Cancer genetics: activated notch takes center stage in T-cell leukemogenesis.
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Animals↗
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Notch-1 and Notch-2 exhibit unique patterns of expression in human B-lineage cells.
The Notch genes encode a conserved family of receptors that influence developmental fate in many species. Prior studies have indicated that Notch-1 and Notch-2 signaling influence the development of hematopoietic stems cells and thymocytes, but little is known regarding Notch expression and function in B-lineage cells. We analyzed the expression of Notch receptors and Notch ligands in human B-lineage cells and bone marrow (BM) stromal cells. Notch-1 mRNA and protein is expressed throughout normal B cell development and in leukemic B-lineage cells. In contrast, Notch-2 expression is limited to pre-B cells expressing low levels of surface mu. The Notch ligand Delta is expressed in BM B-lineage cells. The Notch ligand Jagged-1 is not expressed in B-lineage cells, but is expressed in BM stromal cells. These results suggest a model wherein lateral signaling between Notch and Delta on B-lineage cells and/or Notch/Jagged-1 interactions between B-lineage cells and BM stromal cells may regulate human B cell development.
Animals↗
Notch-1 induction, a novel activity of SV40 required for growth of SV40-transformed human mesothelial cells.
We show that SV40 infection of human mesothelial cells directly causes overexpression of Notch-1, a key cell regulatory gene. Notch-1 induction is achieved at the transcriptional level and requires both the SV40 large T-antigen and the small t-antigen. Notch-1 upregulation is maintained in SV40-transformed human mesothelial clones and in SV40-positive mesotheliomas and derived cell lines. Activation of Notch-1 promotes cell cycle progression and it is required for the growth of SV40-transformed mesothelial cells. Our finding is relevant to the process of SV40-mediated human cell transformation, an effect that cannot be accounted for solely by SV40-Tag inhibition of Rb and p53.
Cell Line, Transformed↗
Induction of Notch signaling by tumor necrosis factor in rheumatoid synovial fibroblasts.
Rheumatoid arthritis (RA) is characterized by progressive inflammation associated with abberrant proliferation of synoviocytes. In order to explore the characteristics of rheumatoid synovial fibroblasts (RSF), we performed the comparative gene expression profile analysis between RSF and normal synovial fibroblasts (NSF) upon tumor necrosis factor (TNF) stimulation. As an initial screening for the genes preferentially induced by TNF in RSF compared with NSF, we have adopted a cDNA array containing well-defined sets of genes responsible for cell growth, cell fate determination, and cellular invasiveness. Differentially expressed genes of interest were confirmed using real-time RT-PCR. We found that TNF induced the expression of Notch-1, Notch-4, and Jagged-2 in RSF. The expression of these proteins was detected in the RA synovial tissues. The nucleus of RA synoviocytes showed strong staining with anti-Notch-1 and Notch-4 antibody. TNF induced the nuclear translocation of Notch intracellular domain in RSF, indicating the elicitation of the Notch signaling. Notch-1, Notch-4, and Jagged-2 proteins were also detected in the developing synovium of mouse embryo. Thus, RSF may have re-acquired the primordial phenotype, accounting for the hyperproliferation and aggressive invasiveness, exhibiting tumor-like phenotype.
Active Transport, Cell Nucleus↗
An essential role of Pak1 phosphorylation of SHARP in Notch signaling.
The p21-activated kinases (Paks), an evolutionarily conserved family of serine/threonine kinases, play an important role in cytoskeletal reorganization in mammalian cells. The Notch signaling pathway plays an important role in the determination of cell fate/differentiation in a number of organs. Notch signaling is a complex process, and the mechanism by which Notch regulates multiple cellular processes is intriguing. The expression of both Notch and Pak1 has been shown to be deregulated in several human cancers. Using yeast two-hybrid screening, we identified SHARP, one of the Notch signaling components, as a Pak1-interacting protein. We found that SHARP is a physiologic interacting substrate of Pak1, and that this interaction enhances SHARP-mediated repression of Notch target genes. Pak1 phosphorylation sites in SHARP were mapped to Ser3486 and Thr3568 within the SHARP repression domain. Mutation of Pak1 phosphorylation sites in SHARP, inhibition of Pak1 functions by a Pak1-autoinhibitory fragment (amino acids 83-149), or expression of Pak1-specific siRNA interfered with SHARP-mediated repression of Notch target reporter gene activation. These results demonstrate that Pak1-SHARP interaction plays an essential role in enhancing the corepressor functions of SHARP, thereby modulating Notch signaling in human cancer cells.
3T3 Cells↗
A novel cell line derived from de novo acute myeloblastic leukaemia with trilineage myelodysplasia which proliferates in response to a Notch ligand, Delta-1 protein.
A novel human leukaemia cell line, designated TMD7, was established from blast cells of a patient with de novo acute myeloblastic leukaemia with trilineage myelodysplasia (AML/TLD). As seen in the original blast cells, TMD7 cells expressed CD7, CD13, CD33 and CD34 and showed an abnormal karyotype containing -5, -7, -8, der(16)t(10;16)(q22;q13). The cells proliferated without added growth factors. Growth was stimulated with the addition of granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF) and interleukin 3. Differentiation was not observed with the addition of various cytokines. As a cell line derived from AML/TLD has not been reported, TMD7 will be a useful tool as a model of AML/TLD cells. Recently, it was reported that the Notch system has crucial roles to regulate the self-renewal and differentiation of haematopoietic stem cells. We found that TMD7 cells expressed Notch-1 and Notch-2 mRNA. The exposure to recombinant Delta-1 protein, which was one of the Notch ligands, significantly stimulated the growth of TMD7 cells. This is the first human cell line which was shown to proliferate in response to Delta-1, without artificially expressed Notch protein. Therefore, TMD7 will also be a useful tool to study the mechanism of the Notch-Notch ligand interaction.
Calcium-Binding Proteins↗
Induction of thymocyte positive selection does not convey immediate resistance to negative selection.
The acquisition of functional competence represents a critical phase during intrathymic development of T cells. Thymocytes reaching this stage represent cells which have been positively selected on the basis of major histocompatibility complex reactivity, but which have also been purged of potentially autoreactive T-cell receptor specificities by negative selection. While the developmental window in which thymocytes are subjected to positive selection is now well defined, the precise developmental timing of negative selection, in relation to positive selection events, is less clear. Moreover, the underlying mechanism allowing single-positive thymocytes to respond to T-cell receptor ligation by activation rather than death, remains controversial. Here we have analysed the developmental timing of negative selection in relation to positive selection, using measurement of thymocyte susceptibility to dendritic cell presentation of the superantigen staphylococcal enterotoxin B (SEB). We show that thymocytes which have received initial positive selection signals, namely CD4+ CD8+ CD69+ thymocytes, like their CD4+ CD8+ CD69minus sign precursors, are susceptible to negative selection, indicating that induction of positive selection does not convey immediate resistance to negative selection. In contrast, newly generated CD4+ CD8minus sign CD69+ cells are not only resistant to deletion by SEB, but respond to SEB-mediated T-cell receptor-ligation by activation, indicating that the acquisition of functional competence occurs at the newly generated CD4+ CD8minus sign CD69+ stage. Finally, by using direct retroviral infection of primary CD4+ CD8+ thymocytes, we also show that Notch-1 activation in CD4+ CD8+ thymocytes does not correlate with, nor convey resistance to superantigen-mediated negative selection. Thus, our data suggest that although Notch-1 has been implicated in resistance to thymocyte apoptosis, the acquisition of resistance to negative selection occurs independently of Notch-1 signalling.
Animals↗
Musashi1, an evolutionarily conserved neural RNA-binding protein, is a versatile marker of human glioma cells in determining their cellular origin, malignancy, and proliferative activity.
Tumor cells often express phenotypic markers that are specific to the cells from which they originated. A neural RNA-binding protein, Musashil, is an evolutionarily well-conserved marker for neural stem cells/ progenitor cells. To examine the origin of gliomas, we examined the expression of the human Musashil homolog, MSI1, in human glioma tissues and in normal human adult and fetal brains. As we had seen previously in rodents, in the normal human brain, MSI1 was expressed in cells located in the ventricular and subventricular zones, in GFAP-negative glial cells, and in GFAP-positive astrocytes. In glioblastomas, MSI1 was expressed in GFAP-negative tumor cells forming foci that were clearly demarcated and surrounded by GFAP-positive cells. Tumor cells arranged in pseudopalisades were also strongly immunoreactive with MSI1 antibodies. The percentage of MSI1-labeled tumor cells increased in higher-grade astrocytomas and correlated with proliferative activity, as estimated by an MIB-1 staining index. Our results indicate that MSI1 is an excellent marker for neural progenitor cells including neural stem cells in normal human brains. Furthermore, the expression of MSI1 correlates well with the immature nature as well as the malignancy of tumor cells in human gliomas. Thus, we expect the analysis of MSI1 expression to contribute to the understanding of the cellular origin and biology of human gliomas.
Adult↗
The distribution of Notch receptors and their ligands during articular cartilage development.
We examined the distribution of Notch family members and their ligands during the development of articular cartilage and the growth plate. Notch 1 was expressed by the chondrocytes of the developing articular surface but became increasingly restricted to the deeper layers after birth whilst expression of this family member was restricted to hypertrophic chondrocytes in the growth plate. Notch 2 and 4, Delta and Jagged 2 showed a broadly similar distribution, being present throughout the articular cartilage during development and becoming increasingly restricted to deeper layers with age. Hypertrophic chondrocytes within the growth plate also expressed Notch 2 and 4, Delta and Jagged 2 (which was also expressed in prehypertrophs). Notch 3 and Jagged 1 were absent from developing articular cartilage but were present in deeper layers at later time points (> 1 month) and both receptor and ligand were expressed in hypertrophic chondrocytes at all ages examined. These results highlight the complex Notch signalling interactions that result in the formation of the heterogeneous articular cartilage and allow for the co-ordinated ossification and elongation of the growth plate. Mechanisms by which these processes are controlled are discussed in light of recent advances in the understanding of Notch signalling pathways.
Animals↗
X11alpha impairs gamma- but not beta-cleavage of amyloid precursor protein.
The phosphotyrosine binding domain of the neuronal protein X11alpha/mint-1 binds to the C-terminus of amyloid precursor protein (APP) and inhibits catabolism to beta-amyloid (Abeta), but the mechanism of this effect is unclear. Coexpression of X11alpha or its PTB domain with APPswe inhibited secretion of Abeta40 but not APPsbetaswe, suggesting inhibition of gamma- but not beta-secretase. To further probe cleavage(s) inhibited by X11alpha, we coexpressed beta-secretase (BACE-1) or a component of the gamma-secretase complex (PS-1Delta9) with APP, APPswe, or C99, with and without X11alpha, in HEK293 cells. X11alpha suppressed the PS-1Delta9-induced increase in Abeta42 secretion generated from APPswe or C99. However, X11alpha did not impair BACE-1-mediated proteolysis of APP or APPswe to C99. In contrast to impaired gamma-cleavage of APPswe, X11alpha or its PTB domain did not inhibit gamma-cleavage of NotchDeltaE to NICD (the Notch intracellular domain). The X11alpha PDZ-PS.1Delta9 interaction did not affect gamma-cleavage activity. In a cell-free system, X11alpha did not inhibit the catabolism of APP C-terminal fragments. These data suggest that X11alpha may inhibit Abeta secretion from APP by impairing its trafficking to sites of active gamma-secretase complexes. By specifically targeting substrate instead of enzyme X11alpha may function as a relatively specific gamma-secretase inhibitor.
Adaptor Proteins, Signal Transducing↗
Inducible nitric oxide synthase up-regulates Notch-1 in mouse cholangiocytes: implications for carcinogenesis.
BACKGROUND & AIMS: Inflammatory mediators and cell fate genes, such as the Notch gene family, both have been implicated in cancer biology. Because cholangiocarcinomas arise in a background of inflammation and express the inflammatory mediator inducible nitric oxide synthase (iNOS), we aimed to determine whether iNOS expression alters Notch expression and signaling. METHODS: Notch receptor and ligand expression in human liver was evaluated by immunohistochemistry. The effect of iNOS and NO on Notch-1 expression was examined in cell lines. RESULTS: Notch-1, but not other Notch receptors, were up-regulated by cholangiocytes in primary sclerosing cholangitis and cholangiocarcinoma. The colocalization of Notch-1 and iNOS also was observed in large bile ducts from the hilar region of primary sclerosing cholangitis patients. Notch-1 expression in murine cholangiocytes was iNOS dependent. iNOS expression also facilitated Notch signaling by inducing the nuclear translocation of its intracellular domain and the expression of a transcriptional target, hairy and enhancer of split (Hes)-1. The gamma-secretase inhibitor N-[N-(3,5-Difluorophenacetyl-L-alanyl)-S-phenylglycine]-t-butyl ester, which blocks Notch signaling, enhanced tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in cholangiocarcinoma cells. CONCLUSIONS: These data implicate a direct link between the inflammatory mediator iNOS and Notch signaling, and have implications for the development and progression of cholangiocarcinoma.
Adenocarcinoma↗
Defective cardiovascular development and elevated cyclin E and Notch proteins in mice lacking the Fbw7 F-box protein.
The mammalian F-box protein Fbw7 and its Caenorhabditis elegans counterpart Sel-10 have been implicated in the ubiquitin-mediated turnover of cyclin E as well as the Notch/Lin-12 family of transcriptional activators. Both unregulated Notch and cyclin E promote tumorigenesis, and inactivating mutations in human Fbw7 suggest that it may be a tumor suppressor. To generate an in vivo system to assess the consequences of such unregulated signaling, we generated mice deficient for Fbw7. Fbw7-null mice die around 10.5 days post coitus because of a combination of deficiencies in hematopoietic and vascular development and heart chamber maturation. The absence of Fbw7 results in elevated levels of cyclin E, concurrent with inappropriate DNA replication in placental giant trophoblast cells. Moreover, the levels of both Notch 1 and Notch 4 intracellular domains were elevated, leading to stimulation of downstream transcriptional pathways involving Hes1, Herp1, and Herp2. These data suggest essential functions for Fbw7 in controlling cyclin E and Notch signaling pathways in the mouse.
Animals↗
Notch-1 activation and dendritic atrophy in prion disease.
In addition to neuronal vacuolation and astrocytic hypertrophy, dendritic atrophy is a prominent feature of prion disease. Because increased Notch-1 expression and cleavage releasing its intracellular domain (NICD) inhibit both dendrite growth and maturation, we measured their levels in brains from mice inoculated with Rocky Mountain Laboratory (RML) prions. The level of NICD was elevated in the neocortex, whereas the level of beta-catenin, which stimulates dendritic growth, was unchanged. During the incubation period, levels of the disease-causing prion protein isoform, PrPSc, and NICD increased concomitantly in the neocortex. Additionally, increased levels of Notch-1 mRNA and translocation of NICD to the nucleus correlated well with regressive dendritic changes. In scrapie-infected neuroblastoma (ScN2a) cells, the level of NICD was elevated compared with uninfected control (N2a) cells. Long neurofilament protein-containing processes extended from the surface of N2a cells, whereas ScN2a cells had substantially shorter processes. Transfection of ScN2a cells with a Notch-1 small interfering RNA decreased Notch-1 mRNA levels, diminished NICD concentrations, and rescued the long process phenotype. These results suggest that PrPSc in neurons and in ScN2a cells activates Notch-1 cleavage, resulting in atrophy of dendrites in the CNS and shrinkage of processes on the surface of cultured cells. Whether diminishing Notch-1 activation in vivo can prevent or even reverse neurodegeneration in prion disease remains to be established.
Active Transport, Cell Nucleus↗
Direct regulation of intestinal fate by Notch.
The signals that maintain the proper balance between adult intestinal cell types are poorly understood. Loss-of-function studies have implicated the Notch pathway in the regulation of intestinal fate during development. However, it is unknown whether Notch has a role in maintaining the balance of different cell types in the adult intestine and whether it acts reversibly. To determine whether Notch has a direct effect on intestinal development and adult intestinal cell turnover, we have used a gain-of-function approach to activate Notch. Ectopic Notch signaling in adult intestinal progenitor cells leads to a bias against secretory fates, whereas ectopic Notch activation in the embryonic foregut results in reversible defects in villus morphogenesis and loss of the proliferative progenitor compartment. We conclude that Notch regulates adult intestinal development by controlling the balance between secretory and absorptive cell types. In the embryo, Notch activation perturbs morphogenesis, possibly through effects on stem or progenitor cells.
Animals↗
RNAs induced by Epstein-Barr virus nuclear antigen 2 in lymphoblastoid cell lines.
Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) association with RBP-Jkappa is essential for regulation of virus and cell gene transcription and B lymphocyte transformation into infinitely proliferating lymphoblastoid cells (LCLs). To identify EBNA2-regulated cell genes in LCLs, an EBV recombinant that expresses EBNA2 with its C terminus fused in frame to a 4-hydroxytamoxifen (4HT)-dependent mutant estrogen receptor (E2HTF) was used to transform primary B lymphocytes to LCLs. In the presence of 4HT, E2HTF expression level and effects on the LMP1 promoter in transfected BJAB lymphoblasts were similar to EBNA2. In 4HT-supplemented medium, E2HTF EBV recombinant infected LCLs were also similar to EBNA2 LCLs in outgrowth but required higher serum and a restricted range of cell concentrations for consistent growth. In medium without 4HT, E2HTF localized to the cytoplasm, c-myc levels substantially decreased within 6 h, cells stopped growing, and levels of other EBNAs and LMP1 remained stable for 24 h. Over this 24-h period, 30 cell RNAs decreased 2-fold, and 51 other RNAs decreased 1.5-fold. These RNAs encode proteins important in cell adhesion or signaling, transcription, RNA processing, cell-cycle regulation, and survival. Real-time RT-PCR confirmed EBNA2-dependent expression of eight RNAs.
Cell Line↗
Notch/Delta signaling constrains reengineering of pro-T cells by PU.1.
PU.1 is essential for early stages of mouse T cell development but antagonizes it if expressed constitutively. Two separable mechanisms are involved: attenuation and diversion. Dysregulated PU.1 expression inhibits pro-T cell survival, proliferation, and passage through beta-selection by blocking essential T cell transcription factors, signaling molecules, and Rag gene expression, which expression of a rearranged T cell antigen receptor transgene cannot rescue. However, Bcl2 transgenic cells are protected from this attenuation and may even undergo beta-selection, as shown by PU.1 transduction of defined subsets of Bcl2 transgenic fetal thymocytes with differentiation in OP9-DL1 and OP9 control cultures. The outcome of PU.1 expression in these cells depends on Notch/Delta signaling. PU.1 can efficiently divert thymocytes toward a myeloid-like state with multigene regulatory changes, but Notch/Delta signaling vetoes diversion. Gene expression analysis distinguishes sets of critical T lineage regulatory genes with different combinatorial responses to PU.1 and Notch/Delta signals, suggesting particular importance for inhibition of E proteins, Myb, and/or Gfi1 (growth factor independence 1) in diversion. However, Notch signaling only protects against diversion of cells that have undergone T lineage specification after Thy-1 and CD25 up-regulation. The results imply that in T cell precursors, Notch/Delta signaling normally acts to modulate and channel PU.1 transcriptional activities during the stages from T lineage specification until commitment.
Animals↗
Combined expression of pTalpha and Notch3 in T cell leukemia identifies the requirement of preTCR for leukemogenesis.
Notch receptors are conserved regulators of cell fate and have been implicated in the regulation of T cell differentiation and lymphomagenesis. However, neither the generality of Notch involvement in leukemia, nor the molecules with which Notch may interact have been clarified. Recently, we showed that transgenic mice expressing the constitutively active intracellular domain of Notch3 in thymocytes and T cells developed early and aggressive T cell neoplasias. Although primarily splenic, the tumors sustained features of immature thymocytes, including expression of pTalpha, a defining component of the pre T cell receptor, known to be a potent signaling complex provoking thymocyte survival, proliferation, and activation. Thus, enforced expression of Notch3, which is ordinarily down-regulated as thymocytes mature, may sustain pre T cell receptor expression, causing dysregulated hyperplasia. This hypothesis has been successfully tested in this article by the observation that deletion of pTalpha in Notch3 transgenic mice abrogates tumor development, indicating a crucial role for pTalpha in T cell leukemogenesis. Parallel observations were made in humans, in that all T cell acute lymphoblastic leukemias examined showed expression of Notch3 and of the Notch target gene HES-1, as well as of pTalpha a and b transcripts, whereas the expression of all these genes was dramatically reduced or absent in remission. Together, these results suggest that the combined expression of Notch3 and pTalpha sustains T cell leukemogenesis and may represent pathognomonic molecular features of human T-ALL.
Animals↗
Gleevec inhibits beta-amyloid production but not Notch cleavage.
Amyloid-beta (Abeta) peptides, consisting mainly of 40 and 42 aa (Abeta40 and Abeta42, respectively), are metabolites of the amyloid precursor protein and are believed to be major pathological determinants of Alzheimer's disease. The proteolytic cleavages that form the Abeta N and C termini are catalyzed by beta-secretase and gamma-secretase, respectively. Here we demonstrate that gamma-secretase generation of Abeta in an N2a cell-free system is ATP dependent. In addition, the Abl kinase inhibitor imatinib mesylate (Gleevec, or STI571), which targets the ATP-binding site of Abl and several other tyrosine kinases, potently reduces Abeta production in the N2a cell-free system and in intact N2a cells. Both STI571 and a related compound, inhibitor 2, also reduce Abeta production in rat primary neuronal cultures and in vivo in guinea pig brain. STI571 does not inhibit the gamma-secretase-catalyzed S3 cleavage of Notch-1. Furthermore, production of Abeta and its inhibition by STI571 were demonstrated to occur to similar extents in both Abl-/- and WT mouse fibroblasts, indicating that the effect of STI571 on Abeta production does not involve Abl kinase. The efficacy of STI571 in reducing Abeta without affecting Notch-1 cleavage may prove useful as a basis for developing novel therapies for Alzheimer's disease.
Amyloid Precursor Protein Secretases↗