The Wnt antagonist DICKKOPF-1 gene is induced by 1alpha,25-dihydroxyvitamin D3 associated to the differentiation of human colon cancer cells.
The Wnt-beta-catenin pathway is aberrantly activated in most colon cancers. DICKKOPF-1 (DKK-1) gene encodes an extracellular Wnt inhibitor that blocks the formation of signalling receptor complexes at the plasma membrane. We report that 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], the most active vitamin D metabolite, increases the level of DKK-1 RNA and protein in human SW480-ADH colon cancer cells. This effect is dose dependent, slow and depends on the presence of a transcription-competent nuclear vitamin D receptor (VDR). Accordingly, 1,25(OH)2D3 activates a 2300 bp fragment of the human DKK-1 gene promoter. Chromatin immunoprecipitation assays revealed that 1,25(OH)2D3 treatment induced a pattern of histone modifications which is compatible with transcriptionally active chromatin. DKK-1 is expressed at high level in colon cancer cell lines with a differentiated phenotype such as Caco-2 or HT-29. Exogenous expression of E-cadherin into SW480-ADH cells results in a strong adhesive phenotype and a 17-fold increase in DKK-1 RNA. In contrast, an E-cadherin blocking antibody inhibits 1,25(OH)2D3-induced differentiation of SW480-ADH cells and DKK-1 gene expression. Remarkably, in vivo treatment with the vitamin D analogue EB1089 induced DKK-1 protein expression in SW480-ADH cells xenografted in immunodeficient mice, and a correlation was observed in the expression of VDR and DKK-1 RNA in a series of 32 human colorectal tumours. These data indicate that 1,25(OH)2D3 activates the transcription of the DKK-1 gene, probably in an indirect way that is associated to the promotion of a differentiated phenotype. DKK-1 gene induction constitutes a novel mechanism of inhibition of Wnt signalling and antitumour action by 1,25(OH)2D3.
Aguilera
Oscar
O
Instituto de Investigaciones Biomédicas Alberto Sols, Facultad de Medicina, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Arturo Duperier, 4, 28029 Madrid, Spain.
Peña
Cristina
C
García
José Miguel
JM
Larriba
María Jesús
MJ
Ordóñez-Morán
Paloma
P
Navarro
Diego
D
Barbáchano
Antonio
A
López de Silanes
Isabel
I
Ballestar
Esteban
E
Fraga
Mario F
MF
Esteller
Manel
M
Gamallo
Carlos
C
Bonilla
Félix
F
González-Sancho
José Manuel
JM
Muñoz
Alberto
A
D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D002843:Chromatin / Q000235:genetics / Q000302:isolation & purification; D003110:Colonic Neoplasms / Q000235:genetics*; D017931:DNA Primers; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012334:RNA, Neoplasm / Q000235:genetics; D015533:Transcriptional Activation; D051153:Wnt Proteins / Q000037:antagonists & inhibitors*
D002843:Chromatin; C501126:DKK1 protein, human; D017931:DNA Primers; D036341:Intercellular Signaling Peptides and Proteins; D012334:RNA, Neoplasm; D051153:Wnt Proteins; D002117:Calcitriol