Apoptosis of T-ALL cell lines treated with BCT-100 under stromal support/ VCR pre-treated stromal support. The protective effect of hMSCs on T-ALLs during BCT-100 treatment could be abolished by pre-treating hMSCs with vincristine. (a) Baseline Apoptosis of T-ALL cell lines was not affected by VCR pre-treatment on hMSCs. CCRF-CEM, Jurkat or MOLT-4 cells were cultured for 36 hours with hMSCs or hTertMSCs transwell co-culture. MSCs were with or without vincristine pre-treatment for 3 days. Annexin V / FITC Propidium iodide (AV/PI) assay was performed to test the percentage of apoptosis. (b) VCR pre-treatment on hMSCs could partly re-establish the chemosensitivity of T-ALL cells to BCT-100 as in those without stromal support. hMSCs or hTertMSCs were pre-treated with or without VCR for 3 days, after washing the cells extensively with PBS, CCRF-CEM, Jurkat or MOLT-4 were co-cultured with the pre-treated hMSCs or hTertMSCs. 1 U/ml BCT-100 was used to treat the co-cultures for 36 hours. Then the T-ALL cells were harvested and AV/PI assay was performed to test the percentage of apoptosis. The average apoptotic percentages of the 3 T-ALL cell lines were obtained under transwell co-culture with hMSCs from different donor including hTertMSCs. All experiments were done in triplicate with error bars showing standard deviation. *: p < 0.05 between T-ALL / hMSCs co-culture and T-ALL/ VCR pre-treated hMSCs co-culture.