Selective Inhibitor Of Nuclear Exports (SINE) KPT-330 In Combination With The Novel Proteasome Inhibitor Carfilzomib As a Novel Therapeutic Regimen For Treating Aggressive B-Cell Lymphomas

Aggressive non-Hodgkin lymphomas (NHL), such as Diffuse Large B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL), are one of a small number of important human cancers increasing in incidence in the US over the last four decades. Although these lymphomas are now potentially curable, almost half the treated patients still develop relapsed/refractory disease with poor survival outcomes, indicating an urgent need for better therapeutic approaches with improved efficacy. Double–hit lymphomas (DHL) constitute a particularly aggressive subtype of DLBCL and are characterized by a chromosomal breakpoint affecting the MYC/8q24 locus in combination with another recurrent breakpoint, usually a t(14;18)(q32;q21) involving BCL2. Prognosis for DHL is extremely poor, indicating a need for new treatment options as well. Multi-drug combination therapies are expected to potentiate therapeutic responses and delay disease recurrence by blocking adaptive resistance responses. Carfilzomib (CFZ), a novel second-generation proteasome inhibitor, and the novel Selective Inhibitor of Nuclear Exports (SINE) KPT-330 are effective treatments for refractory lymphomas. We hypothesized that combining the two would be even more successful because the drugs target different cellular pathways and processes in malignant B-cells. CFZ inhibits chymotrypsin-like, protein-degrading activity in the ubiquitin-proteasome pathway while KPT-330 irreversibly inhibits the major nuclear export receptor, chromosome region maintenance 1, CRM1, also termed XPO1. This study investigates whether the effects of CFZ and KPT-330 in combination are synergistic and thus more effective, reducing side effects and chemoresistance. Two DLBCL cell lines, DOHH-2 and OCI-Ly10, two DH-DLBCL cell lines, CJ and U-2973, and two MCL cell lines, Mino and Jeko-1, were used. Working with these cell lines, we identified and analyzed the increase in the efficacy of the combination over single agents alone through MTS proliferation and Annexin-V binding apoptosis assays. Growth inhibitory combination indexes for each cell line were calculated, and the Chou-Talalay Method was used to quantify additive effects (CI=1), synergistic effects (CI<1), or antagonistic affects (CI>1). Results indicated strong synergistic behavior of the combinatorial therapy, with many of the dose combinations indexes falling below 1. Apoptosis assays also showed a high degree of synergy when combining CFZ with KPT-330. The efficacy of CFZ and KPT-330 in combination signifies the combination’s potential as a foundation for future studies, treatments, and clinical trials.