Insight into the molecular mechanism of LINC00152/miR-215/CDK13 axis in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. Nevertheless, its underlying molecular mechanisms are largely unknown. LINC00152 are recently investigated in several cancer types. In our current investigation, we observed LINC00152 was obviously upregulated in HCC cells. LINC00152 was significantly downregulated by infecting LV-shLINC00152 in HepG2 and SNU449 cells. Loss of LINC00152 remarkably repressed HCC cell proliferation, cell colony formation, induced cell apoptosis, and restrained cell migration/invasion. Growing evidence has reported long noncoding RNAs can sponge microRNAs to modulate cancer process. Here, we indicated miR-215 was greatly decreased in HCC and LINC00152 regulated HCC development via sponging miR-215. For another, the binding association between LINC00152 and miR-215 was proved by a series of functional assays. CDK13 was predicted as the target of miR-215. Upregulation of miR-215 greatly depressed CDK13 in HCC cells. Subsequently, the in vivo results demonstrated that silence of LINC00152 restrained HCC development via modulating miR-215 to up-regulate CDK13. Therefore, it was revealed that LINC00152 contributed to the progression of HCC by the modulation of miR-215 and CDK13.     

Retracted: Long non-coding RNA LINC00152 promotes cell growth and invasion of papillary thyroid carcinoma by regulating the miR-497/BDNF axis

Long intergenic non-coding RNA 152 (LINC00152) was reported to be tightly linked to tumorigenesis and progression in multiple cancers. However, its biological role and modulatory mechanism in papillary thyroid carcinoma (PTC) has not been elucidated. In this study, we determined the expression levels of LINC00152 in PTC tissues and cell lines by quantitative real time polymerase chain reaction (qRT-PCR). Cell proliferation, colony formation, migration, and invasion were measured by a Cell Counting Kit-8 assay, colony formation analysis, wound healing, and transwell invasion assay, respectively. A luciferase reporter assay and qRT-PCR were used to determine whether LINC00152 interacts with miR-497 directly. We established a xenograft mouse model to examine the underlying molecular mechanism and effect of LINC00152 on tumor growth in vivo. We found that LINC00152 expression was significantly increased in PTC tissues and derived cell lines. LINC00152 knockdown significantly inhibited proliferation, colony formation, migration, and invasion in vitro, and impaired tumor growth in vivo. We revealed that LINC00152 functioned as a competing endogenous RNA to the miR-497 sponge, downregulating its downstream target brain-derived neurotrophic factor (BDNF), which is an oncogene in thyroid cancer. These findings suggest that LINC00152 is responsible for PTC cell proliferation and invasion and exerts its function by regulating the miR-497/BDNF axis.     

LINC00261 suppresses human colon cancer progression via sponging miR-324-3p and inactivating the Wnt/β-catenin pathway

Growing evidence indicates long noncoding RNAs (lncRNAs) are significant regulators in the progression of various malignant tumors including colon cancer. Dysregulation of lncRNA LINC00261 has been identified in many cancers. Investigations on LINC00261 function have revealed that LINC00261 could act as a crucial tumor suppressor in various cancers. But, the biological involvement of LINC00261 in colon cancer is still barely known. Here, we found LINC00261 was reduced in colon cancer cells. Meanwhile, overexpressed LINC00261 repressed colon cancer cell viability and proliferation capacity. In addition, colony cancer cell colony formation was inhibited and apoptosis was enhanced by upregulation of LINC00261. Also, colon cancer cell migration and invasion both were restrained by LINC00261. miR-324-3p can exert important functions in several carcinomas, but its role in colon cancer is uninvestigated. In the current study, miR-324-3p was examined and miR-324-3p was greatly increased in colon cancer cells. Moreover, the association between miR-324-3p and LINC00261 was confirmed via performing RNA immunoprecipitation and RNA-pull-down experiments. In cancer biology, aberrant modulation of the Wnt signaling pathway remains a prevalent theme. Overexpression of LINC00261 obviously impaired colon cancer progression via inactivating the Wnt pathway. Furthermore, in the xenograft model assay, an increase of LINC00261 could suppress colon tumor growth via sponging miR-324-3p and inactivating the Wnt pathway. Overall, our results showed that LINC00261 repressed colon cancer progression via regulating miR-324-3p and the Wnt pathway. LINC00261 could be established as a novel therapeutic target for colon cancer.     

LINC00628 suppresses migration and invasion of hepatocellular carcinoma by its conserved region interacting with the promoter of VEGFA

Accumulated evidence revealed that numerous long noncoding RNAs (lncRNAs) have been found to be involved in the development and progression of hepatocellular carcinoma (HCC). LINC00628, a member of lncRNAs, has been reported to act as a tumor suppressor in gastric cancer and breast cancer. However, its potential role in HCC still remains unknown. Herein, we characterized the function of LINC00628 in HCC. Our investigation has revealed that LINC00628 were dramatically decreased in HCC tissues and cells, and inhibited the migration and invasion of HCC cells in vitro and in vivo. Moreover, LINC00628 exerted its tumor suppressive function by repressing the vascular endothelial growth factor A (VEGFA) promoter activity. A highly conserved region element in LINC00628 was identified by a cross-species comparative analysis, which is required for LINC00628 exerted its function. Dual-luciferase reporter assay showed that the conserved sequence mediated the interaction with a specific region of VEGFA promoter, resulting in a decrease of VEGFA expression. In conclusion, our results demonstrated that LINC00628 could function as a tumor suppressor in HCC via its conserved sequence elements interacting with a particular region of VEGFA promoter, suggesting that LINC00628 may serve as a novel promising target for diagnosis and therapy in HCC.     

LINC00152 promotes the proliferation of gastric cancer cells by regulating B-cell lymphoma-2

LINC00152 has been considered to be associated with the tumorigenesis and the occurrence of gastric cancer; however, the mechanism of LINC00152 has yet to be fully elucidated. In the present study, the expression levels of LINC00152 in tissues, serum, and peripheral blood mononuclear cells (PBMCs) of patients with gastric cancer were determined using real-time polymerase chain reaction. The functions of LINC00152 with respect to the proliferation, apoptosis, migration, and invasive abilities of the gastric cancer cells were evaluated by cell proliferation analysis, flow cytometry, cell scratch wound assay, and transwell migration experiments. A mouse xenotransplant model of gastric tumors was established to detect the role of LINC00152 in vivo, and the expression levels of B-cell lymphoma-2 (Bcl-2) family proteins were investigated by Western blot analysis. The results revealed that LINC00152 was overexpressed in tissues, serum, and PBMCs of patients with gastric cancer. Moreover, LINC00152 could promote the migration and invasive abilities and suppress the apoptosis, of gastric cancer cells through regulating the Bcl-2 protein family. LINC00152 could bind with Bcl-2 directly to induce the activation of cell cycle signaling, and this may be a potential target for the therapy of gastric cancer in the future.     

Retracted: LINC00707 contributes to hepatocellular carcinoma progression via sponging miR-206 to increase CDK14

Recently, increasing numbers of long noncoding RNAs (lncRNAs) have been found to be aberrantly expressed in various cancers. However, the roles of lncRNAs in hepatocellular carcinoma (HCC) progression is largely unknown. In our current study, we identified that long intergenic nonprotein-coding RNA 707 (LINC00707) was remarkably elevated in HCC cells, indicating that LINC00707 was involved in HCC development. Subsequently, LINC00707 was significantly decreased in HepG2 and Huh7 cells. The in vitro functional assays demonstrated that knockdown of LINC00707 significantly reduced HCC cell proliferation, induced cell apoptosis, and blocked the cell cycle progression. In addition, HCC cell migration and invasion was also greatly inhibited by downregulation of LINC00707. Increasing evidence has indicated that lncRNAs can act as molecular sponges of microRNAs. Currently, we observed that microRNA-206 (miR-206) was dramatically inhibited in HCC cells and LINC00707 can modulate HCC development through sponging miR-206. The binding correlation between LINC00707 and miR-206 was confirmed by dual-luciferase reporter assay, RNA pull down and RNA immunoprecipitation assay in our study. Moreover, cyclin-dependent kinase 14 (CDK14) was predicted as a target of miR-206 and we found that miR-206 suppressed CDK14 levels in HCC cells. Finally, in vivo assays were used and it was proved that silence of LINC00707 can restrain HCC development through modulating miR-206 to upregulate CDK14. In conclusion, it was implied that LINC00707 can lead to HCC progression through sponging miR-206 and modulating CDK14.     

Long non‐coding RNA LINC01225 promotes proliferation,invasion and migration of gastric cancer via Wnt/β‐catenin signalling pathway

Emerging evidence has classified the aberrant expression of long non‐coding RNAs (lncRNAs) as a basic signature of various malignancies including gastric cancer (GC). LINC01225 has been shown to act as a hepatocellular carcinoma‐related gene, with its expression pattern and biological function not clarified in GC. Here, we verified that LINC01225 was up‐regulated in tumour tissues and plasma of GC. Analysis with clinicopathological information suggested that up‐regulation of LINC01225 was associated with advanced disease and poorer overall survival. Receiver operating characteristic (ROC) analysis showed that plasma LINC01225 had a moderate accuracy for diagnosis of GC. In addition, knockdown of LINC01225 led to retardation of cell proliferation, invasion and migration, and overexpression of LINC01225 showed the opposite effects. Mechanistic investigations showed that LINC01225 silencing inhibited epithelial‐mesenchymal transition (EMT) process and attenuated Wnt/β‐catenin signalling of GC. Furthermore, ectopic expression of Wnt1 or suppression of GSK‐3β abolished the si‐LINC01225‐mediated suppression against EMT, thereby promoting cell proliferation, invasion and migration of GC. In conclusion, LINC01225 promotes the progression of GC through Wnt/β‐catenin signalling pathway, and it may serve as a potential target or strategy for diagnosis or treatment of GC.     

LINC00152 promotes cell cycle progression in hepatocellular carcinoma via miR-193a/b-3p/CCND1 axis

Long intergenic non-coding RNA 00152 (LINC00152) is aberrantly expressed in various human malignancies and plays an important role in the pathogenesis. Here, we found that LINC00152 is upregulated in hepatocellular carcinoma (HCC) tissues as compared to adjacent non-neoplastic tissues; gain-and-loss-of-function analyses in vitro showed that LINC00152 facilitates HCC cell cycle progression through regulating the expression of CCND1. LINC00152 knockdown inhibits tumorigenesis in vivo. MS2-RIP analysis indicated that LINC00152 binds directly to miR-193a/b-3p, as confirmed by luciferase reporter assays. Furthermore, ectopic expression of LINC00152 partially halted the decrease in CCND1 expression and cell proliferation capacity induced by miR-193a/b-3p overexpression. Thus, LINC00152 acts as a competing endogenous RNA (ceRNA) by sponging miR-193a/b-3p to modulate its target gene, CCND1. Our findings establish a ceRNA mechanism regulating cell proliferation in HCC via the LINC00152/miR-193a/b-3p/CCND1 signalling axis, and identify LINC00152 as a potential therapeutic target for HCC.     

Long non‐coding RNA LINC00673 silencing inhibits proliferation and drug resistance of prostate cancer cells via decreasing KLF4 promoter methylation

Prostate cancer is one of the major causes of cancer‐related mortality in men across the world. Recently, long non‐coding RNAs (lncRNAs) and Kruppel‐like factor 4 (KLF4) have been reported to participate in the biology of multiple cancers including prostate cancer. Here, this study aimed to explore the possible role of LINC00673 in prostate cancer via KLF4 gene promoter methylation. Microarray‐based gene expression profiling of prostate cancer was employed to identify differentially expressed lncRNAs and genes, after which the expression of LINC00673 and KLF4 in prostate cancer tissues was determined using RT‐qPCR. Next, the relationship between LINC00673 and KLF4 was evaluated using in silico analysis. Further, the effect of LINC00673 and KLF4 on cell proliferation and drug resistance of transfected cells was examined with gain‐ and loss‐of‐function experimentation. It was found that LINC00673 was highly expressed, while KLF4 was poorly expressed in prostate cancer tissues. Additionally, LINC00673 could bind to KLF4 gene promoter region and recruit methyltransferase to the KLF4 gene promoter region. Moreover, LINC00673 silencing was demonstrated to reduce methylation of the KLF4 gene promoter to elevate the expression of KLF4, thus suppressing the proliferation and drug resistance of prostate cancer cells. In summary, LINC00673 silencing could drive demethylation of the KLF4 gene promoter and thus inhibit the proliferation and drug resistance of prostate cancer cells, suggesting that silencing of LINC00673 and elevation of KLF4 could serve as tumour suppressors in prostate cancer.     

The oncogenic potentials and diagnostic significance of long non‐coding RNA LINC00310 in breast cancer

Recent studies have revealed that long non‐coding RNAs (lncRNAs) are involved in different physiological processes and human diseases. However, to date, the function and overall clinical significance of the vast majority of lncRNAs in breast cancer remain largely unexplored. Here, we focused on LINC00310 by interrogating the breast invasive carcinoma data set of the Cancer Genome Atlas (TCGA). The results showed that LINC00310 was increased as breast cancer progressed, and the deregulation of LINC00310 was significantly associated with patients’ survival. Experiments with knockout (KO) approach by CRISPR/Cas9 system and the subsequent rescue experiments revealed that LINC00310 promoted cell proliferation by regulating c‐Myc expression in vitro. Nude mouse xenograft assay demonstrated that LINC00310 KO significantly suppressed tumour growth in vivo. Furthermore, we found that serum LINC00310 expression was significantly up‐regulated in patients with breast cancer, and receiver operating characteristic (ROC) curve analysis indicated that LINC00310 had a powerful capability of distinguishing patients with breast cancer from healthy individuals (the area under curve 0.828). Taken together, these results provide a more intuitive approach to explore the clinical relevance and functional roles of lncRNAs. As a result, lncRNAs, such as LINC00310, may be used in clinical applications as circulating markers for breast cancer.     

Long intergenic noncoding RNA 00908 promotes proliferation and inhibits apoptosis of colorectal cancer cells by regulating KLF5 expression

Long intergenic noncoding RNAs (lincRNAs) play a vital role in the occurrence and progression of cancer. The mechanism of lincRNAs in colorectal cancer (CRC) has not been fully elucidated. In this context, an integrated comparative long noncoding RNA (lncRNA) microarray technology was used to determine the expression profile of lncRNAs in CRC. The roles of LINC00908 are unclear. We found that LINC00908 was significantly upregulated in CRC. Inhibition of LINC00908 resulted in reduced cell proliferation and G1 cell cycle arrest, which was mediated by cyclin D1, cyclin‐dependent kinase 4, and phosphorylated retinoblastoma. Moreover, inhibition of LINC00908‐induced apoptosis through the intrinsic apoptosis signaling pathway, as shown by the activation of caspase‐9 and caspase‐3. Mechanistically, miR‐143‐3p directly bound to LINC00908. miR‐143‐3p expression was negatively correlated with LINC00908 expression in CRC tissue. Functional experiments revealed opposing roles for miR‐143‐3p and LINC00908, suggesting that LINC00908 negatively regulates miR‐143‐3p. Mechanistically, miR‐143‐3p directly targets LINC00908. The KLF5 inhibitor ML264 affected proliferation and apoptosis, indicating that LINC00908 may act as a competing endogenous RNA to facilitate the expression of the miR‐143‐3p target gene KLF5. Thus, LINC00908 has an important proliferative and antiapoptotic role in CRC by regulating the cell cycle and intrinsic apoptosis. LINC00908 could be a potential biomarker and a new therapeutic target for CRC.     

TUG1: a pivotal oncogenic long non‐coding RNA of human cancers

Long non‐coding RNAs (lncRNAs) are a group greater than 200 nucleotides in length. An increasing number of studies has shown that lncRNAs play important roles in diverse cellular processes, including proliferation, differentiation, apoptosis, invasion and chromatin remodelling. In this regard, deregulation of lncRNAs has been documented in human cancers. TUG1 is a recently identified oncogenic lncRNA whose aberrant upregulation has been detected in different types of cancer, including B‐cell malignancies, oesophageal squamous cell carcinoma, bladder cancer, hepatocellular carcinoma and osteosarcoma. In these malignancies, knock‐down of TUG1 has been shown to suppress cell proliferation, invasion and/or colony formation. Interestingly, TUG1 has been found to be downregulated in non‐small cell lung carcinoma, indicative of its tissue‐specific function in tumourigenesis. Pertinent to clinical practice, TUG1 may act as a prognostic biomarker for tumours. In this review, we summarize current knowledge concerning the role of TUG1 in tumour progression and discuss mechanisms associated with it.     

Reduced LINC00551 expression promotes proliferation and invasion of esophageal squamous cancer by increase in HSP27 phosphorylation

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers, and long noncoding RNAs (lncRNAs) regulate gene expression or activities. This study investigated the role of lncRNA LINC00551 in ESCC development and progression. Three paired ESCC and normal tissues were subjected to next‐generation sequencing and we identified 82 upregulated and 60 downregulated lncRNAs, including LINC00551, which was confirmed to markedly downregulated in 78 ESCC tissues and in the Gene Expression Profiling Interactive Analysis data set. Downregulated LINC00551 expression was associated with lymph node metastasis, advanced TNM stage, and tumor size. Moreover, downregulated LINC00551 expression was also associated with poor progression‐free survival and overall survival of ESCC patients. In vitro and in vivo, LINC00551 overexpression inhibited ESCC cell proliferation and invasion, whereas knockdown of LINC00551 expression promoted ESCC cell proliferation and invasion. RNA pull‐down and mass spectrometry assays identified the potential LINC00551 binding proteins, and HSP27 was a promising LINC00551 targeting proteins after RNA immunoprecipitation assay. At the protein level, LINC00551 bound to and decreased HSP27 phosphorylation, and in turn, downregulated ESCC cell proliferation and invasion. The current study demonstrated the functional significance of LINC00551 in ESCC development, progression, and prognosis. Further study will assess LINC00551 as a novel prognostic marker or therapeutic target for ESCC.     

LINC00152 mediates CD8+ T-cell infiltration in gastric cancer through binding to EZH2 and regulating the CXCL9, 10/CXCR3 axis

This study aimed to annotate the role of long intergenic non-coding RNA 152 (LINC00152) in CD8⁺ T cells mediated immune responses in gastric cancer (GC) and the underlying mechanism. LINC00152 expression levels were detected through RT-PCR. For tumor engraftment, HGC-27 cells that received LINC00152 shRNA, LINC00152 overexpression vectors, enhancer of zeste homolog 2 (EZH2) shRNA or combination transfection were injected into mice. Chromatin immunoprecipitation (ChIP) assay was used to explore the interaction between LINC00152, Cys-X-cys ligand 9 (CXCL9) and Cys-X-cys ligand 10 (CXCL10). Flow cytometry was adopted to measure the CD8⁺ T-cell infiltration in tumor issue. In this study, we found increased LINC00152 expression levels are positively associated with the poor prognosis of GC patients and negatively associated with the CD8 levels. ChIP assay verified that LINC00152 recruits EZH2 to the promoters of CXCL9 and CXCL10, thus the silencing of LINC00152 promoted the production of CXCL9 and CXCL10. Knockdown of LINC00152 suppressed tumor cells growth in vivo and in vitro, increased tumor-infiltrating CD8⁺ T cells numbers and promoted the expression of CXCL9, CXCL10 and C-X-C Motif Chemokine Receptor 3 (CXCR3) in xenograft tumors. While CD8⁺ T cell depletion reversed the tumor suppression effect of LINC00152 silence. Besides, the silencing of EZH2 partly inhibited the promotion effect LINC00152 on tumor growth. Our study indicated that LINC00152 inhibition suppressed the tumor progress may through promoting CD8⁺ T-cell infiltration.

     

Long non-coding RNA Linc00152 is involved in cell cycle arrest,apoptosis, epithelial to mesenchymal transition,cell migration and invasion in gastric cancer

Gastric cancer remains a serious threat to public health with high incidence and mortality worldwide. Accumulating evidence demonstrates that long non-coding RNAs (lncRNAs) play important roles in regulating gene expression and are involved in various pathological processes, including gastric cancer. To investigate the possible role of dysregulated lncRNAs in gastric cancer development, we performed lncRNA microarray and identified 3141 significantly differentially expressed lncRNAs in gastric cancer tissues. Next, some of deregulated lncRNAs were validated among about 60 paired gastric cancer specimens such as Linc00261, DKFZP434K028, RPL34-AS1, H19, HOTAIR and Linc00152. Our results found that the decline of DKFZP434K028 and RPL34-AS1, and the increased expression of Linc00152 positively correlated with larger tumor size. The high expression levels of HOTAIR were associated with lymphatic metastasis and poor differentiation. Since the biological roles of Linc00152 are largely unknown in gastric cancer pathogenesis, we assessed its functions by silencing its up-regulation in gastric cancer cells. We found that Linc00152 knockdown could inhibit cell proliferation and colony formation, promote cell cycle arrest at G1 phase, trigger late apoptosis, reduce the epithelial to mesenchymal transition (EMT) program, and suppress cell migration and invasion. Taken together, we delineate the gastric cancer lncRNA signature and demonstrate the oncogenic functions of Linc00152. These findings may have implications for developing lncRNA-based biomarkers for diagnosis and therapeutics for gastric cancer.     

LINC01303 functions as a competing endogenous RNA to regulate EZH2 expression by sponging miR‐101‐3p in gastric cancer

Long non‐coding RNA (lncRNA) is one of the important regulators of many malignancies. However, the biological function and clinical significance of a large number of lncRNAs in gastric cancer remain unclear. Therefore, we analysed the TCGA data to find that LINC01303 is significantly up‐regulated in gastric cancer tissues. However, the biological function of LINC01303 in GC remains unknown. In our study, we found that the expression of LINC01303 was significantly higher in GC tissues than in adjacent tissues by real‐time quantitative PCR. We can significantly inhibit the malignant proliferation, migration and invasion of GC cells by silencing LINC01303 expression. In addition, LINC01303 knockdown can also inhibit GC growth in vivo. After the bioinformatics analysis, we found that LINC01303 can be used as a miR‐101‐3p sponge to competitively adsorb miR‐101‐3p with EZH2. Therefore, our results indicate that LINC01303 promotes the expression of EZH2 by inhibiting miR‐101‐3p activity and promotes GC progression. In summary, in this study, we demonstrated for the first time that the LINC01303/miR‐101‐3p/EZH2 axis promotes GC progression.