| 1. |
- Astori, Audrey, et al.
(författare)
-
ARID1a Associates with Lymphoid-Restricted Transcription Factors and Has an Essential Role in T Cell Development
- 2020
-
Ingår i: Journal of Immunology. - : AMER ASSOC IMMUNOLOGISTS. - 0022-1767 .- 1550-6606. ; 205:5, s. 1419-1432
-
Tidskriftsartikel (refereegranskat)abstract
- Maturation of lymphoid cells is controlled by the action of stage and lineage-restricted transcription factors working in concert with the general transcription and chromatin remodeling machinery to regulate gene expression. To better understand this functional interplay, we used Biotin Identification in human embryonic kidney cells to identify proximity interaction partners for GATA3, TCF7 (TCF1), SPI1, HLF, IKZF1, PAX5, ID1, and ID2. The proximity interaction partners shared among the lineagerestricted transcription factors included ARID1a, a BRG1-associated factor complex component. CUT&RUN analysis revealed that ARID1a shared binding with TCF7 and GATA3 at a substantial number of putative regulatory elements in mouse T cell progenitors. In support of an important function for ARID1a in lymphocyte development, deletion of Aridla in early lymphoid progenitors in mice resulted in a pronounced developmental arrest in early T cell development with a reduction of CD4(+)CD8(+) cells and a 20-fold reduction in thymic cellularity. Exploring gene expression patterns in DN3 cells from Wt and Aridla-deficient mice suggested that the developmental block resided in the DN3a to DN3b transition, indicating a deficiency in beta-selection. Our work highlights the critical importance of functional interactions between stage and lineage-restricted factors and the basic transcription machinery during lymphocyte differentiation.
|
|
| 2. |
- Elander, Nils, et al.
(författare)
-
Association Between Adenomatosis Polyposis Coli Functional Status and Microsomal Prostaglandin E Synthase-1 Expression in Colorectal Cancer
- 2009
-
Ingår i: Molecular Carcinogenesis. - : Wiley. - 0899-1987 .- 1098-2744. ; 48:5, s. 401-407
-
Tidskriftsartikel (refereegranskat)abstract
- Bioactive metabolites downstream of cyclooxygenase-2 (COX-2) generated prostaglandin H-2 (PGH(2)), in particular prostaglandin E-2 (PGE(2)), are thought to play critical roles during the development of colorectal tumors. Previous reports reveal that defects of the tumor suppressor adenomatosis polyposis coli (APC) contribute to COX-2 upregulation in colon tumor cells. We investigated whether a similar relation was present between APC functional status and the expression of microsomal prostaglandin E synthase-1 (mPGES-1), which acts downstream of COX-2 and catalyses the terminal conversion of PGH(2) into PGE(2). Surprisingly, mPGES-1 mRNA and protein levels were upregulated upon induction of a wild type-APC carrying vector in HT29 colon cancer cells, and downregulated following siRNA silencing of APC in HCT-116 cells. mPGES-1 was overall enhanced in human colorectal tumor specimens versus corresponding non-tumor mucosa and, in accordance with data on HT29 and HCT116 cells, higher levels of mPGES-1 were observed among tumors carrying wild type versus mutant APC. RNAi silencing of beta-catenin and luciferase assays regarding the mPGES-1 promoter region did not reveal a role for APC or beta-catenin/Tcf in controlling mPGES-1 gene transcription. However, RNA degradation assays in HT29 cells revealed a suppressed degradation of mPGES-1 in the presence of wild type APC, implying that mPGES-1 mRNA is stabilized in the APC wild type state. Collectively, we demonstrate a novel association between APC functional status and mPGFS-1 expression in colorectal tumor cells, being most likely related to reduced mPGES-1 mRNA degradation rate in the APC wild type state.
|
|
| 3. |
- Elander, Nils, 1980-, et al.
(författare)
-
Genetic deletion of mPGES-1 accelerates intestinal tumorigenesis in APCMin/+ mice
- 2008
-
Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 372:1, s. 249-253
-
Tidskriftsartikel (refereegranskat)abstract
- The induced synthesis of bioactive prostanoids downstream of cyclooxygenase-2 (COX-2) and prostaglandin H2 (PGH2) exerts a critical event in colorectal carcinogenesis. Here we demonstrate that APCMin/+ mice with genetic deletion of microsomal prostaglandin E synthase-1 (mPGES-1), which catalyses the terminal conversion of PGH2 into PGE2, surprisingly develop more and generally larger intestinal tumors than do mPGES-1 wild type littermates (mean number of tumors/intestine 80 vs. 38, p < 0.0005, mean tumor diameter 1.64 vs. 1.12 mm, p < 0.0005). No deviation regarding the expression of other PGE2 related enzymes (COX-1, COX-2, mPGES-2, cPGES, and 15-PGDH) or receptors (EP1-4) was obvious among the mPGES-1 deficient mice. PGE2 levels were suppressed in tumors of mPGES-1 deficient animals, but the concentrations of other PGH2 derived prostanoids were generally enhanced, being most prominent for TxA2 and PGD2. Thus, we hypothesise that a redirected synthesis towards other lipid mediators might (over)compensate for loss of mPGES-1/PGE2 during intestinal tumorigenesis. Nevertheless, our results question the suitability for mPGES-1 targeting therapy in the treatment or prevention of colorectal cancer. © 2008 Elsevier Inc. All rights reserved.
|
|
| 4. |
|
|
| 5. |
- Hosokawa, Hiroyuki, et al.
(författare)
-
Bcl11b sets pro-T cell fate by site-specific cofactor recruitment and by repressing Id2 and Zbtb16
- 2018
-
Ingår i: Nature Immunology. - : Springer Science and Business Media LLC. - 1529-2908 .- 1529-2916. ; 19:12, s. 1427-1440
-
Tidskriftsartikel (refereegranskat)abstract
- Multipotent progenitor cells confirm their T cell–lineage identity in the CD4–CD8– double-negative (DN) pro-T cell DN2 stages, when expression of the essential transcription factor Bcl11b begins. In vivo and in vitro stage-specific deletions globally identified Bcl11b-controlled target genes in pro-T cells. Proteomics analysis revealed that Bcl11b associated with multiple cofactors and that its direct action was needed to recruit those cofactors to selective target sites. Regions near functionally regulated target genes showed enrichment for those sites of Bcl11b-dependent recruitment of cofactors, and deletion of individual cofactors relieved the repression of many genes normally repressed by Bcl11b. Runx1 collaborated with Bcl11b most frequently for both activation and repression. In parallel, Bcl11b indirectly regulated a subset of target genes by a gene network circuit via the transcription inhibitor Id2 (encoded by Id2) and transcription factor PLZF (encoded by Zbtb16); Id2 and Zbtb16 were directly repressed by Bcl11b, and Id2 and PLZF controlled distinct alternative programs. Thus, our study defines the molecular basis of direct and indirect Bcl11b actions that promote T cell identity and block alternative potentials.
|
|
| 6. |
- Hosokawa, Hiroyuki, et al.
(författare)
-
Transcription Factor PU.1 Represses and Activates Gene Expression in Early T Cells by Redirecting Partner Transcription Factor Binding
- 2018
-
Ingår i: Immunity. - : Elsevier BV. - 1074-7613. ; 48:6, s. 7-1134
-
Tidskriftsartikel (refereegranskat)abstract
- Transcription factors normally regulate gene expression through their action at sites where they bind to DNA. However, the balance of activating and repressive functions that a transcription factor can mediate is not completely understood. Here, we showed that the transcription factor PU.1 regulated gene expression in early T cell development both by recruiting partner transcription factors to its own binding sites and by depleting them from the binding sites that they preferred when PU.1 was absent. The removal of partner factors Satb1 and Runx1 occurred primarily from sites where PU.1 itself did not bind. Genes linked to sites of partner factor “theft” were enriched for genes that PU.1 represses despite lack of binding, both in a model cell line system and in normal T cell development. Thus, system-level competitive recruitment dynamics permit PU.1 to affect gene expression both through its own target sites and through action at a distance. Transcription factors regulate target genes via sequence-specific DNA binding. They may collaborate when bound together, but are assumed to be independent at sites where they bind alone. Hosokawa, Ungerbäck et al. show that PU.1 broadly shifts the genome-wide site choice of Runx1 DNA binding, enabling PU.1 to repress some target genes at a distance.
|
|
| 7. |
|
|
| 8. |
- Jensen, Christina T, et al.
(författare)
-
Dissection of progenitor compartments resolves developmental trajectories in B-lymphopoiesis
- 2018
-
Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 215:7, s. 1947-1963
-
Tidskriftsartikel (refereegranskat)abstract
- To understand the developmental trajectories in early lymphocyte differentiation, we identified differentially expressed surface markers on lineage-negative lymphoid progenitors (LPs). Single-cell polymerase chain reaction experiments allowed us to link surface marker expression to that of lineage-associated transcription factors (TFs) and identify GFRA2 and BST1 as markers of early B cells. Functional analyses in vitro and in vivo as well as single-cell gene expression analyses supported that surface expression of these proteins defined distinct subpopulations that include cells from both the classical common LPs (CLPs) and Fraction A compartments. The formation of the GFRA2-expressing stages of development depended on the TF EBF1, critical both for the activation of stage-specific target genes and modulation of the epigenetic landscape. Our data show that consecutive expression of Ly6D, GFRA2, and BST1 defines a developmental trajectory linking the CLP to the CD19+ progenitor compartment.
|
|
| 9. |
- Karlsson, Anneli, et al.
(författare)
-
Notch1 is a frequent mutational target in chemically induced lymphoma in mouse
- 2008
-
Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 123:11, s. 2720-2724
-
Tidskriftsartikel (refereegranskat)abstract
- Activating Notch1 mutations have been reported in human T-lineage acute lymphoblastic leukemia (T-ALL) and lymphomas from genetically modified mice. We report that Notch1 is a prevalent and major mutational target in chemically induced mouse lymphoma. The regions of the gene that are frequently mutated are the hterodimerization domain and the N-terminal ligand-binding region, important for protein stability, and (he polypeptide rich in proline, glutamate, serine and threonine WEST) domains, which is critical for protein degradation. Another gene, CDC4, is also involved in Notch1 degradation and shows frequent mutations. Mutations in the heterodimerization and the ligand-binding regions may cause ligand-independent signaling. whereas mutations preventing protein degradation result in accumulation of intracellular Notch1. We analyzed 103 chemical-induced mouse lymphomas for mutations in the Notch1 gene using single strand conformation analysis (SSCA) and DNA sequencing. Genetic alterations resulting in premature truncation of Notch I were identified in 28 tumors, whereas 8 revealed alterations in the heterodimerization and 16 harbored deletions in the ligand-binding region. Dideoxycytidine-induced lymphomas displayed the highest frequency of Notch1 mutations (49%). whereas in butadiene- and phenolphthalein-indced tumors showed lower frequencies (26 10%, respectively). In total, 26 novel and 3 previously reported mutations were detected. This report shows that Notch1 is a prevalent and major mtational target for 2,3-dideoxycytidine and butadiene-induced lymphoma..
|
|
| 10. |
- Kristiansen, Trine Ahn, et al.
(författare)
-
Developmental cues license megakaryocyte priming in murine hematopoietic stem cells
- 2022
-
Ingår i: BLOOD ADVANCES. - : ELSEVIER. - 2473-9529 .- 2473-9537. ; 6:24, s. 6228-6241
-
Tidskriftsartikel (refereegranskat)abstract
- The fetal-to-adult switch in hematopoietic stem cell (HSC) behavior is characterized by alterations in lineage output and entry into deep quiescence. Here we identify the emergence of megakaryocyte (Mk)-biased HSCs as an event coinciding with this developmental switch. Single-cell chromatin accessibility analysis reveals a ubiquitous acquisition of Mk lineage priming signatures in HSCs during the fetal-to-adult transition. These molecular changes functionally coincide with increased amplitude of early Mk differentiation events after acute inflammatory insult. Importantly, we identify LIN28B, known for its role in promoting fetal-like self-renewal, as an insulator against the establishment of an Mk-biased HSC pool. LIN28B protein is developmentally silenced in the third week of life, and its prolonged expression delays emergency platelet output in young adult mice. We propose that developmental regulation of Mk priming may represent a switch for HSCs to toggle between prioritizing self-renewal in the fetus and increased host protection in postnatal life.
|
|
| 11. |
- Lança, Telma, et al.
(författare)
-
IRF8 deficiency induces the transcriptional, functional, and epigenetic reprogramming of cDC1 into the cDC2 lineage
- 2022
-
Ingår i: Immunity. - : Elsevier BV. - 1074-7613 .- 1097-4180. ; 55:8, s. 11-1447
-
Tidskriftsartikel (refereegranskat)abstract
- Conventional dendritic cells (cDCs) consist of two major functionally and phenotypically distinct subsets, cDC1 and cDC2, whose development is dependent on distinct sets of transcription factors. Interferon regulatory factor 8 (IRF8) is required at multiple stages of cDC1 development, but its role in committed cDC1 remains unclear. Here, we used Xcr1-cre to delete Irf8 in committed cDC1 and demonstrate that Irf8 is required for maintaining the identity of cDC1. In the absence of Irf8, committed cDC1 acquired the transcriptional, functional, and chromatin accessibility properties of cDC2. This conversion was independent of Irf4 and was associated with the decreased accessibility of putative IRF8, Batf3, and composite AP-1-IRF (AICE)-binding elements, together with increased accessibility of cDC2-associated transcription-factor-binding elements. Thus, IRF8 expression by committed cDC1 is required for preventing their conversion into cDC2-like cells.
|
|
| 12. |
- Okuyama, Kazuki, et al.
(författare)
-
PAX5 is part of a functional transcription factor network targeted in lymphoid leukemia
- 2019
-
Ingår i: PLOS Genetics. - : PUBLIC LIBRARY SCIENCE. - 1553-7390 .- 1553-7404. ; 15:8
-
Tidskriftsartikel (refereegranskat)abstract
- One of the most frequently mutated proteins in human B-lineage leukemia is the transcription factor PAX5. These mutations often result in partial rather than complete loss of function of the transcription factor. While the functional dose of PAX5 has a clear connection to human malignancy, there is limited evidence for that heterozygote loss of PAX5 have a dramatic effect on the development and function of B-cell progenitors. One possible explanation comes from the finding that PAX5 mutated B-ALL often display complex karyotypes and additional mutations. Thus, PAX5 might be one component of a larger transcription factor network targeted in B-ALL. To investigate the functional network associated with PAX5 we used BioID technology to isolate proteins associated with this transcription factor in the living cell. This identified 239 proteins out of which several could be found mutated in human B-ALL. Most prominently we identified the commonly mutated IKZF1 and RUNX1, involved in the formation of ETV6-AML1 fusion protein, among the interaction partners. ChIP- as well as PLAC-seq analysis supported the idea that these factors share a multitude of target genes in human B-ALL cells. Gene expression analysis of mouse models and primary human leukemia suggested that reduced function of PAX5 increased the ability of an oncogenic form of IKZF1 or ETV6-AML to modulate gene expression. Our data reveals that PAX5 belong to a regulatory network frequently targeted by multiple mutations in B-ALL shedding light on the molecular interplay in leukemia cells. Author summary The use of modern high throughput DNA-sequencing has dramatically increased our ability to identify genetic alterations associated with cancer. However, while the mutations per se are rather easily identified, our understanding of how these mutations impact cellular functions and drive malignant transformation is more limited. We have explored the function of the transcription factor PAX5, commonly mutated in human B-lymphocyte leukemia, to identify a regulatory network of transcription factors often targeted in human disease. Hence, we propose that malignant conversion of B-lymphocyte progenitors involves multiple targeting of a central transcription factor network aggravating the impact of the individual mutations. These data increase our understanding for how individual mutations collaborate to drive the formation of B-lineage leukemia.
|
|
| 13. |
- Rothenberg, Ellen V., et al.
(författare)
-
Forging T-Lymphocyte Identity: Intersecting Networks of Transcriptional Control
- 2016
-
Ingår i: Advances in Immunology. - : ELSEVIER ACADEMIC PRESS INC. - 0065-2776 .- 1557-8445. - 9780128047996 ; 129, s. 109-174
-
Forskningsöversikt (refereegranskat)abstract
- T-lymphocyte development branches off from other lymphoid developmental programs through its requirement for sustained environmental signals through the Notch pathway. In the thymus, Notch signaling induces a succession of T-lineage regulatory factors that collectively create the T-cell identity through distinct steps. This process involves both the staged activation of T-cell identity genes and the staged repression of progenitor-cell-inherited regulatory genes once their roles in self-renewal and population expansion are no longer needed. With the recent characterization of innate lymphoid cells (ILCs) that share transcriptional regulation programs extensively with T-cell subsets, T-cell identity can increasingly be seen as defined in modular terms, as the processes selecting and actuating effector function are potentially detachable from the processes generating and selecting clonally unique T-cell receptor structures. The developmental pathways of different classes of T cells and ILCs are distinguished by the numbers of prerequisites of gene rearrangement, selection, and antigen contact before the cells gain access to nearly common regulatory mechanisms for choosing effector function. Here, the major classes of transcription factors that interact with Notch signals during T-lineage specification are discussed in terms of their roles in these programs, the evidence for their spectra of target genes at different stages, and their cross-regulatory and cooperative actions with each other. Specific topics include Notch modulation of PU.1 and GATA-3, PU.1-Notch competition, the relationship between PU.1 and GATA-3, and the roles of E proteins, Bcl11b, and GATA-3 in guiding acquisition of T-cell identity while avoiding redirection to an ILC fate.
|
|
| 14. |
- Safi, Fatemeh, et al.
(författare)
-
Concurrent stem- and lineage-affiliated chromatin programs precede hematopoietic lineage restriction
- 2022
-
Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 39:6
-
Tidskriftsartikel (refereegranskat)abstract
- The emerging notion of hematopoietic stem and progenitor cells (HSPCs) as a low-primed cloud without sharply demarcated gene expression programs raises the question on how cellular-fate options emerge and at which stem-like stage lineage priming is initiated. Here, we investigate single-cell chromatin accessibility of Lineage-, cKit+, and Sca1+ (LSK) HSPCs spanning the early differentiation landscape. Application of a signal-processing algorithm to detect transition points corresponding to massive alterations in accessibility of 571 transcription factor motifs reveals a population of LSK FMS-like tyrosine kinase 3 (Flt3)intCD9high cells that concurrently display stem-like and lineage-affiliated chromatin signatures, pointing to a simultaneous gain of both lympho-myeloid and megakaryocyte-erythroid programs. Molecularly and functionally, these cells position between stem cells and committed progenitors and display multi-lineage capacity in vitro and in vivo but lack self-renewal activity. This integrative molecular analysis resolves the heterogeneity of cells along hematopoietic differentiation and permits investigation of chromatin-mediated transition between multipotency and lineage restriction.
|
|
| 15. |
- Somasundaram, Rajesh, et al.
(författare)
-
Clonal conversion of B lymphoid leukemia reveals cross-lineage transfer of malignant states
- 2016
-
Ingår i: Genes and Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 30:22, s. 2486-2499
-
Tidskriftsartikel (refereegranskat)abstract
- Even though leukemia is considered to be confined to one specific hematopoietic cell type, cases of acute leukemia of ambiguous lineage and patients relapsing in phenotypically altered disease suggest that a malignant state may be transferred between lineages. Because B-cell leukemia is associated with mutations in transcription factors of importance for stable preservation of lineage identity, we here investigated the potential lineage plasticity of leukemic cells. We report that primary pro-B leukemia cells from mice carrying heterozygous mutations in either or both the Pax5 and Ebf1 genes, commonly mutated in human leukemia, can be converted into T lineage leukemia cells. Even though the conversion process involved global changes in gene expression and lineage-restricted epigenetic reconfiguration, the malignant phenotype of the cells was preserved, enabling them to expand as T lineage leukemia cells in vivo. Furthermore, while the transformed pro-B cells displayed plasticity toward myeloid lineages, the converted cells failed to cause myeloid leukemia after transplantation. These data provide evidence that a malignant phenotype can be transferred between hematopoietic lineages. This has important implications for modern cancer medicine because lineage targeted treatment of leukemia patients can be predicted to provoke the emergence of phenotypically altered subclones, causing clinical relapse.
|
|
| 16. |
- Somasundaram, Rajesh, et al.
(författare)
-
EBF1 and PAX5 control pro-B cell expansion via opposing regulation of the Myc gene
- 2021
-
Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 137:22, s. 3037-3049
-
Tidskriftsartikel (refereegranskat)abstract
- Genes encoding B lineage–restricted transcription factors are frequently mutated in B-lymphoid leukemias, suggesting a close link between normal and malignant B-cell development. One of these transcription factors is early B-cell factor 1 (EBF1), a protein of critical importance for lineage specification and survival of B-lymphoid progenitors. Here, we report that impaired EBF1 function in mouse B-cell progenitors results in reduced expression of Myc. Ectopic expression of MYC partially rescued B-cell expansion in the absence of EBF1 both in vivo and in vitro. Using chromosome conformation analysis in combination with ATAC-sequencing, chromatin immunoprecipitation–sequencing, and reporter gene assays, six EBF1-responsive enhancer elements were identified within the Myc locus. CRISPR-Cas9–mediated targeting of EBF1-binding sites identified one element of key importance for Myc expression and pro-B cell expansion. These data provide evidence that Myc is a direct target of EBF1. Furthermore, chromatin immunoprecipitation–sequencing analysis revealed that several regulatory elements in the Myc locus are targets of PAX5. However, ectopic expression of PAX5 in EBF1-deficient cells inhibits the cell cycle and reduces Myc expression, suggesting that EBF1 and PAX5 act in an opposing manner to regulate Myc levels. This hypothesis is further substantiated by the finding that Pax5 inactivation reduces requirements for EBF1 in pro–B-cell expansion. The binding of EBF1 and PAX5 to regulatory elements in the human MYC gene in a B-cell acute lymphoblastic leukemia cell line indicates that the EBF1:PAX5:MYC regulatory loop is conserved and may control both normal and malignant B-cell development.
|
|
| 17. |
- Somasundaram, Rajesh, et al.
(författare)
-
Transcription factor networks in B-cell differentiation link development to acute lymphoid leukemia
- 2015
-
Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 126:2, s. 144-152
-
Forskningsöversikt (refereegranskat)abstract
- B-lymphocyte development in the bone marrow is controlled by the coordinated action of transcription factors creating regulatory networks ensuring activation of the B-lymphoid program and silencing of alternative cell fates. This process is tightly connected to malignant transformation because B-lineage acute lymphoblastic leukemia cellsdisplay a pronounced block in differentiation resulting in the expansion of immature progenitor cells. Over the last few years, high-resolution analysis of genetic changes in leukemia has revealed that several key regulators of normal B-cell development, including IKZF1, TCF3, EBF1, and PAX5, are genetically altered in a large portion of the human B-lineage acute leukemias. This opens the possibility of directly linking the disrupted development as well as aberrant gene expression patterns in leukemic cells to molecular functions of defined transcription factors in normal cell differentiation. This review article focuses on the roles of transcription factors in early B-cell development and their involvement in the formation of human leukemia.
|
|
| 18. |
- Ungerbäck, Jonas, et al.
(författare)
-
Analysis of VEGF polymorphisms, tumor expression of VEGF mRNA and colorectal cancer susceptibility in a Swedish population
- 2009
-
Ingår i: MOLECULAR MEDICINE REPORTS. - : Spandidos Publications. - 1791-2997. ; 2:3, s. 435-439
-
Tidskriftsartikel (refereegranskat)abstract
- Vascular endothelial growth factor (VEGF) plays a significant role in tumor angiogenesis and is found to be overexpressed and involved in the development and progression of colorectal cancer (CRC). The VEGF gene contains several polymorphic sites known to influence VEGF expression. We examined the possible association between five polymorphisms, located in the promoter/5-untranslated region [-2578 (C/A), -2549 (del/ins 18 bp) -1154 (G/A), -634 (G/C)] or 3-untranslated region [+936 (C/T)] of the VEGF gene, and CRC Susceptibility and clinicopathological characteristics in 302 Swedish CRC patients and 336 healthy randomly selected controls. Both genotypes and combined haplotypes were analyzed. No significant differences were observed when VEGF genotype/haplotype frequencies in the CRC cases and controls were compared, nor were any associations found between the genotypes/haplotypes and clinicopathological characteristics. However, when the -2578 C and +936 T alleles were combined, a small but significant association with CRC susceptibility was detected (OR=1.6, 95% CI 1.3-1.9, p=0.01). In addition, VEGF mRNA expression was determined in a Subset of patients, revealing a 2-fold VEGF upregulation in CRC tissue compared to normal colonic mucosa, but no association between the genotypes or haplotypes and VEGF mRNA levels. Linkage analysis was performed, revealing that the polymorphisms in the promoter and 5-untranslated region were in tight linkage disequilibrium (LD) (vertical bar Dvertical bar=0.91-1.00), while the +936 C/T polymorphism was only weakly associated with the others (vertical bar Dvertical bar=0.05-0.19). In conclusion, VEGF is generally upregulated in colorectal tumors. However, the single nucleotide polymorphisms examined do not appear to influence the mRNA expression of VEGF in colorectal tumors, and most likely play a limited role in CRC development and progression.
|
|
| 19. |
- Ungerbäck, Jonas, et al.
(författare)
-
Combined heterozygous loss of Ebf1 and Pax5 allows for T-lineage conversion of B cell progenitors
- 2015
-
Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 212:7, s. 1109-1123
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate how transcription factor levels impact B-lymphocyte development, we generated mice carrying transheterozygous mutations in the Pax5 and Ebf1 genes. Whereas combined reduction of Pax5 and Ebf1 had minimal impact on the development of the earliest CD19(+) progenitors, these cells displayed an increased T cell potential in vivo and in vitro. The alteration in lineage fate depended on a Notch1-mediated conversion process, whereas no signs of de-differentiation could be detected. The differences in functional response to Notch signaling in Wt and Pax5(+/-) Ebf1(+/-) pro-B cells were reflected in the transcriptional response. Both genotypes responded by the generation of intracellular Notch1 and activation of a set of target genes, but only the Pax5(+/-) Ebf1(+/-) pro-B cells down-regulated genes central for the preservation of stable B cell identity. This report stresses the importance of the levels of transcription factor expression during lymphocyte development, and suggests that Pax5 and Ebf1 collaborate to modulate the transcriptional response to Notch signaling. This provides an insight on how transcription factors like Ebf1 and Pax5 preserve cellular identity during differentiation.
|
|
| 20. |
- Ungerbäck, Jonas, et al.
(författare)
-
Genetic variation and alterations of genes involved in NFκB/TNFAIP3- and NLRP3-inflammasome signaling affect susceptibility and outcome of colorectal cancer
- 2012
-
Ingår i: Carcinogenesis. - Oxford, United kingdom : Oxford University Press. - 0143-3334 .- 1460-2180. ; 33:11, s. 2126-2134
-
Tidskriftsartikel (refereegranskat)abstract
- Colorectal tumors are continuously exposed to an inflammatory environment, which together with mitogenic signals sustain several cancer hallmarks. Nuclear factor-kappa B (NFκB) is a major regulator of inflammation and variation in NFκB-associated genes could potentially be used as biomarkers to identify patients with increased risk of colorectal cancer (CRC) development, and/or a rapidly progressing disease. In this study, 348 CRC cases and 806 randomly selected healthy individuals from southeastern Sweden were examined with regard to seven polymorphisms in NFκB pathway-associated genes. Log-rank-tests and Cox proportional hazard regression analysis examined the association between the polymorphisms and CRC-specific survival, whereas chi-square tests and logistic regression analysis were used to test for associations between the polymorphisms and CRC susceptibility. Gene expression and loss of heterozygosity analyses of TNFAIP3 were carried out in a subset of tumors to assess its role as a tumor suppressor in CRC. Heterozygous and polymorphic TNFAIP3 (rs6920220), heterozygous NLRP3 (Q705K) and polymorphic NFκB -94 ATTG ins/del genotypes were found to be associated with poorer survival in patients diagnosed with invasive CRC (aHR = 5.2, 95% CI: 2.5-10.9, P < 0.001). TNFAIP3 mRNA levels were significantly decreased in tumors compared with adjacent non-neoplastic mucosa (P < 0.0001) and loss of heterozygosity of 6q23.3 (TNFAIP3) was detected in 17% of cases, whereas only 2.5% of the investigated specimens displayed TNFAIP3 gene mutations. We propose that TNFAIP3 (rs6920220), NLRP3 (Q705K) and NFκB -94 ATTG ins/del polymorphisms are associated with poor survival in patients with advanced CRC and may be used as prognostic markers. Experimental results indicate that TNFAIP3 may act as a tumor suppressor in CRC.
|
|
| 21. |
- Ungerbäck, Jonas, et al.
(författare)
-
Genetic variation in NFκB signaling pathway genes in colorectal cancer susceptibility and survival
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- PURPOSE: Variations in genes orchestrating inflammatory responses, such as those being connected with NFκB and NLRP3 inflammasome signaling, are associated with chronic inflammatory bowel diseases, which are well-known risk factors for colorectal cancer (CRC). The purpose of this study was to investigate the association between genetic variation and alterations in genes involved in NFκB and NLRP3 inflammasome signaling and their possible influence on susceptibility and clinical outcome of colorectal cancer. EXPERIMENTAL DESIGN: 344 CRC cases and 793 randomly selected healthy individuals from southeastern Sweden were examined with regard to seven polymorphisms in NFκB, TNFAIP3, NLRP3, CARD8 and TLR4 genes. Chi-square tests and multiple logistic regression analysis were used to test for associations between the SNPs and CRC susceptibility, while log-rank tests and Cox proportional hazard regression analysis were used to examine the association between the SNPs and CRC-specific survival. Gene expression assay and loss of heterozygosity analyzes of TNFAIP3 were carried out in a subset of tumors to assess its role as a potential tumor suppressor in CRC. RESULTS: Adjusted for age, gender and polypoid/ulcerative CRC phenotype, a panel of heterozygous and mutant TNFAIP3 (rs6920220), mutant NFκB -94 ATTG ins/del and heterozygous NLRP3 (Q705K) genotypes were found to be associated with poorer survival in patients diagnosed with invasive CRC (aHR = 5.2 95% CI 2.5-10.9, P < 0.001). TNFAIP3 mRNA levels were significantly decreased in tumors compared to adjacent non-neoplastic mucosa (P < 0.0001) and LOH of 6q23.3, (TNFAIP3), was detected in 17% of cases, while only 2.5% of the investigated specimens displayed TNFAIP3 gene mutations. CONCLUSIONS: A panel of the TNFAIP3 (rs6920220), NFκB -94 ATTG ins/del and NLRP3 (Q705K) polymorphisms are associated with poor survival in patients with advanced CRC and may be used as a prognostic marker. Experimental results indicate that TNFAIP3 may act as a tumor suppressor in CRC.
|
|
| 22. |
- Ungerbäck, Jonas
(författare)
-
Inflammation and Intestinal Homeostasis-Associated Genes in Colorectal Cancer
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Colorectal cancer (CRC) is a global ‘killer’ and every year more than 1.2 million new individuals are affected and approximately 600 000 succumb to the disorder. Several mechanisms such as inactivation of tumor suppressor genes, activation of oncogenes and dysregulation of cell fate determinating pathways e.g. Wnt and Notch can initiate a cancerous cell growth and promote colorectal tumorigenesis. In addition, most tumors are exposed to an inflammatory environment, which together with the presence of mitogenic and angiogenic signals may sustain several hallmarks of cancer. Genetic alterations in inflammatory genes are associated with chronic inflammatory bowel disease, which is a strong risk factor of developing CRC. Scientists have for a long time looked for ‘the Key’ that would unlock the ‘cancer door’ but more likely cancer should be considered as not one but many diseases where almost every single patient is genetically and clinically unique. Hence recent research has turned to identify such inter-individual discrepancies and to find disease markers and strategies for guiding clinicians when tailoring individual management and optimized therapy. A deeper understanding of the regulation and genetic variation of inflammation and intestinal-homeostasis associated genes is pivotal to find potential targets for future therapies.The present thesis focuses on genetic variation and alterations in inflammatory genes as well as genes specifically involved in maintaining intestinal homeostasis. The most common anti-inflammatory drugs, NSAIDs, inhibit the prostanoid-generating COX-enzymes and are associated with decreased CRC risk when administered for a long time. Unfortunately, continuous NSAID treatment may lead to severe side-effects such as gastrointestinal bleeding, possibly through the ablation of non-PGE2 prostanoids. Therefore, a more specific inhibition of PGE2 has been suggested to be superior to classical NSAIDs. In papers I and II, the terminal PGE2 generating enzyme mPGES1 was studied in the context of intestinal cancer. Unexpectedly, ApcMin/+ mice with a targeted deletion of the mPGES1 encoding gene displayed significantly more and larger intestinal adenomas as compared to their wilde-type (wt) littermates. Probably this was due to the redirected generation of PGE2 towards non-PGE2 prostanoids seen in the murine tumors, resulting in enhanced pro-tumorigenic activity of these transmitter substances. Next, with a battery of functional and descriptive assays we investigated whether the outcome of mPGES1 expression and activity could depend on the genetic profile of the tumor e.g. the Apc mutational status. Indeed, high expression of mPGES1 was associated with the presence of wt-Apc, both in vitro and in vivo, most likely depending on mPGES1 mRNA stabilization rather than upregulation through β–catenin/Lef/Tcf4 signaling.NFκB is a major regulator of inflammation e.g. through the production of inflammatory cytokines. Variations in genes controlling inflammation and angiogenesis could potentially be used as biomarkers to identify patients with increased risk of CRC development, and/or to identify those with high risk of a rapidly progressing disease. Further, such analyzes have been suggested to select patients, which may benefit from specific anti-inflammatory or anti-angiogenic therapies. In paper III, genetic alterations in NFκB associated genes were studied among CRC patients and healthy controls. The NFκB negative regulator TNFAIP3 was found to exert tumor suppressive functions in CRC and moreover, homozygous mutant TNFAIP3 (rs6920220), homozygous mutant NFκB -94 ATTG ins/del and heterozygous NLRP3 (Q705K) were identified as prognostic markers for identifying CRC patients with a high risk of rapid progression. Further studies, which focus on the potential to treat such patients with anti-inflammatory IL-1β targeting therapies, are warranted.In the intestinal epithelium, Notch and Wnt signaling function in synergy to maintain homeostasis and together these pathways promote stem cell renewal and drive proliferation. Thus, dysregulation and/or overactivation of one of the two pathways could potentially lead to simultaneous activation of the other. While the genetic mechanisms explaining aberrant Wnt signaling in CRC are well-known, the reasons for the Notch pathway activation are less so. Further, relatively little is known about the mechanisms linking the two pathways in CRC. In paper IV, we addressed this question with a set of experimental in vitro assays, hereby identifying Notch2 together with several additional genes classically belonging to the Notch pathway, as putative targets for canonical and non-canonical Wnt signaling. We therefore suggest that aberrant Notch signaling in colon cancer cells may be the result of dysregulated Wnt signaling.In summary, the results here presented add a couple of pieces to the immensely complex jigsaw puzzle connecting intestinal homeostasis, inflammation and CRC. These results may aid in identifying future biomarkers or potential drug targets that could take us to the next level in the war against cancer.
|
|
| 23. |
- Ungerbäck, Jonas, et al.
(författare)
-
Notch-2 and the Notch signaling pathway are regulated by Wnt signaling in colorectal cancer
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Both Notch and Wnt pathways are key regulators of intestinal homeostasis and alterations in these pathways can lead to development of colorectal cancer, where the Apc/β-catenin-genes in the Wnt signaling pathway are frequently mutated, and active Notch signaling contributes to tumorigenesis by keeping the epithelial cells in a proliferative state. These pathways are simultaneously active in proliferative adenoma cells and a crosstalk between them has been indicated. Using bioinformatics, we identified and screened proximal Notch pathway gene promoters for putative TCF/LEF1 sites, targets for β-catenin. Wild type (wt)-Apc negatively regulates β-catenin and by using semi-quantitative PCR, induction of wt-Apc or β-catenin silencing in HT29 cells, we observed that several genes in the Notch pathway, including Notch-2, were downregulated. Electrophoretic mobility-shift assay (EMSA) confirmed binding of Lef-1 to Notch-2 as well as other Notch pathway gene promoters and luciferase assays showed an increased activity for the LEF1/TCF-site at position -110 in the Notch-2 promoter upon cotransfection of HT29 or HCT116 cells with mutated β-catenin. Taken together, these results indicate that activation of the Wnt pathway with increased levels of β-catenin can function as a transcriptional regulator of the Notch pathway in colon cancer cell lines.
|
|
| 24. |
- Ungerbäck, Jonas, 1982-
(författare)
-
Notch signalling in carcinogenesis : With special emphasis on T-cell lymphoma and colorectal cancer
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Notch signalling pathway is an evolutionary conserved pathway, named after the Notch receptors, Notch1-4 in mammals, which upon cell-cell contact and ligand binding releases the intracellular domain (NICD). NICD translocates into the nucleus where it binds the transcriptional repressor RBP-Jk, which together with co-activators belonging to the Mastermind-like family of proteins form a transcriptional activation complex. This complex activates genes controlling cell fate decision, embryonic development, proliferation, differentiation, adult homeostasis and stem cell maintenance. On the other hand, disrupted Notch signalling may result in pathological conditions like cancer, although the mechanisms behind the disruption are often complex and in many cases largely unknown.Notch1 drives the lymphocyte differentiation towards a T-cell fate and activating mutations in the gene have been suggested to be involved in T-cell lymphoma. In paper I, genetic alterations in Notch1 and the Notch1 regulating gene CDC4 were investigated in tumours from murine T-cell lymphoma induced with phenolphthalein, 1,3-butadiene or 2’,3’-dideoxycytidine. We identified activating Notch1 mutations in 39% of the lymphomas, suggesting that Notch1 is an important target gene for mutations in chemically induced lymphomas.While it is known that constitutively activated Notch signalling has a clear oncogenic function in several solid malignancies as well, the molecular mechanisms are less known in this context. Unpublished data of our lab, together with other recent studies, suggest that mutations of Notch and Notch-related genes per se are uncommon in solid malignancies including colorectal cancer, while a growing body of evidence indicates that aberrant Wnt/b-catenin signalling may result in pro-tumoural Notch activation in these contexts. In paper II, we therefore investigated potential transcriptional interactions between the Notch and Wnt signalling pathways in colorectal cancer cell lines. The proximal Notch and Wnt pathway gene promoters were bioinformatically identified and screened for putative TCF/LEF1 and RBP-Jk sites. In canonical Wnt signalling, Apc negatively regulates b-catenin leading to repression of TCF/LEF1 target genes. Upon repression of the Wnt pathway we observed that several genes in the Notch pathway, including Notch2, were transcriptionally downregulated. We also confirmed binding of Lef1 to Notch2 as well as other Notch pathway gene promoters and luciferase assays showed an increased activity for at least one LEF1/TCF-site in the Notch2 promoter upon co-transfection of HT29 or HCT116 cells with mutated b-catenin. HT29 cell lines were also treated with the g-secretase inhibitor DAPT, leading to inactivation of the Notch pathway by preventing release of NICD. However, results showed no effects on Apc, b-catenin or their target cyclin D1. Taken together, these results indicate that the Wnt pathway may function as a regulator of the Notch pathway through the TCF/LEF1 target gene program in colon cancer cell lines.In summary, Notch pathway deregulation is of importance in both murine T-cell lymphoma and human colorectal cancer, although the mechanisms differ. The current results give new insights in Notch pathway alterations as well as the signalling networks in which the Notch pathway interacts, and thus increase the understanding of Notch’s involvement in malignant diseases.
|
|
| 25. |
- Ungerbäck, Jonas, et al.
(författare)
-
Pioneering, chromatin remodeling, and epigenetic constraint in early T-cell gene regulation by SPIT (PU.1)
- 2018
-
Ingår i: Genome Research. - : COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT. - 1088-9051 .- 1549-5469. ; 28:10, s. 1508-1519
-
Tidskriftsartikel (refereegranskat)abstract
- SPI1 (also known as PU.1) is a dominant but transient regulator in early T-cell precursors and a potent transcriptional controller of developmentally important pro-T-cell genes. Before T-lineage commitment, open chromatin is frequently occupied by PU.1, and many PU.1 sites lose accessibility when PU.1 is later down-regulated. Pioneering activity of PU.1 was tested in this developmentally dynamic context by quantitating the relationships between PU.1 occupancy and site quality and accessibility as PU.1 levels naturally declined in pro-T-cell development and by using stage-specific gain- and loss-offunction perturbations to relate binding to effects on target genes. PU.1 could bind closed genomic sites, but rapidly opened many of them, despite the absence of its frequent collaborator, CEBPA. RUNX motifs and RUNX1 binding were often linked to PU.1 at open sites, but highly expressed PU.1 could bind its sites without RUNX1 The dynamic properties of PU.1 engagements implied that PU.1 binding affinity and concentration determine its occupancy choices, but with quantitative trade-offs for occupancy between site sequence quality and stage-dependent site accessibility in chromatin. At nonpromoter sites, PU.1 binding criteria were more stringent than at promoters, and PU.1 was also much more effective as a transcriptional regulator at non promoter sites where local chromatin accessibility depended on the presence of PU.1. Notably, closed chromatin presented a qualitative barrier to occupancy by the PU.1 DNA-binding domain alone. Thus, effective pioneering at closed chromatin sites also depends on requirements beyond site recognition, served by non-DNA-binding domains of PU.1.
|
|
| 26. |
|
|
| 27. |
- Ungerbäck, Jonas, et al.
(författare)
-
The Notch-2 Gene Is Regulated by Wnt Signaling in Cultured Colorectal Cancer Cells
- 2011
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:3, s. 0017957-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Notch and Wnt pathways are key regulators of intestinal homeostasis and alterations in these pathways may lead to the development of colorectal cancer (CRC). In CRC the Apc/beta-catenin genes in the Wnt signaling pathway are frequently mutated and active Notch signaling contributes to tumorigenesis by keeping the epithelial cells in a proliferative state. These pathways are simultaneously active in proliferative adenoma cells and a crosstalk between them has previously been suggested in normal development as well as in cancer. Principal Findings: In this study, in silico analysis of putative promoters involved in transcriptional regulation of genes coding for proteins in the Notch signaling pathway revealed several putative LEF-1/TCF sites as potential targets for beta-catenin and canonical Wnt signaling. Further results from competitive electrophoretic mobility-shift assay (EMSA) studies suggest binding of several putative sites in Notch pathway gene promoters to in vitro translated beta-catenin/Lef-1. Wild type (wt)-Apc negatively regulates beta-catenin. By induction of wt-Apc or beta-catenin silencing in HT29 cells, we observed that several genes in the Notch pathway, including Notch-2, were downregulated. Finally, active Notch signaling was verified in the Apc(Min/+) mouse model where Hes-1 mRNA levels were found significantly upregulated in intestinal tumors compared to normal intestinal mucosa. Luciferase assays showed an increased activity for the core and proximal Notch-2 promoter upon co-transfection of HCT116 cells with high expression recombinant Tcf-4, Lef-1 or beta-catenin. Conclusions: In this paper, we identified Notch-2 as a novel target for beta-catenin-dependent Wnt signaling. Furthermore our data supports the notion that additional genes in the Notch pathway might be transcriptionally regulated by Wnt signaling in colorectal cancer.
|
|
| 28. |
- Vanhee, Stijn, et al.
(författare)
-
Lin28b controls a neonatal to adult switch in B cell positive selection
- 2019
-
Ingår i: Science immunology. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2470-9468. ; 4:39
-
Tidskriftsartikel (refereegranskat)abstract
- The ability of B-1 cells to become positively selected into the mature B cell pool, despite being weakly self-reactive, has puzzled the field since its initial discovery. Here, we explore changes in B cell positive selection as a function of developmental time by exploiting a link between CD5 surface levels and the natural occurrence of self-reactive B cell receptors (BCRs) in BCR wild-type mice. We show that the heterochronic RNA binding protein Lin28b potentiates a neonatal mode of B cell selection characterized by enhanced overall positive selection in general and the developmental progression of CD5(+) immature B cells in particular. Lin28b achieves this by amplifying the CD19/PI3K/c-Myc positive feedback loop, and ectopic Lin28b expression restores both positive selection and mature B cell numbers in CD19(-/-) adult mice. Thus, the temporally restricted expression of Lin28b relaxes the rules for B cell selection during ontogeny by modulating tonic signaling. We propose that this neonatal mode of B cell selection represents a cell-intrinsic cue to accelerate the de novo establishment of the adaptive immune system and incorporate a layer of natural antibody-mediated immunity throughout life.
|
|
| 29. |
- Willander, Kerstin, et al.
(författare)
-
MDM2 SNP309 promoter polymorphism, an independent prognostic factor in chronic lymphocytic leukemia
- 2010
-
Ingår i: European Journal of Haematology. - : Wiley. - 1600-0609 .- 0902-4441. ; 85:3, s. 251-256
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The single nucleotide polymorphism SNP309 with a change from T to G in the promoter region of the MDM2 gene is shown to increase the MDM2 protein levels and attenuate the p53 levels and associates with disease progression in several tumors. Objective: In this study, the role of the polymorphism was investigated with regard to the clinical outcome in B-cell chronic lymphocytic leukemia (B-CLL). Patients: A total of 210 patients with B-CLL were followed for up to 19 yr. Results: The overall survival (OS) of patients with at least one G-allele was significantly shorter when compared with those with two T-alleles (P = 0.024) with a more pronounced difference in patients below the median age. Age at onset of B-CLL was similar irrespective of MDM2 status. The presence of a G-allele in combination with TP53 mutations or unmutated IgVH gene status resulted in an additive risk of death. Conclusion: In this report, with a high proportion of B-CLL patients with an advanced Binet stage and with an unmutated IgVH gene, MDM2 SNP309 was found to be independently associated with OS. The survival difference was more pronounced in younger patients.
|
|
| 30. |
- Willander, Kerstin, et al.
(författare)
-
NOTCH1 mutations influence survival in chronic lymphocytic leukemia patients
- 2013
-
Ingår i: BMC Cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Background: NOTCH1 PEST domain mutations in chronic lymphocytic leukemia have recently been shown to be of prognostic relevance. Both NOTCH1 and NOTCH2 are constitutively activated in B-cell CLL but not expressed in normal B cells and may be involved in survival and resistance to apoptosis in CLL. We screened for mutations in different parts of both NOTCH1 and NOTCH2 genes and related the changes to survival and other known risk factors. Methods: In a cohort of 209 CLL patients, we used single strand conformation analysis to determine which of the samples carrying the NOTCH mutations and direct dideoxy sequencing was used to determine the exact nucleotide changes. Kaplan-Meier curves and log rank test were used to determine overall survival for NOTCH1 mutated cases and Cox regression analysis was used to calculate hazardous ratios. Results: In the present study, we found NOTCH1 PEST domain mutations in 6.7% of the cases. A shorter overall survival was found in patients with NOTCH1 mutations compared to wildtype (p = 0.049). Further, we also examined the extracellular and the heterodimerisation domains of the NOTCH1 gene and the PEST domain and heterodimerisation domain of the NOTCH2 gene, but no mutations were found in these regions. NOTCH1 mutations were most commonly observed in patients with unmutated IGHV gene (10/14), and associated with a more aggressive disease course. In addition, NOTCH1 mutations were almost mutually exclusive with TP53 mutations. In the combined group of NOTCH1 (6.7%) or TP53 (6.2%) mutations, a significant difference in overall survival compared to the wildtype NOTCH1 and TP53 was found (p = 0.002). Conclusions: Both NOTCH1 and TP53 mutations seem to be independent predictive markers for worse outcome in CLL-patients and this study emphasizes the contention that NOTCH1 mutations is a novel risk marker.
|
|
| 31. |
- Yang, Minjun, et al.
(författare)
-
13q12.2 deletions in acute lymphoblastic leukemia lead to upregulation of FLT3 through enhancer hijacking
- 2020
-
Ingår i: Blood. - : AMER SOC HEMATOLOGY. - 0006-4971 .- 1528-0020. ; 136:8, s. 946-956
-
Tidskriftsartikel (refereegranskat)abstract
- Mutations in the FMS-like tyrosine kinase 3 (FLT3) gene in 13q12.2 are among the most common driver events in acute leukemia, leading to increased cell proliferation and survival through activation of the phosphatidylinositol 3-kinase/AKT-, RAS/MAPK-, and STAT5-signaling pathways. In this study, we examine the pathogenetic impact of somatic hemizygous 13q12.2 microdeletions in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) using 5 different patient cohorts (in total including 1418 cases). The 13q12.2 deletions occur immediately 59 of FLT3 and involve the PAN3 locus. By detailed analysis of the 13q12.2 segment, we show that the deletions lead to loss of a topologically associating domain border and an enhancer of FLT3. This results in increased cis interactions between the FLT3 promoter and another enhancer located distally to the deletion breakpoints, with subsequent allele-specific upregulation of FLT3 expression, expected to lead to ligand-independent activation of the receptor and downstream signaling. The 13q12.2 deletions are highly enriched in the high-hyperdiploid BCP ALL subtype (frequency 3.9% vs 0.5% in other BCP ALL) and in cases that subsequently relapsed. Taken together, our study describes a novel mechanism of FLT3 involvement in leukemogenesis by upregulation via chromatin remodeling and enhancer hijacking. These data further emphasize the role of FLT3 as a driver gene in BCP ALL.
|
|
| 32. |
- Åhsberg, Josefine, et al.
(författare)
-
Early B-cell Factor 1 Regulates the Expansion of B-cell Progenitors in a Dose-dependent Manner
- 2013
-
Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 288:46, s. 33449-33461
-
Tidskriftsartikel (refereegranskat)abstract
- Transcription factor doses are of importance for normal and malignant B-lymphocyte development; however, the understanding of underlying mechanisms and functional consequences of reduced transcription factor levels is limited. We have analyzed progenitor and B-lineage compartments in mice carrying heterozygote mutations in the E2a, Ebf1, or Pax5 gene. Although lymphoid progenitors from Ebf1 or Pax5 heterozygote mice were specified and lineage-restricted in a manner comparable with Wt progenitors, this process was severely impaired in E2a heterozygote mutant mice. This defect was not significantly enhanced upon combined deletion of E2a with Ebf1 or Pax5. Analysis of the pre-B-cell compartment in Ebf1 heterozygote mice revealed a reduction in cell numbers. These cells expressed Pax5 and other B-lineage-associated genes, and global gene expression analysis suggested that the reduction of the pre-B-cell compartment was a result of impaired pre-B-cell expansion. This idea was supported by a reduction in IL2R-expressing late pre-B-cells as well as by cell cycle analysis and by the finding that the complexity of the VDJ rearrangement patterns was comparable in Wt and Ebf1(+/-) pre-B-cells, although the number of progenitors was reduced. Heterozygote deletion of Ebf1 resulted in impaired response to IL7 in vitro and reduced expression levels of pre-BCR on the cell surface, providing possible explanations for the observed stage-specific reduction in cellular expansion. Thus, transcription factor doses are critical for specification as well as expansion of B-lymphoid progenitors, providing increased insight into the molecular regulation of B-cell development.
|
|
| 33. |
- Åhsberg, Josefine, et al.
(författare)
-
Ebf1 heterozygosity results in increased DNA damage in pro-B cells and their synergistic transformation by Pax5 haploinsufficiency
- 2015
-
Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 125:26, s. 4052-4059
-
Tidskriftsartikel (refereegranskat)abstract
- Early B-cell factor 1 (Ebf1) is a transcription factor with documented dose-dependent functions in normal and malignant B-lymphocyte development. To understand more about the roles of Ebf1 in malignant transformation, we investigated the impact of reduced functional Ebf1 dosage on mouse B-cell progenitors. Gene expression analysis suggested that Ebf1 was involved in the regulation of genes important for DNA repair and cell survival. Investigation of the DNA damage in steady state, as well as after induction of DNA damage by UV light, confirmed that pro-B cells lacking 1 functional allele of Ebf1 display signs of increased DNA damage. This correlated to reduced expression of DNA repair genes including Rad51, and chromatin immunoprecipitation data suggested that Rad51 is a direct target for Ebf1. Although reduced dosage of Ebf1 did not significantly increase tumor formation in mice, a dramatic increase in the frequency of pro-B cell leukemia was observed in mice with combined heterozygous mutations in the Ebf1 and Pax5 genes, revealing a synergistic effect of combined dose reduction of these proteins. Our data suggest that Ebf1 controls DNA repair in a dose-dependent manner providing a possible explanation to the frequent involvement of EBF1 gene loss in human leukemia.
|
|
