Suppression of tumor angiogenesis by metformin treatment via a mechanism linked to targeting of HER2/HIF-1α/VEGF secretion axis

Neratinib and metformin: A novel therapeutic approach against HER2-Positive Breast Cancer

BACKGROUND

HER2-positive breast cancer (BC) is highly aggressive with a poor prognosis. It is driven by HER2 oncoprotein activation/crosstalk with other receptors like EGFR/(HER1), HER3, and HER4, in addition to IGF-1R, making these receptors ideal therapeutic targets as they are expressed/overexpressed in this subtype. We postulated that targeting HER2 and IGF-1R together is a promising therapy for HER2-positive BC. Thus, we explored the outcome of a novel combination treatment using neratinib, a pan-HER inhibitor, and metformin, an IGF-1R inhibitor, on HER2-positive BC cells.

METHODS

In this investigation, we used cellular and molecular biology techniques in addition to an angiogenesis model and tissue microarray analysis.

RESULTS

Our data revealed that this combination therapy significantly reduced cell viability compared to individual treatments and exhibited a synergistic effect in HER2-positive BC cells. Moreover, the combination disrupted cell cycle progression and inhibited colony formation, and invasion of HER2-positive BC cells; this is accompanied by the deregulation of HER1-3 and IGF-1R expression patterns, in addition to Caspase-3, BCL2, Fascin, and Vimentin. Moreover, key regulator molecular pathways, including, ERK1/2, AKT, p38 MAPK, and mTOR, were significantly downregulated upon treatment with neratinib and metformin combination. Additionally, our data pointed out that neratinib and metformin combination inhibited angiogenesis, in-ovo, an important biological event in cancer progression. Finally, using a cohort of 55 HER2-positive BC samples, we revealed that HER2 and IGF-1R are co-expressed in most of the cases.

CONCLUSIONS

These findings suggest that neratinib and metformin combination can present a promising strategy for targeting multiple pathways in HER2-positive BC.

Hormone Receptor-Dependent Correlations Between Angiopoietins and VEGF-C in Primary Breast Cancer: Insights Into Lymphangiogenic Biomarkers

BACKGROUND

Biomarkers of angiogenesis and lymphangiogenesis have been explored in cancer prognostic models; however, their potential role in assessing local tumor invasiveness remains poorly understood.

AIMS

This study aimed to evaluate the correlations of angiogenic biomarkers, specifically the angiopoietin (ANG)-Tie system and vascular endothelial growth factor-C (VEGF-C), with lymphangiogenesis and the related histopathological characteristics in Iranian women with breast cancer.

METHODS AND RESULTS

In this consecutive case series (n = 149) from the Breast Cancer Risk and Lifestyle (BCRL) study, plasma levels of pro-angiogenic factors, including VEGF-C, ANGs, and Tie-2, were assessed using ELISA. Clinicopathological data were collected, excluding stage IV cases to focus on patients with localized disease. Axillary lymph node metastasis (ANLM), and vascular invasion (VI) were common in the study population, occurring in 61.5% and 77.6% of cases, respectively (p < 0.01). Estrogen receptor-positive (ER+) tumors were observed in 89.1% of ANLM+ participants, while human epidermal growth factor receptor-2-positive (HER-2+) tumors were identified in 22.8% of patients with ALNM. Plasma levels of ANG-1 (r = 0.19) and VEGF-C (r = 0.29) were positively correlated with the ALNM ratio (p < 0.05). Multivariate analysis in patients with grade II tumors revealed significant inverse correlations between VEGF-C and angiogenic biomarkers, including ANG-2 (β = -0.25), the ANG-2/Tie-2 ratio (β = -0.28), and the (ANG-1 + ANG-2)/Tie-2 ratio (β = -0.29) (p < 0.05). Receiver operating characteristic (ROC) curve analysis indicated that ANG-2 could effectively assess ALNM status, with an optimal cutoff of 3.39 pg/mL, identifying ALNM in 66.0% of patients with low VEGF-C levels (95% CI: 0.54-0.78), increasing to 68.0% when combined with ANG-1 as the ANGs/Tie-2 ratio (95% CI: 0.56-0.80). In ER+ tumors, high plasma ANG-2 levels were observed (p < 0.05). Significantly higher levels of the (ANG-1 + ANG-2)/VEGF-C ratio were noted in patients with VI+ (p < 0.05). Findings descriptively highlighted ER+ status as a common characteristic in VI+ and ALNM+ tumors. In HER-2+ patients, both ANG-1 and the (ANG-1 + ANG-2)/Tie-2 ratio showed inverse correlations with VEGF-C, while in ER- breast cancer patients, ANG-2 was inversely correlated with VEGF-C.

CONCLUSION

These findings provide new insights into the inverse correlation between plasma levels of ANGs and VEGF-C, particularly in cases with positive ALNM, underscoring the role of hormone receptor-dependent characteristics. The integration of the triple angiogenic biomarkers ANG-2/Tie-2/VEGF-C within the tumor microenvironment, combined with the regulatory influence of hormonal receptors, merits further investigation as a potential biomarker panel for identifying lymphatic anomalies and VI positivity in breast cancer patients.

Metformin inhibits pathological retinal neovascularization but promotes retinal fibrosis in experimental neovascular age-related macular degeneration

Purpose

This study aims to investigate the effects and mechanism of action of metformin on retinal neovascularization and fibrosis in a mouse model of neovascular age-related macular degeneration (nAMD).

Methods

Very low-density lipoprotein receptor knockout (Vldlr -/-) mice, a mouse model of nAMD, were used in this study. Vldlr -/- mice were administered metformin on postnatal day (P) 20 for 20 days (early stage of pathological change) or at 5.5 months of age for 45 days (late stage of pathological change). Retinal leakage was examined by fundus fluorescein angiography (FFA). Retinal neovascularization was assessed by lectin staining. Retinal fibrosis was assessed by Western blotting, immunofluorescence staining, and Masson's trichrome staining.

Results

Retinal vascular leakage and neovascularization were significantly reduced in Vldlr -/- mice treated with metformin compared to those treated with the vehicle at P40. The protein levels of inflammatory factors and phospho(p)-STAT3 were decreased, and P38 and ERK signaling were suppressed in the retinas of metformin-treated Vldlr -/- mice relative to those in the control group at P40. Fibrotic markers were upregulated in the retinas of Vldlr -/- mice treated with metformin compared to those treated with the vehicle at 7 months. Levels of the inflammatory factors and p-STAT3 were increased, and PI3K/AKT, P38, and ERK signaling were upregulated in the retinas of metformin-treated Vldlr -/- mice compared to those in the control group at 7 months.

Conclusion

Metformin inhibits pathological retinal neovascularization but promotes fibrosis in experimental nAMD. These results provide evidence and highlight important considerations for the clinical use of metformin in different stages of nAMD.

Antiproliferative Mechanisms of Metformin in Breast Cancer: A Systematic Review of the Literature

Metformin is an antidiabetic drug with reported potential antiproliferative activity against different cancer types including breast cancer. However, the mechanism of action of how metformin can induce its antiproliferative activity is still unclear. Thus, the current study is a systematic review of the literature aiming to explore the reported antiproliferative mechanisms of metformin against breast cancer. The study included seventeen research articles that describe different mechanisms of action against breast cancer. While the majority of the studies confirm the antiproliferative potential of metformin, albeit at different potencies, there appear to be various mechanisms and factors that can influence this effect. There are a number of questions yet to be answered pertaining the use of metformin as an anti-cancer agent, warranting further investigation into this emerging area of research.

Intravitreal Metformin Protects Against Choroidal Neovascularization and Light-Induced Retinal Degeneration

Neovascular age-related macular degeneration (nAMD), a leading cause of blindness in older adults, presents a challenging pathophysiology involving choroidal neovascularization (CNV) and retinal degeneration. Current treatments relying on intravitreal (IVT) administration of anti-angiogenic agents are costly and of moderate effectiveness. Metformin, the common anti-diabetic drug, has been associated with decreased odds of developing AMD. Studies have shown that metformin can mitigate cellular aging, neoangiogenesis, and inflammation across multiple diseases. This preclinical study assessed metformin's impact on vessel growth using choroidal explants before exploring IVT metformin's effects on laser-induced CNV and light-induced retinal degeneration in C57BL/6J and BALB/cJ mice, respectively. Metformin reduced new vessel growth in choroidal explants in a dose-dependent relationship. Following laser induction, IVT metformin suppressed CNV and decreased peripheral infiltration of IBA1+ macrophages/microglia. Furthermore, IVT metformin protected against retinal thinning in response to light-induced degeneration. IVT metformin downregulated genes in the choroid and retinal pigment epithelium which are associated with angiogenesis and inflammation, two key processes that drive nAMD progression. These findings underscore metformin's capacity as an anti-angiogenic and neuroprotective agent, demonstrating this drug's potential as an accessible option to help manage nAMD.

Metformin: A Dual-Role Player in Cancer Treatment and Prevention

Cancer continues to pose a significant global health challenge, as evidenced by the increasing incidence rates and high mortality rates, despite the advancements made in chemotherapy. The emergence of chemoresistance further complicates the effectiveness of treatment. However, there is growing interest in the potential of metformin, a commonly prescribed drug for type 2 diabetes mellitus (T2DM), as an adjuvant chemotherapy agent in cancer treatment. Although the precise mechanism of action of metformin in cancer therapy is not fully understood, it has been found to have pleiotropic effects, including the modulation of metabolic pathways, reduction in inflammation, and the regulation of cellular proliferation. This comprehensive review examines the anticancer properties of metformin, drawing insights from various studies conducted in vitro and in vivo, as well as from clinical trials and observational research. This review discusses the mechanisms of action involving both insulin-dependent and independent pathways, shedding light on the potential of metformin as a therapeutic agent for different types of cancer. Despite promising findings, there are challenges that need to be addressed, such as conflicting outcomes in clinical trials, considerations regarding dosing, and the development of resistance. These challenges highlight the importance of further research to fully harness the therapeutic potential of metformin in cancer treatment. The aims of this review are to provide a contemporary understanding of the role of metformin in cancer therapy and identify areas for future exploration in the pursuit of effective anticancer strategies.

Ianus Bifrons: The Two Faces of Metformin

The ancient Roman god Ianus was a mysterious divinity with two opposite faces, one looking at the past and the other looking to the future. Likewise, metformin is an "old" drug, with one side looking at the metabolic role and the other looking at the anti-proliferative mechanism; therefore, it represents a typical and ideal bridge between diabetes and cancer. Metformin (1,1-dimethylbiguanidine hydrochloride) is a drug that has long been in use for the treatment of type 2 diabetes mellitus, but recently evidence is growing about its potential use in other metabolic conditions and in proliferative-associated diseases. The aim of this paper is to retrace, from a historical perspective, the knowledge of this molecule, shedding light on the subcellular mechanisms of action involved in metabolism as well as cellular and tissue growth. The intra-tumoral pharmacodynamic effects of metformin and its possible role in the management of different neoplasms are evaluated and debated. The etymology of the name Ianus is probably from the Latin term ianua, which means door. How many new doors will this old drug be able to open?

Metformin: A Potential Treatment for Acne, Hidradenitis Suppurativa and Rosacea

Metformin is a widely used drug for treatment of diabetes mellitus, due to its safety and efficacy. In addition to its role as an antidiabetic drug, numerous beneficial effects of metformin have enabled its use in various diseases. Considering the anti-androgenic, anti-angiogenic, anti-fibrotic and antioxidant properties of metformin, it may have the potential to improve chronic inflammatory skin diseases. However, further evidence is needed to confirm the efficacy of metformin in dermatological conditions, This review focuses on exploring the therapeutic targets of metformin in acne vulgaris, hidradenitis suppurativa and rosacea, by studying their pathogeneses.

Synergistic Effects of Metformin and Trastuzumab on HER2 Positive Gastroesophageal Adenocarcinoma Cells In Vitro and In Vivo

The incidence of HER2 amplification in advanced gastroesophageal adenocarcinoma (GC) reportedly ranges between 10% and 20%, depending on the population studied and the geographical region. Trastuzumab (Tmab) is the standard treatment for GCs with HER2 amplification. Metformin, a widely used antidiabetic drug, is an activator of AMP kinase that can affect the mTOR signaling pathway. The following GC cells were evaluated: HER2+ NCI-N87, YCC-19, YCC-38, OE19, OE33, and HER2- AGS. The effects of Tmab and metformin on these cell lines were assessed as single agents and in combination using cell viability assays, Western blotting, and xenograft models. Metformin induced phosphorylation of AMP kinase in all tested GC cells and dephosphorylation of mTOR in Tmab-sensitive GC cells. We observed that treatment with Tmab in combination with metformin induced a significant decrease in the number of colonies formed on soft agar by N87, YCC-19, YCC-38, and OE19 cells (88%, 95%, 73%, and 98%, respectively), in comparison to the number formed by control cells or cells in the single-treatment groups. No growth inhibition was detected in OE33 cells treated with Tmab alone. Combination with metformin resulted in decreased phosphorylation of HER2 and its downstream targets, AKT and ERK, in Tmab-sensitive HER2+ cells. Phospho-receptor tyrosine kinase (RTK) arrays were used to profile the phospho-proteome, which demonstrated a synergistic decrease in phosphorylation of EGFR, HER2, and HER3. Furthermore, the combination of Tmab and metformin exhibited enhanced antitumor effects in a xenograft model. Collectively, these data suggest that Tmab and metformin act synergistically in HER2+ GC cells. Since metformin is widely used and relatively non-toxic, its addition to the therapeutic regimen along with Tmab could enhance the clinical efficacy in patients with HER2+ GC.

Effect of metformin use on the risk and prognosis of ovarian cancer: an updated systematic review and meta-analysis

INTRODUCTION

Emerging evidence suggests that metformin has a potential antitumor effect both in vitro and in vivo. Increasing epidemiological studies indicate that diabetic patients receiving metformin therapy have lower incidences of cancer and have better survival rates. However, there are limited and inconsistent studies available about the effect of metformin therapy on ovarian cancer (OC). Thus, we conducted this meta-analysis to study the effect of metformin therapy on OC. Meanwhile, we systematically reviewed relevant studies to provide a framework for future research.

EVIDENCE ACQUISITION

We conducted a systematic literature search on PubMed, Web of Science, Springerlink, CNKI, VIP, SinoMed, and Wanfang up to the period of October 2018. A random-effects meta-analysis model was used to derive pooled effect estimates.

EVIDENCE SYNTHESIS

A total of 13 studies were retrieved of which 5 studies explained the prevention and 8 studies explained the treatment for OC. Our pooled results showed that metformin has a potential preventive effect on OC in diabetic women (pooled odds ratio [OR] 0.62, 95% confidence interval [95% CI] 0.34, 1.11; P<0.001). In addition, metformin can also significantly prolong progression-free survival (PFS) (pooled hazard ratio [HR] 0.49, 95% CI 0.34, 0.70; P=0.002), and overall survival (OS) (HR 0.71, 95%CI 0.61, 0.82; P<0.001) in patients with OC, regardless of whether they had diabetes.

CONCLUSIONS

The use of metformin can potentially reduce the risk of OC among diabetics, and it also can significantly improve PFS and OS in patients with OC. A further large clinical investigation would be needed to adopt our finding in practice, however, our systematic review provides an insight for future study designs.

Metformin and HER2-positive breast cancer: Mechanisms and therapeutic implications

Due to the strong association between diabetes and cancer incidents, several anti-diabetic drugs, including metformin, have been examined for their anticancer activity. Metformin is a biguanide antihyperglycemic agent used as a first-line drug for type II diabetes mellitus. It exhibits anticancer activity by impacting different molecular pathways, such as AMP-inducible protein kinase (AMPK)-dependent and AMPK-independent pathways. Additionally, Metformin indirectly inhibits IGF-1R signaling, which is highly activated in breast malignancy. On the other hand, breast cancer is one of the major causes of cancer-related morbidity and mortality worldwide, where the human epidermal growth factor receptor-positive (HER2-positive) subtype is one of the most aggressive ones with a high rate of lymph node metastasis. In this review, we summarize the association between diabetes and human cancer, listing recent evidence of metformin's anticancer activity. A special focus is dedicated to HER2-positive breast cancer with regards to the interaction between HER2 and IGF-1R. Then, we discuss combination therapy strategies of metformin and other anti-diabetic drugs in HER2-positive breast cancer.

Metformin enhances T lymphocyte anti-tumor immunity by increasing the infiltration via vessel normalization

Abnormal tumor vasculature blocks the extravasation of T lymphocytes into the tumor, thereby suppressing anti-tumor immunity. Recently, metformin has been shown to affect tumor vasculature and enhance T lymphocyte anti-tumor immunity. However, whether or how metformin affects T lymphocyte anti-tumor immunity via a vascular mechanism remains poorly understood. Herein, we show that a large number of CD8⁺ lymphocytes gathered in the peri-tumoral region, while very few infiltrated the tumor. Metformin administration increased the expression of anti-tumor immunity-associated genes and the number of tumor-infiltrating CD8⁺ lymphocytes. Injection of CD8 but not CD4 neutralization antibody into tumor-bearing mice significantly abrogated the anti-tumor effect of metformin. Critically, CD8⁺ lymphocytes were found to pass through the wall of perfused vessel. Further results of immunofluorescent staining showed that metformin greatly elevated tumor perfusion, which was accompanied by increased vascular maturity in the intratumoral region (ITR) but not peritumoral region (PTR). These findings provide evidence for the vascular mechanism involved in metformin-induced enhancement of T lymphocyte anti-tumor immunity. By remodeling the abnormal tumor vasculature, also called vessel normalization metformin increases vascular maturity and tumor perfusion, thus allowing more CD8⁺ lymphocytes to infiltrate the tumor.

HIF-1α inhibitor YC-1 suppresses triple-negative breast cancer growth and angiogenesis by targeting PlGF/VEGFR1-induced macrophage polarization

Triple negative breast cancer (TNBC) is an invasive and metastatic phenotype of breast cancer with limited treatment options. Published studies have demonstrated an inhibitory effect of HIF-α inhibition by its inhibitor YC-1 (lificiguat) on growth and angiogenesis of TNBC. However, the underlying mechanism remains poorly understood. In the current paper, our results show that HIF-1α inhibitor significantly inhibited TNBC growth by increasing cellular apoptosis and decreasing MVD, independent of a cell-autonomous mechanism in both endothelial and tumor cells. Genetic screening and in vivo experiments showed that a large number of M2-polarized TAMs accumulated in the hypoxic peri-necrotic region (PNR), where placental growth factor (PlGF) and its ligand, vascular endothelial growth factor receptor-1 (VEGFR-1) were upregulated. Furthermore, YC-1 skewed the polarization of TAMs away from M2 to M1 phenotype, therefore inhibiting TNBC angiogenesis and growth. This effect was further abrogated by VEGFR-1 neutralization and TAM depletion following clodronate liposome injection. These findings provide preclinical evidence for an indirect mechanism underlying YC-1-induced suppression of TNBC growth and angiogenesis, thereby offering a treatment option for TNBC.

WZB117 Decorated Metformin-Carboxymethyl Chitosan Nanoparticles for Targeting Breast Cancer Metabolism

The "Warburg effect" provides a novel method for treating cancer cell metabolism. Overexpression of glucose transporter 1 (GLUT1), activation of AMP-activated protein kinase (AMPK), and downregulation of mammalian target of rapamycin (mTOR) have been identified as biomarkers of abnormal cancer cell metabolism. Metformin (MET) is an effective therapy for breast cancer (BC), but its efficacy is largely reliant on the concentration of glucose at the tumor site. We propose a WZB117 (a GLUT1 inhibitor)-OCMC (O-carboxymethyl-chitosan)-MET combo strategy for simultaneous GLUT1 and mTOR targeting for alteration of BC metabolism. WZB117 conjugated polymeric nanoparticles were 225.67 ± 11.5 nm in size, with a PDI of 0.113 ± 0.16, and an encapsulation of 72.78 6.4%. OCMC pH-dependently and selectively releases MET at the tumor site. MET targets the mTOR pathway in cancer cells, and WZB117 targets BCL2 to alter GLUT1 at the cancer site. WZB117-OCMC-MET overcomes the limitations of MET monotherapy by targeting mTOR and BCL2 synergistically. WZB117-OCMC-MET activates AMPK and suppresses mTOR in a Western blot experiment, indicating growth-inhibitory and apoptotic characteristics. AO/EB and the cell cycle enhance cellular internalization as compared to MET alone. WZB117-OCMC-MET affects cancer cells' metabolism and is a promising BC therapeutic strategy.

Overcoming chemoresistance in non-angiogenic colorectal cancer by metformin via inhibiting endothelial apoptosis and vascular immaturity

The development of chemoresistance which results in a poor prognosis often renders current treatments for colorectal cancer (CRC). In this study, we identified reduced microvessel density (MVD) and vascular immaturity resulting from endothelial apoptosis as therapeutic targets for overcoming chemoresistance. We focused on the effect of metformin on MVD, vascular maturity, and endothelial apoptosis of CRCs with a non-angiogenic phenotype, and further investigated its effect in overcoming chemoresistance. In situ transplanted cancer models were established to compare MVD, endothelial apoptosis and vascular maturity, and function in tumors from metformin- and vehicle-treated mice. An in vitro co-culture system was used to observe the effects of metformin on tumor cell-induced endothelial apoptosis. Transcriptome sequencing was performed for genetic screening. Non-angiogenic CRC developed independently of angiogenesis and was characterized by vascular leakage, immaturity, reduced MVD, and non-hypoxia. This phenomenon had also been observed in human CRC. Furthermore, non-angiogenic CRCs showed a worse response to chemotherapeutic drugs in vivo than in vitro. By suppressing endothelial apoptosis, metformin sensitized non-angiogenic CRCs to chemo-drugs via elevation of MVD and improvement of vascular maturity. Further results showed that endothelial apoptosis was induced by tumor cells via activation of caspase signaling, which was abrogated by metformin administration. These findings provide pre-clinical evidence for the involvement of endothelial apoptosis and subsequent vascular immaturity in the chemoresistance of non-angiogenic CRC. By suppressing endothelial apoptosis, metformin restores vascular maturity and function and sensitizes CRC to chemotherapeutic drugs via a vascular mechanism.

The Potential Therapeutic Impact of Metformin in Glioblastoma Multiforme

In terms of frequency and aggressiveness, glioblastoma multiforme (GBM) is undoubtedly the most frequent and fatal primary brain tumor. Despite advances in clinical management, the response to current treatments is dismal, with a 2-year survival rate varying between 6 and 12 percent. Metformin, a derivative of biguanide widely used in treating type 2 diabetes, has been shown to extend the lifespan of patients with various malignancies. There is limited evidence available on the long-term survival of GBM patients who have taken metformin. This research examined the literature to assess the connection between metformin's anticancer properties and GBM development. Clinical findings, together with the preclinical data from animal models and cell lines, are included in the present review. This comprehensive review covers not only the association of hyperactivation of the AMPK pathway with the anticancer activity of metformin but also other mechanisms underpinning its role in apoptosis, cell proliferation, metastasis, as well as its chemo-radio-sensitizing behavior against GBM. Current challenges and future directions for developments and applications of metformin-based therapeutics are also discussed.

Metformin and Cervical Cancer Risk in Patients with Newly Diagnosed Type 2 Diabetes: A Population-Based Study in Korea

BACKGRUOUND

Cervical cancer is a prevalent malignancy that is a major health problem for women worldwide. The cancer-preventive properties of metformin are well-known, but insufficient data have been reported regarding its relationship to cervical cancer. Therefore, in a nationwide population-based study, we investigated the association between metformin use and cervical cancer incidence in patients with newly diagnosed type 2 diabetes.

METHODS

This retrospective cohort study used the Korean National Health Insurance claims database. Individuals newly diagnosed with type 2 diabetes between January 2005 and December 2009 were included. The occurrence of cervical cancer was explored by matching for age, economic status, region of residence, and use of anti-diabetic medication.

RESULTS

In total, 66,013 metformin users and 64,756 non-users were analyzed. Cervical cancer occurred in 219 metformin users (0.33%) and 274 metformin non-users (0.42%) (hazard ratio [HR], 0.783; 95% confidence interval [CI], 0.655 to 0.036; P=0.007). Moreover, cervical cancer risk was considerably reduced in those treated with a high dose (>1,200,000 mg) or for an extended period (≥2,000 days) compared to non-users (HR, 0.151; 95% CI, 0.093 to 0.243; P<0.001; and HR, 0.141; 95% CI, 0.077 to 0.258; P<0.001). The incidence was also significantly lower in metformin users among those over 50 years old (HR, 0.791; 95% CI, 0.650 to 0.961; P<0.001).

CONCLUSION

Metformin use in patients with newly diagnosed diabetes was associated with a lower risk of cervical cancer in Korea. Furthermore, a significant association was found between the use of metformin and cervical cancer in a dose- and duration-dependent manner and among those over 50 years old.

The promising therapeutic effects of metformin on metabolic reprogramming of cancer-associated fibroblasts in solid tumors

Tumor-infiltrated lymphocytes are exposed to many toxic metabolites and molecules in the tumor microenvironment (TME) that suppress their anti-tumor activity. Toxic metabolites, such as lactate and ketone bodies, are produced mainly by catabolic cancer-associated fibroblasts (CAFs) to feed anabolic cancer cells. These catabolic and anabolic cells make a metabolic compartment through which high-energy metabolites like lactate can be transferred via the monocarboxylate transporter channel 4. Moreover, a decrease in molecules, including caveolin-1, has been reported to cause deep metabolic changes in normal fibroblasts toward myofibroblast differentiation. In this context, metformin is a promising drug in cancer therapy due to its effect on oncogenic signal transduction pathways, leading to the inhibition of tumor proliferation and downregulation of key oncometabolites like lactate and succinate. The cross-feeding and metabolic coupling of CAFs and tumor cells are also affected by metformin. Therefore, the importance of metabolic reprogramming of stromal cells and also the pivotal effects of metformin on TME and oncometabolites signaling pathways have been reviewed in this study.

A ROS/Akt/NF-κB Signaling Cascade Mediates Epidermal Growth Factor-Induced Epithelial-Mesenchymal Transition and Invasion in Human Breast Cancer Cells

BACKGROUND

As one of the most widely used anti-diabetic drugs for type II diabetes, metformin has been shown to exhibit anti-cancer activity in recent years. Epidermal growth factor (EGF) and its receptor, EGFR, play important roles in cancer metastasis in various tumors, including breast cancer. Epithelial-mesenchymal transition (EMT) is a critical process for cancer invasion and metastasis. In this study, we use EGF as a metastatic inducer to investigate the effect of metformin on cancer cell migration, invasion and EMT.

METHODS

Human breast cancer MCF-7 cells were exposed to EGF with or without metformin or N-acetyl cysteine (NAC). The effects of metformin on breast cancer cell proliferation were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The production of reactive oxygen species (ROS) was tested using 2,7-dichlorodihydrofluorecein diacetate (DCFH-DA). The migratory and invasive abilities of tumor cells were analyzed using wound healing assay and transwell invasion assay, respectively. The expressions of E-cadherin, N-cadherin and Snail were tested using real-time quantitative polymerase chain reaction (qRT-PCR) and western blotting at mRNA and protein levels. The activation of protein kinase B (Akt) and nuclear factor kappa B (NF-κB) were measured by western blotting.

RESULTS

Our results showed that metformin inhibited breast cancer cell proliferation in a dose-dependent manner with or without EGF. EGF-induced alterations in cell morphology that are characteristic of EMT were reversed by metformin. Metformin also inhibited the EGF-modulated expression of E-cadherin, N-cadherin and Snail and further suppressed cell invasion and migration. In addition, metformin suppressed EGF-induced phosphorylation of Akt and NF-κB. ROS is involved in EGF-induced cancer invasion and activation of phosphatidylinositol 3-kinase (PI3K)/Akt/NF-κB pathway.

CONCLUSION

Taken together, these data indicate that metformin suppresses EGF-induced breast cancer cell migration, invasion and EMT through the inhibition of the PI3K/Akt/NF-κB pathway. These results provide a novel mechanism to explain the role of metformin as a potent anti-metastatic agent in breast cancer cells.

Metformin administration is associated with enhanced response to transarterial chemoembolization for hepatocellular carcinoma in type 2 diabetes patients

Transarterial chemoembolization (TACE) is often used as a locoregional therapy for early hepatocellular carcinoma (HCC) when local ablation or resection are not feasible, but incomplete response and recurrence are commonly observed. In this study, we sought to determine the association between metformin administration and TACE outcomes for single nodular HCC in patients with type 2 diabetes mellitus (T2DM). The retrospective cohort analysis included 164 T2DM patients with single nodular HCC who underwent TACE as an initial treatment, and 91 were exposed to metformin before and after TACE. Propensity score (PS) matching was used to balance covariates. Logistic regression analysis was used to determine the predictors of tumor response after TACE, and Cox regression analysis assessed independent predictors of local tumor recurrence (LTR) in patients with complete response after TACE. Metformin use was associated with significantly higher objective response rate (ORR) in the overall and PS-matched cohort (79.1% vs. 60.3 and 78.7% vs. 57.5%; p = 0.008 and p = 0.029, respectively). Logistic regression analysis showed that metformin use was an independent predictor of ORR in all and PS-matched patients (odds ratio = 2.65 and 3.06; p = 0.016 and 0.034, respectively). Cox regression analysis showed metformin administration was an independent predictor for lower LTR in all and PS-matched patients (hazard ratio = 0.28 and 0.27; p = 0.001 and 0.007, respectively). Metformin administration is associated with better initial response and lower local recurrence after TACE for single nodular HCC in T2DM.

Metformin Intervention—A Panacea for Cancer Treatment?

The molecular mechanism of action and the individual influence of various metabolic pathways related to metformin intervention are under current investigation. The available data suggest that metformin provides many advantages, exhibiting anti-inflammatory, anti-cancer, hepatoprotective, cardioprotective, otoprotective, radioprotective, and radio-sensitizing properties depending on cellular context. This literature review was undertaken to provide novel evidence concerning metformin intervention, with a particular emphasis on cancer treatment and prevention. Undoubtedly, the pleiotropic actions associated with metformin include inhibiting inflammatory processes, increasing antioxidant capacity, and improving glycemic and lipid metabolism. Consequently, these characteristics make metformin an attractive medicament to translate to human trials, the promising results of which were also summarized in this review.

Nimbolide, a Neem Limonoid, Inhibits Angiogenesis in Breast Cancer by Abrogating Aldose Reductase Mediated IGF-1/PI3K/Akt Signaling

Background & Objectives:

There is growing evidence to implicate the insulin/IGF-1R/PI3K/Akt signaling cascade in breast cancer development and the central role of aldose reductase (AR) in mediating the crosstalk between this pathway and angiogenesis. The current study was designed to investigate whether nimbolide, a neem limonoid, targets this oncogenic signaling network to prevent angiogenesis in breast cancer.

Methods:

Breast cancer cells (MCF-7, MDA-MB-231), EAhy926 endothelial cells, MDA-MB-231 xenografted nude mice, and tumour tissues from breast cancer patients were used for the study. Expression of AR and key players in IGF-1/PI3K/Akt signaling and angiogenesis was evaluated by qRT-PCR, immunoblotting, and immunohistochemistry. Molecular docking and simulation, overexpression, and knockdown experiments were performed to determine whether nimbolide targets AR and IGF-1R

Results:

Nimbolide inhibited AR with consequent blockade of the IGF-1/PI3K/Akt and HIF-1/VEGF signaling circuit by influencing the phosphorylation and intracellular localisation of key signaling molecules. Downregulation of DNMT-1, HDAC-6, miR-21, HOTAIR, and H19 with upregulation of miR-148a/miR-152 indicated that nimbolide regulates AR and IGF-1/PI3K/Akt signaling via epigenetic modifications. Coadministration of nimbolide with metformin and the chemotherapeutic drugs tamoxifen/cisplatin displayed higher efficacy than single agents in inhibiting IGF-1/PI3K/Akt/AR signaling. Grade-wise increases in IGF-1R and AR expression in breast cancer tissues underscore their value as biomarkers of progression.

Conclusions:

This study provides evidence for the anticancer effects of nimbolide in cellular and mouse models of breast cancer besides providing leads for new drug combinations. It has also opened up avenues for investigating potential molecules such as AR for therapeutic targeting of cancer.

Metformin use and cardiovascular outcomes in patients with diabetes and chronic kidney disease: a nationwide cohort study

BACKGROUND

Metformin has recently been shown not to increase the risk of lactic acidosis in patients with chronic kidney disease (CKD). Thus, the criteria for metformin use in this population has expanded. However, the relationship between metformin use and clinical outcomes in CKD remains controversial.

METHODS

This study considered data from 97,713 diabetes patients with an estimated glomerular filtration rate of <60 mL/min/1.73 m2. The primary outcome was major adverse cardiac and cerebrovascular events (MACCE), and the secondary outcomes were all-cause mortality and incident end-stage renal disease (ESRD).

RESULTS

Metformin users had a significantly higher risk of MACCE than non-users (hazard ratio [HR], 1.20; 95% confidence interval [CI], 1.14-1.26; p < 0.001). However, metformin users had a lower risk of all-cause mortality (HR, 0.78; 95% CI, 0.74-0.81; p < 0.001) and ESRD (HR, 0.44; 95% CI, 0.42-0.47; p < 0.001) during follow-up than non-users did. The relationships between metformin use and clinical outcomes remained consistent in propensity score matching analyses and subgroup analyses of patients with adequate adherence to anti-diabetes medication.

CONCLUSION

Treatment with metformin was associated with an increased risk of MACCE in patients with diabetes and CKD. However, metformin users had a lower risk of all-cause mortality and ESRD during follow-up than non-users did. Therefore, metformin needs to be carefully used in patients with CKD.

The Effect of Body Mass Index and Metformin on Matrix Gene Expression in Arthritic Primary Human Chondrocytes

OBJECTIVE

Obesity is a known risk factor for knee osteoarthritis (OA). Diabetes has been associated with progression of OA and metformin is the first-line treatment in type 2 diabetes. The effect of the body mass index (BMI) and metformin on the expression of certain matrix genes in human chondrocytes is unclear. The purpose of this study was to investigate the effect of BMI and metformin on the expression of matrix genes in primary human chondrocytes.

DESIGN

Adult female patients undergoing knee arthroplasty for end-stage OA were enrolled. Primary chondrocytes were cultivated and stimulated with metformin. Matrix gene expression was analyzed using polymerase chain reaction. Clinical data were used in multivariable regression models to assess the influence of BMI and metformin stimulation on gene expression.

RESULTS

A total of 14 patients were analyzed. BMI was a predictor of increased expression in ADAMTS5 (β = -0.11, P = 0.03). Metformin slightly reduced expression in ADAMTS5 (β = 0.34, P = 0.04), HIF-1a (β = 0.39, P = 0.04), IL4 (β = 0.30, P = 0.02), MMP1 (β = 0.47, P < 0.01), and SOX9 (β = 0.37, P = 0.03). The hip-knee-ankle angle and proton pump inhibitors (PPIs) intake were associated with reduced SOX9 expression (β = 0.23, P < 0.01; β = 2.39, P < 0.01). Higher C-reactive protein (CRP) levels were associated with increased MMP1 expression (β = -0.16, P = 0.02).

CONCLUSION

We found that BMI exerts a destructive effect via induction of ADAMTS5. Metformin reduced the expression of catabolic genes ADAMTS5 and MMP1 and might play a role in disease prevention. Limb malalignment and PPI intake was associated with a reduced expression of SOX9, and higher CRP levels correlated with increased MMP1 expression, indicating a destructive process.

MicroRNAs: Important Players in Breast Cancer Angiogenesis and Therapeutic Targets

The high incidence of breast cancer (BC) is linked to metastasis, facilitated by tumor angiogenesis. MicroRNAs (miRNAs or miRs) are small non-coding RNA molecules that have an essential role in gene expression and are significantly linked to the tumor development and angiogenesis process in different types of cancer, including BC. There's increasing evidence showed that various miRNAs play a significant role in disease processes; specifically, they are observed and over-expressed in a wide range of diseases linked to the angiogenesis process. However, more studies are required to reach the best findings and identify the link among miRNA expression, angiogenic pathways, and immune response-related genes to find new therapeutic targets. Here, we summarized the recent updates on miRNA signatures and their cellular targets in the development of breast tumor angiogenetic and discussed the strategies associated with miRNA-based therapeutic targets as anti-angiogenic response.

Metformin Is Associated with a Lower Incidence of Benign Brain Tumors: A Retrospective Cohort Study in Patients with Type 2 Diabetes Mellitus

Background: The risk of benign brain tumors (BBT) associated with metformin use has not received much attention. Therefore, a retrospective cohort study was designed to investigate such an association in patients with type 2 diabetes mellitus (T2DM). Methods: We used the database of Taiwan's National Health Insurance to enroll 152,176 ever users and 16,120 never users of metformin for the follow-up of incidence of BBT and a more specific outcome of cerebral meningioma. The patients were newly diagnosed with T2DM between 1999 and 2005; and they were followed up from 1 January 2006 until 31 December 2011. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Results: During follow-up, 111 never users and 557 ever users were diagnosed with BBT. For BBT, the respective incidence rates for never users and ever users were 153.95 per 100,000 person-years and 77.61 per 100,000 person-years. While ever users were compared to never users, the hazard ratio was 0.502 (95% confidence interval: 0.409-0.615). A dose-response pattern was seen when ever users were categorized into tertiles of cumulative duration of metformin therapy (cutoffs: <27.10 months, 27.10-58.27 months and >58.27 months) with respective hazard ratios of 0.910 (0.728-1.138), 0.475 (0.375-0.602) and 0.243 (0.187-0.315). For cerebral meningioma, the overall hazard ratio was 0.506 (0.317-0.808); and the hazard ratios comparing the respective tertiles to never users were 0.895 (0.531-1.508), 0.585 (0.346-0.988) and 0.196 (0.104-0.369). Conclusions: A reduced risk of BBT and cerebral meningioma is observed in metformin users in patients with T2DM.

Metformin and Malignant Tumors: Not Over the Hill

Malignant tumors are a major cause of death, and their incidence is increasing worldwide. Although the survival rate for some cancers has improved, treatments for other malignant tumors are limited, and their mortality rate continues to increase. People with type 2 diabetes have a higher risk of malignant tumors and a higher mortality rate than those without diabetes. Metformin is a commonly used hypoglycemic drug. In recent years, a growing number of studies have indicated that metformin has antitumor effects and increases the sensitivity of malignant tumors to chemotherapy. However, the effect of metformin on different tumors is currently controversial, and the mechanism of metformin's antitumor action is not fully understood. Insights into the effect of metformin on malignant tumors and the possible mechanism may contribute to the development of antitumor drugs.

The prognostic outcome of 'type 2 diabetes mellitus and breast cancer' association pivots on hypoxia-hyperglycemia axis

Type 2 diabetes mellitus and breast cancer are complex, chronic, heterogeneous, and multi-factorial diseases; with common risk factors including but not limited to diet, obesity, and age. They also share mutually inclusive phenotypic features such as the metabolic deregulations resulting from hyperglycemia, hypoxic conditions and hormonal imbalances. Although, the association between diabetes and cancer has long been speculated; however, the exact molecular nature of this link remains to be fully elucidated. Both the diseases are leading causes of death worldwide and a causal relationship between the two if not addressed, may translate into a major global health concern. Previous studies have hypothesized hyperglycemia, hyperinsulinemia, hormonal imbalances and chronic inflammation, as some of the possible grounds for explaining how diabetes may lead to cancer initiation, yet further research still needs to be done to validate these proposed mechanisms. At the crux of this dilemma, hyperglycemia and hypoxia are two intimately related states involving an intricate level of crosstalk and hypoxia inducible factor 1, at the center of this, plays a key role in mediating an aggressive disease state, particularly in solid tumors such as breast cancer. Subsequently, elucidating the role of HIF1 in establishing the diabetes-breast cancer link on hypoxia-hyperglycemia axis may not only provide an insight into the molecular mechanisms underlying the association but also, illuminate on the prognostic outcome of the therapeutic targeting of HIF1 signaling in diabetic patients with breast cancer or vice versa. Hence, this review highlights the critical role of HIF1 signaling in patients with both T2DM and breast cancer, potentiates its significance as a prognostic marker in comorbid patients, and further discusses the potential prognostic outcome of targeting HIF1, subsequently establishing the pressing need for HIF1 molecular profiling-based patient selection leading to more effective therapeutic strategies emerging from personalized medicine.

In vivo photoacoustic imaging for monitoring treatment outcome of corneal neovascularization with metformin eye drops

Corneal neovascularization (CNV) compromises corneal avascularity and visual acuity. Current clinical visualization approaches are subjective and unable to provide molecular information. Photoacoustic (PA) imaging offers an objective and non-invasive way for angiogenesis investigation through hemodynamic and oxygen saturation level (sO₂) quantification. Here, we demonstrate the utility of PA and slit lamp microscope for in vivo rat CNV model. PA images revealed untreated corneas exhibited higher sO₂ level than treatment groups. The PA results complement with the color image obtained with slit lamp. These data suggest PA could offer an objective and non-invasive method for monitoring CNV progression and treatment outcome through the sO₂ quantification.

Metformin attenuates expression of angiogenic and inflammatory genes in human endometriotic stromal cells

Endometriosis is a benign gynecological disease that is manifested by the presence and growth of endometrial cells and glands outside the uterine. Active angiogenesis, migration, and invasion of endometrial tissue outside the uterine are critical for the development of endometriosis and lead to the survival and growth of endometriotic lesions. Metformin, as an anti-diabetic agent, represents anti-angiogenic property. Here, we performed a study using human normal endometrial stromal cells (N-ESCs) from healthy endometrial tissue and human eutopic endometrial stromal cells (EU-ESCs) and ectopic endometrial stromal cells (ECT-ESCs) from endometriosis patients. ESCs were cultured and treated with different concentrations of Metformin (0-20 mmol/l) for 72 h to evaluate Metformin effect on cell viability, proliferation, migration was measured by methyl thiazolyl tetrazolium (MTT) assay and scratch test respectively as well as expression of angiogenesis and migration markers. The Metformin reduced cell migration, and proliferation of endometriotic stromal cells in a time and concentration dependently manner. Furthermore, Metformin attenuated the expression of angiogenic and inflammatory genes in human endometriotic stromal cells. The direct anti-proliferative effect on ECT-ESCs combined with the effects of Metformin on inflammatory and angiogenesis-related genes expression supports its therapeutic potential for endometriosis. Metformin could be used as an effective adjuvant in endometriosis treatment.

Anticancer potential of metformin: focusing on gastrointestinal cancers

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

Metformin: The next angiogenesis panacea?

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

Metformin turns 62 in pharmacotherapy: Emergence of non-glycaemic effects and potential novel therapeutic applications

Metformin is the most commonly prescribed oral antidiabetic medication. Direct/indirect activation of Adenosine Monophosphate-activated protein kinase (AMPK) and non-AMPK pathways, amongst others, are deemed to explain the molecular mechanisms of action of metformin. Metformin is an established insulin receptor sensitising antihyperglycemic agent, is highly affordable, and has superior safety and efficacy profiles. Emerging experimental and clinical evidence suggests that metformin has pleiotropic non-glycemic effects. Metformin appears to have weight stabilising, renoprotective, neuroprotective, cardio-vascular protective, and antineoplastic effects and mitigates polycystic ovarian syndrome. Anti-inflammatory and antioxidant effects of metformin seem to qualify it as an adjunct therapy in treating infectious diseases such as tuberculosis, viral hepatitis, and the current novel Covid-19 infections. So far, metformin is the only prescription medicine relevant to the emerging field of senotherapeutics. Non-glycemic effects of metformin favourable to its repurposing in therapeutic use are hereby discussed.

Metformin reduces proteinuria in spontaneously hypertensive rats by activating the HIF-2α-VEGF-A pathway

Metformin has protective effects on diabetic nephropathy. However, the mechanism underlying the renoprotective action of metformin in spontaneously hypertensive rats (SHR) is not completely understood. We determined the role of metformin in proteinuria and investigated the mechanism. We measured the urinary protein concentration (mg/day) in 48-week-old SHR. Matched control animals were of the same genetic strain, Wistar-Kyoto (WKY). The rats received metformin (100 mg/kg/day) or vehicle for 10 months. Metformin improved renal function and reduced the proteinuria (urine protein: 48.4 ± 3.7 vs. 25.4 ± 1.8 mg, P < 0.01) induced by long-term high blood pressure. Metformin increased the production of vascular endothelial growth factor (VEGF)-A in rat kidneys and cultured rat podocytes. Metformin activated hypoxia-inducible factor-2α (Hif-2α) in response to VEGF but did not affect Hif-1α in rat kidneys and cultured rat podocytes. Metformin reduced the proteinuria induced by long-term high blood pressure in vivo and increased the VEGF-A production in rat kidneys and cultured rat podocytes, probably by activating the Hif-2α-VEGF signaling pathway. These findings provide a new mechanism for the renoprotective effects of metformin.

Mechanisms of action of metformin and its regulatory effect on microRNAs related to angiogenesis

Angiogenesis is rapidly initiated in response to pathological conditions and is a key target for pharmaceutical intervention in various malignancies. Anti-angiogenic therapy has emerged as a potential and effective therapeutic strategy for treating cancer and cardiovascular-related diseases. Metformin, a first-line oral antidiabetic agent for type 2 diabetes mellitus (T2DM), not only reduces blood glucose levels and improves insulin sensitivity and exerts cardioprotective effects but also shows benefits against cancers, cardiovascular diseases, and other diverse diseases and regulates angiogenesis. MicroRNAs (miRNAs) are endogenous noncoding RNA molecules with a length of approximately 19-25 bases that are widely involved in controlling various human biological processes. A large number of miRNAs are involved in the regulation of cardiovascular cell function and angiogenesis, of which miR-21 not only regulates vascular cell proliferation, migration and apoptosis but also plays an important role in angiogenesis. The relationship between metformin and abnormal miRNA expression has gradually been revealed in the context of numerous diseases and has received increasing attention. This paper reviews the drug-target interactions and drug repositioning events of metformin that influences vascular cells and has benefits on angiogenesis-mediated effects. Furthermore, we use miR-21 as an example to explain the specific molecular mechanism underlying metformin-mediated regulation of the miRNA signaling pathway controlling angiogenesis and vascular protective effects. These findings may provide a new therapeutic target and theoretical basis for the clinical prevention and treatment of cardiovascular diseases.

Metformin and cancer immunity

The immune system plays an essential and central role in tumor cell differentiation, proliferation, angiogenesis, apoptosis, invasion, and metastasis. Over the past decade, cancer therapy has rapidly evolved from traditional approaches, such as surgery, chemotherapy, and radiotherapy, to revolutionary new treatment options with immunotherapy. This new era of cancer treatment options has now been clinically tested and applied to many forms of human malignancies, often with quite dramatic results. As we develop more effective combinations of cancer treatment, several agents have been recently investigated, putatively identified as anticancer agents, or immunostimulatory molecules. One such agent is metformin, originally developed as a fairly standard first-line therapy for patients with type-2 diabetes mellitus (T2DM). Given the underlying mechanisms of action, researchers began to examine the alternative functions and possible utility of metformin, finding that the cancer risk in patients with T2DM was reduced. It appears that metformin, at least in part, has an antitumor effect through activation of the 5' adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Moreover, numerous studies have demonstrated that metformin interferes with key immunopathological mechanisms that are involved in the pathological processes or associated with malignant progression. Such insights may shed light on further analyzing whether metformin enhances the effectiveness of the immunotherapy and overcomes the immunotherapy resistance in the patients. Herein, we provide a comprehensive review of the literature examining the impact of metformin upon the host immune system and cancer immunity.

Metformin and Chemoprevention: Potential for Heart-Healthy Targeting of Biologically Aggressive Breast Cancer

Currently, tamoxifen is the only drug approved for reduction of breast cancer risk in premenopausal women. The significant cardiovascular side effects of tamoxifen, coupled with lack of a survival benefit, potential for genotoxicity, and failure to provide a significant risk-reduction for estrogen receptor-negative breast cancer, all contribute to the low acceptance of tamoxifen chemoprevention in premenopausal women at high-risk for breast cancer. While other prevention options exist for postmenopausal women, there is a search for well-tolerated prevention agents that can simultaneously reduce risk of breast cancers, cardiovascular disease, and type-2 diabetes. Metformin is a well-tolerated oral biguanide hypoglycemic agent that is prescribed worldwide to over 120 million individuals with type-2 diabetes. Metformin is inexpensive, safe during pregnancy, and the combination of metformin, healthy lifestyle, and exercise has been shown to be effective in preventing diabetes. There is a growing awareness that prevention drugs and interventions should make the “whole woman healthy.” To this end, current efforts have focused on finding low toxicity alternatives, particularly repurposed drugs for chemoprevention of breast cancer, including metformin. Metformin's mechanisms of actions are complex but clearly involve secondary lowering of circulating insulin. Signaling pathways activated by insulin also drive biologically aggressive breast cancer and predict poor survival in women with breast cancer. The mechanistic rationale for metformin chemoprevention is well-supported by the scientific literature. Metformin is cheap, safe during pregnancy, and has the potential to provide heart-healthy breast cancer prevention. On-going primary and secondary prevention trials will provide evidence whether metformin is effective in preventing breast cancer.

Towards an Integral Therapeutic Protocol for Breast Cancer Based upon the New H+-Centered Anticancer Paradigm of the Late Post-Warburg Era

A brand new approach to the understanding of breast cancer (BC) is urgently needed. In this contribution, the etiology, pathogenesis, and treatment of this disease is approached from the new pH-centric anticancer paradigm. Only this unitarian perspective, based upon the hydrogen ion (H+) dynamics of cancer, allows for the understanding and integration of the many dualisms, confusions, and paradoxes of the disease. The new H+-related, wide-ranging model can embrace, from a unique perspective, the many aspects of the disease and, at the same time, therapeutically interfere with most, if not all, of the hallmarks of cancer known to date. The pH-related armamentarium available for the treatment of BC reviewed here may be beneficial for all types and stages of the disease. In this vein, we have attempted a megasynthesis of traditional and new knowledge in the different areas of breast cancer research and treatment based upon the wide-ranging approach afforded by the hydrogen ion dynamics of cancer. The concerted utilization of the pH-related drugs that are available nowadays for the treatment of breast cancer is advanced.

Autonomous glucose metabolic reprogramming of tumour cells under hypoxia: opportunities for targeted therapy

Molecular oxygen (O₂) is a universal electron acceptor that is eventually synthesized into ATP in the mitochondrial respiratory chain of all metazoans. Therefore, hypoxia biology has become an organizational principle of cell evolution, metabolism and pathology. Hypoxia-inducible factor (HIF) mediates tumour cells to produce a series of glucose metabolism adaptations including the regulation of glucose catabolism, glycogen metabolism and the biological oxidation of glucose to hypoxia. Since HIF can regulate the energy metabolism of cancer cells and promote the survival of cancer cells, targeting HIF or HIF mediated metabolic enzymes may become one of the potential treatment methods for cancer. In this review, we summarize the established and recently discovered autonomous molecular mechanisms that can induce cell reprogramming of hypoxic glucose metabolism in tumors and explore opportunities for targeted therapy.

Inhibiting Autophagy in Renal Cell Cancer and the Associated Tumor Endothelium

The clear cell subtype of kidney cancer encompasses most renal cell carcinoma cases and is associated with the loss of von Hippel-Lindau gene function or expression. Subsequent loss or mutation of the other allele influences cellular stress responses involving nutrient and hypoxia sensing. Autophagy is an important regulatory process promoting the disposal of unnecessary or degraded cellular components, tightly linked to almost all cellular processes. Organelles and proteins that become damaged or that are no longer needed in the cell are sequestered and digested in autophagosomes upon fusing with lysosomes, or alternatively, released via vesicular exocytosis. Tumor development tends to disrupt the regulation of the balance between this process and apoptosis, permitting prolonged cell survival and increased replication. Completed trials of autophagic inhibitors using hydroxychloroquine in combination with other anticancer agents including rapalogues and high-dose interleukin 2 have now been reported. The complex nature of autophagy and the unique biology of clear cell renal cell carcinoma warrant further understanding to better develop the next generation of relevant anticancer agents.

Metformin Protects From Rotenone-Induced Nigrostriatal Neuronal Death in Adult Mice by Activating AMPK-FOXO3 Signaling and Mitigation of Angiogenesis

Parkinson’s disease (PD) is a neurodegenerative disease that affects substantia nigra dopamine neurons. Many studies have documented the role of oxidative stress and angiogenesis in the pathogenesis of PD. Metformin (MTF) is an antidiabetic medication and AMP-activated protein kinase (AMPK) regulator that has shown antioxidant and antiangiogenic properties in many disorders. The aim of this study is to investigate the neuroprotective effect of MTF in a mouse model of rotenone-prompted PD with a highlight on its influence on the AMPK/forkhead box transcription factor O3 (FOXO3) pathway and striatal angiogenesis. In the running study, PD was induced in mice using repeated doses of rotenone and concomitantly treated with MTF 100 or 200 mg/kg/day for 18 days. Rotarod and pole tests were used to examine the animals’ motor functionality. After that, animals were sacrificed, and brains were isolated and processed for immunohistochemical investigations or biochemical analyses. Oxidant stress and angiogenic markers were measured, including reduced glutathione, malondialdehyde, the nuclear factor erythroid 2–related factor 2 (Nrf2), hemoxygenase-1, thioredoxin, AMPK, FOXO3, and vascular endothelial growth factor (VEGF). Results indicated that MTF improved animals’ motor function, improved striatal glutathione, Nrf2, hemoxygenase-1, and thioredoxin. Furthermore, MTF upregulated AMPK-FOXO3 proteins and reduced VEGF and cleaved caspase 3. MTF also increased the number of tyrosine hydroxylase (TH)–stained neurons in the substantia nigra neurons and in striatal neuronal terminals. This study is the first to highlight that the neuroprotective role of MTF is mediated through activation of AMPK-FOXO3 signaling and inhibition of the proangiogenic factor, VEGF. Further studies are warranted to confirm this mechanism in other models of PD and neurodegenerative diseases.

Anticancer mechanisms of metformin: A review of the current evidence

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

Systemic hypoxia potentiates anti-tumor effects of metformin in hepatocellular carcinoma in mice

Local hypoxia is a universal phenomenon in most solid tumors. The role of local hypoxia in the tumor microenvironment and cancer growth and metastasis has been well established. However, the effect of acute systemic hypoxia (exposing the whole body to 10% O2 environment) on cancer has not yet been investigated. In this study, we investigated the potential effects of acute systemic hypoxia itself and in combination with metformin on hepatocellular carcinoma (HCC) growth and metastasis in a mouse model of HCC. Acute systemic hypoxia significantly decreased tumor volume and weight in H22 tumor-bearing mice. Interestingly, the combined treatment of acute systemic hypoxia and metformin showed a more pronounced effect in reducing tumor volume and weight. Moreover, acute systemic hypoxia and metformin in combination had a potent inhibitory effect on tumor progression. More importantly, the expressions of hypoxia response genes including hypoxia-inducible factor-1 α, vascular endothelial growth factor, and matrix metalloproteinase 2 were significantly decreased in the tumor tissues with combination treatment. Our study demonstrated that acute systemic hypoxia repressed tumor progression of the HCC and potentiated the anti-tumor activities of metformin. This study supports that combination of systemic hypoxia and metformin treatment may represent a novel strategy for HCC.

A Cohort Study of Exposure to Antihyperglycemic Therapy and Survival in Patients with Lung Cancer

We evaluated the effect of antihyperglycemic therapy on the survival of patients with lung cancer (LC). The analysis included patients with LC and concomitant type 2 diabetes. 15,929 patients were classified into five groups: metformin users, insulin users, metformin and insulin users, sulphonylurea users and non-diabetic group. A multivariate analysis showed that exposure to either metformin or to insulin was associated with a lower risk of LC-specific mortality, and this approached statistical significance (HR 0.82, 95% CI 0.72–92 for metformin and HR 0.65, 95% CI 0.44–95 for insulin). When deaths from all causes were considered, only metformin exposure was associated with a significantly lower risk of death (HR 0.82, 95% CI 0.73–0.92). Users of sulphonylurea were at a higher risk of LC-specific and overall mortality (HRs 1.19, 95% CI 0.99–1.43 and 1.22, 95% CI 1.03–1.45). Our study shows a positive effect of metformin on the survival of patients with LC. Moreover, our results show that exposure to insulin was associated with a lower risk of LC-specific mortality, but not with deaths from all causes. The study results suggested that users of sulphonylurea may be at a higher risk of LC-specific and overall mortality.

The Effect of Metformin on the Clinicopathological Features of Breast Cancer With Type 2 Diabetes

Background

The present study aimed to review the use of hypoglycemic drugs and clinicopathological data in breast cancer patients with type 2 diabetes mellitus (T2DM), and to investigate the effect of metformin on the clinicopathological features of breast cancer in patient with T2DM.

Methods

Eighty-nine patients with breast cancer hospitalized in the Second Affiliated Hospital of Xi’an Jiaotong University from January 2012 to December 2014 were included. Thirty-three patients were on metformin (metformin group) and 56 patients were on control group. Streptavidin-peroxidase (SP) method was used to quantify protein expression of molecular markers (estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2)), molecular markers of proliferation (Ki-67 and epidermal growth factor receptor (EGFR)) and epithelial-mesenchymal transition (EMT) molecular markers (matrix metalloproteinase-2 (MMP-2), E-cadherin and downstream N-cadherin). Fluorescence in situ hybridization was used to detect HER-2 (+ and ++).

Results

The rate of lymph node metastasis and the level of Ki-67/MMP-2 in the metformin group were significantly lower than those in the control group (P < 0.05). The ratio of luminal pattern in metformin group was higher than that in the control group (P < 0.05). However, there were no differences in the parameters of age, duration of diabetes, body mass index, tumor size, histological grade of cancer and clinical pathological features between the two groups. No significant difference was observed in the expressions of ER, PR, HER-2, EGFR, E-cadherin, N-cadherin and the recurrence rate between two groups.

Conclusions

Metformin is associated with luminal breast cancer and can inhibit breast cancer invasion and metastasis in some cases. It may be associated with EMT and is beneficial to the prognosis of breast cancer.

A New and Integral Approach to the Etiopathogenesis and Treatment of Breast Cancer Based upon Its Hydrogen Ion Dynamics

Despite all efforts, the treatment of breast cancer (BC) cannot be considered to be a success story. The advances in surgery, chemotherapy and radiotherapy have not been sufficient at all. Indeed, the accumulated experience clearly indicates that new perspectives and non-main stream approaches are needed to better characterize the etiopathogenesis and treatment of this disease. This contribution deals with how the new pH-centric anticancer paradigm plays a fundamental role in reaching a more integral understanding of the etiology, pathogenesis, and treatment of this multifactorial disease. For the first time, the armamentarium available for the treatment of the different types and phases of BC is approached here from a Unitarian perspective-based upon the hydrogen ion dynamics of cancer. The wide-ranged pH-related molecular, biochemical and metabolic model is able to embrace most of the fields and subfields of breast cancer etiopathogenesis and treatment. This single and integrated approach allows advancing towards a unidirectional, concerted and synergistic program of treatment. Further efforts in this line are likely to first improve the therapeutics of each subtype of this tumor and every individual patient in every phase of the disease.

The impact of diabetes in head and neck cancer

PURPOSE OF REVIEW

A strong association between diabetes mellitus and carcinogenesis has been reported in different organs. The purpose of this review is to summarize the new evidences in relation to diabetes mellitus and its association with the development, prognosis, and therapeutic strategies of head and neck squamous cell carcinomas (HNSCC).

RECENT FINDINGS

Recent publications suggest that glycemic metabolism is altered in HNSCC. Elevated blood glucose levels, before or around the time of diagnosis, have been reported to reduce survival rates in HNSCC. Also, the homeostasis model assessment-insulin resistance has been independently associated with disease-free survival, suggesting that improving the glycemic control may improve the prognosis in this group of patients.Epidemiological studies revealed that cancer patients with diabetes mellitus have less cancer-related mortality after antiglycemic treatment, opening the option to include antiglycolytic agents, such as metformin, in the therapeutic plan. This finding is in accordance with in-vitro studies that demonstrated a decrease in tumor-cell proliferation with antidiabetic medications.

SUMMARY

Recent findings highlight the importance of glucose metabolism in the pathogenesis and progression of cancer cells. The knowledge of these altered pathways gives us an opportunity to design target treatments aimed to modulate glucose catabolism.

Treatment with a Combination of Metformin and 2-Deoxyglucose Upregulates Thrombospondin-1 in Microvascular Endothelial Cells: Implications in Anti-Angiogenic Cancer Therapy

Metformin, the most widely used anti-diabetic drug, also exhibits anti-cancer properties; however, the true potential of metformin as an anticancer drug remains largely unknown. In this study using mouse microvascular endothelial cells (MMECs), we investigated the effects of metformin alone or in combination with the glycolytic inhibitor, 2-deoxyglucose (2DG), on angiogenesis-a process known to be an integral part of tumor growth, cancer cell survival and metastasis. MMECs were exposed to 2DG (1-10 mM) for 48 h in the absence or presence of metformin (2 mM). The status of angiogenic and anti-angiogenic marker proteins, proteins of the mTOR pathway and cell-cycle-related proteins were quantified by Western blot analysis. Assays for cell proliferation, migration and tubulogenesis were also performed. We observed robust up-regulation of anti-angiogenic thrombospondin-1 (TSP1) and increased TSP1-CD36 co-localization with a marked decrease in the levels of phosphorylated vascular endothelial growth factor receptor-2 (pVEGFR2; Y1175) in 2DG (5 mM) exposed cells treated with metformin (2 mM). Additionally, treatment with metformin and 2DG (5 mM) inhibited the Akt/mTOR pathway and down-regulated the cell-cycle-related proteins such as p-cyclin B1 (S147) and cyclins D1 and D2 when compared to cells that were treated with either 2DG or metformin alone. Treatment with a combination of 2DG (5 mM) and metformin (2 mM) also significantly decreased cell proliferation, migration and tubulogenic capacity when compared to cells that were treated with either 2DG or metformin alone. The up-regulation of TSP1, inhibition of cell proliferation, migration and tubulogenesis provides support to the argument that the combination of metformin and 2DG may prove to be an appropriate anti-proliferative and anti-angiogenic therapeutic strategy for the treatment of some cancers.

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.

Atovaquone: An Antiprotozoal Drug Suppresses Primary and Resistant Breast Tumor Growth by Inhibiting HER2/β-Catenin Signaling

Breast cancer is the second leading cause of cancer-related mortality in women. In the current study, we evaluated the anticancer effects of an antiprotozoal drug, atovaquone, against several breast cancer cell lines. Our results showed that atovaquone treatment induced apoptosis and inhibited the growth of all the breast cancer cell lines tested, including several patient-derived cells. In addition, atovaquone treatment significantly reduced the expression of HER2, β-catenin, and its downstream molecules such as pGSK-3β, TCF-4, cyclin D1, and c-Myc in vitro Efficacy of atovaquone was further evaluated in an in vivo tumor model by orthotropic implantation of two highly aggressive 4T1 and CI66 breast cancer cells in the mammary fat pad of female mice. Our results demonstrated that oral administration of atovaquone suppressed the growth of CI66 and 4T1 tumors by 70% and 60%, respectively. Paclitaxel is the first-line chemotherapeutic agent for metastatic breast cancer. We demonstrate that atovaquone administration suppressed the growth of 4T1 paclitaxel-resistant tumors by 40%. Tumors from atovaquone-treated mice exhibited reduced HER2, β-catenin, and c-Myc levels alongside an increase in apoptosis in all the three tumor models when analyzed by Western blotting, IHC, and TUNEL assay. Taken together, our results indicate that atovaquone effectively reduces the growth of primary and paclitaxel-resistant breast tumors. Atovaquone is already in the clinics with high safety and tolerability profile. Therefore, the findings from our studies will potentially prompt further clinical investigation into repurposing atovaquone for the treatment of patients with advanced breast cancer.