Additional Chromosomal Aberrations Research Articles

Induction of unstable and stable chromosomal aberrations by 99mTc: in-vitro and in-vivo studies

Biological dosimetry, which determines the dose of acquired radiation by measuring radiation-induced variation of biological parameters, can help assess radiation damage in an individual. Evaluation of radiation exposure requires setting up reference curves for each type of radiation. To evaluate the potential induction of chromosome aberrations by a clinical diagnostic dose of 99mTc. Dicentrics, rings, excess fragments, complete reciprocal translocations and incomplete reciprocal translocations were scored in peripheral blood lymphocytes from patients exposed to a 99mTc bone scintigraphy. A specific relationship between the radiation dose delivered by 99mTc and the frequency of stable and unstable chromosomal aberrations was established in vitro to estimate whole-body dose. Chromosome analysis using fluorescence plus Giemsa and fluorescence in-situ hybridization was undertaken on six patients before and after a 99mTc bone scintigraphy. Dicentrics, rings, excess fragments, and translocations were scored in blood lymphocytes after in vitro 99mTc external irradiation in order to construct dose calibration curves. Analysis of the in-vitro data shows that the number of both unstable and stable aberrations has a quadratic linear relationship to the dose. Our in-vivo irradiation studies showed that activities of 99mTc-hexamethylene diphosphonate (99mTc-HDP) used for bone investigations do not induce any additional unstable chromosome aberrations and translocations. The frequencies obtained did not differ significantly from background values. 99mTc can produce unstable and stable chromosomal aberrations in vitro. 99mTc-HDP administration does not induce supplementary chromosomal aberrations. The dose-response curves will allow a more accurate evaluation of the risk related to in-vivo administration of 99mTc labelled radiopharmaceuticals, and they can be used to assess the safe upper limit of injected activity in humans.

Cytogenetic and expression profiles associated with transformation to androgen-resistant prostate cancer

The mechanisms underlying the progression of prostate cancer to androgen-resistant cancer are still not fully understood. Here, we studied the genetic events associated with this transformation. The androgen sensitive prostate cancer cells line LNCaP-FGC and its androgen resistant subline LNCaP-r were investigated using SKY, CGH, and cDNA microarray. Karyotypically, several additional chromosomal aberrations were seen in LNCaP-r as compared to the parental line. CGH also revealed unique net chromosomal alterations in LNCaP-r compared to LNCaP-FGC, including gain of 2p13-23, 2q21-32, and 13q and loss of 6p22-pter. cDNA microarray analysis identified several genes involved in DNA methylation, such as DNMT2, DNMT3a, and methyl-CpG binding domain protein 2 and 4 that were higher expressed in LNCaP-r. Interestingly, androgen responsiveness of LNCaP-r was restored after treated with DNA methyltransferase inhibitor. Our findings may serve as a basis for molecular dissection of the mechanisms involved in development of androgen resistant prostate cancer.

High-dose cytarabine and mitoxantrone in consolidation therapy for acute promyelocytic leukemia

The objective of our study was to evaluate high-dose cytarabine in consolidation therapy in patients with newly diagnosed acute promyelocytic leukemia (APL). Patients (age 16-60 years) received induction therapy according to the AIDA protocol (all-trans retinoic acid, idarubicin) followed by one cycle of ICE (idarubicin, cytarabine, etoposide) and two cycles of HAM (cytarabine 3 g/m(2) q12h, days 1-3; mitoxantrone 10 mg/m(2), days 2 and 3). From 1995 to 2003, 82 patients were enrolled. In total, 72 patients (88%) achieved a complete remission, and 10 patients (12%) died from early/hypoplastic death (ED/HD). A total of 71 patients received at least one cycle of HAM. Relapse-free survival (RFS) and overall survival (OS) after 46 months were 83 and 82%, respectively. White blood cell count above 10.0 x 10(9)/l at diagnosis and additional chromosomal aberrations were unfavorable prognostic markers for OS, whereas no prognostic markers for RFS were identified including FLT3 mutations. In conclusion, high-dose cytarabine in consolidation therapy for patients with newly diagnosed APL is an effective treatment approach.

Characterization of quantitative chromosomal abnormalities in renal cell carcinomas by interphase four-color fluorescence in situ hybridization

Renal cell carcinomas (RCC) in adults are histologically heterogeneous solid tumors with specific chromosomal abnormality patterns included in the World Health Organization (WHO) classification. To overcome some of the drawbacks of cytogenetic and comparative genomic hybridization (CGH) analyses, we designed a first-generation cytogenetic diagnostic test using four-color fluorescence in situ hybridization (FISH) on interphase nuclei. We selected 51 bacterial artificial chromosome and P1-derived artificial chromosome clones covering 17 chromosomal regions involved in the abnormalities of the adult RCC histologic subtypes. An initial set of probes allowed the identification of clear-cell RCC, papillary RCC, and other RCC on a single slide. A second test allowed the detection of additional chromosomal abnormalities or aberrations specific to chromophobic RCC and oncocytomas. We tested 25 cases of RCC, and the results were in agreement with those of cytogenetic techniques and/or CGH methods. The techniques appeared to be very sensitive, because small tumoral cell clones that were undetected by other cytogenetic methods were identified with this method. It was concluded that the multicolor FISH test was specific and sensitive, easy to perform, and could be part of the investigation process in RCC.

Clonal evolution with inv(11)(p15q22) and NUP98/DDX10 fusion gene in imatinib-resistant chronic myelogenous leukemia

The BCR/ABL tyrosine kinase inhibitor imatinib has shown remarkable efficacy in treating patients with chronic myelogenous leukemia (CML). In a small portion of patients treated with imatinib, however, the disease may progress to advanced stages, frequently accompanied by cytogenetic clonal evolution with the appearance of additional chromosomal aberrations besides the Philadelphia chromosome. Here we report the appearance of an inv(11)(p15q22) as a clonal evolution in a CML patient undergoing treatment with imatinib. Leukemic cells from the patient were found to express the fusion transcript of NUP98 and DDX10, which is in accordance with previously reported cases of de novo or therapy-related acute myelogenous leukemia and myelodysplastic syndrome with inv(11)(p15q22). Although the patient showed resistance to imatinib with the disease rapidly progressing to blast crisis, sequence analysis failed to reveal any mutation in the kinase domain of BCR/ABL that would explain the imatinib resistance. Furthermore, ex vivo treatment of leukemic cells with imatinib significantly reduced tyrosine phosphorylation of CrkL, a target of the BCR/ABL kinase. These observations raise a possibility that the NUP98/DDX10 fusion might be involved in imatinib resistance as well as in acute transformation of CML.

Role of FISH on Uncultured Amniocytes for the Diagnosis of Aneuploidies in the Presence of Fetal Anomalies

Objective: To assess the accuracy of fluorescent in situ hybridization (FISH) on amniocytes in fetuses affected by structural malformations suggestive of chromosomal anomalies. Methods: FISH of uncultured amniotic fluid cells and conventional cytogenetic analysis were performed on 48 pregnancies with ultrasonographic (US) evidence of fetal anomalies. The AneuVysion^® assay (Vysis) with specific probes for chromosomes 13, 18, 21, X and Y, was used. Amniotic fluid samples were obtained between the 14th and 34th weeks of gestation. Results: In cases with a single abnormal US finding (n = 15), 5 aneuploidies were detected (1 case of trisomy 13 and 4 of trisomy 21). In the group with two or more malformations (n = 33) there were 15 aneuploidies (9 cases of trisomy 18, 2 of trisomy 21, 2 monosomy X, 1 trisomy 13, and 1 triploidy). In this group, conventional cytogenetic analysis revealed two additional chromosomal anomalies not detectable by FISH (1 trisomy 16 mosaic, and a terminal deletion 4p). No sex aneuploidies were observed. Conclusions: The lack of false-positive diagnosis in the FISH analysis in our sample prompts us to consider interphase FISH as a useful tool in pregnancies at high risk for chromosomal aneuploidies. When FISH analysis is normal, the overall risk of chromosomal abnormalities is significantly reduced. However, the finding of two chromosomal anomalies undetectable by AneuVysion^® assay confirms the need for conventional chromosome analysis to complement FISH results. Moreover, the results collected here, in agreement with those already reported in the literature, indicate that FISH analysis on uncultured amniocytes can play an important role in counselling and decision-making, especially in cases at risk for aneuploidies, such as those with structural abnormalities at US.

Additional Chromosome Abnormalities Have No Prognostic Value in Acute Promyelocytic Leukemia Patients Treated with Simultaneous ATRA and Anthracycline-Based Chemotherapy: An Update of the APL96 and APL99 Pethema Protocols.

Acute promyelocytic leukemia (APL) is genetically characterized by a reciprocal translocation between the long arms of chromosomes 15 and 17, the t(15;17)(q22;q21), which results in the fusion gene PML/RARα. Conventional karyotyping on banded methaphases shows that about one third of APL patients carry additional cytogenetics changes in leukemic cells. The aim of the present study was to compare the clinical and biological characteristics of APL patients with or without chromosomal changes in addition to the t(15;17) and their potential impact on outcome. Between November 1996 and July 2004, a total of 640 de novo genetically confirmed APL patients were enrolled in two consecutive PETHEMA trials (APL96 and APL99). Cytogenetic analysis was available in 418 cases (65%) who disclosed the following features:212 M/206 F; median age 40 yrs. (range, 2–83); median WBC count 2.2 x 109/L (range, 0.3–236); median platelet count 22 x 109/L (range, 1–207); 337 M3 typical/81 M3 variant; relapse risk group (Sanz et al, Blood 2000): 81 (19%) low-risk, 235 (56%) intermediate-risk and 102 (25%) high-risk. Treatment consisted of all-trans-retinoic acid (ATRA) and anthracycline monochemotherapy for induction, followed by three consolidation courses of anthracycline/anthaquinone monochemotherapy with or without ATRA, and maintenance therapy with intermittent ATRA and low dose chemotherapy (methotrexate and 6-mercaptopurine). Additional chromosome aberrations were observed in 95 cases (23%). The most frequent secondary changes were + 8 (n=39), either alone (n=32) or associated with other aberrations (n=7), followed by abn(7q) (n=6), i(17) (n=5), abn(3q) (n=4), abn(1p) (n=3), del(9q) (n=3), abn(8q) (n=3), abn(11q) (n=3), +21 (n=3), +5 (n=2), abn(8p) (n=2), abn(13q) (n=2), and -Y (n=2). No clinical, biological, morphological, immunophenotypic or molecular differences were observed between the group of patients with t(15;17) alone and the group of patients with additional changes. Moreover, no statistical differences were found in terms of complete remission rate, 6-year disease-free survival and relapse-risk (92% vs 91%, 87 vs 90% and 10 vs 10% for patients with t(15;17) alone and patients with additional changes, respectively). In conclusion, patients with APL and additional cytogenetic abnormalities do not show distinct features as compared with patients with t(15;17) alone. Moreover, additional chromosomal changes have no influence in outcome of APL patients receiving state-of-the-art therapeutic protocols.

Translocation t(1;6)(p35.3;p25.2): a new recurrent aberration in ‘unmutated’ B-CLL

Although reciprocal chromosomal translocations are not typical for B-cell chronic lymphocytic leukemia (B-CLL), we identified the novel t(1;6)(p35.3;p25.2) in eight patients with this disorder. Interestingly, all cases showed lack of somatically mutated IgV(H). Clinical, morphological, immunologic, and genetic features of these patients are described. Briefly, the age ranged from 33 to 81 years (median: 62.5 years) and the sex ratio was 6M:2F. Most of the patients (6/8) presented with advanced clinical stage. Therapy was required in seven cases. After a median follow-up of 28 months, five patients are alive and three died from disease evolution. Three cases developed transformation into diffuse large B-cell lymphoma. Translocation t(1;6) was found as the primary karyotypic abnormality in three patients. Additional chromosomal aberrations included changes frequently found in unmutated B-CLL, that is, del(11)(q), trisomy 12 and 17p aberrations. Fluorescence in situ hybridization analysis performed in seven cases allowed us to map the t(1;6) breakpoints to the 1p35.3 and 6p25.2 chromosomal bands, respectively. The latter breakpoint was located in the genomic region coding for MUM1/IRF4, one of the key regulators of lymphocyte development and proliferation, suggesting involvement of this gene in the t(1;6). Molecular characterization of the t(1;6)(p35.3;p25.2), exclusively found in unmutated subtype of B-CLL, is in progress.

Tumor necrosis factor alpha induces senescence and chromosomal instability in human leukemic cells.

Previous studies have documented that Tumor necrosis factor alpha (TNFalpha) is a potent negative regulator of normal hematopoiesis. However, the mechanism by which TNFalpha acts at the cellular level is not totally understood. Although apoptotic cell killing appears to be the most common cellular effect of TNFalpha, other studies suggest that this cytokine may elicit other cellular responses such as prolonged growth inhibition. In this context, we have investigated whether TNFalpha may induce senescence in hematopoietic cells, which display intrinsic defect in the apoptotic machinery. The present study described that, in the leukemic KG1 cells, TNFalpha induced no apoptosis but a senescence state characterized by prolonged growth arrest, increased beta-galactosidase activity, p21WAF-1 induction, decreased telomerase activity, telomeric disturbances (shortening, losses, fusions), and additional chromosomal aberrations. Telomerase inhibition correlated with reduced levels of hTERT transcripts. GM-CSF prevented TNFalpha effects and allowed leukemic cells to recover growth capacity. Finally, our study shows for the first time that, at least in some hematopoietic cells, TNFalpha may induce senescence with important functional consequences, including sustained growth inhibition and genetic instability, and that this cellular response is efficiently regulated by hematopoietic growth factors.

Congenital malformations of the diaphragm: findings of the West Midlands Congenital Anomaly Register 1995 to 2000.

To describe trends in incidence, associated anomalies, clinical outcomes and sensitivity of prenatal diagnosis for congenital malformations of the diaphragm in the West Midlands Region between 1995 and 2000. Information was retrieved from a population-based register of major congenital malformations in a health region of England, the West Midlands Congenital Anomaly Register (WMCAR), between 1995 and 2000. One hundred and sixty-one confirmed cases of congenital malformations of the diaphragm were notified from 396 577 births. This gives an incidence of 4.1 per 10,000 births. After natural losses and terminations, the incidence at birth was 2.9 per 10,000 registered births. For live-born cases, the infant mortality rate was 317 per 1000 births. 47% of the cases had additional structural or chromosomal anomalies; the infant mortality rate for these complex cases was 533 per 1000, an increased relative risk of 2.37 compared with isolated lesions. 66% of the cases were diagnosed prenatally, 51% of isolated lesions and 84% of complex cases. Fourteen prenatally diagnosed cases (12%) were false-positives; however, 11 of these cases had other significant pathology. These 14 cases were not included in the 161 confirmed cases. Congenital malformations of the diaphragm remain associated with considerable infant mortality. Most cases are now diagnosed before birth and the prognosis is adversely affected by the presence of other structural or chromosomal anomalies. This presents significant challenges for those involved in counselling the parents of affected fetuses.

Lymphome du manteau : un modèle biologique et clinique

Recent classifications of non-Hodgkin’s lymphomas (NHL) have strictly individualized mantle cell lymphoma (MCL) on the basis of a combination of morphologic, immunophenotypic, and cytogenetic criteria. This clinicopathological entity now appears to be a biological and therapeutic model for the understanding and treatment of hematological malignancies. The lymphomogenesis of MCL could be explained by a series of genetic abnormalities which occur at different steps of the disease: (1) mutation and/or loss of the ATM gene in centrocytic cells of the follicle mantle of lymph nodes, leading to the loss of ATM function, particularly involved during the (D) J recombination process; (2) a (11 ; 14) (q13 ; q32) translocation which induces a constitutive Bcl-1/PRAD1/CCND1 expression, responsible for cell cycle activation of centrocytic cells characteristic of typical MCL; and (3) secondary additional chromosomal aberrations, such as a p53 mutation, observed in blastic transformation of MCL. Despite the evaluation of a number of treatment modalities, the optimal management of MCL has not been defined yet; (1) conventional and intensified chemotherapy and monoclonal anti-CD20 antibody therapy appear to be effective for the improvement of response rates and event-free or overall survival; (2) combinations of different treatment modalities must be tested to modify the natural dismal outcome of the disease; (3) innovative approaches should be developed. From this point of view, all these considerations offer a fine opportunity for extensive medical reflection.

Secondary cytogenetic aberrations in childhood Philadelphia chromosome positive acute lymphoblastic leukemia are nonrandom and may be associated with outcome

Additional chromosomal aberrations occur frequently in Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) of childhood. The treatment outcome of these patients is heterogeneous. This study assessed whether such clinical heterogeneity could be partially explained by the presence and characteristics of additional chromosomal abnormalities. Cytogenetic descriptions were available for 249 of 326 children with Ph+ ALL, diagnosed and treated by 10 different study groups/large single institutions from 1986 to 1996. Secondary aberrations were present in 61% of the cases. Chromosomes 9, 22, 7, 14, and 8 were most frequently abnormal. Most (93%) karyotypes were unbalanced. Three main cytogenetic subgroups were identified: no secondary aberrations, gain of a second Ph and/or >50 chromosomes, or loss of chromosome 7, 7p, and/or 9p, while other secondary aberrations were grouped as combinations of gain and loss or others. Of the three main cytogenetic subgroups, the loss group had the worst event-free survival (P=0.124) and disease-free survival (P=0.013). However, statistical significance was not maintained when adjusted for other prognostic factors and treatment. Karyotypic analysis is valuable in subsets of patients identified by molecular screening, to assess the role of additional chromosomal abnormalities and their correlation with clinical heterogeneity, with possible therapeutic implications.

Chromosomal phenotypes and submicroscopic abnormalities

The finding, during the last decade, that several common, clinically delineated syndromes are caused by submicroscopic deletions or, more rarely, by duplications, has provided a powerful tool in the annotation of the human genome. Since most microdeletion/microduplication syndromes are defined by a common deleted/duplicated region, abnormal dosage of genes located within these regions can explain the phenotypic similarities among individuals with a specific syndrome. As such, they provide a unique resource towards the genetic dissection of complex phenotypes such as congenital heart defects, mental and growth retardation and abnormal behaviour. In addition, the study of phenotypic differences in individuals with the same microdeletion syndrome may also become a treasury for the identification of modifying factors for complex phenotypes. The molecular analysis of these chromosomal anomalies has led to a growing understanding of their mechanisms of origin. Novel tools to uncover additional submicroscopic chromosomal anomalies at a higher resolution and higher speed, as well as the novel tools at hand for deciphering the modifying factors and epistatic interactors, are 'on the doorstep' and will, besides their obvious diagnostic role, play a pivotal role in the genetic dissection of complex phenotypes.

Multicolour fluorescence in situ hybridization analysis of t(14;18)‐positive follicular lymphoma and correlation with gene expression data and clinical outcome

In order fully to identify secondary chromosomal alterations, such as duplications, additions and marker chromosomes that remained unresolved by G banding, 60 cases of t(14;18)-positive follicular lymphoma (FL) were analysed by multicolour karyotyping techniques [multicolour fluorescence in situ hybridization (MFISH)/multicolour banding for chromosome 1 (MBAND1)]. A total of 165 additional structural chromosomal aberrations were delineated. An increased frequency of chromosomal gains involving X, 1q, 2, 3q27-q29, 5, 6p11-p21, 7, 8, 11, 12, 14q32, 17q, 18 and 21 and deletions of 1p36, 3q28-q29, 6q, 10q22-q24 and 17p11-p13 was revealed by the MFISH/MBAND1 analysis. Balanced translocations other than t(14;18) were uncommon, whereas unbalanced translocations were numerous. Deletion of 1p36 and duplication of 1p33-p35, 1p12-p21 and 1q21-q41 were regularly involved in chromosome 1 alterations, seen in 53% of the cases. A strong correlation was demonstrated between gains of individual chromosomal bands and increased gene expression, including 1q22/MNDA, 6p21/CDKN1A, 12q13-q14/SAS, 17q23/ZNF161, 18q21/BCL2 and Xq13/IL2RG. Unfavourable overall survival was associated with del(1)(p36) and dup(18q). These data support the notion that translocation events are primarily responsible for FL disease initiation, whereas the unbalanced chromosomal gains and losses that mirror the gene expression patterns characterize clonal evolution and disease progression, and thus provide further insights into the biology of FL.

Cytogenetic and molecular mechanisms of resistance to imatinib

Selective inhibition of the BCR-ABL tyrosine kinase by imatinib (Gleevec) (formerly STI571) is a promising new therapeutic strategy in patients with chronic myelogenous leukemia (CML). Despite significant hematologic and cytogenetic responses, resistance occurs in patients with chronic phase (CP) and advanced disease. A cohort of 72 patients with CML in myeloid blast crisis (BC) (n = 34), lymphoid BC (n = 2), accelerated phase (AP) (n = 16), CP (n = 18), and BCR-ABL+ acute lymphoblastic leukemia (ALL) (n = 2) resistant to imatinib were investigated. Median levels of BCR-ABL transcripts, determined by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR), were not significantly changed at the time of resistance, but seven of 55 patients showed a greater than 10-fold increase in BCR-ABL levels. Genomic amplification of BCR-ABL was found in two of 32 patients evaluated by fluorescence in situ hybridization (FISH). Additional chromosomal aberrations were observed in 19 of 36 patients and point mutations of the ABL tyrosine kinase domain resulting in reactivation of the BCR-ABL tyrosine kinase were detected in 29 of 72 patients. Resistance may be caused by BCR-ABL-independent or BCR-ABL-dependent mechanisms. A thorough evaluation of resistant cases is required to suggest therapeutic measures in the individual case. Clonal selection of resistant cells harboring a BCR-ABL mutation might be reversed by stopping imatinib therapy and switching to chemotherapy. Combination therapy from the start of treatment to reduce the frequency of resistance is currently being evaluated with several drugs. Semin Hematol 40(suppl 2):69-79. © 2003 Elsevier Inc. All rights reserved.

Computer aided analysis of additional chromosome aberrations in Philadelphia chromosome positive acute lymphoblastic leukaemia using a simplified computer readable cytogenetic notation

BackgroundThe analysis of complex cytogenetic databases of distinct leukaemia entities may help to detect rare recurring chromosome aberrations, minimal common regions of gains and losses, and also hot spots of genomic rearrangements. The patterns of the karyotype alterations may provide insights into the genetic pathways of disease progression.ResultsWe developed a simplified computer readable cytogenetic notation (SCCN) by which chromosome findings are normalised at a resolution of 400 bands. Lost or gained chromosomes or chromosome segments are specified in detail, and ranges of chromosome breakpoint assignments are recorded. Software modules were written to summarise the recorded chromosome changes with regard to the respective chromosome involvement. To assess the degree of karyotype alterations the ploidy levels and numbers of numerical and structural changes were recorded separately, and summarised in a complex karyotype aberration score (CKAS). The SCCN and CKAS were used to analyse the extend and the spectrum of additional chromosome aberrations in 94 patients with Philadelphia chromosome positive (Ph-positive) acute lymphoblastic leukemia (ALL) and secondary chromosome anomalies. Dosage changes of chromosomal material represented 92.1% of all additional events. Recurring regions of chromosome losses were identified. Structural rearrangements affecting (peri)centromeric chromosome regions were recorded in 24.6% of the cases.ConclusionsSCCN and CKAS provide unifying elements between karyotypes and computer processable data formats. They proved to be useful in the investigation of additional chromosome aberrations in Ph-positive ALL, and may represent a step towards full automation of the analysis of large and complex karyotype databases.

Biology and genetic aspects of gastrointestinal stromal tumors: KIT activation and cytogenetic alterations

Recent studies have done much to reveal the biological and genetic underpinnings of gastrointestinal stromal tumors (GISTs). Constitutive activation of the KIT receptor tyrosine kinase is a central pathogenetic event in most GISTs and generally results from oncogenic point mutations which can involve either extracellular or cytoplasmic domains of the receptor. Oncogenic mutations enable the KIT receptor to phosphorylate various substrate proteins, leading to activation of signal transduction cascades which regulate cell proliferation, apoptosis, chemotaxis, and adhesion. KIT mutations can be broadly assigned to 2 groups, those that involve the “regulatory” regions responsible for modulating KIT enzymatic activity and those that involve the enzymatic region itself. In vitro studies suggest that GISTs with regulatory-region KIT mutations are more likely to respond to STI-571 than are GISTs with enzymatic-region mutations. A minority of GISTs lack demonstrable KIT mutations, but KIT is nonetheless strongly activated. Such GISTs might contain KIT mutations which are not readily detected by conventional screening methods, or alternately, KIT might be activated by nonmutational mechanisms. Most GISTs have noncomplex cytogenetic profiles, often featuring deletions of chromosomes 14 and 22. Additional chromosomal aberrations are acquired as the GISTs progress to higher histologic grade. These cytogenetic aberrations are undoubtedly important in GIST pathogenesis, but currently they do not play a key role as diagnostic adjuncts. HUM PATHOL 33:484-495. Copyright 2002, Elsevier Science (USA). All rights reserved.

Molecular cytogenetic characterization of a novel additional chromosomal aberration in blast crisis of a Ph-positive chronic myeloid leukemia

We describe a novel chromosomal aberration acquired in blast crisis (BC) in a patient affected by Philadelphia-positive chronic myeloid leukemia (CML). Conventional cytogenetic studies at onset showed a classic t(9;22)(q34;q11.2) in all bone marrow cells, confirmed by fluorescence in situ hybridization and reverse transcription–polymerase chain reaction (b3a2) analysis. In BC, the malignant clone developed a new additional cytogenetic abnormality consisting of a deletion of chromosome 21. To our knowledge, this is the first case of del(21) reported in literature associated with BC CML. The use of an appropriate set of BAC/PAC clones restricted the breakpoint to an interval of approximately 100 kb. Sequence analysis did not reveal any known gene in this interval. Oncosuppressor genes distal to the breakpoint could be hypothesized to be involved in the progression of disease toward BC. Identification of new chromosome abnormalities in CML may allow further understanding of specific molecular events leading to disease evolution.

Biological and clinical significance of cytogenetic abnormalities in low-risk and high-risk gastrointestinal stromal tumors

We report cytogenetic findings in 19 c-Kit–positive gastrointestinal stromal tumors (GISTs) that represent a heterogenous group of mesenchymal neoplasms with respect to site, histology, and biologic behavior. All of the GISTs (5 low-risk, 11 high-risk, 3 recurrences) displayed clonal chromosomal aberrations; 15 were hypo- to near-diploid, and 4 were near-triploid and hypotetraploid. The most common abnormalities were loss of chromosomes 14 and/or 22, demonstrated in 14 GISTs irrespective of site or predominant phenotype. Ten cases (2 low-risk, 5 high-risk, 3 recurrences) were characterized by loss of both chromosomes 14 and 22, 2 cases (1 low-risk, 1 high- risk), by loss of chromosome 14; and 2 high-risk cases, by loss of chromosome 22. Additional chromosomal aberrations occurred preferentially in high-risk and recurrent GISTs, including loss of 9p and 1p in 8 cases each, loss of 15 in 6 cases, loss of 3p in 5 cases, loss of 13q and 10q in 4 cases each, loss of 19 in 3 cases, and complete or partial gains of chromosomes 5 and 4 in 2 cases each. More significantly, 5 of 6 patients with clinically aggressive GISTs, including 2 recurrences and 3 metastasing GISTs, were additionally characterized by loss of 9p; four of these had additional loss of chromosomes 1p and 15. The presented results herein indicate that loss of chromosome 14 and/or 22 is an early change in GIST tumorigenesis irrespective of site or differentiation, whereas malignant transformation and progression of GISTs appear to be associated with an increasing incidence of additional secondary aberrations. HUM PATHOL 33:316-321. Copyright 2002, Elsevier Science (USA). All rights reserved.

Marked Thrombocytosis Following Relapse of Acute Myeloblastic Leukemia Associated with Development of Translocation (2;14) (p13;q32)

Thrombocytosis is a rare finding in acute myeloblastic leukemia (AML). Here, we describe a patient with AML who relapsed with marked thrombocytosis. The patient was initially diagnosed as having AML (M4) with a low platelet count. The patient was started on combination chemotherapy including high-dose etoposide and achieved complete remission. However, the patient relapsed six months later with an extremely high platelet count (72.5 2 10 4 / w l). Cytogenetic analysis at relapse revealed the development of t(2;14)(p13;q32). Despite the repeated combination chemotherapy, the patient died with progressive disease. This case suggests that the additional chromosomal aberration t(2;14)(p13;q32) may be related to abnormal thrombocytosis in AML.