IL-21 induces cell death via STAT3 and modulation of expression of Bcl-2 family genes but is independent of STAT1. (A) Immunoblotting for Bcl-2 family genes in IL-21–responsive (Mino) and resistant (Jeko-1) MCL cell lines following treatment with IL-21 at indicated time points. (B-D) Mino cells were first transfected with siRNA targeting STAT3 (B), Bax (C), and STAT1 (D), or control siRNA followed by treatment with IL-21 (100 ng/mL) at 24 hours after transfection. (B-D) Indicate cell death analyzed by YO-PRO/PI staining at 48 hours posttreatment. Immunoblotting for STAT3, Bax, and STAT1 was carried out at 24 hours posttransfection to confirm protein knockdown (B-D). Actin and GAPDH served as a loading control. Data are representative of 3 independent experiments. Error bars represent SD between 3 experiments. *P < .05; ***P < .005.