Stability of ras oncogene mutation in the human tumor xenografts through serial passages.

We examined the Ki-ras oncogene point mutation in primary tumors and tumor xenografts as a marker of genetic stability. We detected point mutations at codon 12 of the Ki-ras oncogene in 21.3% (17/80) of the tumor xenografts as well as 21.0% (17/81) of the primary human neoplasms. The mutation from GGT (glycine) to GAT (aspartic acid) was the most frequent mutation in the tumor xenografts (64.7%, 11/17) as well as in the primary human neoplasms (64.7%, 11/17). The point mutation at codon 12 of the Ki-ras gene showed no discrepancy between the original human neoplasms and their xenografts in all 19 cases. The findings suggested that the point mutation at codon 12 of the Ki-ras gene was very stable in human neoplasms and their tumor xenografts through serial transplantation.