PLXNB3 and cancer: Plexin-B3 (PLXNB3) is a large transmembrane protein that interacts with semaphorin 5A to mediate axon guidance during the development of the nervous system.52 PLXNB3 mRNA is expressed in many cancers and is associated with increased pan-cancer patient mortality.53 However, PLXNB3 was not previously implicated in cancer stem cell specification.