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Oncogenic epidermal growth factor receptor mutants with tandem duplication: gene structure and effects on receptor
M J Ciesielski1, R A Fenstermaker
1Department of Neurosurgery, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Roswell Park Cancer Institute, 14263, USA.
Abstract:
A number of epidermal growth factor receptor (EGFR) deletion mutants have been identified in gliomas, in which the EGFR gene is frequently amplified and rearranged. We have previously characterized the structure of a gene in A-172 human glioma cells that encodes a 190-kDa EGFR mutant with tandem duplication of the tyrosine kinase (TK) and calcium-mediated internalization (CAIN) domains. Here we describe a 185-kDa tandem duplication mutant (TDM) that is expressed in KE and A-1235 glioma cells, along with certain functional characteristics of the mutants. The corresponding transcripts in KE and A-1235 cells contain 1053 additional nucleotides representing an in-frame duplication of exons 18 through 25 which encode the entire TK region and a portion of the CAIN domain. As with duplication of the entire TK/CAIN region (exons 18-26) in A-172 cells, duplication of exons 18-25 is associated with a specific genomic rearrangement between flanking introns. Involved introns contain homology to recombination signal sequence (RSS) heptamers present in the V(D)J region of the T lymphocyte receptor gene. In defined medium, both oncogenic TDM are constitutively autophosphorylated and inefficiently downregulated. High-affinity binding is reduced in EGFR.TDM/18-26, although the t1/2 of receptor internalization is not prolonged.
Insights
Scientists identified a new epidermal growth factor receptor (EGFR) tandem duplication mutant (TDM) in glioma cells. This mutant exhibits constitutive autophosphorylation and inefficient downregulation, contributing to glioma development.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Epidermal growth factor receptor (EGFR) gene amplification and rearrangement are common in gliomas.
- EGFR deletion mutants have been identified in glioma cells.
- Previous characterization of a 190-kDa EGFR mutant with tandem duplication in A-172 cells.
Purpose of the Study:
- To describe a novel 185-kDa tandem duplication mutant (TDM) in KE and A-1235 glioma cells.
- To characterize the functional properties of these EGFR tandem duplication mutants.
Main Methods:
- Analysis of gene structure and transcripts in KE and A-1235 glioma cells.
- Investigation of genomic rearrangements associated with exon duplication.
- Functional assays including autophosphorylation, downregulation, ligand binding, and receptor internalization.
Main Results:
- A novel 185-kDa EGFR tandem duplication mutant (TDM) was identified in KE and A-1235 glioma cells.
- The TDM results from an in-frame duplication of exons 18-25, encoding the tyrosine kinase (TK) and part of the calcium-mediated internalization (CAIN) domains.
- Genomic rearrangement involving introns with homology to recombination signal sequences (RSS) mediates the duplication.
- Both oncogenic TDMs are constitutively autophosphorylated and inefficiently downregulated.
- EGFR.TDM/18-26 shows reduced high-affinity binding, but receptor internalization half-life is not prolonged.
Conclusions:
- The identified EGFR tandem duplication mutants (TDMs) are oncogenic, driven by specific genomic rearrangements.
- Constitutive autophosphorylation and impaired downregulation contribute to the aberrant EGFR signaling in gliomas.
- These findings provide insights into the molecular mechanisms underlying EGFR-driven gliomagenesis.