CRM1 Blockade by Selective Inhibitors of Nuclear Export (SINE) attenuates Kidney Cancer Growth.
ABSTRACT Since renal cell carcinoma (RCC) often presents asymptomatically, patients are commonly diagnosed at the metastatic stage when treatment options are limited and survival is poor. Given that progression-free survival with current therapies for metastatic RCC is only one to two years and existing drugs are associated with a high rate of resistance, new pharmacological targets are desperately needed. We identified and evaluated the nuclear exporter protein, chromosome region maintenance protein 1 (CRM1), as a novel potential therapeutic for RCC. PURPOSE: To evaluate novel, selective inhibitors of nuclear export as potential RCC therapeutics. MATERIALS AND METHODS: Efficacy of the CRM1 inhibitors, KPT-185 and -251, was tested in several RCC cell lines and in a RCC xenograft model. Apoptosis and cell cycle arrest were quantified, and localization of p53 family proteins was assessed using standard techniques. RESULTS: KPT-185 attenuated CRM1 and showed increased cytotoxicity in RCC cells in vitro, with evidence of increased apoptosis as well as cell cycle arrest. KPT-185 caused both p53 and p21 to remain primarily in the nucleus in all RCC cell lines, suggesting a mechanism of action of these compounds dependent upon tumor-suppressor protein localization. Furthermore, when administered orally in a high-grade RCC xenograft model, the bioavailable CRM1 inhibitor KPT-251 significantly inhibited tumor growth in vivo with the expected on-target effects and with no obvious toxicity. CONCLUSIONS: The CRM1 inhibitor family of proteins are novel therapeutic targets RCC and deserve further intensive investigation in this and other urologic malignancies.
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ABSTRACT: RNA interference screening identified XPO1 (exportin 1) among the 55 most vulnerable targets in Multiple Myeloma (MM). XPO1 encodes CRM1, a nuclear export protein. XPO1 expression increases with MM disease progression. Patients with MM have a higher expression of XPO1 compared to normal plasma cells (P<0.04) and to patients with monoclonal gammopathy of undetermined significance/smoldering MM (P<0.0001). The highest XPO1 level was found in human MM cell lines (HMCL). A selective inhibitor of nuclear export (SINE) compound KPT-276 specifically and irreversibly inhibits the nuclear export function of XPO1. The viability of 12 HMCL treated with KTP-276 was significantly reduced. KPT-276 also actively induced apoptosis in primary MM patient samples. In gene expression analyses two genes of probable relevance were dysregulated by KPT-276: cell division cycle 25 homolog A (CDC25A) and bromodomain-containing protein 4 (BRD4), both of which are associated with c-MYC pathway. Western blotting and RT-PCR confirm that c-MYC, CDC25A and BRD4 are all down regulated after treatment with KPT-276. KPT-276 reduced monoclonal spikes in the Vk*MYC transgenic MM mouse model, and inhibited tumor growth in a xenograft MM mouse model. A Phase One clinical trial of an analog of KPT-276 is ongoing in hematological malignancies including MM.Leukemia accepted article preview online, 11 June 2013; doi:10.1038/leu.2013.172.Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 06/2013; · 10.16 Impact Factor
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ABSTRACT: Neuroblastoma (NB) is the most common extracranial neoplasm in children. In NB, loss of p53 function is largely due to cytoplasmic sequestration rather than mutation. Ubiquitin-conjugating enzyme E2 N (UBE2N), also known as Ubc13, is an E2 ubiquitin-conjugating enzyme that promotes formation of monomeric p53 that results in its cytoplasmic translocation and subsequent loss of function. Therefore, inhibition of UBE2N may reactivate p53 by promoting its nuclear accumulation. Here, we show that NSC697923, a novel UBE2N inhibitor, exhibits potent cytotoxicity in a panel of NB cell lines evidenced by its ability to induce apoptosis. In p53 wild-type NB cells, NSC697923 induced nuclear accumulation of p53, which led to its increased transcriptional activity and tumor suppressor function. Interestingly, in p53 mutant NB cells, NSC697923 induced cell death by activating JNK pathway. This effect was reversible by blocking JNK activity with its selective inhibitor, SP600125. More importantly, NSC697923 impeded cell growth of chemoresistant LA-N-6 NB cell line in a manner greater than conventional chemotherapy drugs doxorubicin and etoposide. NSC697923 also revealed in vivo antitumor efficacy in NB orthotopic xenografts. Taken together, our results suggest that UBE2N is a potential therapeutic target in NB and provide a basis for the rational use of UBE2N inhibitors like NSC697923 as a novel treatment option for NB patients.Cell Death & Disease 01/2014; 5:e1079. · 6.04 Impact Factor
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ABSTRACT: CRM1 or XPO1 is the major nuclear export receptor in the cell, which controls the nuclear-cytoplasmic localization of many proteins and RNAs. CRM1 is also a promising cancer drug target as the transport receptor is overexpressed in many cancers and quite a few of its cargos are misregulated in the diseases and hence mislocalized to the cytoplasm. Atomic level understanding of CRM1 function has greatly facilitated recent drug discovery and development of CRM1 inhibitors to target a variety of malignancies. Numerous atomic resolution CRM1 structures are now available, explaining how the exporter recognizes nuclear export signals in its cargos, how RanGTP and cargo bind with positive cooperativity, how RanBP1 causes release of export cargos in the cytoplasm and how diverse inhibitors such as Leptomycin B and the new KPT-SINE compounds block nuclear export. This review summarizes the structure-function studies that explain CRM1-cargo recognition, release and inhibition.Seminars in Cancer Biology 01/2014; · 7.44 Impact Factor