Related Experiment Videos
Expression of GPC3, an X-linked recessive overgrowth gene, is silenced in malignant mesothelioma
S S Murthy1, T Shen, A De Rienzo
1Human Genetics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Abstract:
Gene expression changes in rat asbestos-induced malignant mesothelioma (MM) cells were investigated by differential mRNA display. A mRNA transcript identified by this approach was abundant in normal rat mesothelial cells but not expressed in rat MM cell lines. Northern blot analysis confirmed that this transcript is uniformly silenced in rat MM cell lines and primary tumors. Nucleotide sequence analysis revealed that this transcript is encoded by the rat glypican 3 gene (GPC3), whose human homolog is mutated in the Simpson-Golabi-Behmel overgrowth syndrome. Allelic loss at the GPC3 locus was infrequent (6.9%) in MM cell lines, and no mutations were found. GPC3 transcript levels were markedly decreased in 16 of 18 primary tumors and 17 of 22 human MM cell lines. Most of the cell lines were shown to have aberrant methylation of the GPC3 promoter region. In two of four human MM cell lines tested, GPC3 expression was restored after 2-deoxy 5-azacytidine (DAC)-mediated demethylation of its promoter region. Ectopic expression of GPC3 inhibited in vitro colony formation of human MM cells. Collectively, these data suggest that down-regulation of GPC3 is a common occurrence in MM and that GPC3, an X-linked recessive overgrowth gene, may encode a negative regulator of mesothelial cell growth.
Insights
Glypican 3 (GPC3) gene expression is silenced in malignant mesothelioma (MM). Down-regulation of GPC3, a tumor suppressor, is common in MM and may inhibit mesothelial cell growth.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Malignant mesothelioma (MM) is an aggressive cancer originating in mesothelial cells.
- Understanding gene expression changes in MM is crucial for identifying therapeutic targets.
Purpose of the Study:
- To investigate gene expression alterations in rat asbestos-induced MM.
- To identify novel genes involved in MM pathogenesis and progression.
Main Methods:
- Differential mRNA display to identify gene expression changes.
- Northern blot analysis to confirm transcript expression.
- Nucleotide sequencing and GPC3 locus analysis.
- GPC3 promoter methylation analysis and demethylation studies.
- In vitro colony formation assays to assess GPC3 function.
Main Results:
- A novel mRNA transcript, GPC3, was identified and found to be downregulated in rat and human MM cell lines and primary tumors.
- GPC3 promoter hypermethylation was observed in most MM cell lines.
- GPC3 expression restoration after demethylation suggests epigenetic regulation.
- Ectopic GPC3 expression inhibited MM cell proliferation in vitro.
Conclusions:
- Down-regulation of GPC3 is a frequent event in malignant mesothelioma.
- GPC3 acts as a tumor suppressor, potentially regulating mesothelial cell growth.
- Epigenetic silencing via promoter methylation contributes to GPC3 down-regulation in MM.