Fig. 2

RBBP8 promoter methylation in bladder cancer of the TCGA data set. a Visualization of the promoter methylation of the RBBP8 gene as a scatterplot. The β values for each sample were jittered around the probe location and plotted as points. The per sample type 90% quantiles of methylation are shown as smoothed lines. The colors represent different sample groups (BLCA, bladder cancer; HNSC, head-neck squamous cell carcinoma). b The Pearson correlation coefficients (ρ) for probe pairs in the core region of the promoter are shown as heatmap demonstrating a high degree of correlation between probes (ρ > 0.7). c The beta values of all probes of the promoter region were summarized by their median value, stratified by the sample as well as tissue type, and visualized as a box plot. For RBBP8 gene loci, a frequent hypermethylation (β > 0.25 in > 5% of cases) was only observable in 37, 10, and 7% of bladder urothelial carcinoma (BLCA), head-neck squamous cell carcinoma (HNSC), and lung squamous cell carcinoma (LUSC), respectively. d Inverse correlation between RBBP8 methylation (defined CpG gene set) and RBBP8 mRNA expression in primary bladder cancer (BLCA), neck squamous cell carcinoma (HNSC), and lung squamous carcinoma (LUSC) samples of the TCGA data portal. Spearman correlation BLCA: − 0.32, p < 0.001; Spearman correlation HNSC: − 0.04, p = ns; Spearman correlation LUSC: 0.08, p = ns. e Box plot illustrates significant downregulation of RBBP8 methylation in primary tumors featuring increased RBBP8 promoter methylation (β value > 0.4). Horizontal lines — grouped medians. Boxes — 25 to 75% quartiles. Vertical lines — range, peak, and minimum. *p < 0.05, **p < 0.01, ns: not significant. f Box plot shows RBBP8 methylation in primary tumors classified by intrinsic subtypes. g Kaplan-Meier survival curves display overall survival (OS) of patients with high RBBP8 methylation (β value > 0.4, dark gray curve) compared to low RBBP8 methylation (β value ≤ 0.4, gray curve) based on TCGA datasets