Higher-ligand expression in TKI-resistant BM microenvironment linked to leukemic and nonleukemic BMP2 and BMP4 production. (A) ELISA quantification of BMP2 and BMP4 in BM plasma obtained from CCyR patients and resistant patients. Results from individual samples are expressed in picograms per milliliter, and heavy horizontal lines represent mean values ± SEM of the indicated number of analyzed samples. (B-C) MSCs were isolated, as has been described¹⁷  from BM samples of healthy donor or CP-CML patients at remission or who were TKI resistant and analyzed after one passage in culture for their transcriptional expression (B) or de novo production (C) of soluble of BMP2 or BMP4 after 72 h of culture in serum-free media. 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. Transcriptional expression of BMP2 (D) or BMP4 (E) in CD34⁺ cells isolated from healthy BM or CP-CML samples of patients at diagnosis, in remission or from 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. Follow-up of transcriptional expression of BMP2 (F) and BMP4 (G) genes in BM cells from CML patients at diagnosis and when they achieved remission or were declared resistant to TKI treatment in CD34⁺ selected cells. 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.