Biomedical subjects

W Stratford May

Publications and source records attributed to W Stratford May.

At least 19 recordsLinked to original sources

PubMed2006

JAZ mediates G1 cell-cycle arrest and apoptosis by positively regulating p53 transcriptional activity.

We previously identified JAZ as a novel zinc finger (ZF) protein by screening a murine interleukin-3 (IL-3)-dependent NFS/N1.H7 myeloid cell cDNA library. JAZ is a member of a new class of ZFPs that is evolutionarily conserved and preferentially binds to dsRNA, but its function was unknown. Now, we report that the stress of IL-3 growth factor withdrawal up-regulates JAZ expression in hematopoietic cells in association with p53 activation and induction of cell death. Biochemical analysis reveals that JAZ associates with p53 to stimulate its transcriptional activity in p53-expressing cells, but not in p53-null cells unless complemented with p53. JAZ functions to mediate G1 cell-cycle arrest followed by apoptosis in a p53-dependent mechanism that is associated with up-regulation of p21 and BAX, dephosphorylation of Rb, and repression of cyclin A. Of importance, siRNA "knockdown" of endogenous JAZ inhibits p53 transcriptional activity, decreases the G1/G0 population, and attenuates stress-induced cell death. While JAZ directly binds p53 in vitro in a mechanism requiring p53's C-terminal regulatory domain but independent of dsRNA, the dsRNA-binding ZF domains are required for JAZ's stimulatory role of p53 in vivo by dictating its nuclear localization. Thus, JAZ is a novel negative regulator of cell growth by positively regulating p53.

Active Transport, Cell Nucleus↗

PubMed2006

RAX, the PKR activator, sensitizes cells to inflammatory cytokines, serum withdrawal, chemotherapy, and viral infection.

While the interferon (IFN)-inducible double-stranded RNA (dsRNA)-dependent protein kinase PKR is reported to initiate apoptosis in some instances, the mechanism by which diverse stress stimuli activate PKR remains unknown. Now we report that RAX, the only known cellular activator for PKR, initiates PKR activation in response to a broad range of stresses including serum deprivation, cytotoxic cytokine or chemotherapy treatment, or viral infection. Thus, knock-down of RAX expression by 80% using small interfering RNA (siRNA) prevents IFNgamma/tumor necrosis factor alpha (TNFalpha)-induced PKR activation and eIF2alpha phosphorylation, IkappaB degradation, IRF-1 expression, and STAT1 phosphorylation, resulting in enhanced murine embryonic fibroblast (MEF) cell survival. In contrast, expression of exogenous RAX, but not of the nonphosphorylatable, dominant-negative RAX(S18A) mutant, sensitizes cells to IFNgamma/TNFalpha, mitomycin C (MMC), or serum deprivation in association with increased PKR activity and apoptosis. Furthermore, RAX(S18A) expression in Fanconi anemia complementation group C-null MEF cells not only prevents PKR activation but also blocks hypersensitivity to IFNgamma/TNFalpha or mitomycin C that results in enhanced apoptosis. In addition, reduced RAX expression facilitates productive viral infection with vesicular stomatitis virus (VSV) and promotes anchorage-independent colony growth of MEF cells. Collectively, these data indicate that RAX may function as a negative regulator of growth that is required to activate PKR in response to a broad range of apoptosis-inducing stress.

Animals↗

PubMed2006

Bcl2 suppresses DNA repair by enhancing c-Myc transcriptional activity.

Bcl2 and c-Myc are two major oncogenic proteins that can functionally promote DNA damage, genetic instability, and tumorigenesis. However, the mechanism(s) remains unclear. Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most potent carcinogen contained in cigarette smoke that induces cellular DNA damage. Here we found that Bcl2 potently suppresses the repair of NNK-induced abasic sites of DNA lesions in association with increased c-Myc transcriptional activity. The Bcl2 BH4 domain (amino acids 6-31) was found to bind directly to c-Myc MBII domain (amino acids 106-143), and this interaction is required for Bcl2 to enhance c-Myc transcriptional activity and inhibit DNA repair. In addition to mitochondria, Bcl2 is also expressed in the nucleus, where it co-localizes with c-Myc. Expression of nuclear-targeted Bcl2 enhances c-Myc transcriptional activity with suppression of DNA repair but fails to prolong cell survival. Depletion of c-Myc expression from cells overexpressing Bcl2 significantly accelerates the repair of NNK-induced DNA damage, indicating that c-Myc may be essential for the Bcl2 effect on DNA repair. It is known that apurinic/apyrimidinic endonuclease (APE1) plays a crucial role in the repair of abasic sites of DNA lesions. That overexpression of Bcl2 results in up-regulation of c-Myc and down-regulation of APE1 suggests APE1 may function as the downstream target of Bcl2/c-Myc in the DNA repair machinery. Thus, Bcl2, in addition to its survival function, may also suppress DNA repair in a novel mechanism involving c-Myc and APE1, which may lead to an accumulation of DNA damage in living cells, genetic instability, and tumorigenesis.

Carcinogens↗

PubMed2006

Mechanisms of apoptosis sensitivity and resistance to the BH3 mimetic ABT-737 in acute myeloid leukemia.

BCL-2 proteins are critical for cell survival and are overexpressed in many tumors. ABT-737 is a small-molecule BH3 mimetic that exhibits single-agent activity against lymphoma and small-cell lung cancer in preclinical studies. We here report that ABT-737 effectively kills acute myeloid leukemia blast, progenitor, and stem cells without affecting normal hematopoietic cells. ABT-737 induced the disruption of the BCL-2/BAX complex and BAK-dependent but BIM-independent activation of the intrinsic apoptotic pathway. In cells with phosphorylated BCL-2 or increased MCL-1, ABT-737 was inactive. Inhibition of BCL-2 phosphorylation and reduction of MCL-1 expression restored sensitivity to ABT-737. These data suggest that ABT-737 could be a highly effective antileukemia agent when the mechanisms of resistance identified here are considered.

Animals↗

PubMed2006

Bcl2's flexible loop domain regulates p53 binding and survival.

p53 not only functions as a transcription factor but also has a direct, apoptogenic role at the mitochondria. We have discovered that DNA damage-induced p53-Bcl2 binding is associated with decreased Bcl2-Bax interaction and increased apoptotic cell death in a mechanism regulated by Bcl2's flexible loop regulatory domain (FLD), since purified p53 protein can disrupt the Bcl2/Bax complex by directly binding to a negative regulatory region of the FLD (amino acids [aa] 32 to 68). Deletion of the negative regulatory region (Delta32-68) abolishes Bcl2-p53 binding and enhances Bcl2's antiapoptotic function. Conversely, removal of a positive regulatory region (aa 69 to 87) of the FLD, which contains the Bcl2 phosphorylation site(s) T69, S70, and S87, enhances Bcl2-p53 binding and significantly abrogates Bcl2's survival activity. The phospho-mimetic T69E/S70E/S87E (EEE) but not the nonphosphorylatable T69A/S70A/S87A (AAA) Bcl2 mutant displays a reduced capacity to bind p53 and potently inhibits p53-induced cytochrome c release from isolated mitochondria. Furthermore, the FLD-only aa32-87 and aa32-68 peptides but not the aa69-87 peptide can directly bind p53 in vitro. p53-induced cytochrome c release occurs through a mechanism involving Bax's integral insertion into the outer mitochondrial membrane. Either DNA damage to cells or expression of p53 selectively targeted to the mitochondria results in Bcl2-p53 binding followed by exposure of Bcl2's BH3 domain in association with inactivation of Bcl2's antiapoptotic function, indicating a conformational change in Bcl2 can occur upon direct ligation of p53. Thus, Bcl2's FLD contains both positive and negative regulatory regions which functionally regulate Bcl2's antiapoptotic activity by affecting Bax or p53 binding.

Animals↗

PubMed2004

Serine 18 phosphorylation of RAX, the PKR activator, is required for PKR activation and consequent translation inhibition.

It is now apparent that the double-stranded (ds)RNA-dependent protein kinase, PKR, is a regulator of diverse cellular responses to stress. Recently, the murine dsRNA-binding protein RAX and its human ortholog PACT were identified as cellular activators of PKR. Previous reports demonstrate that following stress, RAX/PACT associates with and activates PKR resulting in eIF2alpha phosphorylation, consequent translation inhibition, and cell death via apoptosis. Although RAX/PACT is phosphorylated during stress, any regulatory role for this post-translational modification has been uncertain. Now we have discovered that RAX is phosphorylated on serine 18 in both human and mouse cells. The non-phosphorylatable form of RAX, RAX(S18A), although still able to bind dsRNA and associate with PKR, fails to activate PKR following stress. Furthermore, stable expression of RAX(S18A) results in a dominant-negative effect characterized by deficiency of eukaryotic initiation factor 2 alpha subunit phosphorylation, delay of translation inhibition, and failure to undergo rapid apoptosis following removal of interleukin-3. We propose that the ability of RAX to activate PKR is regulated by a sequential mechanism featuring RAX association with PKR, RAX phosphorylation at serine 18, and activation of PKR.

Amino Acid Sequence↗

PubMed2003

Mono- and multisite phosphorylation enhances Bcl2's antiapoptotic function and inhibition of cell cycle entry functions.

Bcl2 functions to suppress apoptosis and retard cell cycle entry. Single-site phosphorylation at serine 70 (S70) is required for Bcl2's antiapoptotic function, and multisite phosphorylation at threonine 69 (T69), S70, and S87 has been reported to inactivate Bcl2. To address this apparent conflict and identify the regulatory role for Bcl2 phosphorylation in cell death and cell cycle control, a series of serine/threonine (S/T) --> glutamate/alanine (E/A) mutants including T69E/A, S70E/A, S87E/A, T69E/S70A/S87A (EAA), T69A/S70E/S87A (AEA), T69A/S70A/S87E (AAE), T69E/S70E/S87E (EEE), and T69A/S70A/S87A (AAA) was created to mimic or abrogate, respectively, either single-site or multisite phosphorylation. The survival and cell cycle status of cells expressing the phosphomimetic or nonphosphorylatable Bcl2 mutants were compared. Surprisingly, all of the E but not the A Bcl2 mutants potently enhance cell survival after stress and retard G(1)/S cell cycle transition. The EEE Bcl2 mutant is the most potent, indicating a possible cumulative advantage for multisite phosphorylation of Bcl2 in survival and retardation of G(1)/S transition functions. Because the E-containing Bcl2 mutants, but not the A-containing mutants, can more potently block cytochrome c release from mitochondria during apoptotic stress, even at times when steady-state expression levels are similar for all mutants, we conclude that phosphorylation at one or multiple sites within the flexible loop domain of Bcl2 not only stimulates antiapoptotic activity but also can regulate cell cycle entry.

Amino Acid Substitution↗

PubMed2003

A novel role for RAX, the cellular activator of PKR, in synergistically stimulating SV40 large T antigen-dependent gene expression.

The double-stranded (ds) RNA-binding protein RAX was discovered as a stress-induced cellular activator of the dsRNA-dependent protein kinase (PKR), a key regulator of protein synthesis in response to viral infection and cellular stress. We now report a novel function of RAX, independent of PKR, to enhance SV40 promoter (origin)/enhancer-dependent gene expression. Several mammalian cell lines including COS-7, CV-1, and HeLa cells were tested. Results reveal that the SV40 large T antigen is required for RAX-mediated, synergistic enhancement of gene expression. RAX augments SV40 regulatory element-dependent DNA replication and transcription. The mechanism requires the SV40 enhancer, a viral transcriptional element that is necessary for efficient SV40 DNA replication in vivo. Mutational analysis reveals that the dsRNA-binding domains of RAX are required for the gene expression enhancing function. Thus, in addition to stimulating PKR activity, RAX can positively regulate both SV40 large T antigen-dependent DNA replication and transcription in a mechanism that may alter the interaction of the cellular factor(s) with the SV40 enhancer via the dsRNA-binding domains of RAX. This novel function of RAX may have implications for regulation of mammalian DNA replication and transcription because of the many similarities between the viral and cellular processes.

Animals↗

PubMed2003

Bcl2 retards G1/S cell cycle transition by regulating intracellular ROS.

Bcl2's antiapoptotic function is regulated by phosphorylation. Bcl2 also regulates cell cycle progression, but the molecular mechanism is unclear. Bcl2 is functionally expressed in mitochondria where it can act as an antioxidant that may regulate intracellular reactive oxygen species (ROS). Since ROS have been reported to act as second messengers in cell signaling, we tested whether Bcl2 phosphorylation regulates ROS and cell cycle progression. G1 --> S transition and ROS levels were measured in cells expressing either the gain of function phosphomimetic Bcl2 mutants S70E and T69E/S70E/S87E (EEE) or the nonphosphorylatable and survival-deficient mutants S70A and T69A/S70A/S87A (AAA). Expression of S70E and EEE but not the A-containing Bcl2 mutants retards G1 --> S transition by 35% to 50% and significantly slows cell growth in association with reduced levels of intracellular ROS. In addition to expression of the phosphomimetic Bcl2 mutants, either interleukin-3 withdrawal or treatment of cells with the antioxidant pyrrolidine dithiocarbamate (PDTC) also reduces intracellular ROS levels in association with up-regulation of p27 and accumulation of cells in G0/G1. Retardation of G1 --> S transition can be overridden by directly adding H2O2 to the cells in a mechanism that involves down-regulation of p27 and activation of Cdk2. Thus, Bcl2 may regulate G1 --> S transition by a novel signaling mechanism that couples regulation of intracellular ROS with p27 and Cdk2. Furthermore, phosphorylation of Bcl2 may functionally link its antiapoptotic, cell cycle retardation, and antioxidant properties.

Animals↗

PubMed2003

Cleavage of Bax to p18 Bax accelerates stress-induced apoptosis, and a cathepsin-like protease may rapidly degrade p18 Bax.

Bax is cleaved by calpain at aspartate 33 (Asp33) to yield p18 Bax during stress-induced apoptosis. To assess the role of p18 Bax in apoptosis, an ecdysone-inducible expression system was generated. Similar levels of wild-type (WT) and noncleavable Asp33Ala (Asp-->Ala) Bax are induced in 293 cells while expression of N-terminal-deleted p18 (Delta1-33) Bax remains low (20% of full-length p21 Bax) due to a reduced half-life (2 hours versus 12 hours for p21 Bax) resulting from increased sensitivity to cathepsin-like proteolytic degradation. Expression of p18 Bax is enhanced to levels comparable to p21 Bax when induction is carried out in the presence of cathepsin inhibitors, Z-Phe-Gly-NHO-Bz or N-Acetyl-Leu-Leu-Met-CHO. Compared with WT Bax, expression of similar levels of p18 Bax and, surprisingly, Asp33Ala Bax more potently induces apoptosis as indicated by increased cytochrome c release, caspase-9/-3 activation, and DNA fragmentation, potentially due to their increased homo-oligomerization in mitochondrial membranes. Studies in A-549, U-937, K-562, and HL-60 cells confirm that inhibition of Bax cleavage results in 25% to 35% reduction of drug-induced apoptosis, while inhibition of p18 Bax degradation enhances apoptosis by 25% to 40%. Results indicate that although cleavage to p18 Bax is not required for Bax to initiate apoptosis, p18 Bax potently accelerates the apoptotic process.

Animals↗

PubMed2003

Kos1, a nonreceptor tyrosine kinase that suppresses Ras signaling.

Kinase of embryonic stem cells (Kos1), a nonreceptor protein tyrosine kinase (NRPTK), was identified and cloned from differentiating murine embryonic stem cells. Kos1 is localized on mouse chromosome 11 that corresponds to human chromosome 17p13.1 and is homologous to Tnk1, Ack1 and Ack2, making it a new member of the Ack family of NRPTKs. Kos1 is a ubiquitously expressed 47-kDa protein with autotyrosine kinase activity that is developmentally regulated during embryogenesis. Kos1 is also upregulated following IL3 withdrawal from factor-dependent murine NSF/N1.H7 cells that undergo apoptosis, suggesting a role in growth inhibition. Stable overexpression of Kos1 inhibits growth of NIH 3T3 cells, while the kinase-dead Kos1(CN) promotes cell growth in both liquid culture and soft agar. In addition, forced expression of Kos1 inhibits Ras activity in an indirect mechanism that results in the downregulation of the Ras-Raf1-MAPK growth pathway. Furthermore, overexpression of Kos1 in NCI-H82 lung cancer cells that express oncogenic Ha-Ras(G12V) inhibits cell growth under reduced serum (0.5%) conditions in close association with the upregulation of the Ras inhibitor, Rap1A. Collectively, these data support a negative regulatory role for Kos1 in regulating the Ras-Raf1-MAPK growth pathway by a mechanism that requires its autotyrosine kinase activity.

Amino Acid Sequence↗

PubMed2003

Decreased functional caspase-3 expression in umbilical cord blood neutrophils is linked to delayed apoptosis.

Resolution of inflammatory processes depends on the efficient removal of aging neutrophils by the reticuloendothelial system. Neutrophil apoptosis is key to this process, and its impairment may contribute to the pathogenesis of chronic inflammation. We recently discovered that Fas-mediated apoptosis in umbilical cord blood neutrophils was significantly delayed as compared with those of adults. Because execution of apoptosis relies on caspases, we used reverse transcription PCR, immunoblots, and enzymatic assays to study the integrity of several members of those proteases known to mediate Fas-induced apoptosis in neutrophils. Our results indicate that diminished expression of caspase-3 mRNA and the precursor form of the protein, as well as a lower functional enzymatic activity of caspase-3, correlates with delayed apoptosis in umbilical cord blood neutrophils. Our data suggest that functional expression of caspase-3 in neutrophils may be regulated during ontogeny.

Adult↗

PubMed2003

Protein kinase C-dependent phosphorylation and mitochondrial translocation of aldose reductase.

Although aldose reductase (AR) is a critical participant in osmoregulation, and the metabolism of glucose and aldehydes derived from lipid peroxidation, post-translational mechanisms regulating its activity have not been identified. In this paper, we report that stimulation of protein kinase C (PKC) in several cell types induces phosphorylation of AR and translocation of the phosphorylated protein to the mitochondria. In vitro, recombinant AR was directly phosphorylated by activated PKC, suggesting that AR may be an in vivo PKC substrate. Together, these observations reveal a novel link between PKC activation and the regulation of glucose and aldehyde metabolism.

Aldehyde Reductase↗

PubMed2003

Phosphorylation by aurora B converts MgcRacGAP to a RhoGAP during cytokinesis.

Cell division is finely controlled by various molecules including small G proteins and kinases/phosphatases. Among these, Aurora B, RhoA, and the GAP MgcRacGAP have been implicated in cytokinesis, but their underlying mechanisms of action have remained unclear. Here, we show that MgcRacGAP colocalizes with Aurora B and RhoA, but not Rac1/Cdc42, at the midbody. We also report that Aurora B phosphorylates MgcRacGAP on serine residues and that this modification induces latent GAP activity toward RhoA in vitro. Expression of a kinase-defective mutant of Aurora B disrupts cytokinesis and inhibits phosphorylation of MgcRacGAP at Ser387, but not its localization to the midbody. Overexpression of a phosphorylation-deficient MgcRacGAP-S387A mutant, but not phosphorylation-mimic MgcRacGAP-S387D mutant, arrests cytokinesis at a late stage and induces polyploidy. Together, these findings indicate that during cytokinesis, MgcRacGAP, previously known as a GAP for Rac/Cdc42, is functionally converted to a RhoGAP through phosphorylation by Aurora B.

Aurora Kinase B↗

PubMed2002

A functional role for nicotine in Bcl2 phosphorylation and suppression of apoptosis.

Nicotine is not only a major component in tobacco but is also a survival agonist that inhibits apoptosis induced by diverse stimuli including chemotherapeutic drugs. However, the intracellular mechanism(s) involved in nicotine suppression of apoptosis is unclear. Bcl2 is a potent antiapoptotic protein and tumor promotor that is expressed in both small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cells. It is possible that nicotine may regulate Bcl2 to stimulate cell survival. Here we report that nicotine can induce Bcl2 phosphorylation exclusively at the serine 70 site in association with prolonged survival of SCLC H82 cells expressing wild-type but not the phosphorylation-deficient S70A mutant Bcl2 after treatment with chemotherapeutic agents (i.e. cisplatin or VP-16). Nicotine induces activation of PKC alpha and the MAPKs ERK1 and ERK2, which are physiological Bcl2 kinases. Furthermore, ET-18-OCH3, a specific phospholipase C (PLC) inhibitor, blocks nicotine-stimulated Bcl2 phosphorylation and promotes apoptosis, suggesting that PLC may be involved in nicotine activation of Bcl2 kinases. Using a genetic approach, the gain-of-function S70E mutant, which mimics Ser(70) site phosphorylation in the flexible loop domain, potently enhances chemoresistance in SCLC cells. Thus, nicotine-induced cell survival results, at least in part, from a mechanism that involves Bcl2 phosphorylation. Therefore, novel therapeutic strategies for lung cancer in which Bcl2 is expressed may be used to abrogate the anti-apoptotic activity of Bcl2 by inhibiting multiple upstream nicotine-activated pathways.

Antineoplastic Agents↗

PubMed2002

A functional role for the B56 alpha-subunit of protein phosphatase 2A in ceramide-mediated regulation of Bcl2 phosphorylation status and function.

Recently it has been shown that the potent apoptotic agent ceramide activates a mitochondrial protein phosphatase 2A (PP2A) and promotes dephosphorylation of the anti-apoptotic molecule Bcl2 (Ruvolo, P. P., Deng, X., Ito, T., Carr, B. K., and May, W. S. (1999) J. Biol. Chem. 274, 20296-20300). In cells expressing Bcl2, dephosphorylation of Bcl2 appears to be required for ceramide-induced cell death because treatment of cells with low doses of the PP2A inhibitor okadaic acid blocks Bcl2 dephosphorylation and promotes cell survival. Furthermore, the non-phosphorylatable (i.e. PP2A-resistant) gain-of-function S70E mutant Bcl2 can protect cells from ceramide-induced apoptosis. These findings support a model whereby Bcl2 function is regulated by PP2A. PP2A is a heterotrimer that contains a catalytic C-subunit, a structural A-subunit, and a regulatory B-subunit. The A- and C-subunits are fairly conserved and ubiquitously expressed, and they form the catalytic complex of the phosphatase. In contrast, there are at least three families of diverse B-subunit molecules that vary in expression temporally and by tissue type. It is hypothesized that ceramide regulates PP2A via the B-subunit. Thus, understanding the mechanism of how PP2A regulates Bcl2 phosphorylation status and how ceramide might regulate this process requires identification of the regulatory B-subunit of PP2A that comprises the Bcl2 phosphatase. Results indicate that the B56 alpha-subunit is a candidate regulatory subunit of the physiologic Bcl2 phosphatase since (a) B56 alpha associates with Bcl2 as evidenced by pull-down experiments, (b) B56 alpha co-localizes with Bcl2 in mitochondrial membranes, (c) ceramide promotes translocation of B56 alpha to mitochondrial membranes, and (d) overexpression of B56 alpha promotes mitochondrial PP2A activity and Bcl2 dephosphorylation and potentiates cell killing with ceramide. These findings suggest a role for B56 alpha in regulating the Bcl2 phosphatase.

Blotting, Western↗

PubMed2002

Novel triterpenoid CDDO-Me is a potent inducer of apoptosis and differentiation in acute myelogenous leukemia.

It has been shown that the novel synthetic triterpenoid CDDO inhibits proliferation and induces differentiation and apoptosis in myeloid leukemia cells. In the current study the effects of the C-28 methyl ester of CDDO, CDDO-Me, were analyzed on cell growth and apoptosis of leukemic cell lines and primary acute myelogenous leukemia (AML). CDDO-Me decreased the viability of leukemic cell lines, including multidrug resistant (MDR)-1-overexpressing, p53(null) HL-60-Dox and of primary AML cells, and it was 3- to 5-fold more active than CDDO. CDDO-Me induced a loss of mitochondrial membrane potential, induction of caspase-3 cleavage, increase in annexin V binding and DNA fragmentation, suggesting the induction of apoptosis. CDDO-Me induced pro-apoptotic Bax protein that preceded caspase activation. Furthermore, CDDO-Me inhibited the activation of ERK1/2, as determined by the inhibition of mitochondrial ERK1/2 phosphorylation, and it blocked Bcl-2 phosphorylation, rendering Bcl-2 less anti-apoptotic. CDDO-Me induced granulo-monocytic differentiation in HL-60 cells and monocytic differentiation in primary cells. Of significance, colony formation of AML progenitors was significantly inhibited in a dose-dependent fashion, whereas normal CD34(+) progenitor cells were less affected. Combinations with ATRA or the RXR-specific ligand LG100268 enhanced the effects of CDDO-Me on cell viability and terminal differentiation of myeloid leukemic cell lines. In conclusion, CDDO-Me is an MDR-1- and a p53-independent compound that exerts strong antiproliferative, apoptotic, and differentiating effects in myeloid leukemic cell lines and in primary AML samples when given in submicromolar concentrations. Differential effects of CDDO-Me on leukemic and normal progenitor cells suggest that CDDO-Me has potential as a novel compound in the treatment of hematologic malignancies.

Annexin A5↗

PubMed2002

Adult hematopoietic stem cells provide functional hemangioblast activity during retinal neovascularization.

Adults maintain a reservoir of hematopoietic stem cells that can enter the circulation to reach organs in need of regeneration. We developed a novel model of retinal neovascularization in adult mice to examine the role of hematopoietic stem cells in revascularizing ischemic retinas. Adult mice were durably engrafted with hematopoietic stem cells isolated from transgenic mice expressing green fluorescent protein. We performed serial long-term transplants, to ensure activity arose from self-renewing stem cells, and single hematopoietic stem-cell transplants to show clonality. After durable hematopoietic engraftment was established, retinal ischemia was induced to promote neovascularization. Our results indicate that self-renewing adult hematopoietic stem cells have functional hemangioblast activity, that is, they can clonally differentiate into all hematopoietic cell lineages as well as endothelial cells that revascularize adult retina. We also show that recruitment of endothelial precursors to sites of ischemic injury has a significant role in neovascularization.

Animals↗