NRP1 and neoplasm: Most importantly, we found that the tumor cell-secreted PDGF-B-induced MPT event is mediated through NRP-1 (neuroplin-1), which is a co-receptor for semaphorins with key roles in axon guidance, a docking receptor for VEGF165 [38,39] and exhibits a physical interaction with PDGF-B in vascular SMC to enhance their migration [20,38].