Abstract 2163: Increased overall survival in platinum-resistant ovarian cancer: paradigmatic use of novel SINE (selective inhibitor of nuclear export), which restores p53 nuclear localization and activation.

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Abstract Ovarian cancer (OvCa) is the most lethal female reproductive tract malignancy worldwide with >190,000 new cases diagnosed yearly. Overall, ∼60% of patients will relapse after primary therapy and for the majority of women with advanced disease, their platinum-resistant cancers are currently incurable. During OvCa progression, multiple tumor suppressor proteins (TSPs), most notably p53 (>95% of late-stage cases), are inactivated. Chromosomal region maintenance 1 (CRM1) is solely responsible for the nuclear export of the major TSPs, and increased CRM1 expression has been linked to advanced OvCa stage and poor overall survival. To address the therapeutic role of CRM1 inhibition in OvCa, we tested two novel SINEs in vitro and in vivo. For in vitro studies, we used KPT-185 as a single agent and in combination with cisplatinum in the isogenic cell lines A2780 and CP70. KPT-185 cytotoxicity was highly specific for tumor cell lines. The IC50 for the normal ovarian surface epithelial cell line IOSE527 (4000nM) was 40-90 times higher than A2780 (46.5nM) and CP70 (111.7nM) lines. Combination treatment demonstrated an additive effect on cell death, overcoming cisplatinum resistance. A2780 displayed G1/G2 arrest whereas CP70, only G2 arrest. p53 nuclear accumulation, and downstream activation of targets, was demonstrated following SINEs treatment. Two complementary in vivo models were used. First, the orally bioavailable SINE KPT-330, currently in Phase 1 clinical studies, was given as a single agent in a Rag1 KO mouse model with 4 unrelated patient-derived chemonaive cell lines. Oral KPT-330 inhibited subcutaneous tumor growth and markedly increased survival: all chronically treated mice continued to survive longer (>78d) than controls (all died at 23d). Cross-over of control mice to KPT-330 resulted in tumor growth arrest. In the second model, highly aggressive, luciferase positive, cisplatin resistant CP70 cells were injected i.p into nu/nu mice (n=34) and tumor growth followed in real-time using WBLI. SINE treatment led to marked reductions in tumor burden as well as survival improvements: control mice were all dead by 25 days whereas cisplatin (2.5mg/kg, 2x wk; 31d), KPT-330 (15mg/kg, twice weekly; 41d) and KPT-330+cisplatin (same as single treatments, respectively; 48d) treated mice have significantly improved survival outcomes (p<0.0005 for each treatment versus control). Together, these studies demonstrate the first successful use of highly selective, potent and irreversible CRM1 inhibitors in overcoming cisplatin resistance and prolonging survival in OvCa models. Restoration of p53 nuclear localization and functional activity and RNASeq identified pathways at serially increasing doses will be discussed. First-in-man trials have begun and trials in ovarian cancer are planned for 2013. Citation Format: Ying Chen, Eva Kalir, Catalina Camacho-Vanegas, Fei Huang, Elena Pereira, Yosef Landesman, Dilara McCauley, Mansoor Raza Mirza, Michael Kauffman, Sharon Shacham, Peter R. Dottino, John A. Martignetti. Increased overall survival in platinum-resistant ovarian cancer: paradigmatic use of novel SINE (selective inhibitor of nuclear export), which restores p53 nuclear localization and activation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2163. doi:10.1158/1538-7445.AM2013-2163