- Email: [email protected]
Old drug—New insights—Better treatment?
Leukemia Research 34 (2010) 1558–1559
Contents lists available at ScienceDirect
Leukemia Research journal homepage: www.elsevier.com/locate/leukres
Guest editorial
Old drug—New insights—Better treatment?
Childhood acute lymphoblastic leukemia (ALL) is the classical example of a drug responsive malignancy. One essential element of successful contemporary multi-agent ALL chemotherapy – which can cure more than 80% of affected children – is the antifolate drug methotrexate (MTX). MTX was approved for the clinical use by the US Food and Drug Administration in 1953. During 50 years, MTX dosage schedules have evolved largely on empirical basis, which resulted in an up to 100-fold range in MTX dosages in different ALL treatment protocols. Currently, most childhood ALL treatment trials use high-dose MTX (HDMTX) infusions with leucovorin rescue during ALL consolidation therapy, low-dose oral MTX treatment during continuation therapy, and intrathecal MTX instillations to treat/prevent CNS disease. The optimal MTX dosage, however, is still discussed [1]. Childhood ALL has been identified to be a heterogeneous disease, with different lineage and genetic subtypes, including rather unfavourable subtypes like BCR-ABL, MLL-rearranged, and hypodiploid (fewer than 45 chromosomes) ALL, and rather favourable genetic subtypes, like TEL-AML1, E2A-PBX1, and hyperdiploid (more than 50 chromosomes) precursor-B (pB)-ALL. There is evidence from genome wide investigations that the biology of ALL cells is more important for accumulation of the polyglutamylated/active MTX metabolites (MTXPGs) in ALL blasts than inherited factors, that for example, influence MTX pharmacokinetics [2]. Yet, little or no distinction had been made for these differences in determining the optimal MTX dosage. Of note, considerable knowledge on MTX pharmacodynamics in ALL cells exists – and outstanding contributions to this topic were and are made by Dr. Evans at the St. Jude Children’s Research Hospital, Memphis, TN. This begun with the identification, that the ability of ALL blast cells to accumulate high levels of the more active polyglutamylated MTX metabolites (MTXPGs), is one important determinant of in vivo MTX cytotoxic effect. Subsequently, three ALL subtypes with low in vivo MTXPG accumulation (T-ALL, TEL-AML1, and E2A-PBX1 ALL) and one subtype with high MTXPG accumulation (hyperdiploid pB-ALL) had been identified [3]. Cellular MTXPG accumulation is the net effect of many processes, including MTX pharmacokinetics and transport of MTX into the target cells via reduced folate carrier (RFC1), formation of MTXPGs via folylpolyglutamate synthetase (FPGS), degradation of MTXPGs to MTX via gamma-glutamyl hydrolase and export of MTX and/or short-chain MTXPGs via certain ATPbinding cassette (ABC) transporters [4]. Several pharmacogenomic models, that may help to explain differences in MTXPG accumulation among major ALL subtypes, have been established. For example, highest expression of RFC1 was found in hyperdiploid
0145-2126/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.leukres.2010.05.033
pB-ALL, the subtype with highest MTXPG accumulation; whereas lowest expression of RFC1 was found in E2A-PBX1 ALL, the subtype with lowest MTXPG accumulation. Potential mechanisms for low MTXPG accumulation in TEL-AML1 ALL include high expression of breast cancer resistance protein (BCRP or ABCG2, an important exporter of MTX and short-chain MTXPGs) and low expression of FPGS. Low MTXPG accumulation in T-ALL has been attributed to low FPGS expression and high expression of the major MTX exporter ABCC1 [3]. In this issue of Leukemia Research Leclerc et al. [6] provide an additional model that may help to further understand the mechanisms of low MTXPG accumulation in TEL-AML1 ALL (and E2A-PBX1 ALL). First, they analyzed mRNA expression of seven selected MTX/folate pathway genes via real-time RT-PCR in primary leukemia cell samples from 109 children with pB-ALL and found low expression of FPGS mRNA in TEL-AML1 and E2A-PBX1 positive ALL cells. Subsequently, they transfected ALL cell lines with TEL-AML1 and E2A-PBX1 vectors; and the transfected cells had decreased FPGS mRNA levels compared to the controls. They then investigated mechanism on how TEL-AML1 expression may influence cellular FPGS mRNA levels. TEL and AML1 are both transcription factors with an important role in hematopoiesis. TEL is one of the few ETS transcription factor family genes known to be associated with human malignancies, and the only one of them with transcriptional repressor activity. AML1 encodes a transcription factor that is highly expressed only in cells of the hematopoietic system. AML1 is not only essential for the ontogenetic formation of the hematopoietic system but it is also a critical factor for sustained hematopoiesis. It activates transcription to high levels when transfected with tissue-specific factors and thus regulates cellular proliferation and differentiation. Overexpression of the AML1 is oncogenic in cell culture systems and in mice. Despite the advances in understanding the function of TEL and AML1 the full spectrum of their targets and the consequences from TEL-AML1 fusion gene formation are not well understood. Leclerc et al. [6] used immuno-precipitation analysis to explore the role of important transcription factors in the regulation of FPGS expression in TEL-AML1 ALL, and showed that AML1, HDAC1 and mSin3A can directly bind to the FPGS promoter region. In additional experiments they showed that FPGS expression is regulated during the cell cycle and is dependent on acetylation as it changes after use of actylation inhibitors. Finally they demonstrated that cell cycle dependent proteins such as E2F1 and Rb bind to the FPGS promotor during cell cycle. Their approach has shown the involvement of a suppressor complex in the regulation of FPGS promoter that might include AML1, TEL-AML1 or both. Leclerc el al. [6] put forward a
Guest editorial / Leukemia Research 34 (2010) 1558–1559
valid model with new perspectives for further research to get to the bottom of this important mechanism. The ultimate question in this context, however, is which MTX dose is optimal to treat children with TEL-AML1 ALL, and do higher doses of MTX help to overcome the putative MTX resistance mechanism of low MTXPG accumulation in this unique subtype? TEL-AML1 ALL has a favourable prognosis, but relapses are reported to occur in 10–20% of patients, depending on the type of treatment protocol. The Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Muenster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000) trial has used identical treatment schedules for TEL-AML1 ALL, except for MTX doses during consolidation therapy: 2 g/m2 infused over 24 hrs in AIEOP versus 5 g/m2 in BFM; [5] and outcome data from this trial might help to resolve this issue in part. Results from international clinical trials and further insights in to the mechanisms of differences in MTX disposition and effects in ALL blast cells and normal host cells will help to finetune MTX therapy in children with ALL; thereby improving outcome in this heterogeneous disease, which is still amongst the leading causes of death from disease in children aged one to 15 years. Conflict of interest statement C.D. and L.K. have no conflict of interest. Acknowledgement None. Contributions. C.D. and L.K. have written this manuscript.
1559
References [1] Cheok MH, Evans WE, Kager L. High-dose methotrexate: the rationale. J Pediatr Hematol Oncol 2009;31(3):224–5. [2] French D, Yang W, Cheng C, Raimondi SC, Mullighan CG, Downing JR, et al. Acquired variation outweighs inherited variation in whole genome analysis of methotrexate polyglutamate accumulation in leukemia. Blood 2009;113(19):4512–20. [3] Kager L, Cheok M, Yang W, Zaza G, Cheng Q, Panetta JC, et al. Folate pathway gene expression differs in subtypes of acute lymphoblastic leukemia and influences methotrexate pharmacodynamics. J Clin Invest 2005;115(1):110–7. [4] Fotoohi AK, Albertioni F. Mechanisms of antifolate resistance and methotrexate efficacy in leukemia cells. Leuk Lymphoma 2008;49(3):410–26. [5] Conter V, Bartram CR, Valsecchi MG, Schrauder A, Panzer-Grumayer R, Moricke A, et al. Molecular response to treatment redefines all prognostic factors in children and adolescents with B-cell precursor acute lymphoblastic leukemia: results in 3184 patients of the AIEOP-BFM ALL 2000 study. Blood 2010;115(16):3206–14. [6] Leclerc GJ, Sanderson C, Hunger S, Devidas M, Barredo JC. Folylpolyglutamate Synthetase gene transcription is regulated by a multiprotein complex that binds the TEL–AML1 fusion in acute lymphoblastic leukemia. Leuk Res 2010;34(12):1601–9.
Christopher Diakos Leo Kager ∗ Department of Hematology and Oncology, St. Anna Children’s Hospital, Kinderspitalgasse 6, A-1090 Vienna, Austria ∗ Corresponding
author. Tel.: +43 1 40170 1250; fax: +43 1 40170 7000. E-mail address: [email protected] (L. Kager) 26 May 2010 Available online 1 July 2010
Contents lists available at ScienceDirect
Leukemia Research journal homepage: www.elsevier.com/locate/leukres
Guest editorial
Old drug—New insights—Better treatment?
Childhood acute lymphoblastic leukemia (ALL) is the classical example of a drug responsive malignancy. One essential element of successful contemporary multi-agent ALL chemotherapy – which can cure more than 80% of affected children – is the antifolate drug methotrexate (MTX). MTX was approved for the clinical use by the US Food and Drug Administration in 1953. During 50 years, MTX dosage schedules have evolved largely on empirical basis, which resulted in an up to 100-fold range in MTX dosages in different ALL treatment protocols. Currently, most childhood ALL treatment trials use high-dose MTX (HDMTX) infusions with leucovorin rescue during ALL consolidation therapy, low-dose oral MTX treatment during continuation therapy, and intrathecal MTX instillations to treat/prevent CNS disease. The optimal MTX dosage, however, is still discussed [1]. Childhood ALL has been identified to be a heterogeneous disease, with different lineage and genetic subtypes, including rather unfavourable subtypes like BCR-ABL, MLL-rearranged, and hypodiploid (fewer than 45 chromosomes) ALL, and rather favourable genetic subtypes, like TEL-AML1, E2A-PBX1, and hyperdiploid (more than 50 chromosomes) precursor-B (pB)-ALL. There is evidence from genome wide investigations that the biology of ALL cells is more important for accumulation of the polyglutamylated/active MTX metabolites (MTXPGs) in ALL blasts than inherited factors, that for example, influence MTX pharmacokinetics [2]. Yet, little or no distinction had been made for these differences in determining the optimal MTX dosage. Of note, considerable knowledge on MTX pharmacodynamics in ALL cells exists – and outstanding contributions to this topic were and are made by Dr. Evans at the St. Jude Children’s Research Hospital, Memphis, TN. This begun with the identification, that the ability of ALL blast cells to accumulate high levels of the more active polyglutamylated MTX metabolites (MTXPGs), is one important determinant of in vivo MTX cytotoxic effect. Subsequently, three ALL subtypes with low in vivo MTXPG accumulation (T-ALL, TEL-AML1, and E2A-PBX1 ALL) and one subtype with high MTXPG accumulation (hyperdiploid pB-ALL) had been identified [3]. Cellular MTXPG accumulation is the net effect of many processes, including MTX pharmacokinetics and transport of MTX into the target cells via reduced folate carrier (RFC1), formation of MTXPGs via folylpolyglutamate synthetase (FPGS), degradation of MTXPGs to MTX via gamma-glutamyl hydrolase and export of MTX and/or short-chain MTXPGs via certain ATPbinding cassette (ABC) transporters [4]. Several pharmacogenomic models, that may help to explain differences in MTXPG accumulation among major ALL subtypes, have been established. For example, highest expression of RFC1 was found in hyperdiploid
0145-2126/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.leukres.2010.05.033
pB-ALL, the subtype with highest MTXPG accumulation; whereas lowest expression of RFC1 was found in E2A-PBX1 ALL, the subtype with lowest MTXPG accumulation. Potential mechanisms for low MTXPG accumulation in TEL-AML1 ALL include high expression of breast cancer resistance protein (BCRP or ABCG2, an important exporter of MTX and short-chain MTXPGs) and low expression of FPGS. Low MTXPG accumulation in T-ALL has been attributed to low FPGS expression and high expression of the major MTX exporter ABCC1 [3]. In this issue of Leukemia Research Leclerc et al. [6] provide an additional model that may help to further understand the mechanisms of low MTXPG accumulation in TEL-AML1 ALL (and E2A-PBX1 ALL). First, they analyzed mRNA expression of seven selected MTX/folate pathway genes via real-time RT-PCR in primary leukemia cell samples from 109 children with pB-ALL and found low expression of FPGS mRNA in TEL-AML1 and E2A-PBX1 positive ALL cells. Subsequently, they transfected ALL cell lines with TEL-AML1 and E2A-PBX1 vectors; and the transfected cells had decreased FPGS mRNA levels compared to the controls. They then investigated mechanism on how TEL-AML1 expression may influence cellular FPGS mRNA levels. TEL and AML1 are both transcription factors with an important role in hematopoiesis. TEL is one of the few ETS transcription factor family genes known to be associated with human malignancies, and the only one of them with transcriptional repressor activity. AML1 encodes a transcription factor that is highly expressed only in cells of the hematopoietic system. AML1 is not only essential for the ontogenetic formation of the hematopoietic system but it is also a critical factor for sustained hematopoiesis. It activates transcription to high levels when transfected with tissue-specific factors and thus regulates cellular proliferation and differentiation. Overexpression of the AML1 is oncogenic in cell culture systems and in mice. Despite the advances in understanding the function of TEL and AML1 the full spectrum of their targets and the consequences from TEL-AML1 fusion gene formation are not well understood. Leclerc et al. [6] used immuno-precipitation analysis to explore the role of important transcription factors in the regulation of FPGS expression in TEL-AML1 ALL, and showed that AML1, HDAC1 and mSin3A can directly bind to the FPGS promoter region. In additional experiments they showed that FPGS expression is regulated during the cell cycle and is dependent on acetylation as it changes after use of actylation inhibitors. Finally they demonstrated that cell cycle dependent proteins such as E2F1 and Rb bind to the FPGS promotor during cell cycle. Their approach has shown the involvement of a suppressor complex in the regulation of FPGS promoter that might include AML1, TEL-AML1 or both. Leclerc el al. [6] put forward a
Guest editorial / Leukemia Research 34 (2010) 1558–1559
valid model with new perspectives for further research to get to the bottom of this important mechanism. The ultimate question in this context, however, is which MTX dose is optimal to treat children with TEL-AML1 ALL, and do higher doses of MTX help to overcome the putative MTX resistance mechanism of low MTXPG accumulation in this unique subtype? TEL-AML1 ALL has a favourable prognosis, but relapses are reported to occur in 10–20% of patients, depending on the type of treatment protocol. The Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Muenster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000) trial has used identical treatment schedules for TEL-AML1 ALL, except for MTX doses during consolidation therapy: 2 g/m2 infused over 24 hrs in AIEOP versus 5 g/m2 in BFM; [5] and outcome data from this trial might help to resolve this issue in part. Results from international clinical trials and further insights in to the mechanisms of differences in MTX disposition and effects in ALL blast cells and normal host cells will help to finetune MTX therapy in children with ALL; thereby improving outcome in this heterogeneous disease, which is still amongst the leading causes of death from disease in children aged one to 15 years. Conflict of interest statement C.D. and L.K. have no conflict of interest. Acknowledgement None. Contributions. C.D. and L.K. have written this manuscript.
1559
References [1] Cheok MH, Evans WE, Kager L. High-dose methotrexate: the rationale. J Pediatr Hematol Oncol 2009;31(3):224–5. [2] French D, Yang W, Cheng C, Raimondi SC, Mullighan CG, Downing JR, et al. Acquired variation outweighs inherited variation in whole genome analysis of methotrexate polyglutamate accumulation in leukemia. Blood 2009;113(19):4512–20. [3] Kager L, Cheok M, Yang W, Zaza G, Cheng Q, Panetta JC, et al. Folate pathway gene expression differs in subtypes of acute lymphoblastic leukemia and influences methotrexate pharmacodynamics. J Clin Invest 2005;115(1):110–7. [4] Fotoohi AK, Albertioni F. Mechanisms of antifolate resistance and methotrexate efficacy in leukemia cells. Leuk Lymphoma 2008;49(3):410–26. [5] Conter V, Bartram CR, Valsecchi MG, Schrauder A, Panzer-Grumayer R, Moricke A, et al. Molecular response to treatment redefines all prognostic factors in children and adolescents with B-cell precursor acute lymphoblastic leukemia: results in 3184 patients of the AIEOP-BFM ALL 2000 study. Blood 2010;115(16):3206–14. [6] Leclerc GJ, Sanderson C, Hunger S, Devidas M, Barredo JC. Folylpolyglutamate Synthetase gene transcription is regulated by a multiprotein complex that binds the TEL–AML1 fusion in acute lymphoblastic leukemia. Leuk Res 2010;34(12):1601–9.
Christopher Diakos Leo Kager ∗ Department of Hematology and Oncology, St. Anna Children’s Hospital, Kinderspitalgasse 6, A-1090 Vienna, Austria ∗ Corresponding
author. Tel.: +43 1 40170 1250; fax: +43 1 40170 7000. E-mail address: [email protected] (L. Kager) 26 May 2010 Available online 1 July 2010