The biguanides metformin and phenformin inhibit angiogenesis, local and metastatic growth of breast cancer by targeting both neoplastic and microenvironment cells

Abstract

The human white adipose tissue (WAT) contains progenitors with cooperative roles in breast cancer (BC) angiogenesis, local and metastatic progression. The biguanide Metformin (Met), commonly used for Type 2 diabetes, might have activity against BC and was found to inhibit angiogenesis in vivo. We studied Met and another biguanide, phenformin (Phe), in vitro and in vivo in BC models. In vitro, biguanides activated AMPK, inhibited Complex 1 of the respiratory chain and induced apoptosis of BC and WAT endothelial cells. In coculture, biguanides inhibited the production of several angiogenic proteins. In vivo, biguanides inhibited local and metastatic growth of triple negative and HER21 BC in immune-competent and immune-deficient mice orthotopically injected with BC. Biguanides inhibited local and metastatic BC growth in a genetically engineered murine model model of HER21 BC. In vivo, biguanides increased pimonidazole binding (but not HIF-1 expression) of WAT progenitors, reduced tumor microvessel density and altered the vascular pericyte/endothelial cell ratio, so that cancer vessels displayed a dysplastic phenotype. Phe was significantly more active than Met both in vitro and in vivo. Considering their safety profile, biguanides deserve to be further investigated for BC prevention in high-risk subjects, in combination with chemo and/or targeted therapy and/or as post-therapy consolidation or maintenance therapy for the prevention of BC recurrence.There is increasing preclinical evidence that the biguanide Metformin (Met), commonly used for the therapy of Type 2 diabetes, might have activity against several types of neoplastic diseases 1-25 including breast cancer (BC). Another biguanide, phenformin (Phe), which was dismissed from the arsenal of antidiabetes drug because of some side effects, has shown preclinical activity in a model of BC. 26 We and others have recently shown that two populations of human white adipose tissue (WAT) CD45-CD341 progenitors have cooperative roles in BC angiogenesis, local and metastatic progression. [27][28][29][30][31][32][33][34][35] In orthotopic murine models we found that (i) purified human WAT CD341CD131 mesenchymal adipose stromal cell progenitors (ASCs) were not able to migrate but promoted local tumor growth in the mammary fat pad and (ii) purified human WAT CD341CD311 endothelial progenitor cells (EPCs) were able to migrate toward lymph nodes and blood and promoted BC cell EMT, migration, invasion and metastatic growth. 34In another recent study we have found that Met inhibited the formation of capillary-like networks by human umbilical vein endothelial cells (HUVEC), and decreased microvessel density (MVD) in tumor-free mice. 36 Here we report that Met and Phe (with even more efficacy) targeted in vitro and in vivo both BC cells and WAT EPCs, resulting in profound effects on BC angiogenesis, local and metastatic growth that are likely due to additive effects on both tumor and microenvironment cells. These effects were observed both in triple negative and in HER21 models o...

The Antidiabetic Drug Metformin Stimulates Glycolytic Lactate Production in Cultured Primary Rat Astrocytes

“…Millimolar concentrations of metformin stimulated astrocytic glycolysis in a time-and concentration-dependent manner as demonstrated by a doubling of both glucose consumption and lactate production. Metformin-induced stimulation of glycolysis has recently also been reported for rat skeletal muscle [6], human white adipose tissue progenitor cells [8] and mouse astrocytes [32].…”

“…In addition, at least for rats was demonstrated that metformin concentrations in the cerebrospinal fluid are substantially higher than those determined for plasma [16]. For acute experiments in the hour range metformin has frequently been applied to cells in concentrations of 10 mM [6,8]. However, during prolonged incubations less metformin is required to stimulate glycolysis in astrocytes and already 1 mM metformin doubled astrocytic lactate generation within 24 h. It remains to be elucidated whether even micromolar concentrations of metformin would be sufficient to stimulate astrocytic glycolysis during incubations for days or weeks.…”

“…Metformin is transported by organic cation transporters (OCTs) into many cells [5,6]. Exposure of cells to metformin has been reported to strongly affect cell metabolism, for example by stimulating glycolysis via activation of adenosine monophosphate-dependent protein kinase (AMPK) [6][7][8], by inhibition of mitochondrial respiratory chain complex I [8,9] and by inhibition of the mitochondrial glycerol phosphate shuttle [10]. In addition, metformin is known to reduce gluconeogenesis, to improve insulin signalling and to accelerate glucose uptake [11].…”

Microparticulate and nanoparticulate drug delivery systems for metformin hydrochloride

“…Combination of dichloroacetate with metformin was reported to synergistically induce caspase-dependent apoptosis involving oxidative damage (Haugrud et al, 2014). Orecchioni et al (2015) studied the effects of metformin and phenformin on breast cancer using in vitro and in vivo models, and found that phenformin was more effective than metformin in both models. Both drugs were reported to induce apoptosis of breast cancer and the human white adipose tissue (WAT) endothelial cells through the activation of AMPK and inhibition of Complex 1 of the respiratory chain in the in vitro model.…”

Sex differences in aging, life span and spontaneous tumorigenesis in 129/Sv mice neonatally exposed to metformin

“…These data correspond to observations that metformin can increase VEGF expression, intratumoral microvascular density and reduces necrosis thus promoting the angiogenic phenotype and increasing tumorigenic progression. 42 Martin-Montalvo et al 38 supplied male C57BL/6 mice with ad libitum diet with supplementation of 0.1% (1,000 ppm) or 1% (10,000 ppm) of metformin starting from the age of 54 weeks for the remainder of their lives. The mean life span of mice treated with 0.1% of the drug in diet was increased by 5.83% as compared to the relevant control group, whereas the dose 1% was toxic and reduced the mean life span by 14.4%.…”