AML-lysate–pulsed DC vaccines initiated prior to AML challenge reduce AML tumorigenicity by approximately 10-fold, but neither DC vaccines nor Flt3L will protect mice from AML tumorigenicity if initiated as late as 1 day after AML challenge.
Cohorts of naive B6 mice received either 3 weekly doses of tumor-lysate–pulsed DCs (beginning on day −21 or +1, as indicated) or 21 daily subcutaneous Flt3L (30 μg per dose) injections (days +1 to +21) or no treatment followed by a lethal leukemia dose (105 per mouse) on day 0. Results are pooled from 2 independent experiments with similar results (n = 16 mice per group). An additional cohort of control mice was given a lower leukemia cell dose (104 per mouse) (n = 8 mice). A Kaplan-Meier survival plot shows days post–lethal C1498 challenge (day 0) on thex-axis and the proportion of mice surviving on they-axis. The actuarial survival rate of recipients given DC vaccines initiated 3 weeks prior to AML challenge was significantly (P = 000021) higher than controls but not significantly different (P ≥ .1) from recipients of a 10-fold lower AML cell dose (104 per mouse). The actuarial survival rate of recipients of either DC-vaccinated or Flt3L-treated recipients initiated 1 day after live AML challenge was statistically significantly higher (P ≤ .05) than the control animals although the vast majority of animals succumbed to leukemia.
