Different patterns of DNA methylation of the two distinct O6-methylguanine-DNA methyltransferase (O6-MGMT) promoter regions in colorectal cancer
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Colorectal cancer (CRC) is the third most common cancer worldwide. Colorectal cancer incidence differs widely among different geographic regions. In addition to mutational changes, epigenetic mechanisms also play important roles in the pathogenesis of CRCs. O6-methylguanine-DNA methyltransferase (O 6 -MGMT) is a DNA repair protein and in the absence of MGMT activity, G-to-A transition may accumulate in the specific genes such as K-ras and p53. To identify which CpG sites are critical for its downregulation, we analyzed the methylation status of the MGMT gene promoter in two sites in CRC patients. Then we compared the frequency of their methylation changes with the results of our previously reported K-ras gene mutation, APC2 and p16 methylation. MGMT methylation was examined in 92 tumor samples. A methylation specific PCR (MSP) method was performed for two loci of MGMT gene which described as MGMT-A and MGMT-B. The prevalence of MGMT-A, and MGMT-B methylation was 49/91 (53.8 %), and 83/92 (90.2 %), respectively. We detected high frequency of MGMT-B but not MGMT-A methylation in tumor tissues with APC2 methylation. Our results showed that MGMT-B methylation is significantly associated with K-ras gene mutation rather than MGMT-A (p = 0.04). Simultaneously, an inverse correlation was found between p16 and MGMT-B methylation simultaneously (p = 0.02). Our study indicated that hypermethylation of the specific locus near the MGMT start codon is critical for cancer progression. MGMT-B assessment that is associated with K-ras mutation can have a prognostic value in patients with CRC.
KeywordsMGMT K-ras APC2 p16 Colorectal cancer
This study was supported by Grant Number 5084 from Vice-chancellor for Research Affairs of Shiraz University of Medical Sciences. We acknowledge the cooperation of Dr.alizadeh from gastroenterohepatology research center, Shiraz University of Medical Sciences, Shiraz-Iran.
Conflict of interest
The authors declare that they have no conflict of interest.
- 4.Higashidani Y, Tamura S, Morita T, Tadokoro T, Yokoyama Y, Miyazaki J, Yang Y, Takeuchi S, Taguchi H, Onishi S (2003) Analysis of K-ras codon 12 mutation in flat and nodular variants of serrated adenoma in the colon. Dis Colon Rectum 46:327–332. doi: 10.1007/s10350-004-6551-z PubMedCrossRefGoogle Scholar
- 13.Zhong S, Fields CR, Su N, Pan YX, Robertson KD (2007) Pharmacologic inhibition of epigenetic modifications, coupled with gene expression profiling, reveals novel targets of aberrant DNA methylation and histone deacetylation in lung cancer. Oncogene 26:2621–2634. doi: 10.1038/sj.onc.1210041 PubMedCrossRefGoogle Scholar
- 14.Gonzalo V, Lozano JJ, Munoz J, Balaguer F, Pellise M, Rodriguez de Miguel C, Andreu M, Jover R, Llor X, Giraldez MD, Ocana T, Serradesanferm A, Alonso-Espinaco V, Jimeno M, Cuatrecasas M, Sendino O, Castellvi-Bel S, Castells A (2010) Aberrant gene promoter methylation associated with sporadic multiple colorectal cancer. PLoS ONE 5:e8777. doi: 10.1371/journal.pone.0008777 PubMedCrossRefGoogle Scholar
- 17.Nakagawachi T, Soejima H, Urano T, Zhao W, Higashimoto K, Satoh Y, Matsukura S, Kudo S, Kitajima Y, Harada H, Furukawa K, Matsuzaki H, Emi M, Nakabeppu Y, Miyazaki K, Sekiguchi M, Mukai T (2003) Silencing effect of CpG island hypermethylation and histone modifications on O6-methylguanine-DNA methyltransferase (MGMT) gene expression in human cancer. Oncogene 22:8835–8844. doi: 10.1038/sj.onc.1207183 PubMedGoogle Scholar
- 19.Mokarram P, Naghibalhossaini F, Saberi Firoozi M, Hosseini SV, Izadpanah A, Salahi H, Malek-Hosseini SA, Talei A, Mojallal M (2008) Methylenetetrahydrofolate reductase C677T genotype affects promoter methylation of tumor-specific genes in sporadic colorectal cancer through an interaction with folate/vitamin B12 status. World J Gastroenterol 14:3662–3671. doi: 10.3748/wjg.14.3662 PubMedCrossRefGoogle Scholar
- 22.Sidhu S, Deep JS, Sobti RC, Sharma VL, Thaku H (2010) Methylation pattern of MGMT gene in relation to age, smoking, drinking and dietary habits as epigenetic biomarker in prostate cancer patients. Genet Eng Biotechnol J 2010(8):1–11Google Scholar
- 23.Wang J, Sasco AJ, Fu C, Xue H, Guo G, Hua Z, Zhou Q, Jiang Q, Xu B (2008) Aberrant DNA methylation of p16, MGMT, and hMLH1 genes in combination with MTHFR C677T genetic polymorphism in esophageal squamous cell carcinoma. Cancer Epidemiol Biomarkers Prev 17:118–125. doi: 10.1158/1055-9965.EPI-07-0733 PubMedCrossRefGoogle Scholar
- 26.Xiao-fang L, Xian-chun S, Cui-sheng Z, Zheng X, Shao-jun L, Xian-ting Z, Shi-jie S (2010) Promoter hypermethylation of O6-methylguanine-DNA methyltransferase gene in cholangiocarcinoma. J Chin Clin Med 5(8):463–468Google Scholar
- 28.Sciuscio D, Diserens AC, van Dommelen K, Martinet D, Jones G, Janzer RC, Pollo C, Hamou MF, Kaina B, Stupp R, Levivier M, Hegi ME (2011) Extent and patterns of MGMT promoter methylation in glioblastoma- and respective glioblastoma-derived spheres. Clin Cancer Res 17:255–266. doi: 10.1158/1078-0432.CCR-10-1931 PubMedCrossRefGoogle Scholar
- 33.De Vogel S, Weijenberg MP, Herman JG, Wouters KA, De Goeij AF, Van den Brandt PA, De Bruine AP, Van Engeland M (2009) MGMT and MLH1 promoter methylation versus APC, K-ras and BRAF gene mutations in colorectal cancer: indications for distinct pathways and sequence of events. Ann Oncol 20:1216–1222. doi: 10.1093/annonc/mdn782 PubMedCrossRefGoogle Scholar
- 34.Fuchikami M, Morinobu S, Segawa M, Okamoto Y, Yamawaki S, Ozaki N, Inoue T, Kusumi I, Koyama T, Tsuchiyama K, Terao T (2011) DNA methylation profiles of the brain-derived neurotrophic factor (BDNF) gene as a potent diagnostic biomarker in major depression. PLoS ONE 6:e23881. doi: 10.1371/journal.pone.0023881 PubMedCrossRefGoogle Scholar
- 36.Shen L, Kondo Y, Rosner GL, Xiao L, Hernandez NS, Vilaythong J, Houlihan PS, Krouse RS, Prasad AR, Einspahr JG, Buckmeier J, Alberts DS, Hamilton SR, Issa JP (2005) MGMT promoter methylation and field defect in sporadic colorectal cancer. J Natl Cancer Inst 97:1330–1338. doi: 10.1093/jnci/dji275 PubMedCrossRefGoogle Scholar
- 38.Brim H, Mokarram P, Naghibalhossaini F, Saberi-Firoozi M, Al-Mandhari M, Al-Mawaly K, Al-Mjeni R, Al-Sayegh A, Raeburn S, Lee E, Giardiello F, Smoot DT, Vilkin A, Boland CR, Goel A, Hafezi M, Nouraie M, Ashktorab H (2008) Impact of BRAF, MLH1 on the incidence of microsatellite instability high colorectal cancer in populations based study. Mol Cancer 7:68. doi: 10.1186/1476-4598-7-68 PubMedCrossRefGoogle Scholar
- 41.Sugai T, Habano W, Jiao YF, Tsukahara M, Takeda Y, Otsuka K, Nakamura S (2006) Analysis of molecular alterations in left- and right-sided colorectal carcinomas reveals distinct pathways of carcinogenesis: proposal for new molecular profile of colorectal carcinomas. J Mol Diagn 8:193–201. doi: 10.2353/jmoldx.2006.050052 PubMedCrossRefGoogle Scholar