METHYLATION PROFILE OF hMLH1, MGMT, APC AND CDH1 GENES IN GREEK PATIENTS WITH COLON ADENOCARCINOMA

• Published in: Anticancer research 2008-10, Vol.28 (5C)
• Main Authors: Michailidi, C I, Theocharis, SE, Kouraklis, G P, Katsaronis, P, Troungos, C
• Format: Article
• Language: English
• ISSN: 0250-7005

Introduction: Colon cancer is a common malignancy usually arising from a benign neoplasm which is developed into adenocarcinoma through a certain histological progression sequence. Genomic instability and epigenetic alterations - with hypermethylation of cytosine in CpG islands in the promoter of certain genes- play an important role in carcinogenesis and tumour progression of this type of cancer. Epigenetic changes conduce to cancer formation through the transcriptional silencing of certain genes. The aim of this study was to analyze the promoter methylation of genes related with mismatch repair as hMLH1; repair genes like MGMT which interferes in the repair of damages in O super(6) position of guanine by removing alkyl groups; tumour suppressor genes as APC and possible tumour suppressor genes like CDH1 which encodes epithelial cadherin preventing cells from growing and dividing in an uncontrolled way to form a malignant tumour. Materials and Methods: Genomic DNA was isolated from 28 colon cancer patients (14Male/14Female), with mean age 64 years. DNA was then subjected to chemical modification with sodium bisulfate and followed by Methylation Specific PCR (MSP) amplified by primer pairs specific for the methylated and unmethylated sequences. PCR products were analyzed on 2% agarose gel, stained with ethidium bromide and visualized in UV. The methylation results were associated with patients' gender and age, tumours' histological grade and stage. Results: Promoter methylation for hMLHl gene was observed in 1 out of 28 (3%), for MGMT in 15 out of 28 (53%), for APC in 5 out of 28 (18%) and for CDH1 in 24 out of 28 (86%). In 15 out of 28 (61%) cases methylation in 2 or more of the examined genes was noted. Methylation profiles were also associated with clinicopathological characteristics of the colon cancer patients. A statistically significant association between methylation of CDH1 gene and Dukes' stage (stage A, B, C vs. D; p=0.002) was found. Moreover, an association (although not statistically significant) between methylation status in two or more genes with either tumour histological grade (well and moderately vs. poorly differentiated) or Dukes' stage (stage A, B, C vs. D) was also noted (p=0.055 and p=0.063, respectively). Conclusion: Our data confirmed alterations in the methylation status of hMLHl, APC and MGMT genes in colon cancer, although no significant association was noticed with any of the examined clinicopathological parameters. Additional