Abstract C48: Dual targeting of myeloma cells by 2-deoxy-D-glucose and ABT-199 combination respectively through the down-regulation of Mcl-1 and binding to Bcl-2.

Abstract

Abstract Multiple myeloma (MM) is a heterogeneous but incurable plasma cell malignancy which still requires new therapeutic approaches. Several molecular subsets of MM have been defined based on genetic and chromosomal aberrations. Briefly, t(4;14) or t(14;16) translocations and TP53 deletion are most frequent poor-risk genetic features of MM, while t(11;14) confers a neutral prognostic value. Because cancer cells have a high glycolytic metabolism, we investigated the efficiency of 2-deoxy-d-glucose (2-DG), a competitive inhibitor of hexokinase, to kill myeloma cells. For this purpose we used 28 human myeloma cell lines (HMCL) representative of these different molecular subsets. Cell death induced by 2-DG was assessed by Apo-2.7 staining. Investigation of the underlying apoptotic mechanisms was evaluated by analyzing, by western blotting, modulation of the UPR response and implication of the Bcl-2 protein family. Finally, the possibly synergistic effect of the combination of 2-DG and ABT-199 was investigated. Cell death induced by 2DG was very heterogeneous among HMCLs, ranging from 5% to 96%. Of note, HMCLs carrying t(4;14) showed a trend to be more sensitive to 2DG (p=0.06) while HMCLs carrying t(11;14) appeared to be more resistant (p=0.08). Interestingly, 2-DG not only strongly inhibited the glycolytic activity of HMCLs but also interfered with N-glycosylation. Indeed, addition of D-mannose, an N-linked glycosylation precursor, partly reversed 2-DG-induced cell death. However, the D-mannose efficiency was also heterogeneous among HMCLs, suggesting that the inhibition of N-glycosylation was not the only mechanism of 2-DG-induced cell death. An up-regulation of GRP78, CHOP and ATF-4 expression was induced by 2-DG in both sensitive and resistant HMCLs, suggesting that 2DG-induced cell death was independent from the UPR response. Finally, 2-DG uniformly induced Mcl-1 down-regulation in HMCLs, but only those dependent on Mcl-1 for survival were killed by 2-DG. Preliminary results indicate that proteosomal degradation could be involved as part of a more complex mechanism. Of note, most of t(11;14) HMCLs were resistant to Mcl-1 down-regulation but highly sensitive to ABT-199, which targets Bcl-2 and efficiently kills t(11;14) HCMLs depending on this pathway for survival. Because 2-DG uniformly down-regulated Mcl-1, we combined it with ABT-199 in ABT-199-resistant HMCLs i.e., in HMCLs expressing a Bcl-2/Mcl-1 gene expression ratio lower to the threshold required for ABT-199 response. The combination of 2-DG and suboptimal ABT-199 dosage indeed strongly synergized in both t(4;14) and t(14;16) HMCLs. This study highlights the fact that dual targeting of Mcl-1 by 2-DG and Bcl-2 by ABT-199, in MM cell lines or primary samples, is highly efficient to induce apoptosis whatever the molecular subtype, including those with the poorest prognostic value. ABT-199 is presently under evaluation in a phase I clinical trial in relapsed MM patients and the present study provides a biological rationale for evaluating 2-DG in combination with ABT-199 in MM patients. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C48. Citation Format: Maxime Halliez, Sophie Maïga, Cyrille Touzeau, Patricia Gomez-Bougie, Steven Le Gouill, Catherine Pellat-Deceunynck, Martine Amiot. Dual targeting of myeloma cells by 2-deoxy-D-glucose and ABT-199 combination respectively through the down-regulation of Mcl-1 and binding to Bcl-2. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C48.