To further cement the role of PAK1 in HER-signaling, follow-up studies demonstrated a role of HER3 activation-linked HER2 phosphorylation in the rapid activation of PAK1 activity with a mechanism involving PI3-kinase recruitment to the HER2-HER3 heterodimers in HRG-stimulated breast cancer cells [19]. This evidence concerns the gene PAK1 and breast cancer.