Presence of cancer-associated mutations in exhaled breath condensates of healthy individuals by next generation sequencing

// Omar Youssef 1 , Aija Knuuttila 2 , Päivi Piirilä 3 , Tom Böhling 4 , Virinder Sarhadi 1, * , Sakari Knuutila 1, * 1 Faculty of Medicine, Department of Pathology, University of Helsinki, Helsinki, Finland 2 Department of Pulmonary Medicine, University of Helsinki and Helsinki University Hospital, Heart and Lung Center, Helsinki, Finland 3 Unit of Clinical Physiology, HUS-Medical Imaging Center, Helsinki University Hospital and Helsinki University, Helsinki, Finland 4 Department of Pathology, University of Helsinki and HUSLAB, Helsinki University Hospital, Helsinki, Finland * These authors have contributed equally to this work Correspondence to: Sakari Knuutila, email: sakari.knuutila@helsinki.fi Keywords: exhaled breath condensate, mutations, healthy individuals, next generation sequencing Received: December 10, 2016     Accepted: January 16, 2017     Published: February 09, 2017 ABSTRACT Exhaled breath condensate (EBC) is a non-invasive source that can be used for studying different genetic alterations occurring in lung tissue. However, the low yield of DNA available from EBC has hampered the more detailed mutation analysis by conventional methods. We applied the more sensitive amplicon-based next generation sequencing (NGS) to identify cancer related mutations in DNA isolated from EBC. In order to apply any method for the purpose of mutation screening in cancer patients, it is important to clarify the incidence of these mutations in healthy individuals. Therefore, we studied mutations in hotspot regions of 22 cancer genes of 20 healthy, mainly non-smoker individuals, using AmpliSeq colon and lung cancer panel and sequenced on Ion PGM. In 15 individuals, we detected 35 missense mutations in TP53, KRAS, NRAS, SMAD4, MET, CTNNB1, PTEN, BRAF, DDR2, EGFR, PIK3CA, NOTCH1, FBXW7, FGFR3, and ERBB2: these have been earlier reported in different tumor tissues. Additionally, 106 novel mutations not reported previously were also detected. One healthy non-smoker subject had a KRAS G12D mutation in EBC DNA. Our results demonstrate that DNA from EBC of healthy subjects can reveal mutations that could represent very early neoplastic changes or alternatively a normal process of apoptosis eliminating damaged cells with mutations or altered genetic material. Further assessment is needed to determine if NGS analysis of EBC could be a screening method for high risk individuals such as smokers, where it could be applied in the early diagnosis of lung cancer and monitoring treatment efficacy.