CDX2, a homeobox transcription factor, upregulates transcription of the p21/WAF1/CIP1 gene

Intestinal differentiation in zebrafish requires Cdx1b, a functional equivalent of mammalian Cdx2

BACKGROUND & AIMS

The ParaHox transcription factor Cdx2 is an essential determinant of intestinal phenotype in mammals throughout development, influencing gut function, homeostasis, and epithelial barrier integrity. Cdx2 expression demarcates the zones of intestinal stem cell proliferation in the adult gut, with deregulated expression implicated in intestinal metaplasia and cancer. However, in vivo analysis of these prospective roles has been limited because inactivation of Cdx2 in mice leads to preimplantation embryonic lethality. We used the zebrafish, a valuable model for studying gut development, to generate a system to further understanding of the role of Cdx2 in normal intestinal function and in disease states.

METHODS

We isolated and characterized the zebrafish cdx1b ortholog and analyzed its function by antisense morpholino gene knockdown.

RESULTS

We showed that zebrafish Cdx1b replaces the role of Cdx2 in gut development. Evolutionary studies have indicated that the zebrafish cdx2 loci were lost following the genome-wide duplication event that occurred in teleosts. Zebrafish Cdx1b is expressed exclusively in the developing intestine during late embryogenesis and regulates intestinal cell proliferation and terminal differentiation.

CONCLUSIONS

This work established an in vivo system to explore further the activity of Cdx2 in the gut and its impact on processes such as inflammation and cancer.

Prognostic significance of intestinal claudins in high-risk synchronous and metachronous multiple gastric epithelial neoplasias after initial endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is useful in en bloc curative resection and enables patients with early gastric carcinoma (GC) to have a better quality of life. But metachronous recurrence of GC at other sites in the stomach has become a major issue after initial ESD. The purpose of the present paper was to examine gastric (claudin-18) and intestinal claudin (claudin-3 and claudin-4) expression in early GC on immunohistochemistry to clarify the association with clinicopathology, mucin phenotypes, microsatellite instability (MSI) status and the incidence of synchronous and metachronous gastric epithelial neoplasias after initial ESD. According to intestinal claudin expression, a total of 73 early GC were divided into two groups: intestinal claudin-positive (I-CLDN(+)) phenotype (n = 52; 71%); and intestinal claudin-negative (I-CLDN(-)) phenotype (n = 21; 29%). Although no significant association was found with clinicopathology and the MSI status, the I-CLDN(+) early GC correlated with the mucin phenotypes and had a significantly higher incidence of synchronous and metachronous multiple GC and gastric adenomas (P = 0.049). These results indicate that early GC demonstrating I-CLDN(+) phenotype have a high risk of synchronous and metachronous secondary gastric epithelial neoplasias.

Genetic alterations of the Cdx2 gene in gastric cancer

Gastric atrophy and intestinal metaplasia are generally considered precancerous lesions of the stomach; Cdx2 plays an important role in intestinal metaplasia and gastric carcinogenesis. To elucidate the potential etiological role of the Cdx2 gene in gastric carcinogenesis, we analyzed genetic mutations and allelic loss in the Cdx2 gene of 95 sporadic gastric cancers. We found two somatic missense mutations in the Cdx2 gene, P63L in exon 1 and E204K in exon 2, encoding the caudal-like protein activation region (codon 13-180) and the homeobox domain (codon 188-243) of the gene, in the gastric cancers. In addition, 9 (25.0%) of 36 informative cases showed allelic loss at D13S220 and/or D13S260. In 11 cases with a genetic alteration, Cdx2 nuclear staining was observed only in 8 cases of gastric mucosa with intestinal metaplasia. Loss or reduced expression of the Cdx2 gene in cancer cells was found in two cases with a somatic mutation and in three cases with LOH. Interestingly, all of the cases were intestinal-type gastric cancers. Thus, these results suggest that genetic alterations of the Cdx2 gene may contribute to the loss of Cdx2 expression and to the development of gastric cancer, especially in the intestinal-type.

Cdx2 transcription factor regulates claudin-3 and claudin-4 expression during intestinal differentiation of gastric carcinoma

According to the expression of gastric (claudin-18) and intestinal claudins (claudin-3 and claudin-4), the authors have previously proposed a new phenotypic classification of gastric carcinoma (GC): the gastric (G-CLDN), intestinal (I-CLDN) and unclassified claudin (U-CLDN) phenotypes. The aim of the present study was to examine the role of Cdx2, the caudal-related transcription factor, on the regulation of intestinal claudins expression in vitro and in vivo. It was confirmed on immunohistochemistry that non-neoplastic gastric mucosa with intestinal metaplasia (IM) expressed Cdx2 with increased levels of intestinal claudin expression. In addition, Cdx2 expression was detected in 28 (30%) of 94 GC at the invasive front. Interestingly, Cdx2 expression had a significant association with the I-CLDN phenotype (P < 0.001), which was almost identical to the established gastric and intestinal mucin-based GC classification. Furthermore, the transfection of a recombinant human CDX2-expressing vector into TMK-1 (Cdx2-negative) GC cells specifically elevated the expression of claudin-3 and claudin-4 at the mRNA (CLDN3, 3.9-fold; CLDN4, 2.8-fold) and protein levels (claudin-3, 8.6-fold; claudin-4, 9.8-fold), whereas no induction of the other claudins was detected. These findings suggest that Cdx2 plays an important role in the regulation of intestinal claudin expression not only in gastric mucosa with IM but also GC.

A clinicopathological study on the expression of cadherin-17 and caudal-related homeobox transcription factor (CDX2) in human gastric carcinoma

AIMS

To analyse the clinicopathological characteristics of the expression of cadherin-17 (CDH17) and caudal-related homeobox transcription factor (CDX2) in human gastric carcinoma, and to evaluate the clinical significance of these two markers in the histological classification and prognosis of gastric carcinoma.

MATERIALS AND METHODS

CDH17, CDX2 protein expression in paraffin-embedded specimens gathered from 166 patients with gastric carcinoma were detected by immunohistochemistry. The association of CDH17, CDX2 protein expression with the clinicopathological characteristics, and with the prognosis of gastric carcinoma were subsequently assessed.

RESULTS

CDH17, nucleus and cytoplasm CDX2 expression were positively expressed in 101/166 (60.8%), 59/166 (35.5%) and 57/166 (34.3%) gastric carcinoma patients, respectively. The expression of both CDH17 and CDX2 is associated with the intestinal-type gastric carcinoma (P<0.01). Positive expression of CDH17 was significantly associated with the depth of gastric wall invasion (P=0.04), lymph node metastasis (P<0.01) and stages of gastric carcinoma (P=0.01). Positive expression of CDX2 in the nucleus was mainly found in male patients (P=0.02), in early stage (P=0.01) and medullary-type gastric carcinoma (P=0.02). There was a negative association between nuclear CDX2 expression and lymph node metastasis of gastric carcinoma (P<0.01). The combined expression of CDH17 and CDX2 was significantly lower in diffuse-type carcinoma than intestinal- or mixed-type carcinoma (P<0.01 and P=0.01, respectively). The patients with CDH17 expression associated with poor prognosis of gastric carcinoma (P<0.01), as opposed to patients with CDX2 expression (P<0.01). The survival rate of patients with CDH17+/CDX2- expression was the lowest (P<0.01), and conjoined expressions of CDH17+/CDX2- and CDH17+/CDX2+ were independent prognostic indicators of gastric carcinoma (both P<0.01).

CONCLUSION

The results suggest that the expression of CDH17 or CDX2 may be an important feature of gastric carcinoma. A combined detection of CDH17/CDX2 co-expression may benefit us in predicting the prognosis of gastric carcinoma.

Homeoprotein Cdx2 and nuclear PTEN expression profiles are related to gastric cancer prognosis

The aim of the study was to analyze the expression of Cdx2 and nuclear PTEN in relation to clinicopathological features of gastric cancer tissue biopsies in order to determine the value of a combined analysis of Cdx2 and nuclear PTEN expression in distinguishing histological types and prognosis of gastric cancers. The expression of Cdx2 and nuclear PTEN was studied using immunohistochemistry of paraffin-embedded tumor specimens from 99 patients who underwent radical D2 gastrectomy between 1999 and 2001. Cdx2 and nuclear PTEN expression were detected in 39.6% (36 of 91) and 70.3% (64 of 91) of gastric cancer cases, respectively. There was a negative correlation between Cdx2 expression and Lauren classification (p=0.032), and between nuclear PTEN expression and lymph node metastasis (p=0.049). Patients with Cdx2-positive, or nuclear PTEN-positive expression had higher survival rates than those with Cdx2-negative or nuclear PTEN-negative expression (p<0.001 and p=0.003, respectively). Co-expression of Cdx2 and nuclear PTEN showed significantly lower levels in diffuse- or mixed-type cancers than in intestinal-type cancers (p=0.005). Multivariate analysis revealed that Cdx2 expression was an independent prognostic indicator of gastric cancer (p=0.014). These data suggest that combined analysis of Cdx2 and nuclear PTEN expression can have significant value in distinguishing histological types of gastric cancer and assessing prognosis in patients with gastric cancer.

A functional role of Cdx2 in beta-catenin signaling during transdifferentiation in endometrial carcinomas

Nuclear beta-catenin is required for changes in morphology from glandular to morular phenotypes of endometrial carcinoma (Em Ca) cells, with activation of p14(ARF)/p53/p21(Waf1) and alteration of p16(INK4A)/pRb pathways. Having demonstrated previously that the homeodomain transcription factor Cdx2 increases markedly during intestinal epithelial cell differentiation, we have examined its effects in beta-catenin signaling during transdifferentiation of Em Ca cells. In clinical cases, Cdx2 immunoreactivity, along with increased mRNA signals, was found to overlap with nuclear accumulation of beta-catenin and p21(Waf1) in morules, demonstrating an inverse correlation with cell proliferation. In cell lines, over-expression of active form beta-catenin resulted in a significant increase in endogenous Cdx2 expression at both mRNA and protein levels. Furthermore, the Cdx2 promoter was activated by T-cell factor 4 (TCF4) -independent activated beta-catenin, as well as Cdx2 itself, through the region from -39 to +9 bp relative to transcription start site. Cells over-expressing exogenous Cdx2 showed high levels of p21(Waf1) expression due to stabilization of the mRNA status, resulting in significant decrease in the proliferation rate, in contrast to the lack of apparent changes in morphology. Moreover, transfected Cdx2 could inhibit beta-catenin/TCF4-mediated transcriptional activation of target genes, including p14(ARF) and cyclin D1, probably through indirect mechanisms. These data suggest that over-expression of Cdx2 mediated by nuclear beta-catenin and Cdx2 itself can cause an inhibition of Em Ca cell proliferation through up-regulation of p21(Waf1) expression, modulating beta-catenin/TCF4-mediated transcription. We therefore conclude that an association between Cdx2 and beta-catenin signaling may participate in induction of transdifferentiation of Em Ca cells.

Hepatoid adenocarcinoma of the stomach: histogenesis and progression in association with intestinal phenotype

Hepatoid adenocarcinoma is an extrahepatic tumor characterized by morphological similarities to hepatocellular carcinoma. The lesions contain a tubular adenocarcinoma that seems to develop "hepatoid" features, but the relation between the tubular adenocarcinomatous and the hepatoid components remains unclear. We compared the cellular phenotypes of 23 cases of hepatoid adenocarcinoma of the stomach having tubular adenocarcinomatous components with 69 cases of non-hepatoid adenocarcinoma of the stomach. Afterward, we examined the expression of CDX2 and p53 in the tubular adenocarcinomatous and hepatoid components of hepatoid adenocarcinoma. Both components of hepatoid adenocarcinoma were classified into 4 phenotypic categories according to the immunohistochemical results for CD10, MUC2, MUC5AC, and MUC6. The complete intestinal phenotype (CD10+, MUC5AC-, MUC6-) was most frequently observed in the adenocarcinomatous and hepatoid components (61% and 65%, respectively). In contrast, no gastric phenotype (MUC5AC+, MUC6+, MUC2-, CD10-) was observed in any of the hepatoid adenocarcinoma components. The positivity for p53 protein in the adenocarcinomatous and hepatoid components was concordant. The expression of CDX2 with early differentiation and maintenance of intestinal epithelial cells was observed in all of the adenocarcinomatous components, whereas 9 of the 23 hepatoid components (39%) were negative for CDX2. These findings suggest that hepatoid adenocarcinoma arises from an adenocarcinoma with an intestinal phenotype and that its hepatoid component is in some way related to reduced CDX2 expression.

CDX2 expression is increased in gastric cancers with less invasiveness and intestinal mucin phenotype

OBJECTIVE

CDX2 is an intestinal transcription factor that might be involved in the regulation of proliferation and differentiation of intestinal epithelial cells. It is well known that both gastric and intestinal phenotypic cell markers are expressed in gastric cancers. The aims of this study were to analyze the CDX2 expression and its relationship with the patients' clinicopathological characteristics and the mucin phenotypes by performing immunohistochemistry.

MATERIAL AND METHODS

A total of 259 gastric cancer cases (122 early and 137 advanced cancers) were evaluated histologically and phenotypically. CDX2 expression was assessed by immunohistochemistry.

RESULTS

Increased CDX2 expression correlated with a higher proportion of intestinal-type cancers of Lauren and early gastric cancers (p<0.001 and p<0.001, respectively) and a lower proportion of perineural invasion and lymph node metastasis (p<0.001 and p=0.003, respectively). Increased expressions of intestinal mucin (MUC-2, CD10) and decreased gastric mucin (MUC5AC) were associated with an increased CDX2 expression (p<0.001, p=0.045 and p=0.004, respectively). MUC6 expression was not associated with CDX2 expression. There was a significantly increased CDX2 expression in the intestinal phenotype compared with the other phenotypes (p<0.001).

CONCLUSIONS

These results suggest that CDX2 might be a useful marker in predicting the clinical outcome for patients with gastric cancers.

CDX2 does not suppress tumorigenicity in the human gastric cancer cell line MKN45

CDX2 is a Drosophila caudal-related homeobox transcription factor that is expressed specifically in the intestine. In mice, ectopic expression of CDX2 in the gastric mucosa gives rise to intestinal metaplasia and in one model, gastric carcinoma. In humans, increased CDX2 expression is associated with gastric intestinal metaplasia and tubular adenocarcinomas. These patterns of expression have shown that CDX2 is important for the initiation of intestinal metaplasia in the gastric mucosa, but the role of CDX2 in established gastric cancer remains unclear. We sought to determine whether CDX2 contributes to tumorigenic potential in established gastric cancer. The CDX2 gene in MKN45 gastric carcinoma cells was disrupted using targeted homologous recombination. The resulting CDX2-/- cells are essentially identical to their parental cells, with the exception of CDX2 ablation. We found no significant differences in the proliferation of CDX2-/- cells compared to CDX2+/+ cells, in vitro or in vivo. Molecular analyses show that loss of CDX2 predominantly altered the expression of genes involved in intestinal glandular differentiation and adhesion. However, there were no microscopic differences in tumor differentiation. We conclude that disruption of CDX2 in MKN45 cells does not significantly affect their tumorigenic potential.

CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48

CDX2 is a Drosophila caudal-related homeobox transcription factor that is important for the establishment and maintenance of intestinal epithelial cells. CDX2 is a marker of colon cancer, with strong staining in up to 90% of colonic adenocarcinomas. CDX2 heterozygous-null mice develop colonic neoplasms, which have suggested that CDX2 is a tumor suppressor. However, CDX2 has not been reported to affect xenograft growth. Furthermore, CDX2 is rarely mutated in colon cancer, which has led to suggestions that it may play only a minor role as a tumor suppressor in colon cancer. To understand the functional contributions of CDX2 to colon cancer, we disrupted CDX2 in LOVO and SW48 human colon cancer cell lines by targeted homologous recombination. Consistent with the literature, disruption of CDX2 enhanced anchorage-dependent cell proliferation. However, homozygous loss of CDX2 led to significant inhibition of anchorage-independent growth in LOVO cells, and cell lethality in SW48 cells. Further analyses revealed that disruption of CDX2 led to anchorage-independent G1 to S growth arrest and anoikis. In vivo xenograft studies confirmed that disruption of CDX2 inhibited LOVO tumor growth. These data demonstrate that CDX2 mediates anchorage-independent growth and survival. Thus, CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48.

Altered expression of CDX2 in colorectal cancers

CDX2 is a caudal-related homeobox transcription factor whose expression in the adult is normally restricted to the intestinal epithelium; it is implicated in the development and maintenance of the intestinal mucosa. The specific aim of this study was to elucidate the potential etiological role of CDX2 protein in colorectal carcinogenesis. We have analyzed the expression pattern of CDX2 protein in relation to the phenotype of 123 sporadic colorectal cancers by immunohistochemistry using tissue microarray. Strong CDX2 immunostaining was seen in the nuclei of corresponding normal intestinal epithelium. Interestingly, loss of CDX2 immunostaining was observed in 29 (23.6%) of 123 colorectal adenocarcinomas and its expression was correlated with the differentiation grade of the carcinoma (Chi-Square test, p<0.01). Clinically, CDX2 protein was immunopositive in 11 (91.7%) of 12 cases corresponding to stage A, 40 (85.1%) of 47 corresponding to stage B, 39 (69.6%) of 56 corresponding to stage C, and 4 (50.0%) of 8 corresponding to stage D. Statistically, CDX2 protein expression was related to tumor stage (Bartholomew test, p<0.05) and lymph node metastasis (Chi-Square test, p<0.05). These results indicate that loss of expression of CDX2 protein may play an important role in the tumorigenesis of colorectal cancers and that CDX2 expression represents a highly significant marker, which is able to identify a subset of patients at high risk.

Helicobacter pylori regulates the expression of inhibitors of DNA binding (Id) proteins by gastric epithelial cells

Id transcription factors control proliferation, differentiation and apoptosis by inhibiting the DNA binding of basic helix-loop-helix transcription factors. Increased expression of Id proteins promotes proliferation, inhibits differentiation, and is associated with intestinal tumorigenesis. We aimed to determine how Helicobacter pylori may alter the expression of Id proteins by gastric epithelial cells: it was hypothesised that H. pylori, a known carcinogen, would result in increased expression of one or more Id family members. In vitro and in vivo models of infection were employed, including treatment of AGS gastric epithelial cells with wild-type H. pylori strains, 60190 and SS1, and Mongolian gerbils infected with H. pylori SS1. A small cohort of human gastric mucosal biopsies was also examined. Treatment of AGS cells with H. pylori resulted in down-regulation of Id1 and Id3. Unexpectedly, expression of the main target of Id proteins, the basic helix-loop-helix transcription factor E2A, was also suppressed, with an associated decrease in E-box binding activity. In contrast, H. pylori induced the expression of the CDK inhibitor p21(WAF-1/cip1), and the homeobox transcription factor, Cdx2, an early marker of intestinal metaplasia of the stomach epithelium. Gastric epithelium from H. pylori-infected gerbils demonstrated similar changes, with decreased Id2, Id3 and E2A, and elevated p21(WAF-1/cip1) expression. In human gastric epithelium also, H. pylori infection was associated with reduced Id and E2A expression. In conclusion, H. pylori alters the expression of Id proteins, in vitro and in vivo; it is hypothesised that these changes contribute to H. pylori-associated pathologies.

Cdx2 modulates proliferation in normal human intestinal epithelial crypt cells

The homeobox gene Cdx2 is involved in the regulation of the expression of intestine specific markers such as sucrase-isomaltase and lactase-phlorizin hydrolase. Previous studies performed with immortalized or transformed intestinal cell lines have provided evidence that Cdx2 can promote morphological and functional differentiation in these experimental models. However, no data exist concerning the implication of this factor in normal human intestinal cell physiology. In the present work, we have investigated the role of Cdx2 in normal human intestinal epithelial crypt (HIEC) cells that lack this transcription factor. The establishment of HIEC cells expressing Cdx2 in an inducible manner shows that forced expression of Cdx2 significantly alters the proliferation of intestinal crypt cells and stimulates dipeptidylpeptidase IV expression but is not sufficient to trigger intestinal terminal differentiation. These observations suggest that Cdx2 requires additional factors to activate the enterocyte differentiation program in normal undifferentiated cells.

CDX-2 homeobox gene expression in human gastric carcinoma and precursor lesions

BACKGROUND

Recent studies have demonstrated that CDX-2 is expressed in the intestinal metaplasia of the stomach and intestinal-type gastric cancer. To address the role of CDX-2 in carcinogenesis of gastric carcinomas of intestinal type, the expression of CDX-2 in gastric carcinoma and precursor lesions were examined using immunohistochemistry.

METHODS

A total of 160 specimens diagnosed as gastric carcinomas or non-invasive neoplasia from 158 patients were analyzed for CDX-2 expression by immunochemical methods. Patients were classified into histopathologic subgroups according to the Padova international classification: 60 cases of low-grade non-invasive neoplasia, 55 cases of high grade, and 45 cases of invasive intestinal-type adenocarcinoma. The CDX-2 expression in non-neoplastic gastric mucosa including intestinal metaplasia was also evaluated in the areas included in the histologic sections.

RESULTS

The CDX-2 expression was localized in the epithelial cell nuclei in the area of intestinal metaplasia with or without dysplasia and carcinoma, consistent with its role as a transcriptional regulator. No CDX-2 reactivity was noted in the normal mucosa in all cases. The CDX-2 expression was detected in 73.3% of low-grade cases, 85.5% of high-grade cases and 91.1% of intestinal-type adenocarcinoma cases. In the gastric mucosa with intestinal metaplasia, 89.7% of the samples were positive. The CDX-2-expressing cells in intestinal metaplasia were more prevalent than in dysplasia and carcinoma. Expression of CDX-2 showed a statistically significant positive correlation with increasing grade of dysplasia and carcinoma.

CONCLUSIONS

These findings suggest that CDX-2 expression in stomach cancer may be a marker of the progression of gastric carcinogenesis, and that its activation may represent an early event.

The putative tumor suppressor Cdx2 is overexpressed by human colorectal adenocarcinomas

PURPOSE

The current paradigm suggests that the homeodomain transcription factor Cdx2, which directs the development and maintenance of the intestinal epithelium, is a tumor suppressor in the colon and rectum. Although a cardinal property of tumor suppressors is their inactivation during carcinogenesis, the expression of Cdx2 in colorectal tumors has not been compared with that in normal mucosa. Here, Cdx2 expression and function was quantified in tumors and matched normal mucosa from patients with colorectal cancer.

EXPERIMENTAL DESIGN

Cdx2 expression was quantified by reverse transcription-PCR, immunoblot analysis, and immunohistochemistry. Transcriptional activity was explored by quantifying expression of an endogenous downstream target of Cdx2, guanylyl cyclase C (GCC), in tissues by quantitative reverse transcription-PCR and expression of exogenous Cdx2-specific luciferase promoter constructs in epithelial cells isolated from tumors and normal mucosa.

RESULTS

Most (>80%) colorectal tumors overexpressed Cdx2 mRNA and protein compared with normal mucosa, with median fold increases of 3.6 and 1.4, respectively (P<0.002). Concomitantly, immunohistochemistry revealed elevated levels of Cdx2 in nuclei of tumor cells compared with normal epithelial cells. Further, tumors exhibited increased expression of GCC compared with normal mucosa. Moreover, cells isolated from tumors overexpressed a Cdx2-specific luciferase promoter construct compared with normal mucosal cells.

CONCLUSION

These observations show, for the first time, the structural and functional overexpression of Cdx2 by human colorectal tumors compared with matched normal mucosa. They suggest that loss of Cdx2 expression or transcriptional activity is an infrequent event during tumorigenesis, which does not contribute to molecular mechanisms underlying initiation and progression of most colorectal tumors.

Dysregulated expression of P1 and P2 promoter-driven hepatocyte nuclear factor-4α in the pathogenesis of human cancer

Hepatocyte nuclear factor-4alpha (HNF4alpha) exists in multiple isoforms that are generated by alternative promoter (P1 and P2) usage and splicing. Here we establish monoclonal antibodies (mAbs) for detecting P1 and P2 promoter-driven HNF4alpha, and evaluate their expression in normal adult human tissues and surgically resected carcinomas of different origins. Using immunohistochemical analysis, we demonstrate that, while P1 promoter-driven HNF4alpha is expressed in hepatocytes, small intestine, colon, kidney and epididymis, P2 promoter-driven HNF4alpha is expressed in bile duct, pancreas, stomach, small intestine, colon and epididymis. Altered expression patterns of P1 and P2 promoter-driven HNF4alpha were observed in gastric, hepatocellular and colorectal carcinomas. HNF4alpha was expressed in lung metastases from renal cell, hepatocellular and colorectal carcinoma but was not observed in lung tumours. The P1 and P2 promoter-driven HNF4alpha expression pattern of tumour metastases correlated with the primary site of origin. P1 promoter-driven HNF4alpha was also found in intestinal metaplasia of the stomach. These data provide evidence for the tissue distribution of P1 and P2 promoter-driven HNF4alpha at the protein level and suggest that HNF4alpha may be a novel diagnostic marker for metastases of unknown primary. We propose that the dysregulation of alternative promoter usage of HNF4alpha is associated with the pathogenesis of certain cancers.

Phosphorylation of the homeotic tumor suppressor Cdx2 mediates its ubiquitin-dependent proteasome degradation

The Caudal-related homeodomain transcription factor Cdx2 plays a key role in intestinal cell fate determination. Reduction of Cdx2 expression is a feature of many human colon carcinomas and inactivation of one cdx2 allele facilitates the development of invasive adenocarcinoma in the murine colon. Here, we investigated the post-translational regulation of Cdx2. We showed that various forms of Cdx2 coexist in the intestine and colon cancer cell lines, some of them being phosphorylated forms. We found that cyclin-dependent kinase 2 phosphorylated Cdx2 in vitro and in vivo. Using site-specific mutagenesis, we identified serine 281 as a new key residue for Cdx2 phosphorylation. Intriguingly, serine 281 belongs to a conserved motif of four evenly spaced serines (the 4S motif) similar to the one controlling beta-catenin degradation by the proteasome pathway. A nonphosphorylated mutant Cdx2 lacking the 4S motif (4S>A) exhibited reduced polyubiquitination upon proteasome inhibition and increased stability compared to wild-type Cdx2. In addition, we found that this mutant was less efficient to suppress colony formation than wild-type Cdx2. Thus, our data highlight a novel post-translational mechanism controlling Cdx2 degradation via phosphorylation and polyubiquitination, which may be of importance for intestinal development and cancer.

Expression of Cdx2 and hepatocyte antigen in gastric carcinoma: correlation with histologic type and implications for prognosis

PURPOSE

This study was designed to (a) analyze the correlation between the expression of Cdx2 and Hep and the clinicopathologic features of patients with gastric carcinoma, and (b) determine the value of combined analysis of Cdx2 and Hep expression in distinguishing histologic types and prognoses of gastric carcinomas.

EXPERIMENTAL DESIGN

The expression of Cdx2 and Hep were studied using immunohistochemistry of paraffin-embedded tumor specimens from 109 patients who underwent D2 resection for gastric adenocarcinoma from 1995 to 1998.

RESULTS

Nuclear Cdx2 and Hep expression was detected in 36.7% (40 of 109) and 54.1% (59 of 109) of gastric carcinoma cases, respectively. Expression of Cdx2 and Hep was significantly higher in intestinal-type carcinomas than in diffuse-type carcinomas (P = 0.027 and P = 0.037, respectively). There was a clear negative correlation between Cdx2 expression and lymph node metastasis (P = 0.029), as well as between Hep expression and depth of wall invasion (P = 0.011). The patients with Cdx2-positive or Hep-positive expression shows higher survival rate than those with Cdx2-negative or Hep-negative expression (P = 0.0008 and P = 0.003, respectively). Multivariate analysis revealed that the expression of Cdx2 and Hep were independent prognostic indicators of gastric carcinoma. The combination of Cdx2 and Hep expression was significantly lower in diffuse-type carcinoma than in intestinal or mixed-type carcinoma. Multivariate analysis revealed that Cdx2 and Hep expression was an independent prognostic indicator of gastric carcinoma (P < 0.001).

CONCLUSIONS

These data suggest that combined analysis of Cdx2 and Hep has significant value in distinguishing histologic types and in predicting the prognosis of gastric carcinoma.

Homeobox gene expression in cancer: insights from developmental regulation and deregulation

Homeobox genes encode transcription factors that play essential roles in controlling cell growth and differentiation during embryonic development. Many homeobox genes are aberrantly expressed in a wide variety of solid tumours, and their deregulation appears to enhance cell survival and proliferation and to inhibit differentiation. In hematologic malignancies, deregulated homeobox genes profoundly perturb self-renewal and proliferation of hematopoietic stem cells and progenitors. It is increasingly recognised that solid tumours, like hematologic malignancies, could arise from cancer stem cells, and that targeting these cells could be the most effective means of inhibiting tumour progression and disease recurrence. Studying the biological effects and mechanisms of homeobox genes in cancers could provide valuable insights into identifying cancer stem cells and targeting the self-renewal pathways in these cell populations.

The effect of cytostatic drug treatment on intestine-specific transcription factors Cdx2, GATA-4 and HNF-1α in mice

Chemotherapy-induced intestinal damage is a very important dose-limiting side effect for which there is no definitive prophylaxis or treatment. This is in part due to the lack of understanding of its pathophysiology and impact on intestinal differentiation. The objective of this study was to investigate the gene expression of the small intestinal transcription factors HNF-1alpha, Cdx2, GATA-4 in an experimental model of methotrexate (MTX)-induced intestinal damage, and to correlate these alterations with histological damage, epithelial proliferation and differentiation. HNF-1alpha, Cdx2 and GATA-4 are critical transcription factors in epithelial differentiation, and in combination they act as promoting factors of the sucrase-isomaltase (SI) gene, an enterocyte-specific differentiation marker which is distinctly downregulated after MTX treatment. Mice received two doses of MTX i.v. on two consecutive days and were sacrificed 1, 3 and 7 or 9 days after final injection. Segments of the jejunum were taken for morphological, immunohistochemical and quantitative analyses. Intestinal damage was most severe at day 3 and was associated with decreased expression of the transcriptional factors HNF-1alpha, Cdx2 and GATA-4, which correlated well with decreased expression of SI, and seemed inversely correlated with enhanced proliferation of epithelial crypt cells. During severe damage, the epithelium was preferentially concerned with proliferation rather than differentiation, most likely in order to restore the small intestinal barrier function rather than maintaining its absorptive function. Since HNF-1alpha, Cdx2 and GATA-4 are critical for intestine-specific gene expression and therefore crucial in epithelial differentiation, these results may explain, at least in part, why intestinal differentiation is compromised during MTX treatment.

Value of CDX2, villin, and alpha-methylacyl coenzyme A racemase immunostains in the distinction between primary adenocarcinoma of the bladder and secondary colorectal adenocarcinoma

Primary adenocarcinoma of the urinary bladder is an uncommon neoplasm that can be indistinguishable morphologically from colorectal adenocarcinoma secondarily involving the bladder by direct extension or metastasis. In the current study, 17 enteric-type primary adenocarcinomas of the bladder were immunohistochemically examined for the expression of CDX2, villin and alpha-methylacyl coenzyme A racemase (AMACR), immunomarkers preferentially expressed in colorectal adenocarcinoma. For comparison, 17 secondary colorectal adenocarcinomas involving the bladder, 23 primary colorectal adenocarcinomas and 14 conventional urothelial carcinomas were similarly studied. The results show that all 40 (100%) colorectal adenocarcinomas expressed CDX2 and 39 (98%) expressed villin. The expression of these two immunomarkers was less frequent in primary bladder adenocarcinomas, observed in eight (47%) and 11 (65%) cases, respectively (P<0.0001 and P=0.0019, respectively). The frequency of positive AMACR immunostaining was similar between these two types of tumors, detected in 28 (70%) colorectal adenocarcinomas and 11 (65%) primary bladder adenocarcinomas (P=0.694). None of the urothelial carcinomas exhibited CDX2 or villin immunoreactivity; and only two (14%) showed positive staining for AMACR. These results demonstrate that CDX2 and villin are of diagnostic value in aiding in the distinction between primary adenocarcinoma of the bladder and secondary colorectal carcinoma. Lack of CDX2 and villin signals points strongly to a bladder primary.

Differential regulation of intestinal alkaline phosphatase gene expression by Cdx1 and Cdx2

We have examined the role that the caudal-related homeobox transcription factors Cdx1 and Cdx2 play in activating the enterocyte differentiation marker gene intestinal alkaline phosphatase (IAP). Human colon cancer Caco-2 cells were transiently transfected with Cdx1 and/or Cdx2, and semiquantitative RT-PCR was used to study the effects on IAP mRNA expression. Transfections with a variety of IAP-luciferase reporter constructs were used to identify a Cdx response element located within the human IAP gene promoter. Protein-DNA interactions were examined by EMSA. Results showed that Cdx1 markedly induced IAP mRNA expression, whereas Cdx2 did not, and, in fact, inhibited the Cdx1 effects. Functional analysis revealed that Cdx1 transactivates (fourfold, P < 0.05) the IAP promoter through a novel Cdx response element (GTTTAGA) located between -2369 and -2375 upstream of the translational start site. EMSA showed that both Cdx1 and Cdx2 could bind to the cis element, but in cotransfection experiments, Cdx2 inhibited the Cdx1 effects by approximately 50%. Thus we have identified a previously unrecognized interaction between two important gut transcription factors, Cdx1 and Cdx2, in the context of IAP gene regulation. Cdx1 activates the IAP gene via a novel cis element, whereas Cdx2 inhibits the Cdx1 effects.

PKA independent and cell type specific activation of the expression of caudal homeobox gene Cdx-2 by cyclic AMP

Cdx-2 is a transactivator for the proglucagon gene in pancreatic and intestinal endocrine cells. Cdx-2 is also expressed in differentiated intestinal epithelia of nonendocrine origin. Cdx-2-/- mice are embryonic lethal, while Cdx-2+/- mutants show multiple malfunctions including the formation of intestinal polyps. Within the polyps, the remaining wild type Cdx-2 allele ceases its expression, while the expression of both Cdx-2 and proglucagon in the endocrine cells remains unaltered, indicating that Cdx-2 could be haplo-insufficient for nonendocrine cells, but not for proglucagon producing endocrine cells. We propose that mechanisms underlying Cdx-2 expression and auto-regulation [Xu F, Li H & Jin T (1999), J Biol Chem274, 34310-34316] differ in these two types of cells. We show here that forskolin and cAMP upregulate Cdx-2 expression in proglucagon producing cells, but not in colon cancer cells and primary intestinal cell cultures. It is unlikely that the activation is mainly mediated by PKA, because the activation was observed in a PKA deficient cell line. Co-transfecting a dominant negative Ras expression plasmid substantially repressed the Cdx-2 promoter, in contrast to a previous finding that Ras is a negative factor for Cdx-2 expression in colon cancer cells. Furthermore, forskolin activated ERK1/2 phosphorylation in the endocrine cells, and attenuation of ERK1/2 phosphorylation by its inhibitor is associated with attenuated Cdx-2 expression. Finally, an Epac pathway specific cAMP analogue stimulated both ERK1/2 phosphorylation and Cdx-2 expression. Taken together, our observations suggest that Cdx-2 expression is regulated by the second messenger cAMP, cell-type specifically, via the Epac pathway.

Transcriptional regulation of the human DNA methyltransferase 3A and 3B genes by Sp3 and Sp1 zinc finger proteins

The DNMT3A (DNA methyltransferase 3A) and DNMT3B genes encode putative de novo methyltransferases and show complex transcriptional regulation in the presence of three and two different promoters respectively. All promoters of DNMT3A and DNMT3B lack typical TATA sequences adjacent to their transcription start sites and contain several Sp1-binding sites. The importance of these Sp1-binding sites was demonstrated by using a GC-rich DNA-binding protein inhibitor, mithramycin A, i.e. on the basis of decrease in the promoter activities and mRNA expression levels of DNMT3A and DNMT3B. Overexpression of Sp1 and Sp3 up-regulated the promoter activities of these two genes. The physical binding of Sp1 and Sp3 to DNMT3A and DNMT3B promoters was confirmed by a gel shift assay. Interestingly, Sp3 overexpression in HEK-293T cells (human embryonic kidney 293T cells) resulted in 3.3- and 4.0-fold increase in DNMT3A and DNMT3B mRNA expression levels respectively by quantitative reverse transcriptase-PCR, whereas Sp1 overexpression did not. Furthermore, an antisense oligonucleotide to Sp3 significantly decreased the mRNA levels of DNMT3A and DNMT3B. These results indicate the functional importance of Sp proteins, particularly Sp3, in the regulation of DNMT3A and DNMT3B gene expression.

Immunohistochemically detectable Cdx2 is present in intestinal phenotypic elements in early gastric cancers of both differentiated and undifferentiated types, with no correlation to non-neoplastic surrounding mucosa

It has previously been reported that Cdx2 is the useful prognostic and intestinal phenotypic marker in advanced gastric cancers (GC). In this study, Cdx2 expression and phenotype in early GC and non-neoplastic surrounding mucosa were examined. A total of 130 early GC (70 intramucosal and 60 submucosally invasive cancers) histologically and phenotypically were evaluated. The expression of Cdx2 was assessed by immunohistochemistry. The lesions were phenotypically divided into 44 gastric (G), 42 gastric and intestinal mixed (GI), 30 intestinal (I), and 14 null (N) types, independent of the histological classification. Most of the early GC were Cdx2-positive, nuclear staining being strongly associated with intestinal phenotypic expression. Early differentiated cancers tended to feature both Cdx2 and intestinal phenotypic expression, while their undifferentiated counterparts were more likely to demonstrate only gastric phenotypic expression (P < 0.05). The phenotypes of six intramucosal microcarcinomas did not correlate with those of adjacent normal glands. These data suggest that Cdx2 is expressed in the very early stage of gastric carcinogenesis in association with the shift from gastric to intestinal phenotypic expression. This appears to occur in differentiated cancers at an earlier stage than in undifferentiated ones, and may be linked to suppression of expansion of malignant cells.

Cdx1 inhibits human colon cancer cell proliferation by reducing beta-catenin/T-cell factor transcriptional activity

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 beta-catenin/T-cell factor (TCF) transcriptional activity. We report that Cdx1 or Cdx2 expression does inhibit beta-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 beta-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 beta-catenin, suggesting that Cdx1 does not support beta-catenin-mediated transformation. Finally, we show that colon cancer cells effectively reduce Cdx2-mediated inhibition of Wnt/beta-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 beta-catenin signaling and proliferation. We conclude that Cdx1 and Cdx2 inhibit colon cancer cell proliferation by blocking beta-catenin/TCF transcriptional activity.

Cell and molecular biology of the small intestine: new insights into differentiation, growth and repair

PURPOSE OF REVIEW

This paper will discuss recent research that has provided new insights into the molecular and cell biology of the small intestine.

RECENT FINDINGS

Differentiation of the epithelial cell lineages, including the enterocytes, enteroendocrine, Goblet and Paneth cells, from the stem cells is better understood. Important interactions have been demonstrated between these cells, luminal bacteria, and underlying mesenchymal tissue. Intestine-specific gene expression is regulated by transcription factors that are becoming well characterized, including CDX1, CDX2 and HNF1. The actions of growth factors such as GLP-2 and EGF are now known to be complex, demonstrating multiple effects in this tissue at a number of levels.

SUMMARY

Progress in the cellular and molecular biology of the small intestine is producing many intriguing new findings.