SPP1 and acute lymphoblastic leukemia: OPN is promptly upregulated in the inflamed tissues and serum of SLE patients as well as in the plasma of Faslpr/lpr mice, but little is known about OPN contribution to lymphoid malignancies, except from being up-regulated in primary central nervous system lymphomas (PCNSL) [21] and in bone marrow blasts of acute myeloid leukemia patients [22], and promoting the dormancy of acute lymphoblastic leukemia clones in the bone marrow osteoblastic niche [23].