H-ras-1 point mutations in soft tissue sarcomas

Abstract

The H-ras-1 protooncogene is activated by single base substitutions occurring in either codon 12, 13, or 61. These mutations have been described with varying frequencies in several human tumor types. Since ras oncogenes were first discovered as the transforming sequences of Harvey and Kirsten murine sarcoma viruses (which also contain activating point mutations compared to the homologous cellular sequences), we wished to investigate the possibility that ras mutations might also occur in human sarcomas. We extracted DNA from six malignant fibrous histiocytomas (MFH), three embryonal rhabdomyosarcomas (ER), one alveolar rhabdomyosarcoma, one pleomorphic rhabdomyosarcoma, and one leiomyosarcoma. The DNA from regions flanking codons 12/13 and codon 61 was amplified by the polymerase chain reaction and sequenced with an automated DNA sequencer. As controls, we amplified and sequenced normal DNA (placenta) and DNA with known point mutations (T24 bladder carcinoma cells). We found three cases with mutations, all occurring in codon 12. One ER showed a G-to-T mutation in the second position of codon 12 (coding for valine instead of glycine). Two MFHs showed G-to-A mutations in the second position of codon 12 (coding for aspartic acid instead of glycine). Although a limited number of cases were sampled, we conclude that study of H-ras-1 mutations may be relevant to MFH and ER. Additional studies of N and K-ras mutations as well as more cases investigating H-ras will be required before we can ascertain the significance of ras mutations in the oncogenesis of human soft tissue sarcomas.