JAK inhibitor treatment reduces in vitro growth and survival of primary human AML but not normal CD34⁺ cells. (A) Enumeration of AML CD34⁺ cells (n = 8, AML 008, 056, 090, 111, 179, 216, 282, and 404) cultured with AZD1480 for 72 hours. (B) AML CD34⁺ cells (n = 13, AML 008, 028, 056, 090, 111, 179, 216, 282, 294, 335, 404, 422, and 493) treated with AZD1480 for 72 hours were evaluated for apoptosis by Annexin-V labeling. (C) CFC growth from AML CD34⁺ cells (n = 9, AML 090, 179, 282, 335, 404, 419, 422, 493, and 526) treated with AZD1480 for 72 hours. (D-E) Correlation between (D) fractional pSTAT3 inhibition in AML CD34⁺ cells and AZD1480-mediated apoptosis and (E) percent inhibition of CFC with AZD1480 (0.1 µM; n = 9). (F-H) Cord blood CD34⁺ cells (n = 3) treated with AZD1480 for 72 hours were (F) enumerated and evaluated for (G) apoptosis and (H) CFC growth. (I-J) AML CD34⁺ samples (n = 6, AML 373, 413, 519, 532, 663, and 704) treated with INC424 for 72 hours were (I) enumerated and (J) evaluated for apoptosis. (K-L) CB CD34⁺ samples (n = 4) were treated with INC424 for 72 hours and (K) enumerated and (L) evaluated for apoptosis. Results represent mean ± SEM. Significance values: *P < .05, **P < .01, ***P < .001.