Project description:Forty-four paired (from the same patient) samples of head and neck squamous cell carcinoma (HNSCC) and normal tissue were studied with Affymetrix U95A chips. A stringent multi-test approach, combining 7 traditional and microarray-specific statistical tests, was used to analyze the resultant data. Candidate genes were assigned to tiers of significance based on the number of statistical tests that each gene satisfied. Representative genes (both up-regulated and down-regulated) from each of the 3 tiers would be quantified with RT-PCR on both microarray-tested and new samples of HNSCC. The goal of this study is to identify reliable differentially-expressed genes on HNSCC and to testify our hypothesis whether or not a combinatorial approach (multi-tests) to analyzing microarray data can really identify differentially-expressed genes with fewer false-positives. Keywords: disease state; tumor vs. normal
Project description:High-throughput DNA methylation profiling exploits microarray technologies thus providing a wealth of data, which however solicits rigorous, generic and analytical pipelines for an efficient systems level analysis and interpretation. In the present study, we utilize the Illumina's Infinium Human Methylation 450K BeadChip platform in an epidemiological cohort, targeting to associate interesting methylation patterns with breast cancer predisposition. The computational framework proposed here extends the -established in transcriptomic microarrays- logarithmic ratio of the Methylated versus the Unmethylated signal intensities, quoted as M-value. Moreover, intensity-based correction of the M-signal distribution is introduced in order to correct for batch effects and probe-specific errors in intensity measurements. This is accomplished through the estimation of intensity-related error measures from quality control samples included in each chip. Moreover, robust statistical measures based on coefficient variation measurements of DNA methylation between control and case samples alleviate the impact of technical variation. The results presented here are juxtaposed to those derived by applying classical pre-processing and statistical selection methodologies. Overall, in comparison to traditional approaches, the introduced framework's superior performance in terms of technical bias correction, along with its generic character, support its suitability for various microarray technologies.
Project description:To confirm the suitability of C. elegans as a model organism, preliminary gene expression experiments were performed using juglone (5-hydroxy-1,4-naphthoquinone; 97% pure; Sigma-Aldrich, St-Louis, MO), an ROS-generator, as a positive control of oxidative stress (d'Arcy Doherty et al. 1987; Leiers et al. 2003). Reproduction tests were initially performed to establish the sub-lethal effect concentrations used in the microarray experiments.