AKT1 and neoplasm: HER2 activation is dependent on HER2 homodimers or heterodimers with other ErbB family members, which could stimulate constitutive phosphorylation of HER2 and initiate the key downstream PI3K/AKT pathway or MAPK pathway that results in tumor growth and progression (Agus et al., 2002; Baselga and Swain, 2009; Wang et al., 2017).