PIK3CA and cancer: Phosphorylation sites on 4EBP1 (gene name EIF4EBP1) or Ribosomal S6 (gene name RPS6), which are known to be downstream of PI3K/mTOR(Ref [36]), did not correlate with the responses of our cancer cell panel to the PI3K/mTOR inhibitor PI-103 (Figure 7A).