[Von Recklinghausen's disease: experimental models and comparative aspects]

Von Recklinghausen's disease, or neurofibromatosis type 1 (NF-1), is an autosomal dominant syndrome with a highly variable tumorous (neurofibromas, gliomas, Wilms' tumors, leukemia, pheochromocytomas) and non-tumorous (cafe-au-lait skin spots, iris and ciliar hamartomas, osseous lesions) manifestations. NF-1 gene is mapped to chromosome 17. Central or bilateral acoustic neurofibromatosis (NF-2) has a gene mapped to chromosome 22. Hereditary and sporadic NF-1 are recognized. The most typical manifestation of NF-1-skin neurofibroma--has has a characteristic plexiform structure. Spectrum of tumors (schwannomas, gliomas, Wilms' tumors) produced by transplacental treatment with strong environmental mutagens-carcinogens-ethylnitroso- and methylnitrosourea (ENU and MNU, respectively) resembles on the whole that observed in human sporadic NF-1. Location of neurofibromas depends on the species: skin and subcutaneous tissue in humans, cattle and hamsters, trigeminal nerve, spinal roots in rats. Rat schwannomas differ from human neurofibromas by malignant structure, frequently with cystic component, but if induced by ENU treatment at day 15 of the pregnancy they resemble human plexiform neurofibromas with intraneural and extraneural growth of tumor cells. There were attempts to reproduce a transgenerational transmission of ENU carcinogenic effect, i.e. hereditary form of NF-1. In the experiments of this type the offsprings of rats prenatally treated with ENU remained untreated. The incidence of PNS, CNS and Wilms' tumors in these untreated offsprings in some experiments was significantly higher than in controls thus confirming the possibility, in principle, of hereditary NF-1 modelling. Only 10% of tumors developing in such untreated descendants of ENU treated parents contained a specific mutation of neu oncogene compared to 90-100% in tumors arising following direct treatment with ENU. The mechanisms of the transgenerational carcinogenesis are discussed. Lesions imitating NF-1 and in part NF-2 in transgenic mice with an HTLV-1-tax gene as well as in p-53 knockout mice are mentioned.