PlGF-1(also called Placenta Growth Factor-1, PLGF, and PGF) is an angiogenic factor that belongs to the cysteine-knot superfamily of growth factors. PlGF-1 is expressed in placental tissues, colon and mammary carcinomas. It signals throμgh the VEGFR-1/FLT1 receptor and stimulates endothelial cell proliferation and migration. Human PlGF-1 is a 29.7 kDa disulfide-linked homodimeric protein of two 131 amino acid polypeptide chains.