David M Harris

University of Texas MD Anderson Cancer Center, Houston, Texas, United States

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Publications (7)43.89 Total impact

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    ABSTRACT: In chronic lymphocytic leukemia (CLL) stimulation of the B cell receptor (BCR) triggers survival signals. Because in various cells activation of the Janus kinase (JAK)/ signal transducer and activator of transcription (STAT) pathway provides cells with survival advantage, we wondered whether BCR stimulation activates the JAK/STAT pathway in CLL cells. To stimulate the BCR we incubated CLL cells with anti-IgM antibodies. Anti-IgM antibodies induced transient tyrosine phosphorylation and nuclear localization of phosphorylated (p) STAT3. Immunoprecipitation studies revealed that anti-JAK2 antibodies co-immunoprecipitated pSTAT3 and pJAK2 in IgM-stimulated but not unstimulated CLL cells, suggesting that activation of the BCR induces activation of JAK2, which phosphorylates STAT3. Incubation of CLL cells with the JAK-1/2 inhibitor ruxolitinib inhibited IgM-induced STAT3 phosphorylation and induced apoptosis of IgM-stimulated but not unstimulated CLL cells in a dose- and time-dependent manner. Whether ruxolitinib treatment would benefit patients with CLL remains to be determined.
    Blood 04/2014; · 9.78 Impact Factor
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    ABSTRACT: Backgrounds: Approximately 1,000 microRNAs (miRs) are present in the human genome; however, little is known about the regulation of miR transcription. Because miR levels are deregulated in chronic lymphocytic leukemia (CLL) and signal transducer and activator of transcription (STAT)-3 is constitutively activated in CLL, we sought to determine whether STAT3 affects the transcription of miR genes in CLL cells. METHODS: We used publically available data from the ENCODE project to identify putative STAT3 binding sites in the promoters of miR genes. Then we transfected CLL cells with STAT3-shRNA or with an empty vector, and to determine which miRs are differentially expressed, we used a miR microarray approach followed by validation of the microarray results for 6 miRs using quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: We identified putative STAT3 binding sites in 160 promoter regions of 200 miRs, including miR-21, miR-29, and miR-155, whose levels have been reported to be upregulated in CLL. Levels of 72 miRs were downregulated (n = 63) or upregulated (n = 9). qRT-PCR confirmed the array data in 5 of 6 miRs. CONCLUSIONS: The presence of activated STAT3 has a profound effect on miR expression in CLL cells.
    Molecular Cancer 06/2013; 12(1):50. · 5.13 Impact Factor
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    ABSTRACT: The prognosis of patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) is poor. Chemotherapy is rarely curative and tyrosine kinase inhibitors (TKIs) induce only transient responses. Heat shock protein 90 (Hsp90) is a chaperone protein that is important in signal transduction, cell cycle control, and transcription regulation in both normal and leukemia cells. In the current study, we tested the growth inhibitory and apoptotic effects of a novel Hsp90 inhibitor, EC141 on the Ph+ ALL lines Z-119, Z-181, and Z-33, as well as primary bone marrow-derived blasts from patients with newly diagnosed Ph+ ALL. We found that EC141 inhibited the growth of Ph+ ALL cells in a concentration-dependent manner with IC(50) ranged from 1 to 10 nM. EC141 also inhibited the proliferation of primary bone marrow-derived blasts using the ALL blast colony assay. EC141 down-regulated Hsp90 and up-regulated Hsp70 protein levels, inhibited CrkL phosphorylation, and induced degradation of Bcr-Abl p190 protein through ubiquitin-dependent proteasomal pathway. Furthermore, exposure of Ph+ ALL cells to EC141 resulted in activation of caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), and induction of apoptosis. In conclusion, our data suggest that EC141 is a potent Hsp90 inhibitor with activity against Ph+ ALL. Further studies to investigate the anticancer effect of EC141 either as a single agent, or in combination in Ph+ ALL and other hematological malignancies are warranted.
    Investigational New Drugs 12/2011; 29(6):1206-12. · 3.50 Impact Factor
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    ABSTRACT: NF-κB plays a major role in the pathogenesis of B-cell neoplasms. A broad array of mostly extracellular stimuli has been reported to activate NF-κB, to various degrees, in chronic lymphocytic leukemia (CLL) cells. Because CLL cells harbor high levels of unphosphorylated STAT-3 (USTAT-3) and USTAT-3 was reported to activate NF-κB, we sought to determine whether USTAT-3 activates NF-κB in CLL. Using the electrophoretic mobility shift assay (EMSA), we studied peripheral blood low-density cells from 15 patients with CLL and found that CLL cell nuclear extracts from all the samples bound to an NF-κB DNA probe, suggesting that NF-κB is constitutively activated in CLL. Immunoprecipitation studies showed that STAT-3 bound NF-κB p65, and confocal microscopy studies detected USTAT-3/NF-κB complexes in the nuclei of CLL cells, thereby confirming these findings. Furthermore, infection of CLL cells with retroviral STAT-3-short hairpin RNA attenuated the binding of NF-κB to DNA, as assessed by EMSA, and downregulated mRNA levels of NF-κB-regulated genes, as assessed by quantitative PCR. Taken together, our data suggest that USTAT-3 binds to the NF-κB p50/p65 dimers and that the USTAT-3/NF-κB complexes bind to DNA and activate NF-κB-regulated genes in CLL cells.
    Molecular Cancer Research 03/2011; 9(4):507-15. · 4.35 Impact Factor
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    ABSTRACT: Patients with prolonged myelosuppression require frequent platelet and occasional granulocyte transfusions. Multi-donor transfusions induce alloimmunization, thereby increasing morbidity and mortality. Therefore, an autologous or HLA-matched allogeneic source of platelets and granulocytes is needed. To determine whether nonhematopoietic cells can be reprogrammed into hematopoietic cells, human mesenchymal stromal cells (MSCs) and skin fibroblasts were incubated with the demethylating agent 5-azacytidine (Aza) and the growth factors (GF) granulocyte-macrophage colony-stimulating factor and stem cell factor. This treatment transformed MSCs to round, non-adherent cells expressing T-, B-, myeloid-, or stem/progenitor-cell markers. The transformed cells engrafted as hematopoietic cells in bone marrow of immunodeficient mice. DNA methylation and mRNA array analysis suggested that Aza and GF treatment demethylated and activated HOXB genes. Indeed, transfection of MSCs or skin fibroblasts with HOXB4, HOXB5, and HOXB2 genes transformed them into hematopoietic cells. Further studies are needed to determine whether transformed MSCs or skin fibroblasts are suitable for therapy.
    PLoS ONE 01/2011; 6(6):e21250. · 3.53 Impact Factor
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    ABSTRACT: Endothelial progenitor cells (EPCs) have been identified among hematopoietic tissue-derived progenitor cells that are mobilized into the peripheral blood (PB) as a result of tissue injury. It therefore seems likely that circulating EPCs have therapeutic potential by aiding in the neovascularization of ischemic tissue. This study provides clinical data on the availability of circulating EPCs at steady state and after recombinant human granulocyte-colony-stimulating factor (rHuG-CSF) mobilization and their collection by leukapheresis. Eight healthy donors underwent rHuG-CSF treatment over 4 days, followed by leukapheresis. Blood samples taken before rHuG-CSF treatment and before apheresis as well as apheresis-collected samples were analyzed by flow cytometry and by real time reverse transcription-polymerase chain reaction for cells expressing EPC-specific surface markers and tissue markers, respectively, and for EPC colony-forming cells. The median PB concentration of CD34+133+ vascular endothelial growth factor receptor-2 (VEGFR-2)-+ EPCs increased 8-fold from steady state to mobilized, and the concentration of CD34+133-VEGFR-2+ EPCs increased by 10-fold. This mobilization pattern was similar to that of hematopoietic CD34+, CD133+, and CD34+117+ progenitor cells. The increase in the median circulating colony-forming unit EPC concentration was 10-fold over baseline. The median absolute number of CD34+133+VEGFR-2+ cells collected by large-volume leukapheresis was 0.8 x 10(6) per kg of body weight. In addition, a small subset of immature CD133+34- cells coexpressing VEGFR-2 was identified in mobilized PB and in the apheresis collection. EPC-specific cells contained in the apheresis product were also identified as expressing mRNA for the CD31 antigen, Tie-2, and VEGFR-2. Circulating EPCs represent a novel blood cell component that can be collected by apheresis in large quantities and can be used clinically, either unmanipulated or EPC-selected, for therapeutic vasculogenesis.
    Transfusion 11/2006; 46(10):1795-802. · 3.53 Impact Factor
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    ABSTRACT: The naturally occurring compound 3beta,16beta,17alpha-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-beta-D-xylopyranosyl)-(1-->3)-(2-O-acetyl-alpha-L-arabinopyranoside) (OSW-1) is found in the bulbs of Ornithogalum saudersiae and is highly cytotoxic against tumor cell lines. Using various human cancer and nonmalignant cell lines, we investigated the anticancer activity and selectivity of OSW-1 and its underlying mechanisms of action. OSW-1 exhibited extremely potent cytotoxic activity against cancer cells in vitro. Nonmalignant cells were statistically significantly less sensitive to OSW-1 than cancer cells, with concentrations that cause a 50% loss of cell viability 40-150-fold greater than those observed in malignant cells. Electron microscopy and biochemical analyses revealed that OSW-1 damaged the mitochondrial membrane and cristae in both human leukemia and pancreatic cancer cells, leading to the loss of transmembrane potential, increase of cytosolic calcium, and activation of calcium-dependent apoptosis. Clones of leukemia cells with mitochondrial DNA defects and respiration deficiency that had adapted the ability to survive in culture without mitochondrial respiration also were resistant to OSW-1. In vitro analysis revealed that OSW-1 effectively killed primary leukemia cells from chronic lymphocytic leukemia patients with disease refractory to fludarabine. The promising anticancer activity of OSW-1 and its unique mechanism of action make this compound worthy of further investigation for its potential to overcome drug resistance.
    CancerSpectrum Knowledge Environment 12/2005; 97(23):1781-5. · 14.07 Impact Factor