scholarly journals Fra-2 regulates B cell development by enhancing IRF4 and Foxo1 transcription

2017 ◽  
Vol 214 (7) ◽  
pp. 2059-2071 ◽  
Author(s):  
Kenia Ubieta ◽  
Mireia Garcia ◽  
Bettina Grötsch ◽  
Steffen Uebe ◽  
Georg F. Weber ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcription Factors ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development ◽  
Gene Profiling ◽  
B Cell Differentiation

The role of AP-1 transcription factors in early B cell development and function is still incompletely characterized. Here we address the role of Fra-2 in B cell differentiation. Deletion of Fra-2 leads to impaired B cell proliferation in the bone marrow. In addition, IL-7–stimulated pro–B cell cultures revealed a reduced differentiation from large pre–B cells to small B cells and immature B cells. Gene profiling and chromatin immunoprecipitation sequencing analyses unraveled a transcriptional reduction of the transcription factors Foxo1, Irf4, Ikaros, and Aiolos in Fra-2–deficient B cells. Moreover, expression of IL7Rα and Rag 1/2, downstream targets of Irf4 and Foxo1, were also reduced in the absence of Fra-2. Pro–B cell proliferation and small pre–B cell differentiation were fully rescued by expression of Foxo1 and Irf4 in Fra-2–deficient pro–B cells. Hence, Fra-2 is a key upstream regulator of Foxo1 and Irf4 expression and influences proliferation and differentiation of B cells at multiple stages.

The Bcl6 RD2 Domain Is Essential For Pre-Germinal Center B Cell Development

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 783-783
Author(s):  
Chuanxin Huang ◽  
Ann Haberman ◽  
Ari M. Melnick
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Transcriptional Repression ◽  
Cell Development ◽  
B Cell Development ◽  
Wild Type ◽  
Btb Domain ◽  
Repression Domain

Abstract The transcriptional repressor Bcl6 is a master regulator of the germinal center (GC) reaction through directing naïve B cells and CD4+ T cells to differentiate into GC B cells and follicular T helper (TFH) cells respectively. Bcl6 mediates its action largely by recruitment of co-repressors through its N-terminal BTB domain and its middle second repression domain (RD2). The BTB domain repression function is critical for GC B cell survival and proliferation, but not important for TFH cell differentiation. However, the in vivobiological function of RD2 remains unknown. To explore the specific role of RD2 transcriptional repression in the GC reaction, we generated a knockin mouse model in which the endogenous Bcl6 locus encodes a mutant form of the protein that specifically disrupts RD2 mediated transcriptional repression. RD2 mutant mice were developmentally indistinguishable from wild-type mice and displayed normal B cell development prior to the GC phase. However, these mice failed to accumulate GCs after immunization with sheep blood cells and exhibited remarkably impaired production of high-affinity antibodies 21 days after T-cell dependent antigen immunization, indicative of severe deficiency of the GC reaction. Mixed bone marrow transplantation experiments showed that RD2 loss of function led to complete loss of GC B cells and partial impairment of TFH cell differentiation in cell-intrinsic manner. Intravital imaging analysis indicated that RD2-deficent antigen-engaged B cells migrate normally to the inter-follicular zone of lymph nodes and interacted normally with cognate T helper cells. To further understand the nature of the functional defect of RD2 mutant B-cells, hen egg lysosome (HEL)-specific RD2-deficient GFP B cells and wild type RFP B cells (with the ratio 1:1) were transferred together with non-fluorescent ovalbumin (OVA)-specific T cells into SMARTA hosts, which were then immunized at the footpad with HEL-OVA two days later. On day 5 after immunization, draining popliteal lymph nodes were harvested and subjected for immunofluorescence histology analysis. At this time point, wild-type RFP B cells have started to cluster into tiny GC, whereas RD2-deficient GFP B cells did not form GCs. Moreover, wild-type B cells in the follicular interior were predominantly Bcl6hi, a characteristic of pre-GC B cells, suggesting that they could serve as a source of GC B cells. By contrast, RD2-deficient GFP B cells were primarily extra-follicular, and infrequently observed in the follicle interior. Most importantly, these cells were typically Bcl6lo, demonstrating that RD2 repression function is essential for pre-GC B cell differentiation. BCL6 knockout mice display a lethal inflammatory phenotype due to aberrant T-cell and macrophage activation. In striking contrast, RD2-deficient mice experienced normal healthy lives with no inflammation, and had nearly normal inflammation cytokine production in B cells and macrophages as well as differentiation of Th1,Th2 and Th17 subtypes. Hence the RD2 repression domain is specifically involved in humoral immunity but has minimal participation in the anti-inflammatory functions of BCL6. Instead we observed that the BCL6 zing finger domain plays the key role in anti-inflammatory functions in macrophages, and through ChIP-competition assays show that this is mediated by directly competing with STATs for binding to chemokine genes. These results highlight an essential role of RD2-mediated transcriptional repression in pre-GC B cell development specifically at the early B-cell activation phase. This is different than mice with BCL6 BTB mutations where early activation is normal and the defect occurs later on in the proliferative phase of GCs. The data suggest a surprising development and cellular context-specific biochemical functions of Bcl6 governing each distinct phase of the humoral immune response and inflammation. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Increased Frequency of Pre–Pro B Cells in the Bone Marrow of New Zealand Black (NZB) Mice: Implications for aDevelopmental Block in B Cell Differentiation

2002 ◽  
Vol 9 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Zhe-Xiong Lian ◽  
Hiroto Kita ◽  
Tomoyuki Okada ◽  
Tom Hsu ◽  
Leonard D. Shultz ◽  
...  
Keyword(s):  
New Zealand ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
Cell Development ◽  
B Cell Development ◽  
B Cell Differentiation ◽  
Differentiation Markers ◽  
Cell Stage

Reductions in populations of both Pre-B cell (Hardy fractions D) and Pro-B cells (Hardy fractions B–C) have been described in association with murine lupus. Recent studies of B cell populations, based on evaluation of B cell differentiation markers, now allow the enumeration and enrichment of other stage specific precursor cells. In this study we report detailed analysis of the ontogeny of B cell lineage subsets in New Zealand black (NZB) and control strains of mice. Our data suggest that B cell development in NZB mice is partially arrested at the fraction A Pre–Pro B cell stage. This arrest at the Pre-Pro B cell stage is secondary to prolonged lifespan and greater resistance to spontaneous apoptosis. In addition, expression of the gene encoding the critical B cell development transcription factor BSAP is reduced in the Pre–Pro B cell stage in NZB mice. This impairment may influence subsequent B cell development to later stages, and thereby accounts for the down-regulation of the B cell receptor componentIgα(mb-1). Furthermore, levels of expression of theRug2, λ5andIgβ(B29) genes are also reduced in Pre–Pro B cells of NZB mice. The decreased frequency of precursor B cells in the Pre–Pro B cell population occurs at the most primitive stage of B cell differentiation.

Tumor Suppressors BTG1 and BTG2 Fulfill Both Unique and Overlapping Functions During Normal B Lymphocyte Development

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1303-1303
Author(s):  
Esther J.H. Tijchon ◽  
Liesbeth van Emst ◽  
Jørn Havinga ◽  
Jean-Pierre Rouault ◽  
Felice Tirone ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Transcription Factors ◽  
B Cells ◽  
B Cell ◽  
Tumor Suppressors ◽  
Cell Development ◽  
B Cell Development ◽  
B Cell Differentiation ◽  
B Cell Malignancies ◽  
Cell Stage

Abstract Abstract 1303 B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most common form of cancer in children, characterized by genetic aberrations affecting master regulators of lymphoid differentiation, such as RUNX1, IKZF1, TCF3, and PAX5, as well as tumor suppressor genes that control the cell cycle, including RB1 and CDKN2A. Another gene frequently altered in BCP-ALL is BTG1, which displays highly clustered mono-allelic deletions in childhood BCP-ALL (9%) and adult ALL (6%). The frequency of BTG1 deletions is two- to three-fold higher in ETV6-RUNX1- and BCR-ABL1-positive leukemias. BTG1, and its close homologue BTG2 regulate gene expression, for instance by associating with protein arginine methyltransferase 1 (PRMT1), affecting the activity of a variety of transcription factors, including several nuclear hormone receptors and HoxB9. In addition, BTG1 and BTG2 have been implicated in regulating mRNA stability by interacting with the Ccr4-Not complex. Recent studies have also identified missense point mutations in BTG1 and BTG2 in about 20% of non-Hodgkin lymphomas, arguing that altered function of these genes contributes to B cell malignancies. To investigate a role of BTG1 and BTG2 in B cell development, we studied the phenotype of Btg1 and Btg2 single knockout (KO) and Btg1;Btg2 double KO mice. Animals deficient for either BTG1 or BTG2 displayed a mild B cell phenotype with a moderate reduction of ∼20% in the total amount of B220+ progenitor B cells in bone marrow, while splenic B cells were present at normal frequencies. More detailed analyses revealed that Btg1−/− and Btg2−/− mice both showed a partial block at the pre-pro-B cell stage (Hardy fraction A). Methylcellulose colony assays in the presence of interleukin-7 (IL-7) demonstrated 30% fewer colonies using bone marrow from Btg2−/− mice, whereas 70% fewer colonies were obtained using bone marrow derived from Btg1−/− mice. To assess whether BTG1 and BTG2 fulfill redundant functions during B cell development, we analyzed the phenotype of Btg1−/−;Btg2−/− mice. Hence we observed that the combined loss of BTG1 and BTG2 led to a much stronger block in B cell differentiation, with the majority of progenitor B cells arrested at the pre-pro-B cell stage. In the spleens of these double knockout mice we observed a roughly 50% reduction in B220+ IgM+ B cells, suggesting that these genes act to modify the activity of B lineage transcription factors rather than to fully block their activities. This is consistent with a role for these genes as modifiers of transcriptional activity. Current studies are aimed at defining the molecular targets regulated by BTG1 and BTG2 during early B cell development using RNA sequencing and protein interaction experiments. In conclusion, our data demonstrate that BTG1 and BTG2 act as important regulators of normal B cell differentiation, and that this function might be critical for their role as tumor suppressors in (early) B cell malignancies. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Transcriptional Repressor Gfi-1 Integrates Cytokine-Receptor Signals Controlling B Cell Differentiation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 204-204 ◽  
Author(s):  
Chozhavendan Rathinam ◽  
Christoph Klein
Keyword(s):  
Bone Marrow ◽  
Transcription Factors ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
B Cell Development ◽  
B Cell Differentiation ◽  
Rt Pcr ◽  
Hematopoietic Stem ◽  
Deficient Mice

Abstract Hematopoietic stem cell differentiation is specified by cytokines and transcription factors but the mechanisms controlling instructive and permissive signalling networks are poorly understood. We provide evidence that common lymphoid progenitor (CLP)-1-dependent IL7-receptor mediated B cell differentiation is critically controlled by the transcriptional repressor Gfi1. Gfi1 is expressed selectively in CLP1 but not in CLP2 cells. Furthermore, in Gfi1-deficient hematopoiesis, CLP1 cells are significantly reduced, while CLP2 cells are present in normal numbers. Hardy fractions B/C, proposed to represent IL7-sensitive stages of early B cell development, are also reduced in Gfi1-deficient bone marrow. In contrast to bone marrow B cells, the phenotype of Gfi1-deficient thymic B cells was comparable to wildtype mice, suggesting that IL7-mediated signalling is perturbed. This hypothesis was further substantiated by a side-by-side comparison of Gfi1- and IL7-deficient mice; both knockout mice revealed a similar B cell phenotype in bone marrow and thymus. In vitro, Gfi1-deficient Sca1+ckit+lin- hematopoietic stem cells did not differentiate into B220+IgM+ B cells in the presence of SCF and IL7, suggesting that instructive IL7-mediated signals are not operative in the absence of Gfi1. Upon retroviral Gfi1 gene transfer, B differentiation was re-established Furthermore, whereas a combination of SCF and IL7 maintained the viability and induced proliferation of Gfi1-deficient HSC, their viability and proliferative capacity was significantly reduced in the presence of IL7 only, suggesting that both trophic and proliferative responses to IL7 depend on Gfi1. In addition, RT-PCR analysis revealed that in early B cell development the coordinated upregulation of the B cell specific transcription factors E2A, EBF, and Pax5 was significantly reduced in sorted Hardy fractions obtained from Gfi1-deficient mice. We reasoned that defective IL7-mediated responses might be due to defective Jak/Stat signalling. Indeed, phosphorylation of STAT5 was almost undectable in Gfi1-deficient B-progenitor cells. This may be due to enhanced expression levels of SOCS3 as determined by RT-PCR and Western Blot analysis. Thus, Gfi1 selectively specifies IL7-dependent development of B cells from CLP1 progenitors, providing clues to the transcriptional networks integrating cytokine signals and lymphoid differentiation.

scholarly journals Transcription factors of the alternative NF-κB pathway are required for germinal center B-cell development

2016 ◽  
Vol 113 (32) ◽  
pp. 9063-9068 ◽  
Author(s):  
Nilushi S. De Silva ◽  
Michael M. Anderson ◽  
Amanda Carette ◽  
Kathryn Silva ◽  
Nicole Heise ◽  
...  
Keyword(s):  
Transcription Factors ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Plasma Cells ◽  
Alternative Pathway ◽  
Cell Development ◽  
B Cell Development ◽  
Cell Surface Receptor ◽  
Signaling Cascade

The NF-κB signaling cascade relays external signals essential for B-cell growth and survival. This cascade is frequently hijacked by cancers that arise from the malignant transformation of germinal center (GC) B cells, underscoring the importance of deciphering the function of NF-κB in these cells. The NF-κB signaling cascade is comprised of two branches, the canonical and alternative NF-κB pathways, mediated by distinct transcription factors. The expression and function of the transcription factors of the alternative pathway, RELB and NF-κB2, in late B-cell development is incompletely understood. Using conditional deletion of relb and nfkb2 in GC B cells, we here report that ablation of both RELB and NF-κB2, but not of the single transcription factors, resulted in the collapse of established GCs. RELB/NF-κB2 deficiency in GC B cells was associated with impaired cell-cycle entry and reduced expression of the cell-surface receptor inducible T-cell costimulator ligand that promotes optimal interactions between B and T cells. Analysis of human tonsillar tissue revealed that plasma cells and their precursors in the GC expressed high levels of NF-κB2 relative to surrounding lymphocytes. Accordingly, deletion of nfkb2 in murine GC B cells resulted in a dramatic reduction of antigen-specific antibody-secreting cells, whereas deletion of relb had no effect. These results demonstrate that the transcription factors of the alternative NF-κB pathway control distinct stages of late B-cell development, which may have implications for B-cell malignancies that aberrantly activate this pathway.

scholarly journals CtIP is essential for early B cell proliferation and development in mice

2019 ◽  
Vol 216 (7) ◽  
pp. 1648-1663 ◽  
Author(s):  
Xiangyu Liu ◽  
Xiaobin S. Wang ◽  
Brian J. Lee ◽  
Foon K. Wu-Baer ◽  
Xiaohui Lin ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
B Cells ◽  
B Cell ◽  
Essential Gene ◽  
Nuclease Activity ◽  
Cell Development ◽  
Nuclear Body ◽  
B Cell Development ◽  
Immunoglobulin Gene ◽  
End Resection

B cell development requires efficient proliferation and successful assembly and modifications of the immunoglobulin gene products. CtIP is an essential gene implicated in end resection and DNA repair. Here, we show that CtIP is essential for early B cell development but dispensable in naive B cells. CtIP loss is well tolerated in G1-arrested B cells and during V(D)J recombination, but in proliferating B cells, CtIP loss leads to a progressive cell death characterized by ATM hyperactivation, G2/M arrest, genomic instability, and 53BP1 nuclear body formation, indicating that the essential role of CtIP during proliferation underscores its stage-specific requirement in B cells. B cell proliferation requires phosphorylation of CtIP at T847 presumably by CDK, but not its interaction with CtBP or Rb or its nuclease activity. CtIP phosphorylation by ATM/ATR at T859 (T855 in mice) promotes end resection in G1-arrested cells but is dispensable for B cell development and class switch recombination, suggesting distinct roles for T859 and T847 phosphorylation in B cell development.

scholarly journals IFI16Expression Is Related to Selected Transcription Factors during B-Cell Differentiation

2015 ◽  
Vol 2015 ◽  
pp. 1-20 ◽  
Author(s):  
Pier Paolo Piccaluga ◽  
Claudio Agostinelli ◽  
Fabio Fuligni ◽  
Simona Righi ◽  
Claudio Tripodo ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Cell Differentiation ◽  
B Cell ◽  
Peripheral Blood Lymphocytes ◽  
B Cell Differentiation ◽  
Cellular Survival ◽  
Human B Cells ◽  
Proliferation And Differentiation ◽  
B Cell Subsets

The interferon-inducible DNA sensor IFI16 is involved in the modulation of cellular survival, proliferation, and differentiation. In the hematopoietic system, IFI16 is consistently expressed in the CD34+ stem cells and in peripheral blood lymphocytes; however, little is known regarding its regulation during maturation of B- and T-cells. We explored the role of IFI16 in normal B-cell subsets by analysing its expression and relationship with the major transcription factors involved in germinal center (GC) development and plasma-cell (PC) maturation.IFI16mRNA was differentially expressed in B-cell subsets with significant decrease inIFI16mRNA in GC and PCs with respect to naïve and memory subsets.IFI16mRNA expression is inversely correlated with a few master regulators of B-cell differentiation such asBCL6, XBP1, POU2AF1, andBLIMP1. In contrast,IFI16expression positively correlated withSTAT3, REL, SPIB, RELA, RELB, IRF4, STAT5B, andSTAT5A. ARACNE algorithm indicated a direct regulation ofIFI16byBCL6,STAT5B, andRELB, whereas the relationship betweenIFI16and the other factors is modulated by intermediate factors. In addition, analysis of the CD40 signaling pathway showed thatIFI16gene expression directly correlated with NF-κB activation, indicating that IFI16 could be considered an upstream modulator of NF-κB in human B-cells.

The Proto-Oncogene LRF Is Essential for Normal Mature B Cell Development and Germinal Center Formation.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1788-1788
Author(s):  
Nagisa Sakurai ◽  
Manami Maeda ◽  
Sung-UK Lee ◽  
Julie Teruya-Feldstein ◽  
Takahiro Maeda
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Development ◽  
B Cell Development ◽  
Cell Stage ◽  
Transitional B Cells ◽  
Notch Pathways ◽  
Secondary Lymphoid Organs

Abstract LRF (Leukemia/Lymphoma Related Factor, also known as Pokemon, FBI-1, OCZF and ZBTB7a) was originally identified as an interaction partner of the oncoprotein BCL6. LRF can act as a proto-oncogene by repressing the tumor suppressor ARF and cooperates with BCL6 in MEF (mouse embryonic fibroblasts) immortalization. It is highly expressed in human Non-Hodgkin Lymphoma (NHL) cases, in the pathogenesis of which BCL6 is known to be involved (Maeda et al. Nature 2005). Inducible inactivation of the LRF gene in mouse Hematopoietic Stem Cells (HSCs) results in complete block of early B cell development at the HSC/progenitor stages and concomitant development of double positive (DP) T cells in the bone marrow (BM) (Maeda et al. Science 2007). While these findings clearly illustrate key roles of LRF in normal and malignant B cell development, it is not fully identified as to which B cell stages LRF is required during normal B cell development. To elucidate the role of LRF in B cells in vivo, we established and characterized B cell-specific LRF conditional knockout (KO) mice. We took advantage of mb-1 Cre knock-in mice, in which Cre expression is restricted to the B cells after the ProB cell stage. B cell compartments in the BM (PreProB, ProB, PreB and immatureB) are grossly normal in LRFF/ Fmb1-Cre mice. The LRF gene was efficiently eliminated in BM CD19+ B cells revealed by quantitative real-time PCR assay. Furthermore, LRF protein was not detected in purified CD19+ B cells, but seen in CD19-non-B cells, confirming the specific inactivation of the LRF gene in B cells. Thus, despite its critical role at the HSC/progenitor stages, LRF was found to be dispensable for the survival of normal BM B cells. These findings are consistent with the fact that GSI treatment (Maeda et al. Science 2007) or Notch1 loss (Lee and Maeda, unpublished) rescues the defects in early B cell development seen in LRFF/FMx1-Cre+ mice. Notch signaling is necessary for the transitional B cells to commit to the marginal zone B cells (MZB). Inactivation of the component of the Notch pathways in mice results in no MZB development. On the contrary, deletion of the MINT/SHARP gene, a suppressor of Notch signaling, leads to increase of MZB cells and concomitant reduction of follicular B (FOB) cells, indicating that Notch induces MZB cell fate at the transitional B cell stage. Given that LRF is a potent Notch suppressor at the HSC/progenitor stages, we hypothesized that LRF opposes Notch pathway in mature B cells as well. To test this hypothesis, we characterized mature B cell development in LRFF/Fmb1-Cre mice. While transitional B cells were largely unaffected in LRFF/Fmb1-Cre mice, we observed a slight but statistically significant reduction of follicular (FO) B cells (B220+CD19+AA4.1-CD1d-CD23+) and concomitant increase of MZB cells (B220+CD19+AA4.1-CD1d+CD23-) as seen in MINT/SHARP knockout mice. Thus, LRF may also oppose Notch pathways at the branching point for the FOB vs. MZB fate decision. Finally, to determine the role of LRF in Germinal Center (GC) formation in vivo, we characterized secondary lymphoid organs of LRFF/Fmb1-Cre mice after antigen stimulation. Both spleen and Peyer’s Patches were analyzed two weeks after immunization with Chicken Gamma Globulin (NP-CGG). While a GC reaction was robustly induced in control mice upon immunization, GC formation was significantly impaired in LRFF/Fmb1-Cre mice as revealed by immuno-histochemical analysis (IHC) and FACS. Only few GC cells (B220+CD19+FAS+CD38-PNA+) were observed in spleens, and the absolute numbers of GC cells were drastically reduced in LRFF/Fmb1-Cre mice. Residual LRF-deficient GC B cells were mostly negative for CXCR4, which is predominantly expressed in proliferating centroblasts within GCs, suggesting that LRF-deficient GC B cells may have defects in cellular proliferation in response to antigen stimuli. Our data indicates that LRF plays key roles in mature B cell development in the secondary lymphoid organs, but dispensable for the maintenance of early BM B cells.

Precursor B Cell Acute Lymphoblastic Leukemia Induces Pro-Leukemic Changes in the Bone Marrow Microenvironment That Contribute to Therapeutic Resistance

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1466-1466
Author(s):  
Christopher D Chien ◽  
Elizabeth D Hicks ◽  
Paul P Su ◽  
Haiying Qin ◽  
Terry J Fry
Keyword(s):  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
B Cells ◽  
B Cell ◽  
Lymphoblastic Leukemia ◽  
Cell Development ◽  
B Cell Development ◽  
Bone Marrow Microenvironment ◽  
Therapeutic Resistance

Abstract Abstract 1466 Pediatric acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Although cure rates for this disease are approximately 90%, ALL remains one of the leading causes cancer-related deaths in children. Thus, new treatments are needed for those patients that do not respond to or recur following standard chemotherapy. Understanding the mechanisms underlying resistance of pediatric ALL to therapy offers one approach to improving outcomes. Recent studies have demonstrated the importance of communication between cancer cells and their microenvironment and how this contributes to the progression and therapeutic resistance but this has not been well studied in the context of ALL. Since the bone marrow is presumed to be the site of initiation of B precursor ALL we set out in our study to determine how ALL cells utilize the bone marrow milieu in a syngeneic transplantable model of preB cell ALL in immunocompetent mice. In this model, intravenously injected preB ALL develops first in the bone marrow, followed by infiltration into the spleen, lymph node, and liver. Using flow cytometry to detect the CD45.2 isoform following injection into B6CD45.1+ congenic recipients, leukemic cells can be identified in the bone marrow as early as 5 days after IV injection with a sensitivity of 0.01%-0.1%. The pre-B ALL line is B220+/CD19+/CD43+/BP1+/IL-7Ralpha (CD127)+/CD25-/Surface IgM-/cytoplasmic IgM+ consistent with a pre-pro B cell phenotype. We find that increasing amounts of leukemic infiltration in the bone marrow leads to an accumulation of non-malignant developing B cells at stages immediately prior to the pre-pro B cell (CD43+BP1-CD25-) and a reduction in non-malignant developing pre B cells at the developmental stage just after to the pre-pro B cell stage (CD43+BP1+CD25+). These data potentially suggest occupancy of normal B cell developmental niches by leukemia resulting in block in normal B cell development. Further supporting this hypothesis, we find significant reduction in early progression of ALL in aged (10–12 month old) mice known to have a deficiency in B cell developmental niches. We next explored whether specific factors that support normal B cell development can contribute to progression of precursor B cell leukemia. The normal B cell niche has only recently been characterized and the specific contribution of this niche to early ALL progression has not been extensively studied. Using a candidate approach, we examined the role of specific cytokines such as Interleukin-7 (IL-7) and thymic stromal lymphopoietin (TSLP) in early ALL progression. Our preB ALL line expresses high levels of IL-7Ralpha and low but detectable levels of TLSPR. In the presence of IL-7 (0.1 ng/ml) and TSLP (50 ng/ml) phosphSTAT5 is detectable indicating that these receptors are functional but that supraphysiologic levels of TSLP are required. Consistent with the importance of IL-7 in leukemia progression, preliminary data demonstrates reduced lethality of pr-B cell ALL in IL-7 deficient mice. Overexpression of TSLP receptor (TSLPR) has been associated with high rates of relapse and poor overall survival in precursor B cell ALL. We are currently generating a TSLPR overepressing preBALL line to determine the effect on early ALL progression and are using GFP-expressing preB ALL cells to identify the initial location of preB ALL occupancy in the bone marrow. In conclusion, or model of early ALL progression provides insight into the role of the bone marrow microenvironment in early ALL progression and provides an opportunity to examine how these microenvironmental factors contribute to therapeutic resistance. Given recent advances in immunotherapy for hematologic malignancies, the ability to study this in an immunocompetent host will be critical. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Two Distinct Pathways of B-Cell Development in Peyer’s Patches

1995 ◽  
Vol 4 (4) ◽  
pp. 263-277 ◽  
Author(s):  
Philip J. Griebel ◽  
Birgit Kugelberg ◽  
Giorgio Ferrari
Keyword(s):  
Cell Proliferation ◽  
B Cells ◽  
B Cell ◽  
Lymphoid Tissue ◽  
Day Treatment ◽  
Cell Development ◽  
B Cell Development ◽  
Peyer's Patches ◽  
Peyer’S Patches ◽  
Dexamethasone Treatment

The developmental biology of sheep ileal and jejunal Peyer’s patches (PP) was investigated using corticosteroids to deplete immature B lymphocytes. During a 7-day treatment with dexamethasone, ileal PP follicular (iPf)B-cell proliferation was arrested and most iPfB-cells died. This resulted in follicular involution with the survival of mesenchymal cells. No iPfB-cell proliferation was detected in follicular remnants for 4 weeks postdexamethasone treatment, and during a subsequent 3-month period, there was limited iPfB-cell proliferation that resulted in a partial regeneration of follicles. Ileal PP involution was also associated with a severe B lymphopenia that persisted for over 14 weeks and was characterized by the survival of primarily isotype-switched and CD5+sIgM+B-cells in blood. In contrast, the size of jejunal PP follicles was reduced following dexamethasone treatment, but intrafollicular B-cell proliferation was not arrested. Furthermore, within 4 weeks, the jejunal PP follicles had recovered in size and cellularity and there was no disruption in IgA plasma-cell production. Thus, dexamethasone selectively depleted iPfB-cells and revealed that the ileal and jejunal PPs contain functionally distinct B-cell populations. The partial regeneration of the iPfB-cell population indicated that either an intrafollicular, corticosteroid-resistant B-stem cell existed or that ileal PP follicles can be repopulated by circulating B-cells. Finally, the association between ileal PP involution and the absence of circulating, CD5-B-cells confirmed that this lymphoid tissue provides an essential environment for conventional sIgM+B-cell development.

Sign in / Sign up

Export Citation Format

Share Document