- Email: [email protected]
B lymphoblastic leukemia with ETV6 amplification
Cancer Genetics and Cytogenetics 203 (2010) 284e287
Short communication
B lymphoblastic leukemia with ETV6 amplification Hyojin Chaea, Myungshin Kima,*, Jihyang Lima, Yonggoo Kima, Kyungja Hana, Seok Leeb a
Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea b Catholic Blood and Marrow Transplantation Center, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea Received 23 June 2010; received in revised form 2 August 2010; accepted 5 August 2010
Abstract
We presente a case of acute lymphoblastic leukemia caused by ETV6 amplification. Although the cytogenetic result revealed complex karyotype, multicolor fluorescence in situ hybridization and high-resolution multicolor banding supported amplification of a gene on 12p13. Fluorescence in situ hybridization with ETV6 probe confirmed the amplification. ETV6 generally plays as tumorsuppressor gene in leukemia. Their expression is decreased or missed by deletion or mutation. Otherwise, ETV6 protein overexpression was verified in this case by immunohistochemistry. Any translocation or mutation involving ETV6 was not detected. This experience strongly supports the hypothesis that the amplification of ETV6 is a possible mechanism of leukeogenesis as oncogene. Ó 2010 Elsevier Inc. All rights reserved.
1. Introduction Gene amplification is a frequent event in solid tumors, and many oncogenes are known to be activated in this way. Cytogenetically, gene amplification is manifested either intrachromosomally as homogeneous staining regions (hsr) or extrachromosomally as double-minute chromosomes (dmin). But in hematologic malignancies, gene amplification is an uncommon event, with an estimated incidence of 1% in acute myeloid leukemia, and it is even rarer in acute lymphoblastic leukemia, with only a few cases having been reported [1]. Gene amplification in hematologic malignancies usually involves a limited number of genes, with MYC being the most frequent [2]; and MLL is rarely involved [3]. To our knowledge, there has been only one case of myelodysplastic syndrome with excess blasts that reported on ETV6 gene amplification [4]. We report here on a case of ETV6 amplification in the form of hsr in a patient with B lymphoblastic leukemia who presented with a complex karyotype.
2. Case report, methods, and results A 63-year-old woman was admitted to Seoul St. Mary’s Hospital, Seoul, Korea, for myalgia and general weakness. The laboratory findings showed a hemoglobin level of * Corresponding author. Tel.: 82-2-2258-1645; fax: 82-2-2258-1719. E-mail address: [email protected] (M. Kim). 0165-4608/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2010.08.004
7.4 g/dL, a leukocyte count of 11.2 109/L with 30% blast cells, and a platelet count of 8 109/L. Bone marrow examination revealed marked hypercellularity, with most of the nucleated elements being blasts. Immunophenotyping studies with flow cytometry and immunohistochemistry showed that the blasts expressed CD10, CD19, CD20, CD79a, and cytoplasmic CD22. The blasts were negative for CD34, CD33, CD13, CD117, HLA-DR, CD2, CD5, CD7, CD11c, CD64, CD41a, cytoplasmic MPO, and kappa and lambda. The diagnosis of B lymphoblastic leukemia was established according to the World Health Organization classification. G-banding analysis showed that all of the 35 metaphase cells had both numerical and structural abnormalities, including additional material of an unknown origin attached to band 9p24 and 14q32, a hsr on chromosome 12, monosomy 22, trisomy X, and a ring marker chromosome. A representative karyotype is shown in Figure 1a. The application of multicolor fluorescence in situ hybridization (mFISH) using a 24 XCyte Human mFISH Probe Kit (Metasystems, Altussheim, Germany) allowed us to identify the origins of the additional materials and further characterize of the complex karyotype (Fig. 1b). The origins of the additional materials attached to band 9p24 and 14q32 were from chromosome 8. The hsr on chromosome 12 was derived from chromosome 12, and additional material from chromosome 22 was detected at the end of the hsr. The ring marker chromosome was derived from chromosome 22. High-resolution multicolor banding
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287
285
Fig. 1. (a) The representative karyotype demonstrating abnormalities, including the presence of the hsr on chromosome 12. (b) By multicolor fluorescence in situ hybridization analysis, the add(9)(p24), add(12)(p13), and add(14)(q32) was shown to be der(9)t(8;9)(q24;p24),der(12)hsr(12)(p13)t(12;22)(p13;q11.2) and der(14)t(8;14)(q24;q32), and the marker chromosome was shown to be a ring chromosome derived from chromosome 22.
(mBAND) for chromosome 12 was then performed for precise characterization of the hsr using XCyte 12 (Metasystems). mBAND demonstrated the presence of a 12p13 band signal on the hsr (Fig. 2a,b). Considering that ETV6 is located at 12p13 and that hsr represents a form of gene amplification, we performed fluorescence in situ hybridization (FISH) with the ETV6 locus-specific probe (LSI ETV6/ RUNX1 ES dual-color translocation probe; Abbott Molecular, Des Plaines, IL), which demonstrated the amplification of ETV6 in the form of hsr (Fig. 2c). FISH that used MYC (LSI MYC dual-color, break-apart rearrangement probe; Abbott Molecular) and IGH (LSI IGH dual-color, break-apart rearrangement probe; Abbott Molecular) probes was performed to verify the presence of the breakage and formation of the IGH/MYC fusion gene, but the signals were intact. The additional material from chromosome 8 on 9p24 and 14q32 contained MYC signals. Therefore, the modal karyotype was described as
47,XX,þX,der(9)t(8;9)(q24;p24),der(12)hsr(12)(p13)t(12;22) (p13;q11.2),der(14)t(8;14)(q24;q32),r(22)(p13;q13.3). For mutation analysis of ETV6, amplification of all eight exons of ETV6 was performed on genomic DNA using primers and conditions as described previously [5], and sequencing of the forward and reverse strands was performed with the polymerase chain reaction (PCR) primers. Direct sequencing of the coding regions of ETV6 did not detect any mutation or polymorphism. To examine the protein expression level of ETV6 in the patient bone marrow, immunohistochemistry for ETV6 was performed, and normal bone marrow and a case of B lymphoblastic leukemia were analyzed simultaneously as controls. Each bone marrow biopsy specimen in a 4-mm paraffin embedded block was deparaffinized. Endogenous peroxide was blocked with 0.3% hydrogen peroxide for 10 minutes. Antigen was retrieved with heating at 121 C in citrate buffer for 15 minutes. The slides were incubated
Fig. 2. (a) High-resolution multicolor banding (mBAND) for chromosome 12 demonstrating hsr(12)(p13). (b) A normal mBAND for chromosome 12. (c) The signal pattern of the ETV6 probe hybridized to chromosome 12, and this showed ETV6 amplification on hsr. (d) Immunohistochemical demonstration of ETV6 in the patient’s bone marrow biopsy sample, showing the strong nuclear positivity (original magnification, 1,000).
286
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287
with anti-ETV6 antibody (Abcam, Cambridge, MA) as a concentration of 0.5 mg/mL at room temperature for 40 minutes. After visualization with DAB Plus Chromogen and Substrate (Lab Vision, Fremont, CA), hematoxylin counterstaining was performed. The patient’s bone marrow showed strong nuclear staining, whereas the normal bone marrow and the case of B lymphoblastic leukemia used as controls showed negative or trace staining (Fig. 2d). Apart from the hsr, because the additional material attached to band 12p13 was from chromosome 22, we performed nested PCR to detect the ETV6/MN1 fusion transcript corresponding to the previously described t(12;22) (p13;q11e12), even though this translocation has been implicated in myeloid leukemias [6]. The cDNA synthesized by reverse transcription was used and the PCR was performed with the HemaVision kit (DNA Technology, Risskov, Denmark), and ETV6/MN1 fusion transcript was not detected. No other fusion transcripts involving ETV6 as its partners RUNX1, ABL1, and PDGFRB were found. The patient received induction chemotherapy, but she developed pneumonia on day 5 of chemotherapy. Her condition failed to improve. She died 20 days after the diagnosis.
3. Discussion ETV6 is a member of the ets (E-26 transforming specific) family of transcription factors, and it is expressed in hematopoietic tissues and it contributes to fetal hematopoiesis. ETV6 is also required for maintaining a normal pool of lymphoid progenitors in the bone marrow, and it regulates hematopoietic stem-cell survival [7,8]. ETV6 plays pivotal roles as a tumor-suppressor gene in the leukemogenesis of various types of leukemia, not only through forming fusion genes with about 40 partner genes, but also through deletions, point mutations, and possible alterations at the promoter level [9]. ETV6 fusion partners can be grouped as tyrosine kinases, transcription factors, and unproductive fusions. ABL1 (9q34) and JAK2 (9p24) are included in tyrosine kinases associated with acute lymphoblastic leukemia. RUNX1 (21q22) and PAX5 (9q11) are frequent fusion partners as transcription factors found in acute lymphoblastic leukemia. ETV6/RUNX1 is the most common recurrent genetic finding in pediatric acute lymphoblastic leukemia. The ETV6/RUNX1 protein acts as an aberrant transcription factor, and it represses or disrupts the regulation of the RUNX1 target genes and/or it abrogates the mitotic checkpoint function [10,11]. In a large number of ETV6/RUNX1 cases, the second ETV6 allele shows complete or partial deletion. It suggests that this event may be an important secondary event for leukemogenic transformation through the complete loss of normal ETV6 function. The loss of the wild-type ETV6 expression was also found, even in the cases whose second ETV6 allele was present [12]. Moreover, mutations and
a deficient ETV6 protein expression have been demonstrated in some acute myeloid leukemia cases [13]. Therefore, the number and variety of ETV6 translocations, not resulting in a fusion protein, together with loss of ETV6 by deletion and heterozygous or homozygous mutations, makes a mutually supportive and compelling case for loss and haploinsufficiency of ETV6 as a leukemogenic step in acute myeloid leukemia [5]. But amplification of ETV6 as a possible mechanism of leukemogenesis has only been reported in one case of with myelodysplastic syndrome [4]. In our case, the hsr was comprised solely of chromosome 12, as evidenced by the mFISH results, and specifically the results of the band 12p13 material as proven by mBAND. FISH confirmed ETV6 amplification. Neither fusion genes involving ETV6 nor mutation of ETV6 was detected. Markedly increased ETV6 expression was demonstrated. This thus provides further evidence that the tumor-suppressor function of ETV6 was not relevant in the leukemogenesis of the present case. The present case strongly supports the hypothesis that the amplification of ETV6 by gene dosage effect is a possible mechanism of leukemogenesis in certain leukemias. This characteristic function resembles WT1, which works similarly in other forms of leukemias. WT1 encodes a transcription factor and functions as a tumor suppressor in some forms of acute myeloid leukemia. Alternatively, WT1 acts as an oncogene that is overexpressed in some leukemias and is associated with a poor prognosis [14]. Although ETV6 amplification is extremely rare, our present case substantiates the hypothesis that ETV6 amplification could possibly explain a new mechanism of leukemogenesis. A complete understanding of the oncogenic activity of ETV6 would shed further light on the mechanisms that dictate ETV6 overexpression.
References [1] Murray JC, Poplack DG, Mahoney DH Jr, Gresik MV, Harrison WR, Cooley LD. Detection of double minute chromosomes in a child with acute lymphoblastic leukemia. Cancer Genet Cytogenet 1998;101: 138e42. [2] Crossen PE, Savage LM, Heaton DC, Morrison MJ. Characterization of the c-myc amplicon in a case of acute myeloid leukemia with double minute chromosomes. Cancer Genet Cytogenet 1999;112:144e8. [3] Avet-Loiseau H, Godon C, Li JY, Daviet A, Mellerin MP, Talmant P, et al. Amplification of the 11q23 region in acute myeloid leukemia. Genes Chromosome Cancer 1999;26:166e70. [4] Mauvieux L, Helia C, Perrusson N, Lioure B, Sorel N, Brizard F, et al. ETV6 (TEL) gene amplification in a myelodysplastic syndrome with excess of blasts. Leukemia 2004;18:1436e8. [5] Silva FP, Morolli B, Storlazzi CT, Xagaria A, Impera L, Klein B, et al. ETV6 mutations and loss in AML-M0. Leukemia 2008;22:1639e43. [6] Buijs A, van Rompaey L, Molijn AC, Davis JN, Vertegaal AC, Potter MD, et al. The MN1-TEL fusion protein, encoded by the translocation (12;22) (p13;q11) in myeloid leukemia, is a transcription factor with transforming activity. Mol Cell Biol 2000;20:9281e93. [7] Wang LC, Swat W, Fujiwara Y, Davidson L, Visvader J, Kuo F, et al. The TEL/ETV6 gene is required specifically for hematopoiesis in the bone marrow. Genes Dev 1998;12:2392e402.
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287 [8] Hock H, Meade E, Medeiros S, Schindler JW, Valk PJ, Fujiwara Y, et al. Tel/Etv6 is an essential and selective regulator of adult hematopoietic stem cell survival. Genes Dev 2004;18:2336e41. [9] Bohlander SK. ETV6: a versatile player in leukemogenesis. Semin Cancer Biol 2005;15:162e74. [10] Pui C, Relling MV, Downing JR. Acute lymphoblastic leukemia. N Engl J Med 2004;350:1535e48. [11] Krapf G, Kaindl U, Kilbey A, Fuka G, Inthal A, Joas R, et al. ETV6/ RUNX1 abrogates mitotic checkpoint function and targets its key player MDA2L1. Oncogene 2010;29:3307e12.
287
[12] Patel N, Goff LK, Clark T, Ford AM, Foot N, Lillington D, et al. Expression profile of wild-type ETV6 in childhood acute leukaemia. Br J Haematol 2003;122:94e8. [13] Barjesteh van Waalwijk van Doorn-Khosrovani S, Spensberger D, de Knegt Y, Tang M, Lo¨wenberg B, Delwel R. Somatic heterozygous mutations in ETV6 (TEL) and frequent absence of ETV6 protein in acute myeloid leukemia. Oncogene 2005;24: 4129e47. [14] Yang L, Han Y, Saurez Saiz F, Minden MD. A tumor suppressor and oncogene: the WT1 story. Leukemia 2007;21:868e76.
Short communication
B lymphoblastic leukemia with ETV6 amplification Hyojin Chaea, Myungshin Kima,*, Jihyang Lima, Yonggoo Kima, Kyungja Hana, Seok Leeb a
Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea b Catholic Blood and Marrow Transplantation Center, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul, 137-701, Korea Received 23 June 2010; received in revised form 2 August 2010; accepted 5 August 2010
Abstract
We presente a case of acute lymphoblastic leukemia caused by ETV6 amplification. Although the cytogenetic result revealed complex karyotype, multicolor fluorescence in situ hybridization and high-resolution multicolor banding supported amplification of a gene on 12p13. Fluorescence in situ hybridization with ETV6 probe confirmed the amplification. ETV6 generally plays as tumorsuppressor gene in leukemia. Their expression is decreased or missed by deletion or mutation. Otherwise, ETV6 protein overexpression was verified in this case by immunohistochemistry. Any translocation or mutation involving ETV6 was not detected. This experience strongly supports the hypothesis that the amplification of ETV6 is a possible mechanism of leukeogenesis as oncogene. Ó 2010 Elsevier Inc. All rights reserved.
1. Introduction Gene amplification is a frequent event in solid tumors, and many oncogenes are known to be activated in this way. Cytogenetically, gene amplification is manifested either intrachromosomally as homogeneous staining regions (hsr) or extrachromosomally as double-minute chromosomes (dmin). But in hematologic malignancies, gene amplification is an uncommon event, with an estimated incidence of 1% in acute myeloid leukemia, and it is even rarer in acute lymphoblastic leukemia, with only a few cases having been reported [1]. Gene amplification in hematologic malignancies usually involves a limited number of genes, with MYC being the most frequent [2]; and MLL is rarely involved [3]. To our knowledge, there has been only one case of myelodysplastic syndrome with excess blasts that reported on ETV6 gene amplification [4]. We report here on a case of ETV6 amplification in the form of hsr in a patient with B lymphoblastic leukemia who presented with a complex karyotype.
2. Case report, methods, and results A 63-year-old woman was admitted to Seoul St. Mary’s Hospital, Seoul, Korea, for myalgia and general weakness. The laboratory findings showed a hemoglobin level of * Corresponding author. Tel.: 82-2-2258-1645; fax: 82-2-2258-1719. E-mail address: [email protected] (M. Kim). 0165-4608/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2010.08.004
7.4 g/dL, a leukocyte count of 11.2 109/L with 30% blast cells, and a platelet count of 8 109/L. Bone marrow examination revealed marked hypercellularity, with most of the nucleated elements being blasts. Immunophenotyping studies with flow cytometry and immunohistochemistry showed that the blasts expressed CD10, CD19, CD20, CD79a, and cytoplasmic CD22. The blasts were negative for CD34, CD33, CD13, CD117, HLA-DR, CD2, CD5, CD7, CD11c, CD64, CD41a, cytoplasmic MPO, and kappa and lambda. The diagnosis of B lymphoblastic leukemia was established according to the World Health Organization classification. G-banding analysis showed that all of the 35 metaphase cells had both numerical and structural abnormalities, including additional material of an unknown origin attached to band 9p24 and 14q32, a hsr on chromosome 12, monosomy 22, trisomy X, and a ring marker chromosome. A representative karyotype is shown in Figure 1a. The application of multicolor fluorescence in situ hybridization (mFISH) using a 24 XCyte Human mFISH Probe Kit (Metasystems, Altussheim, Germany) allowed us to identify the origins of the additional materials and further characterize of the complex karyotype (Fig. 1b). The origins of the additional materials attached to band 9p24 and 14q32 were from chromosome 8. The hsr on chromosome 12 was derived from chromosome 12, and additional material from chromosome 22 was detected at the end of the hsr. The ring marker chromosome was derived from chromosome 22. High-resolution multicolor banding
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287
285
Fig. 1. (a) The representative karyotype demonstrating abnormalities, including the presence of the hsr on chromosome 12. (b) By multicolor fluorescence in situ hybridization analysis, the add(9)(p24), add(12)(p13), and add(14)(q32) was shown to be der(9)t(8;9)(q24;p24),der(12)hsr(12)(p13)t(12;22)(p13;q11.2) and der(14)t(8;14)(q24;q32), and the marker chromosome was shown to be a ring chromosome derived from chromosome 22.
(mBAND) for chromosome 12 was then performed for precise characterization of the hsr using XCyte 12 (Metasystems). mBAND demonstrated the presence of a 12p13 band signal on the hsr (Fig. 2a,b). Considering that ETV6 is located at 12p13 and that hsr represents a form of gene amplification, we performed fluorescence in situ hybridization (FISH) with the ETV6 locus-specific probe (LSI ETV6/ RUNX1 ES dual-color translocation probe; Abbott Molecular, Des Plaines, IL), which demonstrated the amplification of ETV6 in the form of hsr (Fig. 2c). FISH that used MYC (LSI MYC dual-color, break-apart rearrangement probe; Abbott Molecular) and IGH (LSI IGH dual-color, break-apart rearrangement probe; Abbott Molecular) probes was performed to verify the presence of the breakage and formation of the IGH/MYC fusion gene, but the signals were intact. The additional material from chromosome 8 on 9p24 and 14q32 contained MYC signals. Therefore, the modal karyotype was described as
47,XX,þX,der(9)t(8;9)(q24;p24),der(12)hsr(12)(p13)t(12;22) (p13;q11.2),der(14)t(8;14)(q24;q32),r(22)(p13;q13.3). For mutation analysis of ETV6, amplification of all eight exons of ETV6 was performed on genomic DNA using primers and conditions as described previously [5], and sequencing of the forward and reverse strands was performed with the polymerase chain reaction (PCR) primers. Direct sequencing of the coding regions of ETV6 did not detect any mutation or polymorphism. To examine the protein expression level of ETV6 in the patient bone marrow, immunohistochemistry for ETV6 was performed, and normal bone marrow and a case of B lymphoblastic leukemia were analyzed simultaneously as controls. Each bone marrow biopsy specimen in a 4-mm paraffin embedded block was deparaffinized. Endogenous peroxide was blocked with 0.3% hydrogen peroxide for 10 minutes. Antigen was retrieved with heating at 121 C in citrate buffer for 15 minutes. The slides were incubated
Fig. 2. (a) High-resolution multicolor banding (mBAND) for chromosome 12 demonstrating hsr(12)(p13). (b) A normal mBAND for chromosome 12. (c) The signal pattern of the ETV6 probe hybridized to chromosome 12, and this showed ETV6 amplification on hsr. (d) Immunohistochemical demonstration of ETV6 in the patient’s bone marrow biopsy sample, showing the strong nuclear positivity (original magnification, 1,000).
286
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287
with anti-ETV6 antibody (Abcam, Cambridge, MA) as a concentration of 0.5 mg/mL at room temperature for 40 minutes. After visualization with DAB Plus Chromogen and Substrate (Lab Vision, Fremont, CA), hematoxylin counterstaining was performed. The patient’s bone marrow showed strong nuclear staining, whereas the normal bone marrow and the case of B lymphoblastic leukemia used as controls showed negative or trace staining (Fig. 2d). Apart from the hsr, because the additional material attached to band 12p13 was from chromosome 22, we performed nested PCR to detect the ETV6/MN1 fusion transcript corresponding to the previously described t(12;22) (p13;q11e12), even though this translocation has been implicated in myeloid leukemias [6]. The cDNA synthesized by reverse transcription was used and the PCR was performed with the HemaVision kit (DNA Technology, Risskov, Denmark), and ETV6/MN1 fusion transcript was not detected. No other fusion transcripts involving ETV6 as its partners RUNX1, ABL1, and PDGFRB were found. The patient received induction chemotherapy, but she developed pneumonia on day 5 of chemotherapy. Her condition failed to improve. She died 20 days after the diagnosis.
3. Discussion ETV6 is a member of the ets (E-26 transforming specific) family of transcription factors, and it is expressed in hematopoietic tissues and it contributes to fetal hematopoiesis. ETV6 is also required for maintaining a normal pool of lymphoid progenitors in the bone marrow, and it regulates hematopoietic stem-cell survival [7,8]. ETV6 plays pivotal roles as a tumor-suppressor gene in the leukemogenesis of various types of leukemia, not only through forming fusion genes with about 40 partner genes, but also through deletions, point mutations, and possible alterations at the promoter level [9]. ETV6 fusion partners can be grouped as tyrosine kinases, transcription factors, and unproductive fusions. ABL1 (9q34) and JAK2 (9p24) are included in tyrosine kinases associated with acute lymphoblastic leukemia. RUNX1 (21q22) and PAX5 (9q11) are frequent fusion partners as transcription factors found in acute lymphoblastic leukemia. ETV6/RUNX1 is the most common recurrent genetic finding in pediatric acute lymphoblastic leukemia. The ETV6/RUNX1 protein acts as an aberrant transcription factor, and it represses or disrupts the regulation of the RUNX1 target genes and/or it abrogates the mitotic checkpoint function [10,11]. In a large number of ETV6/RUNX1 cases, the second ETV6 allele shows complete or partial deletion. It suggests that this event may be an important secondary event for leukemogenic transformation through the complete loss of normal ETV6 function. The loss of the wild-type ETV6 expression was also found, even in the cases whose second ETV6 allele was present [12]. Moreover, mutations and
a deficient ETV6 protein expression have been demonstrated in some acute myeloid leukemia cases [13]. Therefore, the number and variety of ETV6 translocations, not resulting in a fusion protein, together with loss of ETV6 by deletion and heterozygous or homozygous mutations, makes a mutually supportive and compelling case for loss and haploinsufficiency of ETV6 as a leukemogenic step in acute myeloid leukemia [5]. But amplification of ETV6 as a possible mechanism of leukemogenesis has only been reported in one case of with myelodysplastic syndrome [4]. In our case, the hsr was comprised solely of chromosome 12, as evidenced by the mFISH results, and specifically the results of the band 12p13 material as proven by mBAND. FISH confirmed ETV6 amplification. Neither fusion genes involving ETV6 nor mutation of ETV6 was detected. Markedly increased ETV6 expression was demonstrated. This thus provides further evidence that the tumor-suppressor function of ETV6 was not relevant in the leukemogenesis of the present case. The present case strongly supports the hypothesis that the amplification of ETV6 by gene dosage effect is a possible mechanism of leukemogenesis in certain leukemias. This characteristic function resembles WT1, which works similarly in other forms of leukemias. WT1 encodes a transcription factor and functions as a tumor suppressor in some forms of acute myeloid leukemia. Alternatively, WT1 acts as an oncogene that is overexpressed in some leukemias and is associated with a poor prognosis [14]. Although ETV6 amplification is extremely rare, our present case substantiates the hypothesis that ETV6 amplification could possibly explain a new mechanism of leukemogenesis. A complete understanding of the oncogenic activity of ETV6 would shed further light on the mechanisms that dictate ETV6 overexpression.
References [1] Murray JC, Poplack DG, Mahoney DH Jr, Gresik MV, Harrison WR, Cooley LD. Detection of double minute chromosomes in a child with acute lymphoblastic leukemia. Cancer Genet Cytogenet 1998;101: 138e42. [2] Crossen PE, Savage LM, Heaton DC, Morrison MJ. Characterization of the c-myc amplicon in a case of acute myeloid leukemia with double minute chromosomes. Cancer Genet Cytogenet 1999;112:144e8. [3] Avet-Loiseau H, Godon C, Li JY, Daviet A, Mellerin MP, Talmant P, et al. Amplification of the 11q23 region in acute myeloid leukemia. Genes Chromosome Cancer 1999;26:166e70. [4] Mauvieux L, Helia C, Perrusson N, Lioure B, Sorel N, Brizard F, et al. ETV6 (TEL) gene amplification in a myelodysplastic syndrome with excess of blasts. Leukemia 2004;18:1436e8. [5] Silva FP, Morolli B, Storlazzi CT, Xagaria A, Impera L, Klein B, et al. ETV6 mutations and loss in AML-M0. Leukemia 2008;22:1639e43. [6] Buijs A, van Rompaey L, Molijn AC, Davis JN, Vertegaal AC, Potter MD, et al. The MN1-TEL fusion protein, encoded by the translocation (12;22) (p13;q11) in myeloid leukemia, is a transcription factor with transforming activity. Mol Cell Biol 2000;20:9281e93. [7] Wang LC, Swat W, Fujiwara Y, Davidson L, Visvader J, Kuo F, et al. The TEL/ETV6 gene is required specifically for hematopoiesis in the bone marrow. Genes Dev 1998;12:2392e402.
H. Chae et al. / Cancer Genetics and Cytogenetics 203 (2010) 284e287 [8] Hock H, Meade E, Medeiros S, Schindler JW, Valk PJ, Fujiwara Y, et al. Tel/Etv6 is an essential and selective regulator of adult hematopoietic stem cell survival. Genes Dev 2004;18:2336e41. [9] Bohlander SK. ETV6: a versatile player in leukemogenesis. Semin Cancer Biol 2005;15:162e74. [10] Pui C, Relling MV, Downing JR. Acute lymphoblastic leukemia. N Engl J Med 2004;350:1535e48. [11] Krapf G, Kaindl U, Kilbey A, Fuka G, Inthal A, Joas R, et al. ETV6/ RUNX1 abrogates mitotic checkpoint function and targets its key player MDA2L1. Oncogene 2010;29:3307e12.
287
[12] Patel N, Goff LK, Clark T, Ford AM, Foot N, Lillington D, et al. Expression profile of wild-type ETV6 in childhood acute leukaemia. Br J Haematol 2003;122:94e8. [13] Barjesteh van Waalwijk van Doorn-Khosrovani S, Spensberger D, de Knegt Y, Tang M, Lo¨wenberg B, Delwel R. Somatic heterozygous mutations in ETV6 (TEL) and frequent absence of ETV6 protein in acute myeloid leukemia. Oncogene 2005;24: 4129e47. [14] Yang L, Han Y, Saurez Saiz F, Minden MD. A tumor suppressor and oncogene: the WT1 story. Leukemia 2007;21:868e76.