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1.  Intracellular CD24 disrupts the ARF–NPM interaction and enables mutational and viral oncogene-mediated p53 inactivation 
Nature Communications  2015;6:5909.
CD24 is overexpressed in nearly 70% human cancers, whereas TP53 is the most frequently mutated tumour-suppressor gene that functions in a context-dependent manner. Here we show that both targeted mutation and short hairpin RNA (shRNA) silencing of CD24 retard the growth, progression and metastasis of prostate cancer. CD24 competitively inhibits ARF binding to NPM, resulting in decreased ARF, increase MDM2 and decrease levels of p53 and the p53 target p21/CDKN1A. CD24 silencing prevents functional inactivation of p53 by both somatic mutation and viral oncogenes, including the SV40 large T antigen and human papilloma virus 16 E6-antigen. In support of the functional interaction between CD24 and p53, in silico analyses reveal that TP53 mutates at a higher rate among glioma and prostate cancer samples with higher CD24 mRNA levels. These data provide a general mechanism for functional inactivation of ARF and reveal an important cellular context for genetic and viral inactivation of TP53.
P53 is a tumour suppressor that is frequently mutated or downregulated in cancer. Here, Wang et al. show that CD24, a molecule frequently overexpressed in cancer, promotes p53 degradation by disrupting a regulatory ARF–MDM2 interaction, and silencing CD24 prevents the downregulation of p53.
doi:10.1038/ncomms6909
PMCID: PMC4300525  PMID: 25600590
2.  Broad and direct interaction between TLR and Siglec families of pattern recognition receptors and its regulation by Neu1 
eLife  2014;3:e04066.
Both pathogen- and tissue damage-associated molecular patterns induce inflammation through toll-like receptors (TLRs), while sialic acid-binding immunoglobulin superfamily lectin receptors (Siglecs) provide negative regulation. Here we report extensive and direct interactions between these pattern recognition receptors. The promiscuous TLR binders were human SIGLEC-5/9 and mouse Siglec-3/E/F. Mouse Siglec-G did not show appreciable binding to any TLRs tested. Correspondingly, Siglece deletion enhanced dendritic cell responses to all microbial TLR ligands tested, while Siglecg deletion did not affect the responses to these ligands. TLR4 activation triggers Neu1 translocation to cell surface to disrupt TLR4:Siglec-E interaction. Conversely, sialidase inhibitor Neu5Gc2en prevented TLR4 ligand-induced disruption of TLR4:Siglec E/F interactions. Absence of Neu1 in hematopoietic cells or systematic treatment with sialidase inhibitor Neu5Gc2en protected mice against endotoxemia. Our data raised an intriguing possibility of a broad repression of TLR function by Siglecs and a sialidase-mediated de-repression that allows positive feedback of TLR activation during infection.
DOI: http://dx.doi.org/10.7554/eLife.04066.001
eLife digest
Many living things have an immune system that is able to detect invading bacteria, viruses and other pathogens and trigger a response targeted against the threat before it causes lasting damage. Cells employ a number of different receptors that can detect these pathogens or the molecules that they produce.
In animals, toll-like receptors (or TLRs) are a type of protein that recognizes patterns or structures that are found in many different types of pathogen, known as pathogen-associated molecular patterns (or PAMPs). Injured cells release proteins that are also recognized by toll-like receptors and are called danger associated molecular patterns (or DAMPs). An immune response is triggered when PAMPs and DAMPs are recognized, but the response must be properly controlled. If it goes awry, it can result in an over-activation of the immune cells that can lead to life-threatening conditions, one of which is called sepsis.
Siglecs are proteins that bind to a sugar molecule, which is found attached to many other proteins, and are known to inhibit the immune response. However, it remained unclear how Siglecs do this and if they can interact directly with toll-like receptors. Chen et al. now show that most (although not all) Siglecs bind to TLRs, and that deleting the gene for a Siglec protein that can bind to multiple TLRs boosted the response of the immune cells to a range of microbial PAMPs. Deleting the gene for another Siglec that did not bind to any TLRs had no effect on the immune response.
Chen et al. suggest that the Siglec proteins that interact with toll-like receptors act a bit like a brake that slows down the activation of the receptors. However, when an immune cell detects a foreign molecule through a TLR, an enzyme called Neu1 is relocated from the inside of the cell to the cell's surface, where it removes the sugar molecules from the TLRs. This disrupts the interaction between the TLRs and the Siglecs, thus activating the receptors and triggering an immune response against the invading pathogen or damaged cells. This represents a newly discovered mechanism that can regulate the signaling of TLRs.
Chen et al. also show that a chemical compound that stops the function of the Neu1 enzyme prevents the toll-like receptors—and hence the immune cells—from becoming overly activated. Mice treated with this compound are protected against sepsis triggered by the presence of a bacterial PAMP. These results suggest that the Neu1 enzyme may be a promising new target for treating sepsis; further work will now be required to assess the potential side effects caused by inhibiting this enzyme.
DOI: http://dx.doi.org/10.7554/eLife.04066.002
doi:10.7554/eLife.04066
PMCID: PMC4168287  PMID: 25187624
Siglec; toll-like receptor; sialidase; E. coli; mouse
3.  Ribosomal protein S27-like is a physiological regulator of p53 that suppresses genomic instability and tumorigenesis 
eLife  2014;3:e02236.
Cell-based studies showed that several Mdm2-binding ribosomal proteins, upon overexpression, stabilize and activate p53. In contrast, here we show in a mouse knockout study that Mdm2-binding ribosomal protein S27-like (Rps27l), upon disruption, activates p53. Germline inactivation of Rps27l triggers ribosomal stress to stabilize Mdm2, which degrades Mdm4 to reduce Mdm2-Mdm4 E3 ligase towards p53, leading to p53-dependent apoptotic depletion of hematopoietic stem cells and postnatal death, which is rescued by Trp53 deletion. Paradoxically, while increased p53 is expected to inhibit tumorigenesis, Rps27l−/−;Trp53+/− mice develop lymphomas at higher incidence with p53 loss-of-heterozygosity and severe genome aneuploidy, suggesting that Rps27l disruption impose a selection pressure against p53. Thus, Rps27l has dual functions in p53 regulation: under Trp53+/+ background, Rps27l disruption triggers ribosomal stress to induce p53 and apoptosis, whereas under Trp53+/− background, Rps27l disruption triggers genomic instability and Trp53 deletion to promote tumorigenesis. Our study provides a new paradigm of p53 regulation.
DOI: http://dx.doi.org/10.7554/eLife.02236.001
eLife digest
There are over a hundred different types of cancer that can affect humans; but, in general, all cancers are caused by mutations that cause cells to grow and divide abnormally. ‘Tumor suppressor genes’ are genes that normally protect a cell from genetic changes that can lead a cell towards becoming cancerous.
About half of all cancers in humans have a mutation in one of the two copies of a tumor suppressor gene that encodes a protein called p53, which helps to control how and when cells grow and divide. In normal cells, the p53 protein can be activated in various ways. Damage to a cell's DNA triggers p53 to stop the cell growing, which gives the cell time to repair the DNA damage. However, if the damage is too severe and cannot be repaired, p53 essentially causes the cell to kill itself, via a process called apoptosis. Furthermore, if a cell has problems building new copies of its protein-making machinery, some of the parts (called ribosomal proteins) that make up these molecular machines can also lead to p53 being activated.
By deleting the gene for a protein called Rps27l that is a newly characterized ribosomal protein, Xiong et al. have discovered that, in mice, Rps27I regulates the p53 protein in two different ways. In normal cells, Rps27l appears to inhibit p53, which is likely to encourage cancer to develop. But, if a cell has already lost a copy of the p53 gene—a situation that would normally encourage the cells to accrue further mutations and become cancerous—Rps27l acts as a tumor suppressor. In these mutated cells, the Rps27l protein helps to maintain the stability of the genome and prevent the loss of the second copy of gene for p53, and so protects the cell from becoming cancerous.
Thus Rps27l can either activate or inactivate p53 activity depending on how many copies of the gene for p53 remain intact. The next challenge is to investigate if Rps27l levels determine the early-onset of tumor development in cancer-prone cells seen in patients with Li-Fraumeni syndrome, who are born with a mutated copy of the p53 gene.
DOI: http://dx.doi.org/10.7554/eLife.02236.002
doi:10.7554/eLife.02236
PMCID: PMC4163686  PMID: 25144937
p53; Mdm2-Mdm4; ribosomal proteins; mouse knockout; aneuploidy; tumorigenesis; human; mouse
4.  Laforin Prevents Stress-Induced Polyglucosan Body Formation and Lafora Disease Progression in Neurons 
Molecular neurobiology  2013;48(1):49-61.
Glycogen, the largest cytosolic macromolecule, is soluble because of intricate construction generating perfect hydrophilic-surfaced spheres. Little is known about neuronal glycogen function and metabolism, though progress is accruing through the neurodegenerative epilepsy Lafora disease (LD) proteins laforin and malin. Neurons in LD exhibit Lafora bodies (LBs), large accumulations of malconstructed insoluble glycogen (polyglucosans). We demonstrated that the laforin-malin complex reduces LBs and protects neuronal cells against endoplasmic reticulum stress-induced apoptosis. We now show that stress induces polyglucosan formation in normal neurons in culture and in brain. This is mediated by increased glucose-6-phosphate allosterically hyperactivating muscle glycogen synthase (GS1), and is followed by activation of the glycogen digesting enzyme glycogen phosphorylase. In the absence of laforin, stress-induced polyglucosans are undigested and accumulate into massive LBs, and in laforin-deficient mice stress drastically accelerates LB accumulation and LD. The mechanism through which laforin-malin mediates polyglucosan degradation remains unclear but involves GS1 dephosphorylation by laforin. Our work uncovers the presence of rapid polyglucosan metabolism as part of the normal physiology of neuroprotection. We propose that deficiency in the degradative phase of this metabolism, leading to LB accumulation and resultant seizure predisposition and neurodegeneration, underlies LD.
doi:10.1007/s12035-013-8438-2
PMCID: PMC3722335  PMID: 23546741
Laforin; muscle glycogen synthase; polyglucosan; ER stress; neuron; Lafora body; Lafora disease; neurodegeneration
5.  Preserving Sialic Acid-dependent Pattern Recognition by CD24-Siglec G Interaction for Therapy of Polybacterial Sepsis 
Nature biotechnology  2011;29(5):428-435.
Control of inflammation is critical for therapy of infectious diseases. Pathogen-associated and/or danger-associated molecular patterns (PAMPs and DAMPs, respectively) are the two major inducers of inflammation. Because the CD24-Siglec G/10 interactions selectively repress inflammatory response to DAMPs, microbial disruption of the negative regulation would provide a general mechanism to exacerbate inflammation. Here we show that the sialic acid-based pattern recognitions of CD24 by Siglec G/10 are targeted by sialidases in polybacterial sepsis. Sialidase inhibitors protect mice against sepsis by a CD24-Siglecg-dependent mechanism, whereas a targeted mutation of either CD24 or Siglecg exacerbates sepsis. Bacterial sialidase and host CD24 and Siglecg genes interact to determine pathogen virulence. Our data demonstrate a critical role for disrupting sialic acid-based pattern recognitions in microbial virulence and suggest a therapeutic approach to dampen harmful inflammatory response during infection.
doi:10.1038/nbt.1846
PMCID: PMC4090080  PMID: 21478876
6.  mTOR Regulation and Therapeutic Rejuvenation of Aging Hematopoietic Stem Cells 
Science signaling  2009;2(98):ra75.
Age-related declines in hematopoietic stem cell (HSC) function may contribute to anemia, poor response to vaccination, and tumorigenesis. Here, we show that mammalian target of rapamycin (mTOR) activity is increased in HSCs from old mice compared to those from young mice. mTOR activation through conditional deletion of Tsc1 in the HSC of young mice mimicked the phenotype of HSC from aged mice in various ways. These included increased abundance of the mRNA encoding the CDK inhibitors p16Ink4a, p19Arf, and p21Cip1, a relative decrease in lymphopoiesis, and impaired capacity to reconstitute the hematopoietic system. In the old mice, rapamycin increased the life span, restored the self renewal and hematopoiesis of HSC, and enabled effective vaccination against a lethal challenge with influenza virus. Together, our data implicate mTOR signaling in HSC aging and demonstrate the potential of mTOR inhibitors for restoring hematopoiesis in the elderly.
doi:10.1126/scisignal.2000559
PMCID: PMC4020596  PMID: 19934433
7.  FOXP3 Regulates Sensitivity of Cancer Cells to Irradiation by Transcriptional Repression of BRCA1 
Cancer research  2013;73(7):10.1158/0008-5472.CAN-12-2481.
FOXP3 is an X-linked tumor suppressor gene and a master regulator in T regulatory cell function. This gene has been found to be mutated frequently in breast and prostate cancers and to inhibit tumor cell growth, but its functional significance in DNA repair has not been studied. We found that FOXP3 silencing stimulates homologous recombination-mediated DNA repair and also repair of γ-irradiation-induced DNA damage. Expression profiling and chromatin-immunoprecipitation analyses revealed that FOXP3 regulated the BRCA1-mediated DNA repair program. Among 48 FOXP3-regulated DNA repair genes, BRCA1 and 12 others were direct targets of FOXP3 transcriptional control. Site-specific interaction of FOXP3 with the BRCA1 promoter repressed its transcription. Somatic FOXP3 mutants identified in breast cancer samples had reduced BRCA1 repressor activity, while FOXP3 silencing and knock-in of a prostate cancer-derived somatic FOXP3 mutant increased the radioresistance of cancer cells. Together our findings provide a missing link between FOXP3 function and DNA repair programs.
doi:10.1158/0008-5472.CAN-12-2481
PMCID: PMC3815443  PMID: 23319807
8.  FOXP3: Genetic and Epigenetic Implications for Autoimmunity 
Journal of autoimmunity  2013;41:72-78.
FOXP3 plays an essential role in the maintenance of self-tolerance and, thus, in preventing autoimmune diseases. Inactivating mutations of FOXP3 cause immunodysregulation, polyendocrinopathy, and enteropathy, X-linked syndrome. FOXP3-expressing regulatory T cells attenuate autoimmunity as well as immunity against cancer and infection. More recent studies demonstrated that FOXP3 is an epithelial cell-intrinsic tumor suppressor for breast, prostate, ovary and other cancers. Corresponding to its broad function, FOXP3 regulates a broad spectrum of target genes. While it is now well established that FOXP3 binds to and regulates thousands of target genes in mouse and human genomes, the fundamental mechanisms of its broad impact on gene expression remain to be established. FOXP3 is known to both activate and repress target genes by epigenetically regulating histone modifications of target promoters. In this review, we first focus on germline mutations found in the FOXP3 gene among IPEX patients, then outline possible molecular mechanisms by which FOXP3 epigenetically regulates its targets. Finally, we discuss clinical implications of the function of FOXP3 as an epigenetic modifier. Accumulating results reveal an intriguing functional convergence between FOXP3 and inhibitors of histone deacetylases. The essential epigenetic function of FOXP3 provides a foundation for experimental therapies against autoimmune diseases.
doi:10.1016/j.jaut.2012.12.004
PMCID: PMC3622774  PMID: 23313429
9.  Cytopenia and Autoimmune Diseases: a Vicious Cycle fueled by mTOR Dysregulation in Hematopoietic Stem Cells 
Journal of autoimmunity  2013;41:182-187.
A long-standing but poorly understood defect in autoimmune diseases is dysfunction of the hematopoietic cells. Leukopenia is often associated with systemic lupus erythematous (SLE) and other autoimmune diseases. In addition, homeostatic proliferation of T cells, which is a host response to T cell lymphopenia, has been implicated as potential cause of rheumatoid arthritis (RA) in human and experimental models of autoimmune diabetes in the NOD mice and the BB rats. Conversely, successful treatments of aplastic anemia by immune suppression suggest that the hematologic abnormality may have a root in autoimmune diseases. Traditionally, the link between autoimmune diseases and defects in hematopoietic cells has been viewed from the prism of antibody-mediated hemolytic cytopenia. While autoimmune destruction may well be part of pathogenesis of defects in hematopoietic system, it is worth considering the hypothesis that either leukopenia or pancytopenia may also result directly from defective hematopoietic stem cells (HSC). We have recently tested this hypothesis in the autoimmune Scurfy mice which has mutation Foxp3, the master regulator of regulatory T cells. Our data demonstrated that due to hyperactivation of mTOR, the HSC in the Scurfy mice are extremely poor in hematopoiesis. Moreover, rapamycin, an mTOR inhibitor rescued HSC defects and prolonged survival of the Scurfy mice. Our data raised the intriguing possibility that targeting mTOR dysregulation in the HSC may help to break the vicious cycle between cytopenia and autoimmune diseases.
doi:10.1016/j.jaut.2012.12.011
PMCID: PMC3622805  PMID: 23375848
Cytopenia; homeostatic proliferation; CD24; mTOR; hematopoietic stem cells; autoimmune diseases; inflammatory cytokines; rapamycin
10.  A Critical Role for Rictor in T-lymphopoiesis1 
Apart from a critical role for Notch and pre-TCR, the signaling pathway required for T-lymphopoiesis is largely unknown. Given the potential link between Notch and mTOR signaling in cancer cells, we used mice with conditional deletion of either Raptor or Rictor genes to determine potential contribution of the mTOR complex I and II in T-lymphopoiesis. Our data demonstrated that targeted mutation of Rictor in the thymocytes drastically reduced the thymic cellularity, primarily by reducing proliferation of the immature thymocytes. Rictor-deficiency caused a partial block of thymocyte development at the double negative 3 stage. The effect of Rictor deficiency is selective for the T cell lineage, as the development of B cells, erythorocytes and myeloid cells are largely unaffected. Analysis of bone marrow chimera generated from a mixture of WT and Rictor-deficient hematopoietic stem cells demonstrated that the function of Rictor is cell-intrinsic. These data revealed a critical function of TORC2 in T-lymphopoiesis.
doi:10.4049/jimmunol.1201057
PMCID: PMC3412163  PMID: 22815285
11.  Laforin is Required for the Functional Activation of Malin in Endoplasmic Reticulum Stress Resistance in Neuronal Cells 
The FEBS journal  2012;279(14):2467-2478.
Mutations in either EPM2A, the gene encoding a dual-specificity phosphatase named laforin, or NHLRC1, the gene encoding an E3 ubiquitin ligase named malin, cause Lafora disease (LD) in humans. LD is a fatal neurological disorder characterized by progressive myoclonus epilepsy, severe neurological deterioration, and accumulation of poorly branched glycogen inclusions, called Lafora bodies (LBs) or polyglucosan bodies (PGBs), within the cell cytoplasm. The molecular mechanism underlying the neuropathogenesis of LD remains unknown. Here we present data demonstrating that in the cells expressing low levels of laforin protein, overexpressed malin and its LD-causing missense mutants are stably polyubiquitinated. Malin and malin mutants form ubiquitin-positive aggregates in or around the nuclei of the cells in which they are expressed. Neither wild type (WT) malin nor its mutants elicit endoplasmic reticulum (ER) stress, although the mutants exaggerate the response to ER stress. Overexpressed laforin impairs the polyubiquitination of malin and recruits malin to PGBs. The recruitment and activities of laforin and malin are both required for the PGB disruption. Consistently, targeted deletion of laforin in brain cells from Epm2a knockout (KO) mice increases polyubiquitinated proteins. Knockdown of Epm2a or Nhlrc1 in neuronal Neuro2a cells shows that they cooperate to allow cells to resist ER stress and apoptosis. These results reveal that a functional laforin-malin complex plays a critical role in destroying LB and relieving ER stress, implying that a causative pathogenic mechanism underlies their deficiency in LD.
doi:10.1111/j.1742-4658.2012.08627.x
PMCID: PMC3407668  PMID: 22578008
Laforin; Malin; Endoplasmic Reticulum Stress; Neuronal Cells and Polyglucosan
12.  CD24 on thymic antigen presenting cells regulates negative selection of myelin antigen specific T lymphocytes 
European Journal of Immunology  2012;42(4):924-935.
Negative selection plays a key role in the clonal deletion of autoreactive T cells in the thymus. However, negative selection is incomplete; as high numbers of autoreactive T cells can be detected in normal individuals, mechanisms that regulate negative selection must exist. In this regard, we previously reported that CD24, a GPI-anchored glycoprotein, is required for thymic generation of autoreactive T lymphocytes. The CD24-deficient 2D2 TCR transgenic mice (2D2+CD24-/-), whose TCR recognizes myelin oligodendrocyte glycoprotein (MOG), fail to generate functional 2D2 T cells. However, it was unclear if the CD24 function involved regulation of negative selection, and if so, what cellular mechanisms were involved. Here we show that elimination of MOG or Aire gene expression in 2D2+CD24-/- mice - through the creation of 2D2+CD24-/-MOG-/- or 2D2+CD24-/-Aire-/-mice - completely restores thymic cellularity and function of 2D2 T cells. Restoration of CD24 expression on dendritic cells (DCs), but not on thymocytes also partially restores 2D2 T-cell generation in 2D2+CD24-/- mice. Taken together, we propose that CD24 expression on thymic antigen presenting cells (mTECs, DCs) down-regulates autoantigen-mediated clonal deletion of autoreactive thymocytes.
doi:10.1002/eji.201142024
PMCID: PMC3359065  PMID: 22213356
13.  FOXP3 Orchestrates H4K16 Acetylation and H3K4 Tri-Methylation for Activation of Multiple Genes through Recruiting MOF and Causing Displacement of PLU-1 
Molecular cell  2011;44(5):770-784.
SUMMARY
Both H4K16 acetylation and H3K4 tri-methylation are required for gene activation. However, it is still largely unclear how these modifications are orchestrated by transcriptional factors. Here we analyzed the mechanism of the transcriptional activation by FOXP3, an X-linked suppressor of autoimmune diseases and cancers. FOXP3 binds near transcriptional start sites of its target genes. By recruiting MOF and displacing histone H3K4 demethylase PLU-1, FOXP3 increases both H4K16 acetylation and H3K4 tri-methylation at the FOXP3-associated chromatins of multiple FOXP3-activated genes. RNAi-mediated silencing of MOF reduced both gene activation and tumor suppression by FOXP3, while both somatic mutations in clinical cancer samples and targeted mutation of FOXP3 in mouse prostate epithelial disrupted nuclear localization of MOF. Our data demonstrate a pull-push model in which a single transcription factor orchestrates two epigenetic alterations necessary for gene activation and provide a mechanism for somatic inactivation of the FOXP3 protein function in cancer cells.
doi:10.1016/j.molcel.2011.10.012
PMCID: PMC3243051  PMID: 22152480
14.  The Tuberous Sclerosis Complex -mTOR Pathway Maintains the Quiescence and Survival of Naïve T Cells 
Naïve T cells receive stimulation from the positive selecting ligand in the periphery for their survival. This stimulation does not normally lead to overt activation of T cells, as the T cells remain largely quiescent until they receive either antigenic or lymphopenic stimuli. The underlying mechanism responsible for survival and quiescence of the naïve T cells remain largely unknown. Here we report that T cell-specific deletion of Tsc1, a negative regulator of mTOR, resulted in both spontaneous losses of quiescence and cellularity, especially within the CD8 subset. The Tsc1-deficient T cells have increased cell proliferation and apoptosis. Tsc1 deletion affects the survival and quiescence of T cells in the absence of antigenic stimulation. Loss of quiescence but not cellularity was inhibited by rapamycin. Our data demonstrate that TSC-mTOR maintains quiescence and survival of T cells.
doi:10.4049/jimmunol.1003968
PMCID: PMC3151493  PMID: 21709159
15.  A hypermorphic SP1-binding CD24 variant associates with risk and progression of multiple sclerosis 
A large number of risk alleles have been identified for multiple sclerosis (MS). However, how genetic variations may affect pathogenesis remains largely unknown for most risk alleles. Through direct sequencing of CD24 promoter region, we identified a cluster of 7 new single nucleotide polymorphisms in the CD24 promoter. A hypermorphic haplotype consisting of 3 SNPs was identified through association studies consisting of 935 control and 764 MS patients (P=0.001, odds ratio 1.3). The variant is also associated with more rapid progression of MS (P=0.016, log rank test). In cells that are heterozygous for the risk allele, chromatin immunoprecipitation revealed that risk allele specifically bind to a transcription factor SP1, which is selectively required for the hypermorphic promoter activity of the variant. In MS patients, the CD24 transcript levels associate with the SP1-binding variant in a dose-dependent manner (P=7x10-4). Our data revealed a potential role for SP1-mediated transcriptional regulation in MS pathogenesis.
PMCID: PMC3426393  PMID: 22937211
Multiple sclerosis (MS); SP-binding CD24; promoter; risk alleles; single nucleotide polymorphisms (SNP)
16.  α-Lactosylceramide as a novel “sugar-capped” CD1d ligand for Natural Killer T-cells: biased cytokine profile and therapeutic activities 
Chembiochem  2008;9(9):1423-1430.
The iNKT cells have emerged as an important regulator for immunity to infection, cancer as well as autoimmune diseases. The iNKT cells can be activated by glycolipids binding CD1d. The most effective iNKT ligand reported to date is α-galactosylceramide (α-GalCer) which stimulates iNKT cells to secrete both Th-1 and Th-2 cytokines. Indiscriminative induction of both types of cytokines may limit the therapeutic potential of iNKT ligands, as Th-1 and Th-2 cytokines play different roles under physiological and pathological conditions. Therefore a ligand with a biased cytokine release profile is highly desirable. Here we report the synthesis and biological activity of α-lactosylceramide (α-LacCer). Our data demonstrates that the α-LacCer can stimulate the iNKT cells to proliferate and release cytokines, both in vitro and in vivo. Interestingly, while α-LacCer is approximately 1,000-fold less efficient in inducing Th-1 cytokine, it is as potent as α-GalCer in the induction of Th-2 cytokine. Thus, α-LacCer is a novel compound that induces a biased cytokine release. The processing by β-glycosidase was critical for α-LacCer activity. Moreover, in experimental therapies, α-LacCer is at least as potent as α-GalCer in the treatment of tumors and experimental autoimmune encephalomyelitis.
doi:10.1002/cbic.200700625
PMCID: PMC3398384  PMID: 18478523
α-GalCer; α-LacCer; iNKT cell; glycolipids; CD1d
17.  Targeting HIF1α eliminates cancer stem cells in hematological malignancies 
Cell stem cell  2011;8(4):399-411.
Molecular targeting of cancer stem cells has therapeutic potential for efficient treatment of cancer although relatively few specific targets have so far been identified. Hypoxia-inducible factor was recently shown to regulate tumorigenic capacity of glioma stem cells under hypoxic condition. Surprisingly, we found that, under normoxia, HIF1α signaling was selectively activated in the stem cells of mouse lymphoma and human acute myeloid leukemia (AML). HIF1a ShRNA and HIF inhibitors abrogated the colony forming unit activity of mouse lymphoma and human AML CSCs. Importantly, the HIF inhibitor echinomycin efficiently eradicated mouse lymphoma and serially transplantable human AML in xenogeneic model by preferential elimination of CSCs. HIF1α maintains mouse lymphoma CSCs by repressing a negative feedback loop in the Notch pathway. Taken together, our results demonstrate an essential function of HIF1α-Notch interaction in maintaining CSCs and provide an effective approach to target CSCs for therapy of hematological malignancies.
doi:10.1016/j.stem.2011.02.006
PMCID: PMC3084595  PMID: 21474104
18.  Identification of a Tumor Suppressor Relay between the FOXP3 and the Hippo Pathways in Breast and Prostate Cancers 
Cancer research  2011;71(6):2162-2171.
Summary
Defective expression of LATS2, a negative regulator of YAP onco-protein, has been reported in cancer of prostate, breast, liver, brain and blood origins. However, no transcriptional regulators for the LATS2 gene have been identified. Defective expression of LATS2, a negative regulator of YAP oncoprotein, has been reported in prostate, breast, liver, brain and blood cancers. However, the basis for LATS2 dysregulation in cancer is undefined. Here we report that spontaneous mutation of the transcription factor FOXP3 reduces expression of the LATS2 gene in mammary epithelial cells. shRNA-mediated silencing of FOXP3 in normal or malignant mammary epithelial cells of mouse and human origin repressed LATS2 expression and increased YAP protein levels. LATS2 induction required binding of FOXP3 to a specific sequence in the LATS2 promoter, and this interaction contributed to FOXP3-mediated growth inhibition of tumor cells. In support of these results, reduced expression and somatic mutations of FOXP3 correlated strongly with defective LATS2 expression in microdissected prostate cancer tissues. Thus, defective expression of LATS2 is attributable to FOXP3 defects and may be a major independent determinant of YAP protein elevation in cancer. Our findings identify a novel mechanism of LATS2 downregulation in cancer and reveal an important tumor suppressor relay between the FOXP3 and HIPPO pathways which are widely implicated in human cancer.
doi:10.1158/0008-5472.CAN-10-3268
PMCID: PMC3070402  PMID: 21278236
prostate cancer; breast cancer; Hippo pathway; FoxP3; tumor suppressor genes
19.  Sialoside-based Pattern Recognitions Discriminating Infections from Tissue Injuries 
Current opinion in immunology  2011;23(1):41-45.
Summary
Recognition of pathogens-associated molecular patterns (PAMPs) by Toll-like receptors (TLR), NOD-like receptors (NLR) and RIG-I-like receptors (RLR) plays a critical role in protecting host against pathogens. In addition, TLR and NLR also recognize danger-associated molecular patterns (DAMPs) to initiate limited innate immune responses. While innate immune response to DAMPs may be important for tissue repairs and wound healing, it is normally well controlled to avoid autoimmune destruction. Recent data support a role for sialoside-based pattern recognition by members of the Siglec family to attenuate innate immunity. In particular, since CD24-Siglec 10/G interaction selectively dampens host response to DAMPs but not PAMPs, this sialoside-based pattern recognition may serve as a foundation to discriminate PAMPs from DAMPs.
doi:10.1016/j.coi.2010.10.004
PMCID: PMC3042481  PMID: 21208791
20.  Signalling through FOXP3 as an X-linked Tumor Suppressor 
The FOXP3 (forkhead box P3) gene is a member of forkhead winged helix family transcription factors and functions as both a transcriptional activator and a repressor. FOXP3 dysfunction is responsible for an X-linked autoimmune syndrome: immune dysregulation, polyendopathy, enterophathy, X-linked syndrome. In addition to its role as an essential transcription factor in regulatory T cells, the FOXP3 gene is an epithelial cell-intrinsic tumor suppressor for breast and prostate cancers. We will focus on the FOXP3 signalling pathway in epithelial cells and discuss how genetic and/or epigenetic inactivation of the FOXP3 contributes to the malignant transformation of cells.
doi:10.1016/j.biocel.2010.07.015
PMCID: PMC2950213  PMID: 20678582
FOXP3; epithelial cell; X-linked tumor suppressor gene; breast cancer; prostate cancer
21.  X-linked Tumor Suppressors: Perplexing Inheritance, a unique Therapeutic Opportunity 
Trends in genetics : TIG  2010;26(6):260-265.
Unlike autosomal genes, the majority of X-linked genes are subject to dosage compensation. As a result, female tissues are comprised of cells exclusively expressing X-linked genes from one or the other parent. The implication of having only one allele of active X-linked genes in cancer pathogenesis, i.e. somatic single-hit inactivation and dominant inheritance has not been explored extensively. Recent studies identified FOXP3 and WTX as two X-linked tumor suppressor genes that are somatically inactivated by single genetic hits. Because the predicted dominant inheritance of cancer risk has not been demonstrated in human, we discuss possible conditions that might prevent such dominant inheritance. We also argue that the existence of a genetically intact allele in cancer cells in women, together with apparent abnormal X-inactivation in cancer cells, might provide an opportunity to selectively reactivate tumor suppressor genes for cancer therapy.
doi:10.1016/j.tig.2010.03.004
PMCID: PMC2901104  PMID: 20434787
22.  CD24-Siglec G/10 discriminates danger- from pathogen-associated molecular patterns 
Trends in immunology  2009;30(12):557-561.
It is now well accepted that the innate immune system recognizes both damage (or danger)- and pathogen-associated molecular patterns (DAMP and PAMP, respectively) through pattern recognition receptors, such as Toll-like receptors (TLR) and/or Nod-like receptors (NLR). Less clear are whether and how the response to PAMP and DAMP are differentially regulated. The answers may reveal whether the primary goal of the immune system is to defend against infections or to alert the host of tissue injuries. We demonstrated recently that the host response to DAMP is controlled by a DAMP-CD24-Siglec axis. Here we propose a key role for the CD24-Siglec pathway in discriminating between DAMPs and PAMPs.
doi:10.1016/j.it.2009.09.006
PMCID: PMC2788100  PMID: 19786366
23.  Mammalian target of rapamycin activation underlies HSC defects in autoimmune disease and inflammation in mice 
The Journal of Clinical Investigation  2010;120(11):4091-4101.
The mammalian target of rapamycin (mTOR) is a signaling molecule that senses environmental cues, such as nutrient status and oxygen supply, to regulate cell growth, proliferation, and other functions. Unchecked, sustained mTOR activity results in defects in HSC function. Inflammatory conditions, such as autoimmune disease, are often associated with defective hematopoiesis. Here, we investigated whether hyperactivation of mTOR in HSCs contributes to hematopoietic defects in autoimmunity and inflammation. We found that in mice deficient in Foxp3 (scurfy mice), a model of autoimmunity, the development of autoimmune disease correlated with progressive bone marrow loss and impaired regenerative capacity of HSCs in competitive bone marrow transplantation. Similarly, LPS-mediated inflammation in C57BL/6 mice led to massive bone marrow cell death and impaired HSC function. Importantly, treatment with rapamycin in both models corrected bone marrow hypocellularity and partially restored hematopoietic activity. In cultured mouse bone marrow cells, treatment with either of the inflammatory cytokines IL-6 or TNF-α was sufficient to activate mTOR, while preventing mTOR activation in vivo required simultaneous inhibition of CCL2, IL-6, and TNF-α. These data strongly suggest that mTOR activation in HSCs by inflammatory cytokines underlies defective hematopoiesis in autoimmune disease and inflammation.
doi:10.1172/JCI43873
PMCID: PMC2964994  PMID: 20972332
24.  Transgenic Expression of P1A Induced Thymic Tumor: A Role for Onco-Fetal Antigens in Tumorigenesis 
PLoS ONE  2010;5(10):e13439.
P1A is the first known tumor rejection antigen. It is expressed in embryonic stem cells and multiple tumors but is silent in adult tissues except for the testis and placenta. Therefore, P1A represents a prototype for onco-fetal antigens. To test the potential function of P1A in tumorigenesis, we used a transgenic mouse expressing P1A in lymphoid cells. We observed that immunodeficient host P1A transgenic mice developed thymic tumors after 7 months of age and had shorter survival rates compared to control groups. Most of the 7 examined tumors displayed B cell lineage markers. The P1A transgenic bone marrow cells had higher proliferation ability and more potential progenitors compared to control bone marrow cells. To our knowledge, our data provided the first example that onco-fetal antigen can promote tumorigenesis.
doi:10.1371/journal.pone.0013439
PMCID: PMC2955541  PMID: 20976169
25.  Somatic Single-hits Inactivate the X-linked Tumor Suppressor FOXP3 in the Prostate 
Cancer cell  2009;16(4):336-346.
Despite clear epidemiological and genetic evidence for X-linked prostate cancer risk, all prostate cancer genes identified are autosomal. Here we report somatic inactivating mutations and deletion of the X-linked FOXP3 gene residing at Xp11.23 in human prostate cancer. Lineage-specific ablation of FoxP3 in the mouse prostate epithelial cells leads to prostate hyperplasia and prostate intraepithelial neoplasia. In both normal and malignant prostate tissues, FOXP3 is both necessary and sufficient to transcriptionally repress cMYC, the most commonly over-expressed oncogene in prostate cancer as well as among the aggregates of other cancers. FOXP3 is an X-linked prostate tumor suppressor in the male. Since the male has only one X chromosome, our data represents a paradigm of “single-genetic-hit” inactivation-mediated carcinogenesis.
doi:10.1016/j.ccr.2009.08.016
PMCID: PMC2758294  PMID: 19800578

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