MEK1 gene mutation in Japanese lung adenocarcinoma patients.

Recently, to identify potential somatic mutations in genes of the epidermal growth factor receptor (EGFR) signaling pathway, the MEK1 gene mutation at exon 2 was identified. The mutant form of MEK1 leads to the constitutive activity of extracellular signal-regulated kinase (ERK)-1/2. We investigated MEK1 gene mutation status in 241 surgically treated lung adenocarcinoma cases from Nagoya City University Hospital. The presence or absence of the MEK1 mutation was analyzed by direct sequencing. EGFR mutation status was previously investigated and reported. We detected only one case (0.4%) of the MEK1 mutation (K57N) in our cohort. Total EGFR mutations were present in 101 patients (41.9%). The MEK1 mutation was mutually exclusive with B-raf, K-ras and EGFR mutations. Thus, it is a rare mutation in Japanese lung cancer patients, and of limited value for lung adenocarcinoma.