Circular RNA circSEMA5A promotes bladder cancer progression by upregulating ENO1 and SEMA5A expression

Role of semaphorins, neuropilins and plexins in cancer progression

Progress in understanding nervous system-cancer interconnections has emphasized the functional role of semaphorins (SEMAs) and their receptors, neuropilins (NRPs) and plexins (PLXNs), in cancer progression. SEMAs are a conserved and extensive family of broadly expressed soluble and membrane-associated proteins that were first described as regulators of axon guidance and neural and vascular development. However, recent advances have shown that they can have a dual role in cancer progression, acting either as tumor promoters or suppressors. SEMAs effects result from their interaction with specific co-receptors/receptors NRPs/PLXNs, that have also been described to play a role in cancer progression. They can influence both cancer cells and tumor microenvironment components modulating various aspects of tumorigenesis such as oncogenesis, tumor growth, invasion and metastatic spread or treatment resistance. In this review we focus on the role of these axon guidance signals and their receptors and co-receptors in various aspects of cancer. Furthermore, we also highlight their potential application as novel approaches for cancer treatment in the future.

Circular RNA PIP5K1A Promotes Glucose and Lipid Metabolism Disorders and Inflammation in Type 2 Diabetes Mellitus

Disorders of glucose and lipid metabolism are an important cause of type 2 diabetes mellitus (T2DM). Identifying the molecular mechanism of metabolic disorders is key to the treatment of T2DM. The study was to investigate the effect of circRNA PIP5K1A (circPIP5K1A) on glucose and lipid metabolism and inflammation in T2DM rats. A T2DM rat model was established, and then the T2DM rats were injected with lentiviral vectors that interfere with circPIP5K1A, miR-552-3p, or ENO1 expression. Fasting blood glucose (FBG) and fasting insulin (FINS) levels of rats were detected by an automatic analyzer and insulin detection kit, and HOMA-IR was calculated. Lipid metabolism was assessed by measuring serum levels of TG, TC, LDL-C, leptin, and resistin. Serum levels of inflammatory factors (TNF-α and IL-6) were detected by ELISA. The pathological conditions of pancreatic tissue were observed by HE staining. circPIP5K1A, miR-552-3p and ENO1 levels were recorded. The experimental results showed that circPIP5K1A and ENO1 were up-regulated, and miR-552-3p was down-regulated in T2DM rats. Down-regulating circPIP5K1A or up-regulating miR-552-3p reduced blood glucose and lipid levels, inhibited inflammation, and improved pancreatic histopathological changes in T2DM rats. In addition, up-regulating ENO1 rescued the ameliorating effects of down-regulated circPIP5K1A on T2DM rats. In general, downregulating circPIP5K1A improves insulin resistance and lipid metabolism disorders and inhibits inflammation by targeting miR-552-3p to mediate ENO1 expression.

The functional roles of competitive endogenous RNA (ceRNA) networks in apoptosis in human cancers: The circRNA/miRNA/mRNA regulatory axis and cell signaling pathways

Circular RNAs are noncoding RNAs with circular conformation mainly due to backsplicing event. CircRNAs can potentially impact cell biological processes by interacting with cell signaling pathways. Numerous circRNAs have been found to be aberrantly expressed in a variety of cancers. These RNAs can act as ceRNA (competitive endogenous RNA) by sponging certain miRNAs to form circRNA/miRNA/mRNA networks. Dysregulation of ceRNA networks may lead to dysfunctions in various cell pathways, which modulate apoptosis-associated genes and ultimately result in cancer progression. Since disruption of apoptosis is one of the leading causes of cancer development, one approach for cancer treatment is to drive cells toward apoptosis. In this review, we present a summary of studies on the role of ceRNA networks in cellular signaling pathways that regulate apoptosis; these networks are suggested to be potential biomarkers for cancer treatment.

Hsa_circ_0005320 affects cell proliferation and the cell cycle via the IGF2BP3/CDK2 axis in bladder cancer

BACKGROUND

Circular RNAs (circRNAs), which are covalently closed non-coding RNAs, are frequently dysregulated in cancer. However, their precise role in bladder cancer (BCa) remains largely unknown.

METHODS

Expression of hsa_circ_0005320 in tissues and cell lines was detected using quantitative real-time PCR. Proliferation and colony forming capacity of BCa cells were assessed using Cell Counting Kit-8, ethynyl-labeled deoxyuridine, and colony formation assays. The cell cycle was analyzed using flow cytometry. Protein expression of insulin-like growth factor II mRNA-binding protein 3 (IGF2BP3) and cyclin dependent kinase 2 (CDK2) was examined using western blots. The binding of RNA and protein was validated using RNA immunoprecipitation. Additionally, xenograft tumor models were established to validate the function of hsa_circ_0005320 in vivo.

RESULTS

We screened hsa_circ_0005320 from previous high-throughput sequencing and found that it was highly expressed in BCa tissues and associated with tumor differentiation and depth of invasion in BCa patients. Through functional experiments, we demonstrated that hsa_circ_0005320 promoted cell proliferation and regulated the cell cycle. Mechanistically, hsa_circ_0005320 interacted with and upregulated the expression of IGF2BP3, which binds to and enhances the stability of CDK2 mRNA. Furthermore, knockdown of hsa_circ_0005320 resulted in a reduction in tumor burden in vivo.

CONCLUSIONS

Collectively, these findings highlight the pro-oncogenic role of hsa_circ_0005320 in BCa through the IGF2BP3/CDK2 axis, providing valuable insights into the mechanism of circRNAs in tumor progression.

circRNA TATA-box binding protein associated factor 15 acts as an oncogene to facilitate bladder cancer progression through targeting miR-502-5p/high mobility group box 3

Circular RNAs (circRNAs) are key in regulating bladder cancer progression. This study explored the effects of circRNA TATA-box binding protein associated factor 15 (circTAF15) on bladder cancer progression. We enrolled 80 bladder cancer patients to examine the relationship between circTAF15 expression and clinical features. The function of circTAF15 on bladder cancer cell viability, proliferation, migration, invasion, and glycolysis was monitored by cell counting kit-8 assay, 5-Ethynyl-2'-deoxyuridine experiment, Transwell experiment, and glycolysis analysis. Dual luciferase reporter gene assay, RNA pull-down assay, and RNA immunoprecipitation assay were used to verify the binding between circTAF15 and miR-502-5p or between miR-502-5p and high mobility group box 3 (HMGB3). circTAF15 effect on in vivo growth of bladder cancer was investigated by xenograft tumor experiment. Quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry were implemented to investigate the expression levels of genes. circTAF15 was upregulated in bladder cancer patients, associated with unfavorable outcomes. circTAF15 knockdown attenuated bladder cancer cell viability, proliferation, migration, invasion, epithelial-mesenchymal transition, and glycolysis. circTAF15 suppressed miR-502-5p expression, and miR-502-5p inhibited HMGB3 expression. Low miR-502-5p expression was associated with unfavorable outcomes in bladder cancer patients. miR-502-5p silencing and HMGB3 overexpression counteracted the inhibition of circTAF15 knockdown on the malignant phenotype of bladder cancer cells. circTAF15 knockdown attenuated the in vivo growth of bladder cancer cells. circTAF15 enhanced the progression of bladder cancer through upregulating HMGB3 via suppressing miR-502-5p. circTAF15 may be a novel target to treat bladder cancer in the future.

Exosome-derived miR-182-5p promoted cholangiocarcinoma progression and vasculogenesis by regulating ADK/SEMA5a/PI3K pathway

BACKGROUND AND AIMS

Increasing evidence suggested that miRNAs regulated the expression of pivotal genes involved in oncogenesis and malignant phenotype. In this project, the purpose was to make an inquiry to the effect and mechanism of miR-182-5p in the progression of cholangiocarcinoma.

METHODS

By analysing TCGA and GEO databases, combined with tissue expression levels, miR-182-5p was identified as one of the most valuable miRNAs for research. The function and relationships between miR-182-5p and downstream target genes were both verified by in vitro and in vivo experiments. Methylation-specific PCR and bisulphite sequencing were used to detect the methylation level changes of downstream gene promoter.

RESULTS

We found that miR-182-5p could be taken up by exosomes secreted from cholangiocarcinoma. Moreover, exosomal derived miR-182-5p promoted vascular endothelial cell proliferation and migration and induced angiogenesis by targeting ADK/SEMA5a. Subsequently, the PI3K/AKT/mTOR signalling pathway was activated and ultimately caused resistance to gemcitabine and cisplatin.

CONCLUSIONS

Our findings suggested that the miR-182-5p/ADK/SEMA5a axis might serve as a potential therapeutic target for cholangiocarcinoma.

CircDLGAP4 overexpression ameliorates neuronal injury in Parkinson's disease by binding to EIF4A3 and increasing HMGA2 expression

Parkinson's disease (PD) is a prevalent neurodegenerative disease, and its prevalence increases steadily with age. Circular RNAs (circRNAs) are involved in various neurodegenerative diseases. Here, we aimed to explore the role of circRNA DLG-associated protein 4 (circDLGAP4) in 1-methyl-4-phenylpyridinium ion (MPP+ )-induced neuronal injury in PD. SH-SY5Y cells were treated with MPP+ to establish PD cell models. The levels of circDLGAP4 and high mobility group AT-hook 2 (HMGA2) in SH-SY5Y cells were detected. SH-SY5Y cell viability and apoptosis were detected. The levels of inflammatory damage (IL-1β, IL-6, TNF-α) and oxidative stress (reactive oxygen species, lactate dehydrogenase, superoxide dismutase, and malondialdehyde)-related factors were measured. The binding of eukaryotic initiation factor 4A3 (EIF4A3) to circDLGAP4 and HMGA2 was analyzed using RNA pull-down or RNA immunoprecipitation. The stability of HMGA2 was detected after actinomycin D treatment, and its effects on neuronal injury were tested. CircDLGAP4 expression was decreased in MPP+ -induced SH-SY5Y cells. CircDLGAP4 upregulation restored cell activity, decreased apoptosis, and reduced inflammatory damage and oxidative stress in PD cell models. CircDLGAP4 bound to EIF4A3 to increase HMGA2 expression and stability. Silencing HMGA2 attenuated the protective effect of circDLGAP4 overexpression. Overall, circDLGAP4 upregulated HMGA2 by recruiting EIF4A3, thus increasing the mRNA stability of HMGA2 and alleviating neuronal injury in PD.

miRNA/epithelial-mesenchymal axis (EMT) axis as a key player in cancer progression and metastasis: A focus on gastric and bladder cancers

The metastasis a major hallmark of tumors that its significant is not only related to the basic research, but clinical investigations have revealed that majority of cancer deaths are due to the metastasis. The metastasis of tumor cells is significantly increased due to EMT mechanism and therefore, inhibition of EMT can reduce biological behaviors of tumor cells and improve the survival rate of patients. One of the gaps related to cancer metastasis is lack of specific focus on the EMT regulation in certain types of tumor cells. The gastric and bladder cancers are considered as two main reasons of death among patients in clinical level. Herein, the role of EMT in regulation of their progression is evaluated with a focus on the function of miRNAs. The inhibition/induction of EMT in these cancers and their ability in modulation of EMT-related factors including ZEB1/2 proteins, TGF-β, Snail and cadherin proteins are discussed. Moreover, lncRNAs and circRNAs in crosstalk of miRNA/EMT regulation in these tumors are discussed and final impact on cancer metastasis and response of tumor cells to the chemotherapy is evaluated. Moreover, the impact of miRNAs transferred by exosomes in regulation of EMT in these cancers are discussed.

Glycolysis in human cancers: Emphasis circRNA/glycolysis axis and nanoparticles in glycolysis regulation in cancer therapy

The metabolism of cancer has been an interesting hallmark and metabolic reprogramming, especially the change from oxidative phosphorylation in mitochondria to glucose metabolism known as glycolysis occurs in cancer. The molecular profile of glycolysis, related molecular pathways and enzymes involved in this mechanism such as hexokinase have been fully understood. The glycolysis inhibition can significantly decrease tumorigenesis. On the other hand, circRNAs are new emerging non-coding RNA (ncRNA) molecules with potential biological functions and aberrant expression in cancer cells which have received high attention in recent years. CircRNAs have a unique covalently closed loop structure which makes them highly stable and reliable biomarkers in cancer. CircRNAs are regulators of molecular mechanisms including glycolysis. The enzymes involved in the glycolysis mechanism such as hexokinase are regulated by circRNAs to modulate tumor progression. Induction of glycolysis by circRNAs can significantly increase proliferation rate of cancer cells given access to energy and enhance metastasis. CircRNAs regulating glycolysis can influence drug resistance in cancers because of theirimpact on malignancy of tumor cells upon glycolysis induction. TRIM44, CDCA3, SKA2 and ROCK1 are among the downstream targets of circRNAs in regulating glycolysis in cancer. Additionally, microRNAs are key regulators of glycolysis mechanism in cancer cells and can affect related molecular pathways and enzymes. CircRNAs sponge miRNAs to regulate glycolysis as a main upstream mediator. Moreover, nanoparticles have been emerged as new tools in tumorigenesis suppression and in addition to drug and gene delivery, then mediate cancer immunotherapy and can be used for vaccine development. The nanoparticles can delivery circRNAs in cancer therapy and they are promising candidates in regulation of glycolysis, its suppression and inhibition of related pathways such as HIF-1α. The stimuli-responsive nanoparticles and ligand-functionalized ones have been developed for selective targeting of glycolysis and cancer cells, and mediating carcinogenesis inhibition.

Circ_0000235 targets MCT4 to promote glycolysis and progression of bladder cancer by sponging miR-330-5p

Warburg effect plays a crucial role in bladder cancer (Bca) development. However, the mechanism by which glycolysis is involved in Bca remains poorly understood. CircRNAs commonly play a regulatory role in tumor progression. Our study discovered and identified a novel circRNA, hsa_circ_0000235 (circ235), and investigated its role in the glycolytic process, which further results in the progression of Bca. We applied qRT-PCR to assess its clinicopathological relevance and evaluated its proliferation, migration, and glycolytic capacity. We investigated its mechanism using RNA immunoprecipitation, dual-luciferase reporters, and fluorescence in situ hybridization. The findings demonstrated that circ235 was dramatically increased in Bca tissues and was related to a worse prognosis. In vitro studies revealed that circ235 accelerated the rate of extracellular acidification and promoted glucose uptake and lactate manufacture in Bca cells. Additionally, it strengthened the proliferative and migratory capacities. Experiments on animals revealed that downregulating circ235 dramatically reduced carcinogenesis and tumor growth. Circ235 activates monocarboxylate transporter 4 (MCT4) by sponging miR-330-5p, which promotes glycolysis and tumor growth. In conclusion, these findings suggest that circ235 may be a viable molecular marker and therapeutic target for Bca.

Molecular profile of non-coding RNA-mediated glycolysis control in human cancers

The glycolysis is a common characteristic of cancer and it is responsible for providing enough energy to ensure growth. The glycolysis suppression is beneficial in tumor growth reduction. The stimulation/inhibition of glycolysis in cancer is tightly regulated by ncRNAs. The regulation of glycolysis by ncRNAs can influence proliferation and therapy response of tumor. The miRNAs are capable of inactivating enzymes responsible for glycolysis and suppressing signaling networks resulting in glycolysis induction. By regulation of glycolysis, miRNAs can affect therapy response. The lncRNAs and circRNAs follow a same pathway and by targeting glycolysis, they affect progression and therapy response of tumor. Noteworthy, lncRNAs and circRNAs sponge miRNAs in glycolysis mechanism control in tumor cells. Furthermore, ncRNA-mediated regulation of glycolysis mechanism can influence metastasis to organs of body. The ncRNAs regulating glycolysis are reliable biomarkers in cancer patients and more importantly, exosomal ncRNAs due to their presence in body fluids, are minimally-invasive biomarkers.

Circular RNA circSEMA5A facilitates colorectal cancer development by regulating microRNA-195-5p to target CCNE1 axis

Colorectal cancer (CRC) is one of the most prevalent malignancies with a high mortality rate worldwide. Circular RNAs (circRNAs) have lately emerged as key molecules involved in cancer development and metastasis. CircSEMA5 is reported to be oncogenic in some cancers, yet its role in the pathogenesis of CRC remains unknown. Herein, we attempted to investigate the functional role and molecular mechanism of circSEMA5A underlying CRC progression. RT-qPCR and RNase R digestion assays were used to evaluate circSEMA5A expression characteristics in CRC cells. Loss-of-function assays were performed to clarify circSEMA5A role in CRC biological processes. Bioinformatics and mechanism experiments were conducted to assess the association of circSEMA5A or CCNE1 with miR-195-5p in CRC cells. Rescue assays were conducted to explore the regulatory function of circSEMA5A-miR-195-5p-CCNE1 in CRC cellular processes. Through bioinformatics and functional screening, we found that circSEMA5A was highly expressed in CRC cells and was mainly localized in the nucleus. CircSEMA5A promoted CRC proliferative, migratory, and invasive capabilities in cultured cells and facilitated the tumorigenic process in xenografts; however, circSEMA5A silencing repressed tumor metastasis in CRC cells. Mechanistically, circSEMA5A was competitively bound with miR-195-5p to upregulate CCNE1 expression. Moreover, the impact of circSEMA5A knockdown on CRC cell proliferative, migratory, and invasive capabilities was countervailed by miR-195-5p inhibitor or CCNE1 overexpression. To summarize, circSEMA5A is a novel circRNA that serves as an oncogene in CRC progression. CircSEMA5A facilitates CRC cell malignancy and tumor growth through sponging miR-195-5p to upregulate CCNE1, thus providing a new direction for CRC diagnosis and targeted therapy.

An Overview of Angiogenesis in Bladder Cancer

PURPOSE OF THE REVIEW

Angiogenesis plays a key role in bladder cancer (BC) pathogenesis. In the last two decades, an increasing number of publications depicting a multitude of novel angiogenic molecules and pathways have emerged. The growing complexity necessitates an evaluation of the breadth of current knowledge to highlight key findings and guide future research.

RECENT FINDINGS

Angiogenesis is a dynamic biologic process that is inherently difficult to assess. Clinical assessment of angiogenesis in BCs is advancing with the integration of image analysis systems and dynamic contrast-enhanced and magnetic resonance imaging (DCE-MRI). Tumour-associated macrophages (TAMs) significantly influence the angiogenic process, and further research is needed to assess their potential as therapeutic targets. A rapidly growing list of non-coding RNAs affect angiogenesis in BCs, partly through modulation of vascular endothelial growth factor (VEGF) activity. Vascular mimicry (VM) has been repeatedly associated with increased tumour aggressiveness in BCs. Standardised assays are needed for appropriate identification and quantification of VM channels. This article demonstrates the dynamic and complex nature of the angiogenic process and asserts the need for further studies to deepen our understanding.

A Circular RNA, hsa_circ_0018180 (circPARD3), Triggers Glycolysis and Promotes Malignancy of Head and Neck Squamous Cell Carcinoma Through the miR-5194/ENO1 Axis

Emerging evidence has demonstrated the pivotal roles of circular RNAs (circRNAs) in the modulation of malignancy and pathological progression among multiple human cancers. Glucose metabolism reprogramming is a widely identified characteristic for contributing to facilitate tumorigenesis. Nonetheless, their contributions to head and neck squamous cell carcinoma (HNSCC) cell glycolysis remain to be further elucidated. Herein, we aim to investigate the role of circRNA, hsa_circ_0018180 (also named as circPARD3) in HNSCC. Expression patterns of circPARD3 in HNSCC tissues and different cell lines were determined by qRT-PCR assay, as well as its correlation with the prognosis of survival. CCK-8, EdU incorporation, and transwell assays were carried out to assess the cell viability, proliferation, migration, and invasion, respectively. Glucose uptake and lactate production were evaluated by preforming glycolysis. Mechanistically, the circPARD3/miR-5194/ENO1 axis was verified by RNA immunoprecipitation (RIP) and luciferase reporter assays. Western blot analysis was employed to measure the epithelial-mesenchymal transition (EMT)-associated biomarkers. Upregulated circPARD3 observed in HNSCC tissues and cell lines indicated the poor prognosis of patients. Stable knockdown of circPARD3 dramatically exerted the suppressive effects on cell viability, proliferation, migration, and invasion, as well as glucose uptake and lactate production. Mechanistically, circPARD3 harbored miR-5194, serving as a miRNA sponge, thereby increasing ENO1 expression. Moreover, ENO1 evidently reversed miR-5194-mediated attenuated malignant behaviors. Collectively, our study identified an oncogenic role of circPARD3 in HNSCC through a novel machinery of circPARD3/miR-5194/ENO1 and provided a promising therapeutic target for HNSCC.

EIF4A3 serves as a prognostic and immunosuppressive microenvironment factor and inhibits cell apoptosis in bladder cancer

EIF4A3 (Eukaryotic translation initiation factor 4A3 (EIF4A3) was recently recognized as an oncogene; however, its role in BLCA (bladder cancer) remains unclear. We explored EIF4A3 expression and its prognostic value in BLCA in public datasets, including the TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus). Thereafter, the association between EIF4A3 expression and the infiltration of immune cells and immune-checkpoint expression was determined using TIMER2 (Tumor Immune Estimation Resource 2) tool. Additionally, the impact of EIF4A3 on cellular proliferation and apoptosis events in BLCA cell lines was determined by siRNA technology. In this study, EIF4A3 was found to be significantly upregulated in BLCA, upregulated expression of EIF4A3 was related to poor prognosis, advanced histologic grade, subtype, pathological stage, white race, and poor primary therapy outcome. The immune infiltration analysis revealed that EIF4A3 expression was negatively associated with CD8⁺ and CD4⁺ T cells and positively with myeloid-derived suppressor cells, macrophage M2, cancer-associated fibroblasts, and Treg cells. Moreover, EIF4A3 was coexpressed with PD-L1 (programmed cell death 1-ligand 1) and its expression was higher in patients responding to anti-PD-L1 therapy. EIF4A3 knockdown significantly inhibited proliferation and promoted apoptosis in 5,637 and T24 cells. In summary, BLCA patients with elevated EIF4A3 expression had an unfavorable prognosis and immunosuppressive microenvironment, and EIF4A3 may facilitate BLCA progression by promoting cell proliferation and inhibiting apoptosis. Furthermore, our study suggests that EIF4A3 is a potential biomarker and therapeutic target for BLCA.

Tumor-derived extracellular vesicles confer 5-fluorouracil resistance in esophageal cancer via long noncoding RNA AC116025.2 delivery

5-Fluorouracil (5-FU) resistance is one of the main causes for treatment failure in esophageal cancer (EC). Here, we intended to elucidate the mechanism of tumor-derived extracellular vesicles (TEVs)-encapsulated long noncoding RNAs (lncRNAs) AC116025.2 in 5-FU resistance in EC. EVs were isolated from the serum samples of EC patients and HEEC, TE-1, and TE-1/5-FU cells, followed by RT-qPCR detection of AC116025.2 expression in EVs. The relationship among AC116025.2, microRNA (miR)-4496, and SEMA5A was evaluated. Next, EC cells were cocultured with EVs, followed by lentivirus transduction and plasmid transfection for studying the role of TEVs-AC116025.2 in EC cells in relation to miR-4496 and SEMA5A. Tumor formation in nude mice was applied for in vivo confirmation. Elevated AC116025.2 expression was seen in the EVs from the serum of 5-FU insensitive patients and from 5-FU-resistant EC cells. Mechanistically, AC116025.2 bound to miR-4496 that inversely targeted SEMA5A in EC cells. EVs-oe-AC116025.2 augmented EC cell viability, colony formation, and 5-FU resistance, but diminished their apoptosis through miR-4496-mediated SEMA5A. Furthermore, EVs-oe-AC116025.2 augmented tumor formation and 5-FU resistance of EC cells in vivo. Conclusively, our data offered evidence of the promoting mechanism of TEVs in the 5-FU resistance of EC by delivering AC116025.2.

LncRNA 122049 suppresses apoptosis of renal tubular epithelial cells in ischemic AKI by targeting the miR-330-5p/ELK1 axis

Several studies have reported that long non-coding RNAs (LncRNAs) were associated with the progression of acute kidney injury (AKI). However, the role and regulation mechanism of lncRNA122049 in ischemic AKI remains unknown. In the present study, we found that lncRNA 122049 protected against the ischemia/reperfusion (I/R) induced apoptosis in BUMPT cells. Mechanistically, the lncRNA 122049 directly sponged miR-330-5p, then increased the expression of ELK1(ETS transcription factor ELK1) to decrease renal cell apoptosis. In addition, miR-330-5p inhibitor completely reversed the pro-apoptotic effect of LncRNA 122049 siRNA on I/R-induced BUMPT cells apoptosis. Finally, overexpression of lncRNA 122049 attenuated ischemic mice AKI via targeting of the miR-330-5p/ELK1 axis. Collectively, the data demonstrated that LncRNA 122049 prevented the I/R-induced renal cell apoptosis via regulation of the miR-330-5p/ELK1 axis, which brings new insights into the pathogenesis and potential targeted treatment of ischemic AKI.

The Role of Circular RNAs in the Carcinogenesis of Bladder Cancer

Circular RNAs (circRNAs) are a group of transcripts with enclosed configurations which can regulate gene expression. These transcripts have important roles in normal development and in the pathogenesis of disorders. Recent evidence has supported involvement of circRNAs in the development of bladder cancer. Several circRNAs such as circ_0058063, hsa-circRNA-403658, circPDSS1, circCASC15, circRNA-MYLK, and circRNA_103809 have been upregulated in bladder cancer samples. On the other hand, hsa_circ_0137606, BCRC-3, circFUT8, hsa_circ_001598, circSLC8A1, hsa_circ_0077837, hsa_circ_0004826, and circACVR2A are among downregulated circRNAs in bladder cancer. Numerous circRNAs have diagnostic or prognostic value in bladder cancer. In this review, we aim to outline the latest findings about the role of circRNAs in bladder cancer and introduce circRNAs for further investigations as therapeutic targets.

Evidence for the Rapid and Divergent Evolution of Mycoplasmas: Structural and Phylogenetic Analysis of Enolases

Mycoplasmas are a group of prokaryotes without cell walls that have evolved through several rounds of degenerative evolution. With a low cell DNA G + C content and definitively long genetic lineages, mycoplasmas are thought to be in a state of rapid evolution. However, little associated evidence has been provided. Enolase is a key enzyme in glycolysis that is widely found in all species from the three domains, and it is evolutionarily conserved. In our previous studies, enolase acted as a virulence factor and participated in cell-surface adhesion in Mycoplasma hyopneumoniae. Furthermore, unique loop regions were first found in the crystal structure of Mhp Eno. Here, enolase structures from Mycoplasma pneumoniae and Mycoplasma bovis were determined. An extra helix 7 is specific and conservatively found in almost all mycoplasma enolases, as confirmed by crystal structures and sequence alignment. Particular motifs for helix 7, which is composed of F-K/G-K-L/F-K-X-A-I, have been proposed and could be regarded as molecular markers. To our surprise, the genetic distances between any two mycoplasma enolases were obviously longer than those between the two corresponding species themselves, indicating divergent evolution of mycoplasma enolases, whereas no horizontal gene transfer was detected in mycoplasma enolase genens. Furthermore, different evolutionary patterns were adopted by different loop regions of mycoplasma enolase. Enolases from different Mycoplasma species also showed different affinities for PLG and fibronectin. Our results indicate the rapid and divergent evolution of mycoplasma enolase and mycoplasmas. This study will also aid understanding the independent evolution of Mycoplasma species after separation from their common ancestor.

Dysregulated expression and functions of microRNA-330 in cancers: A potential therapeutic target

As small non-coding RNAs, MicroRNAs (miRNAs) bind to the 3' untranslated region (3'-UTR) of mRNA targets to control gene transcription and translation. The gene of miR-330 has two miRNA products, including miR-330-3p and miR-330-5p, which exhibit anti-tumorigenesis and/or pro-tumorigenesis effects in many kinds of malignancies. In cancers, miR-330-3p and miR-330-5p aberrant expression can influence many malignancy-related processes such as cell proliferation, migration, invasion, apoptosis and epithelial-mesenchymal transition, as well as angiogenesis and responsiveness to treatment. In many cancer types (such as lung, prostate, gastric, breast, bladder, ovarian, colorectal, and pancreatic cancer, and osteosarcoma), miR-330-5p acts as an anti-tumor agent. These cancers have low levels of miR-330-5p that leads to the upregulation of the tumor promotor target genes leading to tumor progression. Here, overexpression of miR-330-5p using miRNA inducers can prevent tumor development. Dual roles of miR-330-5p have been also indicated in the thyroid, liver and cervical cancers. Moreover, miR-330-3p exhibits pro-tumorigenesis effects in lung cancer, pancreatic cancer, osteosarcoma, bladder cancer, and cervical cancer. Here, downregulation of miR-330-3p using miRNA inhibitors can prevent tumor development. Demonstrated in breast and liver cancers, miR-330-3p also has dual roles. Importantly, the activities of miR-330-3p and/or miR-330-5p are regulated by upstream regulators long non-coding RNAs (lncRNAs), including circular and linear lncRNAs. This review comprehensively explained miR-330-3p and miR-330-5p role in development of cancers, while highlighting their downstream target genes and upstream regulators as well as possible therapeutic strategies.

Knockdown of circSMAD2 inhibits the tumorigenesis of gallbladder cancer through binding with eIF4A3

Background

Gallbladder cancer (GBC) is the seventh most common gastrointestinal cancer worldwide. This study aimed to investigate the function of circSMAD2 in GBC.

Methods

To investigate the function of circSMAD2 in GBC, the level of circSMAD2 in GBC cells was detected by RT-qPCR. CCK-8 assay was performed to investigate the cell viability. Cell apoptosis was tested by flow cytometry. In addition, transwell assay was used to detect the cell migration and invasion. RIP and RNA pull-down were used to explore the relation among circSMAD2, eIF4A3 and SMAD2. Meanwhile, xenograft mice model was established to investigate the function of circSMAD2 in GBC.

Results

The data revealed that circSMAD2 was upregulated in GBC, and circSMAD2 knockdown significantly inhibited the viability of GBC cells. In addition, circSMAD2 siRNA notably induced the apoptosis in GBC cells. The migration and invasion of GBC cells were obviously suppressed in the presence of circSMAD2 siRNA. Meanwhile, circSMAD2 suppressed the binding between eukaryotic translation initiation factor 4A3 (eIF4A3) and SMAD2 through binding with eIF4A3. Knockdown of circSMAD2 notably inhibited the expression of SMAD2 in GBC cells, and SMAD2 overexpression partially reversed the anti-tumor effect of circSMAD2 knockdown. Finally, circSMAD2 siRNA significantly inhibited the tumor growth of GBC in vivo.

Conclusion

Knockdown of circSMAD2 inhibits the tumorigenesis of gallbladder cancer through binding with eIF4A3. Thus, our study provided a new strategy for the treatment of GBC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08895-1.

Hsa_circ_0004296 inhibits metastasis of prostate cancer by interacting with EIF4A3 to prevent nuclear export of ETS1 mRNA

Background

Circular RNAs (circRNAs) have been shown to play vital biological functions in various tumors, including prostate cancer (PCa). However, the roles of circRNAs in the metastasis of PCa remain unclear. In the present study, differentially expressed circRNAs associated with PCa metastasis were screened using high-throughput RNA sequencing, from which hsa_circ_0004296 was identified.

Methods

Quantitative real-time PCR (qRT-PCR) was used to detect the expression of circ_0004296 in PCa tissues and adjacent normal tissues as well as in blood and urine. Gain and loss of function experiments were performed to investigate the function of circ_0004296 in PCa. Bioinformatics analyses, RNA pull-down assay, and mass spectrometry were conducted to identify RNA-binding proteins. RNA immunoprecipitation and RNA and protein nuclear-cytoplasmic fractionation were performed to investigate the underlying mechanism. A xenograft mouse model was used to analyze the effect of circ_0004296 on PCa growth and metastasis in vivo.

Results

The expression of circ_0004296 was decreased in PCa tissues, blood, and urine, which was negatively associated with metastasis. Furthermore, gain and loss of function experiments in vitro and in vivo showed that circ_0004296 inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition of PCa cells. Mechanistically, circ_0004296 regulated host gene ETS1 expression at the post-transcriptional level. EIF4A3 was identified and confirmed as the downstream binding protein of circ_0004296. EIF4A3 expression was significantly upregulated in PCa tissues and associated with PCa metastasis. Silencing EIF4A3 suppressed PCa cell proliferation, migration, invasion, and EMT.

Conclusions

Circ_0004296 overexpression efficiently inhibited ETS1 mRNA nuclear export by promoting EIF4A3 retention in the nucleus, leading to the downregulation of ETS1 expression and suppression of PCa metastasis; thus, circ_0004296 might be a potential biomarker and therapeutic target for patients with PCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02138-8.

The Emerging Functions of Circular RNAs in Bladder Cancer

Simple Summary

The role of circular RNAs has made breakthroughs in understanding the mechanisms of tumor development. Bladder cancer has an increasing incidence, high recurrence rate, high metastatic potential, poor prognosis, and susceptibility to chemotherapy resistance. Thus, it is essential to identify molecules related to the tumorigenesis of bladder cancer. In this review, we summarize current knowledge about the expression of circular RNAs in bladder cancer and their implications in vesical carcinogenesis. We further discuss the limitations of existing studies and provide an outlook for future studies in the hopes of better revealing the association between circular RNAs and bladder cancer.

Abstract

Bladder cancer (BC) is among the top ten most common cancer types worldwide and is a serious threat to human health. Circular RNAs (circRNAs) are a new class of non-coding RNAs generated by covalently closed loops through back-splicing. As an emerging research hotspot, circRNAs have attracted considerable attention due to their high conservation, stability, abundance, and specificity of tissue development. Accumulating evidence has revealed different form of circRNAs are closely related to the malignant phenotype, prognosis and chemotherapy resistance of BC, suggesting that different circRNAs may be promising biomarkers and have therapeutic significance in BC. The intention of this review is to summarize the mechanisms of circRNA-mediated BC progression and their diagnostic and prognostic value as biomarkers, as well as to further explore their roles in chemotherapy resistance.

A Positive Feedback Loop of lncRNA MIR31HG-miR-361-3p -YY1 Accelerates Colorectal Cancer Progression Through Modulating Proliferation, Angiogenesis, and Glycolysis

Background

Colorectal cancer (CRC) is a common malignant tumor with high metastatic and recurrent rates. This study probes the effect and mechanism of long non-coding RNA MIR31HG on the progression of CRC cells.

Materials and Methods

Quantitative real-time PCR (qRT-PCR) was used to analyze the expression of MIR31HG and miR-361-3p in CRC tissues and normal tissues. Gain- or loss-of-function assays were conducted to examine the roles of MIR31HG, miR-361-3p and YY1 transcription factor (YY1) in the CRC progression. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and colony formation experiment were conducted to test CRC cell proliferation. CRC cell invasion was determined by Transwell assay. The glucose detection kit and lactic acid detection kit were utilized to monitor the levels of glucose and lactate in CRC cells. The glycolysis level in CRC cells was examined by the glycolytic stress experiment. Western blot was performed to compare the expression of glycolysis-related proteins (PKM2, GLUT1 and HK2) and angiogenesis-related proteins (including VEGFA, ANGPT1, HIF1A and TIMP1) in HUVECs. The binding relationships between MIR31HG and miR-361-3p, miR-361-3p and YY1 were evaluated by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP).

Results

MIR31HG was up-regulated in CRC tissues and was associated with poorer prognosis of CRC patients. The in-vitro and in-vivo experiments confirmed that overexpressing MIR31HG heightened the proliferation, growth, invasion, glycolysis and lung metastasis of CRC cells as well as the angiogenesis of HUVECs. In addition, MIR3HG overexpression promoted YY1 mRNA and protein level, and forced overexpression of YY1 enhanced MIR31HG level. Overexpressing YY1 reversed the tumor-suppressive effect mediated by MIR31HG knockdown. miR-361-3p, which was inhibited by MIR31HG overexpression, repressed the malignant behaviors of CRC cells. miR-361-3p-mediated anti-tumor effects were mostly reversed by upregulating MIR31HG. Further mechanism studies illustrated that miR-361-3p targeted and negatively regulated the expression of YY1.

Conclusion

This study reveals that MIR31HG functions as an oncogenic gene in CRC via forming a positive feedback loop of MIR31HG-miR-361-3p-YY1.

The Roles of CircRNAs in Bladder Cancer: Biomarkers, Tumorigenesis Drivers, and Therapeutic Targets

Bladder cancer (BCa) is the most prevalent malignancy of the urinary system. Circular RNAs (circRNAs), a novel subtype of non-coding RNAs, play a crucial role in physiological and developmental processes. CircRNAs mainly function as regulators of splicing process and transcription, microRNA sponges, and protein brackets. Recent advances in understanding the pathogenesis of BCa have led to the identification of an abundance of dysregulated circRNAs associated with BCa. These aberrantly expressed circRNAs eventually lead to abnormalities in biological, genetic, and epigenetic information. In this review, we introduce the potential of circRNAs as biomarkers for BCa diagnosis and prognosis. Notably, diverse mechanisms have been proposed for circRNAs driving carcinogenesis, including increasing cell proliferation, promoting invasive and migratory capacity, enhancing endothelial–mesenchymal transition, sustaining stemness, and enabling resistance to chemotherapy. Importantly, a full understanding of circRNA mechanisms is needed to mine promising therapeutic approaches for targeting BCa. In this paper, we present the latest advances in circRNAs and systemically summarize the characteristics and mechanisms of circRNAs in BCa, providing potential perspectives for BCa treatment.

Circular RNAs Regulate Glucose Metabolism in Cancer Cells

Circular RNAs (circRNAs) were originally thought to result from RNA splicing errors. However, it has been shown that circRNAs can regulate cancer onset and progression in various ways. They can regulate cancer cell proliferation, differentiation, invasion, and metastasis. Moreover, they modulate glucose metabolism in cancer cells through different mechanisms such as directly regulating glycolytic enzymes and glucose transporter (GLUT) or indirectly regulating signal transduction pathways. In this review, we elucidate on the role of circRNAs in regulating glucose metabolism in cancer cells, which partly explains the pathogenesis of malignant tumors, and provides new therapeutic targets or new diagnostic and prognostic markers for human cancers.

Circular RNAs: Emerging Regulators of the Major Signaling Pathways Involved in Cancer Progression

Signal transduction is an essential process that regulates and coordinates fundamental cellular processes, such as development, immunity, energy metabolism, and apoptosis. Through signaling, cells are capable of perceiving their environment and adjusting to changes, and most signaling cascades ultimately lead to alterations in gene expression. Circular RNAs (circRNAs) constitute an emerging type of endogenous transcripts with regulatory roles and unique properties. They are stable and expressed in a tissue-, cell-, and developmental stage-specific manner, while they are involved in the pathogenesis of several diseases, including cancer. Aberrantly expressed circRNAs can mediate cancer progression through regulation of the activity of major signaling cascades, such as the VEGF, WNT/β-catenin, MAPK, PI3K/AKT, and Notch signaling pathways, as well as by interfering with signaling crosstalk. Deregulated signaling can then function to induce angiogenesis, promote invasion, migration, and metastasis, and, generally, modulate the hallmarks of cancer. In this review article, we summarize the most recently described and intriguing cases of circRNA-mediated signaling regulation that are involved in cancer progression, and discuss the biomarker potential of circRNAs, as well as future therapeutic applications.

Circ_0007841 accelerates ovarian cancer development through facilitating MEX3C expression by restraining miR-151-3p activity

The critical importance of circular RNAs (circRNAs) in human cancers, including ovarian cancer, has been discovered in the recent years. However, the roles of circ_0007841 in ovarian cancer remain unknown. In the current study, it was found that circ_0007841 expression was upregulated in ovarian cancer tissues and cell lines. Upregulation of circ_0007841 in patients with ovarian cancer predicts poor prognosis. Loss-of-function experiments discovered that circ_0007841 knockdown suppressed the proliferation, migration and invasion of ovarian cancer cells in vitro and in vivo. In terms of mechanism, circ_0007841 worked as a competing endogenous RNA (ceRNA) for miR-151-3p to facilitate MEX3C expression. Restoration of MEX3C level recovered the proliferation, migration and invasion of ovarian cancer cells. In conclusion, this study demonstrated that circ_0007841/miR-151-3p/MEX3C axis exerted important oncogenic functions in ovarian cancer.

Circular RNAs as biomarkers and therapeutic targets in cancer

Circular RNAs (circRNAs) are a class of single-stranded closed non-coding RNA molecules (ncRNAs), which are formed as a result of reverse splicing of mRNAs. Despite their relative abundance, an interest in understanding their regulatory importance is rather recent. High stability, abundance and evolutionary conservation among species underline some of their important traits. CircRNAs perform a variety of cellular functions ranging from miRNA and proteins sponges to transcriptional modulation and splicing. Additionally, most circRNAs are expressed aberrantly in pathological conditions suggesting their possible exploitation as diagnostic biomarkers. Their covalent closed cyclic structure resulting in resistance to RNases further makes them suitable as cancer biomarkers. Studies involving human tumors have verified differences in the expression profiles of circRNAs, indicating a regulatory role in cancer pathogenesis and metastasis. As endogenous competitive RNA, circRNAs can regulate tumor proliferation and invasion. Further, some circRNAs located in the nucleus can regulate transcription of genes by binding to RNA polymerase II. In this review, we elaborate the characteristics, functions and mechanisms of action of circRNAs in cancer. We also discuss the possibility of using circRNAs as potential therapeutic targets and biomarkers for cancer.