ERBB2 and breast cancer: A few years later, Chakrabarty et al. [50] demonstrated that inhibition of PI3K by XL147 (pilaralisib), a highly selective pan-inhibitor of class 1A PI3Ks (α, β, γ, and δ), induced upregulation and activation of HER3 and other RTKs, including IR, IGF1R and FGFRs in HER2-overexpressing BC cell lines, which eventually reactivated PI3K/AKT signalling.