Phenotypic properties of neoplastic cell lines developed from fetal rat brain cells in culture after exposure to ethylnitrosourea in vivo.

We have recently reported that fetal BD IX-rat brain cells (FBC), transferred to long-term culture after a transplacental pulse of EtNU on the 18th day of gestation, undergo neoplastic transformation in vitro ("BT-cell lines"). Tumors developed upon s.c. reimplantation of BT-cells into baby BD IX-rats, appeared histologically as neurinoma-, glioma- or glioblastoma-like, and frequently as pleiomorphic neoplasms. In spite of a more atypic cellular morphology, these tumors grossly resembled the different types of neuroectodermal rat neoplasms induced by EtNU in vivo. Like the neoplastic cell culture lines derived from EtNU-induced, neuroectodermal BD IX-rat tumors ("V-cell lines"), the BT-lines contained multipolar glia-like cells, but also flat cells with fewer and shorter cytoplasmic processes, and occasionally giant cells. Both the V- and BT-lines showed different levels of aneuploidy. They contained multiple subpopulations of cells, as reflected, e.g., by plurimodal pulse-cytophotometric DNA distributions. All lines contained, to varying degrees, the nervous system-specific protein S-100, a "marker" not yet expressed in FBC. There was no indication of more than borderline neurotransmitter activity, suggesting that proliferating (precursor) cells of glial lineages may preferentially undergo malignant transformation after exposure to EtNU during this stage of brain development.