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Table 3 Distribution and density of p14 ARF methylation in tumors and adjacent colon mucosa from patients with colorectal cancer

From: Hypermethylation of the 5′ CpG island of the p14ARF flanking exon 1β in human colorectal cancer displaying a restricted pattern of p53 overexpression concomitant with increased MDM2 expression

CpG site Position relative to ATG % of methylated clones within the 5′ CpG island flanking exon 1β
Tumor samples Normal colon mucosa Tumors with diffuse p53 overexpression pattern Tumors with restricted p53 overexpression pattern
1 −69 13 5 3 17
2 −43 17 1 0 24
3 −40 22 1 0 31
4 −35 25 4 0 36
5 −28 22 2 0 31
6 −22 19 2 0 27
7 −10 22 5 3 30
8 −7 21 3 0 30
9 +4 30 5 3 41
10 +25 41 8 37 43
11 +31 42 12 43 41
12 +34 45 12 50 43
13 +36 43 18 43 43
14 +38 34 12 33 34
15 +42 43 13 43 43
16 +47 41 15 53 36
17 +50 45 9 50 43
18 +52 43 12 57 37
19 +66 47 9 50 46
20 +80 44 9 50 41
21 +82 40 13 37 41
22 +90 38 13 27 43
23 +105 38 13 47 34
24 +114 41 19 50 37
25 +118 34 17 37 33
26 +121 31 24 37 29
27 +133 27 9 13 33
  1. The percentage of methylated clones was calculated in all tumors (n = 10, ≥10 clones analyzed for each tumor) and adjacent normal colon mucosa (n = 10, ≥ 10 clones analyzed for each sample) for every CpG site. The percentage of methylated clones was higher in tumors median 38%, 95% CI 25-41%; range 13-47%), than in normal colon mucosa (median 9%, 95% CI 1 to 24; range 1 to 24%) (Wilcoxon rank sum test, P <0.0001). The percentage of methylated clones on proximal CpG sites was also higher in tumors with a restricted p53 overexpression pattern (median 30%, 95% CI 24 to 36%, range 17 to 36%) than in tumors with a diffuse p53 overexpression pattern (median 0%, 95% CI 0 to 3%, range 0 to 3%) (Wilcoxon rank sum test, P = 0.0003).