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

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 esterstimulated 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.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. Genes detected by these means may be causative or instrumental in tumor induction or/and progression. Looking for such genes, we found that the Cdx1 and Cdx2 homeotic genes were concomitantly down-regulated in about 85% of colorectal cancers (2). Such low expression of Cdx1 or Cdx2 in colon carcinoma was verified by immunohistochemistry (3, 4) and by reverse transcription polymerase chain reaction (5) studies. Cdx1 and Cdx2 are interesting candidates that could play a role in colon cancer pathology because Chawengsaksophak et al. (6) recently reported the occurrence of multiple intestinal adenomatous polyps in the proximal colon of Cdx2 ϩ/Ϫ mice, suggesting that lowering Cdx2 levels in intestinal cells would suffice to induce intestinal tumors. Also, Suh and Traber showed that expre...

The intestine-specific homeobox gene Cdx2 decreases mobility and antagonizes dissemination of colon cancer cells

“…The lower chamber contained 300 ml of growth medium. For the inducible cells, the medium eventually contained doxycycline and was supplemented with 100 nM PMA (Sigma) since parental HT29 cells exhibit a poor intrinsic migration capacity (Mallo et al, 1998). After 24 h, cells having migrated through the filter were fixed with methanol, stained with crystal violet (0.005%) and counted under a microscope in five randomly chosen fields.…”

Prognostic significance of CDX2 and mucin expression in small intestinal adenocarcinoma

“…22 Several previous reports have suggested a tumorsuppressive role for CDX2 in human colorectal and gastric carcinogenesis. 23 CDX2 expression is associated with not only intestinal mucin phenotypes, 14,24 but also an early tumor stage [24][25][26][27][28][29][30] and improved prognosis in patients with gastric cancer. [29][30][31][32] A previous study reported that CDX2 expression is also correlated with an improved prognosis in patients with ampullary adenocarcinomas.…”

Dysregulated expression of HOX and ParaHOX genes in human esophageal squamous cell carcinoma

“…We showed that CDX1 and CDX2 play a role in the development of not only intestinal metaplasia but also ESCC. The roles of CDX1 and CDX2 in carcinogenesis of digestive tract epithelium have been conflicting: there are reports indicating that they function as oncogenic or anti-oncogenic molecules (4,29). Our data may reflect oncogenic function of CDX1/ CDX2 in the development of ESCC since the expression of both genes increased in ESCC.…”

“…Some studies of CDX1 and CDX2 suggest that they are important in the early differentiation and maintenance of the intestinal epithelium. For example, in vitro experiments using rodent and human cell lines indicate that modification of CDX1 or CDX2 expression alters cell growth or the intestinal differentiation phenotype (3,4). In vivo observation of CDX genes and their products during mouse development or phenotypic analysis of CDX-gene-mutant mice identifies a role of CDX genes in the maintenance of the intestinal phenotype (5,6).…”