Colon/Rectal Adenocarcinoma: Correlation between mRNA expression and DNA methylation
Maintained by Richard Park (Boston University/Harvard Medical School)
Overview
Introduction

The role of general epigenetic mechanisms in carcinogenesis and tumor aggressiveness is well documented: CpG island hyper-methylation silences tumor suppressor genes, whereas hypo-methylation promotes the transcriptional activation of oncogenes and induces chromosomal instability. This pipeline calculates and identifies correlations between DNA methylation and gene expression profiles using the available array technologies.

Summary

The top 25 correlated methylation probes per gene are displayed. Total number of matched samples = 6. Number of gene expression samples = 83. Number of methylation samples = 6.

Results
Correlation Histogram

Figure 1. Histogram of methylation correlation values. n is the number of matched samples between Level 3 CpG site methylation and Level 3 gene expression arrays. Number of Matched Samples = 6

Qvalue Summary Plots

Figure 2. Plot 1. The estimated pi_0 versus the tuning parameter lambda. Plot 2. The q-values versus the p-values. Plot 3. The number of significant tests versus each q-value cutoff. Plot 4. The number of expected false positives versus the number of significant tests.The first is a plot of the estimate of pi_0 versus its tuning parameter lambda. In most cases, as lambda gets larger, the bias of the estimate decreases, yet the variance increases. Comparing your estimate of pi_0 to this plot allows one to guage its quality. The remaining three plots show how many tests are significant, as well as how many false positives to expect for each q-value cut-off.

Negative Correlation between Methylation and Gene Expression

Table 1. Get Full Table Top 25 most negatively correlated methylation probes. Correlation Coefficient: See Methods & Data below. Pval and Qval: P- and Q-values of the correlation coefficient. Expression Mean: mean detection level of gene expression probes. Methylation Mean: mean detection level of CpG methylation probes.

Meth_Probe | Gene | Chrom | Position | Corr_Coeff | Pval | Qval | Expr_Mean | Meth_Mean
--- | --- | --- | --- | --- | --- | --- | --- | ---
cg12808596 | ZP1 | 11 | 60397221 | -1 | 0.017 | 0.014 | NA | 0.890588
cg25413843 | VAX2 | 2 | 70980199 | -1 | 0.017 | 0.014 | NA | 0.420550
cg03996398 | TP53AIP1 | 11 | 128318652 | -1 | 0.017 | 0.014 | NA | 0.902484
cg07710481 | SLITRK5 | 13 | 87123385 | -1 | 0.017 | 0.014 | NA | 0.551528
cg04140862 | SLC8A3 | 14 | 69724392 | -1 | 0.017 | 0.014 | NA | 0.600601
cg09634469 | SERPIND1 | 22 | 19458411 | -1 | 0.017 | 0.014 | NA | 0.914573
cg27312603 | RDH8 | 19 | 9993713 | -1 | 0.017 | 0.014 | NA | 0.926286
cg08143803 | PROZ | 13 | 112874198 | -1 | 0.017 | 0.014 | NA | 0.853860
cg26746560 | PLA2G3 | 22 | 29865672 | -1 | 0.017 | 0.014 | NA | 0.348056
cg24162030 | PKD2L1 | 10 | 102080579 | -1 | 0.017 | 0.014 | NA | 0.310751
cg20210051 | PDZRN4 | 12 | 40116333 | -1 | 0.017 | 0.014 | NA | 0.113567
cg02949067 | PCSK2 | 20 | 17411831 | -1 | 0.017 | 0.014 | NA | 0.455140
cg02500479 | PCDHA8 | 5 | 140244178 | -1 | 0.017 | 0.014 | NA | 0.561196
cg15923943 | PCDHA6 | 5 | 140363750 | -1 | 0.017 | 0.014 | NA | 0.261005
cg08448812 | PCDHA4 | 5 | 140187944 | -1 | 0.017 | 0.014 | NA | 0.631587
cg06951122 | PCDHA2 | 5 | 140202837 | -1 | 0.017 | 0.014 | NA | 0.933020
cg26556719 | PCDHA13 | 5 | 140241994 | -1 | 0.017 | 0.014 | NA | 0.458073
cg02004641 | PCDHA1 | 5 | 140286365 | -1 | 0.017 | 0.014 | NA | 0.323209
cg15765486 | PABPC4L | 4 | 135342557 | -1 | 0.017 | 0.014 | NA | 0.399130
cg18243017 | ODZ2 | 5 | 167606874 | -1 | 0.017 | 0.014 | NA | 0.589238
cg14401837 | NPSR1 | 7 | 34664018 | -1 | 0.017 | 0.014 | NA | 0.505999
cg23114866 | NKX2-2 | 20 | 21442977 | -1 | 0.017 | 0.014 | NA | 0.126644
cg15920887 | MSTN | 2 | 190636675 | -1 | 0.017 | 0.014 | NA | 0.813143
cg00902427 | MCHR1 | 22 | 39404937 | -1 | 0.017 | 0.014 | NA | 0.564395
cg04256965 | MAGEL2 | 15 | 21440054 | -1 | 0.017 | 0.014 | NA | 0.898887
cg05687194 | LRRC50 | 16 | 82735562 | -1 | 0.017 | 0.014 | NA | 0.020203

Methods & Data
Input

Methylation Array Platforms: Illumina Infinium HumanMethylation27, Illumina DNA Methylation OMA002, Illumina DNA Methylation OMA003

- methylation file = /xchip/cga/gdac-prod/tcga-gdac/jobResults/GDAC_MethylationPreprocess/COADREAD/1841454/0.GDAC_MethylationPreprocess.Finished/COADREAD.meth.for_correlation.filtered_data.txt

Gene Expression Platforms: Agilent 244K Gene Expression G4502A-07-1, Agilent 244K Gene Expression G4502A-07-2, Agilent 244K Gene Expression G4502A-07-3, Affymetrix Human Exon 1.0 ST Array, Affymetrix HT Human Genome U133 Array

- gene expression file = /xchip/cga/gdac-prod/tcga-gdac/jobResults/mRNAseq_preprocessor/COADREAD/1768747/0.mRNAseq_preprocessor.Finished/COADREAD.mRNAseq_RPKM_log2.txt

Correlation Coefficient

Level 3 methylation and gene expression arrays were paired on the basis of Entrez Gene ID concordance. The association between CpG site methylation and the level of expression of the corresponding genes was determined by calculating a correlation measure between the two platforms.

- correlation measure = Spearman

Download Results

This is an experimental feature. The full results of the analysis summarized in this report can be downloaded from the TCGA Data Coordination Center.

- Analysis Results (MD5 checksum)

- Auxiliary Data (MD5 checksum)

- MAGE-TAB File (MD5 checksum)

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