Year : 2005 | Volume
: 1 | Issue : 2 | Page : 108--110
A three way complex translocation (4;9;22) in two patients with chronic myelocytic leukemia
Frenny J Sheth1, Jayesh J Sheth1, Alain Verhest2,
1 FRIGE (Foundation for Research in Genetics and Endocrinology) Genetic Centre, 20/1, Bima Nagar, Satellite, Ahmedabad-380 015, India
2 Laboratorie de Cytogenetique Institut Jules Bordet Cancer Center of the free University of Brussels (ULB) 1000 Brussels, Belgium
Frenny J Sheth
FRIGE (Foundation for Research in Genetics and Endocrinology) Genetic Centre, 20/1, Bima Nagar, Satellite, Ahmedabad-380 015
Chronic myeloid leukemia (CML) is genetically characterized by the reciprocal translocation of chromosome 9 and 22, t(9;22)(q34;q11) which results in the fusion of BCR/ABL gene observed on the derivative chromosome 22 called Philadelphia (Ph«SQ») chromosome. About 5-8% of Philadelphia positive patients with CML show various complex translocations involving third chromosome in addition to chromosome 9 and 22. In present report we discuss two cases with CML referred at our centre. At the time of initial diagnosis and after 9 months of treatment, one of the patients showed 100% presence of Philadelphia positive in bone marrow culture. During follow-up in an accelerated state, his cytogenetic study revealed a complex translocation (4;9;22)(q25;q34;q11) along with an additional Philadelphia and marker chromosome. The second patient showed a complex (4;9;22)(q25;q34;q11) translocation at the time of diagnosis. He was on hydroxyurea and his follow-up cytogenetic study after the course of chemotherapy showed no changes. Further confirmation of complex translocation was done by FISH study using bcr/abl and whole chromosome 9 probes. Though the additional genes involved in complex variant Ph«SQ» rearrangements have not been characterized, both patients are healthy till 3 to 5 years of initial diagnosis. This could be attributed to the benign effect resulted from reciprocal translocation with no loss or gain of the genetic material.
|How to cite this article:|
Sheth FJ, Sheth JJ, Verhest A. A three way complex translocation (4;9;22) in two patients with chronic myelocytic leukemia.J Can Res Ther 2005;1:108-110
|How to cite this URL:|
Sheth FJ, Sheth JJ, Verhest A. A three way complex translocation (4;9;22) in two patients with chronic myelocytic leukemia. J Can Res Ther [serial online] 2005 [cited 2021 Apr 18 ];1:108-110
Available from: https://www.cancerjournal.net/text.asp?2005/1/2/108/16711
Chronic myeloid leukemia (CML) is a clinical myeloproliferative disorder involving the pluripotent stem cell. The hallmark of CML is the Philadelphia chromosome (Ph'), which results from translocation between chromosomes 9 and 22 where c-abl protooncogene is translocated from chromosome 9 to the break point cluster region on chromosome 22. It may also arise from complex rearrangements involving three or more chromosomes., In 70-80% of CML cases the development of the blastic or acute phase involves additional chromosome abnormalities, such as an isochromosome for the long arm of #17, trisomy 19, occasionally trisomy 8 and a missing Y. In CML, translocations other than the standard reciprocal translocation (9;22) occur in about 5 to 8% of cases. ,,, It is generally accepted that in CML the relationship and significance of such secondary chromosome abnormalities to the evolution of the disease is unclear. The evolution of prognostic features in a limited number of CMLs with classical or variant Ph' rearrangements gave controversial results  owing to the limited number of well documented cases with long-term clinical and cytogenetic follow up.
In the present study we report about the clinical, cytogenetic and molecular findings of two patients with complex translocation involving chromosome 4, 9 and 22.
Two cases presented here have been diagnosed clinically and hematologically as CML. One of the patient, aged 42 years attended Genetic Centre on January 1997 to undergo cytogenetic study from bone marrow. The study showed presence of Philadelphia chromosome in all metaphases and total WBC count was 256 x 10 9 /l. The differential count was: neutrophils 40%, lymphocytes 8%, monocytes 3%, eosinophil 1%, blast 15%, band 16%, promyelocytes 12%, myelocytes 12% and metamyelocytes 12%. The patient had splenomegaly with marked granulocytic hyperplasia and an increased number of megakaryocytes.
He was on a-interferon for 9 months and the hematological picture showed 8 percent premature cells with WBC count of 9.6x10 9 /l. Karyotypic picture showed presence of Philadelphia chromosome in all cells. Proband came after three and half years for follow-up in an accelerated state when WBC count was 72.8x10 9 /l and differential count was: neutrophils 39%, lymphocyte 4%, eosinophil 4%, basophils 10%, monocytes 3%, band 15%, promyelocytes 3%, myelocytes 8% and metamyelocytes 6%. Cytogenetic study from bone marrow has revealed complex translocation involving chromosome t(4;9;22) (q25;q34;q11) with an additional Philadelphia and marker chromosome [Figure 1].
The second patient was diagnosed with CML in October 2000, with total WBC count of 144x10 9 /l. Differential count was: neutrophils 36%, lymphocytes 12%, eosinophil 6%, basophils 3%, band 5%, myelocytes 35% and metamyelocytes 3%. He had moderate splenomegaly with mild hepatomegaly. Bone marrow was hypercellular with severe myeloid hyperplasia and an adequate number of megakaryocytes and LAP score was 2, which was suggestive of chronic phase of CML. Cytogenetic analysis from bone marrow revealed complex translocation t(4;9;22)(q25;q34;q11). Since he could not afford a-interferon he was treated with hydroxyurea. After seven courses of chemotherapy the patient came again for cytogenetic study from bone marrow. It has shown the same cytogenetic report with no evolution. Both patients are healthy after 3 to 5 years of initial diagnosis.
FISH analysis of the bcr/abl in case 1, produced 77% of double Ph', 15% single rearrangement and 2% collocation in 100 interphase nuclei [Figure 2].
Case 2 revealed 66.5% rearrangement, 5% collocation and 28.5% of the 200 nuclei with a normal distribution of the spots.
The painting of chromosome 9 is illustrated on [Figure 3]A and B.
Involvement of chromosome 9 in Ph' positive CML patients is well known. The common molecular event underlying classical, masked and variant Ph' translocations is the production of the BCR/ABL fusion gene. Evolution of prognostic features in a limited number of CMLs with classical or variant Ph' rearrangements gave controversial results. Some studies have indicated that the secondary anomalies in chromosome may be associated with the acute nature of the disease. However as observed in our patients, the complex translocation occurred in the context of chronic phase of CML and their clinical significance is unclear. Clonal evolution resulting from the additional numerical or structural chromosomal abnormalities in patients with CML is very important to note because 50% patients enter an accelerated phase after about 3 years and eventual transformation to acute leukemia., Such abnormal clonal evolution resulting from the complex translocation as observed in the present cases and those reported by others is not known. Tharapel et al noted that reciprocal translocations involving no loss or gain of the genetic material might not involve in abnormal clonal evolution and may have better prognostication than those with unbalanced karyotypic changes. Similar observation made by Hild  suggested that chromosomal abnormalities observed in addition to the Ph' chromosome at the time of initial diagnosis may not be associated with the poor prognosis. Though the specific clonal evolution has not been identified.
FISH analysis of these two cases showed double rearrangements involving complex reciprocal translocation though it is not possible to determine whether these represent abnormal clonal evolution or a unique, initial presentation of the variant Ph chromosome. But it is likely that the reciprocal translocation might display a benign effect on the evolution of the disease as opposed to the more deleterious nature of the unbalanced chromosome arrangement such as trisomy 1, trisomy 19 and iso (17q) which are seen in the blastic phase.[Figure 4]
Our study demonstrates how cytogenetic techniques and conventional molecular (FISH) techniques are helpful in identifying chromosomal abnormalities in a complex karyotypes which would have been missed in case of direct application of FISH at the time of initial diagnosis. More number of cases showing balanced and unbalanced structural and numerical abnormalities needs to be compiled to identify the underline mechanism/s involved in the longer survival of the patients. The molecular characterization of the longevity gene and gene-gene interaction involved in the complex chromosomal rearrangements need detail understanding.
We sincerely acknowledge Ms. Francine Jacque for her skillful FISH contribution, Ms. Ami Shah and Mrs. Manisha Desai for technical assistance. We thank Dr. Ashwin Patel and Dr. Chirag Desai for their reference.
|1||Groffen J, Stephenson JR, Heisterkamp N, de Klein A, Bartram CR, Grosveld G. Philadelphia chromosome break points are clustered within a limited region, bcr, on chromosome 22. Cell 1984;36:93-99. |
|2||Johansson B, Fioretos T, Mitelman F. Cytogenetic and molecular genetic evolution of chronic myeloid leukemia. Acta Haematologica 2002;107:76-94. |
|3||O'Brien S, Thall PF, Siciliano MJ. Cytogenetics of chronic myelogenous leukemia. Baillieres Clinical Haematology 1997;10:259-76.|
|4||Sandberg AA. The chromosome in human Cancer and Leukemia. 2nd edn. Elsevier, New York; 1990.|
|5||Potter Am, Watmore AE, Cooke P, Lilleyman JS, Sokol RJ. Significance of non-standard Philadelphia chromosomes in chronic granulocytic leukemia. British Journal of Cancer 1981;44:51-4.|
|6||Oudat R, Khan Z, CLSp(CG) MS, Glassman AB. A unique, complex variant Philadelphia chromosome translocation in a patient with typical chronic myelogenous leukemia. Arch Path Lab Med 2001;125:437-9.|
|7||Mitelman F, Johansson B, Mertens F. Data base of chromosome aberrations in Cancer. http://cgap.nci.nih.gov/Chromosomes/Mitelman; 2001.|
|8||Puca AA, Daly MJ, Brewster SJ, Matise TC, Barrett J, Shea-Drinkwater M et al . A genome-wide scan for linkage to human exceptional longevity identifies a locus on chromosome 4. Proc Natl Acad Sci 2001;98:10505-8.|
|9||Baccarani M. Prognostic study of alpha-interferon (INF)-treated chronic myelogenous leukemia (CML) patients: II. For The Italian Cooperative study group on chronic myelogenous leukemia. Predicting survival. In: Proceedings of the 2nd International Conference on Chronic Myelogenous Leukemia, Bologona, Italy; 1992. p. 163.|
|10||Hild F, Fonatsch C. Cytogenetic peculiarities in chronic myelogenous leukemia. Cancer Genetic Cytogenetic 1990;47:197-217.|