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Reported here is a piggyBac transposon-based expression system for the generation of doxycycline-inducible,stably transfected mammalian cell cultures for large-scale protein production. The system works with commonly used adherent and suspension-adapted mammalian cell lines and requires only a single transfection step. Moreover,the high uniform expression levels observed among clones allow for the use of stable bulk cell cultures,thereby eliminating time-consuming cloning steps. Under continuous doxycycline induction,protein expression levels have been shown to be stable for at least 2 mo in the absence of drug selection. The high efficiency of the system also allows for the generation of stable bulk cell cultures in 96-well format,a capability leading to the possibility of generating stable cell cultures for entire families of membrane or secreted proteins. Finally,we demonstrate the utility of the system through the large-scale production (140-750 mg scale) of an endoplasmic reticulum-resident fucosyltransferase and two potential anticancer protein therapeutic agents. View Publication

The incidence of human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) has rapidly increased over the past 30 years,prompting the suggestion that an epidemic maybe on the horizon. Therefore,there is a clinical need to develop alternate therapeutic strategies to manage the growing number of HPV-positive HNSCC patients. High-risk HPV E6 inactivates p53 through two distinct mechanisms; association with E6AP to degrade p53 and association with p300 to block p300-mediated p53 acetylation and activation. In this study,we determined if targeting the E6-p300 interaction is an effective approach to reactivate p53 in HPV-positive HNSCC. Ectopic expression of the CH1 domain of p300 in HPV-positive HNSCC blocks the association between E6 and p300,increases total and acetylated p53 levels and enhances p53 transcriptional activity. Moreover,expression of p21,miR-34a and miR-200c are increased,demonstrating functional p53 reactivation. CH1 overexpression in HPV-positive HNSCC has a global anticancer effect resulting in a decrease in cell proliferation and clonogenic survival and an increase in apoptosis. The in vivo tumor-initiating ability of HPV-positive HNSCC is severely compromised with CH1 overexpression,in part through a reduction in the cancer-initiating cell population. A novel small-molecule CH1 inhibitor,CH1iB,reactivates p53 and potentiates the anticancer activity of cis-platinum in HPV-positive HNSCC cells. Our work shows that CH1-domain inhibitors represent a novel class of p53-reactivation therapeutics for managing HPV-positive HNSCC patients. View Publication

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer deaths among women in the United States,but its pathogenesis is poorly understood. Some epithelial cancers are known to occur in transitional zones between two types of epithelium,whereas others have been shown to originate in epithelial tissue stem cells. The stem cell niche of the ovarian surface epithelium (OSE),which is ruptured and regenerates during ovulation,has not yet been defined unequivocally. Here we identify the hilum region of the mouse ovary,the transitional (or junction) area between the OSE,mesothelium and tubal (oviductal) epithelium,as a previously unrecognized stem cell niche of the OSE. We find that cells of the hilum OSE are cycling slowly and express stem and/or progenitor cell markers ALDH1,LGR5,LEF1,CD133 and CK6B. These cells display long-term stem cell properties ex vivo and in vivo,as shown by our serial sphere generation and long-term lineage-tracing assays. Importantly,the hilum cells show increased transformation potential after inactivation of tumour suppressor genes Trp53 and Rb1,whose pathways are altered frequently in the most aggressive and common type of human EOC,high-grade serous adenocarcinoma. Our study supports experimentally the idea that susceptibility of transitional zones to malignant transformation may be explained by the presence of stem cell niches in those areas. Identification of a stem cell niche for the OSE may have important implications for understanding EOC pathogenesis. View Publication

Graft-versus-host disease (GVHD) is the main complication of allogeneic bone marrow transplantation. Current strategies to control GVHD rely on global immunosuppression. These strategies are incompletely effective and decrease the anticancer activity of the allogeneic graft. We previously identified Notch signaling in T cells as a new therapeutic target for preventing GVHD. Notch-deprived T cells showed markedly decreased production of inflammatory cytokines,but normal in vivo proliferation,increased accumulation of regulatory T cells,and preserved anticancer effects. Here,we report that γ-secretase inhibitors can block all Notch signals in alloreactive T cells,but lead to severe on-target intestinal toxicity. Using newly developed humanized antibodies and conditional genetic models,we demonstrate that Notch1/Notch2 receptors and the Notch ligands Delta-like1/4 mediate all the effects of Notch signaling in T cells during GVHD,with dominant roles for Notch1 and Delta-like4. Notch1 inhibition controlled GVHD,but led to treatment-limiting toxicity. In contrast,Delta-like1/4 inhibition blocked GVHD without limiting adverse effects while preserving substantial anticancer activity. Transient blockade in the peritransplant period provided durable protection. These findings open new perspectives for selective and safe targeting of individual Notch pathway components in GVHD and other T cell-mediated human disorders. View Publication

Activation of neural stem/progenitor cells (NSPCs) is a potential therapeutic strategy of neurological disorders. In this study,NSPCs of subventricular zone were isolated and cultured from platelet-derived growth factor-β-receptor-knockout (PDGFR-β(-/-)) mice of postnatal day 1 (P1) and P28,and the roles of PDGFR-β were examined in these cells. In PDGFR-β-preserving control NSPCs,stem cell activities,such as numbers and diameters of secondary neurospheres,cell proliferation and survival rates,were significantly higher in P1 NSPCs than those in P28 NSPCs. In PDGFR-β(-/-) NSPCs,most of these parameters were decreased as compared with age-matched controls. Among them,the decrease of secondary neurosphere formation was most striking in P1 and P28 PDGFR-β(-/-) NSPCs and in P28 control NSPCs as compared with P1 control NSPCs. PCR-array and following quantitative real-time PCR (qRT-PCR) analyses demonstrated that expressions of fibroblast growth factor-2 (FGF2) and exons IV-IX of brain-derived neurotrophic factor (BDNF) were decreased,and noggin was increased in P1 PDGFR-β(-/-) as compared with P1 controls. Addition of BDNF rescued the number and diameter of secondary neurospheres in P1 PDGFR-β(-/-) NSPCs to similar levels as controls. The expressions of PDGFs and PDGFRs in control NSPCs were increased along with the differentiation-induction,where phosphorylated PDGFR-β was co-localized with neuronal and astrocyte differentiation markers. In controls,the neuronal differentiation was decreased,and the glial differentiation was increased from P1 to P28 NSPCs. Compared with P1 controls,neuronal differentiation was reduced in P1 PDGFR-β(-/-) NSPCs,whereas glial differentiation was comparable between the two genotypes. These results suggest that PDGFR-β signaling is important for the self-renewal and multipotency of NSPCs,particularly in neonatal NSPCs. BDNF,FGF2,and noggin may be involved in the effects of PDGFR-β signaling in these cells. Accordingly,the activation of PDGFR-β in NSPCs may be a novel therapeutic strategy of neurological diseases. View Publication

Medulloblastoma is the most common pediatric malignant brain tumor. Although current therapies improve survival,these regimens are highly toxic and are associated with significant morbidity. Here,we report that placental growth factor (PlGF) is expressed in the majority of medulloblastomas,independent of their subtype. Moreover,high expression of PlGF receptor neuropilin 1 (Nrp1) correlates with poor overall survival in patients. We demonstrate that PlGF and Nrp1 are required for the growth and spread of medulloblastoma: PlGF/Nrp1 blockade results in direct antitumor effects in vivo,resulting in medulloblastoma regression,decreased metastasis,and increased mouse survival. We reveal that PlGF is produced in the cerebellar stroma via tumor-derived Sonic hedgehog (Shh) and show that PlGF acts through Nrp1-and not vascular endothelial growth factor receptor 1-to promote tumor cell survival. This critical tumor-stroma interaction-mediated by Shh,PlGF,and Nrp1 across medulloblastoma subtypes-supports the development of therapies targeting PlGF/Nrp1 pathway. View Publication

Activation of the Smoothened (Smo) receptor mediates Hedgehog (Hh) signaling. Hh inhibitors are in clinical trials for cancer,and small-molecule Smo agonists may have therapeutic interests in regenerative medicine. Here,we have generated and validated a pharmacophoric model for Smo agonists and used this model for the virtual screening of a library of commercially available compounds. Among the 20 top-scoring ligands,we have identified and characterized a novel quinolinecarboxamide derivative,propyl 4-(1-hexyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamido) benzoate,(GSA-10),as a Smo agonist. GSA-10 fits to the agonist pharmacophoric model with two hydrogen bond acceptor groups and four hydrophobic regions. Using pharmacological,biochemical,and molecular approaches,we provide compelling evidence that GSA-10 acts at Smo to promote the differentiation of multipotent mesenchymal progenitor cells into osteoblasts. However,this molecule does not display the hallmarks of reference Smo agonists. Remarkably,GSA-10 does not recognize the classic bodipy-cyclopamine binding site. Its effect on cell differentiation is inhibited by Smo antagonists,such as MRT-83,SANT-1,LDE225,and M25 in the nanomolar range,by GDC-0449 in the micromolar range,but not by cyclopamine and CUR61414. Thus,GSA-10 allows the pharmacological characterization of a novel Smo active site,which is notably not targeted to the primary cilium and strongly potentiated by forskolin and cholera toxin. GSA-10 belongs to a new class of Smo agonists and will be helpful for dissecting Hh mechanism of action,with important implications in physiology and in therapy. View Publication

Although current breast cancer treatment guidelines limit the use of HER2-blocking agents to tumors with HER2 gene amplification,recent retrospective analyses suggest that a wider group of patients may benefit from this therapy. Using breast cancer cell lines,mouse xenograft models and matched human primary and metastatic tissues,we show that HER2 is selectively expressed in and regulates self-renewal of the cancer stem cell (CSC) population in estrogen receptor-positive (ER(+)),HER2(-) luminal breast cancers. Although trastuzumab had no effects on the growth of established luminal breast cancer mouse xenografts,administration after tumor inoculation blocked subsequent tumor growth. HER2 expression is increased in luminal tumors grown in mouse bone xenografts,as well as in bone metastases from patients with breast cancer as compared with matched primary tumors. Furthermore,this increase in HER2 protein expression was not due to gene amplification but rather was mediated by receptor activator of NF-$$B (RANK)-ligand in the bone microenvironment. These studies suggest that the clinical efficacy of adjuvant trastuzumab may relate to the ability of this agent to target the CSC population in a process that does not require HER2 gene amplification. Furthermore,these studies support a CSC model in which maximal clinical benefit is achieved when CSC targeting agents are administered in the adjuvant setting. Cancer Res; 73(5); 1635-46. textcopyright2012 AACR. View Publication

Recent advances in the ability to efficiently characterize tumor genomes is enabling targeted drug development,which requires rigorous biomarker-based patient selection to increase effectiveness. Consequently,representative DNA biomarkers become equally important in pre-clinical studies. However,it is still unclear how well these markers are maintained between the primary tumor and the patient-derived tumor models. Here,we report the comprehensive identification of somatic coding mutations and copy number aberrations in four glioblastoma (GBM) primary tumors and their matched pre-clinical models: serum-free neurospheres,adherent cell cultures,and mouse xenografts. We developed innovative methods to improve the data quality and allow a strict comparison of matched tumor samples. Our analysis identifies known GBM mutations altering PTEN and TP53 genes,and new actionable mutations such as the loss of PIK3R1,and reveals clear patient-to-patient differences. In contrast,for each patient,we do not observe any significant remodeling of the mutational profile between primary to model tumors and the few discrepancies can be attributed to stochastic errors or differences in sample purity. Similarly,we observe 96% primary-to-model concordance in copy number calls in the high-cellularity samples. In contrast to previous reports based on gene expression profiles,we do not observe significant differences at the DNA level between in vitro compared to in vivo models. This study suggests,at a remarkable resolution,the genome-wide conservation of a patient's tumor genetics in various pre-clinical models,and therefore supports their use for the development and testing of personalized targeted therapies. View Publication

Corneal transparency depends on a unique extracellular matrix secreted by stromal keratocytes,mesenchymal cells of neural crest lineage. Derivation of keratocytes from human embryonic stem (hES) cells could elucidate the keratocyte developmental pathway and open a potential for cell-based therapy for corneal blindness. This study seeks to identify conditions inducing differentiation of pluripotent hES cells to the keratocyte lineage. Neural differentiation of hES cell line WA01(H1) was induced by co-culture with mouse PA6 fibroblasts. After 6 days of co-culture,hES cells expressing cell-surface NGFR protein (CD271,p75NTR) were isolated by immunoaffinity adsorption,and cultured as a monolayer for one week. Keratocyte phenotype was induced by substratum-independent pellet culture in serum-free medium containing ascorbate. Gene expression,examined by quantitative RT-PCR,found hES cells co-cultured with PA6 cells for 6 days to upregulate expression of neural crest genes including NGFR,SNAI1,NTRK3,SOX9,and MSX1. Isolated NGFR-expressing cells were free of PA6 feeder cells. After expansion as a monolayer,mRNAs typifying adult stromal stem cells were detected,including BMI1,KIT,NES,NOTCH1,and SIX2. When these cells were cultured as substratum-free pellets keratocyte markers AQP1,B3GNT7,PTDGS,and ALDH3A1 were upregulated. mRNA for keratocan (KERA),a cornea-specific proteoglycan,was upregulated more than 10,000 fold. Culture medium from pellets contained high molecular weight keratocan modified with keratan sulfate,a unique molecular component of corneal stroma. These results show hES cells can be induced to differentiate into keratocytes in vitro. Pluripotent stem cells,therefore,may provide a renewable source of material for development of treatment of corneal stromal opacities. View Publication

An essential aspect of stem cell culture is the successful maintenance of the undifferentiated state. Many types of stem cells are FGF2 dependent,and pluripotent stem cells are maintained by replacing FGF2-containing media daily,while tissue-specific stem cells are typically fed every 3rd day. Frequent feeding,however,results in significant variation in growth factor levels due to FGF2 instability,which limits effective maintenance due to spontaneous differentiation. We report that stabilization of FGF2 levels using controlled release PLGA microspheres improves expression of stem cell markers,increases stem cell numbers and decreases spontaneous differentiation. The controlled release FGF2 additive reduces the frequency of media changes needed to maintain stem cell cultures,so that human embryonic stem cells and induced pluripotent stem cells can be maintained successfully with biweekly feedings. View Publication

The formation of clathrin-coated vesicles is essential for intracellular membrane trafficking between subcellular compartments and is triggered by the ARF family of small GTPases. We previously identified SMAP1 as an ARF6 GTPase-activating protein that functions in clathrin-dependent endocytosis. Because abnormalities in clathrin-dependent trafficking are often associated with oncogenesis,we targeted Smap1 in mice to examine its physiological and pathological significance. Smap1-deficent mice exhibited healthy growth,but their erythroblasts showed enhanced transferrin endocytosis. In mast cells cultured in SCF,Smap1 deficiency did not affect the internalization of c-KIT but impaired the sorting of internalized c-KIT from multivesicular bodies to lysosomes,resulting in intracellular accumulation of undegraded c-KIT that was accompanied by enhanced activation of ERK and increased cell growth. Interestingly,approximately 50% of aged Smap1-deficient mice developed anemia associated with morphologically dysplastic cells of erythroid-myeloid lineage,which are hematological abnormalities similar to myelodysplastic syndrome (MDS) in humans. Furthermore,some Smap1-deficient mice developed acute myeloid leukemia (AML) of various subtypes. Collectively,to our knowledge these results provide the first evidence in a mouse model that the deregulation of clathrin-dependent membrane trafficking may be involved in the development of MDS and subsequent AML. View Publication