BM niches influence chemosensitivity of hT-ALL. (A) Absolute numbers of hT-ALL recovered after in vitro treatment of thorax- and tail-derived T-ALL during 72 hours with 10 nM vincristine, 500 nM cytarabine, or 200 nM dexamethasone. Results are from 3 hT-ALL (#1-#3) individually cultured as tri- or quadruplicates. The line shows median cell numbers. (B) Same results calculated as fold decrease compared with untreated conditions. (C) Apoptosis levels in T-ALL cells treated (+) or not (−) with vincristine, cytarabine, or dexamethasone. Shown are apoptotic cell increases (in fold) relative to untreated thorax- or tail-derived hT-ALL cells. (D) Survival of secondary mice transplanted with 1300 to 13 000 cells/mouse following 72 hours in vitro treatment with 10 nM vincristine. Results are from 8 mice/group, hT-ALL#1. Statistics are calculated according to log-rank (Mantel-Cox) test (D) or nonparametric Mann-Whitney U test (*P < .05; **P < .01; ***P < .001).