Kaplan-Meier survival analysis of primary and secondary leukemic mice. (Top graph) Survival data showing the onset of primary leukemia in C57BL/6 mice (CD45.2/Ly5.2) during an observation period of approximately 13 months. A total of 15 mice received a transplant of PIDE-transduced (mock) LSPCs; none developed a disease phenotype. Eight mice received a transplant of either MLL·AF4-tranduced LSPCs or both t(4;11) fusion genes. Three mice that received a transplant of both fusion alleles (MLL·AF4/AF4·MLL) developed acute leukemia. Twenty-three recipients received a transplant of AF4·MLL-transduced LSPCs. Of those, 8 mice developed acute leukemia. y-axis indicates percentage; x-axis, days. (Bottom graph) Survival data showing the onset of secondary leukemia in C57BL/6 mice (CD45.1/Ly5.1). A total of 15 mice received a retransplant of spleen cells deriving from AF4·MLL-mediated leukemic mice. All of these mice developed acute leukemia with a TTL of 25 ± 10 days. Eighteen mice received a retransplant of spleen cells deriving from MLL·AF4/AF4·MLL-mediated leukemic mice. Sixteen of 18 mice developed acute leukemia with TTL of 29 ± 15 days. y-axis indicates percentage; x-axis, days.