Differential regulation of CDX1 and CDX2 gene expression by deficiency in methyl group donors.
The CDX2 and CDX1 homeobox genes have respectively a tumour suppressor and proliferative role in the intestinal epithelium. We analyzed DNA methylation and histones modifications associated with CDX2 and CDX1 promoters in two human colon cancer cell lines expressing differentially these genes, Caco2/TC7 [CDX2 positive-CDX1 negative] and HT29 [CDX2 negative-CDX1 negative] cells. Chromatin immunoprecipitation experiments indicated that CDX2 and CDX1 gene expression correlated with a histone modifications pattern characterizing active chromatin (H3K4 trimethylated and H3 acetylated). Bisulfite DNA sequencing and methylation-specific PCR showed that CDX2 and CDX1 promoters display no methylation in HT29 cells even though both genes are not expressed. In contrast, the CDX1 promoter is methylated in Caco2/TC7. DNA demethylation by 5aza-dC or the combination of 5aza-dC plus SAHA, an inhibitor of histone deacetylases, restored CDX1 expression in Caco2/TC7 cells but these treatments were inefficient on both CDX2 and CDX1 in HT29 cells. Thus, in colon cancer cells the changes in chromatin conformation are heterogeneous and repression of CDX2 and CDX1 in HT29 cells is not due to epigenetic mechanisms. In vivo, dietary deprivation of methyl groups in rats upregulated CDX1 mRNA and downregulated to a lesser extent CDX2 mRNA expression. Moreover, methyl group deprivation downregulated CDX2 protein by changing its phosphorylation pattern. The changes in CDX2 and CDX1 expression determined by methyl group deprivation may constitute one of the mechanisms sustaining the protective role attributed to folate in colon cancer.
Lu
Xiaohong
X
INSERM, UMR-S0724, Vandoeuvre-les-Nancy F-54505, France.
Freund
Jean-Noël
JN
Muller
Marc
M
Ravey
Juliette
J
Nicolas
Jean-Pierre
JP
Gueant
Jean-Louis
JL
Namour
Farès
F
D001483:Base Sequence; D000071616:CDX2 Transcription Factor; D018938:Caco-2 Cells; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D005786:Gene Expression Regulation; D019073:HT29 Cells; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction
C491273:CDX1 protein, human; D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D017931:DNA Primers; D018398:Homeodomain Proteins