To evaluate if the DNA methylation of SLC genes associated with OS and PFI can be proposed as an independent prognostic biomarker, Kaplan Meier (KM) analysis was performed in all TCGA Pan-cancer tumor types stratifying the patients according to the cg06690548 methylation levels of the SLC7A11 gene, which was found to be strictly associated with OS and PFI in several tumor types (Figure 4; Supplementary Tables S4, S5). This evidence concerns the gene CCL21 and neoplasm.