Reagents

Rabbit anti–poly (ADP ribose) polymerase, rabbit anti–IκB-α, rabbit anti–p-NF-κB, rabbit anti–p-JNK, rabbit anti–t-JNK, rabbit anti-IKK2, rabbit anti–p-ERK, rabbit anti–t-ERK, recombinant IGFBP-3 protein, signal-silence control small interfering RNA (siRNA), signal-silence IKK2 siRNA I, SP600125, and ERK inhibitor PD98059 were purchased from Cell Signaling Technology (Beverly, MA, USA). Anti–β-actin antibody, RIPA buffer, phorbol 12-myristate 13-acetate (PMA), protease inhibitor mixture, cryovials, and free fatty acid–free bovine serum albumin (BSA) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Primary antibodies, rabbit anti–IGFBP-3 and rabbit anti–NF-κB were purchased from Santa Cruz Biotechnology (Dallas, TX, USA). Horseradish peroxidase–conjugated secondary antibody and SuperSignal chemiluminescence kits were purchased from Pierce Biotechnology (Rockford, IL, USA). Cell culture medium, insulin, Trizol, Opti-MEM medium, Lipofectamine 2000, BSA, and Western blot supplies were obtained from Thermo Fisher Scientific (Waltham, MA, USA).