PF4 and leukemia: We further injected 10,000 B-ALL cells together with 2 × 105 total BM cells into lethally irradiated recipients, including Cdh5-Cre;Vps33bfl/fl, Prx1-Cre;Vps33bfl/fl and Pf4-Cre;Vps33bfl/fl mice, and monitored the effects on leukemia development (Fig. 1a).