Secondary Chromosomal Changes Research Articles

FISH diagnostics in plasma cell myeloma: recommendations and own experience

Plasma cell myeloma (PCM) is disease with heterogeneous clinical outcomes. It is increasingly evident that the genetic features of the tumor cells largely dictate the clinical heterogeneity of PCM. Primary chromosomal alterations in myeloma can be divided into hyperdiploid and non-hyperdiploid subtypes. Secondary chromosomal changes occur during progression of disease. Cytogenetic abnormalities are important prognostic markers in PCM and some of them were incorporated into the current prognostic staging system of PCM. The presence of t(4;14), t(14;16), t(14;20), gain of 1q or TP53 deletion is considered to be high-risk myeloma. Detection of these alterations can be performed by interphase fluorescence in situ hybridization (FISH) after separation or identification of the plasma cells. The proper FISH examination in myeloma has to meet further requirements regarding aspirating and timing of samples, probe selection and their cut-off levels, the criteria of accurate analysis and reporting. Based on the literature, we here present technical recommendations regarding FISH in PCM. Furthermore, we share our own experience in FISH diagnostics acquired over 12 years. In this period, we have performed nearly 2,050 FISH tests in 603 myeloma patients and used two different methods of myeloma FISH: FISH on immunolabeled plasma cells, and target FISH with the BioView system.

Philadelphia chromosome duplication as a ring-shaped chromosome.

The gain of a second copy of the Philadelphia chromosome is one of the main secondary chromosomal changes related to the clonal evolution of cells with t(9;22) in chronic myelogenous leukemia. This gain causes the acquisition of another copy of the BCR/ABL1 fusion gene. Isochromosomes of the der(22) chromosome or double minute chromosomes are well known to lead an increased copy number of BCR/ABL1 gene. There is no antecedent of Philadelphia chromosome duplication as a ring chromosome. A recent published report contains evidence that strongly suggests that the Philadelphia chromosome was duplicated as a ring chromosome, observation that was overlooked by the authors. The instability inherent to the ring chromosome increases the risk of emergence of clones containing more and more BCR/ABL1 gene copies, which would produce increased fitness for clonal selection, resulting in worsening of the patient’s prognosis.

B-cell Acute Lymphoblastic Leukemia With t(9;22)(q34;q11) Translocation and Clonal Divergence Through ider(22) Chromosome and t(13;17)(q14;q25) Translocation

Dear Editor, The Mitelman Database of Chromosome Aberrations and Gene Fusions in Cancer (MDBGFC) has more than 100 cases for the t(9;22)(q34;q11.2) with divergent patterns of clonal evolution [1]. Here, we present a patient with B-cell ALL who showed t(9;22)(q34;q11.2) and a clonal divergence. Hematological studies from a 54-yr-old woman revealed white blood cell count of 97.2×109/L, platelets 35×109/L, and hemoglobin 6.9 g/dL. Bone marrow blasts displayed L2 morphology and expressed cell-surface differentiation antigens defining a B-cell phenotype, namely, CD10 (80%), CD19 (78%), CD5 (11%), CD3 (0%), and CD13 (0%). The patient received vincristine, prednisone, and daunorubicin-based chemotherapy. However, four months later, the patient was in the terminal phase and died after infiltrations were detected both to the retro-ocular and central nervous systems. We analyzed metaphasic cells from non-stimulated peripheral blood samples obtained eight days before the patient's death. Her karyotype included several sub-clones, which were described according to the International System for Human Cytogenetic Nomenclature (ISCN) (2013) [2], as: 46,XX,t(9;22)(q34;q11.2)[3]/46,idem,ider(22)(22pter→22q11.2::9q34→9q?tel::9q?tel→9q34::22q11.2→22pter)[14]/46,idem,t(13;17)(q14;q25)[3]/46,idem,+1,dic(1;1)(?;?),t(13;17)(q14;q25)[8]/46,XX[1] (Fig. 1A-E). C-banding by barium hydroxide and Giemsa revealed two heterochromatic regions (1q12 band) on the dic(1;1) chromosome (Fig. 1F). Fig. 1 Chromosomes banded with standard techniques. (A) Metaphasic cell with the ider(22). (B) This metaphasic cell contains both t(9;22)(q34;q11.2) and t(13;17)(q14;q25). (C) In addition to the two translocations observed in the above image, a dic(1;1) chromosome ... FISH studies with the dual-color, single-fusion BCR/ABL1 probe (Vysis, Downers Grove, IL, USA) revealed two fusion signals on the ider(22) and only one fusion signal on the standard Philadelphia chromosome (data not shown). FISH study with the RB1 probe (Vysis) disclosed two signals on both normal 13 chromosomes in the clone containing ider(22) (Fig. 2A). Cells with t(13;17) were positive only on the normal chromosome 13 and did not display any signal on either der(13) or der(17) (Fig. 2B and C), thus demonstrating the loss of RB1 by translocation. Fig. 2 FISH analysis with the RB1 probe (red signals) in cells counterstained with DAPI (4',6-diamidino-2-phenylindole; blue color). (A) Metaphase from the clone with ider(22) showing two RB1 signals on both normal 13 chromosomes. (B) Cell with t(13;17) displaying ... Yamamoto et al. [3] reported the presence of first and only ider(22) chromosome similar to the one observed by us in another ALL patient who had a poor prognosis too. These ider(22) chromosomes could result from an U-type sister chromatid exchange. The ider(22) chromosome equals a second copy of der(22) chromosome, which is well known to be one of the main secondary chromosomal changes related to the clonal evolution of cells with t(9;22) [1]. The co-occurrence of t(9;22)(q34;q11) and t(13q14) is rare. There are only six cases registered in the MDBGFC [1], which were previously reported [4,5,6,7]. When both translocations were present, the patients had CML in blast crisis or relapse. Out of four patients tested for chromosome 13 deletions by using FISH [5,6], three tested negative, and only in the fourth patient, there was inconclusive evidence of such a deletion [6]. The t(13;17)(q14;q25), which caused the loss of RB1 sequences in the present patient has not been previously described in ALL [1]. This translocation has only been detected in an AML-M4 patient who did not show deletion of the RB1 gene [8], and in a case of Sezary syndrome in which the status of RB1 gene was not tested [9]. Although we did not know the extent of present 13q deletion, some features of the patient such as genome instability, poor prognosis, and shortened survival suggest that she had a large deletion inclusive of the RB1 gene. Moreover, the chromosomal band 17q25 has been implicated in several translocations also associated with poor prognosis and shorter survival [1]. Imbalances in chromosome 1 are frequent in human neoplasia [1]. The apparently different sizes of two heterochromatic regions observed on the dic (1;1) chromosome (Fig. 1F and ​and2C)2C) suggest a translocation between homologous chromosomes as the forming mechanism of such a dicentric chromosome. Concomitant with the clonal divergence found in peripheral blood, this patient had central nervous system and retro-ocular infiltrations that could not be further studied. Nowicki et al. [10] observed that the circulating CML-blast crisis cells showed major changes than the CML-cells from bone marrow. This observation suggests that leukemic bloodstream cells differ from those in their original niche in survival, growth, invasiveness, and metastatic potential. In our patient, we could not determine whether the divergent sub-clones found in peripheral blood were also present in the infiltrations, or whether each infiltration was derived from a unique and independent sub-clone. This case calls for research on chromosomal and genetic changes that enable the leukemic cells to infiltrate other tissues.

Sequential karyotyping in Burkitt lymphoma reveals a linear clonal evolution with increase in karyotype complexity and a high frequency of recurrent secondary aberrations.

Typical Burkitt lymphoma is characterized by an IG-MYC translocation and overall low genomic complexity. Clinically, Burkitt lymphoma has a favourable prognosis with very few relapses. However, the few patients experiencing disease progression and/or relapse have a dismal outcome. Here we report cytogenetic findings of seven cases of Burkitt lymphoma in which sequential karyotyping was performed at time of diagnosis and/or disease progression/relapse(s). After case selection, karyotype re-review and additional molecular analyses were performed in six paediatric cases, treated in Berlin-Frankfurt-Münster-Non-Hodgkin lymphoma study group trials, and one additional adult patient. Moreover, we analysed 18 cases of Burkitt lymphoma from the Mitelman database in which sequential karyotyping was performed. Our findings show secondary karyotypes to have a significant increase in load of cytogenetic aberrations with a mean number of 2, 5 and 8 aberrations for primary, secondary and third investigations. Importantly, this increase in karyotype complexity seemed to result from recurrent secondary chromosomal changes involving mainly trisomy 21, gains of 1q and 7q, losses of 6q, 11q, 13q, and 17p. In addition, our findings indicate a linear clonal evolution to be the predominant manner of cytogenetic evolution. Our data may provide a biological framework for the dismal outcome of progressive and relapsing Burkitt lymphoma.

Comprehensive cytogenetic and molecular cytogenetic analysis of 44 Burkitt lymphoma cell lines: Secondary chromosomal changes characterization, karyotypic evolution, and comparison with primary samples

Burkitt lymphoma cell lines (BL-CL) are used extensively as in vitro models in genetic studies; however, cytogenetic information is not always available or updated. We provide a comprehensive cytogenetic resource of 44 BL-CL, assessed by G-banding, multicolor-FISH, and FISH with 1q, 3p, 7q, and 13q region-specific probes, including the first cytogenetic characterization of 22 BL-CL and the revision of further 22 commonly used BL-CL. Based on these data, we determined a consensus karyotype, evaluated in detail the secondary chromosomal changes (SCC), and the karyotypic stability of these cell lines. An individual karyotype was identified in all investigated BL-CL, confirming their unique origin. Most of the BL-CL remained cytogenetically relative stable after years of intensive cultivation. The most frequent structural SCC were dup(1q), del(13q) and the most frequent numerical SCC were +7, +13. Common breakpoints were located on 1q12, 7q11, and 13q31. The most common gains were in 1q and 7q and the most common losses were in 11q and 13q. Interestingly, the frequency of 1q gains and 13q losses was significantly higher in the EBV-negative than in the EBV-positive BL-CL. Furthermore, by reviewing karyotypes of 221 primary BL listed in the Mitelman database, we observed similarities between BL-CL and primary BL regarding the frequency of numerical and structural SCC and breakpoint distribution. In BL-CL and in primary BL two SCC, dup(1q), and +12, always occurred mutually exclusive of each other. These findings validate BL-CL as appropriate model for in vitro studies on the significance of SCC in the pathogenesis of BL.

An international study of intrachromosomal amplification of chromosome 21 (iAMP21): cytogenetic characterization and outcome

Intrachromosomal amplification of chromosome 21 (iAMP21) defines a distinct cytogenetic subgroup of childhood B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). To date, fluorescence in situ hybridisation (FISH), with probes specific for the RUNX1 gene, provides the only reliable detection method (five or more RUNX1 signals per cell). Patients with iAMP21 are older (median age 9 years) with a low white cell count. Previously, we demonstrated a high relapse risk when these patients were treated as standard risk. Recent studies have shown improved outcome on intensive therapy. In view of these treatment implications, accurate identification is essential. Here we have studied the cytogenetics and outcome of 530 iAMP21 patients that highlighted the association of specific secondary chromosomal and genetic changes with iAMP21 to assist in diagnosis, including the gain of chromosome X, loss or deletion of chromosome 7, ETV6 and RB1 deletions. These iAMP21 patients when treated as high risk showed the same improved outcome as those in trial-based studies regardless of the backbone chemotherapy regimen given. This study reinforces the importance of intensified treatment to reduce the risk of relapse in iAMP21 patients. This now well-defined patient subgroup should be recognised by World Health Organisation (WHO) as a distinct entity of BCP-ALL.

A Case of Therapy-Related Acute Myeloid Leukemia Following 5-Fluorouracil Chemotherapy

A Case of Therapy-Related Acute Myeloid Leukemia Following 5-Fluorouracil Chemotherapy

Chromosome copy number changes carry prognostic information independent of KIT/PDGFRA point mutations in gastrointestinal stromal tumors

BackgroundOncogenic point mutations in KIT or PDGFRA are recognized as the primary events responsible for the pathogenesis of most gastrointestinal stromal tumors (GIST), but additional genomic alterations are frequent and presumably required for tumor progression. The relative contribution of such alterations for the biology and clinical behavior of GIST, however, remains elusive.MethodsIn the present study, somatic mutations in KIT and PDGFRA were evaluated by direct sequencing analysis in a consecutive series of 80 GIST patients. For a subset of 29 tumors, comparative genomic hybridization was additionally used to screen for chromosome copy number aberrations. Genotype and genomic findings were cross-tabulated and compared with available clinical and follow-up data.ResultsWe report an overall mutation frequency of 87.5%, with 76.25% of the tumors showing alterations in KIT and 11.25% in PDGFRA. Secondary KIT mutations were additionally found in two of four samples obtained after imatinib treatment. Chromosomal imbalances were detected in 25 out of 29 tumors (86%), namely losses at 14q (88% of abnormal cases), 22q (44%), 1p (44%), and 15q (36%), and gains at 1q (16%) and 12q (20%). In addition to clinico-pathological high-risk groups, patients with KIT mutations, genomic complexity, genomic gains and deletions at either 1p or 22q showed a significantly shorter disease-free survival. Furthermore, genomic complexity was the best predictor of disease progression in multivariate analysis.ConclusionsIn addition to KIT/PDGFRA mutational status, our findings indicate that secondary chromosomal changes contribute significantly to tumor development and progression of GIST and that genomic complexity carries independent prognostic value that complements clinico-pathological and genotype information.

Acute myeloid leukemia with t(9;11)(p21-22;q23): common properties of dysregulated ras pathway signaling and genomic progression characterize de novo and therapy-related cases.

We compared pathogenetic features of 32 de novo and 29 therapy-related (t) t(9;11)(p21-22;q23)/MLLT3-MLL acute myeloid leukemia (AML) cases to identify progression factors and to assess whether distinction between these manifestations is warranted. MLLT3-MLL rearrangement was commonly the sole karyotypic abnormality at diagnosis, with many secondary chromosomal changes emerging at relapse in both subgroups. Ras point mutations were common in both groups (overall, 18/50 [36%]) and associated with monocytic phenotype and aneuploid progression. Expression patterns of 675 microRNAs profiled in 7 cases were also similar, with let-7 species linked to Ras down-modulation expressed at low levels. Outcome for both groups was poor (relapsed or refractory in 49/61 [80%] cases); however, patients with t-AML were generally older and female, with worse outcome (P = .03), likely secondary to t-AML mostly arising in patients with breast cancer following topoisomerase inhibitor-containing chemotherapy. Ras activation seems to complement the MLLT3-MLL oncogene in transformation with features of de novo and t-AML with MLLT3-MLL being similar.

A rare case of chronic myeloid leukemia with secondary chromosomal changes including partial trisomy 17q21 to 17qter and partial monosomy of 16p13.3

BackgroundThe so-called Philadelphia (Ph) chromosome is present in almost all cases with chronic myeloid leukemia (CML). Around 5-10% of these patients show complex translocations involving other chromosomes in addition to and/or besides chromosomes 9 and 22. As nowadays most CML cases are treated with Imatinib, variant rearrangements have in general no specific prognostic significance, though events of therapy resistance remain to be studied.ResultsHere we report a Ph chromosome positive patient with hematological typical chronic phase CML. Untypically, an unbalanced complex rearrangement involving chromosomes 16 and 17 leading to a deletion of 16pter and partial trisomy of 17q21 to 17qter, was identified besides a trisomy 8 and an additional Ph chromosome in a part of malignant cells.ConclusionHere a novel and cytogenetically unique case of a Ph chromosome positive CML clinically in chronic phase is reported, having complex secondary chromosomal aberrations. Thus, CML patients with complex chromosomal changes are nonetheless treatable by Imatinib.

Ploidy and karyotype complexity are powerful prognostic indicators in the Ewing's sarcoma family of tumors: A study by the United Kingdom Cancer Cytogenetics and the Children's Cancer and Leukaemia Group

Ewing's sarcoma family tumors (ESFT) are characterized by the presence of EWSR1-ETS fusion genes. Secondary chromosome changes are frequently described, although their clinical significance is not clear. In this study, we have collected and reviewed abnormal karyotypes from 88 patients with primary ESFT and a rearrangement of 22q12. Secondary changes were identified in 80% (70/88) of tumors at diagnosis. Multivariate analysis showed a worse overall and relapse free survival (RFS) for those with a complex karyotype (overall survival, P = 0.005; RFS, P = 0.04), independent of metastatic disease. Univariate survival analysis showed that a chromosome number above 50 or a complex karyotype was associated with a worse overall survival (>50 chromosomes, P = 0.05; complex karyotype, P = 0.04). There was no association between type of cytogenetic abnormality and the presence of metastatic disease at diagnosis. Univariate and multivariate survival analysis of a small subgroup with trisomy 20 indicated that trisomy 20 was associated with a worse overall and RFS. There was no difference in outcome associated with other recurrent trisomies (2, 5, 7, 8, or 12) or the common recurrent secondary structural rearrangements (deletions of 1p36, 9p12, 17p13, and 16q, and gain of 1q), although numbers were small. These data demonstrate the continued value of cytogenetics as a genome-wide screen in ESFT and illustrates the potential importance of secondary chromosome changes for stratification of patients for risk. Specifically, karyotype complexity appears to be a powerful predictor of prognosis, and the presence of trisomy 20 may be a marker of a more aggressive subset of this group.

An inv(16) in Ph-negative cells of a chronic myelogenous leukemia patient after imatinib treatment

Secondary chromosomal changes are known to develop in Philadelphia chromosome-negative (Ph−) cells of chronic myelogenous leukemia (CML) patients after treatment with imatinib mesylate, an ABL kinase inhibitor. We report here a novel case of a pericentric inversion of chromosome 16 as the sole cytogenetic abnormality in Ph− cells after treatment of Ph+ CML with imatinib.

Imbalances of the 9q34 Region Downstream of ABL Gene in CML Are Associated with Blast Crisis.

Chronic myeloid leukaemia (CML) is a pluripotent haematopoietic stem cell disorder defined by expression of the BCR-ABL fusion gene, a constitutively activated tyrosine kinase. The fusion gene commonly results from formation of the Philadelphia chromosome after a t(9;22)(q34;q11) or related variant rearrangement. The disease follows a biphasic course with an initial benign chronic phase (CP) of 3–4 years treatable with agents such as Imatinib, followed by a rapidly fatal transformation resembling an acute leukaemia (blast crisis, BC). The CML blast crisis has been linked to a number of secondary chromosome changes leading to genome imbalances, such as additional Ph, +8, +9, iso17q. Prognostic scores based on clinical criteria (Sokal and Hasford scores) have been replaced with the discovery of other cytogenetic abnormalities occurring simultaneously at the time of translocation, such as deletions flanking the ABL/BCR breakpoint at the der(9)t(9;22) chromosome that lead to a significantly worse prognosis. We undertook array CGH analysis using an oligo based platform (Agilent) on 46 CML patients (25 CP, 19 BC & 8 in both phases) and 12 CML cell lines revealed a range of recurrent genomic imbalances. Two sets of recurrent cryptic imbalances were identified. These represented both gains and high-level amplifications affecting the 9q34.12 region immediately downstream of ABL gene, as well as losses or gains in the distal part of the 9q34-qter segment. These imbalances were found only in patients at the BC stage. Furthermore, in cases with follow-up samples, the 9q34 imbalances were present in the advanced stage of disease thus confirming their secondary nature. Among the genes found to be amplified in CML/BC is NUP-214, a nucleoporin gene, recently implicated in T-cell acute lymphoblastic leukaemia, thus suggesting an important role for cell clone survival. Confirmation of these amplifications was sought using fluorescent in situ hybridisation (FISH). A dual fusion probe targeting the ABL-NUP214 region was applied to a selection of twenty three patients with confirmed CML and features such as deletion of der(9) chromosome or resistance to treatment with Imatinib, shown to be more prone to variation within the CML phenotypeAmplification of the NUP214 region was found in five patients. These findings represent the first reports of NUP214 amplifications in CML, paving the way for future work.

No prognostic effect of additional chromosomal abnormalities in children with acute lymphoblastic leukemia and 11q23 abnormalities

This study characterized the additional chromosomal abnormalities (ACA) associated with 11q23 rearrangements in 450 infants and children with acute lymphoblastic leukemia (ALL) and examined the impact of these ACA on survival. Overall, 213 (47%) cases had ACA but the incidence varied according to patient age and 11q23 subgroup. Infants and patients with t(4;11)(q21;q23) had the lowest incidence of ACA (50/182 (27%) and 57/216 (26%) respectively), whereas patients with del(11)(q23) had the highest incidence (66/93 (71%)). Del(11)(q23) abnormalities were heterogeneous and occasionally secondary to t(9;22)(q34;q11.2). Thus, patients with del(11)(q23) comprised a separate biological entity, which was clearly distinct from those with an 11q23 translocation. The most frequent specific ACA were trisomy X (n = 38), abnormal 12p (n = 32), abnormal 9p (n = 28) and del(6q) (n = 19). The presence of ACA did not change the 5 year event-free survival estimates among children (56% (95% Cl 46-65%) vs 62% (54-69%)) or infants (22% (15-29%) vs 18% (9-29%)), nor when the different 11q23 subgroups were analyzed separately. This study has conclusively demonstrated that there is no prognostic effect of secondary chromosomal changes in association with 11q23 abnormalities in childhood ALL. However, characterization of these ACA is important to determine their potential role in initiation of MLL driven leukemogenesis.

An additional segment at 1p36 derived from der(18)t(14;18) in patients with diffuse large B-cell lymphomas transformed from follicular lymphoma

The particular translocation in follicular lymphomas (FLs) is a t(14;18)(q32;q21), recombining the immunoglobulin heavy chain (IgH) gene on chromosome 14 with the B-cell leukemia/lymphoma 2 (BCL2) gene on chromosome 18. Some low-grade FLs are aggressively transformed into diffuse large B-cell lymphomas, presumably by acquisition of secondary chromosomal changes, including chromosomal band 1p36. A common example is add(1)(p36). Because it is difficult to identify the origin of add(1)(p36) even on high-resolution G-banding analysis, we used spectral karyotyping (SKY) and double-color fluorescence in situ hybridization (DC-FISH) to define the t(14;18) and the extra band at 1p36 in two cases of diffuse large B-cell lymphoma (DLBCL). SKY revealed that the extra chromosomal segment on 1p36 was derived from chromosome 18. DC-FISH defined BCL2/IgH fusion signals at 1p36 in addition to t(14;18), suggesting that BCL2/IgH fusion at 1p36 was an evolutionary alteration following the primary BCL2/IgH translocation on der(18) in both cases. Our results indicate that IgH alleles, implicated in chromosomal rearrangement, may themselves frequently be targets for secondary translocations, suggesting that multiple IgH translocations and insertions are associated with the progression of FL.

Determination of secondary chromosomal aberrations of chronic myelocytic leukemia

Chronic myeloctyic leukemia (CML) is a stem cell disorder characterized by the cytogenetic abnormality of t(9;22)(q34;q11.2), which progresses from a chronic phase to an accelerated phase (AP), and/or a blast phase (BP) of myelocytic or lymphoid phenotype. This progression is frequently preceded or accompanied by recurring secondary chromosomal abnormalities (SCA) that are believed to play a role in the transformation and may also serve as valuable prognostic indicators. Failure to note such abnormalities may lead to an inappropriate clinical evaluation. We observed CML patients with AP or BP who did not show SCA by routine cytogenetic analysis. To determine the presence or absence of specific SCA in those cases, we applied fluorescence in situ hybridization (FISH) to four CML cases with pseudodiploid cytogenetics [t(9;22)(q34;11.2) as the sole abnormality] by conventional karyotyping. Bone marrow biopsies from two AP and two BP of CML patients with pseudodiploid karyotypes by conventional cytogenetics were examined by FISH for trisomy 8 and i(17q). These SCA are major secondary chromosomal changes seen in BP of CML patients. Results were considered positive if more than 2.4% of cells had +8 and >6.25% for i(17q) by FISH. Four out of four patients were positive for +8. These results indicate that FISH techniques are valuable in the determination of SCA in CML, which were t(9;22)(q34;q11.2) positive as the sole cytogenetic abnormality with standard G-banding karyotyping and can be helpful for the early diagnosis of CML progression.

Secondary chromosomal changes in 34 Philadelphia-chromosome–positive chronic myelocytic leukemia patients from the Mexican West

The clonal evolution in t(9;22)-positive chronic myelocytic leukemia (CML) is well established. Four major changes occur in more than 70% of patients: +8, i(17q), +19, and an extra Philadelphia chromosome. The frequencies of secondary chromosomal changes in 34 patients from the states of Jalisco, Nayarit, Michoacán, and Colima (the Mexican West) with Philadelphia-chromosome–positive CML were assessed. The most frequent abnormalities were tetraploidy (12 cases); +8, inv(3)(q21q26), and octoploidy (3 cases each); and +der(22)(2 cases). Some translocations not previously associated with CML were observed, such as t(2;7)(p12;q36), t(3;6)(q26;p25), t(3;17)(q26;p13), and t(6;17)(q21;q23∼q25). Significant differences were found for +8 with respect to population results from Japan and from southern, eastern, and western Europe; for i(17)(q10) from eastern Europe; for +19 from Japan and western Europe; and for +der(22) from Japan, southern Europe, and western Europe. Although polyploidy could result from endomitosis, there is no direct evidence that the BCR/ABL protein influences such a process; however, protein kinases such as MAPK, which are involved in endomitosis, are activated by the BCR/ABL protein, and so the BCR/ABL protein could promote endomitosis through the MAPK pathway.

Derivative (7)t(7;8)(q34;q21): a new additional cytogenetic abnormality in acute promyelocytic leukemia

Cytogenetic abnormalities in acute myelocytic leukemia (AML) have been identified as one of the most important prognostic factors. The t(15;17) is associated with high rates of complete remission and event-free survival. Secondary chromosomal changes are also present in approximately one third of patients with newly diagnosed acute promyelocytic leukemia (APL). Indeed, the gain of whole chromosome 8 may be involved in the course of APL under C-MYC gene dosage effect theory. Complete or partial loss of the long arm of chromosome 7 region has been recognized in preleukemic myelodysplasia or unfavorable AML. We report here two original APL cases in which a new additional chromosomal abnormality, der(7)t(7;8)(q34;q21), is associated with the t(15;17)(q22;q21). This recurrent abnormality results in a partial loss of 7q associated with a partial 8q trisomy. As the 7q and 8q breakpoints were similar in both cases, the involvement of these critical regions in the pathogenesis and outcome of APL disease has to be determined.

Ring chromosome 8 and translocation t(8;21) in a patient with acute myeloblastic leukemia

Recurrent translocation t(8;21)(q22;q22) acute myeloid leukemia (AML) is often associated with secondary chromosome changes of which the clinical significance is not clear since they do not seem to impair the prognosis. Uncommon chromosome changes may lead to the identification of leukemogenetic factors associated with t(8;21) since the AML1/RUNX1-ETO fusion gene resulting from the translocation is thought to be unable alone to induce leukemia. We here report a patient with AML, t(8;21) and ring chromosome 8 resulting in partial chromosome 8 deletion. Another patient with partial 8q deletion has been previously reported. It is suggested that more attention be paid to the genes located in distal 8q in relation to leukemogenesis.

Paternal isodisomy 7q secondary to monosomy 7 at recurrence in a Down syndrome child with acute myelogenous leukemia

We report a boy with Down syndrome and leukemia who acquired uniparental isodisomy of chromosome 7q as a secondary chromosomal change during recurrence of the disease. His karyotype before therapy was 46,XY,der(1)t(1;1)(p36;q32),−7,+21c[17]/46,idem,del(9)(p22)[10], whereas at recurrence it was 46,XY,der(1)t(1;1)(p36;q32,−7,der(7)(qter→p22∼pter::q10→qter),del(9)(p22),+21c[13]/47,XY,+21c[2]. By using polymerase chain reaction amplification of D7S493 and D7S527 markers, we identified the loss of the maternal chromosome 7 with a consequent paternal isodisomy in the clone with dup7q. This rearrangement could be implicated in the progression of the disease by causing (1) nullisomy for a gene or genes located on 7p22→pter, (2) functional double doses of exclusively paternal expressed genes, and (3) restoration of the effects produced by haploinsufficiency of biparental expressed genes.