ERBB2 and breast cancer: We studied a panel of nine HER2 overexpressing breast cancer cell lines, which have been previously determined as sensitive to both trastuzumab and lapatinib (ZR-75-30, BT-474, EFM-192A, SKBR-3 UACC-812), sensitive to trastuzumab and resistant to lapatinib (MDA-361), or resistant to both trastuzumab and lapatinib (JIMT-1, UACC-893, MDA-453) [39].