4911 results for "*oma"

in 33.57 milliseconds.

• Evolution of DNA repair defects during malignant progression of low-grade gliomas after temozolomide treatment.

  Temozolomide (TMZ) increases the overall survival of patients with glioblastoma (GBM), but its role in the clinical management of diffuse low-grade gliomas (LGG) is still being defined. DNA hypermethylation of the O 6 -methylguanine-DNA methyltransferase (MGMT) promoter is associated with an improved response to TMZ treatment, while inactivation of the DNA mismatch repair (MMR) pathway is associated with therapeutic resistance and TMZ-induced mutagenesis. We previously demonstrated that TMZ treatment of LGG induces driver mutations in the RB and AKT-mTOR pathways, which may drive malignant progression to secondary GBM. To better understand the mechanisms underlying TMZ-induced mutagenesis and malignant progression, we explored the evolution of MGMT methylation and genetic alterations affecting MMR genes in a cohort of 34 treatment-naïve LGGs and their recurrences. Recurrences with TMZ-associated hypermutation had increased MGMT methylation compared to their untreated initial tumors and higher overall MGMT methylation compared to TMZ-treated non-hypermutated recurrences. A TMZ-associated mutation in one or more MMR genes was observed in five out of six TMZ-treated hypermutated recurrences. In two cases, pre-existing heterozygous deletions encompassing MGMT, or an MMR gene, were followed by TMZ-associated mutations in one of the genes of interest. These results suggest that tumor cells with methylated MGMT may undergo positive selection during TMZ treatment in the context of MMR deficiency.

  Study EGAS00001001179

• Molecular_characterization_of_invasive_lobular_carcinoma

  Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer accounting for 10-15% of cases. ILC differs from invasive ductal carcinoma (IDC)with respect to epidemiology, histology, and clinical presentation. Moreover, ILC is lesssensitive to chemotherapy, more frequently bilateral, and more prone to form gastrointestinal, peritoneal, and ovarian metastases than IDCs. In contrast to IDC, the prognostic value ofhistological grade (HG) in ILC is controversial. One of the three major components of histological grading (tubule formation) is missing in ILC which hinders the process of gradingin this histological subtype and results in the classification of approximately two thirds of ILC as HG 2.Over the last decade, a number of gene expression signatures have shed light onto breast cancer classification, allowing breast cancer care to become more personalized. Withrespect to the management of estrogen receptor (ER)-positive breast cancer, several gene expression signatures provide prognostic and/or predictive information beyond what is possible with current classical clinico-pathological parameters alone. Nevertheless, most studies using gene expression signature have not considered different histologic subtypesseparately. Recently, a comprehensive research program has elucidated some of the biological underpinnings of invasive lobular carcinoma. Genetic material extracted from 200 ILC tumor samples were studied using gene expression profiling and identified ILCmolecular subtypes. These proliferation-driven gene signatures of ILC appear to have prognostic significance. In particular, the Genomic Grade (GG) gene signature improved upon HG in ILC and added prognostic value to classic clinico-pathologic factors. In addition this study demonstrated that most ILC are molecularly characterized as luminal-A (~75%)followed by luminal-B (~20%) and HER2-positve tumors (~5%). Moreover, we investigated the prognostic value of known gene signatures/ gene modules in the same cohort of ILC. As a second step within the scope of this project, we aim to investigate the interactionsbetween somatic ILC tumor mutations to observed transcriptome findings. To this end, we aim to perform somatic mutation analysis for the ILC tumors for which Affymetrix gene expression profiling is available. To this end, we will use a gene screen assay, which specifically interrogates the mutational status of a few hundreds of cancer genes. We believe that this pioneering effort will be fundamental for a tailored treatment of ILC withimprovement in patients' outcome.

  Study EGAS00001000292

• MGA-NUTM1 fusion in high grade spindle cell sarcoma

  NUT carcinoma (NC) with mesenchymal differentiation have rarely been described in the literature. In this report, we describe the characterization of two cases of high grade spindle cell sarcoma harboring a novel MGA-NUTM1 fusion. Whole genome sequencing identified the presence of complex rearrangements resulting in a MGA-NUTM1 fusion gene in the absence of other significant somatic mutations. The fusion protein was predicted to retain nearly the entire protein sequence of both MGA (exons 1-22) and NUTM1 (exons 3-8). In contrast to typical cases of NC, these cases were successfully treated with aggressive local control measures (surgery and radiation) and both patients remain alive without disease. These cases describe a new subtype of NUTM1-rearranged tumors warranting expansion of diagnostic testing to evaluate for the presence of MGA-NUTM1 or alternative NUTM1 gene fusions in the diagnostic workup of high grade spindle cell sarcomas or small round blue cell tumors of ambiguous lineage.

  Study EGAS00001003341

• Hypermutation of the inactive X chromosome is a frequent event in cancer

  Mutation is a fundamental process in tumorigenesis. However the degree to which the rate of somatic mutation varies across the human genome and the mechanistic basis underlying this variation remain to be fully elucidated. As part of the ICGC PedBrain and Malignant Lymphoma (MMML-Seq) consortium we performed a cross-cancer comparison of whole genomes comprising a diverse set of childhood and adult tumors including both solid and hematopoietic malignancies. In addition we performed whole genome sequencing of clonally expanded hematopoietic stem/progenitor cells (HSPCs) from healthy individuals to compare somatic mutation rates.

  Study EGAS00001000565

• Uveal melanoma patient with germline MBD4 nonsense mutation

  There is currently no effective treatment for metastasised uveal melanoma (UM). Recently, it was reported that a UM patient was responsive to checkpoint inhibitor (CI) treatment, due to a high tumour mutation burden correlated with a germline loss-of-function MBD4 mutation. Here, we report on another UM patient who carried an MBD4 germline nonsense variant (p.Leu563Ter) and her tumour showed a 5-fold higher than average mutation burden. We confirmed the association between germline loss-of-function variant in MBD4 and CI response. The patient experienced stable disease (10 months) and survived two years with metastatic disease, which is twice as long as median survival. Additionally, the frequency of MBD4 loss-of-function variants in reported UM cohorts was >20 times higher than in an aggregated population genome database (P < 5x10-5), implying a potential role as UM predisposition gene. These findings provide a strong basis for the inclusion of MBD4 in screening of potential UM-prone families as well as stratification of immunotherapy.

  Study EGAS00001003362

• RB1 Gene Inactivation by Chromothripsis in Human Retinoblastoma

  Retinoblastoma is a rare childhood cancer of the developing retina. Most retinoblastomas initiate with biallelic inactivation of the RB1 gene through diverse mechanisms including point mutations, nucleotide insertions, deletions, loss of heterozygosity and promoter hypermethylation. Recently, a novel mechanism of retinoblastoma initiation was proposed. Gallie and colleagues discovered that a small proportion of retinoblastomas lack RB1 mutations and had MYCN amplification [1]. In this study, we identified recurrent chromosomal, regional and focal genomic lesions in 94 primary retinoblastomas with their matched normal DNA using SNP 6.0 chips. We also analyzed the RB1 gene mutations and compared the mechanism of RB1 inactivation to the recurrent copy number variations in the retinoblastoma genome. In addition to the previously described focal amplification of MYCN and deletions in RB1 and BCOR, we also identified recurrent focal amplification of OTX2, a transcription factor required for retinal photoreceptor development. We identified 10 retinoblastomas in our cohort that lacked RB1 point mutations or indels. We performed whole genome sequencing on those 10 tumors and their corresponding germline DNA. In one of the tumors, the RB1 gene was unaltered, the MYCN gene was amplified and RB1 protein was expressed in the nuclei of the tumor cells. In addition, several tumors had complex patterns of structural variations and we identified 3 tumors with chromothripsis at the RB1 locus. This is the first report of chromothripsis as a mechanism for RB1 gene inactivation in cancer.

  Study EGAS00001000598

• Deciphering the mutational landscape and the genome organization of LMS

  Leiomyosarcoma (LMS) are an uncommon group of malignant mesenchymal tumors composed of cells showing distinct smooth muscle differentiation. These tumors occur mainly in adults in any location of the body (soft-tissue, viscera or uterine). Soft-tissue LMS represent 10-15% of all soft-tissue sarcomas. The most frequent locations are the limbs followed by the retroperitoneum and uterine.

  Study EGAS00001001262

• Whole exome sequencing of papillary thyroid carcinoma in the Chinese population

  Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Here we submitted the sequencing results for PTC using 91 tumor-normal pairs through exome sequencing in the Chinese Han population.

  Study EGAS00001001268

• Genomic and transcriptomic profiling of signalling networks in follicular lymphoma

  This dataset is composed of sequencing data from 16 patients diagnosed with follicular lymphoma, who developed transformed disease and for whom representative frozen tumor biopsy samples were available. For 14 patients there is paired material from both disease stages. DNA and RNA libraries were constructed and captured with a kinome bait library (Agilent Technologies), before sequencing on an Illumina platform.

  Study EGAS00001002175

• Osteosarcoma_RNAseq

  We propose to definitively characterise the somatic genetics of Osteosarcoma cancer through generation of comprehensive catalogues of somatic mutations by high coverage genome and transcriptome sequencing.

  Study EGAS00001000615