ERBB4 and cancer: These cancer cell lines has been previously characterized by our group for the expression of the four EGF-related growth factor receptors (EGFR, ERBB2, ERBB3, and ERBB4) and of three VEGF receptors (VEGFR-1,VEGFR-2, VEGFR-3), as well as for the expression of three EGFR ligands (amphiregulin, EGF, and TGFα) and of three VEGFR ligands (VEGF-A, VEGF-B, VEGF-C), by using quantitative RT-PCR (qRT-PCR) [12].