Fig. 2. Active STAT3 is essential for survival and leukemic potential of TKI-persistent CML LSCs.

A The sensitive and persistent K562 were treated with LLL12 (1 µM) for 3 days. Treatment was switched to either imatinib (1 µM) or continued with LLL12 (1 µM) for additional 3 days. Cells were analyzed for AnnexinV by flow cytometry. B Dose curve of imatinib for the sensitive and persistent K562 untreated or treated with LLL12 (1 µM) for 3 days. The cells were stained with annexin V and analyzed by flow cytometry. C HSC or LSC count per 10 million BM cells (left), percent AnnexinV stem cells (middle) and 24 hr BrDU incorporation in stem cells (right) of control and CML mice post 4 weeks of imatinib (200 mg/kg) or LLL12 (25 mg/kg) treatment individually or in combination. n = 5. D Survival curves of control and CML mice post 4-week imatinib (200 mg/kg) or LLL12 (25 mg/kg) treatment alone, or in combination. E Limiting dilution CRU (competitive repopulation unit) assay is shown. The indicated numbers of control or leukemic-exposed HSCs were transplanted along with 2 × 10⁵ BM cells of a competitor (CD45.2⁺) into lethally irradiated hosts (CD45.1⁺). Reconstitution was evaluated in the blood at 16 weeks post-transplantation (p = 0.0001). Mice with CD45.1⁺ chimerism <0.3 were considered non-responders. The data is a representative or pool of mean ± SD from two to three independent experiments. Unpaired student t test or Two-way ANOVA was used to determine statistical significance with Tukey’s multiple comparison. p values < 0.05 were considered statistically significant. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001; ns = not significant.