M. Sawada et T. Kamataki, GENETICALLY-ENGINEERED CELLS STABLY EXPRESSING CYTOCHROME-P450 AND THEIR APPLICATION TO MUTAGEN ASSAYS, Mutation research. Reviews in mutation research, 411(1), 1998, pp. 19-43
Genetically engineered cells transiently and stably expressing cytochr
ome P450 (P450), a key enzyme for biotransformation of a wide variety
of compounds, have provided new tools for investigation of P450 functi
ons such as P450-mediated metabolic activation of chemicals. This revi
ew will focus on the development of mammalian cell lines stably expres
sing P450s and application to toxicology testings. Stable expression s
ystems have an advantage over transient ones in that a series of the p
rocess from metabolic activation of test compounds to the appearance o
f toxicological consequences occurs entirely in the same intact cells.
Indeed, many cell lines stably expressing a single form of mammalian
P450 have been established so far and applied to cytotoxic or genotoxi
c assays, the endpoints of which contained mutations at hprt and other
gene loci, chromosomal aberrations, sister chromatid exchanges, micro
nuclei, morphological transformation, and P-32-postlabeling. Analyses
of metabolites of toxic substances have also been carried out, using t
he intact cells or microsomal fractions prepared from the cells. The s
table expression systems clearly indicate the form of P450 enzyme capa
ble of activating a certain chemical. More recently, coexpression of P
450 together with other components of microsomal electron transfer sys
tems such as NADPH-cytochrome P450 reductase has been successfully per
formed to increase the metabolic capacity of the heterologously expres
sed P450. In addition, to reconstruct the entire metabolic activation
system for certain heterocyclic amines, cell lines which simultaneousl
y express a form of human P450 and a phase II enzyme, N-acetyltransfer
ase, were established. These cells were highly sensitive to some carci
nogenic heterocyclic amines. In genetic toxicology, such a coexpressio
n system for two or more enzymes will provide useful materials which m
imic in vivo activation systems. (C) 1998 Elsevier Science B.V. All ri
ghts reserved.