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  • 11
    In: Blood, American Society of Hematology, Vol. 120, No. 21 ( 2012-11-16), p. 225-225
    Abstract: Abstract 225 CD4+CD25+Foxp3+ regulatory T cells (Treg) are known to play a central role in the maintenance of self-tolerance and immune homeostasis. After allogeneic stem cell transplantation, impaired recovery of Treg is associated with the development of cGVHD. Interleukin-2 (IL-2) is a critical regulator of Treg development, expansion and survival and lack of IL-2 results in Treg deficiency. In patients with cGVHD, we previously demonstrated that Treg proliferate at high levels but this subset is also highly susceptible to apoptosis leading to inadequate Treg numbers (Matsuoka et al. JCI 2010). We also reported that low-dose IL-2 administration resulted in selective expansion of Treg in vivo and clinical improvement of cGVHD (Koreth et al. NEJM 2011). To identify mechanisms responsible for increased Treg susceptibility to apoptosis in cGVHD we used a new flow cytometry-based assay to measure mitochondrial membrane depolarization in response to a panel of pro-apoptotic BH3 peptides (BIM, BID, BAD, NOXA, PUMA, BMF, HRK). This assessment allowed us to compare BH3 peptide-induced mitochondrial membrane depolarization (“priming”) in different T cell subsets, including CD4 Treg, conventional CD4 T cells (CD4 Tcon), and CD8 T cells. Expression of Bcl-2, CD95 and Ki67 were also studied in each T cell subset. We studied peripheral blood samples from 36 patients with hematologic malignancies (median age 59 yr) who are 〉 2 years post HSCT (27 patients with cGVHD and 9 patients without cGVHD) and 15 patients who received daily subcutaneous IL-2 for 8 weeks for treatment of steroid-refractory cGvHD. Severity of cGVHD was classified according to NIH criteria. In patients without cGVHD, BH3 priming was similar in all 3 T cell subsets (CD4 Treg, CD4 Tcon and CD8). In patients with cGVHD, CD4 Treg were more primed than CD4 Tcon when challenged with BIM, BAD, PUMA, BMF and the combination of BAD + NOXA peptides (p 〈 0.01 – 0.0001). Treg were more primed than CD8 T cells when challenged with PUMA peptide (p 〈 0.0001), but priming in Treg and CD8 T cells was similar for other BH3 peptides in patients with cGVHD. We also compared BH3 priming of each T cell subset in patients with different grades of cGVHD. When challenged with BH3 peptides, Treg, Tcon and CD8 T cells were less primed in patients with severe cGVHD. In patients with cGVHD, Treg expressed higher levels of Ki-67, higher levels of CD95 and lower levels of Bcl-2 than Tcon. Expression of CD95 did not vary with severity of GVHD in any T cell subset, but expression of Bcl-2 was significantly increased in all subsets in patients with severe cGVHD. Increased BH3 priming and high expression of CD95 indicate that Treg are more susceptible to apoptosis than Tcon in cGVHD. However, both Treg and Tcon become less primed and Bcl-2 levels increase in severe cGVHD suggesting that these cells are less susceptible to mitochondrial pathway apoptosis. Since the total number of Treg and Tcon are significantly reduced in patients with cGVHD, these findings suggest that the remaining circulating cells are relatively resistant to mitochondrial pathway apoptosis. CD95 expression in Treg remains high indicating no change in death receptor pathway apoptosis. Daily treatment with low-dose IL-2 for 8 weeks selectively expands Treg in vivo in patients with severe cGVHD. As the number of Treg increase, BH3 profiling shows that these cells gradually become more primed and therefore more susceptible to mitochondrial pathway apoptosis. Taken together, these studies help define the complex and distinct pathways that regulate survival in different T cell subsets and changes in these pathways that occur in patients with chronic GVHD. These pathways play important roles in the maintenance of T cell homeostasis and targeting these complex pathways can provide new opportunities to promote immune tolerance after allogeneic HSCT. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
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  • 12
    In: Blood, American Society of Hematology, Vol. 120, No. 21 ( 2012-11-16), p. 652-652
    Abstract: Abstract 652 Long-term survival of patients with acute myeloid leukemia (AML) is poor, and new forms of therapy are needed. Many genetic lesions have been identified and studied, and most patients have chromosome translocations or other mutations that promote self-renewal of leukemic stem cells, block differentiation, enhance growth, and block apoptosis. Only a few of these mutations result in druggable targets (e.g., PML-RARa, Kit, PDGFR, FLT3 for instance). In addition to genetic lesions, epigenetic abnormalities have been shown to be very common in AML, and provide opportunities for novel treatments. Using genome-wide approaches to identify alternative splicing, we have recently shown that AML cells have a high level of aberrantly regulated genome-wide alternative splicing (AS) as a frequent epigenetic event. By comparing samples from 62 AML patients with 10 normal donors (NDs) we identified 428 genes differentially spliced in AML. A list of differentially spliced genes includes 50 oncogenes and 52 tumor suppressor genes, as well as genes encoding proteins involved in cell proliferation and differentiation, and apoptosis. We evaluated splicing event frequency in AML compared to NDs and we observed that on average 527 (range 137–1657) genes were identified as differentially spliced in any given patient, out of 62 analyzed. Also, we found that any given differentially spliced gene, of the 3,108 detected, were spliced on average in 26 (range 1–54) AML patients. Thus, splicing aberrations are highly recurrent in AML patients. To identify the causes of aberrant splicing in AML, we evaluated transcript levels of the 24 major splicing factors (SFs) that are involved in the first and second splicing transesterification reactions. These splicing factors are important proteins involved in spliceosomalassembly. Expression levels of these SFs were evaluated in 20 AML patients exhibiting high levels of AS. Quantitative RT-PCR analysis showed significant (up to 30 fold) upregulation of U2AF2 (P 〈 2.00E-07), PTBP (P=3.00E-04) and SFRS12 (P=0.002) SF transcript levels in AML patient samples compared to CD34+ cells from NDs. In preliminary studies, we also detected elevated expression of U2AF2 and PTBP proteins in several patient samples. These results suggest the intriguing possibility that aberrant splicing in AML may be the result of alterations of these SFs. To test this hypothesis we generated stably transfected HEK293 cell lines overexpressing U2AF2 or PTBP. We have developed a synthetic semi-quantitative splicing assay to evaluate the effects of overexpression of these SFs. We have obtained a minigene cassette of the p53 inducible PIG3 gene based on previous splicing studies. The minigene cassette was cloned between RFP (red fluorescent prtoein) and GFP (green fluorescent prtoein) in such a way that translation of the normally spliced transcript results in expression of RFP and GFP, while aberrant splicing results in the expression of RFP only. Production of a similar minigene cassette that includes exons/introns of a gene that is subjected to aberrant splicing in AML (NOTCH2, FLT3 and CD13) is in progress. In studies, completed so far, with the PIG3 minigene cassette construct transiently transfected into the HEK293 cells lines, overexpression of PTBP increased aberrant splicing of the PIG3 minigene. Similar studies testing the effects of elevated levels of U2AF2 and PTBP on NOTCH2 and other genes misspliced in AML (such as FLT3 and CD13) will be presented. Our results indicate that aberrant splicing could be an important event in AML, and development of an in vitro, synthetic splicing assay will enable us to better understand the underlying causes of this process in AML. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
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  • 13
    In: Blood, American Society of Hematology, Vol. 134, No. Supplement_1 ( 2019-11-13), p. 1784-1784
    Abstract: We have previously shown that immune cells, including regulatory T cells, Th17 cells, myeloid-derived suppressor cells and NK cells are abnormal in multiple myeloma (MM). It is well demonstrated that immune-modulatory drugs like pomalidomide (POM) have shown impact on various immune sub-populations in pre-clinical studies. Relapsed/refractory (RR) MM (N=540) patients were randomized to be bortezomib and dexamethasone (Vd) with or without pomalidomide POM (Vd) in a large Phase III CC4047-MM007 (OPTIMISMM, NCT01734928) study, allowing for critical investigation into the impact of POM on immune cell-subset. We have analyzed 197 RRMM patients utilizing 366 peripheral blood samples collected at screening, day 8 of cycle 1 and day 8 of cycle 3 using 98 immune biomarker-panel with multi-color flow to identify changes with POM exposure in various sub-populations of B, T, & NK cells. The primary objective was to investigate association of PFS with the modulation of predictive and prognostic immune bio-markers by POM. The analyzed patient-treatment cohorts had identical characteristics as the total patient population and was balanced for the 2-treatment arms, overall patient characteristics and response. Among B-Cell-subpopulations, we observed significant up-regulation of B1b cells (CD19+CD43+) and down-regulation of regulatory B cells (Bregs, CD19+CD5+CD43-) by the PVd arm as compared with the Vd arm. A significant increase in MZB cells were observed in both arms. Patients with a higher proportion of either CD19+ B cells or Bregs at screening showed significantly favorable PFS (logrank p value 〈 0.05) in the PVd arm as compared with the VD arm, which indicates that these markers are predictive of PFS for PVd treatment. Moreover, patients with a higher proportion of either [naïve B cells (CD19+CD27-IgD+)] or [CD95+ B cells that display germinal center differentiation features (CD19+ CD185+) at cycle 1 day 8] showed significantly favorable PFS in PVd arm (logrank p value 〈 0.05); however, they were not prognostic with the Vd arm alone. This indicates that the early impact of Pom on these cell types may provide a prognostic bio-marker outcome following PVd therapy in B cell-compartment at cycle 1. Among T-Cell subpopulations, we observed that patients with higher proportion of CD4+ T cells at screening showed significantly favorable PFS in PVd arm, indicating a predictive marker. We observed significantly favorable PFS in PVd arm in both patients with a higher number of CD8 T cells expressing OX-40 at cycle 3 day 8 and patients with lower number of CD4 T cells or Tfh cells (CD4+CD185+) expressing PD-1 or regulatory T cells expressing (low CD127+ and high CD25+) HLA-DR at cycle 3 day 8, indicating prognostic markers. The studied markers were neither predictive nor prognostic for the Vd arm alone. The total proportion of NK cells were significantly elevated following the Pom-containing regimen as early as day 8 of cycle 1 and persisted at cycle 3 as compared to the Vd arm. Among NK cell-subpopulations, we observed that the patients with either a higher proportion of NK cells without expressing KIR molecules or a lower proportion of NKT cells expressing CD158b KIR molecule at screening had significantly superior PFS with in the PVd, which indicates that each is a predictive marker. Finally, we showed that patients with either a higher proportion of NK cells expressing activation marker NKG2D, or a lower number of CD158b expressing NK cells at cycle 3 had significantly improved PFS with the PVd arm but not with the Vd arm, which indicates the prognostic nature of these markers. In summary, this large randomized study identified specific immunophenotypes at screening and after exposure to pomalidomide combinations, allowing for the identification of predictive and prognostic markers for favorable PFS, respectively. Disclosures Biyukov: Celgene: Employment, Equity Ownership. Oriol:Celgene, Amgen, Takeda, Jansse: Consultancy, Speakers Bureau. Pierceall:Celgene Corporation: Employment, Equity Ownership. Richardson:Oncopeptides: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees. Anderson:Janssen: Other: Advisory Board; Gilead Sciences: Other: Advisory Board; C4 Therapeutics: Other: Scientific founder ; Sanofi-Aventis: Other: Advisory Board; OncoPep: Other: Scientific founder . Thakurta:Celgene: Employment, Equity Ownership. Munshi:Oncopep: Consultancy; Adaptive: Consultancy; Abbvie: Consultancy; Abbvie: Consultancy; Celgene: Consultancy; Adaptive: Consultancy; Amgen: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Takeda: Consultancy; Janssen: Consultancy; Oncopep: Consultancy; Takeda: Consultancy.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2019
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  • 14
    In: Blood, American Society of Hematology, Vol. 116, No. 21 ( 2010-11-19), p. 1257-1257
    Abstract: Abstract 1257 CD4+CD25+Foxp3+ regulatory T cells (Treg) are known to play an important role in the maintenance of peripheral tolerance and control of cGVHD. Recent studies have shown that Treg undergo extensive homeostatic proliferation after allogeneic HSCT. However, highly proliferating Treg are also susceptible to apoptosis and the inability to maintain adequate Treg survival may contribute to the development of cGVHD. Thus, mechanisms of Treg survival and persistence are of great importance. Telomeres are repetitive DNA sequences, located at the ends of each chromosome. Telomeres gradually shorten with each cell division and eventually lead to cell senescence and death. In rapidly dividing cells, telomere length is maintained by telomerase, a reverse transcriptase that prevents premature senescence. Previous studies have shown that abnormal telomerase activity is found in T cells from patients with autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus, suggesting that telomerase may play a role in the maintenance of immune tolerance. In the present study, we examined whether telomerase activity and telomere length were associated with Treg homeostasis after allogeneic HSCT, particularly in the context of cGVHD. We examined Treg and conventional CD4 T cells (Tcon) in 35 patients with hematologic malignancies (median age 54 yr) who survived without relapse for more than 2 years after HSCT. Patient samples were obtained at 43 months (median, range: 25–99 months) after HSCT. The severity of cGVHD was classified according to NIH criteria. At the time of analysis, 2 patients had no cGVHD, 19 had mild cGVHD, 9 had moderate cGVHD, and 5 had severe cGVHD. CD4+CD25-CD127+ Tcon and CD4+CD25+CD127- Treg were isolated by flow cytometric cell sorting. Relative telomere length was measured by real time PCR. Telomerase activity was measured by PCR-ELISA. Telomere length was significantly shorter in Treg compared to Tcon in all patients (0.05 vs 0.28; p 〈 0.01), but there was no correlation between telomere length and severity of cGVHD (see Table below) in both Treg and Tcon. Telomerase activity was increased in Treg compared to Tcon (29.73 vs 8.95; p 〈 0.01). In contrast to telomere length, telomerase activity of Treg is significantly associated with severity of cGVHD (38.89 in patients with no or mild cGVHD vs. 8.19 in patients with moderate or severe GVHD, p=0.0002). These data indicate that induction of telomerase activity in Treg after allogeneic HSCT does not prevent overall telomere shortening. However, activation of telomerase appears to increase the replicative life span of Treg and provides a mechanism for maintaining survival of these cells in vivo. In contrast, failure to activate telomerase in some patients may lead to shortened survival of Treg, inability to maintain peripheral tolerance and development of severe cGVHD. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2010
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  • 15
    In: Blood, American Society of Hematology, Vol. 108, No. 11 ( 2006-11-16), p. 439-439
    Abstract: Hematopoietic development and long-term homeostasis are tightly regulated by a dynamic balance of stem cell self-renewal and differentiation. To understand the role of the FoxO family of transcription factors in these processes, we studied the impact of somatic deletion of all FoxO genes in the adult hematopoietic system of mice engineered with the interferon-inducible Mx-Cre transgene and various conditional FoxO alleles: FoxO1L/L; FoxO3 L/L; and/or FoxO4 L/L. Cre-mediated excision of FoxO1, FoxO3 and FoxO4 (FoxO1/O3/O4L/L), resulted in myeloid lineage expansion, lymphoid developmental abnormalities and a marked decrease of the lineage-negative, Sca-1+, c-Kit+ (LSK) compartment, containing the hematopoietic stem cell (HSC) population, but normal numbers of myeloid progenitors. Furthermore, FoxO1/O3/O4L/L null bone marrow cells were defective in competitive and noncompetitive repopulation assays. This FoxO deficient defect correlated with enhanced cell cycling and increased apoptosis of HSC cells. Notably, there was an HSC-restricted elevation in the level of reactive oxygen species (ROS) that was not observed in committed progenitors, and was associated with decreased catalase and MnSOD expression. Furthermore, in vivo treatment with the anti-oxidative agent N-acetyl-cysteine (NAC) resulted in complete reversion of the FoxO deficient HSC phenotype. Taken together, these results demonstrate that, in the HSC compartment, FoxO proteins are mediators of quiescence and enhanced survival and play essential regulatory roles in the response to physiologic oxidative stress, a function that may contribute to the long-term regenerative potential of the hematopoietic stem cell compartment.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2006
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  • 16
    In: Blood, American Society of Hematology, Vol. 112, No. 13 ( 2008-12-15), p. 5161-5170
    Abstract: An attractive target for therapeutic intervention is constitutively activated, mutant FLT3, which is expressed in a subpopulation of patients with acute myelocyic leukemia (AML) and is generally a poor prognostic indicator in patients under the age of 65 years. PKC412 is one of several mutant FLT3 inhibitors that is undergoing clinical testing, and which is currently in late-stage clinical trials. However, the discovery of drug-resistant leukemic blast cells in PKC412-treated patients with AML has prompted the search for novel, structurally diverse FLT3 inhibitors that could be alternatively used to override drug resistance. Here, we report the potent and selective antiproliferative effects of the novel mutant FLT3 inhibitor NVP-AST487 on primary patient cells and cell lines expressing FLT3-ITD or FLT3 kinase domain point mutants. NVP-AST487, which selectively targets mutant FLT3 protein kinase activity, is also shown to override PKC412 resistance in vitro, and has significant antileukemic activity in an in vivo model of FLT3-ITD+ leukemia. Finally, the combination of NVP-AST487 with standard chemotherapeutic agents leads to enhanced inhibition of proliferation of mutant FLT3-expressing cells. Thus, we present a novel class of FLT3 inhibitors that displays high selectivity and potency toward FLT3 as a molecular target, and which could potentially be used to override drug resistance in AML.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2008
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  • 17
    In: Biology of Blood and Marrow Transplantation, Elsevier BV, Vol. 15, No. 9 ( 2009-09), p. 1066-1076
    Type of Medium: Online Resource
    ISSN: 1083-8791
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
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