Figure 7.

1α,25(OH)₂D₃ regulates VDR and β-catenin–TCF-4 transcriptional activity and E-cadherin expression in multiple human colon cancer cell lines. (A) Activation of VDR (top) and inhibition of β-catenin–TCF-4 transcriptional activity (bottom) by 1α,25(OH)₂D₃. Cells were transfected with either the 4 × VDRE–DR3-tk-luc construct (top) or the TOP-flash plasmid (bottom) and then treated or not with 1α,25(OH)₂D₃ (10⁻⁷ M) for 48 h in DME supplemented with 0.5% FCS. SW480-R and SW620 cells were used as negative control. Mean values and standard deviation of the mean of triplicated obtained in two or three experiments after normalization are shown. (B) Effect of the same 1α,25(OH)₂D₃ treatment on the expression of E-cadherin in the same cell lines. 20 μg of total cell protein extracts (with the exception of 60 μg in the case of LS-174T cells) were analyzed by Western blot. The result shown is representative of two or three experiments performed with each cell line. Quantification of the stimulation by 1α,25(OH)₂D₃ is shown below.