SPP1 and B-cell acute lymphoblastic leukemia: In addition, OPN, a factor highly enriched in bone multicellular units (BMUs, the sites of bone remodeling), was found to be increased in the bone marrow of AML patients, and its level was correlated with a shortened survival.183 Moreover, Boyerinas et al. showed that OPN plays roles in minimal residual diseases of B-cell acute lymphoblastic leukemia by controlling cell quiescence, but whether it plays a similar role in age-related malignancies such as MDS or AML is unclear and needs to be elucidated184 (Fig. 5.6).