Open AccessDifferences in 2,3,7,8‐tetrachlorodibenzo‐ p ‐dioxin‐inducible CYP1A1 expression in human breast carcinoma cell lines involve altered trans ‐acting factors
Author(s) -
THOMSEN Jane S.,
NISSEN Lena,
STACEY Simon N.,
HINES Ronald N.,
AUTRUP Herman
Publication year - 1991
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1991.tb15946.x
Subject(s) - chloramphenicol acetyltransferase , cell culture , reporter gene , acetyltransferase , microbiology and biotechnology , gene expression , biology , aryl hydrocarbon receptor , cell , chemistry , gene , biochemistry , transcription factor , genetics , acetylation
Differences in expression of the CYP1A1 gene have previously been observed in human breast carcinoma cell lines exposed to 2,3,7,8‐tetrachlorodibenzo‐ p ‐dioxin (TCDD). Using an expression vector containing the functional 5′‐regulatory region of human CYP1A1 (up to – 1140) fused to the reporter gene CAT (for chloramphenicol acetyltransferase), the breast carcinoma cell lines, MCF‐7, T47‐D and ZR‐75‐1, classified as highly responsive to TCDD, were highly responsive to TCDD in the chloramphenicol acetyltransferase assay as well. Gel mobility shift assays have shown that these cell lines express a nuclear protein that binds the aryl hydrocarbon (Ah) receptor responsive element. The low or non‐responsive cell lines, AL‐1, BT‐20 and CAMA‐1, were low or non‐responsive to TCDD in the chloramphenicol acetyltransferase assay, suggesting that the low‐responsive phenotype is caused by altered trans ‐acting factors. However, the mechanism appears to differ among the cell lines. Whereas no induction was observed in AL‐1, a fivefold induction in activity was observed in BT‐20 and CAMA‐1. The TCDD concentration giving half‐maximum induction differed greatly between CAMA‐1 and BT‐20. The gel mobility shift assay showed the presence of a protein that bound specifically to the Ah responsive element in the non‐responsive cell line AL‐1, as well as the low‐responsive cell lines, BT‐20 and CAMA‐1. The high basal activity but low induction observed in CAMA‐1 may be due to an Ah receptor constitutively bound to the Ah responsive element.