Deregulation of various components of the mTOR pathway, such as PI3K amplification/mutation, loss of PTEN function, overexpression of Akt, ribosomal protein S6 kinase beta-1 (S6K1), eukaryotic translation initiation factor 4E binding protein 1 (4EBP1), and overexpression of eukaryotic translation initiation factor 4E (eIF4E), has been reported in numerous cancers, especially melanoma, where variation in key elements of the mTOR signaling have major effects on tumor growth [83]. The gene discussed is PIK3CA; the disease is melanoma.