Overexpression of JUN induces apoptosis via an EGR-1–Survivin–caspase signaling pathway. (A) Western blot analysis compared OCI-My5 (OCI) and OPM-2 myeloma cells when untransfected (CON), carrying empty vector (EV), or overexpressing JUN (JUN). Results showed specificity of JUN overexpression and effects on regulation of Survivin, XIAP, cIAP1, phosphorylated Elk-1(p-Elk-1), Bcl-2, and Bax, and cleavage of caspase-3, -7, -8, and -9. β-Actin was used as a loading control. (B) Western blot analysis of OCI-My5 (OCI) and OPM2 myeloma cell lines with scrambled shRNA (SCR; control), EGR-1 shRNA (EGR1-KD), and/or JUN overexpression (JUN^H). Silencing of EGR-1 activated Survivin expression and reduced Survivin inhibition and caspase cleavage by JUN overexpression. (C) Western blot analysis of OCI-My5 (OCI) and OPM2 myeloma cell lines with PWPI (EV; control), Survivin (Survivin^H), and/or JUN overexpression (JUN^H). Overexpression of Survivin inhibited caspase cleavage triggered by JUN overexpression. (D) Western blot analysis of OCI-My5 (OCI) and OPM2 myeloma cell lines carrying empty vector or overexpressing JUN cultured in the absence or presence of pan-caspase inhibitor Z-VAD-fmk (ZVAD) shows effects on EGR-1 and Survivin levels and on cleavage of caspase-3, -7, -8, and -9. β-Actin was used as a loading control in all Western blots.