SPP1 and acute lymphoblastic leukemia: In the case of B-ALL, Ma and colleagues [132] demonstrated, by means of a 3D organotypic device, recapitulating the complexity and heterogeneity of the BM niche, that leukemic cells can upregulate, upon coculture, OPN expression in MSCs and that OPN can, in turn, crucially mediate leukemic cell adhesion to MSCs.