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D Gisselsson

Publications and source records attributed to D Gisselsson.

At least 19 recordsLinked to original sources
PubMed2004

Telomere shortening and mitotic dysfunction generate cytogenetic heterogeneity in a subgroup of renal cell carcinomas.

Most renal cell carcinomas (RCC) show only simple chromosomal changes. However, a more complex cytogenetic pattern has been found in a subgroup of aggressive RCC, indicating that further accumulation of chromosome changes could play a role in tumour progression. To explore the possible mechanisms behind cytogenetic evolution in RCC, a parallel assessment of chromosome mutations and mitotic segregation pattern in eight tumours was performed. In the majority of cases, no abnormalities in the cell division machinery were found and the rate of alterations in chromosome copy number, as measured by interphase FISH, was similar to that in non-neoplastic cells. This was reflected by relatively simple karyotypes, with little cytogenetic intratumour heterogeneity. In contrast, another group of tumours exhibited several cytogenetically related clones with additional structural chromosomal changes at two or more ploidy levels and a frequency of copy number alterations that was higher than in normal cells. In these cases, the telomere repeat sequences were abnormally short and chromosomal breakage-fusion-bridge events were observed at cell division, as well as multipolar configurations and supernumerary centrosomes. Abnormalities of the cell division machinery may thus contribute to the evolution of complex karyotypes and genetic intratumour heterogeneity in a subgroup of RCC.

Adult↗
PubMed2004

Retained heterodisomy for chromosome 12 in atypical lipomatous tumors: implications for ring chromosome formation.

Atypical lipomatous tumor (ALT) is an intermediate malignant mesenchymal tumor that is characterized by supernumerary ring chromosomes and/or giant rod-shaped marker chromosomes (RGMC). Fluorescence in situ hybridization (FISH) and molecular genetic analyses have disclosed that the RGMCs always contain amplified sequences from the long arm of chromosome 12. Typically, RGMCs are the sole clonal changes and so far no deletions or other morphologic aberrations of the two normal-appearing chromosomes 12 that invariably are present have been detected. The mechanisms behind the formation of the RGMCs are unknown, but it could be hypothesized that RGMC formation is preceded by trisomy 12 or, alternatively, that ring formation of one chromosome 12 is followed by duplication of the remaining homolog. The latter scenario would always result in isodisomy for the two normal-appearing chromosomes 12, whereas the former would yield isodisomy in one-third of the cases. In order to investigate these possible mechanisms behind ring formation, we studied polymorphic loci on chromosome 12 in 14 cases of ALT showing one or more supernumerary ring chromosomes and few or no other clonal aberrations at cytogenetic analysis. The molecular genetic analyses showed that the tumor cells always retained both parental copies of chromosome 12, thus refuting the trisomy 12 and duplication hypotheses.

Adult↗
PubMed2002

Centrosomal abnormalities, multipolar mitoses, and chromosomal instability in head and neck tumours with dysfunctional telomeres.

Carcinomas of the head and neck typically exhibit complex chromosome aberrations but the underlying mutational mechanisms remain obscure. Evaluation of cell division dynamics in low-passage cell lines from three benign and five malignant head and neck tumours revealed a strong positive correlation between multipolarity of the mitotic spindle and the formation of bridges at anaphase in both benign and malignant tumours. Cells exhibiting a high rate of mitotic abnormalities also showed several chromosome termini lacking TTAGGG repeats and a high frequency of dicentric chromosomes. Multicolour karyotyping demonstrated a preferential involvement in structural rearrangements of chromosomes with deficient telomeres. The majority of malignant, mitotically unstable tumours expressed the reverse transcriptase subunit of telomerase. These data indicate that some of the genomic instability in head and neck tumours is initiated by telomere dysfunction, leading to the formation of dicentric chromosomes. These form chromosome bridges at mitosis that could prevent the normal anaphase-telophase transition. In turn, this may cause an accumulation of centrosomes and mitotic multipolarity. Telomerase expression does not confer total stability to the tumour genome but could be crucial for moderating the rate of chromosomal evolution.

Adenoma, Pleomorphic↗
PubMed2002

Tumour morphology--interplay between chromosome aberrations and founder cell differentiation.

Studies of haematological neoplasms have shown that alterations in structure and/or expression of transcription factor genes may play a crucial role for transforming stem cells or progenitor cells into malignant cells. These mutations typically arise through balanced translocations and appear to induce a block in cellular differentiation. The impact of the transforming mutation is highly dependent on the lineage of the founder cell and each specific translocation is limited to one or a few morphological subtypes. Originating from immature cells, these neoplasms have a high self-replicative capacity and are already before transformation protected from senescence by constitutive telomerase expression. Most solid tumours, on the other hand, probably originate from cells at higher levels of differentiation and require multiple mutations in oncogenes and tumour suppressor genes for neoplastic transformation. Absence of telomerase activity in the tumour-founding cell line predisposes to abnormal shortening of telomeric repeats in these cells during early clonal expansion. In turn, this triggers chromosomal breakage-fusion-bridge events through which the tumour genome is constantly reorganised, resulting in a complex and heterogeneous pattern of chromosome aberrations in the tumour cell population; the abnormal mitotic processes also give rise to cellular pleomorphism and nuclear atypia. Tumour morphology thus appears to be determined not only by the lineage of the transformed cell but also by its propensity for chromosomal instability.

Animals↗
PubMed2001

Telomere dysfunction triggers extensive DNA fragmentation and evolution of complex chromosome abnormalities in human malignant tumors.

Although mechanisms for chromosomal instability in tumors have been described in animal and in vitro models, little is known about these processes in man. To explore cytogenetic evolution in human tumors, chromosomal breakpoint profiles were constructed for 102 pancreatic carcinomas and 140 osteosarcomas, two tumor types characterized by extensive genomic instability. Cases with few chromosomal alterations showed a preferential clustering of breakpoints to the terminal bands, whereas tumors with many changes showed primarily interstitial and centromeric breakpoints. The terminal breakpoint frequency was negatively correlated to telomeric TTAGGG repeat length, and fluorescence in situ hybridization with telomeric TTAGGG probes consistently indicated shortened telomeres and >10% of chromosome ends lacking telomeric signals. Because telomeric dysfunction may lead to formation of unstable ring and dicentric chromosomes, mitotic figures were also evaluated. Anaphase bridges were found in all cases, and fluorescence in situ hybridization demonstrated extensive structural rearrangements of chromosomes, with terminal transferase detection showing fragmented DNA in 5-20% of interphase cells. Less than 2% of cells showed evidence of necrosis or apoptosis, and telomerase was expressed in the majority of cases. Telomeric dysfunction may thus trigger chromosomal fragmentation through persistent bridge-breakage events in pancreatic carcinomas and osteosarcomas, leading to a continuous reorganization of the tumor genome. Telomerase expression is not sufficient for completely stabilizing the chromosome complement but may be crucial for preventing complete genomic deterioration and maintaining cellular survival.

Adolescent↗
PubMed2001

Limitations of chromosome classification by multicolor karyotyping.

Multicolor karyotyping technologies, such as spectral karyotyping (SKY) (Schröck et al.1996; Liyanage et al. 1996) and multiplex (M-) FISH (Speicher et al. 1996), have proved to be extremely useful in prenatal, postnatal, and cancer cytogenetics. However, these technologies have inherent limitations that, in certain situations, may result in chromosomal misclassification. In this report, we present nine cases, which fall into five categories, in which multicolor karyotyping has produced erroneous interpretations. Most errors appear to have a similar mechanistic basis.

Animals↗
PubMed2001

Multivariate analyses of genomic imbalances in solid tumors reveal distinct and converging pathways of karyotypic evolution.

A total of 3,016 malignant solid tumors (kidney, colorectal, breast, head and neck, ovarian, and lung carcinomas, neuroglial tumors, malignant melanoma, and testicular germ cell tumors) were selected for statistical analyses regarding karyotypic evolution. Genomic imbalances, i.e., net gains and losses, present in more than 5% of each tumor type were identified. Individual tumors were then classified with respect to absence or presence of these imbalances. To analyze for possible patterns of correlated imbalances, principal component analyses (PCA) were performed. Furthermore, algorithms were developed to analyze the temporal order of the imbalances, as well as the possible selection for early or late appearance in the karyotypic evolution. By analyzing the temporal order of imbalances common to many tumor types, a general order for nine of these emerged, namely, +7, -3p, -6q, -1p, -8p, -17p, -9p, -18, and -22. The distributions of the number of imbalances per case revealed a geometrical distribution, ranging from one to nine imbalances per tumor, in the majority of the tumor types. In tumor types in which cases with a high number of imbalances per case were frequent, notably head and neck, ovarian, and lung carcinomas, the overall distributions were bimodal, indicating the presence of two modes of chromosome evolution. By combining data from the PCA with the temporal analyses, it was possible to identify karyotypic pathways. It was found that the majority of the tumor types displayed more than one cytogenetic route, but, as the karyotypic evolution continued, these converged to a common pathway.

Allelic Imbalance↗
PubMed2001

PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms.

Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.

Child↗
PubMed2001

Abnormal nuclear shape in solid tumors reflects mitotic instability.

Abnormalities in nuclear morphology are frequently observed in malignant tissues but the mechanisms behind these phenomena are still poorly understood. In this study, the relation between abnormal nuclear shape and chromosomal instability was explored in short-term tumor cell cultures. Mitotically unstable ring and dicentric chromosomes were identified by fluorescence in situ hybridization at metaphase and subsequently localized in interphase nuclei from five malignant soft tissue tumors. The vast majority (71 to 86%) of nuclear blebs, chromatin strings, and micronuclei contained material from the unstable chromosomes, whereas few (<11%) were positive for stable chromosomes. Nuclear morphology was also evaluated in fibroblasts and an osteosarcoma cell line exposed to irradiation. A linear correlation was found between the frequency of abnormalities in nuclear shape, on one hand, and cells with unstable chromosomes (r = 0.87) and anaphase bridge configurations (r = 0.98), on the other hand. The relation between nuclear shape and karyotypic pattern was investigated further in cultures from 58 tumors of bone, soft tissue, and epithelium. Blebs, strings, and micronuclei were significantly more frequent in tumors that contained rings, dicentrics, or telomeric associations than in those exhibiting only stable aberrations (P: < 0.001) and a positive correlation (r = 0.78) was found between the frequency of such nuclear abnormalities and the intratumor heterogeneity of structural chromosome aberrations. These results indicate that the formation of nuclear blebs, chromatin strings, and micronuclei in malignant tissues is closely related to the breakage-fusion-bridge type of mitotic disturbances. Abnormalities in nuclear shape may thus primarily be regarded as an indicator of genetic instability and intratumor heterogeneity, independent of cytogenetic complexity and the grade of malignancy.

Cell Line↗
PubMed2001

ETV6 rearrangements in patients with infantile fibrosarcomas and congenital mesoblastic nephromas by fluorescence in situ hybridization.

Congenital mesoblastic nephroma (CMN) and infantile fibrosarcoma (IFS) are two pediatric tumors arising in the kidneys and soft tissues of infants, respectively. Recently, a t(12;15)(p13;q25) resulting in ETV6-NTRK3 gene fusion was detected in patients with IFS and in patients with the cellular type of CMN, suggesting a common pathogenetic pathway. We investigated the presence or absence of ETV6 rearrangements and numerical abnormalities of chromosome 11 by using fluorescence in situ hybridization on paraffin-embedded material from five cases of IFS, two of CMN, and one of mixed type (CMN and IFS) found in our files. In three cases of IFS, we found ETV6 gene rearrangement but a normal copy number of chromosome 11. One case each of IFS, the cellular type of CMN, and the mixed type (CMN and IFS) had both abnormalities. In a case of classic CMN, neither trisomy 11 nor gene rearrangement was found. It is possible that trisomy 11 is a later, nonessential event in the pathogenetic process or that this secondary aberration is associated with still-unrecognized clinical or biological characteristics. We confirmed that IFS and the cellular type of CMN are cytogenetically related and can occur synchronously in the same organ.

Child, Preschool↗
PubMed2001

Characterization of chromosome aberrations in salivary gland tumors by FISH, including multicolor COBRA-FISH.

Fluorescence in situ hybridization (FISH), including COBRA-FISH, was used to characterize 11 salivary gland tumors that had been investigated by banding analysis. Five cases were pleomorphic adenoma (PA), three were adenoid cystic carcinoma, and one case each was mucoepidermoid carcinoma, carcinoma ex-pleomorphic adenoma (CaPA), and adenocarcinoma. All 11 cases were selected on the basis that they had shown rearrangement of 6q or 9p or had unresolved aberrations after karyotyping. The COBRA-FISH and FISH analyses led to a revised karyotype in all informative cases and made it possible to clarify almost all chromosomal rearrangements occurring in the tumors. Of particular note were the confirmation of the existence of 6q deletions, a common change in salivary gland carcinomas, and the demonstration that a seemingly balanced t(6;9) resulted in del(6q). Other rearrangements that were revealed by FISH included amplification of 12q sequences (MDM2 and CDK4) in one PA. We also investigated the status of the PLAG1 gene in four cases (one PA, one CaPA, one adenoid cystic carcinoma, and one mucoepidermoid carcinoma) with 8q12 rearrangements. Only in the former two cases were the FISH results compatible with intragenic rearrangements. Overall, the results of the study show that, even with good banding quality and in karyotypes of modest complexity, much new information will be gained by supplementing the banding analysis with a multicolor FISH approach, such as COBRA-FISH.

Adult↗
PubMed2001

Refined characterisation of chromosome aberrations in tumours by multicolour banding and electronic mapping resources.

Acquired chromosome abnormalities in tumours often reflect pathogenetic events at the gene level. Multicolour fluorescence in situ hybridisation (FISH) with single-copy probes offers extensive possibilities to characterise chromosome breakpoints in relation to the physical map of the human genome. This approach is based on the construction of comprehensive EST- based maps, combinatorial labelling of probes, and tumour cell preparations optimised for metaphase FISH. Information from several electronically available databases is combined into an integrated physical map, to which clones carrying yeast and bacterial artificial chromosomes are anchored. Extracted DNA or PCR products from these clones are then fluorescently labelled by one or several fluors, allowing simultaneous FISH detection of multiple loci. To improve hybridisation efficiency and reduce background fluorescence, standard methods for chromosome preparation from cultured tumour cells are complemented with a prolonged trypsin treatment to obtain complete disaggregation of cells, and exposure of the metaphase spreads to detergent and saline at high temperature, followed by pepsin digestion to remove extracellular matrix and cytoplasmic debris. The resulting colour-banding allows the characterisation of chromosome abnormalities in relation to expressed sequences, even in tumours exhibiting highly complex rearrangements.

Chromosome Banding↗
PubMed2000

Chromosomal breakage-fusion-bridge events cause genetic intratumor heterogeneity.

It has long been known that rearrangements of chromosomes through breakage-fusion-bridge (BFB) cycles may cause variability of phenotypic and genetic traits within a cell population. Because intercellular heterogeneity is often found in neoplastic tissues, we investigated the occurrence of BFB events in human solid tumors. Evidence of frequent BFB events was found in malignancies that showed unspecific chromosome aberrations, including ring chromosomes, dicentric chromosomes, and telomeric associations, as well as extensive intratumor heterogeneity in the pattern of structural changes but not in tumors with tumor-specific aberrations and low variability. Fluorescence in situ hybridization analysis demonstrated that chromosomes participating in anaphase bridge formation were involved in a significantly higher number of structural aberrations than other chromosomes. Tumors with BFB events showed a decreased elimination rate of unstable chromosome aberrations after irradiation compared with normal cells and other tumor cells. This result suggests that a combination of mitotically unstable chromosomes and an elevated tolerance to chromosomal damage leads to constant genomic reorganization in many malignancies, thereby providing a flexible genetic system for clonal evolution and progression.

Chromosome Aberrations↗
PubMed2000

Radiation-associated sarcomas are characterized by complex karyotypes with frequent rearrangements of chromosome arm 3p.

Ionizing radiation is a well-known risk factor for sarcoma development. To investigate whether radiation-associated sarcomas are characterized by chromosome aberrations that distinguish them from de novo sarcomas, we identified those patients in our series of more than 500 cytogenetically abnormal sarcomas that fulfilled the following criteria: (1) each patient should have been irradiated for another malignancy at least 3 years prior to the sarcoma diagnosis, and (2) the sarcoma should have developed within the field of radiation. Ten patients fulfilling these criteria could be retrieved (median age at sarcoma diagnosis was 55 years, range 17-79; median latency period between primary tumor and radiation-associated sarcoma was 9 years, range 4-30). The diagnoses were typical for radiation-associated sarcomas: 2 each of malignant fibrous histiocytoma, leiomyosarcoma, and pleomorphic sarcoma, and 1 each of osteosarcoma, fibrosarcoma, myxofibrosarcoma, and spindle cell sarcoma. All 10 cases had relatively complex karyotypes with multiple, mostly unbalanced, structural rearrangements, similar to what has been reported in de novo sarcomas of the corresponding histologic subtypes. The only cytogenetic features that were unusually frequent among the radiation-associated sarcomas were the finding of unrelated clones in 3 cases, and loss of material from chromosome arm 3p, in particular 3p21-3pter, in 8 cases. Loss of the same chromosome segment has been described in 4 of the 8 previously published cases of radiation-associated sarcomas that have been analyzed after short-term culturing, which makes this imbalance significantly (P < 0.001) more frequent among radiation-associated sarcomas (12 of 18 cases) than among unselected cases of the corresponding histologic subtypes (74 of 282 cases). In contrast to the cytogenetic results, no 3p deletions were detected among the 6 cases of the present series that could be analyzed by comparative genomic hybridization (CGH). The most frequent imbalance detected by CGH was gain of 15cen-q15 (3 cases), followed by loss of chromosome 13 and gain of 5p, and 7cen-q22, each detected in 2 cases.

Adolescent↗
PubMed2000

Cytogenetics of hepatoblastoma: further characterization of 1q rearrangements by fluorescence in situ hybridization: an international collaborative study.

BACKGROUND: Hepatoblastoma (HBT) is the most common hepatic neoplasm in children. This notwithstanding, little is known about pathogenetic factors, such as genetic abnormalities, of importance for the development and progression of this tumor type. To date, only 33 cytogenetically abnormal HBT have been published, and trisomies for chromosomes 2 and 20 have been shown to be the most frequent aberrations. Recently, unbalanced translocations involving proximal 1q have been described in several HBT, suggesting that a pathogenetically important gene maps to 1q. PROCEDURE: Six primary and one recurrent HBT were cytogenetically analyzed after short-term tissue culture. In addition, fluorescence in situ hybridization (FISH) studies, using locus-specific probes, were performed on three of these pediatric HBT as well as on one previously reported adult HBT. RESULTS: Total or partial trisomy 8, gain of chromosome 20, and structural rearrangements of chromosome 1 were detected in three HBT, and overrepresentation of chromosome 2 material was found in two HBT. The adjacent chromosome bands 1q12 and 1q21 were involved in three translocations, t(1;2), t(1;4), and t(1;11), which were all unbalanced and resulted in gain of 1q material. The previously reported adult HBT displayed 1q deletions with breakpoints at 1q12-21. FISH analyses of the 1q rearrangements revealed that all breakpoints were within the heterochromatic region. CONCLUSIONS: These findings provide further support for the importance of trisomies 2, 8, and 20 and rearrangements of 1q in the development of HBT. Furthermore, the consistent localization of breakpoints within the heterochromatic segment of chromosome 1 suggests that the important pathogenetic consequence of 1q abnormalities is the resulting genomic imbalance rather than a specific gene rearrangement.

Child, Preschool↗
PubMed2000

Locus-specific multifluor FISH analysis allows physical characterization of complex chromosome abnormalities in neoplasia.

Novel techniques in molecular cytogenetics have radically improved the ability to characterize genetic changes in neoplastic cells. In parallel, a rapid development in high-throughput genomics has resulted in detailed physical maps of the human genome. Combining these two fields, we have developed a method for the simultaneous visualization of several physically defined segments along a chromosome. Seven YAC clones and one subtelomeric cosmid clone from chromosome 12 were labeled with unique combinations of four fluors and hybridized to metaphase chromosomes from neoplastic cells. In a uterine leiomyoma and a myxoid liposarcoma with translocations 12;14 and 12;16, the breakpoints in chromosome 12 could be localized to the HMGIC and CHOP regions, respectively. In the other tumors, more complex aberrations were visualized, including two inversions in 12q with a common breakpoint between MDM2 and D12S332 in a pleomorphic adenoma, amplification of MDM2 and CDK4 in ring chromosomes from a malignant fibrous histiocytoma, and amplification of KRAS2 together with other unbalanced rearrangements in two pancreatic adenocarcinomas. Combinatorially labeled single-copy probes may thus simultaneously provide physical localization of breakpoints and an overview of complex structural rearrangements. Genes Chromosomes Cancer 28:347-352, 2000.

Chromosome Aberrations↗