Importantly, this conclusion is not restricted to transformed keratinocytes, as EGF-mediated Src, -MEK1, -ERK1/2 and -STAT3 phosphorylations were also severely impaired on KIAA1199 deficiency in breast cancer-derived MCF7 and SK-BR-3 cells, as well as in immortalized breast epithelial NMuMG cells (Fig. 8a–c). Here, MAP2K1 is linked to breast cancer.