Oncogene alterations in in vitro transformed rat tracheal epithelial cells

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.

Ha-ras oncogene mutations in cell lines derived from rat tracheal implants exposed in vivo to 7,12-dimethylbenz[a]anthracene

The frequency of Ha-ras mutations was determined as a function of neoplastic progression in cell lines derived from rat tracheal implants exposed in vivo to 7,12-dimethylbenz[a]anthracene. Restriction fragment-length polymorphism (RFLP) analysis revealed an A----T transversion in the second base of codon 61 in 2 of 11 cell lines. One of the positive cell lines was tumorigenic, but the other was neither tumorigenic nor anchorage independent, thus indicating a lack of correlation between neoplastic stage and ras mutation. Densitometry analysis of the RFLP bands indicated that approximately 50% of the cells within these two heterogeneous populations contained the mutation. Direct sequence analysis of polymerase chain reaction-amplified DNA confirmed these results and did not reveal any other mutations in this region of the Ha-ras gene.