We measured the mutation frequency and spectrum induced by exposure of the mutation reporter plasmid _pSP189 in vivo to phorbol myristate acetate (PMA)-activ-ated human polymorphonuclear leukocytes (PMNs). The mutation frequency induced in the supF tRNA gene of _pSP189 transfected into human Ad293 cells by a 30 min exposure to 4X10⁶ activated PMNs/ml was 3- to 9-fold higher than the background mutation frequency of 0.1–1.8X10^-5. The enhanced ...

We measured the mutation frequency and spectrum induced by exposure of the mutation reporter plasmid _pSP189 in vivo to phorbol myristate acetate (PMA)-activ-ated human polymorphonuclear leukocytes (PMNs). The mutation frequency induced in the supF tRNA gene of _pSP189 transfected into human Ad293 cells by a 30 min exposure to 4X10⁶ activated PMNs/ml was 3- to 9-fold higher than the background mutation frequency of 0.1–1.8X10^-5. The enhanced mutation frequency caused by activated PMNs required replication of the reporter plasmid in host Ad293 cells. Fifty five unique activated PMN-associated mutants characterized by sequencing included base substitutions (55%) and deletions (45%), however, no small (1–3 bp) deletions were observed. Ninety four percent of point mutations occurred at C: G base pairs, with C: G↑T: A transitions (47%) and C: G↑A: T transversions (37%) predominating. A prominent hot-spot was observed at d(_pCAGAC) on the tRNA strand. Although H₂O₂ generation was required for mutagenesis, the mutation spectrum induced in _pSP189 by in vivo exposure to activated PMNs differed from that induced by in vivo exposure to H₂O₂. It also differed from the spectrum induced in single-stranded DNA in vitro by activated PMNs, suggesting that the mutational spectrum is a complex function of the kinetics of reactive oxygen generation and factors contributed by the target cell.