• 생명과학회지
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• 제27권10호
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• pp.1215-1224
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• 2017

현재까지 다양한 암의 발병 원인이 밝혀졌는데, 그 중 하나로써 DNA에 돌연변이가 축적되어 유전체가 불안정 해짐에 따라 암이 발생될 수 있는 기작들이 주목받고 있다. 생물정보학과 유전체학의 발달에 따라 질병 연구에 있어서 보다 더 정확하고 신뢰성 있는 바이오마커를 찾는 것이 가능해졌다. 따라서, 생물정보학과 유전체학의 연구 기반을 바탕으로 한 암의 바이오마커는 암의 조기진단뿐만 아니라, 더 나아가 암 발생 예측과 암환자의 예후 진단에 적용될 수 있다. 최근 들어 인간 유전체에서 약 45%를 차지하는 이동성 유전인자(transposable elements, TEs)가 유전자의 발현 조절과 DNA의 돌연변이를 유도함으로써 다양한 질병에 영향을 미친다는 사실이 밝혀짐에 따라, 이러한 이동성 유전인자들이 암의 발생과 어떤 연관이 있는지에 대한 연구 또한 활발히 진행되고 있다. 따라서 우리는 이동성 유전인자가 대장암과 어떤 연관성이 있는지에 대해 조사를 하였으며, 이를 어떻게 바이오마커로 활용할 수 있는지 알아보았다. 우선, 이동성 유전인자 중 인간 유전체에 많이 존재하면서 유전체에 많은 영향을 미치는 LINE-1 (long interspersed nuclear element-1, L1)과 Alu, LTR (long terminal repeat) 위주로 확인하였다. 흥미롭게도, 대장암 세포에서 LINE-1의 저메틸화, APC 유전자 내에 LINE-1 삽입, Alu의 저메틸화와 과메틸화, LTR 삽입에 따른 isoform 발생 등이 특징적으로 나타나는 것을 알 수 있었다. 또한 원발암유전자에서의 L1 저메틸화가 대장암 전이의 바이오마커로 쓰일 수 있다는 것과 Alu에 의한 MLH1 돌연변이가 가족성 및 유전성 대장암에서 흔히 발견된다는 것을 알 수 있었다. 이 때 이동성 유전인자에 의하여 영향 받는 유전자들의 발현을 in silico 발현 분석을 통하여 분석하였으며, 조직별, 성별 특이적 발현 양상을 제시하였다. 이들을 토대로 대장암 바이오마커를 개발하여 유전성 대장암의 예측 및 대장암 진단 또는 대장암 예후 예측을 통한 개인 맞춤형 치료에 활용할 수 있을 것으로 예상된다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권6호
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• pp.3773-3778
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• 2013

Increased oxidative stress and changes in DNA methylation are frequently detected in bladder cancer patients. We previously demonstrated a relationship between increased oxidative stress and hypomethylation of the transposable long-interspersed nuclear element-1 (LINE-1). Promoter hypermethylation of a tumor suppressor gene, runt-related transcription factor 3 (RUNX3), may also be associated with bladder cancer genesis. In this study, we investigated changes of DNA methylation in LINE-1 and RUNX3 promoter in a bladder cancer cell (UM-UC-3) under oxidative stress conditions, stimulated by challenge with $H_2O_2$ for 72 h. Cells were pretreated with an antioxidant, tocopheryl acetate for 1 h to attenuate oxidative stress. Methylation levels of LINE-1 and RUNX3 promoter were measured by combined bisulfite restriction analysis PCR and methylation-specific PCR, respectively. Levels of LINE-1 methylation were significantly decreased in $H_2O_2$-treated cells, and reestablished after pretreated with tocopheryl acetate. Methylation of RUNX3 promoter was significantly increased in cells exposed to $H_2O_2$. In tocopheryl acetate pretreated cells, it was markedly decreased. In conclusion, hypomethylation of LINE-1 and hypermethylation of RUNX3 promoter in bladder cancer cell line was experimentally induced by reactive oxygen species (ROS). The present findings support the hypothesis that oxidative stress promotes urothelial cell carcinogenesis through modulation of DNA methylation. Our data also imply that mechanistic pathways of ROS-induced alteration of DNA methylation in a repetitive DNA element and a gene promoter might differ.

• Molecules and Cells
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• 제40권5호
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• pp.346-354
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• 2017

Long interspersed nuclear element-1 (LINE-1) is a retrotransposon that contains a CpG island in its 5'-untranslated region. The CpG island of LINE-1 is often heavily methylated in normal somatic cells, which is associated with poor prognosis in various cancers. DNA methylation can differ between formalin-fixed paraffin-embedded (FFPE) and frozen tissues. Therefore, this study aimed to compare the LINE-1 methylation status between the two tissue-storage conditions in gastric cancer (GC) clinical samples and to evaluate whether LINE-1 can be used as an independent prognostic marker for each tissue-storage type. We analyzed four CpG sites of LINE-1 and examined the methylation levels at these sites in 25 FFPE and 41 frozen GC tissues by quantitative bisulfite pyrosequencing. The LINE-1 methylation status was significantly different between the FFPE and frozen GC tissues (p < 0.001). We further analyzed the clinicopathological features in the two groups separately. In the frozen GC tissues, LINE-1 was significantly hypomethylated in GC tissues compared to their corresponding normal gastric mucosa tissues (p < 0.001), and its methylation status was associated with gender, differentiation state, and lymphatic and venous invasion of GC. In the FFPE GC tissues, the methylation levels of LINE-1 differed according to tumor location and venous invasion of GC. In conclusion, LINE-1 can be used as a useful methylation marker for venous invasion in both FFPE and frozen tumor tissues of GC.