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Table 2 The percentage of DNA methylation in CpG rich regions in primary cancerous and histopathologically unchanged tissue samples from patients with CRC.

From: Decreased expression of 17β-hydroxysteroid dehydrogenase type 1 is associated with DNA hypermethylation in colorectal cancer located in the proximal colon

n = 52 Primary cancerous tissues Histopathologically unchanged tissues pa
   Median (range) Mean (± SD) Median (range) Mean (± SD)  
Age       
<60 10 21.05 (12.89-25.79) 20.66 ± 4.205 19.47 (13.16-28.42) 19.32 ± 4.875 0.5181
>60 42 20.00 (4.211-33.16) 20.91 ± 7.074 18.95 (2.105-36.21) 18.42 ± 6.779 0.1076
Gender       
Female 20 24.21 (16.84-33.16) 24.42 ± 4.516 23.68 (13.68-28.42) 21.75 ± 4.499 0.1155
Male 32 18.95 (4.211-32.11) 19.51 ± 7.255 17.37 (2.105-36.21) 18.43 ± 7.206 0.5594
CRC localization       
Proximal colon (cecum to transverse) 20 24.21 ( 13.68-33.16) 23.54 ± 5.793 17.63 ( 2.105435.79) 17.61 ± 6.050 0.0030
Distal colon (splenic flexture to sigmoid) 12 19.47 (4.211-28.95) 19.69 ± 7.159 18.95 (10.53-25.26) 18.85 ± 4.747 0.7498
Rectum 20 19.47 (6.316-28.42) 19.36 ± 6.292 19.47 (4.737-36.21) 19.30 ± 7.851 0.9810
Histologic grade       
G1 4 21.32 (13.68-28.42) 21.18 ± 8.067 17.89 (2.105-27.89) 16.45 ± 10.97 0.5126
G2 35 20.00 (10.53-30.53) 21.17 ± 5.293 19.47 (4.737-28.42) 18.93 ± 5.884 0.0996
G3 13 21.84 (4.211-33.16) 20.21 ± 9.397 15.53 (12.63-36.21) 18.11 ± 6.727 0.4021
  1. The primary cancerous and histopathologically unchanged tissue samples from the same patients were used for genomic DNA isolation, followed by bisulfite conversion of cytosine to uracil. The three DNA fragments of the CpG rich region were then amplified by three pairs of primers complementary to the bisulfite-DNA modified sequence (Additional file 1, Additional file 2). To determine the percentage of methylation, the HRM profiles of the patients' DNA PCR products were compared to HRM profiles of the prepared standard PCR products. DNA methylation for each patient was presented as a percentage of methylation in three DNA amplified fragments located in the CpG rich region (Additional file 1). a Unpaired, two-tailed t-test.