SEARCH:   Advanced

Blood, 1 October 2006, Vol. 108, No. 7, pp. 2416-2419. Prepublished online as a Blood First Edition Paper on June 20, 2006; DOI 10.1182/blood-2006-02-003582. This Article Abstract Full Text (PDF) All Versions of this Article: blood-2006-02-003582v1 108/7/2416    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Lee, Y.-J. Articles by Kogan, S. C. Search for Related Content PubMed PubMed Citation Articles by Lee, Y.-J. Articles by Kogan, S. C. Related Collections Neoplasia Oncogenes and Tumor Suppressors Gene Expression Brief Reports Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  NEOPLASIA Brief report CCAAT/enhancer binding proteins alpha and epsilon cooperate with all-trans retinoic acid in therapy but differ in their antileukemic activities Young-Jin Lee, Letetia C. Jones, Nikolai A. Timchenko, Danilo Perrotti, Daniel G. Tenen, and Scott C. Kogan From the Department of Laboratory Medicine and Comprehensive Cancer Center, University of California San Francisco; Huffington Center on Aging and Department of Pathology, Baylor College of Medicine, Houston, TX; Department of Molecular Virology, Immunology and Medical Genetics and the Comprehensive Cancer Center, The Ohio State University, Columbus; and Harvard Institutes of Medicine, Harvard Medical School, Boston, MA.    Abstract Top Abstract Introduction Study design Results and discussion References   CCAAT/enhancer binding proteins (C/EBPs) play critical roles in myelopoiesis. Dysregulation of these proteins likely contributes to the pathogenesis of myeloid disorders characterized by a block in granulopoiesis. In one such disease, acute promyelocytic leukemia (APL), a promyelocytic leukemia–retinoic acid receptor (PML-RAR) fusion protein is expressed as a result of a t(15;17) chromosomal translocation. Treatment of PML-RAR leukemic cells with all-trans retinoic acid (ATRA) causes them to differentiate into mature neutrophils, an effect thought to be mediated by C/EBPs. In this study, we assess the potential for cooperativity between increased C/EBP activity and ATRA therapy. We demonstrate that although both C/EBP and C/EBP can significantly prolong survival in a mouse model of APL, they are not functionally equivalent in this capacity. We also show that forced expression of C/EBP or C/EBP in combination with ATRA treatment has a synergistic effect on survival of leukemic mice compared with either therapy alone.    Introduction Top Abstract Introduction Study design Results and discussion References   CCAAT/enhancer binding proteins (C/EBPs) are a family of transcription factors that regulate cell growth and differentiation. Two members of this family, C/EBP and C/EBP, are of critical importance in granulopoiesis. Disruption of the C/EBP gene in mice results in the loss of production of neutrophils and eosinophils,1 whereas mice that lack C/EBP generate neutrophils and eosinophils with abnormal function, gene regulation, and morphology.2-4 C/EBP is the founding member of the bZIP class of DNA-binding proteins.5 Members of this family contain distinct N-terminal transactivation domains, C-terminal leucine-zipper dimerization domains, and basic DNA-binding regions.6,7 C/EBP's basic region confers not only its ability to bind DNA but also its inhibition of E2F pathways.8,9 Previous studies have shown that the integrity of DNA binding, transactivation, and E2F inhibition is required for C/EBP-dependent granulocytic differentiation.9-12 Although the functional domains required for C/EBP activity have not been well characterized, C/EBP's role in directing expression of myeloid-specific genes associated with terminal differentiation of granulocytes has been clearly demonstrated.2,13-15 Because C/EBP and C/EBP are required for normal granulocytic differentiation, alterations in expression or function of these proteins likely contribute to the pathogenesis of acute myeloid leukemia (AML), a disease characterized by an early block in granulopoiesis. Prior studies16,17 provide evidence that C/EBP and C/EBP may play a role in the pathogenesis of acute promyelocytic leukemia (APL), a subtype of AML in which a t(15;17) chromosomal translocation juxtaposes the promyelocytic (PML) gene to the retinoic acid receptor (RARA) gene, creating an aberrant PML-RAR fusion protein.18 A unique characteristic of PML-RAR leukemic cells is their sensitivity to all-trans retinoic acid (ATRA).19 Treatment with ATRA induces remissions in patients with APL by causing the leukemic cells to differentiate into mature neutrophils.20 While the mechanism underlying the sensitivity of promyelocytes to ATRA is not completely understood, we and others21,22 have suggested that C/EBPs mediate the ATRA-induced maturation of APL cells. In the present study, we explore the mechanism by which C/EBPs prolong survival in a murine model of APL. We also assess the potential for cooperativity between increased C/EBP activity and ATRA therapy. We demonstrate that both C/EBP and C/EBP significantly prolong survival; however, they are not functionally equivalent in this capacity. We also show that forced expression of C/EBP or C/EBP in combination with ATRA treatment has a synergistic effect on survival of leukemic mice compared with either therapy alone.    Study design Top Abstract Introduction Study design Results and discussion References   Plasmids A rat C/EBP cDNA (rC/EBP) was generated by polymerase chain reaction (PCR) and cloned into the tamoxifen-inducible pBabepuro3:hb estrogen receptor* (pBP3:hbER*) to generate pBP3:rC/EBP-ER. For generation of MIG-rC/EBP-ER, the rC/EBP-ER fragment was excised from pBP3:rC/EBP-ER and cloned into the mouse stem cell virus–internal ribosomal entry site–green fluorescent protein (MSCV-IRES-GFP [MIG]) retroviral vector as a BamHI-HincII fragment into the BglII-HpaI sites in MIG. Construction of MIG-hC/EBP-ER has been previously described.16 Briefly, human C/EBP-ER was cloned into the EcoRI-HpaII sites in MIG as an EcoRI-SacI fragment. Point mutations were made in the DNA-binding domains of rC/EBPR and hC/EBP at positions R289 and R211, respectively, using the QuikChange XL site-directed mutagenesis kit (Stratagene, La Jolla, CA) according to the manufacturer's instructions. Position R211 in C/EBP is equivalent to C/EBPR289. The resulting mutants, C/EBPR211A and C/EBPR289A, were confirmed by DNA sequencing. Cell culture The 32Dcl3 cell line was modified to express high levels of the ecotropic receptor (32Dcl3-eco R), thereby facilitating retroviral transduction. These cells were maintained in Dulbecco modified Eagle medium (DMEM) supplemented with 10% heat-inactivated fetal bovine serum (FBS), 100 U/mL penicillin G, 100 µg/mL streptomycin, and 5% X63Ag8–mouse interleukin-3 (mIL-3)–conditioned media. BOSC23 cells were maintained in DMEM supplemented with 10% heat-inactivated FBS, 100 U/mL penicillin, and 100 µg/mL streptomycin. Freshly harvested leukemic no. 1111 cells23 from bone marrow and spleen of leukemic mice were cultured in stem cell media (Myelocult M5300; StemCell Technologies, Vancouver, BC, Canada) with 15% FBS, 5% IL-3–conditioned media, 0.4 mM glutamine, 100 U/mL penicillin G, 100 µg/mL streptomycin, 10 ng/mL rIL-3, 10 ng/mL IL-6, and 10 ng/mL stem cell factor. Retroviral transduction BOSC23 cells were transfected with retroviral constructs as previously described.24 Retroviral supernatants were collected and used to transduce leukemic bone marrow (#1111; 2 x 106 cells per well) and 32Dcl3 cells (100 000 cells per well) as previously described.16 After transduction, leukemic #1111 and 32Dc13 cells were sorted using the fluorescence-activated cell sorter (FACS) Vantage (Becton Dickinson, San Jose, CA). GFP-positive bone marrow cells were injected into sublethally irradiated mice, and GFP-positive 32Dcl3-eco R cells were maintained in culture in the presence or absence of 20 nM 4-hydroxytamoxifen (4-HT; Sigma, St Louis, MO). At 48-hour intervals, live 32Dc13 cells were counted using trypan blue exclusion, and the percentage of GFP-positive cells was assessed by flow cytometry. Mice Mice were bred and maintained at the University of California at San Francisco, and their care was in accordance with Institutional Animal Care and Use Committee guidelines. To examine C/EBPs in vivo, retrovirally transduced GFP-positive leukemic no. 1111 cells (50 000 cells per mouse) were injected into the lateral tail vein of sublethally irradiated (4.5 Gy) 6- to 8-week-old female FVB/N mice. Each group (C/EBP, C/EBP, or the mutant version of each) contained 20 mice, with 5 animals in each subgroup (placebo, 4-HT, ATRA, and 4-HT plus ATRA). Treatments (placebo, 25 mg 4-HT, and 10 mg ATRA) were administered to each subgroup as 21-day release, subcutaneous pellets (Innovative Research of America, Sarasota, FL). Statistical analysis Statistical analyses were performed in GraphPad Prism using the log-rank test or in Excel 2000 using the Student t test with 2-tailed distribution and unequal variance as appropriate.    Results and discussion Top Abstract Introduction Study design Results and discussion References   C/EBP and C/EBP play central roles in normal myelopoiesis; therefore, it is likely that altered function of these proteins contributes to the pathogenesis of APL. In a previous study,16 we showed that expression of a tamoxifen-inducible form of C/EBP, hC/EBP-ER, in leukemic cells caused them to differentiate into mature neutrophils in vivo. In the present study, we expand this approach to C/EBP and assess the abilities of both C/EBP and C/EBP to prolong survival in a mouse model of APL. To assess the antileukemic effect of C/EBPs in this system, we transduced PML-RAR leukemic cells23 with either C/EBP-ER or C/EBP-ER retrovirus and transplanted them into sublethally irradiated histocompatible mice. After leukemias developed in the recipient animals, the mice were treated with either a placebo or 4-HT to induce C/EBP activity. In mice receiving transplants with C/EBP-ER–transduced leukemias, treatment with 4-HT prolonged mean survival by 7 days compared with animals given a placebo (Figure 1A). Animals that received C/EBP-ER–transduced leukemias demonstrated a more robust response following treatment with 4-HT (Figure 1B), exhibiting a mean increase in survival of 11 days compared with the placebo group. Therefore, tamoxifeninducible forms of both C/EBP and C/EBP significantly prolong survival in a mouse model of APL. Of note, 4-HT treatment of mice receiving untransduced cells had no effect on survival (data not shown). Because C/EBPs belong to the bZIP family of DNA-binding proteins, we asked whether the ability to bind DNA was required for the antileukemic activities of C/EBP and C/EBP. To address this, we mutated R289 in C/EBP and the corresponding amino acid (R211) in C/EBP to alanine-generating mutants (C/EBPR289A and C/EBPR211A) that were devoid of DNA-binding activity (data not shown). We selected these residues for substitution based on the observation that R289 is an integral component of the protein-DNA interface in the crystal structure of a C/EBP bZIP polypeptide bound to its cognate DNA site.25 We then transduced PML-RAR leukemic cells with C/EBPR289A or C/EBPR211A retrovirus and transplanted them as before. In animals receiving transplants with C/EBPR211A-transduced leukemias, we found that treatment with 4-HT had no effect on survival (Figure 1C), thus indicating that the DNA-binding activity of C/EBP is required for its antileukemic effect. We observed a similar phenomenon in the factor-dependent myeloid progenitor cell line 32Dcl3 (Figure 1D). While the wild-type C/EBP suppressed growth of 32Dc13 cells in the presence of 4-HT, the R211A mutant was unable to repress proliferation, suggesting that the DNA-binding activity of C/EBP is required for its function in immature myeloid cells. Interestingly, mice receiving transplants with C/EBPR289A-transduced leukemias exhibited a mean increase in survival of 8 days compared with the placebo group following treatment with 4-HT (Figure 1E). This finding indicates that, unlike C/EBP, C/EBP can suppress leukemia without binding DNA. 32Dc13 cells transduced with either wild-type or mutant C/EBP fail to proliferate following treatment with 4-HT, suggesting that C/EBP has antiproliferative effects that do not require DNA binding (Figure 1F). Together, the results presented in Figure 1 imply that C/EBP and C/EBP are not functionally equivalent in their ability to suppress growth and inhibit leukemogenesis. The results shown in Figure 1, in conjunction with the idea that C/EBPs mediate the antileukemic effects of ATRA, led us to assess the potential for cooperativity between treatment with ATRA and forced expression of C/EBPs. To address this relationship, we transduced PML-RAR leukemic cells with either C/EBP-ER or C/EBP-ER retrovirus and transplanted them as before. After leukemias developed in recipient animals, we treated them with either a placebo, 4-HT, ATRA, or a combination of 4-HT and ATRA. In mice receiving transplants with C/EBP-ER–transduced leukemias, ATRA treatment resulted in a more substantial increase in survival (mean increase of 23 days compared with the placebotreated group) than did treatment with 4-HT (Figure 2A). However, treatment with a combination of 4-HT and ATRA had the greatest impact on survival, with a mean increase of 37 days compared with the placebo group. View larger version (21K): [in this window] [in a new window]   Figure 1.. Tamoxifen-inducible C/EBPs suppress growth of myeloid leukemias and 32Dc13 cells: DNA binding is requisite for the antiproliferative effects of C/EBP but not C/EBP. (A-C,E) Bone marrow of PML-RAR leukemic mice were harvested and transduced with retroviruses expressing C/EBP-ER, C/EBP-ER, or a mutant version of each that is deficient in DNA-binding activity (C/EBPR289A-ER and C/EBPR211A-ER, respectively). Following 2 rounds of transduction, GFP-positive cells were sorted and injected into sublethally irradiated FVB/N females. After leukemias developed in recipient animals, 5 mice from each group were given either a placebo or 25 mg 4-HT. Animals that received C/EBP-ER–transduced leukemias exhibited prolonged survival following treatment with 4-HT (mean survival time of 33 days compared with 26.4 days in the placebo group; P = .002). C/EBPR211A-ER had no effect on survival of leukemic mice (mean survival time of 37.4 days compared with 36.4 days in the placebo group). In animals receiving transplants with C/EBP-ER– or C/EBPR289A-ER–transduced leukemias, treatment with 4-HT significantly prolonged survival (P .003). Mean survival times for placebo and 4-HT–treated groups were 33.8 days and 46.4 days, respectively, for C/EBP-ER mice and 31.4 days and 39.8 days, respectively, for C/EBPR289A-ER mice. (D, F) 32Dcl3 cells were plated in 24-well dishes at 100 000 cells per well; transduced with retroviruses expressing C/EBP-ER, C/EBPR211A-ER, C/EBP-ER, or C/EBPR289A-ER; and cultured in the absence or presence of 20 nM 4-HT. The growth curve represents the number of transduced cells at days 0, 2, 4, and 6. The results are mean ± SD from at least 3 independent experiments. (D) *P < .05 and (F) *P .01.   Animals that received C/EBP-ER–transduced leukemias demonstrated a similar pattern of response; however, the magnitude of each response was greater than that seen in C/EBP-ER mice (Figure 1B). Treatment with 4-HT and ATRA prolonged the survival of C/EBP-ER animals by a mean increase of 11 and 38 days, respectively, but the greatest impact on survival was seen in mice given the combined treatment (mean increase in survival was 67 days). The results presented in Figure 2 demonstrate that forced expression of C/EBP or C/EBP in combination with ATRA treatment has a synergistic effect on survival of leukemic mice compared with either therapy alone. These findings suggest that the ability of ATRA to prolong the survival of leukemic mice includes mechanisms beyond simple induction of C/EBP activity. Furthermore, and of potential clinical importance, our results indicate that agents that increase C/EBP activity might function cooperatively with ATRA to exert antileukemic activity in AML. View larger version (18K): [in this window] [in a new window]   Figure 2.. Forced expression of C/EBPs in combination with ATRA treatment has a synergistic effect on survival of leukemic mice. Leukemic animals expressing either C/EBP-ER (A) or C/EBP-ER (B) were generated as described in Figure 1 and treated with one of the following: a placebo, 25 mg 4-HT, 10 mg ATRA, or a combination of 4-HT and ATRA. The data for each C/EBP group are from 20 animals with 5 mice per treatment. The combined therapy of 4-HT and ATRA resulted in the most profound effect on survival in both groups (P < .001). The mean survival times of placebo, 4-HT, ATRA, and 4-HT plus ATRA groups were 26.4, 33, 49.6, and 63 days, respectively, in animals receiving transplants with C/EBP-ER–transduced leukemias and 30.5, 41.8, 69, and 97.8 days, respectively, in C/EBP-ER animals.      Footnotes   Submitted February 14, 2006; accepted May 28, 2006. Prepublished online as Blood First Edition Paper, June 20, 2006; DOI 10.1182/blood-2006-02-003582. Supported by National Institutes of Health (NIH) grants CA95274 (S.C.K) and CA095512-01 (D.P.). S.C.K. is a scholar of the Leukemia and Lymphoma Society and was a Burroughs-Wellcome Fund Career awardee. Y.-J.L. designed and performed experiments and analyzed data; L.C.J. performed experiments, analyzed data, and wrote the manuscript; N.A.T. designed and performed experiments and edited the manuscript; D.P. provided reagents and edited the manuscript; D.G.T. mentored this line of investigation and edited the manuscript; and S.C.K. designed experiments, analyzed data, provided funding for this work, and edited the manuscript. Y.-J.L. and L.C.J. contributed equally to this work. The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734. Reprints: Scott C. Kogan, Dept of Laboratory Medicine, Box 0134, 513 Parnassus Ave, San Francisco, CA 94143; e-mail: scott.kogan{at}ucsf.edu.    References Top Abstract Introduction Study design Results and discussion References   Zhang DE, Zhang P, Wang ND, Hetherington CJ, Darlington GJ, Tenen DG. Absence of granulocyte colony-stimulating factor signaling and neutrophil development in CCAAT enhancer binding protein alpha-deficient mice. Proc Natl Acad Sci U S A. 1997;94: 569-574.[Abstract/Free Full Text] Yamanaka R, Barlow C, Lekstrom-Himes J, et al. Impaired granulopoiesis, myelodysplasia, and early lethality in CCAAT/enhancer binding protein epsilon-deficient mice. Proc Natl Acad Sci U S A. 1997;94: 13187-13192.[Abstract/Free Full Text] Lekstrom-Himes J, Xanthopoulos KG. CCAAT/enhancer binding protein epsilon is critical for effective neutrophil-mediated response to inflammatory challenge. Blood. 1999;93: 3096-3105.[Abstract/Free Full Text] Kubota T, Kawano S, Chih DY, et al. Representational difference analysis using myeloid cells from C/EBP epsilon deletional mice. Blood. 2000;96: 3953-3957.[Abstract/Free Full Text] Landschulz WH, Johnson PF, McKnight SL. The leucine zipper: a hypothetical structure common to a new class of DNA binding proteins. Science. 1988;240: 1759-1764.[Abstract/Free Full Text] Umek RM, Friedman AD, McKnight SL. CCAAT-enhancer binding protein: a component of a differentiation switch. Science. 1991;251: 288-292.[Abstract/Free Full Text] Landschulz WH, Johnson PF, McKnight SL. The DNA binding domain of the rat liver nuclear protein C/EBP is bipartite. Science. 1989;243: 1681-1688.[Abstract/Free Full Text] Porse BT, Pedersen TA, Xu X, et al. E2F repression by C/EBPalpha is required for adipogenesis and granulopoiesis in vivo. Cell. 2001;107: 247-258.[CrossRef][Medline] [Order article via Infotrieve] Johansen LM, Iwama A, Lodie TA, et al. c-Myc is a critical target for c/EBPalpha in granulopoiesis. Mol Cell Biol. 2001;21: 3789-3806.[Abstract/Free Full Text] D'Alo' F, Johansen LM, Nelson EA, et al. The amino terminal and E2F interaction domains are critical for C/EBP alpha-mediated induction of granulopoietic development of hematopoietic cells. Blood. 2003;102: 3163-3171.[Abstract/Free Full Text] Keeshan K, Santilli G, Corradini F, Perrotti D, Calabretta B. Transcription activation function of C/EBPalpha is required for induction of granulocytic differentiation. Blood. 2003;102: 1267-1275.[Abstract/Free Full Text] Wang QF, Cleaves R, Kummalue T, Nerlov C, Friedman AD. Cell cycle inhibition mediated by the outer surface of the C/EBPalpha basic region is required but not sufficient for granulopoiesis. Oncogene. 2003;22: 2548-2557.[CrossRef][Medline] [Order article via Infotrieve] Khanna-Gupta A, Zibello T, Idone V, Sun H, Lekstrom-Himes J, Berliner N. Human neutrophil collagenase expression is C/EBP-dependent during myeloid development. Exp Hematol. 2005;33: 42-52.[CrossRef][Medline] [Order article via Infotrieve] Gombart AF, Kwok SH, Anderson KL, Yamaguchi Y, Torbett BE, Koeffler HP. Regulation of neutrophil and eosinophil secondary granule gene expression by transcription factors C/EBP epsilon and PU.1. Blood. 2003;101: 3265-3273.[Abstract/Free Full Text] Verbeek W, Lekstrom-Himes J, Park DJ, et al. Myeloid transcription factor C/EBPepsilon is involved in the positive regulation of lactoferrin gene expression in neutrophils. Blood. 1999;94: 3141-3150.[Abstract/Free Full Text] Truong BT, Lee YJ, Lodie TA, et al. CCAAT/enhancer binding proteins repress the leukemic phenotype of acute myeloid leukemia. Blood. 2003;101: 1141-1148.[Abstract/Free Full Text] Park DJ, Chumakov AM, Vuong PT, et al. CCAAT/enhancer binding protein epsilon is a potential retinoid target gene in acute promyelocytic leukemia treatment. J Clin Invest. 1999;103: 1399-1408.[Medline] [Order article via Infotrieve] Jaffe ES, Harris NL, Stein H, Vardiman JW. World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France: IARC Press; 2001. Huang ME, Ye YC, Chen SR, et al. Use of alltrans retinoic acid in the treatment of acute promyelocytic leukemia. Blood. 1988;72: 567-572.[Abstract/Free Full Text] Degos L, Dombret H, Chomienne C, et al. Alltrans-retinoic acid as a differentiating agent in the treatment of acute promyelocytic leukemia. Blood. 1995;85: 2643-2653.[Free Full Text] Duprez E, Wagner K, Koch H, Tenen DG. C/EBP-beta: a major PML-RARA-responsive gene in retinoic acid-induced differentiation of APL cells. EMBO J. 2003;22: 5806-5816.[CrossRef][Medline] [Order article via Infotrieve] Mueller BU, Pabst T. C/EBPalpha and the pathophysiology of acute myeloid leukemia. Curr Opin Hematol. 2006;13: 7-14.[Medline] [Order article via Infotrieve] Brown D, Kogan S, Lagasse E, et al. A PML-RARalpha transgene initiates murine acute promyelocytic leukemia. Proc Natl Acad Sci U S A. 1997;94: 2551-2556.[Abstract/Free Full Text] Pear WS, Nolan GP, Scott ML, Baltimore D. Production of high-titer helper-free retroviruses by transient transfection. Proc Natl Acad Sci U S A. 1993;90: 8392-8396.[Abstract/Free Full Text] Miller M, Shuman JD, Sebastian T, Dauter Z, Johnson PF. Structural basis for DNA recognition by the basic region leucine zipper transcription factor CCAAT/enhancer-binding protein alpha. J Biol Chem. 2003;278: 15178-15184.[Abstract/Free Full Text] CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: T. Pabst and B. U. Mueller Complexity of CEBPA Dysregulation in Human Acute Myeloid Leukemia Clin. Cancer Res., September 1, 2009; 15(17): 5303 - 5307. [Abstract] [Full Text] [PDF] S. Koschmieder, B. Halmos, E. Levantini, and D. G. Tenen Dysregulation of the C/EBP{alpha} Differentiation Pathway in Human Cancer J. Clin. Oncol., February 1, 2009; 27(4): 619 - 628. [Abstract] [Full Text] [PDF] This Article Abstract Full Text (PDF) All Versions of this Article: blood-2006-02-003582v1 108/7/2416    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Lee, Y.-J. Articles by Kogan, S. C. Search for Related Content PubMed PubMed Citation Articles by Lee, Y.-J. Articles by Kogan, S. C. Related Collections Neoplasia Oncogenes and Tumor Suppressors Gene Expression Brief Reports Social Bookmarking                   What's this?

	Copyright © 2006 by American Society of Hematology         Online ISSN: 1528-0020