Abstract B36: Inhibition of Exportin 1 (XPO1) potently suppresses growth of human neuroblastoma cell lines
Authors: Attiyeh Edward F. , McKeon-Fish Aaron , Trillo Rebecca , Landesman Yosef , Senapedis William , McCauley Dilara , Kashyap Trinayan , Shacham Sharon , Kauffman Michael , Maris John M. 
Published: May 2015

Abstract
Background: Most children with high-risk neuroblastoma are not cured, and new therapies are needed. Exportin 1 (XPO1; Chromosome Region Maintenance 1 Protein Homolog, CRM1) is the sole nuclear exporter of TP53, FOXO1, RB1, CDKN1A, and other critical tumor suppressor proteins (TSPs). This suggests that inhibition of XPO1 is a rational anti-cancer strategy. KPT-330 is a Selective Inhibitor of Nuclear Export (SINE) that irreversibly binds XPO1 and is currently in Phase 1 clinical trials. SINE inhibits XPO1-mediated nuclear export across multiple tumor types leading to activation of TSPs and cancer cell death.
Methods: A panel of 14 genomically-characterized neuroblastoma cell lines was treated with KPT-330 across a 5-log range. Growth inhibition was measured using CellTiter-Glo (Promega) viability assays and a real time growth monitoring system (xCELLigence, Roche). Drug combinations were tested in vitro, and the combination index was calculated using CalcySyn (Biosoft). NOD/SCID mice with neuroblastoma xenografts (both flank and tail-vein injected) were treated orally with KPT-330 (15 mg/kg thrice weekly or 20-25 mg/kg twice weekly), and tumor size was monitored by direct measurement and luciferase luminescence.
Results: KPT-330 showed cytotoxicity against 14 neuroblastoma cell lines with a median IC50 of 236 nM (range 51-568). Sensitivity to KPT-330 was independent of MYCN amplification status. Combination of KPT-330 with commonly used cytotoxic agents (irinotecan, topotecan, cisplatin, and doxorubicin) showed additive effects. Flank xenografts using the neuroblastoma cell line SH-SY5Y showed significantly decreased tumor growth after oral administration of KPT-330. After allowing the tumors to grow following 28 days of drug withdrawal, re-exposure to the drug again showed growth suppression. In a model of metastatic neuroblastoma after tail-vein injection of luciferase-transfected neuroblastoma cell lines (SH-SY5Y, IMR-5, and Be2c), KPT-330 showed significant tumor growth inhibition (p&lt;0.001). KPT-330 treatment resulted in decreased Myc family protein levels as well as activation of apoptotic pathways. Major toxicity was weight loss which was overcome with nutritional supplementation.
Conclusions: Neuroblastomas show sensitivity to XPO1 inhibition both in vitro and in vivo. Ongoing work is focused on discovering the cellular and genomic factors responsible for increased sensitivity to nuclear export inhibition and potential synergistic combinations. With the expected completion of the first in human phase I trials this year, treatment with KPT-330 has the potential to be rapidly translated into a clinical trial for children with neuroblastoma.
Citation Format: Edward F. Attiyeh, Aaron McKeon-Fish, Rebecca Trillo, Yosef Landesman, William Senapedis, Dilara McCauley, Trinayan Kashyap, Sharon Shacham, Michael Kauffman, John M. Maris. Inhibition of Exportin 1 (XPO1) potently suppresses growth of human neuroblastoma cell lines. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B36.