MAP2K1 and neoplasm: Agents targeting the MEK components of the MAPK signaling cascade have been investigated for the treatment of various tumor types in recent years, with promising results.1 Seven MEK enzymes (MEK1-7) have been identified so far that operate within 4 distinct MAPK signaling pathways and selectively activate downstream substrates of the signaling cascade.1 Inhibitors targeting MEK1 and MEK2 have received the most attention, with several, including trametinib, cobimetinib, binimetinib, and selumetinib,7-10 approved for clinical use.