Figure 2B shows a differential locus detected in plasma cfDNA at the SULF1 (sulfatase 1) gene. In cancer patients' plasma cfDNA, the 5hmC levels in SULF1 were elevated in both exons and introns, with a peak pattern similar to that of tissue gDNA (Supplementary information, Figure S5). Neighboring differential 5hmC loci showed regionally elevated or decreased 5hmC levels (Figure 2C). For example, the correlation of cancer-associated 5hmC changes between neighboring genes was significantly higher than a null distribution generated by shuffling gene positions within a chromosome (Figure 2D). Here, SULF1 is linked to cancer.