Hence, since selumetinib downregulates ErbB2 protein in detached breast cancer cells (Figure 1), whereas activated Mek upregulates ErbB2 protein in detached breast epithelial cells (Figure 3B), the effect of Mek on ErbB2 protein in such cells does not involve changes in the ErbB2 mRNA. This evidence concerns the gene ERBB2 and breast cancer.