To assess whether the pattern was specific to MAPK pathway inhibitors, rather than generic differences in sensitivity to anti-cancer drugs, we used a cell line screening database37 to examine sensitivity (mean viability) of the same cell lines to 15 anti-cancer drugs, including 5 MAPK inhibitors, 5 inhibitors of non-MAPK targets (PI3K, Akt, mTOR, and Bcl-2), and 5 cytotoxic drugs. The gene discussed is PIK3CA; the disease is cancer.