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Int J Cancer. 2014 Sep 1;135(5):1038-47. doi: 10.1002/ijc.28751. Epub 2014 Feb 11.

Cancer prevention by adult-onset calorie restriction after infant exposure to ionizing radiation in B6C3F1 male mice.

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  • 1Radiobiology for Children's Health Program, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan.

Abstract

Children are especially sensitive to ionizing radiation and chemical carcinogens, and limiting their cancer risk is of great public concern. Calorie restriction (CR) is a potent intervention for suppressing cancer. However, CR is generally not appropriate for children. This study, therefore, examined to see if adult-onset CR influences the lifetime cancer risk in mice after early-life exposure to ionizing radiation. Infant male mice (1-week-old) were exposed to 3.8 Gy X-rays, fed a control 95 kcal/week or CR 65 kcal/week diet from 7 weeks of age (adult stage), and their lifespan and tumor development were assessed. Irrespective of CR, X-rays shortened lifespan by 38%, and irrespective of irradiation CR extended lifespan by 20%. Thymic lymphoma (TL) and early-occurring non-TL were induced by radiation. The liver and Harderian gland were more susceptible to radiation-induced tumors than the lungs and non-thymic lymphoid tissues (late occurring). CR reduced the risk of hepatocellular carcinoma, late-occurring non-TL, lung tumor, Harderian tumor, and hemangioma but had less impact on TL and early-occurring non-TL. Most notably, the effects of X-rays on induction of lung tumors, late-occurring non-TL and hemangioma were essentially canceled by CR. The ability of CR to prevent late-occurring tumors was the same for non-irradiated and irradiated mice, indicating that the mechanism by which CR influences cancer is independent of irradiation. Our results indicate that adult-onset CR significantly inhibits late-occurring tumors in a tissue-dependent manner regardless of infant radiation exposure.

KEYWORDS:

calorie restriction; cancer prevention; infant exposure; ionizing radiation

PMID:
24482070
DOI:
10.1002/ijc.28751
[PubMed - indexed for MEDLINE]
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