Genome-wide analysis of long noncoding RNA signature in human colorectal cancer

The pivotal role of long non-coding RNAs as potential biomarkers and modulators of chemoresistance in ovarian cancer (OC)

Ovarian cancer (OC) is a fatal gynecological disease that is often diagnosed at later stages due to its asymptomatic nature and the absence of efficient early-stage biomarkers. Previous studies have identified genes with abnormal expression in OC that couldn't be explained by methylation or mutation, indicating alternative mechanisms of gene regulation. Recent advances in human transcriptome studies have led to research on non-coding RNAs (ncRNAs) as regulators of cancer gene expression. Long non-coding RNAs (lncRNAs), a class of ncRNAs with a length greater than 200 nucleotides, have been identified as crucial regulators of physiological processes and human diseases, including cancer. Dysregulated lncRNA expression has also been found to play a crucial role in ovarian carcinogenesis, indicating their potential as novel and non-invasive biomarkers for improving OC management. However, despite the discovery of several thousand lncRNAs, only one has been approved for clinical use as a biomarker in cancer, highlighting the importance of further research in this field. In addition to their potential as biomarkers, lncRNAs have been implicated in modulating chemoresistance, a major problem in OC. Several studies have identified altered lncRNA expression upon drug treatment, further emphasizing their potential to modulate chemoresistance. In this review, we highlight the characteristics of lncRNAs, their function, and their potential to serve as tumor markers in OC. We also discuss a few databases providing detailed information on lncRNAs in various cancer types. Despite the promising potential of lncRNAs, further research is necessary to fully understand their role in cancer and develop effective strategies to combat this devastating disease.

LncAABR07053481 inhibits bone marrow mesenchymal stem cell apoptosis and promotes repair following steroid-induced avascular necrosis

The osteonecrotic area of steroid-induced avascular necrosis of the femoral head (SANFH) is a hypoxic microenvironment that leads to apoptosis of transplanted bone marrow mesenchymal stem cells (BMSCs). However, the underlying mechanism remains unclear. Here, we explore the mechanism of hypoxic-induced apoptosis of BMSCs, and use the mechanism to improve the transplantation efficacy of BMSCs. Our results show that the long non-coding RNA AABR07053481 (LncAABR07053481) is downregulated in BMSCs and closely related to the degree of hypoxia. Overexpression of LncAABR07053481 could increase the survival rate of BMSCs. Further exploration of the downstream target gene indicates that LncAABR07053481 acts as a molecular "sponge" of miR-664-2-5p to relieve the silencing effect of miR-664-2-5p on the target gene Notch1. Importantly, the survival rate of BMSCs overexpressing LncAABR07053481 is significantly improved after transplantation, and the repair effect of BMSCs in the osteonecrotic area is also improved. This study reveal the mechanism by which LncAABR07053481 inhibits hypoxia-induced apoptosis of BMSCs by regulating the miR-664-2-5p/Notch1 pathway and its therapeutic effect on SANFH.

Identification of lncRNA and mRNA regulatory networks associated with gastric cancer progression

Gastric cancer is a tumor type characterized by lymph node metastasis and the invasion of local tissues. There is thus a critical need to clarify the molecular mechanisms governing gastric cancer onset and progression to guide the treatment of this disease. Long non-coding RNAs and mRNA expression profiles associated with early and local advanced gastric cancer were examined through microarray analyses, with GO and KEGG analyses being employed as a means of exploring the functional roles of those long non-coding RNAs and mRNAs that were differentially expressed in gastric cancer. In total, 1005 and 1831 lncRNAs and mRNAs, respectively, were found to be differentially expressed between early and local advanced gastric cancer. GO and KEGG analyses revealed several pathways and processes that were dysregulated, including the RNA transport, ECM-receptor interaction, and mRNA splicing pathways. In co-expression networks, E2F1, E2F4, and STAT2 were identified as key transcriptional regulators of these processes. Moreover, thrombospondin-2 was confirmed as being expressed at high levels in more advanced gastric cancer by both the GEO and TCGA databases. RNA-sequencing analyses of SGC-790 cells transfected to express thrombospondin-2 further revealed this gene to enhance NF-kB and TNF pathway signaling activity. These results offer insight into gastric cancer-related regulatory networks and suggest thrombospondin-2 to be an important oncogene that drives the progression of this deadly cancer type.

Geometric complement heterogeneous information and random forest for predicting lncRNA-disease associations

More and more evidences have showed that the unnatural expression of long non-coding RNA (lncRNA) is relevant to varieties of human diseases. Therefore, accurate identification of disease-related lncRNAs can help to understand lncRNA expression at the molecular level and to explore more effective treatments for diseases. Plenty of lncRNA-disease association prediction models have been raised but it is still a challenge to recognize unknown lncRNA-disease associations. In this work, we have proposed a computational model for predicting lncRNA-disease associations based on geometric complement heterogeneous information and random forest. Firstly, geometric complement heterogeneous information was used to integrate lncRNA-miRNA interactions and miRNA-disease associations verified by experiments. Secondly, lncRNA and disease features consisted of their respective similarity coefficients were fused into input feature space. Thirdly, an autoencoder was adopted to project raw high-dimensional features into low-dimension space to learn representation for lncRNAs and diseases. Finally, the low-dimensional lncRNA and disease features were fused into input feature space to train a random forest classifier for lncRNA-disease association prediction. Under five-fold cross-validation, the AUC (area under the receiver operating characteristic curve) is 0.9897 and the AUPR (area under the precision-recall curve) is 0.7040, indicating that the performance of our model is better than several state-of-the-art lncRNA-disease association prediction models. In addition, case studies on colon and stomach cancer indicate that our model has a good ability to predict disease-related lncRNAs.

Long Non-Coding RNAs MALAT1 and NEAT1 in Non-syndromic Orofacial Clefts

Long non-coding RNAs (lncRNAs) are thought to play important roles in non-syndromic orofacial clefts (NSOFC). Clinical diagnosis was categorized as either non-syndromic cleft lip with or without cleft palate (NSCL/P), or non-syndromic cleft palate-only (NSCPO). Tissues excised from the trimmed wound edge were reserved as experimental samples; adjacent normal control was used as a positive control, and tissue from healthy individuals was used as a blank control. Target lncRNAs in the collected tissues were identified using microarrays and quantitative reverse transcription PCR (RT-qPCR). Immunohistochemical (IHC) staining and RT-qPCR were used to verify the target mRNAs. Pathway, gene ontology (GO) enrichment, and TargetScan predictions were employed to construct competing endogenous RNA networks (ceRNA networks) and explore their potential functions. RNA-Seq revealed 24 upregulated and 43 downregulated lncRNAs; MALAT1 and NEAT1 were screened and validated using RT-qPCR. Common NSOFC risk factors were positively correlated with MALAT1 and NEAT1 expression. Bioinformatics predicted four ceRNA networks; GO enrichment focused on their potential functions. RT-qPCR and IHC data were consistent with respect to expression levels of proteins and the mRNAs that encode them. As MALAT1 and NEAT1 are associated with the severity of NSOFC, they represent potential therapeutic targets and prognostic biomarkers.

LDAH2V: Exploring Meta-Paths Across Multiple Networks for lncRNA-Disease Association Prediction

Accumulating evidence has demonstrated dysfunctions of long non-coding RNAs (lncRNAs) are involved in various complex human diseases. However, even today, the relationships between lncRNAs and diseases remain unknown in most cases. Developing effective computational approaches to identify potential lncRNA-disease associations has become a hot topic. Existing network-based approaches are usually focused on the intrinsic features of lncRNAs and diseases but ignore the heterogeneous information of biological networks. Considering the limitations in previous methods, we propose LDAH2V, an efficient computational framework for predicting potential lncRNA-disease associations. LDAH2V uses the HIN2Vec to calculate the meta-path and feature vector for each lncRNA-disease pair in the heterogeneous information network (HIN), which consists of lncRNA similarity network, disease similarity network, miRNA similarity network, and the associations between them. Then, a Gradient Boosting Tree (GBT) classifier to predict lncRNA-disease associations is built with the feature vectors. The results show that LDAH2V performs significantly better than the four existing state-of-the-art methods and gains an AUC of 0.97 in the 10-fold cross-validation test. Furthermore, case studies of colon cancer and ovarian cancer-related lncRNAs have been confirmed in related databases and medical literature.

Long non-coding RNA SNHG20 promotes ovarian cancer development by targeting microRNA-338-3p to regulate MCL1 expression

Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs/miRs) were reported to be associated with the development of ovarian cancer (OC). Increasing evidence demonstrated that lncRNA SNHG20 and miR-338-3p were involved in OC. However, the functional mechanism of lncRNA SNHG20 and miR-338-3p in OC development remains unknown. The expression of SNHG20, miR-338-3p and myeloid cell leukemia 1 (MCL1) was detected by reverse transcription-quantitative PCR. MTT assay, flow cytometry and transwell migration and invasion assays were used to assess cell proliferation, apoptosis, migration and invasion, respectively. The relative protein expression was detected by western blot analysis. The interaction between miR-338-3p and SNHG20 or MCL1 was predicted by starBase v3.0, and subsequently confirmed by dual-luciferase reporter assay. Besides, mouse xenograft assay was carried out to explore the effect of SNHG20 on tumor growth in vivo. The levels of SNHG20 and MCL1 were upregulated, while miR-338-3p level was downregulated in OC tissues and cells. SNHG20 knockdown repressed OC cell proliferation, migration, invasion and epithelial-mesenchymal transition, and induced apoptosis. Interestingly, SNHG20 targeted miR-338-3p to regulate MCL1 expression. miR-338-3p depletion or MCL1 overexpression could reverse the effects of SNHG20 knockdown on OC cells. Besides, SNHG20 knockdown impeded tumor growth in vivo. In conclusion, the present study demonstrated that SNHG20 regulates OC development via modulation of the miR-338-3p/MCL1 axis, providing the theoretical basis for the treatment of OC.

HOXC10 is significantly overexpressed in colorectal cancer

Colorectal cancer (CRC) is one of the most common types of cancer in world and has a high rate of mortality. The majority of cases of CRC are sporadic; however, factors such as age, a family history of inflammatory diseases, diet, lifestyle and genetics increase the risk. HOX genes and lncRNAs are two classes of genes, and alterations in the expression levels of these genes are significantly associated with numerous different types of cancer. In the present study, the expression levels of HOXC10, HOXC-AS3, HOTAIR, HOXC13 and HOXC13-AS in tumor tissues were compared with normal healthy tissues in patients with CRC. Paired tumor and normal tissues were collected from 39 patients with CRC, and reverse transcription-quantitative PCR was used the expression of HOXC-AS3, HOXC13 and HOXC10 in the tumor tissues compared with the respective normal tissues. Expression of these genes were increased in the tumor tissues compared with normal tissues; however, the difference was only significant for HOXC10. Additionally, there was a strong and significant correlation between the expression of HOTAIR and HOXC13, a moderate and significant correlation between the expression of HOTAIR and HOXC13-AS, and between HOXC13 and HOXC13-AS genes. The expression of HOXC10 was significantly higher in tumor tissues compared with the normal tissues; whereas the upregulation of HOXC-AS3 and HOXC13 were not significant. Only the correlation between the expression of HOTAIR and HOXC13 was strong and significant. As HOXC10 expression was significantly upregulated in the tumor tissues relative to normal tissues, it may serve as a biomarker for the diagnosis of CRC and as a potential therapeutic target.

Cluster correlation based method for lncRNA-disease association prediction

BACKGROUND

In recent years, increasing evidences have indicated that long non-coding RNAs (lncRNAs) are deeply involved in a wide range of human biological pathways. The mutations and disorders of lncRNAs are closely associated with many human diseases. Therefore, it is of great importance to predict potential associations between lncRNAs and complex diseases for the diagnosis and cure of complex diseases. However, the functional mechanisms of the majority of lncRNAs are still remain unclear. As a result, it remains a great challenge to predict potential associations between lncRNAs and diseases.

RESULTS

Here, we proposed a new method to predict potential lncRNA-disease associations. First, we constructed a bipartite network based on known associations between diseases and lncRNAs/protein coding genes. Then the cluster association scores were calculated to evaluate the strength of the inner relationships between disease clusters and gene clusters. Finally, the gene-disease association scores are defined based on disease-gene cluster association scores and used to measure the strength for potential gene-disease associations.

CONCLUSIONS

Leave-One Out Cross Validation (LOOCV) and 5-fold cross validation tests were implemented to evaluate the performance of our method. As a result, our method achieved reliable performance in the LOOCV (AUCs of 0.8169 and 0.8410 based on Yang's dataset and Lnc2cancer 2.0 database, respectively), and 5-fold cross validation (AUCs of 0.7573 and 0.8198 based on Yang's dataset and Lnc2cancer 2.0 database, respectively), which were significantly higher than the other three comparative methods. Furthermore, our method is simple and efficient. Only the known gene-disease associations are exploited in a graph manner and further new gene-disease associations can be easily incorporated in our model. The results for melanoma and ovarian cancer have been verified by other researches. The case studies indicated that our method can provide informative clues for further investigation.

Long non-coding RNA expression identified by microarray analysis: Candidate biomarkers in human acral lentiginous melanoma

Melanoma is a rare but fatal form of skin cancer and acral lentiginous melanoma (ALM) is one of its most common types. Long non-coding RNA (lncRNA) has emerged as a crucial molecule in the development and progression of human cancers, and several studies have revealed that lncRNAs may be associated with the pathogenesis, progression and metastasis of melanoma. To demonstrate the association between ALM and lncRNAs, microarray analysis was performed in tumor and adjacent non-tumor tissues. A total of 4,488 lncRNAs and 3,913 mRNAs were identified to be differentially expressed in these samples. Among them, 2,211 and 2,277 lncRNAs were upregulated and downregulated in the ALM samples compared with adjacent tissues, respectively. In addition, 1,191 and 2,722 mRNAs were upregulated and downregulated, respectively. Additionally, five randomly selected lncRNAs (fold-change >2; P<0.05) were validated by reverse transcription-quantitative PCR. An lncRNA and mRNA co-expression network and competing endogenous network analysis were also constructed. In summary, the results of the present study may reveal a novel mechanism associated with the pathogenesis and malignant biological processes of ALM and indicate that lncRNAs may serve as potential targets for the treatment of ALM.

IDLDA: An Improved Diffusion Model for Predicting LncRNA-Disease Associations

It has been demonstrated that long non-coding RNAs (lncRNAs) play important roles in a variety of biological processes associated with human diseases. However, the identification of lncRNA–disease associations by experimental methods is time-consuming and labor-intensive. Computational methods provide an effective strategy to predict more potential lncRNA–disease associations to some degree. Based on the hypothesis that phenotypically similar diseases are often associated with functionally similar lncRNAs and vice versa, we developed an improved diffusion model to predict potential lncRNA–disease associations (IDLDA). As a result, our model performed well in the global and local cross-validations, which indicated that IDLDA had a great performance in predicting novel associations. Case studies of colon cancer, breast cancer, and gastric cancer were also implemented, all lncRNAs which ranked top 10 in both databases were verified by databases and related literature. The results showed that IDLDA might play a key role in biomedical research.

lncRNA KIAA0125 functions as a tumor suppressor modulating growth and metastasis of colorectal cancer via Wnt/β-catenin pathway

Colorectal cancer (CRC) is the third most common cancer in all races worldwide in recent years. The survival of the CRC patients is mostly affected by the stage of the disease at the time of diagnosis. Thus, the current challenge is to find sensitive and reliable biomarkers in early screening of CRC. Recently, emerging evidence has shown that long non-coding RNAs (lncRNAs) may play crucial roles in tumorigenesis. In this study, we found that lncRNA KIAA0125 was downregulated in colorectal tissues and cells. The functional study demonstrated that overexpression of KIAA0125 suppressed cell proliferation, migration, and invasion whereas the reversal effects were seen in silencing experiment. Besides, KIAA0125 inhibited epithelial-mesenchymal transition through Wnt/β-catenin signaling in CRC. Our findings suggested that KIAA0125 may act as an oncosupressor gene and could be considered as a potential diagnosis biomarker in CRC.

MLKL is a potential prognostic marker in gastric cancer

The mixed lineage kinase domain-like protein (MLKL), which is a major mediator of the necroptosis pathway, is involved in a certain cancers. The present study aimed to explore the expression patterns and exact role of MLKL in gastric cancer (GC) tumorigenesis and progression. In Cancer Cell Line Encyclopedia analysis, the MLKL mRNA expression levels in GC cell lines were not higher compared with that in other cancer cell lines. The results of the present study demonstrated that MLKL expression was decreased in gastric cancer tissues compared with that in normal tissues. In the Kaplan-Meier Plotter database survival analyses, decreased MLKL expression was associated with poor overall survival and first progression in patients with gastric cancer. In Oncomine gene co-expression analysis, MLKL expression was significantly associated with fatty acid 2-hydroxylase (FA2H) expression, which also exhibited similar effects on the prognosis of patients with GC in the survival analysis. This result suggested that FA2H may be a downstream molecule of MLKL. The results of the present study indicated that MLKL may be a novel prognostic biomarker for patients with GC.

Fusion of multiple heterogeneous networks for predicting circRNA-disease associations

Circular RNAs (circRNAs) are a newly identified type of non-coding RNA (ncRNA) that plays crucial roles in many cellular processes and human diseases, and are potential disease biomarkers and therapeutic targets in human diseases. However, experimentally verified circRNA-disease associations are very rare. Hence, developing an accurate and efficient method to predict the association between circRNA and disease may be beneficial to disease prevention, diagnosis, and treatment. Here, we propose a computational method named KATZCPDA, which is based on the KATZ method and the integrations among circRNAs, proteins, and diseases to predict circRNA-disease associations. KATZCPDA not only verifies existing circRNA-disease associations but also predicts unknown associations. As demonstrated by leave-one-out and 10-fold cross-validation, KATZCPDA achieves AUC values of 0.959 and 0.958, respectively. The performance of KATZCPDA was substantially higher than those of previously developed network-based methods. To further demonstrate the effectiveness of KATZCPDA, we apply KATZCPDA to predict the associated circRNAs of Colorectal cancer, glioma, breast cancer, and Tuberculosis. The results illustrated that the predicted circRNA-disease associations could rank the top 10 of the experimentally verified associations.

Cervical carcinoma high-expressed long non-coding RNA 1 may promote growth of colon adenocarcinoma through interleukin-17A

Cervical carcinoma high-expressed long non-coding RNA 1 (CCHE1) has been demonstrated to promote several different types of cancer; however, the involvement of CCHE1 in other types of cancer remains unknown. In the present study, the expression levels of CCHE1 and interleukin (IL)-17A were increased in the plasma of patients with metastatic and non-metastatic colon adenocarcinoma (MC and NMC, respectively) compared with the healthy controls. There was no significant difference in the plasma expression levels of CCHE1 and IL-17A in patients with MC compared with patients with NMC. The plasma expression levels of CCHE1 and IL-17A were positively associated with the primary tumor diameter. A significant correlation as demonstrated between the serum levels of CCHE1 and IL-17A in patients with colon adenocarcinoma, but not in the healthy controls. CCHE1 and IL-17A overexpression promoted colon adenocarcinoma cell proliferation. Transfection of small interfering RNA against IL-17A partially reversed the effects of CCHE1 overexpression on cancer cell proliferation. Upregulation of IL-17A was observed after CCHE1 overexpression, while IL-17A overexpression did not significantly change the expression level of CCHE1. Therefore, CCHE1 may promote growth of colon adenocarcinoma through interactions with IL-17A.

LncRNAs with miRNAs in regulation of gastric, liver, and colorectal cancers: updates in recent years

Long noncoding RNA (lncRNA) is a kind of RNAi molecule composed of hundreds to thousands of nucleotides. There are several major types of functional lncRNAs which participate in some important cellular pathways. LncRNA-RNA interaction controls mRNA translation and degradation or serves as a microRNA (miRNA) sponge for silencing. LncRNA-protein interaction regulates protein activity in transcriptional activation and silencing. LncRNA guide, decoy, and scaffold regulate transcription regulators of enhancer or repressor region of the coding genes for alteration of expression. LncRNA plays a role in cellular responses including the following activities: regulation of chromatin structural modification and gene expression for epigenetic and cell function control, promotion of hematopoiesis and maturation of immunity, cell programming in stem cell and somatic cell development, modulation of pathogen infection, switching glycolysis and lipid metabolism, and initiation of autoimmune diseases. LncRNA, together with miRNA, are considered the critical elements in cancer development. It has been demonstrated that tumorigenesis could be driven by homeostatic imbalance of lncRNA/miRNA/cancer regulatory factors resulting in biochemical and physiological alterations inside the cells. Cancer-driven lncRNAs with other cellular RNAs, epigenetic modulators, or protein effectors may change gene expression level and affect the viability, immortality, and motility of the cells that facilitate cancer cell cycle rearrangement, angiogenesis, proliferation, and metastasis. Molecular medicine will be the future trend for development. LncRNA/miRNA could be one of the potential candidates in this category. Continuous studies in lncRNA functional discrepancy between cancer cells and normal cells and regional and rational genetic differences of lncRNA profiles are critical for clinical research which is beneficial for clinical practice.

Long non-coding RNAs are emerging targets of phytochemicals for cancer and other chronic diseases

The long non-coding RNAs (lncRNAs) are the crucial regulators of human chronic diseases. Therefore, approaches such as antisense oligonucleotides, RNAi technology, and small molecule inhibitors have been used for the therapeutic targeting of lncRNAs. During the last decade, phytochemicals and nutraceuticals have been explored for their potential against lncRNAs. The common lncRNAs known to be modulated by phytochemicals include ROR, PVT1, HOTAIR, MALAT1, H19, MEG3, PCAT29, PANDAR, NEAT1, and GAS5. The phytochemicals such as curcumin, resveratrol, sulforaphane, berberine, EGCG, and gambogic acid have been examined against lncRNAs. In some cases, formulation of phytochemicals has also been used. The disease models where phytochemicals have been demonstrated to modulate lncRNAs expression include cancer, rheumatoid arthritis, osteoarthritis, and nonalcoholic fatty liver disease. The regulation of lncRNAs by phytochemicals can affect multi-steps of tumor development. When administered in combination with the conventional drugs, phytochemicals can also produce synergistic effects on lncRNAs leading to the sensitization of cancer cells. Phytochemicals target lncRNAs either directly or indirectly by affecting a wide variety of upstream molecules. However, the potential of phytochemicals against lncRNAs has been demonstrated mostly by preclinical studies in cancer models. How the modulation of lncRNAs by phytochemicals produce therapeutic effects on cancer and other chronic diseases is discussed in this review.

LINC01638 silencing inhibits cancer cell proliferation in colorectal adenocarcinoma through interaction with RUNX2

lncRNA LINC01638 has been revealed to play an oncogenic role in triple negative breast cancer. The present study was carried out to investigate the involvement of LINC01638 in colorectal adenocarcinoma. In the present study it was observed that LINC01638 in plasma was upregulated in colorectal adenocarcinoma patients compared to healthy controls. Plasma levels of LINC01638 were affected by tumor size but not by distant metastasis. Plasma levels of Runt‑related transcription factor 2 (RUNX2) were also higher in colorectal adenocarcinoma patients than in healthy controls, and were positively correlated with plasma levels of LINC01638 in colorectal adenocarcinoma patients but not in healthy controls. ROC curve analysis revealed that upregulation of LINC01638 distinguished colorectal adenocarcinoma at stage I and II from healthy controls. LINC01638 shRNA knockdown led to RUNX2 downregulation, while RUNX2 overexpression exhibited no significant effects on LINC01638. LINC01638 shRNA knockdown inhibited and RUNX2 overexpression promoted the proliferation of colorectal adenocarcinoma cells. RUNX2 overexpression attenuated the effects of LINC01638 shRNA knockdown on cancer cell proliferation. Therefore, lncRNA LINC01638 silencing may inhibit cancer cell proliferation in colorectal adenocarcinoma through its interaction with RUNX2.

Genome-wide identification of lncRNAs and mRNAs differentially expressed in non-functioning pituitary adenoma and construction of an lncRNA-mRNA co-expression network

The involvement of long non-coding RNAs (lncRNAs) during tumorigenesis is a recent emerging theme. Yet no systematic evaluation of lncRNAs has been previously reported for non-functioning pituitary adenoma (NFPA), a fairly common type of intracranial tumor. Here, we report the first genome-wide expression profile for lncRNAs and mRNAs in NFPA, using formalin-fixed and paraffin-embedded tissue specimens. Using microarray analyses, we identified 113 lncRNAs and 80 mRNAs differentially expressed in NFPA; this list includes lncRNAs previously implicated in a variety of cancers. Using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) we further confirmed differential expression in NFPA for ten of the 113 lncRNAs. Using these ten doubly confirmed lncRNAs, we constructed an lncRNA-mRNA co-expression network comprising of 130 specific lncRNA-mRNA co-expression relationships. In addition, we conducted GO and KEGG analyses for the 80 mRNAs differentially expressed in NFPA. Our microarray and qRT-PCR analyses provided a working list of lncRNAs that may be functionally relevant to NFPA tumorigenesis. Our co-expression network in turn connected these largely uncharacterized lncRNAs to specific mRNAs, whose roles we further elucidated via GO and KEGG analyses, thus providing specific, testable hypotheses for the functions of these lncRNAs. Together, our study laid the foundation for future investigation of the specific function and mechanism by which lncRNAs are involved in NFPA tumorigenesis.

Summary statement: We identified long non-coding RNAs and mRNAs differentially expressed in non-functioning pituitary adenomas via microarray analyses, and provided working hypotheses for how these RNAs may function via co-expression network analyses.

Comprehensive analysis of microarray expression profiles of circRNAs and lncRNAs with associated co-expression networks in human colorectal cancer

Increasing data demonstrate that circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs) play important roles in tumorigenesis. However, the mechanisms in colorectal cancer (CRC) remain unclear. Here, hundreds of significantly expressed circRNAs, and thousands of lncRNAs as well as mRNAs were identified. By qRT-PCR, one abnormal circRNA, lncRNA, and three mRNAs were verified in 24 pairs of tissues and blood samples, respectively. Then, by GO analysis, we found that the gene expression profile of linear counterparts of upregulated circRNAs in human CRC tissues preferred positive regulation of GTPase activity, cellular protein metabolic process, and protein binding, while that of downregulated circRNAs of CRC preferred positive regulation of cellular metabolic process, acetyl-CoA metabolic process, and protein kinase C activity. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that p53 signaling pathway was an important pathway in upregulated protein-coding genes, whereas cyclic guanosine monophosphate-protein kinase G (cGMP–PKG) signaling pathway was the top enriched KEGG pathway for downregulated transcripts. Furthermore, lncRNA–mRNA co-expression analysis demonstrated that downregulated lncRNA uc001tma.3 was negatively with CDC45 and positively with ELOVL4, BVES, FLNA, and HSPB8, while upregulated lncRNA NR_110882 was positively with FZD2. In addition, lncRNA–transcription factor (TF) co-expression analysis showed that the most relevant TFs were forkhead box protein A1 (FOXA1), transcription initiation factor TFIID submint 7 (TAF7), and adenovirus early region 1A(E1A)-associated protein p300 (EP300). Our findings offer a fresh view on circRNAs and lncRNAs and provide the foundation for further study on the potential roles of circRNAs and lncRNAs in colorectal cancer.

Emerging roles of long non-coding RNA in cancer

Since comprehensive analysis of the mammalian genome revealed that the majority of genomic products are transcribed in long non‐coding RNA (lncRNA), increasing attention has been paid to these transcripts. The applied next‐generation sequencing technologies have provided accumulating evidence of dysregulated lncRNA in cancer. The implication of this finding can be seen in many forms and at multiple levels. With impacts ranging from integrating chromatin remodeling complexes to regulating transcription and post‐transcriptional processes, aberrant expression of lncRNA may have repercussions in cell proliferation, tumor progression or metastasis. lncRNA may act as enhancers, scaffolds or decoys by physically interacting with other RNA species or proteins, resulting in a direct impact on cell signaling cascades. Even though their functional classification is well‐established in the context of cancer, clearer characterization in terms of their phenotypic outputs is needed to optimize and identify suitable candidates that enable the development of new therapeutic strategies and the design of novel diagnostic approaches. The present article aims to outline different cancer‐associated lncRNA according to their contribution to tumor suppression or tumor promotion based on their most current functional annotations.

LncRNA H19/miR-29b-3p/PGRN Axis Promoted Epithelial-Mesenchymal Transition of Colorectal Cancer Cells by Acting on Wnt Signaling

This investigation was aimed at working out the combined role of lncRNA H19, miR-29b and Wnt signaling in the development of colorectal cancer (CRC). In the aggregate, 185 CRC tissues and corresponding para-carcinoma tissues were gathered. The human CRC cell lines (i.e. HT29, HCT116, SW480 and SW620) and normal colorectal mucosa cell line (NCM460) were also purchased. Si-H19, si-NC, miR-29b-3p mimics, miR-29b-3p inhibitor, si-PGRN and negative control (NC) were, respectively, transfected into the CRC cells. Lucif-erase reporter plasmids were prepared to evaluate the transduction activity of Wnt/β-catenin signaling pathway, and dual-luciferase reporter gene assay was arranged to confirm the targeted relationship between H19 and miR-29b-3p, as well as between miR-29b-3p and PGRN. Finally, the proliferative and invasive capacities of CRC cells were appraised through transwell, MTT and scratch assays. As a result, over-expressed H19 and down-expressed miR-29b-3p displayed close associations with the CRC patients' poor prognosis (P < 0.05). Besides, transfection with si-H19, miR-29b-3p mimic or si-PGRN were correlated with elevated E-cadherin expression, decreased snail and vimentin expressions, as well as less-motivated cell proliferation and cell metastasis (P < 0.05). Moreover, H19 was verified to directly target miR-29b-3p based on the luciferase reporter gene assay (P < 0.05), and miR-29b-3p also bound to PGRN in a direct manner (P < 0.05). Finally, addition of LiCl (Wnt/β-catenin pathway activator) or XAV93920 (Wnt/β-catenin pathway inhibitor) would cause remarkably altered E-cadherin, c-Myc, vimentin and snail expressions, as well as significantly changed transcriptional activity of β-catenin/Tcf reporter plasmid (P < 0.05). In conclusion, the lncRNA H19/miR-29b-3p/PGRN/Wnt axis counted a great deal for seeking appropriate diagnostic biomarkers and treatment targets for CRC.

LncRNA MT1JP functions as a ceRNA in regulating FBXW7 through competitively binding to miR-92a-3p in gastric cancer

Background

Emerging evidence has shown that dysregulation function of long non-coding RNAs (lncRNAs) implicated in gastric cancer (GC). However, the role of the differentially expressed lncRNAs in GC has not fully explained.

Methods

LncRNA expression profiles were determined by lncRNA microarray in five pairs of normal and GC tissues, further validated in another 75 paired tissues by quantitative real-time PCR (qRT-PCR). Overexpression of lncRNA MT1JP was conducted to assess the effect of MT1JP in vitro and in vivo. The biological functions were demonstrated by luciferase reporter assay, western blotting and rescue experiments.

Results

LncRNA MT1JP was significantly lower in GC tissues than adjacent normal tissues, and higher MT1JP was remarkably related to lymph node metastasis and advance stage. Besides, GC patients with higher MT1JP expression had a well survival. Functionally, overexpression of lncRNA MT1JP inhibited cell proliferation, migration, invasion and promoted cell apoptosis in vitro, and inhibited tumor growth and metastasis in vivo. Functional analysis showed that lncRNA MT1JP regulated FBXW7 expression by competitively binding to miR-92a-3p. MiR-92a-3p and down-regulated FBXW7 reversed cell phenotypes caused by lncRNA MT1JP by rescue analysis.

Conclusion

MT1JP, a down-regulated lncRNA in GC, was associated with malignant tumor phenotypes and survival of GC. MT1JP regulated the progression of GC by functioning as a competing endogenous RNA (ceRNA) to competitively bind to miR-92a-3p and regulate FBXW7 expression. Our study provided new insight into the post-transcriptional regulation mechanism of lncRNA MT1JP, and suggested that MT1JP may act as a potential therapeutic target and prognosis biomarker for GC.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0829-6) contains supplementary material, which is available to authorized users.

Integrated analysis of long non-coding RNAs in human colorectal cancer

Accumulating evidence highlights the role of long non-coding RNAs (lncRNAs) in tumors. However, the genome-wide expression and roles of lncRNAs in colorectal cancer (CRC) remain unknown. Here, we systematically examined the global gene expressions in primary and synchronous liver metastases CRC tissue, in which thousands of aberrantly expressed lncRNAs were characterized. Co-expression analysis revealed that some lncRNAs correlated to their neighboring mRNAs in expression levels, whereas others formed networks with protein-coding genes in trans. We observed H3K4me3 was enriched at expressed lncRNA transcription start sites (TSSs) and correlated to dysregulated lncRNAs. Furthermore, we identified primary and metastasis tumor linked lncRNA signatures positively correlated with poor-prognosis gene set. Finally, functional experiments demonstrated two candidate lncRNAs were required for proliferation and migration of CRC cells. In summary, we provided a new framework for lncRNA associated clinical prognosis evaluation and target selection of gene therapy in CRC.

Differential expression profiles of long noncoding RNA and mRNA in colorectal cancer tissues from patients with lung metastasis

Lungs are the most common extra-abdominal site of metastasis of colorectal cancer (CRC), in which long noncoding RNA (lncRNA) may serve a role. In the present study, a high-throughput microarray assay was performed to detect lncRNA expression and identify novel targets for further study of lung metastasis in CRC. In the CRC tissues from patients with lung metastasis, 7,632 lncRNA (3,574 upregulated and 4,058 downregulated) and 6,185 mRNA (3,394 upregulated and 2,791 downregulated) were detected to be differentially expressed with a fold change ≥2 and P<0.05 compared with the CRC tissues without metastasis. A total of six differentially regulated lncRNA were confirmed by reverse transcription-quantitative polymerase chain reaction in 20 pairs of CRC samples. Furthermore, gene ontology and pathway analysis were conducted to predict the possible roles of the identified mRNA. The upregulated mRNA were associated with cell division (biological processes), protein kinase B binding (molecular functions) and cellular components. The downregulated mRNA were associated with cell adhesion, platelet-derived growth factor binding and membrane components. Pathway analysis determined that the upregulated mRNA were associated with the Wnt signaling pathway in the CRC tissues from patients with lung metastasis, while the downregulated mRNA were associated with the phosphoinositide 3-kinase/Akt signaling pathway. The results of the present study suggested that differentially expressed lncRNA may be associated with lung metastasis and may provide insights into the biology and prevention of lung metastasis.

Long non-coding RNA00544 serves as a potential novel predictive and prognostic marker for HR+ HER2- subtype breast cancer

Luminal breast cancers (BC) account for majority of breast cancer. Due to its heterogeneity and the development of treatment resistance, luminal BC patients can vary substantially. Long noncoding RNAs (lncRNAs), as we known, is involved in breast cancer progression. Here, we aim to identify the lncRNAs which are involved in the particular type luminal BC progression. By Gene Chips analysis, we found a novel lncRNA00544, which was highly expressed in the metastatic axillary nodes compared with corresponding luminal BC tissues (fold change = 2.26, P = 0.043). This result was confirmed in luminal BC cell lines (p = 0.0113) and 49 paired breast cancer samples compared with in corresponding controls (p = 0.011). Furthermore, Kaplan-Meier survival curves of 373 breast cancer patients indicated that disease-free survival was significantly poor in breast cancer patients with high lncRNA00544 expression (p < 0.001). Univariate and multivariate Cox regression analyses showed that lncRNA00544 was a significant independent prognostic biomarker in luminal BC patients. Further analysis showed that the prognosis of high lncRNA00544 expression in breast cancer patients was actually related to HR + HER2- subtype. Together, our studies indicate that lncRNA00544 may represent a novel predictive and prognostic indicator in luminal BC patients.

Silibinin suppresses bladder cancer through down-regulation of actin cytoskeleton and PI3K/Akt signaling pathways

Silibinin is the major active constituent of silymarin, an extract of milk thistle seeds. Silibinin has been shown to have significant anti-cancer effects in a variety of malignancies. However, the molecular mechanisms of silibinin action in bladder cancer have not been studied extensively. In the present study, we found that silibinin (10 μM) significantly suppressed proliferation, migration, invasion and induced apoptosis of T24 and UM-UC-3 human bladder cancer cells. Silibinin down-regulated the actin cytoskeleton and phosphatidylinositide 3-kinase (PI3K)/Akt signaling pathways in these cancer cell lines. These pathways were found to crosstalk through RAS cascades. We found that silibinin suppressed levels of trimethylated histone H3 lysine 4 and acetylated H3 at the KRAS promoter. Furthermore, silibinin targets long non-coding RNA: HOTAIR and ZFAS1, which are known to play roles as oncogenic factors in various cancers. This study shows that silibinin exerts anti-cancer effects through down-regulation of actin cytoskeleton and PI3K/Akt pathways and thus suppresses bladder cancer growth and progression.

Involvement of Non-coding RNAs in the Signaling Pathways of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common diagnosed cancers worldwide. The metastasis and development of resistance to anti-cancer treatment are major challenges in the treatment of CRC. Understanding mechanisms underpinning the pathogenesis is therefore critical in developing novel agents for CRC treatments. A large number of evidence has demonstrated that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs have functional roles in both the physiological and pathological processes by regulating the expression of their target genes. These molecules are engaged in the pathobiology of neoplastic diseases and are targets for the diagnosis, prognosis and therapy of a variety of cancers, including CRC. In this regard, ncRNAs have emerged as one of the hallmarks of CRC pathogenesis and they also play key roles in metastasis, drug resistance and the stemness of CRC stem cell by regulating various signaling networks. Therefore, a better understanding the ncRNAs involved in the signaling pathways of CRC may lead to the development of novel strategy for diagnosis, prognosis and treatment of CRC. In this chapter, we summarize the latest findings on ncRNAs, with a focus on miRNAs and lncRNAs involving in signaling networks and in the regulation of pathogenic signaling pathways in CRC.

Non-coding RNAs as Biomarkers for Colorectal Cancer Screening and Early Detection

Early detection of colorectal cancer (CRC) is the key for prevention and the ability to impact long-term survival of CRC patients. Current CRC screening modalities are inadequate for global application because of low sensitivity and specificity in case of conventional stool-based screening tests, and high costs and a low participation compliance in colonoscopy. An accurate stool- or blood-based screening test with use of innovative biomarkers is an appealing alternative as it is non-invasive and poses minimal risk to patients. It is easy to perform, can be repeated at shorter intervals, and therefore would likely lead to a much higher compliance rates. Non-coding RNAs (ncRNAs) have recently gained attention because of their involvement in different biological processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis. An increasing number of studies have demonstrated that mutations or abnormal expression of ncRNAs are closely associated with various cancers, including CRC. The discovery that ncRNAs (mainly microRNAs) are stable in stool and in blood plasma and serum presents the opportunity to develop novel strategies taking advantage of circulating ncRNAs as early diagnostic biomarkers of CRC. This chapter is a comprehensive examination of aberrant ncRNAs expression levels in tumor tissue, stool and blood of CRC patients and a summary of the current findings on ncRNAs, including microRNAs, small nucleolar RNAs, small nuclear RNAs, Piwi-interacting RNAs, circular RNAs and long ncRNAs in regards to their potential usage for screening or early detection of CRC.

Long Noncoding RNA BC032913 as a Novel Therapeutic Target for Colorectal Cancer that Suppresses Metastasis by Upregulating TIMP3

Long noncoding RNAs (lncRNAs) have been shown to play critical roles in the biology of various cancers. However, their expression patterns and biological functions in human colorectal cancer (CRC) remain largely unknown. The aim of this study was to explore lncRNA profiles in CRC and investigate key lncRNAs involved in CRC tumorigenesis and progression. The microarray data of six CRC and matched non-cancerous tissues revealed distinct lncRNA profiles, including 899 upregulated and 1,646 downregulated lncRNAs (p < 0.05, fold change > 2.0). Furthermore, we found that the lncRNA BC032913 was generally underexpressed in 115 CRC samples compared with normal tissues. Reduced BC032913 levels were significantly associated with an advanced tumor, lymph nodes, distant metastasis (TNM) stage and a higher risk of lymph node and distant metastases. BC032913 downregulation indicated poor overall survival in CRC patients. Moreover, BC032913 enhanced the mRNA and protein expression of TIMP3 and inhibited Wnt/β-catenin pathway activity, thus suppressing CRC metastasis in vitro and in vivo. Collectively, the obtained data show that BC032913 plays an inhibitory role in CRC aggression by upregulating TIMP3, followed by inactivation of the Wnt/β-catenin pathway. Our findings indicate that the novel lncRNA BC032913 could serve as a novel prognostic marker and effective therapeutic target for CRC.

Standardising RNA profiling based biomarker application in cancer-The need for robust control of technical variables

Histopathology-based staging of colorectal cancer (CRC) has utility in assessing the prognosis of patient subtypes, but as yet cannot accurately predict individual patient's treatment response. Transcriptomics approaches, using array based or next generation sequencing (NGS) platforms, of formalin fixed paraffin embedded tissue can be harnessed to develop multi-gene biomarkers for predicting both prognosis and treatment response, leading to stratification of treatment. While transcriptomics can shape future biomarker development, currently <1% of published biomarkers become clinically validated tests, often due to poor study design or lack of independent validation. In this review of a large number of CRC transcriptional studies, we identify recurrent sources of technical variability that encompass collection, preservation and storage of malignant tissue, nucleic acid extraction, methods to quantitate RNA transcripts and data analysis pipelines. We propose a series of defined steps for removal of these confounding issues, to ultimately aid in the development of more robust clinical biomarkers.

Meta-signature LncRNAs serve as novel biomarkers for colorectal cancer: integrated bioinformatics analysis, experimental validation and diagnostic evaluation

The aim of this study is to explore the differentially expressed lncRNAs, which may have potential biological function and diagnostic value in colorectal cancer (CRC). Through integrated data mining, we finally identified nine differentially expressed lncRNAs and their potential mRNA targets. After a series of bioinformatics analyses, we screened significant pathways and GO terms that are related to the up-regulated and down-regulated transcripts respectively. Meanwhile, the nine lncRNAs were validated in 30 paired tissues and cell lines by qRT-PCR and the results were basically consistent with the microarray data. We also tested the nine lncRNAs in the serum of 30 CRC patients matched with the CRC tissue, 30 non-cancer patients and 30 health controls. Finally, we found that BLACAT1 was significant for the diagnosis of CRC. The area under the curve (AUC), sensitivity and specificity were 0.858 (95% CI: 0.765-0.951), 83.3% and 76.7% respectively between CRC patients and health controls. Moreover, BLACAT1 also had distinct value to discriminate CRC from other non-cancer diseases. The results indicated that the differentially expressed lncRNAs and their potential target transcripts could be considered as potential therapeutic targets for CRC patients. Meanwhile, lncRNA BLACAT1 might represent a new supplementary biomarker for the diagnosis of CRC.

Transforming Cancer Epigenetics Using Nutritive Approaches and Noncoding RNAs

Cancer is considered one of the leading causes of death in the United States. Although preventive strategies, early detection, and improved treatment options have been developed, novel targets and therapeutics are still needed. Since concluding that cancer is mediated by genetic and epigenetic alterations of the cell, many research groups are now focusing on other means of prevention and therapy via nutrition, epigenetic mechanisms, and non-coding RNAs which have been shown to control gene expression and have many different functions at the cellular level. With the advent of high-throughput sequencing in human cancer, the potential to identify novel biomarkers and therapeutic targets of disease has increased tremendously and led to the identification of many non-coding RNAs that are dysregulated in various cancers. Gene expression and regulation is important in maintaining the homeostasis of normal tissues and cells. Not uncommonly, up- or down-regulation of particular genes are associated with cancer as a result of increased or decreased expression of transcriptional targets. This review focuses on the role of nutrition in cancer and the dysregulation of non-coding RNAs with particular emphasis on long non-coding RNAs and microRNAs in different cancer types.

MALAT1 promoted invasiveness of gastric adenocarcinoma

Background

Gastric cancer is the second leading cause of cancer globally, and the mechanism of its pathogenesis is still largely unknown. Recently, non-coding RNAs have been recognized to promote metastasis in various cancers, including gastric cancer.

Methods

We found that metastasis associated lung adenocarcinoma transcript-1 (MALAT1) is upregulated in gastric cancer tissue compared to adjacent normal tissue, as determined by microarray and subsequent qRT-PCR, then investigated the impact of MALAT1 on apoptosis, cell proliferation, and the cell cycle to dissect the carcinogenesis of gastric cancer, and examined mechanisms of invasion and metastasis. Expression of MALAT1 and U6 was determined by SYBR qRT-PCR in nine-teen gastric cancer cell lines and fifty fresh samples of cancer tissue and adjacent tissues. Downregulation of MALAT1 was accomplished with two different siRNAs. Cell proliferation was determined after treatment with these siRNAs. FACS using PI/Annexin-V staining was carried out. To analyze the invasiveness, a scratch wound-healing assay and a Matrigel invasion assay were performed. Cancer related gene expression assay was done after transfection of siR- MALAT1.

Results

The expression of MALAT1 was significantly elevated in various gastric cancer cell lines and gastric cancer tissues compared to normal cell lines and tissues (p < 0.01). siR-MALAT1 significantly reduced viable AGS cell numbers and induced apoptosis (p < 0.05). Deep invasion of tumor (advanced T stages) was more common in the high MALAT1-level group (p = 0.039). siR-MALAT1 significantly decreased AGS cell invasiveness and migration. siR-MALAT1 reduced expression of snail and N-cadherin, and elevated E-cadherin. The Wnt/β-catenin related genes were significantly decreased by transfection of siRNA MALAT1. MALAT1 is involved in gastric carcinogenesis via inhibition of apoptosis and promotes invasiveness via the epithelial-to-mesenchymal transition.

Conclusions

In our study, we found that deregulation of MALAT1 could be involved in both tumorigenesis and invasiveness in gastric cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2988-4) contains supplementary material, which is available to authorized users.

Long Non-Coding RNAs: A Novel Paradigm for Toxicology

Long non-coding RNAs (lncRNAs) are over 200 nucleotides in length and are transcribed from the mammalian genome in a tissue-specific and developmentally regulated pattern. There is growing recognition that lncRNAs are novel biomarkers and/or key regulators of toxicological responses in humans and animal models. Lacking protein-coding capacity, the numerous types of lncRNAs possess a myriad of transcriptional regulatory functions that include cis and trans gene expression, transcription factor activity, chromatin remodeling, imprinting, and enhancer up-regulation. LncRNAs also influence mRNA processing, post-transcriptional regulation, and protein trafficking. Dysregulation of lncRNAs has been implicated in various human health outcomes such as various cancers, Alzheimer's disease, cardiovascular disease, autoimmune diseases, as well as intermediary metabolism such as glucose, lipid, and bile acid homeostasis. Interestingly, emerging evidence in the literature over the past five years has shown that lncRNA regulation is impacted by exposures to various chemicals such as polycyclic aromatic hydrocarbons, benzene, cadmium, chlorpyrifos-methyl, bisphenol A, phthalates, phenols, and bile acids. Recent technological advancements, including next-generation sequencing technologies and novel computational algorithms, have enabled the profiling and functional characterizations of lncRNAs on a genomic scale. In this review, we summarize the biogenesis and general biological functions of lncRNAs, highlight the important roles of lncRNAs in human diseases and especially during the toxicological responses to various xenobiotics, evaluate current methods for identifying aberrant lncRNA expression and molecular target interactions, and discuss the potential to implement these tools to address fundamental questions in toxicology.

A gene browser of colorectal cancer with literature evidence and pre-computed regulatory information to identify key tumor suppressors and oncogenes

Colorectal cancer (CRC) is a cancer of growing incidence that associates with a high mortality rate worldwide. There is a poor understanding of the heterogeneity of CRC with regard to causative genetic mutations and gene regulatory mechanisms. Previous studies have identified several susceptibility genes in small-scale experiments. However, the information has not been comprehensively and systematically compiled and interpreted. In this study, we constructed the gbCRC, the first literature-based gene resource for investigating CRC-related human genes. The features of our database include: (i) manual curation of experimentally-verified genes reported in the literature; (ii) comprehensive integration of five reliable data sources; and (iii) pre-computed regulatory patterns involving transcription factors, microRNAs and long non-coding RNAs. In total, 2067 genes associating with 2819 PubMed abstracts were compiled. Comprehensive functional annotations associated with all the genes, including gene expression profiles, homologous genes in other model species, protein-protein interactions, somatic mutations, and potential methylation sites. These comprehensive annotations and this pre-computed regulatory information highlighted the importance of the gbCRC with regard to the unexplored regulatory network of CRC. This information is available in a plain text format that is free to download.

LncRNAs and cancer

Long non-coding RNAs (lncRNAs) are a group of non-coding RNAs composed of >200 nucleotides. Recent studies have revealed that lncRNAs exert an important role in the development and progression of cancer. In this review, the involvement of the most extensively investigated lncRNAs in cancers of the digestive, respiratory, reproductive, urinary and central nervous systems are discussed. LncRNAs function via molecular and biochemical mechanisms that include cis- and trans-regulation of gene expression, epigenetic modulation in the nucleus and post-transcriptional control in the cytoplasm. Although the detailed biological functions and molecular mechanisms of the majority of lncRNAs remain to be elucidated, this review aims to provide a novel insight into the diagnosis and treatment of cancer using lncRNAs.

Clinical significance of HOTAIR expression in colon cancer

AIM: To detect the expression of the long noncoding RNA HOTAIR in colon cancer and analyze its relationship with clinicopathological parameters of colon cancer.

METHODS: Total RNA was extracted from 80 colon cancer tissues and matched tumor-adjacent normal colon tissues and reverse transcribed. Quantitative polymerase chain reaction was used to detect the expression of HOTAIR. The relationship between the expression of HOTAIR and clinicopathological parameters of colon cancer was analyzed.

RESULTS: The expression of HOTAIR was significantly higher in colon cancer tissues than in matched tumor-adjacent normal colon tissues (P < 0.05). HOTAIR expression was significantly higher in cases with lymph node metastasis than in those without metastasis; in lowly differentiated and undifferentiated cases than in highly and moderately differentiated cases; and in stages III + IV cases than in stages I + II cases (P < 0.05).

CONCLUSION: HOTAIR expression is upregulated in colon cancer, suggesting that HOTAIR plays an important role in the tumorigenesis, development and metastasis of colon cancer. HOTAIR may act as an oncogene and represents a new molecular target for the treatment of colon cancer.

Genome-wide analysis of long noncoding RNA (lncRNA) expression in colorectal cancer tissues from patients with liver metastasis

The liver is the most frequent site of metastasis in colorectal cancer (CRC), in which long noncoding RNAs (lncRNAs) may play a crucial role. In this study, we performed a genome‐wide analysis of lncRNA expression to identify novel targets for the further study of liver metastasis in CRC. Samples obtained from CRC patients were analyzed using Arraystar human 8 × 60K lncRNA/mRNA v3.0 microarrays chips to find differentially expressed lncRNAs and mRNAs. The results were confirmed by quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR). The differentially expressed lncRNAs and mRNAs were identified through fold change filtering. Gene ontology (GO) and pathway analyses were performed using standard enrichment computational methods. In the CRC tissues from patients with liver metastasis, 2636 lncRNAs were differentially expressed, including 1600 up‐regulated and 1036 down‐regulated over two‐fold compared with the CRC tissues without metastasis. Among the 1584 differentially expressed mRNAs, 548 were up‐regulated and 1036 down‐regulated. GO and pathway analysis of the up‐regulated and down‐regulated mRNAs yielded different results. The up‐regulated mRNAs were associated with single‐organism process (biological process), membrane part (cellular component), and transporter activity (molecular function), whereas the down‐regulated mRNAs were associated with cellular process, membrane, and binding, respectively. In the pathway analysis, 27 gene pathways associated with the up‐regulated mRNAs and 51 gene pathways associated with the down‐regulated mRNAs were targeted. The significant changes in NQO2 (NM_000904) mRNA and six associated lncRNAs were selected for validation by qRT‐PCR. Aberrantly expressed lncRNAs may play an important role in the liver metastasis of CRC. The further study can provide useful insights into the biology and, ultimately, the prevention of liver metastasis.

Microarray Analysis of Long Non-coding RNA Expression Profile Associated with 5-Fluorouracil-Based Chemoradiation Resistance in Colorectal Cancer Cells

BACKGROUND

Preoperative 5-fluorouracil (5-FU)-based chemoradiotherapy is a standard treatment for locally advanced colorectal cancer (CRC). However, CRC cells often develop chemoradiation resistance (CRR). Recent studies have shown that long non-coding RNA (lncRNA) plays critical roles in a myriad of biological processes and human diseases, as well as chemotherapy resistance. Since the roles of lncRNAs in 5-FU-based CRR in human CRC cells remain unknown, they were investigated in this study.

MATERIALS AND METHODS

A 5-FU-based concurrent CRR cell model was established using human CRC cell line HCT116. Microarray expression profiling of lncRNAs and mRNAs was undertaken in parental HCT116 and 5-FU-based CRR cell lines.

RESULTS

In total, 2,662 differentially expressed lncRNAs and 2,398 mRNAs were identified in 5-FU-based CRR HCT116 cells when compared with those in parental HCT116. Moreover, 6 lncRNAs and 6 mRNAs found to be differentially expressed were validated by quantitative real time PCR (qRT-PCR). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis for the differentially expressed mRNAs indicated involvement of many, such as Jak- STAT, PI3K-Akt and NF-kappa B signaling pathways. To better understand the molecular basis of 5-FU-based CRR in CRC cells, correlated expression networks were constructed based on 8 intergenic lncRNAs and their nearby coding genes.

CONCLUSIONS

Changes in lncRNA expression are involved in 5-FU-based CRR in CRC cells. These findings may provide novel insight for the prognosis and prediction of response to therapy in CRC patients.

Non-coding RNAs: Epigenetic regulators of bone development and homeostasis

Non-coding RNAs (ncRNAs) have evolved in eukaryotes as epigenetic regulators of gene expression. The most abundant regulatory ncRNAs are the 20-24 nt small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs, <200 nt). Each class of ncRNAs operates through distinct mechanisms, but their pathways to regulating gene expression are interrelated in ways that are just being recognized. While the importance of lncRNAs in epigenetic control of transcription, developmental processes and human traits is emerging, the identity of lncRNAs in skeletal biology is scarcely known. However, since the first profiling studies of miRNA at stages during osteoblast and osteoclast differentiation, over 1100 publications related to bone biology and pathologies can be found, as well as many recent comprehensive reviews summarizing miRNA in skeletal cells. Delineating the activities and targets of specific miRNAs regulating differentiation of osteogenic and resorptive bone cells, coupled with in vivo gain- and loss-of-function studies, discovered unique mechanisms that support bone development and bone homeostasis in adults. We present here "guiding principles" for addressing biological control of bone tissue formation by ncRNAs. This review emphasizes recent advances in understanding regulation of the process of miRNA biogenesis that impact on osteogenic lineage commitment, transcription factors and signaling pathways. Also discussed are the approaches to be pursued for an understanding of the role of lncRNAs in bone and the challenges in addressing their multiple and complex functions. Based on new knowledge of epigenetic control of gene expression to be gained for ncRNA regulation of the skeleton, new directions for translating the miRNAs and lncRNAs into therapeutic targets for skeletal disorders are possible. This article is part of a Special Issue entitled Epigenetics and Bone.

Long noncoding RNAs and tumorigenesis: genetic associations, molecular mechanisms, and therapeutic strategies

The human genome contains a large number of nonprotein-coding sequences. Recently, new discoveries in the functions of nonprotein-coding sequences have demonstrated that the "Dark Genome" significantly contributes to human diseases, especially with regard to cancer. Of particular interest in this review are long noncoding RNAs (lncRNAs), which comprise a class of nonprotein-coding transcripts that are longer than 200 nucleotides. Accumulating evidence indicates that a large number of lncRNAs exhibit genetic associations with tumorigenesis, tumor progression, and metastasis. Our current understanding of the molecular bases of these lncRNAs that are associated with cancer indicate that they play critical roles in gene transcription, translation, and chromatin modification. Therapeutic strategies based on the targeting of lncRNAs to disrupt their expression or their functions are being developed. In this review, we briefly summarize and discuss the genetic associations and the aberrant expression of lncRNAs in cancer, with a particular focus on studies that have revealed the molecular mechanisms of lncRNAs in tumorigenesis. In addition, we also discuss different therapeutic strategies that involve the targeting of lncRNAs.

KATZLDA: KATZ measure for the lncRNA-disease association prediction

Accumulating experimental studies have demonstrated important associations between alterations and dysregulations of lncRNAs and the development and progression of various complex human diseases. Developing effective computational models to integrate vast amount of heterogeneous biological data for the identification of potential disease-lncRNA associations has become a hot topic in the fields of human complex diseases and lncRNAs, which could benefit lncRNA biomarker detection for disease diagnosis, treatment, and prevention. Considering the limitations in previous computational methods, the model of KATZ measure for LncRNA-Disease Association prediction (KATZLDA) was developed to uncover potential lncRNA-disease associations by integrating known lncRNA-disease associations, lncRNA expression profiles, lncRNA functional similarity, disease semantic similarity, and Gaussian interaction profile kernel similarity. KATZLDA could work for diseases without known related lncRNAs and lncRNAs without known associated diseases. KATZLDA obtained reliable AUCs of 7175, 0.7886, 0.7719 in the local and global leave-one-out cross validation and 5-fold cross validation, respectively, significantly improving previous classical methods. Furthermore, case studies of colon, gastric, and renal cancer were implemented and 60% of top 10 predictions have been confirmed by recent biological experiments. It is anticipated that KATZLDA could be an important resource with potential values for biomedical researches.

Upregulation of long non-coding RNA PRNCR1 in colorectal cancer promotes cell proliferation and cell cycle progression

Colorectal cancer (CRC) is one of the most common cancers worldwide. Long non-coding RNAs (lncRNAs) have been confirmed to play a critical regulatory role in various biological processes including carcinogenesis, which indicates that lncRNAs are valuable biomarkers and therapeutic targets. The novel lncRNA prostate cancer non-coding RNA 1 (PRNCR1) is located in the susceptible genomic area of CRC, however the functional role of PRNCR1 remains unknown. Thus, we aimed to investigate the clinical significance and biological function of PRNCR1 in CRC. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess the expression profile of PRNCR1 in CRC tissues and cell lines. An antisense oligonucleotide (ASO) was designed to knock down PRNCR1. In a cohort of 63 patients, PRNCR1 was significantly overexpressed in CRC tissues compared with the expression in adjacent tissues, with an average fold increase of 10.55 (P=0.006). Additionally, a high level of PRNCR1 was associated with large tumor volume (P<0.05). Based on receiver operating characteristic curve (ROC), we found that the area under the curve (AUC) of PRNCR1 was 0.799 while the AUC of conventional biomarker CEA-CA199 was 0.651, indicating that PRNCR1 could be a sensitive diagnostic biomarker of CRC. Compared with the normal human colorectal epithelial cell line (FHC), PRNCR1 was upregulated in most CRC cell lines (HCT116, SW480, LoVo and HT-29). After knockdown of PRNCR1 by ASO, CRC cell proliferation ability was significantly inhibited. We further found that PRNCR1 knockdown induced cell cycle arrest in the G0/G1 phase and a significant decrease in the proportion of cells in the S phases. In contrast, PRNCR1 knockdown did not affect cell apoptosis or invasive ability. Hence, these data indicate that PRNCR1 promotes the proliferation of CRC cells and is a potential oncogene of CRC.