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Background: Genome-wide sequencing investigations have identified numerous long noncoding RNAs (lncRNAs) among mammals, many of which exhibit aberrant expression in cancers, including esophageal squamous cell carcinoma (ESCC). Herein, this study elucidates the role and mechanism by which LINC01419 regulates the DNA methylation of glutathione S-transferase pi 1 (GSTP1) in relation to ESCC progression and the sensitivity of ESCC cells to 5-fluorouracil (5-FU). Methods: LINC01419 and GSTP1 levels were quantified among 38 paired ESCC and adjacent tissue samples collected from patients with ESCC. To ascertain the contributory role of LINC01419 in the progression of ESCC and identify the interaction between LINC01419 and GSTP1 promoter methylation, LINC01419 was overexpressed or silenced, and the DNA methyltransferase inhibitor 5-Aza-CdR was treated. Results: Data from the GEO database (GSE21362) and the Cancer Genome Atlas displayed elevated levels of LINC01419 and downregulated levels of GSTP1 in the ESCC tissues and cells. The silencing of LINC01419 led to decreased proliferation, increased apoptosis, and enhanced sensitivity to 5-FU in ESCC cells. Notably, LINC01419 could bind to the promoter region of the GSTP1 gene, resulting in elevated GSTP1 methylation and reduced GSTP1 levels via the recruitment of DNA methyltransferase among ESCC cells, whereby ESCC progression was stimulated accompanied by reduced ESCC cell sensitivity to 5-FU. GSTP1 demethylation by 5-Aza-CdR was observed to reverse the effects of LINC01419 overexpression in ESCC cells and the response to 5-FU. Conclusion: Highly expressed LINC01419 in ESCC promotes GSTP1 methylation, which ultimately acts to promote the event of ESCC and diminish the sensitivity of ESCC cells to 5-FU, highlighting a novel potential strategy to improve 5-FU-based chemotherapy in ESCC. [ABSTRACT FROM AUTHOR]

Background and Aim: HOX transcript antisense intergenic RNA (HOTAIR) is a relatively well-understood RNA, which plays a central role in the pathogenesis of various tumors. The aim of the present study was to investigate the effect by which HOTAIR acts to influence the biological processes of colorectal cancer (CRC) through p21.Methods: Reverse transcription quantitative polymerase chain reaction and Western blot methods were employed to provide verification regarding the changes in HOTAIR, PCNA, Ki67, p21, cyclin E, and CDK2 among the CRC tissues and cells. The correlation between the clinicopathological characteristics of patients and expression of HOTAIR and p21 was subsequently evaluated, followed by an analysis into the effects of HOTAIR on the biological processes of M5 cells.Results: HOTAIR was found to be expressed at high levels, while p21 was determined to be at a low level among both the CRC tissues and the CRC cell lines. The expressions of HOTAIR and p21 were determined to be related to lymph node metastasis, tumor node metastasis, Dukes staging, distant metastases, histological types, and the degree of differentiation. Cells transfected with HOTAIR siRNA displayed inhibited rates of proliferation, invasion, and migration, as well as decreased cyclin E and CDK2, while apoptosis and p21 were increased.Conclusion: The principal findings demonstrated that down-regulation of HOTAIR elicits an inhibitory effect on proliferation, invasion, and migration, while promoting the apoptosis of CRC cells through the up-regulation of p21. We believe that HOTAIR could represent a novel target for the treatment of CRC. [ABSTRACT FROM AUTHOR]

Approximately 85% of a single administered dose of 5-fluorouracil (5-FU) will be degraded by dihydropyrimidine dehydrogenase (DYPD). Studies have highlighted a link between the complete or partial loss of DYPD function and clinical responses to 5-FU; however, the underlying molecular basis of DPD deficiency remains poorly understood. Hence, the aim of the present study was to evaluate the prevailing hypothesis which suggests that overexpression of LINC00261 possesses the ability to modulate the methylation-dependent repression of DPYD, ultimately resulting in an elevation of the sensitivity of human esophageal cancer cells to 5-FU. LINC00261 levels were initially quantified, followed by analysis of DYPD methylation within the cancerous tissues collected from 75 patients diagnosed with esophageal cancer undergoing 5-FU-based adjuvant chemotherapy. In an attempt to determine the levels of LINC00261 related to the esophageal cancer cell resistance to 5-FU and to identify the interaction between the levels of LINC00261 and methylation of the DYPD promoter, esophageal cancer cells TE-1 and -5 were prepared, in which LINC00261 and the 5-FU-resistant TE-1 and -5 cells were overexpressed. The levels of LINC00261 were reduced among the cancerous tissues obtained from patients exhibiting resistance to 5-FU. Overexpression of LINC00261 was determined to dramatically inhibit proliferation and resistance to apoptosis among 5-FU-resistant TE-1 and -5 cells, whereas silencing of LINC00261 was determined to enhance proliferation and resistance to apoptosis among the TE-1 and -5 cells. DPYD, a confirmed target of LINC00261, displayed a greater incidence of DNA methylation among patient's sensitive to 5-FU. A key finding revealed that overexpressed LINC00261 could increase the methylation of the DPYD promoter through the recruitment of DNA methyltransferase (DNMT), which, in turn, acts to decrease DPYD activity in 5-FU-resistant TE-1 cells, whereas a reversible change was recorded once the demethylation reagent 5-aza-2'-deoxyctidine was employed to treat the 5-FU-resistant TE-1 cells. Taken together, the results of the study provided evidence emphasizing the distinct antitumor ability of LINC00261 in cases of esophageal cancer, which was manifested by overexpression of LINC00261 detected to increase the sensitivity of human esophageal cancer cells to 5-FU by mediating methylation-dependent repression of DPYD. Our study highlighted the potential of LINC00261 as a novel target capable of improving the chemotherapeutic response and survival of patients with esophageal cancer.-Lin, K., Jiang, H., Zhuang, S.-S., Qin, Y.-S., Qiu, G.-D., She, Y.-Q., Zheng, J.-T., Chen, C., Fang, L., Zhang, S.-Y. Long noncoding RNA LINC00261 induces chemosensitization to 5-fluorouracil by mediating methylation-dependent repression of DPYD in human esophageal cancer.