MAPK3 and breast carcinoma: To understand how Giα proteins regulate ERK1/2, Akt and mTORC1 activation and breast cancer invasion induced by growth factors in normal and breast cancer cells, we first examined whether Giα proteins are involved in the activation of FAK1, which is important for cell migration, and Shp2, which is critical for the activation of ERK1/2 by EGF and IGF-1.