Host factors affecting perinatal carcinogenesis by resorptive alkylnitrosoureas in rats.

Host factors are operative in transplacental carcinogenesis. There are species, strain, sex, and individual differences in susceptibility to carcinogens. Rat fetuses are over 50 times more susceptible than adults to the oncogenic effects of ENU, yet are less susceptible to tumor induction with DMN. Immune mechanisms do not seem to affect the latency period, incidence, location, and type of neurogenic neoplasms, although tumor-specific antigens are demonstrable in neoplastic neuroectodermal cells. Although placental barriers, DNA repair capacities, age at exposure, hormonal interaction, and immune responsiveness may be singled out as possible causes for species, strain, sex, and individual variations in susceptibility to the neuro-oncogenic potential of ENU, no definitive proof of the mechanism of action of any of these factors has yet been presented.