The homeobox gene Cdx1 belongs to the p53-p21(WAF)-Bcl-2 network in intestinal epithelial cells.
Because the Cdx1 homeobox gene stimulates proliferation and induces transformation and tumorigenesis, it has been investigated whether it is involved in the complex network comprising p53, p21(WAF), and Bcl-2 in intestinal epithelial cells. Non-transformed intestinal IEC-6 cells and colon adenocarcinoma SW480 cells were used to study the putative molecular relationship between Cdx1, p53, p21(WAF), and Bcl-2. Wild-type p53 inhibited the transcriptional activity of the Cdx1 promoter whereas the inactive mutant p53(mut22/23) had no effect. Induction of Cdx1 expression had no direct effect on p53 expression and activity. However, it inhibited the transcriptional activity of the p21(WAF) promoter through Cdx1 binding to the p21(WAF) TATA-box and increased the transcriptional activity of the Bcl-2 promoter P2 through a consensus Cdx-binding site. Finally, compared to control cells, Cdx1-overexpressing cells were more resistant to adriamycin-induced apoptosis, probably because they do not show concomitant decrease in endogenous Bcl-2 level. In conclusion, Cdx1 is a negatively regulated target of p53 in intestinal cells. Its regulation of p21(WAF) and Bcl-2 is opposite to that of p53 and is p53-independent. Cdx1 belongs to the regulatory networks of apoptosis, proliferation, and differentiation. These results emphasize the oncogenic potential of Cdx1.
Moucadel
Virginie
V
Centre de Recherche INSERM, EMI 0116, 163 av de Luminy, 13009 Marseille, France.
Totaro
Maria Serena
MS
Dell
Claire Domon
CD
Soubeyran
Philippe
P
Dagorn
Jean Charles
JC
Freund
Jean Noel
JN
Iovanna
Juan Lucio
JL
D001483:Base Sequence; D003110:Colonic Neoplasms; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics*; D017931:DNA Primers; D015972:Gene Expression Regulation, Neoplastic; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007413:Intestinal Mucosa / Q000502:physiology*; D008969:Molecular Sequence Data; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53
C493956:CDKN1A protein, human; C491273:CDX1 protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D018398:Homeodomain Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53