PGF and neoplasm: PlGF signaling is mediated by binding VEGFR1 and the co-receptors neuropilin-1 (NRP1) and neuropilin-2 (NRP2), and the overexpression of these receptors in different tumor types contributes to angiogenesis, extracellular matrix (ECM) invasion, epithelial/mesenchymal transition, and resistance to anti-VEGF-A therapies [16,17,18,19].