Tumor angiogenesis is necessary for continued growth of the tumor beyond the limits of oxygen diffusion. The growth of vessels into the tumor is also important to metastatic potential of the tumor. ET-1 may play an important role in angiogenesis and tumor growth and survival Available online http://respiratory-research.com/content/2/2/090 commentary review reports primary research through induction of vascular endothelial growth factor expression and sprouting of new vessels into the tumor and surrounding tissue [137, 138] . ET-1 binding activity was found in blood vessels and vascular stroma surrounding lung tumors at the time of resection, most markedly surrounding squamous cell tumors [139] . ET-1 production may be further augmented by the hypoxic environment found within large solid tumors [140] . Since metastasis is dependent on neo-vascularization, ET-1 may also be an important mediator of this phenomenon. ET-1 receptor antagonists may have a useful role in the treatment of neoplastic disease by inhibiting growth as well as metastatic potential of human tumors.