Metformin inhibits mammalian target of rapamycin-dependent translation initiation in breast cancer cells

Metformin prevents cell tumorigenesis through autophagy-related cell death

Autophagy is a cellular mechanism by which cells degrade intracellular components in lysosomes, maintaining cellular homeostasis. It has been hypothesized that autophagy could have a role in cancer prevention through the elimination of damaged proteins and organelles; this could explain epidemiological evidence showing the chemopreventive properties of the autophagy-inducer metformin. In this study, we analyzed the autophagy-related effect of metformin in both cancer initiation and progression in non-tumorigenic cells. We also analyzed the induction of tumorigenesis in autophagy-deficient cells, and its correlation with the ER stress. Our results showed that metformin induced massive cell death in preneoplastic JB6 Cl 41-5a cells treated with tumor promoter (phorbol) and in NIH/3T3 treated with H₂O₂. Inhibiting autophagy with wortmannin or ATG7 silencing, the effect of metformin decreased, indicating an autophagy-related cytotoxic activity under stress conditions. We also found an induction of tumorigenesis in ATG7-silenced NIH/3T3 cell clone (3T3-619C3 cells), but not in wild-type and in scrambled transfected cells, and an upregulation of unfolded protein response (UPR) markers in 3T3-619C3 cells treated with H₂O₂. These findings suggest that autophagic cell death could be considered as a new mechanism by which eliminate damaged cells, representing an attractive strategy to eliminate potential tumorigenic cells.

The Potential Effect of Metformin on Cancer: An Umbrella Review

Background: Metformin has been reported to possess anti-cancer properties in addition to glucose-lowering activity and numerous systematic reviews and meta-analyses have studied the association between metformin use and cancer incidence or survival outcomes. We performed an umbrella review to assess the robustness of these associations to facilitate proper interpretation of these results to inform clinical and policy decisions. Methods: We searched PubMed and Embase systematic reviews and meta-analyses investigating the effect of metformin use on cancer incidence or survival outcomes published from inception to September 2, 2018. We estimated the summary effect size, the 95% CI, and the 95% prediction interval, heterogeneity, evidence of small-study effects, and evidence of excess significance bias. Results: We included 21 systematic reviews and meta-analyses covering 11 major anatomical sites and 33 associations. There was strong evidence for the association between metformin use and decreased pancreatic cancer incidence. The association between metformin use and improved colorectal cancer overall survival (OS) was supported by highly suggestive evidence. Seven associations (all cancer incidence, all cancer OS, breast cancer OS, colorectal cancer incidence, liver cancer incidence, lung cancer OS, and pancreatic cancer OS) presented only suggestive evidence. The remaining 24 associations were supported by weak or not-suggestive evidence. Conclusions: Associations between metformin use and pancreatic cancer incidence or colorectal cancer OS are supported by strong or highly suggestive evidence, respectively. However, these results should be interpreted with caution due to the poor methodological quality of the systematic reviews and meta-analyses.

Metformin selectively targets 4T1 tumorspheres and enhances the antitumor effects of doxorubicin by downregulating the AKT and STAT3 signaling pathways

Recent studies have reported that metformin (Met), the first-line medication for the treatment of type 2 diabetes, exhibited anticancer and chemoprotective effects in diverse cancer cells. In this study, we investigated the effects of Met on the drug-resistance of 4T1 murine breast cancer tumorspheres (TS) and the mechanism responsible for its drug-resistance. 4T1 TS exhibited accumulations of cells at the G₀/G₁ phase compared with cells in monolayer culture, which suggested the majority of cells in TS were quiescent. Furthermore, it was identified that activations of the signal transducer and activator of transcription 3 (STAT3) and protein kinase B (AKT) signaling pathways in 4T1 TS conferred drug-resistance to doxorubicin (Dox) and lapatinib (Lapa). However, Met selectively targeted TS rather than cells in monolayer culture and increased the cytotoxic effect of Dox on TS by inhibiting activations of the STAT3 and AKT signaling pathways. These observations suggested that inhibitions of STAT3 and AKT underlie the selective cytotoxic effects of Met on TS. In addition, Met exhibited synergistic antitumor effects with Dox on 4T1 tumor-bearing BALB/c mice. Our findings suggest that combinations of Met and cytotoxic anticancer drugs may offer an advantage for treating drug-resistant breast cancer.

Metabolic Reprogramming of Non-Hodgkin's B-Cell Lymphomas and Potential Therapeutic Strategies

Metabolism is a wide and general term that refers to any intracellular pathways the cell utilizes in order to satisfy its energetic demand and to support cell viability and/or division. Along with phenotypic changes, all mammalian cells including immune cells modulate their metabolic program in order to reach their effector functions. Exacerbated metabolism and metabolic flexibility are also hallmarks of tumor initiation and of tumor cell progression in a complex tumor microenvironment. Metabolic reprogramming is mainly directed by the serine/threonine kinase mTOR (mammalian target of rapamycin). mTOR exists in two structurally and functionally distinct complexes, mTORC1 and mTORC2 that coordinate environmental signals and metabolic/anabolic pathways to provide macromolecules and energy needed for survival and growth. Activation of mTORC1 is required during development, differentiation and activation of immune cells. Aberrant and persistent activation of mTORC1 is often observed in malignant B cells such as Non-Hodgkin's (NH) B-cell lymphomas. Here, we review recent insights on cell metabolism and on basic mechanisms of mTORC1 regulation and metabolic functions. We highlight the distinct mechanisms driving mTORC1 activation in the three most-common types of NH B-cell lymphomas (Diffuse Large B Cell Lymphomas, Follicular Lymphomas, and Mantle Cell Lymphomas), for which the first generation of mTORC1 inhibitors (rapalogs) have been extensively evaluated in preclinical and clinical settings. Finally, we discuss the reasons for limited clinical success of this therapy and focus on potential therapeutic strategies targeting metabolic pathways, upstream and downstream of mTORC1, that can be combined to rapalogs in order to improve patient's outcome.

Absence of antitumor effects of metformin in sorafenib-treated patients with hepatocellular carcinoma recurrence after hepatic resection and liver transplantation

Backgrounds/Aims

Hepatocellular carcinoma (HCC) recurrence following hepatic resection (HR) and liver transplantation (LT) remains a great concern. We assessed the antitumor effects of metformin in patients treated with sorafenib for HCC recurrence after HR or LT.

Methods

The two clinical retrospective studies involved metformin therapy of 304 HR patients and 74 LT recipients who were treated with sorafenib.

Results

In the study involving patients who had undergone HR, death occurred in 245 of the 304 patients (80.6%) during a median follow-up of 10.2 months after sorafenib administration. The metformin HR group (group 1; n=40) showed no prognostic difference in progression-free and overall survival rates compared with the all-HR control group (group 3; n=241) and propensity score-matched HR control group (group 4; n=80). In the clinical study of recipients exposed to LT, death occurred in 62 of the 74 patients (83.8%) during a median follow-up of 13.6 months (range: 3–76 months) after sorafenib administration. The metformin LT group (group 5; n=14) showed no prognostic difference in progression-free and overall survival rates compared with the all-LT control group (group 7; n=43) and propensity score-matched LT control group (group 8; n=28).

Conclusions

Our clinical studies demonstrated absence of synergistic antitumor effects of metformin. Further high-volume studies are necessary to assess the role of metformin in patients treated with sorafenib for advanced HCC.

Changes of Cell Biochemical States Are Revealed in Protein Homomeric Complex Dynamics

We report here a simple and global strategy to map out gene functions and target pathways of drugs, toxins, or other small molecules based on "homomer dynamics" protein-fragment complementation assays (hdPCA). hdPCA measures changes in self-association (homomerization) of over 3,500 yeast proteins in yeast grown under different conditions. hdPCA complements genetic interaction measurements while eliminating the confounding effects of gene ablation. We demonstrate that hdPCA accurately predicts the effects of two longevity and health span-affecting drugs, the immunosuppressant rapamycin and the type 2 diabetes drug metformin, on cellular pathways. We also discovered an unsuspected global cellular response to metformin that resembles iron deficiency and includes a change in protein-bound iron levels. This discovery opens a new avenue to investigate molecular mechanisms for the prevention or treatment of diabetes, cancers, and other chronic diseases of aging.

Energy restriction in renal protection

Energy restriction (ER) has been widely studied as a novel intervention, and its ability to prolong life has been fully demonstrated. For example, ER can significantly extend the lifespans of model flies, worms, rodents and other mammals. The role of ER in renal protection has also been elucidated. In preclinical studies, adjusting total energy intake or consumption of specific nutrients has prophylactic or therapeutic effects on ageing-related kidney disease and acute and chronic kidney injury. Amino acid restriction has gradually attracted attention. ER mimetics have also been studied in depth. The protective mechanisms of ER and ER mimetics for renal injury include increasing AMP-activated protein kinase and sirtuin type 1 (Sirt1) levels and autophagy and reducing mammalian target of rapamycin, inflammation and oxidative stress. However, the renal protective effect of ER has mostly been investigated in rodent models, and the role of ER in patients cannot be determined due to the lack of large randomised controlled trials. To protect the kidney, the mechanism of ER must be thoroughly researched, and more accurate diet or drug interventions need to be identified.

Metformin blocks MYC protein synthesis in colorectal cancer via mTOR-4EBP-eIF4E and MNK1-eIF4G-eIF4E signaling

The antidiabetic drug metformin has been associated with reduced colorectal cancer (CRC) risk and improved prognosis of CRC patients. However, the detailed mechanisms underlying such beneficial effects remain unknown. In this study, we aimed to evaluate metformin activity in CRC models and unveil the underlying molecular mechanisms. We showed that metformin inhibits CRC cell proliferation by arresting cells in the G1 phase of the cell cycle and dramatically reduces colony formation of CRC cells. We discovered that metformin causes a robust reduction of MYC protein level. Through the use of luciferase assay and coincubation with either protein synthesis or proteasome inhibitors, we demonstrated that regulation of MYC by metformin is independent of the proteasome and 3' UTR-mediated regulation, but depends on protein synthesis. Data from polysome profiling and ribopuromycylation assays showed that metformin induced widespread inhibition of protein synthesis. Repression of protein synthesis by metformin preferentially affects cell cycle-associated proteins, by altering signaling through the mTOR-4EBP-eIF4E and MNK1-eIF4G-eIF4E axes. The inhibition of MYC protein synthesis may underlie metformin's beneficial effects on CRC risk and prognosis.

Anti-metastatic effect of metformin via repression of interleukin 6-induced epithelial-mesenchymal transition in human colon cancer cells

Metformin, a first-line drug used to treat type 2 diabetes, has also been shown to have anticancer effects against a variety of malignancies, including colorectal cancer. Although inhibition of the mTOR pathway is known to be the most important mechanism for the antitumor effects of metformin, other mechanisms remain unclear. The purpose of this study was to identify the antitumor mechanism of metformin in colorectal cancer using high-throughput data, and then test the mechanism experimentally. We identified the gene signature of metformin-treated colon cancer cells. This signature was processed for prediction using colon adenocarcinoma patient data from the Cancer Genome Atlas to classify the patients showing a gene expression pattern similar to that in metformin-treated cells. This patient group showed better overall and disease-free survival. Furthermore, pathway analysis revealed that the metformin-predicted group was characterized by decreased interleukin (IL)-6 pathway signaling, epithelial–mesenchymal transition, and colon cancer metastatic signaling. We induced epithelial–mesenchymal transition in colon cancer cell lines via IL-6 treatment, which increased cell motility and promoted invasion. However, these effects were blocked by metformin. These findings suggest that blockade of IL-6-induced epithelial–mesenchymal transition is an antitumor mechanism of metformin.

Effects of metformin use on total mortality in patients with type 2 diabetes and chronic obstructive pulmonary disease: A matched-subject design

BACKGROUNDS

Few studies have investigated the therapeutic effects of metformin in patients with type 2 diabetes mellitus (T2DM) and chronic obstructive pulmonary disease (COPD). We compared the risk of all-cause mortality between metformin users and nonusers.

METHODS

We conducted a retrospective cohort study for patients with T2DM and COPD who were enrolled between January 1, 2000 and June 30, 2012. Individuals with exacerbated symptoms who were hospitalized or sent to the emergency department (ED) were identified as having exacerbated COPD; outpatient claims were identified as having stable COPD. A total of 40,597 metformin users and 39,529 nonusers comprised the cohort of stable COPD; 14,001 metformin users and 21,613 nonusers comprised the cohort of exacerbated COPD. Users and nonusers were matched using propensity score (1:1). Our primary outcome was all-cause mortality.

RESULTS

A total of 19,505 metformin users were matched to 19,505 nonusers in the cohort of diabetes with stable COPD. The mean follow-up time was 3.91 years. All-cause mortality was reported in 1326 and 1609 metformin users and nonusers, respectively. After multivariate adjustment, metformin users had lower risk of mortality (adjusted hazard ratio [aHR] = 0.84, p < 0.0001). Metformin users had significantly lower risk of noncardiovascular death (aHR = 0.86, p = 0.0008). A total of 7721 metformin users were matched to 7721 nonusers in the cohort of diabetes with exacerbated COPD. The mean follow-up time was 3.18 years. All-cause mortality was reported in 1567 and 1865 metformin users and nonusers, respectively. After multivariate adjustment, metformin users had significantly lower risk of mortality (aHR = 0.89, p = 0.002) and cardiovascular death (aHR = 0.70, p = 0.01).

CONCLUSION

This large-series, nationwide cohort study demonstrated that metformin use could significantly lower the risk of all-cause mortality in patients with T2DM and either stable or exacerbated COPD.

Three May Be Better Than Two: A Proposal for Metformin Addition to PI3K/Akt Inhibitor-antiandrogen Combination in Castration-resistant Prostate Cancer

Prostate cancer is a prevalent malignant disease. Castration-resistant prostate cancer (CRPC) is a poor prognosis form that develops upon resistance to first-line androgen deprivation therapy. Intensive research is ongoing to find efficient therapeutics for this refractory state. Actually, the combination of PI3K/Akt inhibitors with new-generation antiandrogens is among the most promising therapeutic schemes, although not yet at the optimal level. Metformin effects on prostate cancer, notably its therapeutic targets shared with antiandrogens and/or PI3K/Akt inhibitors, are reviewed in this article. From that, the hypothesis of PI3K/Akt-antiandrogens dual blockade optimization by metformin addition in CRPC will be deduced.

Bifurcation analysis of insulin regulated mTOR signalling pathway in cancer cells

Insulin induced mTOR signalling pathway is a complex network implicated in many types of cancers. The molecular mechanism of this pathway is highly complex and the dynamics is tightly regulated by intricate positive and negative feedback loops. In breast cancer cell lines, metformin has been shown to induce phosphorylation at specific serine sites in insulin regulated substrate of mTOR pathway that results in apoptosis over cell proliferation. The author models and performs bifurcation analysis to simulate cell proliferation and apoptosis in mTOR signalling pathway to capture the dynamics both in the presence and absence of metformin in cancer cells. Metformin is shown to negatively regulate PI3K through AMPK induced IRS1 phosphorylation and this brings about a reversal of AKT bistablity in codimension-1 bifurcation diagram from S-shaped, related to cell proliferation in the absence of drug metformin, to Z-shaped, related to apoptosis in the presence of drug metformin. The author hypothesises and explains how this negative regulation acts a circuit breaker, as a result of which mTOR network favours apoptosis of cancer cells over its proliferation. The implication of reversing the shape of bistable dynamics from S to Z or vice-versa in biological networks in general is discussed.

Combination therapy with androgen deprivation for hormone sensitive prostate cancer: A new frontier

Androgen deprivation therapy (ADT) has been the standard of care for the last 75 years in metastatic hormone sensitive prostate cancer (PCa). However, this approach is rarely curative. Recent clinical trials have demonstrated that ADT combined with other agents, notably docetaxel and abiraterone, lead to improved survival. The mechanisms surrounding this improved cancer outcomes are incompletely defined. The response of cancer cells to ADT includes apoptosis and cell death, but a significant fraction remains viable. Our laboratory has demonstrated both in vitro and in vivo that cellular senescence occurs in a subset of these cells. Cellular senescence is a phenotype characterized by cell cycle arrest, senescence-associated β-galactosidase (SA-β-gal), and a hypermetabolic state. Positive features of cellular senescence include growth arrest and immune stimulation, although persistence may release cytokines and growth factors that are detrimental. Senescent tumor cells generate a catabolic state with increased glycolysis, protein turnover and other metabolic changes that represent targets for drugs, like metformin, to be applied in a synthetic lethal approach. This review examines the response to ADT and the putative role of cellular senescence as a biomarker and therapeutic target in this context.

Autophagy blockade sensitizes human head and neck squamous cell carcinoma towards CYT997 through enhancing excessively high reactive oxygen species-induced apoptosis

The functional relationship between apoptosis and autophagy in anticancer drug treatment is extremely complex, and the molecular machinery is obscure. This study aims to investigate the efficacy of CYT997, a novel microtubule-disrupting agent, in head and neck squamous cell carcinomas (HNSCCs) and complete the autophagy-apoptosis puzzle involved in drug action. We report here that CYT997 exhibits anticancer activity by triggering oxidative stress-associated apoptosis in HNSCC cells. Interestingly, upregulation of autophagy by mTOR-dependent pathways appears to have a cytoprotective role in preventing apoptosis by inhibiting CYT997-induced excessively high levels of reactive oxygen species (ROS). Blockade of autophagy by ATG7 depletion or addition of autophagy inhibitor hydroxychloroquine (HCQ) sensitizes HNSCC cells to CYT997 as evidenced by enhanced ROS-associated apoptosis. Moreover, HCQ exhibits a good synergism with CYT997 on induction of apoptosis in HNSCC xenografts without cytotoxicity, suggesting combined treatment of CYT997 with autophagy inhibitors would increase the anticancer efficacy of CYT997. These findings unveil the importance of ROS in crosstalk between autophagy and apoptosis in CYT997 treatment, raising concerns that genetic or pharmacologic blockade of autophagy should be considered in the design of new therapeutics for HNSCC.

KEY MESSAGES

• CYT997 exhibits anticancer activity by induction of ROS-associated apoptosis. • mTOR-dependent cytoprotective autophagy prevents CYT997-induced apoptosis. • Blockade of autophagy augments CYT997 efficacy by enhanced ROS-associated apoptosis. • Combination of autophagy inhibitors with CYT997 is more effective against HNSCC.

Challenges and controversies in the conservative management of uterine and ovarian cancer

Uterine cancer is the fifth most common cancer in women worldwide with an estimated 320,000 annual diagnoses. Its most common form, endometrioid adenocarcinoma of the endometrium (endometrial adenocarcinoma [EAC]), is thought to develop through excessive proliferation of endometrial glands, and then increasing steadily in incidence. The current standard treatment for EAC is hysterectomy, which is often curative. However, it may be unacceptably expensive for women with severe medical comorbidities, those who are at risk of intra- and postoperative adverse events and those who desire fertility. Ovarian cancer is the most malignant of all gynaecological cancers, but patients with disease limited to one ovary and patients with non-epithelial tumours may expect a good prognosis. A selected group of young patients who desire fertility may be well treated with conservative surgery. This chapter reviews patient selection, diagnosis, pre-treatment evaluation, treatment options, surveillance and risk of relapse.

Synergistic effect of metformin on sorafenib in in vitro study using hepatocellular carcinoma cell lines

Backgrounds/Aims

Hepatocellular carcinoma (HCC) recurrence remains a great concern following hepatic resection and liver transplantation. We investigated the metformin-induced cytotoxic effects on sorafenib in an in vitro study using HCC cell lines.

Methods

This research was conducted through an in vitro study using one HepG2.2.15 liver tumor and two patient-derived graft HCC cell lines.

Results

An in vitro study revealed noticeable cytotoxic effects of metformin as well as noticeable synergistic cytotoxic effects of metformin and sorafenib on cell viability. Assays for the mechanisms of action of antitumor effects revealed that alpha-fetoprotein expression was suppressed by both metformin and sorafenib, but no synergistic effect was observed. LC3-I and LC3-II assays revealed the synergistic upregulation of autophagy and assays for IL-1β, IL-6, p53, and TNF-α revealed the synergistic upregulation of cell damage and apoptosis. In contrast, metformin did not affect HBx expression, thus no noticeable synergistic effect was considered to be present.

Conclusions

Our in vitro study demonstrated cytotoxic effects of metformin and synergistic antitumor effects of sorafenib. These results should be verified in further clinical studies with patients of advanced HCC.

Emerging evidence for targeting mitochondrial metabolic dysfunction in cancer therapy

Mammalian cells use a complex network of redox-dependent processes necessary to maintain cellular integrity during oxidative metabolism, as well as to protect against and/or adapt to stress. The disruption of these redox-dependent processes, including those in the mitochondria, creates a cellular environment permissive for progression to a malignant phenotype and the development of resistance to commonly used anticancer agents. An extension of this paradigm is that when these mitochondrial functions are altered by the events leading to transformation and ensuing downstream metabolic processes, they can be used as molecular biomarkers or targets in the development of new therapeutic interventions to selectively kill and/or sensitize cancer versus normal cells. In this Review we propose that mitochondrial oxidative metabolism is altered in tumor cells, and the central theme of this dysregulation is electron transport chain activity, folate metabolism, NADH/NADPH metabolism, thiol-mediated detoxification pathways, and redox-active metal ion metabolism. It is proposed that specific subgroups of human malignancies display distinct mitochondrial transformative and/or tumor signatures that may benefit from agents that target these pathways.

Metformin as a Therapeutic Target in Endometrial Cancers

Endometrial cancer is the most common gynecologic malignancy in developed countries. Its increasing incidence is thought to be related in part to the rise of metabolic syndrome, which has been shown to be a risk factor for the development of hyperestrogenic and hyperinsulinemic states. This has consequently lead to an increase in other hormone-responsive cancers as well e.g., breast and ovarian cancer. The correlation between obesity, hyperglycemia, and endometrial cancer has highlighted the important role of metabolism in cancer establishment and persistence. Tumor-mediated reprogramming of the microenvironment and macroenvironment can range from induction of cytokines and growth factors to stimulation of surrounding stromal cells to produce energy-rich catabolites, fueling the growth, and survival of cancer cells. Such mechanisms raise the prospect of the metabolic microenvironment itself as a viable target for treatment of malignancies. Metformin is a biguanide drug that is a first-line treatment for type 2 diabetes that has beneficial effects on various markers of the metabolic syndrome. Many studies suggest that metformin shows potential as an adjuvant treatment for uterine and other cancers. Here, we review the evidence for metformin as a treatment for cancers of the endometrium. We discuss the available clinical data and the molecular mechanisms by which it may exert its effects, with a focus on how it may alter the tumor microenvironment. The pleiotropic effects of metformin on cellular energy production and usage as well as intercellular and hormone-based interactions make it a promising candidate for reprogramming of the cancer ecosystem. This, along with other treatments aimed at targeting tumor metabolic pathways, may lead to novel treatment strategies for endometrial cancer.

Metformin as an Anticancer Agent

Metformin has been a frontline therapy for type 2 diabetes (T2D) for many years. Its effectiveness in T2D treatment is mostly attributed to its suppression of hepatic gluconeogenesis; however, the mechanistic aspects of metformin action remain elusive. In addition to its glucose-lowering effect, metformin possesses other pleiotropic health-promoting effects that include reduced cancer risk and tumorigenesis. Metformin inhibits the electron transport chain (ETC) and ATP synthesis; however, recent data reveal that metformin regulates AMP-activated protein kinase (AMPK) and the mechanistic target of rapamycin complex 1 (mTORC1) by multiple, mutually nonexclusive mechanisms that do not necessarily depend on the inhibition of ETC and the cellular ATP level. In this review, we discuss recent advances in elucidating the molecular mechanisms that are relevant for metformin use in cancer treatment.

Effect of Aspirin on Cancer Chemoprevention in Japanese Patients With Type 2 Diabetes: 10-Year Observational Follow-up of a Randomized Controlled Trial

OBJECTIVE

This study analyzed the efficacy of low-dose aspirin in cancer chemoprevention in patients with diabetes.

RESEARCH DESIGN AND METHODS

This study was a posttrial follow-up of the Japanese Primary Prevention of Atherosclerosis with Aspirin for Diabetes (JPAD) trial. Participants in the JPAD trial (2,536 Japanese patients with type 2 diabetes and without preexisting cardiovascular disease) were randomly allocated to receive aspirin (81 or 100 mg daily) or no aspirin. After that trial ended in 2008, we followed up with the participants until 2015, with no attempt to change the previously assigned therapy. The primary end point was total cancer incidence. We investigated the effect of low-dose aspirin on cancer incidence.

RESULTS

During the median follow-up period of 10.7 years, a total of 318 cancers occurred. The cancer incidence was not significantly different between the aspirin and no-aspirin groups (log-rank, P = 0.4; hazard ratio [HR], 0.92; 95% CI, 0.73-1.14; P = 0.4). In subgroup analyses, aspirin did not affect cancer incidence in men, women, or participants aged ≥65 years. However, it decreased cancer incidence in participants aged <65 years (log-rank, P = 0.05; HR, 0.67; 95% CI, 0.44-0.99; P = 0.048). After adjusting for sex, hemoglobin A_1c, smoking status, and administration of metformin and statins, aspirin significantly reduced cancer incidence in participants aged <65 years (adjusted HR, 0.66; 95% CI, 0.43-0.99; P = 0.04).

CONCLUSIONS

Low-dose aspirin did not reduce cancer incidence in Japanese patients with type 2 diabetes.

Molecular Mechanisms of Metformin for Diabetes and Cancer Treatment

Metformin has been the first-line drug treatment for hyperglycemia and insulin resistance for over 50 years. However, the molecular basis of its therapeutic role remained incompletely understood. Recent advances demonstrate that metformin could exert its glucose-lowering effect by multiple mechanisms, including activation of 5′-AMP-activated protein kinase, decreasing production of cyclic AMP, suppressing mitochondrial complex I of the electron transport chain, targeting glycerophosphate dehydrogenase, and altering the gut microbiome. In addition, epidemiological and clinical observation studies suggest that metformin reduced cancer risk in patients with type 2 diabetes and improved survival outcome of human cancers. Experimental studies have shown that this drug can inhibit cancer cell viability, growth, and proliferation through inhibiting mTORC1 signaling and mitochondrial complex I, suggesting that it may be a promising drug candidate for malignancy. Here, we summarize recent progress in studies of metformin in type 2 diabetes and tumorigenesis, which provides novel insight on the therapeutic development of human diseases.

NGAL is Downregulated in Oral Squamous Cell Carcinoma and Leads to Increased Survival, Proliferation, Migration and Chemoresistance

Oral cancer is a major public health burden worldwide. The lack of biomarkers for early diagnosis has increased the difficulty in managing this disease. Recent studies have reported that neutrophil gelatinase-associated lipocalin (NGAL), a secreted glycoprotein, is upregulated in various tumors. In our study, we found that NGAL was significantly downregulated in primary malignant and metastatic tissues of oral cancer in comparison to normal tissues. The downregulation of NGAL was strongly correlated with both degree of differentiation and stage (I–IV); it can also serve as a prognostic biomarker for oral cancer. Additionally, tobacco carcinogens were found to be involved in the downregulation of NGAL. Mechanistic studies revealed that knockdown of NGAL increased oral cancer cell proliferation, survival, and migration; it also induced resistance against cisplatin. Silencing of NGAL activated mammalian target of rapamycin (mTOR)signaling and reduced autophagy by the liver kinase B1 (LKB1)-activated protein kinase (AMPK)-p53-Redd1 signaling axis. Moreover, cyclin-D1, Bcl-2, and matrix metalloproteinase-9 (MMP-9) were upregulated, and caspase-9 was downregulated, suggesting that silencing of NGAL increases oral cancer cell proliferation, survival, and migration. Thus, from our study, it is evident that downregulation of NGAL activates the mTOR pathway and helps in the progression of oral cancer.

Metformin: oxidative and proliferative parameters in-vitro and in-vivo models of murine melanoma

Cutaneous melanoma is one of the most lethal cancers because of its increased rate of metastasis and resistance to available therapeutic options. Early studies indicate that metformin has beneficial effects on some types of cancer, including melanoma. To clarify knowledge of the mechanism of action of metformin on this disease, two treatment-based approaches are presented using metformin on melanoma progression: an in-vitro and an in-vivo model. The in-vitro assay was performed for two experimental treatment periods (24 and 48 h) at different metformin concentrations. The results showed that metformin decreased cell viability, reduced proliferation, and apoptosis was a major event 48 h after treating B16F10 cells. Oxidative stress was characterized by the decrease in total thiol antioxidants immediately following 24 h of metformin treatment and showed an increase in lipid peroxidation. The in-vivo model was performed by injecting B16F10 cells into the subcutaneous of C57/BL6 mice. Treatment with metformin began on day 3 and on day 14, the mice were killed. Treatment of mice with metformin reduced tumor growth by 54% of its original volume compared with nontreatment. The decrease in systemic vascular endothelial growth factor, restoration of antioxidants glutathione and catalase, and normal levels of lipid peroxidation indicate an improved outcome for melanoma following metformin treatment, meeting a need for new strategies in the treatment of melanoma.

AMP kinase promotes glioblastoma bioenergetics and tumour growth

Stress is integral to tumour evolution, and cancer cell survival depends on stress management. We found that cancer-associated stress chronically activates the bioenergetic sensor AMP kinase (AMPK) and, to survive, tumour cells hijack an AMPK-regulated stress response pathway conserved in normal cells. Analysis of The Cancer Genome Atlas data revealed that AMPK isoforms are highly expressed in the lethal human cancer glioblastoma (GBM). We show that AMPK inhibition reduces viability of patient-derived GBM stem cells (GSCs) and tumours. In stressed (exercised) skeletal muscle, AMPK is activated to cooperate with CREB1 (cAMP response element binding protein-1) and promote glucose metabolism. We demonstrate that oncogenic stress chronically activates AMPK in GSCs that coopt the AMPK-CREB1 pathway to coordinate tumour bioenergetics through the transcription factors HIF1α and GABPA. Finally, we show that adult mice tolerate systemic deletion of AMPK, supporting the use of AMPK pharmacological inhibitors in the treatment of GBM.

Novel therapeutic strategy for cancer and autoimmune conditions: Modulating cell metabolism and redox capacity

Dysregulation of cell metabolism and redox balance is implicated in the pathogenesis and progression of cancer and autoimmune diseases. Because the cell proliferation and apoptotic regulatory pathways are interconnected with metabolic and redox signalling pathways, the current mono-target treatment is ineffective, and multi-drug resistance remains common. Complex diseases are often implicated in a network-based context of pathology; therefore, a new holistic intervention approach is required to block multi-crosstalk in such complicated circumstances. The use of therapeutic agents isolated from herbs to holistically modulate metabolism and redox state has been shown to relieve carcinoma growth and the inflammatory response in autoimmune disorders. Multiple clinically applied or novel herbal chemicals with metabolic and redox modulatory capacity as well as low toxicity have recently been identified. Moreover, new metabolic targets and mechanisms of drug action have been discovered, leading to the exploration of new pathways for drug repositioning, clinical biomarker spectra, clinical treatment strategies and drug development. Taken together with multiple supporting examples, the modulation of cell metabolism and the redox capacity using herbal chemicals is emerging as a new, alternative strategy for the holistic treatment of cancer and autoimmune disorders. In the future, the development of new diagnostic tools based on the detection of metabolic and redox biomarkers, reformulation of optimized herbal compositions using artificial intelligence, and the combination of herbs with mono-targeting drugs will reveal new potential for clinical application.

Metformin Use is Associated with Improved Survival for Patients with Advanced Prostate Cancer on Androgen Deprivation Therapy

PURPOSE

Metformin is commonly prescribed for patients with type 2 diabetes mellitus. We hypothesized that metformin plus androgen deprivation therapy may be beneficial in combination. Our objective was to assess this combination in a retrospective cohort of patients with advanced prostate cancer.

MATERIALS AND METHODS

Using national Veterans Affairs databases we identified all men diagnosed with prostate cancer between 2000 and 2008 who were treated with androgen deprivation therapy with followup through May 2016. Study exclusions included treatment with androgen deprivation therapy for 6 months or longer, or receipt of androgen deprivation therapy concurrently with localized radiation. Three patient cohorts were developed, including no diabetes mellitus, diabetes mellitus with no metformin and diabetes mellitus with metformin. Cox proportional HRs were calculated for overall survival, skeletal related events and cancer specific survival.

RESULTS

After exclusions the cohort consisted of 87,344 patients, including 61% with no diabetes mellitus, 22% with diabetes mellitus and no metformin, and 17% with diabetes mellitus on metformin. Cox proportional hazard analysis of overall survival showed improved survival in men with diabetes mellitus on metformin (HR 0.82, 95% CI 0.78-0.86) compared to those with diabetes mellitus who were not on metformin (HR 1.03, 95% CI 0.99-1.08). The reference group was men with no diabetes mellitus. Cox proportional hazard analysis of predictors of skeletal related events revealed a HR of 0.82 (95% CI 0.72-0.93) in men with diabetes mellitus on metformin. Cox proportional hazard analysis of cancer specific survival showed improved survival in men with diabetes mellitus on metformin (HR 0.70, 95% CI 0.64-0.77) vs those with diabetes mellitus without metformin (HR 0.93, 95% CI 0.85- 1.00). The reference group was men with no diabetes mellitus.

CONCLUSIONS

Metformin use in veterans with prostate cancer who receive androgen deprivation therapy is associated with improved oncologic outcomes. This association should be evaluated in a prospective clinical trial.

Metformin and Autoimmunity: A "New Deal" of an Old Drug

Metformin (dimethyl biguanide) is a synthetic derivative of guanidine, isolated from the extracts of Galega officinalis, a plant with a prominent antidiabetic effect. Since its discovery more than 50 years ago, metformin represents a worldwide milestone in treatment of patients with type 2 diabetes (T2D). Recent evidence in humans indicates novel pleiotropic actions of metformin which span from its consolidated role in T2D management up to various regulatory properties, including cardio- and nephro-protection, as well as antiproliferative, antifibrotic, and antioxidant effects. These findings, together with ground-breaking studies demonstrating its ability to prolong healthspan and lifespan in mice, provided the basis for defining metformin as a potential antiaging molecule. Moreover, emerging in vivo and in vitro evidence support the novel hypothesis that metformin can exhibit immune-modulatory features. Studies suggest that metformin interferes with key immunopathological mechanisms involved in systemic autoimmune diseases, such as the T helper 17/regulatory T cell balance, germinal centers formation, autoantibodies production, macrophage polarization, cytokine synthesis, neutrophil extracellular traps release, and bone or extracellular matrix remodeling. These effects may represent a powerful contributor to antiaging and anticancer properties exerted by metformin and, from another standpoint, may open the way to assess whether metformin can be a candidate molecule for clinical trials involving patients with immune-mediated diseases. In this article, we will review the available preclinical and clinical evidence regarding the effect of metformin on individual cells of the immune system, with emphasis on immunological mechanisms related to the development and maintenance of autoimmunity and its potential relevance in treatment of autoimmune diseases.

Metformin's antitumour and anti-angiogenic activities are mediated by skewing macrophage polarization

Beneficial effects of metformin on cancer risk and mortality have been proved by epidemiological and clinical studies, thus attracting research interest in elucidating the underlying mechanisms. Recently, tumour‐associated macrophages (TAMs) appeared to be implicated in metformin‐induced antitumour activities. However, how metformin inhibits TAMs‐induced tumour progression remains ill‐defined. Here, we report that metformin‐induced antitumour and anti‐angiogenic activities were not or only partially contributed by its direct inhibition of functions of tumour and endothelial cells. By skewing TAM polarization from M2‐ to M1‐like phenotype, metformin inhibited both tumour growth and angiogenesis. Depletion of TAMs by clodronate liposomes eliminated M2‐TAMs‐induced angiogenic promotion, while also abrogating M1‐TAMs‐mediated anti‐angiogenesis, thus promoting angiogenesis in tumours from metformin treatment mice. Further in vitro experiments using TAMs‐conditioned medium and a coculture system were performed, which demonstrated an inhibitory effect of metformin on endothelial sprouting and tumour cell proliferation promoted by M2‐polarized RAW264.7 macrophages. Based on these results, metformin‐induced inhibition of tumour growth and angiogenesis is greatly contributed by skewing of TAMs polarization in microenvironment, thus offering therapeutic opportunities for metformin in cancer treatment.

Glyoxalase 1 sustains the metastatic phenotype of prostate cancer cells via EMT control

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Effective therapeutic intervention in metastatic PCa is undermined by our poor understanding of its molecular aetiology. Defining the mechanisms underlying PCa metastasis may lead to insights into how to decrease morbidity and mortality in this disease. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a potent precursor of advanced glycation end products (AGEs). Hydroimidazolone (MG-H1) and argpyrimidine (AP) are AGEs originating from MG-mediated post-translational modification of proteins at arginine residues. AP is involved in the control of epithelial to mesenchymal transition (EMT), a crucial determinant of cancer metastasis and invasion, whose regulation mechanisms in malignant cells are still emerging. Here, we uncover a novel mechanism linking Glo1 to the maintenance of the metastatic phenotype of PCa cells by controlling EMT by engaging the tumour suppressor miR-101, MG-H1-AP and TGF-β1/Smad signalling. Moreover, circulating levels of Glo1, miR-101, MG-H1-AP and TGF-β1 in patients with metastatic compared with non-metastatic PCa support our in vitro results, demonstrating their clinical relevance. We suggest that Glo1, together with miR-101, might be potential therapeutic targets for metastatic PCa, possibly by metformin administration.

Hypertension in malignancy-an underappreciated problem

Hypertension is one of the most common comorbidities in cancer patients with malignancy, in particular, in the elderly. On the other hand, hypertension is a long-term consequence of antineoplastic treatment, including both chemotherapy and targeted agents. Several chemotherapeutics and targeted drugs may be responsible for development or worsening of the hypertension. The most common side effect of anti-VEGF (vascular endothelial growth factor) treatment is hypertension. However, pathogenesis of hypertension in patients receiving this therapy appears to be associated with multiple pathways and is not yet fully understood. Development of hypertension was associated with improved antitumor efficacy in patients treated with anti-antiangiogenic drugs in some but not in all studies. Drugs used commonly as adjuvants such as steroids, erythropoietin stimulating agents etc, may also cause rise in blood pressure or exacerbate preexisiting hypertension. Hypotensive therapy is crucial to manage hypertension during certain antineoplastic treatment. The choice and dose of antihypertensive drugs depend upon the presence of organ dysfunction, comorbidities, and/or adverse effects. In addition, severity of the hypertension and the urgency of blood pressure control should also be taken into consideration. As there are no specific guidelines on the hypertension treatment in cancer patients we should follow the available guidelines to obtain the best possible outcomes and pay the attention to the individualization of the therapy according to the actual situation.

miR-29a regulated ER-positive breast cancer cell growth and invasion and is involved in the insulin signaling pathway

Increasing amounts of evidence show that insulin can activate different insulin signaling pathways to promote breast cancer growth and invasion. miR-29a plays crucial roles in decreasing glucose-stimulated insulin secretion, as well as in regulating breast cancer cell proliferation and EMT. However, the mechanism responsible for the regulatory effects of miR-29a on breast cancer growth and invasion and the relationship between these effects and insulin signaling remains unclear. Herein, we showed that human insulin increased miR-29a expression in ER-positive breast cancer cells and that miR-29a facilitated the ability of insulin to promote breast cancer cell proliferation and migration. We found that miR-29a-induced cell proliferation and metastasis acceleration occurred primarily through ERK phosphorylation. The IGF-1R is the upstream target gene of miR-29a, while CDC42 and p85α are the downstream target genes of miR-29a. These results have provided us with information regarding the molecular mechanisms by which hyperinsulinemia promotes breast cancer occurrence and development and thus leads to a poor prognosis in breast cancer patients and indicate that miR-29a plays an important role in breast cancer development and invasion.

Liver antioxidant and aerobic status improves after metformin and melatonin administration in a rat model of high-fat diet and mammary carcinogenesis

Oxidative stress is involved in the development of various cancers. In the present study, the effect of long-term administration of peroral antidiabetic metformin and pineal hormone melatonin on liver antioxidant and aerobic status in female Sprague-Dawley rats carrying mammary tumors induced by N-methyl-N-nitrosourea was evaluated. Both substances were administered in a preventive and curative manner (12 days before and 16 weeks after the carcinogen application). Carcinogen administration induced oxidative stress: the level of thiobarbituric acid reactive substances (TBARS) considered as a marker of reactive oxygen species (ROS) generation in liver increased as well as the level of oxidatively modified protein content (OMP; aldehyde and ketone derivates). Metformin administration restored succinate dehydrogenase and lactate dehydrogenase activity and associated ROS production and OMP content to the level of intact rats, with predominant activation of superoxide dismutase (SOD) and glutathione reductase (GR). Melatonin alone and in combination with metformin also decreased TBARS content. OMP content decreased in all groups receiving chemoprevention. The rise in total antioxidant capacity after melatonin and particularly metformin and melatonin combination might result from the initiation of anaerobic metabolism and increasing SOD, GR, and glutathione peroxidase activity. Long-term administration of metformin and melatonin exerts antioxidant properties in liver, especially in combination.

Anti-tumoral effects of exercise on hepatocellular carcinoma growth

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

Pramlintide, an antidiabetic, is antineoplastic in colorectal cancer and synergizes with conventional chemotherapy

Background

Approximately 90% of patients with metastatic colorectal cancer fail therapy mainly due to resistance. Taking advantage of currently approved agents for treatment of disease conditions other than cancer for the identification of new adjuvant anticancer therapies is highly encouraged. Pramlintide is a parenteral antidiabetic agent that is currently approved for treatment of types 1 and 2 diabetes mellitus.

Objectives

To address the antineoplastic potential of pramlintide in colorectal cancer and to evaluate the ability of pramlintide to enhance the cytotoxicity of 5-fluorouracil, oxaliplatin, and irinotecan against colorectal cancer cell lines expressing wild-type and mutant p53.

Materials and methods

The antiproliferative effect of pramlintide alone or in combination with 5-fluorouracil, oxaliplatin, or irinotecan in HCT-116 and HT-29 colorectal cancer cell lines was investigated using MTT cell proliferation assay. IC50 values were calculated using Compusyn software 1.0. Synergy values (R) were calculated using the ratio of IC50 of each primary drug alone divided by combination IC50s. For each two pairs of experiments, Student’s t-test was used for analysis. For combination studies, one-way analysis of variance and Tukey post hoc testing was performed using R 3.3.2 software. A p-value of <0.05 was considered significant.

Results

Pramlintide inhibited the growth of HCT-116 and HT-29 in a dose-dependent manner, with higher efficacy against the latter (IC50s; 48.67 and 9.10 μg/mL, respectively; p-value =0.013). Moreover, the addition of 5, 10, and 20 μg/mL of pramlintide to HCT-116 and HT-29 with 5-fluorouracil, oxaliplatin, or irinotecan induced the antiproliferative effect synergistically (R>1.6, p-value <0.05).

Conclusion

Pramlintide enhances the cytotoxicity of conventional chemotherapy against colorectal cancer cell lines harboring wild-type or mutant p53. Thus, pramlintide is a promising potential adjuvant chemotherapy in colorectal cancer.

Metformin and propranolol combination prevents cancer progression and metastasis in different breast cancer models

Discovery of new drugs for cancer treatment is an expensive and time-consuming process and the percentage of drugs reaching the clinic remains quite low.

Drug repositioning refers to the identification and development of new uses for existing drugs and represents an alternative drug development strategy.

In this work, we evaluated the antitumor effect of metronomic treatment with a combination of two repositioned drugs, metformin and propranolol, in triple negative breast cancer models.

By in vitro studies with five different breast cancer derived cells, we observed that combined treatment decreased proliferation (P < 0.001), mitochondrial activity (P < 0.001), migration (P < 0.001) and invasion (P < 0.001). In vivo studies in immunocompetent mice confirmed the potential of this combination in reducing tumor growth (P < 0.001) and preventing metastasis (P < 0.05).

Taken together our results suggest that metformin plus propranolol combined treatment might be beneficial for triple negative breast cancer control, with no symptoms of toxicity.

Metformin as a new anti-cancer drug in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare heterogeneous malignancy with poor prognosis. Since radical surgery is the only available treatment, more specific and effective drugs are urgently required. The anti-diabetic drug metformin has been associated with a decreased cancer prevalence and mortality in several solid tumors, prompting its possible use for ACC treatment.

This paper evaluates the in vitro and in vivo anti-cancer effects of metformin using the ACC cell model H295R.

Metformin treatment significantly reduces cell viability and proliferation in a dose- and time-dependent manner and associates with a significant inhibition of ERK1/2 and mTOR phosphorylation/activation, as well as with stimulation of AMPK activity. Metformin also triggers the apoptotic pathway, shown by the decreased expression of Bcl-2 and HSP27, HSP60 and HSP70, and enhanced membrane exposure of annexin V, resulting in activation of caspase-3 apoptotic effector. Metformin interferes with the proliferative autocrine loop of IGF2/IGF-1R, which supports adrenal cancer growth. Finally, in the ACC xenograft mouse model, obtained by subcutaneous injection of H295R cells, metformin intraperitoneal administration inhibits tumor growth, confirmed by the significant reduction of Ki67%.

Our data suggest that metformin inhibits H295R cell growth both in vitro and in vivo. Further preclinical studies are necessary to validate the potential anti-cancer effect of metformin in patients affected by ACC.

Multifunctional Nanoflowers for Simultaneous Multimodal Imaging and High-Sensitivity Chemo-Photothermal Treatment

Liver cancer is currently among the most challenging cancers to diagnose and treat. It is of prime importance to minimize the side effects on healthy tissues and reduce drug resistance for precise diagnoses and effective treatment of liver cancer. Herein, we report a facile but high-yield approach to fabricate a multifunctional nanomaterial through the loading of chitosan and metformin on Mn-doped Fe₃O₄@MoS₂ nanoflowers. Mn-doped Fe₃O₄ cores are used as simultaneous T₁/T₂ magnetic resonance imaging (MRI) agents for sensitive and accurate cancer diagnosis, while MoS₂ nanosheets are used as effective near-infrared photothermal conversion agents for potential photothermal therapy. The surface-functionalized chitosan was able not only to improve the dispersibility of Mn-doped Fe₃O₄@MoS₂ nanoflowers in biofluids and increase their biocompatibility, but also to significantly enhance the photothermal effect. Furthermore, metformin loading led to high suppression and eradication of hepatoma cells when photothermally sensitized, but exhibited negligible effects on normal liver cells. Due to its excellent combination of T₁/T₂ MRI properties with sensitive chemotherapeutic and photothermal effects, our study highlights the promise of developing multifunctional nanomaterials for accurate multimodal imaging-guided, and highly sensitive therapy of liver cancer.

Metformin reduces the risk of cancer in patients with type 2 diabetes: An analysis based on the Korean National Diabetes Program Cohort

The epidemiological literature suggests that insulin resistance, hyperinsulinemia, and increased levels of insulin-like growth factors place patients with type 2 diabetes mellitus (T2DM) at greater risk of cancer. The association between cancer incidence and the use of antidiabetic medications in patients with T2DM has been recently examined. There have been conflicting reports regarding an association between metformin and cancer risk. The aim of this study was to investigate the relationship between metformin use and the incidence of cancer in Koreans with T2DM.Data from The Korean National Diabetes Program (KNDP, 2006-2014), a nationwide, large-scale, prospective, multicenter cohort study in Korea, were used to study patients with T2DM. Patients ≥30 years old whose complete medical records were available were included in this study. Patients with a history of any cancer on KNDP registration or those who had been diagnosed with any type of cancer within 1 year of metformin use were excluded. Survival curves with respect to the incidence of cancer were plotted using the Kaplan-Meier method. Hazard ratios and 95% confidence intervals for cancer were estimated in a Cox proportional hazards regression analysis.During a mean 5.8 years of follow-up, 164 of the 1918 study patients (335 metformin nonusers and 1583 metformin users) developed cancer. The incidence per 1000 person-years was 21.8 in metformin nonusers and 13.2 in metformin users. Metformin users had a reduced risk of cancer, even after adjustment for demographic characteristics, metabolic parameters, diabetic complications, and other antidiabetic medications (hazard ratio 0.513, 95% confidence interval 0.318-0.826, P = .0060). Subgroup analysis of metformin users showed a reduced risk of cancer in males, patients < 65 years of age, patients with a T2DM duration < 5 years, nonobese patients, nonsmokers, and good glycemic control group.This large-scale, prospective, multicenter cohort study demonstrated an association between metformin use and reduced cancer risk in patients with T2DM.

Compound C/Dorsomorphin: Its Use and Misuse as an AMPK Inhibitor

The evolutionary conserved energy sensor AMPK plays crucial roles in many biological processes-both during normal development and pathology. Loss-of-function genetic studies in mice as well as in lower organisms underscore its importance in embryonic development, stress physiology in the adult, and in key metabolic disorders including cardiovascular disease, diabetes, cancer, and metabolic syndrome. In contrast to several other kinases important in human health and medicine where specific/selective inhibitors are available, no AMPK-specific inhibitors are available. The only reagent called dorsomorphin or compound C that is occasionally used as an AMPK inhibitor unfortunately inhibits several other kinases much more potently than AMPK and is therefore highly non-specific. In this chapter, we discuss the pros and cons of using this reagent to study AMPK functions.

Metabolic Profiles Associated With Metformin Efficacy in Cancer

Metformin is one of the most commonly prescribed medications for the treatment of type 2 diabetes. Numerous reports have suggested potential anti-cancerous and cancer preventive properties of metformin, although these findings vary depending on the intrinsic properties of the tumor, as well as the systemic physiology of patients. These intriguing studies have led to a renewed interest in metformin use in the oncology setting, and fueled research to unveil its elusive mode of action. It is now appreciated that metformin inhibits complex I of the electron transport chain in mitochondria, causing bioenergetic stress in cancer cells, and rendering them dependent on glycolysis for ATP production. Understanding the mode of action of metformin and the consequences of its use on cancer cell bioenergetics permits the identification of cancer types most susceptible to metformin action. Such knowledge may also shed light on the varying results to metformin usage that have been observed in clinical trials. In this review, we discuss metabolic profiles of cancer cells that are associated with metformin sensitivity, and rationalize combinatorial treatment options. We use the concept of bioenergetic flexibility, which has recently emerged in the field of cancer cell metabolism, to further understand metabolic rearrangements that occur upon metformin treatment. Finally, we advance the notion that metabolic fitness of cancer cells increases during progression to metastatic disease and the emergence of therapeutic resistance. As a result, sophisticated combinatorial approaches that prevent metabolic compensatory mechanisms will be required to effectively manage metastatic disease.

Metformin and cancer: An existing drug for cancer prevention and therapy

Metformin is a standard clinical drug used to treat type 2 diabetes mellitus (T2DM) and polycystic ovary syndrome. Recently, epidemiological studies and meta-analyses have revealed that patients with T2DM have a lower incidence of tumor development than healthy controls and that patients diagnosed with cancer have a lower risk of mortality when treated with metformin, demonstrating an association between metformin and tumorigenesis. In vivo and in vitro studies have revealed that metformin has a direct antitumor effect, which may depress tumor proliferation and induce the apoptosis, autophagy and cell cycle arrest of tumor cells. The mechanism underpinning the antitumor effect of metformin has not been well established. Studies have demonstrated that reducing insulin and insulin-like growth factor levels in the peripheral blood circulation may lead to the inhibition of phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin (mTOR) signaling or activation of AMP-activated protein kinase, which inhibits mTOR signaling, a process that may be associated with the antitumor effect of metformin. The present review primarily focuses on the recent progress in understanding the function of metformin in tumor development.

Effects of metformin on survival outcomes of pancreatic cancer patients with diabetes: A meta-analysis

Pancreatic cancer risk is reduced by metformin treatment in patients with diabetes. However, the effect of metformin on pancreatic cancer overall survival is unclear. The aim of the present study was to determine the association between metformin and clinical outcomes of pancreatic cancer patients with diabetes. An electronic and manual search was conducted using PubMed, Web of Science, Medline-Ovid and Cochrane Library databases between the beginning and March 31, 2017. A total of 8 studies consisting of 4,293 patients with pancreatic cancer with diabetes were included, comprising 2,033 patients who had received metformin and 2,260 patients who had not. The meta-analysis showed that metformin was associated with a relative survival benefit in pancreatic cancer patients [hazard ratio (HR), 0.81; 95% confidence interval (CI), 0.70-0.93]. These associations were also observed in subgroups of Asian countries 0.64 (95% CI, 0.52-0.80) and Western countries 0.88 (95% CI, 0.82-0.95), as well as diabetes (no indication of diabetes type). Excluding the studies considered as be prone to immortal time bias resulted in HRs (95% CIs) of 0.86 (0.69-1.07). The results of this study support the notion that the use of metformin may improve the overall survival of patients with pancreatic cancer with concurrent diabetes. However, the proposed beneficial effect of metformin on pancreatic cancer survival may be based on immortal time bias. Further carefully designed studies with high quality are warranted to confirm this efficacy.

Diabetes Mellitus and Risk of Hepatocellular Carcinoma

The occurrence of hepatocellular carcinoma (HCC) is two to three times higher in patients with diabetes mellitus (DM), the prevalence of which is increasing sharply worldwide. The purpose of this review was to describe clinical links between DM and HCC and potential biological mechanisms that may account for this association. We evaluated the role of potential pathways that could account for the development of HCC with different etiologies in the presence of DM. In addition, we also briefly discuss the potential effect of other factors such as type and dosage of antidiabetic medicines and duration of DM on HCC risk.

Metformin synergistically suppress tumor growth with doxorubicin and reverse drug resistance by inhibiting the expression and function of P-glycoprotein in MCF7/ADR cells and xenograft models

Acquired resistance to chemo-drugs remains a major obstacle to successful cancer therapy. Metformin, a well-documented drug for treating type II diabetes, was recently proposed as a novel agent for tumor treatment. In this study, we found that metformin suppressed MCF7/ADR, a doxorubicin-resistant breast cancer cell line, and acted synergistically with doxorubicin by reversing drug-resistant phenotypes both in vitro and in vivo. Metformin alone dose-dependently inhibited tumor growth, especially the stressful tumor microenvironment of glucose deficiency, and the cytotoxicity of metformin was markedly enhanced by increasing ROS production and ATP depletion. In addition, we found that metformin showed synergistic activity with doxorubicin against MCF7/ADR. Metformin increased nuclear doxorubicin accumulation and overcame drug resistance by down-regulating drug-resistant genes such as P-glycoprotein (Pgp). Metformin alone markedly inhibited MCF7/ADR tumor xenografts and demonstrated synergistic activity with doxorubicin in vivo by eliminating Ki67-positive cancer cells. In addition, metformin suppressed Pgp expression in vivo. In conclusion, our results suggested that metformin could potentially be used in the treatment of chemo-resistant tumors and could restore doxorubicin sensitivity.

Role of metformin on base excision repair pathway in p53 wild-type H2009 and HepG2 cancer cells

The antidiabetic agent metformin was shown to further possess chemopreventive and chemotherapeutic effects against cancer. Despite the advances, the underlying molecular mechanisms involved in decreasing tumor formation are still unclear. The understanding of the participation of oxidative stress in the action mechanism of metformin and its related effects on p53 and on DNA base excision repair (BER) system can help us to get closer to solve metformin puzzle in cancer. We investigated the effects of metformin in HepG2 and H2009 cells, verifying cytotoxicity, oxidative stress, antioxidant status, and DNA BER system. Our results showed metformin induced oxidative stress and reduced antioxidant capacity. Also, metformin treatment with hydrogen peroxide (H2O2) enhanced these effects. Although DNA BER enzyme activities were not changed accordantly together by metformin as a single agent or in combination with H2O2, activated p53 was decreased with increased oxidative stress in H2009 cells. Our study on the relationship between metformin/reactive oxygen species and DNA BER system in cancer cells would be helpful to understand the anticancer effects of metformin through cellular signal transduction pathways. These findings can be a model of the changes on oxidative stress that reflects p53’s regulatory role on DNA repair systems in cancer for the future studies.

Metformin transiently inhibits colorectal cancer cell proliferation as a result of either AMPK activation or increased ROS production

Metformin is a widely used and well-tolerated anti-diabetic drug that can reduce cancer risk and improve the prognosis of certain malignancies. However, the mechanism underlying its anti-cancer effect is still unclear. We studied the anti-cancer activity of metformin on colorectal cancer (CRC) by using the drug to treat HT29, HCT116 and HCT116 p53−/− CRC cells. Metformin reduced cell proliferation and migration by inducing cell cycle arrest in the G0/G1 phase. This was accompanied by a sharp decrease in the expression of c-Myc and down-regulation of IGF1R. The anti-proliferative action of metformin was mediated by two different mechanisms: AMPK activation and increase in the production of reactive oxygen species, which suppressed the mTOR pathway and its downstream targets S6 and 4EBP1. A reduction in CD44 and LGR5 expression suggested that the drug had an effect on tumour cells with stem characteristics. However, a colony formation assay showed that metformin slowed the cells’ ability to form colonies without arresting cell growth, as confirmed by absence of apoptosis, autophagy or senescence. Our finding that metformin only transiently arrests CRC cell growth suggests that efforts should be made to identify compounds that combined with the biguanide can act synergistically to induce cell death.