MAP4K4 Inhibition Promotes Survival of Human Stem Cell-Derived Cardiomyocytes and Reduces Infarct Size In Vivo

Heart disease is a paramount cause of global death and disability. Although cardiomyocyte death plays a causal role and its suppression would be logical, no clinical counter-measures target the responsible intracellular pathways. Therapeutic progress has been hampered by lack of preclinical human validation. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is activated in failing human hearts and relevant rodent models. Using human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) and MAP4K4 gene silencing, we demonstrate that death induced by oxidative stress requires MAP4K4. Consequently, we devised a small-molecule inhibitor, DMX-5804, that rescues cell survival, mitochondrial function, and calcium cycling in hiPSC-CMs. As proof of principle that drug discovery in hiPSC-CMs may predict efficacy in vivo, DMX-5804 reduces ischemia-reperfusion injury in mice by more than 50%. We implicate MAP4K4 as a well-posed target toward suppressing human cardiac cell death and highlight the utility of hiPSC-CMs in drug discovery to enhance cardiomyocyte survival.

Patient-Driven Discovery, Therapeutic Targeting, and Post-Clinical Validation of a Novel AKT1 Fusion-Driven Cancer

Despite the important role of the PI3K/AKT/mTOR axis in the pathogenesis of cancer, to date there have been few functional oncogenic fusions identified involving the AKT genes. A 12-year-old female with a histopathologically indeterminate epithelioid neoplasm was found to harbor a novel fusion between the LAMTOR1 and AKT1 genes. Through expanded use access, she became the first pediatric patient to be treated with the oral ATP-competitive pan-AKT inhibitor ipatasertib. Treatment resulted in dramatic tumor regression, demonstrating through patient-driven discovery that the fusion resulted in activation of AKT1, was an oncogenic driver, and could be therapeutically targeted with clinical benefit. Post-clinical validation using patient-derived model systems corroborated these findings, confirmed a membrane-bound and constitutively active fusion protein, and identified potential mechanisms of resistance to single-agent treatment with ipatasertib. SIGNIFICANCE: This study describes the patient-driven discovery of the first AKT1 fusion-driven cancer and its treatment with the AKT inhibitor ipatasertib. Patient-derived in vitro and in vivo model systems are used to confirm the LAMTOR1-AKT1 fusion as a tumorigenic driver and identify potential mechanisms of resistance to AKT inhibition.This article is highlighted in the In This Issue feature, p. 565.

Inhibiting the stringent response blocks Mycobacterium tuberculosis entry into quiescence and reduces persistence

The stringent response enables Mycobacterium tuberculosis (Mtb) to shut down its replication and metabolism under various stresses. Here we show that Mtb lacking the stringent response enzyme Rel_Mtb was unable to slow its replication rate during nutrient starvation. Metabolomics analysis revealed that the nutrient-starved rel_Mtb -deficient strain had increased metabolism similar to that of exponentially growing wild-type bacteria in nutrient-rich broth, consistent with an inability to enter quiescence. Deficiency of rel_Mtb increased the susceptibility of mutant bacteria to killing by isoniazid during nutrient starvation and in the lungs of chronically infected mice. We screened a pharmaceutical library of over 2 million compounds for inhibitors of Rel_Mtb and showed that the lead compound X9 was able to directly kill nutrient-starved M. tuberculosis and enhanced the killing activity of isoniazid. Inhibition of Rel_Mtb is a promising approach to target M. tuberculosis persisters, with the potential to shorten the duration of TB treatment.

ERK-mediated TIMELESS expression suppresses G2/M arrest in colon cancer cells

The cell cycle is under circadian regulation. Oncogenes can dysregulate circadian-regulated genes to disrupt the cell cycle, promoting tumor cell proliferation. As a regulator of G2/M arrest in response to DNA damage, the circadian gene Timeless Circadian Clock (TIMELESS) coordinates this connection and is a potential locus for oncogenic manipulation. TIMELESS expression was evaluated using RNASeq data from TCGA and by RT-qPCR and western blot analysis in a panel of colon cancer cell lines. TIMELESS expression following ERK inhibition was examined via western blot. Cell metabolic capacity, propidium iodide, and CFSE staining were used to evaluate the effect of TIMELESS depletion on colon cancer cell survival and proliferation. Cell metabolic capacity following TIMELESS depletion in combination with Wee1 or CHK1 inhibition was assessed. TIMELESS is overexpressed in cancer and required for increased cancer cell proliferation. ERK activation promotes TIMELESS expression. TIMELESS depletion increases γH2AX, a marker of DNA damage, and triggers G2/M arrest via increased CHK1 and CDK1 phosphorylation. TIMELESS depletion in combination with Wee1 or CHK1 inhibition causes an additive decrease in cancer cell metabolic capacity with limited effects in non-transformed human colon epithelial cells. The data show that ERK activation contributes to the overexpression of TIMELESS in cancer. Depletion of TIMELESS increases γH2AX and causes G2/M arrest, limiting cell proliferation. These results demonstrate a role for TIMELESS in cancer and encourage further examination of the link between circadian rhythm dysregulation and cancer cell proliferation.

Probing the Anticancer Action of Novel Ferrocene Analogues of MNK Inhibitors

Two novel ferrocene-containing compounds based upon a known MNK1/2 kinase (MAPK-interacting kinase) inhibitor have been synthesized. The compounds were designed to use the unique shape of ferrocene to exploit a large hydrophobic pocket in MNK1/2 that is only partially occupied by the original compound. Screening of the ferrocene analogues showed that both exhibited potent anticancer effects in several breast cancer and AML (acute myeloid leukemia) cell lines, despite a loss of MNK potency. The most potent ferrocene-based compound 5 was further analysed in vitro in MDA-MB-231 (triple negative breast cancer cells). Dose–response curves of compound 5 for 2D assay and 3D assay generated IC₅₀ values (half maximal inhibitory concentration) of 0.55 µM and 1.25 µM, respectively.

Response-Derived Input Function Estimation for Dynamic Contrast-Enhanced MRI Demonstrated by Anti-DLL4 Treatment in a Murine U87 Xenograft Model

PURPOSE

Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) is an accepted method to evaluate tumor perfusion and permeability and anti-vascular cancer therapies. However, there is no consensus on the vascular input function estimation method, which is critical to kinetic modeling and K ^trans estimation. This work proposes a response-derived input function (RDIF) estimated from the response of the tumor, modeled as a linear, time-invariant (LTI) system.

PROCEDURES

In an LTI system, an unknown input can be estimated from the system response. If applied to DCE MRI, this method would eliminate need of distal image-derived inputs, model inputs, or reference regions. The RDIF method first determines each tumor pixel's best-fit input function, and then combines the individual fits into a single input function for the entire tumor. The method was tested with simulations and a xenograft study with anti-vascular drug treatment.

RESULTS

Simulations showed successful estimation of input function expected values and good performance in the presence of noise. In vivo, significant reductions in K ^trans and AUC occurred 2 days following anti-delta-like ligand 4 treatment. The in vivo study results yielded K ^trans consistent with published data in xenograft models.

CONCLUSION

The RDIF method for DCE analysis offers an alternative, easy-to-implement method for estimating the input function in tumors. The method assumes that during the DCE experiment, the changes observed by MRI result solely from vascular perfusion and permeability kinetics, and that information can be used to model the input function. Importantly, the method is demonstrated in a murine xenograft study to yield K ^trans results consistent with literature values and suitable for compound studies.

Identification of lead anti-human cytomegalovirus compounds targeting MAP4K4 via machine learning analysis of kinase inhibitor screening data

Chemogenomic approaches involving highly annotated compound sets and cell based high throughput screening are emerging as a means to identify novel drug targets. We have previously screened a collection of highly characterized kinase inhibitors (Khan et al., Journal of General Virology, 2016) to identify compounds that increase or decrease expression of a human cytomegalovirus (HCMV) protein in infected cells. To identify potential novel anti-HCMV drug targets we used a machine learning approach to relate our phenotypic data from the aforementioned screen to kinase inhibition profiling of compounds used in this screen. Several of the potential targets had no previously reported role in HCMV replication. We focused on one potential anti-HCMV target, MAPK4K, and identified lead compounds inhibiting MAP4K4 that have anti-HCMV activity with little cellular cytotoxicity. We found that treatment of HCMV infected cells with inhibitors of MAP4K4, or an siRNA that inhibited MAP4K4 production, reduced HCMV replication and impaired detection of IE2-60, a viral protein necessary for efficient HCMV replication. Our findings demonstrate the potential of this machine learning approach to identify novel anti-viral drug targets, which can inform the discovery of novel anti-viral lead compounds.

Lipid-modified cell-penetrating peptide-based self-assembly micelles for co-delivery of narciclasine and siULK1 in hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) is the most frequent type of primary liver cancer, and one therapeutic approach is to target both the AMPK and autophagy pathways in order to synergistically promote programmed cell death. Here, a series of amphiphilic, lipid-modified cell-penetrating peptides were synthesized and allowed to self-assemble into micelles loaded with the AMPK activator narciclasine (Narc) and short interfering RNA targeting the unc-51-like kinase 1 (siULK1). The size of these micelles, their efficiency of transfection into cells, and their ability to release drug or siRNA cargo in vitro were pH-sensitive, such that drug release was facilitated in the acidic microenvironment of the tumor. Transfecting the micelles into HCC cells significantly inhibited protective autophagy within tumor cells, and delivering the micelles into mice carrying HCC xenografts induced apoptosis, slowed tumor growth, and inhibited autophagy. Our results indicate that co-delivering Narc and siULK1 in biocompatible micelles can safely inhibit tumor growth and protective autophagy, justifying further studies into this promising therapeutic approach against HCC.

STATEMENT OF SIGNIFICANCE

We have focused on the targeted therapy of HCC via synergistically inhibiting the autophagy and inducing apoptosis. The lipid-modified cell-penetrating peptide can not only aggregate into micelles to load natural product narciclasine and ULK1 siRNA simultaneously, but also facilitate uptake and endosome escape with a pH-sensitive manner in HepG2 cells. HepG2 cell treated with siULK1-M-Narc has increased apoptotic levels and declined autophagy via the targeted regulation of AMPK-ULK1 signaling axis. The in vivo studies have confirmed that siULK1-M-Narc efficiently reduce the growth of tumor on HCC xenograft models with good safety. Thus, we suppose the lipid-modified cell-penetrating peptide has good application prospects in the targeted combinational therapy of HCC.

Identification and Optimization of 4-Anilinoquinolines as Inhibitors of Cyclin G Associated Kinase

4-Anilinoquinolines were identified as potent and narrow-spectrum inhibitors of the cyclin G associated kinase (GAK), an important regulator of viral and bacterial entry into host cells. Optimization of the 4-anilino group and the 6,7-quinoline substituents produced GAK inhibitors with nanomolar activity, over 50 000-fold selectivity relative to other members of the numb-associated kinase (NAK) subfamily, and a compound (6,7-dimethoxy-N-(3,4,5-trimethoxyphenyl)quinolin-4-amine; 49) with a narrow-spectrum kinome profile. These compounds may be useful tools to explore the therapeutic potential of GAK in prevention of a broad range of infectious and systemic diseases.

Suppression of MAPK11 or HIPK3 reduces mutant Huntingtin levels in Huntington's disease models

Most neurodegenerative disorders are associated with accumulation of disease-relevant proteins. Among them, Huntington disease (HD) is of particular interest because of its monogenetic nature. HD is mainly caused by cytotoxicity of the defective protein encoded by the mutant Huntingtin gene (HTT). Thus, lowering mutant HTT protein (mHTT) levels would be a promising treatment strategy for HD. Here we report two kinases HIPK3 and MAPK11 as positive modulators of mHTT levels both in cells and in vivo. Both kinases regulate mHTT via their kinase activities, suggesting that inhibiting these kinases may have therapeutic values. Interestingly, their effects on HTT levels are mHTT-dependent, providing a feedback mechanism in which mHTT enhances its own level thus contributing to mHTT accumulation and disease progression. Importantly, knockout of MAPK11 significantly rescues disease-relevant behavioral phenotypes in a knockin HD mouse model. Collectively, our data reveal new therapeutic entry points for HD and target-discovery approaches for similar diseases.

MNK1/2 inhibition limits oncogenicity and metastasis of KIT-mutant melanoma

Melanoma can be stratified into unique subtypes based on distinct pathologies. The acral/mucosal melanoma subtype is characterized by aberrant and constitutive activation of the proto-oncogene receptor tyrosine kinase C-KIT, which drives tumorigenesis. Treatment of these melanoma patients with C-KIT inhibitors has proven challenging, prompting us to investigate the downstream effectors of the C-KIT receptor. We determined that C-KIT stimulates MAP kinase-interacting serine/threonine kinases 1 and 2 (MNK1/2), which phosphorylate eukaryotic translation initiation factor 4E (eIF4E) and render it oncogenic. Depletion of MNK1/2 in melanoma cells with oncogenic C-KIT inhibited cell migration and mRNA translation of the transcriptional repressor SNAI1 and the cell cycle gene CCNE1. This suggested that blocking MNK1/2 activity may inhibit tumor progression, at least in part, by blocking translation initiation of mRNAs encoding cell migration proteins. Moreover, we developed an MNK1/2 inhibitor (SEL201), and found that SEL201-treated KIT-mutant melanoma cells had lower oncogenicity and reduced metastatic ability. Clinically, tumors from melanoma patients harboring KIT mutations displayed a marked increase in MNK1 and phospho-eIF4E. Thus, our studies indicate that blocking MNK1/2 exerts potent antimelanoma effects and support blocking MNK1/2 as a potential strategy to treat patients positive for KIT mutations.

CSR1 suppresses tumor growth and metastasis of human hepatocellular carcinoma via inhibition of HPIP

OBJECTIVE

Cellular stress response 1 (CSR1) is a tumor suppressor gene that was frequently down-regulated in prostate cancer. CSR1 has critical roles in the regulation of cell apoptosis via inactivation of CPSF3 or preventing the interaction of XIAP with caspases. However, whether CSR1 plays a role in human hepatocellular carcinoma (HCC) is completely unknown.

PATIENTS AND METHODS

The expression of CSR1 in HCC clinic samples and cell lines was detected by Real-time PCR and Western blot. CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 system was used to knockout CSR1 gene in HepG2 cells. The proliferation of HCC cells was measured by MTT assay. The migration and invasion abilities of HepG2 cells were determined by in vitro scratch wounding and matrigel invasion assays. Co-immunoprecipitation assay was used to determine the interaction between CSR1 and hematopoietic PBX interacting protein (HPIP).

RESULTS

The mRNA and protein levels of CSR1 were down-regulated in human HCC cell lines and clinic HCC tissues. Over-expression of CSR1 inhibited cell proliferation, migration and invasion in human HCC cell lines. Knockout of CSR1 gene by CRISPR-Cas9 in HepG2 cells achieved the opposite effects. At the molecular level, we found that CSR1 associated with HPIP and inhibited the activation PI3K/AKT pathway.

CONCLUSIONS

For the first time we demonstrated that CSR1 inhibited HCC cell proliferation, migration and invasion through inactivation of HPIP and its downstream PI3K/AKT signaling pathway and suggested CSR1 as a potential therapy target for HCC treatment.

Down-regulation of C35 decreased the cell viability and migration of breast ductal carcinoma cells

Background

Resistance to human epidermal growth factor receptor-2 (HER2)-targeted therapies is common, and results in treatment failure and new tumor progression. C35 is over-expressed in many invasive breast cancer endogenously, and functions as an oncogene in breast cancer cell lines.

Methods

The current study aims to investigate effects of C35 on cell viability and migration of HER2-positive breast tumor cells and explore possible mechanisms. The protein expression of C35 in BT-474 breast ductal carcinoma cells was interfered by siRNAs. MTT assay was utilized to detect the viability of BT474 breast ductal carcinoma cells after transfection. The migration of BT474 breast ductal carcinoma cells was examined by cell wound scratch assay.

Results

In addition, the protein expression of C35, HER2, AKT and p-AKT in breast ductal carcinoma cells were detected by Western Blot. The protein expression of C35 was weaker in siRNA1 and siRNA2 groups compared with the control group. The relative expression ratio of C35 to β-actin decreased significantly in siRNA2 and siRNA1 groups. When C35 expression was interfered by siRNA1 and siRNA2 for 48 h, the viability of BT474 breast ductal carcinoma cells decreased compared with the control group. In addition, the migration of breast ductal carcinoma cells decreased when C35 expression was interfered by siRNA1 for 24 h, and interfered by siRNA1 and siRNA2 for 48 h.

The EGFR/miR-338-3p/EYA2 axis controls breast tumor growth and lung metastasis

Dysregulation of the epidermal growth factor receptor (EGFR) promotes cancer cell growth, invasion and metastasis. However, its relevant downstream effectors are still limited. Here, we show that EGFR promotes breast tumor growth and metastasis by downregulating the tumor suppressor micoRNA-338-3p (miR-338-3p) and activating the EYA2 (EYA transcriptional coactivator and phosphatase 2) oncoprotein. EGFR represses miR-338-3p expression largely through HIF1α transcription factor. miR-338-3p inhibits EYA2 expression by binding to the 3'-untranslated region of EYA2. EGFR increases EYA2 expression via HIF1α repression of miR-338-3p. Through the miR-338-3p/EYA2 pathway, EGFR increases breast cancer cell growth, epithelial-to-mesenchymal transition, migration, invasion and lung metastasis in vitro and in a allograft tumor mouse model in vivo. In breast cancer patients, miR-338-3p expression negatively correlates with the expression of EGFR and EYA2, EGFR status positively associates with EYA2 expression, and miR-338-3p and EYA2 predict breast cancer lung metastasis when expressed in primary breast cancers. These data suggest that the miR-338-3p/EYA2 axis contributes to EGFR-mediated tumor growth and lung metastasis and that miR-338-3p activation or EYA2 inhibition or combination therapy targeting EGFR/miR-338-3p/EYA2 axis may be a promising way to treat patients with metastatic cancer.

MiR-455-3p acts as a prognostic marker and inhibits the proliferation and invasion of esophageal squamous cell carcinoma by targeting FAM83F

OBJECTIVE

The aim of the current study was to elucidate the role of miR-455-3p in the pathogenesis of esophageal squamous cell carcinoma (ESCC) and its prognostic value in patients with ESCC.

PATIENTS AND METHODS

Expression levels of miR-455-3p and FAM83F mRNA in ESCC tissues and adjacent normal tissues were detected by quantitative RT-PCR. The X2-test was used to assess miR-455-3p expression on clinicopathological parameters. The association with overall survival of patients was analyzed by Kaplan-Meier survival analysis. Cox's multivariate regression model was performed to identify independent prognostic factors of overall survival. The effect of miR-455-3p on proliferation was evaluated by   kit-8 (CCK-8), and cell invasion was evaluated by transwell assays. The molecular target of miR-455-3p was identified using a computer algorithm and confirmed experimentally. Furthermore, the effect of miR-455-3p up-regulation on FAM83F expression was examined by Western blot.

RESULTS

miRNA-455-3p was significantly increased in ESCC tissues and cell lines. Also, miR-455-3p expression was significantly associated with histological grade, lymph nodes metastasis and clinical stage (all p < 0.05). The patients with low miR-455-3p expression had shorter survival time than those with high miR-455-3p expression. Furthermore, univariate and multivariate analysis identified low miR-455-3p expression as an unfavorable prognostic factor for overall survival. Moreover, transfection with the miR-455-3p mimic enhanced the cell proliferation and invasion in ESCC cells. Luciferase reporter assays confirmed that miR-455-3p binding to the 3'-UTR regions of FAM83F inhibited the expression of FAM83F in ESCC cells. Western blot confirmed that overexpression of miR-455-3p resulted in down-regulation of FAM83F in ESCC cells.

CONCLUSIONS

Our findings indicate that miR-455-3p plays an anti-oncogenic role in the development of ESCC by downregulation of FAM83F and could be an independent marker for predicting the clinical outcome of ESCC patients.

Protein network construction using reverse phase protein array data

In this paper, we introduce a novel computational method for constructing protein networks based on reverse phase protein array (RPPA) data to identify complex patterns in protein signaling. The method is applied to phosphoproteomic profiles of basal expression and activation/phosphorylation of 76 key signaling proteins in three breast cancer cell lines (MCF7, LCC1, and LCC9). Temporal RPPA data are acquired at 48h, 96h, and 144h after knocking down four genes in separate experiments. These genes are selected from a previous study as important determinants for breast cancer survival. Interaction networks are constructed by analyzing the expression levels of protein pairs using a multivariate analysis of variance model. A new scoring criterion is introduced to determine relevant protein pairs. Through a network topology based analysis, we search for wiring patterns to identify key proteins that are associated with significant changes in expression levels across various experimental conditions.

Identification of XAF1-MT2A mutual antagonism as a molecular switch in cell-fate decisions under stressful conditions

XIAP-associated factor 1 (XAF1) is a tumor suppressor that is commonly inactivated in multiple human neoplasms. However, the molecular mechanism underlying its proapoptotic function remains largely undefined. Here, we report that XAF1 induction by heavy metals triggers an apoptotic switch of stress response by destabilizing metallothionein 2A (MT2A). XAF1 directly interacts with MT2A and facilitates its lysosomal degradation, resulting in the elevation of the free intercellular zinc level and subsequent activation of p53 and inactivation of XIAP. Intriguingly, XAF1 is activated as a unique transcription target of metal-regulatory transcription factor-1 (MTF-1) in signaling apoptosis, and its protein is destabilized via the lysosomal pathway by MTF-1-induced MT2A under cytostatic stress conditions, indicating the presence of mutual antagonism between XAF1 and MT2A. The antagonistic interplay between XAF1 and MT2A acts as a key molecular switch in MTF-1-mediated cell-fate decisions and also plays an important role in cell response to various apoptotic and survival factors. Wild-type (WT) XAF1 but not MT2A binding-deficient mutant XAF1 increases the free intracellular zinc level and accelerates WT folding of p53 and degradation of XIAP. Consistently, XAF1 evokes a more drastic apoptotic effect in p53+/+ versus isogenic p53-/- cells. Clinically, expression levels of XAF1 and MT2A are inversely correlated in primary colon tumors and multiple cancer cell lines. XAF1-depleted xenograft tumors display an increased growth rate and a decreased apoptotic response to cytotoxic heavy metals with strong MT2A expression. Collectively, this study uncovers an important role for XAF1-MT2A antagonism as a linchpin to govern cell fate under various stressful conditions including heavy metal exposure.

Targeting the centriolar replication factor STIL synergizes with DNA damaging agents for treatment of ovarian cancer

Advanced ovarian cancer is an incurable disease. Thus, novel therapies are required. We wished to identify new therapeutic targets for ovarian cancer. ShRNA screen performed in 42 ovarian cancer cell lines identified the centriolar replication factor STIL as an essential gene for ovarian cancer cells. This was verified in-vivo in orthotopic human ovarian cancer mouse models. STIL depletion by administration of siRNA in neutral liposomes resulted in robust anti-tumor effect that was further enhanced in combination with cisplatin. Consistent with this finding, STIL depletion enhanced the extent of DNA double strand breaks caused by DNA damaging agents. This was associated with centrosomal depletion, ongoing genomic instability and enhanced formation of micronuclei. Interestingly, the ongoing DNA damage was not associated with reduced DNA repair. Indeed, we observed that depletion of STIL enhanced canonical homologous recombination repair and increased BRCA1 and RAD51 foci in response to DNA double strand breaks. Thus, inhibition of STIL significantly enhances the efficacy of DNA damaging chemotherapeutic drugs in treatment of ovarian cancer.

Anticancer kinase inhibitors impair intracellular viral trafficking and exert broad-spectrum antiviral effects

Global health is threatened by emerging viral infections, which largely lack effective vaccines or therapies. Targeting host pathways that are exploited by multiple viruses could offer broad-spectrum solutions. We previously reported that AAK1 and GAK, kinase regulators of the host adaptor proteins AP1 and AP2, are essential for hepatitis C virus (HCV) infection, but the underlying mechanism and relevance to other viruses or in vivo infections remained unknown. Here, we have discovered that AP1 and AP2 cotraffic with HCV particles in live cells. Moreover, we found that multiple viruses, including dengue and Ebola, exploit AAK1 and GAK during entry and infectious virus production. In cultured cells, treatment with sunitinib and erlotinib, approved anticancer drugs that inhibit AAK1 or GAK activity, or with more selective compounds inhibited intracellular trafficking of HCV and multiple unrelated RNA viruses with a high barrier to resistance. In murine models of dengue and Ebola infection, sunitinib/erlotinib combination protected against morbidity and mortality. We validated sunitinib- and erlotinib-mediated inhibition of AAK1 and GAK activity as an important mechanism of antiviral action. Additionally, we revealed potential roles for additional kinase targets. These findings advance our understanding of virus-host interactions and establish a proof of principle for a repurposed, host-targeted approach to combat emerging viruses.

Vitamin D Metabolite, 25-Hydroxyvitamin D, Regulates Lipid Metabolism by Inducing Degradation of SREBP/SCAP

Sterol regulatory element-binding proteins (SREBPs) are transcription factors that control lipid homeostasis. SREBP activation is regulated by a negative feedback loop in which sterols bind to SREBP cleavage-activating protein (SCAP), an escort protein essential for SREBP activation, or to insulin-induced genes (Insigs) (endoplasmic reticulum [ER] anchor proteins), sequestering the SREBP-SCAP-Insig complex in the ER. We screened a chemical library of endogenous molecules and identified 25-hydroxyvitamin D (25OHD) as an inhibitor of SREBP activation. Unlike sterols and other SREBP inhibitors, 25OHD impairs SREBP activation by inducing proteolytic processing and ubiquitin-mediated degradation of SCAP, thereby decreasing SREBP levels independently of the vitamin D receptor. Vitamin D supplementation has been proposed to reduce the risk of metabolic diseases, but the mechanisms are unknown. The present results suggest a previously unrecognized molecular mechanism of vitamin D-mediated lipid control that might be useful in the treatment of metabolic diseases.

RIP3 antagonizes a TSC2-mediated pro-survival pathway in glioblastoma cell death

Glioblastomas are the deadliest type of brain cancer and are frequently associated with poor prognosis and a high degree of recurrence despite removal by surgical resection and treatment by chemo- and radio-therapy. Photodynamic therapy (PDT) is a treatment well known to induce mainly necrotic and apoptotic cell death in solid tumors. 5-Aminolevulinic acid (5-ALA)-based PDT was recently shown to sensitize human glioblastoma cells (LN-18) to a RIP3 (Receptor Interacting Protein 3)-dependent cell death which is counter-acted by activation of autophagy. These promising results led us to investigate the pathways involved in cell death and survival mechanisms occurring in glioblastoma following PDT. In the present study, we describe a new TSC2 (Tuberous Sclerosis 2)-dependent survival pathway implicating MK2 (MAPKAPK2) kinase and 14-3-3 proteins which conducts to the activation of a pro-survival autophagy. Moreover, we characterized a new RIP3/TSC2 complex where RIP3 is suggested to promote cell death by targeting TSC2-dependent survival pathway. These results highlight (i) a new role of TSC2 to protect glioblastoma against PDT-induced cell death and (ii) TSC2 and 14-3-3 as new RIP3 partners.

Notch hyper-activation drives trans-differentiation of hESC-derived endothelium

During development, endothelial cells (EC) display tissue-specific attributes that are unique to each vascular bed, as well as generic signaling mechanisms that are broadly applied to create a patent circulatory system. We have previously utilized human embryonic stem cells (hESC) to generate tissue-specific EC sub-types (Rafii et al., 2013) and identify pathways that govern growth and trans-differentiation potential of hESC-derived ECs (James et al., 2010). Here, we elucidate a novel Notch-dependent mechanism that induces endothelial to mesenchymal transition (EndMT) in confluent monolayer cultures of hESC-derived ECs. We demonstrate density-dependent induction of EndMT that can be rescued by the Notch signaling inhibitor DAPT and identify a positive feedback signaling mechanism in hESC-ECs whereby trans-activation of Notch by DLL4 ligand induces elevated expression and surface presentation of DLL4. Increased Notch activation in confluent hESC-EC monolayer cultures induces areas of EndMT containing transitional cells that are marked by increased Jagged1 expression and reduced Notch signal integration. Jagged1 loss of function in monolayer hESC-ECs induces accelerated feedback stimulation of Notch signaling, increased expression of cell-autonomous, cis-inhibitory DLL4, and EndMT. These data elucidate a novel interplay of Notch ligands in modulating pathway activation during both expansion and EndMT of hESC-derived ECs.

Logical design of an anti-cancer agent targeting the plant homeodomain in Pygopus2

Pygopus2 (Pygo2) is a component of the Wnt signaling pathway, which is required for β-catenin mediated transcription. Plant homeodomain (PHD) finger in Pygo2 intercalates the methylated histone 3 (H3K4me) tail and HD1 domain of BCL9 that binds to β-catenin. Thus, PHD finger may be a potential target for the logical design of an anti-cancer drug. Here, we found that Spiro[2H-naphthol[1,2-b]pyran-2,4'-piperidine]-1'ethanol,3,4-dihydro-4-hydroxy-α-(6-methyl-1H-indol-3-yl)) termed JBC117 interacts with D339, A348, R356, V376 and A378 in PHD corresponding to the binding sites with H3K4me and/or HD1, and has strong anti-cancer effects. For colon (HCT116) and lung (A549) cancer cell lines, IC50 values were 2.6 ± 0.16 and 3.3 ± 0.14 μM, respectively, while 33.80 ± 0.15 μM for the normal human fibroblast cells. JBC117 potently antagonized the cellular effects of β-catenin-dependent activity and also inhibited the migration and invasion of cancer cells. In vivo studies showed that the survival time of mice was significantly prolonged by the subcutaneous injection of JBC117 (10 mg/kg/day). In conclusion, JBC117 is a novel anti-cancer lead compound targeting the PHD finger of Pygo2 and has a therapeutic effect against colon and lung cancer.

Nuclear Perilipin 5 integrates lipid droplet lipolysis with PGC-1α/SIRT1-dependent transcriptional regulation of mitochondrial function

Dysfunctional cellular lipid metabolism contributes to common chronic human diseases, including type 2 diabetes, obesity, fatty liver disease and diabetic cardiomyopathy. How cells balance lipid storage and mitochondrial oxidative capacity is poorly understood. Here we identify the lipid droplet protein Perilipin 5 as a catecholamine-triggered interaction partner of PGC-1α. We report that during catecholamine-stimulated lipolysis, Perilipin 5 is phosphorylated by protein kinase A and forms transcriptional complexes with PGC-1α and SIRT1 in the nucleus. Perilipin 5 promotes PGC-1α co-activator function by disinhibiting SIRT1 deacetylase activity. We show by gain-and-loss of function studies in cells that nuclear Perilipin 5 promotes transcription of genes that mediate mitochondrial biogenesis and oxidative function. We propose that Perilipin 5 is an important molecular link that couples the coordinated catecholamine activation of the PKA pathway and of lipid droplet lipolysis with transcriptional regulation to promote efficient fatty acid catabolism and prevent mitochondrial dysfunction.

Cytotoxic Properties of a DEPTOR-mTOR Inhibitor in Multiple Myeloma Cells

DEPTOR is a 48 kDa protein that binds to mTOR and inhibits this kinase in TORC1 and TORC2 complexes. Overexpression of DEPTOR specifically occurs in a model of multiple myeloma. Its silencing in multiple myeloma cells is sufficient to induce cytotoxicity, suggesting that DEPTOR is a potential therapeutic target. mTORC1 paralysis protects multiple myeloma cells against DEPTOR silencing, implicating mTORC1 in the critical role of DEPTOR in multiple myeloma cell viability. Building on this foundation, we interrogated a small-molecule library for compounds that prevent DEPTOR binding to mTOR in a yeast-two-hybrid assay. One compound was identified that also prevented DEPTOR-mTOR binding in human myeloma cells, with subsequent activation of mTORC1 and mTORC2. In a surface plasmon resonance (SPR) assay, the compound bound to recombinant DEPTOR but not to mTOR. The drug also prevented binding of recombinant DEPTOR to mTOR in the SPR assay. Remarkably, although activating TORC1 and TORC2, the compound induced apoptosis and cell-cycle arrest in multiple myeloma cell lines and prevented outgrowth of human multiple myeloma cells in immunodeficient mice. In vitro cytotoxicity against multiple myeloma cell lines was directly correlated with DEPTOR protein expression and was mediated, in part, by the activation of TORC1 and induction of p21 expression. Additional cytotoxicity was seen against primary multiple myeloma cells, whereas normal hematopoietic colony formation was unaffected. These results further support DEPTOR as a viable therapeutic target in multiple myeloma and suggest an effective strategy of preventing binding of DEPTOR to mTOR. Cancer Res; 76(19); 5822-31. ©2016 AACR.