ROS1 copy number alterations are frequent in non-small cell lung cancer

// Sergi Clavé 1,2 , Javier Gimeno 3 , Ana M. Muñoz-Mármol 4 , Joana Vidal 5 , Noemí Reguart 6 , Enric Carcereny 7 , Lara Pijuan 3 , Sílvia Menéndez 2,3 , Álvaro Taus 5 , José Luís Mate 4 , Sergio Serrano 3 , Joan Albanell 2,5 , Blanca Espinet 1,2 , Edurne Arriola 2,8 and Marta Salido 1,2 1 Laboratori de Citogenètica Molecular, Servei de Patologia, Hospital del Mar, Barcelona, Spain 2 Programa de Recerca en Càncer, IMIM (Institut Hospital del Mar de Investigacions Mèdiques), Barcelona, Spain 3 Servei de Patologia, Hospital del Mar, Barcelona, Spain 4 Servei de Anatomia Patològica, Hospital Universitari Germans Trias i Pujol, Badalona, Spain 5 Servei de Oncologia Mèdica, Hospital del Mar, Barcelona, Spain 6 Servei de Oncologia Mèdica, ICMHO, Hospital Clinic Barcelona, Barcelona, Spain 7 Departament de Oncologia Mèdica, Institut Català de Oncologia (ICO), Hospital Universitari Germans Trias i Pujol, Badalona, Spain 8 Cancer Sciences Unit, University of Southampton. Southampton, United Kingdom Correspondence to: Sergi Clavé, email: // Keywords : ROS1, FISH, copy number alterations, heterogeneity, IHC Received : September 17, 2015 Accepted : January 06, 2016 Published : January 15, 2016 Abstract Objectives: We aimed to determine the prevalence and partners of ROS1 rearrangements, to explore the correlation between FISH and IHC assays, and to investigate clinical implications of ROS1 copy number alterations (CNAs). Methods: A total of 314 NSCLC patients were screened using ROS1 FISH break-apart probes. Of these, 47 surgical tumors were included in TMAs to analyze ROS1 heterogeneity assessed either by FISH and IHC, and chromosome 6 aneusomy. To characterize ROS1 partners, probes for CD74 , EZR , SLC34A2 and SDC3 genes were developed. ROS1 positive FISH cases were screened also by IHC. Results: Five patients were ROS1 positive (1.8%). We identified two known fusion partners in three patients: CD74 and SLC34A2 . Four out of five ROS1 rearranged patients were female, never smokers and with adenocarcinoma histology. Rearranged cases were also positive by IHC as well. According to ROS1 CNAs, we found a prevalence of 37.8% gains/amplifications and 25.1% deletions. Conclusions: This study point out the high prevalence of ROS1 CNAs in a large series of NSCLC. ROS1 gains, amplifications and deletions, most of them due to chromosome 6 polysomy or monosomy, were heterogeneous within a tumor and had no impact on overall survival.