COMPARATIVE-STUDY OF CYP1A1 INDUCTION BY 3-METHYLCHOLANTHRENE IN VARIOUS HUMAN HEPATIC AND EPIDERMAL-CELL TYPES

Hepatocytes and keratinocytes are among the most widely used cells in pharmaco-toxicology, but a limitation of these models is the provision of human tissues on a regular basis. The suitability of HepG2, HaCaT and HESV cell lines as an acceptable substitute for primary cultures w as examined. In these cell types, the effects of 3-methylcholanthrene (3-MC) were analysed on CYP1A1 gene expression, a crucial CYP subfamil y in the activation of chemical carcinogens. Ethoxyresorufin O-deethyl ase (EROD) activity was never detected in HESV cells, but in other cel l types it was stimulated in a concentration-dependent manner (maximal induction, 1-2.5 mu M). Above this peak induction the effect fell rap idly. Northern blot analysis of CYP1A1 mRNA agreed with the trends obt ained for EROD values. However, the decrease of the EROD activity obse rved at the highest 3-MC concentrations was not correlated with CYP1A1 mRNA reduction. This study also demonstrated that 3-MC is capable of significantly inducing CYP1A1 in HaCaT cells (17-fold over control), a s in human hepatocytes (six-to 18-fold) and HepG2 (fourfold). Therefor e, in contrast to SV40-immortalized keratinocytes (HESV), spontaneousl y immortalized keratinocytes (HaCaT) may constitute a valuable tool fo r studying epidermal CYP1A1 gene regulation by xenobiotics. (C) 1997 P ublished by Elsevier Science Ltd.