Figure 2. Primary human bone marrow stroma cell supernatant protects human primary leukemia cells from Ara-C induced cytotoxicity.

Purified human primary leukemia cells from Patient (A) and Patient (B) were cultured in absence (normal medium) or presence of human BMSC SN from HS5 (BM SN HS5) or primary human BMSC SN from AML patient (BM SN AML) for 2 hours before treatment with Ara-C (0.2, 0,6 and 2.5 μg/ml) (A) or Ara-C (0.6, 25 and 10 μg/ml) (B) for 72 hours. Leukemia cell viability was assessed by the MTT assay. Each bar represents the mean ± SD of 3 independent experiments. **p < 0.01, ***p < 0.001 (leukemia cells versus leukemia cells + human BM SN). (C) Overall analysis of IC₅₀s for Ara-C from primary leukemia cells obtained from 20 AML patient samples incubated in normal culture medium (RPMI) or human BMSC SN from HS5 (BM SN HS5) treated with Ara-C for 72 hours. ***p < 0.001 (RPMI IC₅₀s versus SN IC₅₀s). (D) Overall analysis of primary leukemia IC₅₀s from 18 AML patient samples with long-term remission versus patients with treatment failure. Primary leukemia cells were incubated in normal culture medium (RPMI) or BM SN HS5 treated with Ara-C for 72 hours.