KLK3 and neoplasm: The results of this study suggest that the selective pressure induced by the acidic microenvironment may lead to an abnormal release of exosomes expressing either unknown markers or known tumor markers, already shown to be expressed by human tumor-released exosomes, such as prostate-specific antigen (PSA) [28], carcinoembryonic antigen (CEA) [41], or melanoma antigen recognized by T cells 1 (MART-1) [42].