HIC1 Tumor Suppressor Loss Potentiates TLR2/NF-κB Signaling and Promotes Tissue Damage-Associated Tumorigenesis.
Hypermethylated in cancer 1 (HIC1) represents a prototypic tumor suppressor gene frequently inactivated by DNA methylation in many types of solid tumors. The gene encodes a sequence-specific transcriptional repressor controlling expression of several genes involved in cell cycle or stress control. In this study, a Hic1 allele was conditionally deleted, using a Cre/loxP system, to identify genes influenced by the loss of Hic1. One of the transcripts upregulated upon Hic1 ablation is the toll-like receptor 2 (TLR2). Tlr2 expression levels increased in Hic1-deficient mouse embryonic fibroblasts (MEF) and cultured intestinal organoids or in human cells upon HIC1 knockdown. In addition, HIC1 associated with the TLR2 gene regulatory elements, as detected by chromatin immunoprecipitation, indicating that Tlr2 indeed represents a direct Hic1 target. The Tlr2 receptor senses "danger" signals of microbial or endogenous origin to trigger multiple signaling pathways, including NF-κB signaling. Interestingly, Hic1 deficiency promoted NF-κB pathway activity not only in cells stimulated with Tlr2 ligand, but also in cells treated with NF-κB activators that stimulate different surface receptors. In the intestine, Hic1 is mainly expressed in differentiated epithelial cells and its ablation leads to increased Tlr2 production. Finally, in a chemical-induced mouse model of carcinogenesis, Hic1 absence resulted in larger Tlr2-positive colonic tumors that showed increased proportion of proliferating cells.


CONCLUSIONS
The tumor-suppressive function of Hic1 in colon is related to its inhibitory action on proproliferative signaling mediated by the Tlr2 receptor present on tumor cells.
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Lucie
L
Janeckova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Vendula
V
Pospichalova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Bohumil
B
Fafilek
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Martina
M
Vojtechova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Jolana
J
Tureckova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Jan
J
Dobes
CNRS UMR 8161, Institut de Biologie de Lille, Université Lille Nord de France, Institut Pasteur de Lille, Lille Cedex, France.
Marion
M
Dubuissez
CNRS UMR 8161, Institut de Biologie de Lille, Université Lille Nord de France, Institut Pasteur de Lille, Lille Cedex, France.
Dominique
D
Leprince
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Nikol
N
Baloghova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Monika
M
Horazna
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Adela
A
Hlavata
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Jitka
J
Stancikova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Eva
E
Sloncova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Katerina
K
Galuskova
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Hynek
H
Strnad
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic. korinek@img.cas.cz.
Vladimir
V
Korinek
D000818:Animals; D001397:Azoxymethane; D063646:Carcinogenesis / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003110:Colonic Neoplasms; D016264:Dextran Sulfate; D004195:Disease Models, Animal; D004847:Epithelial Cells; D055785:Gene Knockdown Techniques; D006801:Humans; D007422:Intestines / Q000166:cytology; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D015854:Up-Regulation
C096870:Hic1 protein, mouse; D051741:Kruppel-Like Transcription Factors; D016328:NF-kappa B; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D025521:Tumor Suppressor Proteins; D016264:Dextran Sulfate; D001397:Azoxymethane