ERBB2 and breast cancer: Among all the cancer cell lines tested, lapatinib has shown to have the highest cytotoxic effect on the breast cancer cell lines (UACC182: 0.01 μM, SUM190: 0.018 μM, BT474: 0.022 μM, SK-BR-3: 0.037 μM, SUM225: 0.083 μM and MDA-MB-453: 3.9 μM) and this correlated to higher ErbB2 expression (108 to1161 ng/mg) [12,13].