Transplacental and neonatal induction of neurogenic tumors in mice: comparison with related species and with human pediatric neoplasms.

The literature on chemical induction and natural occurrence of neurogenic tumors in mice and some unpublished data from our laboratories are reviewed. Neurogenic tumors are a minor component of the total tumorigenic response of mice to alkylating agents such as ENU and MNU. In comparison with rats, a given dose of ENU induces a much lower incidence of neurogenic tumors in mice, and the mean latency is much longer than in rats. Although most neurogenic tumors induced by ENU in mice by either transplacental or direct postnatal exposure are of glial or Schwann cell origin, as in rats, and occur most frequently in the cerebrum or cranial nerves, respectively, medulloblastomas of the cerebellum also occur in treated mice. Transplacental and neonatal exposure to ENU were much more effective in inducing neurogenic tumors than treatment later in life. Ependymomas were not seen in mice, although they are common in ENU-treated rats. Neuroblastoma of the adrenal medulla, a common human pediatric tumor, has not been induced to either species, but it does occur spontaneously in mice. The induction by ENU of medulloblastomas demonstrates that this rodent equivalent of an embryonal tumor of the human nervous system can result from exposure to exogenous chemical agents.