Figure 1

Effect of 300 mg kg⁻¹ phenformin on human breast MCF7 (A) and MDAMB231 (B), and 300 mg kg⁻¹ metformin on MDAMB231 (C) tumour xenografts. For the phenformin experiment, mice were divided into three groups. Controls received no phenformin. Pre-treatment mice were given phenformin (300 mg kg⁻¹) in 5% sucrose instead of normal drinking water for 2 weeks prior to injection of MCF7 or MDAMB231 cells. The phenformin group received normal drinking water until tumours reached ⩾30 mm³, after which drinking water was replaced with 5% sucrose containing phenformin (300 mg kg⁻¹). Control group also had water replaced with 5% sucrose. For the metformin experiment, mice were divided into two groups. Controls received no metformin and mice with established tumours received metformin (300 mg kg⁻¹) in water. MCF7 tumours pre-treated or treated with phenformin had statistically significant inhibition of tumour growth of 88% relative to the control group (P<0.05). Animals injected with MDAMB231 cells and treated prophylactically with phenformin showed small lumps 6 weeks after inoculation, which remained static for the rest of the experiment. Established MDAMB231 tumours treated with phenformin demonstrated statistically significant inhibition of tumour growth of 60% relative to the control group (P<0.05). There were no statistically significant differences between control mice and mice treated with metformin.