Rare activation of ras oncogenes in radiation induced rat skin tumors.

We examined a large panel of radiation induced rat skin tumors for activation of the H- or K-ras oncogenes. Using oligonucleotide hybridization analysis of tumor DNA we found that only 1 out of 96 tumors tested had an activated K-ras gene, and none of the 78 tumors examined for H-ras mutations were positive. Tumors were induced by high and low LET, and included lesions of various sizes and histologic type. DNA sequencing of tumors and NIH3T3 transfectants from a previous study gave results consistent with a rare occurence of ras activation in this system.