scholarly journals New Insights into PLZF/Rara Mechanism during APL Onset: EZH2 on the Road

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3761-3761
Author(s):  
Mathilde Poplineau ◽  
Nadine Platet ◽  
Lia N'Guyen ◽  
Shuhei Koide ◽  
Julien Vernerey ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Mouse Model ◽  
Fusion Protein ◽  
Cell Line ◽  
Conflicts Of Interest ◽  
Parent Cell ◽  
Promising Therapeutic Approach ◽  
Transcriptomic Signature ◽  
The Impact

INTRODUCTION Inappropriate recruitment of functional Polycomb-Group proteins (PcG) may trigger epigenetic unbalance at very specific genomic loci that substantially contribute to the pathogenesis of Acute Myeloid Leukemia (AML). This concept was first described in Acute Promyelocytic Leukemia (APL) in which PcG proteins were abnormally addressed due to the expression of X-RARA fusion proteins and were involved in the treatment response of the disease. For instance, in the context of APL with t(11;17)(q23;q21) translocation, the resulted oncogenic fusion protein PLZF/RARA leads to abnormal recruitment of PcG at the promoters of genes involved in acid-trans-retinoic acid (ATRA) response (Boukarabila et al.). As a consequence of that and compared to other APL subtypes (e-g: PML/RARA), APL with PLZF/RARA are insensitive to ATRA. In the recent years, a repertoire of cis-regulatory enhancer elements has been dissected to reveal important insight about leukemia onset and define new subsets of the disease with different treatment responses (Bhagwat et al). As we previously reported that PLZF displayed epigenetic specificity on enhancers (Poplineau et al.) we questioned the role of PLZF/RARA on these regulatory regions during APL onset. METHODS We performed in vivo comparative epigenomic profiling (H3K27ac, H3K4me1, H3K27me3 and H3K4me3 ChIPseq) between normal myeloid progenitors (granulocyte-monocyte progenitors purified from wild-type mice) and PLZF/RARA transformed mouse progenitors (late promyelocytes purified from mice developing APL). To question the role of PcG in APL onset, we used retroviral overexpression of PLZF/RARA and transduced Lineage negative cells from a conditional KO EZH2 mouse model. Transformation was tested by replating assay and cells were characterized by FACS and morphology analyses. We also performed EZH2 pharmacological inhibition using GSK126 and UNC1999 on a human cell line expressing the fusion protein PLZF/RARA. We analyzed the impact of this inhibition on their transcriptomic signature (RNAseq) and their proliferative capacity. RESULTS Upon PLZF/RARA expression and APL progression, specific cis-regulatory enhancer elements were targeted by the H3K27me3 PcG repressive mark. This gain in poised enhancer regions, upon PLZF/RARA expression reflected a reoriented PcG activity, from enhancers regulating developmental processes to those regulating stress and immune responses. To demonstrate the importance of this H3K27me3 switch for APL progression, we investigated the effect of EZH2 loss during PLZF/RARA transformation. Using a conditional KO EZH2 mouse model, we demonstrated that PLZF/RARA required EZH2 activity to efficiently transform progenitors since EZH2 loss promoted differentiation that altered the replating capacity of the PLZF/RARA expressing cells. In addition, EZH2 inhibition by GSK126 revealed some interesting benefits since it sensitized PLZF/RARA transformed progenitors to ATRA treatment. Moreover, inhibition of EZH2 with GSK126 or UNC1999 induced a decrease in the proliferation advantage of a human PLZF/RARA-inducible cell line. This was linked to a change of its transcriptomic signature towards an expression pattern closer to the one observed in the parent cell line. CONCLUSION Taken together, our data showed that PLZF/RARA modifies H3K27me3 profiles at enhancer regions and requires EZH2 activity for APL onset. Finally, our results suggest that EZH2 inhibition could be a new promising therapeutic approach for retinoic-acid resistant APL. Disclosures No relevant conflicts of interest to declare.

scholarly journals The PML/RAR alpha oncoprotein is a direct molecular target of retinoic acid in acute promyelocytic leukemia cells

Blood ◽  
1996 ◽  
Vol 88 (8) ◽  
pp. 2826-2832 ◽  
Author(s):  
JV Raelson ◽  
C Nervi ◽  
A Rosenauer ◽  
L Benedetti ◽  
Y Monczak ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Fusion Protein ◽  
Cell Line ◽  
Acute Promyelocytic Leukemia ◽  
Promyelocytic Leukemia ◽  
Dominant Negative ◽  
Myeloid Differentiation ◽  
Wild Type ◽  
Retinoid Receptor ◽  
Western Blots

Acute promyelocytic leukemia (APL) is characterized by the translocation, t(15;17) and the expression of a PML/RAR alpha fusion protein that is diagnostic of the disease. There is evidence that PML/RAR alpha protein acts as a dominant negative inhibitor of normal retinoid receptor function and myeloid differentiation. We now show that the PML/RAR alpha fusion product is directly downregulated in response to retinoic acid (tRA) treatment in the human APL cell line, NB4. tRA treatment induces loss of PML/RAR alpha at the protein level but not at the level of mRNA, as determined by Northern blots, by Western blots, and by ligand binding assays and in binding to RA-responsive DNA elements. We present evidence that this regulation is posttranslational. This evidence suggests that tRA induces synthesis of a protein that selectively degrades PML/RAR alpha. We further show that this loss of PML/ RAR-alpha is not limited to the unique APL cell line. NB4, because PML/RAR alpha protein is selectively downregulated by tRA when expressed in the transfected myeloid cell line U937. The loss of PML/RAR alpha may be directly linked to tRA-induced differentiation, because in a retinoid-resistant subclone of NB4, tRA does not decrease PML/RAR alpha protein expression. In NB4 cells, the specific downregulation of the fusion protein decreases the ratio of PML/RAR alpha to wild-type RAR alpha. Because the ratio of expression of PML/RAR alpha to wild-type RAR alpha and PML may be important in maintaining the dominant negative block of myelocytic differentiation, these data suggest a molecular mechanism for restoration by tRA normal myeloid differentiation in APL cells.

scholarly journals In vivo analysis of the role of aberrant histone deacetylase recruitment and RARα blockade in the pathogenesis of acute promyelocytic leukemia

2006 ◽  
Vol 203 (4) ◽  
pp. 821-828 ◽  
Author(s):  
Hiromichi Matsushita ◽  
Pier Paolo Scaglioni ◽  
Mantu Bhaumik ◽  
Eduardo M. Rego ◽  
Lu Fan Cai ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Fusion Protein ◽  
Acute Promyelocytic Leukemia ◽  
Histone Deacetylases ◽  
Retinoic Acid Receptor ◽  
Promyelocytic Leukemia ◽  
Dominant Negative

The promyelocytic leukemia–retinoic acid receptor α (PML-RARα) protein of acute promyelocytic leukemia (APL) is oncogenic in vivo. It has been hypothesized that the ability of PML-RARα to inhibit RARα function through PML-dependent aberrant recruitment of histone deacetylases (HDACs) and chromatin remodeling is the key initiating event for leukemogenesis. To elucidate the role of HDAC in this process, we have generated HDAC1–RARα fusion proteins and tested their activity and oncogenicity in vitro and in vivo in transgenic mice (TM). In parallel, we studied the in vivo leukemogenic potential of dominant negative (DN) and truncated RARα mutants, as well as that of PML-RARα mutants that are insensitive to retinoic acid. Surprisingly, although HDAC1-RARα did act as a bona fide DN RARα mutant in cellular in vitro and in cell culture, this fusion protein, as well as other DN RARα mutants, did not cause a block in myeloid differentiation in vivo in TM and were not leukemogenic. Comparative analysis of these TM and of TM/PML−/− and p53−/− compound mutants lends support to a model by which the RARα and PML blockade is necessary, but not sufficient, for leukemogenesis and the PML domain of the fusion protein provides unique functions that are required for leukemia initiation.

scholarly journals Role of PTH1R internalization in osteoblasts and bone mass using a phosphorylation-deficient knock-in mouse model

2010 ◽  
Vol 207 (3) ◽  
pp. 355-365 ◽  
Author(s):  
Nabanita S Datta ◽  
Tareq A Samra ◽  
Chandrika D Mahalingam ◽  
Tanuka Datta ◽  
Abdul B Abou-Samra
Keyword(s):  
Mouse Model ◽  
Cyclin D1 ◽  
Intracellular Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Bone Homeostasis ◽  
Low Calcium Diet ◽  
High Calcium ◽  
The Impact

Phosphorylation, internalization, and desensitization of G protein-coupled receptors, such as the parathyroid hormone (PTH) and PTH-related peptide (PTHrP) receptor (PTH1R), are well characterized and known to regulate the cellular responsiveness in vitro. However, the role of PTH1R receptor phosphorylation in bone formation and osteoblast functions has not yet been elucidated. In previous studies, we demonstrated impaired internalization and sustained cAMP stimulation of a phosphorylation-deficient (pd) PTH1R in vitro, and exaggerated cAMP and calcemic responses to s.c. PTH infusion in pdPTH1R knock-in mouse model. In this study, we examined the impact of impaired PTH1R phosphorylation on the skeletal phenotype of mice maintained on normal, low, and high calcium diets. The low calcium diet moderately reduced (P<0.05) bone volume and trabecular number, and increased trabecular spacing in both wild-type (WT) and pd mice. The effects, however, seem to be less pronounced in the female pd compared to WT mice. In primary calvarial osteoblasts isolated from 2-week-old pd or WT mice, PTH and PTHrP decreased phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2), a member of mitogen-activated protein kinase, and cyclin D1, a G1/S phase cyclin, in vitro. In contrast to WT osteoblasts, down-regulation of cyclin D1 was sustained for longer periods of time in osteoblasts isolated from the pd mice. Our results suggest that adaptive responses of intracellular signaling pathways in the pd mice may be important for maintaining bone homeostasis.

BCL2A1 Is A Survival and Immortalization Factor for Primitive Myeloid Hematopoietic Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3365-3365
Author(s):  
Jean-Yves Metais ◽  
Ashley E. Dunfee ◽  
Rodrigo T. Calado ◽  
Cynthia E. Dunbar
Keyword(s):  
Bone Marrow ◽  
Cell Line ◽  
Gene Product ◽  
Myeloid Leukemia ◽  
Hematopoietic Cells ◽  
Marker Genes ◽  
Empty Vector ◽  
Myeloid Progenitor ◽  
The Impact

Abstract We recently reported development of an acute myeloid leukemia in a rhesus macaque transplanted with autologous CD34+ cells transduced with a murine stem cell virus-derived replication defective retrovirus vector expressing only marker genes under control of the strong MCSV LTR. This animal had an unusual clonal reconstitution pattern the first year following transplant, with a single transduced myeloid progenitor cell clone accounting for up to 80% of then normal myelopoiesis (Kelly, 2005). The same vector-containing clone then transformed to AML five years following transplantation, and each tumor cell was shown to contain two vector insertions, one localized 20 kb upstream the CDw92 gene on chromosome 9, and the second localized in the first intron of BCL2A1 on chromosome 15 (Seggewiss, 2006), a gene in the anti-apoptotic BCL2 family not previously linked to myeloid leukemia. BCL2A1 was highly expressed in the tumor cells. This tumor was the first hematopoietic malignancy reported in a recipient of primitive cells transduced with a replication-incompetent vector containing only marker genes, and suggested that BCL2A1 could have potent effects on myeloid cell behavior. To investigate the impact of the BCL2A1 gene product on hematopoietic cells, we cloned the murine and human HA-tagged BCL2A1 cDNAs into lentivirus vectors and transduced the murine BaF3 hematopoietic cell line as a model to study the impact of expression of these proteins on hematopoiesis. We confirmed overexpression of the proteins in the producer cell line as well as in transduced cells by western blot using an anti-HA monoclonal antibody. BaF3 cell proliferation and survival are dependant on IL-3, and under IL-3 replete conditions overexpression of murine or human BCL2A1 did alter proliferation compared with untransduced cells or cells transduced with an empty vector. Removal of IL-3 from the cell culture media leads to rapid apoptosis of BaF3 cells, with cell cycle arrest in the G1 and an apoptotic subpopulation appearing within 24 hours of IL-3 removal. 45% untransduced or empty vector cells were apoptotic, and this fraction decreased to 30% and 15% respectively for BaF3 cells expressing murine or human BCL2A1. These results were confirmed by direct analysis of apoptosis. Only BaF3 cells over-expressing human BCL2A1 were still alive and arrested in G1 after 3 days of culture without IL-3. The murine BCL2A1 had similar but less striking effects. Gene expression analyses on the BaF3 cell populations are ongoing, to identify potential downstream targets of the BCL2A1 protein. The BCL2A1 and empty vectors were also utilized in murine bone marrow cell immortalization assay, previously utilized to identify genes impacting on the survival and expansion of primary myeloid progenitor cells (Du, 2005). In an initial set of experiments, clonal clonal expansion was obtained with marrow cells expressing murine (4 clones) and human (5 clones) BCL2A1 but not for empty vector or untransduced murine marrow. Mice have also been transplanted with primary bone marrow cells transduced with the BCL2A1 and control vectors, and are being followed for in vivo expansion of transduced clones and development of leukemia. In conclusion, we have confirmed the role of BCL2A1 as an anti-apoptotic protein, now in myeloid hematopoietic cells, and will continue to investigate the role of this gene product in hematopoiesis and leukemogenesis.

Kinase Activity of RTKs Is Dispensable for Factor Independent Growth and Transformation of a Myeloid Cell Line 32D in the Presence of Cbl Mutants.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3970-3970
Author(s):  
◽  
Srinivasa Rao Bandi ◽  
Marion Rensinghoff ◽  
Rebekka Grundler ◽  
Lara Tickenbrock ◽  
...  
Keyword(s):  
Cell Line ◽  
Tyrosine Kinases ◽  
Kinase Activity ◽  
Kinase Inhibitors ◽  
Conflicts Of Interest ◽  
Myeloid Cell ◽  
Dominant Negative ◽  
Class Iii ◽  
Primary Resistance

Abstract Abstract 3970 Poster Board III-906 Purpose The Cbl proto-oncogene products have emerged as important components of the signal transduction cascades downstream of both non-receptor and receptor tyrosine kinases (RTKs). By regulation of receptor trafficking and degradation, they have been shown to tightly regulate the intensity and amplitude of RTK activation. c-Kit belongs to the family of the class-III RTKs and plays an important role in the pathogenesis of acute myeloid leukemia (AML). So far, very little is known about the role of c-Cbl mutants in the role of c-Kit signaling. Results We analyzed the interaction of c-Cbl with c-Kit and the functional relevance of this interaction in the IL-3-dependent murine myeloid progenitor cell line 32Dcl3. We recently identified the first c-Cbl mutation in human disease in an AML patient, named Cbl-R420Q. Co-expression of two different dominant negative mutants of c-Cbl (Cbl-R420Q or Cbl-70Z) with Kit induced cytokine-independent proliferation, survival and clonogenic growth. Importantly, transformation was observed also with kinase-dead forms of Kit and Flt3 in the presence of Cbl-70Z, but not in the absence of Kit or Flt3, suggesting a mechanism dependent on RTKs, but independent of their kinase activity. Instead, transformation appeared to depend on Src family kinases (SFKs), as c-Cbl co-immunoprecipitated with SFKs and SFK inhibition abolished transformation. Conclusion Our results indicate that c-Cbl has an important role in c-Kit signal mitigation. They demonstrate that disturbed mechanisms of c-Kit internalization have important implications for its transforming potential, possibly in the development of AML. Furthermore, these findings may explain primary resistance to tyrosine kinase inhibitors targeted at RTKs. Disclosures: No relevant conflicts of interest to declare.

Impaired Hydroxylation of 5-Methylcytosine In TET2 mutated Patients with Myeloid Malignancies

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1-1
Author(s):  
Anna Jankowska ◽  
Myunggon Ko ◽  
Yun Huang (equal contribution) ◽  
Utz J. Pape ◽  
Hadrian Szpurka ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Genomic Dna ◽  
Conflicts Of Interest ◽  
Methylation Pattern ◽  
Myeloid Malignancies ◽  
Cpg Sites ◽  
Low Levels ◽  
Methylation Patterns ◽  
The Impact

Abstract Abstract 1 TET2 mutations are frequently found across broad spectrum of myeloid malignancies but how these mutations contribute to diseases is still unknown. Preliminary results from our laboratory have suggested that TET2 converts 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) and consequently, the levels of 5-hmC may be lower in genomes of mutant bone marrow cells. To facilitate study of TET2 function we developed a blot assay to detect 5-hmC in genomic DNA with a specific antiserum to 5-hmC. In a second improved assay with increased sensitivity and precision, we treated genomic DNA with bisulfite in order to convert 5-hmC to cytosine 5-methylenesulfonate (CMS) and measured 5-hmC levels indirectly using a specific anti-CMS serum. Based on the results of this technique we demonstrate here for the first time that indeed TET2 mutations in predicted catalytic residues and other positions compromised TET2 function. We studied 102 patients with various myeloid malignancies (4/28 MDS, 14%, 26/48 MDS/MPN, 54% and 1/4 MPN, 2% and primary 2/11 AML 18% and 3/11 sAML, 27% TET2 mutants, respectively) and compared to wt cases or controls (N=17). Mutations were found throughout the entire coding region and were mostly inactivating (33/45 TET2 mutations). The levels of 5-hmC in genomic DNA from TET2 mutants were significantly decreased in comparison to wt cases and controls (p=4.5e-08 and p=1.8e-09, respectively). Particularly low levels of 5-hmC were found in patients with homozygous (UPD)/hemizygous (deletion) TET2 mutations and those with biallelic mutations. Surprisingly, 18% of all TET2 WT patients also showed low levels of genomic 5-hmC (despite normal TET2 mRNA expression), suggesting that these patients may carry not yet identified variants/lesions in TET2 or other partner proteins involved in TET2-mediated catalysis. To further investigate the impact of TET2 mutations associated with myeloid malignancies we also introduced 9 different missense mutations corresponding to those found in patients into murine Tet2 cells; severe loss of enzymatic activity was observed in 7/9 cases as measured by greatly diminished 5-hmC levels. To study the role of Tet2 in normal hematopoiesis we depleted Tet2 in C57BL/6 mice by retrovirus-mediated transduction of shRNA against Tet2. Tet2 depletion is associated with skewing of hematopoietic differentiation towards the monocyte/macrophage lineage. To further investigate the function of TET2 we transduced the myeloid THP-1 cell line with lentiviral vector containing TET2 cDNA (TET2+) or an empty vector. This manipulation allowed us to select clones showing 19-fold increase in TET2 mRNA expression without significantly alterations of proliferation kinetics. Using this model we studied the impact of TET2 overexpression on resultant methylation pattern of CpG sites. We have applied Illumina Infinium HumanMethylation27 arrays (27,5K CpG sites/14.4K genes). Overexpression of TET2 resulted in a distinct promoter methylation patterns with 169 altered CpG sites with difference of averaged β>0.5 (considered significant as compared to control). Among these differentially methylated loci, 27 promoters were significantly hypomethylated while 42 were hypermethylated as compared to control cells. Change in methylation pattern observed through overexpression of TET2 in vitro prompted us to analyze methylation patterns in patients with and without TET2 mutations or those with decreased 5-hmC levels. Using methylation arrays a total of 62 cases were analyzed. When patients were grouped based on the levels of 5hmC, an associated methylation signature can be clearly discerned with 2512 differentially methylated loci and distinct skewing towards hypomethylation (2510 sites; e.g., TMEM102, ABCC11) vs. hypermethylation (2 sites, AIM2 and SP140), consistent with the observation made in the TET2+ cells line. In sum, our results provide strong evidence for TET2 as the first mutated gene in myeloid malignancies that is involved in conversion of 5-mC to 5-hmC in DNA, indicating the novel role of TET2 in a substantial component of epigenetic deregulation in myeloid malignancies. Disclosures: No relevant conflicts of interest to declare.

Early Different Downstream Target of Glucocorticoid Receptor Contributing to Glucocorticoids Sensitivity in Kasumi-1 Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5132-5132
Author(s):  
Wenbin Gu ◽  
Meng Li ◽  
Liang Liang ◽  
Jian Zhang ◽  
Chongye Guo ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Fusion Protein ◽  
Cell Line ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Critical Role ◽  
Leukemia Cell ◽  
Leukemia Cells ◽  
Non Coding Rnas

Abstract The t(8;21) chromosome translocation frequently occurs in acute myeloid leukemia (AML), resulting in an in-frame fusion between the DNA-binding domain of AML1 and almost the entire of ETO gene. The fusion AML1-ETO protein is thought to play a critical role in the abnormal proliferation and differentiation of myeloid leukemia cells, such as Kasumi-1 and SKNO-1 cells. Glucocorticoids (GC) can induce apoptosis in these cells at low concentrations, whereas most other myeloid leukemia cell lines are resistant to glucocorticoid-induced apoptosis. To experimentally address possible sensitive mechanisms in leukemia cells with AML1-ETO translocation, we generated aGC-resistant Kasumi-1 cell line by induction of 10-6 M dexamethasone (Dex) for three weeks. The IC50 of Dex to cells is increased from 2.5×10-8 M for original GC-sensitive Kasumi-1 cell line ( K-S cell line) to more than 1×10-5 M for induced GC-resistant Kasumi-1 cell line (K-R cell line). Since GC resistance often results from mutations in the glucocorticoid receptor (GR), all the exons of GR gene were sequenced and no mutation was found in K-R cells. Comparing to those in K-S cells, the GR protein level didn't decrease in K-R cells after 2h, 4h, 8h, 12h and 24h exposure to dexamethasone. Given that the difference of direct GR downstream genes between K-S and K-R cells may play a key role in the GC sensitivity, we systematically analyzed the changes of gene expression induced by Dex versus ethanol vehicle for 8h in K-S and K-R cells by high throughput RNA sequencing. The time point of 8h was selected according to the expression peaks of several foregone GR target genes after Dex induction. There were found 32 genes conversely regulated in K-S and K-R cells, including 14 mRNAs and 18 long non-coding RNAs. Pathway analysis indicated that the upregulated genes in K-S cells might promote the AML1-ETO fusion protein degradation by proteasomes, while the component genes of this pathway were downregulated in K-R cells. Further validation and function studies of these mRNAs and long non-coding RNAs are ongoing. Our data suggested that the downstream targets of GR among GC-sensitive and -resistant Kasumi-1 cells were significant different and they may contribute to the GC sensitivity and resistance by degradation or reservation of AML-ETO fusion protein and the regulation of apoptosis in t(8;21) leukemia cell subtype. Disclosures No relevant conflicts of interest to declare.

scholarly journals Carboxypeptidase B2 Is Protective in a Mouse Model of Shiga Toxin-Induced Hemolytic Uremic Syndrome

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2804-2804
Author(s):  
Toshihiko Nishimura ◽  
John Morser ◽  
Zhifei Shao ◽  
Lawrence L. Leung
Keyword(s):  
Mouse Model ◽  
Hemolytic Uremic Syndrome ◽  
Shiga Toxin ◽  
Conflicts Of Interest ◽  
Severe Thrombocytopenia ◽  
E Coli ◽  
Potential Efficacy ◽  
Significant Difference ◽  
Uremic Syndrome

Abstract Hemolytic uremic syndrome (HUS) is characterized by a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The most common cause of HUS is Shiga toxin (STX)-producing E. coli, and eculizumab, a monoclonal antibody against complement C5, has shown clinical efficacy in some patients. Carboxypeptidase B2 (CPB2) is a metalloprotease activated by the thrombin/thrombomodulin complex that inactivates a number of inflammatory mediators, including complement C3a, and C5a by removing their C-terminal arginine. We hypothesized that in a murine model of STX-induced HUS, Cpb2-/- mice would have exacerbated disease compared to wild type (WT) mice due to excessive C3a and/or C5a in the absence of CPB2. A mouse model of STX-induced HUS was established by giving STX and LPS toxins intraperitoneally. Cpb2-/- mice had worse survival than WT (37% survival vs. 87% at 48h, p=0.0156). At 48h, severe thrombocytopenia developed in both WT and Cpb2-/- mice (WT: 0.096x106/μL; Cpb2-/-: 0.054x106/μL) compared to controls (1.2x106/μL; p>0.0001 vs. either WT or Cpb2-/-), with Cpb2-/- mice showing worse thrombocytopenia. Renal insufficiency was worse in Cpb2-/- mice than WT mice (BUN at 48h: 85 mg/dL vs. 37 mg/dL, p=0.0074; creatinine: 1.33 mg/dL vs. 0.23 mg/dL; p=0.0112, for Cpb2-/- and WT mice respectively, compared with normal baseline BUN and creatinine of 19 mg/dL and 0.1 mg/dL). Cpb2-/- mice developed worse anemia than WT (hemoglobin 9.8 g/dL vs. 12.4 g/dL, p=0.001 in Cpb2-/- vs. WT mice respectively). At 48h, liver function was worse in Cpb2-/- mice than WT mice, while plasma LDH was increased in Cpb2-/- mice more than WT mice. Using a standardized health score, the Cpb2-/- mice were worse than WT mice at all time points. Thus this model recapitulates STX-induced HUS with the Cpb2-/- mice having worse disease than WT. If the animals were treated with STX alone, there were no deaths in either genotype at 48h and only 37.5% mortality in Cpb2-/- mice by 60h compared with no deaths in WT mice. BUN, creatinine, liver enzymes and LDH were increased in both genotypes treated with STX alone compared to untreated mice, but there was no significant difference between the genotypes. Treatment with LPS alone caused thrombocytopenia in both WT and Cpb2-/- mice and LDH, BUN and creatinine levels were higher in Cpb2-/- mice than in WT mice, but there was no death at 48h and no drop in hemoglobin. Thus while either STX alone or LPS alone caused pathological conditions in the mice, the typical triad of HUS was only present when STX and LPS were given in combination. The Cpb2-/- mice had worse disease than WT mice consistent with our hypothesis on the role of CPB2 in inactivating C3a and/or C5a in STX-induced HUS. The potential efficacy of C3a and/or C5a blockade and anti-thrombotic agents will be tested in this model. Disclosures No relevant conflicts of interest to declare.

The PIM Kinase Inhibitor K00135 Sensitizes Primary Acute Lymphoblastic Leukaemia (ALL) Cells to DNA-Damaging Agents

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3238-3238
Author(s):  
David Da Costa ◽  
Victoria J Weston ◽  
Stefan Knapp ◽  
A. Malcolm R Taylor ◽  
Pamela R. Kearns ◽  
...  
Keyword(s):  
Dna Damage ◽  
Myeloid Leukaemia ◽  
Conflicts Of Interest ◽  
Constitutive Expression ◽  
Treatment Resistance ◽  
Tumour Cells ◽  
Leukaemia Virus ◽  
Pim Kinases ◽  
The Impact

Abstract Abstract 3238 Relapsed ALL is the most common cause of death in children, with only 30% being cured despite intensified treatment and stem cell transplantation. We previously showed that a subset of paediatric ALL tumours have a defect in the apoptotic response to DNA damage in vitro which correlates with a poor clinical response in vivo. Proviral integration site for Moloney murine leukaemia virus (PIM) proteins are a family of serine/threonine kinases which mediate prosurvival signals in response to cytokines, growth factors, hypoxia and DNA damage. PIM kinases have been implicated in several haematological malignancies such as chronic myeloid leukaemia (CML), chronic lymphocytic leukaemia (CLL), acute myeloid leukaemia (AML), and T-ALL. However, the role of PIM kinases and their contribution to treatment resistance in a large cohort of primary paediatric ALL has not been comprehensively addressed. To address the frequency of PIM overexpression in ALL we used quantitative real-time PCR to quantify the levels of PIM-1 and PIM-2 in an unselected cohort of 86 primary ALL tumours compared to the PIM-expressing lymphoid cell line K562. We observed high PIM-1 levels in only 2/86 (2.3%) ALLs, whereas PIM-2 was highly expressed in 20/86 (23%) primary tumours. PIM-2 overexpression was detected in tumours with a range of chromosome translocations or hyperdiploidy. In representative samples, the level of PIM-2 protein expression correlated with abundance of mRNA transcript. We then investigated the role of PIM overexpression on apoptosis using the highly specific PIM inhibitor, imidazo[1,2-b]pyridazine K00135, to sensitize tumour cells with high PIM expression to ionising radiation (IR)-induced apoptosis. Pretreatment with K00135 led to sensitization of representative primary tumour cells with high PIM-2 expression to 5Grays IR at an half maximal lethal concentration (LC50) of 10μM, and killing was mediated by caspase-dependant apoptosis. Furthermore, consistent with the role of PIM-2 in the regulation of c-Myc protein stability (Zhang Y, Wang Z, Li X, Magnuson NS. 2008; Oncogene; 27;4890-4819), K00135-induced killing coincided with the downregulation of c-Myc protein. We are currently addressing the impact of PIM inhibition in an ALL xenograft model. Constitutive expression of PIM-2 may be an underlying mechanism of treatment resistance in a subset of paediatric ALL. Pharmacological inhibition of PIM-2 may prove to be a useful therapeutic option for poorly responding ALL in children in the future. Disclosures: No relevant conflicts of interest to declare.

Alcam Mediated Interaction Regulates Normal Hematopoietic Stem Cell Function and Cbfβ-SMMHC Induced Leukemogenesis

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4091-4091
Author(s):  
Robin Jeannet ◽  
Qi Cai ◽  
Hongjun Liu ◽  
Hieu Vu ◽  
Ya-Huei Kuo
Keyword(s):  
Fusion Protein ◽  
Cell Function ◽  
Conflicts Of Interest ◽  
Immunoglobulin Superfamily ◽  
Leukemic Transformation ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
A Cell

Abstract Abstract 4091 The inv(16) acute myeloid leukemia (AML)-associated CBFβ-SMMHC fusion protein impairs hematopoietic differentiation and predisposes to leukemic transformation. Alcam, which encodes the activated leukocyte cell adhesion molecule (CD166), is a cell surface immunoglobulin superfamily member mediating homophilic adhesion as well as heterotypic interactions with CD6. We found that Alcam expression marks long-term repopulating HSCs (LT-HSC), multipotent progenitors (MPP), a subset of granulocyte-macrophage progenitors (GMP), and that Alcam expression is lost or reduced in subsets of pre-leukemic and leukemic progenitors expressing the Cbfβ-SMMHC fusion protein. We characterized the role of Alcam in HSC differentiation and self-renewal using an Alcam-null (Alcam−/−) mouse model (Weiner et al. 2004 Mol Cell Neurosci 27:1, 59–69). We show that Alcam is highly expressed in LT-HSCs where its level progressively increases with age. Young adult Alcam−/− mice had normal homeostatic hematopoiesis, and normal numbers of phenotypic HSCs. However, Alcam−/− HSCs had reduced long-term replating capacity in vitro and reduced long-term engraftment potential upon transplantation. We show that Alcam−/− BM contain a markedly lower frequency of long-term repopulating cells than wild type (WT). Further, the long-term repopulating potential and engraftment efficiency of Alcam−/− LT-HSCs was greatly compromised despite a progressive increase in phenotypic LT-HSC numbers during long-term serial transplantation. In addition, an age-associated increase in phenotypic LT-HSC cellularity was observed in Alcam−/− mice. This increase was predominately within the CD150hi fraction, and was accompanied by significantly reduced leukocyte output. Moreover, Alcam−/− LT-HSCs display premature elevation of Selp expression, a hallmark of HSC aging. To understand the role of Alcam in leukemic transformation, we generated conditional Cbfb-MYH11 knock-in (Cbfb56M/+/Mx1-Cre), Alcam-deficient (Alcam−/−) mice. Interestingly, we found that loss of Alcam drastically delayed or reduced leukemia incidence. Transplantation of Alcam−/−/Cbfb56M/+/Mx1-Cre pre-leukemic bone marrow cells into WT recipients also led to delayed and reduced incidence of leukemia development. These results suggest that Alcam contributes to leukemia transformation in a cell-intrinsic manner. Collectively, our study reveals that Alcam regulates the functional integrity and self-renewal of LT-HSCs, and contributes to leukemia initiation induced by CBFβ-SMMHC. Disclosures: No relevant conflicts of interest to declare.

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