Selective inhibitors of nuclear export (SINE) as novel therapeutics for prostate cancer

Mislocalization of proteins is a common feature of cancer cells. Since localization of proteins is tightly linked to its function, cancer cells can inactivate function of a tumor suppressor protein through mislocalization. The nuclear exportin CRM1/XPO 1 is upregulated in many cancers. Targeting XPO 1 can lead to nuclear retention of cargo proteins such as p53, Foxo, and BRCA1 leading to cell cycle arrest and apoptosis. We demonstrate that selective inhibitors of nuclear export (SINE) can functionally inactivate XPO 1 in prostate cancer cells. Unlike the potent, but toxic, XPO 1 inhibitor leptomycin B, SINE inhibitors (KPT-185, KPT-330, and KPT-251) cause a decrease in XPO 1 protein level through the proteasomal pathway. Treatment of prostate cancer cells with SINE inhibitors lead to XPO 1 inhibition, as evaluated by RevGFP export assay, leading to nuclear retention of p53 and Foxo proteins, consequently, triggering apoptosis. Our data reveal that treatment with SINE inhibitors at nanomolar concentrations results in decrease in proliferation and colonogenic capacity of prostate cancer cells by triggering apoptosis without causing any cell cycle arrest. We further demonstrate that SINE inhibitors can be combined with other chemotherapeutics like doxorubicin to achieve enhanced growth inhibition of prostate cancer cells. Since SINE inhibitors offer increased bioavailability, reduced toxicity to normal cells, and are orally available they can serve as effective therapeutics against prostate cancer. In conclusion, our data reveals that nucleocytoplasmic transport in prostate cancer can be effectively targeted by SINE inhibitors.     

Preclinical antitumor efficacy of selective exportin 1 inhibitors in glioblastoma

Background

Glioblastoma (GBM) is poorly responsive to current chemotherapy. The nuclear transporter exportin 1 (XPO1, CRM1) is often highly expressed in GBM, which may portend a poor prognosis. Here, we determine the efficacy of novel selective inhibitors of nuclear export (SINE) specific to XPO1 in preclinical models of GBM.

Methods

Seven patient-derived GBM lines were treated with 3 SINE compounds (KPT-251, KPT-276, and Selinexor) in neurosphere culture conditions. KPT-276 and Selinexor were also evaluated in a murine orthotopic patient-derived xenograft (PDX) model of GBM. Cell cycle effects were assayed by flow cytometry in vitro and immunohistochemistry in vivo. Apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase 3/7 activity assays.

Results

Treatment of GBM neurosphere cultures with KPT-276, Selinexor, and KPT-251 revealed dose-responsive growth inhibition in all 7 GBM lines [range of half-maximal inhibitory concentration (IC₅₀), 6–354 nM]. In an orthotopic PDX model, treatment with KPT-276 and Selinexor demonstrated pharmacodynamic efficacy, significantly suppressed tumor growth, and prolonged animal survival. Cellular proliferation was not altered with SINE treatment. Instead, induction of apoptosis was apparent both in vitro and in vivo with SINE treatment, without overt evidence of neurotoxicity.

Conclusions

SINE compounds show preclinical efficacy utilizing in vitro and in vivo models of GBM, with induction of apoptosis as the mechanism of action. Selinexor is now in early clinical trials in solid and hematological malignancies. Based on these preclinical data and excellent brain penetration, we have initiated clinical trials of Selinexor in patients with relapsed GBM.     

Nuclear retention of Fbw7 by specific inhibitors of nuclear export leads to Notch1 degradation in pancreatic cancer

Chromosome maintenance region 1 (CRM1) also called Exportin 1 (Xpo1), a protein found elevated in pancreatic ductal adenocarcinoma (PDAC), blocks tumor suppressor protein (TSP) function through constant nuclear export. Earlier we had shown that targeting CRM1 by our newly developed specific inhibitors of nuclear export (SINE) leads to inhibition of pancreatic cancer cell proliferation and tumor growth arrest. In this paper we define the mechanism of SINE action. Our lead SINE KPT-185 inhibits PDAC cell growth, cell migration, tumor invasion and induces apoptosis and G2-M cell cycle arrest in low nano molar range (IC_50s~150 nM). Mechanistically we demonstrate that the activity of KPT-185 is associated with nuclear retention of Fbw7; which degrades nuclear Notch-1 leading to decreased tumor promoting markers such as C-Myc, Cyclin-D1, Hes1 and VEGF. The orally bioavailable SINE (KPT-251) showed potent anti-tumor activity in a Colo-357 PDAC xenografts model; residual tumor analysis showed activation of Fbw7 concomitant with attenuation of Notch1 and its downstream genes. These results suggest that the antitumor activity of KPT-185 is in part due to nuclear retention of Fbw7 and consequent Notch1 degradation. The new CRM1 inhibitors, therefore, hold strong potential and warrant further clinical investigations for PDAC.     

Clinical Implications of Targeting XPO1-mediated Nuclear Export in Multiple Myeloma

Multiple myeloma (MM) is a malignancy of plasma cells that is typically chronic, and relapse is common. Current therapeutic strategies include combination and sequential treatments with corticosteroids, alkylating agents, proteasomal inhibitors, immunomodulators, and monoclonal antibodies. These drugs prolong survival but ultimately become ineffective. Exportin 1 (XPO1), a nuclear export protein, is overexpressed in MM cells, and knockdown studies have suggested that XPO1 is essential for MM cell survival. Selective inhibitor of nuclear export (SINE) compounds are novel, orally bioavailable class of agents that specifically inhibit XPO1. Selinexor (KPT-330) is the first-in-human SINE compound. Early phase clinical trials have established the safety profile of this agent and have shown promising efficacy in combination with low-dose dexamethasone and other anti-MM agents. The combination of selinexor and dexamethasone has demonstrated activity in “penta-refractory” MM, (ie, MM refractory to the 5 most active anti-MM agents currently used in treatment). We have reviewed the available data on the molecular implications of XPO1 inhibition in MM. We also reviewed the pertinent early phase clinical data with SINE compounds and discuss management strategies for common toxicities encountered with use of selinexor.     

KPT-330 inhibitor of XPO1-mediated nuclear export has anti-proliferative activity in hepatocellular carcinoma

Purpose

Exportin-1 (XPO1, CRM1) mediates the nuclear export of several key growth regulatory and tumor suppressor proteins. Cancer cells often overexpress XPO1 resulting in cytoplasmic mislocalization and aberrant activity of its target proteins. Orally bioavailable selective inhibitors of nuclear export (SINE) that irreversibly bind to and inhibit the function of XPO1 have been recently developed. The aim of this study was to investigate the efficacy of the clinical staged, orally available, SINE compound, KPT-330 in hepatocellular carcinoma (HCC).

Methods

In silico, meta-analysis showed that XPO1 is overexpressed in HCC. Six HCC cell lines were treated with KPT-330, and cell proliferation and expression of cell growth regulators were examined by cell proliferation assays and Western blot analysis, respectively. The in vivo anti-cancer activity of KPT-330 was examined in a HCC xenograft murine model.

Results

KPT-330 reduced the viability of HCC cell lines in vitro and this anti-proliferative effect was associated with cell cycle arrest and induction of apoptosis. The expression of the pro-apoptotic protein PUMA was markedly up-regulated by KPT-330. In addition, SINE treatment increased the expression of the tumor suppressor proteins p53 and p27, while it reduced the expression of HCC promoting proteins, c-Myc and c-Met. XPO1 levels itself were also down-regulated following KPT-330 treatment. Finally, a HCC xenograft murine model showed that treatment of mice with oral KPT-330 significantly inhibited tumor growth with little evidence of toxicity.

Conclusion

Our results suggest that SINE compounds, such as KPT-330, are promising novel drugs for the targeted therapy of HCC.     

出核因子CRM1抑制剂KPT-185对人前列腺癌细胞生长的影响

目的 探讨出核因子（chromosome maintenance region 1, CRM1）抑制剂KPT-185对人前列腺癌细胞生长、凋亡、迁徙的影响及影响产生的原因。方法 采用MTT、细胞集落形成能力测定法检测KPT-185对前列腺癌细胞生长的影响;划痕愈合实验检测KPT-185对前列腺癌细胞迁徙能力的影响;流式细胞仪检测KPT-185对细胞周期的影响;人组蛋白（Histone）/DNA 酶联免疫法和膜联蛋白V-FITC/PI双染法流式细胞术检测细胞凋亡;免疫印迹检测蛋白表达。结果 KPT-185能极大地抑制人前列腺癌细胞的生长,使其细胞周期阻滞于G0~G1期,并导致细胞凋亡。KPT-185引起的细胞生长抑制和凋亡是通过其抑制CRM1的核输出,使抑癌蛋白p53 和p21保留于核内而发挥作用的。结论 KPT-185是一种新型的CRM1抑制剂,有望成为治疗前列腺癌的候选药物。     

Association of XPO1 Overexpression with NF-κB and Ki67 in Colorectal Cancer

Objectives: Exportin 1(XPO1), a nuclear exporter protein, has been gaining recognition in cancer progression and treatment. This study aimed to evaluate the association between the overexpression of XPO1 with NF-κB, Ki67 and clinicopathological characteristics in colorectal cancer (CRC) tissue samples and to explore the anti-proliferative effect of KPT-330, as XPO1 inhibitor, in colorectal cancer cell line. Methods: Forty CRC tissue samples were analyzed by immunostaining for the expressions of XPO1, NF-κB and Ki67 and then the anti-proliferative effect of the KPT-330 was also evaluated in HT29 colorectal cancer cell line. Results: XPO1 overexpression was observed in 52.5% of CRC and significantly apparent with strong intensity in tumor cells compared to the normal adjacent epithelium (P<0.001). Regarding to the histopathological characteristics, the XPO1 overexpression significantly associated with advanced tumor stages (P=0.049) and has great tendency towards moderate/poorly differentiated tumors. Although the XPO1 overexpression was strongly associated with high Ki67 expression (P=0.001), only Ki67 expression showed significant association with tumor size (P=0.012). No significant association was detected between the XPO1 overexpression and NF-κB, while the NF-κB positive expression was significantly associated with lymph node metastasis and Ki67 expression at P=0.027 and P= 0.007, respectively. The in vitro experiments showed a great impact of KPT-330, as XPO1 inhibitor, to inhibit cancer growth in dose and time dependent manner and significantly diminished the colony formation (P<0.001) of HT29 cells- associated with the expression of Ki67 (P<0.001). Conclusion: XPO1 overexpression and NF-κB expression may serve as potential biomarker associated with CRC pathogenesis and proliferation, while the KPT-330 is effectively inhibited-colon cancer growth in vitro. Further studies considering the prognostication role of XPO1 overexpression in CRC are required.     

Expression of the nuclear export protein chromosomal region maintenance/exportin 1/Xpo1 is a prognostic factor in human ovarian cancer

BACKGROUND: The human nuclear export protein chromosomal region maintenance/exportin 1/Xpo1 (CRM1) mediates the nuclear export of proteins and messenger RNAs and, thus, is an important regulator of subcellular distribution of key molecules. Whereas cell-biologic studies have suggested a fundamental role for CRM1 in the regulation of mitosis, the expression of this protein in human tumor tissue has not been investigated to date. METHODS: In this study, the expression of CRM1 was analyzed in a cohort of 88 ovarian tumors and 12 ovarian cell lines for the first time to the authors' knowledge. RESULTS: Immunohistochemistry revealed increased nuclear (52.7%) and cytoplasmic (56.8%) expression of CRM1 in 74 carcinomas compared with the expression revealed in borderline tumors and benign lesions. Similarly, CRM1 expression was increased in ovarian cancer cell lines compared with human ovarian surface epithelial cells. Cytoplasmic CRM1 expression was related significantly to advanced tumor stage (P= .043), poorly differentiated carcinomas (P= .011), and higher mitotic rate (P= .008). Nuclear CRM1 was associated significantly with cyclooxygenase-2 (COX-2) expression (P= .002) and poor overall survival (P= .01). Because it was demonstrated previously that blocking of CRM1 by leptomycin B (LMB) contributes to the inhibition of nuclear export, the authors used a set of mechanistic assays to study the effects of CRM1 inhibition in cancer cells. Treatment of OVCAR-3 cells with LMB revealed a significant reduction of cell proliferation and increased apoptosis as well as suppressed interleukin-1beta-induced COX-2 expression. CONCLUSIONS: The current results indicated that CRM1 is expressed in a subpopulation of ovarian carcinomas with aggressive behavior and is related to poor patient outcome. A correlation also was demonstrated between CRM1 and COX-2 expression in ovarian cancer tissue. Furthermore, the treatment of ovarian cancer cells with LMB revealed a reduction in COX-2 expression. Therefore, the authors suggest that CRM1 may be an interesting biomarker for the assessment of patient prognosis and a molecular target for anticancer treatment.     

Knockdown of UBE2I inhibits tumorigenesis and enhances chemosensitivity of cholangiocarcinoma via modulating p27kip1 nuclear export

The asymptomatic nature of cholangiocarcinoma (CCA), particularly during its early stages, in combination with its high aggressiveness and chemoresistance, significantly compromises the efficacy of current therapeutic options, contributing to a dismal prognosis. As a tumor suppressor that inhibits the cell cycle, abnormal cytoplasmic p27kip1 localization is related to chemotherapy resistance and often occurs in various cancers, including CCA. Nevertheless, the underlying mechanism is unclear. SUMOylation, which is involved in regulating subcellular localization and the cell cycle, is a posttranslational modification that regulates p27kip1 activity. Here, we confirmed that UBE2I, as the only key enzyme for SUMOylation, was highly expressed and p27kip1 was downregulated in CCA tissues, which were associated with poor outcomes in CCA. Moreover, UBE2I silencing inhibited CCA cell proliferation, delayed xenograft tumor growth in vivo, and sensitized CCA cells to the chemotherapeutics, which may be due to cell cycle arrest induced by p27kip1 nuclear accumulation. According to the immunoprecipitation result, we found that UBE2I could bind p27kip1, and the binding amount of p27kip1 and SUMO-1 decreased after UBE2I silencing. Moreover, nuclear retention of p27kip1 was induced by UBE2I knockdown and SUMOylation or CRM1 inhibition, further suggesting that UBE2I could cooperate with CRM1 in the nuclear export of p27kip1. These data indicate that UBE2I-mediated SUMOylation is a novel regulatory mechanism that underlies p27kip1 export and controls CCA tumorigenesis, providing a therapeutic option for CCA treatment.     

KPT-330 has antitumour activity against non-small cell lung cancer

Background:

We investigated the biologic and pharmacologic activities of a chromosome region maintenance 1 (CRM1) inhibitor against human non-small cell lung cancer (NSCLC) cells both in vitro and in vivo.

Methods:

The in vitro and in vivo effects of a novel CRM1 inhibitor (KPT-330) for a large number of anticancer parameters were evaluated using a large panel of 11 NSCLC cell lines containing different key driver mutations. Mice bearing human NSCLC xenografts were treated with KPT-330, and tumour growth was assessed.

Results:

KPT-330 inhibited proliferation and induced cell cycle arrest and apoptosis-related proteins in 11 NSCLC cells lines. Moreover, the combination of KPT-330 with cisplatin synergistically enhanced the cell kill of the NSCLC cells in vitro. Human NSCLC tumours growing in immunodeficient mice were markedly inhibited by KPT-330. Also, KPT-330 was effective even against NSCLC cells with a transforming mutation of either exon 20 of EGFR, TP53, phosphatase and tensin homologue, RAS or PIK3CA, suggesting the drug might be effective against a variety of lung cancers irrespective of their driver mutation.

Conclusions:

Our results support clinical testing of KPT-330 as a novel therapeutic strategy for NSCLC.     

Potential effects of CRM1 inhibition in mantle cell lymphoma

Mantle cell lymphoma(MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma.The disease has no known cure,which prompts the urgent need for novel therapeutic agents.Chromosomal region maintenance 1(CRM1) may play a role in human neoplasia and serve as a novel target of cancer treatment.This study summarizes MCL pathogenesis and determines the involvement of CRM1 in the regulation of several vital signaling pathways contributing to MCL pathogenesis,including the pathways of cell cycle progression,DNA damage response,phosphoinositide kinase-3,nuclear factor-κB activation,and chromosomal stability.A preclinical study is also presented to compare the CRM1 status in MCL cell lines and primary MCL cells with normal B cells,as well as the therapeutic efficiency of CRM1 inhibition in MCL in vitro and in vivo,which make these agents potential targets of novel MCL treatments.     

Role of cyclin D1 cytoplasmic sequestration in the survival of postmitotic neurons

Cyclin D-dependent kinases phosphorylate the retinoblastoma (Rb) protein and play a critical role in neuronal cell cycle control and apoptosis. Here we show that cyclin D1 became predominantly cytoplasmic as primary cortical progenitor cells underwent cell cycle withdrawal and terminal differentiation. Furthermore, ectopically expressed cyclin D1 sequestered in the cytoplasm of postmitotic neurons, whereas it efficiently entered the nucleus of proliferating progenitor cells. Cytoplasmic cyclin D1 were complexed with cyclin-dependent kinase 4 (CDK4), and also with CDK inhibitors, p27(Kip)(I) or p21(Cip)(I), which positively regulate assembly and nuclear accumulation of the cyclin D1-CDK4 complex. Although overexpression of p21(Cip)(I) promoted cyclin D1 nuclear localization, inhibition of either glycogen synthase kinase 3beta- or CRM1-mediated cyclin D1 nuclear export did not, suggesting that the inhibition of its nuclear import, rather than the acceleration of nuclear export, contributes to cytoplasmic sequestration of cyclin D1 in postmitotic neurons. In differentiated progenitor cells, nuclear localization of ectopic cyclin D1 induced apoptosis, and the DNA-damaging compound camptothecin caused nuclear accumulation of endogenous cyclin D1, accompanied by Rb phosphorylation. These results indicate that nuclear accumulation of cyclin D1 is inhibited in postmitotic neurons and suggest a role of its subcellular localization in neuronal death and survival.     

重组诱导性质粒Egr1-XPO4 的构建及其与5-FU 联合对肝癌细胞SKHep1的协同抑制作用

目的：构建重组诱导性质粒Egr1-XPO4,探讨其与5-FU联合对肝癌细胞SK-Hep1 的协同抑制作用。方法: 将XPO4基因插入带诱导性启动子Egr1 的质粒载体中,构建Egr1-XPO4 重组质粒。将Egr1-XPO4 质粒转染肝癌细胞SK-Hep1 并经化疗药物5-FU诱导,采用Western blotting 检测转染细胞中XPO4 蛋白表达水平,CCK法检测转染诱导后SK-Hep1 细胞的增殖水平,Annexin V-FITC/PI 流式细胞仪检测SK-Hep1 细胞凋亡情况。动物实验观察Egr1-XPO4 质粒联合5-FU对裸鼠移植瘤的治疗效果。结果: 成功构建携XPO4 基因和启动子Egr1 的重组诱导性质粒Egr1-XPO4,重组质粒转染SK-Hep1 细胞并经5-FU诱导后,细胞中XPO4 蛋白表达量明显增加,且与5-FU的质量浓度明显依赖。Egr1-XPO4 转染联合5-FU诱导对SK-Hep1 细胞增殖抑制明显强于单纯转染或5-FU诱导（P<0.05）,同时导致SK-Hep1 细胞的早期凋亡率显著高于单纯转染或诱导（P<0.05）。以Egr1-XPO4 质粒联合5-FU 治疗后,裸鼠肝癌移植瘤的体积明显小于Egr1-XPO4 或5-FU 单独治疗（P<0.05)。结论: 重组诱导性质粒Egr1-XPO4联合5-FU对肝癌细胞SK-Hep1 产生协同抑制作用。     

Silibinin inhibits aberrant lipid metabolism,proliferation and emergence of androgen-independence in prostate cancer cells via primarily targeting the sterol response element binding protein 1

Prostate cancer (PCA) kills thousands of men every year, demanding additional approaches to better understand and target this malignancy. Recently, critical role of aberrant lipogenesis is highlighted in prostate carcinogenesis, offering a unique opportunity to target it to reduce PCA. Here, we evaluated efficacy and associated mechanisms of silibinin in inhibiting lipid metabolism in PCA cells. At physiologically achievable levels in human, silibinin strongly reduced lipid and cholesterol accumulation specifically in human PCA cells but not in non-neoplastic prostate epithelial PWR-1E cells. Silibinin also decreased nuclear protein levels of sterol regulatory element binding protein 1 and 2 (SREBP1/2) and their target genes only in PCA cells. Mechanistically, silibinin activated AMPK, thereby increasing SREBP1 phosphorylation and inhibiting its nuclear translocation; AMPK inhibition reversed silibinin-mediated decrease in nuclear SREBP1 and lipid accumulation. Additionally, specific SREBP inhibitor fatostatin and stable overexpression of SREBP1 further confirmed the central role of SREBP1 in silibinin-mediated inhibition of PCA cell proliferation and lipid accumulation and cell cycle arrest. Importantly, silibinin also inhibited synthetic androgen R1881-induced lipid accumulation and completely abrogated the development of androgen-independent LNCaP cell clones via targeting SREBP1/2. Together, these mechanistic studies suggest that silibinin would be effective against PCA by targeting critical aberrant lipogenesis.     

Survivin in Solid Tumors: Rationale for Development of Inhibitors

Survivin is a 16.5 kDa protein that functions to inhibit apoptosis, promote proliferation, and enhance invasion. Absent in most adult tissues, survivin is selectively upregulated in many human tumors, where its overexpression correlates with poor outcome and treatment resistance. Consequently, survivin is a promising target for cancer therapy. Preclinical data demonstrate that survivin inhibition reduces cell proliferation, increases apoptosis, and sensitises cells to cytotoxic agents and radiotherapy. The pharmacological survivin inhibitors LY2181308 and YM155 have demonstrated acceptable toxicity and evidence of therapeutic efficacy as single agents in early-phase clinical trials. Current efforts seek to define the optimum use of survivin inhibitors in combination with cytotoxic therapies, where it is hoped that preclinical evidence of treatment synergy will translate into improved therapeutic efficacy. Results from these ongoing studies are keenly awaited.     

Experience with peritoneal mesothelioma at the Milan National Cancer Institute

Diffuse malignant peritoneal mesothelioma (DMPM) is an uncommon and rapidly fatal tumor. Therapeutic options have traditionally been limited and ineffective. The biologic and molecular events correlated with poor responsiveness to therapy are still poorly understood. In recent years, an innovative treatment approach involving aggressive cytoreductive surgery (CRS) and perioperative intraperitoneal chemotherapy has reportedly resulted in improved outcome, as compared to historical controls. Since 1995, at the National Cancer Institute (NCI) of Milan (Italy), patients with DMPM have been treated with CRS and hyperthermic intra-peritoneal chemotherapy (HIPEC). In the present paper, clinical experiences and basic science investigations on DMPM at Milan NCI are reviewed. Peri-operative and long-term outcome results with CRS and HIPEC are presented. Clinico-pathological prognostic factors were investigated by multivariate analysis. The pathologic features and immunohistochemical markers related to DMPM biologic behavior were assessed in a large case-series uniformly treated at our institution. The prevalence and prognostic role of telomere maintenance mechanisms, which account for the limitless cell replicative potential of many malignancies, were studied. The dysregulation of the apoptotic pathways may play a role in the relative chemo-resistance of DMPM and a better understanding of apoptosis-related mechanisms could result in novel targeted therapeutic strategies. On this basis, the expression of survivin and other IAP family members (IAP-1, IAP-2, and X-IAP), the pro-apoptotic protein Smac/DIABLO, and antigens associated with cell proliferation (Ki-67) and apoptosis (caspase-cleaved cytokeratin-18) were analyzed. Finally, analyses of EGFR, PDGFRA and PDGFRB were performed to ascertain if deregulation of RTK could offer useful alternative therapeutic targets.