The p90 ribosomal S6 kinase (RSK) family serine/threonine protein kinases, including the predominant isoforms expressed in AML RSK1 and RSK2, possess the N- and C-terminal kinase domains (NTKD and CTKD) and are activated downstream of the MEK/ERK signaling pathway [15,16]. Here, RPS6KA3 is linked to acute myeloid leukemia.