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Reliable single cell array CGH for clinical samples

ABSTRACT: Establishment and subsequent validation of a aCGH protocol for WGA (whole genome amplification) products originating from single cell or low amount of starting material (i.e. microdissected FFPE tissue samples). The establishment of the protocol involved testing of three DNA labeling protocols. Two labeling protocols were designed specifically for Ampli1(TM) WGA products. Additionally random primed isothermal (Klenow-based) labeling approach was tested (MM-CM-6hlendick et al., PLoS One. 2013 Jun 25;8(6):e67031.). In addition two different types of reference samples were tested and reference based on single-cell WGA products was chosen as most suitable in the end. The validation of the protocol assessed the following aspects: (1) performance of the protocol on primary and reamplified WGA products, (2) accuracy of the protocol in term of sensitivity of the CNA detection, (3) accuracy in terms of recapitulation of complex patterns of CNAs, (4) accuracy in terms of quantitative assessment of the CNAs, (5) ability to detect genomic heterogeneity of single cells (obtained either from in vitro cultures or from clinical patient material), (6) ability to detect minimal regions of aberration within a panel of disseminated cancer cells and corresponding tumor tissues. Establishment and validation of the single-cell aCGH protocol: two condition experiment (i.e. PCR-based labeling technique 1 vs. PCR-based labeling technique 2; PCR-based labeling technique 2 vs. random-primed isothermal (Klenow) labeling approach; reference DNA from cell pool WGA product vs. reference DNA from single-cell WGA products). Validation of the protocol: comparison of the CNA profiles between single-cell WGA products and corresponding bulk DNA. Analysis of the DCC and corresponding FFPE tumor tissue samples: single-condition experiment performed on samples collected at different stages of the disease (DCCs from bone marrow) and/or from different sites (primary tumor-breast; metastasis-lymph nodes; DCCs-bone marrow). Microarray data is corresponding data depicted in the paper manuscript titled: Reliable single cell array CGH for clinical samples

ORGANISM(S): Homo sapiens

SUBMITTER: Zbigniew Czyz

PROVIDER: E-GEOD-52366 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:About 230 clinical trials currently explore the role of circulating tumor cell (CTC) analysis for therapy decisions, but no assays enable comprehensive molecular characterization of CTCs with diagnostic precision. We therefore combined a workflow for CTC enrichment and isolation with 100% purity with a non-random whole genome amplifiation method for single cells and applied it to 510 single CTCs and 189 leukocytes of 66 breast cancer patients. We defined a genome integrity index (GII) to identify cells suited for molecular chracterization by different molecular assay in more than 90% of single cells, such as diagnostic profiling for point mutations, gene amplifications and whole genomes of single cells. The high reliability on clinical samples enabled assessing the molecular heterogeneity of single CTCs of metastatic breast cancer patients. We readily identified therapeutically relevant genomic disparity between primary tumors and CTCs. Microheterogeneity analysis among individual CTCs uncovered preexisting cells reistsant to ERBB2 targeted therapies suggesting ongoing microevolution at late stage disease whose exploration may provide essential information for personalized treatment decisions. The analysis aimed to indentify profiles of copy number changes in genomic DNA of single circulating tumor cells (CTCs). For this, CTCs were enrched using the FDA approved CellSearch System and single-cell were isolated using the DEPArray System. Subsequently, single-cell DNA was amplified using the Ampli1 WGA Kits and subjected to single-cell aCGH analysis according to previously published protocol (Czyz ZT et al., PLoS One. 2014 Jan 21;9(1):e85907). The analysis included 38 single CTCs and 10 white blood cells (WBCs) obtained from 16 breast cancer patient. WBCs were used as controls for the analysis. In addition, four CTC cell pools were included in the analysis. This was done to show the discrepancies between the profiles of individual cells and corresponing average genomic profile of CTCs in a patient material (cell pools), thereby demonstrating the importance of the analysis on the cell-by-cell basis. The reference sample used for all aCGH experiments consisted of a pool of four single-cell WGA products generated from WBCs of a healthy female donor.

Project description:In the study of tumor genetics, formalin-fixed paraffin-embedded (FFPE) tumors are the most readily available tissue samples. While DNA derived from FFPE tissue has been validated for array comparative genomic hybridization (aCGH) application, the suitability of such fragmented DNA for single-nucleotide polymorphism (SNP) array analysis has not been well examined. Furthermore, whole-genome amplification (WGA) has been used in the study of small precursor lesions to produce sufficient amount of DNA for aCGH analysis. It is unclear whether the same approach can be extended to SNP analysis. In this study, we examined the utility and limitations of genotyping platform performed on whole-genome amplified DNA from FFPE tumor samples for both copy number and SNP analyses. We analyzed the results obtained using DNA derived from matched FFPE and frozen tissue samples on Affymetrix 250K Nsp SNP array. Two widely used WGA methods, Qiagen (isothermal protocol) and Sigma (thermocycling protocol), were used to determine how WGA methods affect the results. We found that the use of DNA derived from FFPE tumors (without or with WGA) for high-resolution SNP array application can produce a significant amount of false positive and false negative findings. While some of these misinterpretations appear to cluster in genomic regions with high or low GC contents, the majority appears to occur randomly. Only large-scale chromosome LOH (>10Mb) can be reliably detected from FFPE tumor DNA samples (without or with WGA) but not smaller LOH or copy number alterations. Our findings here indicate a need for caution in SNP array data interpretation when using FFPE tumor-derived DNA, particularly with WGA. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cryopreserved and FFPE mesenchymal tumor samples without or with WGA, as well as genomic snap-frozen non-neoplastic tissue DNA from 5 adult individuals to serve as reference DNA. WGA was performed using the REPLI-g® FFPE kit (Qiagen, Valencia, CA, USA) and GenomePlex® Tissue Whole Genome Amplification WGA5 kit (Sigma, Saint Louis, MO, USA) in parallel in accordance with the manufacturers’ protocols. A two- to eight-hour individualized reaction time was used in the Qiagen platform for each sample. A gradient amount of initial DNA (10ng, 30ng, 60ng, 100ng and 150ng) was tested followed by gel electrophoresis and qualitative multiplex PCR assay to determine the quality of post-WGA products. At least four independent experiments were concurrently performed per template amplification. Four separateWGA reaction products were pooled for each sample for subsequent microarray analysis to minimize the amplification bias and allele dropout. One of the Affymetrix GeneChip® Human Mapping 500K Array Set (Nsp 250K SNP array) was used for genotyping analysis. Four gastrointestinal stromal tumors with known cytogenetic aberrations were included. Two cases were sucessfullly amplified and passed the quality tests. A total of 12 samples were compared between each other, including frozen tissue DNA (as reference), frozen tissue DNA with WGA (two platforms), FFPE tissue DNA, and FFPE tissue DNA with WGA (two platforms) from each case.

Project description:Nasopharyngeal carcinoma (NPC) is a challenging cancer that is rare in the United States but shows exceptionally high incidence in Southern China, Indonesia, and Malaysia. While the hallmark of NPC is striking geographic variation, early detection and clinical management are also critical characteristics of this cancer. The etiology of NPC is complex, involving the interplay of multiple factors, including Epstein Barr Virus (EBV), which appears to play an oncogenic role. While multimodality therapy is the mainstay of treatment for NPC, the impact of this treatment is greatly influenced by the presenting tumor stage, tumor size, nodal involvement, and the histologic subtype classification. Up to 40% percent of NPC cases present at an advanced stage, likely due to its deep location in the lymphatic-rich nasopharynx and its propensity for early lymphatic spread. Recent modifications in the TNM staging schema have attempted to improve prognostic accuracy, but variations in clinical outcome are still reported in patients with the same stage and similar treatment regimens. The various molecular markers developed to monitor disease progression have also proven unreliable. Hence, there is a significant need for a new kind of prognostic biomarker for NPC. Herein different approaches were applied to a set of samples to detect NPC-related miRNAs, potential circulating biomarkers. We have optimized the extraction of total RNA from NPC Formalin-fixed, paraffin-embedded (FFPE) samples and sera from four patients and matched controls and analyzed the miRNA expression profile by microarray, qPCR and RNAseq. The microarray analysis showed that 46 miRNAs were found to be differentially and significantly expressed in carcinogenic tissue compared to healthy tissue. Twenty-three (23) microRNAs were significantly upregulated (21 human microRNAs and 2 EBV miRNAs), whereas 13 were down-regulated. A total of 8 unique samples were analyzed on Agilent human miRNA microarray (miRBase Release 16.0). Of the 8 samples, 4 are from Non-keratinizing NPC tissue. Non-NPC (normal) tissue were taken from 4 individuals that were diagnosed with NPC (2 of which were matched/paired from the NPC case).

Project description:Purpose: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-associated mortality worldwide. Although the molecular mechanisms underpinning HCC are unknown, gene copy number and associated mRNA expression changes are frequently reported. Experimental Design: Comparative genomic hybridization arrays spotted with 4,041 bacterial artificial chromosome clones were used to assess copy number changes in 45 HCC tissues to identify chromosomal regions associated with the pathogenesis of HCC. Seventy more HCC tissues were used to validate candidate genes by using western blots and immunohistochemistry. Results: A total of 259 clones were associated with copy number changes that significantly differed between normal liver and HCC samples. The chromosomal region 1q32.1 containing the nuclear casein kinase and cyclin-dependent kinase substrate 1 (NUCKS1) gene was associated with tumor vascular invasion. Western blot analysis demonstrated that NUCKS1 was up-regulated in 37 of 70 (52.8%) HCC tissues compared with adjacent non-tumor tissues, and over-expressed in a vast majority of HCCs (44/52, 84.6%) as determined by immunohistochemical staining. Furthermore, immunostaining of both NUCKS1 and glypican-3 improved the diagnostic prediction of HCC. Knock-down of NUCKS1 by siRNA decreased the cell viability of the Hep3B cell line and reduced tumor formation in a xenograft mouse model. Functional enrichment analysis revealed the association of NUCKS1 with signal transduction, immunity and defense, and nucleotide metabolism pathways. Conclusions: NUCKS1 was identified as a potential oncogene at chromosomal 1q32.1 in patients with HCC, and it might be a valuable immunodiagnostic marker for HCC. Comparative genomic hybridization arrays spotted with 4,041 bacterial artificial chromosome clones were used to assess copy number changes in 45 HCC tissues and 25 normal liver tissues to identify chromosomal regions associated with the pathogenesis of HCC

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Reliable single cell array CGH for clinical samples

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