Bone Marrow Hypoplasia Induced by Conditional Knockout of the RNase III Domain of Dicer-1

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2226-2226
Author(s):  
Tai-Chung Huang ◽  
Yi Yang ◽  
Cory Brayton ◽  
Wen-Chien Chou ◽  
Akhilesh Pandey
Keyword(s):  
Bone Marrow ◽  
Copy Number ◽  
Conflicts Of Interest ◽  
Histopathological Examination ◽  
Treated Group ◽  
Conditional Knockout ◽  
Rnase Iii ◽  
Qrt Pcr ◽  
Adult Mice ◽  
The Impact

Abstract Abstract 2226 Background: MicroRNAs (miRs) play important roles in normal hematopoiesis as well as in hematopoietic malignancies. In generating mature miRs, Dicer-1, an RNase III in the cytosol, excises the hairpin-loop of precursor miRs and assembles mature miRs onto an RNA-Induced Silencing Complex. Among 27 exons of Dicer1, exons 21 and 22 comprise the RNase IIIa domain. Knockout of this domain was shown to be lethal in mouse embryos. In this study, we used tamoxifen to induce Cre-mediated exon deletion and our goal was to investigate the impact of Dicer1 knockout on hematopoiesis in adult mice. Material and Methods: Two C57BL/6 transgenic mice were crossed: ROSA26-CreERT2 and floxed Dicer1 exons 21 & 22. At the age of 8 week, three female mice were treated with tamoxifen (1 mg/day, Day 1 to 5) and two with placebo. On Day 8, mice were sacrificed for examination. DNA genotyping and qRT-PCR were used to confirm Dicer1 genomic deletion and to quantify the transcription copy number of Dicer1. Cardiocentesis was done for complete peripheral blood count. Femoral and tibial bone marrow, spleen and inguinal lymph nodes were evaluated by flow cytometry whereas formalin-perfused sternum and thymus were subjected to histopathological examination. Results: Two tamoxifen-treated mice presented with unkempt appearance, hunched posture and diarrhea from Day 7. Vehicle-treated control mice remained clinically normal. qRT-PCR showed lower copy number of Dicer1 exons 21 & 22 in tamoxifen-treated group than in control (0.09 vs. 1.00). In tamoxifen-treated group, the spleen weights were lower, white blood cell and platelet counts were lower and bone marrow histopathology revealed hypocellularity, with markedly reduced and immature myeloid elements, consistent with arrested or abrogated development of myelomonocytic and megakaryocytic elements. Conclusions: The RNase III domain of Dicer-1 is crucial for the normal differentiation of marrow myeloid series in adult mice, probably at the stage of common myeloid progenitor. Disclosures: No relevant conflicts of interest to declare.

Tet2 Loss Accelerates The Myeloproliferative Neoplasm (MPN) Phenotype Of Jak2V617F Knockin Mice But Is Insufficient To Cause Leukemic Transformation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4095-4095
Author(s):  
Edwin Chen ◽  
Lawrence J Breyfogle ◽  
Rebekka K. Schneider ◽  
Luke Poveromo ◽  
Ross L. Levine ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasms ◽  
Myeloproliferative Neoplasm ◽  
Conditional Knockout ◽  
The Other ◽  
Myelogenous Leukemia ◽  
Leukemic Transformation ◽  
The Impact

Abstract TET2 mutations are early somatic events in the pathogenesis of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and myeloproliferative neoplasms (MPN) and are one of the most common genetic lesions found in these diseases. In MPN, TET2 mutations are enriched within more advanced disease phenotypes such as myelofibrosis and leukemic transformation and often co-occur with the JAK2V617F mutation, which is present in the majority of MPN patients. We have developed and characterized a Jak2V617F conditional knockin mouse (Jak2VF/+), the phenotype of which closely recapitulates the features of human MPN. To determine the impact of Tet2 loss on Jak2V617F-mediated MPN, we crossed Tet2 conditional knockout mice with Jak2VF/+ knockin and Vav-Cre transgenic mice and backcrossed the compound mutant animals. We then characterized the effects of heterozygous and homozygous loss of Tet2 on the phenotype of Jak2VF/+ mice. We assessed peripheral blood counts, histopathology, hematopoietic differentiation using flow cytometry, colony formation and re-plating capacity. We also evaluated the effects of Tet2 loss on the transcriptome of the HSC compartment using gene expression microarrays and on HSC function using competitive bone marrow transplantation assays. Similar to Jak2VF/+/VavCre+ mice, Tet2+/-/Jak2VF/+/VavCre+ and Tet2-/-/Jak2VF/+/VavCre+ mice develop leukocytosis, elevated hematocrits (HCT) and thrombocytosis. Tet2-/-/Jak2VF/+/VavCre+ mice demonstrate enhanced leukocytosis and splenomegaly compared to the other groups. All groups demonstrate myeloid expansion, erythroid hyperplasia and megakaryocytic abnormalities consistent with MPN in the bone marrow and spleen, while more prominent myeloid expansion and megakaryocytic morphological abnormalities are observed in Tet2-/-/Jak2VF/+/VavCre+ mice as compared to the other groups. Notably, we do not see the development of acute myelogenous leukemia (AML) in Tet2-/-/Jak2VF/+/VavCre+ mice at 6 months. We see enhanced expansion of lineagelowSca1+cKithigh (LSK) cells (enriched for HSC) most prominently in the spleens of Tet2+/-/Jak2VF/+/VavCre+ and Tet2-/-/Jak2VF/+/VavCre+ mice as compared to Jak2VF/+/VavCre+ mice. In colony forming assays, we find that Tet2-/-/Jak2VF/+/VavCre+ LSK cells have enhanced re-plating activity compared to Jak2VF/+/VavCre+ LSK cells and that Tet2-/-/Jak2VF/+/VavCre+ LSK cells form more colonies that Tet2-/-/Jak2+/+/VavCre+ cells. Gene expression analysis demonstrates enrichment of a HSC self-renewal signature inTet2-/-/Jak2VF/+/VavCre+ LSK cells. Concordant with this, we find that Tet2-/-/Jak2VF/+/VavCre+ LSK cells have enhanced competitive repopulation at 16 weeks as compared to Jak2VF/+/VavCre+ and Tet2+/-/Jak2VF/+/VavCre+ LSK cells. In aggregate these findings demonstrate that Tet2 loss promotes disease progression in MPN but is insufficient to drive full leukemic transformation. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Clinical Characteristics, Immunophenotype and Outcomes of Blastic Plasmacytoid Dendritic Cell Neoplasms in a Peruvian Cohort

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 42-43
Author(s):  
Daniela Dueñas ◽  
Elizabeth Cervantes ◽  
Daniel J Enriquez ◽  
Claudio Flores ◽  
Carlos Barrionuevo ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Dendritic Cell ◽  
Clinical Characteristics ◽  
Conflicts Of Interest ◽  
Plasmacytoid Dendritic Cell ◽  
Age At Diagnosis ◽  
Bone Marrow Infiltration ◽  
Maturation Stage ◽  
Female Predominance ◽  
The Impact

Background:Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and fatal myeloid malignancy characterized by clonal proliferation of immature plasmacytoid dendritic cells. BDCN has been frequently described in men and age above 60 years, and usually involves the skin and bone marrow. Immunophenotyping is based on CD123+, CD4+ and CD56+ expression and is necessary rule out other myeloid malignancies. Objective: We aimed to describe the clinical characteristics and immunophenotype of BPDCN cases diagnosed at two tertiary Peruvian cancer institutions between 2018-2019. Methods: We retrospectively reviewed medical records of patients diagnosed of BPDCN at two tertiary Peruvian cancer centers (Instituto Nacional de Enfermedades Neoplasicas and Oncosalud-AUNA, Lima-Peru) between 2008 and 2019. Clinical characteristics, treatments, outcomes and immunophenotype by pathology or flow cytometry review, were collected. Patients were classified according to their maturation stage using CD34 and CD117 expression into three subgroups: Immature-Intermediate blastic (IIB-BPDCN; partial expression of CD117 and absence or minimal expression of CD34), mature (M-BPDCN; absence of CD34 and CD117) and unknown(U-BPDCN). Overall survival (OS) and event-free survival (EFS) curves were estimated using the Kaplan-Meier method and compared with the Log-rank test to determine the impact of immunophenotype. Results: Thirty-eight cases were included during the study period. The median age at diagnosis was 38 years (7-82), only six (16%) were older than 65 years, and a notorious female predominance (F/M ratio: 1.7:1) was observed. Twenty-four cases had CD34/117 expression available and were classified according to the maturation stage in IIB-BPDCN (13) and M-BPDCN(11), additionally 14 cases had unknown stage (U-BPDCN). Table 1 summarizes clinical characteristics, treatment and outcomes according to their immunophenotype. Bone marrow infiltration was more frequent in immature phenotypes (92% IIB-BPDCN vs 73% M-BPDCN, p=0.001), as well as skin infiltration was more common in mature phenotype (72% vs 31%, p=0.008). CNS infiltration at diagnosis was 15% and 55% in IIB-BPDCN and M-BPDCN, respectively. Sixteen patients received treatment based on ALL-like protocols, 8 AML-like, 5 CHOP-like and 9 patients only palliative care. At 5 years median follow-up, median EFS and OS was 12 and 16 months, respectively. IIB-BPDCN had the lowest survival (4 months EFS and 6 months OS). Conclusions: We describe a Peruvian cohort of BPDCN patients with younger age at diagnosis and female predominance than reported previously by other series, however further studies in Latino population are required to confirm these results. Immature phenotypes based on CD34 and CD117 expression were associated with high rate of bone marrow infiltration and fatal outcomes. New successful target therapies must be warranted for this rare and fatal condition. Disclosures No relevant conflicts of interest to declare.

Abnormal Distribution of Erythroid Progenitors Populations in Mice Lacking p45 NF-E2.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1988-1988
Author(s):  
Jadwiga Gasiorek ◽  
Gregory Chevillard ◽  
Zaynab Nouhi ◽  
Volker Blank
Keyword(s):  
Bone Marrow ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Conflicts Of Interest ◽  
Globin Genes ◽  
Erythroid Progenitors ◽  
Erythroid Progenitor ◽  
Adult Mice ◽  
Deficient Mice

Abstract Abstract 1988 Poster Board I-1010 The NF-E2 transcription factor is a heterodimer composed of a large hematopoietic-specific subunit called p45 and widely expressed 18 to 20-kDa small Maf subunits. In MEL (mouse erythroleukemia) cells, a model of erythroid differentiatin, the absence of p45 is inhibiting chemically induced differentiation, including induction of globin genes. In vivo, p45 knockout mice were reported to show splenomegaly, severe thrompocytopenia and mild erythroid abnormalities. Most of the mice die shortly after birth due to haemorrhages. The animals that survive display increased bone, especially in bony sites of hematopoiesis. We confirmed that femurs of p45 deficient mice are filled with bone, thus limiting the space for cells. Hence, we observed a decrease in the number of hematopoietic cells in the bone marrow of 3 months old mice. In order to analyze erythroid progenitor populations we performed flow cytometry using the markers Ter119 and CD71. We found that p45 deficient mice have an increased proportion of early erythroid progenitors (proerythroblasts) and a decreased proportion of late stage differentiated red blood cells (orthochromatic erythroblasts and reticulocytes) in the spleen, when compared to wild-type mice. We showed that the liver of p45 knockout adult mice is also becoming a site of red blood cell production. The use of secondary sites, such as the spleen and liver, suggests stress erythropoiesis, likely compensating for the decreased production of red blood cells in bone marrow. In accordance with those observations, we observed about 2 fold increased levels of erythropoietin in the serum of p45 knockout mice.Overall, our data suggest that p45 NF-E2 is required for proper functioning of the erythroid compartment in vivo. Disclosures: No relevant conflicts of interest to declare.

TIMP-1 and TIMP-2 Levels Are Directly Correlated with Neoangiogenesis and Are Prognostic Factors in Multiple Myeloma Patients.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4866-4866
Author(s):  
Luciana Correa Oliveira de Oliveira ◽  
Juliana Alves Uzuelli ◽  
Ana Paula Alencar de Lima Lange ◽  
Barbara Amelia Aparecida Santana-Lemos ◽  
Marcia Sueli Baggio ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Overall Survival ◽  
Prognostic Factors ◽  
Bone Disease ◽  
Cox Regression ◽  
Conflicts Of Interest ◽  
Newly Diagnosed ◽  
Significant Difference ◽  
The Impact

Abstract Abstract 4866 Background Multiple myeloma (MM) is an incurable malignant disease, characterized by increased angiogenesis in the bone marrow (BM) microenvironment and aberrant BM metabolism. Matrix metalloproteinases (MMP) are a family of zinc-dependent endopeptidases implicated in tumour progression, invasion, metastasis and angiogenesis, via proteolytic degradation of extracellular matrix. MMPs are inhibited by tissue inhibitors of metalloproteinase (TIMP). Although recent studies have implicated MMP 9 in MM bone disease, little is known about the role of the TIMPs. Objectives a) to compare levels of sRANKL, OPG, MMP-2, MMP-9, TIMP-1, TIMP-2, VEGF, bFGF, microvessel density (MVD) between newly diagnosed MM patients and healthy controls; b) to determine the association of these molecules with disease progression, bone disease and neoangiogenesis and c) to evaluate the impact of these variables on survival. Patients and Methods As of July 2009 38 newly diagnosed and untreated multiple myeloma patients were enrolled in the study. The median age was 61years-old (range 39-91) with 24 (63%) males. Patients were diagnosed and categorized according The International Myeloma Working Group criteria and ISS, respectively. Bone involvement was graded according to standard X-ray: patients with no lesions, or with one/ two bones involved or diffuse osteoporosis were classified as low score, whereas patients with lesions in more than two bones or presence of bone fracture were classified as high score. MMP-2 and MMP-9 were determined by PAGE gelatin zymography from plasma as previously described. MMP-9, TIMP-1 and TIMP-2, OPG and sRANKL concentrations were measured by ELISA. The levels of VEGF, bFGF were obtained using cytometric bead array. Ten healthy volunteers were used as controls. Bone marrow MVD measured in hotspots was evaluated in 26 out of 38 patients at diagnosis and 15 patients with Hodgkin Lymphoma stage IA and IIA (used as controls) by staining immunohistochemically for CD34. Comparisons among groups were analyzed by ANOVA and the correlation by the Spearman's correlation coefficient. Cox regression were performed for overall survival (OS) analysis. Results Patients with MM had elevated TIMP-1, TIMP-2 and OPG values compared with controls. No significant difference was found between plasma sRANKL, pro-MMP2, pro-MMP9 and MMP-9 levels. We found that plasma TIMP-1 levels correlated positively with bFGF, VEGF, MVD, beta-2 microglobulin (B2M) and OPG (r: 0.514, p=0,001, r: 0.350, p=0,031; r: 0.610, p<0.0001; r: 0.760, p<0.0001 and r: 0.701, p<0.0001, respectively) and TIMP-2 levels with bFGF, DMV, B2M and OPG (r: 0.512, p=0.002; r: 0.595, p<0.0001; r: 0.587, p<0.0001 and r: 0.552, p<0.0001, respectively). TIMP-1 and TIMP-2 levels correlated with the ISS stage (p<0.0001, p=0.006, respectively). The only variables that correlated with clinical bone disease staging were hemoglobin, B2M and albumin levels, whereas TIMP-1, TIMP-2, bFGF, VEGF and OPG correlated with DMV. On the univariate analyses, age, gender, proMMP2, TIMP-1, TIMP-2, creatinine, B2M and MVD were significantly associated with overall survival. In Cox regression model, TIMP-1, TIMP-2 and B2M levels remained to be significantly associated with OS. In conclusion, our results suggest that TIMP-1 and TIMP-2 levels are strongly associated with neoangiogenesis and are independent prognostic factors in MM. Disclosures No relevant conflicts of interest to declare.

Evolution of Human BCR-ABL1 lymphoblastic Leukaemia-Initiating Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1023-1023
Author(s):  
Faiyaz Notta ◽  
Charles Mullighan ◽  
Jean Wang ◽  
Armando G Poeppl ◽  
Sergei Doulatov ◽  
...  
Keyword(s):  
Patient Outcome ◽  
Genetic Diversity ◽  
Lymphoblastic Leukaemia ◽  
Copy Number ◽  
Copy Number Alteration ◽  
Conflicts Of Interest ◽  
Clonal Diversity ◽  
Poor Patient ◽  
Growth Properties ◽  
The Impact

Abstract Abstract 1023 Many tumour types are composed of genetically diverse cells, however little is known of how diversity evolves or the impact that diversity has on functional properties. Here, using xenografting and DNA copy number alteration (CNA) profiling of human BCR-ABL1 acute lymphoblastic leukaemia, we demonstrate that genetic diversity occurs in functionally defined leukaemia-initiating cells and that many diagnostic patient samples contain multiple genetically distinct subclones. Reconstruction of the subclonal genetic ancestry of several samples by CNA profiling demonstrated a branching multiclonal evolution model of leukaemogenesis, rather than linear succession. For some patient samples, the predominant diagnostic clone repopulated xenografts, while in others it was outcompeted by minor subclones. Reconstitution with the predominant diagnosis clone was associated with more aggressive growth properties in xenografts, deletion of CDKN2A/CDKN2B, and poor patient outcome. Our findings link clonal diversity with function and underscore the importance of developing therapies that eradicate all subclones. Disclosures: No relevant conflicts of interest to declare.

Association of PML Expression with Chemotherapy-Resistance In Multiple Myeloma Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2959-2959
Author(s):  
Daisuke Ohgiya ◽  
Makoto Onizuka ◽  
Hiromichi Matsushita ◽  
Naoya Nakamura ◽  
Hiroshi Kawada ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Cellular Proliferation ◽  
Conflicts Of Interest ◽  
Alkylating Agents ◽  
Chemotherapy Resistance ◽  
Nuclear Body ◽  
Rank Test ◽  
Significant Difference ◽  
The Impact

Abstract Abstract 2959 Background: Although several novel agents have improved the prognosis of patients with multiple myeloma (MM), it still remains an incurable disease because of the difficulty to eradicate MM cells by current therapeutic approaches. Recent studies have revealed that a subset of malignant cells, cancer stem cells, contribute to chemotherapy-resistance in cancer treatment. Promyelocytic leukemia gene product (PML), known as a tumor suppressor through a variety of cellular functions in a nuclear macromolecular structure called the PML nuclear body, has been reported to be responsible for the chemotherapy-resistance by regulating cell cycle in chronic myeloid leukemia. We therefore investigated the impact of PML expression on the cellular proliferation status of MM cells and patients' prognoses. Materials/Methods: Bone marrow clot sections from 48 patients with newly diagnosed MM from Jan 1998 to Dec 2009 before any therapy at diagnosis were obtained, and analyzed, according to appropriate procedure approved by IRB at the Tokai University School of Medicine (Kanagawa, Japan) with written informed consent. They were doubly-stained with a combination of anti-PML/anti-CD138 and anti-Ki67/anti-CD138. For evaluation of the relation between PML status and cellular proliferation, the positive rates of PML and Ki67 in CD138 positive cells were compared. For investigation of the impact of PML expression on the prognosis of MM, the patients were divided into 3 groups, according to the PML positive rates in the CD138 positive cells: negative/low (less than 25 percentile: 12 cases), intermediate (from 25 to 75 percentile: 24 cases) and high (more than 75 percentile: 12 cases). Their overall survivals were compared using log-rank test. Furthermore, the PML positive rates between before and after treatments were compared using paired t-test. Results: The median observation period of 48 cases was 915 days. The median age of the patients was 62.5 (38-76) at diagnosis. All the patients were underwent combination chemotherapies containing alkylating agents as initial therapies. Two and nine patients were underwent allogeneic and autologous stem cell transplantation during the clinical courses, respectively. The numbers of patients of international staging system (ISS) stage I, II and III were 17, 14 and 17 cases. The PML positive rates in each case ranged from 0% to 83.8%. They were not correlated with ISS stages (Spearman r = 0.083) and the Ki67 positive rates (Spearman r = -0.13). The PML positive rates in the negative/low, intermediate and the high groups were less than 22.1%, from 22.1 to 56.6% and more than 56.6%, respectively. No significant difference in overall survival was observed among the 3 groups (p>0.05). However, there were significant differences in two year survival rate when the 3 groups were compared (100%, 85.2% and 54.7%; p=0.015) (Fig. 1). In 13 patients whose bone marrow clot sections were sequentially collected, the PML positive rates after treatments were significantly higher than those at diagnosis (p=0.0042) (Fig. 2). Especially, PML positive rates in all the 3 patients from the negative/low group were progressively increased (0.3 to 82.6%, 14.1 to 100%, 19.0 to 37.5%), and 2 of them died due to disease progression. On the other hand, 2 patients whose PML positive rates decreased after treatment were alive more than 5 years without therapies. Conclusion: Our data indicated that the level of the PML expression at diagnosis was a possible prognostic factor for early course of the disease (2 years after diagnosis). Chemotherapies might induce PML expression in MM cells or select PML positive MM cells. These findings suggest that PML expression presumably reflect chemotherapy-resistance in MM cells. The molecular mechanism of the association is now under investigation. Disclosures: No relevant conflicts of interest to declare.

RhoA Is An Essential Regulator of Mitosis and Survival During Hematopoietic Stem Cell Differentiation to Multipotent Progenitors

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1273-1273
Author(s):  
Xuan Zhou ◽  
Jaime Meléndez ◽  
Yuxin Feng ◽  
Richard Lang ◽  
Yi Zheng
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Intracellular Signaling ◽  
Conflicts Of Interest ◽  
Stem Cell Differentiation ◽  
Conditional Knockout ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Stem ◽  
Differentiated Cells ◽  
Multipotent Progenitors

Abstract Abstract 1273 The maintenance and differentiation of hematopoietic stem cells (HSC) are critical for blood cell homeostasis, which is tightly regulated by a variety of factors. In spite of extensive investigation of HSC biology, however, the mechanism of regulation of HSC and progenitor cell division, particularly the unique molecular events controlling the mitosis process during HSC differentiation, remains unclear. RhoA GTPase is a critical intracellular signaling nodal that has been implicated in signal transduction from cytokines, chemokines, wnt/notch/shh, and adhesion molecules to impact on cell adhesion, migration, cell cycle progression, survival and gene expression. Recent mouse genetic studies in keratinocytes and embryonic fibroblast cells showed that RhoA is a key regulator of mitosis. By using an interferon-inducible RhoA conditional knockout mouse model (Mx-cre;RhoAlox/lox), we have made the discovery that RhoA plays an indispensible role in primitive hematopoietic progenitor differentiation through the regulation of mitosis and survival. RhoA deficient mice die at ∼10 days because of hematopoietic failure, as evidenced by a loss of bone marrow, splenocyte and PB blood cells. Syngenic as well as reverse transplant experiments demonstrate that these effects are intrinsic to the hematopoietic compartment. RhoA loss results in pancytopenia associated with a rapid exhaustion of the lin−c-kit+ (LK) phenotypic progenitor population (within 4 days after two polyI:C injections). Meanwhile, the lin−c-kit+sca1+ (LSK) primitive cell compartment is transiently increased in BM after RhoA deletion due to a compensatory loss of quiescence and increased cell cycle. Interestingly, we find that within the LSK population, there is a significant accumulation of LSKCD34+Flt2− short-term HSCs (ST-HSC) and a corresponding decrease in frequency of LSKCD34+Flt2+ multipotent progenitors (MPPs). Consistent with these phenotypes, the LK and more differentiated hematopoietic cell populations of RhoA knockout mice show an increased apoptosis while the survival activities of LSK and more primitive compartments of WT and RhoA KO mice remain comparable. These data suggest that RhoA plays an indispensible role in the step of ST-HSCs differentiation to MPP cells, possibly through the regulation of MPP cell survival. This hypothesis is further supported by a competitive transplantation experiment. Deletion of RhoA in a competitive transplantation model causes an extinction of donor derived (CD45.2+) differentiated cells (myeloid, erythroid, T and B cells) in the peripheral blood. Interestingly, bone marrow CD45.2+ LSK cells are only marginally affected by deletion of RhoA and RhoA−/− LSK cells are able to engraft into 2nd recipient, whereas CD45.2+ LK and more differentiated cells are mostly eliminated after RhoA deletion. This effect is associated with a decrease in the survival of CD45.2+ RhoA−/− LK, but not LSK cells. Further in vitro culture of isolated lin− progenitors demonstrates that RhoA deficiency results in a failure of cytokinesis, causing an accumulation of multinucleated cells, further suggesting that RhoA is essential for the cytokinesis of hematopoietic progenitors. Surprisingly, the well-defined Rho downstream target, actomyosin machinery, does not appear to be affected by RhoA knockout. We are further exploring the mechanism of RhoA contribution to the differentiation of HSCs by dissecting the signaling and functional relationship of RhoA regulated survival activity and cell cycle mitosis in early hematopoietic progenitors. Disclosures: No relevant conflicts of interest to declare.

Effects of G-CSF On Acute Lymphoblastic Leukemia.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2564-2564
Author(s):  
Jordan Basnett ◽  
Adam Cisterne ◽  
Kenneth F Bradstock ◽  
Linda J Bendall
Keyword(s):  
Bone Marrow ◽  
Disease Progression ◽  
Microarray Analysis ◽  
Environmental Changes ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Hematopoietic Stem ◽  
Childhood All ◽  
Extracellular Matrix Components ◽  
The Impact

Abstract Abstract 2564 G-CSF is commonly used to treat chemotherapy-induced neutropenia and for the mobilization of hematopoietic stem cells for transplantation in patients with leukemia. Administration of G-CSF has profound effects on the bone marrow microenvironment including the cleavage of molecules required for the maintenance of lymphopoiesis, including CXCL12 and VLA-4. We have recently reported that G-CSF results in the dramatic suppression of B-lymphopoiesis. This, together with previous reports by ourselves, and others, showing that disruption of CXCL12 or VLA-4 slow the progression of B-lineage ALL lead us to consider that G-CSF may similarly antagonize the progression of ALL. To explore this possibility, we examined the impact of G-CSF administration on six human ALL xenografts using a NOD/SCID mouse model. Mice were engrafted without radiation and G-CSF commenced when 1% of the bone marrow consisted of ALL cells. G-CSF was administered twice daily for 10 days, at which time all animals were culled and leukemia assessed in the blood, bone marrow and spleens. Surprisingly G-CSF was found to increase disease progression in two of xenografts investigated (1345 and 0398, referred to as G-CSF responsive xenografts hereafter), while the remainder demonstrated a small reduction in leukemia, with one showing a statistical significant decrease. No evidence for a direct mitogenic effect of G-CSF could be demonstrated in any of the xenografts using exogenous G-CSF in vitro cultures in the presence or absence of human or murine stromal support. Consistent with these findings, and previous reports, little to no G-CSF receptor was detected by flow cytometry or microarray analysis of xenografts. Microarray analysis of the xenografts revealed significant differences in gene expression between the G-CSF responsive xenografts and the remainder of the samples. A total of 83 genes were expressed at a higher level and 127 genes at a lower level in the G-CSF responsive xenografts. The more highly expressed genes included cell cycle regulators (eg cyclin A1), adhesion molecules (eg ALCAM), extracellular matrix components and surface receptors. Perhaps the most interesting was the exclusive expression of the acetylcholine receptor (cholinergic receptor, nicotinic, beta 4, nAChRb4) in the G-CSF responsive cases. Analysis of a large public dataset of childhood ALL samples revealed significantly higher expression of this gene in ALL samples with rearranged MLL (p<0.03). However, small numbers of cases in all ALL subgroups had greater than an 2 fold higher expression compared to normal B cell progenitors. The role of nAChR in the response of ALL cells to micro-environmental changes induced by G-CSF remains to be determined, however, nAChR has known roles in cell proliferation and inhibition of apoptosis. Furthermore G-CSF is known to induce acetylcholine production in other tissues. In summary, G-CSF inhibited leukemia progression in the majority of patient xenografts, however, in a subset of samples G-CSF accelerated disease progression. Clinically, G-CSF administration to ALL patients has not been associated with any major adverse outcomes. However our data suggest that a small subset of patients may experience accelerated disease. Identification of features associated with adverse responses to G-CSF will permit the identification of patients for whom G-CSF may present a risk for increased disease progression. Disclosures: No relevant conflicts of interest to declare.

Association of Functional Single Nucleotide Variation in the NLRP3 Gene with Survival Outcomes After Unrelated Bone Marrow Transplantation.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3140-3140
Author(s):  
Akiyoshi Takami ◽  
J. Luis Espinoza ◽  
Keitaro Matsuo ◽  
Yasuo Morishima ◽  
Makoto Onizuka ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Nucleotide Variation ◽  
Single Nucleotide Variation ◽  
Single Nucleotide ◽  
Hematopoietic Stem ◽  
Nlrp3 Gene ◽  
Transplant Outcomes ◽  
Functional Relevance ◽  
The Impact

Abstract Abstract 3140 NLRP3 is an intracellular trigger of IL-1β production that plays important roles in the regulation of inflammation and apoptosis. A single nucleotide variation in the 3'-untranslated region of the NLRP3 gene, rs10754558 (+29940G>C), is linked to several immunological diseases. When we examined the impact of the NLRP3 genotype in a cohort consisting of 392 pairs of patients with hematologic malignancies and their unrelated HLA 12/12 matched bone marrow donors transplanted through the Japan Donor Marrow Program, the recipient NLRP3 GG genotype was found to be associated with a significantly worse 5-year overall survival (OS) rate (34% vs. 50%, P=0.006) (Fig. 1) and a trend toward a higher transplant-related mortality (TRM) rate (39% vs. 27%, P=0.09) than the recipient CC or CG genotype. The recipient GG genotype remained statistically significant in the multivariate analysis for OS (hazard ratio [HR], 1.86; 95% confidence interval [CI], 1.22 to 2.22; P=0.004) and TRM (HR, 2.28; 95% CI, 1.20 to 4.35; P=0.01). The donor NLRP3 genotype did not significantly influence the transplant outcomes. Next, we investigated the functional relevance of the NLRP3 +29940G>C variant. When leukocytes from healthy individuals were stimulated in vitro with NLRP3 ligand, the leukocytes with the NLRP3 GG genotype produced significantly more IL-1β than those with the NLRP3 CC or CG genotype (Fig. 2). These findings substantiate the functional relevance of the NLRP3 variant, and suggest that the higher IL-1β secretion in the peri-transplant period by recipients with the NLRP3 GG genotype likely accounts for their poor transplant outcomes. NLRP3 genotyping could therefore be useful in predicting prognoses and creating therapeutic strategies for improving the final outcomes of patients who undergo allogeneic hematopoietic stem cell transplantation. Disclosures: No relevant conflicts of interest to declare.

Hhex Is a Critical Gene In The Development Of Normal and Malignant Lymphoid Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3788-3788
Author(s):  
Charnise Goodings ◽  
Stephen B. Smith ◽  
Elizabeth Mathias ◽  
Elizabeth Smith ◽  
Rati Tripathi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Transgenic Mice ◽  
Conflicts Of Interest ◽  
Lymphoid Cells ◽  
Conditional Knockout ◽  
Hematopoietic Stem ◽  
Direct Transcriptional Target ◽  
Cell Counts ◽  
Transcriptional Target

Abstract Hematopoietically expressed homeobox (Hhex) is a T-cell oncogene. It is frequently deregulated in murine retroviral insertional mutagenesis screens and its enforced expression induces T-cell leukemia in bone marrow transduction and transplantation experiments. We discovered that HHEX is a direct transcriptional target of an LIM domain Only-2 (LMO2)-associated protein complex. HHEX clusters with LMO2-overexpressing T-ALLs and is especially overexpressed in Early T-cell Precursor (ETP) – ALL where it is a direct transcriptional target of LMO2. To further understand Hhex's function, we induced a conditional knockout in floxed Hhex mice with the Vav-iCre transgene. Mice were viable and showed normal blood cell counts with highly efficient deletion of Hhex in all hematopoietic tissues. Thymocytes from conditional knockouts showed a normal pattern of development. Most impressively, Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice (figure 1). Hhex conditional knockouts (Hhex cKOs) also had a significant decrease in mature B cells in the spleen and bone marrow. Interestingly, hematopoietic stem and progenitor cells plated on OP9-GFP or OP9-DL1 stromal cells showed proliferative defects and incomplete differentiation towards both B and T lineage. Also under stress conditions such as sublethal irradiation and competitive bone marrow transplants, Hhex conditional knockouts show a marked defect in both B and T lineages but an increase in early progenitor populations. Our experiments show that Hhex is a critical transcription factor in lymphoid development and in LMO2-induced T-ALL.Figure 1Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic miceFigure 1. Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice Disclosures: No relevant conflicts of interest to declare.

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