PAK4 and cancer: Combing these findings together, it underlies the essential role of RSK2 and PAK4 in carcinogenesis and chemoresistance, and both factors may become a cancer prevention target for poly‐pharmacological or combinational therapies.[44] Our successful identification of RSK2 and PAK4 as combinational therapeutic targets also proves the feasibility of BE‐mediated screens for characterizing functional phosphorylation sites that can be further applied for discovering key upstream kinases as perturbing targets in a specific process.