All proteomic experimental procedures were performed according to a previous report (Im et al., 2019 ). Exosomal proteins were digested with trypsin (Cho et al., 2017 (link)). The tryptic peptides were analysed using nano‐ultra‐high‐performance LC (UPLC, Waters) and tandem mass spectrometry using a Q‐Tof Premier (Waters) (Cho et al., 2012 ; Moon et al., 2011 (link)). The digested peptides were injected into a 2 cm × 180 μm trap column and resolved using a 25 cm × 75 μm nano ACQUITY C18 column (Waters) on the LC system. All samples were analysed in triplicate. For protein identification, MS raw data were converted into peak lists using MASCOT Distiller version 2.1 (Matrix Science) using the default settings. All MS/MS raw data were analysed using MASCOT version 2.2.1 (Matrix Science). (Cho et al., 2012 ) The MASCOT was used to search the SwissProt database (release 2018_07) with human taxonomy. Quantification was performed using PEAKS Studio version 10.0 (Bioinformatics Solution Inc.). For label‐free protein quantification, the identified peptides were filtered based on a false discovery rate <1%. The abundance of each peptide was determined using ion chromatography extraction and the protein ratio was calculated using the average abundance of the corresponding peptides. Protein ratios were considered acceptable when the proteins contained more than one unique peptide.