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Search Results: 1 - 10 of 88107 matches for " Gunn I Meling "
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A CpG island hypermethylation profile of primary colorectal carcinomas and colon cancer cell lines
Guro E Lind, Lin Thorstensen, Tone L?vig, Gunn I Meling, Richard Hamelin, Torleiv O Rognum, Manel Esteller, Ragnhild A Lothe
Molecular Cancer , 2004, DOI: 10.1186/1476-4598-3-28
Abstract: The cell lines and primary tumors generally showed similar overall distribution and frequencies of gene methylation. Among the cell lines, 15%, 50%, 75%, 65%, 20% and 15% showed promoter methylation for hMLH1, MGMT, p16INK4a, p14ARF, APC, and E-cadherin, respectively, whereas 21%, 40%, 32%, 38%, 32%, and 40% of the primary tumors were methylated for the same genes. hMLH1 and p14ARF were significantly more often methylated in MSI than in MSS primary tumors, whereas the remaining four genes showed similar methylation frequencies in the two groups. Methylation of p14ARF, which indirectly inactivates TP53, was seen more frequently in tumors with normal TP53 than in mutated samples, but the difference was not statistically significant. Methylation of p14ARF and p16INK4a was often present in the same primary tumors, but association to diploidy, MSI, right-sided location and female gender was only significant for p14ARF. E-cadherin was methylated in 14/34 tumors with altered APC further stimulating WNT signaling.The present study shows that colon cancer cell lines are in general relevant in vitro models, comparable with the in vivo situation, as the cell lines display many of the same molecular alterations as do the primary carcinomas. The combined pattern of epigenetic and genetic aberrations in the primary carcinomas reveals associations between them as well as to clinicopathological variables, and may aid in the future molecular assisted classification of clinically distinct stages.During the last decade, epigenetic changes have been reported in many cancers and they are now recognized to be at least as common as genetic changes [1]. Aberrant methylation of cytosine located within the dinucleotide CpG is by far the best-categorized epigenetic change. The genome of the cancer cell demonstrates global hypomethylation [2,3] as well as regional promoter hypermethylation of several tumor suppressor genes [4]. Hypermethylation of selected CpG sites within CpG islands in the p
Hypermethylated MAL gene – a silent marker of early colon tumorigenesis
Guro E Lind, Terje Ahlquist, Matthias Kolberg, Marianne Berg, Mette Ekn?s, Miguel A Alonso, Anne Kallioniemi, Gunn I Meling, Rolf I Skotheim, Torleiv O Rognum, Espen Thiis-Evensen, Ragnhild A Lothe
Journal of Translational Medicine , 2008, DOI: 10.1186/1479-5876-6-13
Abstract: Using methylation-specific polymerase chain reaction (MSP) the promoter methylation status of MAL was analyzed in 218 samples, including normal mucosa (n = 44), colorectal adenomas (n = 63), carcinomas (n = 65), and various cancer cell lines (n = 46). Direct bisulphite sequencing was performed to confirm the MSP results. MAL gene expression was investigated with real time quantitative analyses before and after epigenetic drug treatment. Immunohistochemical analysis of MAL was done using normal colon mucosa samples (n = 5) and a tissue microarray with 292 colorectal tumors.Bisulphite sequencing revealed that the methylation was unequally distributed within the MAL promoter and by MSP analysis a region close to the transcription start point was shown to be hypermethylated in the majority of colorectal carcinomas (49/61, 80%) as well as in adenomas (45/63, 71%). In contrast, only a minority of the normal mucosa samples displayed hypermethylation (1/23, 4%). The hypermethylation of MAL was significantly associated with reduced or lost gene expression in in vitro models. Furthermore, removal of the methylation re-induced gene expression in colon cancer cell lines. Finally, MAL protein was expressed in epithelial cells of normal colon mucosa, but not in the malignant cells of the same type.Promoter hypermethylation of MAL was present in the vast majority of benign and malignant colorectal tumors, and only rarely in normal mucosa, which makes it suitable as a diagnostic marker for early colorectal tumorigenesis.Epigenetic changes – non-sequence-based alterations that are inherited through cell division [1] – are frequently seen in human cancers, and likewise as genetic alterations they may lead to disruption of gene function. In colorectal cancer, several tumour suppressor genes have been identified to be epigenetically inactivated by CpG island promoter hypermethylation, including the DNA mismatch repair gene MLH1 [2-4], the gatekeeper APC [5], and the cell cycle inhibito
Identification of an epigenetic biomarker panel with high sensitivity and specificity for colorectal cancer and adenomas
Guro E Lind, Stine A Danielsen, Terje Ahlquist, Marianne A Merok, Kim Andresen, Rolf I Skotheim, Merete Hektoen, Torleiv O Rognum, Gunn I Meling, Geir Hoff, Michael Bretthauer, Espen Thiis-Evensen, Arild Nesbakken, Ragnhild A Lothe
Molecular Cancer , 2011, DOI: 10.1186/1476-4598-10-85
Abstract: Candidate biomarkers were subjected to quantitative methylation analysis in test sets of tissue samples from colorectal cancers, adenomas, and normal colonic mucosa. All findings were verified in independent clinical validation series. A total of 523 human samples were included in the study. Receiver operating characteristic (ROC) curve analysis was used to evaluate the performance of the biomarker panel.Promoter hypermethylation of the genes CNRIP1, FBN1, INA, MAL, SNCA, and SPG20 was frequent in both colorectal cancers (65-94%) and adenomas (35-91%), whereas normal mucosa samples were rarely (0-5%) methylated. The combined sensitivity of at least two positives among the six markers was 94% for colorectal cancers and 93% for adenoma samples, with a specificity of 98%. The resulting areas under the ROC curve were 0.984 for cancers and 0.968 for adenomas versus normal mucosa.The novel epigenetic marker panel shows very high sensitivity and specificity for both colorectal cancers and adenomas. Our findings suggest this biomarker panel to be highly suitable for early tumor detection.Colorectal cancer is the third most common cancer type in the US and is a major contributor to cancer-death [1]. Most cases of colorectal cancer develop from benign precursors (adenomas) during a long time interval. This provides a good opportunity for detection of colorectal cancer at an early curable stage and to screen for potentially pre-malignant adenomas [2]. Both flexible sigmoidoscopy and the Fecal Occult Blood Test (FOBT) have been tested in randomized trials and shown to reduce mortality from colorectal cancer [3]. By sigmoidoscopy adenomas may be detected and removed and thus the incidence of cancer will be reduced [4], however, this screening is invasive and cumbersome for the patient. FOBT on the other hand is non-invasive and currently the most commonly used screening test for colorectal cancer in Europe. Although the sensitivity and specificity measurements of FOBT have been
Gene methylation profiles of normal mucosa, and benign and malignant colorectal tumors identify early onset markers
Terje Ahlquist, Guro E Lind, Vera L Costa, Gunn I Meling, Morten Vatn, Geir S Hoff, Torleiv O Rognum, Rolf I Skotheim, Espen Thiis-Evensen, Ragnhild A Lothe
Molecular Cancer , 2008, DOI: 10.1186/1476-4598-7-94
Abstract: The methylation status of eleven genes (ADAMTS1, CDKN2A, CRABP1, HOXA9, MAL, MGMT, MLH1, NR3C1, PTEN, RUNX3, and SCGB3A1) was determined in 154 tissue samples including normal mucosa, adenomas, and carcinomas of the colorectum. The gene-specific and widespread methylation status among the carcinomas was related to patient gender and age, and microsatellite instability status. Possible CIMP tumors were identified by comparing the methylation profile with microsatellite instability (MSI), BRAF-, KRAS-, and TP53 mutation status.The mean number of methylated genes per sample was 0.4 in normal colon mucosa from tumor-free individuals, 1.2 in mucosa from cancerous bowels, 2.2 in adenomas, and 3.9 in carcinomas. Widespread methylation was found in both adenomas and carcinomas. The promoters of ADAMTS1, MAL, and MGMT were frequently methylated in benign samples as well as in malignant tumors, independent of microsatellite instability. In contrast, normal mucosa samples taken from bowels without tumor were rarely methylated for the same genes. Hypermethylated CRABP1, MLH1, NR3C1, RUNX3, and SCGB3A1 were shown to be identifiers of carcinomas with microsatellite instability. In agreement with the CIMP concept, MSI and mutated BRAF were associated with samples harboring hypermethylation of several target genes.Methylated ADAMTS1, MGMT, and MAL are suitable as markers for early tumor detection.Most cases of colorectal cancer (CRC) originate from adenomas. The malignant potential of adenomas increases with size, grade of dysplasia, and degree of villous components,[1] along with the number and order of genetic and epigenetic aberrations.[2] The majority (~85%) of the sporadic carcinomas are characterized by chromosomal aberrations, referred to as a chromosomal unstable (CIN) phenotype, whereas the smaller group (~15%) typically show microsatellite instability (MSI) caused by defect DNA mismatch repair.[2] Most CIN tumors are microsatellite stable (MSS). A third molecular phenotyp
Gene expression profiles of primary colorectal carcinomas, liver metastases, and carcinomatoses
Kristine Kleivi, Guro E Lind, Chieu B Diep, Gunn I Meling, Lin T Brandal, Jahn M Nesland, Ola Myklebost, Torleiv O Rognum, Karl-Erik Giercksky, Rolf I Skotheim, Ragnhild A Lothe
Molecular Cancer , 2007, DOI: 10.1186/1476-4598-6-2
Abstract: Transcriptome profiles of colorectal cancer metastases independent of tumor site, as well as separate profiles associated with primary carcinomas, liver metastases, or peritoneal carcinomatoses, were assessed by use of Bayesian statistics. Gains of chromosome arm 5p are common in peritoneal carcinomatoses and several candidate genes (including PTGER4, SKP2, and ZNF622) mapping to this region were overexpressed in the tumors. Expression signatures stratified on TP53 mutation status were identified across all tumors regardless of stage. Furthermore, the gene expression levels for the in vivo tumors were compared with an in vitro model consisting of cell lines representing all three tumor stages established from one patient.By statistical analysis of gene expression data from primary colorectal carcinomas, liver metastases, and carcinomatoses, we are able to identify genetic patterns associated with the different stages of tumorigenesis.Colorectal cancer (CRC) is the second most common cause of cancer related deaths in developed countries, including Norway [1,2]. Despite the fact that metastases are the leading cause of colorectal cancer deaths, the majority of genetic studies of colorectal carcinogenesis have focused on changes found in primary carcinomas, and the knowledge about the underlying molecular changes in more advanced disease stages remain limited. To obtain insights to this process, identification of molecular key events that distinguish primary from metastatic tumors is important. DNA microarray technology has become powerful for whole-genome investigations [3]. Recently, several reports have shown that results obtained by this technology can distinguish among subgroups of the same cancer tissue [4-7] as well as among different cancer types [8]. Additionally, genetic profiles have been identified that predict patients' clinical outcome in cancers of the breast, lung, central nervous system, digestive system, and prostate [9-15]. Several studies has invest
Mapping spin-charge separation without constraints
J. I. Chandler,J. M. F. Gunn
Physics , 1997,
Abstract: The general form of a mapping of the spin and charge degrees of freedom of electrons onto spinless fermions and local `spin'-1/2 operators is derived. The electron Hilbert space is mapped onto a tensor productspin-charge Hilbert space. The single occupancy condition of the t-J model is satisfied exactly without the constraints between the operators required with slave particle methods and the size of the Hilbert space (four states per site) is conserved. The connection and distinction between the physical electron spin and the ``pseudospin'' used in these maps is made explicit. Specifically the pseudospin generates rotations both in spin space and particle-hole space. A geometric description (up to sign) is provided using two component spinors. The form of the mapped t-J Hamiltonian involves the coupling of spin and spinless fermion currents, as one expects.
Turloughs and tiankengs: distinctive doline forms
Gunn John
Speleogenesis and Evolution of Karst Aquifers , 2006,
Abstract: Tiankengs lie at one extreme of the collapse doline spectrum, and a key question is whether there is a distinctive ‘tiankeng process’ or whether the distinction is purely morphological. At the opposite end of the doline spectrum, the turloughs of Ireland are broad closed depressions with seasonal lakes. They may be differentiated from poljes by their smaller dimensions, gentler surrounding slopes and processes of formation. In particular, turloughs are only found in areas where there are glacial deposits and are, at least in part, glaciokarstic landforms whereas poljes occur in many climatic zones and their locations frequently demonstrate a structural influence. Turloughs have been recognised by the European Union as special karst landforms with a distinctive vegetation assemblage, although the term is not widely used because, with one exception, they are confined to Ireland. There are clear parallels with ‘tiankeng’ the majority of which are in China and which are distinguished from collapse dolines by their large size, and special processes of formation. It is argued that the terms ‘turlough’ and ‘tiankeng’ should both become established in the karst geomorphology lexicon.
The dynamics of caribou and muskoxen foraging in arctic ecosystems
Anne Gunn
Rangifer , 1992,
Abstract:
Voles, lemmings and caribou - population cycles revisited?
Anne Gunn
Rangifer , 2003,
Abstract: Although we may be confident that many caribou populations fluctuate, we have not made much progress in linking patterns of fluctuations with their underlying processes. Caribou abundance is relatively synchronized across continents and over decades which points to climatic variation as a causative factor. Progress on describing intrinsic and extrinsic factors for smaller-bodied and larger-bodied mammalian herbivore population dynamics also reveals the role of climatic variation and specifically decadal variations. Based on experience elsewhere, we can expect complex relationships between caribou, climatic variation and their forage rather than simple correlations. Caribou responses to decadal trends in climate likely accumulate through successive cohorts as changes in body mass which, in turn, leads to changes in lifetime reproductive success.
Differences in the sex and age composition of two muskox populations and implications for male breeding strategies
Anne Gunn
Rangifer , 1992,
Abstract:
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