Assessment Of DNA Quality Research Articles

Degraded DNA may induce discordance of KRAS status between primary colorectal cancer and corresponding liver metastases

KRAS mutation is widely accepted as a strong, negative predictive marker for anti-epidermal growth factor receptor antibodies, including cetuximab and panitumumab. Previous reports demonstrated approximately 100 % concordance of KRAS status between primary colorectal cancer and liver metastases; however, mismatched KRAS status still occurs. KRAS status was evaluated in 105 pairs of formalin-fixed primary colorectal cancer and corresponding liver metastases specimens by direct sequencing. DNA quality of patients displaying mismatched KRAS status between primary tumors and metastases was assessed using a Bioanalyzer. KRAS status was successfully analyzed in 90/105 patients (85.7 %). The concordance rate between primary tumors and metastases was 88.2 % in synchronous metastases (n = 76) and 100 % in metachronous metastases (n = 14). Discordance in KRAS status was observed in nine patients. Independent method validation revealed only five samples showed the same KRAS status between the two methods. DNA quality assessment by a Bioanalyzer revealed that the median length of DNA samples in the peak concentration of the mismatched group was significantly shorter than those in the control group (153.5 vs 276.5 bp, P = 0.0059). In addition, the median value of the percentage of degraded DNA (0-200 bp) in each sample in the mismatched group was significantly higher than the control group (35.5 vs 22 %, P = 0.020). These data suggest that the discordant results for these nine patients (18 samples) were due to low quality DNA, which may obscure polymerase chain reaction analysis, affecting sequencing reliability. Quality control and assurance of KRAS genotyping is critical, and standardization of the methodology is warranted.

Abstract 4534: Large-scale DNA copy number analysis as a biomarker study in the ACTS-CC trial (TRICC0706), a phase III trial of adjuvant chemotherapy with S-1 and UFT/LV in stage III colon cancer in Japan

Abstract Background: The ACTS-CC trial is a phase III study designed to validate the non-inferiority of S-1 to UFT/LV, a standard treatment in Japan, as adjuvant chemotherapy for stage III colon cancer. The initial safety results were reported at ASCO 2011. In a biomarker study of the ACTS-CC trial, DNA copy number was studied using formalin fixed, paraffin-embedded (FFPE) specimens. Methods: Blocks of resected tumor specimens for this biomarker study were obtained after receiving informed consent from 779 of 1535 patients enrolled between April 2009 and January 2010. Laser-captured microdissection was performed to extract genomic DNA (gDNA) from 10-αm-thick FFPE specimens of colon cancer. DNA concentrations were measured by spectrophotometry (NanoDrop, Thermo Fisher Scientific Inc., Wilmington, DE). DNA quality was assessed and classified into 4 grades according to DNA fragment length by arbitrary primed PCR (AP-PCR) followed by microfluidic analysis (Bioanalyzer: Agilent Technology, Santa Clara, CA): grade-a, β700 bp; grade-b, <700 bp and β400 bp; grade-c, <400 bp and β200 bp; and grade-d, <200 bp. Genomic copy-number alterations in cancer were analyzed by high-density single-nucleotide polymorphism (SNP) arrays (Human 250K StyI array, Affymetrix, Santa Clara, CA) using samples of grade-a or grade-b quality. For GeneChip arrays, 250 ng of DNA was used according to the manufacturer's protocols. Results: Initial DNA amount was sufficient for GeneChip assays in 647 of 779 samples. DNA quality assessment after AP-PCR revealed that the proportions of grade-a, grade-b, grade-c, and grade-d samples were 25.3%, 48.9%, 18.9%, and 6.9%, respectively. Samples of grade-a or grade-b DNA quality were used for target preparation. After complexity reduction by restricted enzymatic digestion followed by adaptor ligation, PCR amplification, and DNA purification, 162 of 647 purified PCR products were successfully amplified to 90 μg, sufficient for target hybridization. Throughout these stepwise processes, 162 of 779 samples were successfully analyzed by GeneChip. Somatic copy-number alterations of stage III colon cancer will be further investigated. Conclusions: Genome-wide copy number was successfully analyzed for only 21% of initial samples. However, this pre-planned study was designed to identify valid biomarkers. Not only 162 carefully selected genome-wide datasets to screen candidate loci associated with clinical outcomes, but also 617 genomic DNA samples usable as independent validation sets for real-time PCR-based assay were obtained. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4534. doi:1538-7445.AM2012-4534

TaqMan allelic discrimination assay for A1 and A2 alleles of the bovine CSN2 gene

Alleles A1 and A2 of the Bos taurus CSN2 gene are the most frequent in a number of dairy cattle breeds. In this study, a new allelic discrimination assay using TaqMan fluorogenic probes was developed to detect single nucleotide substitution characterizing the A1/A2 alleles of the CSN2 gene. The method was validated using DNA samples of known genotypes with different concentrations and the results were compared with those for the commonly used problematic ACRS-PCR. We found the TaqMan method to be more effective, 100% reliable and hundred times more sensitive for testing the CSN2 genetic marker in cattle than the ACRS-PCR. As it enabled a rapid analysis of a large number of DNA samples in uniform format without previous DNA quality assessment and without the requirement for post-amplification manipulations, it presents an effective tool for the analysis of large-scale sample sets. The method was applied for testing on a sample of 120 Czech Holstein dairy cows. The observed relative genotype and allele frequencies were as follows: A1A1–0.20, A1A2–0.51, A2A2–0.29; A1–0.45, A2–0.55.

Abstract 4918: Quality assessment of DNA derived from up to 30 year old archival tissues from lung cancer patients for PCR-based methylation analysis using SMART-MSP and MS-HRM

Abstract Background: The High-Resolution Melting (HRM) technology has recently been introduced as a rapid and robust analysis tool for the detection of DNA methylation. The methylation status of multiple tumor suppressor genes may serve as biomarkers for early cancer diagnostics, for prediction of prognosis and for prediction of response to treatment. Therefore, it is important that methodologies for detection of DNA methylation continue to evolve. Sensitive Melting Analysis after Real Time - Methylation Specific PCR (SMART-MSP) and Methylation Sensitive - High Resolution Melting (MS-HRM) are two methods for single locus DNA methylation detection based on HRM. Methods: Here, we have assessed the quality of DNA extracted from 30-years-old Formalin Fixed Paraffin Embedded (FFPE) tissue for DNA methylation analysis using SMART-MSP and MS-HRM. The quality assessment was performed on DNA extracted from 54 Non-Small Cell Lung Cancer (NSCLC) samples derived from FFPE tissue, collected over 30 years and grouped into five-years-intervals. For each sample, the methylation level of the CDKN2A (p16) and RARB promoters were estimated using SMART-MSP and MS-HRM assays designed to assess the methylation status of the same CpG positions. This allowed for a direct comparison of the methylation level estimated by the two methods for each sample. Results: The methylation level of the CDKN2A promoter was successfully determined by SMART-MSP and MS-HRM in all of the 54 samples. The same methylation estimates were obtained by the two methods in 46 of samples. The methylation level of the RARB promoter was successfully determined by SMART-MSP in all of samples. When using MS-HRM to assess RARB methylation five samples failed to amplify and 15 samples showed a melting profile characteristic for heterogeneous methylation. Out of the remainder 34 samples, for which the methylation level could be estimated, 27 gave the same result as observed when using SMART-MSP. Conclusion: MS-HRM and SMART-MSP can be successfully used for single locus methylation studies of DNA derived from up to 30-years-old FFPE tissue samples. Furthermore, it can be expected that MS-HRM and SMART-MSP will provide similar methylation estimates when assays are designed to analyze the same CpG positions. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4918.

Quality assessment of DNA derived from up to 30 years old formalin fixed paraffin embedded (FFPE) tissue for PCR-based methylation analysis using SMART-MSP and MS-HRM

BackgroundThe High Resolution Melting (HRM) technology has recently been introduced as a rapid and robust analysis tool for the detection of DNA methylation. The methylation status of multiple tumor suppressor genes may serve as biomarkers for early cancer diagnostics, for prediction of prognosis and for prediction of response to treatment. Therefore, it is important that methodologies for detection of DNA methylation continue to evolve. Sensitive Melting Analysis after Real Time - Methylation Specific PCR (SMART-MSP) and Methylation Sensitive - High Resolution Melting (MS-HRM) are two methods for single locus DNA methylation detection based on HRM.MethodsHere, we have assessed the quality of DNA extracted from up to 30 years old Formalin Fixed Paraffin Embedded (FFPE) tissue for DNA methylation analysis using SMART-MSP and MS-HRM. The quality assessment was performed on DNA extracted from 54 Non-Small Cell Lung Cancer (NSCLC) samples derived from FFPE tissue, collected over 30 years and grouped into five years intervals. For each sample, the methylation levels of the CDKN2A (p16) and RARB promoters were estimated using SMART-MSP and MS-HRM assays designed to assess the methylation status of the same CpG positions. This allowed for a direct comparison of the methylation levels estimated by the two methods for each sample.ResultsCDKN2A promoter methylation levels were successfully determined by SMART-MSP and MS-HRM in all 54 samples. Identical methylation estimates were obtained by the two methods in 46 of the samples. The methylation levels of the RARB promoter were successfully determined by SMART-MSP in all samples. When using MS-HRM to assess RARB methylation five samples failed to amplify and 15 samples showed a melting profile characteristic for heterogeneous methylation. Twenty-seven of the remaining 34 samples, for which the methylation level could be estimated, gave the same result as observed when using SMART-MSP.ConclusionMS-HRM and SMART-MSP can be successfully used for single locus methylation studies using DNA derived from up to 30 years old FFPE tissue. Furthermore, it can be expected that MS-HRM and SMART-MSP will provide similar methylation estimates when assays are designed to analyze the same CpG positions.

A new method for accurate assessment of DNA quality after bisulfite treatment

The covalent addition of methylgroups to cytosine has become the most intensively researched epigenetic DNA marker. The vast majority of technologies used for DNA methylation analysis rely on a chemical reaction, the so-called ‘bisulfite treatment’, which introduces methylation-dependent sequence changes through selective chemical conversion of non-methylated cytosine to uracil. After treatment, all non-methylated cytosine bases are converted to uracil but all methylated cytosine bases remain cytosine. These methylation dependent C-to-T changes can subsequently be studied using conventional DNA analysis technologies.The bisulfite conversion protocol is susceptible to processing errors, and small deviation from the protocol can result in failure of the treatment. Several attempts have been made to simplify the procedure and increase its robustness. Although significant achievements in this area have been made, bisulfite treatment remains the main source of process variability in the analysis of DNA methylation. This variability in particular impairs assays, which strive for the quantitative assessment of DNA methylation. Here we present basic mathematical considerations, which should be taken into account when analyzing DNA methylation. We also introduce a PCR-based assay, which allows ab initio assessment of the DNA quality after bisulfite treatment and can help to prevent inaccurate quantitative measurement resulting from poor bisulfite treatment.

DNA Quality Assessment for Array CGH by Isothermal Whole Genome Amplification

Background: Array Comparative Genomic Hybridization (array CGH) is increasingly applied on DNA obtained from formalin-fixed paraffin-embedded (FFPE) tissue, but in a proportion of cases this type of DNA is unsuitable. Due to the high experimental costs of array CGH and unreliable methods for DNA quality testing, better prediction methods are needed. The aim of this study was to accurately determine the quality of FFPE DNA input in order to predict quality of array CGH outcome. Material and Methods: DNA quality was assessed by isothermal amplification and compared to array CGH quality on 59 FFPE gastric cancer samples, one FFPE colorectal cancer sample, two FFPE normal uvula samples, one fresh frozen and six FFPE HNSCC samples. Gastric cancer DNA was also quality tested by β-globin PCR. Results: Accurate prediction of DNA quality using the isothermal amplification was observed in the colorectal carcinoma, HNSCC and uvula samples. In gastric cancer samples, the isothermal amplification was a more accurate method for selecting good quality DNA for array CGH compared to using PCR product lengths. The isothermal amplification product was used for array CGH and compared to the results achieved using non-amplified DNA in four of the samples. DNAs before and after amplification yielded the same segmentation patterns of chromosomal copy number changes for both the fresh DNA sample and the FFPE samples. Conclusion: The efficiency of isothermal DNA amplification is a reliable predictor for array CGH quality. The amplification product itself can be used for array CGH, even starting with FFPE derived DNA samples.

Evaluation of purification procedures of DNA from maize-meal samples by exploiting different analytical techniques for the assessment of DNA quality.

Two different approaches generally applied to achieve purification of DNA extracted from cells were compared: precipitation by organic solvents and enzymatic treatments. We investigated various experimental protocols reported in literature by evaluating DNA purity, integrity and yield. Reliability of analytical techniques normally employed to assess DNA purity and quantity was studied and comments and conclusions were suggested by comparing results obtained by different analytical techniques. Enzymatic treatments prove to be unable of increasing DNA purity while determining a significant degradation. In contrast, optimised conditions for solvent precipitation enabled a sharp increase of DNA purity to be obtained, associated with the maintenance of the initial DNA integrity. The application of the optimised protocol to maize-meal samples allowed us to achieve a good PCR amplification even with those samples which gave poor amplification by following the protocol recommended by the Italian legislation in force for GMO detection in food.

An Efficient Method for the Assessment of DNA Quality of Archival Microdissected Specimens

There will be an increasing need of methods for assessing the suitability of specimens for genetic-based assays as DNA markers become an integral part of molecular diagnosis. The targeting of specimens for specific analyses will require the ability to rapidly screen for DNA quality. Conventional methods such as Southern analysis and gene specific-polymerase chain reaction (PCR) often require quantities of material that represent a significant portion of the specimen, especially in microdissected samples. Here we describe a novel application of a commonly used PCR-based DNA-fingerprinting technology that requires minimal quantities of DNA to simultaneously assess multiple regions throughout the genome for DNA quality. Randomly amplified polymorphic DNA (RAPD) PCR generates DNA fragments of a broad size range with the product size reflecting the degree of sample fragmentation. Fourteen DNA samples extracted from cells microdissected from seven formalin-fixed, paraffin-embedded oral cancer biopsies were assessed for DNA quality using gene-specific PCR and RAPD-PCR. Although the more conventional assay required 2-ng DNA (or 300-cell equivalents) to examine DNA quality at a single locus, RAPD-PCR provided a more informative profile of DNA quality from the same microdissected archival specimens.