BMPR1b⁺CD34⁺cell survival to TKI is promoted by exogenous treatment with BMP2/4. (A) Experimental protocol for LTC-IC assays performed using CD34⁺ cells from BMPR1b^lo or BMPR1b^hi newly diagnosed CP patients. Medium was supplemented weekly with IM (1 µM), or IM (1 µM) and INF-α2a (1,000 U) (IM + IFN-α2a), with or without BMP2 and BMP4 (10 ng/mL each). (B) LTC-IC output is presented as mean ± SEM of the number of colonies for 10 000 cells of week 5 CFC for BMPR1b^lo (n = 6) or BMPR1b^hi (n = 6) patients. (C) BCR-ABL gene expression was analyzed in individual colonies from week 5 CFC obtained from the BMPR1b^hi patient subgroup. Percentage of BCR-ABL-expressing colonies is indicated at the bottom of the chart. The figure represents the mean ± SEM of BCR-ABL expression in BCR-ABL-positive colonies. (D) Experimental protocol: CD34⁺ cells from newly diagnosed CP patients treated or not in serum-free media with IM at 1 or 2 µM, and in the presence or not of BMP2, BMP4, and with or without sBMPR1b. After 5 days of culture, cells were harvested and analyzed for BMPR1b expression by flow cytometry, for genes expression by quantitative polymerase chain reaction and at functional level by CFC and LTC-IC assays. (E) LTC-IC output presented as mean ± SEM of week 5–derived CFC colonies for 10 000 input cells. (F) TWIST-1 gene expression analyzed in individual colonies from week 5 CFC obtained from BMPR1b^hi patient subgroups that survived IM treatment alone or in the presence of INF-α2a (panel A). Data from individual colonies are expressed in arbitrary units, and heavy horizontal lines represent mean values ± SEM. (G) Comparative transcriptional expression of TWIST-1 gene in PB or BM CD34⁺ selected cells from CCyR patients and TKI-resistant patients. Results from individual samples analyzed are expressed in arbitrary units, and heavy horizontal lines represent mean values ± SEM of the indicated number of analyzed samples. W5, week 5. NS, not significant (P > .05). *P ≤ .05; **P ≤ .01; ***P ≤ .001; ****P ≤ .0001.