Cdx1 Inhibits Human Colon Cancer Cell Proliferation by Reducing β-Catenin/T-cell Factor Transcriptional Activity

Abstract

The cessation of proliferation and the induction of differentiation are highly coordinated processes that occur continuously in the intestinal crypts. The homeodomain transcription factors Cdx1 and Cdx2 regulate intestine-specific gene expression and enterocyte differentiation. Their roles in regulating proliferation are recognized but remain poorly understood. Previously, we demonstrated that Cdx1 expression diminished the proliferation of human colon cancer cells in part by reducing cyclin D1 gene expression. In order to elucidate further the molecular mechanisms underlying this phenomenon, we first hypothesized that Cdx1 or Cdx2 expression reduces colon cancer cell proliferation by inhibiting ␤-catenin/T-cell factor (TCF) transcriptional activity. We report that Cdx1 or Cdx2 expression does inhibit ␤-catenin/TCF transcriptional activity in colon cancer cells. This inhibitory effect is dose-dependent and is observed in different colon cancer cell lines, and the degree of inhibition correlates with the ability of Cdx1 to reduce cell proliferation. Cdx1 expression does not alter ␤-catenin protein levels or intracellular distribution nor does it induce an inhibitory TCF isoform. We also find that Cdx1 expression is lost in Min mouse polyps with increased nuclear localization of ␤-catenin, suggesting that Cdx1 does not support ␤-catenin-mediated transformation. Finally, we show that colon cancer cells effectively reduce Cdx2-mediated inhibition of Wnt/␤-catenin/TCF transcriptional activity when compared with other model systems. This suggests that colon cancer and possibly crypt epithelial cells can modulate the effects of Cdx2 on ␤-catenin signaling and proliferation. We conclude that Cdx1 and Cdx2 inhibit colon cancer cell proliferation by blocking ␤-catenin/ TCF transcriptional activity.

MUC4 expression is regulated by cystic fibrosis transmembrane conductance regulator in pancreatic adenocarcinoma cells via transcriptional and post-translational mechanisms

“…GATA2/3/4, Cdx-1, AP-1 and MAF seem to be of particular importance as their binding sites are uniquely present in both the differentially active promoter fragments (Table 1). Involvement of these transcription factors in mediating cancer cell signaling and/or mucin gene expression has been demonstrated in previous studies (Dhakshinamoorthy and Jaiswal, 2002;Chen et al, 2004;Guo et al, 2004;Hokari et al, 2005) and should further be explored for the regulation of MUC4 expression. Stability of the protein is determined by certain inherent (structural) and external factors.…”

Repression of the Desmocollin 2 Gene Expression in Human Colon Cancer Cells Is Relieved by the Homeodomain Transcription Factors Cdx1 and Cdx2

“…1C). Transient transfection of a Cdx1 expression vector or adenoviral-mediated Cdx1 expression (22,23) both enhanced DSC2 mRNA levels, suggesting that this response is not specific to Colo 205 cells and may be generalizable to all colonocytes and colon cancer cells.…”

“…Whole-cell extracts were prepared as described (22,23,34). Briefly, cells were washed twice in PBS, removed with rubber cell scraper, pelleted, and then resuspended in 80 AL of buffer A (1Â PBS with 2 Ag/mL aprotinin, 2 Ag/mL leupeptin, 0.2 mmol/L phenylmethylsulfonyl fluoride, 1 mmol/L NaF, 1 mmol/L NaVO 4 ).…”

“…For reporter assays, a DNA transfection mixture was prepared consisting of 0.1 to 5 Ag of the reporter construct and 50 ng of pRL-CMV Renilla (Promega). pRC/CMV-Cdx1 or pRC/CMV-Cdx2 expression vectors were used to transiently express Cdx1 or Cdx2 and have been previously described (22,23,34). pCR2.1 vector (Invitrogen) was used to equalize the amount of transfected DNA.…”

Wnt signaling and gastrointestinal tumorigenesis in mouse models

“…For example, an intestinal crypt transcription factor SOX9 is regulated by the Wnt pathway, and represses the Cdx2 and Muc2 genes (Blache et al, 2004). While Cdx1 gene has been shown to be a direct target of Wnt signaling during the mouse embryonic development (Lickert et al, 2000), its gene product CDX1 inhibits human colon cancer cell proliferation by reducing TCF transcriptional activity (Guo et al, 2004), suggesting a negative feedback regulation.…”