MEK inhibitors are actively being developed for cancers with constitutive activation of the RAS/RAF/MEK pathway.6 RAS mutant cancers exhibit a variable response to these compounds, with intrinsic resistance commonly encountered in clinical trials.17 Many MEK inhibitor-resistant cell lines harbour activating mutations in the PI3K pathway, including PIK3CA. 9 This has resulted in investigations into dual inhibition of the MEK and PI3K pathways; however, these combinations have been limited in their clinical usefulness due to significant toxicities. The gene discussed is PIK3CA; the disease is cancer.