REGULATION OF GENE-EXPRESSION AND ACCELERATION OF DIFFERENTIATION IN HUMAN KERATINOCYTES BY 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a suspected human carcinog en, is believed to produce its toxic and carcinogenic effects by alter ing expression of growth-regulatory factors. TCDD alters the expressio n of a number of specific genes in the transformed human keratinocyte cell line, SCC-12F, including transforming growth factor-alpha (TGF-al pha), TGF-beta(2), plasminogen activator inhibitor-2 (PAI-2), and inte rleukin-1 beta (IL-1 beta). To determine whether nontransformed human keratinocytes (NHK) respond similarly to TCDD, we studied the effect o f TCDD on NHK growth and differentiation, and gene expression. NHK wer e treated prior to reaching confluence with 10 nM TCDD and evaluated a t 1, 2, 3, and 5 days following treatment for the effect of TCDD on ce ll number, morphology, involucrin levels, mRNA expression, and protein concentrations. TCDD altered both the mRNA and protein concentrations of TGF-alpha, TGF-beta(2), PAI-2, and IL-1 beta. The mRNA level for u -PA, a plasminogen activator that is inhibited by PAI-2, was not alter ed following TCDD treatment. However, u-PA protein levels were signifi cantly induced, indicating an effect of TCDD on u-PA synthesis, secret ion, or turnover. TCDD enhanced NHK differentiation, as determined by an increase in involucrin expression. TCDD did not alter cell number o r colony-forming efficiency, suggesting that TCDD was enhancing the di fferentiation of cells already committed to terminal differentiation. These results demonstrate that treatment of NHK with TCDD results in t he simultaneous modulation of expression of a number of growth-regulat ory proteins and suggest that the growth and differentiation response of human keratinocytes to TCDD is due to a complex interaction of thes e diverse proteins. (C) 1994 Academic Press, Inc.