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...

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Abstract. Metanephrogenesis has been a long-standing model to study cell-matrix interactions. A number of adhesion molecules, including matrix receptors (i.e., integrins), are believed to be involved in such interactions. The integrins contain a and ~ subunits and are present in various tissues in different heterodimeric forms. In this study, one of the members of the integrin superfamily, av, was characterized, and its relevance in murine nephrogenesis was investigated. Mouse embryonic renal eDNA libraries were prepared and screened for av, and multiple clones were isolated and sequenced. The deduced amino acid sequence of the et v cDNA clones and hydropathic analysis revealed that it has a typical signal sequence and extracellular, transmembrane, and cytoplasmic domains, with multiple Ca 2÷ binding sites. No A(U)nA mRNA instability motifs were present. Conformational analysis revealed no rigid long-range-ordered structure in murine O~v. The O~v was expressed in the embryonic kidney at day 13 of the gestation, with a transcript size of ~7 kb. Its expression increased progressively during the later gestational stages and in the neonatal period. It was distributed in the epithelial elements of developing nephrons and was absent in the uninduced mesenchyme. In mature metanephroi, the expression was relatively high in the glomeruli and blood vessels, as compared to the tubules. Various heterodimeric associations of av, i.e., with [31, [33, [35, and [36, were observed in metanephric tissues. Inclusion of av-antisense-oligodeoxynucleotide or -antibody in metanephric culture induced dysmorphogenesis of the kidney with reduced population of the nephrons, disorganization of the ureteric bud branches, and reduction of mRNA and protein expressions of etv. The expressions of integrin [33, [35, and 136 were unaltered. These findings suggest that the integrin av is developmentally regulated, has a distinct spatio-temporal expression, and is relevant in the mammalian organogenesis.URING development, the interactions between cell adhesion molecules and extraceUular matrix (ECM) 1 glycoproteins are believed to be essential for the morphogenesis of various organs (Hay, 1991;Humphries et al., 1991;Reichardt and Tomaselli, 1991;Ruoslahti, 1991;Toole, 1991;Hynes, 1992;Juliano and Haskill, 1993;Kramer et al., 1993;Gladson and Cheresh, 1994;Hemler et al., 1994;Quaranta et al., 1994). The maturation of the mammalian metanephros constitutes many of the steps which are prototypic of the events relevant to the development of other organ systems (Ekblom, 1993;Clapp and Abrahamson, 1994). The renal organogenesis ensues after an initial reciprocal induction between the metanephric Address all correspondence to Dr. Y.S. Kanwar, Department of Pathology, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, IL 60611. Tel.: (312) 503-0084. Fax: (312) 503-0627.1. Abbreviations used in this paper: ECM, extracellular matrix; ODN, oligodeoxynucleotide; RT, reverse transcriptase. mesenchyme and the ureteric bud, which leads to...

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