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      Functional DNA quantification guides accurate next-generation sequencing mutation detection in formalin-fixed, paraffin-embedded tumor biopsies

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          Abstract

          The formalin-fixed, paraffin-embedded (FFPE) biopsy is a challenging sample for molecular assays such as targeted next-generation sequencing (NGS). We compared three methods for FFPE DNA quantification, including a novel PCR assay (‘QFI-PCR’) that measures the absolute copy number of amplifiable DNA, across 165 residual clinical specimens. The results reveal the limitations of commonly used approaches, and demonstrate the value of an integrated workflow using QFI-PCR to improve the accuracy of NGS mutation detection and guide changes in input that can rescue low quality FFPE DNA. These findings address a growing need for improved quality measures in NGS-based patient testing.

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          Most cited references18

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          Integrative analysis of complex cancer genomics and clinical profiles using the cBioPortal.

          The cBioPortal for Cancer Genomics (http://cbioportal.org) provides a Web resource for exploring, visualizing, and analyzing multidimensional cancer genomics data. The portal reduces molecular profiling data from cancer tissues and cell lines into readily understandable genetic, epigenetic, gene expression, and proteomic events. The query interface combined with customized data storage enables researchers to interactively explore genetic alterations across samples, genes, and pathways and, when available in the underlying data, to link these to clinical outcomes. The portal provides graphical summaries of gene-level data from multiple platforms, network visualization and analysis, survival analysis, patient-centric queries, and software programmatic access. The intuitive Web interface of the portal makes complex cancer genomics profiles accessible to researchers and clinicians without requiring bioinformatics expertise, thus facilitating biological discoveries. Here, we provide a practical guide to the analysis and visualization features of the cBioPortal for Cancer Genomics.
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            A high frequency of sequence alterations is due to formalin fixation of archival specimens.

            Genomic analysis of archival tissues fixed in formalin is of fundamental importance in biomedical research, and numerous studies have used such material. Although the possibility of polymerase chain reaction (PCR)-introduced artifacts is known, the use of direct sequencing has been thought to overcome such problems. Here we report the results from a controlled study, performed in parallel on frozen and formalin-fixed material, where a high frequency of nonreproducible sequence alterations was detected with the use of formalin-fixed tissues. Defined numbers of well-characterized tumor cells were amplified and analyzed by direct DNA sequencing. No nonreproducible sequence alterations were found in frozen tissues. In formalin-fixed material up to one mutation artifact per 500 bases was recorded. The chance of such artificial mutations in formalin-fixed material was inversely correlated with the number of cells used in the PCR-the fewer cells, the more artifacts. A total of 28 artificial mutations were recorded, of which 27 were C-T or G-A transitions. Through confirmational sequencing of independent amplification products artifacts can be distinguished from true mutations. However, because this problem was not acknowledged earlier, the presence of artifacts may have profoundly influenced previously reported mutations in formalin-fixed material, including those inserted into mutation databases.
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              Relative abundance of EGFR mutations predicts benefit from gefitinib treatment for advanced non-small-cell lung cancer.

              Our aim was to determine whether abundance of epidermal growth factor receptor (EGFR) mutations in tumors predicts benefit from treatment with EGFR-tyrosine kinase inhibitors (TKIs) for advanced non-small-cell lung cancer (NSCLC). We detected EGFR mutations in 100 lung cancer samples using direct DNA sequencing and amplification refractory mutation system (ARMS). Mutation-positive tumors by both methods carried high abundance of EGFR mutations. Tumors that were mutation positive by ARMS but mutation negative by direct DNA sequencing harbored low abundance of EGFR mutations. Mutation-negative tumors by both methods carried wild-type EGFR. All patients received gefitinib treatment. The correlation between EGFR mutation abundance and clinical benefit from gefitinib treatment was analyzed. Of 100 samples, 51 and 18 harbored high and low abundances of EGFR mutations, respectively; 31 carried wild-type EGFR. Median progression-free survival (PFS) was 11.3 (95% CI, 7.4 to 15.2) and 6.9 months (95% CI, 5.5 to 8.4) in patients with high and low abundances of EGFR mutations, respectively (P = .014). Median PFS of patients with low abundance of EGFR mutations was significantly longer than that of those with wild-type tumors (2.1 months; 95% CI, 1.0 to 3.2; P = .010). Objective response rates (ORRs) were 62.7%, 44.4%, and 16.1%, and overall survival (OS) rates were 15.9 (95% CI, 13.4 to 18.3), 10.9 (95% CI, 2.7 to 19.1), and 8.7 months (95% CI, 4.6 to 12.7) for patients with high abundance of EGFR mutations, low abundance of EGFR mutations, and wild-type EGFR, respectively. The difference between patients with high and low abundances of EGFR mutations was not significant regarding ORR and OS. The relative EGFR mutation abundance could predict benefit from EGFR-TKI treatment for advanced NSCLC.
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                Author and article information

                Contributors
                Journal
                Genome Med
                Genome Med
                Genome Medicine
                BioMed Central
                1756-994X
                2013
                30 August 2013
                : 5
                : 8
                : 77
                Affiliations
                [1 ]Asuragen, Inc, Austin, TX 78744, USA
                Article
                gm481
                10.1186/gm481
                3978876
                24001039
                eff8845b-4900-4660-9f70-7f6c29fd1976
                Copyright © 2013 Sah et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 27 May 2013
                : 23 August 2013
                Categories
                Method

                Molecular medicine
                Molecular medicine

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