PGF and neoplasm: To determine which growth factors may be responsible for the enhanced tumour angiogenesis in pdgfrβcre+;fakfl/fl mice, synthetic sponges were implanted subcutaneously into pdgfrβcre-;fakfl/fl and pdgfrβcre+;fakfl/fl mice, and angiogenesis was stimulated with PBS (control), PDGF-B, PlGF, or VEGF.