RNA interference-mediated inhibition of JAK/STAT expression reduces growth and survival of human AML CD34⁺ cells. (A) AML CD34⁺ cells (AML 404, 571, and 636) were exposed to siRNA to JAK1, JAK2, STAT3, and STAT5a/b and negative control siRNA by nucleofection. Knockdown of target proteins was evaluated by western blotting. (B-D) Nucleofected cells were cultured for 72 hours and (B) enumerated (n = 3) and assessed for (C) apoptosis (n = 4) and (D) CFC growth (n = 3). (E) AML CD34⁺ cells (AML 545, 614, 704, and 755) were exposed to a second set of siRNA to JAK1, JAK2, STAT3, and STAT5a/b and control siRNA (negative control), and (F) the effect of JAK1/2 knockdown on pSTAT3/5 expression was evaluated by western blotting. Nucleofected cells were cultured for 72 hours and (G) enumerated (n = 3) and assessed for (H) apoptosis (n = 4) and (I) CFC growth (n = 3). (J-L) CB CD34⁺ cells (n = 3) were exposed to siRNA to JAK1, JAK2, STAT3, and STAT5a/b and control siRNA (negative control) and assessed for (J) knockdown of target proteins by western blotting and for (K) apoptosis and (L) CFC growth. Results represent the mean ± SEM. Significance values: *P < .05, **P < .01.