NRP1 and neoplasm: The SEMA3B protein is an antagonist of receptors for neuropilins 1 and 2 (Np1 and Np2) that also act as receptors for several isoforms of vascular endothelial growth factor (VEGF), which is a general initiator of tumor angiogenesis, and thus SEMA3B suppresses vascular growth in tumors [19].