Identification of Activated RRAS2 in Tongue Carcinoma Cell Line

Abstract

To identify tumor-promoting genes in tongue carcinoma, we constructed a retroviral cDNA expression library from a tongue carcinoma cell line, and used it to screen transforming genes by a focus formation assay with mouse 3T3 fibroblasts. One of the cDNA inserts harvested from such cell clones turned out to encode RRAS2 with a glycine-to-aspartic acid substitution at codon 24. The oncogenic potential of RRAS2 (G24D) was further confirmed by injecting the transformed fibroblasts into athymic nude mice. Unfortunately, we failed to detect the nucleotide change corresponding to the G24D mutation in the cDNA or genomic DNA of the cell line, indicating that such change in our transforming cDNA was artificially generated in the process of library construction. Our findings, which are the first to demonstrate the activating mutation at this codon of RRAS2, may help to better understand the role of RRAS2 in human carcinogenesis.