[Carcinogenesis and ontogenesis: chief trends and results of investigations]

A significant role of chemical, physical and hormonal factors modifying transplacental carcinogenesis has been established. It was found that, in tumors induced during gestation by carcinogenic agent treatment, ras oncogenes are activated due to their point mutation. The progeny of male animals exposed to radiation before mating with intact females prove to be more susceptible to such carcinogenic promoters as urethane and TPA than controls while the descendants of older males and young females are more susceptible to NMU treatment than those of young males and females. Convincing evidence of selective DNA damage being relevant to initiation of carcinogenesis was first obtained in experiments involving the use of a synthetic analog of thymidine 5-bromodesoxyuridine. Experimental treatment with carcinogenic agents and tumor promoters at different age has demonstrated age-related accumulation in different tissues of cells which have been randomly exposed to carcinogenic substances and, as a result, are pass at least one stage before complete malignant transformation. It is also assumed that such partially transformed cells are exposed to the carcinogenic effect which increases in proportion to age. Significant differences in age-related changes in the sensitivity of different tissues to the action of different carcinogens have been identified. A direct correlation between the pattern of aging delay in a population affected by a certain geroprotector and its influence on neoplasm development was established on the basis of an evaluation of the evidence on tumor incidence in experimental animals following geroprotector administration.