Abstract 3810: Selinexor (KPT-330), a novel selective inhibitor of nuclear export (SINE), shows single agent efficacy against alveolar soft part sarcoma (ASPS) in vivo

Chromosomal Region Maintenance Protein 1/Exportin 1 (CRM1/XPO1) is a key nuclear export protein whose inhibition leads to the nuclear accumulation of Tumor Suppressor Proteins (TSPs) and renders cancer cells susceptible to apoptosis. Selinexor is orally bioavailable and represents a novel class of small molecule compounds with potent activity against a wide variety of cancers. Selinexor is currently in Phase 1 clinical studies in hematological and solid cancer patients (Clinicaltrials.gov NCT01607892 and NCT01607905). We tested the activity of Selinexor in a soft tissue sarcoma – ASPS that is resistant to traditional chemotherapy and irradiation treatment. Here we report in vitro activity of Selinexor against ASPS and in vivo efficacy results in xenograft models. Methods We used MTT, FACS, qPCR, immunofluorescence, immunostaining and immunoblots to measure the in vitro and in vivo effects of KPT-330 on the ASPS-KY cell line and in xenograft models. Results The IC 50 of the ASPS-KY cell line treated with Selinexor for 72 hours was 10 μM. This concentration induced nuclear accumulation of p53, p21, IκB and FOXO3A within 4 hours of treatment, and by 24 hours cells stopped DNA synthesis and were arrested at G1 phase of the cell cycle. By 72 hours, 25% of the cells died. Prior to cell death, the drug reduced the survival protein BCL2 as well as other pro-proliferative proteins such as CDK4, Cyclin D and E2F. In addition, Selinexor induced dephosphorylation of pRb activating its tumor suppressor activity and also induced Caspase 3/7 and PARP cleavage. To assess the in vivo activity of Selinexor in a xenograft model of ASPS, we treated mice with 10 or 20 mg/kg of KPT-330 using a 3 times weekly oral dosing schedule. Following a week of treatment, tumors showed accumulation of TSPs as well as significant reduction of the proliferation marker Ki-67. Following treatment with Selinexor for 40 days, tumor growth was inhibited by 70% at 10 mg/kg and by 80% at 20 mg/kg compared with vehicle treated animals. Analysis of immunoblots from these tumors showed induction of p21, with corresponding reduction of the pro-survival and proliferation markers c-Jun, c-Met, survivin, ERK and HSP70. Histological analysis revealed apoptosis and large areas of fibrosis in treated tumors. These results indicated that Selinexor not only inhibited tumor growth, but also induced ASPS cell death in vivo. Conclusions Our results demonstrated that Selinexor is effective against ASPS in vivo as a single agent and further support the development of SINE-based therapies for alveolar soft part sarcoma that has currently no cure. We will perform further studies to test Selinexor in drug combination studies to identify synergism with other therapies. Citation Format: Marsha L. Crochiere, Trinayan Kashyap, Boris Klebanov, William Senapedis, Diego del Alamo, Sharon Tamir, Erkan Baloglu, Dilara McCauley, Robert Carlson, Michael Kauffman, Sharon Shacham, George Demetri, Andrew Wagner, Ewa Sicinska, Prafulla Gokhale, Nancy Kohl, Amy Saur, Yosef Landesman. Selinexor (KPT-330), a novel selective inhibitor of nuclear export (SINE), shows single agent efficacy against alveolar soft part sarcoma (ASPS) in vivo . [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 3810. doi:10.1158/1538-7445.AM2014-3810