Periostin is identified as a putative metastatic marker in breast cancer-derived exosomes

// Ioulia Vardaki 1 , Sophia Ceder 1 , Dorothea Rutishauser 2, 3 , George Baltatzis 4 , Theodoros Foukakis 1 , Theocharis Panaretakis 1 1 Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and University Hospital, Stockholm, Sweden 2 Department of Medical Biochemistry and Biophysics, Karolinska Institutet and University Hospital, Stockholm, Sweden 3 Science for Life Laboratory, Stockholm, Sweden 4 Department of Medicine, School of Health Sciences, University of Athens, Athens, Greece Correspondence to: Theocharis Panaretakis, email: theoharis.panaretakis@ki.se Keywords: periostin, biomarkers, exosomes, metastatic, non-metastatic Received: April 13, 2016 Accepted: August 16, 2016 Published: August 29, 2016 ABSTRACT Breast cancer (BrCa) is the most frequent cancer type in women and a leading cause of cancer related deaths in the world. Despite the decrease in mortality due to better diagnostics and palliative care, there is a lack of prognostic markers of metastasis. Recently, the exploitation of liquid biopsies and in particular of the extracellular vesicles has shown promise in the identification of such prognostic markers. In this study we compared the proteomic content of exosomes derived from metastatic and non-metastatic human (MCF7 and MDA-MB-231) and mouse (67NR and 4T1) cell lines. We found significant differences not only in the amount of secreted exosomes but most importantly in the protein content of exosomes secreted from metastatic versus non-metastatic ones. We identified periostin as a protein that is enriched in exosomes secreted by metastatic cells and validated its presence in a pilot cohort of breast cancer patient samples with localized disease or lymph node (LN) metastasis.