Regulation of human cripto‐1 gene expression by TGF‐β1 and BMP‐4 in embryonal and colon cancer cells

Abstract

Human Cripto-1 (CR-1) is a cell membrane protein that is overexpressed in several different types of human carcinomas. In the present study we investigated the mechanisms that regulate the expression of CR-1 gene in cancer cells. We cloned a 2,481 bp 5'-flanking region of the human CR-1 gene into a luciferase reporter vector and transfected NTERA-2 human embryonal carcinoma cells and LS174-T colon cancer cells to test for promoter activity. Activity of CR-1 promoter in both cell lines was modulated by two TGF-beta family members, TGF-beta1 and BMP-4. In particular, TGF-beta1 significantly up-regulated CR-1 promoter activity, whereas a dramatic reduction in CR-1 promoter activity was observed with BMP-4 in NTERA-2 and LS174-T cells. Changes in the CR-1 promoter activity following TGF-beta1 and BMP-4 treatments correlated with changes in CR-1 mRNA and protein expression in NTERA-2 and LS174-T cells. We also identified three Smad binding elements (SBEs) within the CR-1 promoter and point mutation of SBE1 (-2,197/-2,189) significantly reduced response of the CR-1 promoter to both TGF-beta1 and BMP-4 in NTERA-2 and LS174-T cells. Chromatin immunoprecipitation assay also demonstrated binding of Smad-4 to a CR-1 promoter DNA sequence containing SBE1 in LS174-T cells. Finally, BMP-4 inhibited migration of LS174-T cells and F9 mouse embryonal carcinoma cells by downregulation of CR-1 protein. In conclusion, these results suggest a differential modulation of CR-1 gene expression in embryonal and colon cancer cells by two different members of the TGF-beta family.