title: Treatment of acquired drug resistance in multiple myeloma by combination therapy with XPO1 and topoisomerase II inhibitors.
abstract: Acquired drug resistance is the greatest obstacle to the successful treatment of multiple myeloma (MM). Despite recent advanced treatment options such as liposomal formulations, proteasome inhibitors, immunomodulatory drugs, myeloma-targeted antibodies, and histone deacetylase inhibitors, MM is still considered an incurable disease.
  
  
  
  We investigated whether the clinical exportin 1 (XPO1) inhibitor selinexor (KPT-330), when combined with pegylated liposomal doxorubicin (PLD) or doxorubicin hydrochloride, could overcome acquired drug resistance in multidrug-resistant human MM xenograft tumors, four different multidrug-resistant MM cell lines, or ex vivo MM biopsies from relapsed/refractory patients. Mechanistic studies were performed to assess co-localization of topoisomerase II alpha (TOP2A), DNA damage, and siRNA knockdown of drug targets.
  
  
  
  Selinexor was found to restore sensitivity of multidrug-resistant 8226B25, 8226Dox6, 8226Dox40, and U266PSR human MM cells to doxorubicin to levels found in parental myeloma cell lines. NOD/SCID-γ mice challenged with drug-resistant or parental U266 human MM and treated with selinexor/PLD had significantly decreased tumor growth and increased survival with minimal toxicity. Selinexor/doxorubicin treatment selectively induced apoptosis in CD138/light-chain-positive MM cells without affecting non-myeloma cells in ex vivo-treated bone marrow aspirates from newly diagnosed or relapsed/refractory MM patients. Selinexor inhibited XPO1-TOP2A protein complexes (proximity ligation assay), preventing nuclear export of TOP2A in both parental and multidrug-resistant MM cell lines. Selinexor/doxorubicin treatment significantly increased DNA damage (comet assay/γ-H2AX) in both parental and drug-resistant MM cells. TOP2A knockdown reversed both the anti-tumor effect and significantly reduced DNA damage induced by selinexor/doxorubicin treatment.
  
  
  
  The combination of an XPO1 inhibitor and liposomal doxorubicin was highly effective against acquired drug resistance in in vitro MM models, in in vivo xenograft studies, and in ex vivo samples obtained from patients with relapsed/refractory myeloma. This drug combination synergistically induced TOP2A-mediated DNA damage and subsequent apoptosis. In addition, based on our preclinical data, we have initiated a phase I/II study with the XPO1 inhibitor selinexor and PLD (ClinicalTrials.gov NCT02186834). Initial results from both preclinical and clinical trials have shown significant promise for this drug combination for the treatment of MM.
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Turner
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Jana L
authors.initials: JL
authors.lastname: Dawson
authors.affiliation: Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.|Department of Malignant Hematology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Shain
authors.affiliation: Department of Malignant Hematology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.|M2Gen® Biotechnologies, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: William S
authors.initials: WS
authors.lastname: Dalton
authors.affiliation: Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Yun
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Meads
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.|Department of Malignant Hematology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA.
authors.forename: Rachid
authors.initials: R
authors.lastname: Baz
authors.affiliation: Karyopharm Therapeutics, Natick, MA, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Kauffman
authors.affiliation: Karyopharm Therapeutics, Natick, MA, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Shacham
authors.affiliation: Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA. Dan.Sullivan@moffitt.org.|Department of Blood and Marrow Transplantation, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL, USA. Dan.Sullivan@moffitt.org.|H. Lee Moffitt Cancer Center & Research Institute, 12902 Magnolia Drive, Tampa, FL, 33612, USA. Dan.Sullivan@moffitt.org.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D001706:Biopsy; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects; D004317:Doxorubicin / Q000031:analogs & derivatives / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D064593:Heterografts; D006801:Humans; D006834:Hydrazines / Q000627:therapeutic use; D028884:Karyopherins / Q000037:antagonists & inhibitors; D051379:Mice; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology; D011092:Polyethylene Glycols / Q000627:therapeutic use; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D015996:Survival Rate; D059005:Topoisomerase II Inhibitors / Q000627:therapeutic use; D014230:Triazoles / Q000627:therapeutic use; D047368:Tumor Burden / Q000187:drug effects; D000097606:Exportin 1 Protein
chemical_list: D004317:Doxorubicin; D006834:Hydrazines; D028884:Karyopherins; D011092:Polyethylene Glycols; D018160:Receptors, Cytoplasmic and Nuclear; D059005:Topoisomerase II Inhibitors; D014230:Triazoles; D000097606:Exportin 1 Protein; C506643:liposomal doxorubicin; C585161:selinexor
keywords: Acquired drug resistance; Liposomal doxorubicin; Mouse models; Multiple myeloma; Relapsed/refractory myeloma; XPO1 inhibition