- Email: [email protected]
JAK2-V617F mutation in a patient with Philadelphia-chromosome-positive chronic myeloid leukaemia
Case Report
JAK2-V617F mutation in a patient with Philadelphiachromosome-positive chronic myeloid leukaemia Alwin Krämer, Andreas Reiter, Jens Kruth, Philipp Erben, Andreas Hochhaus, Martin Müller, Nicholas C P Cross, Amy V Jones, Anthony D Ho, Manfred Hensel
Department of Internal Medicine V, University of Heidelberg, Heidelberg Germany (Prof A Krämer MD, Prof AD Ho MD, M Hensel MD); Department of Internal Medicine III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany (Prof A Reiter MD, J Kruth MD, P Erben MD, Prof A Hochhaus MD, M Müller MD); Wessex Regional Genetics Laboratory, Salisbury, UK (Prof NCP Cross PhD, AV Jones PhD)
Leucocytes (/nL) and metamyelocytes in peripheral blood (%)
Correspondence to: Prof Alwin Krämer, Clinical Cooperation Unit Molecular Haematology/Oncology, German Cancer Research Centre and Department of Internal Medicine V, University of Heidelberg, 69120 Heidelberg, Germany [email protected]
In July, 2000, a 50-year-old man presented with leukocytosis and splenomegaly (21 cm). Leucocyte concentration was 93×109/L, haemoglobin 150 g/L, and platelets 345×109/L (figure 1). A differential blood count showed 54% neutrophils, 2% lymphocytes, 13% myelocytes, 7% metamyelocytes, 2% promyelocytes, 1% blasts, and 7% basophils. Lactate dehydrogenase (LDH) concentration was increased at 484 U/L. 17 months previously, the blood count had been in the normal range. Bonemarrow aspiration was dry and bone-marrow biopsy showed marked myeloid hyperplasia, increased megakaryopoiesis, and the beginning of fibrosis. Cytogenetic analysis revealed a chromosome translocation (t[9;22][q34;q11]) in all ten metaphases examined. Expression of B3A2 BCR-ABL mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in peripheral-blood leucocytes. A diagnosis of BCR-ABLpositive chronic myeloid leukaemia (CML) was made and treatment with hydroxycarbamide was started, resulting in rapid normalisation of peripheral-blood leucocytes. After 3 weeks, treatment was changed to imatinib (400 mg/day). Within 1 month, a complete haematological response was recorded. Cytogenetic and interphase fluorescence in-situ hybridisation at 6 months after the start of imatinib showed a complete cytogenetic response. The BCR-ABL:ABL ratio dropped from 90% at diagnosis to 0·021% after 6 months. 16 months after starting imatinib, BCR-ABL transcripts became undetectable by real-time and nested RT-PCR
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Lancet Oncol 2007; 8: 658–60
0
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Figure 1: Course of peripheral-blood parameters during treatment with imatinib in a patient with BCR-ABLpositive chronic myeloid leukaemia
658
(figure 2).1 Repeated cytogenetic and quantitative BCRABL RT-PCR analyses showed a continuing complete cytogenetic and molecular response, as shown in figure 2. However, in 2003, an unexpected decrease in platelet count and a continuous increase in serum LDH concentration was noted (figure 1). In 2004, immature myeloid cells began to appear in the peripheral blood and a bone-marrow biopsy in May, 2004, revealed advanced fibrosis. In 2005, leucocyte concentration continually rose above the upper normal limit. The spleen was enlarged to 18 cm. Cytogenetic analysis identified a normal karyotype and BCR-ABL transcripts were still undetectable. Therefore, a JAK2-V617F mutational analysis was done, which highlighted the presence of a heterozygous JAK2-V617F mutation, leading to the diagnosis of idiopathic myelofibrosis (IMF) according to the WHO diagnostic criteria. For JAK2 genotyping, DNA was amplified and PCR products were directly sequenced using the PCR primers JAK2-1F (5’-TGCTGAAAGTAGGAGAAAGTGCAT-3’) and JAK21R (5’-TCCTACAGTGTTTTCAGTTTCAA-3’). The proportion of mutant JAK2-V617F alleles was quantified using pyrosequencing as described.2 Additionally, the allelic ratio of JAK2-V617F was confirmed by a newly established quantitative real-time (RQ) PCR assay based on LightCycler technology (Roche Diagnostics, Mannheim, Germany). DNA was extracted from peripheral blood leucocytes after red-cell lysis by standard procedures. Total JAK2 was established using a forward primer, 5’-AGGCTACATCCATCTACCTCAG-3’, a reverse primer, 5’-CCTAGCTGTGATCCTGAAACTG-3’ (MWG Biotech, Ebersberg, Germany), and the hybridisation probes 5’-ACAGGCTTGACCCATAACACCTGAAATA GAG-3’ and 5’-GAGTGGTACAGGAATCATGAATAATGCCAGTCA-3’ (Tib Molbiol, Berlin, Germany). Mutant JAK2-V617F alleles were quantified using the same forward primer and probes in combination with a mutation-specific reverse primer, 5’-TTTTACTTACTCTCGTCTCCACAGAA-3’ (MWG Biotech, Ebersberg, Germany). The allele copy number was identified using a plasmid standard curve. JAK2-V617F positivity was expressed as the ratio between mutant JAK2-V617F and total JAK2. Dilution experiments showed an assay sensitivity of 1%. Retrospective analysis of frozen samples of peripheralblood leucocytes showed that the JAK2-V617F mutation was already present at initial diagnosis of BCR-ABLpositive CML (figure 3). Consistent with the presence of an acquired somatic mutation, the JAK2-V617F mutation was absent in purified CD3+ T lymphocytes (figure 3) http://oncology.thelancet.com Vol 8 July 2007
Case Report
http://oncology.thelancet.com Vol 8 July 2007
clinical course of the patient could only have been speculated upon. Treatment and response to imatinib might have accelerated the outgrowth of the IMF. Second, our data suggest that in our patient, the JAK2V617F mutation had occurred before the acquisition of the Philadelphia (Ph)-chromosome. Development of a Ph-positive CML has rarely been reported in patients with MPD.15 In the few cases that have been reported, 100 95
BCR-ABL:ABL JAK2/V617F-pyrosequencing JAK2/V617F-PCR
80 75 Percentage of tumour cells
and buccal cells (data not shown). As demonstrated by two independent methods—JAK2-V617F pyrosequencing and PCR—the proportion of the mutant allele stayed roughly constant from diagnosis of CML in July, 2000, to February, 2006 (figure 2). Repeated cytogenetic analysis in May, 2006 again showed a normal karyotype. JAK2 is a tyrosine kinase that has an important role in the signalling pathways of many haemopoietic growthfactor receptors. The single acquired point mutation V617F (1849G>T) in JAK2 occurs in 50–97% of patients with IMF, essential thrombocytosis, and polycythemia vera.2–6 By contrast, the JAK2-V617F mutation has never been identified in a patient with BCR-ABL-positive CML.7 This is the first description of a patient, to our knowledge, in whom the BCR-ABL fusion gene and an acquired somatic JAK2-V617F mutation could be detected contemporaneously, with IMF becoming clinically relevant after successful treatment of CML by imatinib. Several conclusions can be drawn from these data. First, bone-marrow fibrosis was not a consequence of progressive CML. Rather, myelofibrosis developed as a second myeloproliferative disorder (MPD) during complete cytogenetic and molecular remission of CML. Although the BCR-ABL fusion gene might represent the initiating lesion in most cases of CML, clinical manifestations of the disease can be variable. Specifically, bone-marrow fibrosis can occur, sometimes varying greatly during the course of the disease, and has been used to categorise patients into different groups with distinctive survival caracteristics.8 Fibrogenesis in MPD is generally assumed to be mediated by the abnormal release of transforming growth factor-β and plateletderived growth factor (PDGF). Imatinib, a selective inhibitor of ABL, KIT, and PDGF receptor tyrosine kinases, and which is not active against JAK2, has been seen to reduce the content of bone-marrow fibre in patients with CML.9 Regression of myelofibrosis by imatinib is thought to be caused either by a direct PDGFantagonistic effect or by normalisation of megakaryopoiesis from which abnormal concentrations of PDGF are released. However, expression of JAK2-V617F in murine haematopoietic cells leads to MPD associated with myelofibrosis.10 Moreover, expression of a BCR-JAK2 fusion gene has been described in a patient with atypical CML and bone-marrow fibrosis,11 and the PCM1-JAK2 fusion is associated with the development of myelofibrosis in patients with chronic and acute leukaemias.12 These findings suggest that JAK2-V617F contributes to the development of myelofibrosis in MPD,3,10 and might have been responsible for the induction of myelofibrosis in our patient which, consequently, was independent of the presence of BCR-ABL and did not respond to imatinib treatment. This assumption is supported by the absence of clinical and molecular responses of patients with IMF and polycythemia vera treated with imatinib.13,14 If treatment with imatinib had not been initiated, the
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Time (month/year)
Figure 2: BCR-ABL:ABL ratio and JAK2-V617F allele frequency during treatment with imatinib in a patient with BCR-ABL-positive chronic myeloid leukaemia Parameters established by pyrosequencing and PCR. A
B A
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Figure 3: Presence of the JAK2-V617F mutation in a patient with BCR-ABL-positive chronic myeloid leukaemia A heterozygous G→T transversion in JAK2 (arrows) is present in DNA from leucocytes (A,C,D) at different time points (A: July, 2000; C: November, 2001; D: May, 2006) during the course of the disease, but absent in T cells (B; May, 2006), consistent with the existence of an acquired somatic origin of the mutation.
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Case Report
there is a debate as to whether MPD and CML arise separately from each other, representing independent transformation of a normal stem cell, or whether the Phchromosome arises in a stem cell that was part of the MPD clone. In our patient, JAK2-V617F was detectable at an almost constant allele frequency in all peripheralblood samples examined (figure 2). The most likely explanation for this finding is the presence of a heterozygous JAK2-V617F mutation in most of the peripheral-blood leucocytes, implicating the simultaneous presence of the BCR-ABL fusion gene and the JAK2V617F mutation in white blood cells. Because BCR-ABL became undetectable after treatment with imatinib, but the JAK2-V617F allele frequency remained virtually unchanged, the conclusion can be drawn that the Phchromosome was acquired from a haematopoietic cell carrying the JAK2-V617F mutation. Several findings suggest that MPD are caused by a mutation in an, as yet, unknown gene that precedes the acquisition of either a JAK2-V617F mutation or a BCR-ABL fusion gene.3,16 The most reasonable explanation for the findings presented here is that BCR-ABL can, in rare cases, occur on the background of the JAK2-V617F mutation, possibly augmented by an elusive initial mutation predisposing to the acquisition of both a JAK2-V617F mutation and a BCR-ABL translocation. Conflicts of interest The authors declared no conflicts of interest. Acknowledgments We thank Brigitte Schreiter for excellent technical assistance. This work was supported by a grant from the German José Carreras Leukemia Foundation (DJCLS R 06/04). References 1 Emig M, Saussele S, Wittor H, et al. Accurate and rapid analysis of residual disease in patients with CML using specific fluorescent hybridization probes for real time quantitative RT-PCR. Leukemia 1999; 13: 1825–32. 2 Jones AV, Kreil S, Zoi K, et al. Widespread occurrence of the JAK2 V617F mutation in chronic myeloproliferative disorders. Blood 2005; 106: 2162–68.
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Kralovics R, Passamonti F, Buser AS, et al. A gain-of-function mutation of JAK2 in myeloproliferative disorders. N Engl J Med 2005; 352: 1779–90. Baxter EJ, Scott LM, Campbell PJ, et al. Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet 2005; 365: 1054–61. James C, Ugo V, Le Couedic JP, et al. A unique clonal JAK2 mutation leading to constitutive signalling causes polycythaemia vera. Nature 2005; 434: 1144–48. Levine RL, Wadleigh M, Cools J, et al. Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis. Cancer Cell 2005; 7: 387–97. Jelinek J, Oki Y, Gharibyan V, et al. JAK2 mutation 1849G>T is rare in acute leukemias but can be found in CMML, Philadelphia chromosome-negative CML, and megakaryocytic leukemia. Blood 2005; 106: 3370–73. Kvasnicka HM, Thiele J, Schmitt-Graeff A, et al. Bone marrow features improve prognostic efficiency in multivariate risk classification of chronic-phase Ph(1+) chronic myelogenous leukemia: a multicenter trial. J Clin Oncol 2001; 19: 2994–3009. Beham-Schmid C, Apfelbeck U, Sill H, et al. Treatment of chronic myelogenous leukemia with the tyrosine kinase inhibitor STI571 results in marked regression of bone marrow fibrosis. Blood 2002; 99: 381–83. Lacout C, Pisani DF, Tulliez M, Moreau Gachelin F, Vainchenker W, Villeval JL. JAK2V617F expression in murine hematopoietic cells leads to MPD mimicking human PV with secondary myelofibrosis. Blood 2006; 108: 1652–60. Griesinger F, Hennig H, Hillmer F, et al. A BCR-JAK2 fusion gene as the result of a t(9;22)(p24;q11.2) translocation in a patient with a clinically typical chronic myeloid leukemia. Genes Chromosomes Cancer 2005; 44: 329–33. Reiter A, Walz C, Watmore A, et al. The t(8;9)(p22;p24) is a recurrent abnormality in chronic and acute leukemia that fuses PCM1 to JAK2. Cancer Res 2005; 65: 2662–67. Tefferi A, Mesa RA, Gray LA, et al. Phase 2 trial of imatinib mesylate in myelofibrosis with myeloid metaplasia. Blood 2002; 99: 3854–56. Jones AV, Silver RT, Waghorn K, et al. Minimal molecular response in polycythemia vera patients treated with imatinib or interferon alpha. Blood 2006; 107: 3339–41. Curtin NJ, Campbell PJ, Green AR. The Philadelphia translocation and pre-existing myeloproliferative disorders. Br J Haematol 2005; 128: 734–36. Kralovics R, Teo SS, Li S, et al. Acquisition of the V617F mutation of JAK2 is a late genetic event in a subset of patients with myeloproliferative disorders. Blood 2006; 108: 1377–80.
http://oncology.thelancet.com Vol 8 July 2007
JAK2-V617F mutation in a patient with Philadelphiachromosome-positive chronic myeloid leukaemia Alwin Krämer, Andreas Reiter, Jens Kruth, Philipp Erben, Andreas Hochhaus, Martin Müller, Nicholas C P Cross, Amy V Jones, Anthony D Ho, Manfred Hensel
Department of Internal Medicine V, University of Heidelberg, Heidelberg Germany (Prof A Krämer MD, Prof AD Ho MD, M Hensel MD); Department of Internal Medicine III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany (Prof A Reiter MD, J Kruth MD, P Erben MD, Prof A Hochhaus MD, M Müller MD); Wessex Regional Genetics Laboratory, Salisbury, UK (Prof NCP Cross PhD, AV Jones PhD)
Leucocytes (/nL) and metamyelocytes in peripheral blood (%)
Correspondence to: Prof Alwin Krämer, Clinical Cooperation Unit Molecular Haematology/Oncology, German Cancer Research Centre and Department of Internal Medicine V, University of Heidelberg, 69120 Heidelberg, Germany [email protected]
In July, 2000, a 50-year-old man presented with leukocytosis and splenomegaly (21 cm). Leucocyte concentration was 93×109/L, haemoglobin 150 g/L, and platelets 345×109/L (figure 1). A differential blood count showed 54% neutrophils, 2% lymphocytes, 13% myelocytes, 7% metamyelocytes, 2% promyelocytes, 1% blasts, and 7% basophils. Lactate dehydrogenase (LDH) concentration was increased at 484 U/L. 17 months previously, the blood count had been in the normal range. Bonemarrow aspiration was dry and bone-marrow biopsy showed marked myeloid hyperplasia, increased megakaryopoiesis, and the beginning of fibrosis. Cytogenetic analysis revealed a chromosome translocation (t[9;22][q34;q11]) in all ten metaphases examined. Expression of B3A2 BCR-ABL mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in peripheral-blood leucocytes. A diagnosis of BCR-ABLpositive chronic myeloid leukaemia (CML) was made and treatment with hydroxycarbamide was started, resulting in rapid normalisation of peripheral-blood leucocytes. After 3 weeks, treatment was changed to imatinib (400 mg/day). Within 1 month, a complete haematological response was recorded. Cytogenetic and interphase fluorescence in-situ hybridisation at 6 months after the start of imatinib showed a complete cytogenetic response. The BCR-ABL:ABL ratio dropped from 90% at diagnosis to 0·021% after 6 months. 16 months after starting imatinib, BCR-ABL transcripts became undetectable by real-time and nested RT-PCR
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Lancet Oncol 2007; 8: 658–60
0
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Time (month/year)
Figure 1: Course of peripheral-blood parameters during treatment with imatinib in a patient with BCR-ABLpositive chronic myeloid leukaemia
658
(figure 2).1 Repeated cytogenetic and quantitative BCRABL RT-PCR analyses showed a continuing complete cytogenetic and molecular response, as shown in figure 2. However, in 2003, an unexpected decrease in platelet count and a continuous increase in serum LDH concentration was noted (figure 1). In 2004, immature myeloid cells began to appear in the peripheral blood and a bone-marrow biopsy in May, 2004, revealed advanced fibrosis. In 2005, leucocyte concentration continually rose above the upper normal limit. The spleen was enlarged to 18 cm. Cytogenetic analysis identified a normal karyotype and BCR-ABL transcripts were still undetectable. Therefore, a JAK2-V617F mutational analysis was done, which highlighted the presence of a heterozygous JAK2-V617F mutation, leading to the diagnosis of idiopathic myelofibrosis (IMF) according to the WHO diagnostic criteria. For JAK2 genotyping, DNA was amplified and PCR products were directly sequenced using the PCR primers JAK2-1F (5’-TGCTGAAAGTAGGAGAAAGTGCAT-3’) and JAK21R (5’-TCCTACAGTGTTTTCAGTTTCAA-3’). The proportion of mutant JAK2-V617F alleles was quantified using pyrosequencing as described.2 Additionally, the allelic ratio of JAK2-V617F was confirmed by a newly established quantitative real-time (RQ) PCR assay based on LightCycler technology (Roche Diagnostics, Mannheim, Germany). DNA was extracted from peripheral blood leucocytes after red-cell lysis by standard procedures. Total JAK2 was established using a forward primer, 5’-AGGCTACATCCATCTACCTCAG-3’, a reverse primer, 5’-CCTAGCTGTGATCCTGAAACTG-3’ (MWG Biotech, Ebersberg, Germany), and the hybridisation probes 5’-ACAGGCTTGACCCATAACACCTGAAATA GAG-3’ and 5’-GAGTGGTACAGGAATCATGAATAATGCCAGTCA-3’ (Tib Molbiol, Berlin, Germany). Mutant JAK2-V617F alleles were quantified using the same forward primer and probes in combination with a mutation-specific reverse primer, 5’-TTTTACTTACTCTCGTCTCCACAGAA-3’ (MWG Biotech, Ebersberg, Germany). The allele copy number was identified using a plasmid standard curve. JAK2-V617F positivity was expressed as the ratio between mutant JAK2-V617F and total JAK2. Dilution experiments showed an assay sensitivity of 1%. Retrospective analysis of frozen samples of peripheralblood leucocytes showed that the JAK2-V617F mutation was already present at initial diagnosis of BCR-ABLpositive CML (figure 3). Consistent with the presence of an acquired somatic mutation, the JAK2-V617F mutation was absent in purified CD3+ T lymphocytes (figure 3) http://oncology.thelancet.com Vol 8 July 2007
Case Report
http://oncology.thelancet.com Vol 8 July 2007
clinical course of the patient could only have been speculated upon. Treatment and response to imatinib might have accelerated the outgrowth of the IMF. Second, our data suggest that in our patient, the JAK2V617F mutation had occurred before the acquisition of the Philadelphia (Ph)-chromosome. Development of a Ph-positive CML has rarely been reported in patients with MPD.15 In the few cases that have been reported, 100 95
BCR-ABL:ABL JAK2/V617F-pyrosequencing JAK2/V617F-PCR
80 75 Percentage of tumour cells
and buccal cells (data not shown). As demonstrated by two independent methods—JAK2-V617F pyrosequencing and PCR—the proportion of the mutant allele stayed roughly constant from diagnosis of CML in July, 2000, to February, 2006 (figure 2). Repeated cytogenetic analysis in May, 2006 again showed a normal karyotype. JAK2 is a tyrosine kinase that has an important role in the signalling pathways of many haemopoietic growthfactor receptors. The single acquired point mutation V617F (1849G>T) in JAK2 occurs in 50–97% of patients with IMF, essential thrombocytosis, and polycythemia vera.2–6 By contrast, the JAK2-V617F mutation has never been identified in a patient with BCR-ABL-positive CML.7 This is the first description of a patient, to our knowledge, in whom the BCR-ABL fusion gene and an acquired somatic JAK2-V617F mutation could be detected contemporaneously, with IMF becoming clinically relevant after successful treatment of CML by imatinib. Several conclusions can be drawn from these data. First, bone-marrow fibrosis was not a consequence of progressive CML. Rather, myelofibrosis developed as a second myeloproliferative disorder (MPD) during complete cytogenetic and molecular remission of CML. Although the BCR-ABL fusion gene might represent the initiating lesion in most cases of CML, clinical manifestations of the disease can be variable. Specifically, bone-marrow fibrosis can occur, sometimes varying greatly during the course of the disease, and has been used to categorise patients into different groups with distinctive survival caracteristics.8 Fibrogenesis in MPD is generally assumed to be mediated by the abnormal release of transforming growth factor-β and plateletderived growth factor (PDGF). Imatinib, a selective inhibitor of ABL, KIT, and PDGF receptor tyrosine kinases, and which is not active against JAK2, has been seen to reduce the content of bone-marrow fibre in patients with CML.9 Regression of myelofibrosis by imatinib is thought to be caused either by a direct PDGFantagonistic effect or by normalisation of megakaryopoiesis from which abnormal concentrations of PDGF are released. However, expression of JAK2-V617F in murine haematopoietic cells leads to MPD associated with myelofibrosis.10 Moreover, expression of a BCR-JAK2 fusion gene has been described in a patient with atypical CML and bone-marrow fibrosis,11 and the PCM1-JAK2 fusion is associated with the development of myelofibrosis in patients with chronic and acute leukaemias.12 These findings suggest that JAK2-V617F contributes to the development of myelofibrosis in MPD,3,10 and might have been responsible for the induction of myelofibrosis in our patient which, consequently, was independent of the presence of BCR-ABL and did not respond to imatinib treatment. This assumption is supported by the absence of clinical and molecular responses of patients with IMF and polycythemia vera treated with imatinib.13,14 If treatment with imatinib had not been initiated, the
60 55
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Time (month/year)
Figure 2: BCR-ABL:ABL ratio and JAK2-V617F allele frequency during treatment with imatinib in a patient with BCR-ABL-positive chronic myeloid leukaemia Parameters established by pyrosequencing and PCR. A
B A
T
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T
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Figure 3: Presence of the JAK2-V617F mutation in a patient with BCR-ABL-positive chronic myeloid leukaemia A heterozygous G→T transversion in JAK2 (arrows) is present in DNA from leucocytes (A,C,D) at different time points (A: July, 2000; C: November, 2001; D: May, 2006) during the course of the disease, but absent in T cells (B; May, 2006), consistent with the existence of an acquired somatic origin of the mutation.
659
Case Report
there is a debate as to whether MPD and CML arise separately from each other, representing independent transformation of a normal stem cell, or whether the Phchromosome arises in a stem cell that was part of the MPD clone. In our patient, JAK2-V617F was detectable at an almost constant allele frequency in all peripheralblood samples examined (figure 2). The most likely explanation for this finding is the presence of a heterozygous JAK2-V617F mutation in most of the peripheral-blood leucocytes, implicating the simultaneous presence of the BCR-ABL fusion gene and the JAK2V617F mutation in white blood cells. Because BCR-ABL became undetectable after treatment with imatinib, but the JAK2-V617F allele frequency remained virtually unchanged, the conclusion can be drawn that the Phchromosome was acquired from a haematopoietic cell carrying the JAK2-V617F mutation. Several findings suggest that MPD are caused by a mutation in an, as yet, unknown gene that precedes the acquisition of either a JAK2-V617F mutation or a BCR-ABL fusion gene.3,16 The most reasonable explanation for the findings presented here is that BCR-ABL can, in rare cases, occur on the background of the JAK2-V617F mutation, possibly augmented by an elusive initial mutation predisposing to the acquisition of both a JAK2-V617F mutation and a BCR-ABL translocation. Conflicts of interest The authors declared no conflicts of interest. Acknowledgments We thank Brigitte Schreiter for excellent technical assistance. This work was supported by a grant from the German José Carreras Leukemia Foundation (DJCLS R 06/04). References 1 Emig M, Saussele S, Wittor H, et al. Accurate and rapid analysis of residual disease in patients with CML using specific fluorescent hybridization probes for real time quantitative RT-PCR. Leukemia 1999; 13: 1825–32. 2 Jones AV, Kreil S, Zoi K, et al. Widespread occurrence of the JAK2 V617F mutation in chronic myeloproliferative disorders. Blood 2005; 106: 2162–68.
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Kralovics R, Passamonti F, Buser AS, et al. A gain-of-function mutation of JAK2 in myeloproliferative disorders. N Engl J Med 2005; 352: 1779–90. Baxter EJ, Scott LM, Campbell PJ, et al. Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders. Lancet 2005; 365: 1054–61. James C, Ugo V, Le Couedic JP, et al. A unique clonal JAK2 mutation leading to constitutive signalling causes polycythaemia vera. Nature 2005; 434: 1144–48. Levine RL, Wadleigh M, Cools J, et al. Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis. Cancer Cell 2005; 7: 387–97. Jelinek J, Oki Y, Gharibyan V, et al. JAK2 mutation 1849G>T is rare in acute leukemias but can be found in CMML, Philadelphia chromosome-negative CML, and megakaryocytic leukemia. Blood 2005; 106: 3370–73. Kvasnicka HM, Thiele J, Schmitt-Graeff A, et al. Bone marrow features improve prognostic efficiency in multivariate risk classification of chronic-phase Ph(1+) chronic myelogenous leukemia: a multicenter trial. J Clin Oncol 2001; 19: 2994–3009. Beham-Schmid C, Apfelbeck U, Sill H, et al. Treatment of chronic myelogenous leukemia with the tyrosine kinase inhibitor STI571 results in marked regression of bone marrow fibrosis. Blood 2002; 99: 381–83. Lacout C, Pisani DF, Tulliez M, Moreau Gachelin F, Vainchenker W, Villeval JL. JAK2V617F expression in murine hematopoietic cells leads to MPD mimicking human PV with secondary myelofibrosis. Blood 2006; 108: 1652–60. Griesinger F, Hennig H, Hillmer F, et al. A BCR-JAK2 fusion gene as the result of a t(9;22)(p24;q11.2) translocation in a patient with a clinically typical chronic myeloid leukemia. Genes Chromosomes Cancer 2005; 44: 329–33. Reiter A, Walz C, Watmore A, et al. The t(8;9)(p22;p24) is a recurrent abnormality in chronic and acute leukemia that fuses PCM1 to JAK2. Cancer Res 2005; 65: 2662–67. Tefferi A, Mesa RA, Gray LA, et al. Phase 2 trial of imatinib mesylate in myelofibrosis with myeloid metaplasia. Blood 2002; 99: 3854–56. Jones AV, Silver RT, Waghorn K, et al. Minimal molecular response in polycythemia vera patients treated with imatinib or interferon alpha. Blood 2006; 107: 3339–41. Curtin NJ, Campbell PJ, Green AR. The Philadelphia translocation and pre-existing myeloproliferative disorders. Br J Haematol 2005; 128: 734–36. Kralovics R, Teo SS, Li S, et al. Acquisition of the V617F mutation of JAK2 is a late genetic event in a subset of patients with myeloproliferative disorders. Blood 2006; 108: 1377–80.
http://oncology.thelancet.com Vol 8 July 2007