Expression of the Cdx1and Cdx2Homeotic Genes Leads to Reduced Malignancy in Colon Cancer-derived Cells

Gustavo Vidal Mallo,Philippe Soubeyran,Jean-Claude Lissitzky,Frédéric André,Catherine Farnarier,Jacques Marvaldi,Jean-Charles Dagorn,Juan Lucio Iovanna

doi:10.1074/jbc.273.22.14030

Abstract

We have previously described an inverse relationship between Cdx1 and Cdx2 mRNA levels and the extent of dysplasia and severity of clinical outcome in colorectal carcinoma, suggesting that altered expression of these genes was associated with colorectal carcinogenesis or tumor progression. To investigate further their involvement in the physiopathology of colorectal cancer, HT29 colon carcinoma cells that show very low Cdx expression were transfected with Cdx1 and/or Cdx2 cDNA to elicit their overexpression. Growth rate, tumorigenicity, resistance to apoptosis, and migration potential of the corresponding cells were analyzed. Growth rate of cells overexpressing Cdx2 decreased by half, whereas overexpression of Cdx1 had no effect. However, cells overexpressing both Cdxs had a growth rate reduced to 20% of control. In cells overexpressing Cdx1 or Cdx2, tumorigenicity and resistance to apoptosis induced by serum starvation, ceramide, or staurosporine were not changed compared with control cells; yet phorbol ester-stimulated cell migration was decreased by 50%. In cells overexpressing both Cdx1 and Cdx2, tumorigenicity was decreased by 50%, resistance to apoptosis was significantly lowered, and stimulated cell migration was further decreased to 15% of control compared with cells expressing Cdx1 or Cdx2. Finally, cells overexpressing both Cdxs showed strongly decreased Bcl-2 expression, which could account for their increased sensitivity to apoptosis. These findings show that, in HT29 cells, both Cdx1 and Cdx2 genes must be expressed to reduce tumorigenic potential, to increase sensitivity to apoptosis, and to reduce cell migration, suggesting that the two genes control the normal phenotype by independent pathways. This may explain why loss of Cdx1 or Cdx2 expression is associated with tumor development and invasiveness in colorectal tumors.

Highlights

In an effort to characterize the mechanisms involved in colorectal cancer initiation and progression, we have developed a strategy based on the constitution of a large repertoire of transcripts from a colorectal tumor, all characterized by partial sequencing [1]
We have previously described an inverse relationship between Cdx1 and Cdx2 mRNA levels and the extent of dysplasia and severity of clinical outcome in colorectal carcinoma, suggesting that altered expression of these genes was associated with colorectal carcinogenesis or tumor progression
In cells overexpressing Cdx1 or Cdx2, tumorigenicity and resistance to apoptosis induced by serum starvation, ceramide, or staurosporine were not changed compared with control cells; yet phorbol esterstimulated cell migration was decreased by 50%

Summary

Introduction

In an effort to characterize the mechanisms involved in colorectal cancer initiation and progression, we have developed a strategy based on the constitution of a large repertoire of transcripts from a colorectal tumor, all characterized by partial sequencing [1] Expression of these expressed sequence tags in normal and cancerous colon was compared, and those most differentially expressed were selected. In the present paper we have used HT29, a cell line derived from a colon tumor that shows very low Cdx and Cdx expression, to investigate the role of these homeotic genes in the physiopathology of colorectal cancer. To this end, HT29 cells were transfected with Cdx and Cdx expression plasmids, alone or in combination. It was found that Cdx and Cdx cooperate to reduce the malignancy of HT29 cells

Methods

Results

Conclusion