TYROBP and acute lymphoblastic leukemia: Though we have demonstrated the high pathologic expression of Sig15 in B-ALL, none of the B-ALL cell lines expressed the primary Sig15 binding partner DAP12 (Fig. 1C) or alternative binding partner FcRγ (Supplementary Fig. S1C), which are required for downstream activation of Syk kinase and PI3K in myeloid cells (13).