Bagci Binnur, Sari Musa, Karadayi Kursat, Turan Mustafa, Ozdemir Ozturk, Bagci Gokhan
Department of Nutrition and Dietetics, Faculty of Health Sciences, Cumhuriyet University, Sivas, Turkey.
Advanced Technology Research Center (CÜTAM), Cumhuriyet University, Sivas, Turkey.
Cancer Biomark. 2016 Jun 24;17(2):133-43. doi: 10.3233/CBM-160624.
Colorectal cancer is a serious disease that causes significant morbidity and mortality in developed countries. Genetic changes, such as mutations in proto-oncogenes and DNA repair genes, and loss of function in the tumor suppressor genes cause colorectal cancer development. Abnormal DNA methylation is also known to play a crucial role in colorectal carcinogenesis.
In this study, frequencies of KRAS and BRAF mutations, promoter hypermethylation profiles of SFRP2, DAPK1, MGMT, HIC1 and p16 genes, and possible associations between hypermethylation of these genes and KRAS and BRAF mutations were aimed to find out.
Ninety three colorectal cancer tissues and 14 normal colon mucosas were included in the study. Common twelve KRAS gene mutation were investigated with using reverse-hybridization strip assay method. BRAF V600E mutations were investigated with RFLP method. Hypermethylation status of five tumor suppressor genes were detected by using reverse-hybridization strip assay method after bisulfite modification of DNA.
KRAS and BRAF mutation frequencies were determined as 54.84% and 12.9%, respectively. Promoter hypermethylation frequencies of tumor suppressor genes SFRP2, DAPK1, MGMT, HIC1 and p16 were determined as 66.7%, 45.2%, 40.9%, 40.9% and 15.1%, respectively. Statistically significant associations were found between BRAF mutation and SFRP2 and p16 tumor suppressor genes hypermethylation (SFRP2; p= 0.005, p16; p= 0.016). Compared to rectum, SFRP2 (p= 0.017) and MGMT (p= 0.013) genes have statistically significantly higher promoter hypermethylation in colon.
Results of the current study have confirmed that KRAS mutations and SFRP2 hypermethylation can be used as genetic markers in colorectal cancer.
在发达国家，结直肠癌是一种导致严重发病和死亡的疾病。基因变化，如原癌基因和DNA修复基因的突变以及肿瘤抑制基因功能的丧失会导致结直肠癌的发生。异常的DNA甲基化在结直肠癌的发生过程中也起着关键作用。
在本研究中，旨在找出KRAS和BRAF突变的频率、SFRP2、DAPK1、MGMT、HIC1和p16基因的启动子高甲基化谱，以及这些基因的高甲基化与KRAS和BRAF突变之间的可能关联。
本研究纳入了93个结直肠癌组织和14个正常结肠黏膜。采用反向杂交条带分析法研究常见的12种KRAS基因突变。采用RFLP法研究BRAF V600E突变。DNA经亚硫酸氢盐修饰后，采用反向杂交条带分析法检测5个肿瘤抑制基因的高甲基化状态。
KRAS和BRAF突变频率分别确定为54.84%和12.9%。肿瘤抑制基因SFRP2、DAPK1、MGMT、HIC1和p16的启动子高甲基化频率分别确定为66.7%、45.2%、40.9%、40.9%和15.1%。发现BRAF突变与SFRP2和p16肿瘤抑制基因高甲基化之间存在统计学显著关联（SFRP2；p = 0.005，p16；p = 0.016）。与直肠相比，结肠中SFRP2（p = 0.017）和MGMT（p = 0.013）基因的启动子高甲基化在统计学上显著更高。
本研究结果证实，KRAS突变和SFRP2高甲基化可作为结直肠癌的遗传标志物。
