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Leiden, Netherlands

De Ruijter T.C.,Maastricht University | De Hoon J.P.,Maastricht University | Slaats J.,Maastricht University | De Vries B.,Maastricht University | And 8 more authors.
Laboratory Investigation | Year: 2015

Current genome-wide methods to detect DNA-methylation in healthy and diseased tissue require high-quality DNA from fresh-frozen (FF) samples. However, well-annotated clinical samples are mostly available as formalin-fixed, paraffin-embedded (FFPE) tissues containing poor-quality DNA. To overcome this limitation, we here aimed to evaluate a DNA restoration protocol for usage with the genome-wide Infinium HumanMethylation450 BeadChip assay (HM-450K). Sixty-six DNA samples from normal colon (n=9) and breast cancer (n=11) were interrogated separately using HM-450K. Analyses included matched FF/FFPE samples and technical duplicates. FFPE DNA was processed with (FFPEr) or without a DNA restoration protocol (Illumina). Differentially methylated genes were finally validated in 24 additional FFPE tissues using nested methylation-specific PCR (MSP). In summary, β-values correlation between FFPEr duplicates was high (ρ=0.9927 (s.d. ±0.0015)). Matched FF/FFPEr correlation was also high (ρ=0.9590 (s.d. ±0.0184)) compared with matched FF/FFPE (ρ=0.8051 (s.d. ±0.1028). Probe detection rate in FFPEr samples (98.37%, s.d. ±0.66) was comparable to FF samples (99.98%, s.d. ±0.019) and substantially lower in FFPE samples (82.31%, s.d. ±18.65). Assay robustness was not decreased by sample archival age up to 10 years. We could also demonstrate no decrease in assay robustness when using 100 ng of DNA input only. Four out of the five selected differentially methylated genes could be validated by MSP. The gene failing validation by PCR showed high variation of CpG β-values in primer-binding sites. In conclusion, by using the FFPE DNA restoration protocol, HM-450K assays provide robust, accurate and reproducible results with FFPE tissue-derived DNA, which are comparable to those obtained with FF tissue. Most importantly, differentially methylated genes can be validated using more sensitive techniques, such as nested MSP, altogether providing an epigenomics platform for molecular pathological epidemiology research on archived samples with limited tissue amount. © 2015 USCAP, Inc All rights reserved. Source


Jewell R.,St Jamess Hospital | Conway C.,St Jamess Hospital | Mitra A.,St Jamess Hospital | Randerson-Moor J.,St Jamess Hospital | And 15 more authors.
Clinical Cancer Research | Year: 2010

Purpose: To use gene expression profiling of formalin-fixed primary melanoma samples to detect expression patterns that are predictive of relapse and response to chemotherapy. Experimental Design: Gene expression profiles were identified in samples from two studies (472 tumors). Gene expression data for 502 cancer-related genes from these studies were combined for analysis. Results: Increased expression of DNA repair genes most strongly predicted relapse and was associated with thicker tumors. Increased expression of RAD51 was the most predictive of relapse-free survival in unadjusted analysis (hazard ratio, 2.98; P = 8.80 × 10-6). RAD52 (hazard ratio, 4.73; P = 0.0004) and TOP2A (hazard ratio, 3.06; P = 0.009) were independent predictors of relapse-free survival in multivariable analysis. These associations persisted when the analysis was further adjusted for demographic and histologic features of prognostic importance (RAD52 P = 0.01; TOP2A P = 0.02). Using principal component analysis, expression of DNA repair genes was summarized into one variable. Genes whose expression correlated with this variable were predominantly associated with the cell cycle and DNA repair. In 42 patients treated with chemotherapy, DNA repair gene expression was greater in tumors from patients who progressed on treatment. Further data supportive of a role for increased expression of DNA repair genes as predictive biomarkers are reported, which were generated using multiplex PCR. Conclusions: Overexpression of DNA repair genes (predominantly those involved in double-strand break repair) was associated with relapse. These data support the hypothesis that melanoma progression requires maintenance of genetic stability and give insight into mechanisms of melanoma drug resistance and potential therapies. ©2010 AACR. Source


Schilthuizen M.,Endless Forms group | Schilthuizen M.,Leiden University | Schilthuizen M.,University of Groningen | Pimenta L.P.S.,Leiden University | And 27 more authors.
PeerJ | Year: 2016

The integration of invasive species into native food webs represent multifarious dynamics of ecological and evolutionary processes. We document incorporation of Prunus serotina (black cherry) into native insect food webs. We find that P. serotina harbours a herbivore community less dense but more diverse than its native relative, P. padus (bird cherry), with similar proportions of specialists and generalists. While herbivory on P. padus remained stable over the past century, that on P. serotina gradually doubled. We show that P. serotina may have evolved changes in investment in cyanogenic glycosides compared with its native range. In the leaf beetle Gonioctena quinquepunctata, recently shifted from native Sorbus aucuparia to P. serotina, we find divergent host preferences on Sorbus-versus Prunus-derived populations, and weak host-specific differentiation among 380 individuals genotyped for 119 SNP loci. We conclude that evolutionary processes may generate a specialized herbivore community on an invasive plant, allowing prognoses of reduced invasiveness over time. On the basis of the results presented here, we would like to caution that manual control might have the adverse effect of a slowing down of processes of adaptation, and a delay in the decline of the invasive character of P. serotina. © 2016 Schilthuizen et al. Source


Doorduin L.,Leiden University | Gravendeel B.,Leiden University | Lammers Y.,Leiden University | Ariyurek Y.,Leiden University | And 2 more authors.
DNA Research | Year: 2011

Invasive individuals from the pest species Jacobaea vulgaris show different allocation patterns in defence and growth compared with native individuals. To examine if these changes are caused by fast evolution, it is necessary to identify native source populations and compare these with invasive populations. For this purpose, we are in need of intraspecific polymorphic markers. We therefore sequenced the complete chloroplast genomes of 12 native and 5 invasive individuals of J. vulgaris with next generation sequencing and discovered single-nucleotide polymorphisms (SNPs) and microsatellites. This is the first study in which the chloroplast genome of that many individuals within a single species was sequenced. Thirty-two SNPs and 34 microsatellite regions were found. For none of the individuals, differences were found between the inverted repeats. Furthermore, being the first chloroplast genome sequenced in the Senecioneae clade, we compared it with four other members of the Asteraceae family to identify new regions for phylogentic inference within this clade and also within the Asteraceae family. Five markers (ndhC-trnV, ndhC-atpE, rps18-rpl20, clpP and psbM-trnD) contained parsimony-informative characters higher than 2. Finally, we compared two procedures of preparing chloroplast DNA for next generation sequencing. © 2011 The Author. Source


Pontillo C.,Mosaiques Diagnostics GmbH | Pontillo C.,Charite - Medical University of Berlin | Filip S.,Charite - Medical University of Berlin | Filip S.,Academy of Athens | And 8 more authors.
Proteomics - Clinical Applications | Year: 2015

CE-MS is applied in clinical proteomics for both the identification of biomarkers of disease and assessment of biomarkers in clinical diagnosis. The analysis is reproducible, fast, and requires only small sample volumes. However, successful CE-MS analysis depends on several critical steps that can be consolidated as follows: (i) proper sample preparation and fractionation, (ii) application of suitable capillary coating and appropriate CE-MS interfaces, to ensure the reproducibility and stability of the analysis, and (iii) an optimized clinical and statistical study design to increase the chances for obtaining clinically relevant results. In this review, we cover all these aspects, and present several examples of the application of CE-MS in clinical proteomics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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