@misc{oai:repo.qst.go.jp:00069219,
 author = {Tomita, Takae and Lee, Gan-hon and Kakinuma, Shizuko and Yamauchi, Kazumi and Imaoka, Tatsuhiko and Hatano, Yukiko and Shimada, Yoshiya and 富田 貴絵 and 李 康弘 and 柿沼 志津子 and 甘崎 佳子 and 今岡 達彦 and 西村 由希子 and 島田 義也},
 month = {Nov},
 note = {Effect of exposure to radiation at the childhood and following an environmental chemical carcinogen on cancer induction is not sufficiently examined. The aim is to elucidate the age-dependency of hepato- and lung-carcinogenesis after exposure to X-rays, diethylnitrosamine (DEN), or combined exposure in B6C3F1 mice.
At an age of 2 or 7 weeks, the male B6C3F1 mice were irradiated at 2 Gy of X-rays followed by an i.p. injection of DEN (80mg/kg body weight) 2 or 5 weeks later. The mice were sacrificed at the age of 1 year and counted macroscopically the number and size of tumors in liver and lung. The tumors were investigated pathologically and immunohistochemically.
 Liver tumor: Young mice were more susceptible to the radiation and DEN.  The combined exposure increased tumor number in an additive fashion.  The large tumors more than 10 mm were found frequently in the mice exposed at young of age.
Lung tumor: While mice at 9 weeks old were more susceptible to DEN than young mice, X-rays did not induce lung tumor at any age. The combined exposure at 7 weeks old induced the several large size tumors.  However, number of tumors did not increase by combined exposure, which might result from high dose of DEN concealing the effect of X-rays. 
These results suggested that the susceptibility to combined exposure to X-rays and DEN was dependent on not only tissues but also age at exposure.  Ongoing immunohistchemistry to beta-catenin in liver tumors suggests activation of beta-catenin is not involved in hepatocarcinogenesis., 1st Asian Conference on Environmental Mutagens, 36th Annual Meeting of the Japanese Environmental Mutagen Society},
 title = {Age-dependency and tissue specificity of tumors induced by combined exposure of X-rays and dietylnitrosamine},
 year = {2007}
}