It is known that MAP kinase pathway is a key downstream pathway in the HER2 signaling cascade and it has been found that phosphor-MED1 levels are significantly higher in HER2-positive BT474 BC cells than in MCF-7 BC cells and the overexpression of HER2 in MCF-7 cells is sufficient to increase MED1 phosphorylation [95]. This evidence concerns the gene MED1 and breast cancer.