JAK1 and precursor B-cell acute lymphoblastic leukemia: We also studied the effects of JAK1 mutations on human B-ALL NALM-6 cell line, and observed that NALM-6 cells transduced with S646P mutation had an increased percentage of S/G2 phase relative to other groups (Supplementary Figure 1), further confirming the promoting effect on cancer cell proliferation of JAK1 S646P mutation.