Overexpression of long noncoding RNA H19 indicates a poor prognosis for cholangiocarcinoma and promotes cell migration and invasion by affecting epithelial-mesenchymal transition

The Diagnostic and Prognostic Potentials of Non-Coding RNA in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare biliary tract tumor with high malignancy. CCA is the second most common primary hepatobiliary cancer after hepatocarcinoma. Despite its rarity, the incidence of CCA is steadily increasing globally. Most patients with CCA are asymptomatic in the early stages, resulting in a late-stage diagnosis and poor prognosis. Finding reliable biomarkers is essential to improve CCA's early diagnosis and survival rate. Non-coding RNAs (ncRNAs) are non-protein coding RNAs produced by genomic transcription. This includes microRNAs, long non-coding RNAs, and circular RNAs. ncRNAs have multiple functions in regulating gene expression and are crucial for maintaining normal cell function and developing diseases. Many studies have shown that aberrantly expressed ncRNAs can regulate the occurrence and development of CCA. ncRNAs can be easily extracted and detected through tumor tissue and liquid biopsies, representing a potential tool for diagnosing and prognosis CCA. This review will provide a detailed update on the diagnostic and prognostic potentials of lncRNAs and cirRNAs as biomarkers in CCA.

Long non-coding RNA H19: a potential biomarker and therapeutic target in human malignant tumors

Long non-coding RNAs play important roles in cellular functions and disease development. H19, as a long non-coding RNA, is pervasively over-expressed in almost all kinds of human malignant tumors. Although many studies have reported that H19 is closely associated with tumor cell proliferation, apoptosis, invasion, metastasis, and chemoresistance, the role and mechanism of H19 in gene regulation and tumor development are largely unclear. In this review, we summarized the recent progress in the study of the major functions and mechanisms of H19 lncRNA in cancer development and progression. H19 possesses both oncogenic and tumor-suppressing activities, presumably through regulating target gene transcription, mRNA stability and splicing, and competitive inhibition of endogenous RNA degradation. Studies indicate that H19 may involve in cell proliferation and apoptosis, tumor initiation, migration, invasion, metastasis and chemoresistance and may serve as a potential biomarker for early diagnosis, prognosis, and novel molecular target for cancer therapy.

Long Noncoding RNA H19: A Novel Oncogene in Liver Cancer

Liver cancer is the second leading cause of cancer-related death globally, with limited treatment options. Recent studies have demonstrated the critical role of long noncoding RNAs (lncRNAs) in the pathogenesis of liver cancers. Of note, mounting evidence has shown that lncRNA H19, an endogenous noncoding single-stranded RNA, functions as an oncogene in the development and progression of liver cancer, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), the two most prevalent primary liver tumors in adults. H19 can affect many critical biological processes, including the cell proliferation, apoptosis, invasion, and metastasis of liver cancer by its function on epigenetic modification, H19/miR-675 axis, miRNAs sponge, drug resistance, and its regulation of downstream pathways. In this review, we will focus on the most relevant molecular mechanisms of action and regulation of H19 in the development and pathophysiology of HCC and CCA. This review aims to provide valuable perspectives and translational applications of H19 as a potential diagnostic marker and therapeutic target for liver cancer disease.

A review on the role of ncRNAs in the pathogenesis of cholangiocarcinoma

Cholangiocarcinoma is a rare tumor but a challenging cancer in terms of pathological changes, clinical manifestations and therapeutic options. Recent studies have provided evidence for participation of non-coding RNAs in the carcinogenic process of cholangiocarcinoma. We demonstrate the role of long non-coding RNAs, microRNAs and circular RNAs in the pathogenesis of cholangiocarcinoma and highlight their significant position as therapeutic targets and biomarkers for this type of cancer. We also list a number of molecular axes comprising these non-coding RNAs that represent potential targets for therapeutic options in cholangiocarcinoma, based on their significant roles in the regulation of cell proliferation, differentiation and apoptosis of these cells.

Long Non-Coding RNAs as Molecular Biomarkers in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a biliary system cancer that has the characteristics of strong invasiveness, poor prognosis, and few therapy choices. Furthermore, the absence of precise biomarkers for early identification and prognosis makes it hard to intervene in the early phase of initial diagnosis or recurring cholangiocarcinoma following surgery. Encouragingly, previous studies found that long non-coding RNA (lncRNA), a subgroup of RNA that is more than 200 nucleotides long, can affect cell proliferation, migration, apoptosis, and even drug resistance by altering numerous signaling pathways, thus reaching pro-cancer or anti-cancer outcomes. This review will take a retrospective view of the recent investigations on the work of lncRNAs in cholangiocarcinoma progression and the potential of lncRNAs serving as promising clinical biomarkers and therapeutic targets for CCA.

Prognostic and Predictive Molecular Markers in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is the second most common primary liver cancer and subsumes a heterogeneous group of malignant tumors arising from the intra- or extrahepatic biliary tract epithelium. A rising mortality from CCA has been reported worldwide during the last decade, despite significant improvement of surgical and palliative treatment. Over 50% of CCAs originate from proximal extrahepatic bile ducts and constitute the most common CCA entity in the Western world. Clinicopathological characteristics such as lymph node status and poor differentiation remain the best-studied, but imperfect prognostic factors. The identification of prognostic molecular markers as an adjunct to traditional staging systems may not only facilitate the selection of patients who would benefit the most from surgical, adjuvant or palliative treatment strategies, but may also be helpful in defining the aggressiveness of the disease and identifying patients at high-risk for tumor recurrence. The purpose of this review is to provide an overview of currently known molecular prognostic and predictive markers and their role in CCA.

Cholangiocarcinoma and liver transplantation: What we know so far?

Cholangiocarcinoma (CCA) is a type of cancer with increasing prevalence around the world that originates from cholangiocytes, the epithelial cells of the bile duct. The tumor begins insidiously and is distinguished by high grade neoplasm, poor outcome, and high risk for recurrence. Liver transplantation has become broadly accepted as a treatment option for CCA. Liver transplantation is expected to play a crucial role as palliative and curative therapy for unresectable hilar CCA and intrahepatic CCA. The purpose of this study was to determine which cases with CCA should be subjected to liver transplantation instead of resection, although reported post-transplant recurrence rate averages approximately 20%. This review also aims to highlight the molecular current frontiers of CCA and directions of liver transplantation for CCA.

LncRNA H19: A novel oncogene in multiple cancers

Long non-coding RNAs (lncRNAs) are a series of non-coding RNAs that lack open reading frameworks. Accumulating evidence suggests important roles for lncRNAs in various diseases, including cancers. Recently, lncRNA H19 (H19) became a research focus due to its ectopic expression in human malignant tumors, where it functioned as an oncogene. Subsequently, H19 was confirmed to be involved in tumorigenesis and malignant progression in many tumors and had been implicated in promoting cell growth, invasion, migration, epithelial-mesenchymal transition, metastasis, and apoptosis. H19 also sequesters some microRNAs, facilitating a multilayer molecular regulatory mechanism. In this review, we summarize the abnormal overexpression of H19 in human cancers, which suggests wide prospects for further research into the diagnosis and treatment of cancers.

Hypomethylation of lncRNA H19 as a potential prognostic biomarker for oral squamous cell carcinoma

OBJECTIVES

Dysregulated DNA methylation is common in cancers and is considered one of the most important triggers in cancer development and progression. The expression and promoter methylation status of long non-coding RNA (lncRNA) H19 play a key role in several cancers, but its role is unclear in oral cancer. The aim of this study was to evaluate the potential of lncRNA H19 as a prognostic biomarker for oral cancer.

DESIGNS

The transcript levels and the methylation status of lncRNA H19 in OSCC cell lines and OSCC patient tissues were investigated by quantitative real-time RT-PCR (qRT-PCR) and methylation-specific PCR (MSP). Methylation ratio (%) were calculated from the intensity of the MSP in the gel image and Kaplan-Meier survival analysis of OSCC patient survival was performed for patients grouped according to the lncRNA H19 promoter methylation ratio.

RESULTS

lncRNA H19 was highly expressed and its promoter region was hypomethylated in OSSC cell lines as compared to normal control. Almost all OSCC patients tissues (63 out of 65, 97 %) showed hypomethylation of lncRNA H19 compared to normal oral mucosa tissues. There was a significant correlation between methylation ratio and tumor histopathologic grade. OSCC patients with hypomethylation of lncRNA H19 had a significantly lower 5-year survival rate.

CONCLUSIONS

Hypomethylation of lncRNA H19 may serve as a potential prognostic biomarker for oral cancer.

LINC01559 promotes colorectal cancer via sponging miR-1343-3p to modulate PARP1/PTEN/AKT pathway

BACKGROUND

Colorectal cancer (CRC) is considered as one of the commonest tumors and is the major reason of cancer-related deaths around the world. Plentiful evidences have validated that long non-coding RNAs (lncRNAs) play a significant part in various cancers, including CRC. LINC01559 is implicated in the development of various cancers. However, the detailed function of LINC01559 in CRC has not been illustrated.

METHODS

LINC01559 expression was examined via RT-qPCR, and a series of functional experiments were conducted to explore the role of LINC01559 in CRC progression. Mechanism experiments were carried out to examine the underlying mechanism of LINC01559.

RESULTS

LINC01559 expression was increased in CRC cells and tissues, and LINC01559 depletion restrained the biological behaviors of CRC cells. Also, LINC01559 sponged miR-1343-3p in CRC, and PARP1 was the target of miR-1343-3p. Besides, miR-1343-3p overexpression or PARP1 down-regulation affected the biological behaviors of CRC cells. In addition, up-regulation of PARP1 or adding SC79 (AKT pathway activator) could remedy the repressive effects of LINC01559 silencing on CRC cell biological behaviors.

CONCLUSIONS

LINC01559 promotes CRC through sponging miR-1343-3p to modulate PARP1/PTEN/AKT pathway, which may be conducive to offering a new idea for CRC therapeutic treatment.

Role of long non-coding RNA H19 in therapy resistance of digestive system cancers

Digestive system cancers are associated with high morbidity and mortality. Chemotherapy and radiotherapy are the main treatment modalities for these cancers. However, the development of therapy resistance leads to high rates of tumor recurrence and metastasis, resulting in dismal prognosis. Long non-coding RNA (LncRNA) H19, one of the most intriguing non-coding RNAs, has been shown to play a key role in the development and therapy resistance of various digestive system cancers (including hepatocellular carcinoma, colorectal cancer, pancreatic ductal adenocarcinoma, esophageal carcinoma, gastric cancer, and biliary system cancer) by regulating the abnormal expression of genes. In this review, we discuss the potential mechanisms of LncRNA H19 related therapy resistance in the context of digestive system cancers. LncRNA H19 is a potential novel therapeutic target for amelioration of cancer therapy resistance.

HDAC2 inhibits EMT-mediated cancer metastasis by downregulating the long noncoding RNA H19 in colorectal cancer

BACKGROUND

Emerging evidence suggests that epithelial mesenchymal transition (EMT) and epigenetic mechanisms promote metastasis. Histone deacetylases (HDACs) and noncoding RNAs (ncRNAs) are important epigenetic regulators. Here, we elucidated a novel role of histone deacetylase 2 (HDAC2) in regulating EMT and CRC metastasis via ncRNA.

METHODS

The expression of HDACs in CRC was analyzed using the public databases and matched primary and metastatic tissues, and CRC cells with different metastatic potentials (DLD1, HCT116, SW480 and SW620). Microarray analysis was used to identify differential genes in parental and HDAC2 knockout CRC cells. EMT and histone modifications were determined using western blot and immunofluorescence. Migration ability was assessed by transwell assay, and metastasis was assessed in vivo using a tail vain injection. Gene expression and regulation was assessed by RT-PCR, chromatin immunoprecipitation and reporter assays. Protein interaction was assessed by immunoprecipitation. Specific siRNAs targeting H19, SP1 and MMP14 were used to validate their role in HDAC2 loss induced EMT and metastasis.

RESULTS

Reduced HDAC2 expression was associated with poor prognosis in CRC patients and found in CRC metastasis. HDAC2 deletion or knockdown induced EMT and metastasis by upregulating the long noncoding RNA H19 (LncRNA H19). HDAC2 inhibited LncRNA H19 expression by histone H3K27 deacetylation in its promoter via binding with SP1. LncRNA H19 functioned as a miR-22-3P sponge to increase the expression of MMP14. HDAC2 loss strongly promoted CRC lung metastasis, which was suppressed LncRNA H19 knockdown.

CONCLUSION

Our study supports HDAC2 as a CRC metastasis suppressor through the inhibition of EMT and the expression of H19 and MMP14.

Emerging roles of long noncoding RNAs in cholangiocarcinoma: Advances and challenges

Cholangiocarcinoma (CCA), a cancer with a relatively low incidence rate, is usually associated with poor prognosis. Current modalities for the diagnosis and treatment of CCA patients are still far from satisfactory. In recent years, numerous long noncoding RNAs (lncRNAs) have been identified as crucial players in the development of various cancers, including CCA. Abnormally expressed lncRNAs in CCA, regulated by some upstream molecules, significantly influence the biological behavior of tumor cells and are involved in tumor development through various mechanisms, including interactions with functional proteins, participation in competing for endogenous RNA (ceRNA) regulatory networks, activation of cancer‐related signaling pathways and epigenetic modification of gene expression. Furthermore, several lncRNAs are closely associated with the clinicopathological features of CCA patients, and are promising biomarkers for diagnosing and prognostication of CCA. Some of these lncRNAs play an important role in chemotherapy drug resistance. In addition, lncRNAs have also been shown to be involved in the inflammation microenvironment of CCA and malignant outcome of CCA risk factors, such as cholestatic liver diseases. In view of the difficulty of diagnosing CCA, more attention should be paid to detectable lncRNAs in the serum or bile. This review summarizes the recent knowledge on lncRNAs in CCA and provides a new outlook on the molecular mechanisms of CCA development from the perspective of lncRNAs. Moreover, we also discussed the limitations of the current studies and differential expression of lncRNAs in different types of CCA.

LncRNA TUG1 Promotes Growth and Metastasis of Cholangiocarcinoma Cells by Inhibiting miR-29a

Background

As a highly malignant tumor, cholangiocarcinoma poses a serious threat to human life and health, so exploring the mechanisms of its development and progression at a molecular level is of great significance to the diagnosis and treatment of the disease.

Objective

This study was aimed at investigating the effects and related mechanisms of LncRNA TUG1 on cholangiocarcinoma cells.

Methods

Cholangiocarcinoma tissues and adjacent tissues (n=82 each), human cholangiocarcinoma cell lines (RBE, QBC939, HuH28), and a human normal biliary epithelial cell line (HIBE) were collected. miR-29a-mimics, miR-29a-inhibitor, miR-NC, si-TUG1, pcDNA3.1 TUG1, and NC were transfected into the cholangiocarcinoma cells. qRT-PCR was performed to detect TUG1 and miR-29a expression in the cholangiocarcinoma tissues and cells. Western blotting (WB) was conducted to detect the expression of Bax, Caspase-3, and Bcl-2 in the cells. CCK-8 assay, Transwell, and flow cytometry were carried out to detect cell proliferation, invasion, and apoptosis. Dual luciferase reporter gene assay (DLRGA) was performed to confirm the correlation of TUG1 with miR-29a.

Results

TUG1 was highly expressed while miR-29a was poorly expressed in cholangiocarcinoma cells. TUG1 expression was negatively correlated with miR-29a expression, and TUG1 had a relatively high diagnostic value for cholangiocarcinoma. Cell experiments showed that inhibiting TUG1 expression or up-regulating miR-29a expression could inhibit cholangiocarcinoma cells from proliferation and invasion, and promote their apoptosis, while up-regulating TUG1 or inhibiting miR-29a could promote the proliferation and invasion but inhibit the apoptosis. Rescue experiment showed that overexpressing miR-29a could reverse the effects of high TUG1 expression on cholangiocarcinoma cells. DLRGA confirmed that there was a regulatory relationship between TUG1 and miR-29a.

Conclusion

TUG1 is highly expressed in cholangiocarcinoma tissues. It can promote the growth and metastasis of cholangiocarcinoma cells by inhibiting miR-29a, so it may be a new target for diagnosing and treating cholangiocarcinoma.

Transcription factor HIF1α promotes proliferation, migration, and invasion of cholangiocarcinoma via long noncoding RNA H19/microRNA-612/Bcl-2 axis

Cholangiocarcinoma, which is the most common invasive malignant tumor of the biliary tract, has poor prognosis. There is evidence suggesting that hypoxia-inducible factor 1α (HIF1α) plays an important role in cholangiocarcinoma. Also, microRNA-612 (miR-612) is another key regulator of cholangiocarcinoma. In this study, we investigate the scantly documented interaction of HIF1α and miR-612 in cholangiocarcinoma. We first undertook microarray-based cholangiocarcinoma gene expression profiles to screen out the differentially expressed long noncoding RNAs (lncRNAs) and genes. We used reverse transcription quantitative polymerase chain reaction to detect the expression of HIF1α in normal bile duct and cholangiocarcinoma tissues, and in corresponding cells lines. Cell counting kit 8, scratch, and Transwell assays were used to detect the proliferation, migration and invasion of cholangiocarcinoma cells. Cell cycle distribution and apoptosis were detected by flow cytometry. ChIP, dual luciferase reporter gene assay, RNA pull-down, and RNA immunoprecipitation were used to verify relationship between HIF1α and lncRNA H19, and lncRNA H19 and miR-612. We also monitored tumor formation in nude mice to verify the effect of HIF1α on cholangiocarcinoma. HIF1α expression was elevated in cholangiocarcinoma tissues and cells. Silencing HIF1α reduced proliferation, migration, and invasion of cholangiocarcinoma cells. HIF1α transcriptionally activated the expression of lncRNA H19. Overexpression of miR-612 could rescue the proliferation, migration and invasion of cholangiocarcinoma cells caused by lncRNA H19 overexpression. Taken together, HIF1α activated lncRNA H19-mediated miR-612/Bcl-2 pathway to promote cholangiocarcinoma, suggesting a promising therapeutic target for cholangiocarcinoma.

Omics-Based Platforms: Current Status and Potential Use for Cholangiocarcinoma

Cholangiocarcinoma (CCA) has been identified as a highly malignant cancer that can be transformed from epithelial cells of the bile duct, including intrahepatic, perihilar and extrahepatic. High-resolution imaging tools (abdominal ultrasound, computed tomography and percutaneous transhepatic cholangial drainage) are recruited for diagnosis. However, the lack of early diagnostic biomarkers and treatment evaluation can lead to serious outcomes and poor prognosis (i.e., CA19-9, MUC5AC). In recent years, scientists have established a large number of omics profiles to reveal underlying mechanisms and networks (i.e., IL-6/STAT3, NOTCH). With these results, we achieved several genomic alteration events (i.e., TP53_mut, KRAS_mut) and epigenetic modifications (i.e., DNA methylation, histone modification) in CCA cells and clinical patients. Moreover, we reviewed candidate gene (such as NF-kB, YAP1) that drive gene transcription factors and canonical pathways through transcriptomics profiles (including microarrays and next-generation sequencing). In addition, the proteomics database also indicates which molecules and their directly binding status could trigger dysfunction signatures in tumorigenesis (carbohydrate antigen 19-9, mucins). Most importantly, we collected metabolomics datasets and pivotal metabolites. These results reflect the pharmacotherapeutic options and evaluate pharmacokinetic/pharmacodynamics in vitro and in vivo. We reversed the panels and selected many potentially small compounds from the connectivity map and L1000CDS² system. In this paper, we summarize the prognostic value of each candidate gene and correlate this information with clinical events in CCA. This review can serve as a reference for further research to clearly investigate the complex characteristics of CCA, which may lead to better prognosis, drug repurposing and treatment strategies.

Panel of potential lncRNA biomarkers can distinguish various types of liver malignant and benign tumors

PURPOSE

Liver cancers are among the deadliest malignancies due to a limited efficacy of early diagnostics, the lack of appropriate biomarkers and insufficient discrimination of different types of tumors by classic and molecular methods. In this study, we searched for novel long non-coding RNA (lncRNA) as well as validated several known candidates suitable as probable biomarkers for primary liver tumors of various etiology.

METHODS

We described a novel lncRNA HELIS (aka "HEalthy LIver Specific") and estimated its expression by RT-qPCR in 82 paired tissue samples from patients with hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), combined HCC-CCA, pediatric hepatoblastoma (HBL) and non-malignant hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH). Additionally, we examined expression of cancer-associated lncRNAs HULC, MALAT1, UCA1, CYTOR, LINC01093 and H19, which were previously studied mainly in HCC.

RESULTS

We demonstrated that down-regulation of HELIS strongly correlates with carcinogenesis; whereas in tumors with non-hepatocyte origin (HBL, CCA) or in a number of poorly differentiated HCC, this lncRNA is not expressed. We showed that recently discovered LINC01093 is dramatically down-regulated in all malignant liver cancers; while in benign tumors LINC01093 expression is just twice decreased in comparison to adjacent samples.

CONCLUSION

Our study revealed that among all measured biomarkers only down-regulated HELIS and LINC01093, up-regulated CYTOR and dysregulated HULC are perspective for differential diagnostics of liver cancers; whereas others demonstrated discordant results and cannot be considered as potential universal biomarkers for this purpose.

Cancer Susceptibility Candidate 9 (CASC9): A Novel Targetable Long Noncoding RNA in Cancer Treatment

Based on epidemiological data provided by the World Health Organization (2018), cancer is the second most prevalent cause of death worldwide. Several factors are thought to contribute to the high mortality rate in cancer patients, including less-than-optimal diagnostic and therapeutic strategies. Thus, there is an urgent need to identify accurate biomarkers with diagnostic, prognostic, and potential therapeutic applications. In this regard, long noncoding RNAs (lncRNAs) hold immense potential due to their regulatory roles in cancer development and associated cancer hallmarks. Recently, CASC9 transcripts have attracted significant attention due to their altered expression during the pathogenesis of cancer and their apparent contributions to various cancer-associated phenotypes involving a broad spectrum of molecular mechanisms. Here, we have provided an in-depth review describing the known functions of the lncRNA CASC9 in cancer development and progression.

Role of noncoding RNAs in cholangiocarcinoma (Review)

Cholangiocarcinoma (CCA) is a malignant tumour originating from biliary epithelial cells, and is increasing in incidence. Radical surgery is the main treatment. However, the pathogenesis of CCA is unclear. Noncoding RNAs (ncRNAs) are non‑protein‑coding RNAs produced by genomic transcription that include microRNAs (miRNAs), circular RNAs (circRNAs) and long noncoding RNAs (lncRNAs). They play important roles in gene expression, epigenetic modification, cell proliferation, differentiation and reproduction. ncRNAs also serve key roles in cancer development. Numerous studies have been carried out on ncRNAs, and associated publications have shown that ncRNAs are closely associated with the physiological and pathological mechanisms of CCA. The findings of these studies can provide new insights into the diagnosis, treatment and prognosis of CCA. The present review summarizes the pathophysiological mechanisms of different types of ncRNAs, including miRNAs, circRNAs and lncRNAs in CCA, and their applications in the diagnosis and treatment of CCA.

Long Non-Coding RNAs in Biliary Tract Cancer-An Up-to-Date Review

The term long non-coding RNA (lncRNA) describes non protein-coding transcripts with a length greater than 200 base pairs. The ongoing discovery, characterization and functional categorization of lncRNAs has led to a better understanding of the involvement of lncRNAs in diverse biological and pathological processes including cancer. Aberrant expression of specific lncRNA species was demonstrated in various cancer types and associated with unfavorable clinical characteristics. Recent studies suggest that lncRNAs are also involved in the development and progression of biliary tract cancer, a rare disease with high mortality and limited therapeutic options. In this review, we summarize current findings regarding the manifold roles of lncRNAs in biliary tract cancer and give an overview of the clinical and molecular consequences of aberrant lncRNA expression as well as of underlying regulatory functions of selected lncRNA species in the context of biliary tract cancer.

Concise Review: Functional Roles and Therapeutic Potentials of Long Non-coding RNAs in Cholangiopathies

Long non-coding RNAs (lncRNAs) are RNAs with lengths exceeding 200 nucleotides that are not translated into proteins. It is well-known that small non-coding RNAs, such as microRNAs (miRNAs), regulate gene expression and play an important role in cholangiopathies. Recent studies have demonstrated that lncRNAs may also play a key role in the pathophysiology of cholangiopathies. Patients with cholangiopathies often develop cholangiocarcinoma (CCA), which is cholangiocyte-derived cancer, in the later stage. Cholangiocytes are a primary target of therapies for cholangiopathies and CCA development. Previous studies have demonstrated that expression levels of lncRNAs are altered in the liver of cholangiopathies or CCA tissues. Some lncRNAs regulate gene expression by inhibiting functions of miRNAs leading to diseased liver conditions or CCA progression, suggesting that lncRNAs could be a novel therapeutic target for those disorders. This review summarizes current understandings of functional roles of lncRNAs in cholangiopathies and seek their potentials for novel therapies.

The prognostic value of long non-coding RNA H19 in various cancers: A meta-analysis based on 15 studies with 1584 patients and the Cancer Genome Atlas data

BACKGROUND

Recent studies have shown that long noncoding RNA (lncRNA) H19 is aberrantly expressed in various cancers. However, the prognostic significance of H19 in cancer patients remains to be elucidated. Here, we designed and conducted a meta-analysis to evaluate the prognostic value of this lncRNA for malignant solid neoplasms.

METHODS

Relevant publications were collected from PubMed, Cochrane Library, Web of Science, and Embase databases. The relevant survival data of patients with H19-associated cancers were downloaded from The Cancer Genome Atlas (TCGA) project. Statistically significant relationships between H19 expression levels and overall survival were analyzed by hazard ratios (HRs) and corresponding 95% confidence intervals (CIs).

RESULTS

A total of 15 studies with 1584 patients were ultimately included for this literature meta-analysis. An elevated level of H19 expression was found to be negatively correlated with the overall survival (OS) (HR = 1.62, 95% CI = 1.36-1.93, P < .001) in various cancers. Abnormal H19 expression was also positively correlated with poor tumor differentiation (P < .0001), more advanced clinical stage (P < .0001), earlier lymph node metastasis (P < .0001), and earlier distant metastasis (P < .05). The relationship between elevated H19 expression and overall survival was further validated by a TCGA dataset consisting of 7462 cancer patients (HR = 1.12, 95% CI = 1.03-1.22, P < .05).

CONCLUSION

Our study indicates that H19 expression is closely relevant to clinical outcome and suggests that lncRNA H19 could be a crucial prognostic biomarker for certain carcinoma types.

H19 lncRNA: Roles in tumorigenesis

H19 is a long non-coding RNA [lncRNA] which was firstly described as an oncofetal transcript. The imprinted gene is normally expressed from the maternal allele. However, this pattern of imprinting is dysregulated in several cancers leading to aberrant up-regulation of H19 in malignant tissues. Several studies have utilized this aberrant expression pattern to find specific biomarkers for detection of cancer in tumoral tissues or peripheral blood. Moreover, single nucleotide polymorphisms within H19 have been associated with risk of oral squamous cell carcinoma, hepatocellular carcinoma, breast cancer, bladder cancer, gastric cancer and colorectal cancer. Taken together, H19 is regarded as a biomarker for cancer and a putative therapeutic target in these human disorders.

The long non-coding RNA H19: an active player with multiple facets to sustain the hallmarks of cancer

Cancer cells exhibit hallmarks in terms of proliferation, resistance to cell death, angiogenesis, invasion, metastasis, and genomic instability. Despite the progress in cancer research and the comprehension of tumorigenesis mechanisms, cancer remains a major issue in public health. A better understanding of the molecular factors associated with the appearance or progression of cancer may allow the development of therapeutic alternatives. Increasing data highlight the role of long non-coding RNAs in many diseases, including cancer. The long non-coding RNA H19 was the first discovered riboregulator, and it has been shown to be involved at multiple steps of tumorigenesis. Indeed, this lncRNA exert its action at various molecular scales. Understanding the role of H19 in cancer progression may allow to set up therapeutic strategies to prevent tumor expansion and metastatic dissemination. In this review, we will summarize the overexpression of the long non-coding RNA H19 in several types of cancer and the multiple implications of the long non-coding RNA H19 in the different hallmarks that define human cancer.

Comprehensive analysis of competing endogenous RNA networks associated with cholangiocarcinoma

Cholangiocarcinoma (CCA) is the second most common type of primary malignancy of the liver. Certain long non-coding RNAs (lncRNAs) have been demonstrated to have key roles in tumor pathogenesis by binding to microRNAs (miRNAs). However, the competing endogenous RNA (ceRNA) network of CCA remains to be fully determined. In the present study, the RNA expression profiles for CCA were downloaded from The Cancer Genome Atlas and further analyzed. A total of 318 differentially expressed (DE) lncRNAs, 87 DE miRNAs and 3,851 DE mRNAs were identified from 36 CCA samples and 9 adjacent non-tumor samples (for lncRNAs and miRNAs, fold change ≥2.5 and P<0.01; for mRNAs, fold change ≥2 and P<0.01). Further bioinformatics analyses were performed and the ceRNA network for CCA was constructed, which included 16 lncRNAs, 55 miRNAs and 373 mRNAs. Survival analysis of all genes in the network revealed that high expression of the mRNAs fucosyltransferase 4 (P<0.005) and huntingtin-interacting protein 1 related (P<0.001) has a positive impact on the overall survival of patients with CAA. Furthermore, the lncRNAs H19 and PVT1, and the miRNAs Homo sapiens (hsa)-miR-16-5p and hsa-miR-424-5p, together with peroxisome proliferator-activated receptors, may also have important roles in the pathogenesis of CCA. The present study provided data to further the understanding of and research into the molecular mechanisms implicated in CCA.

Long non-coding RNA H19 knockdown inhibits the cell viability and promotes apoptosis of thyroid cancer cells through regulating the PI3K/AKT pathway

Certain long non-coding (lnc)RNAs have been reported to serve important roles in the genesis and progression of thyroid cancer (TC). Recent studies have demonstrated that the expression of lncRNA H19 is upregulated in TC tissues; however, knowledge of the associated molecular mechanisms is limited. Therefore, the present study aimed to clarify the roles of H19 in TC. The mRNA expression of lncRNA H19 in TC tissues was determined using reverse transcription-quantitative polymerase chain reaction analysis, and the effects of H19 knockdown on cell viability and apoptosis in vitro were assessed using MTT and flow cytometric assays, respectively. Finally, the signaling pathways involved in the effects of H19 were examined. The results indicated that H19 was upregulated in TC tissues. Silencing of H19 inhibited the cell viability and promoted apoptosis of FTC-133 and TPC-1 TC cells, accompanied by an increased expression of B-cell lymphoma 2 (Bcl-2)-associated X protein and caspase 3, and repressed expression of Bcl-2. The results of western blot analysis suggested that the levels of phosphorylated phosphoinositide-3 kinase (PI3K) and phosphorylated AKT were attenuated by H19 silencing. These results suggest that lncRNA H19 exerts an oncogenic function in TC, in part through the PI3K/AKT pathway.

Long non-coding RNA LOXL1-AS1 acts as a ceRNA for miR-324-3p to contribute to cholangiocarcinoma progression via modulation of ATP-binding cassette transporter A1

Accumulating evidence has appreciated long non-coding RNAs (lncRNAs) as novel prognostic markers and therapeutic targets in malignant carcinomas. Here, we aim to investigate the value of a novel cancer-related lncRNA, LOXL1-AS1, in cholangiocarcinoma (CCA). LOXL1-AS1 was found overexpressed in CCA tissues screened by high-throughput sequencing technology. Upregulation of LOXL1-AS1 was identified by TCGA database and qRT-PCR analysis. Additionally, upregulation of LOXL1-AS1 was associated with lymph node invasion, advanced TNM stages and unfavorable prognosis. Loss-of-function and gain-of-function experiments were conducted and validated that LOXL1-AS1 could facilitate cell proliferation, migration and invasion and attenuate cell apoptosis. Moreover, luciferase reporter and rescue assays indicated that LOXL1-AS1 functioned as a ceRNA to elevate ATP-binding cassette transporter A1 (ABCA1) level by sponging miR-324-3p and exhibited the malignant phenotypes of CCA cells, thereby playing an oncogenic role in CCA. Taken together, this study reveals that LOXL1-AS1 might act as a potential biomarker and therapeutic target for CCA clinical application.

Functions and roles of long noncoding RNA in cholangiocarcinoma

Cholangiocarcinoma (CCA) is one of the most fatal cancers in humans, with a gradually increasing incidence worldwide. The efficient diagnostic and therapeutic measures for CCA to reduce mortality are urgently needed. Long noncoding RNAs (lncRNAs) may provide the potential diagnostic and therapeutic option for suppressing the CCA development. LncRNAs are a type of non-protein-coding RNAs, which are larger than 200 nucleotides in length. Increasing evidence reveals that lncRNAs exhibit critical roles in the carcinogenesis and development of CCA. Deregulation of lncRNAs impacts the proliferation, migration, invasion, and antiapoptosis of CCA cells by multiple sophisticated mechanisms. Consequently, lncRNAs likely represent promising biomarkers or intervention targets of CCA. In this review, we summarize current studies regarding the biological functions and regulatory mechanisms of diverse lncRNAs in CCA.

E2F1-induced upregulation of long non-coding RNA LMCD1-AS1 facilitates cholangiocarcinoma cell progression by regulating miR-345-5p/COL6A3 pathway

Cholangiocarcinomas (CCA) is a refractory cancer with increasing incidence worldwide. Long non-coding RNAs (lncRNAs) have been shown to associate with the occurrence and development of CCA. A previous study identified upregulation of LMCD1-AS1 in CCA tissues relative to their normal counterparts by Agilent human lncRNA + mRNA arrayV4.0. However, the biological roles and molecular mechanisms of LMCD1-AS1-regulated tumorigenesis and progression of CCA remain to be elucidated. In our study, we confirmed that LMCD1-AS1 expression was significantly higher in CCA tissues and cell lines than in normal tissues and HIBEC, respectively. E2F1 could bind directly to the promoter region of LMCD1-AS1 and activate its transcription. Function study showed depletion of LMCD1-AS1 suppressed cell proliferation, clone formation and invasion, and induced apoptosis of CCA cells. Whereas, ectopic expressed LMCD1-AS1 facilitated CCA cell progression. In addition, LMCD1-AS1 could sponge miR-345-5p in CCA cells. Moreover, collagenVI-alpha3 chain (COL6A3) was found as a downstream target of miR-345-5p by bioinformatic prediction and dual luciferase reporter assay. Furthermore, we demonstrated that the oncogenic role of LMCD1-AS1 is partly dependent on COL6A3 expression. Taken together, we reported a newly identified regulatory mechanism of E2F1/LMCD1-AS1/miR-345-5p/COL6A3 axis, which might lead to a better understanding of CCA tumorigenesis and progression and provide potential therapeutic targets for CCA.

lncRNAs as potential molecular biomarkers in the clinicopathology and prognosis of cholangiocarcinoma: a systematic review and meta-analysis

Background

Cholangiocarcinoma (CCA) is the second most common fatal primary hepatobiliary malignant carcinoma, characterized by early invasion and extremely poor outcomes. It is therefore necessary to identify a novel biomarker to better diagnose CAA and predict its prognosis. Recently, emerging evidence has revealed that some lncRNAs play an important role in the tumorigenesis and progression of CAA. In order to support this search for novel diagnostic and prognostic biomarkers for CAA, we conducted a meta-analysis to analyze the published association between lncRNA expression and its clinical value in CAA.

Methods

Eligible studies were pooled and analyzed according to our inclusion and exclusion criteria after a comprehensive literature search. Stata 14.0 software was used to analyze the data from relevant studies and to construct a forest plot. Different effect sizes were selected for the meta-analysis.

Results

In total, 24 publications were included in this meta-analysis. After review of their full-text, 16 articles studied the association between lncRNAs and clinicopathological characteristics, 2 discussing diagnosis and 16 discussing prognosis. Our results showed that overexpression of CCAT1 was significantly correlated with tumor stage (I + II vs III + IV) (OR, 4.99; 95% CI 2.77–8.99; P<0.001) and lymph node metastasis in CCA (OR, 4.75; 95% CI 2.65–8.52; P<0.001). Furthermore, elevated CCAT lncRNA family expression predicted a shorter overall survival (HR, 2.09; 95% CI 1.17–3.00; P<0.001), especially CCAT2. Upregulation of CCAT2 was also obviously associated with tumor stage in CCA (OR, 5.29; 95% CI 2.64–10.58; P=0.001).

Conclusion

This is the first meta-analysis to assess the relationship between expression of lncRNAs and the clinical values of patients with CCA. lncRNAs can function as potential molecular biomarkers of the clinicopathology and prognosis of CCA.

The Advancement of Long Non-Coding RNAs in Cholangiocarcinoma Development

Cholangiocarcinoma (CCA) is a malignancy with increasing incidence in recent years. CCA patients are usually diagnosed at advanced stage due to lack of apparent symptoms and specifically diagnostic markers. Nowadays, surgical removal is the only effective method for CCA whereas overall 5-year-survival rate keeps around 10%. Long-noncoding RNA (lncRNA), a subtype of noncoding RNA, is widely studied to be abnormally expressed in multiple cancers including CCA. LncRNA can promote proliferation, migration, invasion and inhibit apoptosis of CCA. Moreover, lncRNA is negatively correlated with the prognosis of CCA. LncRNA may contribute to the development of CCA via modulating gene transcription, sponging microRNA, regulating CCA-related signaling pathways or protein expression. LncRNA is thought to be potential diagnostic markers and therapeutic targets for CCA.

Upregulated long noncoding RNA LINC01296 indicates a dismal prognosis for pancreatic ductal adenocarcinoma and promotes cell metastatic properties by affecting EMT

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease that responds poorly to chemotherapy and radiotherapy and whose incidence has increased worldwide. Long noncoding RNAs have been demonstrated to play important roles in cancer initiation and progression. Long intergenic non-coding RNA 01296 (LINC01296) has been reported to be upregulated in several malignancies, but the clinical relevance and biological role of LINC01296 in PDAC are still unclear.

METHODS

RT-qPCR was performed to evaluate the expression of LINC01296 in 85 pared PDAC tissue samples and a panel of PDAC cell lines. The clinical value and prognostic role of LINC01296 in patients with PDAC were further explored. Furthermore, we explored the functional roles of LINC01296 depletion in PANC-1 and SW1990 cells, including cell proliferation, apoptosis, migration, invasion, and epithelial-to-mesenchymal transition (EMT).

RESULTS

LINC01296 was enhanced in PDAC tissues and cell lines, and this overexpression was correlated with advanced tumor stages and positive lymph node metastasis in patients with PDAC. In addition, upregulation of LINC01296 was an independent prognostic predictor for patients with PDAC after surgery. Moreover, silencing of LINC01296 followed by treatment with small interfering RNAs suppressed cell proliferation and promoted cell apoptosis by affecting the Bcl-2/caspase-3 pathway. Importantly, LINC01296 attenuation impaired the migratory and invasive potential partly by reversing EMT.

CONCLUSIONS

Overall, our work may help to develop a novel prognostic biomarker and therapeutic target for PDAC.

Enhanced expression of lncRNA TP73-AS1 predicts adverse phenotypes for cholangiocarcinoma and exerts oncogenic properties in vitro and in vivo

Cholangiocarcinoma (CCA) is one of the most aggressive malignancies with increasing incidence worldwide. Various evidence documents that abnormally expressed long non-coding RNAs (lncRNAs) play important roles in tumorigenesis and progression. TP73-AS1 is a novel cancer-related lncRNA that contributes to the development of several malignancies. However, its clinical value and potential effects on CCA remains unknown. RT-qPCR was used to measure the expression levels of TP73-AS1 in CCA tissues and paired non-tumor tissues and the association between TP73-AS1 expression and clinicopathological characteristics was analyzed. In addition, the functional roles of TP73-AS1 in CCA were detected both in vitro and in vivo. The results illustrated that TP73-AS1 transcription is enhanced in both CCA tissue samples and cell lines, and this upregulation is closely associated with larger tumor size (p=0.008) and advanced TNM stage (p=0.026) in patients with CCA. For the part of functional assays, silencing of TP73-AS1 could attenuate CCA cell growth both in vitro and in vivo. Additionally, silencing of TP73-AS1 facilitates apoptosis via activating caspase-3 and caspase-9. Importantly, TP73-AS1 expression did not affect HIBEC cell growth and apoptosis. Moreover, TP73-AS1 could also facilitate migration and invasion potential of CCA cells. Collectively, these findings may help to develop a potential therapeutic target for the patients with CCA.

Prognostic biomarkers for cholangiocarcinoma and their clinical implications

INTRODUCTION

Cholangiocarcinoma (CCA) is a poorly prognostic cancer with limited treatment options. Most patients have unresectable tumors when they are diagnosed and the chemotherapies provided are of limited benefit. Prognostic markers are therefore necessary to predict the disease outcome, risk of relapse, or to suggest the best treatment option. Areas covered: This article provides an up-to-date review of biomarkers with promising characteristics to be prognostic markers for CCA reported in the past 5 years. The biomarkers are sub-classified into tissue and serum markers. Proteins, RNAs, peripheral blood cells etc., that are associated with aggressive phenotypes, signal pathways, chemo-drug resistance, and those that reflect the survival time of CCA patients are evaluated for their prognostic prediction values. Expert commentary: CCAs are heterogeneous tumors of different histo-pathological subtypes and genetic influences and, therefore, potential markers should be validated in larger collectives with varied epidemiological backgrounds. A systematic review and meta-analysis should be done to clarify the impact of the reported biomolecules for their potential prognostic values. Non- or low-invasive sample collections, as well as the simple and affordable determination methods, should be constructed to make the prognostic biomarkers available in clinical practice.

SP1-induced upregulation of lncRNA SPRY4-IT1 exerts oncogenic properties by scaffolding EZH2/LSD1/DNMT1 and sponging miR-101-3p in cholangiocarcinoma

Background

Accumulating evidence has indicated that long non-coding RNAs (lncRNAs) behave as a novel class of transcription products during multiple cancer processes. However, the mechanisms responsible for their alteration in cholangiocarcinoma (CCA) are not fully understood.

Methods

The expression of SPRY4-IT1 in CCA tissues and cell lines was determined by RT-qPCR, and the association between SPRY4-IT1 transcription and clinicopathologic features was analyzed. Luciferase reporter and chromatin immunoprecipitation (ChIP) assays were performed to explore whether SP1 could bind to the promoter region of SPRY4-IT1 and activate its transcription. The biological function of SPRY4-IT1 in CCA cells was evaluated both in vitro and in vivo. ChIP, RNA binding protein immunoprecipitation (RIP) and luciferase reporter assays were performed to determine the molecular mechanism of SPRY4-IT1 in cell proliferation, apoptosis and invasion.

Results

SPRY4-IT1 was abnormally upregulated in CCA tissues and cells, and this upregulation was correlated with tumor stage and tumor node metastasis (TNM) stage in CCA patients. SPRY4-IT1 overexpression was also an unfavorable prognostic factor for patients with CCA. Additionally, SP1 could bind directly to the SPRY4-IT1 promoter region and activate its transcription. Furthermore, SPRY4-IT1 silencing caused tumor suppressive effects via reducing cell proliferation, migration and invasion; inducing cell apoptosis and reversing the epithelial-to-mesenchymal transition (EMT) process in CCA cells. Mechanistically, enhancer of zeste homolog 2 (EZH2) along with the lysine specific demethylase 1 (LSD1) or DNA methyltransferase 1 (DNMT1) were recruited by SPRY4-IT1, which functioned as a scaffold. Importantly, SPRY4-IT1 positively regulated the expression of EZH2 through sponging miR-101-3p.

Conclusions

Our data illustrate how SPRY4-IT1 plays an oncogenic role in CCA and may offer a potential therapeutic target for treating CCA.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0747-x) contains supplementary material, which is available to authorized users.

Upregulated long non-coding RNA SPRY4-IT1 predicts dismal prognosis for pancreatic ductal adenocarcinoma and regulates cell proliferation and apoptosis

Recently, long noncoding RNAs (lncRNAs) have been emerged as pivotal regulators in various human cancers, including pancreatic ductal adenocarcinoma (PDAC). SPRY4-intronic transcript 1 (SPRY4-IT1) was reported to be upregulated in some kind of human cancers. Here, we elucidated the biological functions and possible clinical values of SPRY4-IT1 on PDAC. In present study, expression of SPRY4-IT1 in PDAC tissues and corresponding normal tissues were explored by qRT-PCR experiments. The link between SPRY4-IT1 expression levels and clinicopathological significance was further analyzed. In addition, the oncogenic role of SPRY4-IT1 was detected both in vitro and in vivo. The results demonstrated that SPRY4-IT1 was abnormally upregulated in PDAC tissues and cell lines. Tumor stage and differentiation grade was closely correlated with SPRY4-IT1 expression. Additionally, decreased SPRY4-IT1 contributed to tumor suppressive effect through attenuating cell growth, clonogenic ability and facilitating apoptosis via Bcl-2/caspase-3 pathway in PANC1 and Capan-2 cells. Furthermore, the xenograft study confirmed the tumor proliferation-promoting role of SPRY4-IT1 in PANC1 cells. Taken together, these findings indicated that SPRY4-IT1 is a potential therapeutic target and prognosis biomarker for the patients with PDAC.

Long non-coding RNA H1 promotes cell proliferation and invasion by acting as a ceRNA of miR‑138 and releasing EZH2 in oral squamous cell carcinoma

Long non-coding RNAs (lncRNAs) have been shown to play pivotal roles in various types of human cancer, including oral squamous cell carcinoma (OSCC). However, the potential mechanisms of action of lncRNAs in OSCC remain to be fully elucidated. The aim of the present study was to further explore the potential mechanisms of action of lncRNAs in OSCC. We first analyzed Gene Expression Omnibus (GEO) datasets to investigate aberrantly expressed lncRNAs which may be involved in the development of OSCC. Reverse transcription‑quantitative PCR (RT‑qPCR) was performed to analyze the expression levels of lncRNA H19. In addition, the correlation between H19 expression and the clinical characteristics and prognosis of patients with OSCC was statistically analyzed. The effects of H19 expression on OSCC cells were examined by using overexpression and RNA interference approaches in vitro and in vivo. To examine the competitive endogenous RNA (ceRNA) mechanisms, bioinformatics analysis and luciferase reporter assay were performed. In addition, the correlation between H19 and microRNA (miR)‑138 was detected. H19 was found to be upregulated in OSCC tissues and its high expression level was associated with the TNM stage and nodal invasion, and also correlated with a shorter overall survival of patients with OSCC. The knockdown of H19 significantly inhibited OSCC cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT), and induced apoptosis in vitro; it also suppressed subcutaneous tumor growth in vivo. In addition, H19 was found to regulate the expression of oncogene enhancer of zeste homolog 2 (EZH2) by competing with miR‑138; the inhibition of miR‑138 attenuated the inhibitory effects of H19 knockdown on OSCC cells. On the whole, our findings suggest that H19 functions as an oncogene by inhibiting miR‑138 and facilitating EZH2 expression in OSCC. Thus, lncRNA H1 may represent a potential therapeutic target for OSCC.

Downregulated circular RNA hsa_circ_0001649 regulates proliferation, migration and invasion in cholangiocarcinoma cells

Cholangiocarcinoma (CCA) is one of the most aggressive malignancies with increasing worldwide incidence and is characterized by unfavorable prognosis due to its early invasive characteristics and poor response to chemotherapy or radiotherapy. Accumulating evidence has indicated that aberrantly expressed circular RNAs (circRNAs) are involved in cancer development and progression. However, their clinical values and biological roles in CCA remain unclear. Hsa_circ_0001649, a novel cancer-related circRNA, has been previously reported to be downregulated in hepatocellular carcinoma and gastric cancer. In the present study, qRT-PCR was carried out to measure the expression of hsa_circ_0001649 in CCA tissue samples and cell lines, and the correlation between hsa_circ_0001649 expression and clinicopathologic features was analyzed. The biological functions of hsa_circ_0001649 in CCA cells were evaluated both in vitro and in vivo. As a result, hsa_circ_0001649 was aberrantly downregulated in CCA tissues and cells, and this downregulation was associated with tumor size and differentiation grade in CCA. In addition, hsa_circ_0001649 overexpression caused tumor suppressive effects via inhibiting cell proliferation, migration and invasion; inducing cell apoptosis in KMBC and Huh-28 cells. On the contrary, silencing of hsa_circ_0001649 caused the opposite phenotypes. Furthermore, tumor xenograft study confirmed the in vitro results. Collectively, our findings suggest that hsa_circ_0001649 might be a rational CCA-related therapeutic target.

Long non-coding RNA CCAT2 promotes cholangiocarcinoma cells migration and invasion by induction of epithelial-to-mesenchymal transition

Cholangiocarcinoma (CCA) is one of the most aggressive malignancies in humans. Emerging evidence has indicated that abnormally expressed long non-coding RNAs (lncRNAs) could conduce to tumorigenesis and progression. Specifically, colon cancer-associated transcript 2 (CCAT2) has been reported to be overexpressed in several carcinomas. However, its clinical significance and functional roles in CCA is still unknown. qRT-PCR experiments were conducted to assess the CCAT2 expression in CCA tissue samples and cell lines. In addition, the link between CCAT2 expression and clinicopathological characteristics was analyzed. The potential effects of CCAT2 in CCA cells was evaluated in vitro including cell proliferation, colony-forming ability, apoptosis, migration, invasion and epithelial-to-mesenchymal transition (EMT). As a result, CCAT2 was aberrantly overexpressed in CCA tissue samples and cells, and this upregulation was correlated with tumor size, lymph node invasion, TNM stage and postoperative recurrence in CCA patients. Overexpression of CCAT2 could serve as an independent prognostic indicator for CCA. Additionally, overexpression of CCAT2 was a dismal prognostic indicator for patients with CCA. Furthermore, CCAT2 silencing caused tumor suppressive effects via reducing cell proliferation, migration and invasion, inducing cell apoptosis and reversing the EMT process in HuCCT1 and CCLP1 cells. Collectively, our data illustrated that lncRNA CCAT2 played an oncogenic role in CCA and may offer a potential therapeutic target for treating this fatal disease.

NcRNAs and Cholangiocarcinoma

Cholangiocarcinoma (CCA) is the most common primary biliary malignancy with poor prognosis. Less understanding of its etiology and pathogenesis makes the diagnosis and therapy difficult. Recently, accumulating evidences have demonstrated that deregulated expression of non-coding RNAs (ncRNAs) is closely associated with the etiopathogenesis of CCA. NcRNAs which lack open reading frame are a heterogeneous class of transcribed RNA molecules, including microRNAs, long non-coding RNAs and circular RNAs. Several studies have shown ncRNAs dysregulation is a common central event occurring in CCA and has the potential of being therapy targets. Moreover, ncRNAs can be easily detected in cancer tissues and biofluids, representing valuable tools for diagnosis. In this review, we illustrate the role of ncRNA in the CCA and discuss their potential clinical value.

Roles of Long Noncoding RNAs in Recurrence and Metastasis of Radiotherapy-Resistant Cancer Stem Cells

Radiotherapy is a well-established therapeutic regimen applied to treat at least half of all cancer patients worldwide. Radioresistance of cancers or failure to treat certain tumor types with radiation is associated with enhanced local invasion, metastasis and poor prognosis. Elucidation of the biological characteristics underlying radioresistance is therefore critical to ensure the development of effective strategies to resolve this issue, which remains an urgent medical problem. Cancer stem cells (CSCs) comprise a small population of tumor cells that constitute the origin of most cancer cell types. CSCs are virtually resistant to radiotherapy, and consequently contribute to recurrence and disease progression. Metastasis is an increasing problem in resistance to cancer radiotherapy and closely associated with the morbidity and mortality rates of several cancer types. Accumulating evidence has demonstrated that radiation induces epithelial–mesenchymal transition (EMT) accompanied by increased cancer recurrence, metastasis and CSC generation. CSCs are believed to serve as the basis of metastasis. Previous studies indicate that CSCs contribute to the generation of metastasis, either in a direct or indirect manner. Moreover, the heterogeneity of CSCs may be responsible for organ specificity and considerable complexity of metastases. Long noncoding RNAs (lncRNAs) are a class of noncoding molecules over 200 nucleotides in length involved in the initiation and progression of several cancer types. Recently, lncRNAs have attracted considerable attention as novel critical regulators of cancer progression and metastasis. In the current review, we have discussed lncRNA-mediated regulation of CSCs following radiotherapy, their association with tumor metastasis and significance in radioresistance of cancer.