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Digital archive of theses discussed at the University of Pisa


Thesis etd-03192012-170140

Thesis type
Tesi di dottorato di ricerca
Thesis title
Epigenetic biomarkers, folates and genetic susceptibility in colorectal carcinoma
Academic discipline
Course of study
tutor Prof. Migliore, Lucia
relatore Prof. Miccoli, Paolo
  • colorectal carcinoma
  • Epigenetic
  • folates
Graduation session start date
The implications of DNA hypomethylation and hypermethylation in the etiology of tumorigenesis have become quite clear. Since epigenetic modifications are reversible, methylation studies are extremely promising to better characterize colorectal cancer (CRC) and to identify new tools for diagnosis and prognosis. In the frame of a wider study ongoing aimed at searching for possible correlations among genetic, epigenetic and environmental factors in colorectal cancer, this thesis took into account a cohort of CRC subjects until now recruited, focusing on the following items: 1) the validation of the MS-HRM protocol, used for the methylation analysis, by comparing it with a widely employed technique (Pyrosequencing); 2) the evaluation of the influence of an immunomagnetic method with microbeads coated with the antibody CD326+, specific for epithelial cells, to clarify if cancer epithelial cells from the surgically resected CRC tissue could give more accurate results in DNA methylation levels detection with respect to the whole CRC tissue; 3) the detection of methylation levels (performed by MS-HRM) in promoters of of APC, CDKN2A, hMLH1, MGMT and RASSF1A genes in CRC and healthy adjacent tissue specimens; 4) the analysis of the correlation among the methylation status of the chosen genes and the clinical-pathological features of the patients; 5) the analysis of the correlation among MTHFR C677T, DNMT3B C-149T polymorphisms and the methylation levels of APC, CDKN2A, hMLH1 and MGMT gene promoters. Results obtained by using MS-HRM and Pyrosequencing have shown to be quantitatively comparable. No statistically significant difference between the epithelial cells CD326+ fraction and the whole tissue about the promoter methylation of APC, CDKN2A, MGMT and hMLH1 genes was observed, although some patients showed individually a statistically significant difference between the two experimental conditions regarding the degree of methylation of these genes. It was also seen, for all of the studied genes, a higher methylation level in CRC tissue respect to the healthy adjacent tissue. No statistically significant association between stage (TNM), gender, sex, tumor size, and location with regard to the methylation profile of each of the analyzed genes was found in the examined cohort. However, it was found an interesting positive association between age and both hMLH1 (P value= 0.007) and MGMT (P value= 0.03). Finally significant interactions between MTHFR 677C>T, DNMT3B -149C>T polymorphisms and gene promoter methylation were observed.