Frequent k- ras -2 mutations and p16(INK4A)methylation in hepatocellular carcinomas in workers exposed to vinyl chloride.
Vinyl chloride (VC) is a know animal and human carcinogen associated with liver angiosarcomas (LAS) and hepatocellular carcinomas (HCC). In VC-associated LAS mutations of the K- ras -2 gene have been reported; however, no data about the prevalence of such mutations in VC associated HCCs are available. Recent data indicate K- ras -2 mutations induce P16 methylation accompanied by inactivation of the p16 gene. The presence of K- ras -2 mutations was analysed in tissue from 18 patients with VC associated HCCs. As a control group, 20 patients with hepatocellular carcinoma due to hepatitis B (n = 7), hepatitis C (n = 5) and alcoholic liver cirrhosis (n = 8) was used. The specific mutations were determined by direct sequencing of codon 12 and 13 of the K- ras -2 gene in carcinomatous and adjacent non-neoplastic liver tissue after microdissection. The status of p16 was evaluated by methylation-specific PCR (MSP), microsatellite analysis, DNA sequencing and immunohistochemical staining. All patients had a documented chronic quantitated exposure to VC (average 8883 ppmy, average duration: 245 months). K- ras -2 mutations were found in 6 of 18 (33%) examined VC-associated HCCs and in 3 cases of adjacent non-neoplastic liver tissue. There were 3 G --> A point mutations in the tumour tissue. All 3 mutations found in non-neoplastic liver from VC-exposed patients were also G --> A point mutations (codon 12- and codon 13-aspartate mutations). Hypermethylation of the 5' CpG island of the p16 gene was found in 13 of 18 examined carcinomas (72%). Of 6 cancers with K- ras -2 mutations, 5 specimens also showed methylated p16. Within the control group, K- ras -2 mutation were found in 3 of 20 (15%) examined HCC. p16 methylation occurred in 11 out of 20 (55%) patients. K- ras -2 mutations and p16 methylation are frequent events in VC associated HCCs. We observed a K- ras -2 mutation pattern characteristic of chloroethylene oxide, a carcinogenic metabolite of VC. Our results strongly suggest that K- ras -2 mutations play an important role in the pathogenesis of VC-associated HCC.
Weihrauch
M
M
Institute of Occupational and Environmental Medicine, University of Hannover, Germany.
Benicke
M
M
Lehnert
G
G
Wittekind
C
C
Wrbitzky
R
R
Tannapfel
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002273:Carcinogens / Q000009:adverse effects*; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D018899:CpG Islands / Q000187:drug effects; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects; D019942:Genes, p16 / Q000187:drug effects* / Q000235:genetics; D011905:Genes, ras / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D017354:Point Mutation; D014752:Vinyl Chloride / Q000009:adverse effects*
D002273:Carcinogens; D019941:Cyclin-Dependent Kinase Inhibitor p16; D014752:Vinyl Chloride