OncologyAberrant methylation-mediated downregulation of long noncoding RNA LOC100130476 correlates with malignant progression of esophageal squamous cell carcinoma
Introduction
Esophageal cancer presents symptomatically late in the course of the disease and, despite currently available therapies, carries a poor survival rate [1]. The incidence and mortality of esophageal cancer continue to rise in the United States and United Kingdom during recent years [2]. Adenocarcinoma (AC) and squamous cell carcinoma (SCC) are the two main histological types of esophageal cancer. Esophageal squamous cell carcinoma (ESCC) is the main type of esophageal cancer in China, and has great geographical as well as sociocultural variation in incidence [3]. Some of the high incidence areas of ESCC are in northern China, especially in some counties bordering Hebei, Henan, and Shanxi Provinces [4]. There is a strong tendency toward familial aggregation of ESCC in these high-risk areas; however, a large proportion of the etiology of ESCC in these populations still remains largely unknown for the moment.
As a type of non-coding RNAs (ncRNAs), long non-coding RNAs (lncRNAs) are molecules greater than 200 nt in length, frequently ranging up to 100 kb [5], [6]. Although initially argued to be spurious transcriptional noise, recent evidence suggests that lncRNAs, the proverbial ‘dark matter’ of the genome may play important roles in a wide range of biological processes including stress response, alternative splicing, chromatin remodeling, mRNA decay, cellular development, differentiation, and metabolism [7], [8]. LncRNAs are highly conserved and may function as key regulators in gene regulation via various ways in the cytoplasm and the nucleus. It is not surprising that dysregulated lncRNAs are involved in many complicated human diseases including cancer [9]. LncRNAs have cell-type-specific expression patterns, and increasing evidence has shown altered expression level of lncRNAs in various types of human cancer and dysregulated lncRNAs may function as tumor suppressors or oncogenes, which may be used as potential early tumor diagnostic, metastatic or prognostic markers and molecular-targeted therapy sites in the future [10]. Though only a handful of lncRNAs have been characterized, recent studies have demonstrated that certain lncRNA are specifically associated with ESCC. Plasma levels of POU3F3 were significantly higher in ESCC patients compared with normal controls [11]. Patients with higher depth of invasion, neoplastic grading and TNM usually demonstrated lower lncRNA 91H expression [12]. Upregulation of the lncRNA PlncRNA-1, MALAT1, TUG1 promoted proliferation and migration of ESCC [13], [14], [15]. Furthermore, dysregulated expression of HOTAIR, CCAT2, PCAT-1, UCA1, LOC285194, FOXCUT, and SPRY4-IT1 were associated with prognosis in patients with ESCC [16], [17], [18], [19], [20], [21], [22].
More recently, it has been recognized that the misregulation of lncRNAs is involved in cancer epigenetics [23], [24]. DNA methylation was one of the first epigenetic alterations identified in cancer. Hypermethylation of specific CpG islands can lead to the silencing of tumor suppressor genes involved in key cellular pathways [25]. Promoter methylation may account for the loss of expression of some lncRNAs including H19, MEG3, and SRHC [26], [27], [28]. We and Cao et al. respectively found a new lncRNA, LOC100130476, which demonstrated greatly reduced expression in ESCC by analyzing ESCC lncRNA expression microarrays [29]. LOC100130476 is located on 6q23.3 (GRCh 38/hg38 database, from chr6: 137823670 to 137868233, NCBI: NR_049793.1) (Fig. 1A) and has three CpG islands spanning the regions from +208 to +1539 bp determined by MethPrimer program. We hypothesized that dysregulation of LOC100130476 may be associated with the occurrence and progression of ESCC and aberrant CpG island methylation may be one of the mechanisms to lead to the inactivation of LOC100130476 in ESCC. In the present study, we examined the function and methylation status of LOC100130476 in esophageal cancer cell lines and ESCC tumor tissues, and further elucidate the role of LOC100130476 in the pathogenesis and prognosis of ESCC.
Section snippets
Cell culture and treatment
A total of four human esophageal cancer cell lines TE1, TE13, T.Tn, and Eca109 were examined in this study. Cells were seeded at a low density and incubated for 24 h prior to treatment with DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine (5-Aza-dC). All four esophageal cancer cells (2 × 105/mL) were treated with 5 μmol/L 5-Aza-dC (Sigma, St Louis, MO, USA) for 72 h and medium containing 5-Aza-dC was changed every 24 h. Control cells received no drug treatment.
Patients and specimens
Surgical primary ESCC tissues and
Frequent silencing of LOC100130476 and up-regulation of the gene by 5-Aza-dC treatment in esophageal cancer cell lines
As shown in Fig. 1B and C, the expression of LOC100130476 was remarkably reduced or silenced in four esophageal cancer cell lines. After treatment with DNA methyltransferase inhibitor 5-Aza-dC, the expression level of LOC100130476 was significantly increased in the four esophageal cancer cell lines, indicating the important role of aberrant methylation in the inactivation of LOC100130476 in esophageal cancer cell lines.
Inhibition effect of LOC100130476 on esophageal cancer cell proliferation
CCK-8 assay was used to examine the proliferation of 5-Aza-dC treated or
Discussion
Dysregulation of lncRNAs have been found in a number of cancers, suggesting the potential possibility of lncRNAs as prospective novel therapeutic targets in cancers. Here, we found a new long noncoding RNA LOC100130476 that may play tumor suppressor gene role in ESCC progression. To our best knowledge, the roles and epigenetic inactivation mechanism of LOC100130476 on tumor progression and prognosis have not been investigated and clarified so far. In the present study, we found silenced or
Conflict of interest
None declared.
Funding
This study was supported by grants from the National Natural Science Foundation (No. 81472335), Natural Science Foundation of Hebei Province (No. H2015206196), and Financial Department of Hebei Province [No. (2012) 2056].
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2019, Journal of Investigative DermatologyCitation Excerpt :Recently, Tsoi et al. (2015) profiled lncRNA expression in psoriasis skin, revealing LOC100130476 as top downregulated in lesional compared with nonlesional skin of psoriasis patients, which is a chronic inflammatory skin disease sharing some features with wounded skin, for example, epidermis thickening and inflammation (Morhenn et al., 2013; Nickoloff et al., 2006). Also, LOC100130476 was recently reported to be downregulated in esophageal squamous cell carcinoma (Guo et al., 2016a). Among the 53 human tissues characterized in the Genotype-Tissue Expression Project (Lonsdale et al., 2013), the skin has the highest LOC100130476 expression, suggesting its functional role in the skin.
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2019, GenomicsCitation Excerpt :LOC100130476 is downregulated in ESCC, and its downregulation is attributed to the hypermethylation of CpG sites in exon 1. Its hypermethylation was also associated with malignant progression and poor patient survival in ESCC [83]. In a very recent study, ADAMTS9-AS1 and another lncRNA, AP000696.2, were introduced together as a novel prognostic biomarker for ESCC [84].
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2018, Cancer LettersCitation Excerpt :LOC100130476 is a lncRNA that contains 3 CpG islands. Guo et al. [32] found that this lncRNA is significantly downregulated in ESCC due to unusual hypermethylation of the CpG sites in exon 1, which is close to the transcription start site of LOC100130476. This finding indicates that LOC100130476 may play a critical role in gene silencing and may lead to an advanced TNM stage and poor differentiation.
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2023, Egyptian Journal of Medical Human Genetics
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These authors contributed equally to this work.