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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Clin Cancer Res. Author manuscript; available in PMC Jul 15, 2010.
Published in final edited form as:
PMCID: PMC2777758
NIHMSID: NIHMS122287

Relationship of CDX2 Loss with Molecular Features and Prognosis in Colorectal Cancer: Implications for Clinical and Pathology Practice

Abstract

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 (MSI) 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), β-catenin activation (OR=0.60; p=0.037), but not with body mass index, tumor location, MSI, BRAF, KRAS, PIK3CA, p21 or COX-2. CDX2 loss was not independently associated with patient survival. However, the prognostic effect of CDX2 loss appeared to differ according to family history of colorectal cancer (Pinteraction=0.0094). CDX2 loss was associated with high overall mortality [multivariate hazard ratio (HR)=2.40; 95% CI, 1.28–4.51] among patients with a family history of colorectal cancer; no such association was present (multivariate HR=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.

Keywords: colon cancer, CDX2, CIMP, family history, prognosis

INTRODUCTION

The Caudal-related homeodomain transcription factor CDX2 regulates development and differentiation of intestinal epithelium (1). Immunohistochemical detection of CDX2 expression is clinically useful as a relatively specific marker for epithelial neoplasms of the gastrointestinal tract, particularly colon and rectum (25). Different lines of evidence suggest that CDX2 may suppress colorectal tumorigenesis (69) and CDX2 expression is often lost in colorectal cancers with high tumor grade, advanced tumor stage or microsatellite instability (MSI-high) (10, 11). Since colorectal cancer represents a heterogeneous group of tumors with diverse genetic/epigenetic signatures (12), the frequency of CDX2 loss likely depends on clinical and molecular features of colorectal cancer. Understanding features associated with CDX2 loss is crucially important in clinical and pathology practice. No previous study has comprehensively examined clinical, pathological and molecular features that influence the frequency of CDX2 expression (i.e., sensitivity of CDX2 testing) in colorectal cancer.

Promoter CpG island methylation is an important mechanism for silencing tumor suppressor genes in the carcinogenic process (13). A subset of colorectal cancers exhibits widespread promoter CpG island methylation, referred to as the CpG island methylator phenotype (CIMP) (14). CIMP-high colorectal cancers are associated with female gender, proximal tumor location, high tumor grade, MSI-high, BRAF mutation, and inactive WNT/β-catenin (1517). MSI and CIMP status reflect global genomic and epigenomic aberrations in tumor cells and influence clinical, pathologic and molecular characteristics of colorectal cancer (12). Thus, a molecular classification based on MSI and CIMP status is increasingly important (12, 18). However, no prior study has examined CDX2 expression in relation to CIMP or deciphered independent relationship of CDX2 loss with clinical, pathologic and molecular variables in colorectal cancer.

Utilizing a database of 621 colorectal cancers, we therefore examined CDX2 expression in relation to patient survival and molecular features such as MSI, CIMP and LINE-1 methylation. We have found that CDX2 loss is independently associated with CIMP and high-level LINE-1 methylation. In addition, we have found a possible modifying effect of family history on the relation between CDX2 loss and patient survival.

MATERIALS AND METHODS

Study group

We utilized the databases of two independent, prospective cohort studies; the Nurses’ Health Study (N = 121,701 women followed since 1976) (19), and the Health Professional Follow-up Study (N = 51,529 men followed since 1986) (19). Every 2 years, participants have been sent follow-up questionnaires to update information on potential risk factors and to identify newly diagnosed cancers in themselves and their first degree relatives (father, mother and sibling). We defined a family history as the presence of colorectal cancer in any first-degree relative. We calculated body mass index (BMI, kg/m2) using self-reported height and weight. Study physicians, while blinded to exposure data, reviewed all records related to colorectal cancer, and recorded TNM tumor stage and tumor location. We collected paraffin-embedded tissue blocks from hospitals where patients underwent tumor resections (19). We excluded cases preoperatively treated with radiation and/or chemotherapy. Tissue sections from all colorectal cancer cases were reviewed and confirmed by one of the investigators (S.O.). Based on availability of adequate tissue specimens and results, a total of 621 colorectal cancers (diagnosed up to 2003) were included. For survival analysis, we excluded the patients with any cancer at baseline and the patients with no follow-up data, resulting in analysis of 598 patients. Among our cohort studies, there was no significant difference in demographic features between cases with tissue available and those without available tissue (19). This current analysis represents a new analysis of CDX2 on the existing colorectal cancer database that has been previously characterized for CIMP, MSI, LINE-1 methylation and clinical outcome (1922), which is analogous to novel studies using the well-described cell lines or animal models. We have not examined CDX2 expression or the relationship between CDX2 and clinical outcome or other molecular events in any of our previous studies. Written informed consent was obtained from all study subjects. Tissue collection and analyses were approved by the Harvard School of Public Health and Brigham and Women’s Hospital Institutional Review Boards.

Measurement of mortality

Patients were observed until death or June 30, 2006, whichever came first. Ascertainment of deaths included reporting by the family or postal authorities. In addition, the names of persistent nonresponders were searched in the National Death Index. More than 98% of deaths in the cohorts were identified by these methods. The cause of death was assigned by physicians blinded to information on lifestyle exposures and molecular features in colorectal cancer.

Histopathologic evaluations

Hematoxylin and eosin (H&E) stained tissue sections were examined by one of the investigators (S.O.) unaware of other data. The tumor grade was categorized as low (≥50% gland formation) vs. high (<50% gland formation). The presence and extent of extracellular mucin were categorized as 0% (no mucin), 1–49% or ≥50% of the tumor volume. The presence and extent of signet ring cells were categorized as absent (0%) or present (>0%).

Sequencing of KRAS, BRAF and PIK3CA and microsatellite instability (MSI) analysis

Genomic DNA was extracted from tumor and PCR and Pyrosequencing targeted for KRAS (codons 12 and 13) (23), BRAF (codon 600) (24) and PIK3CA (exons 9 and 20) (25) were performed as previously described. MSI analysis was performed, using 10 microsatellite markers (D2S123, D5S346, D17S250, BAT25, BAT26, BAT40, D18S55, D18S56, D18S67 and D18S487) (26). MSI-high was defined as the presence of instability in ≥30% of the markers. MSI-low was defined as instability in 10–29% of the markers, and “microsatellite stable” (MSS) tumors were defined as tumors without an unstable marker (26).

Real-time PCR to measure CpG island methylation

Sodium bisulfite treatment on genomic DNA and subsequent real-time PCR (MethyLight) were validated and performed as previously described (27). We quantified DNA methylation in 8 CIMP-specific promoters [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1] (15, 20, 28). CIMP-high was defined as the presence of ≥6 of 8 methylated promoters, CIMP-low as the presence of 1/8–5/8 methylated promoters, and CIMP-0 as the absence (0/8) of methylated promoters, according to the previously established criteria (20).

Pyrosequencing to measure LINE-1 methylation

In order to accurately quantify relatively high methylation levels in LINE-1 repetitive elements, we utilized Pyrosequencing as previously described (22).

Immunohistochemistry for CDX2, p53, p21, β-catenin and COX-2

Tissue microarrays (TMAs) were constructed as previously described (19). Methods of immunohistochemical procedure, interpretation and evaluation were previously described for p53 and P21 (CDKN1A) (29, 30) and β-catenin (17); and COX-2 (cyclooxygenase-2) (19, 26). For CDX2 staining, antigen retrieval was done in 10 mM sodium citrate buffer pH 6.0 in a decloaking chamber (Biocare Medical, Concord, CA) for 2 minutes. Endogenous peroxidases were blocked using 0.03% hydrogen peroxide containing sodium azide for 30 minutes. A primary antibody [mouse monoclonal to CDX2 (CDX2–88), 1:50 dilution; Biogenex Laboratories, San Roman, CA] was applied, and the slides were maintained overnight at 4°C. The remaining procedure was performed using Dako EnVision+ System (DAKO Corporation, Carpinteria, CA). The stained slides were counterstained with hematoxylin and blueing reagent. Nuclear CDX2 expression was recorded as no, weak, moderate or strong expression (Figure 1). CDX2 loss (CDX2 negative expression) was defined as no expression, based on examination of two tissue cores per tumor in TMAs. Appropriate positive and negative controls were included in each run of immunohistochemistry. A whole tissue section of colonic carcinoma known to be CDX2 positive was used as a positive control, and a whole tissue section of colonic carcinoma known to be CDX2 negative was used as a negative control. Each immunohistochemical maker was interpreted by one of the investigators (CDX2 by Y.B.; β-catenin by K.N.; p53, p21 and COX-2 by S.O.) unaware of other data. A random selection of 118 cases was examined for CDX2 by a second observer (K.S.) unaware of other data, and the κ coefficient between the two observers was 0.84 (p<0.0001), indicating substantial agreement. For each of the other immunohistochemical markers, a second observer (S.O. for β-catenin; K.S. for p21; K.N. for p53 and COX-2) examined a random sample of 108–402 tumors, unaware of other data. The κ coefficients between the two observers were 0.65 for β-catenin (p<0.0001; N=402), 0.62 for p21 (p<0.0001; N=179), 0.75 for p53 (p<0.0001; N=118), and 0.62 for COX-2 (p<0.0001; N=108), indicating substantial agreement.

Figure 1
CDX2 expression in normal colonic mucosa and colon cancer

Statistical analysis

All statistical analyses used SAS program (Version 9.1, SAS Institute, Cary, NC). All p values were two-sided, and statistical significance was set at p ≤ 0.05. Nonetheless, p values were conservatively interpreted, considering multiple hypothesis testing. For categorical data, the chi-square test was performed and odds ratio (OR) with 95% confidence interval (CI) was computed. The κ coefficient was calculated to assess an agreement between the two interpreters in immunohistochemical analyses. We also examined the possibility of a non-linear relation between CDX2 loss and LINE-1 methylation, non-parametrically with restricted cubic spines (31). This flexible method allowed us to examine the relation to CDX2 loss without any categorization of LINE-1 methylation level, or without the assumption of a linear relationship of LINE-1 methylation level with CDX2 loss.

To assess independent relations of CDX2 loss with other variables, a multivariate logistic regression analysis was performed. OR was adjusted for sex, age (continuous), body mass index (BMI, <30 vs. ≥30 kg/m2), family history of colorectal cancer (present vs. absent), tumor location (rectum vs. colon), tumor stage (I-III vs. IV), tumor grade (low vs. high), mucinous component (0 vs. ≥1%), signet ring cell component (0 vs. >0%), CIMP status (high vs. low vs. 0), MSI status (high vs. low/MSS), LINE-1 methylation (continuous), BRAF, KRAS, PIK3CA, p53, p21, β-catenin and COX-2. For CIMP (2.9% missing) and tumor grade (3.2% missing), we assigned indicator (“missing”) variables to those cases with missing data, and included those cases in multivariate analysis. For cases missing LINE-1 data (4.0% missing), we assigned the median LINE-1 methylation level. For cases with missing information in other variables [BMI (5.8% missing), tumor location (1.6%), stage (6.1%), MSI (0.8%), BRAF (2.7%), KRAS (0.5%), PIK3CA (11%), p53 (1.1%), p21 (2.6%) and COX-2 (0.5%)], we included those cases in a majority category of the missing variable, in order to minimize the number of indicator variables in multivariate analysis. We confirmed that excluding cases with missing information in any of the covariates did not substantially alter results (data not shown). An interaction was assessed by including the cross product of two variables of interest (without data-missing cases) in a multivariate logistic regression model, and the Wald test was performed.

For survival analysis, Kaplan-Meier method was used to assess survival time distribution according to CDX2 status, and log-rank test was used to test significance of a deviation from the null hypothesis. For analyses of colorectal cancer-specific mortality, death as a result of colorectal cancer was the primary end point and deaths as a result of other causes were censored. To assess independent effect of CDX2 loss on mortality, we constructed a multivariate, stage-matched (stratified) conditional Cox proportional hazard model to compute a hazard ratio (HR) according to CDX2 status, adjusted for sex, age, BMI, family history of colorectal cancer, tumor location, tumor grade, mucinous component, signet ring cell component, CIMP, MSI, BRAF, KRAS, PIK3CA, LINE-1 methylation, p53, p21, β-catenin and COX-2. Tumor stage (I, IIA, IIB, IIIA, IIIB, IIIC, IV, unknown) was used as a stratifying (matching) variable in Cox models. The proportionality of hazard assumption was satisfied by evaluating time-dependent variables, which were the cross-product of the CDX2 variable and survival time (p=0.76 for colon cancer-specific mortality; p=0.91 for overall mortality). For cases with missing data in any of the covariates were dealt as in the multivariate logistic regression analysis described above. An interaction was assessed by including the cross product of the CDX2 variable and another variable of interest (without data-missing cases) in a multivariate Cox model, and the Wald test was performed.

RESULTS

CDX2 loss in relation to clinical, pathologic and molecular features in colorectal cancer

Among 621 colorectal cancers, we observed CDX2 expression in 438 tumors (71%) and CDX2 loss in 183 tumors (29%) by immunohistochemistry (Figure 1). Table 1 shows the frequency of CDX2 loss in relation to various clinical, pathologic and molecular features. CDX2 loss was associated with female gender [odds ratio (OR) 3.33; 95% confidence interval (CI), 2.22–4.98; p<0.0001], proximal location (compared to rectum; OR 4.08; 95% CI, 2.32–7.17; p<0.0001), stage IV (compared to stage I; OR 3.39; 95% CI, 1.87–6.16; p<0.0001), high tumor grade (OR 5.41; 95% CI, 3.03–9.67; p<0.0001), mucinous component (≥50% vs. 0%; OR 2.29; 95% CI, 1.37–3.85; p=0.0014), signet ring cell component (OR 2.54; 95% CI, 1.34–4.80; p=0.0032), CIMP-high (compared to CIMP-0; OR 11.1; 95% CI, 6.47–19.1; p<0.0001), MSI-high (OR 4.39; 95% CI, 2.79–6.91; p<0.0001) and BRAF mutation (OR 5.78; 95% CI, 3.57–9.33; p<0.0001), and inversely associated with KRAS mutation (OR 0.57; 95% CI, 0.39–0.83; p=0.0034), LINE-1 hypomethylation, p53 expression (OR 0.44; 95% CI, 0.30–0.64; p<0.0001), loss of p21 (OR 0.38; 95% CI, 0.25–0.58; p<0.0001), β-catenin activation (OR 0.46; 95% CI, 0.30–0.69; p=0.0002).

Table 1
Frequency of CDX2 loss in colorectal cancer according to clinical, pathologic and molecular features

Relationship between CDX2 loss and LINE-1 hypomethylation

We examined the possibility of a non-linear relationship between LINE-1 hypomethylation and CDX2 loss by using a nonparametric method with restricted cubic splines (31). This flexible method allowed us to evaluate the relationship without predetermined LINE-1 categorization or assumption of a linear relation. The OR for CDX2 loss decreased precipitously as LINE-1 methylation level decreased, indicating an inverse association between LINE-1 hypomethylation and CDX2 loss (Figure 2A).

Figure 2Figure 2
A. Smoothing spline plot for the CDX2 loss / LINE-1 relation, showing odds ratio (OR) for CDX2 loss (y axis) according to LINE-1 methylation level (x axis) with high LINE-1 methylation level as a referent. Hatched lines indicate 95% confidence interval ...

Multivariate analysis to assess independent relations with CDX2 loss

To examine which variables were independently associated with CDX2 loss, we performed multivariate logistic regression analysis (Table 2). CDX2 loss was significantly associated with female gender (OR 3.32; 95% CI, 2.00–5.52; p<0.0001), CIMP-high (vs. CIMP-0; OR 4.42; 95% CI, 1.98–9.86; p=0.0003), and inversely with LINE-1 hypomethylation (for a 30% decline; OR 0.33; 95% CI, 0.16–0.69; p=0.0031). Considering multiple hypothesis testing, any of the associations with p values between 0.05 and 0.005 (including those with CIMP-low, high tumor grade, p53, stage IV and β-catenin) might represent chance events. In multivariate analysis, CDX2 loss was not significantly associated with age, BMI, family history of colorectal cancer, tumor location, mucin, signet ring cells, MSI, KRAS, BRAF, PIK3CA, p21 or COX-2.

Table 2
Multivariate analysis of the relations with CDX2 loss in colorectal cancer

We examined whether the relations of CDX2 loss with any one of the 7 variables listed in Table 2 (sex, CIMP, LINE-1, tumor grade, p53, stage and β-catenin) is influenced by any of the other six. There was no evidence for a significant interaction between any pair among these 7 variables (all p values for interaction >0.11).

Loss of CDX2 expression and patient survival

During follow-up of 598 patients who were eligible for survival analysis, there were 255 deaths, including 156 deaths attributed to colorectal cancer. We assessed the influence of CDX2 loss on patient mortality. In Kaplan-Meier analysis, the 5-year colorectal cancer-specific survival was 68% in patients with CDX2-lost tumors and 80% in patients with CDX2-expressing tumors (log-rank p=0.0010), and the 5-year overall survival was 63% in patients with CDX2-lost tumors and 76% in patients with CDX2-expressing tumors (log-rank p=0.0051) (Figure 2B). In univariate Cox regression analysis, compared to patients with CDX2-expressing tumors, those with CDX2-lost tumors experienced significantly higher colorectal cancer-specific [hazard ratio (HR) 1.71; 95% CI, 1.24–2.36; p=0.0012] and overall (HR 1.44; 95% CI, 1.12–1.87; p=0.0053) mortality (Table 3). In the multivariate Cox model adjusting for potential predictors of patient outcome, CDX2 loss was not significantly associated with cancer-specific mortality (multivariate HR 1.02; 95% CI, 0.65–1.61) or overall mortality (multivariate HR 1.16; 95% CI, 0.82–1.64) (Table 3). Elimination of the prognostic influence of CDX2 loss in multivariate analysis was essentially due to adjusting for tumor stage: when we simply adjusted for tumor stage, adjusted HRs for colorectal cancer-specific mortality and overall mortality were 1.22 (95% CI, 0.87–1.72) and 1.16 (95% CI, 0.88–1.52), respectively. No other major confounder was identified.

Table 3
CDX2 status in colorectal cancer and patient mortality

Modifying effect of family history of colorectal cancer on the relation between CDX2 loss and mortality

We examined whether the prognostic influence of CDX2 loss was modified by any of the variables we examined. We found a significant modifying effect of family history of colorectal cancer on the relation between CDX2 loss and mortality [p for interaction=0.011 (for cancer specific mortality) and p for interaction=0.0094 (for overall mortality)], although this could be a chance event considering multiple hypothesis testing. Among patients with family history of colorectal cancer, CDX2 loss was associated with a significant increase in colorectal cancer-specific mortality in both stage-matched Cox regression analysis (HR 3.06; 95% CI, 1.47–6.34) and multivariate analysis (HR 2.53; 95% CI, 1.13–5.65) (Table 4). In contrast, among patients without family history of colorectal cancer, CDX2 did not appear to be related with prognosis. Similar results were obtained when overall mortality was used as the endpoint (Table 4).

Table 4
CDX2 status in colorectal cancer and patient mortality in strata of family history of colorectal cancer

For any of the other variables including sex, age, BMI, tumor location, stage, grade, mucinous component, signet ring cells, CIMP, MSI, BRAF, KRAS, PIK3CA, LINE-1 methylation, p53, p21, β-catenin and COX-2, we did not observe a significant interaction with CDX2 loss in survival analysis (all p for interaction >0.05).

DISCUSSION

We conducted this study to examine loss of CDX2 expression in colorectal cancer, in relation to clinical, pathologic and molecular features including the CpG island methylator phenotype (CIMP) and patient mortality. CDX2 is used as an immunohistochemical marker to distinguish adenocarcinomas of a colorectal origin from those arising in other organs (25). We have demonstrated that CDX2 loss is independently associated with female gender, CIMP-high and high tumor grade, and inversely with LINE-1 hypomethylation and p53 expression. Moreover, we show that CDX2 loss is associated with advanced tumor stage (stage IV) and inferior survival. The relationship of CDX2 loss with high mortality is especially remarkable among patients with family history of colorectal cancer. Thus, this study provides useful information on CDX2 expression patterns in colorectal cancer and may refine the role of CDX2 immunohistochemistry in clinical and pathology practice.

Studying molecular alterations is important in cancer research (3236). Accumulating evidence suggests that CDX2 is a tumor suppressor gene (79). Heterozygous CDX2 knock-out mice develop multiple hamartomatous polyps in the proximal colon (7). Furthermore, while APC+/- mice develop adenomatous polyposis of the small intestine, APC+/- CDX2+/- mice develop polyposis of the colon (8). The procarcinogen azoxymethane induced invasive colon adenocarcinoma in CDX2+/- mice but not wild-type littermates (9). Considering the potential role of CDX2 as a tumor suppressor, molecular correlates with CDX2 loss may be important to better understand the interrelationship of multiple genetic and epigenetic alterations during carcinogenic process.

CDX2 expression, a marker of intestinal differentiation, may be expressed in any gastrointestinal cancer but also in gynecologic cancer (37); based on abundant evidence (25), it is commonly used as a relatively specific marker for adenocarcinoma of the lower digestive tract. Previous results on the frequency and significance of CDX2 loss in colorectal cancer have not been uniform. Some studies investigating the utility of CDX2 as a marker for intestinal adenocarcinomas report that CDX2 is detected in 98–100% of cases, although staining pattern and intensity vary and focal expression/loss is quite common (35); other studies report loss of CDX2 expression in 14–37% of cases (2, 11), which agrees with our data. The discrepancy may be due to a difference in antibody sensitivity and specificity or methods of assessing CDX2 expression [e.g., tissue microarray (TMA)-based vs. whole-tissue-based]. We must of course consider a limitation of TMA-based assessment; tumors with partial or heterogeneous positivity in whole sections might have been scored as “negative” in TMA cores. Despite this limitation, we were able to detect highly-significant and independent relations of CDX2 loss with female gender, CIMP and LINE-1 methylation, due to the large sample size and our meticulous laboratory and statistical evaluations.

Loss of CDX2 expression in colorectal cancer has previously been associated with high tumor grade, advanced tumor stage and MSI-high (10, 11). Low-level CDX2 mRNA has been related with MSI-high in colorectal cancer (38). However, CIMP status has not been examined in these previous studies (10, 11, 38). Our multivariate analysis reveals that CDX2 loss is independently associated with CIMP-high, high tumor grade and advanced tumor stage, whereas MSI-high is associated with CDX2 loss in only univariate analysis, but not in multivariate analysis. As there is a strong association between MSI-high and CIMP-high (12, 15), the association of MSI-high with CDX2 loss in previous studies (10, 11) and our univariate analysis likely reflects enrichment of CIMP-high in MSI-high colorectal cancers. In addition, we demonstrate independent relations of CDX2 loss with female gender and high-level LINE-1 methylation. In using CDX2 as a marker for colorectal cancer, clinicians should recognize that female gender, high tumor grade, advanced stage, high-level LINE-1 methylation and CIMP-high increases the likelihood of CDX2 loss. In light of the lack of evidence for significant interactions between these variables, the presence of two or more of these features may further increase the likelihood of CDX2 loss. Thus, our findings have useful clinical implications and delineate caveats for interpreting absence of CDX2 expression in a metastatic tumor of an unknown origin, especially in a small biopsy specimen where a whole tumor profile is not available (somewhat analogous to the current TMA-based study); further studies are necessary to confirm these features of tumors with CDX2 loss.

The mechanisms for loss of CDX2 expression during colorectal carcinogenesis are not well characterized. CDX2 mutations occur infrequently in colorectal cancers with defective DNA mismatch repair (i.e., MSI-high) (39, 40). In a population-based case control study, CDX2 polymorphisms do not play a role in reduced CDX2 expression (38). Though not likely a major cause, loss of heterozygosity at the CDX2 locus (13q12–13) may account for loss of CDX2 expression in a small subset of colorectal cancer (41). A study using colon cancer cell lines has shown evidence for a dominant transcriptional repressor of CDX2 and indicated the possibility that an epigenetic alteration, such as promoter CpG island methylation, might be responsible for CDX2 silencing (42). Our finding of the relationship between CDX2 loss and CIMP-high supports the possibility of epigenetic CDX2 silencing in a subset of colorectal tumors.

An important question is whether loss of CDX2 expression can predict clinical outcome. Considering the role of CDX2 in promoting cellular differentiation (1) and inhibiting proliferation (8), CDX2 loss could conceivably contribute to aggressive tumor behavior. In malignancies other than colorectal cancer, CDX2 loss has been associated with poor prognosis (43, 44). In colorectal cancer, CDX2 loss has been associated with poor survival in only univariate analysis, but not in multivariate analysis (11), which is in agreement with our data. These results likely reflect the association of CDX2 loss with advanced tumor stage. Nonetheless, loss of CDX2 expression in colorectal cancer increases the likelihood of metastatic disease and its loss may therefore serve as a marker to warrant more intensive surveillance in colorectal cancer patients.

The effect of tumoral CDX2 loss on prognosis appears to differ according to family history of colorectal cancer. Specifically, CDX2 loss is independently associated with poor prognosis among patients with family history of colorectal cancer, but not among patients lacking such a family history. A family history of colorectal cancer approximately doubles the risk of developing the disease (45). Excluding studies on familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC), several large-scale studies address the influence of family history on colorectal cancer recurrence and survival (4650). Some studies (4850) have shown that family history of colorectal cancer is associated with a significant reduction in cancer recurrence or death, while other studies (46, 47) have reported no such significant effect of family history. To date, no large-scale study (other than our current study) has examined a potential modifying effect of family history of colorectal cancer on any molecular predictor of patient outcome. These intriguing findings on interactions between CDX2 loss, family history of colorectal cancer, and tumor behavior need to be confirmed in independent cohorts in the future.

In conclusion, our large-scale study has shown that loss of CDX2 expression in colorectal cancer is independently associated with female gender, CIMP-high, high-level LINE-1 methylation, high tumor grade and advanced stage (stage IV). Our results should alert pathologists and clinicians that the usefulness of CDX2 testing to identify metastatic colorectal tumors may be affected by clinical and molecular variables. In addition, CDX2 loss in colorectal cancer is also independently associated with poor prognosis among patients with a family history of colorectal cancer. Loss of CDX2 expression may also serve as a marker to predict outcome for patients with a family history of colorectal cancer. Further studies are necessary to confirm our findings.

Statement of Clinical Relevance

CDX2 plays a critical role in development and differentiation of intestinal epithelium and is clinically useful as a relatively specific marker for colorectal cancer. Understanding of CDX2 expression patterns in colorectal cancer is therefore important in clinical and pathology practice. We utilized a database of 621 colorectal cancers in two independent, prospective cohort studies with clinical information, adequate follow-up, and key molecular data. To our knowledge, this is the first study to comprehensively examine the relationship between CDX2 expression and clinicopathologic, prognostic and molecular variables, including MSI (microsatellite instability), CIMP (CpG island methylator phenotype), KRAS, BRAF, PIK3CA, p53 and β-catenin. Our results will alert pathologists and clinicians that sensitivity of CDX2 testing to identify a colorectal origin for metastatic tumors depends on patient and tumor characteristics, and that the prognostic significance of CDX2 loss is related to a family history of colorectal cancer.

Acknowledgments

This work was supported by The U.S. National Institute of Health (NIH) grants P01 CA87969 (to S. Hankinson), P01 CA55075 (to W Willett), P50 CA127003 (to C.S.F.), K07 CA122826 (to S.O.), K07 CA97992 (to J.A.M.); and in part by grants from the Bennett Family Fund and the Entertainment Industry Foundation National Colorectal Cancer Research Alliance (NCCRA). K.N. was supported by a fellowship grant from the Japan Society for Promotion of Science. These funding sponsors had no role or involvement in the study design, the collection, analysis and interpretation of data, or writing and submission of the manuscript. We deeply thank the Nurses’ Health Study and Health Professionals Follow-up Study cohort participants who have generously agreed to provide us with biological specimens and information through responses to questionnaires. We thank Frank Speizer, Walter Willett, Susan Hankinson, Graham Colditz, Meir Stampfer, and many other staff members who implemented and have maintained the cohort studies.

Abbreviations

BMI
body mass index
CI
confidence interval
CIMP
CpG island methylator phenotype
COX-2
cyclooxygenase-2
HPFS
Health Professionals Follow-up Study
HR
hazard ratio
LINE-1
long interspersed nucleotide element-1
MSI
microsatellite instability
MSS
microsatellite stable
NHS
Nurses’ Health Study
OR
odds ratio
TMA
Tissue microarray

Footnotes

The content is solely the responsibility of the authors and does not necessarily represent the official views of NCI or NIH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No conflicts of interest exist.

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