Furthermore, we reveal that when PDX-ALL cells are co-cultured with 3D BM-MSC-spheroids they show greater reduction in sensitivity, compared to the 2D co-culture arm, against dexamethasone, ABT-199 (a molecularly targeted therapy against BCL-2 positive blood cancers), and dexamethasone-ABT-199 combination in a sample subgroup that exhibited reducedin vivo efficacy (obtained from previously unpublishedin vivo data existing in the lab from earlier studies). This evidence concerns the gene BCL2 and acute lymphoblastic leukemia.