ERBB3 and cancer: HER3 is a member of the ErbB/HER protein kinase family, and while HER3 itself is not an oncoprotein and lacks tyrosine kinase activity, HER3 heterodimerizes with other RTKs to activate oncogenic signaling via the PI3K/AKT/mTOR pathway and also MEK/MAPK, Jak/Stat, Src kinase signaling leading to cell proliferation and ultimately the promotion of cancer cell survival, proliferation, and progression52,53.