Tumor necrosis factor alpha negatively regulates the expression of the carcinoma-associated antigen epithelial cell adhesion molecule.
BACKGROUND
The epithelial cell adhesion molecule (EpCAM) is a homophilic and Ca2+ independent adhesion molecule that is expressed de novo in squamous cell carcinoma (SCC) but is absent in the majority of healthy squamous epithelia. EpCAM expression correlates with cell proliferation and dedifferentiation along with a progression in tumorigenicity. To date, nothing is known about the molecular mechanisms responsible for the regulation of the EpCAM gene.


METHODS
The authors analyzed the regulation of a fragment of the EpCAM promoter.


RESULTS
The analyzed fragment has significant activity in EpCAM positive cells, and it is regulated negatively by tumor necrosis factor alpha (TNFalpha). This negative regulation results in diminished mRNA expression and in the down-regulation of EpCAM protein at the cell surface in SCC cells. Both effects can be mimicked by the treatment of cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). TNFalpha-induced inhibition of the EpCAM expression is mediated by TNF receptor 1 through the TNF receptor-associated death domain protein (TRADD) and by the activation of nuclear factor kappaB (NF-kappaB), and it can be blocked by dominant-negative variants of TRADD and the NF-kappaB inhibitor, IkappaB. The authors provide further evidence that NF-kappaB represses EpCAM expression by competing for the transcriptional coactivator p300/CREB binding protein (p300/CBP).


CONCLUSIONS
The current results provide the first insights into the regulation of EpCAM expression, which is regulated negatively by TNFalpha and TPA through the activation of NF-kappaB. The repression may rely on the competition of NF-kappaB for p300/CBP histone acetyl transferase activity, because the overexpression of p300 reverts TNFalpha effects.
Gires
O
O
Department of Otorhinolaryngology, Ludwig-Maximilian University, Marchioninstrasse 15, D-81377 Munich, Germany. ogires@hno.med.uni-muenchen.de
Kieu
C
C
Fix
P
P
Schmitt
B
B
Münz
M
M
Wollenberg
B
B
Zeidler
R
R
D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000235:genetics; D015536:Down-Regulation; D000071858:Epithelial Cell Adhesion Molecule; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha