Related Experiment Video
Updated: Aug 14, 2026
3D Culturing of Organoids from the Intestinal Villi Epithelium Undergoing Dedifferentiation
Published on: April 1, 2021
The putative tumor suppressor Cdx2 is overexpressed by human colorectal adenocarcinomas
Matthew E Witek1, Karl Nielsen, Rhonda Walters
1Division of Clinical Pharmacology, Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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.
Insights
Colorectal tumors frequently overexpress the Cdx2 transcription factor, contradicting its proposed tumor suppressor role. This suggests Cdx2 loss is not a key driver in most colorectal cancer development.
Area of Science:
- Molecular Biology
- Oncology
- Gastroenterology
Background:
- Cdx2 is a homeodomain transcription factor crucial for intestinal epithelium development and maintenance.
- Tumor suppressors are typically inactivated during carcinogenesis, but Cdx2 expression in colorectal tumors remains uncharacterized.
- This study investigates Cdx2 expression and function in colorectal tumors versus normal adjacent tissues.
Purpose of the Study:
- To compare Cdx2 expression levels (mRNA and protein) in colorectal tumors and matched normal mucosa.
- To assess the functional activity of Cdx2 in colorectal tumors by examining downstream targets.
- To determine if Cdx2 inactivation is a common event in colorectal tumorigenesis.
Main Methods:
- Quantification of Cdx2 mRNA and protein via RT-PCR and immunoblotting.
- Immunohistochemistry to localize Cdx2 expression in tumor and normal tissues.
- Assessment of Cdx2 transcriptional activity using a downstream target (guanylyl cyclase C) and reporter gene assays.
Main Results:
- Over 80% of colorectal tumors showed significantly higher Cdx2 mRNA and protein expression compared to normal mucosa.
- Elevated nuclear Cdx2 levels were observed in tumor cells.
- Increased expression of the Cdx2 target gene, guanylyl cyclase C, was detected in tumors.
- Tumor-derived cells demonstrated enhanced Cdx2-specific promoter activity.
Conclusions:
- Colorectal tumors exhibit structural and functional overexpression of Cdx2.
- Loss of Cdx2 expression or activity is infrequent in colorectal tumorigenesis.
- These findings challenge the role of Cdx2 as a tumor suppressor in most colorectal cancers and suggest it's not a primary driver of initiation or progression.
Related Concept Videos
02:23Abnormal Proliferation
01:05Cancer-Critical Genes II: Tumor Suppressor Genes
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...
01:05Cancer-Critical Genes II: Tumor Suppressor Genes
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...
01:12Loss of Tumor Suppressor Gene Functions
When the tumor suppressor genes develop mutations or are lost, cells start growing out of control, leading to cancer. However, a single functional copy of the tumor suppressor gene is enough for the cells to maintain their normal functions and cell...
01:33Cancer-Critical Genes I: Proto-oncogenes
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...
02:34Inhibition of Cdk Activity