Data from Obatoclax Interacts Synergistically with the Irreversible Proteasome Inhibitor Carfilzomib in GC- and ABC-DLBCL Cells <i>In Vitro</i> and <i>In Vivo</i>

Abstract

&lt;div&gt;Abstract&lt;p&gt;Interactions between the irreversible proteasome inhibitor carfilzomib and the pan-BH3 mimetic obatoclax were examined in germinal center (GC)- and activated B-cell–diffuse large B-cell lymphoma (ABC-DLBCL) cells. Cotreatment with minimally toxic concentrations of carfilzomib (i.e., 2–6 nmol/L) and subtoxic concentrations of obatoclax (0.05–2.0 μmol/L) synergistically increased apoptosis in multiple DLBCL cell lines and increased lethality toward primary human DLBCL but not normal CD34&lt;sup&gt;+&lt;/sup&gt; cells. Synergistic interactions were associated with sharp increases in caspase-3 activation, PARP cleavage, p-JNK induction, upregulation of Noxa, and AKT dephosphorylation. Combined treatment also diminished carfilzomib-mediated Mcl-1 upregulation whereas immunoprecipitation analysis revealed reduced associations between Bak and Mcl-1/Bcl-xL and Bim and Mcl-1. The carfilzomib/obatoclax regimen triggered translocation, conformational change, and dimerization of Bax and activation of Bak. Genetic interruption of c-&lt;i&gt;jun&lt;/i&gt;-NH&lt;sub&gt;2&lt;/sub&gt;-kinase (JNK) and Noxa by short hairpin RNA knockdown, ectopic Mcl-1 expression, or enforced activation of AKT significantly attenuated carfilzomib/obatoclax-mediated apoptosis. Notably, coadministration of carfilzomib/obatoclax sharply increased apoptosis in multiple bortezomib-resistant DLBCL models. Finally, &lt;i&gt;in vivo&lt;/i&gt; administration of carfilzomib and obatoclax to mice inoculated with SUDHL4 cells substantially suppressed tumor growth, activated JNK, inactivated AKT, and increased survival compared with the effects of single-agent treatment. Together, these findings argue that a strategy combining carfilzomib and obatoclax warrants attention in DLBCL. &lt;i&gt;Mol Cancer Ther; 11(5); 1122–32. ©2012 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;