ERBB2 and breast cancer: However, there were also breast cancer cell lines which showed high lapatinib cytotoxic effect (MDA-MB-175: 0.012 μM, EFM-19: 4.6 μM, MCF-7: 7.7 μM and MDA-MB-435: 8.5 μM) but expressed a moderate or low level of both ErbB1 and ErbB2 (2.2 to 20 ng/mg) [12,13].