PLXNA3 and neuroblastoma: Interestingly, a portion of the 20% of NB-derived exosomal proteins not present in the Exocarta database, such as MDK, DBH, CNTN1, NCAM1, CNTFR, PLXNA3 and ADRB2, may represent a “signature” of cells of neuroblastic origin (see Table S1).