Benzene exposure, glutathione S-transferase theta homozygous deletion, and sister chromatid exchanges

Recent studies have shown a strong positive correlation between chromosomal aberrations and future cancer risk. Sister chromatid exchange (SCE) has been widely applied in monitoring early biological effects to assess human genetic risk of cancer at the population level. We studied 45 Chinese workers (23 in the painting workshop of a glass factory with occupational exposure to benzene, and 22 fitters and planers in the punching and planing machine workshops of a nearby shipyard without such an exposure) to examine the association between occupational exposure to benzene and SCE frequency in peripheral blood lymphocytes. We also sought to investigate whether the glutathione S-transferase class theta gene (GSTT1) affects individual susceptibility to cytogenetic damage induced by in vivo exposure to benzene or in vitro exposure to diepoxybutane. The time-weighted average concentrations of benzene were 0.71 ppm in the exposed group and 0.03 ppm in the non-exposed group. Controlling for age, gender and educational level, cigarette smoking was significantly associated with increased SCE frequencies (P < 0.05), while GSTT1 genotype was significantly associated with DEB-induced SCEs (P < 0.01). There was no relationship between benzene exposure and baseline or DEB-induced SCEs. After stratification by smoking status, the GSTT1 deletion was a significant predictor of DEB-induced SCEs for both smokers (P < 0.05) and nonsmokers (P < 0.01). A significant benzene-GSTT1 interaction was found in nonsmokers (P < 0.05). Our study suggests that GSTT1 is an important determinant of heterogeneity in individual susceptibility to chromosomal damage associated with exposure to benzene.