Invasive pattern and phenotypic properties of malignant neurogenic rats cells in vivo and in vitro.

Twelve malignant neurogenic rat cell lines induced by the carcinogen ethylnitrosourea (EtNU) have been investigated for invasiveness in an in vitro three-dimensional culture system. The histological pattern of invasiveness into embryonic chick heart fragments has been compared to the morphology in subcutaneous and intracerebral solid tumours as well as to other phenotypic properties of the cells. In all the cell lines invasiveness was seen both in vivo and in vitro. The site of in vivo transplantation seemed to influence the tumour-host tissue interface, since intracerebral tumours were more sharply delimited than subcutaneous tumours and primary EtNU-induced CNS tumours. The histological patterns in vivo (glioma versus neurinoma-like) were in most cases similar to invasive growth in vitro. The pattern of invasiveness did not correlate to other phenotypic properties of the cells (e.g. ploidy, doubling time, latency for tumour formation and surface microarchitecture). A rat fibroblastic cell line, RE-E was non-tumourigenic in rats and non-invasive in culture, but formed small subcutaneous tumours in nude mice.