TKI-resistant BM immature cells express higher levels of BMP1b receptors. (A) Frequency of BMPR1b^lo or BMPR1b^hi patients in CML patients at diagnosis defined as previously described,¹⁷  and presented here in a pie chart. Comparative transcriptional expression of BMPR1b genes in BM cells from healthy donors, or CML patients in chronic phase at diagnosis (CP-Diag), resistant (RES) to TKI or in remission (CCyR) in MNC (B) or CD34⁺ selected cells (C). Cell membrane analysis of BMPR1b was performed by flow cytometry, and data represent the percentage of positive cells at cell surface in CD34⁺ (D) or CD34⁺CD38⁻ (E) stem cells and CD34⁺CD38⁺ (F) progenitor compartment in BM samples obtained from healthy donors, or CML patients in chronic phase at diagnosis, resistant to TKI treatment or in remission. 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. NS, not significant (P > .05). *P ≤ .05; **P ≤ .01; ***P ≤ .001; ****P ≤ .0001.