PMID: 2501022Aug 1, 1989Paper

Growth factor binding to 7,12-dimethylbenz(a)anthracene-induced mammary tumors from rats subject to chronic caloric restriction

Cancer Research
B A RuggeriR W Furlanetto

Abstract

Caloric restriction (CR) inhibits tumorigenesis in rodents. To understand the basis for this effect the binding of insulin, insulin-like growth factor I/somatomedin C (IGF-I/Sm-C), insulin-like growth factor II/multiplication stimulating activity (IGF-II/MSA), and epidermal growth factor were examined to membrane preparations of 7,12-dimethylbenz(a)anthracene-induced mammary adenocarcinomas and several normal tissues from female Sprague-Dawley rats. Animals were fed ad libitum (AL) or 25% and 40% calorically restricted diets. Large, palpable (LP) and small, less than or equal to 100 mg, nonpalpable (SNP) tumors were evaluated. Growth factor binding to tumors was differentially affected by CR. IGF-I/Sm-C binding was comparable for AL-LP, AL-SNP, and 25% CR-LP tumors, but elevated in 25% CR-SNP tumors. Scatchard analysis revealed high and low affinity IGF-I/Sm-C binding sites, with AL-SNP and 25% CR-SNP tumors exhibiting similar levels of high affinity sites and at a greater concentration than AL-LP and 25% CR-LP tumors. Insulin binding to mammary tumors was low, i.e., 8- to 13-fold lower than IGF-I/Sm-C binding. The 25% CR-LP and SNP tumors bound 2- to 5-fold more insulin than corresponding AL-LP and SNP tumors. Binding of IGF-I...Continue Reading

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