PUF60-SCRIB fusion transcript in a patient with 8q24.3 microdeletion and atypical Verheij syndrome.

Expression of the fusion genes is considered to be an important mechanism of tumorigenesis. However it is hardly ever discussed in relation to the neurodevelopmental disorders. Here we report on an 18-years-old female patient with 13.1 kb deletion of 8q24.3 fusing the 5'-portion of SCRIB with the 3'-portion of PUF60 and presenting with borderline intellectual disability, eye coloboma, short stature, scoliosis, heart defects and interestingly postnatal megalencephaly, in contrast to microcephaly, which is usually associated with 8q24.3 deletion (Verheij syndrome). Using next generation sequencing we mapped the breakpoints at nucleotide resolution and showed that the deletion preserved the reading frame. In contrast to the laborious techniques previously used for the precise mapping of deletion breakpoints, our approach identified an accurate interval very rapidly. We demonstrated the expression of the PUF60-SCRIB fusion gene in patient's cells and suggest that the fusion transcript might be a cause of the atypical clinical presentation.

Interstitial deletion 1p36.32 in two brothers with a distinct phenotype--overgrowth, macrocephaly and nearly normal intellectual function.

We report on two adult patients, who both presented with overgrowth and one of them additionally with macrocephaly while carrying an 1p36 microdeletion of about 2.1 Mb. They are full brothers born to unaffected parents. Although both brothers attended special schools, they lived independently without a legal guardian and were able to succeed in regular jobs. One of the brothers received a professional education. Genetic analysis of the parents revealed neither the microdeletion nor a cryptical translocation or inversion. We suggest that the recurrent deletion is a result of germline mosaicism, a phenomenon reported only once in the context of the 1p36 microdeletion syndrome. Our report confirms the recurrence of the apparently de novo 1p36 microdeletion due to a likely germline mosaicism of one of the parents. Furthermore, it illustrates the possibility of the distinct phenotype with a nearly normal intellectual outcome of the 1p36 microdeletion syndrome that might be due to the region involved in our patients.

Distinct phenotype of PHF6 deletions in females.

We report on two female patients carrying small overlapping Xq26.2 deletions of 100 kb and 270 kb involving the PHF6 gene. Mutations in PHF6 have been reported in individuals with Borjeson-Forssman-Lehmann syndrome, a condition present almost exclusively in males. Two very recent papers revealed de novo PHF6 defects in seven female patients with intellectual disability and a phenotype resembling Coffin-Siris syndrome (sparse hair, bitemporal narrowing, arched eyebrows, synophrys, high nasal root, bulbous nasal tip, marked clinodactyly with the hypoplastic terminal phalanges of the fifth fingers and cutaneous syndactyly of the toes, Blaschkoid linear skin hyperpigmentation, dental anomalies and occasional major malformations). The clinical presentation of these patients overlaps completely with our first patient, who carries a germline deletion involving PHF6. The second patient has a mosaic deletion and presented with a very mild phenotype of PHF6 loss in females. Our report confirms that PHF6 loss in females results in a recognizable phenotype overlapping with Coffin-Siris syndrome and distinct from Borjeson-Forssman-Lehmann syndrome. We expand the clinical spectrum and provide the first summary of the recommended medical evaluation.

Severe forms of Baraitser-Winter syndrome are caused by ACTB mutations rather than ACTG1 mutations.

ACTB and ACTG1 mutations have recently been reported to cause Baraitser-Winter syndrome (BRWS) - a rare condition characterized by ptosis, colobomata, neuronal migration disorder, distinct facial anomalies and intellectual disability. One of the patients carrying an ACTB mutation was previously diagnosed with Fryns-Aftimos syndrome (FAS), which is a rare and severe, multiple congenital anomaly (MCA) syndrome whose symptoms partially overlap with that of BRWS. However, several patients with Fryns-Aftimos were considered not to fit into the ACTB and ACTG1 spectrum because of their severe impairment and additional malformations. We report on three patients who had been diagnosed with FAS. All three patients carry a mutation in the ACTB gene. On the basis of the ACTB mutations and analysis of the clinical findings, we reclassify the diagnosis of these patients as severe BRWS. We suggest that mutations in ACTB cause a distinctly more severe phenotype than ACTG1 mutations, despite the structural similarity of beta- and gamma-actins and their overlapping expression pattern. We expand the spectrum of BRWS and confirm that FAS is not a separate entity but an early and severe manifestation of BRWS.

The prognostic value of IDH mutations and MGMT promoter status in secondary high-grade gliomas.

Reports about the prognostic value of IDH mutations and the promoter region of the O6-Methyl-guanyl-methyl-transferase gene in secondary high-grade gliomas (sHGG) are few in number. We investigated the prognostic value of IDH mutations and methylation of the promoter region of the MGMT gene in 99 patients with sHGG and analyzed the clinical course of those tumors. Patients with sHGG were screened for IDH mutations by direct sequencing, and, for promoter status of MGMT gene, by the methylation-specific polymerase chain reaction. A total of 48 of 99 patients (48.5 %) had secondary anaplastic gliomas (Group 1), while 51 patients had secondary glioblastomas (Group 2). The median survival time after malignant progression of all patients with sHGG and with an IDH mutation was 4 years, which is significantly longer than in patients with wild-type IDH (1.2 years, p = 0.009). Patients' survival was not significantly influenced by the tumors' MGMT promoter status, both in Group 1- 9.7 years vs. 6.1 years, methylated vs. unmethylated promoter (p = 0.330)-as well as in Group 2-1.5 years vs. 1.6 years, methylated versus unmethylated promoter (p = 0.829). In our population, the IDH mutation status was not associated with increased PFS or median survival time in sGBM patients. However, patients with secondary anaplastic glioma and IDH mutation had a significantly improved outcome. In addition, IDH mutations are a more powerful prognostic marker concerning both PFS and MS than the MGMT promoter status in those patients.

Macrocephaly, obesity, mental (intellectual) disability, and ocular abnormalities: alternative definition and further delineation of MOMO syndrome.

MOMO syndrome, previously defined as Macrosomia, Obesity, Macrocephaly, and Ocular abnormalities (OMIM 157980) is a rare intellectual disability syndrome of unknown cause. We describe two further patients with MOMO syndrome. Reported data of patients with MOMO syndrome and our own findings indicate that overgrowth does not appear to be a specific feature. We propose to form the acronym "MOMO" from Macrocephaly, Obesity, Mental (intellectual) disability, and Ocular abnormalities, excluding macrosomia from the syndrome name. The combination of obesity, macrocephaly, and colobomas is unique, therefore these features can be used as major diagnostic criteria of MOMO syndrome.

A further patient with van Maldergem syndrome.

We report on a male patient with the proposed diagnosis of the rare but very distinct entity of van Maldergem syndrome. His parents are first cousins. At the age of 4 years the boy presented with severe developmental delay, talipes equinovarus, finger camptodactyly with interphalangeal pterygium, joint laxity, bilateral microtia, and a dysmorphic facies. He showed bilateral epicanthus, telecanthus, short palpebral fissures, broad flat nasal bridge, and dental malocclusion. The combination of the specific facial features with camptodactyly, interphalangeal pterygium, joint laxity and developmental delay led to the diagnosis of van Maldergem syndrome. The medical history was further on significant for pharyngeal instability requiring the placement of a tracheostomy tube, an inguinal hernia, hip subluxation, small kidneys and genital abnormalities (micropenis, bifid scrotum, cryptorchidism). Due to severe feeding difficulties permanent tube feeding was required. Metabolic tests (newborn metabolic screening, 7-dehydrocholesterol, amino acids, organic acids in urine) and chromosomal analysis (450-500 bands; 46,XY) were normal. Molecular karyotyping revealed two parental CNVs (paternal deletion of 9q33.1; maternal duplication of 11p15.1), which are unlikely to contribute to the patient's phenotype. Taken together, the report on a further patient with van Maldergem syndrome expands the clinical spectrum of the condition by adding genital malformations, hernia, pharyngeal instability, and subluxation of the hip.

Selection of a highly invasive neuroblastoma cell population through long-term human cytomegalovirus infection.

The human cytomegalovirus (HCMV) is suspected to increase tumour malignancy by infection of cancer and/or stroma cells (oncomodulation). So far, oncomodulatory mechanisms have been attributed to the presence of HCMV and direct action of its gene products on cancer cells. Here, we investigated whether the prolonged presence of HCMV can result in the irreversible selection of a cancer cell population with increased malignancy. The neuroblastoma cell line UKF-NB-4 was long-term (200 passages) infected with the HCMV strain Hi91 (UKF-NB-4(Hi)) before virus eradication using ganciclovir (UKF-NB-4(HiGCV)). Global gene expression profiling of UKF-NB-4, UKF-NB-4(Hi) and UKF-NB-4(HiGCV) cells and subsequent bioinformatic signal transduction pathway analysis revealed clear differences between UKF-NB-4 and UKF-NB-4(Hi), as well as between UKF-NB-4 and UKF-NB-4(HiGCV) cells, but only minor differences between UKF-NB-4(Hi) and UKF-NB-4(HiGCV) cells. Investigation of the expression of a subset of five genes in different chronically HCMV-infected cell lines before and after virus eradication suggested that long-term HCMV infection reproducibly causes specific changes. Array comparative genomic hybridisation showed virtually the same genomic differences for the comparisons UKF-NB-4(Hi)/UKF-NB-4 and UKF-NB-4(HiGCV)/UKF-NB-4. UKF-NB-4(Hi) cells are characterised by an increased invasive potential compared with UKF-NB-4 cells. This phenotype was completely retained in UKF-NB-4(HiGCV) cells. Moreover, there was a substantial overlap in the signal transduction pathways that differed significantly between UKF-NB-4(Hi)/UKF-NB-4(HiGCV) and UKF-NB-4 cells and those differentially regulated between tumour tissues from neuroblastoma patients with favourable or poor outcome. In conclusion, we present the first experimental evidence that long-term HCMV infection can result in the selection of tumour cell populations with enhanced malignancy.

A new autosomal dominant syndrome of distinctive face showing ptosis and prominent eyes associated with cleft palate, ear anomalies, and learning disability.

We report on three patients from two families with apparently a novel clinical entity. The main features of which include unusual craniofacial dysmorphism with ptosis, prominent eyes, flat midface, Cupid's bow configuration of the upper lip, low-set, posteriorly rotated small ears, as well as conductive hearing loss, cleft palate, heart defect, and mild developmental delay. We suggest that this entity is an autosomal dominant disorder given the occurrence in a mother and daughter as well as in an unrelated boy.

Multiple putative oncogenes at the chromosome 20q amplicon contribute to colorectal adenoma to carcinoma progression.

OBJECTIVE: This study aimed to identify the oncogenes at 20q involved in colorectal adenoma to carcinoma progression by measuring the effect of 20q gain on mRNA expression of genes in this amplicon. METHODS: Segmentation of DNA copy number changes on 20q was performed by array CGH (comparative genomic hybridisation) in 34 non-progressed colorectal adenomas, 41 progressed adenomas (ie, adenomas that present a focus of cancer) and 33 adenocarcinomas. Moreover, a robust analysis of altered expression of genes in these segments was performed by microarray analysis in 37 adenomas and 31 adenocarcinomas. Protein expression was evaluated by immunohistochemistry on tissue microarrays. RESULTS: The genes C20orf24, AURKA, RNPC1, TH1L, ADRM1, C20orf20 and TCFL5, mapping at 20q, were significantly overexpressed in carcinomas compared with adenomas as a consequence of copy number gain of 20q. CONCLUSION: This approach revealed C20orf24, AURKA, RNPC1, TH1L, ADRM1, C20orf20 and TCFL5 genes to be important in chromosomal instability-related adenoma to carcinoma progression. These genes therefore may serve as highly specific biomarkers for colorectal cancer with potential clinical applications.

Molecular cytogenetic characterization of pancreas cancer cell lines reveals high complexity chromosomal alterations.

Karyotype analysis can provide clues to significant genes involved in the genesis and growth of pancreas cancer. The genome of pancreas cancer is complex, and G-band analysis cannot resolve many of the karyotypic abnormalities seen. We studied the karyotypes of 15 recently established cell lines using molecular cytogenetic tools. Comparative genomic hybridization (CGH) analysis of all 15 lines identified genomic gains of 3q, 8q, 11q, 17q, and chromosome 20 in nine or more cell lines. CGH confirmed frequent loss of chromosome 18, 17p, 6q, and 8p. 14/15 cell lines demonstrated loss of chromosome 18q, either by loss of a copy of chromosome 18 (n = 5), all of 18q (n = 7) or portions of 18q (n = 2). Multicolor FISH (Spectral Karyotyping, or SKY) of 11 lines identified many complex structural chromosomal aberrations. 93 structurally abnormal chromosomes were evaluated, for which SKY added new information to 67. Several potentially site-specific recurrent rearrangements were observed. Chromosome region 18q11.2 was recurrently involved in nine cell lines, including formation of derivative chromosomes 18 from a t(18;22) (three cell lines), t(17;18) (two cell lines), and t(12;18), t(15;18), t(18;20), and ins(6;18) (one cell line each). To further define the breakpoints involved on chromosome 18, YACs from the 18q11.2 region, spanning approximately 8 Mb, were used to perform targeted FISH analyses of these lines. We found significant heterogeneity in the breakpoints despite their G-band similarity, including multiple independent regions of loss proximal to the already identified loss of DPC4 at 18q21.

Spectral karyotyping of human, mouse, rat and ape chromosomes--applications for genetic diagnostics and research.

Spectral karyotyping (SKY) is a widely used methodology to identify genetic aberrations. Multicolor fluorescence in situ hybridization using chromosome painting probes in individual colors for all metaphase chromosomes at once is combined with a unique spectral measurement and analysis system to automatically classify normal and aberrant chromosomes. Based on countless studies and investigations in many laboratories worldwide, numerous new chromosome translocations and other aberrations have been identified in clinical and tumor cytogenetics. Thus, gene identification studies have been facilitated resulting in the dissection of tumor development and progression. For example, different translocation partners of the TEL/ETV6 transcription factor that is specially required for hematopoiesis within the bone marrow were identified. Also, the correct classification of complex karyotypes of solid tumors supports the prognostication of cancer patients. Important accomplishments for patients with genetic diseases, leukemias and lymphomas, mesenchymal tumors and solid cancers are summarized and exemplified. Furthermore, studies of disease mechanisms such as centromeric DNA breakage, DNA double strand break repair, telomere shortening and radiation-induced neoplastic transformation have been accompanied by SKY analyses. Besides the hybridization of human chromosomes, mouse karyotyping has also contributed to the comprehensive characterization of mouse models of human disease and for gene therapy studies.

Nijmegen breakage syndrome (NBS) with neurological abnormalities and without chromosomal instability.

BACKGROUND: Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability disorder with hypersensitivity to ionising radiation. The clinical phenotype is characterised by congenital microcephaly, mild dysmorphic facial appearance, growth retardation, immunodeficiency, and greatly increased risk for lymphoreticular malignancy. Most NBS patients are of Slavic origin and homozygous for the founder mutation 657del5. The frequency of 657del5 heterozygotes in the Czech population is 1:150. Recently, another NBS1 mutation, 643C>T(R215W), with uncertain pathogenicity was found to have higher frequency among tumour patients of Slavic origin than in controls. This alteration results in the substitution of the basic amino acid arginine with the non-polar tryptophan and thus could potentially interfere with the function of the NBS1 protein, nibrin. METHODS AND RESULTS: Children with congenital microcephaly are routinely tested for the 657del5 mutation in the Czech and Slovak Republics. Here, we describe for the first time a severe form of NBS without chromosomal instability in monozygotic twin brothers with profound congenital microcephaly and developmental delay who are compound heterozygotes for the 657del5 and 643C>T(R215W) NBS1 mutations. Both children showed reduced expression of full length nibrin when compared with a control and a heterozygote for the 657del5 mutation. Radiation response processes such as phosphorylation of ATM and phosphorylation/stabilisation of p53, which are promoted by NBS1, are strongly reduced in cells from these patients. CONCLUSIONS: Interestingly, the patients are more severely affected than classical NBS patients. Consequently, we postulate that homozygosity for the 643C>T(R215W) mutation will also lead to a, possibly very, severe disease phenotype.

Molecular cytogenetic characterization of the mantle cell lymphoma cell line GRANTA-519.

Combining fluorescence R-banding, fluorescence in situ hybridization and spectral karyotyping allowed us to precisely define chromosomal breakpoints, gains, losses and a newly detected amplification in the human mantle cell lymphoma (MCL) cell line GRANTA-519. GRANTA-519 is characterized by the t(11;14)(q13;q32) resulting in overexpression of cyclin D1, a key player in cell cycle control. Hitherto unresolved complex rearrangements involve 1p, 1q, 3cen, 9p, 11q, 12p, 12q, 16p, 17p, and 18cen. Moreover, a 4- to 6-fold gain of sequences on 18q leads to a low-level amplification of the BCL2 gene and to an overexpression of the BCL2 protein. These results provide the basis for the identification of not only candidate oncogenes responsible for MCL in gained regions, but also for the identification of putative tumor suppressor genes in commonly deleted regions like 1p22, which would eventually enable functional studies of these genes.

[Genetic alterations in sinonasal adenocarcinoma in wood workers studies with comparative genomic hybridization]. / Alteraciones genéticas en adenocarcinomas nasosinusales de trabajadores de la madera mediante hibridación genómica comparativa.

Eleven wood-workers with sinonasal adenocarcinoma were analyzed by comparative genomic hybridization. This technique serves as a screening test for regions of copy number changes in tumor genomes. We have applied the technique to map DNA gains and losses in 9 cases of formalin-fixed, paraffin-embedded tumors and 2 cases of frozen tumors. Gains were found most frequently than losses. Whole arm chromosomic gains were detected in high frequencies at 8q, 7q, 12q and 18p and losses at 18q, 8p, 10q, 5q, 14q and 17p. The segment most frequently amplified was 18p11.1-q11 (45%), even though others like 7q21-22 (18%) were related with lower survival rates. This analysis allows us to know for the first time the chromosomic aberrations that occur and may play an important role in sinonasal adenocarcinoma. In the future, comparative genomic hybridization could be used in the woodworkers with long exposition to wood dust to detect initial genetic aberrations and obtain an early treatment and diagnosis of the disease.

Alteraciones genéticas en adenocarcinomas nasosinusales de trabajadores de la madera mediante hibridación genómica comparativa / Genetical disorders in sinonasal adenocarcinomas in wood-workers by comparative genomic hybridization

Se estudian 11 pacientes trabajadores de la madera que desarrollaron adenocarcinomas nasosinusales. Se utilizó la hibridación genómica comparativa como método de análisis en el conjunto del contenido genómico en 9 tumores parafinados y 2 tumores congelados.Encontramos alteraciones en todos los casos predominando las ganancias cromosómicas frente a las pérdidas. Las ganancias más frecuentes de brazos cromosómicos se observan en 8q, 7q, 12q y 18p y las pérdidas o deleciones en 18q, 8p, 10q, 5q, 14q y 17p. El mayor número de amplificaciones se encontró en 18p11.1-q11 (45 por ciento), aunque otras como 7q21-22 (18 por ciento) se relacionaron con menor supervivencia. Por primera vez, este análisis permite conocer las alteraciones cromosómicas ocurridas en los adenocarcinomas nasosinusales y es un primer paso en el diseño de un modelo de progresión. En un futuro, la hibridación genómica comparativa podría ser utilizada en trabajadores expuestos al polvo de madera para detectar las alteraciones genéticas iniciales y contribuir al diagnóstico y tratamiento precoz de la enfermedad. (AU)

Eleven wood-workers with sinonasal adenocarcinoma were analyzed by comparative genomic hybridization. This technique serves as a screening test for regions of copy number changes in tumor genomes. We have applied the technique to map DNA gains and losses in 9 cases of formalin-fixed, paraffin-embedded tumors and 2 cases of frozen tumors. Gains were found most frequently than losses. Whole arm chromosomic gains were detected in high frequencies at 8q, 7q, 12q and 18p and losses at 18q, 8p, 10q, 5q, 14q and 17p. The segment most frequently amplified was 18p11.1-q11 (45%), even though others like 7q21-22 (18%) were related with lower survival rates. This analysis allows us to know for the first time the chromosomic aberrations that occur and may play an important role in sinonasal adenocarcinoma. In the future, comparative genomic hybridization could be used in the woodworkers with long exposition to wood dust to detect initial genetic aberrations and obtain an early treatment and diagnosis of the disease (AU)

Spectral karyotyping and fluorescence in situ hybridization detect novel chromosomal aberrations, a recurring involvement of chromosome 21 and amplification of the MYC oncogene in acute myeloid leukaemia M2.

Recurring chromosomal aberrations are of aetiological, diagnostic, prognostic and therapeutic importance in acute myeloid leukaemia (AML). However, aberrations are detected in only two thirds of AML cases at diagnosis and recurrent balanced translocations in only 50%. Spectral karyotyping (SKY) enables simultaneous visualization of all human chromosomes in different colours, facilitating the comprehensive evaluation of chromosomal abnormalities. Therefore, SKY was used to characterize 37 cases of newly diagnosed AML-M2, previously analysed using G-banding. In 15/23 patients it was possible to obtain metaphases from viably frozen cells; in 22 additional cases, fixed-cell suspensions were used. Of the 70 chromosomal aberrations identified by SKY, 30 aberrations were detected for the first time, 18 aberrations were redefined and 22 were confirmed. SKY detected two reciprocal translocations, t(X;3) and t(11;19). In five cases, eight structural aberrations resulted in partial gains of chromosome 21, six of which were undetected by G-banding. In 4/5 cases, these resulted in copy number increases for AML1. Amplification of MYC was detected in three cases. Using SKY and FISH, clonal aberrations were identified in 5/18 cases with a presumed normal karyotype; 3/5 aberrations were of known unfavourable prognostic significance. Karyotypes were entered into a custom-designed SKY database, which will be integrated with other cytogenetic and genomic databases.

Jumping translocations are common in solid tumor cell lines and result in recurrent fusions of whole chromosome arms.

Jumping translocations (JTs) and segmental jumping translocations (SJTs) are unbalanced translocations involving a donor chromosome arm or chromosome segment that has fused to multiple recipient chromosomes. In leukemia, where JTs have been predominantly observed, the donor segment (usually 1q) preferentially fuses to the telomere regions of recipient chromosomes. In this study, spectral karyotyping (SKY) and FISH analysis revealed 188 JTs and SJTs in 10 cell lines derived from carcinomas of the bladder, prostate, breast, cervix, and pancreas. Multiple JTs and SJTs were detected in each cell line and contributed to recurrent unbalanced whole-arm translocations involving chromosome arms 5p, 14q, 15q, 20q, and 21q. Sixty percent (113/188) of JT breakpoints occurred within centromere or pericentromeric regions of the recipient chromosomes, whereas only 12% of the breakpoints were located in the telomere regions. JT breakpoints of both donor and recipient chromosomes coincided with numerous fragile sites as well as viral integration sites for human DNA viruses. The JTs within each tumor cell line promoted clonal progression, leading to the acquisition of extra copies of the donated chromosome segments that often contained oncogenes (MYC, ABL, HER2/NEU, etc.), consequently resulting in tumor-specific genomic imbalances. Published 2001 Wiley-Liss, Inc.

Comparative genomic hybridization (CGH)--detection of unbalanced genetic aberrations using conventional and micro-array techniques.

This unit presents comparative genomic hybridization (CGH), a genome-wide screening technique for genetic aberrations in tumor samples. Specific emphasis is placed on recent applications to the analysis of murine model systems for human cancer. CGH is an invaluable tool for identifying the characteristic genetic rearrangements in these models. The authors discuss an exciting new method currently being developed, array CGH, which results in a tremendous increase in resolution. Oncogene amplifications and deletions of tumor-suppressor genes are detected on a single-gene level. Detailed protocols are supplied for CGH analysis of both human and mouse chromosomes.

Spectral Karyotyping (SKY) of Hematologic Malignancies.

The discovery of the Philadelphia chromosome in chronic myeloid leukemia (CML) by Novell and Hungerford in 1960 (1), the subsequent clarification of this chromosomal abnormality as areciprocal translocation t(9;22)(q34;q1 1) by Rowley in 1973 (2), the identification of the genes involved at the translocation breakpoints (3,4), and ultimately the demonstration of the leukemogenic activity of the resulting fusion product (5), represent hallmarks for our understanding of malignant diseases as genetic disorders. The elucidation of the Philadelphia translocation emphasizes the importance of cytogenetic analysis of hematologic malignancies. Clarification of this chromosomal aberration as a reciprocal translocation became only possible after the development of cytogenetic banding techniques by Caspersson et al. in 1970 (6). Chromosome banding analysis revealed numerous nonrandom chromosomal aberrations, particularly balanced translocations in leukemias and lymphomas, e.g., the translocation t(8;21)(q22;q22) in acute myeloid leukemia (AML) first described by Rowley et al. in 1973 (7). These balanced translocations were shown to be of etiologic as well as diagnostic, prognostic, and therapeutic importance. They result in an altered gene function by two main mechanisms: (1) sequences of, in most instances, a transcription factor or receptor tyrosine kinase gene are fused to a normally unrelated gene, creating specific fusion proteins with oncogenic properties, and (2) protooncogenes are repositioned to the vicinity of promoter/enhancer elements of the immunoglobulin- or T-cell receptor genes, thereby initiating their activation (8).