PLG and neoplasm: Tumour angiogenesis depends on both the angiogenic growth factors, with stimulants such as angiogenin, angiopoietin-1, cyclo-oxygenase, hepatocyte growth factor, and tumour growth factor produced by the tumour cells and those of the host, and the antiangiogenic factors, which are inhibitors and include angiopoietin-2, angiostatin, interferon-α/β endostatin, and vasostatin, which keep the existing blood vessels in a state of quiescence [164].