Abstract 2075: Combination tTerapy KPT-SINE (selective inhibitors of nuclear export) with radiotherapy have additive effects in non-small cell lung cancer (NSCLC) cells in vitro and in vivo.
Authors: Rashal Tami , McCauley Dilara , Ilouze Maya , Raphael Nir , Solomonik Inessa , Lawrence Yaccov , Shavit Ronen , Shacham Sharon , Kauffman Michael , Peled Nir 
Published: August 2014

Radiation therapy is an established therapeutic option for lung cancer, but its use is limited due to side effects. Combining radiosensitizers with RT is a way to augment the efficacy of RT. Chromosome Region Maintenance Protein 1/Exportin 1 (CRM1/XPO1) is a key nuclear export protein, the cargoes of which are Tumor Suppressor Proteins (TSPs) such as p53, FOXO, PTEN, pRB and I-κB. Small molecule SINE block CRM1-dependent nuclear export and force the nuclear retention of TSPs, potentially sensitizing cells to RT. Suggested mechanisms include: 1) Induction of “genome fidelity review” by forced nuclear retention of TSPs; 2) Prevention of single stranded DNA break repair, and thereby reduction of resistance of cancer cells to RT.

Methods: IC50 of KPT-SINE e.g. KPT-185 and clinical compound KPT-330, were determined in MTT assays using human NSCLC p53 wild type (wt) cancer cell lines H1299 and A549. Clonogenic assays in the SINE sensitive H1299 (IC50 100nM) and SINE-resistant A549 (IC50 1.7μM) lines were conducted in the presence or absence of escalating doses of radiation. An in vivo tumor xenograft model using the A-549 cell line in SCID mice was also conducted with KPT-330.

Results: KPT-185 demonstrated inhibitory effects on the clonogenicity of two NSCLC cell lines in a dose dependent fashion. We showed that, while RT alone treatment caused coloines growing curve reduced to less than &lt;40% of colonies in both cell lines. Combination of both agents (RT and SINE at IC25 concentrations) demonstrated an additive effect for A549 cell line, and a dose-related effect for H1299 cell line. In vivo, we demonstrated significant reductions in tumor growth, where treatment with KPT-330 caused a &gt;75% tumor volume reduction when compared to vehicle, and a &gt;65% reduction when compared to Cisplatin. In this model, KPT-330 was fairly well-tolerated, with minimal body weight loss by animals over the course of the study.

Conclusions: These studies showed that KPT-SINE significantly inhibited the growth of two p53 wt NSCLC lines by MTT assay. Similar inhibition was observed in clonogenic assays with cells (A549) resistant to SINE. We described the additive effects of SINE and RT on NSCLC cell lines, suggesting that SINEs can act as radiosensitizers. We further demonstrated that SINEs are efficacious in vivo in the A549 xenograft model, and display superior efficacy when compared to Cisplatin. SINE compounds represent a promising novel therapy against NSCLC both as stand-alone agents and in combination with RT. These data support further development of SINE-based therapies for NSCLC. Further work on in vivo studies of KPT-SINE in combination with RT will be reported.

Citation Format: Tami Rashal, Dilara McCauley, Maya Ilouze, Nir Raphael, Inessa Solomonik, Yaccov Lawrence, Ronen Shavit, Sharon Shacham, Michael Kauffman, Nir Peled. Combination tTerapy KPT-SINE (selective inhibitors of nuclear export) with radiotherapy have additive effects in non-small cell lung cancer (NSCLC) cells in vitro and in vivo. [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 2075. doi:10.1158/1538-7445.AM2013-2075