• Akihiko Kawahara, Chizuko Yamamoto, Kazutaka Nakashima, Koichi Azuma, Satoshi Hattori, Masaki Kashihara, Hisamichi Aizawa, Yuji Basaki, Michihiko Kuwano, Masayoshi Kage, Tetsuya Mitsudomi, and Mayumi Ono.
• Department of Diagnostic Pathology, Kurume University Hospital, Kurume, Japan.
• Clin Cancer Res. 2010 Jun 15; 16 (12): 3163-70.

PurposeTherapeutic responses of non-small cell lung carcinoma (NSCLC) to epidermal growth factor receptor (EGFR)-targeted drugs, such as gefitinib and erlotinib, are closely associated with activating EGFR mutations. The most common mutations are delE746-A750 in exon 19 and L858R in exon 21, accounting for approximately 90% of all EGFR mutations. Recently, EGFR mutation-specific antibodies were developed and did well in immunohistochemical analysis, giving a sensitivity of approximately 90%. We have investigated whether this method detects activating EGFR mutations with sensitivity comparable with direct DNA sequencing, which is used to detect these mutations in NSCLC.Experimental DesignWe used antibodies specific for the E746-A750 deletion mutation in exon 19 and the L858R point mutation in exon 21 in Western blot analysis and immunohistochemistry to determine the presence of these mutations in NSCLC cell lines. We also examined these EGFR mutations in NSCLC tumor samples from 60 patients by immunohistochemically and direct DNA sequencing.ResultsWe were able to identify EGFR mutations in NSCLC tumor samples immunohistochemically with a sensitivity of 79% using the anti-delE746-A750 antibody and 83% using the anti-L858R antibody. Additional DNA sequencing markedly improved the sensitivity obtained by immunohistochemistry.ConclusionsThis simple and rapid assay for detecting EGFR mutations, even in the small bronchial biopsies obtained in stage IV NSCLC patients, will be useful for diagnosing responsiveness to EGFR-targeted drugs in patients with NSCLC. Combining this with DNA sequencing is recommended for the development of improved personalized EGFR-targeted therapeutics.(c) 2010 AACR.

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