The expression of anchorage independence by malignant rat oral keratinocytes after colony formation in vitro and tumour formation in vivo.

The expression of anchorage independence in malignant oral epithelial cells retrieved from colonies formed in agarose and tumours formed in athymic mice was examined. The original epithelial cell lines were derived from lingual and palatal squamous cell carcinomas induced in rats by the carcinogen 4-nitroquinoline N-oxide. The capacity to express anchorage independence varied considerably between the original cell lines and essentially increased with passage in culture. In three out of four colony-derived subpopulations, the colony-forming efficiency was significantly greater than that of the original cell lines. Xenograft subpopulations expressed higher colony-forming efficiencies than their original counterparts in only two of five cell lines. Undifferentiated tumour xenografts resulted in more homogeneous tumour-derived subpopulations, in contrast to the more heterogeneous cell lines from well-differentiated tumours. The findings demonstrate functional diversity within and between malignant rat oral epithelial cell lines and their colony- and xenograft-derived subpopulations.