Role of H-ras in the malignant progression of rat tracheal epithelial cells.
The effect of an activated H-ras oncogene on the progression of neoplasia was studied in transformed rat tracheal epithelial cells. Nude mouse tumours produced by injection of these cells exhibited a higher fraction of cells containing the mutant ras gene that did the injected cells, while a subclone that lacked the ras mutation was much less tumorigenic than parental cells. Serial passage of one cell line containing a ras mutation resulted in an increase in the fraction of ras-mutated cells, which suggests that, in this line, ras activation may confer a selective advantage in vitro as well. However, this was not seen in another ras-containing line, suggesting the importance of alternative pathways in malignant progression of rat tracheal epithelial cells.