Abstract 1758: Deconstructing protein and gene expression pathways to define the anticancer effects of XPO1 inhibition in ovarian cancer

Abstract

Abstract Emerging evidence across multiple cancers, including ovarian cancer (OvCA), has identified disruption in nuclear-cytoplasmic shuttling with overexpression of exportin-1 (XPO1), a key regulator of nuclear transport, being linked to cancer aggressiveness, chemoresistance, and decreased patient survival. These findings and that XPO1 is the sole transporter of a number of tumor suppressors and cell cycle regulators including TP53, BRCA1, CDKN1A, CDKN1B and FOXO, establishes the rationale for targeted therapeutic inhibition of XPO1. KPT-185 and KPT-330 (generic name: selinexor) are two Selective Inhibitors of Nuclear Export (SINE) that inhibit XPO1 and selinexor is currently in phase I trials. We now demonstrate that despite similar XPO1 expression levels, patient-derived ovarian cancer cell lines (PD-OvCA) exhibit a broad differential IC50 response to SINE. To define the mechanism(s) of action underlying sensitivity and resistance and better understand the role of defective nuclear:cytoplasmic shuttling in OvCa, we examined the global differences between pathway activation/inhibition following XPO1 inhibition using nuclear:cytoplasmic fractionated protein lysates (reverse phase protein arrays, RPPA) and genome-wide RNA expression analysis. Treatment of differentially KPT-185 sensitive OvCa cell lines resulted in nuclear accumulation of XPO1 and multiple known XPO1 cargo proteins including TP53 and CDKN1A, with a subsequent decrease in cytoplasmic XPO1 levels. RPPA analysis (MD Anderson RPPA Core) was then used to examine the expression and subcellular localization of >200 proteins involved in a variety of biological and cancer-relevant processes. Numerous proteins accumulated in the nucleus including several known XPO1 cargoes (TP53 and YWHAZ), whereas a number of oncoproteins had decreased nuclear levels including MYC and RELA. These findings were shared across multiple cell lines. However, many of the proteins had differential accumulation patterns between cell lines. The effects of these changes on the transcriptome were defined by microarray analysis (Illumina, HumanHT12, v4 Expression BeadChip). Ingenuity Pathway Analysis (IPA) revealed multiple shared pathways activated by XPO1 inhibition between OvCa cell lines (TP53, FOXO3, EPAS1, MITF, and MYOD1) and these were consistent with the RPPA data. However, multiple pathways, both activated and inhibited, did not overlap between OvCa cell lines. These data begin to reveal not only the multiple pathways by which SINE effect their anticancer activity but also that depending on cell context, these pathways can differ and may not overlap completely. The pathways and their more complete investigation defining their effect on differential sensitivity to XPO1 inhibition and their role in OvCa will be discussed. Citation Format: Brad R. Evans, Thomas R. Silvers, Ying A. Chen, Jason Garcia, Catalina Camacho, Andrew J. Sharp, Paras Garag, Srinivas V. Koduru, Jean-Noel Billaud, Richard L. Halpert, Peter R. Dottino, Yosef Landesman, Sharon Shacham, John A. Martignetti. Deconstructing protein and gene expression pathways to define the anticancer effects of XPO1 inhibition in ovarian cancer. [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 1758. doi:10.1158/1538-7445.AM2015-1758