selinexor and Osteosarcoma

The nuclear pore complexes (NPCs) are built of about 30 different nucleoporins and act as key regulators of molecular traffic between the cytoplasm and the nucleus for sizeable proteins (> 40 kDa) which must enter the nucleus. Various nuclear transport receptors are involved in import and export processes of proteins through the nuclear pores. The most prominent nuclear export receptor is chromosome region maintenance 1 (CRM1), also known as exportin 1 (XPO1). One of its cargo proteins is the prolyl hydroxylase 2 (PHD2) which is involved in the initiation of the degradation of hypoxia-inducible factors (HIFs) under normoxia. HIFs are proteins that regulate the cellular adaptation under hypoxic conditions. They are involved in many aspects of cell viability and play an important role in the hypoxic microenvironment of cancer. In cancer, CRM1 is often overexpressed thus being a putative target for the development of new cancer therapies. The newly FDA-approved pharmaceutical Selinexor (KPT-330) selectively inhibits nuclear export via CRM1 and is currently tested in additional Phase-III clinical trials. In this study, we investigated the effect of CRM1 inhibition on the subcellular localization of HIF-1α and radiosensitivity.. Human hepatoma cells Hep3B and human osteosarcoma cells U2OS were treated with Selinexor. Intranuclear concentration of HIF-1α protein was measured using immunoblot analysis. Furthermore, cells were irradiated with 2-8 Gy after treatment with Selinexor compared to untreated controls.. Selinexor significantly reduced the intranuclear level of HIF-1α protein in human hepatoma cells Hep3B and human osteosarcoma cells U2OS. Moreover, we demonstrated by clonogenic survival assays that Selinexor leads to dose-dependent radiosensitization in Hep3B-hepatoma and U2OS-osteosarcoma cells.. Targeting the HIF pathway by Selinexor might be an attractive tool to overcome hypoxia-induced radioresistance.

Topics: Apoptosis; Bone Neoplasms; Carcinoma, Hepatocellular; Cell Proliferation; Exportin 1 Protein; Gene Expression Regulation, Neoplastic; Humans; Hydrazines; Hypoxia-Inducible Factor 1, alpha Subunit; Karyopherins; Liver Neoplasms; Osteosarcoma; Radiation Tolerance; Radiation-Sensitizing Agents; Receptors, Cytoplasmic and Nuclear; Triazoles; Tumor Cells, Cultured

The nuclear export protein, exportin-1 (XPO1/CRM1), is overexpressed in many cancers and correlates with poor prognosis. Selinexor, a first-in-class Selective Inhibitor of Nuclear Export (SINE) compound, binds covalently to XPO1 and blocks its function. Treatment of cancer cells with selinexor results in nuclear retention of major tumor suppressor proteins and cell cycle regulators, leading to growth arrest and apoptosis. Recently, we described the selection of SINE compound resistant cells and reported elevated expression of inflammation-related genes in these cells. Here, we demonstrated that NF-κB transcriptional activity is up-regulated in cells that are naturally resistant or have acquired resistance to SINE compounds. Resistance to SINE compounds was created by knockdown of the cellular NF-κB inhibitor, IκB-α. Combination treatment of selinexor with proteasome inhibitors decreased NF-κB activity, sensitized SINE compound resistant cells and showed synergistic cytotoxicity in vitro and in vivo. Furthermore, we showed that selinexor inhibited NF-κB activity by blocking phosphorylation of the IκB-α and the NF-κB p65 subunits, protecting IκB-α from proteasome degradation and trapping IκB-α in the nucleus to suppress NF-κB activity. Therefore, combination treatment of selinexor with a proteasome inhibitor may be beneficial to patients with resistance to either single-agent.

Topics: Active Transport, Cell Nucleus; Animals; Antineoplastic Combined Chemotherapy Protocols; Bone Neoplasms; Bortezomib; Cell Death; Cell Line, Tumor; Cell Nucleus; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Synergism; Exportin 1 Protein; Female; Fibrosarcoma; Humans; Hydrazines; Karyopherins; Mice, Inbred ICR; Mice, SCID; NF-kappa B; NF-KappaB Inhibitor alpha; Osteosarcoma; Phosphorylation; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteolysis; Receptors, Cytoplasmic and Nuclear; RNA Interference; Signal Transduction; Time Factors; Transcription Factor RelA; Transfection; Triazoles