Figure 4B shows the typical histological appearance of these tumors as well as the strong HER2 overexpression detected by immunohistochemistry. Mice with established BT474 tumor masses were treated with lapatinib (or vehicle) for three days. Thereafter, Grb7 mRNA in the tumors was quantified by Q-PCR. Indeed, lapatinib treatment upregulated Grb7 mRNA by about two folds, indicating that increased Grb7 levels are likely to be found in HER2+ tumors in vivo in response to this drug. This evidence concerns the gene ERBB2 and neoplasm.