<i>NDRG2</i> revealed a divergent expression and methylation pattern in basal- compared to luminal-type breast cancer.

<p><b>(A)</b> Box plot analysis (based on our own subtype classified tissue collective) illustrates a decreased <i>NDRG2</i> mRNA expression in breast cancer compared with normal breast tissue. An increased <i>NDRG2</i> mRNA expression (median expression level: 0.334) in triple negative tumors is observed comparing to HER2-enriched (median expression level: 0.275) and luminal-type (median expression level: 0.229) carcinomas. <b>(B)</b> Heatmap of <i>NDRG2</i> expression is shown. <i>Red</i>: high-, <i>black</i>: mean-, <i>green</i>: low-expression. <i>Left panel</i>: breast cancer subtypes. <i>Middle panel</i>: <i>NDRG2</i> mRNA expression. <i>Right panel</i>: sample type (<i>dark grey</i>: primary tumor; <i>light grey</i>: solid normal tissues). Breast tumor samples are stratified by subtypes [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159073#pone.0159073.ref003" target="_blank">3</a>]. <b>(C)</b> Box plot demonstrating a significant loss of <i>NDRG2</i> mRNA expression in luminal-type and HER2-enriched tumors with respect to basal-type cancer specimens. <b>(D)</b> Statistical association of <i>NDRG2</i> mRNA expression and <i>NDRG2</i> hypermethylation in breast cancer. Pearson correlation coefficient: r = -0.5478, P<0.001. <b>(E)</b> Box plot analysis (based on our own subtype classified tissue collective) showing significant increased CpG-hypermethylation of the <i>NDRG2</i> promoter in luminal-type and HER2-enriched tumors compared to normal tissue samples. Horizontal lines: grouped medians. Boxes: 25–75% quartiles. Vertical lines: range, peak, and minimum. ***P<0.001, **P<0.01, ns: not significant.