Fig. 1: Eμ-Ret leukemia progression characteristics.

A An expanded BCP population is detectable in bone marrow (BM), spleen, and peripheral blood of 4-week-old Eμ-Ret mice (Tg+), based on their characteristic cell surface phenotype, compared to their transgene-negative (Tg-) littermates. Numbers shown indicate BCP cells as % of total viable cells. B The size of the preleukemic cell population shows considerable variation between individual 4-week-old Eμ-Ret mice (n = 15). C When monitored over the first 120 days, no significant expansion of the abnormal BCP population is observed before 65 days of age, the earliest age of onset on leukemia in this model (p = 0.7412), or afterwards (p = 0.3016), using a linear mixed effects model. The concentration of preleukemic BCP cells in peripheral blood was measured for each Eμ-Ret mouse at a single time-point; no mouse contributed more than one data point (n = 45). D Leukemia progression kinetics in 182 Eμ-Ret mice housed under SPF-conditions in 2 separate facilities. Leukemia is >95% penetrant in Eμ-Ret mice on a BALB/c background within one year. E Leukemic Eμ-Ret mice present with significantly higher number of cells in their spleens compared to wild-type (WT) BALB/c and preleukemic Eμ-Ret controls (PL). F The cellularity of organs at time of leukemia onset is dominated by leukemic blasts with the characteristic abnormal BCP phenotype. G Numbers of blasts (identified by their B220^int/CD43^int/BP-1^hi phenotype) in bone marrow and spleen of leukemic mice are significantly higher than in healthy Eμ-Ret mice of similar age (n = 15 for both). H Survival of NSG and BALB/c recipients injected with 1–3 × 10⁵ preleukemia cells obtained from young Eμ-Ret mice (Primary, left panel) or with 10⁵ leukemic cells that developed in the primary NSG recipients (Secondary, right panel). Four NSG and 4 BALB/c mice received preleukemia cells and 5 NSG and 6 BALB/c mice received the resultant leukemia cells. (**** = p < 0.0001).