Nerve growth factor modification of the ethylnitrosourea model for multiple schwannomas.

The administration of ethylnitrosourea (ENU) to pregnant rats late in gestation or to neonatal rats results in the induction of Schwann cell tumors in a high percentage of perinatally exposed animals. Exogenous administration of nerve growth factor (NGF) significantly reduces the number of Schwann cell tumors and other neurogenic tumors developing in ENU-treated rats. Administration of antibodies directed against NGF prior to neonatal ENU exposure results in a substantial increase in the incidence of Schwann cell tumors, particularly in the trigeminal nerves of both rats and mice. Transplacental ENU treatment causes early neoplastic proliferation (ENP) at 90 days of age in the Schwann cell population of trigeminal nerves in nearly all exposed rats. A variety of NGF treatment protocols (single or multiple inoculations or microinfusion prior to or following ENU exposure) resulted in a significant reduction in ENU-induced ENP in trigeminal nerves. These results indicate that NGF may convey protection either directly or indirectly, by an unknown mechanism, to Schwann cells and other supportive neural cells by reducing their sensitivity to ENU-induced neoplastic transformation.