Differential Methylation

Introduction: Differential Methylation of Sample Groups

Differential methylation analysis was conducted on site and region level according to the sample groups specified in the analysis.

Comparisons

The following comparisons were made:

P-values

In the following anlyses, p-values on the site level were computed using the limma method. I.e. hierarchical linear models from the limma package were employed and fitted using an empirical Bayes approach on derived M-values.

Site Level

Differential methylation on the site level was computed based on a variety of metrics. Of particular interest for the following plots and analyses are the following quantities for each site: a) the difference in mean methylation levels of the two groups being compared, b) the quotient in mean methylation and c) a statistical test (t-test or limma depending on the settings) assessing whether the methylation values in the two groups originate from distinct distributions. Additionally each site was assigned a rank based on each of these three criteria. A combined rank is computed as the maximum (i.e. worst) rank among the three ranks. The smaller the combined rank for a site, the more evidence for differential methylation it exhibits. This section includes scatterplots of the site group means as well as volcano plots of each pairwise comparison colored according to the combined ranks or p-values of a given site.

The following rank cutfoffs have been automatically selected for the analysis of differentially methylated sites:

Rank Cutoff
Control Analyte vs. non.Control Analyte (based on Type) 111928
Metastatic vs. non.Metastatic (based on Type) 9048
Primary Blood Derived Cancer - Peripheral Blood vs. non.Primary Blood Derived Cancer - Peripheral Blood (based on Type) 104493
Primary solid Tumor vs. non.Primary solid Tumor (based on Type) 130459
Recurrent Solid Tumor vs. non.Recurrent Solid Tumor (based on Type) 27438
Solid Tissue Normal vs. non.Solid Tissue Normal (based on Type) 106831
Acute Myeloid Leukemia vs. non.Acute Myeloid Leukemia (based on Study) 104493
Breast invasive carcinoma vs. non.Breast invasive carcinoma (based on Study) 95716
Colon adenocarcinoma vs. non.Colon adenocarcinoma (based on Study) 106549
Glioblastoma multiforme vs. non.Glioblastoma multiforme (based on Study) 119784
Head and Neck squamous cell carcinoma vs. non.Head and Neck squamous cell carcinoma (based on Study) 113705
Kidney renal clear cell carcinoma vs. non.Kidney renal clear cell carcinoma (based on Study) 60341
Lung adenocarcinoma vs. non.Lung adenocarcinoma (based on Study) 86511
Lung squamous cell carcinoma vs. non.Lung squamous cell carcinoma (based on Study) 112672
Rectum adenocarcinoma vs. non.Rectum adenocarcinoma (based on Study) 109642
Thyroid carcinoma vs. non.Thyroid carcinoma (based on Study) 147645
Uterine Corpus Endometrioid Carcinoma vs. non.Uterine Corpus Endometrioid Carcinoma (based on Study) 104213
FEMALE vs. MALE (based on Gender) 87947
comparison
differential methylation measure

Figure 1

Figure 1

Scatterplot for differential methylation (sites). If the selected criterion is not rankGradient: The transparency corresponds to point density. If the number of points exceeds 2e+06 then the number of points for density estimation is reduced to that number by random sampling.The1% of the points in the sparsest populated plot regions are drawn explicitly (up to a maximum of 10000 points).Additionally, the colored points represent differentially methylated sites (according to the selected criterion). If the selected criterion is rankGradient: median combined ranks accross hexagonal bins are shown as a gradient according to the color legend.

comparison
difference metric
significance metric

Figure 2

Figure 2

Volcano plot for differential methylation quantified by various metrics. Color scale according to combined ranking.

Differential Methylation Tables

A tabular overview of measures for differential methylation on the site level for the individual comparisons are provided in this section. Below, a brief explanation of the different columns can be found:

The tables for the individual comparisons can be found here:

Region Level

Differential methylation on the region level was computed based on a variety of metrics. Of particular interest for the following plots and analyses are the following quantities for each region: the mean difference in means across all sites in a region of the two groups being compared and the mean of quotients in mean methylation as well as a combined p-value calculated from all site p-values in the region [1]. Additionally each region was assigned a rank based on each of these three criteria. A combined rank is computed as the maximum (i.e. worst) value among the three ranks. The smaller the combined rank for a region, the more evidence for differential methylation it exhibits. Regions were defined based on the region types specified in the analysis. This section includes scatterplots of the region group means as well as volcano plots of each pairwise comparison colored according to the combined rank of a given region.

The following rank cutfoffs have been automatically selected for the analysis of differentially methylated regions:

tiling genes promoters cpgislands
Control Analyte vs. non.Control Analyte (based on Type) 4520 857 1442 1307
Metastatic vs. non.Metastatic (based on Type) 5062 975 1610 2136
Primary Blood Derived Cancer - Peripheral Blood vs. non.Primary Blood Derived Cancer - Peripheral Blood (based on Type) 5262 0 2034 1587
Primary solid Tumor vs. non.Primary solid Tumor (based on Type) 6922 2757 3819 3715
Recurrent Solid Tumor vs. non.Recurrent Solid Tumor (based on Type) 5809 1543 2235 1900
Solid Tissue Normal vs. non.Solid Tissue Normal (based on Type) 10720 1826 3791 3125
Acute Myeloid Leukemia vs. non.Acute Myeloid Leukemia (based on Study) 5262 0 2034 1587
Breast invasive carcinoma vs. non.Breast invasive carcinoma (based on Study) 6895 958 2040 2017
Colon adenocarcinoma vs. non.Colon adenocarcinoma (based on Study) 3815 546 2842 3941
Glioblastoma multiforme vs. non.Glioblastoma multiforme (based on Study) 6376 726 1283 3008
Head and Neck squamous cell carcinoma vs. non.Head and Neck squamous cell carcinoma (based on Study) 10567 1694 2485 2327
Kidney renal clear cell carcinoma vs. non.Kidney renal clear cell carcinoma (based on Study) 3156 747 2432 2767
Lung adenocarcinoma vs. non.Lung adenocarcinoma (based on Study) 6116 1260 2687 3517
Lung squamous cell carcinoma vs. non.Lung squamous cell carcinoma (based on Study) 9573 1504 3452 2496
Rectum adenocarcinoma vs. non.Rectum adenocarcinoma (based on Study) 3452 996 3033 4201
Thyroid carcinoma vs. non.Thyroid carcinoma (based on Study) 1017 371 2360 964
Uterine Corpus Endometrioid Carcinoma vs. non.Uterine Corpus Endometrioid Carcinoma (based on Study) 6527 454 1997 2963
FEMALE vs. MALE (based on Gender) 5308 1308 883 2179
comparison
regions
differential methylation measure

Figure 3

Figure 3

Scatterplot for differential methylation (regions). If the selected criterion is not rankGradient: The transparency corresponds to point density. The 1% of the points in the sparsest populated plot regions are drawn explicitly. Additionally, the colored points represent differentially methylated regions (according to the selected criterion). If the selected criterion is rankGradient: median combined ranks accross hexagonal bins are shown as a gradient according to the color legend.

comparison
regions
difference metric
significance metric

Figure 4

Figure 4

Volcano plot for differential methylation quantified by various metrics. Color scale according to combined ranking.

Differential Methylation Tables

A tabular overview of measures for differential methylation on the region level for the individual comparisons are provided in this section.

The tables for the individual comparisons can be found here:

tiling genes promoters cpgislands
Control Analyte vs. non.Control Analyte (based on Type) csv csv csv csv
Metastatic vs. non.Metastatic (based on Type) csv csv csv csv
Primary Blood Derived Cancer - Peripheral Blood vs. non.Primary Blood Derived Cancer - Peripheral Blood (based on Type) csv csv csv csv
Primary solid Tumor vs. non.Primary solid Tumor (based on Type) csv csv csv csv
Recurrent Solid Tumor vs. non.Recurrent Solid Tumor (based on Type) csv csv csv csv
Solid Tissue Normal vs. non.Solid Tissue Normal (based on Type) csv csv csv csv
Acute Myeloid Leukemia vs. non.Acute Myeloid Leukemia (based on Study) csv csv csv csv
Breast invasive carcinoma vs. non.Breast invasive carcinoma (based on Study) csv csv csv csv
Colon adenocarcinoma vs. non.Colon adenocarcinoma (based on Study) csv csv csv csv
Glioblastoma multiforme vs. non.Glioblastoma multiforme (based on Study) csv csv csv csv
Head and Neck squamous cell carcinoma vs. non.Head and Neck squamous cell carcinoma (based on Study) csv csv csv csv
Kidney renal clear cell carcinoma vs. non.Kidney renal clear cell carcinoma (based on Study) csv csv csv csv
Lung adenocarcinoma vs. non.Lung adenocarcinoma (based on Study) csv csv csv csv
Lung squamous cell carcinoma vs. non.Lung squamous cell carcinoma (based on Study) csv csv csv csv
Rectum adenocarcinoma vs. non.Rectum adenocarcinoma (based on Study) csv csv csv csv
Thyroid carcinoma vs. non.Thyroid carcinoma (based on Study) csv csv csv csv
Uterine Corpus Endometrioid Carcinoma vs. non.Uterine Corpus Endometrioid Carcinoma (based on Study) csv csv csv csv
FEMALE vs. MALE (based on Gender) csv csv csv csv

Enrichment Analysis

Enrichment Analysis was conducted. The wordclouds and tables below contains significant GO terms as determined by a hypergeometric test.

comparison
Hypermethylation/hypomethylation
ontology
regions
differential methylation measure

Figure 5

Figure 5

Wordclouds for GO enrichment terms.

comparison
Hypermethylation/hypomethylation
ontology
regions
differential methylation measure

GOMFID Pvalue OddsRatio ExpCount Count Size Term
GO:0007264 1e-04 14.1206 0.5178 5 486 small GTPase mediated signal transduction
GO:0006184 9e-04 11.4756 0.4645 4 436 GTP catabolic process
GO:0060764 0.0011 Inf 0.0011 1 1 cell-cell signaling involved in mammary gland development
GO:1901068 0.0011 10.9768 0.4847 4 455 guanosine-containing compound metabolic process
GO:0009150 0.0012 8.1077 0.8757 5 822 purine ribonucleotide metabolic process
GO:0019693 0.0013 7.9323 0.8938 5 839 ribose phosphate metabolic process
GO:0035483 0.0021 1004.5714 0.0021 1 2 gastric emptying
GO:0007266 0.0025 31.2062 0.0756 2 71 Rho protein signal transduction
GO:0009203 0.0026 8.6567 0.6083 4 571 ribonucleoside triphosphate catabolic process
GO:0009146 0.0026 8.6093 0.6115 4 574 purine nucleoside triphosphate catabolic process
GO:0046130 0.0027 8.5004 0.619 4 581 purine ribonucleoside catabolic process
GO:0006979 0.0028 12.6774 0.293 3 275 response to oxidative stress
GO:0046578 0.003 12.3984 0.2994 3 281 regulation of Ras protein signal transduction
GO:0009261 0.003 8.2467 0.6371 4 598 ribonucleotide catabolic process
GO:0009164 0.0031 8.1891 0.6413 4 602 nucleoside catabolic process
GO:0009117 0.0031 6.4836 1.0781 5 1012 nucleotide metabolic process
GO:0060435 0.0032 502.25 0.0032 1 3 bronchiole development
GO:0060574 0.0032 502.25 0.0032 1 3 intestinal epithelial cell maturation
GO:0009205 0.0034 7.9392 0.6605 4 620 purine ribonucleoside triphosphate metabolic process
GO:0006195 0.0038 7.6908 0.6808 4 639 purine nucleotide catabolic process
GO:0055086 0.0038 6.147 1.1325 5 1063 nucleobase-containing small molecule metabolic process
GO:0009141 0.0039 7.6403 0.685 4 643 nucleoside triphosphate metabolic process
GO:0051461 0.0043 334.8095 0.0043 1 4 positive regulation of corticotropin secretion
GO:0060455 0.0043 334.8095 0.0043 1 4 negative regulation of gastric acid secretion
GO:0060482 0.0043 334.8095 0.0043 1 4 lobar bronchus development
GO:0060535 0.0043 334.8095 0.0043 1 4 trachea cartilage morphogenesis
GO:2000987 0.0043 334.8095 0.0043 1 4 positive regulation of behavioral fear response
GO:1901292 0.0044 7.4092 0.7053 4 662 nucleoside phosphate catabolic process
GO:0042278 0.0051 7.0811 0.7362 4 691 purine nucleoside metabolic process
GO:0060480 0.0053 251.0893 0.0053 1 5 lung goblet cell differentiation
GO:0009119 0.0056 6.8808 0.7564 4 710 ribonucleoside metabolic process
GO:0031175 0.0062 6.6618 0.7798 4 732 neuron projection development
GO:0060452 0.0064 200.8571 0.0064 1 6 positive regulation of cardiac muscle contraction
GO:0060547 0.0064 200.8571 0.0064 1 6 negative regulation of necrotic cell death
GO:0006927 0.0074 167.369 0.0075 1 7 transformed cell apoptotic process
GO:0042756 0.0074 167.369 0.0075 1 7 drinking behavior
GO:2000252 0.0074 167.369 0.0075 1 7 negative regulation of feeding behavior
GO:1901215 0.0076 17.4384 0.1332 2 125 negative regulation of neuron death
GO:1901657 0.0077 6.2614 0.8267 4 776 glycosyl compound metabolic process
GO:0043117 0.0085 143.449 0.0085 1 8 positive regulation of vascular permeability
GO:0045647 0.0085 143.449 0.0085 1 8 negative regulation of erythrocyte differentiation
GO:1901564 0.0093 4.3664 1.9911 6 1869 organonitrogen compound metabolic process
GO:0032099 0.0096 125.5089 0.0096 1 9 negative regulation of appetite
GO:0060638 0.0096 125.5089 0.0096 1 9 mesenchymal-epithelial cell signaling

References

  1. Makambi, K. (2003) Weighted inverse chi-square method for correlated significance tests. Journal of Applied Statistics, 30(2), 225234