MET expression and copy number heterogeneity in nonsquamous non-small cell lung cancer (nsNSCLC)

Abstract

// David Casadevall 1, 6, * , Javier Gimeno 2, * , Sergi Clavé 3, 4, * , Álvaro Taus 1 , Lara Pijuan 2 , Miriam Arumí 1 , Marta Lorenzo 4 , Silvia Menéndez 4 , Israel Cañadas 4 , Joan Albanell 1, 4, 5 , Sergio Serrano 2 , Blanca Espinet 3, 4 , Marta Salido 3, 4 , Edurne Arriola 1, 4, # 1 Servei d’Oncologia Mèdica, Hospital del Mar, Barcelona, Spain 2 Servei de Patologia, Hospital del Mar, Barcelona, Spain 3 Laboratori de Citogenètica Molecular, Servei de Patologia, Hospital del Mar, Barcelona, Spain 4 Cancer Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain 5 Universitat Pompeu Fabra, Barcelona, Spain 6 Universitat Autònoma de Barcelona, Bellaterra, Spain # Cancer Sciences Unit, University of Southampton, Southampton, UK * These authors have contributed equally to this work Correspondence to: David Casadevall, e-mail: dcasadevall@parcdesalutmar.cat Keywords: c-MET, immunohistochemistry, FISH, non-small-cell lung cancer, heterogeneity Received: February 25, 2015      Accepted: May 05, 2015      Published: May 15, 2015 ABSTRACT Objective: We aimed to assess MET intratumoral heterogeneity and its potential impact on biomarker-based patient selection as well as potential surrogate biomarkers of MET activation. Methods: Our study included 120 patients with non-squamous Non-small-cell Lung Cancer (nsNSCLC), of which 47 were incorporated in tissue microarrays (TMA). Four morphologically distinct tumor areas were selected to assess MET heterogeneity. MET positivity by immunohistochemistry (IHC) was defined as an above-median H-score and by +2/+3 staining intensity in >50% of tumor cells (Metmab criteria). MET FISH positivity was defined by MET /CEP7 ratio ≥ 2.0 and/or MET ≥ 5.0. MET staining pattern (cytoplasmic vs. membranous) and mesenchymal markers were investigated as surrogates of MET activation. Results: Median MET H-score was 140 (range 0–400) and 47.8% of patients were MET positive by Metmab criteria. Eight cases (6.8%) were MET FISH positive and showed higher H-scores ( p = 0.021). MET positivity by IHC changed in up to 40% of cases among different tumor areas, and MET amplification in 25–50%. Cytoplasmic MET staining and positivity for vimentin predicted poor survival ( p = 0.042 and 0.047, respectively). Conclusions: MET status is highly heterogeneous among different nsNSCLC tumor areas, hindering adequate patient selection for MET-targeted therapies. MET cytoplasmic staining and vimentin might represent surrogate markers for MET activation.