Nuclear export inhibition activates TP53 pathways and is a potent therapeutic strategy in atypical teratoid rhabdoid tumors.

Abstract

BACKGROUND: Atypical teratoid/rhabdoid tumor (ATRT) is an aggressive central nervous system tumor mostly affecting young children. Improved and less toxic therapies for children with ATRT are imperative due to the toxicities associated with current treatments. Furthermore, existing therapies do not address the underlying genetic drivers of ATRT. In this study, we sought to determine whether exportin-1 (XPO1) is a genetic dependency and therapeutic target in ATRT. METHODS: We utilized an integrative approach harnessing patient-derived ATRT cell lines, functional genomics, pharmacologic assays, transcriptomics, and in vivo intracranial xenograft models to systematically test the hypothesis that XPO1 is a novel dependency in ATRT. RESULTS: Analysis of RNA-sequencing datasets revealed high XPO1 expression in ATRT cells compared to other pediatric brain tumor cell lines. Both CRISPR/Cas9 genetic knockdown and pharmacologic inhibition of XPO1 using 6 selective inhibitors of nuclear export (SINEs) in patient-derived atypical teratoid/rhabdoid tumor (ATRT) cells led to significant reduction in cell viability and proliferation. Furthermore, we observed increased apoptosis, G0 phase cell cycle arrest, and upregulation of TP53 signaling pathways in cells treated with the SINE selinexor. Consistently, our transcriptomic data revealed the upregulation of apoptosis and TP53 signaling pathways and concomitant depletion of cell cycle gene sets. In vivo, selinexor in combination with radiation and cyclophosphamide led to significant reduction in tumor volume and increased animal survival in intracranial ATRT xenograft models. CONCLUSIONS: Our data reveals XPO1 as a novel genetic dependency and potent therapeutic target in ATRT.