AML microenvironment conditioned HSC accrue persistent DDR and gain a proliferative advantage.Figure 6A schematic diagram demonstrating the serial replating experiment. KSL were sorted from primary recipient control mice (black, n=4), or Molm-14-xenografts (red, n=4) and plated in triplicate (500 cells/plate/mouse) in methylcellulose media. Seven days later, colonies were counted and serially replated in triplicate (5000 cells/plate/mouse). The replating process was repeated twice for a total of three rounds (labeled week "WK" 1, 2 and 3). Serial replating CFU-C analysis presented as mean ± SEM showing: (B) the number of colonies per 1000 plated cells, and (C) the number of cells per colony, for each week time-point. DNA-damage assessment in KSL from primary recipients and after two turns of replating. (D, F, H) Number of γH2AX foci in control-derived and Molm-14-xenograft-derived: (D) Primary recipient KSL, n=211 and 321, All cells were stained with phosphoH2axser139 and the nuclear stain Hoechst (blue), imaged using the GE/API DV widefield microscope (60X objective) to show the γH2AX foci (green) and counted using Imaris software. qRT-PCR gene expression analysis showing the fold-change of select DNA-damage response-genes panel in Molm-14-xenograft-derived: (E) Primary recipient KSL, n=6 Data indicated by bars of fold-change calculated relative to matching controls, normalized to the endogenous control Gapdh and presented as means ± SEM. Number of γH2AX foci in control-derived and Molm-14-xenograft-derived: cells from W1 plating, n=218 and 369 All cells were stained with phosphoH2axser139 and the nuclear stain Hoechst (blue), imaged using the GE/API DV widefield microscope (60X objective) to show the γH2AX foci (green) and counted using Imaris software. Scale bars are 2μm. qRT-PCR gene expression analysis showing the fold-change of select DNA-damage response-genes panel in Molm-14-xenograft-derived: Cells from W1 plating, n=4, Data indicated by bars of fold-change calculated relative to matching controls, normalized to the endogenous control Gapdh and presented as means ± SEM. Number of γH2AX foci in control-derived and Molm-14-xenograft-derived: cells from W2 plating, n=770 and 853. All cells were stained with phosphoH2axser139 and the nuclear stain Hoechst (blue), imaged using the GE/API DV widefield microscope (60X objective) to show the γH2AX foci (green) and counted using Imaris software. qRT-PCR gene expression analysis showing the fold-change of select DNA-damage response-genes panel in Molm-14-xenograft-derived: Cells from W2 plating n=4. Data indicated by bars of fold-change calculated relative to matching controls, normalized to the endogenous control Gapdh and presented as means ± SEM. Scheme of DDR assessment in KSL and LT-HSC derived from serial in vivo repopulation. umber of γH2AX foci, respectively, in control- and Molm-14-xenograft-derived: (K) KSL, n=101 / 204, and (L) LT-HSC, n=33 / 53. Images were processed similar to D-F. Scale bars are 3μm. Statistics: Student's t-test. (** P< 0.01). qRT-PCR analysis of the DNA-damage-genes panel in Molm-14-xenograft-derived: (M) KSL, and (N) LT-HSC, relative to matched controls. Data depicted as fold-change relative to matching controls, normalized to the endogenous control Gapdh and presented as mean ± SEM.