EFNA1 and neoplasm: The resistance to VEGF blockade was strongly correlated with hypoxia-induced upregulation of Ephrin A1 and other compensatory pro-angiogenic factors.35 In pancreatic tumors, overexpression of Eph A2 and Ephrin A1 was observed in VEGF-treated tumors and furthermore the elevated levels were correlated with tumor refractoriness.35, 36