Placenta growth factor (PLGF or PIGF) is a dimeric glycoprotein showing the highest degree of sequence similarity to the vascular endothial growth factor. Alternative splicing of the PLGF primary transcript gives rise to three forms named PIGF-1, 2 and 3, which differ only in the insertion of a highly basic 21-amino acid stretch at the carboxyl end. PLGF is active in angiogenesis and endothelial cell growth by stimulating their proliferation and migration. PLGF binds to receptor VEGFR-1/FLT1. PLGF-2 binds neuropilin-1 and 2 in a heparin-dependent manner. Whereas the three forms are present in most placental tissues, PIGF-2 is specific to early (8 week) placenta and only PIGF-1 is found in the colon and mammary carcinomas.