Figure 4.

Leukemia-initiating cells (LICs) are enriched in PDLS internal niches. (A) Secondary spheroid colonization assay was performed with purified PDLS-in and PDLS-out leukemic cells from primary PDLS (n = 8). (B) Schematic representation of experimental design, Leukemic cells were cultured during 48 h on stromal-free (SF), MSC monolayers (2D), and PDLS and 3,000 CD45⁺ cells were transplanted into NSG mice. (C) Leukemia burden was monitored in peripheral blood by FACS (upper panel) and overall survival was plotted (lower panel) when RS4:11 cells were used (n = 5). (D) Engraftment was determined in BM after 6 weeks of xenotransplantation of RS4:11 cells (upper panel) or three different primary B-ALL cells (representative plots are shown in lower panel) (n = 5). B-ALL, B-cell acute lymphoblastic leukemia; PDLS, patient-derived leukemia spheroids; MSCs, mesenchymal stromal cells; FACS, Fluorescence-activated cell sorting. *P < 0.05; **P < 0.01; ***P < 0.001, ***P < 0.0001. Error bars represent SD.