MAPK1 and neoplasm: The results of these analyses provided the structural underpinnings for understanding the role played by MK linear motifs, the role of ERK-independent activation of RAS-induced senescence via ribosomal S6 kinase (RSK), the role of RSK inhibitors in dampening ERK activity, how ERK via RSK can regulate cell motility [86], and how MK5/p38-regulated-activated protein kinase (PRAK) can act as a tumor suppressor [87].