The long non-coding RNA DDX11-AS1 facilitates cell progression and oxaliplatin resistance via regulating miR-326/IRS1 axis in gastric cancer

LncRNA-associated competing endogenous RNA network analysis uncovered key lncRNAs involved in temozolomide resistance and tumor recurrence of glioblastoma

Temozolomide (TMZ) is a common alkylating chemotherapeutic agent used to treat brain tumors such as glioblastoma multiforme (GBM) and anaplastic astrocytoma. GBM patients develop resistance to this drug, which has an unclear and complicated molecular mechanism. The competing endogenous RNAs (ceRNAs) play critical roles in tumorigenesis, drug resistance, and tumor recurrence in cancers. This study aims to predict ceRNAs, their possible involvement, and underlying molecular mechanisms in TMZ resistance. Therefore, we analyzed coding and non-coding RNA expression levels in TMZ-resistant GBM samples compared to sensitive GBM samples and performed pathway analysis of mRNAs differentially expressed (DE) in TMZ-resistant samples. We next applied a mathematical model on 950 DE long non-coding RNAs (lncRNAs), 116 microRNAs (miRNAs), and 7977 mRNAs and obtained 10 lncRNA-associated ceRNAs that may be regulating potential target genes involved in cancer-related pathways by sponging 25 miRNAs in TMZ-resistant GBM. Among these, two lncRNAs named ARFRP1 and RUSC2 regulate five target genes (IRS1, FOXG1, GNG2, RUNX2, and CACNA1E) involved in AMPK, AKT, mTOR, and TGF-β signaling pathways that activate or inhibit autophagy causing TMZ resistance. The novel lncRNA-associated ceRNA network predicted in GBM offers a fresh viewpoint on TMZ resistance, which might contribute to treating this malignancy.

LncRNAs-associated to genomic instability: A barrier to cancer therapy effectiveness

Although a large part of the genome is transcribed, only 1.9% has a protein-coding potential; most of the transcripts are non-coding RNAs such as snRNAs, tRNAs, and rRNAs that participate in mRNA processing and translation. In addition, there are small RNAs with a regulatory role, such as siRNAs, miRNAs, and piRNAs. Finally, the long non-coding RNAs (lncRNAs) are transcripts of more than 200 bp that can positively and negatively regulate gene expression (both in cis and trans), serve as a scaffold for protein recruitment, and control nuclear architecture, among other functions. An essential process regulated by lncRNAs is genome stability. LncRNAs regulate genes associated with DNA repair and chromosome segregation; they are also directly involved in the maintenance of telomeres and have recently been associated with the activity of the centromeres. In cancer, many alterations in lncRNAs have been found to promote genomic instability, which is a hallmark of cancer and is associated with resistance to chemotherapy. In this review, we analyze the most recent findings of lncRNA alterations in cancer, their relevance in genomic instability, and their impact on the resistance of tumor cells to anticancer therapy.

Circ_0082182 upregulates the NFIB level via sponging miR-326 to promote oxaliplatin resistance and malignant progression of colorectal cancer cells

Circular RNAs (circRNAs) are key regulators in tumor metastasis and drug resistance. This study was designed to investigate circ_0082182 function and mechanism in oxaliplatin (OXA) resistance and cancer progression of colorectal cancer (CRC). The circ_0082182, microRNA-326 (miR-326), and nuclear factor I B (NFIB) levels were quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell sensitization was analyzed by Cell Counting Kit-8 assay. The proliferation ability was determined via EdU assay, and apoptosis was measured by flow cytometry. Transwell assay and wound healing assay were performed to assess cell invasion and migration. The protein level was examined through Western blot. The binding interaction was conducted via dual-luciferase reporter assay. Xenograft tumor assay was used to explore the circ_0082182 function in vivo. The circ_0082182 level was upregulated in OXA-resistant CRC samples and cells. Downregulation of circ_0082182 suppressed OXA resistance, proliferation, invasion, and migration but promoted apoptosis of OXA-resistant CRC cells. Circ_0082182 acted as a sponge for miR-326. The regulatory role of circ_0082182 was ascribed to the miR-326 sponging function. MiR-326 directly targeted NFIB to impede OXA resistance and cancer progression in CRC cells. NFIB level was regulated by circ_0082182 via sponging miR-326. Circ_0082182 promoted tumor growth in OXA-resistant xenograft tumor model through mediating the miR-326/NFIB axis. These data suggested that circ_0082182 elevated the NFIB expression to regulate OXA resistance and CRC progression by absorbing miR-326.

Non-coding RNA in cancer drug resistance: Underlying mechanisms and clinical applications

Cancer is one of the most frequently diagnosed malignant diseases worldwide, posing a serious, long-term threat to patients’ health and life. Systemic chemotherapy remains the first-line therapeutic approach for recurrent or metastatic cancer patients after surgery, with the potential to effectively extend patient survival. However, the development of drug resistance seriously limits the clinical efficiency of chemotherapy and ultimately results in treatment failure and patient death. A large number of studies have shown that non-coding RNAs (ncRNAs), particularly microRNAs, long non-coding RNAs, and circular RNAs, are widely involved in the regulation of cancer drug resistance. Their dysregulation contributes to the development of cancer drug resistance by modulating the expression of specific target genes involved in cellular apoptosis, autophagy, drug efflux, epithelial-to-mesenchymal transition (EMT), and cancer stem cells (CSCs). Moreover, some ncRNAs also possess great potential as efficient, specific biomarkers in diagnosis and prognosis as well as therapeutic targets in cancer patients. In this review, we summarize the recent findings on the emerging role and underlying mechanisms of ncRNAs involved in cancer drug resistance and focus on their clinical applications as biomarkers and therapeutic targets in cancer treatment. This information will be of great benefit to early diagnosis and prognostic assessments of cancer as well as the development of ncRNA-based therapeutic strategies for cancer patients.

Regulatory Roles of Noncoding RNAs in the Progression of Gastrointestinal Cancers and Health Disparities

Annually, more than a million individuals are diagnosed with gastrointestinal (GI) cancers worldwide. With the advancements in radio- and chemotherapy and surgery, the survival rates for GI cancer patients have improved in recent years. However, the prognosis for advanced-stage GI cancers remains poor. Site-specific GI cancers share a few common risk factors; however, they are largely distinct in their etiologies and descriptive epidemiologic profiles. A large number of mutations or copy number changes associated with carcinogenesis are commonly found in noncoding DNA regions, which transcribe several noncoding RNAs (ncRNAs) that are implicated to regulate cancer initiation, metastasis, and drug resistance. In this review, we summarize the regulatory functions of ncRNAs in GI cancer development, progression, chemoresistance, and health disparities. We also highlight the potential roles of ncRNAs as therapeutic targets and biomarkers, mainly focusing on their ethnicity-/race-specific prognostic value, and discuss the prospects of genome-wide association studies (GWAS) to investigate the contribution of ncRNAs in GI tumorigenesis.

Prognostic Roles of ceRNA Network-Based Signatures in Gastrointestinal Cancers

Gastrointestinal cancers (GICs) are high-incidence malignant tumors that seriously threaten human health around the world. Their complexity and heterogeneity make the classic staging system insufficient to guide patient management. Recently, competing endogenous RNA (ceRNA) interactions that closely link the function of protein-coding RNAs with that of non-coding RNAs, such as long non-coding RNA (lncRNA) and circular RNA (circRNA), has emerged as a novel molecular mechanism influencing miRNA-mediated gene regulation. Especially, ceRNA networks have proven to be powerful tools for deciphering cancer mechanisms and predicting therapeutic responses at the system level. Moreover, abnormal gene expression is one of the critical breaking events that disturb the stability of ceRNA network, highlighting the role of molecular biomarkers in optimizing cancer management and treatment. Therefore, developing prognostic signatures based on cancer-specific ceRNA network is of great significance for predicting clinical outcome or chemotherapy benefits of GIC patients. We herein introduce the current frontiers of ceRNA crosstalk in relation to their pathological implications and translational potentials in GICs, review the current researches on the prognostic signatures based on lncRNA or circRNA-mediated ceRNA networks in GICs, and highlight the translational implications of ceRNA signatures for GICs management. Furthermore, we summarize the computational approaches for establishing ceRNA network-based prognostic signatures, providing important clues for deciphering GIC biomarkers.

Long non-coding RNA DDX11-AS1 promotes the proliferation and migration of glioma cells by combining with HNRNPC

Glioma is a malignant tumor of the central nervous system with complex pathogenesis, difficult operation, and a high postoperative recurrence rate. At present, there is still a lack of effective treatment. Long non-coding RNA DDX11 antisense RNA 1 (DDX11-AS1) has been shown to promote tumor development, such as hepatocellular carcinoma, esophageal cancer, etc. However, its molecular mechanism in glioma is poorly understood. In this study, we found that the expression of DDX11-AS1 was elevated in glioma tissues, and patients with high expression of DDX11-AS1 had poor prognosis. DDX11-AS1 was a potential prognostic marker. Functionally, DDX11-AS1 promoted glioma cell proliferation and migration. Mechanistically, DDX11-AS1 interacted with RNA-binding protein heterogeneous nuclear ribonucleoprotein C (HNRNPC) to promote Wnt/β-catenin and AKT pathways and the epithelial-mesenchymal transition process. In summary, our study manifests that the DDX11-AS1/HNRNPC axis may play a vital part in the occurrence and development of glioma, which provides new ideas and therapeutic targets for the diagnosis, treatment, and prognosis of glioma.

Long Non-Coding RNA in Gastric Cancer: Mechanisms and Clinical Implications for Drug Resistance

Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide, with high recurrence and mortality rate. Chemotherapy, including 5-fluorouracil (5-FU), adriamycin (ADR), vincristine (VCR), paclitaxel (PTX), and platinum drugs, remains one of the fundamental methods of GC treatment and has efficiently improved patients’ prognosis. However, most patients eventually develop resistance to chemotherapeutic agents, leading to the failure of clinical treatment and patients’ death. Recent studies suggest that long non-coding RNAs (lncRNAs) are involved in the drug resistance of GC by modulating the expression of drug resistance-related genes via sponging microRNAs (miRNAs). Moreover, lncRNAs also play crucial roles in GC drug resistance via a variety of mechanisms, such as the regulation of the oncogenic signaling pathways, inhibition of apoptosis, induction of autophagy, modulation of cancer stem cells (CSCs), and promotion of the epithelial-to-mesenchymal transition (EMT) process. Some of lncRNAs exhibit great potential as diagnostic and prognostic biomarkers, as well as therapeutic targets for GC patients. Therefore, understanding the role of lncRNAs and their mechanisms in GC drug resistance may provide us with novel insights for developing strategies for individual diagnosis and therapy. In this review, we summarize the recent findings on the mechanisms underlying GC drug resistance regulated by lncRNAs. We also discuss the potential clinical applications of lncRNAs as biomarkers and therapeutic targets in GC.

Mechanisms of Action And Clinical Implications of MicroRNAs in the Drug Resistance of Gastric Cancer

Gastric cancer (GC) is one of the most common malignant tumors of digestive systems worldwide, with high recurrence and mortality. Chemotherapy is still the standard treatment option for GC and can effectively improve the survival and life quality of GC patients. However, with the emergence of drug resistance, the clinical application of chemotherapeutic agents has been seriously restricted in GC patients. Although the mechanisms of drug resistance have been broadly investigated, they are still largely unknown. MicroRNAs (miRNAs) are a large group of small non-coding RNAs (ncRNAs) widely involved in the occurrence and progression of many cancer types, including GC. An increasing amount of evidence suggests that miRNAs may play crucial roles in the development of drug resistance by regulating some drug resistance-related proteins as well as gene expression. Some also exhibit great potential as novel biomarkers for predicting drug response to chemotherapy and therapeutic targets for GC patients. In this review, we systematically summarize recent advances in miRNAs and focus on their molecular mechanisms in the development of drug resistance in GC progression. We also highlight the potential of drug resistance-related miRNAs as biomarkers and therapeutic targets for GC patients.

Depletion of hsa_circ_0000144 Suppresses Oxaliplatin Resistance of Gastric Cancer Cells by Regulating miR-502-5p/ADAM9 Axis

Background

Circular RNAs (circRNAs) have been disclosed to exert important roles in human cancers, including gastric cancer (GC). CircRNA hsa_circ_0000144 was identified as an oncogene in GC development. The aim of our study was to explore the role of hsa_circ_0000144 in oxaliplatin (OXA) resistance of GC.

Methods

Expression levels of hsa_circ_0000144, microRNA-502-5p (miR-502-5p) and A disintegrin and metalloproteinase 9 (ADAM9) were examined by quantitative real-time PCR (RT-qPCR) or Western blot assay. The OXA resistance of GC cells was evaluated by Cell Counting Kit-8 (CCK-8) assay. Colony formation assay was performed to assess the colony formation capacity. Cell apoptosis was determined by flow cytometry and caspase 3 activity. And cell migration and invasion were detected by Transwell assay. Target association between miR-502-5p and hsa_circ_0000144 or ADAM9 was demonstrated by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Moreover, role of hsa_circ_0000144 in vivo was analyzed by xenograft tumor assay.

Results

Hsa_circ_0000144 and ADAM9 were highly expressed, while miR-502-5p was downregulated in OXA-resistant GC tissues and cells. Depletion of hsa_circ_0000144 could inhibit OXA resistance, proliferation and metastasis in OXA-resistant GC cells, which was attenuated by miR-502-5p inhibition. Hsa_circ_0000144 sponged miR-502-5p to positively regulate ADAM9 expression. MiR-502-5p suppressed OXA resistance, proliferation and metastasis in OXA-resistant GC cells by targeting ADAM9. Hsa_circ_0000144 knockdown could hamper tumor growth in vivo.

Conclusion

Hsa_circ_0000144 exerted inhibitory effects on OXA resistance, proliferation and metastasis of OXA-resistant GC cells by regulating miR-502-5p/ADAM9 axis, at least in part.

circATP2B1 Promotes Aerobic Glycolysis in Gastric Cancer Cells Through Regulation of the miR-326 Gene Cluster

The discovery of circular RNA (circRNA) enormously complimented the repertoire of traditional gene expression theory. As a type of endogenous noncoding RNA, circRNA participates in the occurrence of many kinds of tumors in addition to regulating their development. The Warburg effect (aerobic glycolysis is taken with priority for cancer cells instead of oxidative phosphorylation) is one of the most important factors involved in the excessive proliferation of gastric cancer cells. Our data showed that circRNA circATP2B1 (also called hsa_circ_000826) was overexpressed in gastric cancer tissues instead of linear ATP2B1 mRNA, and it promoted aerobic glycolysis in gastric cancer cells. Bioinformatic Gene Ontology analysis showed that the potential downstream targets of circATP2B1 include the microRNA miR-326 gene cluster (miR-326-3p/miR-330-5p), which is functionally focused on cell growth and metabolic processes. The expressions of miR-326-3p/miR-330-5p were downregulated in gastric cancer, and circATP2B1 functionally targeted miR-326-3p/miR-330-5p in an RNA-induced silencing complex (RISC) dependent manner. Dual-luciferase reporter assays demonstrated that pyruvate kinase M2 (PKM2) was one of the targets of miR-326-3p/miR-330-5p. As a rate-limiting enzyme in the aerobic glycolytic pathway, PKM2 accelerated gastric cancer cells' glucose uptake and increased cell viability. Taken together, circATP2B1 captured miR-326-3p/miR-330-5p and decreased the suppression of PKM2 by miR-326-3p/miR-330-5p, thus aiding the aerobic glycolysis and proliferation of gastric cancer cells. This study identified a novel molecular pathway in gastric cancer that may provide more targets for reversing cancer metabolic reprogramming, as well as a potential strategy for targeted therapy of gastric cancer.

lncRNA PCAT6 facilitates cell proliferation and invasion via regulating the miR-326/hnRNPA2B1 axis in liver cancer

Liver cancer is one of the most common malignant human tumors with the highest morbidity and mortality rates of all cancer types in China. Evidence suggests that long non-coding RNA prostate cancer-associated transcript 6 (PCAT6) plays an essential role in tumor progression. However, the roles and mechanism of PCAT6 in liver cancer remain unclear. The present study showed that the expression of PCAT6 and heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) was upregulated in liver cancer tissues compared with non-cancerous tissues and were associated with poor overall survival time, whereas microRNA (miR)-326 expression was downregulated. Moreover, knockdown of PCAT6 significantly inhibited the proliferation and invasion of liver cancer cells in vitro and in vivo. A dual-luciferase reporter gene assay demonstrated that PCAT6 could bind to miR-326 and that hnRNPA2B1 was a direct target gene of miR-326. Mechanistically, silenced PCAT6 suppressed the malignant phenotype of liver cancer cells through upregulating the inhibitory effect of miR-326 on hnRNPA2B1 expression. Taken together, these data demonstrated that knockdown of PCAT6 inhibited liver cancer progression through regulation of the miR-326/hnRNPA2B1 axis, suggesting that PCAT6 functions as an oncogene and may be a useful biomarker for the future diagnosis and treatment of liver cancer.

Role of Long Non-Coding RNAs in the Chemoresistance of Gastric Cancer: A Systematic Review

PURPOSE

Accumulating evidence demonstrates that long non-coding RNAs (lncRNAs) play a vital role in the chemoresistance of gastric cancer (GC). The present systematic review summarises the emerging role, potential targets or pathways and regulatory mechanisms of lncRNAs involved in chemoresistance and proposes a number of clinical implications of lncRNAs as novel therapeutic targets for GC.

METHODS

Studies on lncRNAs involved in the chemoresistance of GC published until July 2020 in the PubMed and Web of Science databases were systematically reviewed and the expression form, role in chemoresistance, targets or pathways, corresponding drugs and potential mechanisms of relevant lncRNAs were summarised in detail.

RESULTS

A total of 48 studies were included in this systematic review. Amongst these studies, 32 involved single drug resistance and 16 involved in multidrug resistance (MDR). The 48 studies collected described 38 lncRNAs in the drug-resistant cells of GC, including 33 upregulated and 5 downregulated lncRNAs. Cisplatin (DDP) was the most studied drug and lncRNA MALAT1 was the most studied lncRNA related to the chemoresistance of GC. The potential mechanisms of chemoresistance for lncRNAs in GC mainly included, amongst others, reduction of apoptosis, induction of autophagy, repair of DNA damage, promotion of epithelial-mesenchymal transition (EMT) and regulation of the related signalling pathways.

CONCLUSION

LncRNAs play a vital role in the chemoresistance of GC and are novel therapeutic targets for the disease. Detailed chemoresistance mechanisms, translational studies and clinical trials on lncRNAs in GC are urgently needed.

LncRNA DDX11-AS1 Exerts Oncogenic Roles in Glioma Through Regulating miR-499b-5p/RWDD4 Axis

Background

Long noncoding RNAs (lncRNA) exert essential functions during tumorigenesis. However, how lncRNAs participate in glioma development remains poorly researched. This study aimed to determine how DDX11-AS1 affects glioma progression.

Methods

Gene expression was analyzed by qRT-PCR. Survival rate curve was plotted in 56 glioma patients. Loss-of-function assays were performed to analyze proliferation, migration, and invasion through CCK8, colony formation, and transwell assays. Luciferase assay and RNA pulldown assays were conducted to illustrate the underlying molecular mechanism.

Results

DDX11-AS1 expression was upregulated in glioma tissues and cells. DDX11-AS1 overexpression was linked with poor prognostic value. DDX11-AS1 knockdown suppressed proliferation, migration, and invasion while inducing apoptosis. DDX11-AS1 interacted with miR-499b-5p to eliminate it, leading to upregulation of RWDD4 expression. RWDD4 was upregulated in glioma while miR-499b-5p was downregulated.

Conclusion

DDX11-AS1 upregulation promotes glioma progression through acting as a competing endogenous RNA for miR-499b-5p to upregulate RWDD4.

Seven-Gene Signature Based on Glycolysis Is Closely Related to the Prognosis and Tumor Immune Infiltration of Patients With Gastric Cancer

Background: Gastric cancer (GC) is one of the most common malignancies worldwide, exhibiting a high morbidity, and mortality. As the various treatment methods for gastric cancer are limited by disadvantages, many efforts to improve the efficacy of these treatments are being taken. Metabolic recombination is an important characteristic of cancer and has gradually caused a recent upsurge in research. However, systematic analysis of the interaction between glycolysis and GC patient prognosis and its potential associations with immune infiltration is lacking but urgently needed.

Methods: We obtained the gene expression data and clinical materials of GC derived from The Cancer Genome Atlas (TCGA) dataset. Univariate and multivariate Cox proportional regression analyses were performed to select the optimal prognosis-related genes for subsequent modeling. We then validated our data in the GEO database and further verified the gene expression using the Oncomine database and PCR experiments. Besides, Gene set variation analysis (GSVA) analysis was employed to further explore the differences in activation status of biological pathways between the high and low risk groups. Furthermore, a nomogram was adopted to predict the individualized survival rate of GC patients. Finally, a violin plot and a TIMMER analysis were performed to analyse the characteristics of immune infiltration in the microenvironment.

Results: A seven-gene signature, including STC1, CLDN9, EFNA3, ZBTB7A, NT5E, NUP50, and CXCR4, was established. Based on this seven-gene signature, the patients in the training set and testing sets could be divided into high-risk and low-risk groups. In addition, a nomogram based on risk and age showed good calibration and moderate discrimination. The results proved that the seven-gene signature had a strong capacity to predict the GC patient prognosis. Collectively, the violin plot and TIMMER analysis demonstrated that an immunosuppressive tumor microenvironment caused by hyperglycolysis led to poor prognosis.

Conclusion: Taken together, these results established a genetic signature for gastric cancer based on glycolysis, which has reference significance for the in-depth study of the metabolic mechanism of gastric cancer and the exploration of new clinical treatment strategies.

LncRNA DDX11-AS1: a novel oncogene in human cancer

Long noncoding RNA (lncRNA) is a newly identified type of noncoding RNA with a length of more than 200 nucleotides. The latest research shows that lncRNAs play important roles in the occurrence and development of human tumours by acting both as carcinogenic genes and as tumour suppressor genes. LncRNAs plays a role in various biological processes, such as cell growth, apoptosis, migration and invasion. The newly discovered lncRNA DDX11-AS1 is abnormally highly expressed in various malignant tumours, such as hepatocellular carcinoma, colorectal cancer, osteosarcoma, bladder cancer, NSCLC and gastric cancer. DDX11-AS1 mainly regulates the expression of related genes through direct or indirect ways to perform its functions in carcinogenicity. These results indicate that DDX11-AS1 may be a marker or therapeutic target of tumours. This review summarizes the biological function and mechanism of DDX11-AS1 in the process of tumour development.