JAK1 and leukemia: We treated these leukemias with the combination of DEX and inhibitors of JAK1/2 (ruxolitinib), MEK (trametinib), or Akt (MK2206) at concentrations that attenuated TSLP-induced signaling in the CRLF2R Ph-like ALL cell line Mutz-5 (S2B–S2D Fig) and that did not demonstrate toxicity in healthy PBMCs (S2E Fig).