of the drug. As a solution to this situation, our study aimed to increase the anticarcinogenic effects and reduce the side effects of metformin in colon cancer by liposomal encapsulation. For this purpose, in our study, liposome production was carried out using the thin film hydration method. The amount of metformin loaded in liposomes was determined by a standard absorbance curve at 237 nm. Size distributions and membrane zeta potentials of the liposomes were evaluated with Malvern Zetasizer ZS90. Transmission electron microscopy was performed by staining the liposomes negatively with uranyl acetate. Cultured HT-29 cells were treated with liposomal metformin or free metformin at concentrations of 0, 10, 20, and 40 mM for 24 and 48 h. At the end of the treatment period, cell viability was evaluated by CellTiter-Glo luminescent cell viability test. The anticarcinogenic effects of liposomal and free metformin on HT-29 cells were compared. As a result, liposome encapsulated metformin treatment for 24 h was more effective on HT-29 cells at 20- and 40-mM concentrations causing significantly greater decrease in the IC-50 dose compared to the free metformin. The result suggests that liposomal encapsulated metformin may offer a promising approach to increase the efficacy of the drug in the treatment of colon cancer.

Metformin-mediated epigenetic modifications in diabetes and associated conditions: Biological and clinical relevance

An intricate interplay between genetic and environmental factors contributes to the development of type 2 diabetes (T2D) and its complications. Therefore, it is not surprising that the epigenome also plays a crucial role in the pathogenesis of T2D. Hyperglycemia can indeed trigger epigenetic modifications, thereby regulating different gene expression patterns. Such epigenetic changes can persist after normalizing serum glucose concentrations, suggesting the presence of a 'metabolic memory' of previous hyperglycemia which may also be epigenetically regulated. Metformin, a derivative of biguanide known to reduce serum glucose concentrations in patients with T2D, appears to exert additional pleiotropic effects that are mediated by multiple epigenetic modifications. Such modifications have been reported in various organs, tissues, and cellular compartments and appear to account for the effects of metformin on glycemic control as well as local and systemic inflammation, oxidant stress, and fibrosis. This review discusses the emerging evidence regarding the reported metformin-mediated epigenetic modifications, particularly on short and long non-coding RNAs, DNA methylation, and histone proteins post-translational modifications, their biological and clinical significance, potential therapeutic applications, and future research directions.

Metformin is a metabolic modulator and radiosensitiser in rectal cancer

Resistance to neoadjuvant chemoradiation therapy, is a major challenge in the management of rectal cancer. Increasing evidence supports a role for altered energy metabolism in the resistance of tumours to anti-cancer therapy, suggesting that targeting tumour metabolism may have potential as a novel therapeutic strategy to boost treatment response. In this study, the impact of metformin on the radiosensitivity of colorectal cancer cells, and the potential mechanisms of action of metformin-mediated radiosensitisation were investigated. Metformin treatment was demonstrated to significantly radiosensitise both radiosensitive and radioresistant colorectal cancer cells in vitro. Transcriptomic and functional analysis demonstrated metformin-mediated alterations to energy metabolism, mitochondrial function, cell cycle distribution and progression, cell death and antioxidant levels in colorectal cancer cells. Using ex vivo models, metformin treatment significantly inhibited oxidative phosphorylation and glycolysis in treatment naïve rectal cancer biopsies, without affecting the real-time metabolic profile of non-cancer rectal tissue. Importantly, metformin treatment differentially altered the protein secretome of rectal cancer tissue when compared to non-cancer rectal tissue. Together these data highlight the potential utility of metformin as an anti-metabolic radiosensitiser in rectal cancer.

Natural Products for the Prevention, Treatment and Progression of Breast Cancer

In this review, we summarize the most used natural products as useful adjuvants in BC by clarifying how these products may play a critical role in the prevention, treatment and progression of this disease. BC is the leading cancer, in terms of incidence, that affects women. The epidemiology and pathophysiology of BC were widely reported. Inflammation and cancer are known to influence each other in several tumors. In the case of BC, the inflammatory component precedes the development of the neoplasm through a slowly increasing and prolonged inflammation that also favors its growth. BC therapy involves a multidisciplinary approach comprising surgery, radiotherapy and chemotherapy. There are numerous observations that showed that the effects of some natural substances, which, in integration with the classic protocols, can be used not only for prevention or integration in order to prevent recurrences and induce a state of chemoquiescence but also as chemo- and radiosensitizers during classic therapy.

Metformin: new applications for an old drug

Metformin is a biguanide, evolved as one of the most widely used medicines. The applications of this component include but are not limited to reducing blood glucose, weight loss, and polycystic ovary syndrome. Studies about other probable indications have emerged, indicating that this agent can also be utilized for other purposes. In this review, applications of metformin are noticed based on the current evidence. Metformin commonly is used as an off-label drug in non-alcoholic fatty liver disease (NAFLD), but it worsens inflammation and should not be used for this purpose, according to the latest research. Metformin decreased the risk of death in patients with liver cirrhosis. It is an effective agent in the prevention and improvement of survival in patients suffering hepatocellular carcinoma. There is evidence of the beneficial effects of metformin in colorectal cancer, early-stage prostate cancer, breast cancer, urothelial cancer, blood cancer, melanoma, and bone cancer, suggesting metformin as a potent anti-tumor agent. Metformin shows neuroprotective effects and provides a potential therapeutic benefit for mild cognitive impairment and Alzheimer's disease (AD). It also has been shown to improve mental function and reduce the incidence of dementia. Another condition that metformin has been shown to slow the progression of is Duchenne muscular dystrophy. Regarding infectious diseases, tuberculosis (TB) and coronavirus disease (COVID-19) are among the conditions suggested to be affected by metformin. The beneficial effects of metformin in cardiovascular diseases were also reported in the literature. Concerning renal function, studies showed that daily oral administration of metformin could ameliorate kidney fibrosis and normalize kidney structure and function. This study reviewed the clinical and preclinical evidence about the possible benefits of metformin based on recent studies. Numerous questions like whether these probable indications of metformin can be observed in non-diabetics, need to be described by future basic experiments and clinical studies.

Action Mechanism of Metformin and Its Application in Hematological Malignancy Treatments: A Review

Hematologic malignancies (HMs) mainly include acute and chronic leukemia, lymphoma, myeloma and other heterogeneous tumors that seriously threaten human life and health. The common effective treatments are radiotherapy, chemotherapy and hematopoietic stem cell transplantation (HSCT), which have limited options and are prone to tumor recurrence and (or) drug resistance. Metformin is the first-line drug for the treatment of type 2 diabetes (T2DM). Recently, studies identified the potential anti-cancer ability of metformin in both T2DM patients and patients that are non-diabetic. The latest epidemiological and preclinical studies suggested a potential benefit of metformin in the prevention and treatment of patients with HM. The mechanism may involve the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway by metformin as well as other AMPK-independent pathways to exert anti-cancer properties. In addition, combining current conventional anti-cancer drugs with metformin may improve the efficacy and reduce adverse drug reactions. Therefore, metformin can also be used as an adjuvant therapeutic agent for HM. This paper highlights the anti-hyperglycemic effects and potential anti-cancer effects of metformin, and also compiles the in vitro and clinical trials of metformin as an anti-cancer and chemosensitizing agent for the treatment of HM. The need for future research on the use of metformin in the treatment of HM is indicated.

Metformin Induces Apoptosis in Human Pancreatic Cancer (PC) Cells Accompanied by Changes in the Levels of Histone Acetyltransferases (Particularly, p300/CBP-Associated Factor (PCAF) Protein Levels)

Accumulating evidence (mainly from experimental research) suggests that metformin possesses anticancer properties through the induction of apoptosis and inhibition of the growth and proliferation of cancer cells. However, its effect on the enzymes responsible for histone acetylation status, which plays a key role in carcinogenesis, remains unclear. Therefore, the aim of our study was to evaluate the impact of metformin on histone acetyltransferases (HATs) (i.e., p300/CBP-associated factor (PCAF), p300, and CBP) and on histone deacetylases (HDACs) (i.e., SIRT-1 in human pancreatic cancer (PC) cell lines, 1.2B4, and PANC-1). The cells were exposed to metformin, an HAT inhibitor (HATi), or a combination of an HATi with metformin for 24, 48, or 72 h. Cell viability was determined using an MTT assay, and the percentage of early apoptotic cells was determined with an Annexin V-Cy3 Apoptosis Detection Assay Kit. Caspase-9 activity was also assessed. SIRT-1, PCAF, p300, and CBP expression were determined at the mRNA and protein levels using RT-PCR and Western blotting methods, respectively. Our results reveal an increase in caspase-9 in response to the metformin, indicating that it induced the apoptotic death of both 1.2B4 and PANC-1 cells. The number of cells in early apoptosis and the activity of caspase-9 decreased when treated with an HATi alone or a combination of an HATi with metformin, as compared to metformin alone. Moreover, metformin, an HATi, and a combination of an HATi with metformin also modified the mRNA expression of SIRT-1, PCAF, CBP, and p300. However, metformin did not change the expression of the studied genes in 1.2B4 cells. The results of the Western blot analysis showed that metformin diminished the protein expression of PCAF in both the 1.2B4 and PANC-1 cells. Hence, it appears possible that PCAF may be involved in the metformin-mediated apoptosis of PC cells.

Lipids Alterations Associated with Metformin in Healthy Subjects: An Investigation Using Mass Spectrometry Shotgun Approach

Metformin is an orally effective insulin-sensitizing drug widely prescribed for treating type 2 diabetes mellitus (T2DM). Metformin has been reported to alter lipid metabolism. However, the molecular mechanisms behind its impact on lipid metabolism remain partially explored and understood. In the current study, mass spectrometry-based lipid profiling was used to investigate the lipidomic changes in the serum of 26 healthy individuals after a single-dose intake of metformin. Samples were analyzed at five-time points: preadministration, before the maximum concentration of metformin (Cmax), Cmax, after Cmax, and 36 h post-administration. A total of 762 molecules were significantly altered between the five-time points. Based on a comparison between baseline level and Cmax, metformin significantly increased and decreased the level of 33 and 192 lipids, respectively (FDR ≤ 0.05 and fold change cutoff of 1.5). The altered lipids are mainly involved in arachidonic acid metabolism, steroid hormone biosynthesis, and glycerophospholipid metabolism. Furthermore, several lipids acted in an opposed or similar manner to metformin levels and included fatty acyls, sterol lipids, glycerolipids, and glycerophospholipids. The significantly altered lipid species pointed to fundamental lipid signaling pathways that could be linked to the pleiotropic effects of metformin in T2DM, insulin resistance, polycystic ovary syndrome, cancer, and cardiovascular diseases.

Risk factors for gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs): a three-centric case-control study

PURPOSE

Risk factors for sporadic GEP-NENs are still not well defined. To identify the main clinical risk factors represents the aim of this study performed by three Italian referral centers for NENs.

METHODS

We performed a retrospective case-control study including 148 consecutive sporadic GEP-NENs and 210 age- and sex-matched controls. We collected data on clinical features, cancer family history and other potential risk factors.

RESULTS

Mean age was 58.3 ± 15.8 years; 50% males, primary site was pancreas (50.7%), followed by ileum (22.3%). The 62.8% and 29.1% of cases were G1 and G2, respectively; the 40% had locally advanced or metastatic disease at diagnosis. Independent risk factors for GEP-NENs were: family history of non-neuroendocrine GEP cancer (OR 2.16, 95% CI 1.31-3.55, p = 0.003), type 2 diabetes mellitus (T2DM) (OR 2.5, 95% CI 1.39-4.51, p = 0.002) and obesity (OR 1.88, 95% CI 1.18-2.99, p = 0.007). In the T2DM subjects, metformin use was a protective factor (OR 0.28, 95% CI 0.08-0.93, p = 0.049). T2DM was also associated with a more advanced (OR 2.39, 95% CI 1.05-5.46, p = 0.035) and progressive disease (OR 2.47, 95% CI 1.08-5.34, p = 0.03). Stratifying cases by primary site, independent risk factors for pancreatic NENs were T2DM (OR 2.57, 95% CI 1.28-5.15, p = 0.008) and obesity (OR 1.98, 95% CI 1.11-3.52, p = 0.020), while for intestinal NENs family history of non-neuroendocrine GEP cancer (OR 2.46, 95% CI 1.38-4.38, p = 0.003) and obesity (OR 1.90, 95% CI 1.08-3.33, p = 0.026).

CONCLUSION

This study reinforces a role for family history of non-neuroendocrine GEP cancer, T2DM and obesity as independent risk factors for GEP-NENs and suggests a role of metformin as a protective factor in T2DM subjects. If confirmed, these findings could have a significant impact on prevention strategies for GEP-NENs.

The Effect of Metformin on Expression of Long Non-coding RNA H19 in Endometrial Cancer

Background: Endometrial cancer is the fourth most widespread cancer among females, with a growing prevalence in recent years. Management by combined therapies along with surgery, radiotherapy, and chemotherapy have improved patients' prognoses. Besides, the development of new therapies helps preserve fertility and prognosis in aggressive tumors. The purpose of this research was to identify the efficacy of metformin on the H19 long non-coding RNA expression in endometrial cancer to provide further insight into the pathogenesis and treatment of the disease. Methods: A total of 23 patients with endometrial cancer, diagnosed by biopsy or diagnostic curettage, were recruited and divided into three groups, before and after metformin treatment and placebo. Real-time PCR was used to evaluate the H19 expression in cancer tissue in all patients. Results: : It has been observed that in endometrial tissue of the "after-metformin" treatment group, the H19 expression level was significantly reduced, compared with the "before-metformin" treatment group, but not in comparison with the placebo. These findings indicate that metformin reduced the H19 expression in endometrial cancer. Conclusion: Anti-diabetic drugs, such as metformin, may be beneficial by reducing the H19 expression in endometrial cancer due to the H19 relation to cancer progression.

Patient-derived tumor models are attractive tools to repurpose drugs for ovarian cancer treatment: Pre-clinical updates

Despite advances in understanding of ovarian cancer biology, the progress in translation of research findings into new therapies is still slow. It is associated in part with limitations of commonly used cancer models such as cell lines and genetically engineered mouse models that lack proper representation of diversity and complexity of actual human tumors. In addition, the development of de novo anticancer drugs is a lengthy and expensive process. A promising alternative to new drug development is repurposing existing FDA-approved drugs without primary oncological purpose. These approved agents have known pharmacokinetics, pharmacodynamics, and toxicology and could be approved as anticancer drugs quicker and at lower cost. To successfully translate repurposed drugs to clinical application, an intermediate step of pre-clinical animal studies is required. To address challenges associated with reliability of tumor models for pre-clinical studies, there has been an increase in development of patient-derived xenografts (PDXs), which retain key characteristics of the original patient’s tumor, including histologic, biologic, and genetic features. The expansion and utilization of clinically and molecularly annotated PDX models derived from different ovarian cancer subtypes could substantially aid development of new therapies or rapid approval of repurposed drugs to improve treatment options for ovarian cancer patients.

The Impact of Epithelial-Mesenchymal Transition and Metformin on Pancreatic Cancer Chemoresistance: A Pathway towards Individualized Therapy

Globally, pancreatic ductal adenocarcinoma remains among the most aggressive forms of neoplastic diseases, having a dismal prognostic outcome. Recent findings elucidated that epithelial-mesenchymal transition (EMT) can play an important role in pancreatic tumorigenic processes, as it contributes to the manifestation of malignant proliferative masses, which impede adequate drug delivery. An organized literature search with PubMed, Scopus, Microsoft Academic and the Cochrane library was performed for articles published in English from 2011 to 2021 to review and summarize the latest updates and knowledge on the current understanding of EMT and its implications for tumorigenesis and chemoresistance. Furthermore, in the present paper, we investigate the recent findings on metformin as a possible neoadjuvant chemotherapy agent, which affects EMT progression and potentially provides superior oncological outcomes for PDAC patients. Our main conclusions indicate that selectively suppressing EMT in pancreatic cancer cells has a promising therapeutic utility by selectively targeting the chemotherapy-resistant sub-population of cancer stem cells, inhibiting tumor growth via EMT pathways and thereby improving remission in PDAC patients. Moreover, given that TGF-β1-driven EMT generates the migration of tumor-initiating cells by directly linking the acquisition of abnormal cellular motility with the maintenance of tumor initiating potency, the chemoprevention of TGF-β1-induced EMT may have promising clinical applications in the therapeutic management of PDAC outcomes.

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 and Risk of Malignant Brain Tumors in Patients with Type 2 Diabetes Mellitus

The risk of malignant brain tumors associated with metformin use has rarely been investigated in humans. This retrospective cohort study investigated such an association. Patients with new-onset type 2 diabetes mellitus diagnosed from 1999 to 2005 in the nationwide database of Taiwan’s national health insurance were used to enroll study subjects. We first identified an unmatched cohort of 153,429 ever users and 16,222 never users of metformin. A cohort of 16,222 ever users and 16,222 never users matched on propensity score was then created from this unmatched cohort. All patients were followed up from 1 January 2006 until 31 December 2011. The incidence density was calculated and hazard ratios were derived from Cox regression incorporated with the inverse probability of treatment weighting using a propensity score. The results showed that 27 never users and 155 ever users developed malignant brain tumors in the unmatched cohort. The incidence rate was 37.11 per 100,000 person-years in never users and 21.39 per 100,000 person-years in ever users. The overall hazard ratio comparing ever users versus never users was 0.574 (95% confidence interval: 0.381–0.863). The respective hazard ratios comparing the first (<27.13 months), second (27.13–58.33 months), and third (>58.33 months) tertiles of cumulative duration of metformin therapy versus never users were 0.897 (0.567–1.421), 0.623 (0.395–0.984), and 0.316 (0.192–0.518). In the matched cohort, the overall hazard ratio was 0.317 (0.149–0.673) and the respective hazard ratios were 0.427 (0.129–1.412), 0.509 (0.196–1.322), and 0.087 (0.012–0.639) for the first, second, and third tertile of cumulative duration of metformin therapy. In conclusion, this study shows a risk reduction of malignant brain tumors associated with metformin use in a dose–response pattern. The risk reduction is more remarkable when metformin has been used for approximately 2–5 years.

PHENSIM: Phenotype Simulator

Despite the unprecedented growth in our understanding of cell biology, it still remains challenging to connect it to experimental data obtained with cells and tissues’ physiopathological status under precise circumstances. This knowledge gap often results in difficulties in designing validation experiments, which are usually labor-intensive, expensive to perform, and hard to interpret. Here we propose PHENSIM, a computational tool using a systems biology approach to simulate how cell phenotypes are affected by the activation/inhibition of one or multiple biomolecules, and it does so by exploiting signaling pathways. Our tool’s applications include predicting the outcome of drug administration, knockdown experiments, gene transduction, and exposure to exosomal cargo. Importantly, PHENSIM enables the user to make inferences on well-defined cell lines and includes pathway maps from three different model organisms. To assess our approach’s reliability, we built a benchmark from transcriptomics data gathered from NCBI GEO and performed four case studies on known biological experiments. Our results show high prediction accuracy, thus highlighting the capabilities of this methodology. PHENSIM standalone Java application is available at https://github.com/alaimos/phensim, along with all data and source codes for benchmarking. A web-based user interface is accessible at https://phensim.tech/.

Despite the unprecedented growth in our understanding of cell biology, it still remains challenging to connect it to experimental data obtained with cells and tissues’ physiopathological status under precise circumstances. This knowledge gap often results in difficulties in designing validation experiments, which are usually labor-intensive, expensive to perform, and hard to interpret. In this context, ’in silico’ simulations can be extensively applied in massive scales, testing thousands of hypotheses under various conditions, which is usually experimentally infeasible. At present, many simulation models have become available. However, complex biological networks might pose challenges to their performance.

We propose PHENSIM, a computational tool using a systems biology approach to simulate how cell phenotypes are affected by the activation/inhibition of one or multiple biomolecules, and it does so by exploiting signaling pathways. We implemented our tool as a freely accessible web application, hoping to allow ’in silico’ simulations to play a more central role in the modeling and understanding of biological phenomena.

The Effect of Metformin on Male Reproductive Function and Prostate: An Updated Review

Metformin is the first-line oral antidiabetic drug that shows multiple pleiotropic effects of anti-inflamation, anti-cancer, anti-aging, anti-microbia, anti-atherosclerosis, and immune modulation. Metformin's effects on men's related health are reviewed here, focusing on reproductive health under subtitles of erectile dysfunction (ED), steroidogenesis and spermatogenesis; and on prostate-related health under subtitles of prostate specific antigen (PSA), prostatitis, benign prostate hyperplasia (BPH), and prostate cancer (PCa). Updated literature suggests a potential role of metformin on arteriogenic ED but controversial and contradictory effects (either protective or harmful) on testicular functions of testosterone synthesis and spermatogenesis. With regards to prostate-related health, metformin use may be associated with lower levels of PSA in humans, but its clinical implications require more research. Although there is a lack of research on metform's effect on prostatitis, it may have potential benefits through its anti-microbial and anti-inflammatory properties. Metformin may reduce the risk of BPH by inhibiting the insulin-like growth factor 1 pathway and some but not all studies suggest a protective role of metformin on the risk of PCa. Many clinical trials are being conducted to investigate the use of metformin as an adjuvant therapy for PCa but results currently available are not conclusive. While some trials suggest a benefit in reducing the metastasis and recurrence of PCa, others do not show any benefit. More research works are warranted to illuminate the potential usefulness of metformin in the promotion of men's health.

Combining a High Dose of Metformin With the SIRT1 Activator, SRT1720, Reduces Life Span in Aged Mice Fed a High-Fat Diet

SRT1720, a sirtuin1-activator, and metformin (MET), an antidiabetic drug, confer health and life-span benefits when administered individually. It is unclear whether combination of the two compounds could lead to additional benefits. Groups of 56-week-old C57BL/6J male mice were fed a high-fat diet (HFD) alone or supplemented with either SRT1720 (2 g/kg food), a high dose of MET (1% wt/wt food), or a combination of both. Animals were monitored for survival, body weight, food consumption, body composition, and rotarod performance. Mice treated with MET alone did not have improved longevity, and life span was dramatically reduced by combination of MET with SRT1720. Although all groups of animals were consuming similar amounts of food, mice on MET or MET + SRT1720 showed a sharp reduction in body weight. SRT1720 + MET mice also had lower percent body fat combined with better performance on the rotarod compared to controls. These data suggest that co-treatment of SRT1720 with MET is detrimental to survival at the doses used and, therefore, risk-benefits of combining life-span-extending drugs especially in older populations needs to be systematically evaluated.

Metformin and Androgen Receptor-Axis-Targeted (ARAT) Agents Induce Two PARP-1-Dependent Cell Death Pathways in Androgen-Sensitive Human Prostate Cancer Cells

We explored whether the anti-prostate cancer (PC) activity of the androgen receptor-axis-targeted agents (ARATs) abiraterone and enzalutamide is enhanced by metformin. Using complementary biological and molecular approaches, we determined the associated underlying mechanisms in pre-clinical androgen-sensitive PC models. ARATs increased androgren receptors (ARs) in LNCaP and AR/ARv7 (AR variant) in VCaP cells, inhibited cell proliferation in both, and induced poly(ADP-ribose) polymerase-1 (PARP-1) cleavage and death in VCaP but not LNCaP cells. Metformin decreased AR and ARv7 expression and induced cleaved PARP-1-associated death in both cell lines. Metformin with abiraterone or enzalutamide decreased AR and ARv7 expression showed greater inhibition of cell proliferation and greater induction of cell death than single agent treatments. Combination treatments led to increased cleaved PARP-1 and enhanced PARP-1 activity manifested by increases in poly(ADP-ribose) (PAR) and nuclear accumulation of apoptosis inducing factor (AIF). Enhanced annexin V staining occurred in LNCaP cells only with metformin/ARAT combinations, but no caspase 3 recruitment occurred in either cell line. Finally, metformin and metformin/ARAT combinations increased lysosomal permeability resulting in cathepsin G-mediated PARP-1 cleavage and cell death. In conclusion, metformin enhances the efficacy of abiraterone and enzalutamide via two PARP-1-dependent, caspase 3-independent pathways, providing a rationale to evaluate these combinations in castration-sensitive PC.

Metformin: Targeting the Metabolo-Epigenetic Link in Cancer Biology

Metabolism can directly drive or indirectly enable an aberrant chromatin state of cancer cells. The physiological and molecular principles of the metabolic link to epigenetics provide a basis for pharmacological modulation with the anti-diabetic biguanide metformin. Here, we briefly review how metabolite-derived chromatin modifications and the metabolo-epigenetic machinery itself are both amenable to modification by metformin in a local and a systemic manner. First, we consider the capacity of metformin to target global metabolic pathways or specific metabolic enzymes producing chromatin-modifying metabolites. Second, we examine its ability to directly or indirectly fine-tune the activation status of chromatin-modifying enzymes. Third, we envision how the interaction between metformin, diet and gut microbiota might systemically regulate the metabolic inputs to chromatin. Experimental and clinical validation of metformin's capacity to change the functional outcomes of the metabolo-epigenetic link could offer a proof-of-concept to therapeutically test the metabolic adjustability of the epigenomic landscape of cancer.

Pharmacological preconditioning protects from ischemia/reperfusion-induced apoptosis by modulating Bcl-xL expression through a ROS-dependent mechanism

Myocardial ischemia/reperfusion (I/R) injury is a frequent perioperative threat, with numerous strategies developed to limit and/or prevent it. One interesting axis of research is the anesthetic preconditioning (APc) agent's hypothesis (such as sevoflurane, SEV). However, APc's mode of action is still poorly understood and volatile anesthetics used as preconditioning agents are often not well suited in clinical practice. Here, in vitro using H9C2 cells lines (in myeloblast state or differentiated toward cardiomyocytes) and in vivo in mice, we identified that SEV-induced APc is mediated by a mild induction of reactive oxygen species (ROS) that activates Akt and induces the expression of the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-xL), therefore protecting cardiomyocytes from I/R-induced death. Furthermore, we extended these results to human cardiomyocytes (derived from induced pluripotent stem - IPS - cells). Importantly, we demonstrated that this protective signaling pathway induced by SEV could be stimulated using the antidiabetic agent metformin (MET), suggesting the preconditioning properties of MET. Altogether, our study identified a signaling pathway allowing APc of cardiac injuries as well as a rational for the use of MET as a pharmacological preconditioning agent to prevent I/R injuries.

Metabolic Targeting of Cancer Stem Cells

Most human tumors possess a high heterogeneity resulting from both clonal evolution and cell differentiation program. The process of cell differentiation is initiated from a population of cancer stem cells (CSCs), which are enriched in tumor-regenerating and tumor-propagating activities and responsible for tumor maintenance and regrowth after treatment. Intrinsic resistance to conventional therapies, as well as a high degree of phenotypic plasticity, makes CSCs hard-to-target tumor cell population. Reprogramming of CSC metabolic pathways plays an essential role in tumor progression and metastatic spread. Many of these pathways confer cell adaptation to the microenvironmental stresses, including a shortage of nutrients and anti-cancer therapies. A better understanding of CSC metabolic dependences as well as metabolic communication between CSCs and the tumor microenvironment are of utmost importance for efficient cancer treatment. In this mini-review, we discuss the general characteristics of CSC metabolism and potential metabolic targeting of CSC populations as a potent strategy to enhance the efficacy of conventional treatment approaches.

Risk of Skin Cancer Associated with Metformin Use: A Meta-Analysis of Randomized Controlled Trials and Observational Studies

Previous studies demonstrate mixed evidence regarding the association between metformin and skin cancer risk. To synthesize prior evidence and evaluate the association between metformin and skin cancer risk in patients with diabetes/prediabetes, we conducted a meta-analysis. A systematic literature search was performed up to March 23, 2020 to identify randomized controlled trials (RCT) and observational studies of metformin that reported any event of squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and melanoma. In a meta-analysis of 6 trials involving 8,541 patients (Peto method), compared with controls, metformin was not significantly associated with decreased risk of melanoma [OR, 0.82; 95% confidence interval (CI), 0.27-2.43], BCC (OR, 0.75; 95% CI, 0.36-1.57), SCC (OR, 0.98; 95% CI, 0.06-15.60), total nonmelanoma skin cancer (NMSC; OR, 0.69; 95% CI, 0.38-1.24), or total skin cancer (OR, 0.71; 95% CI, 0.42-1.20). This nonsignificant association pattern was consistent with the random-effects meta-analysis of 4 cohort studies with 354,746 patients (melanoma: RR, 0.91; 95% CI, 0.62-1.33; NMSC: RR, 0.65; 95% CI, 0.35-1.18; total skin cancer: RR, 0.83; 95% CI, 0.59-1.16). In conclusion, meta-analyses of both RCT and cohort studies showed no statistically significant association between metformin and skin cancer risks, although suggestive evidence of modestly reduced risks of skin cancer among metformin users was observed. Further studies are needed. PREVENTION RELEVANCE: Meta-analyses of RCT and cohort studies showed no significant association between metformin and skin cancer, although suggestive evidence of modestly reduced skin cancer risks among metformin users was observed. These findings suggest metformin use should not influence current medical decision making for diabetes patients at risk of developing skin cancer.

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.

Genome-Wide DNA Methylation and LncRNA-Associated DNA Methylation in Metformin-Treated and -Untreated Diabetes

Metformin, which is used as a first line treatment for type 2 diabetes mellitus (T2DM), has been shown to affect epigenetic patterns. In this study, we investigated the DNA methylation and potential lncRNA modifications in metformin-treated and newly diagnosed adults with T2DM. Genome-wide DNA methylation and lncRNA analysis were performed from the peripheral blood of 12 screen-detected and 12 metformin-treated T2DM individuals followed by gene ontology (GO) and KEGG pathway analysis. Differentially methylated regions (DMRs) observed showed 22 hypermethylated and 11 hypomethylated DMRs between individuals on metformin compared to screen-detected subjects. Amongst the hypomethylated DMR regions were the SLC gene family, specifically, SLC25A35 and SLC28A1. Fifty-seven lncRNA-associated DNA methylation regions included the mitochondrial ATP synthase-coupling factor 6 (ATP5J). Functional gene mapping and pathway analysis identified regions in the axon initial segment (AIS), node of Ranvier, cell periphery, cleavage furrow, cell surface furrow, and stress fiber. In conclusion, our study has identified a number of DMRs and lncRNA-associated DNA methylation regions in metformin-treated T2DM that are potential targets for therapeutic monitoring in patients with diabetes.

Benefits of Metformin in Attenuating the Hallmarks of Aging

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

Mechanisms of action of metformin in type 2 diabetes: Effects on mitochondria and leukocyte-endothelium interactions

Type 2 diabetes (T2D) is a very prevalent, multisystemic, chronic metabolic disorder closely related to atherosclerosis and cardiovascular diseases. It is characterised by mitochondrial dysfunction and the presence of oxidative stress. Metformin is one of the safest and most effective anti-hyperglycaemic agents currently employed as first-line oral therapy for T2D. It has demonstrated additional beneficial effects, unrelated to its hypoglycaemic action, on weight loss and several diseases, such as cancer, cardiovascular disorders and metabolic diseases, including thyroid diseases. Despite the vast clinical experience gained over several decades of use, the mechanism of action of metformin is still not fully understood. This review provides an overview of the existing literature concerning the beneficial mitochondrial and vascular effects of metformin, which it exerts by diminishing oxidative stress and reducing leukocyte-endothelium interactions. Specifically, we describe the molecular mechanisms involved in metformin's effect on gluconeogenesis, its capacity to interfere with major metabolic pathways (AMPK and mTORC1), its action on mitochondria and its antioxidant effects. We also discuss potential targets for therapeutic intervention based on these molecular actions.

Phase II clinical trial of metformin as a cancer stem cell-targeting agent in ovarian cancer

BACKGROUNDEpidemiologic studies suggest that metformin has antitumor effects. Laboratory studies indicate metformin impacts cancer stem-like cells (CSCs). As part of a phase II trial, we evaluated the impact of metformin on CSC number and on carcinoma-associated mesenchymal stem cells (CA-MSCs) and clinical outcomes in nondiabetic patients with advanced-stage epithelial ovarian cancer (EOC).METHODSThirty-eight patients with stage IIC (n = 1)/III (n = 25)/IV (n = 12) EOC were treated with either (a) neoadjuvant metformin, debulking surgery, and adjuvant chemotherapy plus metformin or (b) neoadjuvant chemotherapy and metformin, interval debulking surgery, and adjuvant chemotherapy plus metformin. Metformin-treated tumors, compared with historical controls, were evaluated for CSC number and chemotherapy response. Primary endpoints were (a) a 2-fold or greater reduction in aldehyde dehydrogenase-positive (ALDH+) CD133+ CSCs and (b) a relapse-free survival at 18 months of more than 50%.RESULTSMetformin was well tolerated. Median progression-free survival was 18.0 months (95% CI 14.0-21.6) with relapse-free survival at 18 months of 59.3% (95% CI 38.6-70.5). Median overall survival was 57.9 months (95% CI 28.0-not estimable). Tumors treated with metformin had a 2.4-fold decrease in ALDH+CD133+ CSCs and increased sensitivity to cisplatin ex vivo. Furthermore, metformin altered the methylation signature in CA-MSCs, which prevented CA-MSC-driven chemoresistance in vitro.CONCLUSIONTranslational studies confirm an impact of metformin on EOC CSCs and suggest epigenetic change in the tumor stroma may drive the platinum sensitivity ex vivo. Consistent with this, metformin therapy was associated with better-than-expected overall survival, supporting the use of metformin in phase III studies.TRIAL REGISTRATIONClinicalTrials.gov NCT01579812.

The Effect of Metformin on Prognosis in Patients With Locally Advanced Gastric Cancer Associated With Type 2 Diabetes Mellitus

OBJECTIVES

This study examined the effect of metformin use on the prognosis of gastric cancer patients.

MATERIALS AND METHODS

The study population comprised 2187 patients who underwent curative gastrectomy for the treatment of gastric cancer. They were divided into 3 groups: metformin (n=103), non-metformin (n=139), and non-diabetes mellitus (DM) (n=1945) according to their history of type 2 DM and metformin use. Survival, disease recurrence, and the pathologic stage were analyzed.

RESULTS

Overall survival was better in the metformin group than in the non-DM group (P=0.005). Metformin use was an independent prognostic factor of overall survival, cancer recurrence, and peritoneal recurrence. An effect of metformin use was especially notable in patients with T4 or N0 disease.

CONCLUSIONS

Metformin improves the survival of patients with gastric cancer and type 2 DM.

Loss of Rb1 Enhances Glycolytic Metabolism in Kras-Driven Lung Tumors In Vivo

Dysregulated metabolism is a hallmark of cancer cells and is driven in part by specific genetic alterations in various oncogenes or tumor suppressors. The retinoblastoma protein (pRb) is a tumor suppressor that canonically regulates cell cycle progression; however, recent studies have highlighted a functional role for pRb in controlling cellular metabolism. Here, we report that loss of the gene encoding pRb (Rb1) in a transgenic mutant Kras-driven model of lung cancer results in metabolic reprogramming. Our tracer studies using bolus dosing of [U-¹³C]-glucose revealed an increase in glucose carbon incorporation into select glycolytic intermediates. Consistent with this result, Rb1-depleted tumors exhibited increased expression of key glycolytic enzymes. Interestingly, loss of Rb1 did not alter mitochondrial pyruvate oxidation compared to lung tumors with intact Rb1. Additional tracer studies using [U-¹³C,¹⁵N]-glutamine and [U-¹³C]-lactate demonstrated that loss of Rb1 did not alter glutaminolysis or utilization of circulating lactate within the tricarboxylic acid cycle (TCA) in vivo. Taken together, these data suggest that the loss of Rb1 promotes a glycolytic phenotype, while not altering pyruvate oxidative metabolism or glutamine anaplerosis in Kras-driven lung tumors.

Metformin activates KDM2A to reduce rRNA transcription and cell proliferation by dual regulation of AMPK activity and intracellular succinate level

Metformin is used to treat type 2 diabetes. Metformin activates AMP-activated kinase (AMPK), which may contribute to the action of metformin. Metformin also shows anti-proliferation activity. However, the mechanism is remained unknown. We found that treatment of MCF-7 cells with metformin induced the demethylase activity of KDM2A in the rDNA promoter, which resulted in reductions of rRNA transcription and cell proliferation. AMPK activity was required for activation of KDM2A by metformin. Because demethylase activities of JmjC-type enzymes require a side reaction converting α-ketoglutarate to succinate, these organic acids may affect their demethylase activities. We found that metformin did not induce KDM2A demethylase activity in conditions of a reduced level of α-ketoglutarate. A four-hour treatment of metformin specifically reduced succinate, and the replenishment of succinate inhibited the activation of KDM2A by metformin, but did not inhibit the activation of AMPK. Metformin reduced succinate even in the conditions suppressing AMPK activity. These results indicate that metformin activates AMPK and reduces the intracellular succinate level, both of which are required for the activation of KDM2A to reduce rRNA transcription. The results presented here uncover a novel factor of metformin actions, reduction of the intracellular succinate, which contributes to the anti-proliferation activity of metformin.

Metformin decreases hyaluronan synthesis by vascular smooth muscle cells

Metformin is the first-line drug in the treatment of type 2 diabetes worldwide based on its effectiveness and cardiovascular safety. Currently metformin is increasingly used during pregnancy in women with gestational diabetes mellitus, even if the long-term effects of metformin on offspring are not exactly known. We have previously shown that high glucose concentration increases hyaluronan (HA) production of cultured human vascular smooth muscle cells (VSMC) via stimulating the expression of hyaluronan synthase 2 (HAS2). This offers a potential mechanism whereby hyperglycemia leads to vascular macroangiopathy. In this study, we examined whether gestational metformin use affects HA content in the aortic wall of mouse offspring in vivo. We also examined the effect of metformin on HA synthesis by cultured human VSMCs in vitro. We found that gestational metformin use significantly decreased HA content in the intima-media of mouse offspring aortas. In accordance with this, the synthesis of HA by VSMCs was also significantly decreased in response to treatment with metformin. This decrease in HA synthesis was shown to be due to the reduction of both the expression of HAS2 and the amount of HAS substrates, particularly UDP-N-acetylglucosamine. As shown here, gestational metformin use is capable to program reduced HA content in the vascular wall of the offspring strongly supporting the idea, that metformin possesses long-term vasculoprotective effects.

Disseminated Well-Differentiated Gastro-Entero-Pancreatic Tumors Are Associated with Metabolic Syndrome

The association of well-differentiated gastro-entero-pancreatic neuroendocrine tumors (WD GEP-NETs) with metabolic syndrome (MetS), abdominal obesity, and fasting glucose abnormalities was recently described. The aim of this study was to evaluate whether the presence of MetS or any MetS individual component was also influenced by GEP-NET characteristics at diagnosis. A cohort of patients with WD GEP-NETs (n = 134), classified according to primary tumor location (gastrointestinal or pancreatic), pathological grading (G1 (Ki67 ≤ 2%) and G2 (>3 ≤ 20%) (WHO 2010), disease extension (localized, loco-regional, and metastatic), and presence of hormonal secretion syndrome (functioning/non-functioning), was evaluated for the presence of MetS criteria. After adjustment for age and gender, the odds of having MetS was significantly higher for patients with WD GEP-NET grade G1 (OR 4.35 95%CI 1.30-14.53) and disseminated disease (OR 4.52 95%CI 1.44-14.15). GEP-NET primary tumor location or secretory syndrome did not influence the risk for MetS. None of the tumor characteristics evaluated were associated with body mass index, fasting plasma glucose category, or any of the individual MetS components. Patients with GEP-NET and MetS depicted a higher risk of presenting a lower tumor grade and disseminated disease. The positive association between MetS and GEP-NET characteristics further highlights the potential link between the two conditions.

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

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

A New Method for Ethical and Efficient Evidence Generation for Off-Label Medication Use in Oncology (A Case Study in Glioblastoma)

In oncology, preclinical and early clinical data increasingly support the use of a number of candidate "non-cancer" drugs in an off-label setting against multiple tumor types. In particular, metabolically targeted drugs show promise as adjuvant chemo and radiosensitizers, improving or restoring sensitivity to standard therapies. The time has come for large scale clinical studies of off-label drugs in this context. However, it is well recognized that high-cost randomized controlled trials may not be an economically viable option for studying patent-expired off-label drugs. In some cases, randomized trials could also be considered as ethically controversial. This perspective article presents a novel approach to generating additional clinical data of sufficient quality to support changes in clinical practice and relabeling of such drugs for use in oncology. Here, we suggest that a pluralistic evidence base and triangulation of evidence can support clinical trial data for off-label drug use in oncology. An example of an off-label drug protocol brought to the clinic for glioblastoma patients is presented, along with preliminary retrospective data from the METRICS study (NCT02201381). METRICS is a novel participant-funded, open-label, non-randomized, single-arm real-world study designed to gather high-quality evidence on the safety, tolerability, and effectiveness of four off-label metabolically targeted medicines as an adjunctive cancer treatment for glioblastoma patients.

Overcoming platinum-acquired resistance in ovarian cancer patient-derived xenografts

Background:

Epithelial ovarian cancer is the most lethal gynecological cancer and the high mortality is due to the frequent presentation at advanced stage, and to primary or acquired resistance to platinum-based therapy.

Methods:

We developed three new models of ovarian cancer patient-derived xenografts (ovarian PDXs) resistant to cisplatin (cDDP) after multiple in vivo drug treatments. By different and complementary approaches based on integrated metabolomics (both targeted and untargeted mass spectrometry-based techniques), gene expression, and functional assays (Seahorse technology) we analyzed and compared the tumor metabolic profile in each sensitive and their corresponding cDDP-resistant PDXs.

Results:

We found that cDDP-sensitive and -resistant PDXs have a different metabolic asset. In particular, we found, through metabolomic and gene expression approaches, that glycolysis, tricarboxylic acid cycle and urea cycle pathways were deregulated in resistant versus sensitive PDXs. In addition, we observed that oxygen consumption rate and mitochondrial respiration were higher in resistant PDXs than in sensitive PDXs under acute stress conditions. An increased oxidative phosphorylation in cDDP-resistant sublines led us to hypothesize that its interference could be of therapeutic value. Indeed, in vivo treatment of metformin and cDDP was able to partially reverse platinum resistance.

Conclusions:

Our data strongly reinforce the idea that the development of acquired cDDP resistance in ovarian cancer can bring about a rewiring of tumor metabolism, and that this might be exploited therapeutically.

Metformin Reduces Renal Uptake of Radiotracers and Protects Kidneys from Radiation-Induced Damage

Metformin is the most widely prescribed drug for type 2 diabetes. Chemically, metformin is a hydrophilic base that functions as an organic cation, suggesting that it may have the capacity to inhibit the tubular reabsorption of peptide radiotracers. The purpose of this study was to investigate whether metformin could reduce renal uptake of peptidyl radiotracers and serve as a radioprotective agent for peptide receptor radionuclide therapy (PRRT).

METHODS

We used two radiolabeled peptides: a ⁶⁸Ga-labeled cyclic (TNYL-RAW) peptide (⁶⁸Ga-NOTA-c(TNYL-RAW) (NOTA: 1,4,7 triazacyclononane-1,4,7-trisacetic acid) targeting EphB4 receptors and an ¹¹¹In- or ⁶⁴Cu-labeled octreotide (¹¹¹In/⁶⁴Cu-DOTA-octreotide) (DOTA: 1,4,7,10 triazacyclododecane-1,4,7,10-tetraacetic acid) targeting somatostatin receptors. Each radiotracer was injected intravenously into normal Swiss mice or tumor-bearing nude mice in the presence or absence of metformin administered intravenously or orally. Micropositron emission tomography or microsingle-photon emission computed tomography images were acquired at different times after radiotracer injection, and biodistribution studies were performed at the end of the imaging session. To assess the radioprotective effect of metformin on the kidneys, normal Swiss mice received two doses of ¹¹¹In-DOTA-octreotidein the presence or absence of metformin, and renal function was analyzed via blood chemistry and histology.

RESULTS

Intravenous injection of metformin with ⁶⁸Ga-NOTA-c(TNYL-RAW) or ¹¹¹In-DOTA-octreotide reduced the renal uptake of the radiotracer by 60% and 35%, respectively, compared to uptake without metformin. These reductions were accompanied by greater uptake in the tumors for both radiolabeled peptides. Moreover, the renal uptake of ¹¹¹In-DOTA-octreotide was significantly reduced when metformin was administered via oral gavage. Significantly more radioactivity was recovered in the urine collected over a period of 24 h after intravenous injection of ⁶⁴Cu-DOTA-octreotide in mice that received oral metformin than in mice that received vehicle. Finally, coadministration of ¹¹¹In-DOTA-octreotide with metformin mitigated radio-nephrotoxicity.

CONCLUSION

Metformin inhibits kidney uptake of peptidyl radiotracers, protecting the kidney from nephrotoxicity. Further studies are needed to elucidate the mechanisms of these finding and to optimize mitigation of radiation-induced damage to kidney in PRRT.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Metformin and risk of developing nasopharyngeal cancer in patients with type 2 diabetes mellitus

BACKGROUND

Metformin has anticancer effects, but whether it can reduce the risk of nasopharyngeal cancer (NPC) is not known.

METHODS

A total of 15,486 ever-users and 15,486 never-users of metformin matched by propensity score were enrolled from among patients with new-onset type 2 diabetes mellitus diagnosed during the period 1999-2005 and who were found in the reimbursement database of Taiwan's National Health Insurance. The patients were followed until December 31, 2011. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity scores.

RESULTS

NPC incidence was 33.41 and 106.04 per 100,000 person-years in ever-users and never-users, respectively. The overall hazard ratio (95% confidence interval) of 0.312 (0.197-0.494) favored a significantly lower risk among metformin ever-users than in never-users. Hazard ratios comparing the first (<26.03 months), second (26.03-58.03 months) and third (>58.03 months) tertiles of cumulative duration of metformin use to never-users were 0.690 (0.389-1.224), 0.187 (0.076-0.463) and 0.168 (0.068-0.415), respectively. A significantly lower risk of NPC was consistently observed among metformin users in subgroup analyses of age (<50 years and ≥50 years), sex (men and women), and patients with or without nephropathy, liver diseases or diseases of the esophagus, stomach, and duodenum, respectively.

CONCLUSIONS

Metformin use is associated with a significantly lower risk of NPC.

Metformin as an anti-cancer agent: actions and mechanisms targeting cancer stem cells

Metformin, a first line medication for type II diabetes, initially entered the spotlight as a promising anti-cancer agent due to epidemiologic reports that found reduced cancer risk and improved clinical outcomes in diabetic patients taking metformin. To uncover the anti-cancer mechanisms of metformin, preclinical studies determined that metformin impairs cellular metabolism and suppresses oncogenic signaling pathways, including receptor tyrosine kinase, PI3K/Akt, and mTOR pathways. Recently, the anti-cancer potential of metformin has gained increasing interest due to its inhibitory effects on cancer stem cells (CSCs), which are associated with tumor metastasis, drug resistance, and relapse. Studies using various cancer models, including breast, pancreatic, prostate, and colon, have demonstrated the potency of metformin in attenuating CSCs through the targeting of specific pathways involved in cell differentiation, renewal, metastasis, and metabolism. In this review, we provide a comprehensive overview of the anti-cancer actions and mechanisms of metformin, including the regulation of CSCs and related pathways. We also discuss the potential anti-cancer applications of metformin as mono- or combination therapies.

Targeted Therapy: Attacking Cancer with Molecular and Immunological Targeted Agents

Today, personalized cancer therapy with targeted agents has taken center stage, and offers individualized treatment to many. As the mysteries of the genes in a cell's DNA and their specific proteins are defined, advances in the understanding of cancer gene mutations and how cancer evades the immune system have been made. This article provides a basic and simplified understanding of the available (Food and Drug Administration- approved) molecularly and immunologically targeted agents in the USA. Other agents may be available in Asia, and throughout the USA and the world, many more agents are being studied. Nursing implications for drug classes are reviewed.

Metformin-Induced Mitochondrial Complex I Inhibition: Facts, Uncertainties, and Consequences

Metformin is the most widely prescribed drug to treat patients with type II diabetes, for whom retrospective studies suggest that metformin may have anticancer properties. However, in experiments performed with isolated cells, authors have reported both pro- and anti-apoptotic effects of metformin. The exact molecular mechanism of action of metformin remains partly unknown despite its use for over 60 years and more than 17,000 articles in PubMed. Among the various widely recognized or recently proposed targets, it has been reported consistently that metformin is capable of inhibiting mitochondrial respiratory chain Complex I. Since most of the effects of metformin have been replicated by other inhibitors of Complex I, it has been suggested that the mechanism of action of metformin involved the inhibition of Complex I. However, compared to conventional Complex I inhibitors, the metformin-induced inhibition of Complex I has unique characteristics. Among these, the most original one is that the concentrations of metformin required to inhibit Complex I are lower in intact cells than in isolated mitochondria. Experiments with isolated mitochondria or Complex I were generally performed using millimolar concentrations of metformin, while plasma levels remain in the micromolar range in both human and animal studies, highlighting that metformin concentration is an important issue. In order to explain the effects in animals based on observations in cells and mitochondria, some authors proposed a direct effect of the drug on Complex I involving an accumulation of metformin inside the mitochondria while others proposed an indirect effect (the drug no longer having to diffuse into the mitochondria). This brief review attempts to: gather arguments for and against each hypothesis concerning the mechanism by which metformin inhibits Complex I and to highlight remaining questions about the toxicity mechanism of metformin for certain cancer cells.

Metformin, an Anti-diabetic Drug to Target Leukemia

Metformin, a widely used anti-diabetic molecule, has attracted a strong interest in the last 10 years as a possible new anti-cancer molecule. Metformin acts by interfering with mitochondrial respiration, leading to an activation of the AMPK tumor-suppressive pathway to promote catabolic-energy saving reactions and block anabolic ones that are associated with abnormal cell proliferation. Metformin also acts at the organism level. In type 2 diabetes patients, metformin reduces hyperglycemia and increases insulin sensitivity by enhancing insulin-stimulated glucose uptake in muscles, liver, and adipose tissue and by reducing glucose output by the liver. Lowering insulin and insulin-like growth factor 1 (IGF-1) levels that stimulate cancer growth could be important features of metformin's mode of action. Despite continuous progress in treatments with the use of targeted therapies and now immunotherapies, acute leukemias are still of very poor prognosis for relapse patients, demonstrating an important need for new treatments deriving from the identification of their pathological supportive mechanisms. In the last decade, it has been realized that if cancer cells modify and reprogram their metabolism to feed their intense biochemical needs associated with their runaway proliferation, they develop metabolic addictions that could represent attractive targets for new therapeutic strategies that intend to starve and kill cancer cells. This Mini Review explores the anti-leukemic potential of metformin and its mode of action on leukemia metabolism.