Long non-coding RNAs involved in metastasis of gastric cancer

Molecular Mechanism of lncRNAs in Regulation of Breast Cancer Metastasis; a Comprehensive Review

Although the number of breast cancer deaths has decreased, and there have been developments in targeted therapies and combination treatments for the management of metastatic illness, metastatic breast cancer is still the second most common cause of cancer-related deaths in U.S. women. Numerous phases and a vast number of proteins and signaling molecules are involved in the invasion-metastasis cascade. The tumor cells penetrate and enter the blood or lymphatic vessels, and travel to distant organs via the lymphatic or blood vessels. Tumor cells enter cell cycle arrest, adhere to capillary beds in the target organ, and then disseminate throughout the organ's parenchyma, proliferating and enhancing angiogenesis. Each of these processes is regulated by changes in the expression of different genes, in which lncRNAs play a role in this regulation. Transcripts that are longer than 200 nucleotides and do not translate into proteins are called RNAs. LncRNA molecules, whose function depends on their unique molecular structure, play significant roles in controlling the expression of genes at various epigenetic levels, transcription, and so on. LncRNAs have essential functions in regulating the expression of genes linked to cell development in healthy and pathological processes, specialization, programmed cell death, cell division, invasion, DNA damage, and spread to other parts of the body. A number of cancer types have been shown to exhibit aberrant expression of lncRNAs. In this review, we describe the general characteristics, potential molecular mechanisms and targeted therapy of lncRNAs and discuss the emerging functions of lncRNAs in breast cancer.

Overcoming Microbiome-Acquired Gemcitabine Resistance in Pancreatic Ductal Adenocarcinoma

Gastrointestinal cancers (GICs) are one of the most recurrent diseases in the world. Among all GICs, pancreatic cancer (PC) is one of the deadliest and continues to disrupt people's lives worldwide. The most frequent pancreatic cancer type is pancreatic ductal adenocarcinoma (PDAC), representing 90 to 95% of all pancreatic malignancies. PC is one of the cancers with the worst prognoses due to its non-specific symptoms that lead to a late diagnosis, but also due to the high resistance it develops to anticancer drugs. Gemcitabine is a standard treatment option for PDAC, however, resistance to this anticancer drug develops very fast. The microbiome was recently classified as a cancer hallmark and has emerged in several studies detailing how it promotes drug resistance. However, this area of study still has seen very little development, and more answers will help in developing personalized medicine. PC is one of the cancers with the highest mortality rates; therefore, it is crucial to explore how the microbiome may mold the response to reference drugs used in PDAC, such as gemcitabine. In this article, we provide a review of what has already been investigated regarding the impact that the microbiome has on the development of PDAC in terms of its effect on the gemcitabine pathway, which may influence the response to gemcitabine. Therapeutic advances in this type of GIC could bring innovative solutions and more effective therapeutic strategies for other types of GIC, such as colorectal cancer (CRC), due to its close relation with the microbiome.

A comprehensive insight into the role of small nucleolar RNAs (snoRNAs) and SNHGs in human cancers

Long non-coding RNAs (lncRNAs), which comprise most non-coding RNAs (ncRNAs), have recently become a focus of cancer research. How many functional ncRNAs exist is still a matter of debate. Although insufficient evidence supports that most lncRNAs function as transcriptional by-products, it is widely known that an increasing number of lncRNAs play essential roles in cells. Small nucleolar RNAs (snoRNAs), 60-300 nucleotides in length, have been better studied than long non-coding RNAs (lncRNAs) and are predominantly present in the nucleolus. Most snoRNAs are encoded in introns of protein- and non-protein-coding genes called small nucleolar RNA host genes (SNHGs). In this article, we explore the biology and characteristics of SNHGs and their role in developing human malignancies. In addition, we provide an update on the ability of these snoRNAs to serve as prognostic and diagnostic variables in various forms of cancer.

In Silico and Experimental Analyses of Long Non-coding RNA TMPO-AS1 Expression in Iranian Patients with Gastric Cancer

Background: In recent decades, many long non-coding RNAs (lncRNAs) have been reported to play a prominent role in tumorigenesis and the progression of human cancers, including gastric cancer (GC), a leading cause of cancer death in Iranian men and women. Studies have demonstrated that thymopoietin antisense transcript 1 (TMPO-AS1) was upregulated in different cancers by acting as an oncogenic lncRNA. Objectives: This study aimed to evaluate the expression of lncRNA TMPO-AS1 in Iranian patients with GC. Methods: In order to conduct the present study, 40 gastric tumor samples and 40 marginal noncancerous counterparts were collected. The characteristics of patients’ samples were recorded, and the TMPO-AS1 expression levels were evaluated by qRT-PCR analysis. The Cancer Genome Atlas (TCGA) data for TMPO-AS1 were used and analyzed through GEPIA and TANRIC online tools. Receiver operating characteristic (ROC) curve analysis was used to estimate the diagnostic value. Student t-test, one-way ANOVA, and chi-square test were accomplished via SPSS software. Results: Our data demonstrated that TMPO-AS1 was overexpressed in cancerous tissues compared to adjacent nonmalignant ones (P = 0.0076). None of the demographic and clinicopathological data were associated with TMPO-AS1 expression levels. The TCGA data demonstrated that TMPO-AS1 was upregulated in GC tissues in comparison to adjacent nonmalignant ones (P = 0.001). ROC curve analysis suggested that TMPO-AS1 expression levels could discriminate GC tumor tissues from normal ones (AUC = 0.699, P = 0.001). Conclusions: Altogether, in our study, we demonstrated that lncRNA TMPO-AS1 may be considered a biomarker in Iranian patients with GC. However, further investigations are required to confirm the potential application of this lncRNA in diagnosis, prognosis, and therapeutic applications of GC.

Inhibitory role of LINC00332 in gastric cancer progression through regulating cell EMT and stemness

OBJECTIVE

Gastric cancer (GC) is one of the most common lethal malignancies worldwide. The molecular mechanisms underlying GC early detection are poorly understood. Identifying potential coding and non-coding markers and related pathways in the GC progression is essential. Some Long non-coding RNAs (lncRNAs) reportedly play vital roles during gastric GC development. However, the clinical significance and biological function of LINC00332 in GC remain largely unclear.

METHODS

The gene expression patterns of GC from an RNAseq dataset (GSE122401) were retrieved from the Gene Expression Omnibus (GEO) database to recognize differentially expressed genes (DEGs) and lncRNAs (DELs) between normal and GC samples through several bioinformatic analysis. The expression of LINC00332 and MMP-13 as a target gene was quantified in fresh frozen tissues obtained from GC patients. In addition, we investigated the potential function of LINC00332 in silico and in vitro.

RESULTS

The expressions of LINC00332 and MMP-13 were significantly downregulated and upregulated in GC tissues, respectively. A significant inverse correlation between LINC00332 and MMP-13 mRNA expression was observed in tumor samples. The mRNA expression level of mesenchymal markers, stem cell factors, and MMP genes were significantly decreased after the LINC00332 ectopic expression, while epithelial markers expression was significantly increased. The LINC00332 overexpression markedly repressed proliferation, migration, and invasion and did not induce apoptosis in AGS cells. In addition, LINC00332 overexpression notably promoted the E-cadherin protein expression. Moreover, LINC00332 significantly decreased the cisplatin resistance.

CONCLUSION

Our findings indicated that LINC00332 may be a critical anti-EMT factor and provided a new efficient therapeutic strategy for GC treatment.

Long non-coding RNAs: Biogenesis, functions, and clinical significance in gastric cancer

Gastric cancer (GC) is one of the most prevalent malignant tumor types and the third leading cause of cancer-related death worldwide. Its morbidity and mortality are very high due to a lack of understanding about its pathogenesis and the slow development of novel therapeutic strategies. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs with a length of more than 200 nt. They play crucial roles in a wide spectrum of physiological and pathological processes by regulating the expression of genes involved in proliferation, differentiation, apoptosis, cell cycle, invasion, metastasis, DNA damage, and carcinogenesis. The aberrant expression of lncRNAs has been found in various cancer types. A growing amount of evidence demonstrates that lncRNAs are involved in many aspects of GC pathogenesis, including its occurrence, metastasis, and recurrence, indicating their potential role as novel biomarkers in the diagnosis, prognosis, and therapeutic targets of GC. This review systematically summarizes the biogenesis, biological properties, and functions of lncRNAs and highlights their critical role and clinical significance in GC. This information may contribute to the development of better diagnostics and treatments for GC.

LncRNA POT1-AS1 accelerates the progression of gastric cancer by serving as a competing endogenous RNA of microRNA-497-5p to increase PDK3 expression

BACKGROUND

Gastric cancer (GC) is the most common malignant tumor of the digestive system. Although progress has been reported in terms of treatment, it is still the second leading cause of cancer-related death. Long non-coding RNAs have been shown to play a key role in human cancers in recent investigations. However, the role of POT1-AS1 in GC is still unclear.

METHODS

The relative POT1-AS1 level in GC tissues and paracancerous tissues was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The biological function of POT1-AS1 was studied by CCK8 and Transwell assays in vitro experiments. Moreover, the downstream target genes of POT1-AS1 were predicted by bioinformatics.

RESULTS

In this study, high POT1-AS1 expression in GC cells was confirmed, and its elevated expression was linked to patients' negative clinicopathological characteristics, as well as shorter disease-free survival (DFS) and overall survival (OS). POT1-AS1 was shown to serve as a competing endogenous RNA (ceRNA) by sponging miR-497-5p to increase PDK3 expression. The impact of POT1-AS1 silencing on GC malignant phenotypes could be reversed by suppressing miR-497-5p or restoring PDK3, according to rescue experiments.

CONCLUSIONS

In brief, POT1-AS1 acted as an oncogenic lncRNA in GC, facilitating GC development by affecting the miR-497-5p/PDK3 axis, implying that the POT1-AS1/miR-497-5p/PDK3 axis is a useful target in anticancer therapy.

An updated review on the therapeutic, diagnostic, and prognostic value of long non-coding RNAs in gastric cancer

As a novel group of non-coding RNAs, long non-coding RNA (lncRNAs) can substantially regulate various biological processes. Downregulated tumor-suppressive lncRNAs and upregulated oncogenic lncRNAs (onco-lncRNAs) have been implicated in gastric cancer (GC) development. These dysregulations have been associated with decreased chemosensitivity, inhibited apoptosis, and increased tumor migration in GC. Besides, growing evidence indicates that lncRNAs can be a valuable diagnostic and prognostic biomarker, and their expression levels are substantially associated with the clinicopathological features of affected patients. The current study aims to review the recent findings of the tumor-suppressive lncRNAs and onco-lncRNAs in GC development and highlight their therapeutic, diagnostic, and prognostic values in treating GC cells. Besides, it intends to highlight the future direction of lncRNAs in treating GC.

Crosstalk between lncRNAs and miRNAs in gastrointestinal cancer drug resistance

Gastrointestinal cancers are one of the most prevalent malignancies worldwide. Dysregulation of lncRNAs by epigenetic alteration is crucial in gastrointestinal carcinogenesis. Epigenetic alteration includes DNA methylation, chromatin remodeling, histone modifications, and deregulated-gene expression by miRNAs. LncRNAs are involved in biological processes, including, uncontrolled cell division, migration, invasion, and resistance to apoptosis and drugs. Multiple-drug resistance (MDR) is a crucial obstacle in effective chemotherapy for gastrointestinal cancers. MDR can be associated with the prognosis and diagnosis of patients receiving chemotherapeutic agents (i.e. cisplatin, oxaliplatin, platinum, 5-fluorouracil, gefitinib, methotrexate, taxol, cetuximab, docetaxel, and gemcitabine). In this review, we focused on recently known lncRNAs and their relation with miRNAs and chemotherapeutic drugs, and their modulation in gastrointestinal cancers. Moreover, we mentioned the future prospective and clinical application of lncRNAs as a critical indicator and biomarker in diagnosis, prognosis, staging, grading, and treatment of gastrointestinal cancers.

Survival Analysis of Gastric Cancer Patients Using Illness-Death Model In Kerman City, Southeast Iran during 2001-2016

BACKGROUND Gastric cancer (GC) is the fifth most common cancer and the third most common cause of cancer death worldwide. The aim of this study was to investigate the factors affecting the survival of patients with GC using the illness-death model (metastasis as an intermediate event). METHODS In this retrospective cohort study, 339 patients with GC who were referred to Shahid Bahonar and Afzalipour Hospitals in Kerman, Southeast Iran during 2001-2016 were included. Demographic, therapeutic, and clinical data were collected from the patients' medical records. To evaluate the factors affecting patients' survival and the relationship between the factors, the illness-death model (metastasis as an intermediate event) was used. RESULTS One, three, and five-year survival rates in patients with GC were estimated to be 63%, 40%, and 30%, respectively. The results of analysis of illness-death model showed that age (HR = 0.98, 95% CI: 0.97- 0.99; p = 0.007) and histological grade (HR = 1.77; 95% CI: 1.68- 2.67; p =0.007) affected metastasis whereas history of cigarette smoking (HR = 1.89; 95% CI: 1.08- 3.3; p = 0.02) and chemotherapy (HR = 0.63; 95% CI: 0.4-0.93; p = 0.02) affected death hazard without metastasis. History of opium use (HR=2.11; 95% CI: 1.17- 3.8; p = 0.002), family history of GC (HR = 2.48; 95% CI: 1.2-5.15; p = 0.01) and histological grade (HR = 1.85; 95% CI: 1.11- 3.08; p = 0.02) were identified as factors affecting death hazard in patients with metastasis. CONCLUSION According to the results, patients' age at the time of diagnosis and histological grade have a significant effect on the occurrence of metastasis. In addition, using the disease-death model, a complete understanding of the behavior and effects of the studied variables on different disease states can be realized.

Down-regulation of hsa_circ_0006470 predicts tumor invasion: A new biomarker of gastric cancer

Background

Gastric cancer (GC) is a common cancer. Circular RNAs (circRNAs) regulate the pathogenesis of GC. This study aims to explore its potential as a GC biomarker.

Methods

The expression of hsa_circ_0006470 in GC tissues and GC cell lines was measured by quantitative reverse transcription‐polymerase chain reaction. The diagnostic value of hsa_circ_0006470 was estimated by the receiver operating characteristic (ROC) curve.

Results

Compared with adjacent normal tissues, the expression of hsa_circ_0006470 in GC tissues was significantly lower. The expression levels of hsa_circ_0006470 in different TNM stages and different invasion degrees were significantly different. The area under the ROC curve was 0.783, with sensitivity and specificity 0.725 and 0.750, respectively.

Conclusions

Hsa_circ_0006470 has a high value as a diagnostic biomarker for GC.

RP11-874J12.4, a novel lncRNA, confers chemoresistance in human gastric cancer cells by sponging miR-3972 and upregulating SSR2 expression

Increasing evidence has revealed the contributions of long noncoding RNAs (lncRNAs) in the modulation of drug resistance in gastric cancer. In the present study, we explored the role of a novel lncRNA, RP11-874J12.4, in regulating chemoresistance in gastric cancer and determined the underlying molecular mechanisms. We observed that compared with normal controls, human gastric cancer tissues and cell lines, including MKN-45 and AGS cells, expressed higher RP11-874J12.4 levels. RP11-874J12.4 knockdown sensitized MKN-45 and AGS cells to docetaxel and cisplatin in terms of cell viability and apoptosis rate. In addition, RP11-874J12.4 was found to be a competing endogenous RNA that sponged microRNA (miR)-3972, which showed significantly reduced expression in human gastric cancer tissues and cell lines. Furthermore, signal sequence receptor subunit 2 (SSR2) was identified as a downstream target of miR-3972, and the miR-3972/SSR2 axis was found to regulate chemoresistance in MKN-45 and AGS cells. SSR2 downregulation further sensitized gastric cancer cells with RP11-874J12.4 knockdown to chemotherapeutic drugs via enhanced apoptosis, which was evidenced by significantly upregulated expressions of cleaved caspase-3, cleaved caspase-9, and Bax and downregulated expression of Bcl-2. Furthermore, RP11-874J12.4 knockdown markedly inhibited the growth of xenograft MKN-45 cells in nude mice, which was associated with an increased expression of miR-3972 and decreased expression of SSR2 in tumors. Therefore, the RP11-874J12.4/miR-3972/SSR2 axis plays important roles in the regulation of chemoresistance in MKN-45 and AGS cells and may serve as a target for the diagnosis and treatment of human gastric cancer.

Clinical value of lncRNA CCAT1 in serum extracellular vesicles as a potential biomarker for gastric cancer

Long non-coding RNAs (lncRNAs) in extracellular vesicles (EVs) are considered to be novel non-invasive biomarkers for gastric cancer (GC). lncRNA colon cancer-associated transcript 1 (CCAT1) is aberrantly expressed in certain types of cancer. However, the role of EV lncRNA CCAT1 in patients with GC remains unclear. The current study aimed to assess the expression levels of lncRNA CCAT1 in the serum EVs of patients with GC and evaluate its potential clinical value. EVs were isolated from serum using a commercial kit and ultracentrifugation, and were identified by transmission electron microscopy, nanoparticle tracking analysis and western blotting. Serum EV lncRNA CCAT1 levels in patients with GC, chronic gastritis or atypical hyperplasia and healthy control subjects were detected by reverse transcription-quantitative PCR. Additionally, lncRNA CCAT1 was detected in GC and adjacent non-cancerous tissue samples. Serum EVs were successfully isolated and identified in all patients. The results revealed that serum EV lncRNA CCAT1 levels in patients with GC were significantly higher compared with those in healthy controls, patients with chronic gastritis or atypical hyperplasia (all P<0.05). Additionally, EV lncRNA CCAT1 expression levels were significantly different among various groups based on the depth of invasion, distant metastasis and the Tumor-Node-Metastasis stage. The area under the curve (AUC) value of EV lncRNA CCAT1 was 0.890 [95% confidence interval (CI), 0.826–0.937] with 79.6% sensitivity and 92.6% specificity. The combination of EV lncRNA CCAT1 and carcinoembryonic antibody produced an AUC value of 0.910 (95% CI, 0.849–0.951) with the sensitivity and specificity of 80.5 and 92.6%, respectively. In addition, lncRNA CCAT1 was determined to be stable in serum EVs. The expression levels of lncRNA CCAT1 in GC tissue were positively correlated with those in serum EVs, and high levels of lncRNA CCAT1 were associated with a low disease-free survival rate in patients with GC. The results of the present study demonstrated that serum EV lncRNA CCAT1 levels were upregulated in patients with GC compared with those healthy subjects and patients with other illnesses, and may therefore be used as a novel biomarker for this type of cancer.

DLX6 Antisense RNA 1 Modulates Glucose Metabolism and Cell Growth in Gastric Cancer by Targeting microRNA-4290

BACKGROUND

Gastric cancer (GC) is one of the most commonly diagnosed malignancy worldwide. DLX6 antisense RNA 1 (DLX6-AS1) is a long noncoding RNA (lncRNA) that exhibits oncogenic effects on multiple human carcinomas.

AIMS

This study aimed to investigate the regulatory effect of DLX6-AS1 in GC progression.

METHODS

The expression of DLX6-AS1 in GC tissues and cell lines was examined. The cell viability, number of clones, and apoptosis, aerobic glycolysis, and mitochondrial respiration was assessed. The effect of DLX6-AS1 on tumor growth in nude mice was also evaluated.

RESULTS

DLX6-AS1 was overexpressed in GC tissues and cell lines. DLX6-AS1 knockdown by short hairpin RNA (shRNA) significantly inhibited cell viability and colony formation, and induced apoptosis. DLX6-AS1 silencing impaired aerobic glycolysis but stimulated mitochondrial respiration in GC cells. miR-4290 was confirmed as a downstream target of DLX6-AS1, and their expression levels were inversely correlated. GC cells expressing sh-DLX6-AS1 showed significantly lower level of 3-phosphoinositide-dependent protein kinase 1 (PDK1), a target of miR-4290, compared to cells expressing control shRNA. In addition, the suppressed GC cell malignancy upon DLX6-AS1 knockdown could be prominently reversed by PDK1 overexpression. Meanwhile, PDK1 overexpression enhanced aerobic glycolysis but repressed mitochondrial respiration under sh-DLX6-AS1 treatment. Furthermore, DLX6-AS1 knockdown significantly delayed the tumor growth in a mouse xenograft model inoculated with GC cells.

CONCLUSIONS

LncRNA DLX6-AS1 regulated tumor growth and aerobic glycolysis in GC by targeting miR-4290 and PDK1, suggesting DLX6-AS1 might serve as a novel potential therapeutic target for GC treatment from bench to clinic.

Long Noncoding RNAs: New Regulators of Resistance to Systemic Therapies for Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant disease, with approximately 951,000 new cases diagnosed and approximately 723,000 cases of mortality each year. The highest mortality rate of GC is in East Asia, and the lowest is in North America. A large number of studies have demonstrated that GC patients are characterized by higher morbidity, metastasis rates, and mortality and lower early diagnosis rates, radical resection rates, and 5-year survival rates. All cases of GC can be divided into two important stages, namely, early- and advanced-stage GC, and the stage mainly determines the treatment strategy for and the therapeutic effect in GC patients. Patients with early-stage GC undergo radical surgery followed by chemotherapy, and the 5-year survival rate can be as high as 90%. However, patients with advanced-stage GC cannot undergo radical surgery because they are at risk for metastasis; therefore, they can choose only radiotherapy or chemotherapy and have a poor prognosis. Based on the lack of specific clinical manifestations and detection methods, most GC patients (>70%) are diagnosed in the advanced stage; therefore, continued efforts toward developing treatments have been focused on advanced-stage GC patients and include molecular targeted therapy, immunotherapy, and small molecular therapy. Nevertheless, in recent years, accumulating evidence has indicated that small molecules, especially long noncoding RNAs (lncRNAs), are involved in the occurrence, development, and progression of GC, and their abundantly dysregulated expression has been identified in GC tissues and cell lines. Therefore, lncRNAs are considered easily detectable molecules and ideal biomarkers or target-specific agents for the future diagnosis or treatment of GC. In this review, we primarily discuss the status of GC, the role of lncRNAs in GC, and the emerging systemic treatments for GC.

Integrated Profiling Revealed Potential Regulatory Networks Among Long Noncoding RNAs and mRNAs in Mucosal Gastric Cancer

Gastric cancer is one of the most commonly occurring cancers worldwide. Investigation of long noncoding RNAs is of increasing interest, particularly in relation to their contribution to progression and prognosis of gastric cancers; however, insufficient studies been performed investigating the part of long noncoding RNAs play in gastric cancer carcinogenesis. Patterns of dysregulated long noncoding RNA and messenger RNA between mucosa gastric cancer and adjacent normal tissues were identified using long noncoding RNAs microarray analysis. Quantitative real-time polymerase chain reaction was conducted as a means to verify the obtained data. Both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes  (KEGG) pathway analyses were subsequently used to investigate the function of dysregulated long noncoding RNAs and messenger RNAs. Cis and trans action was used to predict the possible targets of long noncoding RNAs, and a coexpression network was created to simulate the complex intergenic interactions. Ninety-five dysregulated long noncoding RNAs and 123 messenger RNAs were identified, and quantitative real-time polymerase chain reaction was used to validate 6 filtered long noncoding RNAs. Gene Ontology and KEGG pathway analyses identified several remarkably biological processes and signaling pathways, including spliceosome, RNA transport, and ubiquitin-mediated proteolysis. The transcriptional factors MYC, GABPA, and E2F1 were found to play a central function in the long noncoding RNAs process, as indicated by the coexpression network. This study revealed the dysregulated long noncoding RNA profiles of mucosal gastric cancer. The results shed light on the biological function of long noncoding RNAs in gastric cancer pathogenesis. This provides useful information for exploring potential early screening biomarkers in gastric cancer.

Molecular Alterations in Metastatic Ovarian Cancer From Gastrointestinal Cancer

Reports indicate that most metastatic ovarian cancer (MOC) originates from gastrointestinal cancer (GIC). Notably, GICs metastasize to the ovary frequently via 3 main routes including hematogenous spread, lymphogenous spread, and transcoelomic spread. Nonetheless, the mechanism of the progression remains unknown, and only a handful of literature exists on the molecular alteration implicated in MOC from GIC. This work collected existing evidence and literature on the vital molecules of the metastatic pathway and systematically analyzed them geared toward exploring the mechanism of the metastatic pathway of MOC. Further, this review described dominating molecular alteration in the metastatic process from cancer cells detaching away from lesions to arrive at the ovary, including factors for regulating signaling pathways in epithelial-interstitial transformation, invading, and surviving in the circulatory system or abdominal cavity. We interrogated the basis of the ovary as a distant metastatic site. This article provides new insights into the metastatic pathway and generates novel therapeutic targets for effective treatment and satisfactory outcomes in GIC patients.

The landscape of long non-coding RNAs in tumor stroma

AIMS

Long non-coding RNAs (lncRNAs) are associated with cancer development, while their relationship with the cancer-associated stromal components remains poorly understood. In this review, we performed a broad description of the functional landscape of stroma-associated lncRNAs in various cancers and their roles in regulating the tumor-stroma crosstalk.

MATERIALS AND METHODS

We carried out a systematic literature review of PubMed, Scopus, Medline, Bentham, and EMBASE (Elsevier) databases by using the keywords "LncRNAs in cancer," "LncRNAs in tumor stroma," "stroma," "cancer-associated stroma," "stroma in the tumor microenvironment," "tumor-stroma crosstalk," "drug resistance of stroma," and "stroma in immunosuppression" till July 2020. We collected the latest articles addressing the biological functions of stroma-associated lncRNAs in cancer.

KEY FINDINGS

These articles reported that dysregulated stroma-associated lncRNAs play significant roles in modulating the tumor microenvironment (TME) by the regulation of tumor-stroma crosstalk, epithelial to mesenchymal transition (EMT), endothelial to mesenchymal transition (EndMT), extracellular matrix (ECM) turnover, and tumor immunity.

SIGNIFICANCE

The tumor stroma is a substantial portion of the TME, and the dysregulation of tumor stroma-associated lncRNAs significantly contributes to cancer initiation, progression, angiogenesis, immune evasion, metastasis, and drug resistance. Thus, stroma-associated lncRNAs could be potentially useful targets for cancer therapy.

The emerging roles of non-coding competing endogenous RNA in hepatocellular carcinoma

Accumulating evidence has emerged revealing that noncoding RNAs (ncRNAs) play essential roles in the occurrence and development of hepatocellular carcinoma (HCC). However, the complicated regulatory interactions among various ncRNAs in the development of HCC are not entirely understood. The newly discovered mechanism of competing endogenous RNAs (ceRNAs) uncovered regulatory interactions among different varieties of RNAs. In recent years, a growing number of studies have suggested that ncRNAs, including long ncRNAs, circular RNAs and pseudogenes, play major roles in the biological functions of the ceRNA network in HCC. These ncRNAs can share microRNA response elements to affect microRNA affinity with target RNAs, thus regulating gene expression at the transcriptional level and both physiological and pathological processes. The ncRNAs that function as ceRNAs are involved in diverse biological processes in HCC cells, such as tumor cell proliferation, epithelial-mesenchymal transition, invasion, metastasis and chemoresistance. Based on these findings, ncRNAs that act as ceRNAs may be promising candidates for clinical diagnosis and treatments. In this review, we discuss the mechanisms and research methods of ceRNA networks. We also reviewed the recent advances in studying the roles of ncRNAs as ceRNAs in HCC and highlight possible directions and possibilities of ceRNAs as diagnostic biomarkers or therapeutic targets. Finally, the limitations, gaps in knowledge and opportunities for future research are also discussed.

SNP-SNP interactions of oncogenic long non-coding RNAs HOTAIR and HOTTIP on gastric cancer susceptibility

Genetic variants within oncogenic long non-coding RNAs HOTAIR and HOTTIP may affect their gene expression levels, thereby modifying genetic susceptibility to gastric cancer (GC). In a hospital-based study in Ardabil-a very high-risk area in North-West Iran, 600 blood samples from 300 GC patients and 300 healthy controls were recruited for genotyping. Seven HOTAIR (i.e., rs17720428, rs7958904, rs1899663, and rs4759314) and HOTTIP (i.e., rs3807598, rs17501292, and rs1859168) 'tag' single nucleotide polymorphisms (SNPs) were genotyped by the Infinium HTS platform. The rs17720428, rs7958904, and rs1899663 tagSNPs significantly increased GC risk under dominant models by 1.5-, 1.57-, and 1.5-fold, respectively. The G-C-T-A haplotype of HOTAIR tagSNPs increased the risk of GC by 1.31-fold. No significant association was found between HOTTIP SNPs and the risk of GC. HOTAIR and HOTTIP variants were also not associated with any clinicopathologic characteristics. The SNP-SNP interaction of HOTAIR rs17720428/rs7958904 with HOTTIP rs1859168 was associated with an increased risk of GC (rs17720428 TG-rs1859168 CC, OR = 1.76; rs7958904 GC-rs1859168 CC, OR = 1.85; rs7958904 CC-rs1859168 CC, OR = 1.86). Interestingly, the SNP-SNP interaction of HOTAIR rs1899663 with HOTTIP rs1859168 strongly increased the risk of GC (rs1899663 GT-rs1859168 CC, OR = 4.3; rs1899663 TT-rs1859168 CC, OR = 9.37; rs1899663 TT-rs1859168 CA, OR = 6.59). We showed that the HOTAIR rs17720428, rs7958904, and rs1899663 tagSNPs and their interactions with the HOTTIP rs1859168 polymorphism significantly increased the risk of GC. Specifically, novel SNP-SNP interactions between HOTAIR and HOTTIP tagSNPs have a larger impact than individual SNP effects on GC risk, thereby providing us with valuable information to reveal potential biological mechanisms for developing GC.

Epidermal growth factor-like domain multiple 6 (EGFL6) promotes the migration and invasion of gastric cancer cells by inducing epithelial-mesenchymal transition

Epidermal growth factor-like domain multiple 6 (EGFL6) is implicated in tumor growth, metastasis and angiogenesis, and its ectopic alteration has been detected in aggressive malignancies. However, the pathophysiologic roles and molecular mechanisms of EGFL6 in gastric cancer (GC) remain to be elucidated. In this study, we investigated EGFL6 expression in GC cell lines and tissues using western blotting and immunohistochemistry. We found that EGFL6 was elevated expression in GC cell lines and tissues. The high expression of EGFL6 significantly was correlated with histological grade, depth of invasion, lymph node involvement, distant metastasis and TNM stage in GC and predicted poorer prognosis, and it could act an independent prognostic factor for GC patients. EGFL6 enhanced the proliferation, migration and invasion of GC cells. In addition, we identified the possible molecular mechanisms of EGFL6-involved epithelial-mesenchymal transition (EMT). EGFL6 regulated EMT process and induced metastasis partly through FAK/PI3K/AKT/mTOR, Notch and MAPK signaling pathways. In conclusion, EGFL6 confers an oncogenic function in GC progression and may be proposed as a potential therapeutic target for GC.

Lnc-MCEI mediated the chemosensitivity of esophageal squamous cell carcinoma via miR-6759-5p to competitively regulate IGF2

Large amounts of long non-coding RNAs (lncRNAs) have been annotated whereas most of them have not been functionally characterized. Here we identified lncRNA ENST00000441932 as an oncogenic lncRNA in esophageal squamous cell carcinoma (ESCC) and named lnc-MCEI (lncRNA mediated the chemosensitivity of ESCC by regulating IGF2). What's more, the effect of lnc-MCEI on the chemosensitivity of ESCC was further evaluated. Bioinformatics analysis demonstrated that lnc-MCEI was involved in the tumorigenesis of ESCC and lnc-MCEI levels were significantly increased in ESCC cells and tissues. Additionally, lnc-MCEI knockdown retarded cell proliferation, colony formation of ESCC cells, but induced cell apoptosis. Moreover, lnc-MCEI knockdown significantly improved the chemosensitivity of ESCC to cisplatin (DDP) both in vivo and in vitro. Further mechanisms disclosed that lnc-MCEI functioned as a competing endogenous RNA (ceRNA) via sponging miR-6759-5p and IGF2 was a target of miR-6759-5p. Meanwhile, we found that IGF2 suppressed chemosensitivity of ESCC cells via PI3K/AKT pathway. These data suggested that lnc-MCEI was an oncogenic lncRNA and lnc-MCEI knockdown enhanced chemosensitivity of ESCC cells to cisplatin by targeting miR-6759-5p /IGF2/PI3K/AKT axis.

Long non-coding RNA ASB16-AS1 inhibits proliferation, migration, and invasion of gastric cancer cells by regulating miR-670-3p/ATXN7L3 axis

BACKGROUND

Many long non-coding RNAs (lncRNAs) have been shown to play a role in suppressing or promoting the progression of gastric cancer (GC). However, there are still a large number of lncRNAs whose roles in the progression of GC are still unclear. Therefore, it is still necessary to identify lncRNAs that affect the proliferation, migration, and invasion of GC cells to provide potential targets for the prevention and treatment of GC.

AIM

To investigate the effect of lncRNA ASB16-AS1 on the proliferation, migration, and invasion of GC cells and the underlying mechanism.

METHODS

The expression levels of ASB16-AS1, miR-670-3p, and ATXN7L3 in human gastric mucosal cell line GES-1 and GC cell lines HGC-27, AGS, and NUGC-4 were detected by real-time fluorescent quantitative PCR (RT-qPCR) and Western blot. HGC-27 cells were divided into si-NC, si-ASB16-AS1, miR-NC, miR-670-3p, si-ATXN7L3, si-ASB16-AS1 + anti-miR-NC, si-ASB16 -AS1 + anti-miR-670-3p, si-ASB16-AS1 + pcDNA-NC, and si-ASB16-AS1 + pcDNA-ATXN7L3 groups. Cell counting kit-8 and transwell assay were used to detect cell viability and migration invasion , respectively. Dual luciferase reportor assay, RT-qPCR, and Western blot were used to determine the interaction between ASB16-AS1 and miR-670-3p and between miR-670-3p and ATXN7L3.

RESULTS

ASB16-AS1 and ATXN7L3 were highly expressed in GC cells, while miR-670-3p was lowly expressed (P < 0.05). After inhibiting the expression of ASB16-AS1, overexpressing miR-670-3p, or inhibiting the expression of ATXN7L3, the proliferation, migration, and invasion of HGC-27 cells were significantly reduced (P < 0.05). ASB16-AS1 targets and negatively regulates miR-670-3p expression. MiR-670-3p targets and negatively regulates ATXN7L3 expression. Inhibiting miR-670-3p partially reversed the effects of inhibiting ASB16-AS1 on the proliferation, migration, and invasion of HGC-27 cells (P < 0.05). Overexpressing ATXN7L3 partially reversed the effect of inhibiting ASB16-AS1 on the proliferation, migration, and invasion of HGC-27 cells (P < 0.05).

CONCLUSION

Inhibiting ASB16-AS1 inhibits the proliferation, migration, and invasion of GC cells by regulating the miR-670-3p/ATXN7L3 axis.

Non-coding RNAS and colorectal cancer liver metastasis

More than 50% of colorectal cancer (CRC) deaths are attributed to metastasis, and the liver is the most common distant metastatic site of CRC. The molecular mechanisms underlying CRC liver metastasis are very complicated and remain largely unknown. Accumulated evidence has shown that non-coding RNAs (NcRNAs) play critical roles in tumor development and progression. Here we reviewed the roles and underlying mechanisms of NcRNAs in CRC liver metastasis.

LINC01272 Promotes Migration and Invasion of Gastric Cancer Cells via EMT

PURPOSE

Gastric cancer (GC) is the fifth most common tumor in the world, and most patients with GC have a poor prognosis. This study aimed to explore the biological influence and mechanism of LINC01272 in GC.

MATERIALS AND METHODS

Using bioinformatic analyses, we investigated the expression of LINC01272 in TCGA database and predicted the biological functions and mechanism of LINC01272 in GC. Then, we detected the expression of LINC01272 in GC cell lines, GC tissues, and corresponding normal tissues using real-time polymerase chain reaction (RT-PCR). Finally, we explored the migration and invasion ability of LINC01272 by wound-healing and Transwell assays and examined the expression of epithelial-mesenchymal transition (EMT)-related proteins through Western blotting.

RESULTS

We found that LINC01272 was upregulated in GC and was associated with GC staging and lymph node metastasis. The results of wound-healing and Transwell assays revealed that the LINC01272 was closely related to GC cell migration and invasion. LINC01272 knockdown inhibited the migration and invasion ability of GC cells by reducing the expression of EMT-related proteins. Overexpression of LINC01272 had the opposite effect.

CONCLUSION

Together, our results showed that LINC01272 promoted GC metastasis ability by regulating the expression of EMT-related proteins and could serve as a potential diagnostic biomarker for GC.

Long noncoding RNA LINC00339 promotes the oncogenicity of gastric cancer by regulating SRY-box 9 expression via sponging of microRNA-539

Differential expression of LINC00339 is involved in the malignancy of multiple human cancer types. Nonetheless, the expression profile, functions, and potential mechanisms of action of LINC00339 in gastric cancer are yet to be fully elucidated. This study aimed at measuring LINC00339 expression in gastric cancer and examining the prognostic significance of LINC00339 in patients with gastric cancer. The detailed functions of LINC00339 with regard to the aggressive characteristics of gastric cancer cells and the underlying molecular mechanisms were investigated. Here, we found that LINC00339 expression was aberrantly high in gastric cancer and significantly associated with lymph node metastasis, invasive depth, and TNM stage. Patients with gastric cancer in a LINC00339 high-expression group showed shorter overall survival than patients in a LINC00339 low-expression group. A knockdown of LINC00339 suppressed gastric cancer cell proliferation, migration, and invasion and induced apoptosis in vitro and slowed tumor growth in vivo. In terms of the mechanism, LINC00339 was found to act as a molecular sponge on microRNA-539 (miR-539). SRY-box 9 (SOX9) was confirmed as a direct target gene of miR-539 in gastric cancer cells. An miR-539 knockdown attenuated the effects of the LINC00339 knockdown on the malignant characteristics of gastric cancer cells. Overall, LINC00339 plays a critical role in the malignancy of gastric cancer by regulating SOX9 via sponging of miR‑539. Our findings highlight the importance of the LINC00339-miR-539-SOX9 pathway in gastric cancer pathogenesis and may point to novel targets for the diagnosis, prognosis, and/or treatment of gastric cancer.

Current Understanding of Circular RNAs in Gastric Cancer

Gastric cancer (GC) is the third most common cause of cancer-related death worldwide. Advanced diagnosis and high rates of relapse and metastasis are associated with the poor prognosis of this disease. GC has a complex etiopathogenesis of which the underlying mechanisms remain to be explored. Studies on circular RNAs (circRNAs), noncoding RNAs that may be potential targets in GC, have made substantial progress over the past few years. CircRNAs exert important effects on the onset and progression of GC. Hence, this article aims to summarize the findings of recent studies of circRNAs related to GC and to describe the underlying mechanisms and potential applications. The findings indicate that circRNAs participate in GC regulation, proliferation, invasion, and metastasis through regulating microRNAs, proteins, genes, and signaling pathways. In addition, dysregulated circRNAs may be used as novel diagnostic and prognostic biomarkers or therapeutic targets. This review is expected to facilitate a better understanding of GC, and it suggests novel circRNA-based methods to inhibit or prevent GC.

A three long non-coding RNA signature to improve survival prediction in patients with Wilms' tumor

The prognostic significance of long non-coding RNAs (lncRNAs) in Wilms' tumor (WT) remains unclear. The present study identified differential lncRNA expression patterns between WT and normal tissues; and evaluated the prognostic value of these lncRNAs. Multidimensional data from 136 samples were retrieved from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database. Computational data analyses were performed to detect survival-associated molecular signatures. Kaplan-Meier survival curves revealed the prognostic prediction values for three of these lncRNAs, namely DLGAP1 antisense RNA 2 (DLGAP1-AS2), RP11-93B14.6 and RP11554F20.1. Cox regression analysis revealed that the three-lncRNA signature was significantly associated with patient survival (P<0.01). Functional enrichment analyses suggested that the target genes of these three lncRNAs may be involved in known cancer-associated pathways. The present study revealed a three-lncRNA signature consisting of DLGAP1-AS2, RP11-93B14.6 and RP11554F20.1 that may be used as a prognostic marker for patients with WT.

Quantitative Proteomics Analysis Revealed the Potential Role of lncRNA Ftx in Promoting Gastric Cancer Progression

PURPOSE

The molecular pathogenesis of gastric cancer is still ambiguous till now. Here, it is demonstrated that long noncoding RNA (lncRNA) Ftx acts as a novel tumor promotor of gastric cancer and a potent regulator of hexokinase-2 (HK2).

EXPERIMENTAL DESIGN

The role of lncRNA Ftx is detected in the loss and gain-of-function models of gastric cancer cells. Tandem mass tags combined with multidimensional LC and MS analyses are performed to decipher comparative proteomic profiles of gastric cancer cells in response to lncRNA Ftx knockdown and overexpression. Real-time roteomics-clinical applications (PCR) and western blot are used to validate the proteomic data.

RESULTS

A total of 5124 proteins are quantified and indicated in diverse biological functions and metabolic related signaling pathways. Interestingly, HK2, which is downregulated when lncRNA Ftx is deleted and upregulated while lncRNA Ftx is overexpressed, is further validated in gastric cancer cells.

CONCLUSIONS AND CLINICAL RELEVANCE

The present study suggests lncRNA Ftx promotes gastric cancer progression by upregulating HK2, which provides a new perspective for the mechanism of gastric cancer progression, and thus identifies potential therapeutic targets for gastric cancer.

Spondin 2 promotes the proliferation, migration and invasion of gastric cancer cells

Spondin 2 (SPON2), a member of the Mindin F‐Spondin family, identifies pathogens, activates congenital immunity and promotes the growth and adhesion of neurons as well as binding to their receptors, but its role in promoting or inhibiting tumour metastasis is controversial. Here, we investigated its expression levels and mechanism of action in gastric cancer (GC). Western blotting and GC tissue arrays were used to determine the expression levels of SPON2. ELISAs were performed to measure the serum levels of SPON2 in patients with GC. Two GC cell lines expressing low levels of SPON2 were used to analyse the effects of regulating SPON2 expression on proliferation, migration, invasion, the cell cycle and apoptosis. The results revealed that SPON2 was highly expressed in GC tissues from patients with relapse or metastasis. The levels of SPON2 in sera of patients with GC were significantly higher compared with those of healthy individuals and patients with atrophic gastritis. Knockdown of SPON2 expression significantly inhibited the proliferation, migration and invasion of GC cells in vitro and in vivo. Down‐regulation of SPON2 arrested the cell cycle in G1/S, accelerated apoptosis through the mitochondrial pathway and inhibited the epithelial‐mesenchymal transition by blocking activation of the ERK1/2 pathway. In summary, this study suggests that SPON2 acts as an oncogene in the development of GC and may serve as a marker for the diagnosing GC as well as a new therapeutic target for GC.

Overexpression of PURPL and downregulation of NONHSAT062994 as potential biomarkers in gastric cancer

AIMS

Long non-coding RNAs (LncRNAs) play central roles in the formation and development of gastric cancer (GC). The aim of this study was to evaluate the expression of PURPL and NONHSAT062994 and the relationship between their expressions with clinical characteristics in GC.

MAIN METHODS

PURPL and NONHSAT062994 LncRNAs and p53 gene expression levels were analyzed both in 50 pairs of cancerous and adjacent noncancerous tissue samples in GC patients using qRT-PCR and in four sets of data obtained from Gene Expression Omnibus (GEO) database. Chi-square (χ2) test was used to determine the relationship between PURPL, NONHSAT062994 RNA levels and the clinicopathological characteristics of GC. Receiver operating characteristic (ROC) curves were drawn to represent sensitivity and specificity of PURPL and NONHSAT062994 expression as markers of GC.

KEY FINDINGS

Expression of PURPL was significantly upregulated in 50 GC samples as well as in GC tissues from GSE13911 and GSE27342 datasets. Our results demonstrated that PURPL RNA level in GC was significantly related to tumor size and histopathological grade. p53 expression at both protein and mRNA levels were significantly decreased in GC tissues compared to adjacent control samples. NONHSAT062994 expression was downregulated in 50-pair GC and GC tissues from GSE13915 dataset. However, NONHSAT062994 showed no consistently differential expression in GSE2637dataset. NONHSAT062994 was significantly associated with histological grade and tumor size.

SIGNIFICANCE

Overall, these results suggest that PURPL and NONHSAT062994 may play critical roles in the progression of GC and therefore might be considered as candidate tumor markers for therapeutic goals.

New prognostic markers revealed by RNA-Seq transcriptome analysis after MYC silencing in a metastatic gastric cancer cell line

MYC overexpression is considered a driver event in gastric cancer (GC), and is frequently correlated with poor prognosis and metastasis. In this study, we evaluated the prognostic value of genes upregulated by MYC in patients with GC. Metastatic GC cells (AGP01) characterized by MYC amplification, were transfected with siRNAs targeting MYC. RNA-seq was performed in silenced and non-silenced AGP01 cells. Among the differentially expressed genes, CIAPIN1, MTA2, and UXT were validated using qRT-PCR, western blot, and immunohistochemistry in gastric tissues of 213 patients with GC; and their expressions were correlated with clinicopathological and survival data. High mRNA and protein levels of CIAPIN1, MTA2, and UXT were strongly associated with advanced GC stages (P < 0.0001). However, only CIAPIN1 and UXT gene expressions were able to predict distant metastases in patients with early-stage GC (P < 0.0001), with high sensitivity (> 92%) and specificity (> 90%). Overall survival rate of patients with overexpressed CIAPIN1 or UXT was significantly lower (P < 0.0001). In conclusion, CIAPIN1 and UXT may serve as potential molecular markers for GC prognosis.

A Feedback Loop Regulation Of LINC01433 And YAP Promotes Malignant Behavior In Gastric Cancer Cells

Background

Gastric cancer (GC) is one of the most common cancers and the second leading cause of cancer-related death worldwide. Long noncoding RNAs (lncRNAs) are associated with GC development and progression. However, the functional roles and underlying mechanism of LINC01433 on GC progression remain elusive.

Methods

Firstly, the expression of LINC01433 was examined in 76 pairs of primary GC and corresponding adjacent non-tumorous tissues. Next, overexpression and knockdown experiments were conducted in GC cells to explore the effect of LINC01433 on the malignant behaviors of GC cells. Then, the interaction between LINC01433 and YAP was detected by RNA immunoprecipitation (RIP) and RNA pull-down assays.

Results

We found that LINC01433 was significantly upregulated in GC tissues and cell lines and correlated with poor prognosis. Through gain- and loss-of-function experiments, we demonstrated that LINC01433 promoted proliferation, migration, invasion and chemotherapy resistance in GC cells. Further mechanistic investigation revealed that LINC01433 could stabilize oncoprotein YAP through enhancing the interaction between deubiquitinase USP9X and YAP. LINC01433 decreased the phosphorylation of YAP via suppressing YAP-LATS1 association. Intriguingly, YAP directly bound to LINC01433 promoter region and activated its transcription. Thus, LINC01433 and YAP formed a positive feedback loop.

Conclusion

Collectively, our study demonstrates that the positive feedback loop between LINC01433 and YAP promotes GC progression, and implies that the LINC01433-YAP feedback loop may be a promising therapeutic target for GC treatment.

Identification of functional lncRNAs in gastric cancer by integrative analysis of GEO and TCGA data

Gastric cancer (GC) is a prevalent malignant cancer of digestive system, identification of novel diagnostic and prognostic biomarkers for GC is urgently demanded. The aim of this study was to determine potential long noncoding RNAs (lncRNAs) associated with the pathogenesis and prognosis of GC. Raw noncoding RNA microarray data (GSE53137, GSE70880, and GSE99417) was downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes between GC and adjacent normal gastric tissue samples were screened by an integrated analysis of multiple gene expression profile after gene reannotation and batch normalization. Differentially expressed genes were further confirmed by The Cancer Genome Atlas (TCGA) database. Competing endogenous RNA (ceRNA) network, Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway, survival analysis were extensively applied to identify hub lncRNAs and discover potential biomarkers related to diagnosis and prognosis of GC. In total of 246 integrated differential genes including 15 lncRNAs and 241 messenger RNAs (mRNAs) were obtained after intersections of differential genes between GEO and TCGA database. ceRNA network comprised of three lncRNAs (UCA1, HOTTIP, and HMGA1P4), 26 microRNAs (miRNAs) and 72 mRNAs. Functional analysis revealed that three lncRNAs were mainly dominated in cell cycle and cellular senescence. Survival analysis showed that HMGA1P4 was statistically related to the overall survival rate. For the first time, we identified that HMGA1P4, a target of miR-301b/miR-508, is involved in cell cycle and senescence process by regulating CCNA2 in GC. Finally, the expression levels of three lncRNAs were validated to be upregulated in GC tissues. Thus, three lncRNAs including UCA1, HOTTIP, and HMGA1P4 may contribute to GC development and their potential functions might be associated with the prognosis of GC.

LncRNA HOTAIR in Tumor Microenvironment: What Role?

lncRNAs participate in many cellular processes, including regulation of gene expression at the transcriptional and post-transcriptional levels. In addition, many lncRNAs can contribute to the development of different human diseases including cancer. The tumor microenvironment (TME) plays an important role during tumor growth and metastatic progression, and most of these lncRNAs have a key function in TME intracellular signaling. Among the numerous identified lncRNAs, several experimental evidences have shown the fundamental role of the lncRNA HOTAIR in carcinogenesis, also highlighting its use as a circulating biomarker. In this review we described the contribution of HOTAIR in the TME modulation, highlighting its relation with cellular and non-cellular components during tumor evolution and progression.

Hsa_circ_0067997 promotes the progression of gastric cancer by inhibition of miR-515-5p and activation of X chromosome-linked inhibitor of apoptosis (XIAP)

Circular RNAs (circRNAs) have been revealed to play vital roles in modulating gene expression and participate in several pathological responses including gastric cancer (GC). However, the larger numbers of the circRNAs in GC progression remain undetermined. In the present study, four GC related circRNAs expression profiles from the Gene Expression Omnibus (GEO) database were enrolled. We identified hsa_ circRNA_00067997 (circ_0067997) as an oncogene in GC. qRT-PCR was used to validate the expression of circ_0067997 in GC tissues and cell lines. The results revealed that circ_0067997 was upregulated in GC, and high circ_0067997 expression was associated with the poor overall survival rate of GC patients. Knockdown of circ_0067997 significantly reduced cell viability, inhibited colony formation, and attenuated invasive ability, whereas overexpression of circ_0067997 exhibited opposed effects. Circ_0067997 was identified to be a sponge for miR-515-5p directly. Moreover, XIAP was demonstrated to be targeted and regulated by miR-515-5p. In conclusion, circ_0067997 was identified to be an oncogene in GC by regulating miR-515-5p/XIAP axis.

Comprehensive analysis of potential prognostic genes for the construction of a competing endogenous RNA regulatory network in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is an extremely common malignant tumor with worldwide prevalence. The aim of this study was to identify potential prognostic genes and construct a competing endogenous RNA (ceRNA) regulatory network to explore the mechanisms underlying the development of HCC.

METHODS

Integrated analysis was used to identify potential prognostic genes in HCC with R software based on the GSE14520, GSE17548, GSE19665, GSE29721, GSE60502, and the Cancer Genome Atlas databases. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway-enrichment analyses were performed to explore the molecular mechanisms of potential prognostic genes. Differentially expressed miRNAs (DEMs) and lncRNAs (DELs) were screened based on the Cancer Genome Atlas database. An lncRNA-miRNA-mRNA ceRNA regulatory network was constructed based on information about interactions derived from the miRcode, TargetScan, miRTarBase, and miRDB databases.

RESULTS

A total of 152 potential prognostic genes were screened that were differentially expressed in HCC tissue and significantly associated with overall survival of HCC patients. There were 13 key potential prognostic genes in the ceRNA regulatory network: eleven upregulated genes (CCNB1, CEP55, CHEK1, EZH2, KPNA2, LRRC1, PBK, RRM2, SLC7A11, SUCO, and ZWINT) and two downregulated genes (ACSL1 and CDC37L1) whose expression might be regulated by eight DEMs and 61 DELs. Kaplan-Meier curve analysis showed that nine DELs (AL163952.1, AL359878.1, AP002478.1, C2orf48, C10orf91, CLLU1, CLRN1-AS1, ERVMER61-1, and WARS2-IT1) in the ceRNA regulatory network were significantly associated with HCC-patient prognoses.

CONCLUSION

This study identified potential prognostic genes and constructed an lncRNA- miRNA-mRNA ceRNA regulatory network of HCC, which not only has important clinical significance for early diagnoses but also provides effective targets for HCC treatments and could provide new insights for HCC-interventional strategies.