Cytogenetic and molecular genetic studies on the atomic-bomb survivors

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Cytogenetic and molecular genetic studies were carried out on the atomic-bomb survivors who had been exposed within 500 meters from the hypocenter.The main results obtained in the past three years :1.Follow up of the heavily exposed A-bomb survivorsAnnual follow up of the exposed people revealed six death, one each of acute myeloid leukemia, T cell malignant lymphoma and neoplasia of the kidney, and three of cerebral bleeding. Two survivors were found to have colon cancer (studied conducted in 1994,1995 and 1996 year)2.Establishment of methodology for biological dose estimation by FISHFluorescence in situ hybridization method which identify six painted chromosomes by two color was established. The detection rate of chromosome aberrations was almost the same as that of G-banding method, representing its utility for many exposed people.3.A high incidence of meningioma was found among heavily exposed groupAs two A-bomb survivors were found to have meningioma among 36 heavily exposed people, 38 meningioma patients in exposed group as well as 607 patients in non-exposed group were collected from the database of Hiroshima Tumor Registration. The group exposed more than one gray had significantly higher incidence of meningioma.4.A significant difference was observed in cytogenetic and molecular genetic findings between heavily exposed leukemia patients and non-exposedLeukemia patients exposed to more than one gray had complex chromosome aberration (p<0.05), less frequencies of leukemia-type specific chromosome translocation (p<0.005), RAS point mutation (p<0.07), MLL rearrangement (p<0.03), p53 mutation (p<0.07). These findings suggest different leukemogenesis process from that of de novo leukemia (studies conducted in 1994,1995 and 1996 year).