Long non-coding RNAs in ovarian cancer

The Challenges and Opportunities of LncRNAs in Ovarian Cancer Research and Clinical Use

Ovarian cancer is one of the most lethal gynecological malignancies worldwide because it tends to be detected late, when the disease has already spread, and prognosis is poor. In this review we aim to highlight the importance of long non-coding RNAs (lncRNAs) in diagnosis, prognosis and treatment choice, to make progress towards increasingly personalized medicine in this malignancy. We review the effects of lncRNAs associated with ovarian cancer in the context of cancer hallmarks. We also discuss the molecular mechanisms by which lncRNAs become involved in cellular physiology; the onset, development and progression of ovarian cancer; and lncRNAs' regulatory mechanisms at the transcriptional, post-transcriptional and post-translational stages of gene expression. Finally, we compile a series of online resources useful for the study of lncRNAs, especially in the context of ovarian cancer. Future work required in the field is also discussed along with some concluding remarks.

LncRNA LEF1-AS1 silencing diminishes EZH2 expression to delay hepatocellular carcinoma development by impairing CEBPB-interaction with CDCA7

Hepatocellular carcinoma (HCC) is recognized for its high mortality rate worldwide. Based on intensive studies, long non-coding RNA (lncRNA) expression exerts significant effects on tumor suppression. Herein, we investigated the molecular mechanism of lymphoid enhancer-binding factor-1 antisense RNA 1 (LEF1-AS1) in HCC cells. Microarray-based gene expression analysis was adopted to predict and verify the differentially expressed genes in HCC, which predicted cell division cycle-associated 7 (CDCA7) and LEF1-AS1 to be highly expressed in HCC. The expression of LEF1-AS1, CDCA7, CCAAT/enhancer-binding protein beta (CEBPB) and enhancer of zeste homolog 2 (EZH2) was determined by means of reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. LncMap was used to predict the lncRNA-transcription factor-gene interaction in HCC. ChIP, RIP assay and dual luciferase reporter gene assay were employed to verify the relationship between the transcription factor and gene. Silencing of LEF1-AS1 could downregulate CDCA7 expression through CEBPB. Overexpression of LEF1-AS1, EZH2 and CDCA7 promoted proliferation and invasion in HCC cells. LEF1-AS1 promoted CDCA7 expression to further upregulate EZH2. Tumor formation in nude mice was assessed to verify the experimental results. Silencing of LEF1-AS1 inhibited the growth of tumors in vivo. Collectively, silencing LEF1-AS1 inhibited the proliferation and invasion of HCC cells by down-regulating EZH2 through the CEBPB-CDCA7 signaling pathway, which provides scientific evidence for the treatment of HCC.Abbreviations: HCC: Hepatocellular carcinoma; lncRNA: long non-coding RNA; LEF1-AS1: lymphoid enhancer-binding factor-1 antisense RNA 1; EZH2: enhancer of zeste homolog 2; CDCA7: cell division cycle-associated 7; GEO: Gene Expression Omnibus; NC: negative control; oe: overexpressed; RT-qPCR: reverse transcription quantitative polymerase chain reaction; PBS: phosphate buffered saline; HRP: horseradish peroxidase; OD: optical density; RIP: Radioimmunoprecipitation; ChIP: Chromatin immunoprecipitation; WT: wild type.

Upregulation of long non‑coding RNA CCEPR is associated with poor prognosis and contributes to the progression of ovarian cancer through regulating the Wnt/β‑catenin signaling pathway

Accumulating evidence has demonstrated that the expression of long non‑coding RNAs (lncRNAs) is altered in various types of cancer, which may prove beneficial for their use as biomarkers. Cervical carcinoma expressed PCNA regulatory lncRNA (CCEPR) is a recently identified lncRNA, which has an important role in regulating cell proliferation and apoptosis in cervical and bladder cancer; however, whether CCEPR is involved in the progression of ovarian cancer (OC) remains largely unclear. The aim of the present study was to determine the clinical significance of CCEPR in OC and to investigate its biological roles. Cell Counting Kit‑8 assay was used to analyze cell proliferation, Transwell assay was used to assess invasion, flow cytometric analysis was used to analyze apoptosis, and western blotting was used to perform mechanistic studies. CCEPR expression levels were significantly elevated in OC tissues compared with adjacent non‑cancer tissues. Similarly, significant increases in CCEPR expression were observed in OC cell lines (SK‑OV‑3 and OVCAR‑3) compared with the ovarian surface epithelial cell line, HOSEpiC. The increased expression levels of CCEPR were associated with increased invasion, higher International Federation of Gynecology and Obstetrics stage and a poorer overall survival rate. In vitro, the genetic silencing of CCEPR decreased the cell proliferation rate and invasive ability of OC cells, and promoted apoptosis. CCEPR‑silenced OC cells also demonstrated decreased expression levels of four proteins involved in the Wnt/β‑catenin signaling pathway: Cyclin D1, β‑catenin, Myc and matrix metallopeptidase‑7. In conclusion, the present study demonstrated that increased expression levels of CCEPR may predict poor prognosis in patients with OC and contribute to the progression of OC through regulating the Wnt/β‑catenin signaling pathway.

Long non-coding RNA TTN-AS1 promotes tumorigenesis of ovarian cancer through modulating the miR-139-5p/ROCK2 axis

Long non-coding RNA (lncRNA) TTN antisense RNA 1 (TTN-AS1) was reported to be crucial modulators in the tumorigenesis of several types of cancers. However, it is unclear whether TTN-AS1 can regulate the progression of ovarian cancer (OC). The present study aimed to explore functional roles and molecular mechanism of TTN-AS1 in OC. Quantitative reverse transcriptase-polymerase chain reaction assay (qRT-PCR) was used to detect the expression of TTN-AS1 in OC tissues and cell lines. The biological function of TTN-AS1 in OC was identified by a series of in vitro and in vivo assays. Bioinformatics analysis and mechanism experiments were used to analyze and identify the molecular mechanism of TTN-AS1 in OC progression. A high level of TTN-AS1 was found in OC tissues and cell lines. High TTN-AS1 was positively associated with advanced FIGO stage, lymph node metastasis, and poorer overall survival of OC patients. Functionally, knockdown of TTN-AS1 inhibited cell proliferation, colony formation, invasion and migration of OC cells in vitro, and suppressed tumor formation in vivo. Mechanistically, TTN-AS1 functioned as a competing endogenous RNA by sponging microRNA-139-5p (miR-139-5p) to elevate Rho-associated coiled-coil containing protein kinase 2 (ROCK2). Downregulation of miR-139-5p or upregulation of ROCK2 partially rescued the inhibitory impact of TTN-AS1 knockdown on OC cells. These results obtained in the present study suggested that TTN-AS1 promoted the progression of OC by regulating the miR-139-5p/ROCK2 axis.

Wnt/β-catenin signalling in ovarian cancer: Insights into its hyperactivation and function in tumorigenesis

Epithelial ovarian cancer (EOC) is the deadliest female malignancy. The Wnt/β-catenin pathway plays critical roles in regulating embryonic development and physiological processes. This pathway is tightly regulated to ensure its proper activity. In the absence of Wnt ligands, β-catenin is degraded by a destruction complex. When the pathway is stimulated by a Wnt ligand, β-catenin dissociates from the destruction complex and translocates into the nucleus where it interacts with TCF/LEF transcription factors to regulate target gene expression. Aberrant activation of this pathway, which leads to the hyperactivity of β-catenin, has been reported in ovarian cancer. Specifically, mutations of CTNNB1, AXIN, or APC, have been observed in the endometrioid and mucinous subtypes of EOC. In addition, upregulation of the ligands, abnormal activation of the receptors or intracellular mediators, disruption of the β-catenin destruction complex, inhibition of the association of β-catenin/E-cadherin on the cell membrane, and aberrant promotion of the β-catenin/TCF transcriptional activity, have all been reported in EOC, especially in the high grade serous subtype. Furthermore, several non-coding RNAs have been shown to regulate EOC development, in part, through the modulation of Wnt/β-catenin signalling. The Wnt/β-catenin pathway has been reported to promote cancer stem cell self-renewal, metastasis, and chemoresistance in all subtypes of EOC. Emerging evidence also suggests that the pathway induces ovarian tumor angiogenesis and immune evasion. Taken together, these studies demonstrate that the Wnt/β-catenin pathway plays critical roles in EOC development and is a strong candidate for the development of targeted therapies.

Zearalenone Exposure Induces the Apoptosis of Porcine Granulosa Cells and Changes Long Noncoding RNA Expression To Promote Antiapoptosis by Activating the JAK2-STAT3 Pathway

Zearalenone (ZEA), a pathogenic toxin produced by Fusarium, is widely detected in moldy feed materials. Previous studies have reported that ZEA exerts a harmful influence on animal reproductive systems; however, its effects on the changes of long noncoding RNAs (lncRNAs) remain unclear. Here, tackling this question, we performed RNA sequencing on porcine granulosa cells (GCs) after being exposed to 10 and 30 μM ZEA in vitro. The results showed that ZEA exposure observably changed the expression of lncRNAs in porcine GCs and increased the rate of apoptosis. Furthermore, Gene Ontology analysis showed that ZEA exposure induced variation of the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) signaling pathway in porcine GCs. To verify our bioinformatics analysis, western blotting and immunofluorescence analysis were performed and the results demonstrated that porcine GCs after ZEA exposure increased the expression of key proteins in the JAK2-STAT3 signaling pathway. Further bioinformatics analysis found that MSTRG.22680 and MSTRG.23882 played a pivotal role in activating the JAK2-STAT3 signaling pathway. To summarize, our results throw light on the fact that ZEA exposure dramatically increases the apoptosis of porcine GCs and alters the expression of lncRNAs that play an antiapoptotic role in porcine GCs via activating the JAK2-STAT3 signaling pathway.

Circulating non-coding RNAs in recurrent and metastatic ovarian cancer

Ovarian cancer has a poor outcome because it is usually detected at advanced tumor stages, and the majority of the patients develop disease relapse as a result of chemotherapy resistance. This most lethal gynecological malignancy metastasizes within the peritoneal fluid or ascites to pelvic and distal organs. In ovarian cancer progression and metastasis, small non-coding RNAs (ncRNAs), including long noncoding RNAs and microRNAs have been recognized as important regulators. Their dysregulation modulates gene expression and cellular signal pathways and can be detected in liquid biopsies. In this review, we provide an overview on circulating plasma and serum ncRNAs participating in tumor cell migration and invasion, and contributing to recurrence and metastasis of ovarian cancer. We will also discuss the development of potential, novel therapies using ncRNAs as target molecules or tumor markers for ovarian cancer.

A long noncoding RNAs signature to improve survival prediction in endometrioid endometrial cancer

PURPOSE

The dysregulation of long noncoding RNAs (lncRNAs) has been reported to be correlated to carcinogenesis and cancer progression. Endometrial cancer (EC), arising from the endometrium or the inner lining of the uterus, is one of the most common gynecological malignancies. We aim to explore the prognostic value of the lncRNAs in patients with endometrioid endometrial cancer (EEC) and to identify the potential lncRNA signature for predicting survival of patients with EEC.

METHODS

We performed a genome-wide analysis of the lncRNA expression profiling in The Cancer Genome Atlas (TCGA)-Uterine Corpus Endometrial Carcinoma database (408 EEC) to identify the prognosis related lncRNAs for the EEC. The patients with EEC were randomly divided into a training set (204 for endometrioid) and a testing set (204 for endometrioid). The lncRNA signature was identified in the training set, and then independently validated in the testing set and the complete set (training set plus testing set).

RESULTS

We developed a nine-lncRNA signature-based risk score in the patients with EEC. The risk score based on the novel lncRNAs signature was able to separate patients of training set into high-and low-risk groups with significantly different overall survival and progression-free survival. These can also be successfully confirmed in the testing set and complete set.

CONCLUSION

A nine-lncRNA expression signature was identified and validated which can predict EEC patient's survival. These findings may have important implications in the understanding of the potential therapeutic methods for patients with EEC.

Emerging roles of long non-coding RNAs in cancer

Cancer is a physiological condition that has both the endogenous and exogenous influences on its progression. It originates from unusual cell growth, where the cells undergo massive genetic alterations, bypass the signaling machinery and compromise its genetic cohesion. Literature has well narrated the DNA damage studies including driver mutations that interfere with the treatment strategies. However, with evolving medical excellence, recent day studies are trying to unveil the contribution of RNAs in the progression of tumor malignancies. A number of non-coding RNAs have been identified as an active component in cancer genomics. This article aims to review the role of long non-coding RNAs in the spectra of cancers and its prognostic value as the biomarkers in molecular targeting with clinical utility and therapeutic beneficence.

LncRNAs in ovarian cancer

Ovarian cancer is one of the most common gynecologic malignancies and has a poor prognosis. Recently, long noncoding RNAs (lncRNAs) have been identified as key regulators of cancer development. Studies have shown that the dysregulation of lncRNAs is frequently observed in ovarian cancer and greatly contributes to malignant phenotypical changes. In this review, we provide perspectives on the involvement of lncRNAs in the proliferation, apoptosis, cell cycle, migration, invasion, metastasis and drug resistance of ovarian cancer based on recent discoveries. Then, we discuss the role of lncRNAs in predicting the prognosis of ovarian cancer. Finally, we provide insight into the potential of lncRNAs for evaluating the diagnosis and prognosis of ovarian cancer.

METCAM/MUC18 Decreases the Malignant Propensity of Human Ovarian Carcinoma Cells

METCAM/MUC18 is an integral membrane cell adhesion molecule (CAM) in the Ig-like gene super-family. It can carry out common functions of CAMs which is to perform intercellular interactions and interaction of cell with extracellular matrix in tumor microenvironment, to interact with various signaling pathways and to regulate general behaviors of cells. We and other two groups previously suggested that METCAM/MUC18 probably be utilized as a biomarker for predicting the malignant tendency of clinical ovarian carcinomas, since METAM/MUC18 expression appears to associate with the carcinoma at advanced stages. It has been further postulated to promote the malignant tendency of the carcinoma. However, our recent research results appear to support the conclusion that the above positive correlation is fortuitous; actually METCAM/MUC18 acts as a tumor and metastasis suppressor for the ovarian carcinoma cells. We also suggest possible mechanisms in the METCAM/MUC18-mediated early tumor development and metastasis of ovarian carcinoma. Moreover, we propose to employ recombinant METCAM/MUC18 proteins and other derived products as therapeutic agents to treat the ovarian cancer patients by decreasing the malignant potential of ovarian carcinoma.