Document Type : Research Articles
Gastroenterohepatology Research Center, Nemazi Hospital, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Internal Medicine, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Biotechnology, School of Advanced Medical Science and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Internal Medicine Hamadan University of Medical Sciences, School of Medicine, Hamedan, Iran.
Department of Pathology, School of Medicine, Shiraz University of Medical sciences, Shiraz, Iran.
Colorectal Research Center, Nemazi hospital, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Introduction: Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide but current molecular targeted
therapy is not providing major success in CRC treatment, so early detection by non-invasive methods continues to
be vital. Aberrant methylation of CpG islands in promoter regions is associated with inactivation of various tumor
suppressor genes. O6-methyguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that removes mutagenic
and cytotoxic adducts from O6-guanine in DNA. Aberrant hypermethylation of the MGMT promoter has been
associated with lack of mRNA expression, with concomitant loss of protein content and enzyme activity. AIM: Our
aim was to determine whether MGMT promoter methylation might be detectable in circulating free DNA in the serum
of CRC patients and normal individuals using a methylation specific (MSP) polymerase chain reaction (PCR) method.
Methods: A total of 70 subjects were enrolled in the study. Of these, 30 patients who were diagnosed previously as
untreated colon adenocarcinoma by a gastroenterologist and the other 40 were nearly age-matched individuals who had
a normal colonoscopic evaluation (except for hemorrhoids or fissures) and normal pathologic reports. After bisulphite
modification of DNA, serum samples were examined for MGMT promoter methylation using MSP. Results: Ninety
percent of CRC patients had MGMT promoter hypermethylation as compared to no methylation in normal subjects’
serum. Most of the cancers were stage П and moderately differentiated adenocarcinomas; nearly 60% were found in
the left colon. No statistically significant correlation was found between the promoter methylation status and gender
and age. Discussion and Conclusions: MGMT hypermethylation can be detected in free circulating DNA in serum of
CRC patients and can be used “as a clinical biomarker” for early diagnosis and prognostic assessment of the disease.
Our data confirm previous studies indicating utility for free circulating DNA as a serum biomarker for early detection,
diagnosis and monitoring of CRC patients.