Figure 2.
Inhibition of IL7R delays leukemogenesis in xenograft mice. (A) NSG mice were xenografted with 697 cells bearing an shRNA against the IL7Rα (shIL7Rα) or a control shRNA (shGFP). Animals were euthanized at day 26 upon detection of >75% leukemic blasts in the peripheral blood or clinical leukemia (loss of weight or activity, organomegaly, hind-limb paralysis) in first control mice. Spleen (Sp) and BM infiltration by human leukemic blasts in control and treated animals. (B) CNS infiltration as determined by histology (hematoxylin and eosin stain; original magnification ×100 [i,iii] and ×40 [ii]). The arrows indicate human leukemic blasts in an example for the semiquantitative scoring used.13 (C) A total of 1 × 106 E2A-PBX1+ patient cells were xenografted into NSG mice. Xenografted mice were treated with vehicle only, ruxolitinib (Ruxo) only, chemotherapy (Chemo) only (dexamethasone, vincristine, and polyethylene glycol–asparaginase), or a combination of ruxolitinib and chemotherapy (n = 7 per group). Mice were euthanized upon appearance of leukemic symptoms. Statistics for survival were performed according to the Mantel-Cox log-rank method. P1, Control vs Ruxo; P2, Control vs Chemo; P3, Control vs Ruxo/Chemo. (D) A total of 1 × 106 E2A-PBX1+ patient cells were xenografted into NSG mice. Xenografted mice were treated with an anti-IL7R antibody or an isotype antibody (n = 7 and n = 6 per group, as indicated). The experiment was ended on day 135. Statistics for survival were performed according to the Mantel-Cox log-rank method. (E-G) A total of 1 × 106 E2A-PBX1+ patient cells were xenografted into NSG mice. Xenografted mice were treated with control antibody, ruxolitinib, with an anti-IL7R antibody (Ab) or with both ruxolitinib and the antibody (n = 7 per group). One mouse of the Ruxo/anti-IL7R group died during the experiment and accordingly was excluded. The experiment was ended on day 65 and spleen sizes (E), the percentages of Sp and BM blasts (F), and CNS infiltration (G) were assessed (Fisher exact test, 2-sided). Treatment protocol: 60 mg/kg ruxolitinib (LC Laboratories) was administered Monday through Friday by oral gavage. Chemotherapy was administered as previously published.15,22 A total of 1 mg/kg anti-IL7R antibody (monoclonal mouse immunoglobulin G1 [IgG1], clone 40131; R&D Systems) or isotype control antibody were administered on days 0, +3, +7, +21, +35, +48, and +56 postinjection.