Abstract 1772: Overcoming drug-resistance in multiple myeloma by CRM1 inhibitor combination therapy
Authors: Turner Joel G. , Shain Kenneth H. , Dai Yun , Dawson Jana L. , Cubitt Christopher L. , Shacham Sharon , Kauffman Michael , Grant Steven , Sullivan Daniel M. 
Published: May 2015

Abstract
Introduction
Significant progress has been made over the past several years in the treatment of multiple myeloma (MM). However patients eventually develop drug resistance and die from progressive disease. The incurable nature of MM clearly demonstrates the need for novel agents and treatments.
The overall objective of this study was to investigate the use of CRM1 inhibitors (KPT330 and KOS2464) to sensitize de novo and acquired drug-resistant MM cells to the proteosome inhibitors bortezomib (BTZ)and carfilzomib (CFZ) and to the topoisomerase II (topo II) inhibitor doxorubicin (DOX).
Methods
Drug resistant U266 and 8226 MM cell lines were developed at VCU (Steven Grant) and the Moffitt Cancer Center (Ken Shain) respectively by the incremental exposure to BTZ. Cells were treated in vitro with CRM1 inhibitors (KPT330 or KOS2464) +/- either BTZ, CFZ or DOX. Sensitivity was measured by both cell viability (CellTiter-Blue) and apoptosis (activated caspase 3). U266 resistant cells were also used to challenge NOD/SCID-gamma mice which were then treated with combinations of KPT330 and BTZ or DOX. Mononuclear cells were isolated from patients with newly diagnosed and refractory (drug-resistant) MM. Patient bone marrow aspirates were treated with drug combinations (KPT330 or KOS2464 +/- either BTZ, CFZ or DOX) and CD138/light chain positive MM cells assayed for apoptosis.
Results
BTZ selected U266 and 8226 MM cells were assayed and found to be resistant to BTZ, CFZ, and DOX as compared to parental cell lines. Both U266 and 8226 resistant MM cell lines were found to be &gt;10-fold resistant to BTZ. Cell viability was decreased synergistically when the CRM1 inhibitor KPT330 was used in combination with BTZ or DOX. Combinatorial index values were &lt; 1.0 (synergistic) in both parental and drug resistant U266 and 8226 MM cells. Resistant U266 and 8226 MM cell lines were sensitized by the CRM1 inhibitors KPT330 and KOS2464 to both BTZ and CFZ as shown by apoptosis assay. CD138/light chain double-positive MM cells derived from both newly diagnosed and refractory (drug-resistant) MM patients were sensitized by CRM1 inhibitors to BTZ, CFZ and DOX as shown by apoptosis. NOD/SCID-gamma mice treated with CRM1 inhibitors and either BTZ or DOX had a significantly better response to combined treatment than single agents.
Conclusions
CRM1 inhibitors KPT330 and KOS2464 sensitized drug-resistant and refractory multiple myeloma to proteosome inhibitors (BTZ and CFZ) or the topo II inhibitor DOX in cell lines, animal models and CD138/light chain double positive patient MM cells. These combination therapies may be effective for the treatment of refractory multiple myeloma.
Citation Format: Joel G. Turner, Kenneth H. Shain, Yun Dai, Jana L. Dawson, Christopher L. Cubitt, Sharon Shacham, Michael Kauffman, Steven Grant, Daniel M. Sullivan. Overcoming drug-resistance in multiple myeloma by CRM1 inhibitor combination therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1772. doi:10.1158/1538-7445.AM2014-1772