KDR and neoplasm: Of the three VEGFRs, VEGFR1 (fms-like tyrosine kinase-1), VEGFR2 (fetal liver kinase-1/kinase insert domain receptor), and VEGFR3 (fms-like tyrosine kinase-4), VEGFR2 has the most significant role in mediating the growth of blood vessels necessary for tumor growth.[59] Activation of the VEGFR pathway has been well documented in ACC and provides the rationale for targeting these receptors.[60, 61]