The nuclear export inhibitor selinexor inhibits hypoxia signaling pathways and 3d spheroid growth of cancer cells

Purpose: The nucleocytoplasmic transport of macromolecules is critical for both cell physiology and pathophysiology. Exportin 1 (XPO1), the major nuclear export receptor, is involved in the cellular adaptation to reduced oxygen availability by controlling the nuclear activity of the hypoxia-inducible factors (HIFs). Recently, a specific inhibitor of XPO1, selinexor (KPT-330), has been identified that inhibits nuclear export of cargo proteins by binding to the XPO1 cargo-binding pocket. Patients and methods: We used different cancer cell lines from human tissues and evaluated the physiological activity of selinexor on the hypoxia response pathway in twodimensional (2D) monolayer cell cultures in quantitative real-time (qRT)-PCR experiments and luciferase reporter gene assays. A three-dimensional (3D) tumor spheroid culture model of MCF-7 breast cancer cells was established to analyze the effect of selinexor on 3D tumor spheroid structure, formation and viability. Results: Selinexor treatment reduces HIF-transcriptional activity and expression of the HIF- 1 target gene solute carrier family 2 member 1 (SLC2A1). Moreover, 3D tumor spheroid structure, formation and viability are inhibited in response to selinexor-induced nuclear export inhibition. Conclusion: Here, we demonstrate the effect of specific XPO1-inhibition on the hypoxic response on the molecular level in 2D and 3D culture models of MCF-7 cells.