Good engraftment of B-cell precursor ALL in NOD-SCID mice

Background In vivo models for human B cell precursor ALL have been established by transplanting human leukemic cells onto immune-deficient SCID mice. High risk and relapsed leukemias engraft very well in these mice, however, good prognosis pediatric ALL often grow poorly if at all. Recently a new, even more immune-deficient mouse strain has been bred by crossing the scid mutation onto the NOD mouse background. As these NOD-SCID mire have been shown to be better recipients for human myeloid cells the goal of this study was to test these mice as hosts for human acute lymphoblastic leukemia cells. Patients and methods Bone marrow or peripheral blood cells from 7 pediatric and one adult patient with B-cell precursor ALL were transplanted onto immune-deficient NOD-SCID mice according to established protocols. Main results ALL cells from 6 out of the 8 patients (75%) successfully engrafted the NOD-SCID mice and from 4 patients (50%) led to an extensive leukemic infiltration in the murine marrow (>10%). High level human cell engraftment could be demonstrated. by flow cytometry, Southern blot analysis and cytology. By cytology and immunophenotype the leukemia in the mice was indistinguishable from the original leukemia in the patients, The presence of few human eosinophils in the marrow of highly engrafted mice indicates minimal coengraftment of residual normal cells. Development of overt leukemia in the mice after transplantation of cells from different patients varied between 1.5 and 7 months. Interestingly and in contrast to myeloid cells, conditioning of the mice by sublethal irradiation was not necessary for successful engraftment. Limiting dilution experiments with leukemic blasts from one patient showed that as few as 10 000 cells were sufficient to transfer the leukemia onto NOD-SCID mice. Conclusions NOD-SCID mice are sensitive recipients for human ALL xenografts.