A chemical genetic screen identifies inhibitors of regulated nuclear export of a Forkhead transcription factor in PTEN-deficient tumor cells

AKT/GSK3β signaling pathway is critically involved in human pluripotent stem cell survival

Human embryonic and induced pluripotent stem cells are self-renewing pluripotent stem cells (PSC) that can differentiate into a wide range of specialized cells. Basic fibroblast growth factor is essential for PSC survival, stemness and self-renewal. PI3K/AKT pathway regulates cell viability and apoptosis in many cell types. Although it has been demonstrated that PI3K/AKT activation by bFGF is relevant for PSC stemness maintenance its role on PSC survival remains elusive. In this study we explored the molecular mechanisms involved in the regulation of PSC survival by AKT. We found that inhibition of AKT with three non-structurally related inhibitors (GSK690693, AKT inhibitor VIII and AKT inhibitor IV) decreased cell viability and induced apoptosis. We observed a rapid increase in phosphatidylserine translocation and in the extent of DNA fragmentation after inhibitors addition. Moreover, abrogation of AKT activity led to Caspase-9, Caspase-3, and PARP cleavage. Importantly, we demonstrated by pharmacological inhibition and siRNA knockdown that GSK3β signaling is responsible, at least in part, of the apoptosis triggered by AKT inhibition. Moreover, GSK3β inhibition decreases basal apoptosis rate and promotes PSC proliferation. In conclusion, we demonstrated that AKT activation prevents apoptosis, partly through inhibition of GSK3β, and thus results relevant for PSC survival.

Recurrent mutations of the exportin 1 gene (XPO1) and their impact on selective inhibitor of nuclear export compounds sensitivity in primary mediastinal B-cell lymphoma

Primary mediastinal B-cell lymphoma (PMBL) is an entity of B-cell lymphoma distinct from the other molecular subtypes of diffuse large B-cell lymphoma (DLBCL). We investigated the prevalence, specificity, and clinical relevance of mutations of XPO1, which encodes a member of the karyopherin-β nuclear transporters, in a large cohort of PMBL. PMBL cases defined histologically or by gene expression profiling (GEP) were sequenced and the XPO1 mutational status was correlated to genetic and clinical characteristics. The XPO1 mutational status was also assessed in DLBCL, Hodgkin lymphoma (HL) and mediastinal gray-zone lymphoma (MGZL).The biological impact of the mutation on Selective Inhibitor of Nuclear Export (SINE) compounds (KPT-185/330) sensitivity was investigated in vitro. XPO1 mutations were present in 28/117 (24%) PMBL cases and in 5/19 (26%) HL cases but absent/rare in MGZL (0/20) or DLBCL (3/197). A higher prevalence (50%) of the recurrent codon 571 variant (p.E571K) was observed in GEP-defined PMBL and was associated with shorter PFS. Age, International Prognostic Index and bulky mass were similar in XPO1 mutant and wild-type cases. KPT-185 induced a dose-dependent decrease in cell proliferation and increased cell-death in PMBL cell lines harboring wild type or XPO1 E571K mutant alleles. Experiments in transfected U2OS cells further confirmed that the XPO1 E571K mutation does not have a drastic impact on KPT-330 binding. To conclude the XPO1 E571K mutation represents a genetic hallmark of the PMBL subtype and serves as a new relevant PMBL biomarker. SINE compounds appear active for both mutated and wild-type protein. Am. J. Hematol. 91:923-930, 2016. © 2016 Wiley Periodicals, Inc.

Inhibiting cancer cell hallmark features through nuclear export inhibition

Treating cancer through inhibition of nuclear export is one of the best examples of basic research translation into clinical application. Nuclear export factor chromosomal region maintenance 1 (CRM1; Xpo1 and exportin-1) controls cellular localization and function of numerous proteins that are critical for the development of many cancer hallmarks. The diverse actions of CRM1 are likely to explain the broad ranging anti-cancer potency of CRM1 inhibitors observed in pre-clinical studies and/or clinical trials (phase I–III) on both advanced-stage solid and hematological tumors. In this review, we compare and contrast the mechanisms of action of different CRM1 inhibitors, and discuss the potential benefit of unexplored non-covalent CRM1 inhibitors. This emerging field has uncovered that nuclear export inhibition is well poised as an attractive target towards low-toxicity broad-spectrum potent anti-cancer therapy.

The development of high-content screening (HCS) technology and its importance to drug discovery

INTRODUCTION

High-content screening (HCS) was introduced about twenty years ago as a promising analytical approach to facilitate some critical aspects of drug discovery. Its application has spread progressively within the pharmaceutical industry and academia to the point that it today represents a fundamental tool in supporting drug discovery and development.

AREAS COVERED

Here, the authors review some of significant progress in the HCS field in terms of biological models and assay readouts. They highlight the importance of high-content screening in drug discovery, as testified by its numerous applications in a variety of therapeutic areas: oncology, infective diseases, cardiovascular and neurodegenerative diseases. They also dissect the role of HCS technology in different phases of the drug discovery pipeline: target identification, primary compound screening, secondary assays, mechanism of action studies and in vitro toxicology.

EXPERT OPINION

Recent advances in cellular assay technologies, such as the introduction of three-dimensional (3D) cultures, induced pluripotent stem cells (iPSCs) and genome editing technologies (e.g., CRISPR/Cas9), have tremendously expanded the potential of high-content assays to contribute to the drug discovery process. Increasingly predictive cellular models and readouts, together with the development of more sophisticated and affordable HCS readers, will further consolidate the role of HCS technology in drug discovery.

Akt mediated phosphorylation of LARP6; critical step in biosynthesis of type I collagen

La ribonucleoprotein domain family, member 6 (LARP6) is the RNA binding protein, which regulates translation of collagen mRNAs and synthesis of type I collagen. Posttranslational modifications of LARP6 and how they affect type I collagen synthesis have not been studied. We show that in lung fibroblasts LARP6 is phosphorylated at 8 serines, 6 of which are located within C-terminal domain. Phosphorylation of LARP6 follows a hierarchical order; S451 phosphorylation being a prerequisite for phosphorylations of other serines. Inhibition of PI3K/Akt pathway reduced the phosphorylation of LARP6, but had no effect on the S451A mutant, suggesting that PI3K/Akt pathway targets S451 and we have identified Akt as the responsible kinase. Overexpression of S451A mutant had dominant negative effect on collagen biosynthesis; drastically reduced secretion of collagen and induced hyper-modifications of collagen α2 (I) polypeptides. This indicates that LARP6 phosphorylation at S451 is critical for regulating translation and folding of collagen polypeptides. Akt inhibitor, GSK-2141795, which is in clinical trials for treatment of solid tumors, reduced collagen production by human lung fibroblasts with EC50 of 150 nM. This effect can be explained by inhibition of LARP6 phosphorylation and suggests that Akt inhibitors may be effective in treatment of various forms of fibrosis.

The ERα-PI3K Cascade in Proopiomelanocortin Progenitor Neurons Regulates Feeding and Glucose Balance in Female Mice

Estrogens act upon estrogen receptor (ER)α to inhibit feeding and improve glucose homeostasis in female animals. However, the intracellular signals that mediate these estrogenic actions remain unknown. Here, we report that anorexigenic effects of estrogens are blunted in female mice that lack ERα specifically in proopiomelanocortin (POMC) progenitor neurons. These mutant mice also develop insulin resistance and are insensitive to the glucose-regulatory effects of estrogens. Moreover, we showed that propyl pyrazole triol (an ERα agonist) stimulates the phosphatidyl inositol 3-kinase (PI3K) pathway specifically in POMC progenitor neurons, and that blockade of PI3K attenuates propyl pyrazole triol-induced activation of POMC neurons. Finally, we show that effects of estrogens to inhibit food intake and to improve insulin sensitivity are significantly attenuated in female mice with PI3K genetically inhibited in POMC progenitor neurons. Together, our results indicate that an ERα-PI3K cascade in POMC progenitor neurons mediates estrogenic actions to suppress food intake and improve insulin sensitivity.

KPT-330, a potent and selective exportin-1 (XPO-1) inhibitor, shows antitumor effects modulating the expression of cyclin D1 and survivin [corrected] in prostate cancer models

BACKGROUND AND AIMS

Increased expression of Chromosome Region Maintenance (CRM-1)/exportin-1 (XPO-1) has been correlated with poor prognosis in several aggressive tumors, making it an interesting therapeutic target. Selective Inhibitor of Nuclear Export (SINE) compounds bind to XPO-1 and block its ability to export cargo proteins. Here, we investigated the effects of a new class of SINE compounds in models of prostate cancer.

MATERIAL AND METHODS

We evaluated the expression of XPO-1 in human prostate cancer tissues and cell lines. Next, six SINE (KPT-127, KPT-185, KPT-205, KPT-225, KPT-251 and KPT-330) compounds having different potency with broad-spectrum, tumor-selective cytotoxicity, tolerability and pharmacokinetic profiles were tested in a panel of prostate cancer cells representing distinct differentiation/progression states of disease and genotypes. Two SINE candidates for clinical trials (KPT-251 and KPT-330) were also tested in vivo in three cell models of aggressive prostate cancer engrafted in male nude mice.

RESULTS AND CONCLUSIONS

XPO-1 is overexpressed in prostate cancer compared to normal or hyperplastic tissues. Increased XPO-1 expression, mainly in the nuclear compartment, was associated with increased Gleason score and bone metastatic potential supporting the use of SINEs in advanced prostate cancer. SINE compounds inhibited proliferation and promoted apoptosis of tumor cells, but did not affect immortalized non-transformed prostate epithelial cells. Nuclei from SINE treated cells showed increased protein localization of XPO-1, survivin and cyclin D1 followed by degradation of these proteins leading to cell cycle arrest and apoptosis. Oral administration of KPT-251 and KPT-330 in PC3, DU145 and 22rv1 tumor-bearing nude mice reduced tumor cell proliferation, angiogenesis and induced apoptosis. Our results provide supportive evidence for the therapeutic use of SINE compounds in advanced/castration resistant prostate cancers and warrants further clinical investigation.

DYNAMICS OF GLI REGULATION AND A STRATEGY TO CONTROL CANCEROUS SITUATION: HEDGEHOG SIGNALING PATHWAY REVISITED

The hedgehog signaling cascade generates highly diverse, fine-tuned responses in response to the external stimulus by the sonic hedgehog (SHH) protein. This is required for the flawless functioning of the cell, its development, survival and proliferation; maintained through production of Glioma protein (GLI) and transcriptional activation of its target genes. Any change in the behavior of GLI response by ectopic expression of SHH or mutations in the core pathway components may cause serious consequences in the cell fate through rapid, uncontrolled and elevated production of GLI. Here, we present a simple but extensive computational model that considers the detailed reaction mechanisms involved in the hedgehog signal transduction and provides a detailed insight into regulation of GLI. For the first time, by explicit involvement of suppressor of fused (SUFU) and Hedgehog interacting protein (HHIP) reaction kinetics in the model, we try to demonstrate the vital importance of HHIP and SUFU in maintaining the graded response of GLI in response to SHH. By performing parameter variations, we capture the conversion of a graded response of GLI to an ultrasensitive switch under SUFU-deficient conditions that might predispose abnormal embryonic development and the irreversible switching response of GLI that corresponds to signal-independent pathway activation observed in cancers.

MiR-182 Is Associated with Growth, Migration and Invasion in Prostate Cancer via Suppression of FOXO1

BACKGROUND

MicroRNA (miRNA) have been shown to regulate gene expression in many cancers. MiR-182 has recently been found to be prognostic for patients treated with radical prostatectomy for prostate cancer. We sought to assess miR-182 as a prognostic marker and understand its role in prostate cancer progression and metastasis.

METHODS

We analysed miR-182 expression among 147 men treated for prostate cancer using biochemical recurrence and metastasis as the endpoints. We examined miR-182 expression in prostate cancer cells and created cell lines that overexpressed miR-182 for functional assays. Finally, we examined pathways through which miR-182 may function using prediction algorithms and confirmed by Western blotting and knock-down assays.

RESULTS

We found that miR-182 was not associated with biochemical recurrence (p=0.1111) or metastasis (p=0.9268) following radical prostatectomy. However, in mechanistic assays, we found that miR-182 expression was higher among aggressive prostate cancer cells and that ectopic miR-182 expression resulted in increased proliferation, migration and invasion in vitro. We identified FOXO1 as regulated by miR-182 in prostate cancer cells, confirmed that ectopic miR-182 expression resulted in diminished FOXO1 levels, and showed that miR-182 inhibition results in increased FOXO1 levels. Expression of FOXO1 (p=0.0014) in tumors from patients who developed biochemical recurrence compared to tumors from patients who were recurrence-free five years after their radical prostatectomy.

CONCLUSIONS

Our findings suggest that miR-182 may act to increase prostate cancer proliferation, migration and invasion through suppression of FOXO1. This may be valuable in the development of further therapeutic interventions.

Structural Basis of Targeting the Exportin CRM1 in Cancer

Recent studies have demonstrated the interference of nucleocytoplasmic trafficking with the establishment and maintenance of various cancers. Nucleocytoplasmic transport is highly regulated and coordinated, involving different nuclear transport factors or receptors, importins and exportins, that mediate cargo transport from the cytoplasm into the nucleus or the other way round, respectively. The exportin CRM1 (Chromosome region maintenance 1) exports a plethora of different protein cargoes and ribonucleoprotein complexes. Structural and biochemical analyses have enabled the deduction of individual steps of the CRM1 transport cycle. In addition, CRM1 turned out to be a valid target for anticancer drugs as it exports numerous proto-oncoproteins and tumor suppressors. Clearly, detailed understanding of the flexibility, regulatory features and cooperative binding properties of CRM1 for Ran and cargo is a prerequisite for the design of highly effective drugs. The first compound found to inhibit CRM1-dependent nuclear export was the natural drug Leptomycin B (LMB), which blocks export by competitively interacting with a highly conserved cleft on CRM1 required for nuclear export signal recognition. Clinical studies revealed serious side effects of LMB, leading to a search for alternative natural and synthetic drugs and hence a multitude of novel therapeutics. The present review examines recent progress in understanding the binding mode of natural and synthetic compounds and their inhibitory effects.

Reengineered tricyclic anti-cancer agents

The phenothiazine and dibenzazepine tricyclics are potent neurotropic drugs with a documented but underutilized anti-cancer side effect. Reengineering these agents (TFP, CPZ, CIP) by replacing the basic amine with a neutral polar functional group (e.g., RTC-1, RTC-2) abrogated their CNS effects as demonstrated by in vitro pharmacological assays and in vivo behavioral models. Further optimization generated several phenothiazines and dibenzazepines with improved anti-cancer potency, exemplified by RTC-5. This new lead demonstrated efficacy against a xenograft model of an EGFR driven cancer without the neurotropic effects exhibited by the parent molecules. Its effects were attributed to concomitant negative regulation of PI3K-AKT and RAS-ERK signaling.

Novel reversible selective inhibitor of nuclear export shows that CRM1 is a target in colorectal cancer cells

Colorectal cancer arises via a multistep carcinogenic process and the deregulation of multiple pathways. Thus, the simultaneous targeting of multiple pathways may be a promising therapeutic approach for colorectal treatment. CRM1 is an attractive cancer drug target, because it can regulate multiple pathways and tumor suppressor proteins. In this study, we investigated the anti-tumor activity of a novel reversible CRM1 inhibitor S109 in colorectal cancer. Our data demonstrate that S109 inhibits proliferation and induces cell cycle arrest in colorectal cancer cells. Mechanistically, we demonstrate that the activity of S109 is associated with the nuclear retention of major tumor suppress proteins. Furthermore, the Cys528 mutation of CRM1 prevented the ability of S109 to block nuclear export and inhibit the proliferation of colorectal cancer cells. Interestingly, S109 decreased the CRM1 protein level via proteasomal pathway. We argue that reversible CRM1 inhibitors but not irreversible inhibitors can induce the degradation of CRM1, because the dissociation of reversible inhibitors of CRM1 changes the conformation of CRM1. Taken together, these findings demonstrate that CRM1 is a valid target for the treatment of colorectal cancer and provide a basis for the development of S109 therapies for colorectal cancer.

AKT phosphorylates H3-threonine 45 to facilitate termination of gene transcription in response to DNA damage

Post-translational modifications of core histones affect various cellular processes, primarily through transcription. However, their relationship with the termination of transcription has remained largely unknown. In this study, we show that DNA damage-activated AKT phosphorylates threonine 45 of core histone H3 (H3-T45). By genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) analysis, H3-T45 phosphorylation was distributed throughout DNA damage-responsive gene loci, particularly immediately after the transcription termination site. H3-T45 phosphorylation pattern showed close-resemblance to that of RNA polymerase II C-terminal domain (CTD) serine 2 phosphorylation, which establishes the transcription termination signal. AKT1 was more effective than AKT2 in phosphorylating H3-T45. Blocking H3-T45 phosphorylation by inhibiting AKT or through amino acid substitution limited RNA decay downstream of mRNA cleavage sites and decreased RNA polymerase II release from chromatin. Our findings suggest that AKT-mediated phosphorylation of H3-T45 regulates the processing of the 3' end of DNA damage-activated genes to facilitate transcriptional termination.

Anticancer/antiviral agent Akt inhibitor-IV massively accumulates in mitochondria and potently disrupts cellular bioenergetics

Inhibitors of the PI3-kinase/Akt (protein kinase B) pathway are under investigation as anticancer and antiviral agents. Akt inhibitor-IV (ChemBridge 5233705, CAS 681281-88-9, AKTIV), a small molecule reported to inhibit this pathway, exhibits potent anticancer and broad-spectrum antiviral activity. However, depending on concentration, this cationic benzimidazole derivative exhibits paradoxical positive or negative effects on the phosphorylation of Akt that are not well understood. To elucidate its mechanism of action, we investigated its spectroscopic properties. This compound proved to be sufficiently fluorescent (excitation λ_max = 388 nm, emission λ_max = 460 nm) to enable examination of its uptake and distribution in living mammalian cells. Despite a low quantum yield of 0.0016, imaging of HeLa cells treated with AKTIV (1 μM, 5 min) by confocal laser scanning microscopy, with excitation at 405 nm, revealed extensive accumulation in mitochondria. Treatment of Jurkat lymphocytes with 1 μM AKTIV for 15 min caused accumulation to over 250 μM in these organelles, whereas treatment with 5 μM AKTIV yielded concentrations of over 1 mM in mitochondria, as analyzed by flow cytometry. This massive loading resulted in swelling of these organelles, followed by their apparent disintegration. These effects were associated with profound disruption of cellular bioenergetics including mitochondrial depolarization, diminished mitochondrial respiration, and release of reactive oxygen species. Because mitochondria play key roles in both cancer proliferation and viral replication, we conclude that the anticancer and antiviral activities of AKTIV predominantly result from its direct and immediate effects on the structure and function of mitochondria.

LKB1 Loss induces characteristic patterns of gene expression in human tumors associated with NRF2 activation and attenuation of PI3K-AKT

Introduction:

Inactivation of serine/threonine kinase 11 (STK11 or LKB1) is common in lung cancer, and understanding the pathways and phenotypes altered as a consequence will aid the development of targeted therapeutic strategies. Gene and protein expressions in a murine model of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (Kras)-mutant lung cancer have been studied to gain insight into the biology of these tumors. However, the molecular consequences of LKB1 loss in human lung cancer have not been fully characterized.

Methods:

We studied gene expression profiles associated with LKB1 loss in resected lung adenocarcinomas, non–small-cell lung cancer cell lines, and murine tumors. The biological significance of dysregulated genes was interpreted using gene set enrichment and transcription factor analyses and also by integration with somatic mutations and proteomic data.

Results:

Loss of LKB1 is associated with consistent gene expression changes in resected human lung cancers and cell lines that differ substantially from the mouse model. Our analysis implicates novel biological features associated with LKB1 loss, including altered mitochondrial metabolism, activation of the nuclear respiratory factor 2 (NRF2) transcription factor by kelch-like ECH-associated protein 1 (KEAP1) mutations, and attenuation of the phosphatidylinositiol 3-kinase and v-akt murine thymoma viral oncogene homolog (PI3K/AKT) pathway. Furthermore, we derived a 16-gene classifier that accurately predicts LKB1 mutations and loss by nonmutational mechanisms. In vitro, transduction of LKB1 into LKB1-mutant cell lines results in attenuation of this signature.

Conclusion:

Loss of LKB1 defines a subset of lung adenocarcinomas associated with characteristic molecular phenotypes and distinctive gene expression features. Studying these effects may improve our understanding of the biology of these tumors and lead to the identification of targeted treatment strategies.

Long‑term exposure to leptin enhances the growth of prostate cancer cells

Obesity correlates with an increased risk of developing prostate cancer (PCa) and leptin plays an important role in PCa progression. Since leptin is produced by adipocytes, the serum leptin level is higher in obese than in non-obese individuals. However, the effects of leptin remain controversial and unclear. The aim of the present study was to investigate the effect of leptin on PCa cell aggressiveness. Three human PCa cell lines (LNCaP, DU145 and PC-3) were treated with recombinant leptin for 28 days. Cell proliferation, migration, and invasion were estimated using the WST assay, a wound-healing assay, and a BD Matrigel invasion assay, respectively. The mechanism underlying the proliferative effect of leptin was investigated by cell transfections with small interfering RNA (siRNA) against the leptin receptor (ObR) or forkhead box O1 (FOXO1), and by immunocytochemistry. Long-term exposure of PCa cells to leptin enhanced their proliferation, migration and invasion. Leptin increased ObR expression and enhanced Akt phosphorylation constitutively. Leptin also increased the phosphorylation of FOXO1 via PI3K signaling and FOXO1 gene silencing enhanced PCa cell proliferation. Leptin induced the translocation of FOXO1 from the nucleus to the cytoplasm. Furthermore, the PI3K inhibitor, LY294002 suppressed this translocation. These results suggested that leptin regulated the subcellular localization of FOXO1 and induced Akt phosphorylation. Additionally, we revealed that leptin increased the expression of cyclin D1 and decreased the expression of p21 protein. In conclusion, long-term exposure to leptin increased the cell proliferation, migration, and invasion of PCa cells through inactivation of FOXO1. This inactivation resulted from exclusion of FOXO1 from the nucleus and its restriction to the cytoplasm through PI3K/Akt signaling. Our findings contribute to an understanding of the association between obesity and PCa aggressiveness.

Bioactive benzofuran derivatives: An insight on lead developments, radioligands and advances of the last decade

Benzofuran core is a highly versatile, presents in many important natural products and natural drugs. Many benzofuran containing synthetic drugs and clinical candidates have been derived from natural products. The present review will provide an insight on lead design-developments of the decade, clinical candidates and PET tracer radio-ligands containing benzofuran core along with brief target biology. Brief of the all approved drugs containing benzofuran core also have been enclosed. Main therapeutic areas covered are Cancer, Neurological disorders including anti-psychotic agent and diabetes.

MicroRNA-486 regulates normal erythropoiesis and enhances growth and modulates drug response in CML progenitors

MicroRNAs (miRNAs) are key regulators of hematopoietic cell differentiation and may contribute to altered growth of leukemic stem cells. Using microarray-based miRNA profiling, we found that miRNA 486 (miR-486) is significantly upregulated in chronic myeloid leukemia (CML) compared with normal CD34(+) cells, particularly in the megakaryocyte-erythroid progenitor population. miR-486-5p expression increased during erythroid differentiation of both CML and normal CD34(+) cells. Ectopic miR-486-5p expression enhanced in vitro erythroid differentiation of normal CD34(+) cells, whereas miR-486-5p inhibition suppressed normal CD34(+) cell growth in vitro and in vivo and inhibited erythroid differentiation and erythroid cell survival. The effects of miR-486-5p on hematopoietic cell growth and survival are mediated at least in part via regulation of AKT signaling and FOXO1 expression. Using gene expression and bioinformatics analysis, together with functional screening, we identified several novel miR-486-5p target genes that may modulate erythroid differentiation. We further show that increased miR-486-5p expression in CML progenitors is related to both kinase-dependent and kinase-independent mechanisms. Inhibition of miR-486-5p reduced CML progenitor growth and enhanced apoptosis following imatinib treatment. In conclusion, our studies reveal a novel role for miR-486-5p in regulating normal hematopoiesis and of BCR-ABL-induced miR-486-5p overexpression in modulating CML progenitor growth, survival, and drug sensitivity.

Targeting nucleocytoplasmic transport in cancer therapy

The intracellular location and regulation of proteins within each cell is critically important and is typically deregulated in disease especially cancer. The clinical hypothesis for inhibiting the nucleo-cytoplasmic transport is based on the dependence of certain key proteins within malignant cells. This includes a host of well-characterized tumor suppressor and oncoproteins that require specific localization for their function. This aberrant localization of tumour suppressors and oncoproteins results in their their respective inactivation or over-activation. This incorrect localization occurs actively via the nuclear pore complex that spans the nuclear envelope and is mediated by transport receptors. Accordingly, given the significant need for novel, specific disease treatments, the nuclear envelope and the nuclear transport machinery have emerged as a rational therapeutic target in oncology to restore physiological nucleus/cytoplasmic homeostasis. Recent evidence suggests that this approach might be of substantial therapeutic use. This review summarizes the mechanisms of nucleo-cytoplasmic transport, its role in cancer biology and the therapeutic potential of targeting this critical cellular process.

Compound library screening identified Akt/PKB kinase pathway inhibitors as potential key molecules for the development of new chemotherapeutics against schistosomiasis

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A wide range of PK inhibitors affects schistosome viability and reproduction.

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Structure and activity of the Akt/PKB protein are highly conserved in Schistosoma mansoni.

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Commercial Akt inhibitors are active on the recombinant SmAkt protein.

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Akt pathway inhibitors have schistosomicidal activity in vitro.

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SmAkt can be considered as a potential target for the control of schistosomiasis.

Protein kinases (PKs) are one of the largest protein families in most eukaryotic organisms. These enzymes are involved in the control of cell proliferation, differentiation and metabolism and a large number of the anticancer drugs currently used are directed against PKs. The structure and function of PKs are well conserved throughout evolution. In schistosome parasites, PKs were shown to be involved in essential functions at every stage of the parasite life cycle, making these enzymes promising anti-parasite drug targets. In this study, we tested a panel of commercial inhibitors for various PKs and analyzed their effects on pairing and egg production by schistosomes as well as their toxicity towards schistosomula larvae. Results obtained confirmed the deleterious effect of PK targeting on Schistosoma mansoni physiology and the important function of different tyrosine and serine/threonine kinases in the biology and reproduction of this parasite. They also indicated for the first time that the Protein kinase B (also called Akt) which is a major downstream target of many receptor tyrosine kinases and a central player at the crossroads of signal transduction pathways activated in response to growth factors and insulin, can constitute a novel target for anti-schistosome chemotherapy. Structural and functional studies have shown that SmAkt is a conserved kinase and that its activity can be inhibited by commercially available Akt inhibitors. In treated adult worms, Akt/PKB kinase pathway inhibitors induced profound alterations in pairing and egg laying and they also greatly affected the viability of schistosomula larvae.

Nerve growth factor (NGF) regulates activity of nuclear factor of activated T-cells (NFAT) in neurons via the phosphatidylinositol 3-kinase (PI3K)-Akt-glycogen synthase kinase 3β (GSK3β) pathway

The Ca(2+)/calcineurin-dependent transcription factor nuclear factor of activated T-cells (NFAT) plays an important role in regulating many neuronal functions, including excitability, axonal growth, synaptogenesis, and neuronal survival. NFAT can be activated by action potential firing or depolarization that leads to Ca(2+)/calcineurin-dependent dephosphorylation of NFAT and its translocation to the nucleus. Recent data suggest that NFAT and NFAT-dependent functions in neurons can also be potently regulated by NGF and other neurotrophins. However, the mechanisms of NFAT regulation by neurotrophins are not well understood. Here, we show that in dorsal root ganglion sensory neurons, NGF markedly facilitates NFAT-mediated gene expression induced by mild depolarization. The effects of NGF were not associated with changes in [Ca(2+)]i and were independent of phospholipase C activity. Instead, the facilitatory effect of NGF depended on activation of the PI3K/Akt pathway downstream of the TrkA receptor and on inhibition of glycogen synthase kinase 3β (GSK3β), a protein kinase known to phosphorylate NFAT and promote its nuclear export. Knockdown or knockout of NFATc3 eliminated this facilitatory effect. Simultaneous monitoring of EGFP-NFATc3 nuclear translocation and [Ca(2+)]i changes in dorsal root ganglion neurons indicated that NGF slowed the rate of NFATc3 nuclear export but did not affect its nuclear import rate. Collectively, our data suggest that NGF facilitates depolarization-induced NFAT activation by stimulating PI3K/Akt signaling, inactivating GSK3β, and thereby slowing NFATc3 export from the nucleus. We propose that NFAT serves as an integrator of neurotrophin action and depolarization-driven calcium signaling to regulate neuronal gene expression.

High-throughput nonlinear optical microscopy

High-resolution microscopy methods based on different nonlinear optical (NLO) contrast mechanisms are finding numerous applications in biology and medicine. While the basic implementations of these microscopy methods are relatively mature, an important direction of continuing technological innovation lies in improving the throughput of these systems. Throughput improvement is expected to be important for studying fast kinetic processes, for enabling clinical diagnosis and treatment, and for extending the field of image informatics. This review will provide an overview of the fundamental limitations on NLO microscopy throughput. We will further cover several important classes of high-throughput NLO microscope designs with discussions on their strengths and weaknesses and their key biomedical applications. Finally, this review will close with a perspective of potential future technological improvements in this field.

New small-molecule inhibitors effectively blocking picornavirus replication

Few drugs targeting picornaviruses are available, making the discovery of antivirals a high priority. Here, we identified and characterized three compounds from a library of kinase inhibitors that block replication of poliovirus, coxsackievirus B3, and encephalomyocarditis virus. Using an in vitro translation-replication system, we showed that these drugs inhibit different stages of the poliovirus life cycle. A4(1) inhibited both the formation and functioning of the replication complexes, while E5(1) and E7(2) were most effective during the formation but not the functioning step. Neither of the compounds significantly inhibited VPg uridylylation. Poliovirus resistant to E7(2) had a G5318A mutation in the 3A protein. This mutation was previously found to confer resistance to enviroxime-like compounds, which target a phosphatidylinositol 4-kinase IIIβ (PI4KIIIβ)-dependent step in viral replication. Analysis of host protein recruitment showed that E7(2) reduced the amount of GBF1 on the replication complexes; however, the level of PI4KIIIβ remained intact. E7(2) as well as another enviroxime-like compound, GW5074, interfered with viral polyprotein processing affecting both 3C- and 2A-dependent cleavages, and the resistant G5318A mutation partially rescued this defect. Moreover, E7(2) induced abnormal recruitment to membranes of the viral proteins; thus, enviroxime-like compounds likely severely compromise the interaction of the viral polyprotein with membranes. A4(1) demonstrated partial protection from paralysis in a murine model of poliomyelitis. Multiple attempts to isolate resistant mutants in the presence of A4(1) or E5(1) were unsuccessful, showing that effective broad-spectrum antivirals could be developed on the basis of these compounds.

IMPORTANCE

Diverse picornaviruses can trigger multiple human maladies, yet currently, only hepatitis A virus and poliovirus can be controlled with vaccination. The development of antipicornavirus therapeutics is also facing significant difficulties because these viruses readily generate resistance to compounds targeting either viral or cellular factors. Here, we describe three novel compounds that effectively block replication of distantly related picornaviruses with minimal toxicity to cells. The compounds prevent viral RNA replication after the synthesis of the uridylylated VPg primer. Importantly, two of the inhibitors are strongly refractory to the emergence of resistant mutants, making them promising candidates for further broad-spectrum therapeutic development. Evaluation of one of the compounds in an in vivo model of poliomyelitis demonstrated partial protection from the onset of paralysis.

Structure-based virtual screening approach for discovery of covalently bound ligands

We present a fast and effective covalent docking approach suitable for large-scale virtual screening (VS). We applied this method to four targets (HCV NS3 protease, Cathepsin K, EGFR, and XPO1) with known crystal structures and known covalent inhibitors. We implemented a customized "VS mode" of the Schrödinger Covalent Docking algorithm (CovDock), which we refer to as CovDock-VS. Known actives and target-specific sets of decoys were docked to selected X-ray structures, and poses were filtered based on noncovalent protein-ligand interactions known to be important for activity. We were able to retrieve 71%, 72%, and 77% of the known actives for Cathepsin K, HCV NS3 protease, and EGFR within 5% of the decoy library, respectively. With the more challenging XPO1 target, where no specific interactions with the protein could be used for postprocessing of the docking results, we were able to retrieve 95% of the actives within 30% of the decoy library and achieved an early enrichment factor (EF1%) of 33. The poses of the known actives bound to existing crystal structures of 4 targets were predicted with an average RMSD of 1.9 Å. To the best of our knowledge, CovDock-VS is the first fully automated tool for efficient virtual screening of covalent inhibitors. Importantly, CovDock-VS can handle multiple chemical reactions within the same library, only requiring a generic SMARTS-based predefinition of the reaction. CovDock-VS provides a fast and accurate way of differentiating actives from decoys without significantly deteriorating the accuracy of the predicted poses for covalent protein-ligand complexes. Therefore, we propose CovDock-VS as an efficient structure-based virtual screening method for discovery of novel and diverse covalent ligands.

Benzofuran derivatives as anticancer inhibitors of mTOR signaling

A series of 32 derivatives and isosteres of the mTOR inhibitor 2 were synthesized and compared for their cytotoxicity in radioresistant SQ20B cancer cell line. Several of these compounds, in particular 30b, were significantly more cytotoxic than 2. Importantly, 30b was shown to block both mTORC1 and Akt signaling, suggesting insensitivity to the resistance associated to Akt overactivation observed with rapamycin derivatives currently used in clinic.

Promising SINEs for embargoing nuclear-cytoplasmic export as an anticancer strategy

In cancer cells, the nuclear-cytoplasmic transport machinery is frequently disrupted, resulting in mislocalization and loss of function for many key regulatory proteins. In this review, the mechanisms by which tumor cells co-opt the nuclear transport machinery to facilitate carcinogenesis, cell survival, drug resistance, and tumor progression will be elucidated, with a particular focus on the role of the nuclear-cytoplasmic export protein. The recent development of a new generation of selective inhibitors of nuclear export (XPO1 antagonists) and how these novel anticancer drugs may bring us closer to the implementation of this therapeutic strategy in the clinic will be discussed.

TGFBI (βIG-H3) is a diabetes-risk gene based on mouse and human genetic studies

Transforming growth factor beta-induced (TGFBI/βIG-H3), also known as βig-H3, is a protein inducible by TGFβ1 and secreted by many cell types. It binds to collagen, forms part of the extracellular matrix and interacts with integrins on the cell surface. Recombinant TGFBI and transgenic TGFBI overexpression can promote both islet survival and function. In this study, we generated TGFBI KO mice and further assessed TGFBI function and signaling pathways in islets. Islets from KO mice were of normal size and quantity, and these animals were normoglycemic. However, KO islet survival and function was compromised in vitro. In vivo, KO donor islets became inferior to wild-type donor islets in achieving normoglycemia when transplanted into KO diabetic recipients. TGFBI KO mice were more prone to straptozotocin-induced diabetes than the wild-type counterpart. Phosphoprotein array analysis established that AKT1S1, a molecule linking the AKT and mTORC1 signaling pathways, was modulated by TGFBI in islets. Phosphorylation of four molecules in the AKT and mTORC1 signaling pathway, i.e. AKT, AKT1S1, RPS6 and EIF4EBP1, was upregulated in islets upon TGFBI stimulation. Suppression of AKT activity by a chemical inhibitor, or knockdown of AKT1S1, RPS6 and EIF4EBP1 expression by small interfering RNA, modulated islet survival, proving the relevance of these molecules in TGFBI-triggered signaling. Human genetic studies revealed that in the TGFBI gene and its vicinity, three single-nucleotide polymorphisms were significantly associated with type 1 diabetes risks, and one with type 2 diabetes risks. Our study suggests that TGFBI is a potential risk gene for human diabetes.

Antitumor effects of a novel chromosome region maintenance 1 (CRM1) inhibitor on non-small cell lung cancer cells in vitro and in mouse tumor xenografts

BACKGROUND

Chromosome Region Maintenance 1 (CRM1) is a nuclear exporter and its inhibitor has anti-tumor activity in various cancers. This study assessed the therapeutic efficiency of the novel CRM1 inhibitor KPT-185 on non-small cell lung cancer (NSCLC).

METHODS

NSCLC cell lines were treated with KPT-185 to assess changes in cell viability, cell cycle, apoptosis, and protein expression. NOD-SCID mice carrying NSCLC cell xenografts were orally treated with KPT-276, a clinical analog of KPT-185, to examine the efficacy and side effects of KPT-276 in vivo.

RESULTS

KPT-185 significantly reduced the viability of six NSCLC cell lines in a time- and dose-dependent manner, including epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-resistant H1975 and H1650GR cell lines. In addition, KPT-185 induced these NSCLC cells to arrest at G1 phase of the cell cycle and caused apoptosis in a dose-dependent manner. KPT-185 treatment also reduced CRM1 protein levels in six NSCLC cell lines, and the reduction could be completely abolished by the proteasome inhibitor bortezomib. KPT-185 activated caspase 3, 8, and 9, but inhibited survivin expression in NSCLC cells. In a mouse H1975 cell xenograft model, tumor growth was significantly inhibited by oral KPT-276 administration, and there was no significant mouse body weight loss or other side effects.

CONCLUSIONS

The current study demonstrated the anti-tumor effects of KPT-185 in NSCLC cells, including EGFR-TKI-resistant NSCLC cell lines. Further studies will assess anti-tumor activity of KPT-185 in a clinical trial for NSCLC patients.

Nestin regulates proliferation, migration, invasion and stemness of lung adenocarcinoma

Lung cancer is the most common cancer and the most common cause of cancer-related death in the world. Nestin, a class VI intermediate filament, is known to be a cancer stem cell (CSC) marker as well as a neuroepithelial stem cell marker. High expression levels of nestin are reported in several types of cancers including lung, pancreatic and prostate cancers. Nestin is thought to regulate tumor cell proliferation, migration, invasion and CSC properties. Here, we confirmed nestin expression in non-small cell lung cancer (NSCLC): Immunohistochemical analysis in surgical specimens detected nestin protein expression in the cytoplasm of 20 of 48 adenocarcinoma (AD) cases (41.7%) and 25 of 47 squamous cell carcinoma cases (53.2%). Nestin immunoreactivity significantly correlated with not only tumor size and lymph node metastasis in NSCLC, but also poor survival in surgical patients with AD. High and moderate expression levels of nestin were confirmed in several lung AD cell lines including H1975 and PC-3. Nestin inhibition by shRNA decreased proliferation, migration, invasion and sphere formation in AD cells. Correspondingly, nestin upregulation by nestin gene transfection resulted in the opposite changes. Moreover, Akt inhibitor IV effectively decreased nestin expression via SRY-box containing protein 2 (Sox2) downregulation and overcame the enhanced sphere formation induced by nestin upregulation. Overall, our results show that nestin correlates with the aggressiveness and stemness of AD. Regulation of nestin via Akt/Sox2 is, thus, a promising candidate for novel therapeutic approaches to eradicate CSCs in lung AD.

Dual inactivation of Akt and ERK by TIC10 signals Foxo3a nuclear translocation, TRAIL gene induction, and potent antitumor effects

Recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an antitumor protein that is in clinical trials as a potential anticancer therapy but suffers from drug properties that may limit efficacy such as short serum half-life, stability, cost, and biodistribution, particularly with respect to the brain. To overcome such limitations, we identified TRAIL-inducing compound 10 (TIC10), a potent, orally active, and stable small molecule that transcriptionally induces TRAIL in a p53-independent manner and crosses the blood-brain barrier. TIC10 induces a sustained up-regulation of TRAIL in tumors and normal cells that may contribute to the demonstrable antitumor activity of TIC10. TIC10 inactivates kinases Akt and extracellular signal-regulated kinase (ERK), leading to the translocation of Foxo3a into the nucleus, where it binds to the TRAIL promoter to up-regulate gene transcription. TIC10 is an efficacious antitumor therapeutic agent that acts on tumor cells and their microenvironment to enhance the concentrations of the endogenous tumor suppressor TRAIL.

Prognostic significance of nuclear RNA export factor 3 in hepatocellular carcinoma

Studies have highlighted important features of the nucleocytoplasmic transport of mRNAs and proteins. Nuclear RNA export factor 3 (NXF3) is a member of the nuclear RNA export factor family that plays a role in mediating the export of cellular mRNA from the nucleus to the cytoplasm for translation. However, little is known about the clinical significance of NXF3 in human tumors. To evaluate the prognostic significance of NXF3 in hepatocellular carcinoma (HCC), the expression levels of NXF3 in a cohort of 112 patients with primary HCC who had undergone hepatectomy for histologically confirmed HCC were assessed by immunohistochemistry. It was identified that the expression levels of NXF3 were higher in the primary HCC tissues compared with those in paired peritumoral liver tissues. The overexpression of NXF3 in the HCC tissues was correlated with decreased survival time [hazard ratio (HR) = 1.954, 95% confidence interval (CI) = 1.034–3.695, P=0.039] and earlier tumor recurrence (HR = 2.101, 95% CI = 1.186–3.722, P=0.011) in postoperative patients with HCC. Notably, overexpression of NXF3 was correlated with a poor survival time and increased recurrence following HCC resection in male patients (P=0.020 and P=0.007, respectively) but not in female patients (P=0.916 and P=0.821, respectively). In conclusion, the findings provide evidence that implicates NXF3 as a prospective predictor of HCC prognosis as well as a potential therapeutic target for cancer treatment.

Phenothiazines induce PP2A-mediated apoptosis in T cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive cancer that is frequently associated with activating mutations in NOTCH1 and dysregulation of MYC. Here, we performed 2 complementary screens to identify FDA-approved drugs and drug-like small molecules with activity against T-ALL. We developed a zebrafish system to screen small molecules for toxic activity toward MYC-overexpressing thymocytes and used a human T-ALL cell line to screen for small molecules that synergize with Notch inhibitors. We identified the antipsychotic drug perphenazine in both screens due to its ability to induce apoptosis in fish, mouse, and human T-ALL cells. Using ligand-affinity chromatography coupled with mass spectrometry, we identified protein phosphatase 2A (PP2A) as a perphenazine target. T-ALL cell lines treated with perphenazine exhibited rapid dephosphorylation of multiple PP2A substrates and subsequent apoptosis. Moreover, shRNA knockdown of specific PP2A subunits attenuated perphenazine activity, indicating that PP2A mediates the drug's antileukemic activity. Finally, human T-ALLs treated with perphenazine exhibited suppressed cell growth and dephosphorylation of PP2A targets in vitro and in vivo. Our findings provide a mechanistic explanation for the recurring identification of phenothiazines as a class of drugs with anticancer effects. Furthermore, these data suggest that pharmacologic PP2A activation in T-ALL and other cancers driven by hyperphosphorylated PP2A substrates has therapeutic potential.

Benzofuran derivatives as a novel class of inhibitors of mTOR signaling

High-throughput screening (HTS) hit 1 was previously identified as an inhibitor of the Akt/mTOR (Akt/mammalian target of rapamycin) signaling, which is a major target in oncology. The cytotoxicity of 1 was determined on a panel of human cancer cells lines with an IC₅₀ comprised between 30 and 140 μM. Subsequent structure--activity relationship (SAR) studies led us to the identification of compounds that displayed an enhanced cytotoxicity. We demonstrated also that these molecules directly bind to mTOR complex 1 (mTORC1) and inhibit its kinase activity.

CRM1 is a cellular target of curcumin: new insights for the myriad of biological effects of an ancient spice

Curcumin is the major constituent of turmeric plant, an ancient spice widely used in Indian cuisine and traditional herbal medicine. Recently, the potential medical use of curcumin as anti-cancer and anti-inflammatory agent has set off an upsurge in research into the mechanism for its broad biological effects. We showed that CRM1, an important nuclear exportin, is a cellular target of curcumin by serious experimental and theoretical investigation. Using a nuclear export functional assay, we observed a clear and rapid shift of cargo proteins from a cytoplasmic localization to the nucleus when treated with curcumin or its structural analogue dibenzylideneacetone (DBA). We demonstrated that curcumin could specifically target the conserved Cys(528) of CRM1 through mass spectrometric analysis and in vivo experiments. Furthermore, computational modeling has revealed that curcumin could be correctly docked into the hydrophobic pocket of CRM1 judged from shape complementarity and putative molecular interactions. The Michael acceptor moiety on curcumin is within the appropriate distance to enable Michael reaction with Cys residue of CRM1. More importantly, we showed that nuclear retention of FOXO1 could be observed in the presence of Leptomycin B (LMB) or curcumin whereas in cells expressing the CRM1-Cys(528) mutant, only a cytoplasmic localization was observed. The inhibition of nuclear traffic by curcumin may account for its myriad of biological effects, particularly for its therapeutic properties in cancer and inflammatory diseases. Our findings may have important implications for further clinical investigation of curcumin.

CRM1 Inhibition Sensitizes Drug Resistant Human Myeloma Cells to Topoisomerase II and Proteasome Inhibitors both In Vitro and Ex Vivo

Multiple myeloma (MM) remains an incurable disease despite improved treatments, including lenalidomide/pomalidomide and bortezomib/carfilzomib based therapies and high-dose chemotherapy with autologous stem cell rescue. New drug targets are needed to further improve treatment outcomes. Nuclear export of macromolecules is misregulated in many cancers, including in hematological malignancies such as MM. CRM1 (chromosome maintenance protein-1) is a ubiquitous protein that exports large proteins (>40 kDa) from the nucleus to the cytoplasm. We found that small-molecule Selective Inhibitors of Nuclear Export (SINE) prevent CRM1-mediated export of p53 and topoisomerase IIα (topo IIα). SINE's CRM1-inhibiting activity was verified by nuclear-cytoplasmic fractionation and immunocytochemical staining of the CRM1 cargoes p53 and topo IIα in MM cells. We found that SINE molecules reduced cell viability and induced apoptosis when used as both single agents in the sub-micromolar range and when combined with doxorubicin, bortezomib, or carfilzomib but not lenalidomide, melphalan, or dexamethasone. In addition, CRM1 inhibition sensitized MM cell lines and patient myeloma cells to doxorubicin, bortezomib, and carfilzomib but did not affect peripheral blood mononuclear or non-myeloma bone marrow mononuclear cells as shown by cell viability and apoptosis assay. Drug resistance induced by co-culture of myeloma cells with bone marrow stroma cells was circumvented by the addition of SINE molecules. These results support the continued development of SINE for patients with MM.

Phenothiazine Inhibitors of TLKs Affect Double-Strand Break Repair and DNA Damage Response Recovery and Potentiate Tumor Killing with Radiomimetic Therapy

The Tousled-like kinases (TLKs) are involved in chromatin assembly, DNA repair, and transcription. Two TLK genes exist in humans, and their expression is often dysregulated in cancer. TLKs phosphorylate Asf1 and Rad9, regulating double-strand break (DSB) repair and the DNA damage response (DDR). TLKs maintain genomic stability and are important therapeutic intervention targets. We identified specific inhibitors of TLKs from several compound libraries, some of which belong to the family of phenothiazine antipsychotics. The inhibitors prevented the TLK-mediated phosphorylation of Rad9(S328) and impaired checkpoint recovery and DSB repair. The inhibitor thioridazine (THD) potentiated tumor killing with chemotherapy and also had activity alone. Staining for γ-H2AX revealed few positive cells in untreated tumors, but large numbers in mice treated with low doxorubicin or THD alone, possibly the result of the accumulation of DSBs that are not promptly repaired as they may occur in the harsh tumor growth environment.

PTEN/PI3K and MAPK signaling in protection and pathology following CNS injuries

Brain and spinal cord injuries initiate widespread temporal and spatial neurodegeneration, through both necrotic and programmed cell death mechanisms. Inflammation, reactive oxidation, excitotoxicity and cell-specific dysregulation of metabolic processes are instigated by traumatic insult and are main contributors to this cumulative damage. Successful treatments rely on prevention or reduction of the magnitude of disruption, and interfering with injurious cellular responses through modulation of signaling cascades is an effective approach. Two intracellular signaling pathways, the phosphatase and tensin homolog (PTEN)/phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling cascades play various cellular roles under normal and pathological conditions. Activation of both pathways can influence anatomical and functional outcomes in multiple CNS disorders. However, some mechanisms involve inhibiting or enhancing one pathway or the other, or both, in propagating specific downstream effects. Though many intracellular mechanisms contribute to cell responses to insult, this review examines the evidence exploring PTEN/PI3K and MAPK signaling influence on pathology, neuroprotection, and repair and how these pathways may be targeted for advancing knowledge and improving neurological outcome after injury to the brain and spinal cord.

Modulation of the Akt pathway reveals a novel link with PERK/eIF2α, which is relevant during hypoxia

The unfolded protein response (UPR) and the Akt signaling pathway share several regulatory functions and have the capacity to determine cell outcome under specific conditions. However, both pathways have largely been studied independently. Here, we asked whether the Akt pathway regulates the UPR. To this end, we used a series of chemical compounds that modulate PI3K/Akt pathway and monitored the activity of the three UPR branches: PERK, IRE1 and ATF6. The antiproliferative and antiviral drug Akt-IV strongly and persistently activated all three branches of the UPR. We present evidence that activation of PERK/eIF2α requires Akt and that PERK is a direct Akt target. Chemical activation of this novel Akt/PERK pathway by Akt-IV leads to cell death, which was largely dependent on the presence of PERK and IRE1. Finally, we show that hypoxia-induced activation of eIF2α requires Akt, providing a physiologically relevant condition for the interaction between Akt and the PERK branch of the UPR. These data suggest the UPR and the Akt pathway signal to one another as a means of controlling cell fate.

High cytoplasmic FOXO1 and pFOXO1 expression in astrocytomas are associated with worse surgical outcome

FOXO1 is at a convergence point of receptor tyrosine kinase (RTK) signaling, which is one of the three core pathways implicated in glioblastoma. It was recently shown that FOXO1 can effectively induce glioma cell death and inhibit tumor growth through cell cycle arrest and apoptosis. We therefore evaluated FOXO1 and pFOXO1 protein expression in 181 primary astrocytoma samples and 16 normal brain samples. Astrocytoma samples expressed higher cytoplasmic FOXO1 and pFOXO1 than normal brain samples. Nuclear pFOXO1 level was significantly higher than nuclear FOXO1 in astrocytomas. High cytoplasmic FOXO1 expression was associated with older onset age (P = 0.001) and higher WHO grade (P = 0.001). The trend was also observed between cytoplasmic pFOXO1 expression and WHO grade although not significant. Univariate survival analysis showed that both high cytoplasmic FOXO1 and pFOXO1 expression indicated a significantly shorter median overall survival and progression-free survival. Multivariate survival analysis revealed cytoplasmic FOXO1 expression, cytoplasmic pFOXO1 expression, WHO grade, gender, extent of resection and radiotherapy to be independent prognostic factors for overall survival and progression-free survival. Thus, our data suggested that cytoplasmic FOXO1 and pFOXO1 expression may serve as valuable prognostic variables in astrocytomas and may have significant implications for the development and application of targeted therapy.

Differential regulation of CC chemokine ligand 2 and CXCL8 by antifungal agent nystatin in macrophages

The polyene antifungal antibiotic nystatin can interact with cholesterol, thereby altering the composition of the plasma membrane in eukaryotic cells. We investigated whether nystatin influences responses to the infection by inducing expression of chemokines. THP-1 macrophages rarely expressed CC chemokine ligand 2 (CCL2) and CXCL8. However, nystatin dose-dependently increased CCL2 and CXCL8 expression at the mRNA and protein levels. To understand the molecular mechanisms of the antifungal agent, we identified cellular factors activated by nystatin and those involved in nystatin-induced upregulation of CCL2 and CXCL8. Treatment with nystatin resulted in enhanced phosphorylation of Akt, ERK1/2, p38 MAPK, and JNK. Treatment with cholesterol, LY294002, Akt inhibitor IV, U0126, and SP6001250 resulted in abrogation or significant attenuation of nystatin-induced CCL2 expression. Nystatin-mediated CXCL8 expression was attenuated in the presence of Akt inhibitor IV and SP6001250. These results indicate that exposure of human macrophages to nystatin can lead to differential regulation of CCL2 and CXCL8 via the activation of multiple cellular kinases. We propose that upregulation of CCL2 and CXCL8 contributes to pharmacological effects of nystatin.

Selective inhibitors of nuclear export for the treatment of non-Hodgkin's lymphomas

The nuclear export protein chromosome maintenance region 1, found to be elevated in non-Hodgkin's lymphomas, controls localization of critical tumor suppressor proteins. Nuclear localization of tumor suppressor proteins is necessary for their cell surveillance function. However, their nuclear exclusion by chromosome maintenance region 1 renders them ineffective making this nuclear transporter an attractive therapeutic target. We have identified selective inhibitors of nuclear export that lock tumor suppressor proteins in the cell nucleus leading to apoptosis of lymphoid but not normal cells. Our inhibitors induce tumor suppressor protein nuclear retention-dependent growth inhibition and apoptosis in a panel of non-Hodgkin's lymphoma cell lines. Western blot of nuclear protein fraction and confocal microscopy analysis demonstrated retention of major tumor suppressor proteins in the cell nucleus. Co-immunoprecipitation studies showed disruption of the tumor suppressor protein-chromosome maintenance region 1 interaction. Small inhibitor RNA knockdown of two major tumor suppressor proteins, p53 in wild-type protein-53 and protein 73 in mutant-protein-53, abrogated inhibitor activity. Oral administration of related inhibitor at 75 and 150 mg/kg resulted in 65 and 70% tumor reduction, respectively and subcutaneous injections of inhibitor (25 and 75 mg/kg) resulted in 70 and 74% suppression of non-Hodgkin's lymphoma tumor growth with no toxicity; residual tumors showed activation of the protein 73 pathway. Our study verifies chromosome maintenance region 1 as a therapeutic target in non-Hodgkin's lymphoma, indicating that this nuclear export protein warrants further clinical investigations.

Remarkably reduced expression of FoxO3a in metaplastic colorectum, primary colorectal cancer and liver metastasis

The forkhead family members of transcription factors (FoxOs) are expected to be potential cancer-related drug targets and thus are being extremely studied recently. In the present study, FoxO3a, one major member of this family, was identified to be down-regulated in colorectal cancer through micro-array analysis, which was confirmed by RT-PCR and Western blot in 28 patients. Moreover, immunohistochemistry (IHC) showed that the expression levels of FoxO3a were remarkably reduced in 99 cases of primary colorectal cancer, liver metastasis, and even in metaplastic colorectal tissue. IHC also revealed an exclusion of FoxO3a from the nucleus of most cells of tumor-associated tissues. Silencing FoxO3a by siRNA led to elevation of G2-M phase cells. We conclude that the downregulation of FoxO3a may greatly contribute to tumor development, and thus FoxO3a may represent a novel therapeutic target in colorectal cancer.