Affymetrix SNP array data of mixtures of tumor and normal DNA
Ontology highlight
ABSTRACT: Single nucleotide polymorphism (SNP) microarrays are commonly applied to tumors to identify genomic regions with copy number alterations (CNA) or loss of heterozygosity (LOH). However, in typical tumor specimens collected in clinical studies, up to 60% of the DNA derives from stromal cells with a normal genome, resulting in attenuated sensitivity to true somatic aberrations in the tumor. Here we describe SNPfilter, a model-based method to decompose SNP array data from heterogeneous tumor specimens into their corresponding normal and tumor profiles. Unlike existing methods, SNPfilter does not require paired normal control data. We assessed the performance of this method using SNP array data representing cancer cell lines with aberrant genomes, B-cell lymphoblastoid cell lines with normal genomes, and defined mixtures of the two. In the pure tumor samples, SNPfilter identified CNA and LOH regions with accuracy similar to existing methods. In the mixture samples containing 40–80% tumor genomic DNA, SNPfilter yielded prediction sensitivity superior to existing methods. Thus, SNPfilter provides a powerful tool for discovery of clinically relevant somatic aberrations in tumor genomes.
Project description:This study aims to stratify stage II and III colon cancer patients for risk of disease recurrence based on DNA aberrations, including DNA copy number aberrations (CNA) and CNA-associated chromosomal breakpoints. To this end, high quality array-CGH data of clinically well-annotated colon cancer specimens was generated using FFPE material from a selected series of primary tumor and patient-matched normal tissue.
Project description:Genome-wide 10k SNP profiling of FOXM1B-transduced N/TERT and primary normal human epidermal keratinocytes (NHEK). The aim of this study was to study the cancer initiation role of UVB and FOXM1B upregulation in NHEK. Upregulation of FOXM1B alone (without UVB) was found to directly induce genomic instability in the form of copy number aberration (CNA) and low levels of loss of heterozygosity (LOH) in primary NHEK. The FOXM1B-induced CNA was found to be retained and accumulated in subsequent cell culture passages. UVB-exposure resulted in significant chromosomal LOH and CNA in N/TERT cells expressing FOXM1B but not in EGFP-expressing cells. This indicates that UVB corroborated with FOXM1B to recruit LOH and CNA which may predispose cell to malignant transformation. Collectively, these results indicate that aberrant upregulation of FOXM1B in skin keratinocytes following UVB exposure may be an early mechanism whereby cells acquire genomic changes required for oncogenesis. Keywords: Genome-wide SNP profiling for loss of heterozygosity (LOH) and copy number aberration (CNA), FOXM1, UVB, Keratinocytes, Basal cell carcinoma, genomic instability, carcinogenesis, squamous cell carcinoma.
Project description:High-resolution microarray-based whole genome genotyping (WGG) techniques based on SNP analysis have successfully been applied in cancer genomics to study gene copy number alterations and allele-specific aberrations such as loss-of-heterozygosity (LOH). Problems in data interpretation arise when WGG is applied on tumor tissue specimens, in which normal cell components and tumor subpopulations frequently exist. Such heterogeneity may lead to reduced detection of cancer cell specific genomic alterations. To circumvent problems with sample heterogeneity, we propose using a segmentation strategy derived from DNA copy number analysis for detection of LOH and allelic imbalance. We generated an experimental dilution series of a tumor cell line mixed with its paired normal cell line and simulated data for such dilutions to test the strategy. We also used data sets generated on both Affymetrix and Illumina WGG platforms, including paired tumor-normal samples and tumors previously characterized by FISH. We tested the segmentation strategy against several reported algorithms. We demonstrate high sensitivity and specificity of the segmentation strategy for detecting both minute and gross allelic imbalances originating from DNA copy number gain, loss, and neutral events in tumor specimens. For example, hemizygous copy number loss can be detected in samples containing only 20-25% tumor cells. Furthermore, the strategy can identify cell subpopulation specific events and accurately estimate the fraction of cells affected by an allelic imbalance. Thus, the segmentation strategy extends the usefulness of WGG platforms for investigation of allelic imbalances in heterogeneous tumor genomes.
Project description:Genome-wide 10k SNP profiling of FOXM1B-transduced N/TERT and primary normal human epidermal keratinocytes (NHEK). The aim of this study was to study the cancer initiation role of UVB and FOXM1B upregulation in NHEK. Upregulation of FOXM1B alone (without UVB) was found to directly induce genomic instability in the form of copy number aberration (CNA) and low levels of loss of heterozygosity (LOH) in primary NHEK. The FOXM1B-induced CNA was found to be retained and accumulated in subsequent cell culture passages. UVB-exposure resulted in significant chromosomal LOH and CNA in N/TERT cells expressing FOXM1B but not in EGFP-expressing cells. This indicates that UVB corroborated with FOXM1B to recruit LOH and CNA which may predispose cell to malignant transformation. Collectively, these results indicate that aberrant upregulation of FOXM1B in skin keratinocytes following UVB exposure may be an early mechanism whereby cells acquire genomic changes required for oncogenesis. Keywords: Genome-wide SNP profiling for loss of heterozygosity (LOH) and copy number aberration (CNA), FOXM1, UVB, Keratinocytes, Basal cell carcinoma, genomic instability, carcinogenesis, squamous cell carcinoma. 1) Three individual normal primary NHEK cultures were retrovirally transduced (with either EGFP or EGFP-FOXM1B) and left to grow for 4 days prior to SNP array analysis. 2) EGFP or EGFP-FOXM1B-tansduced NHEK cells were harvested at passage 1, 2 and 3 for SNP array analysis to investigate if genomic instability is maintained and accumulated in subsequent passages. 3) N/TERT cells transduced with either EGFP or EFOX were UVB-irradiated and left to grow for 50 days in culture prior to SNP array analysis.
Project description:Genome-wide profiling of Copy Number Alterations (CNA) and Loss of Heterozygosity (LOH), gene expression and resequencing of pediatric AML. This study characterizes the CNA and LOH in a representative cross-section through subtypes of pediatric AML. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples.
Project description:Genome-wide profiling of Copy Number Alterations (CNA) and Loss of Heterozygosity (LOH), gene expression and resequencing of pediatric AML. This study characterizes the CNA and LOH in a representative cross-section through subtypes of pediatric AML. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples.
Project description:Genome-wide profiling of Copy Number Alterations (CNA) and Loss of Heterozygosity (LOH), gene expression and resequencing of pediatric AML. This study characterizes the CNA and LOH in a representative cross-section through subtypes of pediatric AML. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples.
Project description:Genome-wide profiling of Copy Number Alterations (CNA) and Loss of Heterozygosity (LOH), gene expression and resequencing of pediatric AML. This study characterizes the CNA and LOH in a representative cross-section through subtypes of pediatric AML. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples.
Project description:Affymetrix 10K SNP mapping arrays were used to profile 14 basal cell carcinomas (BCCs) with matched blood DNA samples. Loss of heterozygosity (LOH) and copy number abnormality (CNA) profiles were derived from each tumour-blood pair. Experiment Overall Design: 14 BCC/Blood pairs were used in this study to obtain genome-wide SNP profiles. By comparing tumour and blood DNA, LOH for each SNP could be obtained. Signal intensity for each SNP were used to deternime CNA.
Project description:Genome-wide profiling of Copy Number Alterations (CNA) and Loss of Heterozygosity (LOH), gene expression and resequencing of pediatric AML. This study characterizes the CNA and LOH in a representative cross-section through subtypes of pediatric AML. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples. 111 pediatric AML samples were studied using either Affymetrix 100K + 500K 5.0 SNP arrays, 65 of the samples had paired germ line material. The supplemental file 'GSE15732_AML_175_SNP_Xba_signal.txt' contains the raw signals generated by dChip without normalization. The CNA and LOH data can be found in the Supplemental Information of the associated manuscript.