Epidermal growth factor receptor domain II, IV, and kinase domain mutations in human solid tumors

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Mutations in the epidermal growth factor receptor (EGFR) kinase domain are crucial for predicting response to ATP-mimetic EGFR inhibitors in lung adenocarcinomas and bronchioloalveolar carcinomas (BACs).
• Limited data exist on the frequency of EGFR mutations in the extracellular domains (II and IV) across various human neoplasms.
• Understanding these mutations is vital for targeted cancer therapies.

Purpose of the Study:

• To investigate the frequency of mutations in specific EGFR exons encoding the kinase domain (exons 18-21) and extracellular domains II (exons 6-7) and IV (exons 14-15) in a diverse range of human tumors.
• To determine the prevalence of these mutations beyond lung adenocarcinomas and BACs.

Main Methods:

• Screening of approximately 4,500 EGFR exons across 566 human neoplasms using denaturing high-performance liquid chromatography (DHPLC).
• Sequencing of samples with abnormal DHPLC findings to identify specific mutations.
• Fluorescence in situ hybridization (FISH) was used to assess gene copy number in lung cancers with mutated EGFR.

Main Results:

• EGFR kinase domain mutations (exons 19 or 21) were identified in 8 (11%) of 40 lung adenocarcinomas and 33 BACs.
• Only one mutation was detected in the extracellular domain IV (glioblastoma); no mutations were found in domain II.
• No EGFR mutations were found in other tumor types investigated.
• Most lung cancers with mutated EGFR showed three to six copies of the mutated gene via FISH.

Conclusions:

• EGFR kinase domain mutations are frequent in lung adenocarcinoma and BACs, but rare in most other human cancers.
• Mutations in the extracellular domains of EGFR are infrequent across most investigated neoplasms.
• Mutated EGFR is typically not amplified in lung cancer, suggesting distinct oncogenic mechanisms.