In vivo sensitivity of xenografts ALL-3, ALL-8, ALL-11, and ALL-19 to vincristine, dexamethasone, and methotrexate. Mice were inoculated with ALL-3 (A), ALL-8 (B), ALL-11 (C), or ALL-19 (D), monitored for engraftment, and treated with vincristine (V; bold dotted lines), dexamethasone (D; bold lines), methotrexate (M; thin dotted lines), or saline control (C; thin lines) as described in “Materials and methods.” The EFS of NOD/SCID mice was quantified as the time taken from the initiation of treatment for the leukemic population to reach 25% in the peripheral blood, or for the animals to show evidence of leukemia-related morbidity. Each line represents the proportion of mice remaining event free over time. Xenografts ALL-3 (A) and ALL-11 (C) were highly responsive, and ALL-8 (B) relatively resistant, to all 3 drugs, whereas ALL-19 (D) was resistant to dexamethasone, of intermediate sensitivity to vincristine, and sensitive to methotrexate.