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Transcriptional defects underlie loss of E-cadherin expression in breast cancer
1Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0638, USA.
Abstract:
Decreased expression of E-cadherin (E-cad), a calcium-dependent cell adhesion molecule, has been seen in many different epithelial cancers. Although somatic mutations in the E-cad gene have been identified in a small subset of tumors, in the majority of cancers, the mechanisms underlying loss of E-cad expression are poorly understood. We have cloned the human E-cad promoter and defined its critical components in functional assays. In eight human breast cancer cell lines, there was a striking correlation between endogenous E-cad gene expression and E-cad promoter activity observed following the introduction of reporter gene constructs into the lines. These and other observations suggest that defects in trans-acting pathways regulation E-cad expression are the primary basis for the loss of its expression in most breast cancers. The results have significant implications for understanding the gene expression differences that underlie tumor heterogeneity and progression events in breast and other epithelial cancers.
Insights
Loss of E-cadherin (E-cad) in epithelial cancers is common. This study reveals that defects in gene regulation, not mutations, primarily cause reduced E-cad expression in most breast cancers.
Area of Science:
- Molecular Biology
- Cancer Biology
- Genetics
Background:
- Decreased E-cadherin (E-cad) expression is observed in various epithelial cancers.
- Mechanisms for E-cad loss are poorly understood, as somatic mutations are rare.
Purpose of the Study:
- To investigate the regulatory mechanisms underlying E-cadherin gene expression in breast cancer.
- To determine if promoter activity correlates with E-cad expression levels.
Main Methods:
- Cloned the human E-cadherin promoter.
- Performed functional assays using reporter gene constructs in breast cancer cell lines.
- Correlated endogenous E-cad expression with E-cad promoter activity.
Main Results:
- A strong correlation was found between endogenous E-cad gene expression and E-cad promoter activity in eight human breast cancer cell lines.
- These findings suggest transcriptional dysregulation is key.
Conclusions:
- Defects in trans-acting regulatory pathways are the primary cause of E-cadherin loss in most breast cancers.
- Understanding these regulatory defects is crucial for comprehending tumor heterogeneity and progression.