The specific methylation characteristics of cancer related genes in Chinese colorectal cancer patients

Tumour Biol. 2014 Aug;35(8):8267-79. doi: 10.1007/s13277-014-2100-0. Epub 2014 May 23.

Abstract

Aberrant DNA methylation at CpG islands has been implicated as a critical player in colorectal cancer (CRC). However, its biological role and clinical significance in carcinogenesis have not been clearly clarified in Chinese CRC patients. In order to examine the methylation status of cancer-related genes in CRC progression, 184 tumor tissues were collected from Chinese patients diagnosed with CRC during 2008-2011. Promoter methylation was assessed by combined bisulphite-restriction analysis, methylation-specific PCR, and bisulphite sequencing PCR . The relationship between the gene promoter methylation status and clinicopathological factors/CRC mortality was examined by using the chi-square test/Cox-proportional hazards models. Promoter hypermethylation of MLH1, p16, SFRP2, PHD3, KLOTHO, and IGFBP7 was observed in 1.6, 10.9, 97.3, 44.0, 59.8, and 88.6 % of CRC samples, respectively. KLOTHO promoter methylation reduced with age (P = 0.018) whereas p16 promoter methylation increased with age (P = 0.044) and was more frequent among males (P = 0.017). Tumor tissues (73.9 %) had concurrent methylation of two or more genes, with the most frequent combination as KLOTHO and IGFBP7 (53.8 %). Concurrent methylation of KLOTHO and IGFBP7 occurred more frequently among patients less than 70 years old (P = 0.035) and those with poor differentiation (P = 0.024). CRC-specific mortality was not associated with promoter methylation and clinicopathological features except for age (P = 0.038; risk ratio (RR), 1.96; 95 % confidence interval (CI), 1.04-3.70) and TNM stage (P = 0.034; RR, 3.47; 95 % CI, 1.10-10.92). Methylation frequencies of MLH1, p16, PHD3, KLOTHO, and IGFBP7 in CRC tissues were significantly higher than that in the paired normal tissues, while promoter hypermethylation of SFRP2 was widespread in normal tissues. In conclusion, we suggest that methylation of some genes (MLH1, PHD3, KLOTHO, p16, and IGFBP7) is important in CRC progression whereas SFRP2 methylation is unlikely to contribute to CRC development in Chinese patients. Besides, by identifying the characteristics of concordant methylation, we confirm the multifactorial nature of tumor progression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adult
  • Aged
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • DNA Methylation*
  • Female
  • Glucuronidase / genetics
  • Humans
  • Hypoxia-Inducible Factor-Proline Dioxygenases / genetics
  • Insulin-Like Growth Factor Binding Proteins / genetics
  • Klotho Proteins
  • Male
  • Membrane Proteins / genetics
  • Middle Aged
  • MutL Protein Homolog 1
  • Neoplasm Staging
  • Nuclear Proteins / genetics
  • Promoter Regions, Genetic

Substances

  • Adaptor Proteins, Signal Transducing
  • Insulin-Like Growth Factor Binding Proteins
  • MLH1 protein, human
  • Membrane Proteins
  • Nuclear Proteins
  • SFRP2 protein, human
  • insulin-like growth factor binding protein-related protein 1
  • EGLN3 protein, human
  • Hypoxia-Inducible Factor-Proline Dioxygenases
  • Glucuronidase
  • Klotho Proteins
  • MutL Protein Homolog 1