Aurora and IKK kinases cooperatively interact to protect multiple myeloma cells from Apo2L/TRAIL

Constitutive activation of the canonical and noncanonical nuclear factor-kappa B (NF-kappa B) pathways is frequent in multiple myeloma (MM) and can compromise sensitivity to TRAIL. In this study, we demonstrate that Aurora kinases physically and functionally interact with the key regulators of canonical and noncanonical NF-kappa B pathways I kappa B kinase beta (IKK beta) and IKK alpha to activate NF-kappa B in MM, and the pharmacological blockade of Aurora kinase activity induces TRAIL sensitization in MM because it abrogates TRAIL-induced activation of NF-kappa B. We specifically found that TRAIL induces prosurvival signaling by increasing the phosphorylation state of both Aurora and IKK kinases and their physical interactions, and the blockade of Aurora kinase activity by pan-Aurora kinase inhibitors (pan-AKIs) disrupts TRAIL-induced survival signaling by effectively reducing Aurora-IKK kinase interactions and NF-kappa B activation. Pan-AKIs consistently blocked TRAIL induction of the antiapoptotic NF-kappa B target genes A1/Bfl-1 and/or Mcl-1, both important targets for TRAIL sensitization in MM cells. In summary, these results identify a novel interaction between Aurora and IKK kinases and show that these pathways can cooperate to promote TRAIL resistance. Finally, combining pan-AKIs with TRAIL in vivo showed dramatic efficacy in a multidrug-resistant human myeloma xenograft model. These findings suggest that combining Aurora kinase inhibitors with TRAIL may have therapeutic benefit in MM.