COL4A3 and neoplasm: “Angiogenic switch” activators are the tumor microenvironment; mutation in oncogenes or tumor-suppressor genes; pro-angiogenic molecules (VEGF, FGF-2, EGF, PDGF, PIGF, and MMPs); and anti-angiogenic factors (thrombospondin, angiostatin, tumstatin, and endostatin) [20,21].