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J Thorac Oncol 2012 May 01;75:913-8. doi: 10.1097/JTO.0b013e31824c7f7a.
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A novel mass spectrometry-based assay for diagnosis of EML4-ALK-positive non-small cell lung cancer.

Sakai K , Okamoto I , Takezawa K , Hirashima T , Kaneda H , Takeda M , Matsumoto K , Kimura H , Fujita Y , Nakagawa K , Arao T , Nishio K .

INTRODUCTION: The presence of the transforming fusion gene echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) in non-small-cell lung cancer (NSCLC) is a predictive marker for the efficacy of anaplastic lymphoma kinase inhibitors. However, the currently available assays for the detection of the different variants of EML4-ALK have limitations. METHODS: We developed an assay system for the detection of EML4-ALK variants 1, 2, 3a, 3b, 4, 5a, 5b, 6, or 7 transcripts in total RNA obtained from formalin-fixed, paraffin-embedded (FFPE) specimens of NSCLC tissue. The assay is based on region-specific polymerase chain reaction amplification of EML4-ALK complementary DNA followed by specific single-base primer extension and analysis of the extension products by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. The assay was validated by fluorescence in situ hybridization and the results confirmed by subcloning and sequencing of polymerase chain reaction products. RESULTS: Evaluation of the analytic sensitivity of the assay with serial dilutions of plasmids containing EML4-ALK complementary DNA sequences revealed it to be capable of the reliable detection of one copy of each plasmid per reaction. The assay also detected EML4-ALK variants 1 or 3 in three FFPE samples of surgically resected NSCLC shown to be positive for anaplastic lymphoma kinase rearrangement by fluorescence in situ hybridization. Furthermore, the assay identified variant 1 of EML4-ALK in 3 of 20 FFPE biopsy samples from patients with advanced NSCLC. All positive samples were confirmed by subcloning and sequencing. CONCLUSIONS: Our novel assay is highly sensitive and effective for the detection of EML4-ALK in FFPE specimens.

PubMed ID: 22722791
Article link: J Thorac Oncol