Development of a human lymphoblastoid cell line constitutively expressing human CYP1A1 cDNA: substrate specificity with model substrates and promutagens.

AHH-1 TK+/- cell derivatives were developed that stably express human CYP1A1 cDNA, and an AHH-1 TK+/- derivative expressing higher levels of CYP1A2 cDNA in extrachromosomal vectors which confer resistance to 1-histidinol. The CYP1A1-expressing cell lines, designated h1A1 and h1A1v2, differ by containing one and two CYP1A1 cDNA expression units per vector. The CYP1A2-expressing cell line, designated h1A2v2, also has two CYP1A2 cDNA expression units per vector. Microsomes prepared from CYP1A1 cDNA expressing cells exhibit high, constitutive levels of 7-ethoxyresorufin deethylase (EROD), 7-ethoxycoumarin deethylase (ECD), 7-ethoxy-4-trifluoromethylcoumarin deethylase (EFCD), benzo[a]-pyrene hydroxylase (BPH) activities and spectrally quantifiable cytochrome P450. Kinetic comparisons between cDNA-expressed CYP1A1 and CYP1A2 indicate that CYP1A1 is more active than CYP1A2 for EROD, ECD, EFCD and BPH. CYP1A2 was more active than CYP1A1 for acetanilide hydroxylation and activation of aflatoxin B1 (AFB1). The mutagenicity of selected promutagens were examined in h1A1 cells and control cells. Relative to control cells, the h1A1 cell line exhibits increased sensitivity to the mutagenicity of benzo[a]pyrene, cyclopenta[c,d]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and AFB1.