Project description:Genome wide DNA methylation profiling of DNA samples obtained from normal lung tissue and lung carcinoma, either fixed by formalin (FFPE), HOPE (paraffin embedded) or cryo-preserved. Illumina's HumanMethylation450 BeadChip was used to obtain DNA methylation profiles across approximately 450.000 CpGs.
Project description:Background: To date, few studies have systematically characterized microarray gene expression signal performance with degraded RNA from formalin-fixed paraffin-embedded (FFPE) specimens in comparison to intact RNA from unfixed fresh-frozen (FF) specimens. Methodology: RNA was extracted and isolated from paired tumor and normal samples from both FFPE and FF kidney, lung and colon tissue specimens. Microarray signal dynamics on both the raw probe and probeset level were evaluated. A contrast metric was developed to directly compare microarray signal derived from RNA extracted from matched FFPE and FF specimens. Gene-level summaries were then compared to determine the degree of overlap in expression profiles. Results: RNA extracted from FFPE material was more degraded and fragmented than FF, resulting in reduced dynamic range of expression signal. It was found that probe performance is not affected uniformly and declines sharply toward 5￢ﾀﾙ end of genes. The most significant differences in FFPE vs. FF signal were consistent across three tissue types and enriched with ribosomal genes. Significance: Our results show that archived FFPE samples can be used to profile for expression signatures and assess differential expression similar to unfixed tissue sources. This study provides guidelines for application of these methods in the discovery, validation, and clinical application of microarray expression profiling with FFPE material. 53 samples: 16 FF colon, 7 FFPE colon, 6 FF lung, 8 FFPE lung, 8 FF kidney, and 8 FFPE kidney specimens. Samples are paired tumor and normal tissue. 1-4 biological replicates.
Project description:Genome-wide DNA methylation profiling of normal and lung adenocarcinoma fresh tissue samples. The Illumina Infinium MethylationEPIC BeadChip (850K) was used to obtain DNA methylation profiles across 860,000 CpGs in fresh tissue of lung adenocarcinoma and adjacent histological normal lung tissue samples. Samples included 30 paired tumor-normal driver gene-negative lung adenocarcinoma tissues and 35 paired tumor-normal EGFR-mutation positive lung adenocarcinoma tissues.
