Experimental model of tumors associated with neurofibromatosis

Four groups of animals, each composed of 22 pregnant Wistar rats, were used in this study. Single intraperitoneal (IP) injections of ethylnitrosourea (ENU) at a dose of 15 mg/kg body weight (BW) were given to the animals of two groups on days 15 and 21 of pregnancy, respectively. The progeny of a third group received by subcutaneous injection (SC) the same dose of ENU, 15 mg/kg BW, on day 1 postnatally. The descendants of the fourth group served as untreated controls. The most striking findings were observed in the progeny of the mothers treated on day 15 of pregnancy, in which group 64 of 180 descendants developed peripheral nervous system (PNS) tumors, 30% of which had plexiform pattern. One hundred fifteen of the 180 descendants developed central nervous system (CNS) gliomas, mainly oligodendrogliomas, and five animals presented with Wilms' tumors. No tumors of these types were observed in the untreated controls. Although descendants of mothers treated on day 21 of pregnancy had the highest number of PNS tumors (130 of 172 animals), only 21% of these tumors were plexiform; CNS gliomas were observed in 78 animals and Wilm's tumors in one animal. The lowest percentage of PNS tumors with plexiform pattern (16%) was found in the group of 157 descendants treated postnatally on day 1, in which 88 animals developed PNS tumors, 76 developed CNS gliomas, and no animals developed Wilms' tumors. The higher percentage of plexiform PNS tumors found in the descendants treated prenatally on day 15 of pregnancy was statistically significant (P less than 0.05) when compared with the percentage found in the group treated postnatally. This significance was also valid for the plexiform tumors that developed selectively from branches of the trigeminal nerves (of the PNS tumors from this location, 48% showed a plexiform pattern), but only in the progeny exposed to ENU on day 15 of pregnancy. This same progeny also had the highest numbers of CNS and Wilms' tumors. Because in humans, plexiform neurofibromas are considered to be the neoplastic markers of neurofibromatosis, and CNS gliomas as well as Wilms' tumors are associated with this disease, it is suggested that exposure to ENU on day 15 of pregnancy, under the experimental conditions described here, may offer a model for investigating tumors associated with neurofibromatosis, as well as aspects of the spontaneous, noninherited forms of this disease.