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odds ratios (& 95% confidence intervals [CI]) for plasma-positivitywere 4.11 ... in the lower-exposed workers & 6.53 ... in thehigher-exposed workers, & there was a linear trend between exposure& plasma-positivity ... . After adjusting for age & drinkingstatus, the odds ratios (& 95% CIs) were 1.64 ..., & 2.65 ...,respectively, & there was a significant linear trend between exposure& plasma-positivity ... . In summary, Asp13-Ki-ras oncoprotein can befound in the plasma of VC workers ..., & a significant dose-responserelationship exists between plasma oncoprotein expression & VCexposure.[Luo JC et al; J Occup Environ Med 40 (12): 1053-1058(1998)]**PEER REVIEWED**Gap junctional intercellular communication is often impaired in cancers,& the genes which encode the connexin gap junction proteins areconsidered to be tumor-suppressor genes. In this study, we analyzed thepresence of mutations in the connexin 37 (Cx37) gene in 22 human hepaticangiosarcomas, 6 & 4 of which were associated with exposure to vinylchloride & Thorotrast, respectively. The other 12 samples were frompatients with no history of exposure to these 2 agents. In 9 samples, aproline (ACC) to serine (ACT) amino acid change in codon 319 was detected.However, DNA from non-tumorigenic tissue of the same patients also showedthis amino acid change, suggesting that this is a polymorphism rather thana mutation. Subsequent analysis of 84 DNA samples from normal donorsrevealed the frequencies of Pro/Pro, Pro/Ser & Ser/Ser alleles to be65.5%, 23.8% & 10.7%, respectively, while among the group ofangiosarcoma patients the corresponding figures were 59.1%, 31.8% and 9.1%, respectively. Thus, there was no correlation between the polymorphismat codon 319 & hepatic angiosarcoma occurrence. However, among the 6cases of vinyl chloride-associated angiosarcoma, the percentages of thepolymorphic alleles were 33.3%, 66.7% & 0%, respectively. While thenumber of samples was too small to allow us to conclude that the Ser319allele in Cx37 predisposes to this rare type of human cancer, it may benoted that codon 319 is located at the cytoplasmic tail of Cx37, wheremost regulatory sequences reside, and that it could be a site ofphosphorylation for some protein kinases, which may in turn affect thefunction of Cx37, including intercellular communication. [Saito T et al;Int J Cancer 86 (1): 67-70 (2000)]**PEER REVIEWED**Two human carcinogens that have been extensively studied are vinylchloride & benzene. The active metabolites used in this study arechloroacetaldehyde (CAA) & para-benzoquinone (pBQ). Each formsexocyclic adducts between the N1 & N6 of A, the N3 & N4 of C &the N1 & N2 of G. Only CAA has been found to form the N2,3 adduct ofG. CAA & pBQ adducts differ structurally in size & in the numberof added rings, pBQ adding 2 rings to the base, while etheno bases have asingle 5-membered ring. The mechanism of repair of these 2 types ofadducts by human enzymes has been studied in our laboratory with definedoligodeoxynucleotides & a site-specific adduct. The etheno derivativesare repaired by DNA glycosylase activity; two mammalian glycosylases areresponsible: alkylpurine-DNA-N-glycosylase (APNG) & mismatch-specificthymine-DNA glycosylase. The former repairs 1,N6-ethenoA (epsilon A) asrapidly as the original substrate, 3-methyladenine, while the latterrepairs 3,N4-ethenoC (epsilon C) more efficiently than the G/T mismatch.Our finding that there are separate enzymes for epsilon A & epsilon Chas been confirmed by the use of tissue extracts from an APNG knockoutmouse. ... Furthermore, the pBQ adduct-containing oligomers are cleaved,to various extents by a different class of enzyme: human & bacterial