Expression status and mutational analysis of the ras and B-raf genes in ovarian granulosa cell and epithelial tumors.

OBJECTIVES: The molecular pathogenesis of granulosa cell tumors of the ovary (GCT) is not understood. Activating mutations in the K-, N-, and H-ras protooncogenes have been identified in a wide range of human cancers, including ovarian epithelial tumors. Furthermore, an apparent association has recently been reported between the presence of ras and B-raf mutations in the same cancer types. Activation of the ras/raf pathway would be predicted to be tumorigenic in granulosa cells.
METHODS: Gene expression patterns of the three ras and B-raf genes were determined in a panel of GCT and ovarian epithelial tumors, and in normal premenopausal ovaries. Expression was determined by RT-PCR using gene-specific primers combined with Southern blot analysis of the PCR products using gene-specific (32)P-labeled probes. Direct sequence analysis was used to screen for known activating mutations.
RESULTS: Widespread expression of the four genes was observed in all tumor types examined. Compared to the normal ovaries, none of the genes was expressed at significantly higher levels in any of the tumor types examined. A heterozygous point mutation in codon 12 of the K-ras gene was found in five of the 10 mucinous tumors. No B-raf mutations were detected in the mucinous tumors. No mutations were detected in any of the genes in the cohort of GCT.
CONCLUSION: These results suggest that neither overexpression nor activating mutations of the ras or B-raf genes are associated with the development of GCT.