Leukemia reconstitution in vivo is driven by cells in early cell cycle and low metabolic state

To characterize LICs in ALL irrespective of surface markers expression, we investigated leukemia initiating activities of cellular subfractions of patient-derived xenograft BCP-ALL cells sorted according to different cell cycle phases (i.e. G0/G1 and G2/M) followed by transplantation onto NOD/SCID mice. All cell fractions led to leukemia engraftment indicating LIC activity irrespective of cell cycle stage. Most importantly, cells isolated from G0/G1 cell cycle phases led to early leukemia engraftment in contrast to cells from late cell cycle (G2/M). To further characterize cells with different engraftment potential in vivo, we analyzed the gene expression profiles of early (G1b early) and late (G2/M) engrafting cells. Gene expression was measured using Affymetrix platform in 8 BCP-ALL patient derived xenograft samples sorted according to cell cycle annotations