Figure 4
AML-derived exosomes reduce stem cell activities, limit ability of stroma to support normal HSCs and accelerate AML progression; disruption of exosome production delays AML progression. (a) Repopulation ability of marrow from normal PBMC-derived or AML (KG1A)-derived exosome-treated donors was assayed 22 weeks after transplantation into congenic recipients (n=5–6 mice per group in two independent experiments). (b) CD45.1 HSCs were co-cultured with the AML cell/exosome-modified stroma for 48 h and transplanted (100 per mouse) into lethally irradiated WT CD45.2 recipients along with 200 000 unfractionated CD45.2 helper BM cells. Ability of control and AML cell/exosome co-cultured HSCs to repopulate the blood of recipient mice was assayed 19 weeks after transplantation (n=6–8 mice per group in three independent experiments). (c) Three weekly doses of AML-derived or normal PBMC-derived exosomes, or PBS vehicle control, were injected intravenously into 6- to 8-week-old DKO mice. Mice were irradiated and injected with 20 million KG1A cells. AML cell engraftment in peripheral blood was assayed 20 days later (middle). Kaplan–Meier survival analysis of control or treated mice (right; n=8–13 mice in at least two independent experiments). (d) MV411 AML cells were transduced with lentiviral shRNA against Rab27a, a protein involved in exosome release. qRT-PCR of Rab27a levels (left) and total exosome protein quantification (middle). Kaplan–Meier survival curve for mice transplanted with lentiviral shRab27a-transduced MV411 cells (right; n=8–10 mice in two independent experiments). ns, not significant, *P<0.05, **P<0.01, ***P<0.001.
