Molecular analysis of hprt mutant lymphocytes from 1,3‐butadiene–exposed workers

Abstract

1,3-Butadiene (BD) has been shown to be a potent animal carcinogen and a probable human carcinogen, yet the molecular mechanisms of BD genotoxicity and carcinogenicity still are not fully understood. Our hypothesis is that metabolites of BD induce specific structural changes in the human hprt gene like those observed in vitro in TK6 cells and in vivo in the mouse. Characteristic mutations in BD-exposed subjects can be identified and used as biomarkers for monitoring genotoxic effects associated with BD exposure. Molecular analysis of hprt mutant lymphocytes from BD-exposed workers and unexposed control subjects was carried out to identify changes in the structure of the hprt gene. A multiplex polymerase chain reaction (PCR) assay was used to detect exon deletions in 360 hprt mutant clones. We determined that exon deletions were significantly more frequent (P < 0.05) in BD-exposed workers (17.5%) than in control subjects (9.7%). Sequence analysis of hprt cDNA from 175 independent mutants indicated that the distribution of the types of mutations was different between the workers and the unexposed control subjects. There was a significant increase in -1 frameshift mutations in BD-exposed workers, predominantly in repeated DNA sequences, and single-base substitutions were decreased to 66% in the workers compared to 83% in the control subjects (P < 0.05). In addition to the spectral changes, hprt clonal assays revealed an elevation in mutant frequency in the lymphocytes of workers (N = 10) when compared with that in unexposed control subjects (N = 11; P < 0. 05). There also was a twofold increase of A:T --> T:A transversions in BD-exposed workers (16% in BD-exposed workers compared to 8% in controls, P = 0.25). Some of the BD-associated changes in mutational spectra observed in our study have the potential for application in monitoring genotoxic effects related to butadiene exposure.

Microdoses Levels of Butadiene Diepoxide (BDO&lt;sub&gt;2&lt;/sub&gt;) Induced Toxicity in Prostate Cancer Cells

“…The metabolism and genetic toxicity of 1,3-butadiene and its oxidative metabolites in humans and rodents is well established. Experimental animal studies support the theory that butadiene and its metabolites are human carcinogenic agents [3,[7][8][9][10]. Theses animal studies have suggest a specie difference in the carcinogenicity of 1,3-butadiene in mice and rats.…”

“…Theses animal studies have suggest a specie difference in the carcinogenicity of 1,3-butadiene in mice and rats. Tumor induced by 1,3-butadiene occurs in the hematopoietic system-heart (hemangiosarcomas), lung, preputial gland, liver, mammary gland, ovary, and kidney and prostate [9][10][11][12][13]. Although the tumors induced by 1,3-butadiene in these tissues are thought to be due to genotoxic alteration, the exact genes that are mutated or altered in each type of tumor are unknown.…”

Assessment of 1,3-Butadiene Exposure in Polymer Production Workers Using HPRT Mutations in Lymphocytes as a Biomarker

“…They were compared to clones of mutant lymphocytes in control subjects who did not work in the petrochemical industry. Results of this study have been published separately (35). The mutant frequency (Mf) in the cloning assay in 10 high-exposure workers was significantly higher (p < 0.05) than the Mf in 11 controls (Mf ± SD = 17.63 + 5.05 × 10 -6 vs. 8.47 + 2.88 × 10 -6 , respectively).…”

“…In BD-exposed workers, a significantly higher proportion of mutant clones contained deletions of one or more exons (p < 0.05). A 2-fold, but nonsignificant, increase in the proportion of base substitution mutations at A-T base pairs was observed, and a higher proportion of frameshift mutations was seen in the exposed group (p < 0.05) (35). These observations are consistent with the types of mutations induced by BD and DEB in cell culture (16,37) and in animals (11,12,17,38).…”

“…Hayes et al (42) found no difference between the butadieneexposed group and the control group in the frequency of HPRT mutants using the cloning assay. The Mfs in both the exposed and control groups averaged 15-20 × 10 -6 , which is much higher than the Mfs for the unexposed control group in our cloning assay study (35). Tates et al (43) studied workers in a butadiene monomer production unit near Prague in the Czech Republic.…”