Abstract 19: Antitumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma: the role of survivin
Authors: Zaffaroni Nadia , De Cesare Michelandrea , Cominetti Denis , Doldi Valentina , Lopergolo Alessia , Deraco Marcello , Gandellini Paolo , Landesman Yosef , Friedlander Sharon , Kauffman Michael G. , Shacham Sharon , Pennati Marzia 
Published: August 2015

Abstract
Survivin, which is highly expressed and promotes cell survival in diffuse malignant peritoneal mesothelioma (DMPM), exclusively relies on the nuclear exportin 1 (XPO1/CRM1) to be released in the cytoplasm and perform its anti-apoptotic function. Here, we explored the efficacy of selective inhibitors of nuclear export (SINEs) in patient-derived DMPM preclinical models. Exposure to individual SINE (KPT-251, KPT-276, KPT-330) was able to induce a time- and dose-dependent inhibition of the growth of two DMPM cell lines without affecting normal cell proliferation. Such a cell growth inhibition was preceded by a decline in the nuclear XPO1/CRM1 levels and an increase in the nuclear accumulation of its cargo proteins p53 and p21, which led to a cell cycle arrest at G1-phase. Our results also indicated that survivin is an essential component of the downstream signaling pathway of XPO1/CRM1 inhibition in DMPM cells. In fact, in both cell lines, exposure to SINEs led to a time-dependent reduction of cytoplasmic survivin levels and, after an initial survivin nuclear accumulation, also to a progressive decrease in the nuclear protein abundance, through the ubiquitin-proteasomal degradation pathway, leading to the complete depletion of total survivin levels. In both DMPM cell models, according to survivin anti-apoptotic activity, drug-induced reduction of cytoplasmic survivin levels correlated with the onset of caspase-dependent apoptosis. We further observed that SINEs can be combined with other survivin inhibitors, such as the survivin suppressant YM155 to achieve enhanced growth inhibition in DMPM cells. Initial in vivo experiments with orally administered KPT-251, KPT-276 and the orally available, clinical stage KPT-330 (selinexor) indicated that each compound was able to significantly reduce the growth of early-stage subcutaneous DMPM xenografts. Interestingly, additional experiments carry out with selinexor demonstrated that the compound was also able to inhibit the growth of late-stage subcutaneous DMPM xenografts in nude mice. Most importantly, oral administration of selinexor to SCID mice reduced the growth of orthotopic DMPM xenografts, which properly recapitulate the dissemination pattern in the peritoneal cavity of human DMPM and, for this reason, represent a valuable model for investigating novel therapeutic approaches for the disease. Consistent with an important role of survivin as a determinant of anti-cancer activity of SINE compounds, a reduction of the protein expression was observed in tumor specimens obtained from selinexor treated mice. Overall, our results (i) demonstrate a marked efficacy of SINEs in DMPM preclinical models, which is, at least in part, dependent on the interference with survivin intracellular distribution and function, and (ii) suggest SINE-mediated XPO1/CRM1 inhibition as a novel therapeutic option for the disease.
Citation Format: Nadia Zaffaroni, Michelandrea De Cesare, Denis Cominetti, Valentina Doldi, Alessia Lopergolo, Marcello Deraco, Paolo Gandellini, Yosef Landesman, Sharon Friedlander, Michael G. Kauffman, Sharon Shacham, Marzia Pennati. Antitumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma: the role of survivin. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 19. doi:10.1158/1538-7445.AM2015-19