CDX2 polymorphisms, RNA expression, and risk of colorectal cancer

Potential predictors for CDX2 expression loss and mismatch repair deficiency in colorectal cancer

CDX2 expression loss is commonly associated with mismatch repair deficiency (dMMR) in colorectal cancer (CRC). However, there are only a few studies that have attempted to correlate CDX2 expression loss with specific MMR genes (MLH1, MSH2, MSH6, PMS2). This is a retrospective study of 327 patients who underwent surgery due to CRC. Nine patients (2.9%) had two synchronous CRCs, making the total sample 336 CRC. Histopathological data such as tumor type, tumor grade, perineural, lymphatic, and vascular invasion, pT stage, pN stage, peritumoral and intratumoral lymphocytic infiltration were collected and recorded in the database. After immunohistochemical analysis, CDX2 expression, MLH1, MSH2, MSH6, and PMS2 deficiency were also recorded. CDX2 expression loss was detected in 19 out of 336 CRCs (5.9%) and was associated with ascending colon CRC, partially mucinous adenocarcinoma, poorly differentiated carcinoma, and dMMR. Forty-four (13.1%) of CRCs were dMMR. We found a statistically significant association between CDX2 expression loss and MLH1 and PMS2 deficiency. Considering that most expression phenotypes include pairs of MMR genes, we analyzed MLH1/PMS2 and MSH2/MSH6 as heterodimers. Analysis of heterodimers showed a similar result, namely, that MLH1/PMS2 heterodimer deficiency was significantly associated with CDX2 expression loss. We also constructed a regression model for CDX2 expression loss and for dMMR. Poor tumor differentiation and MLH1/PMS2 heterodimer deficiency have been identified as potential predictors for CDX2 expression loss. CRC in the ascending colon and CDX2 expression loss have been identified as positive potential predictors of dMMR with rectal cancer as negative potential predictor of dMMR. Our study showed a significant association between CDX2 expression loss and MLH1 and PMS2 deficiency in CRC. We also managed to produce a regression model for CDX2 expression and showed that poor tumor differentiation and MLH1/PMS2 heterodimer deficiency are independent factors for CDX2 expression loss. We were the first to include CDX2 expression in a regression model for dMMR and showed that CDX2 expression loss can be used as a predictive factor for dMMR, which should be confirmed by further studies.

CDX-2 Protein and mRNA Expression in Canine Intestinal Adenocarcinoma

Caudal-related homeobox transcription factor 2 (CDX-2) is a specific cell marker employed in the diagnosis of human colorectal cancer. Reduced CDX-2 expression is associated with several indicators of poor prognosis in human colorectal cancer. In the present study, CDX-2 protein levels were evaluated and patterns of CDX-2 mRNA accumulation are described for the first time in canine intestinal adenocarcinoma (CIA). Canine intestinal epithelial biopsies from 21 CIAs and 14 non-neoplastic control tissues were retrospectively evaluated for CDX-2 expression and CDX-2 mRNA levels by immunohistochemistry and RNA in-situ hybridization (RNA-ISH), respectively. The mean percentage or intensity of expression was decreased in the CIA group (P = 0.000). RNA-ISH demonstrated a significant correlation between the decrease in CDX-2 mRNA levels and CDX-2 protein expression (P = 0.000). CDX-2 downregulation, in terms of protein as well as mRNA levels, may serve as a diagnostic marker in CIA.

The role of transcription factor caudal-related homeobox transcription factor 2 in colorectal cancer

Colorectal cancer (CRC) is one of the most malignant tumors in humans and causes mass mortality. In the age of precise medicine, more and more subtypes of CRC were classified. The caudal-related homeobox transcription factor 2 (CDX2) is an intestine-specific transcription factor which is implicated in differentiation, proliferation, cell-adhesion, and migration. The loss of CDX2 in immunohistochemical stain was reported to be a prognostic factor of colon cancer, but the clinical application remained controversial. Most of the CRCs expressed or over-expressed CDX2. Homeobox genes can display either an oncogenic or a tumor-suppressing activity. CDX2 regulates the developing intestinal epithelium and CRC by different pathways. The complex regulation of CDX2 and its complex targets cause the difficulties of application for CDX2 in the prediction of prognosis. However, CDX2 is a potential biomarker applied in the precise classification of CRC for personalized medicine. This review partially clarifies the role of CDX2 in CRC.

Are Colon and Rectal Cancer Two Different Tumor Entities? A Proposal to Abandon the Term Colorectal Cancer

Colon cancer (CC) and rectal cancer (RC) are synonymously called colorectal cancer (CRC). Based on our experience in basic and clinical research as well as routine work in the field, the term CRC should be abandoned. We analyzed the available data from the literature and results from our multicenter Research Group Oncology of Gastrointestinal Tumors termed FOGT to confirm or reject this hypothesis. Anatomically, the risk of developing RC is four times higher than CC, while physical activity helps to prevent CC but not RC. Obvious differences exist in molecular carcinogenesis, pathology, surgical topography and procedures, and multimodal treatment. Therefore, we conclude that CC is not the same as RC. The term "CRC" should no longer be used as a single entity in basic and clinical research as well as other areas of classification.

Loss of CDX2 expression is associated with poor prognosis in colorectal cancer patients

AIM: To investigate the clinicopathologic characteristics and prognostic implications associated with loss of CDX2 expression in colorectal cancers (CRCs).

METHODS: We immunohistochemically evaluated CDX2 expression in 713 CRCs and paired our findings to clinicopathologic and molecular characteristics of each individual. Endpoints included cytokeratin 7 and CK20 expression, microsatellite instability, CpG island methylator phenotype, and KRAS and BRAF mutation statuses. Univariate and multivariate survival analysis was performed to reveal the prognostic value of CDX2 downregulation.

RESULTS: CDX2 expression was lost in 42 (5.9%) patients. Moreover, loss of CDX2 expression was associated with proximal location, infiltrative growth, advanced T, N, M and overall stage. On microscopic examination, loss of CDX2 expression was associated with poor differentiation, increased number of tumor-infiltrating lymphocytes, luminal serration and mucin production. Loss of CDX2 expression was also associated with increased CK7 expression, decreased CK20 expression, CpG island methylator phenotype, microsatellite instability and BRAF mutation. In a univariate survival analysis, patients with loss of CDX2 expression showed worse overall survival (P < 0.001) and progression-free survival (P < 0.001). In a multivariate survival analysis, loss of CDX2 expression was an independent poor prognostic factor of overall survival [hazard ratio (HR) = 1.72, 95%CI: 1.04-2.85, P = 0.034] and progression-free survival (HR = 1.94, 95%CI: 1.22-3.07, P = 0.005).

CONCLUSION: Loss of CDX2 expression is associated with aggressive clinical behavior and can be used as a prognostic marker in CRCs.

The clinical perspectives of CDX2 expression in colorectal cancer: a qualitative systematic review

INTRODUCTION

Homeobox genes are often deregulated in cancer. They can have both oncogenic and tumor-suppressing potential. The Caudal-related homeobox transcription factor 2 (CDX2) is an intestine-specific transcription factor. It is implicated in differentiation, proliferation, cell-adhesion, and migration. CDX2 has been proposed as a tumor suppressor in colorectal cancer but its role is still controversial. This systematic review were undertaken in order to clarify CDX2s role in colorectal cancer.

METHODS

A literature search was performed in the MEDLINE database from 1966 to February 2014. Only studies in which all or a part of the experimental design were performed on human colorectal cancer tissue were included. Thus, studies solely performed in cell-lines or animal models were excluded.

RESULTS

Fifty-two articles of relevance were identified. CDX2 expression was rarely lost in colorectal cancers, however the expression pattern may often be heterogeneous within the tumor and can be selectively down regulated at the invasive front and in tumor buddings. Loss of CDX2 expression is probably correlated to tumor grade, stage, right-sided tumor location, MMR-deficiency, CIMP, and BRAF mutations. The CDX2 gene is rarely mutated but the locus harboring the gene is often amplified and may suggest CDX2 as a linage-survival oncogene. CDX2 might be implicated in cell proliferation and migration through cross-talk with the Wnt-signaling pathway, tumor-stroma proteins, and inflammatory cytokines.

CONCLUSION

A clear role for CDX2 expression in colorectal cancer remains to be elucidated, and it might differ in relation to the underlying molecular pathways leading to the cancer formation.

Molecular mechanisms of Barrett's esophagus

Barrett's esophagus (BE) is defined as the metaplastic conversion of esophageal squamous epithelium to intestinalized columnar epithelium. As a premalignant lesion of esophageal adenocarcinoma (EAC), BE develops as a result of chronic gastroesophageal reflux disease (GERD). Many studies have been conducted to understand the molecular mechanisms of this disease. This review summarizes recent results involving squamous and intestinal transcription factors, signaling pathways, stromal factors, microRNAs, and other factors in the development of BE. A conceptual framework is proposed to guide future studies. We expect elucidation of the molecular mechanisms of BE to help in the development of improved management of GERD, BE, and EAC.

Gene expression differences between colon and rectum tumors

PURPOSE

Colorectal cancer studies typically include both colon and rectum tumors as a common entity, though this assumption is controversial and only minor differences have been reported at the molecular and epidemiologic level. We conducted a molecular study based on gene expression data of tumors from colon and rectum to assess the degree of similarity between these cancer sites at transcriptomic level.

EXPERIMENTAL DESIGN

A pooled analysis of 460 colon tumors and 100 rectum tumors from four data sets belonging to three independent studies was conducted. Microsatellite instable tumors were excluded as these are known to have a different expression profile and have a preferential proximal colon location. Expression differences were assessed with linear models, and significant genes were identified using adjustment for multiple comparisons.

RESULTS

Minor differences at a gene expression level were found between tumors arising in the proximal colon, distal colon, or rectum. Only several HOX genes were found to be associated with tumor location. More differences were found between proximal and distal colon than between distal colon and rectum.

CONCLUSIONS

Microsatellite stable colorectal cancers do not show major transcriptomic differences for tumors arising in the colon or rectum. The small but consistent differences observed are largely driven by the HOX genes. These results may have important implications in the design and interpretation of studies in colorectal cancer.

Comprehensive analysis of CpG island methylator phenotype (CIMP)-high, -low, and -negative colorectal cancers based on protein marker expression and molecular features

CpG island methylator phenotype (CIMP) is being investigated for its role in the molecular and prognostic classification of colorectal cancer patients but is also emerging as a factor with the potential to influence clinical decision-making. We report a comprehensive analysis of clinico-pathological and molecular features (KRAS, BRAF and microsatellite instability, MSI) as well as of selected tumour- and host-related protein markers characterizing CIMP-high (CIMP-H), -low, and -negative colorectal cancers. Immunohistochemical analysis for 48 protein markers and molecular analysis of CIMP (CIMP-H: ≥ 4/5 methylated genes), MSI (MSI-H: ≥ 2 instable genes), KRAS, and BRAF were performed on 337 colorectal cancers. Simple and multiple regression analysis and receiver operating characteristic (ROC) curve analysis were performed. CIMP-H was found in 24 cases (7.1%) and linked (p < 0.0001) to more proximal tumour location, BRAF mutation, MSI-H, MGMT methylation (p = 0.022), advanced pT classification (p = 0.03), mucinous histology (p = 0.069), and less frequent KRAS mutation (p = 0.067) compared to CIMP-low or -negative cases. Of the 48 protein markers, decreased levels of RKIP (p = 0.0056), EphB2 (p = 0.0045), CK20 (p = 0.002), and Cdx2 (p < 0.0001) and increased numbers of CD8+ intra-epithelial lymphocytes (p < 0.0001) were related to CIMP-H, independently of MSI status. In addition to the expected clinico-pathological and molecular associations, CIMP-H colorectal cancers are characterized by a loss of protein markers associated with differentiation, and metastasis suppression, and have increased CD8+ T-lymphocytes regardless of MSI status. In particular, Cdx2 loss seems to strongly predict CIMP-H in both microsatellite-stable (MSS) and MSI-H colorectal cancers. Cdx2 is proposed as a surrogate marker for CIMP-H.

Right-side and left-side colon cancer follow different pathways to relapse

There is growing evidence that cancer of the ascending (right-side) colon is different from cancer of the descending (left-side) colon at the molecular level. Using microarray data from 102 right-side colon carcinomas and 95 left-side colon carcinomas we show that different pathways dominate progression to relapse in right-side and left-side colon cancer. Right-side tumors at a high risk for relapse exhibit elevated expression of cell cycle control genes and elevated Wnt signaling. On the other hand, relapse-prone left-side tumors show elevated expression of genes that promote stromal expansion and reduced expression of tumor suppressor genes that initiate Wnt signaling. Single gene prognostic biomarkers are found separately for right-side and left-side disease. In left-side tumors with low expression levels of NADPH oxidase 4 (NOX4) the 5-yr relapse-free survival probability is 0.89 95% CI (0.80-0.99), and in tumors with elevated NOX4 expression the probability is 0.51 95% CI (0.37-0.70). Right-side tumors with elevated expression levels of caudal type homeobox 2 (CDX2) have a 5-yr relapse-free survival probability of 0.88 95% CI (0.80-0.96), and those with low CDX2 expression have a corresponding probability of 0.39 95% CI (0.15-0.78). Both NOX4 and CDX2 are much less prognostic on the opposite sides. This newly identified role of NOX4 in colon cancer is further investigated using the SW620 lymph node metastasis colon adenocarcinoma cell line and RNA interference. We show that NOX4 is expressed in the SW620 cell line and that application of NOX4 siRNA causes a significant reduction in reactive oxidative species production.

Vitamin D receptor polymorphisms in patients with cutaneous melanoma

The vitamin D receptor (VDR) gene has been associated with cancer risk, but only a few polymorphisms have been studied in relation to melanoma risk and the results have been inconsistent. We examined 38 VDR gene single nucleotide polymorphisms (SNPs) in a large international multicenter population-based case-control study of melanoma. Buccal DNAs were obtained from 1,207 people with incident multiple primary melanoma and 2,469 with incident single primary melanoma. SNPs with known or suspected impact on VDR activity, haplotype tagging SNPs with ≥ 10% minor allele frequency in Caucasians, and SNPs reported as significant in other association studies were examined. Logistic regression was used to calculate the relative risks conferred by the individual SNP. Eight of 38 SNPs in the promoter, coding, and 3' gene regions were individually significantly associated with multiple primary melanoma after adjusting for covariates. The estimated increase in risk for individuals who were homozygous for the minor allele ranged from 25 to 33% for six polymorphisms: rs10875712 (odds ratios [OR] 1.28; 95% confidence interval (CI), 1.01-1.62), rs4760674 (OR 1.33; 95% CI, 1.06-1.67), rs7139166 (OR 1.26; 95%CI, 1.02-1.56), rs4516035 (OR 1.25; 95%CI, 1.01-1.55), rs11168287 (OR 1.27; 95%CI, 1.03-1.57) and rs1544410 (OR 1.30; 95%CI, 1.04-1.63); for two polymorphisms, homozygous carriers had a decreased risk: rs7305032 (OR 0.81; 95%CI 0.65-1.02) and rs7965281 (OR, 0.78; 95%CI, 0.62-0.99). We recognize the potential false positive findings because of multiple comparisons; however, the eight significant SNPs in our study outnumbered the two significant tests expected to occur by chance. The VDR may play a role in melanomagenesis.

Double primary adenocarcinomas of the jejunum and descending colon with lung metastases presenting rare immunohistochemical phenotypes: a case report

We report a male patient with double advanced tumors in the jejunum and descending colon and multiple lung tumors. The intestinal cancers were surgically resected. Immunoprofiling of the specimens revealed a rare phenotype: the jejunal cancer was positive for cytokeratin (CK) 7, partially positive for CK20, and Cdx-2-negative, whereas the colon cancer was CK7(+), CK20(-), and Cdx-2(-). Biopsied lung tumor was diagnosed as tubular adenocarcinoma, and CK7(+)/CK20(+)/Cdx-2(-). Together with clinical information, we deduced that the jejunal adenocarcinoma had presumably metastasized to the lung. Moreover, postoperative oxaliplatin, including chemotherapy, significantly reduced the lung metastases, suggesting that this regimen is a promising treatment option for advanced small bowel adenocarcinoma.

Relationship of CDX2 loss with molecular features and prognosis in colorectal cancer

PURPOSE

The homeodomain transcription factor CDX2 is a relatively specific immunohistochemical marker for gastrointestinal carcinoma. However, no study has comprehensively examined the relationship between CDX2 expression in colon cancer and clinical, pathologic, prognostic, and molecular features, including microsatellite instability and CpG island methylator phenotype (CIMP).

EXPERIMENTAL DESIGN

Utilizing 621 colorectal cancers with clinical outcome and molecular data, CDX2 loss was detected in 183 (29%) tumors by immunohistochemistry.

RESULTS

In multivariate logistic regression analysis, CDX2 loss was associated with female gender [odds ratio (OR), 3.32; P < 0.0001], CIMP-high (OR, 4.42; P = 0.0003), high tumor grade (OR, 2.69; P = 0.0085), stage IV disease (OR, 2.03; P = 0.019), and inversely with LINE-1 hypomethylation (for a 30% decline; OR, 0.33; P = 0.0031), p53 expression (OR, 0.55; P = 0.011), and beta-catenin activation (OR, 0.60; P = 0.037), but not with body mass index, tumor location, microsatellite instability, BRAF, KRAS, PIK3CA, p21, or cyclooxygenase-2. CDX2 loss was not independently associated with patient survival. However, the prognostic effect of CDX2 loss seemed to differ according to family history of colorectal cancer (P(interaction) = 0.0094). CDX2 loss was associated with high overall mortality (multivariate hazard ratio, 2.40; 95% CI, 1.28-4.51) among patients with a family history of colorectal cancer; no such association was present (multivariate hazard ratio, 0.97; 95% CI, 0.66-1.41) among patients without a family history of colorectal cancer.

CONCLUSIONS

CDX2 loss in colorectal cancer is independently associated with female gender, CIMP-high, high-level LINE-1 methylation, high tumor grade, and advanced stage. CDX2 loss may be associated with poor prognosis among patients with a family history of colorectal cancer.

Relationship of CDX2 loss with molecular features and prognosis in colorectal cancer

PURPOSE

The homeodomain transcription factor CDX2 is a relatively specific immunohistochemical marker for gastrointestinal carcinoma. However, no study has comprehensively examined the relationship between CDX2 expression in colon cancer and clinical, pathologic, prognostic, and molecular features, including microsatellite instability and CpG island methylator phenotype (CIMP).

EXPERIMENTAL DESIGN

Utilizing 621 colorectal cancers with clinical outcome and molecular data, CDX2 loss was detected in 183 (29%) tumors by immunohistochemistry.

RESULTS

In multivariate logistic regression analysis, CDX2 loss was associated with female gender [odds ratio (OR), 3.32; P < 0.0001], CIMP-high (OR, 4.42; P = 0.0003), high tumor grade (OR, 2.69; P = 0.0085), stage IV disease (OR, 2.03; P = 0.019), and inversely with LINE-1 hypomethylation (for a 30% decline; OR, 0.33; P = 0.0031), p53 expression (OR, 0.55; P = 0.011), and beta-catenin activation (OR, 0.60; P = 0.037), but not with body mass index, tumor location, microsatellite instability, BRAF, KRAS, PIK3CA, p21, or cyclooxygenase-2. CDX2 loss was not independently associated with patient survival. However, the prognostic effect of CDX2 loss seemed to differ according to family history of colorectal cancer (P(interaction) = 0.0094). CDX2 loss was associated with high overall mortality (multivariate hazard ratio, 2.40; 95% CI, 1.28-4.51) among patients with a family history of colorectal cancer; no such association was present (multivariate hazard ratio, 0.97; 95% CI, 0.66-1.41) among patients without a family history of colorectal cancer.

CONCLUSIONS

CDX2 loss in colorectal cancer is independently associated with female gender, CIMP-high, high-level LINE-1 methylation, high tumor grade, and advanced stage. CDX2 loss may be associated with poor prognosis among patients with a family history of colorectal cancer.

Gene expression patterns in mismatch repair-deficient colorectal cancers highlight the potential therapeutic role of inhibitors of the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway

PURPOSE

High-frequency microsatellite-instable (MSI-H) tumors account for approximately 15% of colorectal cancers. Therapeutic decisions for colorectal cancer are empirically based and currently do not emphasize molecular subclassification despite an increasing collection of gene expression information. Our objective was to identify low molecular weight compounds with preferential activity against MSI colorectal cancers using combined gene expression data sets.

EXPERIMENTAL DESIGN

Three expression/query signatures (discovery data set) characterizing MSI-H colorectal cancer were matched with information derived from changes induced in cell lines by 164 compounds using the systems biology tool "Connectivity Map." A series of sequential filtering and ranking algorithms were used to select the candidate compounds. Compounds were validated using two additional expression/query signatures (validation data set). Cytotoxic, cell cycle, and apoptosis effects of validated compounds were evaluated in a panel of cell lines.

RESULTS

Fourteen of the 164 compounds were validated as targeting MSI-H cell lines using the bioinformatics approach; rapamycin, LY-294002, 17-(allylamino)-17-demethoxygeldanamycin, and trichostatin A were the most robust candidate compounds. In vitro results showed that MSI-H cell lines due to hypermethylation of MLH1 are preferentially targeted by rapamycin (18.3 versus 4.4 mumol/L; P = 0.0824) and LY-294002 (15.02 versus 10.37 mumol/L; P = 0.0385) when compared with microsatellite-stable cells. Preferential activity was also observed in MSH2 and MSH6 mutant cells.

CONCLUSION

Our study shows that the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathway is of special relevance in mismatch repair-deficient colorectal cancer. In addition, we show that amalgamation of gene expression information across studies provides a robust approach for selection of potential therapies corresponding to specific groups of patients.

PI3KCA/PTEN deregulation contributes to impaired responses to cetuximab in metastatic colorectal cancer patients

BACKGROUND

It has been reported that KRAS mutations (and to a lesser extent KRAS mutations with the BRAF V600E mutation) negatively affect response to anti-epidermal growth factor receptor (EGFR) mAbs in metastatic colorectal cancer (mCRC) patients, while the biological impact of the EGFR pathway represented by PI3K/PTEN/AKT on anti-EGFR treatment is still not clear.

PATIENTS AND METHODS

We analysed formalin-fixed samples from a cohort of 32 mCRC patients treated with cetuximab by means of EGFR immunohistochemistry, EGFR and PTEN FISH analysis, and KRAS, BRAF, PI3KCA, and PTEN genomic sequencing.

RESULTS

Ten (31%) of 32 patients showed a partial response to cetuximab and 22 (69%) did not [nonresponder (NR)]. EGFR immunophenotype and FISH-based gene status did not predict an anti-EGFR mAb response, whereas KRAS mutations (24%) and PI3K pathway activation, by means of PI3KCA mutations (13%) or PTEN mutation (10%)/loss (13%), were significantly restricted to, respectively, 41% and 37% of NRs.

CONCLUSION

These findings suggested that KRAS mutations and PI3KCA/PTEN deregulation significantly correlate with resistance to cetuximab. In line with this, patients carrying KRAS mutations or with activated PI3K profiles can benefit from targeted treatments only by switching off molecules belonging to the downstream signalling of activated EGFR, such as mammalian target of rapamycin.

Biology of intestinal metaplasia in 2008: more than a simple phenotypic alteration

This review concentrates on one main aspect of cancerization in the oesophagus and stomach: principally, intestinal metaplasia. There are at least two other important pathways that lead to cancer and do not need such a morphological transformation. One is the gastric type of carcinoma on the Lauren classification, which arises directly from the stem cell zone and is the signet ring form of cancer, while the other is spasmolytic polypeptide-expressing metaplasia (SPEM)--spasmolytic polypeptide (TFF2) expressing metaplasia, where the gastric glands become filled with TFF2-expressing cells and may also lead to gastric dysplasia and cancer. The development of intestinal metaplasia is complex. Here, we examine intestinal metaplasia in molecular terms, noting the over-expression of Cdx1, Cdx2, Pdx1, Oct1, TFF3 and the downregulation of Hedgehog signalling; Runx3 is deactivated by epigenetic silencing, and pathways such as Wnt and MARK/ERK are involved. These changes start to explain the principles of the development of intestinal metaplasia and suggest that the regulation of these genes is of importance in the development of gastric cancer.

Epigenetic silencing of CDX2 is a feature of squamous esophageal cancer

CDX2, a mammalian homologue of the homeobox gene 'caudal,' is expressed in gut epithelia and plays an important role in establishing the intestinal phenotype during development. Mice heterozygously disrupted for CDX2 develop disorganized polypoid hamartomas with glandular epithelium and stratified squamous metaplasia resembling foregut mucosa. Since no genetic disruptions of CDX2 have been reported to explain loss of gene function, we examined whether epigenetic mechanisms altered CDX2 expression. Eleven of 17 squamous esophageal cancer cell lines lacked expression of CDX2 that was restored following treatment with 5-aza-2'-deoxycytidine, while all colorectal cancer cell lines expressed CDX2. Loss of expression was associated with DNA methylation in the 5' region of CDX2 determined by methylation specific PCR and bisulfite sequencing. Methylation of CDX2 was rare in primary colorectal (1 of 44 tumors, 2%) and esophageal adenocarcinoma neoplasms (2 of 43 tumors, 5%), but was common in esophageal squamous carcinoma (24 of 45 tumors, 49%). No CDX2 methylation was found in normal tissues. Using semi-quantitative RT-PCR, expression of CDX2 was found in low level in normal esophagus, at higher levels in primary adenocarcinoma of the esophagus, but not in primary squamous cancers of the esophagus. Restoration of CDX2 in silenced cell lines resulted in expression of the CDX2 target gene MUC2, a gene important in glandular differentiation. Our results suggest that the inactivation of CDX2 in esophageal cancer associated with DNA methylation may be an important determinant of the squamous or non-adenomatous phenotype.

Vitamin D receptor genotypes/haplotypes and prostate cancer risk

The vitamin D receptor (VDR) gene has been associated with prostate cancer, although previous results are somewhat equivocal. To further study this, we did a family-based case-control study (N = 918) of the association between prostate cancer and six common VDR variants: Cdx2, FokI, BsmI, ApaI, TaqI, and the poly-A microsatellite. Looking at each variant alone, only FokI and ApaI were associated with disease. The FokI FF genotype was inversely associated with prostate cancer among men with less advanced disease (i.e., Gleason score <7 and tumor stage <T2c), where the odds ratio OR was 0.56 [95% confidence interval (95% CI), 0.31-1.01; P = 0.05]. ApaI, carrying one or two copies of the A allele, exhibited a weak inverse association with disease (OR, 0.64; 95% CI, 0.39-1.03; P = 0.06); this association was strengthened in Caucasian men with more advanced disease (OR, 0.44; 95% CI, 0.21-0.93; P = 0.03). We observed inverse associations between disease and the four-locus FBAt haplotype (OR, 0.48; 95% CI, 0.30-0.76; P = 0.002) and the fbaT haplotype (OR, 0.60; 95% CI, 0.38-0.95; P = 0.03; i.e., in comparison with the FbaT haplotype). These were stronger among men with more advanced disease: for FBAt, the OR was 0.31 (95% CI, 0.16-0.61; P = 0.0008); for fbaT, the OR was 0.32 (95% CI, 0.16-0.64; P = 0.001). These observations support a role for VDR variants in prostate cancer risk but suggest that any potential causal variant(s) may reside on the haplotypes reported here. This would help explain the somewhat equivocal results for VDR genotype-level associations with prostate cancer.

Frequent rearrangements and amplification of the CDX2 homeobox gene in human sporadic colorectal cancers with chromosomal instability

The expression of the CDX2 gene, a crucial regulator of gut homeostasis, is altered in human colorectal cancers in parallel with de-differentiation. Here, we have investigated the chromosomal status of CDX2 in human sporadic colorectal cancers with the phenotype of chromosomal instability. Allelic imbalance determination showed frequent rearrangements at the CDX2 locus. The rearrangements correlated with CDX2 gene amplification, as assessed by quantitative PCR analysis. However, they were not predictive of the Cdx2 protein pattern. These data suggest that mechanisms other than structural alterations at the CDX2 locus account for the change of expression in colorectal cancers.

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.

Molecular models for the tissue specificity of DNA mismatch repair-deficient carcinogenesis

A common feature of all the known cancer genetic syndromes is that they predispose only to selective types of malignancy. However, many of the genes mutated in these syndromes are ubiquitously expressed, and influence seemingly universal processes such as DNA repair or cell cycle control. The tissue specificity of cancers that arise from malfunction of these apparently universal traits remains a key puzzle in cancer genetics. Mutations in DNA mismatch repair (MMR) genes cause the most common known cancer genetic syndrome, hereditary non-polyposis colorectal cancer, and the fundamental biology of MMR is one of the most intensively studied processes in laboratories all around the world. This review uses MMR as a model system to understand mechanisms that may explain the selective development of tumors in particular cell types despite the universal nature of this process. We evaluate recent data giving insights into the specific tumor types that are attributable to defective MMR in humans and mice under different modes of inheritance, and propose models that may explain the spectrum of cancer types observed.