Some mRNAs specific to or upregulated in breast cancer cells may also serve as HER2-EV biomarkers, includingEpCAM which affects intercellular adhesion and is relevant to tumour progression21;BIRC5 (baculoviral IAP repeat-containing protein 5, the gene that encodes the survivin protein and a member of Inhibitor of apoptosis family) which is involved in regulation of mitosis and apoptotic inhibition22; andYBX1 (the Y-box binding protein) which is an oncogenic transcription and translation regulator that regulates cell invasion and migration23. Here, BIRC5 is linked to breast cancer.