K-ras activation in premalignant and malignant epithelial lesions of the human uterus

We previously reported (Cancer Res., 50:6139-6145, 1990) a significant frequency of activating point mutations in codon 12 of the K-ras oncogene in endometrial adenocarcinomas of the uterine corpus (series 1). To further define the role of ras activation in the development of endometrial adenocarcinoma, we surveyed cystic, adenomatous, and atypical hyperplasias of uterine endometrium and additional cases of endometrial and cervical carcinoma (series 2) for the presence of activating mutations in cellular protooncogenes of the ras family. Polymerase chain reaction was performed from deparaffinized sections of formalin-fixed paraffin-embedded tissue. We screened for point mutations in codons 12, 13, and 61 of the K-, H-, and N-ras genes by dot blot hybridization analysis with mutation-specific oligomers. Mutations in K-ras were also confirmed by direct genomic DNA sequencing. Of 19 endometrial adenocarcinomas in series 2, point mutations in ras genes were found in 7 tumors. Six contained single-base substitutions, five in codon 12 of K-ras and one in codon 12 of N-ras. The seventh tumor contained two different point mutations in codon 12 of K-ras. In one endometrial adenocarcinoma, tumor cells with point mutations in K-ras were predominantly localized to a portion that had a more aggressive histological pattern. In endometrial hyperplasia, K-ras mutations, one in codon 12 and one in codon 13, were found in 2 of 16 hyperplasias histologically classified as atypical and clinically considered premalignant. None of 6 adenomatous hyperplasias and none of 12 cystic hyperplasias, the latter of which is considered clinically benign, contained any detectable ras mutations. No mutations in H-ras were detected in either carcinomas or hyperplastic tissue.