We identified four cell lines with mTORC1-activating MTOR mutations (C1483Y in MOLT16; E1799K in HEC59 and SNU349; and S2215Y in JHUEM7)...only the cell lines with activating MTOR mutations, the PI3K-p110α mutant, or the NPRL2-null SW780 cells were hypersensitive to rapamycin treatment (Figure 4B). Consistent with these and published results, the growth of HeLa xenografts was partially rapamycin sensitive, while rapamycin completely halted the growth of HEC59 xenografts, which carry the hyperactivating mTOR E1799K mutation (Figure 4C).