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Long-term in vitro culture of undifferentiated human embryonic stem cells (hESCs) traditionally requires a fibroblast feeder cell layer. Using feeder cells in hESC cultures is highly laborious and limits large-scale hESC production for potential application in regenerative medicine. Replacing feeder cells with defined human extracellular matrix (ECM) components or synthetic biomaterials would be ideal for large-scale production of clinical-grade hESCs. We tested and compared different feeder cell-free hESC culture methods based on different human ECM proteins,human and animal sera matrices,and a Matrigel matrix. Also selected biomaterials were tested for feeder cell-free propagation of undifferentiated hESCs. The matrices were tested together with conventional and modified hESC culture media,human foreskin fibroblast-conditioned culture medium,chemically defined medium,TeSR1,and modified TeSR1 media. The results showed the undefined,xenogeneic Matrigel to be a superior matrix for hESC culture compared with the purified human ECM proteins,serum matrices,and the biomaterials tested. A long-term,feeder cell-free culture system was successful on Matrigel in combination with mTeSR1 culture medium,but a xeno-free,fully defined,and reproducible feeder cell-free hESC culture method still remains to be developed. View Publication

Cancer stem cells are known for their inherent resistance to therapy. Here we investigated whether normal stem cells with acquired resistance to stress can be used to identify novel markers of cancer stem cells. For this,we generated a human embryonic stem cell line resistant to Trichostatin A and analyzed changes in its gene expression. The resistant cells over-expressed various genes associated with tumor aggressiveness,many of which are also expressed in the CD133+ glioma cancer stem cells. These findings suggest that stress-resistant stem cells generated in vitro may be useful for the discovery of novel markers of cancer stem cells. View Publication

The demonstration of the brain's ability to initiate repair in response to disease or injury has sparked considerable interest in therapeutic strategies to stimulate adult neurogenesis. In this study we examined the effect of a progressive neurodegenerative condition on neural precursor activity in the subventricular zone (SVZ) and hippocampus of the R6/1 transgenic mouse model of Huntington's disease (HD). Our results revealed an age-related decline in SVZ precursor numbers in both wild-type (WT) and HD mice. Interestingly,hippocampal precursor numbers declined with age in WT mice,although we observed maintenance in hippocampal precursor number in the HD animals in response to advancement of the disease. This maintenance was consistent with activation of a recently identified latent hippocampal precursor population. We found that the small latent stem cell population was also maintained in the HD hippocampus at 33 weeks,whereas it was not present in the WT. Our findings demonstrate that,despite a loss of neurogenesis in the HD hippocampus in vivo,there is a unique maintenance of the precursor and stem cells,which may potentially be activated to ameliorate disease symptoms. View Publication

The MAPK pathway is one of the most important pathways for novel anticancer drug development. We performed high-throughput screening for compounds that induce expression of p15INK4b,and identified JTP-74057 (GSK1120212),which is being evaluated in ongoing phase I,II and III clinical trials. We characterized its antitumor activities in vitro and in vivo. JTP-74057 strongly inhibited MEK1/2 kinase activities,but did not inhibit another 98 kinase activities. Treatment by JTP-74057 resulted in growth inhibition accompanied with upregulation of p15INK4b and/or p27KIP1 in most of the colorectal cancer cell lines tested. Daily oral administration of JTP-74057 for 14 days suppressed tumor growth of HT-29 and COLO205 xenografts in nude mice. Notably,tumor regression was observed only in COLO205 xenografts,and COLO205 was much more sensitive to JTP-74057-induced apoptosis than HT-29 in vitro. Treatment with an Akt inhibitor enhanced the JTP-74057-induced apoptosis in HT-29 cells. Finally,JTP-74057 exhibited an additive or a synergistic effect in combination with the standard-of-care agents,5-fluorouracil,oxaliplatin or SN-38. JTP-74057,a highly specific and potent MEK1/2 inhibitor,exerts favorable antitumor activities in vitro and in vivo. Sensitivity to JTP-74057-induced apoptosis may be an important factor for the estimation of in vivo efficacy,and sensitivity was enhanced by an Akt inhibitor. These results suggest the usefulness of JTP-74057 in therapeutic applications for colorectal cancer patients. View Publication

ETV6::RUNX1,the most common oncogenic fusion in pediatric B cell precursor acute lymphoblastic leukemia (BCP-ALL),induces a clinically silent preleukemic state that can persist in carriers for over a decade and may progress to overt leukemia upon acquisition of secondary lesions. The mechanisms contributing to quiescence of ETV6::RUNX1+ preleukemic cells still remain elusive. In this study,we identify linker histone H1-0 as a critical mediator of the ETV6::RUNX1+ preleukemic state by employing human -induced pluripotent stem cell (hiPSC) models engineered by using CRISPR/Cas9 gene editing. Global gene expression analysis revealed upregulation of H1-0 in ETV6::RUNX1+ hiPSCs that was preserved upon hematopoietic differentiation. Moreover,whole transcriptome data of 1,727 leukemia patient samples showed significantly elevated H1-0 levels in ETV6::RUNX1+ BCP-ALL compared to other leukemia entities. Using dual-luciferase promoter assays,we show that ETV6::RUNX1 induces H1-0 promoter activity. We further demonstrate that depletion of H1-0 specifically inhibits ETV6::RUNX1 signature genes,including RAG1 and EPOR. Single-cell sequencing showed that H1-0 is highly expressed in quiescent hematopoietic cells. Importantly,H1-0 protein levels correspond to susceptibility of BCP-ALL cells towards histone deacetylase inhibitors (HDACis) and combinatorial treatment using the H1-0-inducing HDACi Quisinostat showed promising synergism with established chemotherapeutic drugs. Taken together,our data identify H1-0 as a key regulator of the ETV6::RUNX1+ transcriptome and indicate that the addition of Quisinostat may be beneficial to target non-responsive or relapsing ETV6::RUNX1+ BCP-ALL. View Publication

BackgroundNatural killer (NK) cells are key effector cells of antitumor immunity. However,tumors can acquire resistance programs to escape NK cell-mediated immunosurveillance. Identifying mechanisms that mediate this resistance enables us to define approaches to improve immune-mediate antitumor activity. In previous studies from our group,a genome-wide CRISPR-Cas9 screen identified Charged Multivesicular Body Protein 2A (CHMP2A) as a novel mechanism that mediates tumor intrinsic resistance to NK cell activity.MethodsHere,we use an immunocompetent mouse model to demonstrate that CHMP2A serves as a targetable regulator of not only NK cell-mediated immunity but also other immune cell populations. Using the recently characterized murine 4MOSC model system,a syngeneic,tobacco-signature murine head and neck squamous cell carcinoma model,we deleted mCHMP2A using CRISPR/Cas9-mediated knock-out (KO),following orthotopic transplantation into immunocompetent hosts.ResultsWe found that mCHMP2A KO in 4MOSC1 cells leads to more potent NK-mediated tumor cell killing in vitro in these tumor cells. Moreover,following orthotopic transplantation,KO of mCHMP2A in 4MOSC1 cells,but not the more immune-resistant 4MOSC2 cells enables both T cells and NK cells to better mediate antitumor activity compared with wild type (WT) tumors. However,there was no difference in tumor development between WT and mCHMP2A KO 4MOSC1 or 4MOSC2 tumors when implanted in immunodeficient mice. Mechanistically,we find that mCHMP2A KO 4MOSC1 tumors transplanted into the immunocompetent mice had significantly increased CD4+T cells,CD8+T cells. NK cell,as well as fewer myeloid-derived suppressor cells (MDSC).ConclusionsTogether,these studies demonstrate that CHMP2A is a targetable inhibitor of cellular antitumor immunity. View Publication

Tumor patients often exhibit limited responses to immunotherapy owing to the low immunogenicity and immunosuppressive environment of tumors. Our previous studies revealed that cryo-thermal therapy caused tumor cell rupture due to mechanical compression,notably causing the release of a substantial amount of DAMPs (danger-associated molecular patterns),such as heat shock protein 70,calreticulin and high-mobility group box protein 1; the release of these DAMPs increased myeloid cell maturation,thereby reshaping the systemic immune environment and ultimately inducing durable CD4+ T helper type 1 (Th1) cell-dominated antitumor immunity. In fact,under conditions of mechanical stress and rapid temperature changes,the disruption of tumor cells caused by cryo-thermal therapy results in extensive deoxyribonucleic acid (DNA) damage and the rapid release of substantial amounts of DNA. Consequently,tumor-derived DNA,which potently activates innate immunity by engaging multiple DNA sensors,plays a pivotal role in orchestrating antitumor immunity. We hypothesized that cryo-thermal therapy induces the transient release of high levels of DNA,which modulates CD11b+ myeloid cell function,subsequently influencing CD4+ Th1-cell dominated antitumor immune responses. In this study,a B16F10 melanoma model was established,and DNA concentrations were measured at different time points after cryo-thermal therapy. Deoxyribonuclease I (DNase I) was subsequently administered immediately following cryo-thermal therapy to deplete extracellular DNA,allowing an investigation of the role of DNA in regulating CD11b+ myeloid cell function and CD4+ T cell differentiation. The phenotype and function of CD11b+ myeloid cells and CD4+ T cells were assessed by flow cytometry,RNA sequencing,and cell culture in vitro. Our studies confirmed that cryo-thermal therapy triggered a transient release of high levels of DNA,which was internalized by CD11b+ myeloid cells via C-type lectin receptors and subsequently sensed by inflammasomes. Then,the intracellular sensing of DNA induced the production of the mature form of interleukin (IL)-18,ultimately promoting the Th1 differentiation of CD4+ T cells. This study highlights the pivotal role of DNA release after cryo-thermal therapy in driving CD4+ Th1 cell-dominant antitumor immunity. View Publication

RNA-binding motif protein 15 (RBM15) is involved in the RBM15-megakaryoblastic leukemia 1 fusion in acute megakaryoblastic leukemia. Although Rbm15 has been reported to be required for B-cell differentiation and to inhibit myeloid and megakaryocytic expansion,it is not clear what the normal functions of Rbm15 are in the regulation of hematopoietic stem cell (HSC) and megakaryocyte development. In this study,we report that Rbm15 may function in part through regulation of expression of the proto-oncogene c-Myc. Similar to c-Myc knockout (c-Myc-KO) mice,long-term (LT) HSCs are significantly increased in Rbm15-KO mice due to an apparent LT-HSC to short-term HSC differentiation defect associated with abnormal HSC-niche interactions caused by increased N-cadherin and beta(1) integrin expression on mutant HSCs. Both serial transplantation and competitive reconstitution capabilities of Rbm15-KO LT-HSCs are greatly compromised. Rbm15-KO and c-Myc-KO mice also share related abnormalities in megakaryocyte development,with mutant progenitors producing increased,abnormally small low-ploidy megakaryocytes. Consistent with a possible functional interplay between Rbm15 and c-Myc,the megakaryocyte increase in Rbm15-KO mice could be partially reversed by ectopic c-Myc. Thus,Rbm15 appears to be required for normal HSC-niche interactions,for the ability of HSCs to contribute normally to adult hematopoiesis,and for normal megakaryocyte development; these effects of Rbm15 on hematopoiesis may be mediated at least in part by c-Myc. View Publication

We had earlier reported the derivation and characterization of two new sibling human embryonic stem cell lines BJNhem19 and BJNhem20,from discarded grade III embryos of Indian origin. We report here the characteristics of the two sibling cell lines after long-term continuous culture for over 2 yr during which they have been passaged over 200 times. We show that both cell lines adapt well to culture on various mouse and human feeders as well as in feeder-free conditions. The cells show normal diploid karyotype and continue to express all pluripotency markers. Both cell lines differentiate to derivatives of all three germ layers in vitro. However as reported earlier,BJNhem19 is unable to generate teratomas in nude or SCID mice or differentiate to beating cardiomyocytes when tested over several passages during long-term stable culture. On the other hand,the cardiac differentiation capacity of BJNhem20 is greatly increased,and it can generate beating cardiomyocytes that proliferate when isolated and cultured further. In conclusion,the two cell lines have maintained a stable phenotype for over 2 yr and are indeed immortal. Their derivation from grade III embryos does not seem to have any adverse effect on their long-term phenotype. The cells can be obtained for research purposes from the UK Stem Cell Bank and from the authors. View Publication

In this report we describe a quantitative in vitro assay for the most primitive type of leukemic precursors yet defined in patients with chronic myeloid leukemia (CML). This assay is based on the recently described long-term culture-initiating cell" (LTC-IC) assay for primitive normal human hematopoietic cells. Such cells� View Publication

Therapies that target signaling pathways critical to the pathogenesis and progression of squamous cell carcinoma of the head and neck (HNSCC) are needed. One such target,phosphatidylinositol 3-kinase,and its downstream target serine/threonine kinase,Akt,are up-regulated in HNSCC. Targeted therapy could consist of inhibitors of these kinases or,alternatively,of inhibitors of the pathways that they regulate. To explore the effect of Akt inhibition on the growth and survival of HNSCC tumors,we evaluated the effect of a novel Akt inhibitor,KP372-1,on the growth,survival,and sensitivity to anoikis of HNSCC cell lines in culture. Using Western blotting of head and neck cancer cell lines and squamous mucosa and carcinoma specimens,we found that Akt was highly phosphorylated in head and neck cancer cell lines and human head and neck squamous carcinoma specimens. Treatment of HNSCC cell lines with KP372-1 blocked the activation of Akt,inhibited head and neck cancer cell proliferation,and induced apoptosis and anoikis in several HNSCC cell lines. Furthermore,KP372-1 decreased the phosphorylation of the S6 ribosomal (Ser240/244) protein,which is a downstream target of Akt. Taken together,these findings indicate that KP372-1 may be a useful therapeutic agent for HNSCC and should be further evaluated in preclinical models of HNSCC. View Publication

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. In addition to cognitive deficits,FXS patients exhibit hyperactivity,attention deficits,social difficulties,anxiety,and other autistic-like behaviors. FXS is caused by an expanded CGG trinucleotide repeat in the 5' untranslated region of the Fragile X Mental Retardation (FMR1) gene leading to epigenetic silencing and loss of expression of the Fragile X Mental Retardation protein (FMRP). Despite the known relationship between FMR1 CGG repeat expansion and FMR1 silencing,the epigenetic modifications observed at the FMR1 locus,and the consequences of the loss of FMRP on human neurodevelopment and neuronal function remain poorly understood. To address these limitations,we report on the generation of induced pluripotent stem cell (iPSC) lines from multiple patients with FXS and the characterization of their differentiation into post-mitotic neurons and glia. We show that clones from reprogrammed FXS patient fibroblast lines exhibit variation with respect to the predominant CGG-repeat length in the FMR1 gene. In two cases,iPSC clones contained predominant CGG-repeat lengths shorter than measured in corresponding input population of fibroblasts. In another instance,reprogramming a mosaic patient having both normal and pre-mutation length CGG repeats resulted in genetically matched iPSC clonal lines differing in FMR1 promoter CpG methylation and FMRP expression. Using this panel of patient-specific,FXS iPSC models,we demonstrate aberrant neuronal differentiation from FXS iPSCs that is directly correlated with epigenetic modification of the FMR1 gene and a loss of FMRP expression. Overall,these findings provide evidence for a key role for FMRP early in human neurodevelopment prior to synaptogenesis and have implications for modeling of FXS using iPSC technology. By revealing disease-associated cellular phenotypes in human neurons,these iPSC models will aid in the discovery of novel therapeutics for FXS and other autism-spectrum disorders sharing common pathophysiology. View Publication