In vivo responses of xenografts derived from patients 2, 3, 7, 8, 17, and 19 to vincristine.

Mice were inoculated with human leukemia cells, monitored for engraftment, and treated with vincristine (A) or saline control (B) as described in “Patients and methods.” During and following treatment, the leukemic burden was monitored by estimating the proportion of human CD45⁺ cells in murine peripheral blood. (A) The xenografts from patients 2 (open circles) and 3 (closed circles) took approximately 6 and 7 weeks, respectively, to reappear in the peripheral blood following the initiation of vincristine treatment, whereas xenografts from patients 7 (open triangles) and 19 (open diamonds) essentially grew through the vincristine. Xenografts from patients 8 (open squares) and 17 (closed squares) exhibited an intermediate response. (B) Xenografts exposed to saline exhibited equivalent growth rates. Arrows indicate vincristine or saline treatment times.