Long noncoding RNA CCAT2 promotes breast tumor growth by regulating the Wnt signaling pathway

Long Noncoding RNA and Cancer: A New Paradigm

In addition to mutations or aberrant expression in the protein-coding genes, mutations and misregulation of noncoding RNAs, in particular long noncoding RNAs (lncRNA), appear to play major roles in cancer. Genome-wide association studies of tumor samples have identified a large number of lncRNAs associated with various types of cancer. Alterations in lncRNA expression and their mutations promote tumorigenesis and metastasis. LncRNAs may exhibit tumor-suppressive and -promoting (oncogenic) functions. Because of their genome-wide expression patterns in a variety of tissues and their tissue-specific expression characteristics, lncRNAs hold strong promise as novel biomarkers and therapeutic targets for cancer. In this article, we have reviewed the emerging functions and association of lncRNAs in different types of cancer and discussed their potential implications in cancer diagnosis and therapy. Cancer Res; 77(15); 3965-81. ©2017 AACR.

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.

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.

Clinical roles of the aberrantly expressed lncRNAs in lung squamous cell carcinoma: a study based on RNA-sequencing and microarray data mining

Lung squamous cell carcinoma (LUSC) accounts for a significant proportion of lung cancer and there have been few therapeutic alternatives for recurrent LUSC due to the lack of specific driver molecules. To investigate the prospective role of lncRNAs in the tumorigenesis and progression of LUSC, the aberrantly expressed lncRNAs were calculated based on The Cancer Genome Atlas RNA-seq data. Of 7589 lncRNAs with 504 LUSC cases, 884 lncRNAs were identified as being aberrantly expressed (|log2 fold change| >2 and adjusted P<0.05) by DESeq R. The top 10 lncRNAs with the highest diagnostic value were SFTA1P,LINC00968, LINC00961, LINC01572,RP1-78O14.1, FENDRR, LINC01314,LINC01272, GATA6-AS1, and MIR3945HG. In addition to the significant roles in the carcinogenesis of LUSC, several lncRNAs also played vital parts in the survival and progression of LUSC. SFTA1P, LINC01272, GATA6-AS1 and MIR3945HG were closely related to the survival time of LUSC. Furthermore, LINC01572 and LINC01314 could distinguish the LUSC at early stage from that at advanced stage. The prospective molecular assessment of key lncRNAs showed that a certain series of genes could be involved in the regulation network. Furthermore, the OncoPrint from cBioPortal indicated that 14% (69/501) LUSC cases with genetic alterations could be obtained, including amplification, deep deletion and mRNA upregulation. More interestingly, the cases with genetic alterations had a poorer survival as compared to those without alterations. Overall, the study propounds a potentiality for interpreting the pathogenesis and development of LUSC with lncRNAs, and provides a novel platform for searching for more capable diagnostic biomarkers for LUSC.

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.

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.

Long non-coding RNA CCAT2 is associated with poor prognosis in hepatocellular carcinoma and promotes tumor metastasis by regulating Snail2-mediated epithelial-mesenchymal transition

Increasing evidence has demonstrated that aberrant expressions of long non-coding RNAs (lncRNAs) are involved in various malignancies, including hepatocellular carcinoma (HCC). This study aimed to investigate the role of lncRNA colon cancer-associated transcript 2 (CCAT2) in the progression of HCC. Quantitative real-time polymerase chain reaction analysis confirmed that CCAT2 was upregulated in HCC cell lines and cancerous tissues compared with normal liver cell line and adjacent normal tissue samples. The level of CCAT2 was positively associated with tumor-node-metastasis stages and vessel invasion. Survival analyses revealed that high CCAT2 expression predicted poor prognostic outcomes, serving as an independent prognostic factor for HCC patients. Patients with high CCAT2 expression had a 1.849-fold increased risk of death compared with those with low CCAT2 expression. Moreover, we also found that knockdown of CCAT2 expression reduced cell migration and invasion in vitro. We further demonstrated that CCAT2 played a key role in enhancing the epithelial-mesenchymal transition (EMT) through the regulation of vimentin, E-cadherin and transcription factor snail2 expression. Taken together, our findings showed that high CCAT2 expression is associated with poor survival in HCC patients. CCAT2 promotes HCC progression by regulating Snail2-induced EMT. CCAT2 may be a prognostic biomarker and therapeutic target for HCC.

Knockdown of Long Noncoding RNA CCAT2 Inhibits Cellular Proliferation, Invasion, and Epithelial-Mesenchymal Transition in Glioma Cells

Long noncoding RNA (lncRNA) colon cancer-associated transcript 2 (CCAT2) has been demonstrated to play an important role in diverse tumorigenesis. However, the biological function of lncRNAs in glioma is still unknown. In this study, we found that lncRNA CCAT2 was overexpressed in glioma tissues and cell lines and associated with tumor grade and size. Furthermore, patients with high levels of lncRNA CCAT2 had poorer survival than those with lower levels of lncRNA CCAT2. Knocking down lncRNA CCAT2 expression significantly suppressed the glioma cell growth, migration, and invasion, as well as induced early apoptosis of glioma cells in vitro. Moreover, lncRNA CCAT2 regulated epithelial-mesenchymal transition (EMT)-associated gene expression. In conclusion, lncRNA CCAT2 plays an important role in glioma tumorigenesis and progression and may act as a potential biomarker for therapeutic strategy and prognostic prediction.

Long noncoding RNAs are novel potential prognostic biomarkers for esophageal squamous cell carcinoma: an overview

Esophageal squamous cell carcinoma (ESCC) still has a poor prognosis. The prognostic biomarkers of ESCC are not yet well established. Long noncoding RNAs (lncRNAs) have recently been intensively investigated in various cancers including ESCC, and are found to be closely correlated to ESCC. Dysregulated expression of lncRNAs was widely observed in ESCC tumor tissue and was closely related to the tumorigenesis and progression of ESCC. More and more studies have found that lncRNAs were significantly correlated with the prognosis and diagnosis of patients with ESCC. Therefore, all those accumulating evidence indicated that lncRNAs could serve as a prognostic biomarker of ESCC. In this, we summarized the relation between lncRNAs and ESCC as well as the potential biomarker role of lncRNAs in ESCC, especially the prognostic value of lncRNAs. Our current review highlighted the need of further studies to explore the biomarker functions as well as therapeutic values of lncRNAs in ESCC.

Current Status of Long Non-Coding RNAs in Human Breast Cancer

Breast cancer represents a major health burden in Europe and North America, as recently published data report breast cancer as the second leading cause of cancer related death in women worldwide. Breast cancer is regarded as a highly heterogeneous disease in terms of clinical course and biological behavior and can be divided into several molecular subtypes, with different prognosis and treatment responses. The discovery of numerous non-coding RNAs has dramatically changed our understanding of cell biology, especially the pathophysiology of cancer. Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts >200 nucleotides in length. Several studies have demonstrated their role as key regulators of gene expression, cell biology and carcinogenesis. Deregulated expression levels of lncRNAs have been observed in various types of cancers including breast cancer. lncRNAs are involved in cancer initiation, progression, and metastases. In this review, we summarize the recent literature to highlight the current status of this class of long non-coding lncRNAs in breast cancer.

Expression Profile and Function Analysis of LncRNAs during Priming Phase of Rat Liver Regeneration

Emerging evidences have revealed that long non-coding RNAs (lncRNAs) functioned in a wide range of physiological and pathophysiological processes including rat liver regeneration, and could regulate gene expression in the transcriptional and post-transcriptional levels. However, the underlying mechanism for lncRNAs participation in liver regeneration is largely unknown. To define the mechanisms how the lncRNAs regulate LR, we performed bio-chip technology, high-throughput sequencing and RT-PCR to detect the expression of lncRNAs at 0, 2 and 6 h during LR after 2/3 hepatectomy (PH). The results indicated that 28 lncRNAs were involved in LR. Bioinformatics analysis predicated 465 co-expression target genes including 10 regulatory genes were related to these 28 lncRNAs. Ingenuity Pathway Analysis (IPA) was employed to analyze the signaling pathways and physiological activities that regulated by these genes, and the results suggested that these genes were potentially related to ILK, SAPK/JNK and ERK/MAPK signaling pathways, and possibly regulate many important physiological activities in LR in terms of cell proliferation, cell differentiation, cell survival, apoptosis and necrosis.

The long non-coding RNA CCAT2 is up-regulated in ovarian cancer and associated with poor prognosis

BACKGROUND

Ovarian cancer is a malignant tumor with a poor prognosis. Accumulating evidence demonstrates that long non-coding RNAs (lncRNAs) are emerging regulators in cancer biology, and can be used as potential biomarkers for cancer diagnosis, prognosis and targeted therapy. The lncRNA CCAT2 (colon cancer associated transcript 2) was recently shown to be involved in several cancers; however, its role in ovarian cancer remains unknown.

METHODS

Expression levels of the lncRNA CCAT2 in ovarian cancer tissues, adjacent normal tissues, and cell lines were assessed by quantitative real-time PCR. Then, the associations of CCAT2 expression levels with clinicopathological features and prognosis were evaluated. In addition, CCAT2 functions in tumor progression and invasion were further determined by siRNA-induced CCAT2 silencing in vitro.

RESULTS

Expression levels of the lncRNA CCAT2 in ovarian cancer tissues and cell lines were significantly higher compared with values obtained for adjacent non-tumor tissues and normal ovarian epithelial cells. Interestingly, higher CCAT2 expression levels were associated with a shorter overall survival (P = 0.006) and disease-free survival (P = 0.001) in ovarian cancer patients. In addition, CCAT2 expression was positively correlated with FIGO stage (P = 0.002), tumor grade (P = 0.006) and distant metastasis (P < 0.001). Moreover, CCAT2 knockdown in ovarian cancer cells markedly suppressed cell proliferation, migration, and invasion.

CONCLUSIONS

The lncRNA CCAT2 is a novel factor involved in ovarian cancer progression, and constitutes a potential prognostic biomarker and therapeutic target for patients with ovarian cancer.

shRNA targeting long non-coding RNA CCAT2 controlled by tetracycline-inducible system inhibits progression of bladder cancer cells

Recent reports show that long non-coding RNAs (lncRNAs) are emerging as significant functional regulators in the development of tumors, including bladder cancer. Here, we found that CCAT2 was upregulated in bladder cancer tissues and cell lines. Through the statistical analyses, we also found that the high expression level of CCAT2 was positively correlated with histological grade and TNM stage of bladder cancer. Further experimental results revealed that knockdown of CCAT2 could decrease cell proliferation and migration as well as induce apoptosis in bladder cancer cells. Besides, using the post-transcriptional device of synthetic biology, we create the tetracycline-inducible double small hairpin RNAs (shRNAs) vector to control the expression level of CCAT2 which was induced by doxycycline in a dosage-dependent manner. In summary, our data indicated that CCAT2 may be an oncogene and a therapeutic target in bladder cancer. The expression of CCAT2 can be quantitatively controlled by the synthetic "tetracycline-on" switch system in bladder cancer in response to different concentrations of doxycycline to inhibit the development of bladder cancer cells.

Roles of Long Non-Coding RNA CCAT2 in Cervical Cancer Cell Growth and Apoptosis

BACKGROUND

This study aimed to analyze the potential function of lncRNA CCAT2 in cervical cancer cell proliferation and apoptosis.

MATERIAL/METHODS

Expression level of CCAT2 in cervical cancer cell lines (HeLa, CaSki, and SiHa) was detected by quantitative real-time PCR. CCAT2 knockdown was established by transfecting siRNA into human cervical cancer cells. Its effects on cell proliferation were studied using cell-counting kit-8 assay. The effect of CCAT2 on cervical cancer cells cycle and apoptosis was assessed by flow cytometry assay.

RESULTS

CCK8 assay showed that CCAT2 knockdown inhibited cell proliferation in HeLa, CaSki, and SiHa cells. The flow cytometry confirmed the results that knockdown of CCAT2 could induce cervical cancer cells cycle G1 phase arrestment and trigger the cells apoptosis.

CONCLUSIONS

LncRNA CCAT2 promoted the proliferation and survival of cervical cancer cells.