Single-base deletion induced by benzo[a]pyrene diol epoxide at the adenine phosphoribosyltransferase locus in human fibrosarcoma cell lines.

Benzo[a]pyrene diol epoxide (BPDE), a metabolic product of benzo[a]pyrene, is one of the most widely distributed environmental carcinogens. In this study, we demonstrate that BPDE produces a dose-dependent increase in the frequency of APRT gene reversion in the APRT-deficient cell line, HTD114, which contains single nucleotide insertions at different positions in each APRT allele. The highest reversion frequency observed after BPDE exposure was 3.3 +/- 0.9 x 10(-5), at least 10(3)-fold greater than the spontaneous frequency. Reversion of either mutant allele was observed to be a consequence of a frame-restoring loss of a single nucleotide. A similar frequency of BPDE-induced reversion at APRT also was observed in a cell line containing only one type of the mutant alleles of HTD114, thus eliminating the possibility that gene conversion plays a major role in APRT gene reversion in HTD114 cells. Therefore, the data demonstrate that BPDE can function as an effective frameshift mutagen in human cells.