Analysis of N-ethyl-N-nitrosourea-induced brain carcinogenesis by sequential culturing during the latent period. I. Morphology and tumorigenicity of the cultured cells and their growth in agar

Roscoe, J.P.; Claisse, P.J.

Journal of the National Cancer Institute 61(2): 381-390


ISSN/ISBN: 0027-8874
PMID: 277725
Accession: 068525369

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Pregnant inbred BD IX rats were given injections of buffer or N-ethyl-N-nitrosourea (ENU) at 40-50 mg/kg on day 15 or 16 of gestation. The average latent period for cerebral tumors was 246 days. Brain cultures were prepared 2, 3, 5, 34-35, 57-60, 90-91, 111-112 and 138-145 days post injection (Pl) and examined for morphology, tumorigenicity and growth in agar. Cultures in the last 3 groups derived from animals exposed transplacentally to ENU contained cells characteristic of brain tumor cultures. These were called basal layer cells (BLC). They were not observed in control cultures. BLC persisted in several cultures belonging to the last 2 groups, and these cultures were tumorigenic and grew in agar. BLC did not persist in cultures prepared 90-91 days Pl, which did not produce tumors or grow in agar. Three morphologic types of BLC were observed: fried eggs, crescents and pyramids. These occurred in different proportions in the cultures. Predominance of the pyramidal type was associated with a shorter latency for cell-induced tumors compared with those cultures in which other types of BLC were in the majority. The fried-egg type was predominant in cultures in which BLC disappeared on passaging. Cultures prepared at earlier times did not contain BLC and did not grow in agar or in animals at early passages. Cultures derived 2 days Pl became tumorigenic after prolonged cultruing, which indicated that they already acquired the malignant potential.