The cell surface expression of HAVCR2 and ITGAX, as measured by FACS analysis, are highly correlated and can further separate the previously identified Lin-CD3+KITmid LSC-enriched subpopulation into several subgroups (Figure 1D, upper panel), among which the HAVCR2high or HAVCR2high ITGAXhigh subgroups are most abundant in the thymus, the critical organ for T cell development and T-ALL initiation (Guo et al., 2008;Guo et al., 2011) (Figure 1D, lower panel). This evidence concerns the gene ITGAX and acute lymphoblastic leukemia.