Table 3.

Summary of Metformin Treatment on Mammary Tumor Development in Rodent Models of Breast Cancer

Mouse Model [treatment period] (reference)	Metformin dose (route of administration)	Length of treatment	Outcome
MMTV-neu mice [treatment started at 8 wks of age] (40)	100 mg/kg for 5 days/week in water (= 300 mg/m2) (note error in paper says month)	44 weeks	Slight decrease in food intake but not consistent. Body weight not affected. Significant survival effect in the metformin mice for both mean and maximal life span. Mean tumor size reduced and tumor development delayed. Metastases (lung) not affected.
MMTV-neu mice [treatment started at 8 wks of age] (41)	100 mg/kg for 5 days/week in water (= 300 mg/m2)	lifespan	Some effect on food intake around 7 months. Body weight at 8 months 12% lower. Tumor latency extended 13% for 50% point but no reported effect on tumor number and metastases.
MMTV-neu mice ]treatment 8 wks of age] (30)	250 mg/kg daily Ip injections	10 weeks	Mammary morphogenesis studied- whole mounts metformin decreased lateral branching and alveolar structure Sphere formation reduced in metformin mammary tissues MECs. Affecting stem cells? Metformin downregulated ERbB2 and EGFR expression as well as phosphorylation and activated AMPK
Mammary tumors by MNU- induced @ 50 days of age in Sprague-Dawley rats [treatment from 30 days of age] (43)	5 mg/kg or 50 mg/kg in water	21 weeks (Started at 30 days of age before MNU and maintained until 25 week of age)	No effect of metformin on body weight. No effect on mammary tumor incidence. 50 mg dose extended latency by 10% and serum IGF-I increased.
Mammary tumors by MNU- in obese ovariectomized Wistar rats @~52 days of age [treatment post ovariectomy] (44)	2 mg/mL in water	3 weeks post ovariectomy which were performed at 18 weeks of age	Tumor burden decreased 75% at end. Tumor receptor status one week of treatment by biopsy, reduced progesterone receptor but no effect on estrogen receptor-alpha or HER2
Mammary tumors by MNU Sprague-Dawley rats @ 20 days of age [Treatment as per described for 3 different experiments] (25)	Interventions began 6 days after MNU and metformin included in food Experiment 1 0.5% or 1% metformin for 5 days then 0.05 or 0.25% for 28 days	33 days	Experiment 1. No effect on mammary tumor incidence but latency significantly extended and tumor burden reduced. AMPK activated in tumors. Serum insulin and leptin reduced at higher dose. No effect on IGF-I, glucose or adiponectin.
	Experiment 2 0.3% metformin	63 days	Experiment 2. Some effect on tumor latency but not incidence or tumor burden
	Experiment 3 40% calorie restriction 40% restriction + 0.25% metformin	56 days	Experiment 3. Mammary tumor incidence reduced by calorie restriction or calorie restriction + 0.25% metformin – marginally significant
MMTV-TGF-alpha female lean and obese mice [Treatment started @ 30 weeks of age] (unpublished)	250 mg/kg (in food)	Until 90 weeks of age	Study underway results expected mid 2015
MMTV-PyVT [7 weeks of age] {Orecchioi, 2015 6549/id}	2/1.65 mg/ml (in drinking water) metformin/phenformin	7 weeks of age for 5 weeks (note mistake in paper says days not weeks)	Similar effects of metformin and phenformin on significantly reducing tumor weight, tumor number and lung metastases.