The Molecular Basis of Lmo2-Induced T-Cell Acute Lymphoblastic Leukemia

Published OnlineFirst September 22, 2010; DOI: 10.1158/1078-0432.CCR-10-0440

Clinical Cancer Molecular Pathways Research

David J. Curtis1,2 and Matthew P. McCormack1,2

Abstract T-cell acute lymphoblastic leukemia (T-ALL) is commonly caused by the overexpression of oncogenic transcription factors in developing T cells. In a mouse model of one such oncogene, LMO2, the cellular effect is to induce self-renewal of committed T cells in the thymus, which persist long-term while acquiring additional mutations and eventually giving rise to leukemia. These precancerous stem cells (pre-CSC) are intrinsically resistant to radiotherapy, implying that they may be refractory to conventional cancer therapies. However, they depend on an aberrantly expressed stem cell–like self-renewal program for their maintenance, in addition to a specialized thymic microenvironmental niche. Here, we discuss potential approaches for targeting pre-CSCs in T-ALL by using therapies directed at oncogenic transcription factors themselves, downstream self-renewal pathways, and the supportive cell niche. Clin Cancer Res; 16(23); 5618–23. 2010 AACR.

Background provide rational approaches for identifying new therapeutic strategies. T-cell acute lymphoblastic leukemia (T-ALL) is a com- Aberrant expression of the LMO2 gene in T cells accounts mon pediatric leukemia representing approximately 20% for about 9% of T-ALL (4). In addition, activation of LMO2 of all ALL (1). Around half of T-ALL cases harbor recurrent by retroviral insertion was the cause of T-ALL in four chromosomal translocations, leading to aberrant T-cell patients receiving gene therapy for X-linked severe com- expression of a variety of oncogenic transcription factors. bined immunodeficiency (X-SCID; refs. 5–8). In normal The transcription factors most commonly invoved are the hematopoiesis, expression of LMO2 is restricted to adult homeobox genes TLX1 or TLX3, or components of basic hematopoietic stem cells (HSC) and the erythroid lineage, helix-loop helix (bHLH) complexes, including bHLH and is tightly regulated by a network of transcription factors factors themselves (SCL/TAL1, LYL1) and their binding including LMO2 itself, SCL, GATA1, and ETS factors (9). partners, the LIM-domain only (LMO) factors, LMO1 or LMO2 is essential for the formation of yolk sac erythropoi- LMO2 (2). Expression profiling of T-ALL reveals distinct esis, leading to embryonic death at E10.5 (10). In contrast, gene signatures according to the underlying chromoso- LMO2 expression is extinguished early in T-cell develop- mal abnormality, suggesting that the mechanism of ment and is not required for normal development of this leukemogenesis is oncogene specific (3). Despite this lineage (11). In erythroid cells, Lmo2 functions as a brid- genetic heterogeneity, current therapies for both B- and ging molecule assembling a multiprotein transcriptional T-cell ALL are essentially identical, using multidrug com- complex that includes hetero-dimers of E proteins (E47 or binations, prolonged low-dose maintenance chemother- HEB) and Scl or Lyl1, as well as Gata1 and Ldb1 (12). This apy, and allogeneic bone marrow transplant for high-risk complex binds to DNA through the bHLH factors and or relapsed disease. Unfortunately, with this generic GATA1, recognizing a bipartite DNA sequence comprising approach, 20% of children and 50% of adults succumb an E box and a GATA site. This core bHLH-GATA complex to relapsed disease (1). A better understanding of how can act as a repressor or activator of transcription depend- these chromosomal translocations cause leukemia will ing upon the recruitment of other partner proteins, which occurs in a cell stage–specific manner. In a mouse model of Lmo2-induced T-ALL, a different multiprotein complex was identified in the immature Authors' Affiliations: 1Rotary Bone Marrow Research Laboratories, Royal CD4 CD8 double negative (DN) T cells of the thymus, Melbourne Hospital; 2Department of Medicine, University of Melbourne, comprising Lmo2, Scl, E47, and Ldb1, which binds to a Parkville, Australia bipartite E-box motif (13). Differing multiprotein com- Corresponding Author: Matthew P. McCormack, Royal Melbourne plexes in normal and T-ALL cells provide a window for Hospital and University of Melbourne, Rotary Bone Marrow Research Laboratories and Department of Medicine, Grattan St, Parkville, Victoria specificity of therapeutics that could disrupt the leukemic 3050, Australia. Phone: 0061-3-9342-7573; Fax: 0061-3-9342-8634; Lmo2 complex, but spare the normal complex that may be E-mail: [email protected] essential for maintenance of HSCs and/or erythropoiesis. doi: 10.1158/1078-0432.CCR-10-0440 Animal models of Lmo2-induced T-ALL provide an 2010 American Association for Cancer Research. invaluable tool for understanding the mechanism of

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Molecular Basis of Lmo2-Induced T-ALL

Differentiation pTα Fig. 1. Molecular pathways in block Lmo2-induced self-renewing thymocytes. LMO2-LDB1 forms a Self-renewal bridge between heterodimers of PML E47 and LYL1. This formation body PML leads to repression of T-cell HHEX LMO2 differentiation genes including LDB1 LMO2 pTa, perhaps through loss of E E47

protein dimers. The LMO2 E47 LYL1 LYL1 complex also activates expression STAT 3/5 of the homeodomain protein Survival CATCTG CATCTG HHEX that resides in the nucleolar PML body, and the NF-kB signaling pathway. These changes KIT induce a self-renewal program AKT NFKβ that is restricted to DN3 P thymocytes, which receive PI3K γ-secretase survival and/or proliferation SCF signals such as Notch ligands and DL4 Proliferation SCF from the thymic stroma. Notch1 Self-renewal of these pre-CSCs allows acquisition of other genetic mutations, such as activating mutations of Notch or PI3K Thymic pathways, which may allow the stroma pre-CSCs to expand and escape from their thymic niche.

leukemogenesis and testing new therapies. Transgenic and reduced E-protein expression in Scl-transgenic mice mice expressing Lmo2 in T cells develop T-ALL, albeit accelerates T-cell leukemogenesis (25, 26). Together, these after a long latency period (14, 15). A similar mouse studies have concluded that the SCL and LMO oncogenes model of T-ALL involves the overexpression of Scl with or induce leukemia by perturbed T-cell differentiation without Lmo1 (16–18). Owing to the similarity between through loss of E-protein function. Lmo1 and Lmo2, and the fact that Scl binds to Lmo2 and Given the multigenic nature of LMO2-induced T-ALL, can accelerate Lmo2-driven leukemogenesis (19, 20), we we reasoned that impaired differentiation would not will consider these models together, although the possi- alone be sufficient for DN thymocytes to acquire the bility remains that distinct molecular mechanisms under- requisite additional genetic mutations. Indeed, blocked lie the two models. In both transgenic models, a delayed T-cell development due to impaired T-cell receptor (TCR) onset of T-ALL is due to the requirement for additional recombination or expression is insufficient to induce genetic mutations, which include activating mutations of T-ALL in mouse models (27). Accordingly, using a com- Notch signaling and loss of the Cdkn2a locus, both of bination of in vivo cell marking and transplantation of which are also observed in LMO2-associated human T- thymocytes from young Lmo2-transgenic mice, we ALL (7, 8, 21–23). have recently shown that the primary cellular effect of To understand the mechanism of leukemogenesis by Lmo2 is to induce self-renewal–committed T cells in the SCL/LMO proteins, a number of groups have examined thymus at the DN3 stage of T-cell development þ the thymi of preleukemic transgenic mice. These studies (CD4 CD8 CD44 CD25 ;ref.28).Thispopulationof reveal a preleukemic phenotype characterized by a small cells has many features of cancer stem cells (CSC), thymus with increased apoptosis and an expanded propor- including the ability to serially transplant, the ability to tion of immature DN T cells (20, 24). Gene expression generate mature T cells, and the expression of a stem cell studies of these preleukemic thymocytes reveal a loss of signature. However, as these self-renewing thymocytes T-cell differentiation genes, most notably the pre–T-cell were evident soon after birth, up to 1 year before overt receptor alpha subunit (pTa; Fig. 1), which is required T-ALL, we refer to them as precancerous stem cells (pre- þ þ for progression of DN T cells to the CD4 CD8 double- CSCs). positive (DP) stage (17). The phenotype of E-protein– Evidence for CSCs in T-ALL is provided by the ability to deficient mice is similar to that of Scl/Lmo-transgenic mice, propagate human T-ALL in NOD-SCID mice (29). Similar

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Curtis and McCormack

to acute myelogenous leukemia and B-cell ALL, CSC activ- essential for the oncogenic function of Lmo2. Secondly, þ ity is enriched in the rare CD34 CD4 CD7 subfraction of LMO2 interacts with the Lim domain-binding (LDB) pro- T-ALL (30–32). The CSC hypothesis posits that the stem tein LDB1. The phenotype of Ldb1 knockout mice suggests cell–like properties of CSCs make them more resistant to that it is an essential cofactor for Lmo2 (37). therapies including chemo-radiation. As experimental evi- With regard to targeting LMO2, two successful dence for this hypothesis, we have shown that self-renew- approaches have been recently developed by the Rabbitts ing Lmo2-transgenic thymocytes can survive high-dose laboratory. Firstly, intracellular single-chain antibodies, or irradiation (28). This intrinsic resistance suggests that intrabodies, with LMO2-binding specificity, have been pre-CSCs may survive conventional cancer therapies and shown to effectively block leukemic T-cell growth (38). mediate disease relapse. In support of this notion, array As intracellular delivery of such large molecules remains CGH studies of matched diagnosis and relapse samples problematic, a peptide library screen was undertaken and show that a significant number of relapses arise from an eight–amino acid peptide aptamer was shown to disrupt cells that are ancestral to the predominant clone at diag- the Zn-binding CysXXCys motif of the LIM finger 4 domain nosis (33). of LMO2 (36). Like the intrabody-mediated approach, this To elucidate the molecular basis of LMO2-induced self- peptide aptamer could block both normal and leukemic renewal, we performed gene expression analysis using DN functions of Lmo2. These studies provide proof of principle thymocytes from young, preleukemic Lmo2-transgenic that targeting the LMO2 complex may be an effective mice. Surprisingly, this analysis revealed fewer than 200 therapy for LMO2-induced T-ALL. gene expression changes, many fewer than similar analyses of overt leukemic cells, likely reflecting the lack of further Targeting critical downstream mediators of self- genetic mutations in Lmo2-induced pre-CSCs. In addition renewal to the previously reported loss of T-cell differentiation An alternate approach to targeting the LMO2 complex genes, we identified 81 upregulated genes, of which 48 were directly would be to target critical downstream compo- more highly expressed in normal HSCs than in immature nents of the LMO2-induced self-renewal program. Our thymocytes, implying that Lmo2 may induce self-renewal gene expression analysis revealed a small number of via upregulation of an HSC-associated gene expression HSC-associated candidate genes that may be responsible program. Gene set enrichment analysis (GSEA) of this stem for self-renewal (28). The most compelling of these genes is cell signature with overt human T-ALL showed that this was the hematopoietic-expressed homeobox gene Hhex, significantly associated with the LMO2/LYL1-expressing which is overexpressed 10 fold in Lmo2-transgenic thymo- subset of T-ALL. This finding suggests that LMO2-induced cytes. The central homeodomain of Hhex is most similar to self-renewal pathways persist into overt T-ALL in humans, the T-cell oncogene TLX1, with an identical threonine at and implies that studying pre-CSCs provides a rationale for position 47 that determines DNA-binding specificity (39). understanding how to overcome therapeutic resistance. Enforced expression of Hhex was able to induce self- Here, we discuss potential avenues for targeting pre-CSCs renewal of T cells similarly to Lmo2, and this gene has in T-ALL including targeting transcription factors them- previously been shown to induce T-ALL in mice, implying selves, downstream self-renewal pathways, and microenvir- that it could be a critical downstream component of the onmental survival signals (Fig. 1). Lmo2-induced gene expression program (28, 40). The N- terminal domain of HHEX localizes it to the nucleolar PML Clinical-Translational Advances body through interactions with the PML protein (41). Although currently, no therapeutics target homeodomain Targeting the Lmo2-containing transcription complex transcription factors, a speculative possibility is that arsenic The Lmo2 complex provides a rational target for therapy trioxide, which eradicates CSCs in promyelocytic leukemia on the basis of the observation of oncogenic addiction, by targeting the PML body for degradation, might likewise which has been best shown experimentally by inducible reduce HHEX expression (42, 43). models of c-myc driven lymphoma (34, 35). Oncogenic The NF-kB signaling pathway is commonly deregulated addiction infers that secondary mutations are unlikely to in a variety of cancers. It is activated early in Scl-induced replace the function of the initiating oncogenic event. leukemogenesis, possibly through transcriptional activa- Accordingly, it has been shown that Lmo2 function is tion of IkB kinase (IKK) or repression of p50 (44, 45). essential for the maintenance of Lmo2-induced T-ALL in Moreover GSEA of the Lmo2-induced pre-CSC gene signa- mice (36). ture revealed enrichment for targets of the NF-kB pathway.3 When considering therapeutic targeting of transcription Irrespective of the mechanism, the NF-kB pathway is acti- factors, eliminating their expression poses a major techni- vated in the majority of T-ALL patient samples and has cal hurdle, whereas targeting critical protein-protein inter- been shown to be a major mediator of Notch-driven T-ALL actions is a more viable strategy. In the case of Lmo2, it is a (46, 47). Although NF-kB signaling was shown to be bridging molecule, hence at least two protein-protein interactions can serve as targets. Firstly, LMO2 does not bind to DNA directly, but rather interacts with the DNA-binding bHLH factors LYL1 or SCL. This interaction should be 3D. J. Curtis and M. P. McCormack, unpublished data.

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Molecular Basis of Lmo2-Induced T-ALL

dispensable for maintenance of Scl-induced T-ALL cell Notch signaling is not increased in young thymocytes, lines, its role in the maintenance of self-renewing pre-CSCs supporting the premise that Notch mutations seem to be remains to be investigated (44). secondary events (60, 61). Taken together, these results suggest that Notch mutations allow pre-CSCs to escape Targeting the precancerous stem cell niche the cell niche requirement of DN3 thymocytes. However, Although Lmo2-induced pre-CSCs show inherent capa- it remains to be determined whether, like normal DN3 city for self-renewal, this can only occur within the cells, Lmo2-induced pre-CSCs require cell niche–derived thymus, implying that survival signals are provided by Notch signals for survival. the thymic epithelium to provide a supportive environ- Chemical g-secretase inhibitors (GSI) can effectively ment in which self-renewal can occur. Among the likely inhibit Notch signaling and show efficacy in T-ALL cell candidates for such niche signals are two stromal-derived lines and in xenograft models (62). However, the use of signals that are key components of normal thymic T-cell GSIs in vivo is limited by gut toxicity from inhibition of development. both NOTCH1 and NOTCH2 (63, 64). Such toxicity can be Lmo2-transgenic thymocytes specifically self-renew the largely ameliorated by concomitant treatment with the DN3 stage of T-cell development (28). Among the signals anti–T-ALL therapeutic dexamethasone, suggesting that required for normal DN3 cell survival is stem cell factor combined use of these two agents may be a more effective (SCF), which is presented in membrane-bound form by the therapy (62). Moreover, recently, small molecule inhibitors thymic stroma (48). The SCF receptor Kit is overexpressed and antibodies targeting specific Notch receptors have been in Lmo2-induced pre-CSCs, as are two targets of Kit- developed that are likely to have fewer toxic side effects (64, mediated signaling, the transcription factors Stat3 and 65). Stat5 (28). Together, these data suggest that SCF-induced Finally, in addition to inducing self-renewal, SCL/LMO Stat signaling may be a critical survival signal for these cells. proteins inhibit T-cell differentiation through transcrip- Indeed STAT5 has been previously associated with T-ALL tional repression of target genes required for progression through activation of the kinases JAK1 and JAK2, by acti- through the beta-selection checkpoint. Foremost among vating mutations and chromosomal translocations, respec- these is pTa, which is a direct transcriptional target of these tively (49, 50). If Stat proteins are required for Lmo2- oncogenes (17). Restoration of these molecules could induced pre-CSC survival, they represent attractive targets foreseeably force differentiation of pre-CSCs and inhibit for therapy, either directly, through the use of Stat-inhibi- the self-renewal process. tory drugs, or via inhibition of upstream Kit signaling using Although relevant mouse models have existed for almost the kinase inhibitor imatinib. 20 years, much remains to be learned about how transcrip- AnothercriticalsurvivalfactorattheDN3stageofT-cell tion factor oncogenes, such as LMO2, cause leukemia. A development is Notch signaling (51, 52). The Notch similar time lag between the discovery of the BCR-ABL ligand DL4 expressed on the thymic stromal epithelial chromosomal translocation and effective tyrosine kinase cells is required for survival and proliferation of DN3 cells inhibitors provides the fortitude to continue this pursuit. through regulation of multiple pathways including Through this understanding, we can hope to develop CSC- c-myc, the interleukin (IL)-7 receptor, and the phosphoi- targeted therapies that will improve the treatment of resis- nositide 3-kinase (PI3K) and NF-kB pathways (47, 53– tant or relapsed disease. 56). Activation of the Notch signaling pathway by mutations in either the heterodimerization or PEST domains Disclosure of Potential Conflicts of Interest are found in more than 50% of all T-ALL, including Lmo2-induced T-ALL (23). In mouse models, activation No potential conflicts of interest were disclosed. of Notch cooperates with Scl/Lmo1 in inducing T-ALL (57). Notch signaling can also be increased by loss-of- Grant Support function mutations of FBW7, a component of the E3– D.J. Curtis and M.P. McCormack were supported by a grant from the National ubiquitin-ligase complex required for degradation of Health and Medical Research Council of Australia (NHMRC; project grant 628386). active intracellular Notch (58). Constitutive Notch sig- D.J. Curtis is an RD Wright Biomedical Research Fellow of the NHMRC. naling allows T-cell development to occur independent of Received 08/09/2010; revised 09/01/2010; accepted 09/02/2010; the thymic cell niche (59). In Lmo2-transgenic mice, published OnlineFirst 09/22/2010.

References 1. Pui CH, Evans WE. Treatment of acute lymphoblastic leukemia. N Engl 4. Van Vlierberghe P, van Grotel M, Beverloo HB, et alThe cryptic J Med 2006;354:166–78. chromosomal deletion del(11)(p12p13) as a new activation mechan- 2. Aifantis I, Raetz E, Buonamici S. Molecular pathogenesis of T-cell ism of LMO2 in pediatric T-cell acute lymphoblastic leukemia. Blood leukaemia and lymphoma. Nat Rev Immunol 2008;8:380–90. 2006;108:3520–9. 3. Ferrando AA, Neuberg DS, Staunton J, et alGene expression signa- 5. Hacein-Bey-Abina S, Von Kalle C, Schmidt M, et alLMO2-associated tures define novel oncogenic pathways in T cell acute lymphoblastic clonal T cell proliferation in two patients after gene therapy for SCID- leukemia. Cancer Cell 2002;1:75–87. X1. Science 2003;302:415–9.

www.aacrjournals.org Clin Cancer Res; 16(23) December 1, 2010 5621

Curtis and McCormack

6. McCormack MP, Rabbitts TH. Activation of the T-cell oncogene 28. McCormack MP, Young LF, Vasudevan S, et alThe Lmo2 oncogene LMO2 after gene therapy for X-linked severe combined immunode- initiates leukemia in mice by inducing thymocyte self-renewal. ficiency. N Engl J Med 2004;350:913–22. Science 2010;327:879–83. 7. Hacein-Bey-Abina S, Garrigue A, Wang GP, et alInsertional oncogen- 29. Cesano A, O’Connor R, Lange B, Finan J, Rovera G, Santoli D. esis in 4 patients after retrovirus-mediated gene therapy of SCID-X1. J Homing and progression patterns of childhood acute lymphoblastic Clin Invest 2008;118:3132–42. leukemias in severe combined immunodeficiency mice. Blood 8. Howe SJ, Mansour MR, Schwarzwaelder K, et alInsertional mutagen- 1991;77:2463–74. esis combined with acquired somatic mutations causes leukemogen- 30. Cox CV, Evely RS, Oakhill A, Pamphilon DH, Goulden NJ, Blair A. esis following gene therapy of SCID-X1 patients. J Clin Invest Characterization of acute lymphoblastic leukemia progenitor cells. 2008;118:3143–50. Blood 2004;104:2919–25. 9. Landry JR, Bonadies N, Kinston S, et alExpression of the leukemia 31. Cox CV, Martin HM, Kearns PR, Virgo P, Evely RS, Blair A. Char- oncogene Lmo2 is controlled by an array of tissue-specific elements acterization of a progenitor cell population in childhood T-cell acute dispersed over 100 kb and bound by Tal1/Lmo2, Ets, and Gata lymphoblastic leukemia. Blood 2007;109:674–82. factors. Blood 2009;113:5783–92. 32. Lapidot T, Sirard C, Vormoor J, et alA cell initiating human acute 10. Warren AJ, Colledge WH, Carlton MB, Evans MJ, Smith AJ, Rabbitts myeloid leukaemia after transplantation into SCID mice. Nature TH. The oncogenic cysteine-rich LIM domain protein rbtn2 is essential 1994;367:645–8. for erythroid development. Cell 1994;78:45–57. 33. Mullighan CG, Phillips LA, Su X, et alGenomic analysis of the clonal 11. McCormack MP, Forster A, Drynan L, Pannell R, Rabbitts TH. The origins of relapsed acute lymphoblastic leukemia. Science LMO2 T-cell oncogene is activated via chromosomal translocations 2008;322:1377–80. or retroviral insertion during gene therapy but has no mandatory 34. Jain M, Arvanitis C, Chu K, et alSustained loss of a neoplastic role in normal T-cell development. Mol Cell Biol 2003;23:9003–13. phenotype by brief inactivation of MYC. Science 2002;297:102–4. 12. Wadman IA, Osada H, Grutz GG, et alThe LIM-only protein Lmo2 is a 35. Sharma SV, Settleman J. Oncogene addiction: setting the stage for bridging molecule assembling an erythroid, DNA-binding complex molecularly targeted cancer therapy. Genes Dev 2007;21: which includes the TAL1, E47, GATA-1 and Ldb1/NLI proteins. EMBO 3214–31. J 1997;16:3145–57. 36. Appert A, Nam CH, Lobato N, et alTargeting LMO2 with a peptide 13. Grutz GG, Bucher K, Lavenir I, Larson T, Larson R, Rabbitts TH. The aptamer establishes a necessary function in overt T-cell neoplasia. oncogenic T cell LIM-protein Lmo2 forms part of a DNA-binding Cancer Res 2009;69:4784–90. complex specifically in immature T cells. EMBO J 1998;17:4594–605. 37. Mukhopadhyay M, Teufel A, Yamashita T, et alFunctional ablation of 14. Larson RC, Fisch P, Larson TA, et al. T cell tumours of disparate the mouse Ldb1 gene results in severe patterning defects during phenotype in mice transgenic for Rbtn-2. Oncogene 1994;9:3675–81. gastrulation. Development 2003;130:495–505. 15. Neale GA, Rehg JE, Goorha RM. Ectopic expression of rhombotin-2 38. Nam CH, Lobato MN, Appert A, Drynan LF, Tanaka T, Rabbitts TH. An causes selective expansion of CD4-CD8- lymphocytes in the thymus antibody inhibitor of the LMO2-protein complex blocks its normal and and T-cell tumors in transgenic mice. Blood 1995;86:3060–71. tumorigenic functions. Oncogene 2008;27:4962–8. 16. Aplan PD, Jones CA, Chervinsky DS, et alAn scl gene product lacking 39. Bedford FK, Ashworth A, Enver T, Wiedemann LM. HEX: a novel the transactivation domain induces bony abnormalities and coop- homeobox gene expressed during haematopoiesis and conserved erates with LMO1 to generate T-cell malignancies in transgenic mice. between mouse and human. Nucleic Acids Res 1993;21: EMBO J 1997;16:2408–19. 1245–9. 17. Herblot S, Steff AM, Hugo P, Aplan PD, Hoang T. SCL and LMO1 alter 40. George A, Morse HC3rd, Justice MJ. The homeobox gene Hex thymocyte differentiation: inhibition of E2A-HEB function and pre-T induces T-cell-derived lymphomas when overexpressed in hemato- alpha chain expression. Nat Immunol 2000;1:138–44. poietic precursor cells. Oncogene 2003;22:6764–73. 18. O’Neil J, Billa M, Oikemus S, Kelliher M. The DNA binding activity of 41. Topcu Z, Mack DL, Hromas RA, Borden KL. The promyelocytic TAL-1 is not required to induce leukemia/lymphoma in mice. Onco- leukemia protein PML interacts with the proline-rich homeodomain gene 2001;20:3897–905. protein PRH: a RING may link hematopoiesis and growth control. 19. Wadman I, Li J, Bash RO, et alSpecific in vivo association between the Oncogene 1999;18:7091–100. bHLH and LIM proteins implicated in human T cell leukemia. EMBO J 42. Ito K, Bernardi R, Morotti A, et alPML targeting eradicates quiescent 1994;13:4831–9. leukaemia-initiating cells. Nature 2008;453:1072–8. 20. Larson RC, Lavenir I, Larson TA, et alProtein dimerization between 43. Zhang XW, Yan XJ, Zhou ZR, et alArsenic trioxide controls the fate of Lmo2 (Rbtn2) and Tal1 alters thymocyte development and potentiates the PML-RARalpha oncoprotein by directly binding PML. Science T cell tumorigenesis in transgenic mice. EMBO J 1996;15:1021–7. 2010;328:240–3. 21. O’Neil J, Calvo J, McKenna K, et alActivating Notch1 mutations in 44. O’Neil J, Ventura JJ, Cusson N, Kelliher M. NF-kappaB activation in mouse models of T-ALL. Blood 2006;107:781–5. premalignant mouse tal-1/scl thymocytes and tumors. Blood 22. Lin YW, Nichols RA, Letterio JJ, Aplan PD. Notch1 mutations are 2003;102:2593–6. important for leukemic transformation in murine models of precursor- 45. Chang PY, Draheim K, Kelliher MA, Miyamoto S. NFKB1 is a direct T leukemia/lymphoma. Blood 2006;107:2540–3. target of the TAL1 oncoprotein in human T leukemia cells. Cancer Res 23. Weng AP, Ferrando AA, Lee W, et alActivating mutations of NOTCH1 in 2006;66:6008–13. human T cell acute lymphoblastic leukemia. Science 2004;306:269–71. 46. Kordes U, Krappmann D, Heissmeyer V, Ludwig WD, Scheidereit C. 24. Chervinsky DS, Lam DH, Melman MP, Gross KW, Aplan PD. scid Transcription factor NF-kappaB is constitutively activated in acute Thymocytes with TCRbeta gene rearrangements are targets for the lymphoblastic leukemia cells. Leukemia 2000;14:399–402. oncogenic effect of SCL and LMO1 transgenes. Cancer Res 47. Vilimas T, Mascarenhas J, Palomero T, et alTargeting the NF-kappaB 2001;61:6382–7. signaling pathway in Notch1-induced T-cell leukemia. Nat Med 25. Bain G, Engel I, Robanus Maandag EC, et alE2A deficiency leads to 2007;13:70–7. abnormalities in alphabeta T-cell development and to rapid develop- 48. Waskow C, Paul S, Haller C, Gassmann M, Rodewald HR. Viable c-Kit ment of T-cell lymphomas. Mol Cell Biol 1997;17:4782–91. (W/W) mutants reveal pivotal role for c-kit in the maintenance of 26. O’Neil J, Shank J, Cusson N, Murre C, Kelliher M. TAL1/SCL induces lymphopoiesis. Immunity 2002;17:277–88. leukemia by inhibiting the transcriptional activity of E47/HEB. Cancer 49. Flex E, Petrangeli V, Stella L, et alSomatically acquired JAK1 Cell 2004;5:587–96. mutations in adult acute lymphoblastic leukemia. J Exp Med 27. Haines BB, Ryu CJ, Chang S, et alBlock of T cell development in P53- 2008;205:751–8. deficient mice accelerates development of lymphomas with charac- 50. Lacronique V, Boureux A, Valle VD, et alA TEL-JAK2 fusion protein teristic RAG-dependent cytogenetic alterations. Cancer Cell 2006; with constitutive kinase activity in human leukemia. Science 9:109–20. 1997;278:1309–12.

5622 Clin Cancer Res; 16(23) December 1, 2010 Clinical Cancer Research

Molecular Basis of Lmo2-Induced T-ALL

51. Ciofani M, Zuniga-Pflucker JC. Notch promotes survival of pre-T cells 58. Thompson BJ, Buonamici S, Sulis ML, et alThe SCFFBW7 ubiquitin at the beta-selection checkpoint by regulating cellular metabolism. ligase complex as a tumor suppressor in T cell leukemia. J Exp Med Nat Immunol 2005;6:881–8. 2007;204:1825–35. 52. Maillard I, Tu L, Sambandam A, et alThe requirement for Notch 59. Pui JC, Allman D, Xu L, et alNotch1 expression in early lymphopoiesis signaling at the beta-selection checkpoint in vivo is absolute and in- fluences B versus T lineage determination. Immunity 1999;11:299– independent of the pre-T cell receptor. J Exp Med 2006;203: 308. 2239–45. 60. Mansour MR, Duke V, Foroni L, et alNotch-1 mutations are secondary 53. Sharma VM, Calvo JA, Draheim KM, et alNotch1 contributes to mouse events in some patients with T-cell acute lymphoblastic leukemia. Clin T-cell leukemia by directly inducing the expression of c-myc. Mol Cell Cancer Res 2007;13:6964–9. Biol 2006;26:8022–31. 61. Chiang MY, Xu L, Shestova O, et alLeukemia-associated NOTCH1 54. Weng AP, Millholland JM, Yashiro-Ohtani Y, et alc-Myc is an impor- alleles are weak tumor initiators but accelerate K-ras-initiated leuke- tant direct target of Notch1 in T-cell acute lymphoblastic leukemia/ mia. J Clin Invest 2008;118:3181–94. lymphoma. Genes Dev 2006;20:2096–109. 62. Real PJ, Tosello V, Palomero T, et alGamma-secretase inhibitors 55. Palomero T, Sulis ML, Cortina M, et alMutational loss of PTEN induces reverse glucocorticoid resistance in T cell acute lymphoblastic leu- resistance to NOTCH1 inhibition in T-cell leukemia. Nat Med kemia. Nat Med 2009;15:50–8. 2007;13:1203–10. 63. van Es JH, van Gijn ME, Riccio O, et alNotch/gamma-secretase 56. Gonzalez-Garcia S, Garcia-Peydro M, Martin-Gayo E, et alCSL- inhibition turns proliferative cells in intestinal crypts and adenomas MAML-dependent Notch1 signaling controls T lineage-specific IL- into goblet cells. Nature 2005;435:959–63. 7R{alpha} gene expression in early human thymopoiesis and leuke- 64. Wu Y, Cain-Hom C, Choy L, et alTherapeutic antibody targeting of mia. J Exp Med 2009;206:779–91. individual Notch receptors. Nature 2010;464:1052–7. 57. Tremblay M, Tremblay CS, Herblot S, et alModeling T-cell acute 65. Moellering RE, Cornejo M, Davis TN, et alDirect inhibition of lymphoblastic leukemia induced by the SCL and LMO1 oncogenes. the NOTCH transcription factor complex. Nature 2009;462: Genes Dev 2010;24:1093–105. 182–8.

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The Molecular Basis of Lmo2-Induced T-Cell Acute Lymphoblastic Leukemia

David J. Curtis and Matthew P. McCormack

Clin Cancer Res 2010;16:5618-5623. Published OnlineFirst September 22, 2010.

Updated version Access the most recent version of this article at: doi:10.1158/1078-0432.CCR-10-0440

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