The endothelin A receptor (ET A R) autocrine pathway is overexpressed in many malignancies, including nasopharyngeal carcinoma (NPC). In this tumor, ET A R expression is an independent determinant of survival and a robust independent predictor of distant metastasis. To evaluate whether ET A R represents a new target in NPC treatment, we tested the therapeutic role of ET A R in NPC. N asopharyngeal carcinoma is common in Southern China, with an annual incidence of 15-50 cases per 100 000 people.(1) NPC is distinct from other epithelial malignancies in the head and neck region in that it affects a relatively young population and has a propensity for distant metastases.(2) NPC is a radiosensitive tumor for which there is a high local control rate after radical radiotherapy. However, for patients with locoregionally advanced disease, the rate of distant metastasis is high and the 5-year overall survival rate is poor.(3) Randomized trials have confirmed that chemotherapy improves the distant metastasis control rate in patients with locoregionally advanced NPC; however, approximately 20% or more of the patients still have distant metastasis develop despite intensive chemotherapy.(4,5) These findings underscore the need to develop novel strategies in the management of patients with advanced NPC.The family of ET, including ET-1, ET-2 and ET-3, are 21-amino acid peptides exerting many biological effects.(6) Two major receptor subtypes belonging to the G protein-coupled family of receptors mediate ET signals: ET A R, which binds ET-1 and ET-2 with high affinity and ET-3 with low affinity; and ET B R, which binds all ET isopeptides with equal affinity.(7) ET-1, which is the most common circulating form of ET, is produced by many epithelial tumors.(8) ET-1 induces cell proliferation directly or synergistically with other growth factors that are relevant in cancer progression. Engagement of ET A R by ET-1 triggers activation of tumor proliferation, (9-13) VEGF-induced angiogenesis, (14,15) invasiveness (16) and inhibition of apoptosis. (17,18) The ET-1-ET A R autocrine pathway has a key role in the development and progression of prostatic, ovarian and cervical cancers.(9) The major relevance of ET A R in tumor development has led to an extensive search of highly selective antagonists. ABT-627 (Atrasentan), one such antagonist, is orally bioavailable and has suitable pharmacokinetic and toxicity profiles for clinical use. (19,20) ABT-627 has been given to cancer patients in phase II trials for prostate cancer and delayed the time to clinical and prostate-specific antigen progression.(21) Two pivotal randomized, double-blind, placebo-controlled, multinational phase III trials are ongoing in patients with hormone-refractory prostate cancer to verify these findings.We reported previously that patients with advanced-stage NPC had elevated plasma big ET-1 levels compared with the levels in healthy control participants; high pretreatment plasma big ET-1 levels are generally associated with post-treatment distant failure.(22) Our pr...