Biomedical subjects

Ludmila Gorunova

Publications and source records attributed to Ludmila Gorunova.

9 recordsLinked to original sources

PubMed2005

Structural and numerical chromosome changes in colon cancer develop through telomere-mediated anaphase bridges, not through mitotic multipolarity.

Telomere dysfunction has been associated with chromosomal instability in colorectal carcinoma, but the consequences of telomere-dependent instability for chromosome integrity and clonal evolution have been little explored. We show here that abnormally short telomeres lead to a wide spectrum of mitotic disturbances in colorectal cancer cell lines, including anaphase bridging, whole-chromosome lagging, and mitotic multipolarity. These abnormalities were found in both the presence and absence of microsatellite instability. The mean telomere length varied extensively between cells from the same tumor, allowing the establishment of tumor cell subpopulations with highly different frequencies of mitotic disturbances. Anaphase bridging typically resulted in either inter-centromeric chromatin fragmentation or centromere detachment, leading to pericentromeric chromosome rearrangements and loss of whole chromosomes, respectively. There was a strong correlation between anaphase bridges and multipolar mitoses, and the induction of dicentric chromosomes by gamma irradiation and telomerase inhibition led to an elevated frequency of multipolar mitotic spindles, suggesting that multipolarity could result from polyploidization triggered by anaphase bridging. Chromatid segregation in multipolar mitoses was close to random, resulting in frequent nullisomies and nonviable daughter cells. In contrast, there was a high clonogenic survival among cells having gone through anaphase bridging in bipolar mitoses. Bridging of telomere-deficient chromosomes could thus be a major mutational mechanism in colorectal cancer, whereas mitotic multipolarity appears to be a secondary phenomenon that rarely, if ever, contributes to clonal evolution.

Anaphase↗

PubMed2005

Microarray analyses reveal strong influence of DNA copy number alterations on the transcriptional patterns in pancreatic cancer: implications for the interpretation of genomic amplifications.

DNA copy number alterations are believed to play a major role in the development and progression of human neoplasms. Although most of these genomic imbalances have been associated with dysregulation of individual genes, their large-scale transcriptional consequences remain unclear. Pancreatic carcinomas frequently display gene copy number variation of entire chromosomes as well as of chromosomal subregions. These changes range from homozygous deletions to high-level amplifications and are believed to constitute key genetic alterations in the cellular transformation of this tumor type. To investigate the transcriptional consequences of the most drastic genomic changes, that is, genomic amplifications, and to analyse the genome-wide transcriptional effects of DNA copy number changes, we performed expression profiling of 29 pancreatic carcinoma cell lines and compared the results with matching genomic profiling data. We show that a strong association between DNA copy numbers and mRNA expression levels is present in pancreatic cancer, and demonstrate that as much as 60% of the genes within highly amplified genomic regions display associated overexpression. Consequently, we identified 67 recurrently overexpressed genes located in seven precisely mapped commonly amplified regions. The presented findings indicate that more than one putative target gene may be of importance in most pancreatic cancer amplicons.

Chromosome Mapping↗

PubMed2005

Clear cell hidradenoma of the skin-a third tumor type with a t(11;19)--associated TORC1-MAML2 gene fusion.

Recent studies have shown that the t(11;19)(q21;p13) translocation in mucoepidermoid carcinomas and benign Warthin's tumors results in a fusion of the N-terminal CREB-binding domain of the cAMP coactivator TORC1 (a.k.a. MECT1 and WAMTP1) to the Notch coactivator MAML2. Here we show that a third tumor type, clear cell hidradenoma of the skin, also expresses this gene fusion. RT-PCR analysis of a clear cell hidradenoma with a t(11;19)(q21;p13) translocation revealed expression of a TORC1-MAML2 fusion transcript consisting of exon 1 of TORC1 fused to exons 2-5 of MAML2. Because the fusion was only detected in a single case, the frequency of this aberration in clear cell hidradenomas remains unknown. These results demonstrate that the t(11;19) in mucoepidermoid carcinoma, Warthin's tumor, and clear cell hidradenoma targets the same genes and results in identical gene fusions, indicating that at least subgroups of these glandular tumors evolve through activation of the same molecular pathways.

Artificial Gene Fusion↗

PubMed2004

Genome-wide array-based comparative genomic hybridization reveals multiple amplification targets and novel homozygous deletions in pancreatic carcinoma cell lines.

Pancreatic carcinomas display highly complex chromosomal abnormalities, including many structural and numerical aberrations. There is ample evidence indicating that some of these abnormalities, such as recurrent amplifications and homozygous deletions, contribute to tumorigenesis by altering expression levels of critical oncogenes and tumor suppressor genes. To increase the understanding of gene copy number changes in pancreatic carcinomas and to identify key amplification/deletion targets, we applied genome-wide array-based comparative genomic hybridization to 31 pancreatic carcinoma cell lines. Two different microarrays were used, one containing 3,565 fluorescence in situ hybridization-verified bacterial artificial chromosome clones and one containing 25,468 cDNA clones representing 17,494 UniGene clusters. Overall, the analyses revealed a high genomic complexity, with several copy number changes detected in each case. Specifically, 60 amplicons at 32 different locations were identified, most frequently located within 8q (8 cases), 12p (7 cases), 7q (5 cases), 18q (5 cases), 19q (5 cases), 6p (4 cases), and 8p (4 cases). Amplifications of 8q and 12p were mainly clustered at 8q23-24 and 12p11-12, respectively, whereas amplifications on other chromosome arms were more dispersed. Furthermore, our analyses identified several novel homozygously deleted segments located to 9p24, 9p21, 9q32, 10p12, 10q22, 12q24, and 18q23. The individual complexity and aberration patterns varied substantially among cases, i.e., some cell lines were characterized mainly by high-level amplifications, whereas others showed primarily whole-arm imbalances and homozygous deletions. The described amplification and deletion targets are likely to contain genes important in pancreatic tumorigenesis.

Cell Line, Tumor↗

PubMed2003

Pancreatic carcinoma cell lines with SMAD4 inactivation show distinct expression responses to TGFB1.

Transforming growth factor beta-1 (TGFB1)-induced gene expression was studied in five pancreatic carcinoma cell lines and one known TGFB1-sensitive cell line (HaCaT) by use of high-density filter-based cDNA microarrays representing over 4,000 human genes. The results indicate a complex cellular response to TGFB1 with 10% of the investigated genes showing altered expression after 3 or 48 hr of TGFB1 exposure. The tumor cell lines displayed a gradually inversed gene expression pattern, which correlated with reduced sensitivity to TGFB1, as compared to the HaCaT cell line. In the HaCaT cells, several proapoptotic genes showed increased expression in response to TGFB1, whereas the expression of antiapoptotic genes was decreased. In contrast, two pancreatic carcinoma cell lines, previously found to be growth stimulated by TGFB1, displayed an expression pattern opposite to that of these genes. Similarly, the expression of other functional groups of genes, such as cell cycle and transcription factor related genes, was almost completely reversed in these two tumor cell lines. Importantly, three of the five investigated pancreatic carcinoma cell lines responded to TGFB1, although they had SMAD4 inactivations, suggesting that the observed gene expression changes in these cell lines must be accomplished by SMAD-independent pathways.

Cluster Analysis↗

PubMed2003

Chromosomal abnormalities in inflammatory pseudotumor of the urinary bladder.

Inflammatory pseudotumors of the urinary bladder are rare, benign, nonepithelial tumors. Fewer than 30 have been reported, and no data are available on their karyotypic characteristics and/or the molecular mechanisms of pathogenesis. We performed short-term culturing and cytogenetic analysis of an inflammatory pseudotumor of the bladder, finding a der(20)t(12;20)(q13 approximately q15;q13) as the only cytogenetic aberration. The detection of a 12q13 approximately q15 rearrangement in the inflammatory pseudotumor indicates that this lesion is pathogenetically related to other benign mesenchymal tumors displaying, for example, lipogenic or leiomyomatous differentiation, something that is in sharp contrast to the karyotypic profile of epithelial tumors of the urinary bladder mucosa.

Chromosome Aberrations↗

PubMed2002

Cytogenetic abnormalities in a hemangiopericytoma of the spleen.

To date, only 16 cytogenetically abnormal hemangiopericytomas (HP) have been reported. Despite this low number, some characteristic karyotypic features have already emerged: most HP are near-diploid and breakpoints in 12q13, 12q24, and 19q13 seem to be common, with t(12;19)(q13;q13) being a recurrent translocation. Here, we report the first case of a probably benign splenic HP with chromosomal abnormalities. The abnormal karyotype was 47,XX,t(5;22;11)(q31;q11;q13),+10. None of these abnormalities have previously been reported in HP, suggesting that the karyotypic pattern of splenic HP may differ from soft tissue HP.

Chromosome Aberrations↗

PubMed2002

Detailed genomic mapping and expression analyses of 12p amplifications in pancreatic carcinomas reveal a 3.5-Mb target region for amplification.

Previous cytogenetic and comparative genomic hybridization (CGH) analyses have shown that the gain of chromosome arm 12p is frequent in pancreatic carcinomas. We investigated 15 pancreatic carcinoma cell lines using CGH, fluorescence in situ hybridization (FISH), and semiquantitative polymerase chain reaction (PCR) to characterize 12p amplifications in detail. The CGH analysis revealed gains of 12p in four of the cell lines and local amplification within 12p11-12 in six cell lines. By FISH analysis, using precisely mapped YAC clones, the commonly amplified region was found to be approximately 5 Mb. The amplified segment extended from YAC 753f12, covering the KRAS2 locus, to YAC 891f1, close to the centromere. A semiquantitative PCR methodology was used to estimate genomic copy numbers of 14 precisely mapped expressed sequence tags (ESTs) and sequence-tagged sites, located within this interval. The level of amplification ranged from two- to 12-fold. The produced gene copy profiles revealed a 3.5-Mb segment with various local amplifications. This region includes KRAS2 and ranges from D12S1617 to sts-N38796. Two of the cell lines (primary and metastatic tumor from the same patient) showed amplification peaks within the distal region of this segment, two had peaks within the proximal region, one showed subpeaks in both regions, and one displayed amplification of the entire region. Chromosome segment-specific cDNA array analysis of 29 expressed sequences within the whole interval between D12S1617 and sts-N38796 indicated overexpression of four ESTs, two corresponding to DEC2 and PPFIBP1, and two to ESTs with unknown function. Expression analysis of these and of KRAS2 showed specific overexpression in the six cell lines with local 12p amplifications. These findings indicate two target regions within the 3.5-Mb segment in 12p11-12, one proximal including PPFIBP1, and one distal including KRAS2.

Carcinoma↗

PubMed2002

Frequent amplification of 8q24, 11q, 17q, and 20q-specific genes in pancreatic cancer.

Genetic changes involved in the development and progression of pancreatic cancer are still partly unknown, despite the progress in recent years. In this study, comparative genomic hybridization analysis in 31 pancreatic cancer cell lines showed that chromosome arms 8q, 11q, 17q, and 20q are frequently gained in this tumor type. Copy number analysis of selected genes from these chromosome arms by fluorescence in situ hybridization showed amplification of the MYC oncogene in 54% of the cell lines, whereas CCND1 was amplified in 28%. In the 17q arm, the ERBB2 oncogene was amplified in 20% of the cell lines, TBX2 in 50%, and BIRC5 in 58%, indicating increased involvement toward the q telomere of chromosome 17. In the 20q arm, the amplification frequencies varied from 32% to 83%, with the CTSZ gene at 20q13 being most frequently affected. These results illustrate that amplification of genes from the 8q, 11q, 17q, and 20q chromosome arms is common in pancreatic cancer.

Chromosomes, Human↗