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Thomas Ried

Publications and source records attributed to Thomas Ried.

At least 37 records · Page 2Linked to original sources
PubMed2005

The extent of chromosomal aberrations induced by chemotherapy in non-human primates depends on the schedule of administration.

We utilized a non-human primate model, the rhesus monkey (Macaca mulatta), to quantitate the extent of chromosomal damage in bone marrow cells following chemotherapy. Thiotepa, etoposide, and paclitaxel were chosen as the chemotherapy agents due to their distinct mechanisms of action. Chromosomal aberrations were quantitated using traditional Giemsa stain. We sought to evaluate the extent to which genotoxicity was dependent on the schedule of administration by giving chemotherapy as either a bolus or a 96 h continuous infusion. Neutropenia and areas under the concentration curve (AUCs) were monitored to ensure comparable cytotoxicity and dose administered. At least 100 metaphases were scored in each marrow sample by an investigator unaware of the treatment history of the animals. All three drugs produced a statistically significant higher percentage of abnormal metaphases following bolus chemotherapy (p<0.0001, p=0.0015 and p<0.0001 for thiotepa, etoposide and paclitaxel, respectively). We conclude that infusional administration of thiotepa, etoposide and paclitaxel is less genotoxic to normal bone marrow cells than is bolus administration. These results suggest infusional regimens may be considered where there are concerns about long-term genotoxic sequelae, including secondary cancer, teratogenicity, or possibly the development of drug resistance. We believe this approach provides a reproducible model in which drugs and eventually, regimens can be compared.

Animals↗
PubMed2005

Effectiveness of gene expression profiling for response prediction of rectal adenocarcinomas to preoperative chemoradiotherapy.

PURPOSE: There is a wide spectrum of tumor responsiveness of rectal adenocarcinomas to preoperative chemoradiotherapy ranging from complete response to complete resistance. This study aimed to investigate whether parallel gene expression profiling of the primary tumor can contribute to stratification of patients into groups of responders or nonresponders. PATIENTS AND METHODS: Pretherapeutic biopsies from 30 locally advanced rectal carcinomas were analyzed for gene expression signatures using microarrays. All patients were participants of a phase III clinical trial (CAO/ARO/AIO-94, German Rectal Cancer Trial) and were randomized to receive a preoperative combined-modality therapy including fluorouracil and radiation. Class comparison was used to identify a set of genes that were differentially expressed between responders and nonresponders as measured by T level downsizing and histopathologic tumor regression grading. RESULTS: In an initial set of 23 patients, responders and nonresponders showed significantly different expression levels for 54 genes (P < .001). The ability to predict response to therapy using gene expression profiles was rigorously evaluated using leave-one-out cross-validation. Tumor behavior was correctly predicted in 83% of patients (P = .02). Sensitivity (correct prediction of response) was 78%, and specificity (correct prediction of nonresponse) was 86%, with a positive and negative predictive value of 78% and 86%, respectively. CONCLUSION: Our results suggest that pretherapeutic gene expression profiling may assist in response prediction of rectal adenocarcinomas to preoperative chemoradiotherapy. The implementation of gene expression profiles for treatment stratification and clinical management of cancer patients requires validation in large, independent studies, which are now warranted.

Adenocarcinoma↗
PubMed2005

Insertion of c-Myc into Igh induces B-cell and plasma-cell neoplasms in mice.

We used gene targeting in mice to insert a His(6)-tagged mouse c-Myc cDNA, Myc(His), head to head into the mouse immunoglobulin heavy-chain locus, Igh, just 5' of the intronic enhancer, Emu. The insertion of Myc(His) mimicked both the human t(8;14)(q24;q32) translocation that results in the activation of MYC in human endemic Burkitt lymphomas and the homologous mouse T(12;15) translocation that deregulates Myc in certain mouse plasmacytomas. Beginning at the age of 6 months, Myc(His) transgenic mice developed B-cell and plasma neoplasms, such as IgM(+) lymphoblastic B-cell lymphomas, Bcl-6(+) diffuse large B-cell lymphomas, and CD138(+) plasmacytomas, with an overall incidence of 68% by 21 months. Molecular studies of lymphoblastic B-cell lymphoma, the most prevalent neoplasm (50% of all tumors), showed that the lymphomas were clonal, overexpressed Myc(His), and exhibited the P2 to P1 promoter shift in Myc expression, a hallmark of MYC/Myc deregulation in human endemic Burkitt lymphoma and mouse plasmacytoma. Only 1 (6.3%) of 16 lymphoblastic B-cell lymphomas contained a BL-typical point mutation in the amino-terminal transactivation domain of Myc(His), suggesting that most of these tumors are derived from naive, pregerminal center B cells. Twelve (46%) of 26 lymphoblastic B-cell lymphomas exhibited changes in the p19(Arf)-Mdm2-p53 tumor suppressor axis, an important pathway for Myc-dependent apoptosis. We conclude that Myc(His) insertion into Igh predictably induces B-cell and plasma-cell tumors in mice, providing a valuable mouse model for understanding the transformation-inducing consequences of the MYC/Myc-activating endemic Burkitt lymphoma t(8;14)/plasmacytoma T(12;15) translocation.

Amino Acid Sequence↗
PubMed2005

SMC1 involvement in fragile site expression.

Common fragile sites have been involved in neoplastic transformation, although their molecular basis is still poorly understood. Here, we demonstrate that inhibition of the SMC1 by RNAi is sufficient to induce fragile site expression. By investigating normal, ATM- and ATR-deficient cell lines, we provide evidence that the contribution of SMC1 in preventing the collapse of stalled replication fork is an Atr-dependent pathway. Using a fluorescent antibody specific for gamma-H2AX, we show that very rare discrete nuclear foci appear 1 and 2 h after exposure to aphidicolin and/or RNAi-SMC1, but became more numerous and distinct after longer treatment times. In this context, fragile sites might be viewed as an in vitro phenomenon originating from double-strand breaks formed because of a stalled DNA replication that lasted too long to be managed by physiological rescue acting through the Atr/Smc1 axis. We propose that in vivo, following an extreme replication block, rare cells could escape checkpoint mechanisms and enter mitosis with a defect in genome assembly, eventually leading to neoplastic transformation.

Aphidicolin↗
PubMed2005

Extraosseous IL-6 transgenic mouse plasmacytoma sometimes lacks Myc-activating chromosomal translocation.

The cellular oncogene MYC and plasma cell growth, differentiation, and survival factor IL-6 play critical roles in the natural history of human plasma cell neoplasms such as multiple myeloma (MM). Myc and IL-6 also are at the center of neoplastic plasma cell transformation in BALB/c mice that carry a human IL-6 transgene and, therefore, predictably develop plasmacytomas (PCTs). We showed previously that, much like advanced MM or human myeloma cell lines (HMCLs), in which MYC is frequently deregulated in cis because of complex cytogenetic aberrations juxtaposing MYC to immunoglobulin enhancers, IL-6 transgenic PCTs commonly deregulate Myc in cis by chromosomal translocation, predominantly T(12;15)(Igh-Myc). In this article, we show that, analogous to primary MM in which MYC is mostly deregulated in trans by signaling pathways converging at the MYC promoter, IL-6 transgenic PCTs sometimes develop in the absence of Myc translocations, thus activating Myc in trans. We present cytogenetic and molecular evidence on two IL-6 transgenic PCTs that contained overexpressed Myc protein but lacked T(12;15)(Igh-Myc) and two related Myc--deregulating translocations that juxtapose Myc to immunoglobulin light-chain instead of heavy-chain enhancers: T(6;15)(Igkappa-Pvt1) and T(15;16)(Pvt1-Iglambda). We conclude that Myc translocations are not strictly required for IL-6-driven PCT development in mice. IL-6 transgenic PCTs may provide a valuable model system for elucidating both trans and cis mechanisms of Myc deregulation of great relevance for MYC deregulation in human MM.

Animals↗
PubMed2005

The interactive online SKY/M-FISH & CGH database and the Entrez cancer chromosomes search database: linkage of chromosomal aberrations with the genome sequence.

To catalog data on chromosomal aberrations in cancer derived from emerging molecular cytogenetic techniques and to integrate these data with genome maps, we have established two resources, the NCI and NCBI SKY/M-FISH & CGH Database and the Cancer Chromosomes database. The goal of the former is to allow investigators to submit and analyze clinical and research cytogenetic data. It contains a karyotype parser tool, which automatically converts the ISCN short-form karyotype into an internal representation displayed in detailed form and as a colored ideogram with band overlay, and also has a tool to compare CGH profiles from multiple cases. The Cancer Chromosomes database integrates the SKY/M-FISH & CGH Database with the Mitelman Database of Chromosome Aberrations in Cancer and the Recurrent Chromosome Aberrations in Cancer database. These three datasets can now be searched seamlessly by use of the Entrez search and retrieval system for chromosome aberrations, clinical data, and reference citations. Common diagnoses, anatomic sites, chromosome breakpoints, junctions, numerical and structural abnormalities, and bands gained and lost among selected cases can be compared by use of the "similarity" report. Because the model used for CGH data is a subset of the karyotype data, it is now possible to examine the similarities between CGH results and karyotypes directly. All chromosomal bands are directly linked to the Entrez Map Viewer database, providing integration of cytogenetic data with the sequence assembly. These resources, developed as a part of the Cancer Chromosome Aberration Project (CCAP) initiative, aid the search for new cancer-associated genes and foster insights into the causes and consequences of genetic alterations in cancer.

Base Sequence↗
PubMed2005

Pediatric pancreatoblastoma: histopathologic and cytogenetic characterization of tumor and derived cell line.

Little is known of the molecular events underlying the genesis of pancreatoblastoma tumors in the pediatric population. Such studies have been limited by the rare nature of the disease, infrequent reports detailing cytogenetic alterations, and the lack of availability of cell lines for biologic studies. We present the isolation of a cell line from a 14-year-old boy with malignant pancreatoblastoma, and its cytogenetic characterization using spectral karyotyping and comparative genomic hybridization (CGH). The cytogenetic analysis revealed an exceedingly complex cytogenetic karyotype, with 33 aberrant chromosomes. CGH revealed multiple regions of chromosomal loss and gain, including a region on 8q gained in adult pancreatic cancers, one that frequently contains the MYC oncogene.

Adolescent↗
PubMed2005

A comprehensive continuous-time model for the appearance of CGH signal due to chromosomal missegregations during mitosis.

Aneuploidy, the gain or loss of large regions of the genome, is a common feature in cancer cells. Irregularities in chromosomal copy number caused by missegregations of chromosomes during mitosis can be visualized by cytogenetic techniques including fluorescence in situ hybridization (FISH), spectral karyotyping (SKY) and comparative genomic hybridization (CGH). In the current work, we consider the propagation of irregular copy numbers throughout a cell population as the individual cells progress through ordinary mitotic cell cycles. We use an algebraic model to track the different copy numbers as states in a stochastic process, based on the model of chromosome instability of Gusev, Kagansky, and Dooley, and consider the average copy number of a particular chromosome within a cell population as a function of the cell division rate. We review a number of mathematical models for determining the length of the cell cycle, including the Smith-Martin transition probability model and the 'sloppy size' model of Wheals, Tyson and Diekmann. The program MITOSIM simulates the growth of a population of cells using the aforementioned models of the cell cycle. MITOSIM allows the cell population to grow, with occasional resampling, until the average copy number of a given chromosome in the population reaches a preset threshold signifying a positive copy number alteration in this region. MITOSIM calculates the relationship between the missegregation rate and the growth rate of the cell population. This allows the user to test hypotheses regarding the effect chromosomal aberrations have upon the cell cycle, cell growth rates, and time to population dominance.

Aneuploidy↗
PubMed2005

Genomic amplification of the human telomerase gene (TERC) in pap smears predicts the development of cervical cancer.

Invasive cervical carcinomas almost invariably carry extra copies of chromosome arm 3q, resulting in a gain of the human telomerase gene (TERC). This provided the rationale for the development of a multicolor fluorescence in situ hybridization (FISH) probe set as a diagnostic tool for the direct detection of TERC gains in Pap smears. We previously used this probe set to show that cervical intraepithelial neoplasia (CIN) 2 and CIN3 lesions could be distinguished from normal samples, atypical squamous cell of undetermined significance (ASCUS) and CIN1, with a sensitivity and specificity exceeding 90%, independent of the cytomorphological assessment. In the current study, we explored whether gain of 3q and amplification of TERC could predict progression from CIN1/CIN2 to CIN3 and invasive carcinoma. We applied our probe set to a series of 59 previously stained Pap smears for which repeat Pap smears and clinical follow-up were available. The samples included CIN1/CIN2 lesions that progressed to CIN3 (progressors), CIN1/CIN2 lesions that regressed spontaneously (regressors), and normal Pap smears from women who subsequently developed CIN3 or cervical cancer. Here, we show that progressors displayed a gain of 3q whereas none of the regressors showed this genetic aberration. These data suggest that 3q gain is required for the transition from CIN1/CIN2 to CIN3 and that it predicts progression. Of note, 3q gain was found in 33% of cytologically normal Pap smears from women who were diagnosed with CIN3 or invasive cervical carcinoma after a short latency. The sensitivity of our test for predicting progression from CIN1/CIN2 to CIN3 was 100% and the specificity, ie, the prediction of regression, was 70%. We conclude that the detection of 3q gain and amplification of TERC in routinely collected Pap smears can assist in identifying low-grade lesions with a high progression risk and in decreasing false-negative cytological screenings.

Adult↗
PubMed2005

53BP1 cooperates with p53 and functions as a haploinsufficient tumor suppressor in mice.

p53 binding protein 1 (53BP1) is a putative DNA damage sensor that accumulates at sites of double-strand breaks (DSBs) in a manner dependent on histone H2AX. Here we show that the loss of one or both copies of 53BP1 greatly accelerates lymphomagenesis in a p53-null background, suggesting that 53BP1 and p53 cooperate in tumor suppression. A subset of 53BP1-/- p53-/- lymphomas, like those in H2AX-/- p53-/- mice, were diploid and harbored clonal translocations involving antigen receptor loci, indicating misrepair of DSBs during V(D)J recombination as one cause of oncogenic transformation. Loss of a single 53BP1 allele compromised genomic stability and DSB repair, which could explain the susceptibility of 53BP1+/- mice to tumorigenesis. In addition to structural aberrations, there were high rates of chromosomal missegregation and accumulation of aneuploid cells in 53BP1-/- p53+/+ and 53BP1-/- p53-/- tumors as well as in primary 53BP1-/- splenocytes. We conclude that 53BP1 functions as a dosage-dependent caretaker that promotes genomic stability by a mechanism that preserves chromosome structure and number.

Alleles↗
PubMed2004

Chromosome transfer induced aneuploidy results in complex dysregulation of the cellular transcriptome in immortalized and cancer cells.

Chromosomal aneuploidies are observed in essentially all sporadic carcinomas. These aneuploidies result in tumor-specific patterns of genomic imbalances that are acquired early during tumorigenesis, continuously selected for and faithfully maintained in cancer cells. Although the paradigm of translocation induced oncogene activation in hematologic malignancies is firmly established, it is not known how genomic imbalances affect chromosome-specific gene expression patterns in particular and how chromosomal aneuploidy dysregulates the genetic equilibrium of cells in general. To model specific chromosomal aneuploidies in cancer cells and dissect the immediate consequences of genomic imbalances on the transcriptome, we generated artificial trisomies in a karyotypically stable diploid yet mismatch repair-deficient, colorectal cancer cell line and in telomerase immortalized, cytogenetically normal human breast epithelial cells using microcell-mediated chromosome transfer. The global consequences on gene expression levels were analyzed using cDNA arrays. Our results show that regardless of chromosome or cell type, chromosomal trisomies result in a significant increase in the average transcriptional activity of the trisomic chromosome. This increase affects the expression of numerous genes on other chromosomes as well. We therefore postulate that the genomic imbalances observed in cancer cells exert their effect through a complex pattern of transcriptional dysregulation.

Aneuploidy↗
PubMed2004

Transforming growth factor-beta pathway serves as a primary tumor suppressor in CD8+ T cell tumorigenesis.

Tumorigenesis in rodents, as well as in humans, has been shown to be a multistep process, with each step reflecting an altered gene product or gene regulatory process leading to autonomy of cell growth. Initial genetic mutations are often associated with dysfunctional growth regulation, as is demonstrated in several transgenic mouse models. These changes are often followed by alterations in tumor suppressor gene function, allowing unchecked cell cycle progression and, by genomic instability, additional genetic mutations responsible for tumor metastasis. Here we show that reduced transforming growth factor-beta signaling in T lymphocytes leads to a rapid expansion of a CD8+ memory T-cell population and a subsequent transformation to leukemia/lymphoma as shown by multiple criteria, including peripheral blood cell counts histology, T-cell receptor monoclonality, and host transferability. Furthermore, spectral karyotype analysis of the tumors shows that the tumors have various chromosomal aberrations. These results suggest that reduced transforming growth factor-beta signaling acts as a primary carcinogenic event, allowing uncontrolled proliferation with consequent accumulation of genetic defects and leukemic transformation.

Animals↗
PubMed2004

Carcinogen-induced colon tumors in mice are chromosomally stable and are characterized by low-level microsatellite instability.

The azoxymethane (AOM)-induced mouse colon tumor model recapitulates many of the histopathological features associated with the multistage progression of human sporadic colorectal cancers (CRCs). To better define the genetic events associated with tumorigenesis in this murine model, we analysed tumors from A/J mice for chromosomal (CIN) and microsatellite (MSI) instabilities, two fundamental pathways of genomic instability that play a critical role in the pathogenesis of human CRCs. Male A/J mice, 6-week old, were injected with either AOM (n=5) (10 mg/kg b.w., i.p.) or vehicle (n=5) (0.9% NaCl solution) once a week for 6 weeks. At 32 weeks after the last dose, comparative genomic hybridization (CGH) was performed on 16 tumors harvested from five animals. Although 25% of the tumors displayed either a gain of chromosome 2 or loss of Y, the majority (75%) showed no genomic imbalances. Further analysis of chromosomal aberrations, using CGH and spectral karyotyping (SKY) was performed in our recently established A/J colon tumor-derived cell line, AJ02-NM0. Results showed a pseudotetraploid karyotype with loss of only the Y chromosome in these cultured cells, thereby providing additional evidence for the minimal role of CIN in the primary AOM-induced tumors. Interestingly, the majority (81%) of A/J tumors displayed low-level microsatellite instability (MSI-L) when analysed using mono- and dinucleotide repeat markers, and showed a significant expansion to high-level instability (MSI-H) in the AJ02-NM0 cells. This finding in cultured cells additionally provides evidence that a mild mutator pathway may contribute to the development of behaviorally benign carcinomas in situ in A/J mice. To better understand the tumorigenic process in the A/J colons, we screened for mutational alterations in key regions of the K-ras and Apc genes. Results showed a very low frequency (6%) of K-ras activating mutations, together with the absence of Apc truncation mutations in primary tumors and AJ02-NM0 cells. However, these tumors displayed intense nuclear accumulation of beta-catenin protein, indicating activation of the Wnt signaling pathway. Based on our molecular and cytogenetic findings, we propose that carcinogen-induced tumors may develop via mechanisms independent of the 'classical' CIN or MSI pathways.

Aneuploidy↗
PubMed2004

Recapitulation of the Roberts syndrome cellular phenotype by inhibition of INCENP, ZWINT-1 and ZW10 genes.

Roberts syndrome is an autosomal recessive disorder characterised primarily by symmetric reduction of all limbs and growth retardation. Patients have been reported to have premature separation of heterochromatin regions of many chromosomes and abnormalities in cell cycle. Given the rarity of the syndrome, the linkage analysis approach is not suitable to identify the responsible gene. In this work, a cell line derived from a patient affected by Roberts syndrome was characterized by cell biology and molecular cytogenetics, including comparative genomic hybridization and spectral karyotype. No recurrent chromosomal rearrangements were identified. Thereafter, based on the fact that premature chromatide separation is a reliable marker of the disease, we used antisense oligonucleotide technologies to inhibit six genes involved in various steps of the correct chromosome segregation, such as chromosome cohesion, kinetochore assembling, spindle checkpoint and spindle formation. We found that the inhibition of INCENP, ZWINT-1, ZW10 genes results in the appearance of mitotic cells characterised by centromere separation, chromosome aneuploidy and micronuclei formation. In addition, INCENP, ZWINT-1, ZW10 antisense-treated chromosome morphology was very similar to that of Roberts chromosome when analysed by atomic force microscopy. We concluded that INCENP, ZWINT-1, ZW10 gene inhibition results in cellular phenocopies of Roberts syndrome. Taken together, these findings support a possible role of these genes in the pathogenesis of Roberts syndrome.

Abnormalities, Multiple↗
PubMed2004

From silencing to gene expression: real-time analysis in single cells.

We have developed an inducible system to visualize gene expression at the levels of DNA, RNA and protein in living cells. The system is composed of a 200 copy transgene array integrated into a euchromatic region of chromosome 1 in human U2OS cells. The condensed array is heterochromatic as it is associated with HP1, histone H3 methylated at lysine 9, and several histone methyltransferases. Upon transcriptional induction, HP1alpha is depleted from the locus and the histone variant H3.3 is deposited suggesting that histone exchange is a mechanism through which heterochromatin is transformed into a transcriptionally active state. RNA levels at the transcription site increase immediately after the induction of transcription and the rate of synthesis slows over time. Using this system, we are able to correlate changes in chromatin structure with the progression of transcriptional activation allowing us to obtain a real-time integrative view of gene expression.

Animals↗
PubMed2004

Loss of CCAAT/enhancer binding protein delta promotes chromosomal instability.

The transcription factor CCAAT/enhancer binding protein delta (Cebpd, also known as C/EBPdelta, CRP3, CELF, NF-IL6beta) is implicated in diverse cellular functions such as the acute phase response, adipocyte differentiation, learning and memory, and mammary epithelial cell growth control. Here, we report that lack of Cebpd causes genomic instability and centrosome amplifications in primary embryonic fibroblasts derived from 129S1 mice. Upon spontaneous immortalization, Cebpd-deficient fibroblasts acquire transformed features such as impaired contact inhibition and reduced serum dependence. These data identify a novel role for Cebpd in the maintenance of chromosomal stability and suggest a potential tumor suppressor function in vivo.

Animals↗