ABL1 and osteonecrosis: Using a murine model of osteonecrosis, our group previously found that mice treated with a discontinuous regimen of dexamethasone developed less osteonecrosis than those treated with a continuous regimen,[17] consistent with clinical data in ALL [15, 16] and systemic lupus erythematosus patients.[18] Herein, we compared the antileukemic efficacy of these same dexamethasone regimens in a murine BCR-ABL Arf-/- preB cell ALL model in two different strains of mice [19] and in xenograft models of eight different primary ALL samples.