Long Noncoding RNA PVT1 Acts as a "Sponge" to Inhibit microRNA-152 in Gastric Cancer Cells

17β-estradiol suppresses H2O2-induced senescence in human umbilical vein endothelial cells by inducing autophagy through the PVT1/miR-31/SIRT3 axis

OBJECTIVE

17β-estradiol (17β-E₂) has been implicated in activating autophagy by upregulating SIRT3 (Sirtuin 3) expression, thereby inhibiting the senescence of vascular endothelial cells. Herein, we further examined the molecular mechanisms that regulate SIRT3 expression in 17β-E₂-induced autophagy.

METHODS

Reverse-transcription-polymerase chain reaction was employed to measure the expression of plasmacytoma variant translocation 1 (PVT1), microRNAs (miRNAs), and SIRT3, and the dual-luciferase assay was used to determine their interaction. Electron microscopy observes autophagosomes, green fluorescent protein-microtubule-associated protein 1 light chain 3 (GFP-LC3) staining, and immunoblot analysis with antibodies against LC3，beclin-1, and P62 were conducted to measure autophagy. Cellular senescence was determined using immunoblot analysis with anti-phosphorylated retinoblastoma and senescence-associated β-galactosidase staining.

RESULTS

Women with higher estrogen levels (during the 10-13th day of the menstrual cycle or premenopausal) exhibit markedly higher serum levels of PVT1 than women with lower estrogen levels (during the menstrual period or postmenopausal). The dual-luciferase assay showed that PVT1 acts as a sponge for miR-31, and miR-31 binds to its target gene, SIRT3. The 17β-E₂ treatment increased the expression of PVT1 and SIRT3 and downregulated miR-31 expression in human umbilical vein endothelial cells (HUVECs). Consistently, PVT1 overexpression suppresses miR-31 expression, promotes 17β-E2-induced autophagy, and inhibits H₂O₂-induced senescence. miR-31 inhibitor increases SIRT3 expression and leads to activation of 17β-E₂-induced autophagy and suppression of H₂O₂-induced senescence.

CONCLUSION

Our findings demonstrated that 17β-E₂ upregulates PVT1 gene expression and PVT1 functions as a sponge to inhibit miR-31, resulting in the upregulation of SIRT3 expression and activation of autophagy and subsequent inhibition of H₂O₂-induced senescence in HUVECs.

miRNAs are now starring in "No Time to Die: Overcoming the chemoresistance in cancer"

Cancer is a leading cause of death globally, with about 19.3 million new cases reported each year. Current therapies for cancer management include-chemotherapy, radiotherapy, and surgery. However, they are loaded with side effects and tend to cause toxicity in the patient's body posttreatment, ultimately hindering the response towards the treatment building up resistance. This is where noncoding RNAs such as miRNAs help provide us with a helping hand for taming the chemoresistance and providing potential holistic cancer management. MicroRNAs are promising targets for anticancer therapy as they perform critical regulatory roles in various signaling cascades related to cell proliferation, apoptosis, migration, and invasion. Combining miRNAs and anticancer drugs and devising a combination therapy has managed cancer well in various independent studies. This review aims to provide insights into how miRNAs play a mechanistic role in cancer development and progression and regulate drug resistance in various types of cancers. Furthermore, next-generation novel therapies using miRNAs in combination with anticancer treatments in multiple cancers have been put forth and how they improve the efficacy of the treatments. Exemplary studies currently in the preclinical and clinical models have been summarized. Ultimately, we briefly talk through the challenges that come forward with it and minimize them.

Upregulation of the c-MYC oncogene and adjacent long noncoding RNAs PVT1 and CCAT1 in esophageal squamous cell carcinoma

BACKGROUND

All cell types express long non-coding RNAs (lncRNAs), which have the potential to play a role in carcinogenesis by altering the levels of their expression. Squamous cell carcinoma of the esophagus (ESCC) is a deadly disease with a poor prognosis and a high frequency of lymphatic metastases. Understanding the functional role and signaling pathways of two neighboring lncRNAs, CCAT1 and PVT1, in this oncogene's pathogenesis may help us determine ESCC. Furthermore, it is still unclear whether these lncRNAs are linked to the clinicopathological characteristics of patients with ESCC.

METHODS

For this study, we used biopsy from the Imam Khomeini Cancer Institute's tumor bank in Tehran, Iran to obtain 40 ESCC tumor samples and their normal margin counterparts. The expression levels of the CCAT1, PVT1, and c-MYC genes were assessed using quantitative Real-Time RT-PCR. Additionally, demographic data and clinical-pathologic characteristics, such as tumor grade, tumor stage, lymph node, and metastasis, were taken into consideration. Graphpad prism version 8 was used for bioinformatics analyses.

RESULTS

Comparing ESCC tissues to non-tumor tissues, we found significant upregulation of PVT1, CCAT1, and c-MYC. Patients with ESCC who had increased PVT1 expression also had higher rates of advanced stage and lymph node metastasis, whereas increased CCAT1 expression was only linked to advanced stage and wasn't associated with lymph node metastasis. In predicting ESCC, CCAT1 (p < 0.05) was found to be an important factor. Overall survival was reduced by c-MYC and PVT1 overexpression (p < 0.001), according to Kaplan-Meier analysis. PVT1, CCAT1, and c-MYC were found to interact with 23 miRNAs with high and medium score classes, as shown in a bioinformatics study. We summarized the experimentally proven interactions between c-MYC, PVT1, and CCAT1 and other miRNAs, lncRNAs, and proteins.

CONCLUSION

This is the first report that CCAT1, PVT1 and c-MYC have been found to be up-regulated simultaneously in ESCC. It is possible that these genes may be involved in ESCC as a result of these findings. Therefore, as consequence, more research is needed to determine whether or not these lncRNAs play an oncogenic role in ESCC development and progression, as well as the regulatory mechanisms that control them.

lncRNA PVT1: a novel oncogene in multiple cancers

Long noncoding RNAs are involved in epigenetic gene modification, including binding to the chromatin rearrangement complex in pre-transcriptional regulation and to gene promoters in gene expression regulation, as well as acting as microRNA sponges to control messenger RNA levels in post-transcriptional regulation. An increasing number of studies have found that long noncoding RNA plasmacytoma variant translocation 1 (PVT1) plays an important role in cancer development. In this review of a large number of studies on PVT1, we found that PVT1 is closely related to tumor onset, proliferation, invasion, epithelial–mesenchymal transformation, and apoptosis, as well as poor prognosis and radiotherapy and chemotherapy resistance in some cancers. This review comprehensively describes PVT1 expression in various cancers and presents novel approaches to the diagnosis and treatment of cancer.

PVT1 is a stress-responsive lncRNA that drives ovarian cancer metastasis and chemoresistance

Metastatic growth of ovarian cancer cells into the peritoneal cavity requires adaptation to various cellular stress factors to facilitate cell survival and growth. Here, we demonstrate the role of PVT1, one such stress induced long non-coding RNA, in ovarian cancer growth and metastasis. PVT1 is an amplified and overexpressed lncRNA in ovarian cancer with strong predictive value for survival and response to targeted therapeutics. We find that expression of PVT1 is regulated by tumor cells in response to cellular stress, particularly loss of cell-cell contacts and changes in matrix rigidity occurring in a YAP1-dependent manner. Induction of PVT1 promotes tumor cell survival, growth, and migration. Conversely, reducing PVT1 levels robustly abrogates metastatic behavior and tumor cell dissemination in cell lines and syngeneic transplantation models in vivo. We find that reducing PVT1 causes widespread changes in the transcriptome leading to alterations in cellular stress response and metabolic pathways including doxorubicin metabolism, which impacts chemosensitivity. Together, these findings implicate PVT1 as a promising therapeutic target to suppress metastasis and chemoresistance in ovarian cancer.

Long Non-Coding RNAs Might Regulate Phenotypic Switch of Vascular Smooth Muscle Cells Acting as ceRNA: Implications for In-Stent Restenosis

Coronary in-stent restenosis is a late complication of angioplasty. It is a multifactorial process that involves vascular smooth muscle cells (VSMCs), endothelial cells, and inflammatory and genetic factors. In this study, the transcriptomic landscape of VSMCs’ phenotypic switch process was assessed under stimuli resembling stent injury. Co-cultured contractile VSMCs and endothelial cells were exposed to a bare metal stent and platelet-derived growth factor (PDGF-BB) 20 ng/mL. Migratory capacity (wound healing assay), proliferative capacity, and cell cycle analysis of the VSMCs were performed. RNAseq analysis of contractile vs. proliferative VSMCs was performed. Gene differential expression (DE), identification of new long non-coding RNA candidates (lncRNAs), gene ontology (GO), and pathway enrichment (KEGG) were analyzed. A competing endogenous RNA network was constructed, and significant lncRNA–miRNA–mRNA axes were selected. VSMCs exposed to “stent injury” conditions showed morphologic changes, with proliferative and migratory capacities progressing from G0-G1 cell cycle phase to S and G2-M. RNAseq analysis showed DE of 1099, 509 and 64 differentially expressed mRNAs, lncRNAs, and miRNAs, respectively. GO analysis of DE genes showed significant enrichment in collagen and extracellular matrix organization, regulation of smooth muscle cell proliferation, and collagen biosynthetic process. The main upregulated nodes in the lncRNA-mediated ceRNA network were PVT1 and HIF1-AS2, with downregulation of ACTA2-AS1 and MIR663AHG. The PVT1 ceRNA axis appears to be an attractive target for in-stent restenosis diagnosis and treatment.

CircPVT1: a pivotal circular node intersecting Long Non-Coding-PVT1 and c-MYC oncogenic signals

The role of circular RNAs in oncogenesis has begun to be widely studied in recent years, due to the significant impact that these molecules have in disease pathogenesis, as well as their potential for the future of innovative therapies. Moreover, due to their characteristically circular shape, circular RNAs are very resistant molecules to RNA degradation whose levels are easily assessed in body fluids. Accordingly, they represent an opportunity for the discovery of new diagnostic and prognostic markers in a wide range of diseases. Among circular RNAs, circPVT1 is a rather peculiar one that originates from the circularization of the exon 2 of the PVT1 gene that encodes a pro-tumorigenic long non-coding RNA named lncPVT1. There are a few examples of circular RNAs that derive from a locus producing another non-coding RNA. Despite their apparent transcriptional independence, which occurs using two different promoters, a possible synergistic effect in tumorigenesis cannot be excluded considering that both have been reported to correlate with the oncogenic phenotype. This complex mechanism of regulation appears to also be controlled by c-MYC. Indeed, the PVT1 locus is located only 53 Kb downstream c-MYC gene, a well-known oncogene that regulates the expression levels of about 15% of all genes. Here, we review circPVT1 origin and biogenesis highlighting the most important mechanisms through which it plays a fundamental role in oncogenesis, such as the well-known sponge activity on microRNAs, as well as its paradigmatic interactome link with lncPVT1 and c-MYC expression.

CRISPR-Based Approaches for the High-Throughput Characterization of Long Non-Coding RNAs

Over the last decade, tens of thousands of new long non-coding RNAs (lncRNAs) have been identified in the human genome. Nevertheless, except for a handful of genes, the genetic characteristics and functions of most of these lncRNAs remain elusive; this is partially due to their relatively low expression, high tissue specificity, and low conservation across species. A major limitation for determining the function of lncRNAs was the lack of methodologies suitable for studying these genes. The recent development of CRISPR/Cas9 technology has opened unprecedented opportunities to uncover the genetic and functional characteristics of the non-coding genome via targeted and high-throughput approaches. Specific CRISPR/Cas9-based approaches were developed to target lncRNA loci. Some of these approaches involve modifying the sequence, but others were developed to study lncRNAs by inducing transcriptional and epigenetic changes. The discovery of other programable Cas proteins broaden our possibilities to target RNA molecules with greater precision and accuracy. These approaches allow for the knock-down and characterization of lncRNAs. Here, we review how various CRISPR-based strategies have been used to characterize lncRNAs with important functions in different biological contexts and how these approaches can be further utilized to improve our understanding of the non-coding genome.

The association between polymorphism of the long noncoding RNA, Plasmacytoma variant translocation 1, and the risk of gastric cancer

Genetic polymorphisms of plasmacytoma variant translocation 1 can affect various tumors including gastro-intestinal, sexual hormone sensitive cancers and lymphoma. Accumulated evidence have shown that plasmacytoma variant translocation 1 acts as an oncogene and tumor suppressor in various cancers. In fact, the rs13255292 and rs2608053 single nucleotide polymorphisms of plasmacytoma variant translocation 1are known to affect lymphoma; however, their effects on gastric cancer are primarily unknown. In this study, we evaluated the association between these plasmacytoma variant translocation 1 polymorphisms and the risk of gastric cancer.In the present study, 462 patients diagnosed with gastric cancer and 377 cancer-free controls were enrolled. The TaqMan genotyping assay was used to analyze the association between rs13255292 and rs2608053 single nucleotide polymorphisms and the risk of gastric cancer.The rs2608053 dominant model (CT + TT) was associated with a decreased risk of gastric cancer in T3 + T4 (odds ratio [OR] = 0.61, confidence interval (CI) = 0.41 - 0.92, P = .019), and stage III Gastric cancer subgroups (OR = 0.59, 95% CI = 0.38 - 0.91, P = .017) compared to the CC genotype. When stratified analysis by sex was carried out, the rs13255292 dominant model (CT + TT) had a significant association with an increased risk of gastric cancer in the female negative lymph node metastasis gastric cancer subgroup, compared to the CC genotype (OR = 1.96, 95% CI = 1.16 - 3.30, P = .012). The recessive model (TT) of rs13255292 was associated with an increased risk of gastric cancer in the male T3 + T4 gastric cancer subgroups compared to the CC + CT genotype (OR = 3.82, 95% CI = 1.02 - 14.33, P = .047). The dominant model (CT + TT) of rs2608053 was related to a decreased risk of gastric cancer in male T3 + T4 (OR = 0.57, 95% CI = 0.33 - 0.98, P = .042) and stage III gastric cancer subgroups (OR = 0.49, 95% CI = 0.27 - 0.89, P = .020) compared to the CC genotype.The rs13255292 and rs2608053 single nucleotide polymorphisms in plasmacytoma variant translocation 1 may contribute to susceptibility of gastric cancer. Further studies with more subjects and different ethnic groups are needed to validate our results.

LncRNA-URHC Functions as ceRNA to Regulate DNAJB9 Expression by Competitively Binding to miR-5007-3p in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is often diagnosed at a late stage, when the prognosis is poor. The regulation of long noncoding RNAs (lncRNAs) plays a crucial role in HCC. However, the precise regulatory mechanisms of lncRNA signaling in HCC remain largely unknown. Our study aims to investigate the underlying mechanisms of lncRNA (upregulated in hepatocellular carcinoma) URHC in HCC.

OBJECTIVE

To study the in vivo and in vitro localization and biological effects of URHC on liver cancer cells. Through bioinformatics analysis, dual-luciferase reporter gene analysis and rescue experiments revealed the possible mechanism of URHC.

METHODS

RT-qPCR, fluorescence in situ hybridization (FISH) staining, EdU, colony formation, and tumor xenograft experiments were used to identify localized and biological effects of URHC on HCC cells in vitro and in vivo. The bioinformatics analysis, dual-luciferase reporter assay, and rescue experiments revealed the potential mechanism of URHC.

RESULTS

URHC silencing may inhibit the HCC cells' proliferation in vitro and in vivo. We found that URHC was mainly localized in the cytoplasm. The expression of miR-5007-3p was negatively regulated by URHC. And miR-5007-3p could reverse the effect of URHC in HCC cells. The expression of DNAJB9 was negatively regulated by miR-5007-3p but positively regulated by URHC. These suggestive of lncRNA-URHC positively regulated the level of DNAJB9 by sponging miR-5007-3p.

CONCLUSION

Together, our study elucidated the role of URHC as a miRNA sponge in HCC and shed new light on lncRNA-directed diagnostics and therapeutics in HCC.

Comprehensive analysis of lncRNAs as biomarkers for diagnosis, prognosis, and treatment response in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common histological type of renal carcinoma and has a high recurrence rate and poor outcome. Accurate patient risk stratification based on genetic markers can help to identify the high-risk patient for early and further treatments and would promote patient survival. Long non-coding RNAs (lncRNAs) have attracted widespread attention as biomarkers for early diagnosis, treatment, and prognosis because of their high specificity and sensitivity. Here, we performed a systematic search in NCBI PubMed and found 44 lncRNAs as oncogenes, 18 lncRNAs as tumor suppressors, 199 lncRNAs as diagnostic biomarkers, 62 lncRNAs as prognostic biomarkers, and 3 lncRNAs as predictive biomarkers for ccRCC. We also comprehensively discuss the biological functions and molecular regulatory mechanisms of lncRNAs in ccRCC. Overall, the present study is a systemic analysis to assess the expression and clinical value of lncRNAs in ccRCC, and lncRNAs hold promise to be diagnostic, prognostic, and predictive biomarkers.

MyoData: An expression knowledgebase at single cell/nucleus level for the discovery of coding-noncoding RNA functional interactions in skeletal muscle

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Regulation of gene expression through non-coding RNAs at single myofiber and nucleus resolution.

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Reinterpretation of KEGG pathways with microRNA and long non-coding RNA activities.

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miR-149, -214, and let-7e alter mitochondrial shape.

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The long non-coding RNA Pvt1 is a sponge for miR-27a.

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miR-208b regulates Sox6; miR-214 regulates both Sox6 and Slc16a3.

Non-coding RNAs represent the largest part of transcribed mammalian genomes and prevalently exert regulatory functions. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) can modulate the activity of each other. Skeletal muscle is the most abundant tissue in mammals. It is composed of different cell types with myofibers that represent the smallest complete contractile system. Considering that lncRNAs and miRNAs are more cell type-specific than coding RNAs, to understand their function it is imperative to evaluate their expression and action within single myofibers. In this database, we collected gene expression data for coding and non-coding genes in single myofibers and used them to produce interaction networks based on expression correlations. Since biological pathways are more informative than networks based on gene expression correlation, to understand how altered genes participate in the studied phenotype, we integrated KEGG pathways with miRNAs and lncRNAs. The database also integrates single nucleus gene expression data on skeletal muscle in different patho-physiological conditions. We demonstrated that these networks can serve as a framework from which to dissect new miRNA and lncRNA functions to experimentally validate. Some interactions included in the database have been previously experimentally validated using high throughput methods. These can be the basis for further functional studies. Using database information, we demonstrate the involvement of miR-149, -214 and let-7e in mitochondria shaping; the ability of the lncRNA Pvt1 to mitigate the action of miR-27a via sponging; and the regulatory activity of miR-214 on Sox6 and Slc16a3. The MyoData is available at https://myodata.bio.unipd.it.

Research updates on the clinical implication of long noncoding RNA in digestive system cancers and chemoresistance

Long noncoding RNAs (lncRNAs) are implicated in various biological processes, such as cell proliferation, differentiation, apoptosis, migration, and invasion. They are also key players in various biological pathways. LncRNA was considered as 'translational noise' before 1980s. It has been reported that lncRNAs are aberrantly expressed in different cancers, either as oncogene or tumor suppressor gene. Therefore, more and more lncRNAs are recognized as potential diagnostic biomarkers and/or therapeutic targets. As competitive endogenous RNA, lncRNAs can interact with microRNA to alter the expression of target genes, which may have extensive clinical implications in cancers, including diagnosis, treatment, prognosis, and chemoresistance. This review comprehensively summarizes the functions and clinical relevance of lncRNAs in digestive system cancers, especially as a potential tool to overcome chemoresistance.

Tetraspanins: Novel Molecular Regulators of Gastric Cancer

Gastric cancer is the fourth and fifth most common cancer worldwide in men and women, respectively. However, patients with an advanced stage of gastric cancer still have a poor prognosis and low overall survival rate. The tetraspanins belong to a protein superfamily with four hydrophobic transmembrane domains and 33 mammalian tetraspanins are ubiquitously distributed in various cells and tissues. They interact with other membrane proteins to form tetraspanin-enriched microdomains and serve a variety of functions including cell adhesion, invasion, motility, cell fusion, virus infection, and signal transduction. In this review, we summarize multiple utilities of tetraspanins in the progression of gastric cancer and the underlying molecular mechanisms. In general, the expression of TSPAN8, CD151, TSPAN1, and TSPAN4 is increased in gastric cancer tissues and enhance the proliferation and invasion of gastric cancer cells, while CD81, CD82, TSPAN5, TSPAN9, and TSPAN21 are downregulated and suppress gastric cancer cell growth. In terms of cell motility regulation, CD9, CD63 and CD82 are metastasis suppressors and the expression level is inversely associated with lymph node metastasis. We also review the clinicopathological significance of tetraspanins in gastric cancer including therapeutic targets, the development of drug resistance and prognosis prediction. Finally, we discuss the potential clinical value and current limitations of tetraspanins in gastric cancer treatments, and provide some guidance for future research.

Knockdown of cir_RNA PVT1 Elevates Gastric Cancer Cisplatin Sensitivity via Sponging miR-152-3p

BACKGROUND

Cisplatin (DDP) resistance is a key problem for effective treatment of gastric cancer (GC). Circular RNA PVT1 (circPVT1) acts as a vital regulator in the progression and development of various cancers. However, the in-depth mechanism of circPVT1 in GC resistance to DDP is still unclear.

MATERIALS AND METHODS

Quantitative real-time polymerase chain reaction was executed for the detection of the expression of circPVT1, miR-152-3p, and hepatoma-derived growth factor (HDGF) mRNA in GC tissues and cells. Western blot was used to detect the levels of HDGF protein, Bax, cleaved-casp-3, Bcl-2, p-PI3K, and p-AKT in tissue samples and/or cells. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry assays were performed to determine the viability, proliferation, and apoptosis of DDP-resistant GC cells. The relationship between miR-152-3p and circPVT1 or HDGF was confirmed by dual-luciferase reporter assay. The biological role of circPVT1 in vivo was confirmed with a xenograft tumor model.

RESULTS

CircPVT1 and HDGF mRNA were upregulated while miR-152-3p was downregulated in chemoresistance tissues and DDP-resistant GC cells. Both circPVT1 and HDGF inhibition elevated cell sensitivity to DDP, suppressed cell viability, proliferation, and induced cell apoptosis in DDP-resistant GC cells. The MiR-152-3p inhibitor reversed the influence of circPVT1 silencing on DDP sensitivity, viability, proliferation, and apoptosis of DDP-resistant GC cells. Moreover, circPVT1 regulated the HDGF/PI3K/AKT pathway through sponging miR-152-3p. In addition, circPVT1 knockdown reduced the malignancy of DDP-resistant GC cells in vivo.

CONCLUSIONS

CircPVT1 regulated the chemoresistance and malignancy of GC through modulating HDGF expression via sponging miR-152-3p, providing a theoretical basis for the development of effective therapeutic strategies for GC.

LINC01207 is up-regulated in gastric cancer tissues and promotes disease progression by regulating miR-671-5p/DDX5 axis

LINC01207 is involved in the progression of some cancers. This study was designed to delve into the biological function and mechanism of LINC01207 in gastric cancer. qPCR was adopted to examine the expression levels of LINC01207, miR-671-5p, DDX5 mRNA in gastric cancer tissues and cells. After LINC01207 was overexpressed or depleted, MTT and BrdU assays were conducted to detect cell proliferation. Transwell assay was employed to detect cell migration and invasion. Western blot was used to detect the expression of DDX5 protein in cells. Bioinformatics analysis, luciferase reporter assay and RNA pull-down assay were performed to predict and validate the binding site between miR-671-5p and LINC01207 or DDX5. LINC01207, DDX5 mRNA were up-regulated in gastric cancer, while miR-671-5p was down-regulated; high expression of LINC01207 and transfection of miR-671-5p inhibitors facilitated the proliferation of gastric cancer cells; however, knocking down LINC01207 and the overexpression of miR-671-5p mimics had opposite biological effects. LINC01207 and miR-671-5p were interacted and miR-671-5p was negatively regulated by LINC01207. MiR-671-5p could reverse the function of LINC01207. DDX5 was a downstream target of miR-671-5p and was positively modulated by LINC01207. LINC01207 promotes the proliferation and metastasis of gastric cancer cells by regulating miR-671-5p/DDX5 axis.

The effects of LncRNA PVT1 on clinical characteristics and survival in breast cancer patients: A protocol for systematic review and meta analysis

BACKGROUND

Currently, an increasing number of long noncoding RNAs (LncRNAs) have been reported to be abnormally expressed in human carcinomas and play a vital role in tumourigenesis. Some studies were carried out to investigate the influence of the expression of plasmacytoma variant translocation 1 (PVT1) on prognosis and its clinical significance in patients with breast cancer, while the results were contradictory and uncertain. A meta-analysis was conducted with controversial data to accurately assess the issue.

METHODS

A detailed search of relevant researches was performed in Wanfang, Chinese Biomedical Literature Database, Chinese National Knowledge Infrastructure, Chongqing VIP Chinese Science and Technology Periodical Database, PubMed, Embase, and Web of Science. Two reviewers independently conducted data extraction and literature quality evaluation. Odd ratio and its 95% confidence intervals were applied to evaluate the relationship between PVT1 and clinicopathological characteristics of breast cancer patients. Hazard ratios and its 95% confidence intervals were adopted to assess the prognostic effects of PVT1 on overall survival and disease-free survival. Meta-analysis was conducted with Stata 14.0 software.

RESULTS

This study will provide high-quality evidence-based medical evidence for the correlation between PVT1 expression and overall survival, and disease-free survival and clinicopathological features.

CONCLUSION

The study will provide updated evidence to evaluate whether the expression of PVT1 is in association with poor prognosis in patients with breast cancer.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/C2TYE.

PVT1: A long non-coding RNA recurrently involved in neoplasia-associated fusion transcripts

NGS technologies and bioinformatics tools allow the rapid identification of chimeric transcripts in cancer. More than 40,000 fusions are so far reported in the literature; however, for most of them, the role in oncogenesis is still not fully understood. This is the case for fusions involving the long non-coding RNA (lncRNA) Plasmacytoma variant translocation 1 (PVT1) (8q24.21). This lncRNA displays oncogenic functions in several cancer types interacting with microRNAs and proteins, but the role of PVT1 fusion transcripts is more obscure. These chimeras have been identified in both hematological malignancies and solid tumors, mainly arising from rearrangements and/or amplification of the 8q24 chromosomal region. In this review, we detail the full spectrum of PVT1 fusions in cancer, summarizing current knowledge about their genesis, function, and role as biomarkers.

LINC00467 facilitates osteosarcoma progression by sponging miR‑217 to regulate KPNA4 expression

Osteosarcoma (OS) is a musculoskeletal malignancy that originates from interstitial cells. An increasing number of studies have verified that long non-coding RNAs (lncRNAs) participate in the progression of numerous types of cancer. It has been reported that LINC00467 is a cancer-promoting gene in some types of cancer; however, the regulatory mechanism of LINC00467 in OS remains unknown. In the present study, reverse transcription-quantitative PCR was used to determine LINC00467 expression in OS tissues and cells. Additionally, the impact of LINC00467-knockdown on OS cell proliferation, migration and invasion was analyzed using Cell Counting Kit-8, colony formation and Transwell assays, as well as western blot analysis. RNA pulldown and luciferase reporter assays were conducted to investigate the regulatory mechanism of LINC00467 in OS. The results delineated that LINC00467 expression was elevated in OS tissues and cells, and that high LINC00467 expression was associated with a poor prognosis in patients with OS. LINC00467 inhibition suppressed OS progression by inhibiting cell proliferation, migration, invasion and epithelial-mesenchymal transition. LINC00467 served as a molecular sponge for microRNA (miR)-217, while karyopherin subunit α4 (KPNA4) was a downstream target gene of miR-217. Moreover, the overexpression of KPNA4 reversed the inhibitory effects of LINC00467 inhibition on OS progression. Therefore, the present study elucidated the potential mechanism of LINC00467 in OS and indicated that LINC00467 exerted its carcinogenic effects on OS through the miR-217/KPNA4 axis, implying that LINC00467 may be a novel potential therapeutic target for OS.

Long Noncoding RNAs in Gastrointestinal Cancer: Tumor Suppression Versus Tumor Promotion

Approximately 80% of the human genome harbors biochemical marks of active transcription that its majority transcribes to noncoding RNAs, namely long noncoding RNAs (lncRNAs). LncRNAs are heterogeneous RNA transcripts that regulate critical biological processes such as cell survival and death. They involve in the progression of different cancers by affecting transcriptional and post-transcriptional modifications as well as epigenetic control of numerous tumor suppressors and oncogenes. Recent findings show that aberrant expression of lncRNAs is associated with tumor initiation, progression, invasion, and overall survival of patients with gastrointestinal (GI) cancers. Some lncRNAs play as tumor suppressors in all GI cancers, but others play as tumor promoters. However, some other lncRNAs might function as a tumor suppressor in one GI cancer, but as a tumor promoter in another GI cancer type. This fact highlights possible context dependency of the expression patterns and roles of at least some lncRNAs in GI cancer development and progression. Here, we review the functional relation of lncRNAs involved in the development and progression of GI cancer by focusing on their roles as tumor suppressor and tumor promoter genes.

Exposure to ozone impacted Th1/Th2 imbalance of CD4+ T cells and apoptosis of ASMCs underlying asthmatic progression by activating lncRNA PVT1-miR-15a-5p/miR-29c-3p signaling

This investigation attempted to elucidate whether lncRNA PVT1-led miRNA axes participated in aggravating ozone-triggered asthma progression. One hundred and sixty-eight BALB/c mice were evenly divided into saline+air group, ovalbumin+air group, saline+ozone group and ovalbumin+ozone group. Correlations were evaluated between PVT1 expression and airway smooth muscle function/inflammatory cytokine release among the mice models. Furthermore, pcDNA3.1-PVT1 and si-PVT1 were, respectively, transfected into CD⁴⁺T cells and airway smooth muscle cells (ASMCs), and activities of the cells were observed. Ultimately, a cohort of asthma patients was recruited to estimate the diagnostic performance of PVT1. It was demonstrated that mice of ovalbumin+ozone group were associated with higher PVT1 expression, thicker trachea/airway smooth muscle and smaller ratio of Th1/Th2-like cytokines than mice of ovalbumin+air group and saline+ozone group (P<0.05). Moreover, pcDNA3.1-PVT1 significantly brought down Th1/Th2 ratio in CD⁴⁺ T cells by depressing miR-15a-5p expression and activating PI3K-Akt-mTOR signaling (P<0.05). The PVT1 also facilitated ASMC proliferation by sponging miR-29c-3p and motivating PI3K-Akt-mTOR signaling (P<0.05). Additionally, PVT1 seemed promising in diagnosis of asthma, with favorable sensitivity (i.e. 0.844) and specificity (i.e. 0.978). Conclusively, lncRNA PVT1-miR-15a-5p/miR-29c-3p-PI3K-Akt-mTOR axis was implicated in ozone-induced asthma development by promoting ASMC proliferation and Th1/Th2 imbalance.

TUSC8 inhibits the development of osteosarcoma by sponging miR‑197‑3p and targeting EHD2

Osteosarcoma (OS) is one of the most common malignant bone tumours and generally occurs in children and adolescents. Increasing evidence has demonstrated that dysregulated long non-coding RNAs (lncRNAs) play crucial roles in the progression of various human neoplasms. Among these, tumour suppressor candidate 8 (TUSC8) is a novel lncRNA and has been reported to function as a tumour suppressor in cervical cancer. However, the exact role of TUSC8 in OS remains largely unknown. In the present study, it was observed that TUSC8 was markedly downregulated in OS tissues and cell lines. Functional experiments demonstrated that the overexpression of TUSC8 significantly suppressed the proliferation, migration, invasion and epithelial-mesenchymal transition (EMT), whereas it accelerated the apoptosis of OS cells. Mechanistically, TUSC8 served as a sponge for miR-197-3p, and EH-domain containing 2 (EHD2) was identified as a downstream target molecule of miR-197-3p. Further investigations indicated that EHD2 knockdown significantly reversed the effects on OS cellular processes induced by TUSC8 overexpression. On the whole, these findings indicate that TUSC8 functions as a competing endogenous RNA (ceRNA) to suppress OS cell growth and EMT via the miR-197-3p/EHD2 axis. TUSC8 may thus function as a potential therapeutic target in OS treatment.

The Complex Network between MYC Oncogene and microRNAs in Gastric Cancer: An Overview

Despite the advancements in cancer treatments, gastric cancer is still one of the leading causes of death worldwide. In this context, it is of great interest to discover new and more effective ways of treating this disease. Accumulated evidences have demonstrated the amplification of 8q24.21 region in gastric tumors. Furthermore, this is the region where the widely known MYC oncogene and different microRNAs are located. MYC deregulation is key in tumorigenesis in various types of tissues, once it is associated with cell proliferation, survival, and drug resistance. microRNAs are a class of noncoding RNAs that negatively regulate the protein translation, and which deregulation is related with gastric cancer development. However, little is understood about the interactions between microRNAs and MYC. Here, we overview the MYC role and its relationship with the microRNAs network in gastric cancer aiming to identify potential targets useful to be used in clinic, not only as biomarkers, but also as molecules for development of promising therapies.

Long Noncoding RNA DLX6-AS1 Promotes the Progression in Cervical Cancer by Targeting miR-16-5p/ARPP19 Axis

Background: Cervical cancer (CC) is regarded as one of the most common gynecological malignancies. LncRNA DLX6-AS1 has been proven vital in various cancers, whereas its exact function is still largely unestablished in CC. Materials and Methods: The expression pattern of DLX6-AS1 and miR-16-5p in CC cells was determined by real-time quantitative polymerase chain reaction (RT-qPCR). ARPP19 expression was assessed by RT-qPCR and Western blot assays in CC cells. The precise function of DLX6-AS1 in CC was detected by Cell-Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), caspase-3 activity, transwell, and Western blot experiments. RNA immunoprecipitation (RIP) and luciferase reporter assays were employed to certify the combination between miR-16-5p and DLX6-AS1 (or ARPP19). Nuclear cytoplasmic segmentation determined the localization of DLX6-AS1 in CC cells. A xenograft mouse model assay studied the influences of DLX6-AS1 silencing on CC progression in vivo. Results: Elevated DLX6-AS1 expression was disclosed in CC cells. DLX6-AS1 silence attenuated proliferation, migration, and epithelial-mesenchymal transition program as well as enhanced CC cell apoptosis. DLX6-AS1 was uncovered to sponge and negatively modulate miR-16-5p in CC. Besides, ARPP19 was uncovered as a downstream target gene of miR-16-5p in CC. Rescue experiments indicated that DLX6-AS1 enhanced the cellular process of CC cells through upregulating ARPP19. Moreover, in vivo assay confirmed that DLX6-AS1 promoted CC growth. Conclusions: DLX6-AS1 accelerates the progression of CC through sponging miR-16-5p and upregulates ARPP19, which offers a novel insight into prognosis and remedy of CC.

Oncogenic Role of PVT1 and Therapeutic Implications

PVT1, a long non-coding RNA has been implicated in a variety of human cancers. Recent advancements have led to increasing discovery of the critical roles of PVT1 in cancer initiation and progression. Novel insight is emerging about PVT1's mechanism of action in different cancers. Identifying and understanding the variety of activities of PVT1 involved in cancers is a necessity for the development of PVT1 as a diagnostic biomarker or therapeutic target in cancers where PVT1 is dysregulated. PVT1's varied activities include overexpression, modulation of miRNA expression, protein interactions, targeting of regulatory genes, formation of fusion genes, functioning as a competing endogenous RNA (ceRNA), and interactions with MYC, among many others. Furthermore, bioinformatic analysis of PVT1 interactions in cancers has aided understanding of the numerous pathways involved in PVT1 contribution to carcinogenesis in a cancer type-specific manner. However, these recent findings show that there is much more to be learned to be able to fully exploit PVT1 for cancer prognostication and therapy. In this review, we summarize some of the latest findings on PVT1's oncogenic activities, signaling networks and how targeting these networks can be a strategy for cancer therapy.

PVT1 Long Non-coding RNA in Gastrointestinal Cancer

Whole genome and transcriptome sequencing technologies have led to the identification of many long non-coding RNAs (lncRNAs) and stimulated the research of their role in health and disease. LncRNAs participate in the regulation of critical signaling pathways including cell growth, motility, apoptosis, and differentiation; and their expression has been found dysregulated in human tumors. Thus, lncRNAs have emerged as new players in the initiation, maintenance and progression of tumorigenesis. PVT1 (plasmacytoma variant translocation 1) lncRNA is located on chromosomal 8q24.21, a large locus frequently amplified in human cancers and predictive of increased cancer risk in genome-wide association studies (GWAS). Combined, colorectal and gastric adenocarcinomas are the most frequent tumor malignancies and also the leading cause of cancer-related deaths worldwide. PVT1 expression is elevated in gastrointestinal tumors and correlates with poor patient prognosis. In this review, we discuss the mechanisms of action underlying PVT1 oncogenic role in colorectal and gastric cancer such as MYC upregulation, miRNA production, competitive endogenous RNA (ceRNA) function, protein stabilization, and epigenetic regulation. We also illustrate the potential role of PVT1 as prognostic biomarker and its relationship with resistance to current chemotherapeutic treatments.

Polymorphisms in the PVT1 Gene and Susceptibility to the Lung Cancer in a Chinese Northeast Population: a Case-control Study

Background: Long non-coding RNA (lncRNA) PVT1 has been identified to be related to risk of a variety of cancers, such as gastric cancer, pancreatic cancer and follicular lymphoma. This study assesses the association between genetic polymorphisms of PVT1 and the susceptibility to lung cancer as well as gene-environmental interaction. Method: A hospital-based case-control study, including 515 lung cancer patients and 582 healthy controls, was carried out in Shenyang, China. Unconditional logistic regression analyses calculated the odds ratios (ORs) and their 95% confidence intervals (CIs) to assess the associations between polymorphisms of rs2608053, rs1561927, rs13254990 and susceptibility to lung cancer. The gene-environment interaction was evaluated by additive model and multiplicative model. Results: There were no statistically significant associations between rs2608053 and rs1561927 polymorphisms in PVT1 and risk of lung cancer in the overall population. The relationship between polymorphism rs13254990 in PVT1 gene and lung adenocarcinoma was significant. Composed with individuals carrying CC genotypes, TT genotype carriers were more likely to develop lung adenocarcinoma (adjusted OR=2.095; 95%CI=1.084-4.047, P=0.028). In the recessive model, it also showed a statistically significant difference (TT vs CT+CC: adjusted OR=2.251, 95%CI=1.174-4.318, P=0.015). In nonsmokers, individuals carrying genotype CT had a lower risk of lung cancer than those with CC genotype (adjusted OR=0.673, 95%CI=0.472-0.959, P=0.028). Comparing with the homozygous CC, the patients with the heterozygous CT had a lower risk of NCSLC in the non-smoking group (adjusted OR =0.685, 95%CI=0.477-0.984, P=0.040). Additionally, gene-environment interaction results were not statistically significant in either additive model or multiplicative model. Conclusion: The polymorphism rs13254990 in PVT1 gene is associated with the risk of lung adenocarcinoma in a Chinese northeast population.

The HPA/SDC1 axis promotes invasion and metastasis of pancreatic cancer cells by activating EMT via FGF2 upregulation

Pancreatic cancer is characterized by the absence of early specific clinical symptoms, accompanied with rapid metastasis and invasion. It is one of the most prevalent types of cancer and more importantly, one of the most common types of malignant cancer with the highest mortality rate of all cancer types. The heparanase (HPA)/syndecan-1 (SDC1) axis has been reported to promote tumor growth, invasion, metastasis and angiogenesis in a variety of cancer types; however, studies into the role and mechanism of the HPA/SDC1 axis in pancreatic cancer are limited. The present study aimed to investigate the biological function and clinical significance of the HPA/SDC1 axis in pancreatic cancer. The results demonstrated that HPA is elevated in pancreatic cancer tissues and cell lines, and that its high expression was associated with poor prognosis. HPA was revealed to mediate an increase in fibroblast growth factor 2 (FGF2) expression by upregulating the expression of SDC1. Conversely, silencing HPA mediated the suppression of FGF2 expression. Furthermore, upregulated FGF2 was observed to increase the expression of downstream Palladin proteins by activating the PI3K/Akt signaling pathway and also lead to the activation of epithelial-mesenchymal transition (EMT). Subsequently, EMT was found to promote the migration and invasion of pancreatic cancer cells. In summary, the HPA/SDC1 axis was revealed to serve an important role in the regulation of FGF2, and was found to promote the invasion and metastasis of pancreatic cancer cells. These findings indicated that the HPA/SDC1 axis may be used as an effective therapeutic target for pancreatic cancer.

LINC00858 promotes retinoblastoma cell proliferation, migration and invasion by inhibiting miR-3182

The aim of the present study was to determine the role of long intergenic non-protein coding RNA 858 (LINC00858) in retinoblastoma (RB) and investigate the underlying molecular mechanisms. RB tissues and paracancerous tissues of 27 RB cases were obtained. RB cell lines (SO-RB50, Y79, HXO-RB44 and WERI-Rb1) and a normal retinal epithelial cell line (ARPE-19) were cultured for in vitro experiments. Batches of SO-RB50 and Y79 cells were assigned to groups transfected with small interfering RNA targeting LINC00858 (si-LINC00858 group), microRNA (miR)-3182 mimics or inhibitor, or the respective controls. A Cell Counting Kit-8 and Transwell assays were performed to assess the effect of the transfections on the proliferation, migration and invasion of SO-RB50 and Y79 cells. A luciferase reporter assay was performed using SO-RB50 cells to demonstrate the direct binding of LINC00858 and miR-3182. Reverse transcription-quantitative PCR was employed to detect LINC00858 and miR-3182 expression. Pearson correlation analysis was used to assess the correlation between the expression of LINC00858 and miR-3182. The results indicated that RB tissues and cells exhibited aberrantly elevated LINC00858 expression (P<0.05). Compared with those in the control-transfected group, SO-RB50 and Y79 cells of the si-LINC00858 group had a lower cell proliferation, as well as a lower number of migrated and invaded cells (all P<0.05). miR-3182 was proven to be a target gene of LINC00858, to be abnormally downregulated in RB tissues and cells (P<0.05) and to be negatively correlated with LINC00858 expression. Compared with those in the si-LINC00858 + inhibitor-negative control group, SO-RB50 and Y79 cells of the si-LINC00858 + miR-3182 inhibitor group exhibited a significantly higher relative proliferation, migration and invasion (all P<0.05). In conclusion, LINC00858 promoted RB cell proliferation, migration and invasion, at least partially by inhibiting miR-3182.

Long Non-coding RNA PVT1 as a Prognostic and Therapeutic Target in Pediatric Cancer

In recent decades, biomedical research has focused on understanding the functionality of the human translated genome, which represents a minor part of all genetic information transcribed from the human genome. However, researchers have become aware of the importance of non-coding RNA species that constitute the vast majority of the transcriptome. In addition to their crucial role in tissue development and homeostasis, mounting evidence shows non-coding RNA to be deregulated and functionally contributing to the development and progression of different types of human disease including cancer both in adults and children. Small non-coding RNAs (i.e., microRNA) are in the vanguard of clinical research which revealed that RNA could be used as disease biomarkers or new therapeutic targets. Furthermore, many more expectations have been raised for long non-coding RNAs, by far the largest fraction of non-coding transcripts, and still fewer findings have been translated into clinical applications. In this review, we center on PVT1, a large and complex long non-coding RNA that usually confers oncogenic properties on different tumor types. We focus on the compilation of early advances in the field of pediatric tumors which often lags behind clinical improvements in adult tumors, and provide a rationale to continue studying PVT1 as a possible functional contributor to pediatric malignancies and as a potential prognostic marker or therapeutic target.

Long non-coding RNA PVT1 interacts with MYC and its downstream molecules to synergistically promote tumorigenesis

Numerous studies have shown that non-coding RNAs play crucial roles in the development and progression of various tumor cells. Plasmacytoma variant translocation 1 (PVT1) mainly encodes a long non-coding RNA (lncRNA) and is located on chromosome 8q24.21, which constitutes a fragile site for genetic aberrations. PVT1 is well-known for its interaction with its neighbor MYC, which is a qualified oncogene that plays a vital role in tumorigenesis. In the past several decades, increasing attention has been paid to the interaction mechanism between PVT1 and MYC, which will benefit the clinical treatment and prognosis of patients. In this review, we summarize the coamplification of PVT1 and MYC in cancer, the positive feedback mechanism, and the latest promoter competition mechanism of PVT1 and MYC, as well as how PVT1 participates in the downstream signaling pathway of c-Myc by regulating key molecules. We also briefly describe the treatment prospects and research directions of PVT1 and MYC.

LncRNAs as potential diagnostic and prognostic biomarkers in gastric cancer: A novel approach to personalized medicine

Gastric cancer is the third leading cause of cancer death with 5-year survival rate of about 30-35%. Since early detection is associated with decreased mortality, identification of novel biomarkers for early diagnosis and proper management of patients with the best response to therapy is urgently needed. Long noncoding RNAs (lncRNAs) due to their high specificity, easy accessibility in a noninvasive manner, as well as their aberrant expression under different pathological and physiological conditions, have received a great attention as potential diagnostic, prognostic, or predictive biomarkers. They may also serve as targets for treating gastric cancer. In this review, we highlighted the role of lncRNAs as tumor suppressors or oncogenes that make them potential biomarkers for the diagnosis and prognosis of gastric cancer. Relatively, lncRNAs such as H19, HOTAIR, UCA1, PVT1, tissue differentiation-inducing nonprotein coding, and LINC00152 could be potential diagnostic and prognostic markers in patients with gastric cancer. Also, the impact of lncRNAs such as ecCEBPA, MLK7-AS1, TUG1, HOXA11-AS, GAPLINC, LEIGC, multidrug resistance-related and upregulated lncRNA, PVT1 on gastric cancer epigenetic and drug resistance as well as their potential as therapeutic targets for personalized medicine was discussed.

lncRNA CCAT1 contributes to the growth and invasion of gastric cancer via targeting miR-219-1

Gastric cancer (GC) is one of the most malignant tumors that seriously threaten human health. Increased reports have indicated that long noncoding RNAs (lncRNAs) are associated with GC. This study aims to investigate the regulatory role of colon cancer-associated transcript-1 (CCAT1) in GC. The results exhibited the fact that CCAT1 was expressed higher in 57 GC tissue samples than in 57 paired adjacent normal tissue samples. The expression of CCAT1 was also increased in GC cell lines (MKN45, Hs746T, and SGC-7901) compared with the gastric epithelial cell line GES-1. Besides this, decreased cell proliferation with increased cell apoptosis was detected in SGC-7902 cells transfected with CCAT1 short hairpin RNA (shRNA). At the same time, a lower cell invasion ability was measured in SCG-7901 cells transfected with CCAT1 shRNA.In addition, miR-219-1 was predicted and convinced a direct target of CCAT1. The expression of miR-219-1 was decreased in GC tissues and GC cell lines. Further studies demonstrated that the roles of CCAT1 in cell proliferation, apoptosis, and invasion were inhibited by miR-219-1. Finally, in vivo experiment indicated that tumor growth of GC was suppressed through knockdown of CCAT1. In conclusion, these results suggested that CAT1 promotes the tumorigenesis and progression of GC by negatively regulating miR-219-1.

LncRNA XIST depletion prevents cancer progression in invasive pituitary neuroendocrine tumor by inhibiting bFGF via upregulation of microRNA-424-5p

Background

Long noncoding RNAs (lncRNAs) are vital mediators in human cancers including pituitary neuroendocrine tumor (PitNET) and could function as competing endogenous RNAs (ceRNAs) of microRNAs (miRNAs). The main objective of this study is to identify effect of lncRNA X-inactive specific transcript (XIST) and microRNA-424-5p (miR-424-5p) on PitNET.

Methods

Microarray analysis was employed to identify the PitNET-related differentially expressed lncRNAs. PitNET tissues, including both invasive and non-invasive subtypes in parallel with normal pituitary tissues were collected for the determination of the expression of XIST, miR-424-5p and basic fibroblast growth factor (bFGF) and the interaction among them. Subsequently, the expression of XIST, miR-424-5p and bFGF in PitNET cells was altered to elucidate their biological significance in the aspects of proliferation, migration, invasion, and the apoptosis.

Results

Both XIST and bFGF exhibited high expression, but miR-424-5p had a low expression in invasive PitNET tissues as compared to non-invasive PitNET normal pituitary tissues. Additionally, XIST competitively bound to miR-424-5p to elevate the expression of bFGF. Furthermore, depleted XIST or bFGF, or elevated miR-424-5p was revealed to suppress the proliferation, migration, invasion, and promote cell cycle arrest and apoptosis of invasive PitNET cells. miR-424-5p repressed the proliferation, migration, invasion of invasive PitNET cells by targeting bFGF.

Conclusion

In conclusion, the fundamental findings of the present study suggested that the functional suppression of XIST downregulated bFGF to inhibit the development of PitNET by increasing miR-424-5p expression, proposing XIST as a novel therapeutic target for PitNET.

Regulatory Mechanisms and Clinical Applications of the Long Non-coding RNA PVT1 in Cancer Treatment

Cancer is the second leading cause of death worldwide, and no obvious decline in incidence and mortality has occurred in recent years. It is imperative to further investigate the mechanisms underlying tumor progression. Long non-coding RNAs have received considerable attention in recent years because of their major regulatory roles in gene expression. Among them, PVT1 is well-studied, and substantial evidence indicates that PVT1 plays critical roles in the onset and development of cancers. Normally, PVT1 acts as an oncogenic factor by promoting cancer cell proliferation, invasion, metastasis, and drug resistance. Herein, we summarize current knowledge regarding the regulatory effects of PVT1 in cancer progression, as well as the related underlying mechanisms, such as interaction with Myc, modulation of miRNAs, and regulation of gene transcription and protein expression. In extracellular fluid, PVT1 mainly promotes cancer initiation, and it normally enhances cellular cancer characteristics in the cytoplasm and cell nucleus. Regarding clinical applications, its role in drug resistance and its potential use as a diagnostic and prognostic marker have received increasing attention. We hope that this review will contribute to a better understanding of the regulatory role of PVT1 in cancer progression, paving the way for the development of PVT1-based therapeutic approaches in cancer treatment.

Long noncoding RNA PVT1: A highly dysregulated gene in malignancy

Recent studies have verified the contribution of several long noncoding RNAs (lncRNAs) in the carcinogenesis. Among the highly acknowledged lncRNAs is the human homolog of the plasmacytoma variant translocation gene, which is called PVT1. PVT1 resides near Myc oncogene and regulates the oncogenic process through modulation of several signaling pathways, such as TGF-β, Wnt/ β-catenin, PI3K/AKT, and mTOR pathways. This lncRNA has a circular form as well. Expression analyses and functional studies have appraised the oncogenic roles of PVT1 and circPVT1. Experiments in several cancer cell lines have shown that PVT1 silencing suppresses cancer cell proliferation, whereas its overexpression has the opposite effect. Its silencing has led to the accumulation of cells in the G0/G1 phase and diminished the number of cells in the S phase. Moreover, genome-wide association studies have signified the role of single nucleotide polymorphisms of this lncRNA in conferring risk of lymphoma in different populations. In the current study, we have summarized recent data about the role of PVT1 and circPVT1 in the carcinogenesis process.

PVT1 Signaling Is a Mediator of Cancer Progression

There is increasing evidence that PVT1 has oncogenic properties and regulates proliferation and growth of many cancers. Themolecular mechanisms of action of PVT1 are mediated, in part, by microRNAs (miRNAs). However, some well-established transcription factors involved in cancer cell proliferation share a common thread of microRNA associations with PVT1. Furthermore, these microRNAs are also involved in mechanisms that lead to the development of drug resistance in cancer cells. While several microRNAs have been implicated directly in PVT1-mediated tumorigenesis, significant steps need to be taken to elucidate these important relationships. We synthesize the current knowledge of the miRNAs and associated genes by which PVT1 contributes to tumorigenesis. Overall, the trend suggests a negative correlation of microRNA expression with PVT1. It is clear that future studies involving PVT1 should be carried out in conjunction with microRNA analysis and should include large scale lncRNA-miRNA-mRNA network analysis. Likewise, the relationship between established transcription factors such as p53 and MYC, and processes like epithelial-mesenchymal transition may offer valuable insight into the yet unknown mechanisms of PVTI-mediated cancer progression via microRNA-dependent signaling networks.

Circular PVT1: an oncogenic non-coding RNA with emerging clinical importance

The importance of circular RNAs (circRNAs) in pathological processes like cancer is evident. Among the circRNAs, recent studies have brought circPVT1 under focus as the most potent oncogenic non-coding RNA. Recent studies on various aspects of circPVT1, including its biogenesis, molecular alteration and its probable role in oncogenesis, have been conducted for research and clinical interest. In this review, a first attempt has been made to summarise the available data on circPVT1 from PubMed and other relevant databases with special emphasis on its role in development, progression and prognosis of various malignant conditions. CircPVT1 is derived from the same genetic locus encoding for long non-coding RNA lncPVT1; however, existing literature suggested circPVT1 and lncPVT1 are transcripted independently by different promoters. The interaction between circRNA and microRNA has been highlighted in majority of the few malignancies in which circPVT1 was studied. Besides its importance in diagnostic and prognostic procedures, circPVT1 seemed to have huge therapeutic potential as evident from differential drug response of cancer cell line as well as primary tumors depending on expression level of the candidate. circPVT1 in cancer therapeutics might be promising as a biomarker to make the existing treatment protocol more effective and also as potential target for designing novel therapeutic intervention.

LncRNA PVT1 Mediates Antiapoptosis and 5-Fluorouracil Resistance via Increasing Bcl2 Expression in Gastric Cancer

Purpose

Plasmacytoma variant translocation 1 (PVT1) is a long noncoding RNA encoded by the human PVT1 gene, which has been verified to mediate tumorigenesis in gastric cancer. However, the underlying molecular mechanisms of PVT1 in gastric cancer (GC) remain largely unknown.

Methods

The tumorigenic ability of PVT1 was verified by subcutaneous and orthotopic mouse models. Flow cytometry assay and TdT-mediated dUTP Nick-End Labeling staining were conducted to explore the effects of PVT1 on gastric cancer cell apoptosis. We investigated the relative gene and protein that are involved in apoptosis in real-time PCR and western blot assay. The resistance to 5- Fluorouracil (5-Fu) caused by PVT1 was evaluated using cell viability assay. Then, to confirm the effects of PVT1 on 5-Fu resistance, we conducted the Kaplan-Meier analysis based on three public databases.

Results

We confirmed that PVT1 can promote the progression of gastric cancer. PVT1 inhibited the apoptosis of GC cells, which may account for its promotion on GC. We confirmed that PVT1 can regulate the expression of Bcl2 and enhance drug-resistance of gastric cancer to 5-Fu. Kaplan-Meier analysis showed that patients with high PVT1 expression do not experience survival related benefits from 5-Fu based chemotherapy; instead, therapy containing no 5-Fu chemotherapy can improve the first progression survival and overall survival of high PVT1 expression GC patients significantly.

Conclusion

Our results showed that PVT1 can inhibit the apoptosis and enhance the 5-Fu resistance of gastric cancer through the activation of Bcl2. PVT1 has the potential to serve as an indicator to predict 5-Fu treatment resistance.

Long non-coding RNA LINC01314 represses cell migration, invasion, and angiogenesis in gastric cancer via the Wnt/β-catenin signaling pathway by down-regulating KLK4

Background

In recent years, gastric cancer (GC) has become a major cause of mortality among various malignancies worldwide with high incidence rates. Long non-coding RNA (lncRNAs) may serve as oncogenes and tumor suppressors in cancers. Therefore, we investigated the effect of LINC01314 on the development of GC cells in relation to the Wnt/β-catenin signaling pathway.

Methods

Microarray data analysis was conducted to screen GC-related differentially expressed lncRNAs, followed by determination of the binding interaction between LINC01314 and kallikrein 4 (KLK4). Human GC cell line SGC-7901 was treated with over-expressed or silenced LINC01314 or KLK4 to investigate the mechanism LINC01314 affecting GC cellular activities. The levels of KLK4, Wnt-1, β-catenin, cyclin D1, N-cadherin and E-cadherin were measured, and cell invasion and migration were evaluated. Next, the tumor weight, micro-vessel density (MVD) and the expression of VEGF-C and VEGFR-3 in transplanted tumors were measured.

Results

LINC01314 was poorly expressed in GC cells and KLK4 was revealed to be a direct target gene of LINC01314. Overexpressed LINC01314 or silencing of KLK4 led to inhibited GC cell migration and invasion, corresponding to decreased Wnt-1, β-catenin, cyclin D1 and N-cadherin while increased E-cadherin. Also, in response to over-expression of LINC01314 or silencing of KLK4, tumor weight and the MVD of transplanted tumors were reduced and angiogenesis was suppressed, which was indicated by down-regulated positive expression of VEGF-C and VEGFR-3.

Conclusion

The findings indicated that over-expression of LINC01314 down-regulated KLK4 to inhibit the activation of the Wnt/β-catenin signaling pathway, thus suppressing migration, invasion, and angiogenesis in GC cells, which provides new insight for the treatment of GC.

Long non-coding RNAs as pan-cancer master gene regulators of associated protein-coding genes: a systems biology approach

Despite years of research, we are still unraveling crucial stages of gene expression regulation in cancer. On the basis of major biological hallmarks, we hypothesized that there must be a uniform gene expression pattern and regulation across cancer types. Among non-coding genes, long non-coding RNAs (lncRNAs) are emerging as key gene regulators playing powerful roles in cancer. Using TCGA RNAseq data, we analyzed coding (mRNA) and non-coding (lncRNA) gene expression across 15 and 9 common cancer types, respectively. 70 significantly differentially expressed genes common to all 15 cancer types were enlisted. Correlating with protein expression levels from Human Protein Atlas, we observed 34 positively correlated gene sets which are enriched in gene expression, transcription from RNA Pol-II, regulation of transcription and mitotic cell cycle biological processes. Further, 24 lncRNAs were among common significantly differentially expressed non-coding genes. Using guilt-by-association method, we predicted lncRNAs to be involved in same biological processes. Combining RNA-RNA interaction prediction and transcription regulatory networks, we identified E2F1, FOXM1 and PVT1 regulatory path as recurring pan-cancer regulatory entity. PVT1 is predicted to interact with SYNE1 at 3′-UTR; DNAJC9, RNPS1 at 5′-UTR and ATXN2L, ALAD, FOXM1 and IRAK1 at CDS sites. The key findings are that through E2F1, FOXM1 and PVT1 regulatory axis and possible interactions with different coding genes, PVT1 may be playing a prominent role in pan-cancer development and progression.

FBXL19-AS1 exerts oncogenic function by sponging miR-431-5p to regulate RAF1 expression in lung cancer

Lung cancer is the leading cause of cancer-related mortality worldwide, characterized by uncontrolled proliferation and metastasis of lung cancer cells. Tumor angiogenesis plays a key role in proliferation and metastasis in cancers, and is an essential component in microenvironment. It has been reported that long non-coding RNA FBXL19-AS1 plays an oncogenic role in colorectal cancer. However, the molecular mechanism of FBXL19-AS1 in lung cancer has not been fully elucidated. In the present study, we found that FBXL19-AS1 expression was up-regulated in lung cancer tissues and cell lines. FBXL19-AS1 knockdown inhibited cell proliferation, migration, invasion, and angiogenesis in lung cancer cells. Molecular mechanism exploration uncovered that FBXL19-AS1 acted as a molecular sponge of miR-431-5p and that RAF1 was a downstream target of miR-431-5p in lung cancer. Moreover, there was a negative association between miR-431-5p expression and FBXL19-AS1 or RAF1 expression in tumor tissues. Through rescue experiments, we discovered that overexpression of RAF1 partially rescued FBXL19-AS1 knockdown-mediated inhibition of angiogenesis and progression in lung cancer. Together, these results indicated that FBXL19-AS1 was involved in progression and angiogenesis in lung cancer by targeting miR-431-5p/RAF1 axis, which provided a new insight into the therapeutic strategies of lung cancer.

Prognostic values of long noncoding RNA PVT1 in various carcinomas: An updated systematic review and meta-analysis

Cancers have been a worldwide health problem with a high mortality rate, but ideal biomarkers are not available to effectively screen and diagnose patients. Currently, an increasing number of long noncoding RNAs have been reported to be abnormally expressed in human carcinomas and play a vital role in tumourigenesis. Plasmacytoma variant translocation 1 (PVT1) is upregulated in various carcinomas, and its overexpression is associated with poor survival in cancer patients. We conduct an updated meta-analysis to determine its potential in prognosis for tumours. In total, 14 studies comprising 2435 patients were enrolled according to Reporting Recommendations for Tumour Marker Prognostic Studies guidelines. High PVT1 expression indicated poor overall survival (hazard ratio [HR] = 1.98, 95% confidence interval [CI]: 1.62-2.42, P < 0.00001) and disease-free survival (HR = 1.63, 95% CI: 1.45-1.84, P < 0.00001). Additionally, increased PVT1 expression was positively associated with lymphatic node metastasis (odd ratio [OR] = 2.87, 95% CI: 1.66-4.96, P = 0.0002), distant metastasis (OR = 2.47, 95% CI: 1.74-3.50, P < 0.00001), advanced tumour-node-metastasis stages (OR = 2.59, 95% CI: 1.38-4.88, P = 0.003). New findings highlight that PVT1 acts as competing RNA to microRNAs to protect mRNAs from miRNAs repression. Therefore, we also discuss PVT1-related microRNAs and their interaction in tumourigenesis. In conclusion, PVT1 may be a potential biomarker of poor prognosis for patients with different cancer types.

Long non-coding RNA MIF-AS1 promotes gastric cancer cell proliferation and reduces apoptosis to upregulate NDUFA4

Long non‐coding RNA MIF‐AS1 (lncMIF‐AS1) has been found to be upregulated in the tumor tissues of gastric cancer; however, its importance for the progression of gastric cancer remains unknown. Thus, the present study was designed to determine the role of the lncMIF‐AS1‐based signal transduction pathway in mediating the proliferation and apoptosis of gastric cancer cells. Differentially expressed lncRNAs and mRNAs were screened out using microarray analysis, based on the published data (GSE63288), and validated using quantitative RT‐PCR. Target relationships between lncRNA‐micro RNA (miRNA) and miRNA‐mRNA were predicted by bioinformatics analysis and verified by dual‐luciferase reporter assay. Protein expression of NDUFA4, COX6C and COX5B was detected by western blot. Cell proliferation, cell cycle and apoptosis were determined using colony formation assay and flow cytometry analysis. Oxidative phosphorylation in gastric cancer cells was assessed by levels of oxygen consumption and ATP synthase activity. Expression of lncMIF‐AS1 and NDUFA4 were upregulated in gastric cancer tissues and cells as compared with non‐cancerous gastric tissues and cells (P < .05). MiR‐212‐5p was identified as the most important miRNA linker between lncMIF‐AS1 and NDUFA4, which was negatively regulated by lncMIF‐AS1 and its depletion is the main cause of NDUFA4 overexpression (P < .01). The upregulated expression of NDUFA4 then greatly promoted the proliferation and decreased the apoptosis of gastric cancer cells through activation of the oxidative phosphorylation pathway. Taken together, the present study implies that inhibition of lncMIF‐AS1/miR‐212‐5p/NDUFA4 signal transduction may provide a promising therapeutic target for the treatment of gastric cancer.

LncRNA PVT1 regulates growth, migration, and invasion of bladder cancer by miR-31/ CDK1

PURPOSE

The aim of our study was to validate the sway of long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) on the metabolism and growth of bladder cancer cells by microRNA-31 (miR-31)/cyclin-dependent kinase 1 ( CDK1).

METHODS

The Gene Expression Omnibus database was used for analyzing the differentially expressed lncRNA and messenger RNA (mRNA) in bladder cancer tissues, with the highly expressed lncRNA PVT1 and mRNA CDK1 screened out. The expression level of PVT1 was detected by quantitative reverse-transcription polymerase chain reaction, cell viability by Cell Counting Kit-8 assay, cell proliferation and scratch by 5-bromo-2'-deoxyuridine assay, cell migration and invasion by transwell assays, the expression level of CDK1 by immunohistochemistry and western blot analysis, transcription factor targeting by dual-luciferase assay, and the effect of PVT1 on bladder cancer growth by nude mice tumor formation experiment.

RESULTS

LncRNA PVT1 and mRNA CDK1 had a higher expression in bladder cancer cells than that in neighboring tissues. Activity, proliferation, colony formation, migration, and invasion of bladder cancer cell were noticeably reduced by the PVT1 inhibitor than that of control group. PVT1 and CDK1 have binding sites with miR-31. When miR-31 decreased, CDK1 mRNA and protein levels increased in vivo experiments in nude mice. When PVT1 was downregulated, the tumor size was significantly reduced and tumor proliferation was curbed. Immunohistochemistry showed that the positive rate of CDK1 and Ki-67 decreased and the expression of miR-31 increased after PVT1 was inhibited.

CONCLUSIONS

LncRNA PVT1 was overexpressed in bladder cancer cells, and it was downregulated miR-31 to enhance CDK1 expression and facilitate bladder cancer cells proliferation, migration, and invasion.

LncRNA PVT1 promotes malignant progression in squamous cell carcinoma of the head and neck

Long non-coding RNAs (lncRNAs) are potentially critical regulators of cancer malignant behaviours. Aberrant expression and dysfunction of lncRNA PVT1 have been reported in multiple human cancers. However, its role in squamous cell carcinoma of the head and neck (SCCHN) remains largely unknown. Our current study demonstrated that PVT1 expression was increased in SCCHN. High PVT1 expression was positively correlated with SCCHN clinical parameters including T classification, clinical stages and cervical lymph node metastasis. More importantly, high PVT1 expression predicted a poor prognosis in SCCHN patients. Gain-of function and loss-of function studies further indicated that PVT1 promoted the proliferation and invasion of SCCHN both in vitro and in vivo, which was accompanied by epithelial-mesenchymal transition and enhanced cancer stem cell-like properties. Further mechanistic investigation revealed that PVT1 activated Wnt/β-catenin signalling pathway, and inhibition of Wnt/β-catenin signalling reversed the malignant progression caused by PVT1 overexpression. Together, our study reveals that PVT1 accelerates the malignant progression of SCCHN and represents a potential biomarker and therapeutic target in SCCHN.

lncRNA PVT1 identified as an independent biomarker for prognosis surveillance of solid tumors based on transcriptome data and meta-analysis

Purpose

Long noncoding RNA PVT1 is dysregulated in some human tumors and has been found to increase the risk of tumor progression and poor prognosis. This study aimed to reanalyze the effect of PVT1 on tumorous prognosis.

Materials and methods

The effect of PVT1 on metastasis and survival were analyzed by univariate logistic regression and Cox proportional hazards model for 32 types of cancer in the Cancer Genome Atlas database (TCGA), and the relationship between PVT1 level and expression of relative genes was assessed by Pearson correlation analysis. RevMan5.3 and STATA14.0 were used to estimate pooled effects of PVT1 on cancer prognosis with data from TCGA and published studies.

Results

In TCGA data, high PVT1 expression tended to increase the risk of TNM progression and decreased the overall survival (OS) time in most of cancers. The pooled effect of PVT1 on TNM (pooled-OR=1.46, 95% CI: 1.29-1.65) and OS (pooled HR=1.32, 95% CI: 1.22-1.43), calculated from 37 and 48 cohorts, identified that high PVT1 expression promoted the metastasis and poor prognosis of cancer. Furthermore, the pooled ORs of 2.77 (95% CI: 1.65-4.66), 4.32 (95% CI: 1.99-9.36), 1.35 (95% CI: 1.01-1.80), 1.62 (95% CI: 1.21-2.18) and 1.48 (95% CI: 1.02-2.15) provided evidence that PVT1 played a role in lymph node metastasis, depth of invasion, distant metastasis, differentiation and lymphatic invasion; while the expression of 24 identified target genes was significantly associated with PVT1 level, and high PVT1 expression dependently decreased the OS time under the influence of co-expression genes (OR=1.29, 95% CI: 1.25-1.32) in high-throughput RNA sequencing merging data. In addition, the expression of PVT1 could be upregulated by smoking, with the pooled OR being 1.09 (95% CI 1.01-1.16).

Conclusion

PVT1 is a dependent biomarker for tumorous prognosis surveillance. However, the reference value of PVT1 needs further study.

Long non-coding RNA PVT1 promotes malignancy in human endometrial carcinoma cells through negative regulation of miR-195-5p

The plasmacytoma variant translocation 1 (PVT1)1 gene is a long non-coding RNA (lncRNA)2 that has been shown to be an oncogene in many cancers. Herein, the function and potential molecular mechanisms connecting PVT1 and miR-195-5p were elucidated in endometrial cancer cell lines. Quantitative real-time PCR and fluorescence in situ hybridization (FISH)3 demonstrated that PVT1 is up-regulated concomitant with miR-195-5p down-regulation in human endometrial carcinoma tissues. PVT1 knockdown inhibited cell proliferation, migration, and invasion while facilitating apoptosis of endometrial cancer cells. Moreover, restoration of miR-195-5p due to PVT1 knockdown exerted tumor-suppressive functions. We observed that PVT1 promotes malignant cell behavior by decreasing miR-195-5p expression. Binding of PVT1 and miR-195-5p was confirmed using luciferase assays. Furthermore, expression of miR-195-5p negatively correlates with PVT1 expression. At the molecular level, either PVT1 knockdown or miR-195-5p overexpression resulted in a decrease of acidic fibroblast growth factor receptor (FGFR1)4 and basic fibroblast growth factor (FGF2).5 FGFR1 and FGF2 are targets of miR-195-5p that play a critical role in endometrial carcinoma by activating PI3K/AKT and MAPK/Erk pathways. Remarkably, PVT1 knockdown combined with miR-195-5p overexpression led to tumor regression in vivo. Overall, these results depict a novel pathway mediated by PVT1 in endometrial carcinoma, which may have potential application for endometrial carcinoma therapy.

A tetracycline-inducible CRISPR/Cas9 system, targeting two long non-coding RNAs, suppresses the malignant behavior of bladder cancer cells

Clustered regularly interspaced short palindromic repeats (CRISPR) associated protein 9 (Cas9) technology has been applied in varied biological studies, including cancer studies. However, stable mRNA expression of Cas9 has potential risks in future gene therapy. Therefore, in the present study, a tetracycline-inducible switch was used to control the mRNA expression of Cas9. Long non-coding RNAs (lncRNAs) may be important functional regulators in tumor development, including in bladder cancer. RNA was designed to simultaneously target two lncRNAs, PVT1 and ANRIL, which are considered to be bladder cancer oncogenes. The mRNA expression of Cas9 was controlled by doxycycline. Reverse transcription-quantitative polymerase chain reaction revealed that the expression of PVT1 and ANRIL was significantly inhibited by the tetracycline-inducible CRISPR/Cas9 system. Functional assays demonstrated that this system could inhibit proliferation, induce apoptosis and suppress cell migration. Therefore, the tetracycline-inducible CRISPR/Cas9 system was demonstrated to repress the malignant behavior of bladder cancer cells by controlling the expression of Cas9 and simultaneously targeting two oncogenic lncRNAs.

Interactions between short and long noncoding RNAs

It is now evident that noncoding RNAs play key roles in regulatory networks determining cell fate and behavior, in a myriad of different conditions, and across all species. Among these noncoding RNAs are short RNAs, such as MicroRNAs, snoRNAs, and Piwi-interacting RNAs, and the functions of those are relatively well understood. Other noncoding RNAs are longer, and their modes of action and functions are also increasingly explored and deciphered. Short RNAs and long noncoding RNAs (lncRNAs) interact with each other with reciprocal consequences for their fates and functions. LncRNAs serve as precursors for many types of small RNAs and, therefore, the pathways for small RNA biogenesis can impinge upon the fate of lncRNAs. In addition, lncRNA expression can be repressed by small RNAs, and lncRNAs can affect small RNA activity and abundance through competition for binding or by triggering small RNA degradation. Here, I review the known types of interactions between small and long RNAs, discuss their outcomes, and bring representative examples from studies in mammals.