Fig. 6: bHLH/LMO human L-ICs are quiescent and chemotolerant.

(Left) Representative FACS plot showing decreased in vivo BrdU incorporation of L-ICs compared to leukemic blasts and (Right) quantification of BrdU/7-AAD cell cycle profile. Data are from REL-14 (A; n = 5), REL-13 (B; n = 3), DX-9 (C; n = 5), and DX-8 (D; n = 4). NSG mice engrafted with relapsed (REL) or diagnostic (DX) T-ALL PDX samples were pulsed with BrdU 1 h prior to sacrifice. Cell cycle profiles of human L-ICs (CD45⁺/CD1a^- red, left) or blasts (CD45⁺/CD1a⁺ blue, right) are shown. E Schematic for assessing chemotherapy response of human T-ALL subpopulations. F Representative FACS plots for REL-14 treated with vehicle (DMSO) or Dex (5 mg/kg)/VXL for 48 h, G REL-13 treated with vehicle (DMSO) or Dex/VXL for 24 h H DX-9 treated with vehicle (DMSO) or VXL for 24 h. I DX-8 treated with vehicle (DMSO) or VXL for 24 h. J Percent survival of human L-ICs (CD45⁺/CD1a^- red) vs blasts (CD45⁺/CD1a⁺ blue) are shown. N = 5, 5, 5, and 8 xenografts analyzed for DX-8, DX-9, REL-13 and REL-14, respectively. All comparisons by paired two-sided t-test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < .0001.