- Email: [email protected]
Multiple copies of a rare rearrangement of Philadelphia chromosome in a chronic myeloid leukemia patient: a case report
Cancer Genetics and Cytogenetics 199 (2010) 66e68
Letter to the editor
Multiple copies of a rare rearrangement of Philadelphia chromosome in a chronic myeloid leukemia patient: a case report Chronic myeloid leukemia (CML) is a stem cell neoplasm characterized by the uncontrolled proliferation of myeloid cells in the bone marrow. The observed incidence of CML in Singapore is markedly lower compared to the United States of America, at 0.7 compared to 1.48 per 100,000 patients [1]. The BCR-ABL fusion oncogene occurs in more than 95% of CML patients, and is seen as a Philadelphia (Ph) chromosome, where the ABL1 gene on 9q34 is juxtaposed to the BCR gene on chromosome 22q11.2. The resulting fusion oncogene is a tyrosine kinase, due to the originating nature of the ABL gene, which in turn results in the uncontrolled proliferation of the cells in which this mutation occurs [2]. Most of the isoderivatives (ider) of chromosome 22 or the isodicentric (idic) Ph chromosomes reported in the literature have been described to be a fusion occurring at the p arms, resulting in multiple copies of this fusion oncogene. We describe here a rare case of an isoderivative Philadelphia chromosome formed by a fusion in the q arm, in a 74-year-old Indian woman diagnosed with de novo CML in the hematologic chronic phase. She presented with loss of appetite, accompanying loss of weight, upper respiratory tract infection, and a history of diabetes mellitus. Upon admission, the patient’s total white cell count was 46.438 109/L, with neutrophils accounting for 82% and myelocytes at 2%. Peripheral blood film showed moderate anisopoikilocytosis, marked neutrophilia with moderate left shift, with occasional myelocytes, metamyelocytes, and promyelocytes noted. This was accompanied by a mild increase in basophils, and blast cells accounted for around 2% of cells seen. At the time of diagnosis, bone marrow investigation indicated a hypercellular marrow with markedly increased granulopoiesis and megakaryopoiesis. Erythropoiesis was quantitatively reduced. Myelocytes were increased in number, and mild basophilia was observed. Myeloblasts comprised 1% of total nucleated cells. Features were consistent with that of a CML in chronic phase. Flow cytometry of the bone marrow was also consistent with that of a myeloproliferative disorder. The patient passed away before the start of treatment. Cytogenetic investigation on GTL-banded chromosomes revealed Philadelphia chromosome rearrangements in all the cells analyzed. Of 20 cells analyzed, 16 cells had an 0165-4608/$ e see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2010.01.012
isoderivative chromosome 22 / idic Ph chromosome, while 4 cells had an additional copy of the isoderivative chromosome 22 (Fig. 1A), resulting in a final karyotype of 46,X X,der(9)t(9;22)(q34;q11.2),ider(22)(q11.2)t(9;22)(q34;q11.2) [16]/47,idem,þder(22)idic(22)(q11.2)t(9;22)(q34;q11.2)[4]. None of the cells showed the most commonly observed classical Ph chromosome, which occurs as a result of the t(9;22)(q34;q11.2). Reverse-transcriptase polymerase chain reaction confirmed the presence of the BCR-ABL fusion, resulting in the 210-kDa BCR-ABL transcript, while molecular studies [3] showed the lack of mutations at the imatinib-binding region on the fusion product. Fluorescence in situ hybridization using the LSI BCR/ ABL ES Dual Color translocation probe (Abbott Molecular, Des Plains, IL), was helpful in refining the characterization of the idic Ph chromosome by demonstrating the presence of two fusion signals within the rearrangement. Not only did it pick up the clones seen by routine cytogenetics with one to two copies of the idic Ph chromosome (70%), but it also detected the presence of cells with three to five copies of the idic Ph chromosome (21%) (Fig. 1B), resulting in multiple copies of the BCR-ABL fusion oncogene. The remaining 9% of the cells seen were normal. Reports of isodicentric Ph chromosomes in CML have been infrequent, with most of them formed as a result of a fusion at the band p13. From a cytogenetic viewpoint, isodicentric Ph chromosomes formed by fusion at the band q11 have been rare, and have only been reported by two groups, in CML [4] and in acute lymphoblastic leukemia (ALL) [5]. The former study reported two patients with the most commonly observed classic t(9;22) in the initial phase at diagnosis. Both patients failed to respond to treatment with Gleevec, and subsequent analysis showed copies of these similar idic Ph chromosomes with a break in the band q11. The presence of multiple gene copies of the BCR-ABL oncogene seems to be the cause for the ineffectiveness or resistance to the drug, despite increased drug dosage. Cytogenetic studies often provide evidence of progression of disease at an earlier phase than hematologic markers. It is known that expression of BCR-ABL is elevated in progenitor cells in blast crisis, compared to chronic-phase CML [6]. While the findings of the patient’s
Letter to the editor / Cancer Genetics and Cytogenetics 199 (2010) 66e68
67
Fig. 1. (A) Karyogram of patient’s abnormal karyotype, showing an additional isoderivative (22) chromosome. (B) Metaphase FISH using Vysis LSI BCR/ ABL ES Dual Color translocation probe showing 5 copies of ider (22) chromosome.
peripheral blood and bone marrow were suggestive of CML in the chronic phase, given the presence of multiple copies of the isodicentric Ph chromosome, it was possible that cytogenetics indicated progression of the disease toward an accelerated phase. The patient subsequently died
of the disease before treatment could start. Despite the absence of mutations in the drug-binding site, the presence of multiple copies of the BCR-ABL oncogene is indicative of a poor prognosis and higher possibilities for resistance to drug treatment [7].
68
Letter to the editor / Cancer Genetics and Cytogenetics 199 (2010) 66e68
Constance Li Ming Chua Yvoonne Yam Fang Tan Sok Peng Chua Hui Bao Ma Department of Laboratory Medicine National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Evelyn Koay Departments of Laboratory Medicine and Pathology Yong Loo Lin School National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Michelle Li Min Poon Te Chih Liu Departments of Laboratory Medicine and Haematology-Oncology, National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Leena Gole* Department of Laboratory Medicine National University Hospital 5 Lower Kent Ridge Road
Singapore 119074 *Corresponding author. E-mail address: [email protected] (L. Gole)
References [1] Au WY, Caguioa PB, Chuah C, Hsu SC, Jootar S, Kim DW, Kweon IY, O’Neil WM, Saikia TK, Wang J. Chronic myeloid leukemia in Asia. Int J Hematol 2009;89:14e23. [2] Goldman JM, Melo JV. Chronic myeloid leukemiadadvances in biology and new approaches to treatment. N Engl J Med 2003;349:1451e64. [3] Bradford S, Hughes T. Detection of BCR-ABL mutations and resistance to imatinib mesylate. In: Iland H, Hertzberg M, Marlton P, editors. Myeloid Leukemia. Clifton, NJ: Humana Press, 2006. pp. 93e106. [4] Szych CM, Liesveld JL, Iqbal MA, Li L, Siebert S, Asmus C, O’Malley J, Lee A, Wang N. Isodicentric Philadelphia chromosomes in imatinib mesylate (Gleevec)-resistant patients. Cancer Genet Cytogenet 2007;174:132e7. [5] Yamamoto K, Nagata K, Morita Y, Inagaki K, Hamaguchi H. Isodicentric Philadelphia chromosome in acute lymphoblastic leukemia with der(7;12)(q10;q10). Leuk Res 2007;31:713e8. [6] Barnes DJ, Palaiologou D, Panousopoulou E, Schultheis B, Yong AS, Wong A, Pattacini L, Goldman JM, Melo JV. Bcr-Abl expression levels determine the rate of development of resistance to imatinib mesylate in chronic myeloid leukemia. Cancer Res 2005;65:8912e9. [7] le Coutre P, Tassi E, Varella-Garcia M, Barni R, Mologni L, Cabrita G, Marchesi E, Supino R, Gambacorti-Passerini C. Induction of resistance to the Abelson inhibitor STI571 in human leukemic cells through gene amplification. Blood 2000;95:175866.
Letter to the editor
Multiple copies of a rare rearrangement of Philadelphia chromosome in a chronic myeloid leukemia patient: a case report Chronic myeloid leukemia (CML) is a stem cell neoplasm characterized by the uncontrolled proliferation of myeloid cells in the bone marrow. The observed incidence of CML in Singapore is markedly lower compared to the United States of America, at 0.7 compared to 1.48 per 100,000 patients [1]. The BCR-ABL fusion oncogene occurs in more than 95% of CML patients, and is seen as a Philadelphia (Ph) chromosome, where the ABL1 gene on 9q34 is juxtaposed to the BCR gene on chromosome 22q11.2. The resulting fusion oncogene is a tyrosine kinase, due to the originating nature of the ABL gene, which in turn results in the uncontrolled proliferation of the cells in which this mutation occurs [2]. Most of the isoderivatives (ider) of chromosome 22 or the isodicentric (idic) Ph chromosomes reported in the literature have been described to be a fusion occurring at the p arms, resulting in multiple copies of this fusion oncogene. We describe here a rare case of an isoderivative Philadelphia chromosome formed by a fusion in the q arm, in a 74-year-old Indian woman diagnosed with de novo CML in the hematologic chronic phase. She presented with loss of appetite, accompanying loss of weight, upper respiratory tract infection, and a history of diabetes mellitus. Upon admission, the patient’s total white cell count was 46.438 109/L, with neutrophils accounting for 82% and myelocytes at 2%. Peripheral blood film showed moderate anisopoikilocytosis, marked neutrophilia with moderate left shift, with occasional myelocytes, metamyelocytes, and promyelocytes noted. This was accompanied by a mild increase in basophils, and blast cells accounted for around 2% of cells seen. At the time of diagnosis, bone marrow investigation indicated a hypercellular marrow with markedly increased granulopoiesis and megakaryopoiesis. Erythropoiesis was quantitatively reduced. Myelocytes were increased in number, and mild basophilia was observed. Myeloblasts comprised 1% of total nucleated cells. Features were consistent with that of a CML in chronic phase. Flow cytometry of the bone marrow was also consistent with that of a myeloproliferative disorder. The patient passed away before the start of treatment. Cytogenetic investigation on GTL-banded chromosomes revealed Philadelphia chromosome rearrangements in all the cells analyzed. Of 20 cells analyzed, 16 cells had an 0165-4608/$ e see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2010.01.012
isoderivative chromosome 22 / idic Ph chromosome, while 4 cells had an additional copy of the isoderivative chromosome 22 (Fig. 1A), resulting in a final karyotype of 46,X X,der(9)t(9;22)(q34;q11.2),ider(22)(q11.2)t(9;22)(q34;q11.2) [16]/47,idem,þder(22)idic(22)(q11.2)t(9;22)(q34;q11.2)[4]. None of the cells showed the most commonly observed classical Ph chromosome, which occurs as a result of the t(9;22)(q34;q11.2). Reverse-transcriptase polymerase chain reaction confirmed the presence of the BCR-ABL fusion, resulting in the 210-kDa BCR-ABL transcript, while molecular studies [3] showed the lack of mutations at the imatinib-binding region on the fusion product. Fluorescence in situ hybridization using the LSI BCR/ ABL ES Dual Color translocation probe (Abbott Molecular, Des Plains, IL), was helpful in refining the characterization of the idic Ph chromosome by demonstrating the presence of two fusion signals within the rearrangement. Not only did it pick up the clones seen by routine cytogenetics with one to two copies of the idic Ph chromosome (70%), but it also detected the presence of cells with three to five copies of the idic Ph chromosome (21%) (Fig. 1B), resulting in multiple copies of the BCR-ABL fusion oncogene. The remaining 9% of the cells seen were normal. Reports of isodicentric Ph chromosomes in CML have been infrequent, with most of them formed as a result of a fusion at the band p13. From a cytogenetic viewpoint, isodicentric Ph chromosomes formed by fusion at the band q11 have been rare, and have only been reported by two groups, in CML [4] and in acute lymphoblastic leukemia (ALL) [5]. The former study reported two patients with the most commonly observed classic t(9;22) in the initial phase at diagnosis. Both patients failed to respond to treatment with Gleevec, and subsequent analysis showed copies of these similar idic Ph chromosomes with a break in the band q11. The presence of multiple gene copies of the BCR-ABL oncogene seems to be the cause for the ineffectiveness or resistance to the drug, despite increased drug dosage. Cytogenetic studies often provide evidence of progression of disease at an earlier phase than hematologic markers. It is known that expression of BCR-ABL is elevated in progenitor cells in blast crisis, compared to chronic-phase CML [6]. While the findings of the patient’s
Letter to the editor / Cancer Genetics and Cytogenetics 199 (2010) 66e68
67
Fig. 1. (A) Karyogram of patient’s abnormal karyotype, showing an additional isoderivative (22) chromosome. (B) Metaphase FISH using Vysis LSI BCR/ ABL ES Dual Color translocation probe showing 5 copies of ider (22) chromosome.
peripheral blood and bone marrow were suggestive of CML in the chronic phase, given the presence of multiple copies of the isodicentric Ph chromosome, it was possible that cytogenetics indicated progression of the disease toward an accelerated phase. The patient subsequently died
of the disease before treatment could start. Despite the absence of mutations in the drug-binding site, the presence of multiple copies of the BCR-ABL oncogene is indicative of a poor prognosis and higher possibilities for resistance to drug treatment [7].
68
Letter to the editor / Cancer Genetics and Cytogenetics 199 (2010) 66e68
Constance Li Ming Chua Yvoonne Yam Fang Tan Sok Peng Chua Hui Bao Ma Department of Laboratory Medicine National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Evelyn Koay Departments of Laboratory Medicine and Pathology Yong Loo Lin School National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Michelle Li Min Poon Te Chih Liu Departments of Laboratory Medicine and Haematology-Oncology, National University Hospital 5 Lower Kent Ridge Road Singapore 119074 Leena Gole* Department of Laboratory Medicine National University Hospital 5 Lower Kent Ridge Road
Singapore 119074 *Corresponding author. E-mail address: [email protected] (L. Gole)
References [1] Au WY, Caguioa PB, Chuah C, Hsu SC, Jootar S, Kim DW, Kweon IY, O’Neil WM, Saikia TK, Wang J. Chronic myeloid leukemia in Asia. Int J Hematol 2009;89:14e23. [2] Goldman JM, Melo JV. Chronic myeloid leukemiadadvances in biology and new approaches to treatment. N Engl J Med 2003;349:1451e64. [3] Bradford S, Hughes T. Detection of BCR-ABL mutations and resistance to imatinib mesylate. In: Iland H, Hertzberg M, Marlton P, editors. Myeloid Leukemia. Clifton, NJ: Humana Press, 2006. pp. 93e106. [4] Szych CM, Liesveld JL, Iqbal MA, Li L, Siebert S, Asmus C, O’Malley J, Lee A, Wang N. Isodicentric Philadelphia chromosomes in imatinib mesylate (Gleevec)-resistant patients. Cancer Genet Cytogenet 2007;174:132e7. [5] Yamamoto K, Nagata K, Morita Y, Inagaki K, Hamaguchi H. Isodicentric Philadelphia chromosome in acute lymphoblastic leukemia with der(7;12)(q10;q10). Leuk Res 2007;31:713e8. [6] Barnes DJ, Palaiologou D, Panousopoulou E, Schultheis B, Yong AS, Wong A, Pattacini L, Goldman JM, Melo JV. Bcr-Abl expression levels determine the rate of development of resistance to imatinib mesylate in chronic myeloid leukemia. Cancer Res 2005;65:8912e9. [7] le Coutre P, Tassi E, Varella-Garcia M, Barni R, Mologni L, Cabrita G, Marchesi E, Supino R, Gambacorti-Passerini C. Induction of resistance to the Abelson inhibitor STI571 in human leukemic cells through gene amplification. Blood 2000;95:175866.