Figure 4. Horvath methylation clock estimates of pediatric brain tumor samples in comparison to healthy blood and brain, and reactive tumor microenvironment. (A) Horvath methylation age vs chronological age in pediatric brain tumors (n = 1112), healthy blood (n= 188) and brain tissue (n = 45) from children and reactive tumor microenvironment (RTM; n = 14) displaying an accelerated methylation age in a majority of the brain tumor samples. (B) The methylation age is significantly increased compared to normal brain tissue, in both RTM (adj. p = 1.1e-05) and four types of pediatric brain tumors; ATRT (adj. p = 1.3e-13), ependymoma (EPN; adj. p = <2e-16), glioma (adj. p = <2e-16) and medulloblastoma (MB; adj. p = <2e-16).