MAP2K4 and breast carcinoma: Lastly, MKK4 knockdown with silencing RNA (siRNA) in a MKK4‐positive breast cancer cell line resulted in decreased anchorage‐independent growth, increased apoptosis in serum‐deprived conditions, and suppressed tumor growth in a mouse xenograft model, indicating that in some genetic contexts MKK4 can promote tumorigenic phenotypes.