APLN and neoplasm: Apart from the factors above and downstream pathways shown in Fig. 3, Apelin/APLNR family,339 Slit/Robo family,340 adrenomedullin,341,342 COX-2,343,344 CXC chemokines,345,346 interleukins,347 interferons,348–350 nitric oxide synthase (NOS),351 pleiotrophin (PTN),352 steroid hormones,353 thrombospondin (TSP),354,355 and many other molecules also involve tumor angiogenesis to encourage tumor progression.