ERK1 and ERK2 are closely related serine/threonine kinases and participate in the Ras-Raf-MEK-ERK signal transduction cascade, which is involved in many biological processes including cell adhesion, cell cycle progression, cell migration, cell survival, differentiation, metabolism, proliferation, and transcription by catalyzing the phosphorylation of hundreds of cytoplasmic and nuclear substrates.218,219 This signaling pathway is implicated in numerous cancers. The gene discussed is MARK2; the disease is cancer.