Failure of diepoxybutane to enhance sister chromatid exchange levels in Fanconi's anemia patients and heterozygotes.

Peripheral lymphocytes of three Fanconi's anemia (FA) patients and of five heterozygotes have been tested for their susceptibility to chromosomal breakage and sister chromatid exchange (SCE) induction by diepoxybutane (DEB). As previously shown, DEB dramatically increases the chromosomal breakage level in both homozygotes and heterozygotes. Slightly, but significantly, reduced spontaneous levels of SCE were found in cultures from FA patients and FA gene carriers as compared with controls. SCE rates were not enhanced in lymphocytes grown in the presence of DEB, irrespective of the time at which it had been added to the culture, and were comparable in cells of FA patients and FA heterozygotes. This was in contrast with SCE rates in control cells, which showed increases positively related to the length of DEB treatment.