Aberrant DNA Hypermethylation Silenced LncRNA Expression in Gastric Cancer.

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.

MiR-193a-5p and -3p Play a Distinct Role in Gastric Cancer: miR-193a-3p Suppresses Gastric Cancer Cell Growth by Targeting ETS1 and CCND1.

BACKGROUND/AIM: MicroRNAs (miRNAs) are small non-protein-coding RNAs, that can be generated from the 5p or 3p arm of precursor miRNA (pre-miRNA). Differential miRNA arm selection has been reported between tumor and normal tissue in many cancer types; however, the biological function and mechanism of miRNA arm switching in gastric cancer remain unclear. MATERIALS AND METHODS: Profiles of miRNA expression in gastric cancer were obtained from The Cancer Genome Atlas (TCGA). The biological role of miR-193a-5p/-3p in tumor growth and invasive abilities was assessed through a gain-of-function approach. Target genes of miR-193a-3p were identified using bioinformatics and an experimental approach. RESULTS: The expression levels of miR-193a-5p, and not of miR-193a-3p, were significantly decreased in gastric cancer compared to adjacent normal tissues. Ectopic expressions of miR-193a-5p and miR-193a-3p revealed that they both inhibited gastric cancer cell growth, but only miR-193a-3p significantly suppressed cell invasion ability. Using a bioinformatics approach, we identified 18 putative target genes of miR-193a-3p. Both mRNA and protein levels of cyclin D1 (CCND1) and ETS proto-oncogene 1 (ETS1) were significantly decreased in AGS cells transfected with miR-193a-3p mimics. ETS1 or CCND1 knockdown significantly suppressed gastric cancer cell growth, similar to miR-193a-3p overexpression. CONCLUSION: Our results indicated that miR-193a-3p suppressed gastric growth and motility, at least partly, by directly targeting CCND1 and ETS1 expression.

Targeting DTL induces cell cycle arrest and senescence and suppresses cell growth and colony formation through TPX2 inhibition in human hepatocellular carcinoma cells.

BACKGROUND: Hepatocellular carcinoma (HCC) has an increasing incidence and high mortality. Surgical operation is not a comprehensive strategy for liver cancer. Moreover, tolerating systemic chemotherapy is difficult for patients with HCC because hepatic function is often impaired due to underlying cirrhosis. Therefore, a comprehensive strategy for cancer treatment should be developed. DTL (Cdc10-dependent transcript 2) is a critical regulator of cell cycle progression and genomic stability. In our previous study, the upregulation of DTL expression in aggressive HCC correlated positively with tumor grade and poor patient survival. We hypothesize that targeting DTL may provide a novel therapeutic strategy for liver cancer. DTL small interference RNAs were used to knock down DTL protein expression. METHODS: A clonogenic assay, immunostaining, double thymidine block, imaging flow cytometry analysis, and a tumor spheroid formation assay were used to analyze the role of DTL in tumor cell growth, cell cycle progression, micronucleation, ploidy, and tumorigenicity. RESULTS: Our results demonstrated that targeting DTL reduced cell cycle regulators and chromosome segregation genes, resulting in increased cell micronucleation. DTL depletion inhibited liver cancer cell growth, increased senescence, and reduced tumorigenesis. DTL depletion resulted in the disruption of the mitotic proteins cyclin B, CDK1, securin, seprase, Aurora A, and Aurora B as well as the upregulation of the cell cycle arrest gene p21. A rescue assay indicated that DTL should be targeted through TPX2 downregulation for cancer cell growth inhibition. Moreover, DTL silencing inhibited the growth of patient-derived primary cultured HCC cells. CONCLUSION: Our study results indicate that DTL is a potential novel target gene for treating liver cancer through liver cancer cell senescence induction. Furthermore, our results provide insights into molecular mechanisms for targeting DTL in liver cancer cells. The results also indicate several other starting points for future preclinical and clinical studies on liver cancer treatment.

Ten-eleven translocation 1 dysfunction reduces 5-hydroxymethylcytosine expression levels in gastric cancer cells.

A sixth base, 5-hydroxymethylcytosine (5hmC), is formed by the oxidation of 5-methylcytosine (5mC) via the catalysis of the ten-eleven translocation (TET) protein family in cells. Expression levels of 5hmC are frequently depleted during carcinogenesis. However, the detailed mechanisms underlying the depletion of 5hmC expression in gastric cancer cells remains unclear, and further research is required. The present study examined the expression levels of 5mC and 5hmC and the expression levels of TET1 and TET2 in gastric cancer tissues using immunohistochemistry. The results revealed that 5hmC expression levels were markedly lower in gastric cancer tissues compared with corresponding adjacent normal tissues. Furthermore, a decrease in 5hmC expression levels was associated with a decrease in TET1 protein expression levels in gastric cancer tissues. The ectopic expression level of TET1 may increase the 5hmC expression level in gastric cancer cells. In addition, the results revealed that TET1 protein expression was markedly different in regards to subcellular localization, and mislocalization was significantly associated with the depletion of 5hmC expression levels in gastric cancer. Together, the results of the present study indicated that TET1 dysfunction reduces 5hmC expression levels, and this phenomenon may serve a crucial role in gastric cancer progression.

Isocitrate Dehydrogenase 2 Dysfunction Contributes to 5-hydroxymethylcytosine Depletion in Gastric Cancer Cells.

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.

Analysis of Recurrence Management in Patients Who Underwent Nonsurgical Treatment for Acute Appendicitis.

The recurrence rate for acute appendicitis treated nonoperatively varies between studies. Few studies have adequately evaluated the management of these patients when appendicitis recurs. We aimed to explore the recurrence rate and management of patients with acute appendicitis that were first treated nonoperatively.We identified patients in the Taiwan National Health Insurance Research Database who were hospitalized due to acute appendicitis for the first time between 2000 and 2010 and received nonsurgical treatment. The recurrence and its management were recorded. Data were analyzed to access the risk factors for recurrence and factors that influenced the management of recurrent appendicitis.Among the 239,821 patients hospitalized with acute appendicitis for the first time, 12,235 (5.1%) patients were managed nonoperatively. Of these, 864 (7.1%) had a recurrence during a median follow-up of 6.5 years. Appendectomy was performed by an open and laparoscopic approach in 483 (55.9%) and 258 (29.9%) patients, respectively. The remaining 123 (14.2%) patients were again treated nonsurgically. Recurrence was independently associated with young age, male sex, percutaneous abscess drainage, and medical center admission by multivariable analysis. In addition, age <18, a (CCI) <2, medical center admission, and a longer time to recurrence were correlated with using laparoscopy to treat recurrence. Neither type of appendicitis, percutaneous abscess drainage, nor length of first time hospital stay had an influence on the selection of surgical approach.In conclusion, a laparoscopic appendectomy can be performed in recurrent appendicitis cases, and its application may not be related to previous appendicitis severity.