Publications by authors named "Danilo Perrotti"

92 Publications

Cytoplasmic DROSHA and non-canonical mechanisms of MiR-155 biogenesis in FLT3-ITD acute myeloid leukemia.

Leukemia 2021 Feb 15. Epub 2021 Feb 15.

Gehr Family Center for Leukemia Research, Hematology Malignancies and Stem Cell Transplantation Institute, City of Hope Medical Center, Duarte, CA, USA.

We report here on a novel pro-leukemogenic role of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) that interferes with microRNAs (miRNAs) biogenesis in acute myeloid leukemia (AML) blasts. We showed that FLT3-ITD interferes with the canonical biogenesis of intron-hosted miRNAs such as miR-126, by phosphorylating SPRED1 protein and inhibiting the "gatekeeper" Exportin 5 (XPO5)/RAN-GTP complex that regulates the nucleus-to-cytoplasm transport of pre-miRNAs for completion of maturation into mature miRNAs. Of note, despite the blockage of "canonical" miRNA biogenesis, miR-155 remains upregulated in FLT3-ITD+ AML blasts, suggesting activation of alternative mechanisms of miRNA biogenesis that circumvent the XPO5/RAN-GTP blockage. MiR-155, a BIC-155 long noncoding (lnc) RNA-hosted oncogenic miRNA, has previously been implicated in FLT3-ITD+ AML blast hyperproliferation. We showed that FLT3-ITD upregulates miR-155 by inhibiting DDX3X, a protein implicated in the splicing of lncRNAs, via p-AKT. Inhibition of DDX3X increases unspliced BIC-155 that is then shuttled by NXF1 from the nucleus to the cytoplasm, where it is processed into mature miR-155 by cytoplasmic DROSHA, thereby bypassing the XPO5/RAN-GTP blockage via "non-canonical" mechanisms of miRNA biogenesis.
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http://dx.doi.org/10.1038/s41375-021-01166-9DOI Listing
February 2021

PP2A-activating Drugs Enhance FLT3 Inhibitor Efficacy through AKT Inhibition-Dependent GSK-3β-Mediated c-Myc and Pim-1 Proteasomal Degradation.

Mol Cancer Ther 2021 04 10;20(4):676-690. Epub 2021 Feb 10.

The University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center,

-like tyrosine-like kinase 3 internal tandem duplication (FLT3-ITD) is present in acute myeloid leukemia (AML) in 30% of patients and is associated with short disease-free survival. FLT3 inhibitor efficacy is limited and transient but may be enhanced by multitargeting of FLT3-ITD signaling pathways. FLT3-ITD drives both STAT5-dependent transcription of oncogenic Pim-1 kinase and inactivation of the tumor-suppressor protein phosphatase 2A (PP2A), and FLT3-ITD, Pim-1, and PP2A all regulate the c-Myc oncogene. We studied mechanisms of action of cotreatment of FLT3-ITD-expressing cells with FLT3 inhibitors and PP2A-activating drugs (PADs), which are in development. PADs, including FTY720 and DT-061, enhanced FLT3 inhibitor growth suppression and apoptosis induction in FLT3-ITD-expressing cell lines and primary AML cells and MV4-11 growth suppression PAD and FLT3 inhibitor cotreatment independently downregulated c-Myc and Pim-1 protein through enhanced proteasomal degradation. c-Myc and Pim-1 downregulation was preceded by AKT inactivation, did not occur in cells expressing myristoylated (constitutively active) AKT1, and could be induced by AKT inhibition. AKT inactivation resulted in activation of GSK-3β, and GSK-3β inhibition blocked downregulation of both c-Myc and Pim-1 by PAD and FLT3 inhibitor cotreatment. GSK-3β activation increased c-Myc proteasomal degradation through c-Myc phosphorylation on T58; infection with c-Myc with T58A substitution, preventing phosphorylation, blocked downregulation of c-Myc by PAD and FLT3 inhibitor cotreatment. GSK-3β also phosphorylated Pim-1L/Pim-1S on S95/S4. Thus, PADs enhance efficacy of FLT3 inhibitors in FLT3-ITD-expressing cells through a novel mechanism involving AKT inhibition-dependent GSK-3β-mediated increased c-Myc and Pim-1 proteasomal degradation.
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http://dx.doi.org/10.1158/1535-7163.MCT-20-0663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8027945PMC
April 2021

Persistence of Drug-Resistant Leukemic Stem Cells and Impaired NK Cell Immunity in CML Patients Depend on Antiproliferative and PP2A-Activating Functions.

Blood Cancer Discov 2020 Jul;1(1):48-67

Department of Haematology, Hammersmith Hospital, Imperial College London, London, United Kingdom.

Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK) cell immune response account for relapse of chronic myelogenous leukemia (CML). Inactivation of protein phosphatase 2A (PP2A) is essential for CML-quiescent LSC survival and NK cell antitumor activity. Here we show that has antiproliferative and PP2A-activating functions that are dose dependently differentially induced by CCND2/CDK6 and SET inhibition, respectively. is upregulated in CML LSCs and NK cells by bone marrow microenvironment (BMM) signals to induce quiescence and impair immune response, respectively. Conversely, BCR-ABL1 downregulates in CML progenitors to prevent growth arrest and PP2A-mediated apoptosis. Quiescent LSCs escape apoptosis by upregulating long noncoding RNA that uncouples and limits function to cytostasis. Genetic and pharmacologic modulation and/or PP2A-activating drug treatment restore NK cell activity, inhibit BMM-induced growth arrest, and selectively trigger LSC apoptosis and in patient-derived xenografts; hence, the importance of and PP2A activity for CML development and therapy.
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http://dx.doi.org/10.1158/0008-5472.BCD-19-0039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510943PMC
July 2020

Comment on "PP2A inhibition sensitizes cancer stem cells to ABL tyrosine kinase inhibitors in BCR-ABL human leukemia".

Sci Transl Med 2019 07;11(501)

School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia.

LB100 does not sensitize CML stem cells to tyrosine kinase inhibitor-induced apoptosis.
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http://dx.doi.org/10.1126/scitranslmed.aau0416DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7402218PMC
July 2019

Somatic variants in epigenetic modifiers can predict failure of response to imatinib but not to second-generation tyrosine kinase inhibitors.

Haematologica 2019 12 9;104(12):2400-2409. Epub 2019 May 9.

Centre for Haematology, Department of Medicine, Imperial College, London, UK.

There are no validated molecular biomarkers to identify newly-diagnosed individuals with chronic-phase chronic myeloid leukemia likely to respond poorly to imatinib and who might benefit from first-line treatment with a more potent second-generation tyrosine kinase inhibitor. Our inability to predict these 'high-risk' individuals reflects the poorly understood heterogeneity of the disease. To investigate the potential of genetic variants in epigenetic modifiers as biomarkers at diagnosis, we used Ion Torrent next-generation sequencing of 71 candidate genes for predicting response to tyrosine kinase inhibitors and probability of disease progression. A total of 124 subjects with newly-diagnosed chronic-phase chronic myeloid leukemia began with imatinib (n=62) or second-generation tyrosine kinase inhibitors (n=62) and were classified as responders or non-responders based on the transcript levels within the first year and the European LeukemiaNet criteria for failure. Somatic variants affecting 21 genes (e.g. ) were detected in 30% of subjects, most of whom were non-responders (41% non-responders, 18% responders to imatinib, 38% non-responders, 25% responders to second-generation tyrosine kinase inhibitors). The presence of variants predicted the rate of achieving a major molecular response, event-free survival, progression-free survival and chronic myeloid leukemia-related survival in the imatinib but not the second-generation tyrosine kinase inhibitors cohort. Rare germline variants had no prognostic significance irrespective of treatment while some pre-leukemia variants suggest a multi-step development of chronic myeloid leukemia. Our data suggest that identification of somatic variants at diagnosis facilitates stratification into imatinib responders/non-responders, thereby allowing earlier use of second-generation tyrosine kinase inhibitors, which, in turn, may overcome the negative impact of such variants on disease progression.
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http://dx.doi.org/10.3324/haematol.2018.200220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6959189PMC
December 2019

Precision immunotherapy, mutational landscape, and emerging tools to optimize clinical outcomes in patients with classical myeloproliferative neoplasms.

Hematol Oncol 2018 Dec 3;36(5):740-748. Epub 2018 Aug 3.

Research Center for Molecular Medicine of the Austrian Academy of Science, Vienna, Austria.

Following the 47th American Society of Hematology Meeting in 2005, the late John Goldman and Tariq Mughal commenced a conference, the 1st Post-ASH Workshop, which brought together clinicians and scientists, to accelerate the adoption of new therapies for patients with myeloproliferative neoplasms (MPNs). The concept began with recognition of the CML success story following imatinib therapy, the discovery of JAK2 , and the demonstration that BCR-ABL1-negative MPNs are driven by abnormal JAK2 activation. This review is based on the presentations and deliberations at the XIIth Post-ASH Workshop on BCR-ABL1 positive and negative MPNs that took place on December 12 to 13, 2017, in Atlanta, Georgia, immediately following the 59th American Society of Hematology Meeting. We have selected some of the translational research and clinical topics, rather than an account of the proceedings. We discuss the role of immunotherapy in MPNs and the impact of the mutational landscape on TKI treatment in CML. We also consider how we might reduce TKI cardiovascular side effects, the potential role of nutrition as adjunctive nonpharmacologic intervention to reduce chronic inflammation in MPNs, and novel investigational therapies for MPNs.
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http://dx.doi.org/10.1002/hon.2537DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6613211PMC
December 2018

BCR-ABL1 mediated miR-150 downregulation through MYC contributed to myeloid differentiation block and drug resistance in chronic myeloid leukemia.

Haematologica 2018 12 26;103(12):2016-2025. Epub 2018 Jul 26.

Institute of Hematology and Blood Transfusion, Prague, Czech Republic

The fusion oncoprotein BCR-ABL1 exhibits aberrant tyrosine kinase activity and it has been proposed that it deregulates signaling networks involving both transcription factors and non-coding microRNAs that result in chronic myeloid leukemia (CML). Previously, microRNA expression profiling showed deregulated expression of miR-150 and miR-155 in CML. In this study, we placed these findings into the broader context of the MYC/miR-150/MYB/miR-155/PU.1 oncogenic network. We propose that up-regulated MYC and miR-155 in CD34 leukemic stem and progenitor cells, in concert with BCR-ABL1, impair the molecular mechanisms of myeloid differentiation associated with low miR-150 and PU.1 levels. We revealed that MYC directly occupied the -11.7 kb and -0.35 kb regulatory regions in the gene. MYC occupancy was markedly increased through BCR-ABL1 activity, causing inhibition of gene expression in CML CD34 and CD34 cells. Furthermore, we found an association between reduced miR-150 levels in CML blast cells and their resistance to tyrosine kinase inhibitors (TKIs). Although TKIs successfully disrupted BCR-ABL1 kinase activity in proliferating CML cells, this treatment did not efficiently target quiescent leukemic stem cells. The study presents new evidence regarding the MYC/miR-150/MYB/miR-155/PU.1 leukemic network established by aberrant BCR-ABL1 activity. The key connecting nodes of this network may serve as potential druggable targets to overcome resistance of CML stem and progenitor cells.
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http://dx.doi.org/10.3324/haematol.2018.193086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6269310PMC
December 2018

Bone marrow niche trafficking of miR-126 controls the self-renewal of leukemia stem cells in chronic myelogenous leukemia.

Nat Med 2018 05 5;24(4):450-462. Epub 2018 Mar 5.

Department of Immuno-oncology, City of Hope Medical Center, Duarte, California, USA.

Leukemia stem cells (LSCs) in individuals with chronic myelogenous leukemia (CML) (hereafter referred to as CML LSCs) are responsible for initiating and maintaining clonal hematopoiesis. These cells persist in the bone marrow (BM) despite effective inhibition of BCR-ABL kinase activity by tyrosine kinase inhibitors (TKIs). Here we show that although the microRNA (miRNA) miR-126 supported the quiescence, self-renewal and engraftment capacity of CML LSCs, miR-126 levels were lower in CML LSCs than in long-term hematopoietic stem cells (LT-HSCs) from healthy individuals. Downregulation of miR-126 levels in CML LSCs was due to phosphorylation of Sprouty-related EVH1-domain-containing 1 (SPRED1) by BCR-ABL, which led to inhibition of the RAN-exportin-5-RCC1 complex that mediates miRNA maturation. Endothelial cells (ECs) in the BM supply miR-126 to CML LSCs to support quiescence and leukemia growth, as shown using mouse models of CML in which Mir126a (encoding miR-126) was conditionally knocked out in ECs and/or LSCs. Inhibition of BCR-ABL by TKI treatment caused an undesired increase in endogenous miR-126 levels, which enhanced LSC quiescence and persistence. Mir126a knockout in LSCs and/or ECs, or treatment with a miR-126 inhibitor that targets miR-126 expression in both LSCs and ECs, enhanced the in vivo anti-leukemic effects of TKI treatment and strongly diminished LSC leukemia-initiating capacity, providing a new strategy for the elimination of LSCs in individuals with CML.
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http://dx.doi.org/10.1038/nm.4499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5965294PMC
May 2018

Concurrent Inhibition of Pim and FLT3 Kinases Enhances Apoptosis of FLT3-ITD Acute Myeloid Leukemia Cells through Increased Mcl-1 Proteasomal Degradation.

Clin Cancer Res 2018 01 26;24(1):234-247. Epub 2017 Oct 26.

University of Maryland Greenebaum Comprehensive Cancer Center, Baltimore, Maryland.

-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is present in 30% of acute myeloid leukemia (AML), and these patients have short disease-free survival. FLT3 inhibitors have limited and transient clinical activity, and concurrent treatment with inhibitors of parallel or downstream signaling may improve responses. The oncogenic serine/threonine kinase Pim-1 is upregulated downstream of FLT3-ITD and also promotes its signaling in a positive feedback loop, suggesting benefit of combined Pim and FLT3 inhibition. Combinations of clinically active Pim and FLT3 inhibitors were studied and Concurrent treatment with the pan-Pim inhibitor AZD1208 and FLT3 inhibitors at clinically applicable concentrations abrogated growth of FLT3-ITD, but not wild-type FLT3 (FLT3-WT), cell lines. AZD1208 cotreatment increased FLT3 inhibitor-induced apoptosis of FLT3-ITD, but not FLT3-WT, cells measured by sub-G fraction, annexin V labeling, mitochondrial membrane potential, and PARP and caspase-3 cleavage. Concurrent treatment with AZD1208 and the FLT3 inhibitor quizartinib decreased growth of MV4-11 cells, with FLT3-ITD, in mouse xenografts, and prolonged survival, enhanced apoptosis of FLT3-ITD primary AML blasts, but not FLT3-WT blasts or remission marrow cells, and decreased FLT3-ITD AML blast colony formation. Mechanistically, AZD1208 and quizartinib cotreatment decreased expression of the antiapoptotic protein Mcl-1. Decrease in Mcl-1 protein expression was abrogated by treatment with the proteasome inhibitor MG132, and was preceded by downregulation of the Mcl-1 deubiquitinase USP9X, a novel mechanism of Mcl-1 regulation in AML. The data support clinical testing of Pim and FLT3 inhibitor combination therapy for FLT3-ITD AML. .
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http://dx.doi.org/10.1158/1078-0432.CCR-17-1629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6444348PMC
January 2018

Twisting IL-1 signaling to kill CML stem cells.

Blood 2016 12;128(23):2592-2593

UNIVERSITY OF MARYLAND SCHOOL OF MEDICINE.

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http://dx.doi.org/10.1182/blood-2016-10-741009DOI Listing
December 2016

Targeting the RAS/MAPK pathway with miR-181a in acute myeloid leukemia.

Oncotarget 2016 Sep;7(37):59273-59286

Molecular Cellular and Developmental Biology, The Ohio State University, Columbus, OH, USA.

Deregulation of microRNAs' expression frequently occurs in acute myeloid leukemia (AML). Lower miR-181a expression is associated with worse outcomes, but the exact mechanisms by which miR-181a mediates this effect remain elusive. Aberrant activation of the RAS pathway contributes to myeloid leukemogenesis. Here, we report that miR-181a directly binds to 3'-untranslated regions (UTRs); downregulates KRAS, NRAS and MAPK1; and decreases AML growth. The delivery of miR-181a mimics to target AML cells using transferrin-targeting lipopolyplex nanoparticles (NP) increased mature miR-181a; downregulated KRAS, NRAS and MAPK1; and resulted in decreased phosphorylation of the downstream RAS effectors. NP-mediated upregulation of miR-181a led to reduced proliferation, impaired colony formation and increased sensitivity to chemotherapy. Ectopic expression of KRAS, NRAS and MAPK1 attenuated the anti-leukemic activity of miR-181a mimics, thereby validating the relevance of the deregulated miR-181a-RAS network in AML. Finally, treatment with miR-181a-NP in a murine AML model resulted in longer survival compared to mice treated with scramble-NP control. These data support that targeting the RAS-MAPK-pathway by miR-181a mimics represents a novel promising therapeutic approach for AML and possibly for other RAS-driven cancers.
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http://dx.doi.org/10.18632/oncotarget.11150DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5312311PMC
September 2016

Cooperation of imipramine blue and tyrosine kinase blockade demonstrates activity against chronic myeloid leukemia.

Oncotarget 2016 08;7(32):51651-51664

Department of Dermatology, Emory University School of Medicine, Atlanta, GA 30322, USA.

The use of tyrosine kinase inhibitors (TKI), including nilotinib, has revolutionized the treatment of chronic myeloid leukemia (CML). However current unmet clinical needs include combating activation of additional survival signaling pathways in persistent leukemia stem cells after long-term TKI therapy. A ubiquitous signaling alteration in cancer, including CML, is activation of reactive oxygen species (ROS) signaling, which may potentiate stem cell activity and mediate resistance to both conventional chemotherapy and targeted inhibitors. We have developed a novel nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, imipramine blue (IB) that targets ROS generation. ROS levels are known to be elevated in CML with respect to normal hematopoietic stem/progenitor cells and not corrected by TKI. We demonstrate that IB has additive benefit with nilotinib in inhibiting proliferation, viability, and clonogenic function of TKI-insensitive quiescent CD34+ CML chronic phase (CP) cells while normal CD34+ cells retained their clonogenic capacity in response to this combination therapy in vitro. Mechanistically, the pro-apoptotic activity of IB likely resides in part through its dual ability to block NF-κB and re-activate the tumor suppressor protein phosphatase 2A (PP2A). Combining BCR-ABL1 kinase inhibition with NADPH oxidase blockade may be beneficial in eradication of CML and worthy of further investigation.
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http://dx.doi.org/10.18632/oncotarget.10541DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5239504PMC
August 2016

Pim kinase inhibition sensitizes FLT3-ITD acute myeloid leukemia cells to topoisomerase 2 inhibitors through increased DNA damage and oxidative stress.

Oncotarget 2016 Jul;7(30):48280-48295

University of Maryland Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA.

Internal tandem duplication of fms-like tyrosine kinase-3 (FLT3-ITD) is frequent (30 percent) in acute myeloid leukemia (AML), and is associated with short disease-free survival following chemotherapy. The serine threonine kinase Pim-1 is a pro-survival oncogene transcriptionally upregulated by FLT3-ITD that also promotes its signaling in a positive feedback loop. Thus inhibiting Pim-1 represents an attractive approach in targeting FLT3-ITD cells. Indeed, co-treatment with the pan-Pim kinase inhibitor AZD1208 or expression of a kinase-dead Pim-1 mutant sensitized FLT3-ITD cell lines to apoptosis triggered by chemotherapy drugs including the topoisomerase 2 inhibitors daunorubicin, etoposide and mitoxantrone, but not the nucleoside analog cytarabine. AZD1208 sensitized primary AML cells with FLT3-ITD to topoisomerase 2 inhibitors, but did not sensitize AML cells with wild-type FLT3 or remission bone marrow cells, supporting a favorable therapeutic index. Mechanistically, the enhanced apoptosis observed with AZD1208 and topoisomerase 2 inhibitor combination treatment was associated with increased DNA double-strand breaks and increased levels of reactive oxygen species (ROS), and co-treatment with the ROS scavenger N-acetyl cysteine rescued FLT3-ITD cells from AZD1208 sensitization to topoisomerase 2 inhibitors. Our data support testing of Pim kinase inhibitors with topoisomerase 2 inhibitors, but not with cytarabine, to improve treatment outcomes in AML with FLT3-ITD.
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http://dx.doi.org/10.18632/oncotarget.10209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5217017PMC
July 2016

Cellular and Molecular Networks in Chronic Myeloid Leukemia: The Leukemic Stem, Progenitor and Stromal Cell Interplay.

Curr Drug Targets 2017 ;18(4):377-388

Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States.

The use of imatinib, second and third generation ABL tyrosine kinase inhibitors (TKI) (i.e. dasatinib, nilotinib, bosutinib and ponatinib) made CML a clinically manageable and, in a small percentage of cases, a cured disease. TKI therapy also turned CML blastic transformation into a rare event; however, disease progression still occurs in those patients who are refractory, not compliant with TKI therapy or develop resistance to multiple TKIs. In the past few years, it became clear that the BCRABL1 oncogene does not operate alone to drive disease emergence, maintenance and progression. Indeed, it seems that bone marrow (BM) microenvironment-generated signals and cell autonomous BCRABL1 kinase-independent genetic and epigenetic alterations all contribute to: i. persistence of a quiescent leukemic stem cell (LSC) reservoir, ii. innate or acquired resistance to TKIs, and iii. progression into the fatal blast crisis stage. Herein, we review the intricate leukemic network in which aberrant, but finely tuned, survival, mitogenic and self-renewal signals are generated by leukemic progenitors, stromal cells, immune cells and metabolic microenvironmental conditions (e.g. hypoxia) to promote LSC maintenance and blastic transformation.
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http://dx.doi.org/10.2174/1389450117666160615074120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5970649PMC
September 2017

c-MYC Generates Repair Errors via Increased Transcription of Alternative-NHEJ Factors, LIG3 and PARP1, in Tyrosine Kinase-Activated Leukemias.

Mol Cancer Res 2015 Apr 31;13(4):699-712. Epub 2015 Mar 31.

Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland. Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland.

Unlabelled: Leukemias expressing the constitutively activated tyrosine kinases (TK) BCR-ABL1 and FLT3/ITD activate signaling pathways that increase genomic instability through generation of reactive oxygen species (ROS), DNA double-strand breaks (DSB), and error-prone repair. The nonhomologous end-joining (NHEJ) pathway is a major pathway for DSB repair and is highly aberrant in TK-activated leukemias; an alternative form of NHEJ (ALT-NHEJ) predominates, evidenced by increased expression of DNA ligase IIIα (LIG3) and PARP1, increased frequency of large genomic deletions, and repair using DNA sequence microhomologies. This study, for the first time, demonstrates that the TK target c-MYC plays a role in transcriptional activation and subsequent expression of LIG3 and PARP1 and contributes to the increased error-prone repair observed in TK-activated leukemias. c-MYC negatively regulates microRNAs miR-150 and miR-22, which demonstrate an inverse correlation with LIG3 and PARP1 expression in primary and cultured leukemia cells and chronic myelogenous leukemia human patient samples. Notably, inhibition of c-MYC and overexpression of miR-150 and -22 decreases ALT-NHEJ activity. Thus, BCR-ABL1 or FLT3/ITD induces c-MYC expression, leading to genomic instability via augmented expression of ALT-NHEJ repair factors that generate repair errors.

Implications: In the context of TK-activated leukemias, c-MYC contributes to aberrant DNA repair through downstream targets LIG3 and PARP1, which represent viable and attractive therapeutic targets.
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http://dx.doi.org/10.1158/1541-7786.MCR-14-0422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4398615PMC
April 2015

A "RANning" leap with "XPOrt" into TKI resistance.

Blood 2015 Mar;125(11):1686-8

UNIVERSITY OF MARYLAND SCHOOL OF MEDICINE.

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http://dx.doi.org/10.1182/blood-2015-01-622217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4357578PMC
March 2015

From the Biology of PP2A to the PADs for Therapy of Hematologic Malignancies.

Front Oncol 2015 16;5:21. Epub 2015 Feb 16.

Department of Medicine, The Greenebaum Cancer Center, University of Maryland School of Medicine , Baltimore, MD , USA.

Over the past decades, an emerging role of phosphatases in the pathogenesis of hematologic malignancies and solid tumors has been established. The tumor-suppressor protein phosphatase 2A (PP2A) belongs to the serine-threonine phosphatases family and accounts for the majority of serine-threonine phosphatase activity in eukaryotic cells. Numerous studies have shown that inhibition of PP2A expression and/or function may contribute to leukemogenesis in several hematological malignancies. Likewise, overexpression or aberrant expression of physiologic PP2A inhibitory molecules (e.g., SET and its associated SETBP1 and CIP2A) may turn off PP2A function and participate to leukemic progression. The discovery of PP2A as tumor suppressor has prompted the evaluation of the safety and the efficacy of new compounds, which can restore PP2A activity in leukemic cells. Although further studies are needed to better understand how PP2A acts in the intricate phosphatases/kinases cancer network, the results reviewed herein strongly support the development on new PP2A-activating drugs and the immediate introduction of those available into clinical protocols for leukemia patients refractory or resistant to current available therapies.
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http://dx.doi.org/10.3389/fonc.2015.00021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329809PMC
March 2015

Intronic miR-3151 within BAALC drives leukemogenesis by deregulating the TP53 pathway.

Sci Signal 2014 Apr 15;7(321):ra36. Epub 2014 Apr 15.

The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA.

The BAALC/miR-3151 locus on chromosome 8q22 contains both the BAALC gene (for brain and acute leukemia, cytoplasmic) and miR-3151, which is located in intron 1 of BAALC. Older acute myeloid leukemia (AML) patients with high expression of both miR-3151 and the BAALC mRNA transcript have a low survival prognosis, and miR-3151 and BAALC expression is associated with poor survival independently of each other. We found that miR-3151 functioned as the oncogenic driver of the BAALC/miR-3151 locus. Increased production of miR-3151 reduced the apoptosis and chemosensitivity of AML cell lines and increased leukemogenesis in mice. Disruption of the TP53-mediated apoptosis pathway occurred in leukemia cells overexpressing miR-3151 and the miR-3151 bound to the 3' untranslated region of TP53. In contrast, BAALC alone had only limited oncogenic activity. We found that miR-3151 contains its own regulatory element, thus partly uncoupling miR-3151 expression from that of the BAALC transcript. Both genes were bound and stimulated by a complex of the transcription factors SP1 and nuclear factor κB (SP1/NF-κB). Disruption of SP1/NF-κB binding reduced both miR-3151 and BAALC expression. However, expression of only BAALC, but not miR-3151, was stimulated by the transcription factor RUNX1, suggesting a mechanism for the partly discordant expression of miR-3151 and BAALC observed in AML patients. Similar to the AML cells, in melanoma cell lines, overexpression of miR-3151 reduced the abundance of TP53, and knockdown of miR-3151 increased caspase activity, whereas miR-3151 overexpression reduced caspase activity. Thus, this oncogenic miR-3151 may also have a role in solid tumors.
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http://dx.doi.org/10.1126/scisignal.2004762DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4165404PMC
April 2014

Role of altered growth factor receptor-mediated JAK2 signaling in growth and maintenance of human acute myeloid leukemia stem cells.

Blood 2014 May 25;123(18):2826-37. Epub 2014 Mar 25.

Division of Hematopoietic Stem Cell and Leukemia Research.

Acute myeloid leukemia (AML) is sustained by small populations of leukemia stem cells (LSCs) that can resist available treatments and represent important barriers to cure. Although previous studies have shown increased signal transducer and activator of transcription (STAT)3 and STAT5 phosphorylation in AML leukemic blasts, the role of Janus kinase (JAK) signaling in primary AML compared with normal stem cells has not been directly evaluated. We show here that JAK/STAT signaling is increased in LSCs, particularly from high-risk AML. JAK2 inhibition using small molecule inhibitors or interference RNA reduced growth of AML LSCs while sparing normal stem cells both in vitro and in vivo. Increased JAK/STAT activity was associated with increased expression and altered signaling through growth factor receptors in AML LSCs, including receptor tyrosine kinase c-KIT and FMS-related tyrosine kinase 3 (FLT3). Inhibition of c-KIT and FLT3 expression significantly inhibited JAK/STAT signaling in AML LSCs, and JAK inhibitors effectively inhibited FLT3-mutated AML LSCs. Our results indicate that JAK/STAT signaling represents an important signaling mechanism supporting AML LSC growth and survival. These studies support continued evaluation of strategies for JAK/STAT inhibition for therapeutic targeting of AML LSCs.
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http://dx.doi.org/10.1182/blood-2013-05-505735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4007609PMC
May 2014

SETting OP449 into the PP2A-activating drug family.

Clin Cancer Res 2014 Apr 14;20(8):2026-8. Epub 2014 Mar 14.

Authors' Affiliations: The Ohio State University Comprehensive Cancer Center, Columbus, Ohio; and Department of Medicine, The Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland.

The protein phosphatase 2A (PP2A) tumor suppressor is inactivated in different leukemias through the activity of its endogenous inhibitors (e.g., SET), which are aberrantly regulated by oncogenic tyrosine kinases. Like other effective and nontoxic PP2A-activating drugs (PAD), OP449 inhibits SET and impairs leukemogenesis. This further supports the immediate use of PADs in patients with leukemia.
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http://dx.doi.org/10.1158/1078-0432.CCR-14-0166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4286336PMC
April 2014

SPARC promotes leukemic cell growth and predicts acute myeloid leukemia outcome.

J Clin Invest 2014 Apr 3;124(4):1512-24. Epub 2014 Mar 3.

Aberrant expression of the secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) gene, which encodes a matricellular protein that participates in normal tissue remodeling, is associated with a variety of diseases including cancer, but the contribution of SPARC to malignant growth remains controversial. We previously reported that SPARC was among the most upregulated genes in cytogenetically normal acute myeloid leukemia (CN-AML) patients with gene-expression profiles predictive of unfavorable outcome, such as mutations in isocitrate dehydrogenase 2 (IDH2-R172) and overexpression of the oncogenes brain and acute leukemia, cytoplasmic (BAALC) and v-ets erythroblastosis virus E26 oncogene homolog (ERG). In contrast, SPARC was downregulated in CN-AML patients harboring mutations in nucleophosmin (NPM1) that are associated with favorable prognosis. Based on these observations, we hypothesized that SPARC expression is clinically relevant in AML. Here, we found that SPARC overexpression is associated with adverse outcome in CN-AML patients and promotes aggressive leukemia growth in murine models of AML. In leukemia cells, SPARC expression was mediated by the SP1/NF-κB transactivation complex. Furthermore, secreted SPARC activated the integrin-linked kinase/AKT (ILK/AKT) pathway, likely via integrin interaction, and subsequent β-catenin signaling, which is involved in leukemia cell self-renewal. Pharmacologic inhibition of the SP1/NF-κB complex resulted in SPARC downregulation and leukemia growth inhibition. Together, our data indicate that evaluation of SPARC expression has prognosticative value and SPARC is a potential therapeutic target for AML.
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http://dx.doi.org/10.1172/JCI70921DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3973087PMC
April 2014

PP2A-activating drugs selectively eradicate TKI-resistant chronic myeloid leukemic stem cells.

J Clin Invest 2013 Oct 3;123(10):4144-57. Epub 2013 Sep 3.

The success of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML) depends on the requirement for BCR-ABL1 kinase activity in CML progenitors. However, CML quiescent HSCs are TKI resistant and represent a BCR-ABL1 kinase-independent disease reservoir. Here we have shown that persistence of leukemic HSCs in BM requires inhibition of the tumor suppressor protein phosphatase 2A (PP2A) and expression--but not activity--of the BCR-ABL1 oncogene. Examination of HSCs from CML patients and healthy individuals revealed that PP2A activity was suppressed in CML compared with normal HSCs. TKI-resistant CML quiescent HSCs showed increased levels of BCR-ABL1, but very low kinase activity. BCR-ABL1 expression, but not kinase function, was required for recruitment of JAK2, activation of a JAK2/β-catenin survival/self-renewal pathway, and inhibition of PP2A. PP2A-activating drugs (PADs) markedly reduced survival and self-renewal of CML quiescent HSCs, but not normal quiescent HSCs, through BCR-ABL1 kinase-independent and PP2A-mediated inhibition of JAK2 and β-catenin. This led to suppression of human leukemic, but not normal, HSC/progenitor survival in BM xenografts and interference with long-term maintenance of BCR-ABL1-positive HSCs in serial transplantation assays. Targeting the JAK2/PP2A/β-catenin network in quiescent HSCs with PADs (e.g., FTY720) has the potential to treat TKI-refractory CML and relieve lifelong patient dependence on TKIs.
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http://dx.doi.org/10.1172/JCI68951DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784537PMC
October 2013

Preclinical and clinical efficacy of XPO1/CRM1 inhibition by the karyopherin inhibitor KPT-330 in Ph+ leukemias.

Blood 2013 Oct 22;122(17):3034-44. Epub 2013 Aug 22.

Human Cancer Genetics Program, Department Molecular Virology Immunology and Medical Genetics.

As tyrosine kinase inhibitors (TKIs) fail to induce long-term response in blast crisis chronic myelogenous leukemia (CML-BC) and Philadelphia chromosome-positive (Ph(+)) acute lymphoblastic leukemia (ALL), novel therapies targeting leukemia-dysregulated pathways are necessary. Exportin-1 (XPO1), also known as chromosome maintenance protein 1, regulates cell growth and differentiation by controlling the nucleocytoplasmic trafficking of proteins and RNAs, some of which are aberrantly modulated in BCR-ABL1(+) leukemias. Using CD34(+) progenitors from CML, B-ALL, and healthy individuals, we found that XPO1 expression was markedly increased, mostly in a TKI-sensitive manner, in CML-BC and Ph(+) B-ALL. Notably, XPO1 was also elevated in Ph(-) B-ALL. Moreover, the clinically relevant XPO1 inhibitor KPT-330 strongly triggered apoptosis and impaired the clonogenic potential of leukemic, but not normal, CD34(+) progenitors, and increased survival of BCR-ABL1(+) mice, 50% of which remained alive and, mostly, became BCR-ABL1 negative. Moreover, KPT-330 compassionate use in a patient with TKI-resistant CML undergoing disease progression significantly reduced white blood cell count, blast cells, splenomegaly, lactate dehydrogenase levels, and bone pain. Mechanistically, KPT-330 altered the subcellular localization of leukemia-regulated factors including RNA-binding heterogeneous nuclear ribonucleoprotein A1 and the oncogene SET, thereby inducing reactivation of protein phosphatase 2A tumor suppressor and inhibition of BCR-ABL1 in CML-BC cells. Because XPO1 is important for leukemic cell survival, KPT-330 may represent an alternative therapy for TKI-refractory Ph(+) leukemias.
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http://dx.doi.org/10.1182/blood-2013-04-495374DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3811176PMC
October 2013

Antagonistic activities of the immunomodulator and PP2A-activating drug FTY720 (Fingolimod, Gilenya) in Jak2-driven hematologic malignancies.

Blood 2013 Sep 7;122(11):1923-34. Epub 2013 Aug 7.

Human Cancer Genetics Program, Department of Molecular Virology Immunology and Medical Genetics.

FTY720 (Fingolimod, Gilenya) is a sphingosine analog used as an immunosuppressant in multiple sclerosis patients. FTY720 is also a potent protein phosphatase 2A (PP2A)-activating drug (PAD). PP2A is a tumor suppressor found inactivated in different types of cancer. We show here that PP2A is inactive in polycythemia vera (PV) and other myeloproliferative neoplasms characterized by the expression of the transforming Jak2(V617F) oncogene. PP2A inactivation occurs in a Jak2(V617F) dose/kinase-dependent manner through the PI-3Kγ-PKC-induced phosphorylation of the PP2A inhibitor SET. Genetic or PAD-mediated PP2A reactivation induces Jak2(V617F) inactivation/downregulation and impairs clonogenic potential of Jak2(V617F) cell lines and PV but not normal CD34(+) progenitors. Likewise, FTY720 decreases leukemic allelic burden, reduces splenomegaly, and significantly increases survival of Jak2(V617F) leukemic mice without adverse effects. Mechanistically, we show that in Jak2(V617F) cells, FTY720 antileukemic activity requires neither FTY720 phosphorylation (FTY720-P) nor SET dimerization or ceramide induction but depends on interaction with SET K209. Moreover, we show that Jak2(V617F) also utilizes an alternative sphingosine kinase-1-mediated pathway to inhibit PP2A and that FTY720-P, acting as a sphingosine-1-phosphate-receptor-1 agonist, elicits signals leading to the Jak2-PI-3Kγ-PKC-SET-mediated PP2A inhibition. Thus, PADs (eg, FTY720) represent suitable therapeutic alternatives for Jak2(V617F) MPNs.
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http://dx.doi.org/10.1182/blood-2013-03-492181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772499PMC
September 2013

miR-29 acts as a decoy in sarcomas to protect the tumor suppressor A20 mRNA from degradation by HuR.

Sci Signal 2013 Jul 30;6(286):ra63. Epub 2013 Jul 30.

Department of Molecular Virology, Immunology, and Medical Genetics, Human Cancer Genetics Program, The Ohio State University, Columbus, OH 43210, USA.

In sarcoma, the activity of NF-κB (nuclear factor κB) reduces the abundance of the microRNA (miRNA) miR-29. The tumor suppressor A20 [also known as TNFAIP3 (tumor necrosis factor-α-induced protein 3)] inhibits an upstream activator of NF-κB and is often mutated in lymphomas. In a panel of human sarcoma cell lines, we found that the activation of NF-κB was increased and, although the abundance of A20 protein and mRNA was decreased, the gene encoding A20 was rarely mutated. The 3' untranslated region (UTR) of A20 mRNA has conserved binding sites for both of the miRNAs miR-29 and miR-125. Whereas the expression of miR-125 was increased in human sarcoma tissue, that of miR-29 was decreased in most samples. Overexpression of miR-125 decreased the abundance of A20 mRNA, whereas reconstituting miR-29 in sarcoma cell lines increased the abundance of A20 mRNA and protein. By interacting directly with the RNA binding protein HuR (human antigen R; also known as ELAVL1), miR-29 prevented HuR from binding to the A20 3'UTR and recruiting the RNA degradation complex RISC (RNA-induced silencing complex), suggesting that miR-29 can act as a decoy for HuR, thus protecting A20 transcripts. Decreased miR-29 and A20 abundance in sarcomas correlated with increased activity of NF-κB and decreased expression of genes associated with differentiation. Together, the findings reveal a unique role of miR-29 and suggest that its absence may contribute to sarcoma tumorigenesis.
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http://dx.doi.org/10.1126/scisignal.2004177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3885907PMC
July 2013

Protein phosphatase 2A: a target for anticancer therapy.

Lancet Oncol 2013 May;14(6):e229-38

Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, and Comprehensive Cancer Center, Ohio State University, Columbus, OH 43210-2207, USA.

Protein phosphatase 2A (PP2A), one of the main serine-threonine phosphatases in mammalian cells, maintains cell homoeostasis by counteracting most of the kinase-driven intracellular signalling pathways. Unrestrained activation of oncogenic kinases together with inhibition of tumour suppressors is often required for development of cancer. PP2A has been shown to be genetically altered or functionally inactivated in many solid cancers and leukaemias, and is therefore a tumour suppressor. For example, the phosphatase activity of PP2A is suppressed in chronic myeloid leukaemia and other malignancies characterised by aberrant activity of oncogenic kinases. Preclinical studies show that pharmacological restoration of PP2A tumour-suppressor activity by PP2A-activating drugs (eg, FTY720) effectively antagonises cancer development and progression. Here, we discuss PP2A as a druggable tumour suppressor in view of the possible introduction of PP2A-activating drugs into anticancer therapeutic protocols.
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http://dx.doi.org/10.1016/S1470-2045(12)70558-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913484PMC
May 2013

Estrogen mediated-activation of miR-191/425 cluster modulates tumorigenicity of breast cancer cells depending on estrogen receptor status.

PLoS Genet 2013 7;9(3):e1003311. Epub 2013 Mar 7.

Department of Molecular Virology, Immunology, and Medical Genetics, School of Medicine, The Ohio State University, Columbus, Ohio, United States of America.

MicroRNAs (miRNAs), single-stranded non-coding RNAs, influence myriad biological processes that can contribute to cancer. Although tumor-suppressive and oncogenic functions have been characterized for some miRNAs, the majority of microRNAs have not been investigated for their ability to promote and modulate tumorigenesis. Here, we established that the miR-191/425 cluster is transcriptionally dependent on the host gene, DALRD3, and that the hormone 17β-estradiol (estrogen or E2) controls expression of both miR-191/425 and DALRD3. MiR-191/425 locus characterization revealed that the recruitment of estrogen receptor α (ERα) to the regulatory region of the miR-191/425-DALRD3 unit resulted in the accumulation of miR-191 and miR-425 and subsequent decrease in DALRD3 expression levels. We demonstrated that miR-191 protects ERα positive breast cancer cells from hormone starvation-induced apoptosis through the suppression of tumor-suppressor EGR1. Furthermore, enforced expression of the miR-191/425 cluster in aggressive breast cancer cells altered global gene expression profiles and enabled us to identify important tumor promoting genes, including SATB1, CCND2, and FSCN1, as targets of miR-191 and miR-425. Finally, in vitro and in vivo experiments demonstrated that miR-191 and miR-425 reduced proliferation, impaired tumorigenesis and metastasis, and increased expression of epithelial markers in aggressive breast cancer cells. Our data provide compelling evidence for the transcriptional regulation of the miR-191/425 cluster and for its context-specific biological determinants in breast cancers. Importantly, we demonstrated that the miR-191/425 cluster, by reducing the expression of an extensive network of genes, has a fundamental impact on cancer initiation and progression of breast cancer cells.
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http://dx.doi.org/10.1371/journal.pgen.1003311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591271PMC
June 2013

Silvestrol exhibits significant in vivo and in vitro antileukemic activities and inhibits FLT3 and miR-155 expressions in acute myeloid leukemia.

J Hematol Oncol 2013 Mar 16;6:21. Epub 2013 Mar 16.

Division of Hematology, Department of Medicine, The Ohio State University, Columbus, OH, USA.

Background: Activating mutations [internal tandem duplication (ITD)] or overexpression of the FMS-like tyrosine kinase receptor-3 (FLT3) gene are associated with poor outcome in acute myeloid leukemia (AML) patients, underscoring the need for novel therapeutic approaches. The natural product silvestrol has potent antitumor activity in several malignancies, but its therapeutic impact on distinct molecular high-risk AML subsets remains to be fully investigated. We examined here the preclinical activity of silvestrol in FLT3-ITD and FLT3 wild-type (wt) AML.

Methods: Silvestrol in vitro anti-leukemic activity was examined by colorimetric cell viability assay, colony-forming and flow cytometry assays assessing growth inhibition and apoptosis, respectively. Pharmacological activity of silvestrol on FLT3 mRNA translation, mRNA and protein expression was determined by RNA-immunoprecipitation, qRT-PCR and immunoblot analyses, respectively. Silvestrol in vivo efficacy was investigated using MV4-11 leukemia-engrafted mice.

Results: Silvestrol shows antileukemia activity at nanomolar concentrations both in FLT3-wt overexpressing (THP-1) and FLT3-ITD (MV4-11) expressing AML cell lines (IC50 = 3.8 and 2.7 nM, respectively) and patients' primary blasts [IC50 = ~12 nM (FLT3-wt) and ~5 nM (FLT3-ITD)]. Silvestrol increased apoptosis (~4fold, P = 0.0001), and inhibited colony-formation (100%, P < 0.0001) in primary blasts. Silvestrol efficiently inhibited FLT3 translation reducing FLT3 protein expression by 80-90% and decreased miR-155 levels (~60%), a frequently co-regulated onco-miR in FLT3-ITD-positive AML. The median survival of silvestrol-treated vs vehicle-treated mice was 63 vs 29 days post-engraftment, respectively (P < 0.0001).

Conclusions: Silvestrol exhibits significant in vivo and in vitro antileukemic activities in AML through a novel mechanism resulting in inhibition of FLT3 and miR-155 expression. These encouraging results warrant a rapid translation of silvestrol for clinical testing in AML.
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http://dx.doi.org/10.1186/1756-8722-6-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3623627PMC
March 2013

Targeted delivery of microRNA-29b by transferrin-conjugated anionic lipopolyplex nanoparticles: a novel therapeutic strategy in acute myeloid leukemia.

Clin Cancer Res 2013 May 14;19(9):2355-67. Epub 2013 Mar 14.

Molecular, Cellular and Developmental Biology, The Ohio State University, Columbus, Ohio 43210, USA.

Purpose: miR-29b directly or indirectly targets genes involved in acute myeloid leukemia (AML), namely, DNMTs, CDK6, SP1, KIT, and FLT3. Higher miR-29b pretreatment expression is associated with improved response to decitabine and better outcome in AML. Thus, designing a strategy to increase miR-29b levels in AML blasts may be of therapeutic value. However, free synthetic miRs are easily degraded in bio-fluids and have limited cellular uptake. To overcome these limitations, we developed a novel transferrin-conjugated nanoparticle delivery system for synthetic miR-29b (Tf-NP-miR-29b).

Experimental Design: Delivery efficiency was investigated by flow cytometry, confocal microscopy, and quantitative PCR. The expression of miR-29b targets was measured by immunoblotting. The antileukemic activity of Tf-NP-miR-29b was evaluated by measuring cell proliferation and colony formation ability and in a leukemia mouse model.

Results: Tf-NP-miR-29b treatment resulted in more than 200-fold increase of mature miR-29b compared with free miR-29b and was approximately twice as efficient as treatment with non-transferrin-conjugated NP-miR-29b. Tf-NP-miR-29b treatment significantly downregulated DNMTs, CDK6, SP1, KIT, and FLT3 and decreased AML cell growth by 30% to 50% and impaired colony formation by approximately 50%. Mice engrafted with AML cells and then treated with Tf-NP-miR-29b had significantly longer survival compared with Tf-NP-scramble (P = 0.015) or free miR-29b (P = 0.003). Furthermore, priming AML cell with Tf-NP-miR-29b before treatment with decitabine resulted in marked decrease in cell viability in vitro and showed improved antileukemic activity compared with decitabine alone (P = 0.001) in vivo.

Conclusions: Tf-NP effectively delivered functional miR-29b, resulting in target downregulation and antileukemic activity and warrants further investigation as a novel therapeutic approach in AML.
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http://dx.doi.org/10.1158/1078-0432.CCR-12-3191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3644023PMC
May 2013