Methylation Levels of LINE-1 As a Useful Marker for Venous Invasion in Both FFPE and Frozen Tumor Tissues of Gastric Cancer

• Published in: Molecules and cells Vol. 40; no. 5; pp. 346 - 354
• Main Authors: Min, Jimin, Choi, Boram, Han, Tae-Su, Lee, Hyuk-Joon, Kong, Seong-Ho, Suh, Yun-Suhk, Kim, Tae-Han, Choe, Hwi-Nyeong, Kim, Woo Ho, Hur, Keun, Yang, Han-Kwang
• Format: Journal Article
• Language: English
• Published: United States Korean Society for Molecular and Cellular Biology 01.05.2017; 한국분자세포생물학회
• Subjects: Aged; Biomarkers, Tumor - genetics; Cryopreservation - methods; DNA Methylation; Female; Formaldehyde; Humans; Long Interspersed Nucleotide Elements; Lymphatic Metastasis - genetics; Lymphatic Metastasis - pathology; Male; Middle Aged; Paraffin Embedding; Stomach Neoplasms - genetics; Stomach Neoplasms - pathology; Tissue Fixation - methods; Veins - pathology; 생물학; LINE-1; pyrosequencing; gastric cancer; venous invasion
• ISSN: 1016-8478; 0219-1032
• DOI: 10.14348/molcells.2017.0013

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 ( < 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 ( < 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.