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Deletion of CBFB in a patient with acute myelomonocytic leukemia (AML M4Eo) and inversion 16
Cancer Genetics and Cytogenetics 154 (2004) 60–62
Short communication
Deletion of CBFB in a patient with acute myelomonocytic leukemia (AML M4Eo) and inversion 16 Nicole Egan*, John O’Reilly, Lucia Chipper, Melinda Higgins, Richard Herrmann, Paul Cannell Department of Haematology, Royal Perth Hospital, GPO Box X2213, Perth WA 6001, Australia Received 25 September 2003; received in revised form 19 December 2003; accepted 22 January 2004
Abstract
Acute myelomonocytic leukemia with bone marrow eosinophilia (AML M4Eo) is a subtype of AML with distinct morphological features. Inversion (16)(p13.1q22), t(16;16)(p13.1;q22), and del(16)(q22) are nonrandom abnormalities associated with AML M4Eo and a favorable prognosis, compared with the standard risk group for AML. Deletions of the proximal region of the MYH11 gene located at 16p13.1 have been detected in about 20% of patients with inv(16), with an undetermined effect on patient survival. We present the case of a patient with AML M4Eo and inversion 16 with a distal deletion of the CBFB gene at 16q22 detected with fluorescence in situ hybridization. To our knowledge, only one previous report of a similar deletion has appeared in the literature. 쑖 2004 Elsevier Inc. All rights reserved.
1. Introduction Inversion (16) and its variants result in the fusion of the smooth muscle myosin heavy chain gene (MYH11) at 16p13.1 and the β subunit of the core binding factor gene (CBFB) at 16q22. This results in a transcriptionally active fusion gene, CBFB/MYH11, which can be detected with fluorescence in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR). The presence of this abnormality in acute myeloblastic leukemia (AML) patients is associated with a more favorable prognosis [1], with 57% and 61% five-year overall survival rates reported from two large trials [2,3]. This case details a patient with inv(16)(p13.1q22) and a partial deletion of the distal region of the CBFB gene. This patient had a relatively early relapse, and the presence of this cryptic deletion in association with inv(16) may have prognostic significance.
A bone marrow aspirate confirmed a diagnosis of AML M4. He was treated with two induction cycles of cytarabine (AraC) and daunorubicin, then consolidation chemotherapy including Ara-C with l-asparaginase. Complete remission was confirmed with a bone marrow aspirate 4 months post diagnosis. The patient relapsed 14 months post therapy and presented to our institution with a 2-week history of fever and infection. A bone marrow aspirate contained 5% eosinophils and 80% blasts positive for CD13/33, CD34, and CD68 by immunophenotyping, confirming relapse. The patient was again treated with induction chemotherapy and entered a second remission, which was followed by autologous peripheral blood stem cell transplantation. At 15 months after transplant, the patient again relapsed and was treated with reinduction chemotherapy. A search has been initiated to locate a matched unrelated bone marrow donor, but is proving difficult due to the patient’s rare HLA haplotype. The patient currently has normal blood counts and has returned home.
2. Case history A 17-year-old male presented in June 1999 at an overseas hospital with a 7-day history of lassitude, bone pain, bruising, and pallor. A full blood picture revealed hemoglobin 132 g/L, platelets 33 × 109/L, and white blood cell count 93.4 × 109/L. * Corresponding author. Tel.: ⫹61-8-9224-2407; fax: ⫹61-8-92243449. E-mail address: [email protected] (N. Egan). 0165-4608/04/$ – see front matter 쑖 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2004.01.022
3. Materials and methods Cytogenetic studies were performed on bone marrow nucleated cells using a 24-hour unstimulated short-term synchronized culture and a 24-hour short-term synchronized culture stimulated with interleukin-3 in RPMI medium supplemented with 20% fetal calf serum. Metaphase cells were harvested according to standard cytogenetic procedures.
N. Egan et al. / Cancer Genetics and Cytogenetics 154 (2004) 60–62
Slides were GTG-banded and 20 metaphase cells were analyzed. The karyotype was described according to International System for Human Cytogenetic Nomenclature (ISCN 1995) [4]. FISH studies were performed using the Oncor (Gaithersburg, MD) partial chromosome paint spanning the 16p13.1 break region and a dual-color LSI probe (Vysis, Downers Grove, IL) spanning the CBFB gene breakpoint at 16q22, with the proximal CBFB probe labeled with SpectrumRed and the distal probe labeled with SpectrumGreen. Testing was performed according to the probe manufacturer’s instructions and fluorescent signals were imaged from a Leitz Dialux 22 to the Vysis FISH imaging system. For the PCR analysis, total RNA was extracted from the patient’s bone marrow and peripheral blood samples using the ULTRASPEC RNA isolation system (Fisher Biotec, West Perth, WA, Australia). The CBFB/MYH11 fusion gene was detected using a nested PCR approach [5]. PCR products were detected on a 3% agarose gel stained with ethidium bromide and were visualized on a transilluminator (UVP, Upland, CA). A type A fusion transcript generates a 271-bp band.
4. Results Two abnormal clones were detected with conventional cytogenetic analysis. Seventeen cells contained the inv(16) abnormality consistent with AML M4Eo and three cells made up a sideline clone containing the inv(16) with an additional trisomy 22 abnormality, which is commonly associated with inv(16) in patients with AML M4Eo [6]. The karyotype was 46,XY,inv(16)(p13.1q22)[17]/47,idem,⫹22[3]. ish inv(16)(p13.1q22)(pcp16p sp,CBFB sp). With FISH techniques, the Oncor probe revealed a split signal on the inv(16) chromosome, confirming the inversion in all 10 metaphase cells analyzed (Fig. 1). The Vysis dual-color probe revealed a deletion of the distal region of the CBFB gene in the inv(16) chromosome (Fig. 2). A 271-bp product was detected with RT-PCR, indicating a CBFB/MYH11 fusion with breakpoints in intron 5 (CBFB) and intron 12 (MYH11), resulting in a type A fusion. The type A fusion is the most common, seen in ~88% of all inv(16) cases [7].
61
Fig. 1. FISH analysis of the inv(16) using the Oncor partial chromosome paint. The partial chromosome paint spans the 16p13 break region, resulting in a green hybridization signal. The normal chromosome 16 shows a single green signal. A split green signal is seen on the inv(16) chromosome.
have been detected in ~20% of patients with inv(16) [8]. A correlation between this deletion and survival has not been confirmed in other reports [9,10]. The present case highlights the importance of FISH in detecting small deletions in association with AML M4Eo and inv(16), and may explain why a population of patients with inv(16) and a favorable prognosis have a more aggressive course of disease. Such deletions have been reported in other types of leukemia, such as the proximal ABL deletions seen in chronic myeloid leukemia (CML). CML patients with this deletion have had a significantly shorter survival than those without the deletion [8,11–13].
5. Discussion We have shown in this patient a 3′ deletion of the CBFB gene in association with inv(16). This is a unique finding. We know of only one previous report of deletions distal to the CBFB breakpoint, a retrospective study of newly diagnosed AML patients [8]. In this study, 2 of 20 patients with inv(16) displayed a partial deletion of the 3′ sequences of the CBFB gene when analyzed with FISH; the disease in these two patients followed an unusually aggressive course. Deletions of the 5′ region of the MYH11 gene
Fig. 2. FISH analysis of the inv(16) using the Vysis LSI dual-color probe spanning the CBFB gene breakpoint at 16q22. The SpectrumGreen-labeled probe hybridizes to the region distal to the CBFB gene breakpoint; the SpectrumRed-labeled probe hybridizes to the region proximal to the CBFB gene breakpoint. The normal chromosome 16 demonstrates a fused yellow signal. The inv(16) chromosome shows a single red signal and no green signal, indicating a deletion of the region 3′ to the CBFB gene.
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N. Egan et al. / Cancer Genetics and Cytogenetics 154 (2004) 60–62
The patient we describe had a relatively short remission, suggesting that deletion of CBFB in association with inv(16) may have prognostic significance. The loss of genes distal to CBFB on 16q may also influence the clinical outcome in these patients. With only a few reported cases of submicroscopic deletions of 16q, however, the assessment of the clinical significance of this abnormality in association with inv(16) will require the recruitment of more patients.
Acknowledgments This work was supported by the Western Australian Adult Leukaemia Foundation.
References [1] Larson RA, Williams SF, Le Beau MM, Bitter MA, Vardiman JW, Rowley JD. Acute myelomonocytic leukemia with abnormal eosinophils and inv(16) or t(16;16) has a favorable prognosis. Blood 1986; 68:1242–9. [2] Grimwade D, Walker H, Oliver F, Wheatley K, Harrison C, Harrison G, Rees J, Hann I, Stevens R, Burnett A, Goldstone A; Medical Research Council Adult and Children’s Leukaemia Working Parties. The importance of diagnostic cytogenetics on outcome in AML: analysis of 1,612 patients entered into the MRC AML10 trial. Blood 1998;92:2322–33. [3] Byrd JC, Mrozek K, Dodge RK, Carroll AJ, Edwards CG, Arthur DC, Pettenati MJ, Patil SR, Rao KW, Watson MS, Koduru PRK, Moore JO, Stone RM, Mayer RJ, Feldman EJ, Davey FR, Schiffer CA, Larson RA, Bloomfield CD; Cancer and Leukemia Group B (CALGB 8461). Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse and overall survival in adult patients with de novo acute myeloid leukemia: results from Cancer and Leukemia Group B (CALGB 8461). Blood 2002;100: 4325–36. [4] Mitelman F, editor. An international system for human cytogenetic nomenclature. Basel: S. Karger, 1995.
[5] Van Dongen JJM, MacIntyre EA, Gabert JA, Delabesse E, Rossi V, Saglio G, Gottardi E, Rambaldi A, Dotti G, Griesinger F, Parreira A, Gameiro P, Gonzales Diaz M, Malec M, Langerak AW, San Miguel JF, Biondi A. Standardized RT-PCR analysis of fusion gene transcripts from chromosome aberrations in acute leukemia for detection of minimal residual disease. Report of the BIOMED-1 Concerted Action: investigation of minimal residual disease in acute leukemia. Leukemia 1999;13:1901–28. [6] Marlton P, Keating M, Kantarjian H, Pierce S, O’Brien S, Freireich EJ, Estey E. Cytogenetic and clinical correlations in AML patients with abnormalities of chromosome 16. Leukemia 1995;9:965–71. [7] Claxton DF, Liu P, Hsu HB, Marlton P, Hester J, Collins F, Deisseroth AB, Rowley JD, Siciliano MJ. Detection of fusion transcripts generated by the inversion 16 chromosome acute myelogenous leukemia. Blood 1994;83:1750–6. [8] Kolomietz E, Al-Maghrabi J, Brennan S, Karaskova J, Minkin S, Lipton J, Squire J. Primary chromosomal rearrangements of leukemia are frequently accompanied by extensive submicroscopic deletions and may lead to altered prognosis. Blood 2001;97:3581–8. [9] Martinet D, Muhlematter D, Leeman M, Parlier V, Hess U, Gmur J, Jotterand M. Detection of 16p deletions by FISH in patients with inv(16) or t(16;16) in acute myeloid leukemia (AML). Leukemia 1997;11:964–70. [10] Marlton P, Claxton DF, Liu P, Estey EH, Beran M, LeBeau M, Testa JR, Collins FS, Rowley JD, Siciliano MJ. Molecular characterization of 16p deletions associated with inversion 16 defines the critical fusion for leukemogenesis. Blood 1995;85:772–9. [11] Huntly BJP, Reid AG, Bench AJ, Campbell LJ, Telford N, Shepherd P, Szer J, Prince HM, Turner P, Grace C, Nacheva EP, Green AR. Deletions of the derivative chromosome 9 occur at the time of the Philadelphia translocation and provide a powerful and independent prognostic indicator in chronic myeloid leukemia. Blood 2001;98:1732–8. [12] Cohen N, Rozenfeld-Granot G, Hardan I, Brok-Simoni F, Amariglio N, Rechavi G, Trakhtenbrot L. Subgroup of patients with Philadelphiapositive chronic myelogenous leukemia characterized by a deletion of 9q proximal to ABL gene: expression profiling, resistance to interferon therapy, and poor prognosis. Cancer Genet Cytogenet 2001;128:114–9. [13] Herens C, Tassin F, Lemaire V, Beguin Y, Collard E, Lampertz S, Croisiau C, Lecomte M, De Prijk B, Longree L, Koulischer L. Deletion of the 5′-ABL region: a recurrent anomaly detected by fluorescence in situ hybridization in about 10% of Philadelphia-positive chronic myeloid leukaemia patients. Br J Haematol 2000;110:214–6.
Short communication
Deletion of CBFB in a patient with acute myelomonocytic leukemia (AML M4Eo) and inversion 16 Nicole Egan*, John O’Reilly, Lucia Chipper, Melinda Higgins, Richard Herrmann, Paul Cannell Department of Haematology, Royal Perth Hospital, GPO Box X2213, Perth WA 6001, Australia Received 25 September 2003; received in revised form 19 December 2003; accepted 22 January 2004
Abstract
Acute myelomonocytic leukemia with bone marrow eosinophilia (AML M4Eo) is a subtype of AML with distinct morphological features. Inversion (16)(p13.1q22), t(16;16)(p13.1;q22), and del(16)(q22) are nonrandom abnormalities associated with AML M4Eo and a favorable prognosis, compared with the standard risk group for AML. Deletions of the proximal region of the MYH11 gene located at 16p13.1 have been detected in about 20% of patients with inv(16), with an undetermined effect on patient survival. We present the case of a patient with AML M4Eo and inversion 16 with a distal deletion of the CBFB gene at 16q22 detected with fluorescence in situ hybridization. To our knowledge, only one previous report of a similar deletion has appeared in the literature. 쑖 2004 Elsevier Inc. All rights reserved.
1. Introduction Inversion (16) and its variants result in the fusion of the smooth muscle myosin heavy chain gene (MYH11) at 16p13.1 and the β subunit of the core binding factor gene (CBFB) at 16q22. This results in a transcriptionally active fusion gene, CBFB/MYH11, which can be detected with fluorescence in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR). The presence of this abnormality in acute myeloblastic leukemia (AML) patients is associated with a more favorable prognosis [1], with 57% and 61% five-year overall survival rates reported from two large trials [2,3]. This case details a patient with inv(16)(p13.1q22) and a partial deletion of the distal region of the CBFB gene. This patient had a relatively early relapse, and the presence of this cryptic deletion in association with inv(16) may have prognostic significance.
A bone marrow aspirate confirmed a diagnosis of AML M4. He was treated with two induction cycles of cytarabine (AraC) and daunorubicin, then consolidation chemotherapy including Ara-C with l-asparaginase. Complete remission was confirmed with a bone marrow aspirate 4 months post diagnosis. The patient relapsed 14 months post therapy and presented to our institution with a 2-week history of fever and infection. A bone marrow aspirate contained 5% eosinophils and 80% blasts positive for CD13/33, CD34, and CD68 by immunophenotyping, confirming relapse. The patient was again treated with induction chemotherapy and entered a second remission, which was followed by autologous peripheral blood stem cell transplantation. At 15 months after transplant, the patient again relapsed and was treated with reinduction chemotherapy. A search has been initiated to locate a matched unrelated bone marrow donor, but is proving difficult due to the patient’s rare HLA haplotype. The patient currently has normal blood counts and has returned home.
2. Case history A 17-year-old male presented in June 1999 at an overseas hospital with a 7-day history of lassitude, bone pain, bruising, and pallor. A full blood picture revealed hemoglobin 132 g/L, platelets 33 × 109/L, and white blood cell count 93.4 × 109/L. * Corresponding author. Tel.: ⫹61-8-9224-2407; fax: ⫹61-8-92243449. E-mail address: [email protected] (N. Egan). 0165-4608/04/$ – see front matter 쑖 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2004.01.022
3. Materials and methods Cytogenetic studies were performed on bone marrow nucleated cells using a 24-hour unstimulated short-term synchronized culture and a 24-hour short-term synchronized culture stimulated with interleukin-3 in RPMI medium supplemented with 20% fetal calf serum. Metaphase cells were harvested according to standard cytogenetic procedures.
N. Egan et al. / Cancer Genetics and Cytogenetics 154 (2004) 60–62
Slides were GTG-banded and 20 metaphase cells were analyzed. The karyotype was described according to International System for Human Cytogenetic Nomenclature (ISCN 1995) [4]. FISH studies were performed using the Oncor (Gaithersburg, MD) partial chromosome paint spanning the 16p13.1 break region and a dual-color LSI probe (Vysis, Downers Grove, IL) spanning the CBFB gene breakpoint at 16q22, with the proximal CBFB probe labeled with SpectrumRed and the distal probe labeled with SpectrumGreen. Testing was performed according to the probe manufacturer’s instructions and fluorescent signals were imaged from a Leitz Dialux 22 to the Vysis FISH imaging system. For the PCR analysis, total RNA was extracted from the patient’s bone marrow and peripheral blood samples using the ULTRASPEC RNA isolation system (Fisher Biotec, West Perth, WA, Australia). The CBFB/MYH11 fusion gene was detected using a nested PCR approach [5]. PCR products were detected on a 3% agarose gel stained with ethidium bromide and were visualized on a transilluminator (UVP, Upland, CA). A type A fusion transcript generates a 271-bp band.
4. Results Two abnormal clones were detected with conventional cytogenetic analysis. Seventeen cells contained the inv(16) abnormality consistent with AML M4Eo and three cells made up a sideline clone containing the inv(16) with an additional trisomy 22 abnormality, which is commonly associated with inv(16) in patients with AML M4Eo [6]. The karyotype was 46,XY,inv(16)(p13.1q22)[17]/47,idem,⫹22[3]. ish inv(16)(p13.1q22)(pcp16p sp,CBFB sp). With FISH techniques, the Oncor probe revealed a split signal on the inv(16) chromosome, confirming the inversion in all 10 metaphase cells analyzed (Fig. 1). The Vysis dual-color probe revealed a deletion of the distal region of the CBFB gene in the inv(16) chromosome (Fig. 2). A 271-bp product was detected with RT-PCR, indicating a CBFB/MYH11 fusion with breakpoints in intron 5 (CBFB) and intron 12 (MYH11), resulting in a type A fusion. The type A fusion is the most common, seen in ~88% of all inv(16) cases [7].
61
Fig. 1. FISH analysis of the inv(16) using the Oncor partial chromosome paint. The partial chromosome paint spans the 16p13 break region, resulting in a green hybridization signal. The normal chromosome 16 shows a single green signal. A split green signal is seen on the inv(16) chromosome.
have been detected in ~20% of patients with inv(16) [8]. A correlation between this deletion and survival has not been confirmed in other reports [9,10]. The present case highlights the importance of FISH in detecting small deletions in association with AML M4Eo and inv(16), and may explain why a population of patients with inv(16) and a favorable prognosis have a more aggressive course of disease. Such deletions have been reported in other types of leukemia, such as the proximal ABL deletions seen in chronic myeloid leukemia (CML). CML patients with this deletion have had a significantly shorter survival than those without the deletion [8,11–13].
5. Discussion We have shown in this patient a 3′ deletion of the CBFB gene in association with inv(16). This is a unique finding. We know of only one previous report of deletions distal to the CBFB breakpoint, a retrospective study of newly diagnosed AML patients [8]. In this study, 2 of 20 patients with inv(16) displayed a partial deletion of the 3′ sequences of the CBFB gene when analyzed with FISH; the disease in these two patients followed an unusually aggressive course. Deletions of the 5′ region of the MYH11 gene
Fig. 2. FISH analysis of the inv(16) using the Vysis LSI dual-color probe spanning the CBFB gene breakpoint at 16q22. The SpectrumGreen-labeled probe hybridizes to the region distal to the CBFB gene breakpoint; the SpectrumRed-labeled probe hybridizes to the region proximal to the CBFB gene breakpoint. The normal chromosome 16 demonstrates a fused yellow signal. The inv(16) chromosome shows a single red signal and no green signal, indicating a deletion of the region 3′ to the CBFB gene.
62
N. Egan et al. / Cancer Genetics and Cytogenetics 154 (2004) 60–62
The patient we describe had a relatively short remission, suggesting that deletion of CBFB in association with inv(16) may have prognostic significance. The loss of genes distal to CBFB on 16q may also influence the clinical outcome in these patients. With only a few reported cases of submicroscopic deletions of 16q, however, the assessment of the clinical significance of this abnormality in association with inv(16) will require the recruitment of more patients.
Acknowledgments This work was supported by the Western Australian Adult Leukaemia Foundation.
References [1] Larson RA, Williams SF, Le Beau MM, Bitter MA, Vardiman JW, Rowley JD. Acute myelomonocytic leukemia with abnormal eosinophils and inv(16) or t(16;16) has a favorable prognosis. Blood 1986; 68:1242–9. [2] Grimwade D, Walker H, Oliver F, Wheatley K, Harrison C, Harrison G, Rees J, Hann I, Stevens R, Burnett A, Goldstone A; Medical Research Council Adult and Children’s Leukaemia Working Parties. The importance of diagnostic cytogenetics on outcome in AML: analysis of 1,612 patients entered into the MRC AML10 trial. Blood 1998;92:2322–33. [3] Byrd JC, Mrozek K, Dodge RK, Carroll AJ, Edwards CG, Arthur DC, Pettenati MJ, Patil SR, Rao KW, Watson MS, Koduru PRK, Moore JO, Stone RM, Mayer RJ, Feldman EJ, Davey FR, Schiffer CA, Larson RA, Bloomfield CD; Cancer and Leukemia Group B (CALGB 8461). Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse and overall survival in adult patients with de novo acute myeloid leukemia: results from Cancer and Leukemia Group B (CALGB 8461). Blood 2002;100: 4325–36. [4] Mitelman F, editor. An international system for human cytogenetic nomenclature. Basel: S. Karger, 1995.
[5] Van Dongen JJM, MacIntyre EA, Gabert JA, Delabesse E, Rossi V, Saglio G, Gottardi E, Rambaldi A, Dotti G, Griesinger F, Parreira A, Gameiro P, Gonzales Diaz M, Malec M, Langerak AW, San Miguel JF, Biondi A. Standardized RT-PCR analysis of fusion gene transcripts from chromosome aberrations in acute leukemia for detection of minimal residual disease. Report of the BIOMED-1 Concerted Action: investigation of minimal residual disease in acute leukemia. Leukemia 1999;13:1901–28. [6] Marlton P, Keating M, Kantarjian H, Pierce S, O’Brien S, Freireich EJ, Estey E. Cytogenetic and clinical correlations in AML patients with abnormalities of chromosome 16. Leukemia 1995;9:965–71. [7] Claxton DF, Liu P, Hsu HB, Marlton P, Hester J, Collins F, Deisseroth AB, Rowley JD, Siciliano MJ. Detection of fusion transcripts generated by the inversion 16 chromosome acute myelogenous leukemia. Blood 1994;83:1750–6. [8] Kolomietz E, Al-Maghrabi J, Brennan S, Karaskova J, Minkin S, Lipton J, Squire J. Primary chromosomal rearrangements of leukemia are frequently accompanied by extensive submicroscopic deletions and may lead to altered prognosis. Blood 2001;97:3581–8. [9] Martinet D, Muhlematter D, Leeman M, Parlier V, Hess U, Gmur J, Jotterand M. Detection of 16p deletions by FISH in patients with inv(16) or t(16;16) in acute myeloid leukemia (AML). Leukemia 1997;11:964–70. [10] Marlton P, Claxton DF, Liu P, Estey EH, Beran M, LeBeau M, Testa JR, Collins FS, Rowley JD, Siciliano MJ. Molecular characterization of 16p deletions associated with inversion 16 defines the critical fusion for leukemogenesis. Blood 1995;85:772–9. [11] Huntly BJP, Reid AG, Bench AJ, Campbell LJ, Telford N, Shepherd P, Szer J, Prince HM, Turner P, Grace C, Nacheva EP, Green AR. Deletions of the derivative chromosome 9 occur at the time of the Philadelphia translocation and provide a powerful and independent prognostic indicator in chronic myeloid leukemia. Blood 2001;98:1732–8. [12] Cohen N, Rozenfeld-Granot G, Hardan I, Brok-Simoni F, Amariglio N, Rechavi G, Trakhtenbrot L. Subgroup of patients with Philadelphiapositive chronic myelogenous leukemia characterized by a deletion of 9q proximal to ABL gene: expression profiling, resistance to interferon therapy, and poor prognosis. Cancer Genet Cytogenet 2001;128:114–9. [13] Herens C, Tassin F, Lemaire V, Beguin Y, Collard E, Lampertz S, Croisiau C, Lecomte M, De Prijk B, Longree L, Koulischer L. Deletion of the 5′-ABL region: a recurrent anomaly detected by fluorescence in situ hybridization in about 10% of Philadelphia-positive chronic myeloid leukaemia patients. Br J Haematol 2000;110:214–6.