Figure 1.
Methylomes of the colorectal tissues analysed. Unsupervised hierarchical clustering was performed based on the methylation status of the 1000 CpG islands displaying the highest variability in the tissues analysed: 18 precancerous tumours from the proximal colon (10 SSLs, 8 cADNs) and 30 NM samples (18 from the SSL or cADN donors, 12 from TF donors). a. Heatmap of all 48 samples. In both precancerous tumour types, the 1000 CpG islands considered are far more methylated than in any of the four groups of NM samples. SSLs and cADNs can also be distinguished from one other. b. Heatmap of the 12 NM samples from TF donors (1 CEC + 1 SIG per donor). Hierarchical clustering was performed within each age group. The CpG islands were more highly methylated in samples from TF donors >70 (TF-O NM) than in those from younger (<40y) TF donors (TF-Y NM). In both age groups, caecal and sigmoid NM samples (TF NMCEC and TF NMSIG) could also be distinguished. Abbreviations: ASC, ascending colon; cADN, conventional adenoma; CEC, caecum; NM, normal mucosa; O, older; SSL, sessile serrated lesion; SIG, sigmoid colon; TF, tumour-free; Y, younger.