Sporadic and Thorotrast-induced angiosarcomas of the liver manifest frequent and multiple point mutations in K-ras-2.

Abstract

Hepatic angiosarcoma (HA) is an uncommon neoplasm associated with known etiologic factors in 25% to 42% of cases. It is, however, one of the most common sarcomas found in the liver. The aim of this study was to find was to find mutations in the K-ras-2 oncogene in sporadic and Thorotrast (TT)-induced HA. Point mutations in K-ras-2 were sought in archival, formalin-fixed tissue blocks from 24 patients with angiosarcoma. Of these, 19 cases were sporadic and 5 were TT-induced. Mutational analysis was performed by topographic microdissection with PCR amplification followed by genotyping. Specific mutations were determined by two independent methods: (a) direct sequencing of the PCR product confirmed by rePCR and by using a different sequencing primer, and (b) PCR-based selective enrichment of mutant DNA by endonuclease digestion followed by heteroduplex DNA analysis using denaturing gradient gel electrophoresis. Eleven K-ras-2 point mutations were detected in 7 of 24 (29%) tumors, including 5 of 19 (26%) sporadic HA and 2 of 5 (40%) TT-induced HA. There were seven G:C > A:T and four G:C > T:A mutations. All seven mutated tumors contained a codon 12-aspartate amino acid substitution. In addition, a second codon 12-cysteine mutant cell population was present in one of two codon 12-aspartate mutated TT-induced HA and in three of five codon 12-aspartate sporadic tumors. Of these four tumors, three contained both aspartate and cysteine mutations and were composed of multiple nodules; the fourth was a single mass. Seventeen tumors had multiple nodules; whereas 5 had a K-ras-2 mutation, 12 were wild-type. The molecular pathology of both sporadic and TT-induced HA is characterized by a high rate of K-ras-2 mutations characteristic of oxidative damage (ie, G:C > A:T and G:C > T:A mutations) resulting in two mutated population sets: codon 12 GGT > GAT and GGT > TGT (glycine to aspartic acid and cysteine). This is, to date, the first study to characterize the K-ras-2 gene mutations within human sporadic and TT-induced HA by direct sequence analysis and denaturing gradient gel electrophoresis. These data further support the hypothesis linking adduct-forming vinyl chloride exposure to HA containing a much higher frequency of K-ras-2 mutations and a mutational spectrum characteristic of chloroethylene oxide, a carcinogenic metabolite of vinyl chloride.

• Authors: R M Przygodzki, S D Finkelstein, P Keohavong, D Zhu, A Bakker, P A Swalsky, Y Soini, K G Ishak, W P Bennett
• Journal: Laboratory investigation; a journal of technical methods and pathology (Lab Invest) Vol. 76 Issue 1 Pg. 153-9 (Jan 1997) ISSN: 0023-6837 [Print] United States
• PMID: 9010458 (Publication Type: Journal Article)

Chemical References

• Carcinogens
• Thorium Dioxide

Topics

• Adult
• Aged
• Carcinogens
• Female
• Genes, ras
• Hemangiosarcoma (etiology, genetics, pathology)
• Humans
• Liver Neoplasms (etiology, genetics, pathology)
• Male
• Middle Aged
• Neoplasms, Radiation-Induced (etiology, genetics)
• Occupational Exposure
• Point Mutation
• Polymerase Chain Reaction
• Thorium Dioxide