Establishment of a NOD/SCID/γc−/−-Dependent Lymphoid Leukemia Cell Line, D593, with Novel RUNX1-LAF4 Fusion Gene.

We established a NOD/SCID/γc−/−(NOG mouse)-dependent human lymphoid leukemia cell line, D593, by repeated xenotransplantation of pediatric T-cell acute lymphoblastic leukemia cells with the translocation t(2;21). The cell line, D-593, could be serially transplanted from mouse to mouse over a 2-year period. D593 had the same immuno-phenotype as the original leukemia cells: positive for CD2, 5, 7, 14, and 34, and negative for CD3, 4, 8, 19, and 41a. Cytoplasmic CD3 was positive and the rearrangement of T-cell receptor was detected by Southern blot analysis. A previously unreported translocation of t(2;21)(q11;q22) was observed in both the original patient sample and D593. The split signal of RUNX1 was detected by fluorescence in site hybridization in D593 indicating the involvement of RUNX1. Using 3′-RACE and RT-PCR analysis, we identified novel chimeric transcripts of RUNX1-LAF4 joining exon 7 of RUNX1 to exon 4 of LAF4. In the transplanted NOG mice, D593 homed into the trabecular endosteal region of bone marrow (BM), and proliferated from the endosteum to medulla. At the late stage of engraftment, the BM was filled with human lymphoblasts and metastases into the trabecular of the spleen and Glisson’s sheath of the liver were also observed. These findings suggest that D593 is a useful cell line to study not only the leukemia-related biology of RUNX1-LAF4 but also the novel therapeutic model against core-binding factor (CBF) leukemia.