PAK4 and breast cancer: In a study by Rafn and co-workers, ErbB2 activation was shown to induce the invasion of breast cancer cell spheroids via activation of a signaling network that involves TGFβ receptor 1 and 2 (TGFBR1 and 2), ERK2 (MAPK1), PAK4, PAK5 and PAK6 (PAK4, PAK5 and PAK6), cdc42 binding protein kinase beta (CDC42BPB), and protein kinase Cα (PKCα; PRKCA).