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Lack of effect of metformin on mammary carcinogenesis in nondiabetic rat and mouse models.

ABSTRACT: Epidemiologic studies have shown that diabetics receiving the biguanide metformin, as compared with sulfonylureas or insulin, have a lower incidence of breast cancer. Metformin increases levels of activated AMPK (AMP-activated protein kinase) and decreases circulating IGF-1; encouraging its potential use in both cancer prevention and therapeutic settings. In anticipation of clinical trials in nondiabetic women, the efficacy of metformin in nondiabetic rat and mouse mammary cancer models was evaluated. Metformin was administered by gavage or in the diet, at a human equivalent dose, in standard mammary cancer models: (i) methylnitrosourea (MNU)-induced estrogen receptor-positive (ER(+)) mammary cancers in rats, and (ii) MMTV-Neu/p53KO ER(-) (estrogen receptor-negative) mammary cancers in mice. In the MNU rat model, metformin dosing (150 or 50 mg/kg BW/d, by gavage) was ineffective in decreasing mammary cancer multiplicity, latency, or weight. Pharmacokinetic studies of metformin (150 mg/kg BW/d, by gavage) yielded plasma levels (Cmax and AUC) higher than humans taking 1.5 g/d. In rats bearing small palpable mammary cancers, short-term metformin (150 mg/kg BW/d) treatment increased levels of phospho-AMPK and phospho-p53 (Ser20), but failed to reduce Ki67 labeling or expression of proliferation-related genes. In the mouse model, dietary metformin (1,500 mg/kg diet) did not alter final cancer incidence, multiplicity, or weight. Metformin did not prevent mammary carcinogenesis in two mammary cancer models, raising questions about metformin efficacy in breast cancer in nondiabetic populations.

SUBMITTER: Thompson MD

PROVIDER: S-EPMC4355096 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Lack of effect of metformin on mammary carcinogenesis in nondiabetic rat and mouse models.

Thompson Matthew D MD Grubbs Clinton J CJ Bode Ann M AM Reid Joel M JM McGovern Renee R Bernard Philip S PS Stijleman Inge J IJ Green Jeffrey E JE Bennett Christina C Juliana M Margaret MM Moeinpour Fariba F Steele Vernon E VE Lubet Ronald A RA

Cancer prevention research (Philadelphia, Pa.) 20150213 3

Epidemiologic studies have shown that diabetics receiving the biguanide metformin, as compared with sulfonylureas or insulin, have a lower incidence of breast cancer. Metformin increases levels of activated AMPK (AMP-activated protein kinase) and decreases circulating IGF-1; encouraging its potential use in both cancer prevention and therapeutic settings. In anticipation of clinical trials in nondiabetic women, the efficacy of metformin in nondiabetic rat and mouse mammary cancer models was eval ...[more]

PMID: 25681088

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Project description:7,12-Dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinoma is a well-recognized model, however, the genetic alterations during its carcinogenesis have yet to be determined. We used laser capture microdissection to specifically isolate cells from terminal end buds (TEBs), the origin of carcinoma, at 2 weeks after sesame oil- treatment (control) or DMBA-treatment (DMBA-TEBs), ductal carcinoma in situ (DCIS) and invasive mammary carcinoma (MC). Using an oligonucleotide microarray representing 20600 rat probe sequences, we analyzed gene expression profiles and validated mRNA and protein levels of genes of interest by real-time quantitative PCR, immunohistochemistry and immunofluorescence. The number of differentially expressed genes was smallest in DMBA-TEBs (63), followed by DCIS (798) and MC (981). Only the expression of PEP-19, an anti-apoptic gene, showed significant increases in DMBA-TEBs (4-fold), DCIS (10-fold) and MC (16-fold). MMP-13 expression was increased markedly in DCIS (19-fold) and MC (61-fold) while OPN expression was increased 6-fold in DCIS and 8-fold in MC. MMP-7 expression was increased 4-fold in MC. Nidogen-1; a participant in the assembly of basement membranes, TSP-2; an inhibitor of angiogenesis and COUP-TFI; a transcription repressor showed significant decreases in DCIS (4-, 9-, and 17-fold, respectively) and MC (10-, 37-, and 100-fold). Network analyses with IPA software revealed that the most significant network was centered on Akt groups in DCIS and ERK groups in MC. The present findings provide insights into the molecular changes and suggest the importance of PEP-19 overexpression very early on during mammary carcinogenesis. Keywords: Comparative experiments of sesame oil treatmentM-oM-<M-^HcontrolM-oM-<M-^Iand 7,12-Dimethylbenz[a]anthraceneM-oM-<M-^HDMBAM-oM-<M-^Itreatment group. Or comparative experiments of tissue type ExperimentM-oM-<M-^Z7,12-Dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinoma is a well-recognized model, however, the genetic alterations during carcinogenesis have yet to be determined. We used laser capture microdissection to specifically isolate the cells from terminal end buds (TEBs), the origin of MC, at 2 weeks after sesame oil-(control) or DMBA-treatment (DMBA-TEBs), ductal carcinoma in situ (DCIS) and invasive mammary carcinoma (MC). At 50 days after birth, inbred Sprague-Dawley female rats were given 1ml sesame oil (control) or 20 mg DMBA (Nacalai tesque, Inc. Kyoto Japan) dissolved in 1ml sesame oil, by gastric intubations. Animals in control group were euthanized after 2 weeks (W) and DMBA-treated group were euthanized after 2 weeks (W), 6W and 8W, respectively. From for 4 sample(control, DMBA-TEBs, DCIS, MC), we performed a hybridization repeatedly, respectively.

Dataset Information

Lack of effect of metformin on mammary carcinogenesis in nondiabetic rat and mouse models.

Publications

Lack of effect of metformin on mammary carcinogenesis in nondiabetic rat and mouse models.

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