CCAT2, a novel long non-coding RNA in breast cancer: expression study and clinical correlations

Long noncoding RNA NSCLCAT1 increases non-small cell lung cancer cell invasion and migration through the Hippo signaling pathway by interacting with CDH1

Metastatic growth is the leading cause of cancer-related death in non-small cell lung cancer (NSCLC). Metastasis is believed to be initiated by an increase in cell motility mediated by the loss of cell-cell adhesion because of the suppression of E-cadherin [encoded by cadherin 1 ( CDH1)]. However, very little is known about the molecular mechanism of CDH1 regulation. Therefore, we hypothesized that non-small cell lung cancer-associated transcript-1 (NSCLCAT1) suppresses functional CDH1 and mediates the Hippo signaling pathway, resulting in increased cell migration and invasion, and reduced apoptosis. Initially, microarray profiling and target prediction programs were employed to identify whether NSCLCAT1 targets CDH1. Next, quantitative PCR was used to determine the expression pattern of NSCLCAT1 in 114 specimens. The biologic functions of NSCLCAT1 in NSCLC were assessed through the up-regulation and down-regulation of the levels of endogenous NSCLCAT1 with the use of NSCLCAT1 vector or small interfering RNA against NSCLCAT1 in NSCLC cells. Furthermore, the Hippo signaling pathway in NSCLC cells was blocked by applying the verteporfin treatment to have a better understanding on the pivotal role of the Hippo signaling pathway in NSCLC. Microarray expression profiles of long noncoding RNAs, GSE19804 and GSE27262), revealed that NSCLCAT1 was up-regulated in NSCLC. Among patients with NSCLC, we determined that the NSCLCAT1 was robustly induced, whereas CDH1 was suppressed. The luciferase activity determination identified CDH1 as a NSCLCAT1 target. NSCLCAT1 was found to increase cell viability, migration, and invasion and to reduce apoptosis in NSCLC cells. The results from the quantitative PCR and Western blot analysis revealed that NSCLCAT1 modulated the Hippo signaling pathway. Furthermore, the inhibition of the Hippo signaling pathway by verteporfin treatment led to the loss of the effect of NSCLCAT1 on NSCLC cells. In summary, our findings suggested that NSCLCAT1 potentially has a role in NSCLC and NSCLCAT1-mediated regulation of the Hippo signaling pathway through the transcriptional repression of CDH1; therefore, the functional suppression or inhibition of NSCLCAT1 could be used as a novel therapeutic pathway in the control of aggressive and metastatic NSCLC.-Zhao, W., Zhang, L.-N., Wang, X.-L., Zhang, J., Yu, H.-X. Long noncoding RNA NSCLCAT1 increases non-small cell lung cancer cell invasion and migration through the Hippo signaling pathway by interacting with CDH1.

Downregulation of long non-coding RNA Opa interacting protein 5-antisense RNA 1 inhibits breast cancer progression by targeting sex-determining region Y-box 2 by microRNA-129-5p upregulation

Several studies have shown an important role for long non‐coding RNA (lncRNA) in breast cancer progression. The present study investigated the role of lncRNA Opa interacting protein 5‐antisense RNA 1 (OIP5‐AS1) in the progression of breast cancer. OIP5‐AS1 was significantly upregulated in breast cancer tissues and in breast cancer cell lines, and OIP5‐AS1 downregulation inhibited the malignant behavior of breast cancer in vitro and in vivo. For in‐depth exploration of the mechanism of OIP5‐AS1 in breast cancer, we found that expression of microRNA‐129‐5p(miR‐129‐5p), which was found to bind sites in the sequence of OIP5‐AS1, in breast cancer tissues was negatively correlated with OIP5‐AS1. Also, luciferase assays indicated that OIP5‐AS1 acted as a miR‐129‐5p sponge, resulting in upregulated expression of the sex‐determining region Y‐box 2 (SOX2) transcription factor. Our study showed that OIP5‐AS1 plays a critical role in promoting breast cancer progression and that OIP5‐AS1 downregulation targets SOX2 by miR‐129‐5p upregulation.

Non-Coding RNAs in Breast Cancer: Intracellular and Intercellular Communication

Non-coding RNAs (ncRNAs) are regulators of intracellular and intercellular signaling in breast cancer. ncRNAs modulate intracellular signaling to control diverse cellular processes, including levels and activity of estrogen receptor α (ERα), proliferation, invasion, migration, apoptosis, and stemness. In addition, ncRNAs can be packaged into exosomes to provide intercellular communication by the transmission of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) to cells locally or systemically. This review provides an overview of the biogenesis and roles of ncRNAs: small nucleolar RNA (snRNA), circular RNAs (circRNAs), PIWI-interacting RNAs (piRNAs), miRNAs, and lncRNAs in breast cancer. Since more is known about the miRNAs and lncRNAs that are expressed in breast tumors, their established targets as oncogenic drivers and tumor suppressors will be reviewed. The focus is on miRNAs and lncRNAs identified in breast tumors, since a number of ncRNAs identified in breast cancer cells are not dysregulated in breast tumors. The identity and putative function of selected lncRNAs increased: nuclear paraspeckle assembly transcript 1 (NEAT1), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), steroid receptor RNA activator 1 (SRA1), colon cancer associated transcript 2 (CCAT2), colorectal neoplasia differentially expressed (CRNDE), myocardial infarction associated transcript (MIAT), and long intergenic non-protein coding RNA, Regulator of Reprogramming (LINC-ROR); and decreased levels of maternally-expressed 3 (MEG3) in breast tumors have been observed as well. miRNAs and lncRNAs are considered targets of therapeutic intervention in breast cancer, but further work is needed to bring the promise of regulating their activities to clinical use.

Plant natural modulators in breast cancer prevention: status quo and future perspectives reinforced by predictive, preventive, and personalized medical approach

In contrast to the genetic component in mammary carcinogenesis, epigenetic alterations are particularly important for the development of sporadic breast cancer (BC) comprising over 90% of all BC cases worldwide. Most of the DNA methylation processes are physiological and essential for human cellular and tissue homeostasis, playing an important role in a number of key mechanisms. However, if dysregulated, DNA methylation contributes to pathological processes such as cancer development and progression. A global hypomethylation of oncogenes and hypermethylation of tumor-suppressor genes are characteristic of most cancer types. Moreover, histone chemical modifications and non-coding RNA-associated multi-gene controls are considered as the key epigenetic mechanisms governing the cellular homeostasis and differentiation states. A number of studies demonstrate dietary plant products as actively affecting the development and progression of cancer. "Nutri-epigenetics" focuses on the influence of dietary agents on epigenetic mechanisms. This approach has gained considerable attention; since in contrast to genetic alterations, epigenetic modifications are reversible affect early carcinogenesis. Currently, there is an evident lack of papers dedicated to the phytochemicals/plant extracts as complex epigenetic modulators, specifically in BC. Our paper highlights the role of plant natural compounds in targeting epigenetic alterations associated with BC development, progression, as well as its potential chemoprevention in the context of preventive medicine. Comprehensive measures are stated with a great potential to advance the overall BC management in favor of predictive, preventive, and personalized medical services and can be considered as "proof-of principle" model, for their potential application to other multifactorial diseases.

Research progresses in roles of LncRNA and its relationships with breast cancer

Some progresses have been made in research of long non-coding RNA (hereunder referred to as LncRNA) related to breast cancer. Lots of data about LncRNA transcription concerning breast cancer have been obtained from large-scale omics research (e.g. transcriptomes and chips). Some LncRNAs would become indices for detecting breast cancer and judging its development and prognosis. LncRNAs may affect genesis and development of breast cancer in multiple ways. Perhaps they could develop into potential targets for treating breast cancer if they are carcinogenic. Like those from other studies of breast cancer, many data gained from omics research remain to be validated by much experimental work. For instance, it is still necessary to demonstrate reliability of LncRNAs as indices for diagnosing breast cancer and judging its prognosis (particularly for various subtypes of breast cancer), effectiveness and feasibility of these genes for treating breast cancer as targets. In this paper, recent years’ literatures about LncRNAs which are related to breast cancer are summarized and sorted out to review the research progresses in relationships between LncRNAs and breast cancer.

Aberrant miRNAs expressed in HER-2 negative breast cancers patient

Background

Breast cancer is a highly heterogeneous pathology, exhibiting a number of subtypes commonly associated with a poor outcome. Due to their high stability, microRNAs are often regarded as non-invasive cancer biomarkers, having an expression pattern specific for their ‘cell of origin’.

Method

Triple negative breast cancer (TNBC: ER-, PR-, Her-2-) and double positive breast cancer (DPBC: ER+, PR+, Her-2) miRNA expression patterns were obtained by analysis of the TCGA (The Cancer Genome Atlas) data, followed by PCR-array analysis on plasma samples from 20 TNBC patients, 14 DPBC patients and 11 controls.

Results

Three downregulated and nine upregulated miRNAs were obtained from the TNBC analysis. Five overexpressed miRNAs were identified in the DPBC group. Four of the dysregulated miRNAs (miR-10a, miR-125b, miR-210 and miR-489) were common for both groups. The cluster miR-17-92 (miR-17, miR-20a, miR-20b, and miR-93), along with miR-130, miR-22 and miR-29a/c, were found to differentiate between TNBC and DPBC. A panel of five transcripts (miR-10a, miR-125, miR-193b, miR-200b and miR-489) was validated in a new set of plasma samples. The overlapping of TCGA and plasma profiling data revealed miR-200b, miR-200c, miR-210 and miR-29c as common signature. MiR-200b was validated on additional normal and tumor tissue samples. The expression level of this transcript from the TCGA data was correlated with lung and bone metastatic genes.

Conclusion

The miR-200b presents a great potential for the future advancements in the diagnostic/prognostic and therapeutic approach of TNBC, along with other coding or non-coding transcripts. However, this needs to be further integrated in a regulatory network that acts in conjunction with other markers that affect the patients’ prognosis or response to therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0920-2) contains supplementary material, which is available to authorized users.

The Network of Non-coding RNAs in Cancer Drug Resistance

Non-coding RNAs (ncRNAs) have been implicated in most cellular functions. The disruption of their function through somatic mutations, genomic imprinting, transcriptional and post-transcriptional regulation, plays an ever-increasing role in cancer development. ncRNAs, including notorious microRNAs, have been thus proposed to function as tumor suppressors or oncogenes, often in a context-dependent fashion. In parallel, ncRNAs with altered expression in cancer have been reported to exert a key role in determining drug sensitivity or restoring drug responsiveness in resistant cells. Acquisition of resistance to anti-cancer drugs is a major hindrance to effective chemotherapy and is one of the most important causes of relapse and mortality in cancer patients. For these reasons, non-coding RNAs have become recent focuses as prognostic agents and modifiers of chemo-sensitivity. This review starts with a brief outline of the role of most studied non-coding RNAs in cancer and then highlights the modulation of cancer drug resistance via known ncRNAs based mechanisms. We identified from literature 388 ncRNA-drugs interactions and analyzed them using an unsupervised approach. Essentially, we performed a network analysis of the non-coding RNAs with direct relations with cancer drugs. Within such a machine-learning framework we detected the most representative ncRNAs-drug associations and groups. We finally discussed the higher integration of the drug-ncRNA clusters with the goal of disentangling effectors from downstream effects and further clarify the involvement of ncRNAs in the cellular mechanisms underlying resistance to cancer treatments.

The Impact of lncRNA Dysregulation on Clinicopathology and Survival of Breast Cancer: A Systematic Review and Meta-analysis

Dysregulation of multiple long non-coding RNAs (lncRNAs) was reported to play major roles in breast cancer (BC). Here we aimed to collect most of the relevant literature to assess the prognostic value of lncRNAs in BC. To this end, we systematically searched PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), and Wanfang to identify published articles on the associations of lncRNAs with clinicopathology and/or survival of BC. Via this searching, we identified 70 articles involving 9,307 BC patients and regarding 48 lncRNAs. The expression of 41 lncRNAs was related to one or more clinicopathological parameters of BC, including tumor size; lymph node metastasis; histological grade; TNM stage; and estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) statuses (p < 0.05). Dysregulation of 28 lncRNAs was associated with overall survival, and abnormal expression of 9 lncRNAs was linked to disease-free survival. Furthermore, the expression level of 3 lncRNAs was correlated with metastasis-free survival, 3 lncRNAs with relapse-free survival, and 3 lncRNAs with progression-free survival. Our analysis showed that multiple lncRNAs were significantly associated with BC clinicopathology and survival. A large-scale study is needed to verify the prognostic value of these lncRNAs in BC.

Long non-coding RNAs: implications in targeted diagnoses, prognosis, and improved therapeutic strategies in human non- and triple-negative breast cancer

Triple-negative breast cancer (TNBC) has been clinically difficult to manage because of tumor aggressiveness, cellular and histological heterogeneity, and molecular mechanisms’ complexity. All this in turn leads us to evaluate that tumor biological behavior is not yet fully understood. Additionally, the heterogeneity of tumor cells represents a great biomedicine challenge in terms of the complex molecular—genetical-transcriptional and epigenetical—mechanisms, which have not been fully elucidated on human solid tumors.

Recently, human breast cancer, but specifically TNBC is under basic and clinical-oncology research in the discovery of new molecular biomarkers and/or therapeutic targets to improve treatment responses, as well as for seeking algorithms for patient stratification, seeking a positive impact in clinical-oncology outcomes and life quality on breast cancer patients.

In this sense, important knowledge is emerging regarding several cancer molecular aberrations, including higher genetic mutational rates, LOH, CNV, chromosomal, and epigenetic alterations, as well as transcriptome aberrations in terms of the total gene-coding ribonucleic acids (RNAs), known as mRNAs, as well as non-coding RNA (ncRNA) sequences. In this regard, novel investigation fields have included microRNAs (miRNAs), as well as long ncRNAs (lncRNAs), which have been importantly related and are likely involved in the induction, promotion, progression, and/or clinical therapeutic response trackers of TNBC. Based on this, in general terms according with the five functional archetype classification, the lncRNAs may be involved in the regulation of several molecular mechanisms which include genetic expression, epigenetic, transcriptional, and/or post-transcriptional mechanisms, which are nowadays not totally understood.

Here, we have reviewed the main dis-regulated and functionally non- and well-characterized lncRNAs and their likely involvement, from a molecular enrichment and mechanistic point of view, as tumor biomarkers for breast cancer and its specific histological subtype, TNBC. In reference to the abovementioned, it has been described that some lncRNA expression profiles correspond or are associated with the TNBC histological subtype, potentially granting their use for TNBC malignant progression, diagnosis, tumor clinical stage, and likely therapy. Based on this, lncRNAs have been proposed as potential biomarkers which might represent potential predictive tools in the differentiated breast carcinomas versus TNBC malignant disease. Finally, elucidation of the specific or multi-functional archetypal of lncRNAs in breast cancer and TNBC could be fundamental, as these molecular intermediary-regulator “lncRNAs” are widely involved in the genome expression, epigenome regulation, and transcriptional and post-transcriptional tumor biology, which in turn will probably represent a new prospect in clinical and/or therapeutic molecular targets for the oncological management of breast carcinomas in general and also for TNBC patients.

The long noncoding RNA ANRIL acts as an oncogene and contributes to paclitaxel resistance of lung adenocarcinoma A549 cells

Long non-coding RNAs (lncRNAs) are a family of non-protein-coding RNAs that might affect Lung adenocarcinoma (LAD) chemo-resistance and most of them could be used as biomarkers and therapy targets. However, the potential function of lncRNA ANRIL contributed paclitaxel chemo-resistance in LAD is still unknown. This study aimed to observe the expression of ANRIL in LAD, evaluate its biological role in the resistance of LAD cells to paclitaxel and explore the apoptosis role in the ANRIL associated mechanism. Our results showed that ANRIL functioning as a potential oncogene was up-regulated in LAD, and promoted the acquisition of chemo-resistance in paclitaxel partly through the mitochondrial pathway by modulating the expression of apoptosis-related protein cleaved-PARP and Bcl-2. These findings might improve LAD patients' paclitaxel treatment and made ANRIL to be a new target for paclitaxel-based chemotherapy in LAD.

A novel long non-coding RNA linc-ZNF469-3 promotes lung metastasis through miR-574-5p-ZEB1 axis in triple negative breast cancer

Triple-negative breast cancer (TNBC) patients usually lead to poor prognosis and survival because of metastasis. The major sites for TNBC metastasis include the lungs, brain, liver, and bone. Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts longer than 200 nucleotides and have been reported as important regulators in BC metastasis. However, the underlying mechanisms for lncRNAs regulating TNBC metastasis are not fully understood. Here we found that linc-ZNF469-3 was highly expressed in lung-metastatic LM2-4175 TNBC cells and overexpression of linc-ZNF469-3 enhanced invasion ability and stemness properties in vitro and lung metastasis in vivo. Furthermore, we found linc-ZNF469-3 physically interacted with miR-574-5p and overexpression of miR-574-5p attenuated ZEB1 expression. Importantly, endogenous high expressions of linc-ZNF469-3 and ZEB1 were correlated with tumor recurrence in TNBC patients with lung metastasis. Taken together, our findings suggested that linc-ZNF469-3 promotes lung metastasis of TNBC through miR-574-5p-ZEB1 signaling axis and may be used as potential prognostic marker for TNBC patients.

Deciphering the roles of lncRNAs in breast development and disease

Breast cancer is the second leading cause of cancer related deaths in women. It is therefore important to understand the mechanisms underlying breast cancer development as well as raises the need for enhanced, non-invasive strategies for novel prognostic and diagnostic methods. The emergence of long non-coding RNAs (lncRNAs) as potential key players in neoplastic disease has received considerable attention over the past few years. This relatively new class of molecular regulators has been shown from ongoing research to act as critical players for key biological processes. Deregulated expression levels of lncRNAs have been observed in a number of cancers including breast cancer. Furthermore, lncRNAs have been linked to breast cancer initiation, progression, metastases and to limit sensitivity to certain targeted therapeutics. In this review we provide an update on the lncRNAs associated with breast cancer and mammary gland development and illustrate the versatility of such lncRNAs in gene control, differentiation and development both in normal physiological conditions and in diseased states. We also highlight the therapeutic and diagnostic potential of lncRNAs in cancer.

Cancer-associated rs6983267 SNP and its accompanying long noncoding RNA CCAT2 induce myeloid malignancies via unique SNP-specific RNA mutations

The cancer-risk-associated rs6983267 single nucleotide polymorphism (SNP) and the accompanying long noncoding RNA CCAT2 in the highly amplified 8q24.21 region have been implicated in cancer predisposition, although causality has not been established. Here, using allele-specific CCAT2 transgenic mice, we demonstrate that CCAT2 overexpression leads to spontaneous myeloid malignancies. We further identified that CCAT2 is overexpressed in bone marrow and peripheral blood of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) patients. CCAT2 induces global deregulation of gene expression by down-regulating EZH2 in vitro and in vivo in an allele-specific manner. We also identified a novel non-APOBEC, non-ADAR, RNA editing at the SNP locus in MDS/MPN patients and CCAT2-transgenic mice. The RNA transcribed from the SNP locus in malignant hematopoietic cells have different allelic composition from the corresponding genomic DNA, a phenomenon rarely observed in normal cells. Our findings provide fundamental insights into the functional role of rs6983267 SNP and CCAT2 in myeloid malignancies.

LncRNA CCAT2 promoted osteosarcoma cell proliferation and invasion

Long non‐coding RNA (lncRNA) plays important roles in tumour progression. Accumulating studies demonstrated that lncRNA colon cancer‐associated transcript 2 (CCAT2) acted as an oncogene in many tumours. However, the role of CCAT2 in the development of osteosarcoma has not been elucidated. In our study, we indicated that CCAT2 expression was up‐regulated in osteosarcoma tissues and cell lines (SOSP‐9607, MG‐63, U2OS and SAOS‐2). In addition, osteosarcoma cases with higher CCAT2 expression had a poorer disease‐free survival and shorter the overall survival time compared to those with lower expression. Overexpression of CCAT2 promoted osteosarcoma cell proliferation, invasion and cell cycle. Furthermore, ectopic expression of CCAT2 increased the expression of mesenchymal markers N‐cadherin, vimentin and snail and reduced the expression of N‐cadherin marker E‐cadherin. CCAT2 overexpression promoted the LATS2 and c‐Myc expression in osteosarcoma cell. These data indicated that CCAT2 served as an oncogene in osteosarcoma and promoted osteosarcoma cell proliferation, cell cycle and invasion.

Dysregulation of long non-coding RNA in breast cancer: an overview of mechanism and clinical implication

Long non-coding RNAs (lncRNAs), which occupy nearly 98% of genome, have crucial roles in cancer development, including breast cancer. Breast cancer is a disease with high incidence. Despite of recent progress in understanding the molecular mechanisms and combined therapy strategies, the functions and mechanisms of lncRNAs in breast cancer remains unclear. This review presents the currently basic knowledge and research approaches of lncRNAs. We also highlight the latest advances of seven classic lncRNAs and three novel lncRNAs in breast cancer, elucidating their mechanisms and possible therapeutic targets. Additionally, association between lncRNA and specific molecular subtype of breast cancer is reported. Lastly, we briefly delineate the potential roles of lncRNAs in clinical applications as biomarkers and treatment targets.

Long noncoding RNA CCAT2 is activated by E2F1 and exerts oncogenic properties by interacting with PTTG1 in pituitary adenomas

Pituitary adenomas, arising from the pituitary gland cells, are one of the most frequent tumors found in the sella region. However, the molecular mechanisms involved in the carcinogenesis and progression of pituitary adenomas is still not understood in detail. Long noncoding RNA (lncRNA) colon cancer-associated transcript 2 (CCAT2), a newly identified lncRNA, has been reported to be abnormally expressed in some cancers. In the present study, we found that CCAT2 was significantly upregulated in pituitary adenomas tissues. Elevated CCAT2 expression was correlated with poor prognosis in patients with pituitary adenomas. Moreover, CCAT2 expression was activated by E2F1. Loss-of-function and gain-of-function assays showed that CCAT2 positively regulated pituitary adenoma cell proliferation, migration, and invasion. Further investigation demonstrated that CCAT2 interacted with PTTG1, and promoted its stability. Furthermore, CCAT2 affected the expression of downstream genes regulated by PTTG1, including SOX2, DLK1, MMP2, and MMP13. Cumulatively, CCAT2 functions as an oncogene in pituitary adenomas and its overexpression contributes to pituitary adenoma carcinogenesis and progression.

Epigenetics of breast cancer: Biology and clinical implication in the era of precision medicine

In the last years, mortality from breast cancer has declined in western countries as a consequence of a more widespread screening resulting in earlier detection, as well as an improved molecular classification and advances in adjuvant treatment. Nevertheless, approximately one third of breast cancer patients will develop distant metastases and eventually die for the disease. There is now a compelling body of evidence suggesting that epigenetic modifications comprising DNA methylation and chromatin remodeling play a pivotal role since the early stages of breast cancerogenesis. In addition, recently, increasing emphasis is being placed on the property of ncRNAs to finely control gene expression at multiple levels by interacting with a wide array of molecules such that they might be designated as epigenetic modifiers. In this review, we summarize the current knowledge about the involvement of epigenetic modifications in breast cancer, and provide an overview of the significant association of epigenetic traits with the breast cancer clinicopathological features, emphasizing the potentiality of epigenetic marks to become biomarkers in the context of precision medicine.

The hypoxia-responsive long non-coding RNAs may impact on the tumor biology and subsequent management of breast cancer

Long non-coding RNAs (lncRNAs) are DNA transcripts longer than 200 nucleotides without protein-coding potential. As they are key regulators of gene expression at chromatic, transcriptional and posttranscriptional level, they play important role in various biological and pathological processes. Dysregulation of lncRNAs has been observed in several diseases including cancer. Breast cancer is heterogeneous disease with many molecular subtypes specific in different prognosis and treatment responses. Hypoxia, a common micro-environmental feature of rapidly growing tumour is associated with metastases, recurrences and resistance to therapy. Aberrant expression of hypoxia related lncRNAs significantly correlates with poor outcomes in cancer patients, as the lncRNAs play an important regulatory role in the breast cancer-cell survival. Thus, a better understanding of lncRNAs role in the hypoxic conditions of breast cancer is crucial for precise understanding of the tumorigenesis, disease features and poor clinical outcome, especially in highly aggressive breast cancer subtypes (HER2-positive and triple-negative types). Moreover, lncRNAs may represent tumour marker predicting prognosis and therapeutic targets improving precise and personalized therapy for better patient´s survival. In this review, we summarize the recent information on lncRNAs in breast cancer with special focus on the hypoxia-responsive lncRNAs and their potential impact on the prognosis, therapy algorithms and individual outcomes. Presented data helps in better understanding of the specific mechanisms predicting new therapeutic agents and strategies for the pharmacological intervention.

Natural Antisense Transcripts: Molecular Mechanisms and Implications in Breast Cancers

Natural antisense transcripts are RNA sequences that can be transcribed from both DNA strands at the same locus but in the opposite direction from the gene transcript. Because strand-specific high-throughput sequencing of the antisense transcriptome has only been available for less than a decade, many natural antisense transcripts were first described as long non-coding RNAs. Although the precise biological roles of natural antisense transcripts are not known yet, an increasing number of studies report their implication in gene expression regulation. Their expression levels are altered in many physiological and pathological conditions, including breast cancers. Among the potential clinical utilities of the natural antisense transcripts, the non-coding|coding transcript pairs are of high interest for treatment. Indeed, these pairs can be targeted by antisense oligonucleotides to specifically tune the expression of the coding-gene. Here, we describe the current knowledge about natural antisense transcripts, their varying molecular mechanisms as gene expression regulators, and their potential as prognostic or predictive biomarkers in breast cancers.

Long non-coding RNA CCAT2 promotes epithelial-mesenchymal transition involving Wnt/β-catenin pathway in epithelial ovarian carcinoma cells

Long non-coding RNA colon cancer-associated transcript 2 (CCAT2) is dysregulated in a variety of types of human cancer. However, the role of CCAT2 in epithelial ovarian carcinoma (EOC) remains largely unknown. The aim of this study is to investigate the effect of CCAT2 on epithelial-mesenchymal transition (EMT) and related molecular mechanisms in epithelial ovarian cancer cells. In the current paper, we found that CCAT2 was significantly upregulated in EOC SKOV3, A2780 and HO8910 cell lines compared with the normal ovarian epithelial HUM-CELL-0088 cell line. Functional assays demonstrated that the knockdown of CCAT2 inhibited migration and invasion of EOC cells in vitro. Moreover, our results showed that silencing CCAT2 inhibited EMT by the upregulation of epithelial cadherin and downregulation of neural cadherin, zinc finger protein SNAI and Twist-related protein 1 in SKOV3 and A2780 cell lines. But, that was reversed by the treatment with lithium chloride (LiCl), by which the canonical Wnt/β-catenin pathway could be activated. In addition, we further investigated the role of CCAT2 in the modulation of Wnt/β-catenin signaling pathway. Our results revealed that knockdown of CCAT2 inhibited the expression of β-catenin and the activity of T-cell factor/lymphoid enhancer factor, acting as a key transcription factor of Wnt signaling pathway. Collectively, these results indicate that CCAT2 may promote EMT, at least partly through Wnt/β-catenin signaling pathway in EOC cells. Thus, CCAT2 might play a critical role in EOC progression and serve as a valuable target for the treatment of ovarian cancer.

Knockdown of lncRNA CCAT2 inhibits endometrial cancer cells growth and metastasis via sponging miR-216b

OBJECTIVE

Colon cancer-associated transcript 2 (CCAT2), a novel lncRNA has been reported as an oncogene in several cancers. This study was aimed to explore whether CCAT2 also exerted oncogenic roles in endometrial cancer cells.

MATERIALS AND METHODS

The expression of CCAT2 in 30 pairs of endometrial cancer and matched non-cancerous tissues were detected by qRT-PCR. Two endometrial cancer cell lines HEC-1-A and RL95-2 were used throughout this study. CCAT2 in cells was silenced by transfection with shRNA targeted CCAT2, then cell growth and metastasis were assessed by performing trypan blue staining, Transwell assay, and flow cytometry. Dual-luciferase reporter assay was used to detect the combination of miR-216b and CCAT2. Besides, the expression of miR-216b and Bcl-2 in cells were overexpressed or suppressed by transfection with their correspondingly mimic/vector or inhibitor/shRNA. qRT-PCR and western blot analysis were performed to detect the expression of Bcl-2 and main factors in PTEN/PI3K/AKT and mTOR signaling pathways.

RESULTS

CCAT2 was highly expressed in endometrial cancer tissues when compared to non-cancerous endometrial tissues. Knockdown of CCAT2 inhibited HEC-1-A and RL95-2 cells viability, migration, invasion, but induced apoptosis. CCAT2 was an endogenous sponge by competing for miR-216b, and miR-216b suppression alleviated CCAT2 silence-diminished cell growth and metastasis. miR-216b negatively regulated Bcl-2 and Bcl-2 could further active PTEN/PI3K/AKT and mTOR signaling pathways.

CONCLUSIONS

To conclude, these results demonstrated lncRNA CCAT2 was highly expressed in endometrial cancer tissues. Knockdown of CCAT2 inhibited cell growth and metastasis of endometrial cancer cells by sponging miR-216b.

uc.38 induces breast cancer cell apoptosis via PBX1

Long non-coding RNAs (lncRNAs) are transcripts longer than 200 bp with no protein-coding capacity. Transcribed ultraconserved regions (T-UCRs) are a type of lncRNA and are conserved among human, chick, dog, mouse and rat genomes. These sequences are involved in cancer biology and tumourigenesis. Nevertheless, the clinical significance and biological mechanism of T-UCRs in breast cancer remain largely unknown. The expression of uc.38, a T-UCR, was down-regulated in both breast cancer tissues and breast cancer cell lines. However, uc.38 was expressed at significantly lower levels in larger tumours and tumours of more advanced stages. Based on the results of in vitro and in vivo experiments, up-regulation of uc.38 expression inhibited cell proliferation and induced cell apoptosis. Thus, uc.38 suppressed breast cancer. Additional experiments revealed that uc.38 negatively regulated the expression of the pre-B-cell leukaemia homeobox 1 (PBX1) protein and subsequently affected the expression of Bcl-2 family members, ultimately inducing breast cancer cell apoptosis. Describing the uc.38/PBX1 axis has improved our understanding of the molecular mechanisms involved in breast cancer apoptosis and has suggested that this axis is a potential therapeutic target for breast cancer.

Silencing CCAT2 inhibited proliferation and invasion of epithelial ovarian carcinoma cells by regulating Wnt signaling pathway

Long non-coding RNA CCAT2 (colon cancer-associated transcript 2) is dysregulated in varieties of human tumors. However, the role of CCAT2 in epithelial ovarian carcinoma (EOC) is not yet known clearly. The aim of this study is to investigate the effects of CCAT2 on proliferation and invasion of EOC cells and the potential mechanisms by which CCAT2 functions. In the present paper, we found that knockdown of CCAT2 impaired cell proliferation and invasion in vitro. Furthermore, we also studied the role of CCAT2 in the modulation of Wnt/β-catenin signaling pathway. Our results showed that knockdown of CCAT2 inhibited the expression of β-catenin and the activity of TCF/LEF (T-cell factor/lymphoid enhancer factor) acting as a key transcription factor of Wnt/β-catenin signaling pathway. In addition, we found that silencing CCAT2 down-regulated the expression of c-MYC and MMP-7. But, that was reversed by the treatment with LiCl (lithium chloride) which could activate canonical Wnt/β-catenin signaling pathway. Taken together, these results indicate that CCAT2 may promote ovarian cancer progression, at least partly, through Wnt/β-catenin signaling pathway. Thus, CCAT2 might represent a novel therapeutic target for ovarian cancer.

A novel mechanism of lncRNA and miRNA interaction: CCAT2 regulates miR-145 expression by suppressing its maturation process in colon cancer cells

Background

Although both long and micro RNAs are emerging as important functional components in colorectal cancer (CRC) progression and metastasis, the mechanism of their interaction remains poorly understood. CCAT2 (Colon cancer-associated transcript-2), a long noncoding RNA (lncRNA), has been reported to be over-expressed in CRC and is found to promote tumor growth. miRNAs, a class of naturally occurring short RNAs negatively control the expression of target genes by cleaving mRNA or through translation repression. Recently, we reported that miR-145 and miR-21 cooperate to regulate colon cancer stem cell (CSC) proliferation and differentiation. Considering that CCAT2 is mainly located in the nucleus and miRNA maturation process begins in the nucleus, we hypothesize that CCAT2 selectively blocks miR-145 maturation process, resulting in decreased mature miR-145 affecting colon CSC proliferation and differentiation.

Methods

The levels of CCAT2 were manipulated by transfection of CCAT2 expression plasmid or knockdown by siRNA or by CRISPR/Cas9. Quantitative RT-PCR was performed to examine the expression of CCAT2 and pri-, pre- and mature miR-145/21. Fluorescence in situ hybridization (FISH) was used to visualize CCAT2 in the cells. In vitro processing of pri-miRNA-145 was performed using T7 RNA polymerase and recombinant human Dicer.

Results

We have observed that modulated expression of CCAT2 regulates the expression of miR-145 in colon cancer HCT-116 and HT-29 cells. Knockout of CCAT2 increases miR-145 and negatively regulates miR-21 in HCT-116 cells, impairs proliferation and differentiation. In contrast, stable up-regulation of CCAT2 decreases mature miR-145 and increases the expression of several CSC markers in colon cancer cells. We have also observed that CCAT2 is enriched in the nucleus and correlates with the expression of pre-miR-145 but not pre-miR-21 in HCT-116 cells. These results indicate CCAT2 selectively blocks miR-145 maturation by inhibiting pre-miR-145 export to cytoplasm. Further, we revealed that CCAT2 blocks cleavage of pre-miR-145 by Dicer in vitro.

Conclusions

Our results identify CCAT2 as a negative regulator of miRNA-145 biogenesis, and expose a novel mechanism of lncRNA-miRNA crosstalk.

Electronic supplementary material

The online version of this article (10.1186/s12943-017-0725-5) contains supplementary material, which is available to authorized users.

Long noncoding RNA CCAT2 as a novel biomaker of metastasis and prognosis in human cancer: a meta-analysis

Colon cancer-associated transcript2 (CCAT2), a long noncoding RNA (LncRNA), has been found to function as an oncogene in various cancers. However, the clinical value of CCAT2 in cancers remains unclear. Therefore, we performed this meta-analysis to investigate the association between CCAT2 level and metastasis & prognosis in malignant tumors. The meta analysis was performed by using a systematic search in PubMed, Web of Science, and Cochrane Library from inception to NOV 17, 2016. According to the inclusion and exclusion criteria,9 studies with 1084 patients were included in the meta-analysis.The result showed that overexpression of CCAT2 is positively correlated with lymph node metastasis (Odds ratio,OR=3.57, 95 % confidence interval(CI): 1.79-7.13, p<0.001) in a random-effects model (I²=71%, p=0.008) and distant metastasis(OR=7.68, 95 % CI: 3. 29-17.96, p<0.001) in a random-effects model (I²=41.9%, p=0.16).Likewise,we also found that high CCAT2 expression could predict unfavourable overall survival with pooled hazard ratio (HR) of 2.23 (95 % CI 1.68-2.96, p<0.00001) by a random-effects model (I²=37.5%, p=0.143) and poor metastasis-free survival in cancer patients (HR= 2.08, 95%CI:1.37-3.18 p=0.001) by a fixed-effects model (I²=0.0%, p=0.807). In conclusion,CCAT2 might be served as a novel molecular marker for predicting metastasis and prognosis in various human-cancers.

Long non-coding RNA growth arrest specific transcript 5 acts as a tumour suppressor in colorectal cancer by inhibiting interleukin-10 and vascular endothelial growth factor expression

Long non-coding RNAs (lncRNAs) are highly involved in diverse biological processes of human malignancies. The expression profile and underlying mechanism of lncRNA growth arrest specific transcript 5 (GAS5) in colorectal cancer (CRC) is poorly understood. In this study, we found that GAS5 was commonly downregulated in CRC tissues, serum of CRC patients and CRC cell lines. Knockdown of GAS5 promoted CRC cell proliferation and colony formation, whereas overexpression of GAS5 produced the opposite result. We further demonstrated that knockdown of GAS5 increased the expression and secretion of interleukin-10 (IL-10) and vascular endothelial growth factor (VEGF-A) via NF-κB and Erk1/2 pathways. Neutralization of IL-10 and VEGF-A reduced tumour proliferation caused by GAS5 knockdown. Moreover, GAS5 expression showed a statistically significant correlation with the mRNA levels of IL-10 and VEGF-A in CRC tissues. We further illustrated that GAS5 was markedly downregulated and negatively correlated with the cytokine expression in a mouse model of colitis-associated cancer (CAC). These results delineate a novel mechanism of lncRNA GAS5 in suppressing colorectal carcinogenesis. The cytokines IL-10 and VEGF-A inhibited by GAS5 may provide targets for lncRNA-based therapies for CRC.

Long non-coding RNA linc-ITGB1 promotes cell proliferation and migration in human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) represents a major endpoint of chronic liver diseases and is the third leading cause of cancer-related mortality. Long intergenic non-coding RNA-integrin subunit β1 ITGB1 (linc-ITGB1) is a novel long non-coding RNA, which is implicated in the development and progression of human tumors. However, its involvement in hepatocarcinogenesis remains to be elucidated. In the present study, the specific roles of linc-ITGB1 on cell proliferation and metastasis in HCC were investigated. It was initially observed that the expression of linc-ITGB1 was significantly elevated in 30 cases of clinical HCC tissues relative to their adjacent non-cancerous tissues. Expression of linc-ITGB1 was particularly elevated in the highly invasive cell line, HCCLM3. Knockdown of linc-ITGB1 in HCCLM3 cells using a specific short hairpin RNA decreased cell viability and colony formation in vitro. In addition, cell cycle analysis demonstrated that linc-ITGB1-depleted cells accumulated in the G0/G1 phase. HCCLM3 cells with linc-ITGB1 depletion exhibited significantly decreased migration and invasion abilities, when compared with control cells (P<0.05). These data suggest that linc-ITGB1 promotes HCC progression by inducing cell-cycle arrest. Therefore, targeted therapy against linc-ITGB1 may be a novel strategy to treat HCC.

Remote intracranial recurrence of IDH mutant gliomas is associated with TP53 mutations and an 8q gain

Most IDH mutant gliomas harbor either 1p/19q co-deletions or TP53 mutation; 1p/19q co-deleted tumors have significantly better prognoses than tumors harboring TP53 mutations. To investigate the clinical factors that contribute to differences in tumor progression of IDH mutant gliomas, we classified recurrent tumor patterns based on MRI and correlated these patterns with their genomic characterization. Accordingly, in IDH mutant gliomas (N = 66), 1p/19 co-deleted gliomas only recurred locally, whereas TP53 mutant gliomas recurred both locally and in remote intracranial regions. In addition, diffuse tensor imaging suggested that remote intracranial recurrence in the astrocytomas, IDH-mutant with TP53 mutations may occur along major fiber bundles. Remotely recurrent tumors resulted in a higher mortality and significantly harbored an 8q gain; astrocytomas with an 8q gain resulted in significantly shorter overall survival than those without an 8q gain. OncoScan^® arrays and next-generation sequencing revealed specific 8q regions (i.e., between 8q22 and 8q24) show a high copy number. In conclusion, only tumors with TP53 mutations showed patterns of remote recurrence in IDH mutant gliomas. Furthermore, an 8q gain was significantly associated with remote intracranial recurrence and can be considered a poor prognostic factor in astrocytomas, IDH-mutant.

The role of a new class of long noncoding RNAs transcribed from ultraconserved regions in cancer

Ultraconserved regions (UCRs) represent a relatively new class of non-coding genomic sequences highly conserved between human, rat and mouse genomes. These regions can reside within exons of protein-coding genes, despite the vast majority of them localizes within introns or intergenic regions. Several studies have undoubtedly demonstrated that most of these regions are actively transcribed in normal cells/tissues, where they contribute to regulate many cellular processes. Interestingly, these non-coding RNAs exhibit aberrant expression levels in human cancer cells and their expression profiles have been used as prognostic factors in human malignancies, as well as to unambiguously distinguish among distinct cancer types. In this review, we first describe their identification, then we provide some updated information about their genomic localization and classification. More importantly, we discuss about the available literature describing an overview of the mechanisms through which some transcribed UCRs (T-UCR) contribute to cancer progression or to the metastatic spread. To date, the interplay between T-UCRs and microRNAs is the most convincing evidence linking T-UCRs and tumorigenesis. The limitations of these studies and the future challenges to be addressed in order to understand the biological role of T-UCRs are also discussed herein. We envision that future efforts are needed to convincingly include this class of ncRNAs in the growing area of cancer therapeutics.

Long non-coding RNAs may serve as biomarkers in breast cancer combined with primary lung cancer

Long non-coding RNAs (lncRNAs) have been shown to play important regulatory role in certain type of cancers biology, including breast and lung cancers. However, the lncRNA expression in breast cancer combined with primary lung cancer remains unknown. In this study, databases of the Cancer Genome Atlas (TCGA) and the lncRNA profiler of contained candidate 192 lncRNAs were utilized. 11 lncRNAs were differentially expressed in breast cancer, 9 candidate lncRNAs were differentially expressed in lung cancer. In order to find the aberrant expression of lncRNAs in breast cancer combined with primary lung cancer, seven samples of primary breast cancer and lung cancer were studied for the expression of selected lncRNAs. The results showed that SNHG6 and NEAT1 were reversely expressed in breast cancer combined with primary lung cancer compared with primary breast or lung cancer. In addition, a significant correlation of lncRNAs was found in the patients whose age was above 56 in breast cancer. What's more, PVT1 expression was negatively correlated with the pathological stage, and the level of ER, PR, HER2, p53 in breast cancer. Furthermore, lncRNA expression did not have significant relationship with the 5-year survival of patients with breast cancer combined with primary lung cancer. The findings revealed that PVT1, SNHG6, NEAT1 may serve as a prognostic marker for breast cancer combined with primary lung cancer. Therefore, these lncRNAs are potential molecular indicators in the diagnosis and prognosis of cancer in the future.

Long non-coding RNAs on the stage of cervical cancer (Review)

Cervical cancer is one of most malignant gynecological tumors. However, effective means for diagnosing and treating cervical cancer have yet to be identified. A few decades ago, long non-coding RNAs (lncRNAs) were regarded as useless parts of the genome, however, increasing data have demonstrated the importance of lncRNAs in the diagnosis and treatment of cervical cancers. The aim of the present study is to summarize the role(s) of HOTAIR, MALAT1, CCAT2, SPRY4-IT1, RSU1P2, CCHE1, lncRNA-EBIC and PVT1. Approximately 14 lncRNAs are involved in cervical cancer and several important proteins, miRNAs and other molecules and play crucial roles in a few traditional signaling pathways that have been proven to be related to those lncRNAs. In conclusion, lncRNAs may be useful as exact treatment targets and diagnostic biomarkers for improving therapies in cervical cancer patients and lncRNAs may contribute to effective diagnosis and treatment methods for cervical cancer.

Colon cancer associated transcripts in human cancers

Long non-coding RNAs serve as important regulators in complicated cellular activities, including cell differentiation, proliferation and death. Dysregulation of long non-coding RNAs occurs in the formation and progression of cancers. The family of colon cancer associated transcripts, long non-coding RNAs colon cancer associated transcript-1 and colon cancer associated transcript-2 are known as oncogenes involved in various cancers. Colon cancer associated transcript-1 is a novel lncRNA located in 8q24.2, and colon cancer associated transcript-2 maps to the 8q24.21 region encompassing rs6983267. Colon cancer associated transcripts have close associations with clinical characteristics, such as lymph node metastasis, high TNM stage and short overall survival. Knockdown of them can reverse the malignant phenotypes of cancer cells, including proliferation, migration, invasion and apoptosis. Moreover, they can increase the expression level of c-MYC and oncogenic microRNAs via activating a series of complex mechanisms. In brief, the family of colon cancer associated transcripts may serve as potential biomarkers or therapeutic targets for human cancers.

Prognostic and clinicopathological significance of CCAT2 in Chinese patients with various tumors

BACKGROUND

Colon cancer-associated transcript 2 (CCAT2) as a long noncoding RNA (lncRNA) is overexpressed and plays a significant prognostic role in patients with tumors. The present study aimed to comprehensively evaluate the clinical value of CCAT2 in the Chinese population, as a potential prognostic marker in multiple cancers.

METHODS

A systematic search of eligible studies was conducted in the PubMed, Web of Science, Cochrane Library, Wanfang and the China National Knowledge Infrastructure databases as of March 31, 2017. Approximately 1,711 tumor patients from 16 eligible studies were selected. Analyses of the pooled data were performed, and the odds ratio (OR) or hazard ratio (HR) and the 95% confidence interval (95% CI) were calculated and summarized to evaluate the strength of this association using a fixed- or random-effects model.

RESULTS

Overall analyses showed that increased CCAT2 expression was associated with a higher risk of lymph node metastasis (LNM), an increased potential for distant metastasis (DM) and higher clinical stage (p<0.001 for LNM, p = 0.001 for DM, p<0.001 for clinical stage). HR and the 95% CI for overall survival (OS) were assessed to pool the effect size using a fixed-effects model. A significant association was observed between increased CCAT2 expression and poor OS (pooled HR = 1.91, 95% CI, 1.63-2.22, p<0.001).

CONCLUSIONS

These results indicate that CCAT2 is a biomarker to predict tumor progression and a potential prognostic marker in multiple cancers. Additional well-designed clinical studies are needed to validate these findings.

A positive feedback loop of long noncoding RNA CCAT2 and FOXM1 promotes hepatocellular carcinoma growth

Hepatocellular carcinoma (HCC) is one of the most common malignancies around the world. Long noncoding RNAs (lncRNAs) are greater than 200 nucleotides without protein-coding potential and play critical roles in tumorigenesis, cell differentiation, and cancer metastasis. Colon cancer-associated transcript 2 (CCAT2), a newly identified lncRNA, was shown to be dysregulated in cancers. However, the functional role of CCAT2 in HCC remains questionable. In the present study, we found a significant upregulation of CCAT2 in HCC tissues as compared to non-tumor tissues. Functional assays showed that CCAT2 promotes cell growth in vivo and in vitro. In addition, we found a positive feedback loop between CCAT2 and FOXM1. CCAT2 upregulates FOXM1 expression through interaction with, and suppression of, miR-34a, and FOXM1 activates CCAT2 transcription. We evaluated the therapeutic potential of ultrasound-targeted microbubble destruction (UTMD)-mediated siRNA delivery to specifically target CCAT2. UTMD-mediated siCCAT2 delivery significantly suppressed tumor growth in vivo. Thus, CCAT2-FOXM1 may be a novel target for the treatment of HCC.

Long noncoding RNA CCAT2 promotes proliferation and metastasis in non-small cell lung cancer through the Wnt pathway

Colon cancer associated transcript 2 (CCAT2), a long non-coding RNA (lncRNA), was shown to be associated with colon, ovarian and prostate cancer. Recent studies showed CCAT2 was highly expressed in various tumors, including non-small cell lung cancer (NSCLC) and probably being an independent prognostic factor of this disease. However, the physiological and biochemical mechanisms for CCAT2 with NSCLC were still unknown. In this study, we performed the analysis focused on the expression, biological functions and mechanism of CCAT2 in NSCLC and found that CCAT2 was significantly up-regulated in NSCLC tissues compared with corresponding non-cancerous tissues. Knockout of CCAT2 in NSCLC cell lines using lentivirus-mediated RNA interference significantly inhibited the proliferation and metastasis of the NSCLC cells. Most importantly, Wnt/β-catenin pathway was found to be inactivated in the NSCLC cell lines after CCAT2 knockout experiment. These results indicated that CCAT2 maybe serve as an oncogenic lncRNA that promoted proliferation and metastasis of NSCLC and activated the Wnt/β-catenin pathway.

Overexpression of long non-coding RNA zinc finger antisense 1 in acute myeloid leukemia cell lines influences cell growth and apoptosis

The association between long non-coding RNA zinc finger antisense 1 (ZFAS1) and acute myeloid leukemia (AML) has not yet been investigated. The present study aimed to assess the potential role of ZFAS1 in AML cell proliferation and apoptosis. The expression of ZFAS1 mRNA in various AML cell lines (HL-60, KG-1, ML-1 and SKNO-1) was measured by reverse transcription-quantitative polymerase chain reaction. The results showed that ZFAS1 expression was increased in all four human AML cell lines compared with the control cell lines (T lymphocytic leukemia or Burkitt's lymphoma). Transfection with small interfering RNA into human AML cells established ZFAS1 knockdown. A cell-counting kit-8 (CCK-8) assay was used to investigate the effect of ZFAS1 on AML cell proliferation and the effect of ZFAS1 on the cell cycle and cell apoptosis was assessed using flow cytometry. Notably, the CCK-8 assay demonstrated that ZFAS1 knockdown inhibited cell proliferation in HL-60 and SKNO-1 cell lines and flow cytometry analysis indicated that ZFAS1 knockdown induced AML cell cycle G1 phase arrest and triggered cell apoptosis. Therefore, the present study indicated that ZFAS1 promoted the proliferation and inhibited the apoptosis of AML cells.

Long Noncoding RNA CCAT2 as a Potential Novel Biomarker to Predict the Clinical Outcome of Cancer Patients: A Meta-Analysis

Background: Colon Cancer-Associated Transcript 2 (CCAT2) has been demonstrated associated with clinical outcomes in various tumors. However, the results from each study were unfortunately insufficient and not completely consistent. Therefore, we conduct a systematic meta-analysis to evaluate the value for a feasible biomarker for metastasis and prognosis.

Methods: A meta-analysis was performed using data obtained through a systematic search of PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure, Wanfang database and VIP database. The pooled odds ratio (OR) and hazard ratio (HR) with 95% Confidence interval (CI ) using random-effect were used to identify the relationship of CCAT2 with clinical outcome of cancer patients. Subgroup analysis and sensitivity analysis were performed.

Results: A total of 867 patients from eight studies were finally included. Patients with high CCAT2 expression underwent an increased risk of lymph node metastasis (LNM) (OR=3.09, 95% CI: 1.53-6.26) and distant metastasis (DM) (OR=7.70, 95% CI: 3.26-18.17). CCAT2 was also significantly correlated with overall survival (OS) (HR=2.19, 95%CI: 1.70-2.82) and progression-free survival (PFS) (HR=2.59, 95% CI: 1.78-3.76). Moderate heterogeneity was observed in meta-analysis for LNM. However, the results remained robust in multiple sensitivity analyses.

Conclusions: High expression of CCAT2 was linked with poor clinical outcome. CCAT2 can serve as a potential molecular marker for prognosis in different types of cancers.

Upregulation of CCAT2 promotes cell proliferation by repressing the P15 in breast cancer

BACKGROUND

Long non-coding RNAs (lncRNAs) are demonstrated to function as modulators of both transcriptional and post-transcriptional regulation in various types of tumors progression. The objective of the study is to investigate the clinical significance and underlying mechanism of Colon cancer associated transcript 2 (CCAT2) involved in breast cancer.

METHODS

QT-PCR was performed to examine the relative expression levels of CCAT2 in breast cancer tissues and adjacent normal tissues. Kaplan-Meier survival curves and log rank test were applied to assess the correlation between CCAT2 expression and the overall survival (OS) time in patients. MTT cell proliferation assay, transwell invasion assay and cell cycle analysis were conducted to detect the cell proliferation and invasion. Western blot analysis, RNA immunoprecipitation (RIP) and Chromatin immunoprecipitation (ChIP) assays were performed to detect the association between CCAT2 and P15. The tumor xenograft in nude mice was performed to evaluate the effect of CCAT2 expression on tumor growth in vivo.

RESULTS

Our results confirmed that CCAT2 expression levels in tumor tissues were markedly increased than that in adjacent normal tissues. Higher CCAT2 expression was found to show a significantly correlation with advanced TNM stage and lymph node metastasis in patients. Kaplan-Meier survival curves and log-rank test showed that higher CCAT2 expression was closely correlated with shorter over survival (OS) time in patients. In vitro, knockdown of CCAT2 showed that cell proliferation and invasion capabilities were suppressed and increased G0-G1 phase cell proportion but reduced S phase cell proportion in MCF-7 and MDA-MB-231 cells. Moreover, when CCAT2 silencing, the cell cycle relative protein CyclinD1, CyclinE1 and CDK4 expression were downregulated, but p15 was up-regulated in MCF-7 and MDA-MB-231 cells. Besides, we confirmed that CCAT2 suppressed the p15 expression level via interacting with EZH2 in breast cancer cells. In vivo, the tumor growth was inhibited after knockdown of CCAT2.

CONCLUSION

Our results indicated that CCAT2 may be a potential prognostic marker and therapeutic target for breast cancer.

Expression Study and Clinical Correlations of MYC and CCAT2 in Breast Cancer Patients

Background:

Colon cancer-associated transcript 2 (CCAT2) is a newly recognized lncRNA transcribed from the 8q24 genomic region. It functions as an oncogene in various types of cancers including breast cancer, in which it affects Wnt/β-catenin pathway. Previous studies have shown a putative interaction between this lncRNA and MYC proto-oncogene.

Methods:

In the current study, we evaluated the expression of CCAT2 in breast cancer tissues with regards to the expression of its target MYC. In addition, we assessed the relationship between CCAT2 and MYC expression levels in tumor tissues and the clinical prognostic characteristics of breast cancer patients.

Results:

MYC expression levels were significantly up-regulated in tumor tissues compared with adjacent non-cancerous tissues (ANCTs), while such analysis showed no statistically significant difference between these two tissue types in CCAT2 expression. Starkly increased CCAT2 gene expression levels were found in 12/48 (25%) of cancer tissue samples compared with their corresponding ANCTs. Furthermore, significant inverse correlations were found between CCAT2 expression and stage, as well as lymph node involvement. Besides, a significant inverse correlation was found between the relative MYC expression in tumor tissues compared with their corresponding ANCTs and disease stage.

Conclusions:

These results highlight the significance of MYC and CCAT2 expressions in the early stages of breast cancer development and suggest a potentially significant role for CCAT2 in a subset of breast cancer patients, which could be applied as a potential therapeutic target in these patients.

Long Non-coding RNAs and their Role in Metastasis

The perception of long non-coding RNAs as chunk RNA and transcriptional noise has been steadily replaced by their role as validated targets for a diverse set of physiological processes in the past few years. However, for the vast majority of lncRNAs their precise mode of action and physiological function remain to be uncovered. A large body of evidence has revealed their essential role in all stages of cancirogenesis and metastasis. In this review we focus on the role of lncRNAs in metastasis. We grouped selected lncRNAs into three categories based on in vitro and in vivo mode of action-related studies and clinical relevance for metastasis. Grouped according to their mode of action, in category I we discuss lncRNAs such as CCAT2, DREH, LET, NKILA, treRNA, HOTAIR, H19, FENDRR, lincROR, MALAT, GClnc1, BCAR4, SCHLAP1 and lncRNA ATP, all lncRNAs with in vitro and in vivo metastasis-related data and clinical significance. In category II we discuss lncRNAs CCAT1, PCAT1, PTENgp1, GPLINC, MEG3, ZEB2-AS, LCT13, ANRIL, NBAT1 and lncTCF7 all characterized by their mode of action in vitro and clinical significance, but pending or preliminary in vivo data. Finally, under category III, we discuss lncRNAs BANCR, FRLnc1, SPRY4-IT1 and LIMT with partially or poorly-resolved mode of action and varying degree of validation in clinical metastasis. Finally we discuss metastasis-related translational aspects of lncRNAs.

Insights into the involvement of noncoding RNAs in 5-fluorouracil drug resistance

5-Fluorouracil is a classic chemotherapeutic drug that is widely used to treat various cancers. However, patients often exhibit primary or acquired drug resistance during treatment with 5-fluorouracil chemotherapy. 5-Fluorouracil resistance is a multifactorial event that involves abnormal enzyme metabolism, transport deregulation, cell cycle disorders, apoptosis resistance, and mismatch repair deficiency. Despite advancements in bioresearch technologies in the past several decades, the molecular mechanisms of 5-fluorouracil resistance have not been completely clarified. Recently, microarray analyses have shown that noncoding RNAs (i.e. microRNAs and long noncoding RNAs) play a vital role in 5-fluorouracil resistance in multiple cancer cell lines. These noncoding RNAs can function as oncogenes or tumor suppressors, contributing to 5-fluorouracil drug resistance. In this review, we discuss the effects of microRNAs on 5-fluorouracil sensitivity via targeting of metabolic enzymes, the cell cycle, apoptosis, autophagy, the epithelial–mesenchymal transition, and cancer stem cells. In particular, we focus on summarizing current knowledge on the molecular mechanisms through which long noncoding RNAs mediate 5-fluorouracil drug resistance. Moreover, we describe the specific microRNAs that may function as markers for prediction of chemotherapeutic response to 5-fluorouracil. This review will help to improve the current understanding of how to reverse 5-fluorouracil resistance and may facilitate the establishment of new strategies for alleviating drug resistance in the future.

Long noncoding RNA CCAT2 can predict metastasis and a poor prognosis: A meta-analysis

BACKGROUND

Colon cancer associated transcript 2 (CCAT2), a novel long non-coding RNA (lncRNA), plays a key role in tumorigenesis. This meta-analysis systematically summarizes the relationship between CCAT2 and cancers.

METHODS

A comprehensive, computerized literature search was conducted in PubMed, Cochrane library, Chinese National Knowledge Infrastructure, and Chinese Wan Fang database. Odds ratios (ORs), hazard ratios (HRs) and their 95% confidence interval (95% CI) were calculated to assess the effect size. A total of 9 studies were enrolled in this meta-analysis, which was performed by Revman5.3 software and Stata12.0.

RESULTS

Our meta-analysis indicates that patients with elevated expression of CCAT2 are prone to developing distant metastasis (DM) (OR=12.42; 95% CI=5.77-26.74; P < 0.00001), which is associated with a tendency for lymph nodes metastasis (LNM) (OR=3.60 95% CI=1.65-7.87, P=0.001). Further analyses reveal that patients with high CCAT2 expression have poorer overall survival (OS) (HR=1.53, 95% CI=1.15-2.02, P=0.003, random-effects) and progression-free survival (PFS) (HR=2.88, 95% CI=1.81-4.56, P < 0.00001, fixed-effects).

CONCLUSIONS

Therefore, CCAT2 may be a potential novel biomarker for indicating clinical outcomes of human cancers.

Influence of microRNAs and Long Non-Coding RNAs in Cancer Chemoresistance

Innate and acquired chemoresistance exhibited by most tumours exposed to conventional chemotherapeutic agents account for the majority of relapse cases in cancer patients. Such chemoresistance phenotypes are of a multi-factorial nature from multiple key molecular players. The discovery of the RNA interference pathway in 1998 and the widespread gene regulatory influences exerted by microRNAs (miRNAs) and other non-coding RNAs have certainly expanded the level of intricacy present for the development of any single physiological phenotype, including cancer chemoresistance. This review article focuses on the latest research efforts in identifying and validating specific key molecular players from the two main families of non-coding RNAs, namely miRNAs and long non-coding RNAs (lncRNAs), having direct or indirect influences in the development of cancer drug resistance properties and how such knowledge can be utilised for novel theranostics in oncology.

A three-long noncoding RNA signature as a diagnostic biomarker for differentiating between triple-negative and non-triple-negative breast cancers

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive cancer with unfavorable outcome and it is useful to explore noninvasive biomarkers for its early diagnosis. Here, we identified differentially expressed long noncoding RNAs (lncRNAs) in blood samples of patients with TNBC to assess their diagnostic value.

METHODS

Differential expression of lncRNAs in plasma of patients with TNBC (n = 25) and non-TNBC (NTNBC; n = 35) and in healthy controls was compared by microarray analysis and validated by real-time PCR. lncRNA expression between plasma and BC tissues was compared using Pearson correlation test. Logit model was used to obtain a new lncRNA-based score. Receiver operating characteristic analysis was performed to assess the diagnostic value of the selected lncRNAs.

RESULTS

Microarray data showed that 41 lncRNAs were aberrantly expressed. Among these, antisense noncoding RNA in the INK4 locus (ANRIL), hypoxia inducible factor 1alpha antisense RNA-2 (HIF1A-AS2), and urothelial carcinoma-associated 1 (UCA1) were markedly upregulated in plasma of patients with TNBC compared with patients with NTNBC (P < 0.01). HIF1A-AS2 expression was positively associated with its tissue levels (r = 0.670, P < 0.01). AUC (95% CI) of ANRIL, HIF1A-AS2, and UCA1 was 0.785 (0.660-0.881), 0.739 (0.610-0.844), and 0.817 (0.696-0.905), respectively. TNBCSigLnc-3, a new score obtained using the logit model, showed excellent diagnostic performance, with AUC of 0.934 (0.839-0.982), sensitivity of 76.0%, and specificity of 97.1%.

CONCLUSION

ANRIL, HIF1A-AS2, and UCA1 expression was significantly increased in plasma of patients with TNBC, suggesting their use as TNBC-specific diagnostic biomarkers.

CCAT2: A novel oncogenic long non-coding RNA in human cancers

Colon cancer-associated transcript 2 (CCAT2) was originally identified as an oncogenic long non-coding RNA in colorectal cancer. Since its discovery, the oncogenic role of CCAT2 has been increasingly demonstrated in human cancers. In this connection, CCAT2 upregulation is frequently reported and very often associated with tumour progression and poor clinical outcomes. Functionally, knockdown of CCAT2 could induce cancer cell apoptosis and suppress cell proliferation and invasiveness, suggesting that CCAT2 might be a therapeutic target. The present review summarized current literature concerning the expression and functional role of CCAT2 in human malignancies.