PGF and neoplasm: VEGFR1 is a receptor not only for VEGF, but also for placental growth factor (PGF), and is associated with tumour progression and neovascularization (Pajusola et al, 1992; Galland et al, 1993; Ferrara & Davis-Smyth, 1997; Shibuya et al, 1999; Hiratsuka et al, 2001).