Project description:Breast cancer ranks top in the incidence among the main sites of female cancer in Japan. The epidemiological study on atomic bomb survivors has suggested that the excess relative risk for breast cancer is higher than any other sites. Little is known, however, about the molecular mechanisms of breast cancer induction by radiation. Therefore, we analyzed here the genome-wide copy number aberration of radiation-induced rat mammary carcinomas using microarray-based comparative genomic hybridization (array-CGH). Mammary carcinomas were induced by 2 Gy gamma irradiation of Sprague-Dawley (SD) rats at 3 or 7 weeks of age. We examined 14 mammary carcinomas induced by gamma-irradiation (2 Gy) and found 26 aberrations including trisomies of chromosomes 4 and 10 in 3 and 1 carcinomas, respectively, and deletion of chromosomes 3q35q36 and 5q32 (Cdkn2a and Cdkn2b region) in 2 and 2 carcinomas, respectively. On the other hand, only one aberration (amplification of chromosome 10q31) was observed in four spontaneous mammary carcinomas. These results suggest that the trisomy of chromosome 4 and deletion of chromosomes 3q35q36 and 5q32 were associated with radiation exposure.
Project description:Breast cancer ranks top in the incidence among the main sites of female cancer in Japan. The epidemiological study on atomic bomb survivors has suggested that the excess relative risk for breast cancer is higher than any other sites. Little is known, however, about the molecular mechanisms of breast cancer induction by radiation. Therefore, we analyzed here the genome-wide copy number aberration of radiation-induced rat mammary carcinomas using microarray-based comparative genomic hybridization (array-CGH). Mammary carcinomas were induced by 2 Gy gamma irradiation of Sprague-Dawley (SD) rats at 3 or 7 weeks of age. We examined 14 mammary carcinomas induced by gamma-irradiation (2 Gy) and found 26 aberrations including trisomies of chromosomes 4 and 10 in 3 and 1 carcinomas, respectively, and deletion of chromosomes 3q35q36 and 5q32 (Cdkn2a and Cdkn2b region) in 2 and 2 carcinomas, respectively. On the other hand, only one aberration (amplification of chromosome 10q31) was observed in four spontaneous mammary carcinomas. These results suggest that the trisomy of chromosome 4 and deletion of chromosomes 3q35q36 and 5q32 were associated with radiation exposure. We performed aCGH on mammary carcinoma in Sprague-Dawley rat to identify radiation-specific DNA copy number aberration compared with spontaneous mammary carcinoma.
Project description:Understanding the relationship between radiation-induced breast cancer and obesity, together with information on underlying mechanisms, are potentially useful in risk management and prevention of second cancer in patients receiving radiotherapy. The present study aims to develop a novel animal model to study the relationship by combining two Sprague-Dawley rat models of radiation carcinogenesis and diet-induced obesity. Mammary carcinomas were induced in female obese and lean rats by irradiation with 4 Gy of gamma rays. Gene expression of mammary carcinomas and normal mammary tissues were analyzed with Agilent Whole Rat Genome DNA microarray. The result indicated that genes related to translation and oxidative phosphorylation were upregulated in carcinomas of obese rats.
Project description:Although various mechanisms have been inferred for combinatorial actions of multiple carcinogens, these mechanisms have not been well demonstrated in experimental carcinogenesis models. We evaluated mammary carcinogenesis initiated by combined exposure to various doses of radiation and chemical carcinogens. Female rats at 7 weeks of age were γ-irradiated (0.2–2 Gy) and/or exposed to 1-methyl-1-nitrosourea (20 or 40 mg/kg, single intraperitoneal injection) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (40 mg/kg/day by gavage for 10 days) and were observed until 50 weeks of age. The incidence of mammary carcinoma increased steadily as a function of radiation dose in the absence of chemicals; mathematical analysis supported an additive increase when radiation was combined with a chemical carcinogen, irrespective of the chemical species and its dose. Hras mutations were characteristic of carcinomas that developed after chemical carcinogen treatments and were overrepresented in carcinomas induced by the combination of radiation and MNU (but not PhIP), indicating an interaction of radiation and MNU at the level of initiation. The expression profiles of seven classifier genes, previously shown to distinguish two classes of rat mammary carcinomas, categorized almost all examined carcinomas that developed after individual or combined treatments with radiation (1 Gy) and chemicals as belonging to a single class; more comprehensive screening using microarrays and a separate test sample set failed to identify differences in gene expression profiles among these carcinomas. These results suggest that a complex, multilevel interaction underlies the combinatorial action of radiation and chemical carcinogens in the experimental model.
