Vlaykova T, Mitkova A, Stancheva G, Kadiyska T, Gulubova M, Yovchev Y, Cirovski G, Chilingirov P, Damyanov D, Kremensky I, Mitev V, Kaneva R
Department of Chemistry and Biochemistry, Medical Faculty, Trakia University, Stara Zagora, Bulgaria.
J BUON. 2011 Apr-Jun;16(2):265-73.
Inactivation of the genes involved in DNA mismatch repair (MMR) is associated with microsatellite instability (MSI) and loss of heterozygosity (LOH). The aim of the current study was to assess the presence of MSI and promoter hypermethylation of MLH1 and MSH2 in Bulgarian PATIENTS WITH SPORADIC COLORECTAL CANCER (CRC) AND TO ANALYZE THEIR POSSIBLE EFFECT ON THE DEVELOPMENT, PROGRESSION AND PROGNOSIS OF THE DISEASE.
We examined MSI in 126 patients with sporadic CRC and the methylation status of the MLH1 and MSH2 promoter regions in the cases with MSI/LOH by using a panel of 5 microsatellite markers (BAT26, D5S346, D18S35, D2S123 and FGA) and methyl-specific PCR (MSP) of bisulfite converted DNA.
MSI/LOH was found in 36 (28.6%) patients. Among them, 30 were analyzed for promoter hypermethylation of MLH1 and we detected hypermethylation in 15 (50%) of them, whereas promoter hypermethylation of MSH2 was observed only in one case. The presence of MSI/LOH was associated with younger age (p=0.002), more advanced stage (III/IV stage) (p=0.029), lower degree of differentiation (p=0.001), and right-sided tumor localization (p=0.0002), but not with overall survival (log rank, p=0.566).
Our data suggest that sporadic CRCs with MSI/LOH are more aggressive, develop earlier and progress faster to more advanced stage. The most frequent cause of failure of DNA MMR system appeared to be the hypermethylation of CpG islands of the promoter region of MLH1, whereas the methylation of MSH2 was a rare event.
DNA错配修复（MMR）相关基因的失活与微卫星不稳定性（MSI）和杂合性缺失（LOH）有关。本研究的目的是评估保加利亚散发性结直肠癌（CRC）患者中MSI的存在以及MLH1和MSH2启动子高甲基化情况，并分析它们对疾病发生、发展和预后的可能影响。
我们使用一组5个微卫星标记（BAT26、D5S346、D18S35、D2S123和FGA）以及亚硫酸氢盐转化DNA的甲基化特异性PCR（MSP），检测了126例散发性CRC患者的MSI以及MSI/LOH病例中MLH1和MSH2启动子区域的甲基化状态。
在36例（28.6%）患者中发现了MSI/LOH。其中，对30例进行了MLH1启动子高甲基化分析，我们在其中15例（50%）中检测到高甲基化，而仅在1例中观察到MSH2启动子高甲基化。MSI/LOH的存在与较年轻的年龄（p = 0.002）、更晚期（III/IV期）（p = 0.029）、较低的分化程度（p = 0.001）以及肿瘤位于右侧（p = 0.0002）相关，但与总生存期无关（对数秩检验，p = 0.566）。
我们的数据表明，伴有MSI/LOH的散发性CRC更具侵袭性，发病更早且进展更快至更晚期。DNA错配修复系统功能障碍最常见的原因似乎是MLH1启动子区域CpG岛的高甲基化，而MSH2的甲基化则较为罕见。
