Fig. 3.

Hydroxyurea (HU) synergizes with ponatinib in inducing growth inhibition in BCR-ABL1 positive cell lines and suppresses out-growth of cells harboring T315I-inculding BCR-ABL1 mutations. (A-C) Human CML cell lines (A), Ba/F3 cells expressing various mutant forms of BCR/ABL1 (B), and primary leukemic cells obtained from CML patients (C), were incubated in control medium (Co) or in various concentrations of HU, ponatinib or the combination of both drugs as indicated at 37 °C for 48 h. Thereafter, ³H-thymidine-uptake was measured. Results are expressed as percent of control and represent the mean±S.D. from triplicates. Patients' numbers in (C) refer to Table 2. (D) Human CML cell lines were incubated with control medium (Co) or medium containing various concentrations of HU, ABL001 or the combination of both drugs as indicated at 37 °C for 48 h. Thereafter, ³H-thymidine-uptake was measured Results are expressed as percent of control and represent the mean±S.D. of triplicates. (E) Ba/F3p210^WT (labeled by Venus), Ba/F3p210^T315I (labeled by GFP) and Ba/F3p210^T315I/E255V (labeled by tdTomato) were mixed in a 1:1:1 ratio and incubated together in control medium or in the presence of HU (100 µM), ponatinib (10 nM) or the combination of both drugs for 72 h (h). Thereafter, the ratio between clones in each condition was measured by flow cytometry. The percentage of non-viable cells was determined by trypan blue staining. Results show one typical experiment. Almost identical data were obtained in 2 other independent experiments.