The pro-angiogenic activity of CgA1-373 requires the binding of its Pro-Gly-Pro-Leu-Arg373 site (PGPQLR373) to neuropilin-1: accordingly, antibodies against this site (which is cryptic in CgA1-439) can reduce angiogenesis and tumor growth in various animal models of solid tumors (8). This evidence concerns the gene NRP1 and neoplasm.