PSAP and pancreatic neoplasm: We have further investigated whether these 15 proteins were already identified in PDAC-derived exosomes and seven of them, namely PROCR, TIMP1, EZR, PSAP, VIM, CLSTN1 and CFL1, were detected in the proteome of pancreatic cancer exosomes using mass spectrometry [38], which suggests their roles as key signaling molecules.