p21WAF1/CDKN1 Function In Hematopoietic Progenitor Cell Proliferation Is Inversely Regulated by Wild-Type Flt3 and Internal Tandem Duplication Mutation of Flt3

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4175-4175
Author(s):  
Mariko Abe ◽  
Louis M. Pelus ◽  
Pratibha Singh ◽  
Seiji Yamaguchi ◽  
Takeshi Taketani ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Growth Factor ◽  
Tandem Duplication ◽  
Hematopoietic Progenitor Cell ◽  
Mouse Bone Marrow ◽  
Functional Difference ◽  
Wild Type ◽  
Hematopoietic Progenitor ◽  
Internal Tandem Duplication

Abstract Abstract 4175 Internal Tandem Duplication mutations in the Flt3 tyrosine kinase gene (ITD-Flt3) induce constitutive activation of Flt3 signaling and are frequently found in acute myeloid leukemia patients with poor prognosis. We have previously reported that Survivin enhances proliferation of mouse primary hematopoietic progenitor cells (HPC) and that this enhancing effect on HPC proliferation is absent when p21WAF1/CDK1 (p21) is deleted, suggesting that p21 is required for Survivin to enhance normal HPC proliferation by hematopoietic growth factors (Fukuda et al. Blood 2004). Our subsequent studies showed that several ITD-Flt3 mutations increase expression of both Survivin and p21 and enhance growth factor independent HPC proliferation through up regulation of Survivin (Fukuda et al. Blood 2009). These findings suggest that p21 may also regulate growth factor independent HPC proliferation mediated by ITD-Flt3. However, our previous studies and those of others suggest that p21 function can vary and affect cell proliferation in diverse ways depending on cell type, and that intracellular signals generated by the wild-type Flt3 and ITD-Flt3 receptors can be qualitatively different. In the present study, we evaluated functional differences in the Survivin/p21 axis between wild-type Flt3 versus ITD-Flt3 signaling on HPC proliferation using p21-/- mouse bone marrow cells. P21 gene deletion significantly enhances growth factor independent proliferation of ITD-Flt3 transduced CFU-GM in vitro compared to p21+/+ mice (221±5% increase: P<0.02), suggesting that p21 inhibits growth factor independent proliferation of HPC by ITD-Flt3. This is in contrast to Survivin deletion, which significantly reduced growth factor-independent CFU-GM proliferation (74% reduction, P<0.05). Similar to ITD-Flt3, Flt3 ligand (FL) induced marginal expression of p21 in Ba/F3 cells expressing wild-type Flt3 and stimulated proliferation of p21+/+ CFU-GM transduced with wild-type Flt3. In contrast to the negative role of p21 in ITD-Flt3 mediated growth factor independent HPC proliferation, p21 deletion significantly reduced proliferation of CFU-GM over-expressing wild-type Flt3 and incubated with FL compared to p21+/+ CFU-GM (59±6% reduction: P<0.01), indicating that p21 positively regulates proliferation of HPC stimulated by wild-type Flt3 signaling, which is consistent with our report and others where p21-/- CFU-GM incubated with GM-CSF and/or SCF were significantly decreased compared to p21+/+ cells (Mantel et al. Blood 1996, Fukuda et al. Blood 2004). Our data indicates that while both wild-type Flt3 and ITD-Flt3 signaling up-regulate p21, wild-type Flt3 and ITD-Flt3 differentially modify p21 function that inversely regulates proliferation of HPC. The positive regulatory role of p21 in HPC proliferation by wild-type Flt3 signaling is in good agreement with our study that the Survivin/p21 axis positively regulates growth factor dependent HPC proliferation. This suggests that the Survivin/p21 axis may enhance HPC proliferation in the presence of wild-type Flt3 signaling. In contrast, p21 negatively regulates aberrant growth factor independent proliferation in primary HPC transformed by ITD-Flt3, whereas Survivin positively regulates ITD-Flt3 signaling, suggesting that the Survivin/p21 functional axis does not exist or play a role in aberrant growth factor independent proliferation by ITD-Flt3 signaling as opposed to normal HPC proliferation. Our study uncovers one functional difference between wild-type Flt3 and ITD-Flt3 signaling that may aid in developing specific therapeutic molecules for ITD-Flt3+ hematological malignancies that target ITD-Flt3+ transformed cells without affecting normal hematopoiesis. Disclosures: No relevant conflicts of interest to declare.

The Survivin/p21WAF1/Cip1 Axis and the CXC Chemokine SDF1α Regulate Growth Factor Independent Survival of Primary Hematopoietic Progenitor Cells Induced by Internal Tandem Duplication Mutations of Flt3.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1611-1611
Author(s):  
Seiji Fukuda ◽  
Huimin Bian ◽  
Edward M. Conway ◽  
Louis M. Pelus
Keyword(s):  
Growth Factor ◽  
Signaling Pathways ◽  
Tandem Duplication ◽  
Hematopoietic Progenitor Cell ◽  
Wild Type ◽  
Hematopoietic Progenitor ◽  
Internal Tandem Duplication ◽  
Over Expression ◽  
Cxcr4 Signaling ◽  
Primary Mouse

Abstract Internal Tandem Duplication mutations in the Flt3 tyrosine kinase gene (ITD-Flt3) and aberrant over-expression of the inhibitor of apoptosis protein Survivin, are frequently found in patients with acute myeloid leukemia (AML) and are associated with poor prognosis. We have shown that ITD-Flt3 increases expression of Survivin and the cyclin dependent kinase inhibitor p21WAF1/Cip1 in Ba/F3 cells and that Survivin regulates hematopoietic progenitor cell (HPC) proliferation through p21WAF1/Cip1 dependent and independent pathways (Fukuda et al. Blood, 2004.103:120), which functionally link Survivin and p21 downstream of ITD-Flt3 signaling. Elevated CXCR4 expression associated with ITD-Flt3 mutations has been recently reported in AML patients and may confer an adverse prognosis. Although it is not known whether ITD-Flt3 signaling interacts with the CXCR4 signaling pathway to regulate cell survival, our recent data indicate that ITD-Flt3 and SDF1α/CXCR4 signaling pathways functionally interact to enhance hematopoietic cell migration (Fukuda et al. Blood, 2005.105:3117). This suggests that these two pathways may coordinate or regulate trafficking of transformed hematopoietic cells and may be involved in AML disease progression. In order to investigate whether Survivin, p21 and SDF1α/CXCR4 mediate enhanced HPC survival as a consequence of constitutive ITD-Flt3 signaling, we utilized marrow cells from control, p21−/− or Tamoxifen-Cre conditional Survivinfloxed/floxed knockout mice and evaluated if disrupting Survivin or p21 can block the aberrant enhanced HPC proliferation induced by ITD-Flt3 in vitro and whether SDF1α could accentuate the enhanced survival of primary mouse HPC induced by ITD-Flt3. Over-expression of human wild-type Flt3 failed to induce growth factor independent proliferation of marrow CFU-GM, however, ectopic expression of ITD-Flt3 mutants cloned from AML patients significantly enhanced survival of CFU-GM from control mice after growth factor deprivation and allowed for factor independent proliferation. In contrast, conditional deletion of Survivin or loss of p21 significantly reduced growth factor independent survival of CFU-GM induced by ITD-Flt3 (53±17% and 41±9% reduction in Survivin and p21 KO cells, respectively; P&lt;0.05), suggesting that Survivin and p21 are required for enhanced survival of HPC induced by ITD-Flt3. Furthermore, SDF-1α dose-dependently increased the number of growth factor independent CFU-GM expressing ITD-Flt3 (40–140% increase), suggesting that SDF-1α/CXCR4 and ITD-Flt3 signaling functionally interact to enhance HPC survival, an effect consistent with the synergistic enhancement of normal HPC survival induced by the combination of Flt3 ligand plus SDF-1α and enhanced migration to SDF1α induced by ITD-Flt3. This effect is unlikely due to up-regulation of CXCR4, since CXCR4 in Ba/F3 and 32D cells expressing ITD-Flt3 was significantly down-regulated compared to wild type Flt3. These reults provide evidence that the Survivin/p21 axis and SDF1α/CXCR4 mediate resistance to apoptosis and transformation of HPC and/or cell trafficking by ITD-Flt3, and that disruption of these signaling pathways may be additional therapeutic strategies for patients with AML expressing ITD-Flt3.

Overlapping but Distinct Role of p21WAF1/CDKN1 and Survivin in Hematopoietic Progenitor Cell Proliferation.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1334-1334
Author(s):  
Seiji Fukuda ◽  
Mariko Abe ◽  
Seiji Yamaguchi ◽  
Louis M. Pelus
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Cell Proliferation ◽  
Growth Factor ◽  
Bone Marrow Cells ◽  
Mouse Bone Marrow ◽  
Hematopoietic Progenitor ◽  
Primary Mouse ◽  
Marrow Cells

Abstract Survivin is a member of the inhibitor of apoptosis protein family that has been implicated in cell cycle control, anti-apoptosis and cell division. Our previous studies and others have shown that Survivin and the cyclin dependent kinase inhibitor p21WAF1/CDKN1 (p21) are functionally associated and are involved in cell cycle, anti-apoptosis and cytokinesis in cancer cells and in normal hematopoietic progenitor cells (HPC). P21 is highly expressed in quiescent hematopoietic stem cells (HSC) in steady state, but the proportion of quiescent HSCs in G0 phase is reduced in p21−/− mice. In contrast, p21 has been shown as positive regulator on cell cycle of normal HPC since p21 deficiency results in fewer total CFU in mouse bone marrow (BM) cells with fewer CFU in S-phase and retrovirus transduction of p21 in p21 deficient bone marrow cells restores total and cycling CFU. We have previously reported that Survivin increases the proliferation of mouse primary HPC and that this enhancing effect is on HPC proliferation is absent when p21 is functionally deleted, suggesting that p21 is required for Survivin to enhance HPC proliferation. In addition, ITD-Flt3 mutations that are normally expressed in patients with acute myeloid leukemia and associate poor prognosis increase expression of both Survivin and p21, implicating their involvement in aberrant proliferation of HPC expressing ITD-Flt3. Herein we have characterized the functional association between p21 and Survivin in normal and transformed cell proliferation. Antagonizing wild-type Survivin in mouse BaF3 cells by retrovirus transduction of a T34A dominant negative mutant Survivin or anti-sense increased p21 expression, even though Survivin requires p21 to enhance HPC proliferation. Ectopic p21 in Survivin+/+ primary mouse bone marrow cells increased the number of immunophenotypically defined c-kit+, lin− (KL) cells, which is consistent with a positive role of p21 in HPC proliferation, however; ectopic expression of p21 failed to increase HPC proliferation in Survivin deficient primary bone marrow cells, suggesting that p21 alone is not sufficient to substitute for Survivin’s enhancing function on normal HPC proliferation. Over-expression of ITD-Flt3 enhanced growth factor independent proliferation of primary mouse marrow c-kit+, Sca-1+, lin− (KSL) cell number; however, co-expression of p21 with ITD-Flt3 dramatically decreased the number of growth factor independent KSL cells (80±6% reduction: P&lt;0.01). Furthermore, the inhibitory effect of p21 on KLS proliferation was further enhanced by Survivin knockout bone marrow cells (64±5% reduction compared with presence of Survivin: P&lt;0.05). These findings indicate that Survivin and p21 have a overlapping but distinct roles in regulating normal HPC proliferation and that manipulating p21 and Survivin may represent a potential therapeutic target for acute leukemia cells expressing ITD-Flt3.

scholarly journals Survivin mediates aberrant hematopoietic progenitor cell proliferation and acute leukemia in mice induced by internal tandem duplication of Flt3

Blood ◽  
2009 ◽  
Vol 114 (2) ◽  
pp. 394-403 ◽  
Author(s):  
Seiji Fukuda ◽  
Pratibha Singh ◽  
Akira Moh ◽  
Mariko Abe ◽  
Edward M. Conway ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Acute Leukemia ◽  
Tandem Duplication ◽  
Survivin Expression ◽  
Dominant Negative ◽  
Hematopoietic Progenitor Cell ◽  
Hematopoietic Progenitor ◽  
Kinase Gene ◽  
Internal Tandem Duplication ◽  
Primary Mouse

Abstract Internal tandem duplication mutations in the Flt3 tyrosine kinase gene (ITD-Flt3) and overexpression of Survivin are frequently found in patients with acute myeloid leukemia (AML). We investigated whether Survivin mediates the enhanced survival of primary hematopoietic progenitor cells (HPCs) resulting from ITD-Flt3 signaling. Ectopic ITD-Flt3 mutants increased Survivin expression in Ba/F3 cells downstream of PI3-kinase/Akt. Treatment of ITD-Flt3+ human MV4-11 leukemia cells with the ITD-Flt3 inhibitor SU5416 reduced Survivin expression and inhibited cell proliferation. ITD-Flt3 dramatically increased the number of primary mouse marrow c-kit+, Sca-1+, LinNeg cells and colony-forming unit granulocyte-macrophages (CFU-GMs) able to proliferate in the absence of growth factors, whereas Survivin deletion significantly reduced growth factor–independent proliferation and increased apoptosis, which was further accentuated by SU5416. Ectopic ITD-Flt3 reduced differentiation of LinNeg marrow cells cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) plus stem cell factor, which was partially blocked by Survivin deletion. In addition, Survivin deletion decreased secondary colony formation induced by ITD-Flt3. Dominant-negative (dn)–Survivin delayed development of acute leukemia in mice that received a transplant of Ba/F3 cells expressing ITD-Flt3. These results suggest that Survivin regulates expansion of ITD-Flt3–transformed HPCs with self-renewal capability and development of ITD-Flt3+ acute leukemia and that antagonizing Survivin may provide therapeutic benefit for patients with acute leukemia expressing ITD-Flt3.

Internal Tandem Duplication Mutations of Flt3 (ITD-Flt3) up-Regulate p21 WAF1/CDKN1 Protein That Negatively Regulates Aberrant Proliferation of Hematopoietic Cells Induced by ITD-Flt3.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 5037-5037
Author(s):  
Mariko Abe ◽  
Louis M. Pelus ◽  
Takeshi Taketani ◽  
Seiji Yamaguchi ◽  
Seiji Fukuda
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Growth Factor ◽  
Gene Deletion ◽  
Tandem Duplication ◽  
Bone Marrow Cells ◽  
Ectopic Expression ◽  
Wild Type ◽  
Internal Tandem Duplication ◽  
Flt3 Inhibitors

Abstract Abstract 5037 Internal Tandem Duplication mutations in the Flt3 tyrosine kinase gene (ITD-Flt3) are frequently found in patients with acute myeloid leukemia (AML) and are associated with poor prognosis. However, lack of significant efficacy in patients with AML treated with ITD-Flt3 inhibitors in several clinical trials underscores the need for identification of pathways down-stream of ITD-Flt3 that are distinct from normal hematopoietic cells in order to develop novel therapeutic approaches. We have shown that ITD-Flt3 induces expression of the antiapoptotic protein Survivin and cyclin dependent kinase inhibitor (CDKI) p21WAF1/CDKN1 (p21) and that antagonizing Survivin in primary mouse hematopoietic progenitor cells (HPC) expressing ITD-Flt3 inhibits growth factor-independent proliferation (Fukuda et al. Blood 2009). Similarly, ectopic Survivin increases proliferation of mouse primary HPC and this enhancing effect is absent when p21 is functionally deleted (Fukuda et al. Blood 2004). These previous findings suggest that p21 lies down stream of Survivin and involved in facilitating growth factor independent HPC proliferation mediated by ITD-Flt3 signaling. However, analysis of p21 function in growth factor-independent ITD-Flt3 transduced HPC now indicates that p21 in fact negatively regulates ITD-Flt3 signaling. Flt3 ligand (FL) induced marginal proliferation and p21 protein expression in Ba/F3 cells expressing wild-type Flt3. Expression of ITD-Flt3 significantly enhanced proliferation, cell cycle progression and inhibition of apoptosis coincident with up-regulation of p21 in Ba/F3 cells in the absence of FL or IL-3. In contrast, down-regulation of p27Kip1 by ITD-Flt3 was coincidently observed. In addition, higher levels of p21 were observed in ITD-Flt3+ MV4-11 human acute leukemia cells compared to ITD-Flt3- RS4;11 cells. Treatment of MV4-11 cells and Ba/F3 cells expressing ITD-Flt3 with the ITD-Flt3 inhibitor AG1296 significantly reduced p21 expression. In BaF3 cells, elevated p21 expression induced by ITD-Flt3 was suppressed by selective inhibitors for protein kinase A (H89), MAPK (PD98059), PI3-kinase (LY294002), Akt (Akt inhibitor) and p53 (pifithrin-α), suggesting involvement of these signaling pathways in ITD-Flt3 mediated p21 up-regulation. Although ITD-Flt3 induces p21 expression and growth factor-independent proliferation in Ba/F3 cells, control cells expressing both ectopic wild-type Flt3 and p21 did not proliferate in the absence of growth factors, indicating that p21 is not sufficient to substitute for ITD-Flt3. In Ba/F3 cells expressing ITD-Flt3, p21 knock down by shRNA enhanced growth factor-independent proliferation. Ectopic expression of ITD-Flt3 in CFU-GM from p21+/+ mice resulted in significant growth of growth factor-independent CFU-GM in vitro, which was further accelerated by gene deletion of p21 (170 % increase: P<0.05), while co-expression of p21 with ITD-Flt3 in bone marrow cells from p21+/+ mice dramatically decreased growth factor-independent proliferation of c-kit+, Sca-1+, lin- cells (80±6% reduction: P<0.01). In contrast, Survivin gene deletion significantly reduced growth factor-independent CFU-GM proliferation by 74% (P<0.05). Although ITD-Flt3 up-regulates p21 and Survivin independent of hematopoietic growth factors in primary HPC transformed by ITD-Flt3, p21 negatively regulates aberrant growth factor-independent proliferation. This is in contrast to Survivin, which functions up-stream of p21 in normal HPC proliferation and positively regulates ITD-Flt3 signaling. This suggests that p21 antagonizes Survivin down-stream of ITD-Flt3 signaling but cooperates/synergizes with Survivin to enhance proliferation in normal HPC. Since p21 deficiency has been shown to result in fewer total and S-phase CFU and ectopic expression of p21 in p21 −/− bone marrow cells restores total and cycling CFU, p21 positively regulates cell cycle and proliferation of normal HPC, but negatively regulates growth factor-independent proliferation of CFU induced by ITD-Flt3. Our data also suggests that CDKIs p21 and p27 have divergent function in ITD-Flt3 signaling. Manipulation of p21 signaling based on their functional difference between normal and transformed HPC may represent an alternative therapeutic strategy for hematological malignancies expressing ITD-Flt3 that are refractory to ITD-Flt3 inhibitors. Disclosures No relevant conflicts of interest to declare.

scholarly journals TLR5 signaling in murine bone marrow induces hematopoietic progenitor cell proliferation and aids survival from radiation

2017 ◽  
Vol 1 (21) ◽  
pp. 1796-1806 ◽  
Author(s):  
Benyue Zhang ◽  
Damilola Oyewole-Said ◽  
Jun Zou ◽  
Ifor R. Willliams ◽  
Andrew T. Gewirtz
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Progenitor Cell ◽  
Hematopoietic Progenitor Cell ◽  
Mouse Bone Marrow ◽  
Hematopoietic Progenitor ◽  
Murine Bone Marrow ◽  
Key Points ◽  
Progenitor Cell Proliferation ◽  
Lethal Irradiation

Key Points Flagellin activates TLR5 signaling in mouse bone marrow and induces hematopoietic progenitor cell proliferation. Flagellin-induced MPP3 cells aid the survival of mice exposed to lethal irradiation.

Cyclin Dependent Kinase Inhibitor P21 Negatively Regulates PBX-1 Via Internal Tandem Duplication of Flt3 Dependent Manner, a Novel Mechanism That Does Not Exist in Normal Hematopoietic Progenitor Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1310-1310
Author(s):  
Mariko Abe ◽  
Seiji Yamaguchi ◽  
Takeshi Taketani ◽  
Seiji Fukuda
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Mrna Expression ◽  
Tandem Duplication ◽  
Kinase Inhibitor ◽  
Hematopoietic Progenitor Cells ◽  
Cyclin Dependent Kinase ◽  
Hematopoietic Progenitor ◽  
Internal Tandem Duplication ◽  
Cyclin Dependent Kinase Inhibitor

Abstract Abstract 1310 The cyclin dependent kinase inhibitor p21 CDKN1 (p21) regulates proliferation of diverse cell types by modulating cell cycle and apoptosis in variety of ways, however, its molecular mechanism underlying cell fate decisions remains to be explored. We previously reported that p21 expression is up-regulated in mouse Ba/F3 cells by Internal Tandem Duplication mutations on the Flt3 gene (ITD-Flt3), which induce constitutive activation of Flt3 signaling and associate with poor prognosis of patients with acute myeloid leukemia (AML). However, despite up-regulation of p21 by ITD-Flt3, deletion of p21 gene accentuated growth factor independent proliferation of primary mouse hematopoietic progenitor cells (HPC) transformed by ITD-Flt3 (Abe et al. ASH 2010). The data suggests that the paradoxical increase of p21 induced by ITD-Flt3 negatively regulates oncogenic proliferation of ITD-Flt3+ HPC. Although p21 is generally considered to reduce cell proliferation by inhibiting G1/S transition, p21 can enhance proliferation of normal HPC stimulated by hematopoietic growth factors (Mantel et al. 1995, Fukuda et al. 2004). These data suggest that differential mechanism is involved in regulating p21 function between normal versus transformed HPC. Herein in order to determine the mechanism responsible for growth factor independent proliferation of ITD-Flt3+HPC regulated by p21, we identified selective molecules regulated by p21 exclusively in ITD-Flt3+ HPC that are distinct from normal HPC. Deletion of p21 gene modulated expression of 247 genes in c-kit+, Sca-1+, lineage− (KSL) cells over-expressing ITD-Flt3. Out of 247 genes modulated by p21 deletion in ITD-Flt3+ KSL cells, 112 genes were either not modulated or inversely regulated by p21 in normal mouse marrow KSL cells in vivo. The results implicate that alteration of 112 mRNA expression by p21 may be specific for transformed KSL cells by ITD-Flt3, which is distinct from normal KSL cells. Out of 112 genes, 13 genes are listed in the known genes deregulated in human AML stem cells (LSC) (Majeti et al. 2009). Among the 13 molecules that are also deregulated in AML LSC, pbx-1, a transcriptional factor, which is profoundly associated with hematopoietic stem cell function but down-regulated in AML LSC (Ficara et al. 2008), was up-regulated by 1.6±0.2 fold in ITD-Flt3+ KSL cells lacking p21 (P<0.05, N=3) compared to p21+/+ counterparts. Whereas, loss of p21 did not affect pbx-1 expression in normal KSL cells (1.1±0.1 fold compared to p21+/+ KSL cells, NS). Pbx-1 mRNA expression was significantly lower in ITD-Flt3 transduced KSL cells compared to freshly isolated KSL cells (P<0.05, N=3), regardless of p21 status, a finding consistent with down-regulation of pbx-1 in AML LSC compared to normal CD34+CD38− cells and presence of ITD-Flt3 in AML LSC (Levis et al. 2005). In contrast, p21 mRNA expression was coincidently elevated in ITD-Flt3+KSL cells (P<0.05) compared to normal KSL cells, indicating that p21 and pbx-1 are concomitantly but inversely modulated by ITD-Flt3 in ITD-Flt3+ KSL cells. Consistently, p21 expression was negatively correlated with pbx-1 expression in 293 AML subjects obtained from a public database Gene Expression Omnibus (GEO: GSE1159). However, the association between p21 and pbx-1 was not observed in the gene expression profile of normal human CD34+CD38− cells. In addition, pbx-1 expression was significantly lower in ITD-Flt3+ AML cells (N=78) compared to the ITD-Flt3 negative AML cells (N=215, P<0.05) listed in GSE1159, providing additional evidence for the negative regulation of pbx-1 by ITD-Flt3 in AML cells. These results suggest that p21 and ITD-Flt3 down-regulate pbx-1 expression, but the effect of p21 on pbx-1 is ITD-Flt3 dependent. As opposed to p21/pbx1 axis identified in transformed HPC and AML, pbx-1 and p21 is not associated in normal KSL cells and CD34+CD38− cells. The data suggests that p21/pbx-1 axis selectively exist in AML cells, a mechanism that is not present in normal HPC. Enhancement of growth factor independent proliferation of ITD-Flt3+ KSL cells resulting from p21 deletion may be partly due to up-regulation of pbx-1induced by p21 deletion, rather than merely a consequence of modulation of G1/S transition by p21. In this regard, manipulation of selective p21/pbx-1 axis that is dependent on ITD-Flt3 may represent a novel therapeutic strategy for ITD-Flt3+AML that are refractory to ITD-Flt3 inhibitors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals AZD1208, a potent and selective pan-Pim kinase inhibitor, demonstrates efficacy in preclinical models of acute myeloid leukemia

Blood ◽  
2014 ◽  
Vol 123 (6) ◽  
pp. 905-913 ◽  
Author(s):  
Erika K. Keeton ◽  
Kristen McEachern ◽  
Keith S. Dillman ◽  
Sangeetha Palakurthi ◽  
Yichen Cao ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Myeloid Leukemia ◽  
Tandem Duplication ◽  
Kinase Inhibitor ◽  
Wild Type ◽  
Internal Tandem Duplication ◽  
Rna Translation ◽  
Key Points ◽  
Messenger Rna Translation ◽  
Flt3 Internal Tandem Duplication

Key Points AZD1208 is a selective pan-Pim kinase inhibitor with efficacy in AML cells, xenografts, and Flt3-internal tandem duplication or Flt3 wild-type patient samples. AML cell growth inhibition is associated with suppression of p70S6K, 4EBP1 phosphorylation, and messenger RNA translation.

scholarly journals GAGA Factor Isoforms Have Distinct but Overlapping Functions In Vivo

2001 ◽  
Vol 21 (24) ◽  
pp. 8565-8574 ◽  
Author(s):  
Anthony J. Greenberg ◽  
Paul Schedl
Keyword(s):  
Fusion Protein ◽  
Transcriptional Activation ◽  
Functional Difference ◽  
Wild Type ◽  
Gaga Factor ◽  
Phenotypic Analysis ◽  
Alternatively Spliced

ABSTRACT The Drosophila melanogaster GAGA factor (encoded by the Trithorax-like [Trl] gene) is required for correct chromatin architecture at diverse chromosomal sites. The Trl gene encodes two alternatively spliced isoforms of the GAGA factor (GAGA-519 and GAGA-581) that are identical except for the length and sequence of the C-terminal glutamine-rich (Q) domain. In vitro and tissue culture experiments failed to find any functional difference between the two isoforms. We made a set of transgenes that constitutively express cDNAs coding for either of the isoforms with the goal of elucidating their roles in vivo. Phenotypic analysis of the transgenes in Trl mutant background led us to the conclusion that GAGA-519 and GAGA-581 perform different, albeit largely overlapping, functions. We also expressed a fusion protein with LacZ disrupting the Q domain of GAGA-519. This LacZ fusion protein compensated for the loss of wild-type GAGA factor to a surprisingly large extent. This suggests that the Q domain either is not required for the essential functions performed by the GAGA protein or is exclusively used for tetramer formation. These results are inconsistent with a major role of the Q domain in chromatin remodeling or transcriptional activation. We also found that GAGA-LacZ was able to associate with sites not normally occupied by the GAGA factor, pointing to a role of the Q domain in binding site choice in vivo.

Sign in / Sign up

Export Citation Format

Share Document