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Amplification of the structurally and functionally altered epidermal growth factor receptor gene (c-erbB) in human
H Yamazaki1, Y Fukui, Y Ueyama
1Department of Genetics, University of Tokyo, Japan.
Abstract:
By using Southern blot analysis, we found that in two cases of human glioblastoma multiforme, cells carried amplified c-erbB genes which bore short deletion mutations within the ligand-binding domain of the epidermal growth factor (EGF) receptor. The products of these mutated c-erbB genes were about 30 kilodalton (kDa) smaller than the normal 170-kDa EGF receptor, and the tumor cell membrane fractions containing the 140-kDa abnormal EGF receptor showed a significant elevation of tyrosine kinase activity without its ligand. In view of the similarity to the activated viral and cellular erbB genes in the avian system, these mutated and overexpressed EGF receptors might play a role in the onset or development of human glioblastoma cells.
Insights
Amplified and mutated epidermal growth factor (EGF) receptor genes were found in human glioblastoma cells. These alterations may contribute to the development of this aggressive brain tumor.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Glioblastoma multiforme is an aggressive brain tumor with complex genetic alterations.
- The epidermal growth factor (EGF) receptor is a key protein involved in cell growth and signaling.
- Aberrant EGF receptor signaling is implicated in various cancers, including glioblastoma.
Purpose of the Study:
- To investigate genetic mutations in the epidermal growth factor (EGF) receptor in human glioblastoma multiforme.
- To determine the functional consequences of these mutations on receptor activity.
Main Methods:
- Southern blot analysis was used to detect gene amplification.
- Protein analysis was performed on tumor cell membrane fractions.
- Tyrosine kinase activity assays were conducted.
Main Results:
- Two cases of glioblastoma multiforme exhibited amplified c-erbB genes with deletions in the EGF receptor's ligand-binding domain.
- A truncated 140-kDa EGF receptor protein was detected, approximately 30 kDa smaller than the normal 170-kDa receptor.
- Tumor cells showed elevated tyrosine kinase activity of the abnormal EGF receptor, independent of ligand binding.
Conclusions:
- Mutated and overexpressed EGF receptors in glioblastoma may be constitutively active.
- These findings suggest a potential role for altered EGF receptor signaling in glioblastoma pathogenesis.
- The observed mutations share similarities with activated viral and cellular erbB genes in avian systems.