Spectral karyotyping identifies recurrent complex rearrangements of chromosomes 8, 17, and 20 in osteosarcomas

Conventional cytogenetic studies have shown that osteosarcomas (OSs) are often highly aneuploid, with a large number of both structural and numerical chromosomal alterations. To investigate the complexity of OS karyotypes in detail, we applied spectral karyotyping (SKY) to a series of 14 primary OS tumors and four established OS cell lines. A total of 531 rearrangements were identified by SKY, of which 300 breakpoints could be assigned to a specific chromosome band. There was an average of 38.5 breakpoints identified by SKY per primary tumor. Chromosome 20 was involved in a disproportionately high number of structural rearrangements, with 38 different aberrations being detected. Chromosomal rearrangements between chromosomes 20 and 8 were evident in four tumors. FISH analysis using a 20q13 subtelomeric probe identified frequent involvement of 20q in complex structural rearrangements of OS cell lines. Characterization of the structural aberrations of chromosomes 8 and 17 by use of SKY demonstrated frequent duplication or partial gains of chromosome bands 8q23-24 and 17p11-13. Other chromosomes frequently involved in structural alteration were chromosomes 1 (47 rearrangements) and 6 (38 rearrangements). Centromeric rearrangements often involving chromosomes 1, 6, 13, 14, 17, and 20 were present. Four of the 14 primary OS tumors were characterized by nonclonal changes that included both structural and numerical alterations. In summary, OS tumors have a very high frequency of structural and numerical alterations, compounded by gross changes in ploidy. This intrinsic karyotype instability leads to a diversity of rearrangements and the acquisition of composite chromosomal rearrangements, with the highest frequency of alteration leading to gain of 8q23-24 and 17p11-13 and rearrangement of 20q. These findings suggest that specific sequences mapping to these chromosomal regions will likely have a role in the development and progression of OS.     

Clear cell sarcoma case report: complex karyotype including t(12;22) in primary and metastatic tumor

Clear cell sarcoma (CCS) is a rare and aggressive tumor, arising mainly in the soft tissue of the extremities in young adults. A distinctive chromosomal translocation, t(12;22)(q13;q12), has been found in most reported cases. We performed cytogenetic analyses on a primary and subsequent metastatic CCS that contained the t(12;22), along with other complex karyotypic changes. G-banding chromosome analysis was supplemented by spectral karyotyping (SKY), a 24-color chromosome-paint FISH technique, thus allowing identification of three marker chromosomes, unbalanced translocations, and other complex abnormalities. Four of these involved additional copies and structural abnormalities of chromosome 8. Clarifying such secondary karyotypic changes in CCS may prove valuable to the understanding of tumor cell biology and clinical behavior.     

Spectral karyotyping reveals 17;22 fusions in a cytogenetically atypical dermatofibrosarcoma protuberans with a large marker chromosome as a sole abnormality

The presence of an extra ring chromosome containing material from 17q and 22q, or, less frequently, a t(17;22)(q22;q13), is a cytogenetic hallmark of dermatofibrosarcoma protuberans (DFSP). However, occasionally tumors with other, atypical karyotypes are encountered. We describe a case of recurrent DFSP without a ring chromosome or a t(17;22) on standard cytogenetic analysis. In all cells analyzed by G-banding, an additional, large marker chromosome was present as a sole abnormality. This chromosome apparently included chromosome 8 or the 8q arm, but the origin of its remaining part could not be determined with certainty. To characterize further the abnormal chromosome, we applied spectral karyotyping (SKY). SKY confirmed the presence of an extra chromosome 8 or arm 8q in the marker and showed that its remaining part was composed of segments from chromosomes 7, 17, 21, and 22, with two copies of a 17;22 fusion. Our results and the literature data suggest that, in addition to a specific 17;22 fusion, amplification of material from chromosomes 17, 22, 8, 5, 7, and 21 may play a role in DFSP development and/or progression. Furthermore, our case demonstrates the usefulness of SKY in detection of a diagnostically relevant 17;22 fusion in DFSP patients who have unusual karyotypic features.     

Comprehensive karyotyping of the HT-29 colon adenocarcinoma cell line

The tumor cell line HT-29 was derived from a primary adenocarcinoma of the rectosigmoid colon. HT-29 is hypertriploid (3n+) and has accumulated numerous chromosomal structural aberrations. To identify material involved in chromosome rearrangements, we performed a comprehensive cytogenetic analysis using G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH). The combination of molecular cytogenetic techniques enabled us to define the first comprehensive karyotype for HT-29. Seventeen marker chromosomes were found in 75-100% of metaphase cells, generally in a single copy per cell. We confirmed the composition of eight previously described markers, refined the classification of seven others, and identified two novel marker chromosomes. Notable aberrations included a reciprocal translocation between chromosomes 6 and 14 and an unusual, large derivative chromosome 8 composed entirely of 8q material. The telomere status, evaluated by FISH, revealed telomeric signals at the termini of all chromosomes. No interstitial telomeric sequences were observed in any cell. Although numerous chromosomal aberrations are present in HT-29, the cell line appears to have retained a high level of genomic stability during passage in culture since undergoing transformation. The excellent resolving power of SKY, coupled with additional information obtained from molecular cytogenetic analyses, will improve our ability to identify genetic lesions characteristic of cancer.     

Characterization of complex chromosomal abnormalities in uveal melanoma by fluorescence in situ hybridization, spectral karyotyping, and comparative genomic hybridization

Several nonrandom recurrent chromosomal changes are observed in uveal melanoma. Some of these abnormalities, e.g., loss of chromosome 3, gain of the q arm of chromosome 8, and chromosome 6 abnormalities, are of prognostic value. Cytogenetic analysis and/or fluorescence in situ hybridization (FISH) are used to detect these changes. In some cases, however, detailed cytogenetic analysis is not possible due to the presence of complex abnormalities. To define more accurately these cytogenetic changes, we have applied comparative genomic hybridization (CGH) and/or spectral karyotyping (SKY) to two uveal melanoma cell lines and five primary uveal melanomas, with partially defined and/or complex abnormalities. SKY provided additional information on 34/39 partially defined aberrant chromosomes and revealed a new abnormality, a der(17)t(7;17)(?;q?), that had not been recognized by conventional cytogenetics. Additionally, using SKY, abnormalities involving chromosome 6 or 8 were found to be twice as common as observed with cytogenetic analysis. CGH was especially useful in assigning the abnormalities identified by SKY to specific chromosomal regions and, in addition, resulted in the detection of a small deletion of chromosome region 3q13 approximately 21. We conclude that SKY and CGH, as methods complementary to cytogenetic and FISH analysis, provide more complete information on the chromosomal abnormalities occurring in uveal melanoma.     

Assessment of molecular cytogenetic methods for the detection of chromosomal abnormalities

Some marker chromosomes and chromosome rearrangements are difficult to identify using G-bands by Giemsa staining after trypsin treatment (G-banding) alone. Molecular cytogenetic techniques, such as spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH), can help to detect chromosomal aberrations precisely. We analyzed the karyotypes in 6 cases of multiple congenital abnormalities and 1 case of spontaneous abortion (case 2). Three cases (cases 1, 6, and 7) had marker chromosomes, and 4 cases (cases 2-5) had chromosomal rearrangements. The karyotypes in cases 1, 2, and 3 were determined using FISH with probes based on the clinical findings and family histories. Spectral karyotyping (SKY) analysis in cases 4-7 showed that this method is useful and saves time. The combination of SKY and FISH analyses defined the range of the ring chromosome in case 7. We demonstrated that a combination of G-banding, FISH, and SKY can be applied effectively to the investigation of chromosomal rearrangement and to the detection of marker chromosome origins. We suggest the use of these methods for prenatal diagnosis, in which the inherent time limitations are particularly important.     

Chromosome arm 20q gains and other genomic alterations in colorectal cancer metastatic to liver, as analyzed by comparative genomic hybridization and fluorescence in situ hybridization.

Comprehensive information about the molecular cytogenetic changes in metastases of colorectal cancer is not yet available. To define such changes in metastases, we measured relative DNA sequence copy numbers by comparative genomic hybridization (CGH). Samples from 27 liver metastases and 6 synchronous primary tumors were analyzed. An average of 9.9 aberrations per tumor was found in the metastases. Gains of chromosome arms 20q (85%), 13q (48%), 7p (44%), and 8q (44%) and losses of chromosome arms 18q (89%), 8p (59%), 1p (56%), and 18p (48%) were detected most frequently. Chromosomes 14 and 15 were lost in 26% and 30% of the metastases, respectively. No consistent differences were observed between primary tumors and synchronous metastases. Fluorescence in situ hybridization (FISH) was used for further characterization of gains of chromosome arm 20q. Touch preparations of 13 tumors that had demonstrated 20q gain with CGH were examined with FISH by use of a set of probes mapping to different parts of 20q. A probe for 20p was used as a reference. FISH showed relative gain of at least one 20q locus in 12 of the tumors. High-level gains were detected in 38% of the tumors, preferentially for probes mapping to band 20q13. Our CGH data indicate that colorectal metastases show chromosomal changes similar to those that have been reported for primary tumors. Chromosomal losses were seen at higher frequency, particularly for chromosomes 14 and 15. By FISH, we identified subregions on chromosome arm 20q that are frequently involved in DNA amplifications in colorectal cancer and that may harbor candidate proto-oncogenes.     

Recurrent chromosomal imbalances and structurally abnormal breakpoints within complex karyotypes of malignant peripheral nerve sheath tumour and malignant triton tumour: a cytogenetic and molecular cytogenetic study

BACKGROUND: Cytogenetic studies of malignant peripheral nerve sheath tumours (MPNSTs) and malignant triton tumours (MTTs) are rare. AIMS: To undertake cytogenetic analysis of these tumours. METHODS: Conventional cytogenetic analysis of 21 MPNSTs and MTTs from 17 patients (nine with peripheral neurofibromatosis (NF1)) was carried out using standard culture and harvesting procedures. For a more precise identification of composite structural rearrangements and marker chromosomes, spectral karyotypic analysis (SKY) was applied to a subset of cases. In addition, EGFR gene copy number was assessed by fluorescence in situ hybridisation (FISH) analysis in a subset of cases. RESULTS: Cytogenetic analysis revealed predominantly complex karyotypes. SKY analysis was useful in further defining many structural anomalies. Structural aberrations most frequently involved chromosomal bands or regions 1p31-36, 4q28-35, 7p22, 11q22-23, 19q13, 20q13, and 22q11-13. Overall, loss of chromosomal material was much more common than gain. Loss of chromosomes or chromosomal regions 1p36 (48%), 3p21-pter (52%), 9p23-pter (57%), 10 (48%), 11q23-qter (48%), 16/16q24 (62%), 17(43%), and 22/22q (48%), and gains of 7/7q (29%) and 8/8q (29%) were most prominent. These gains and losses were distributed equally between MPNST and MTT, demonstrating that these entities are similar with respect to recurrent genomic imbalances. Similarly, none of the recurrent chromosomal breakpoints or imbalances was restricted to either NF1 associated or sporadic MPNSTs. FISH analysis was negative for amplification. CONCLUSIONS: These cytogenetic and molecular cytogenetic findings expand the knowledge of chromosomal alterations in MPNST and MTT, and point to possible recurring regions of interest.     

Comparative genomic hybridization analysis identifies gains of 1p35 approximately p36 and chromosome 19 in osteosarcoma.

Osteosarcomas (OS) are aggressive tumors of the bone and often have a poor prognosis. Conventional cytogenetic analyses of OS have revealed highly complex karyotypes, with numerous abnormalities. In this study, we analyzed 18 untreated OS tumors from 17 patients of the younger incidence age group by comparative genomic hybridization (CGH), 4 tumors by spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). Comparative genomic hybridization identified frequent copy number changes of the chromosomal region 1p (10/17) and gain of part or all of chromosome 19(8/17). In addition gains were observed at 5p(3/17), 8q(3/17), 16p(3/17), and 17p(5/17); and losses at chromosomes 2q(3/17), 10(4/17) and 13(3/17). High level gains were detected in the 8q23 approximately q24 region in two tumors as well as at 17p in one primary and a metastatic tumor. Minimal regions of gain were present at 1p35 approximately p36.3 (8/17); 5p14 approximately p15.2 (3/17), and 8q22 approximately q24.3 (3/17). SKY analysis demonstrated that OS has a complex pattern of clonal and non-clonal rearrangements and helped confirm the structural basis for the imbalances detected by CGH. Spectral karyotyping confirmed an overall pattern of chromosomal gain affecting 1p in all four tumors. Fluorescence in situ hybridization analysis from these tumors confirmed the gain of the 1p36 region in 2 tumors as determined by CGH analysis as well as the amplification of 8q.     

Cytogenetic and molecular approaches of polyploidization in colorectal adenocarcinomas

We present the cytogenetic analysis of 23 cases of polyploid colorectal adenocarcinomas. We took advantage of the high intratumoral heterogeneity of the karyotypes to identify clones, subclones, and cell-to-cell variations. This allowed us to reconstruct the chromosomal evolution of each tumor and to propose a schema of the chromosomal changes in relation to the endoreduplication process. All but one case were characterized by a relative deficiency of chromosomes 17p and 18. Other deficiencies affecting the late-replicating X, and to a lesser degree, 1p, 5q, 14, 15, 8p, 10, 21, and 4, and excesses affecting the early-replicating X, 8q, 13, 16, 17q, and 11 were frequently associated. This pattern of imbalances is very similar to that of the monosomic type previously described in near-diploid tumors. The pattern of the 23rd tumor corresponded to those of the trisomic type tumors. These data largely confirm the existence of two distinct processes of chromosomal evolution in colorectal adenocarcinomas, with a strong tendency to undergo endoreduplication for the monosomic type near-diploid tumors. To correlate cytogenetic and molecular data, allelic losses analyses were investigated for probes of chromosomes 17p and 18. In all 12 informative tumors, a loss of heterozygosity for probes of the short arm of chromosome 17 indicated the occurrence of a rearrangement of chromosome 17 before the endoreduplication. The same was true for allelic losses for probes of chromosome 18 found in 11 of 12 informative tumors. The correlation between cytogenetic and molecular data is thus excellent and indicates that losses of 17p and 18 are early events in the tumor process.     

Molecular cytogenetic analysis of two primary squamous cell carcinomas of the lung using multicolor fluorescence in situ hybridization

To fully characterize the numerous chromosomal aberrations in two human squamous cell carcinomas (SCCs) of the lung, molecular cytogenetic characterization was carried out utilizing conventional banding analysis and multicolor fluorescence in situ hybridization (mFISH), providing simultaneous color discrimination of all 24 human chromosomes. Both tumors displayed complex aneuploid karyotypes with a host of numerical and structural chromosome abnormalities. Structural aberrations common to both SCCs included rearrangements of chromosomes 1, 3p, 7q, and 8q, contributing to net loss of chromosomal sequences on 1p, 3p, and 8p, and a net gain of 8q. The recently introduced mFISH technique enabled the disclosure of cryptic translocations and the chromosomal composition of previously unrecognized marker chromosomes. Furthermore, mFISH greatly enhanced the ability to delineate chromosomal breakpoints when integrating banding information from conventional banding analysis. Eventually, the application of mFISH as a powerful approach to refine complex tumor karyotypes is expected to result in a more detailed and complete picture of cytogenetic events associated with the development and progression of solid tumors.     

Molecular cytogenetic characterization of early and late renal cell carcinomas in von Hippel-Lindau disease

Deletions of 3p25, gains of chromosomes 7 and 10, and isochromosome 17q are known cytogenetic aberrations in sporadic renal cell carcinoma (RCC). In addition, a majority of RCCs have loss of heterozygosity (LOH) of the Von Hippel-Lindau (VHL) gene located at chromosome band 3p25. Patients who inherit a germline mutation of the VHL gene can develop multifocal RCCs and other solid tumors, including malignancies of the pancreas, adrenal medulla, and brain. VHL tumors follow the two-hit model of tumorigenesis, as LOH of VHL, a classic tumor suppressor gene, is the critical event in the development of the neoplastic phenotype. In an attempt to define the cytogenetic aberrations from early tumors to late RCC further, we applied spectral karyotyping (SKY) to 23 renal tumors harvested from 6 unrelated VHL patients undergoing surgery. Cysts and low-grade solid lesions were near-diploid and contained 1-2 reciprocal translocations, dicentric chromosomes, and/or isochromosomes. A variety of sole numerical aberrations included gains of chromosomes 1, 2, 4, 7, 10, 13, 21, and the X chromosome, although no tumors had sole numerical losses. Three patients shared a breakpoint at 2p21-22, and three others shared a dicentric chromosome 9 or an isochromosome 9q. In contrast to the near-diploidy of the low-grade lesions, a high-grade lesion and its nodal metastasis were markedly aneuploid, revealed loss of VHL by fluorescence in situ hybridization (FISH), and contained recurrent unbalanced translocations and losses of chromosome arms 2q, 3p, 4q, 9p, 14q, and 19p as demonstrated by comparative genomic hybridization (CGH). By combining SKY, CGH, and FISH of multiple tumors from the same VHL kidney, we have begun to identify chromosomal aberrations in the earliest stages of VHL-related renal cell tumors. Our current findings illustrate the cytogenetic heterogeneity of different VHL lesions from the same kidney, which supports the multiclonal origins of hereditary RCCs. Published 2001 Wiley-Liss, Inc.     

Chromosomal aberrations in neuroblastoma cell lines identified by cross species color banding and chromosome painting

We have studied cytogenetic rearrangements in karyotypes of five neuroblastoma cell lines [SK-N-AS, SK-N-SH, SH-SY5Y, SK-N-MC, SMS-KCNR] by G-banding, cross species color banding (RxFISH), and fluorescence in situ hybridization (FISH) with chromosome painting probes. Each neuroblastoma cell line had unique modal karyotypic characteristics and showed a variable number of numerical and structural clonal cytogenetic aberrations. The number of rearranged chromosomes in SK-N-AS, SK-N-SH, SH-SY5Y, SK-N-MC, and SMS-KCNR was 11, 3, 7, 14 (tetraploid, 20-21), and 6, respectively. The origins of abnormal chromosomes were effectively analyzed by RxFISH and FISH with multiple chromosome painting probes. The chromosomal origin of the homogeneously staining region in SH-SY5Y was identified as coamplification of chromosome bands 2p13 and 2p24 by chromosome microdissection and FISH. The non-random rearrangements of chromosomes were determined on 1p34 approximately p36, 6q16 approximately q21, 8q24, 9q34, 11q13 approximately q23, 16q23 approximately q24, 17q21, and 22q31. These results may provide useful information for further molecular characterization of neuroblastoma.     

Molecular cytogenetic evaluation of 10 uveal melanoma cell lines

Uveal melanoma is the most common intraocular tumor in adults and often results in unilateral blindness and/or death. Previous cytogenetic characterizations of this tumor consistently revealed chromosomal abnormalities involving chromosomes 3, 6, and 8; reports of other abnormalities vary in frequency. We defined cytogenetic abnormalities of this tumor using complementary in situ hybridization techniques on 10 uveal melanoma cell lines. Synthesis of comparative genomic hybridization (CGH) and spectral karyotyping (SKY) results revealed that chromosomal rearrangement is involved in DNA sequence copy number abnormalities throughout the genome, but monosomy 3 was not found. Monosomy 3 is thought to be a significant prognostic indicator, so its absence was investigated further. Fluorescence in situ hybridization (FISH) for chromosome 3 revealed approximately 1 centromere signal per cell, but probes for 3p and 3q revealed multiple telomere signals per cell, suggesting chromosomal rearrangement without whole-chromosome loss. Based on combined CGH, SKY, and FISH data, we propose that chromosome 3 is more frequently involved in chromosomal rearrangements than whole-chromosome loss in uveal melanoma. Future approaches should be designed to confirm and enhance the resolution of regions of imbalance in primary tumors. Once identified, conserved chromosomal alterations that contribute to uveal melanoma may reveal the underlying aspects of uveal melanoma onset, metastasis and resistance to current treatment modalities.     

Existence of two distinct processes of chromosomal evolution in near-diploid colorectal tumors

The comparison of all the karyotypes established in each of 18 near-diploid colorectal tumors made it possible to reconstruct a clonal evolution and to distinguish between early and late chromosomal aberrations. Because no abnormalities were observed in all tumors, and as even the most frequent changes, i.e., monosomy 17p and monosomy 18, may be present in mosaic, no chromosomal change can be regarded as a common primary event in the carcinogenetic process. However, the repeated occurrence of several changes favors the hypothesis of two karyotypic evolutionary processes. In most tumors, monosomy 17p and 18 were found, and the karyotypic evolution involved mainly several additional monosomies due to unbalanced rearrangements or losses that affect, by order of decreasing frequency, chromosomes 1p, 4, 14, 5q, 6q, 2p, and 11q, as well as gains of chromosomes 20, 8q, 13, 17q, and X. In this group of tumors, the mean number of chromosomes remains close to 46. In the other tumors, either only a monosomy 17p or a monosomy 18 was found and the karyotypic evolution involved essentially trisomies, resulting from gains with, by order of decreasing frequency, a preferential involvement of chromosomes 7, 8q, 13, 17q, 20, X, 2p, 5, and 16, the only additional recurrent deletion affecting chromosome 1p. In these tumors, the mean chromosome number is close to 51. Ten out of 11 polyploid sidelines emerged from monosomic-type tumors.     

Cytogenetic characterization of complex karyotypes in seven established melanoma cell lines by multiplex fluorescence in situ hybridization and DAPI banding

We report the use of multiplex fluorescence in situ hybridization (M-FISH) to resolve chromosomal aberrations in seven established melanoma cell lines with hypotriploid to hypertetraploid complex karyotypes. By simultaneous identification of all human chromosomes in single FISH experiments using a set of 52 directly labeled, whole chromosome painting probes, cryptic chromosomal translocations and the origin of unclear chromosomal material in structural rearranged and marker chromosomes could be identified, refining the tumor karyotypes in all seven cell lines. The number of structural aberrations in each cell line assigned with combined M-FISH and DAPI banding analysis ranged from 15 to 45. Altogether, 275 breakpoints could be assigned to defined chromosomal regions or bands. The chromosome arms 1p, 6q, 7p, 9p, and 11q which are known to be nonrandomly associated with melanoma tumorigenesis, were frequently involved in chromosomal breaks and/or copy number changes. This study also demonstrated the practical usefulness of combining M-FISH with conventional cytogenetic banding techniques for the characterization of complex tumor karyotypes with massive genomic alterations.     

Cytogenetic analysis of 57 primary prostatic adenocarcinomas.

Cytogenetic analysis after short-term culture in vitro of primary tumor samples was attempted in 82 patients with prostatic cancer. Tumor material was obtained by radical prostatectomy or transurethral resection. Successful cytogenetic studies were performed on 57 tumors of which five were well, 30 moderately, and 22 poorly differentiated adenocarcinomas. Only normal karyotypes were found in 24 tumors. Structural nonclonal aberrations were detected in 18 and clonal karyotypic abnormalities in 15 tumors. The most common clonal numerical aberration was loss of the Y chromosome; a missing Y was found in six tumors, in three of these as the sole anomaly. Clonal structural chromosomal rearrangements, usually accompanied by numerical changes, were detected in 12 tumors. The rearrangements involved 18 of the 22 autosomes and the X chromosome. Chromosomes 1, 7, and 10 were most frequently affected. Deletions, duplications, inversions, insertions, and balanced as well as unbalanced translocations were represented. The breakpoints in chromosome 1 were scattered along both the short and long arms with no obvious clustering, whereas those in chromosomes 7 and 10 were clustered at bands 7q22 (two deletions and two duplications in four different tumors) and 10q24 (two translocations, one deletion, and one inversion in four tumors). One additional tumor displayed a derivative chromosome 10 with a breakpoint in 10q23, and one had monosomy 10. Altogether, these abnormalities resulted in loss of 10q24----qter in five tumors. Monosomy 8 and rearrangements of the short arm of chromosome 8 leading to loss of 8p21----pter were seen in four tumors. Double minute chromosomes were found in two tumors.     

Identification of recurrent chromosomal rearrangements and the unique relationship between low-level amplification and translocation in glioblastoma

To elucidate the structural abnormalities and the relationship between chromosome structural disorders and DNA copy number aberrations in tumor cells, we applied the techniques of spectral karyotyping (SKY), comparative genomic hybridization (CGH), and fluorescence in situ hybridization (FISH), using yeast artificial chromosome (YAC) probes for nine human glioblastoma cell lines. One striking finding was that independently derived cell lines had the same recurrent marker chromosomes. Seven recurrent chromosomes were detected by these cytogenetic methods. In particular, cell lines U251, SNB-19, and U373-MG showed very similar karyotypes. It is also interesting that regions of DNA amplification were found translocated and/or inserted at a high rate (91.7%). In all, there were 12 amplified loci in five of the nine cell lines. These amplified chromosomal bands were scattered on the chromosomes, including the normal chromosome, with one exception (7q32-qter in U373-MG). FISH with YAC clones mapping to these chromosomal regions as DNA probes often showed DNA probe signals not only at original chromosomal sites but also in translocated or inserted segments. This form of DNA amplification was characterized by low-level increases (four- to 10-fold) and by translocation or insertion of the relevant chromosomal locus. These studies shed light on typical derivative chromosomes and the relationship between DNA amplification and chromosomal translocation in glioblastoma.     

Spectral karyotyping study of chromosome abnormalities in human leukemia.

Chromosomal analysis plays an important role in the diagnosis, treatment and prognosis of human leukemia. Currently, the GTG-banding technique (G-banding) is the most commonly used diagnostic method in clinical cytogenetics. G-banding analysis of subtle chromosomal rearrangements or complex karyotypes with multiple markers can be inadequate because of poor chromosome morphology and/or an insufficient yield of analyzable metaphases. Fluorescence in situ hybridization (FISH) is a highly sensitive and specific method to detect chromosomal alterations. Conventional FISH is used optimally in instances where only one or a few abnormalities are investigated. Spectral karyotyping (SKY), a novel cytogenetic technique, has been developed to unambiguously display and identify all chromosomes at one time using a spectrum of 24 different colors. This report presents the use of SKY for examination of the entire karyotype in specimens with complex chromosomal abnormalities from three leukemia patients. Conventional cytogenetic analysis (G-banding) showed complex hyperdiploid clones with multiple markers in each case. SKY was able to clarify and identify additional cryptic chromosomal translocations [e.g., t(2;10), t(3;10), t(5;7), t(7;18), t(9;17), t(10;12), t(13;16)] insertions [e.g., ins(17;9), ins(20;Y)], duplications [e.g., i(8)(q10), dup(4)(q31q35)] and marker chromosomes in each case. This study demonstrates that the combination of SKY and G-band techniques results in a more complete characterization of the complex chromosomal aberrations seen in leukemia.