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Background/aim: Long noncoding RNAs (lncRNAs) are noncoding transcripts that are >200 nucleotides in length. However, the biological functions and regulation mechanisms of lncRNAs in gastric carcinogenesis remain unknown., Materials and Methods: The expression levels of Linc00472 were analyzed by real-time PCR. The DNA methylation status was assessed using Combined Bisulfite Restriction Analysis (COBRA). The biological role of Linc00472 was assessed in AGS cells with Linc00472 overexpression., Results: Using the next-generation sequencing approach, we identified DNA methylation-associated lncRNAs in gastric cancer cells. Among them, the expression level of Linc00472 significantly decreased in gastric cancer tissues compared to adjacent normal tissues. Furthermore, we observed a more frequent hypermethylation of CpG islands upstream of Linc00472 in gastric cancer tissues. Ectopic Linc00472 expression could significantly inhibit gastric cancer cell growth and migration., Conclusion: Epigenetically regulated Linc00472 expression plays a crucial role in modulating gastric cancer cell growth and motility., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background: Long noncoding RNAs (lncRNAs) are more than 200 nucleotides in length and lack transcriptional ability. The biological function of lncRNAs in oral squamous cell carcinoma (OSCC) remains unclear. The aim of this study was to identify the dysfunction of lncRNA in OSCC., Results: We analyzed the transcriptome profiles of human OSCC tissues and paired adjacent normal tissues from two patients through a next-generation sequencing approach. A total of 14 lncRNAs were upregulated (fold change ≥3) and 13 were downregulated (fold change ≤-3) in OSCC tissues compared with the adjacent normal tissues. SOX21-AS1 was subjected to further analysis, revealing that the expression levels of SOX21-AS1 significantly decreased in OSCC compared with the adjacent normal tissue. The promoter activity of SOX21-AS1 was obviously suppressed by in vitro methylation. The DNA methylation status of the SOX21-AS1 promoter was analyzed using combined bisulfite restriction analysis, revealing that the aberrant promoter hypermethylation of SOX21-AS1 was observed frequently in OSCC tissues. The effects of SOX21-AS1 on cell proliferation and invasion were examined through transient transfection. Our data showed that SOX21-AS1 could significantly suppress oral cancer cell growth and invasion. Furthermore, the low expression level of SOX21-AS1 was significantly correlated with an advanced stage ( P  = 0.047), large tumor size ( P  = 0.033), and poor disease-specific survival in OSCC patients ( P  = 0.002)., Conclusions: SOX21-AS1 was identified as susceptible dysfunction correlated with promoter hypermethylation in OSCC. Low SOX21-AS1 expression may be an adverse prognostic biomarker for OSCC.

The isocitrate dehydrogenase (IDH) family of enzymes comprises of the key functional metabolic enzymes in the Krebs cycle that catalyze the conversion of isocitrate to α-ketoglutarate (α-KG). α-KG acts as a cofactor in the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). However, the relationship between 5hmC and IDH in gastric cancer remains unclear. Our study revealed that the 5hmC level was substantially lower and 5mC level was slightly higher in gastric cancer tissues; however, 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) levels did not change significantly in these tissues. We further examined the expression levels of IDH1 and IDH2 in gastric cancer tissues and observed that IDH2 levels were significantly lower in gastric cancer tissues than in the adjacent normal tissues. The ectopic expression of IDH2 can increase 5hmC levels in gastric cancer cells. In conclusion, our results suggested that IDH2 dysfunction is involved in 5hmC depletion during gastric cancer progression., (Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Backgrounds: Oral cancer is the 4th leading cause of cancer death for males and the top cancer in young adult males in Taiwan. Tongue squamous cell carcinoma (TSCC) is a common oral cancer and generally associated with poor prognosis. Global DNA hypomethylation at the 5 position of cytosine (5mC) is a well-known epigenetic feature of cancer. Therefore, the purpose of this study was to investigate the relationship of the global 5mC content with the tumorigenesis and prognosis of patients with TSCC., Methods: The levels of global 5mC were evaluated by immunohistochemistry using tissue microarray slides of 248 surgically resected TSCC and 202 corresponding tumor adjacent normal (TAN) tissues., Results: We found that the level of 5mC in TSCC (P < 0.001) was significantly decreased as compared to TAN. Among TSCC tissues, decreased levels of 5mC were associated with female gender (P = 0.036). In addition, the global hypomethylation was associated with the poor disease-specific survival in TSCC patients (adjusted hazard ratio: 1.55, P = 0.043), especially for patients in older age group (> 50 years, P = 0.013), with moderate or poor cell differentiation (P = 0.044), early stage of disease (I-II, P = 0.046), small tumor size (T1-T2, P = 0.005), without lymph node involvement (P = 0.041), and ever received postoperative radiotherapy (P = 0.009)., Conclusions: Global hypomethylation was an independent biomarker for the development and poor prognosis of TSCC., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

DNA methylation at the 5 position of cytosine (5 mC) is an epigenetic hallmark in cancer. The 5 mC can be converted to 5-hydroxymethylcytosine (5 hmC) through a ten-eleven-translocation (TET). We investigated the impact of 5 mC, 5 hmC, TET1, and TET2 on tumorigenesis and prognosis of breast cancer. Immunohistochemistry was used to assess the levels of 5 mC, 5 hmC, TET1, and TET2 in the corresponding tumor adjacent normal (n = 309), ductal carcinoma in situ (DCIS, n = 120), and invasive ductal carcinoma (IDC, n = 309) tissues for 309 breast ductal carcinoma patients. 5 mC, 5 hmC, TET1-n, and TET2-n were significantly decreased during DCIS and IDC progression. In IDC, the decrease of 5 hmC was correlated with the cytoplasmic mislocalization of TET1 (p < 0.001) as well as poor disease-specific survival (DSS) (adjusted hazard ratio [AHR] 1.95, p = 0.003) and disease-free survival (DFS) (AHR 1.91, p = 0.006). The combined decrease of 5 mC and 5 hmC was correlated with worse DSS (AHR 2.19, p = 0.008) and DFS (AHR 1.99, p = 0.036). Stratification analysis revealed that the low level of 5 mC was associated with poor DSS (AHR 1.89, p = 0.044) and DFS (AHR 2.02, p = 0.035) for the ER/PR-positive subtype. Conversely, the low level of 5 hmC was associated with worse DSS (AHR 2.77, p = 0.002) and DFS (AHR 2.69, p = 0.006) for the ER/PR-negative subtype. The decreases of 5 mC, 5 hmC, TET1-n, and TET2-n were biomarkers of tumor development. The global reduction of 5 hmC was a poor prognostic factor for IDC, especially for ER/PR-negative subtype.

MicroRNAs are small non-coding RNA molecules that play important roles in the multistep process of colorectal carcinoma (CRC) development. The present study evaluated the relationship between miR-1-1 and miR-133a-2 expression and DNA methylation, and its putative biological role in CRC. The results indicated that DNA methylation regulated the expression of the miR-1-1 and miR-133a-2 cluster in CRC cell lines. Expression of miR-1 and miR-133a was further evaluated in 64 paired tissue samples (CRC tumor and adjacent normal mucosa) using the stem-loop real-time polymerase chain reaction. The miR-1-133a cluster displayed significantly lower expression in CRC tissue compared to adjacent normal mucosa (P<0.001). The results also indicated frequent hypermethylation of the CpG islands upstream of miR-1-133a (54.6%). Liver metastatic tissues exhibited significantly lower miR-1 (P<0.001) and miR-133a (P<0.001) expression compared to adjacent normal mucosa. Expression of the miR-1-133a cluster inversely correlated with TAGLN2 in the tumor specimens. In conclusion, epigenetic repression of the miR-1-133a cluster may play a critical role in colorectal cancer metastasis by silencing TAGLN2.

MicroRNAs (miRNAs) are small noncoding RNAs that play fundamental roles in diverse biological and pathological processes by targeting the expression of specific genes. Here, we identified 38 methylation-associated miRNAs, the expression of which could be epigenetically restored by cotreatment with 5-aza-2'-deoxycytidine and trichostatin A. Among these 38 miRNAs, we further analyzed miR-34b, miR-127-3p, miR-129-3p and miR-409 because CpG islands are predicted adjacent to them. The methylation-silenced expression of these miRNAs could be reactivated in gastric cancer cells by treatment with demethylating drugs in a time-dependent manner. Analysis of the methylation status of these miRNAs showed that the upstream CpG-rich regions of mir-34b and mir-129-2 are frequently methylated in gastric cancer tissues compared to adjacent normal tissues, and their methylation status correlated inversely with their expression patterns. The expression of miR-34b and miR-129-3p was downregulated by DNA hypermethylation in primary gastric cancers, and the low expression was associated with poor clinicopathological features. In summary, our study shows that tumor-specific methylation silences miR-34b and miR-129 in gastric cancer cells., (Copyright © 2011 UICC.)