Neuropilin 1 and 2 (NRP1, NRP2) bind both semaphorins (SEMA) and VEGF through their a1a2 and b1b2 extracellular domains, respectively. NRPs mediate axon guidance by forming complexes with plexins and mediate angiogenesis by forming complexes with VEGF receptor tyrosine kinases. Overexpression of NRP1 in tumor cells results in larger, more vascular tumors, probably via the VEGF/NRP1 pathway.