In view of the fact that Sema3A is highly expressed in and secreted by cells of osteoblastic origin, and previous findings that implicated Nrp1 and Nrp2 receptors in osteosarcoma26,27, we examined the role of Sema3A in osteolysis and abnormal bone formation associated with osteosarcoma. This evidence concerns the gene NRP1 and osteosarcoma.