EIF4A3-induced circular RNA MMP9 (circMMP9) acts as a sponge of miR-124 and promotes glioblastoma multiforme cell tumorigenesis

Regulatory feedback loop between circ-EIF4A3 and EIF4A3 Enhances autophagy and growth in colorectal cancer cells

Recent studies indicate that circular RNAs (circRNAs) are crucial in the progression of colorectal cancer (CRC). Eukaryotic translation initiation factor 4A3 (EIF4A3) has been identified as a promoter of circRNA production. The biological roles and mechanisms of EIF4A3-derived circRNA (circEIF4A3) in CRC cell autophagy remain poorly understood. This study explores the effects of circEIF4A3 on CRC cell growth and autophagy, aiming to elucidate the underlying molecular mechanisms. We discovered that EIF4A3 and circEIF4A3 synergistically enhance CRC cell growth. CircEIF4A3 sequesters miR-3126-5p, consequently upregulating EIF4A3. Further, circEIF4A3 increases EIF4A3 expression, which promotes autophagy by stabilizing ATG5 mRNA and enhances ATG7 protein stability through the stabilization of USP14 mRNA, a deubiquitinating enzyme. Upregulation of ATG5 and ATG7 counteracts the growth-inhibitory effects of EIF4A3 knockdown on CRC cells. Moreover, our findings demonstrate that EIF4A3 induces the formation of circEIF4A3 in CRC cells. In conclusion, a positive feedback loop between circEIF4A3 and EIF4A3 supports CRC cell growth by facilitating autophagy.

New insights into the potential of exosomal circular RNAs in mediating cancer chemotherapy resistance and their clinical applications

Chemotherapy resistance typically leads to tumour recurrence and is a major obstacle to cancer treatment. Increasing numbers of circular RNAs (circRNAs) have been confirmed to be abnormally expressed in various tumours, where they participate in the malignant progression of tumours, and play important roles in regulating the sensitivity of tumours to chemotherapy drugs. As exosomes mediate intercellular communication, they are rich in circRNAs and exhibit a specific RNA cargo sorting mechanism. By carrying and delivering circRNAs, exosomes can promote the efflux of chemotherapeutic drugs and reduce intracellular drug concentrations in recipient cells, thus affecting the cell cycle, apoptosis, autophagy, angiogenesis, invasion and migration. The mechanisms that affect the phenotype of tumour stem cells, epithelial-mesenchymal transformation and DNA damage repair also mediate chemotherapy resistance in many tumours. Exosomal circRNAs are diagnostic biomarkers and potential therapeutic targets for reversing chemotherapy resistance in tumours. Currently, the rise of new fields, such as machine learning and artificial intelligence, and new technologies such as biosensors, multimolecular diagnostic systems and platforms based on circRNAs, as well as the application of exosome-based vaccines, has provided novel ideas for precision cancer treatment. In this review, the recent progress in understanding how exosomal circRNAs mediate tumour chemotherapy resistance is reviewed, and the potential of exosomal circRNAs in tumour diagnosis, treatment and immune regulation is discussed, providing new ideas for inhibiting tumour chemotherapy resistance.

EIF4A3-Induced Circ_0059914 Promoted Angiogenesis and EMT of Glioma via the miR-1249/VEGFA Pathway

Gliomas are common brain tumors. Despite extensive research, the 5-year survival rate of glioma remains low. Many studies have reported that circular RNAs (circRNAs) play a role in promoting the malignant progression of glioma; however, the role of circ_0059914 in this process remains unclear. In this study, we aimed to investigate the function and underlying mechanism of circ_0059914 in glioma. Western blotting and qRT-PCR were used to determine the levels of circ_0059914, miR-1249, VEGFA, N-cadherin, vimentin, Snail, and EIF4A3. EDU and colony formation assays were conducted to evaluate cell proliferation. Transwell assays were used to explore cell migration and invasion and tube formation assays were used to analyze angiogenesis. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were used to explore the relationship between EIF4A3, circ_0059914, miR-1249, and VEGFA. A xenograft tumor assay was performed to determine the role of circ_0059914 in vivo. Circ_0059914 expression was upregulated in gliomas. Knockdown of gliomal circ_0059914 expression reduced the proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), angiogenesis, and growth of glioma cells in vivo. Circ_0059914 sponged miR-1249, and miR-1249 inhibition reversed the circ_0059914 knockdown-mediated effects in glioma cells. VEGFA was found to be a target gene of miR1249; overexpression of VEGFA reversed the effect of miR-1249 up-regulation in glioma. Finally, EIF4A3 increased the expression of circ_0059914. EIF4A3-induced circ_0059914 expression plays a role in promoting glioma via the miR-1249/VEGFA axis.

CircFgfr2 promotes osteogenic differentiation of rat dental follicle cells by targeting the miR-133a-3p/DLX3 signaling pathway

Dental follicle cells (DFCs) promote bone regeneration in vivo and in vitro. Circular RNAs (circRNAs) play crucial roles in bone development and regeneration. Our previous study demonstrated the upregulation of circFgfr2 expression during the osteogenic differentiation of DFCs. However, the molecular mechanisms and functional roles of circFgfr2 in DFCs osteogenesis remain unclear. In this study, we aimed to investigate the subcellular localization of circFgfr2 in DFCs using fluorescence in situ hybridization. In vitro investigations demonstrated that circFgfr2 overexpression promoted osteogenic differentiation, as evidenced by real-time quantitative polymerase chain reaction. By integrating the outcomes of bioinformatics analyses, dual luciferase reporter experiments, and chromatin isolation by RNA purification, we identified circFgfr2 as a sponge for miR-133a-3p, a key regulator of osteogenic differentiation. Moreover, miR-133a-3p suppressed osteogenic differentiation by targeting DLX3 and RUNX2 in DFCs. We validated that circFgfr2 promoted the osteogenic differentiation of DFCs through the miR-133a-3p/DLX3 axis. To further investigate the therapeutic potential of circFgfr2 in bone regeneration, we conducted in vivo experiments and histological analyses. Overall, these results confirmed the crucial role of circFgfr2 in promoting osteogenesis. In summary, our findings demonstrated that the circFgfr2/miR-133a-3p/DLX3 pathway acts as a cascade, thereby identifying circFgfr2 as a promising molecular target for bone tissue engineering.

Genetic Biomarkers in Astrocytoma: Diagnostic, Prognostic, and Therapeutic Potential

Astrocytoma is the most common adult brain tumor, with glioblastoma being the deadliest neuro-related malignancy. Despite advances in oncology, the prognosis for astrocytoma, especially glioblastoma, remains poor, and tracking disease progression is challenging due to a lack of robust biomarkers. Genetic biomarkers, including microRNAs, cell-free DNA, circulating tumor DNA, circular RNA, and long noncoding RNA, can serve as potential diagnostic and therapeutic targets. In this review, we examine the existing literature, analyzing the various less established liquid and tumor genetic biomarkers and their potential to act as diagnostic, prognostic, and therapeutic targets. We highlight the clinical challenges and limitations in implementing liquid biopsy strategies in clinical practice. The article discusses the potential of liquid biopsies as valuable tools for personalized astrocytoma management while emphasizing the need for standardized protocols and further advancements to establish their clinical utility and therapeutic application.

Circ_0005015 upregulates BACH1 to promote aggressive behaviors in glioblastoma by sponging microRNA-382-5p

To investigate the potential role and molecular mechanism of circ_0005015 in GBM progression. Circ_0005015, microRNA-382-5p (miR-382-5p), and BTB domain and CNC homolog 1 (BACH1) levels were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation was determined by MTT, colony formation, and EdU assays. Cell apoptosis was analyzed using flow cytometry. Cell migration and invasion were assessed using wound healing and transwell assays. Glucose accumulation and lactate levels were examined by the corresponding kit. RNA pull-down and dual-luciferase reporter assays were performed to confirm the interaction between miR-382-5p and circ_0005015 or BACH1. Protein levels of MMP9, PCNA, and BACH1 were examined using western blot assay. Role of circ_0005015 on tumor growth in vivo was analyzed using a xenograft tumor model. Circ_0005015 content was up-regulated in GBM patients and cells, its knockdown restrained GBM cell proliferation, migration, invasion, glycolysis, and triggered apoptosis. Mechanistically, we found that circ_0005015 could directly interact with miR-382-5p and serve as a miRNA sponge to regulate BACH1 expression. In addition, circ_0005015 knockdown might repress tumor growth in vivo. Circ_0005015 boosted GBM progression via binding to miR-382-5p to up-regulate BACH1, which may offer new effective targets for GBM treatment.

Decoding the molecular landscape: A novel prognostic signature for uveal melanoma unveiled through programmed cell death-associated genes

Uveal melanoma (UM) is a rare but aggressive malignant ocular tumor with a high metastatic potential and limited therapeutic options, currently lacking accurate prognostic predictors and effective individualized treatment strategies. Public databases were utilized to analyze the prognostic relevance of programmed cell death-related genes (PCDRGs) in UM transcriptomes and survival data. Consensus clustering and Lasso Cox regression analysis were performed for molecular subtyping and risk feature construction. The PCDRG-derived index (PCDI) was evaluated for its association with clinicopathological features, gene expression, drug sensitivity, and immune infiltration. A total of 369 prognostic PCDRGs were identified, which could cluster UM into 2 molecular subtypes with significant differences in prognosis and clinicopathological characteristics. Furthermore, a risk feature PCDI composed of 11 PCDRGs was constructed, capable of indicating prognosis in UM patients. Additionally, PCDI exhibited correlations with the sensitivity to 25 drugs and the infiltration of various immune cells. Enrichment analysis revealed that PCDI was associated with immune regulation-related biological processes and pathways. Finally, a nomogram for prognostic assessment of UM patients was developed based on PCDI and gender, demonstrating excellent performance. This study elucidated the potential value of PCDRGs in prognostic assessment for UM and developed a corresponding risk feature. However, further basic and clinical studies are warranted to validate the functions and mechanisms of PCDRGs in UM.

EIF4A3-negatively driven circular RNA β-catenin (circβ-catenin) promotes colorectal cancer progression via miR-197-3p/CTNND1 regulatory axis

BACKGROUND

Circβ-catenin, our first reported circRNA, has been reported to mediate tumorigenesis in various cancers. However, its biological functions and underlying mechanisms in colorectal cancer (CRC) remain unknown.

METHODS

The qRT-PCR examination was used to detect the expression of circβ-catenin, miR-197-3p, and CTNND1 in cells and human tissues. Western blot was conducted to detect the protein expression levels. The biological function of circβ-catenin was verified by MTT, colony formation, wound healing, and transwell assays. The in vivo effects of circβ-catenin were verified by nude mice xenograft and metastasis models. The regulatory network of circβ-catenin/miR-197-3p/CTNND1 was confirmed via dual-luciferase reporter and RIP assays.

RESULTS

In the present study, circβ-catenin was found to promote CRC cell proliferation and metastasis in vitro and in vivo. Mechanistically, circβ-catenin served as miRNA decoy to directly bind to miR-197-3p, then antagonized the repression of the target gene CTNND1, and eventually promoted the malignant phenotype of CRC. More interestingly, the inverted repeated Alu pairs termed AluJb1/2 and AluY facilitated the biogenesis of circβ-catenin, which could be partially reversed by EIF4A3 binding to Alu element AluJb2.

CONCLUSIONS

Our findings illustrated a novel mechanism of circβ-catenin in modulating CRC tumorigenesis and metastasis, which provides a potential therapeutic target for CRC patients.

A unique circ_0067716/EIF4A3 double-negative feedback loop impacts malignant transformation of human bronchial epithelial cells induced by benzo(a)pyrene

Benzo(a)pyrene as a pervasive environmental contaminant is characterized by its substantial genotoxicity, and epidemiological investigations have established a correlation between benzo(a)pyrene exposure and the susceptibility to human lung cancer. Notably, much research has focused on the link between epigenetic alterations and lung cancer induced by chemicals, although circRNAs are also emerging as relevant contributors to the carcinogenic process of benzo(a)pyrene. In this study, we identified circ_0067716 as being significantly upregulated in response to stress injury and downregulated during malignant transformation induced by benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE) in human bronchial epithelial cells. The observed differential expression of circ_0067716 in cells treated with BPDE for varying durations suggests a strong correlation between this circRNA and BPDE exposure. The tissue samples of lung cancer patients also suggest that a lower circ_0067716 expression is associated with BPDE-DNA adduct levels. Remarkably, we demonstrate that EIF4A3, located in the nucleus, interacts with the flanking sequences of circ_0067716 and inhibits its biogenesis. Conversely, circ_0067716 is capable of sequestering EIF4A3 in the cytoplasm, thereby preventing its translocation into the nucleus. EIF4A3 and circ_0067716 can form a double-negative feedback loop that could be affected by BPDE. During the initial phase of BPDE exposure, the expression of circ_0067716 was increased in response to stress injury, resulting in cell apoptosis through the involvement of miR-324-5p/DRAM1/BAX axis. Subsequently, as cellular adaptation progressed, long-term induction due to BPDE exposure led to an elevated EIF4A3 and a reduced circ_0067716 expression, which facilitated the proliferation of cells by stabilizing the PI3K/AKT pathway. Thus, our current study describes the effects of circ_0067716 on the genotoxicity and carcinogenesis induced by benzo(a)pyrene and puts forwards to the possible regulatory mechanism on the occurrence of smoking-related lung cancer, providing a unique insight based on epigenetics.

Role of Hsa_circ_0000880 in the Regulation of High Glucose-Induced Apoptosis of Retinal Microvascular Endothelial Cells

Purpose

Circular RNAs (circRNAs) have been verified to participate in multiple biological processes and disease progression. Yet, the role of circRNAs in the pathogenesis of diabetic retinopathy (DR) is still poorly understood and deserves further study. This study aimed to investigate the role of circRNAs in the regulation of high glucose (HG)-induced apoptosis of retinal microvascular endothelial cells (RMECs).

Methods

Epiretinal membranes from patients with DR and nondiabetic patients with idiopathic macular epiretinal membrane were collected for this study. The circRNA microarrays were performed using high-throughput sequencing. Hierarchical clustering, functional enrichment, and network regulation analyses were used to analyze the data generated by high-throughput sequencing. Next, RMECs were subjected to HG (25 mM) conditions to induce RMECs apoptosis in vitro. A series of experiments, such as Transwell, the Scratch wound, and tube formation, were conducted to explore the regulatory effect of circRNA on RMECs. Fluorescence in situ hybridization (FISH), immunofluorescence staining, and Western blot were used to study the mechanism underlying circRNA-mediated regulation.

Results

A total of 53 differentially expressed circRNAs were found in patients with DR. Among these, hsa_circ_0000880 was significantly upregulated in both the diabetic epiretinal membranes and in an in vitro DR model of HG-treated RMECs. Hsa_circ_0000880 knockout facilitated RMECs vitality and decreased the paracellular permeability of RMECs under hyperglycemia. More importantly, silencing of hsa_circ_0000880 significantly inhibited HG-induced ROS production and RMECs apoptosis. Hsa_circ_0000880 acted as an endogenous sponge for eukaryotic initiation factor 4A-III (EIF4A3). Knockout of hsa_circ_0000880 reversed HG-induced decrease in EIF4A3 protein level.

Conclusions

Our findings suggest that hsa_circ_0000880 is a novel circRNA can induce RMECs apoptosis in response to HG conditions by sponging EIF4A3, offering an innovative treatment approach against DR.

Translational Relevance

The circRNAs participate in the dysregulation of microvascular endothelial function induced by HG conditions, indicating a promising therapeutic target for DR.

CircZCCHC2 decreases pirarubicin sensitivity and promotes triple-negative breast cancer development via the miR-1200/TPR axis

Triple-negative breast cancer (TNBC) has attracted attention due to its poor prognosis and limited treatment options. The mechanisms underlying the association between circular RNAs (circRNAs) and the occurrence and development of TNBC remain unclear. CircZCCHC2 is observed to be upregulated in TNBC cells, tissues, and plasma exosomes. Knockdown of circZCCHC2 inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition of TNBC cells in vitro and in vivo. Pirarubicin (THP) treatment downregulated circZCCHC2, and circZCCHC2 affected the sensitivity to THP. CircZCCHC2/miR-1200/translocated promoter region, the nuclear basket protein (TPR) pathway was cascaded and verified. It is demonstrated that circZCCHC2 plays a crucial role in the malignant progression of TNBC via the miR-1200/TPR axis, thereby activating the RAS-RAF-MEK-ERK pathway. The present results indicate that circZCCHC2 has the potential to serve as a novel prognostic biomarker for TNBC.

CircGLIS3 promotes gastric cancer progression by regulating the miR-1343-3p/PGK1 pathway and inhibiting vimentin phosphorylation

BACKGROUND

Circular RNAs (circRNAs) have been proved to play crucial roles in the development of various cancers. However, the molecular mechanism of circGLIS3 involved in gastric cancer (GC) tumorigenesis has not been elucidated.

METHODS

The higher expression level of circGLIS3 was identified in GC through RNA sequencing and subsequent tissue verification using Quantitative real-time PCR (qRT-PCR). A series of functional experiments in vitro and in vivo were performed to evaluated the effects of circGLIS3 on tumor growth and metastasis in GC. The interaction and regulation of circGLIS3/miR-1343-3p/PGK1 axis was confirmed by RNA pulldown, western blot, and rescue experiments. RIP and western blot were performed to demonstrate the role of circGLIS3 in regulating phosphorylation of VIMENTIN. We then used qRT-PCR and co culture system to trace circGLIS3 transmission via exosomal communication and identify the effect of exosomal circGLIS3 on gastric cancer and macrophages. Finally, RIP experiments were used to determine that EIF4A3 regulates circGLIS3 expression.

RESULTS

CircGLIS3(hsa_circ_0002874) was significantly upregulated in GC tissues and high circGLIS3 expression was associated with advanced TNM stage and lymph node metastasis in GC patients. We discovered that overexpression of circGLIS3 promoted GC cell proliferation, migration, invasion in vitro and in vivo, while suppression of circGLIS3 exhibited the opposite effect. Mechanistically, circGLIS3 could sponge miR-1343-3p and up-regulate the expression of PGK1 to promote GC tumorigenesis. We also found that circGLIS3 reduced the phosphorylation of VIMENTIN at ser 83 site by binding with VIMENTIN. Moreover, it was proven that exosomal circGLIS3 could promote gastric cancer metastasis and the M2 type polarization of macrophages. In the final step, the mechanism of EIF4A3 regulating the generation of circGLIS3 was determined.

CONCLUSION

Our findings demonstrate that circGLIS3 promotes GC progression through sponging miR-1343-3p and regulating VIMENTIN phosphorylation. CircGLIS3 is a potential therapeutic target for GC patients.

Circ_0027446 promotes malignant development of glioblastoma by interacting with miR-346 to up-regulate PGK1

Circular RNAs (circRNAs) can play essential roles in tumor development, including glioblastoma (GBM). The current study was performed to explore the function and mechanism of circ_0027446 in GBM progression. Circ_0027446, microRNA-346 (miR-346) and Phosphoglycerate kinase 1 (PGK1) levels were detected using reverse transcription-quantitative polymerase chain reaction assay. Cell behaviors were examined using Cell Counting Kit-8 assay, colony formation assay, EdU assay, flow cytometry, and transwell assay. Glycolytic metabolism was analyzed by commercial kits. The protein level was determined via western blot. The target interaction was analyzed by dual-luciferase reporter assay. Circ_0027446 function in vivo was explored by tumor xenograft assay. Circ_0027446 expression was significantly up-regulated in GBM samples and cells. Circ_0027446 down-regulation suppressed proliferation, invasion, glycolytic metabolism and enhanced apoptosis of GBM cells. MiR-346 was a target of circ_0027446, and circ_0027446 promoted GBM progression by sponging miR-346. PGK1 acted as a target gene of miR-346, and circ_0027446 interacted with miR-346 to regulate PGK1 expression. Overexpression of miR-346 inhibited malignant behaviors of GBM cells through down-regulating PGK1. Circ_0027446 contributed to tumor growth in vivo via miR-346/PGK1 axis. The current evidences demonstrated that circ_0027446 facilitated malignant progression of GBM through binding to miR-346 to up-regulate PGK1.

Biological role and regulation of circular RNA as an emerging biomarker and potential therapeutic target for cancer

Circular RNAs (circRNAs) are a unique family of endogenous RNAs devoid of 3' poly-A tails and 5' end caps. These single-stranded circRNAs, found in the cytoplasm, are synthesized via back-splicing mechanisms, merging introns, exons, or both, resulting in covalently closed circular loops. They are profusely expressed across the eukaryotic transcriptome and offer heightened stability against exonuclease RNase R compared to linear RNA counterparts. This review endeavors to provide a comprehensive overview of circRNAs' characteristics, biogenesis, and mechanisms of action. Furthermore, aimed to shed light on the potential of circRNAs as significant biomarkers in various cancer types. It has been performed an exhaustive literature review, drawing on recent studies and findings related to circRNA characteristics, synthesis, function, evaluation techniques, and their associations with oncogenesis. CircRNAs are intricately associated with tumor progression and development. Their multifaceted roles encompass gene regulation through the sponging of proteins and microRNAs, controlling transcription and splicing, interacting with RNA binding proteins (RBPs), and facilitating gene translation. Due to these varied roles, circRNAs have become a focal point in tumor pathology investigations, given their promising potential as both biomarkers and therapeutic agents. CircRNAs, due to their unique biogenesis and multifunctionality, hold immense promise in the realm of oncology. Their stability, widespread expression, and intricate involvement in gene regulation underscore their prospective utility as reliable biomarkers and therapeutic targets in cancer. As our understanding of circRNAs deepens, advanced techniques for their detection, evaluation, and manipulation will likely emerge. These advancements might catalyze the translation of circRNA-based diagnostics and therapeutics into clinical practice, potentially revolutionizing cancer care and prognosis.

IGF2BP2-m6A-circMMP9 axis recruits ETS1 to promote TRIM59 transcription in laryngeal squamous cell carcinoma

Laryngeal squamous cell carcinoma (LSCC) is a common malignancy of the head and neck. Recently, circular RNA (circRNA) has been studied extensively in multisystem diseases. However, there are few research on biological functions and molecular mechanisms of circRNAs in LSCC. CircRNA array was used to detect the differentially expressed circRNAs. Kaplan-Meier and cox regression analysis were used to identify survival based on circMMP9. The qRT-PCR, RNase R treatment, sanger sequencing and in situ hybridization were used to verify circMMP9 expression, characteristics and localization in LSCC tissues and cells. Functionally, colony formation, MTS, transwell and in vivo assays were proceeded to detect the biological function of circMMP9 in LSCC progression. The RNA-seq was conducted to identify the molecular targets of circMMP9. Mechanically, MeRIP, RNA Immunoprecipitation (RIP), RNA pulldown, Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were carried on to verify the regulatory mechanism of circMMP9. CircMMP9 was discovered upregulated in LSCC tissues and cells, and high level of circMMP9 was associated with poor prognosis, low degree of pathological grading, high TNM stage and lymph node metastasis of LSCC. CircMMP9 knockdown prevented LSCC progression both in vitro and in vivo, whereas, circMMP9 overexpression had the opposite effect. CircMMP9 was stabilized by IGF2BP2 in m6A-dependent manner. TRIM59 was identified as downstream target of circMMP9. CircMMP9 recruited ETS1 to stimulate TRIM59 transcription. Moreover, TRIM59 accelerated LSCC progression via activating the PI3K/AKT signal pathway. Our findings offered a unique regulatory mechanism for circMMP9 in LSCC, as well as a novel proof that circMMP9 may be utilize as a diagnostic marker and therapeutic target for LSCC patients.

Lipid-based nanoparticles to address the limitations of GBM therapy by overcoming the blood-brain barrier, targeting glioblastoma stem cells, and counteracting the immunosuppressive tumor microenvironment

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, characterized by high heterogeneity, strong invasiveness, poor prognosis, and a low survival rate. A broad range of nanoparticles have been recently developed as drug delivery systems for GBM therapy owing to their inherent size effect and ability to cross the blood-brain barrier (BBB). Lipid-based nanoparticles (LBNPs), such as liposomes, solid lipid NPs (SLNs), and nano-structured lipid carriers (NLCs), have emerged as the most promising drug delivery system for the treatment of GBM because of their unique size, surface modification possibilities, and proven bio-safety. In this review, the main challenges of the current clinical treatment of GBM and the strategies on how novel LBNPs overcome them were explored. The application and progress of LBNP-based drug delivery systems in GBM chemotherapy, immunotherapy, and gene therapy in recent years were systematically reviewed, and the prospect of LBNPs for GBM treatment was discussed.

EIF4A3-mediated biogenesis of circSTX6 promotes bladder cancer metastasis and cisplatin resistance

BACKGROUND

Cisplatin (CDDP)-based chemotherapy is a standard first-line treatment for metastatic bladder cancer (BCa) patients, and chemoresistance remains a major challenge in clinical practice. Circular RNAs (circRNAs) have emerged as essential regulators in carcinogenesis and cancer progression. However, the role of circRNAs in mediating CDDP chemosensitivity has yet to be well elucidated in BCa.

METHODS

CircSTX6 (hsa_circ_0007905) was identified by mining the public circRNA datasets and verified by Sanger sequencing, agarose gel electrophoresis, RNase R treatment and qRT-PCR assays. Then, function experiments were performed to evaluate the effects of circSTX6 on BCa metastasis. Luciferase reporter assay, RNA pull-down, RNA immunoprecipitation (RIP), RNA stability assay, Fluorescence in situ hybridization (FISH) and Immunofluorescence (IF) were conducted to evaluate the interaction among circSTX6, miR-515-3p, PABPC1 and SUZ12. Animal experiments were performed to explore the function of circSTX6 in tumor metastasis and CDDP sensitivity.

RESULTS

We identified that circSTX6 was significantly upregulated in clinical samples and cells of BCa. Functionally, circSTX6 promoted cell migration and invasion both in vitro and in vivo. Mechanistically, circSTX6 could act as a miR-515-3p sponge and abolish its effect on SUZ12. Moreover, circSTX6 was confirmed to increase the stability of SUZ12 mRNA by interacting with a mRNA stabilizer PABPC1 and subsequently promote the expression of SUZ12. Importantly, silencing of circSTX6 improved the chemosensitivity of CDDP-resistant bladder cancer cells to CDDP. Furthermore, in vivo analysis supported that knockdown of circSTX6 attenuated CDDP resistance in BCa tumors.

CONCLUSION

These studies demonstrate that circSTX6 plays a pivotal role in BCa metastasis and chemoresistance, and has potential to serve as a therapeutic target for treatment of BCa.

eIF4A3-mediated circEHMT1 regulation in retinal microvascular endothelial dysfunction in diabetic retinopathy

BACKGROUND AND OBJECTIVE

Literature has reported that circular RNAs (circRNAs) are crucially associated with diabetic retinopathy (DR). Furthermore, circEHMT1 has been identified to maintain endothelial cell barrier function. This study aimed to investigate the mechanisms that regulate aberrant circEHMT1 expression and its role in the pathogenesis of DR.

METHODS

In this study, retinal microvascular endothelial cells were exposed to a high glucose (HG) environment, and subsequently, tube formation and intercellular junction proteins were evaluated. Furthermore, the biological functions of circEHMT1 and its potential regulatory factor, eIF4A3, in microvascular endothelial cells under HG conditions were also assessed. In addition, the regulatory role of eIF4A3 on circEHMT1 expression was confirmed. Moreover, to elucidate the in vivo functions of eIF4A3 and circEHMT1, streptozotocin (STZ) was used to establish a DR model in rats.

RESULTS

It was revealed that HG condition decreased circEHMT1 and eIF4A3 expressions and reduced ZO-1, Claudin-5, and Occludin levels in retinal microvascular endothelial cells. Furthermore, it was observed that eIF4A3 could regulate the expression of circEHMT1. Overexpression of eIF4A3 or circEHMT1 under HG conditions improved endothelial cell injury and decreased tube-formation ability. Additionally, in the DR rat model, eIF4A3 overexpression restored circEHMT1 levels and ameliorated retinal vasculature changes.

CONCLUSION

Altogether, eIF4A3 regulates circEHMT1 expression, thereby affecting microvascular endothelial cell injury and tube formation. Further understanding the regulatory effect of eIF4A3 on circEHMT1 may provide novel therapeutic targets for DR.

Circular RNAs: Emerging Modulators in the Pathophysiology of Polycystic Ovary Syndrome and their Clinical Implications

Polycystic ovary syndrome (PCOS) is a prevalent endocrine/metabolic disorder in women of reproductive age. PCOS is characterized by hyperandrogenism, polycystic ovary morphology, and ovulatory dysfunction/anovulation. It involves multiple effects in patients, including granulosa/theca cell hyperplasia, menstrual disturbances, infertility, acne, obesity, insulin resistance, and cardiovascular disorders. Biochemical analyses and the results of RNA sequencing studies in recent years have shown a type of non-coding RNAs as a splicing product known as circular RNAs (circRNAs). Several biological functions have been identified in relation to circRNAs, including a role in miRNA sponge, protein sequestration, increased parental gene expression, and translation leading to polypeptides. These circular molecules are more plentiful and specialized than other types of RNAs. For this reason, they are referred to as potential biomarkers in different diseases. Evidence suggests that circRNAs may have regulatory potentials through different signaling pathways, such as the miRNA network. Probably most experts in the field of obstetricians are not aware of circRNAs as a useful biomarker. Therefore, this review focused on the researches that have been done on the involvement of circRNAs in PCOS and summarized recent supportive evidence, and evaluated the circRNA association and mechanisms involved in PCOS.

Hsa_circ_0001162 Inhibition Alleviates High Glucose-Induced Human Podocytes Injury by the miR-149-5p/MMP9 Signaling Pathway

Emerging evidences suggested that circular RNAs (circRNAs) are involved in diabetic nephropathy (DN). Accumulating evidence had suggested that the degree of podocyte is a major prognostic determinant of DN progression. However, the function and in-depth mechanisms of hsa_circ_0001162 in podocyte injury of DN remain unclear. Hsa_circ_0001162 expression was detected by real-time quantitative PCR (RT-qPCR) in peripheral blood of DN patients and high glucose-induced podocytes injury model. The cell counting kit 8, 5-ethynyl-2'-deoxyuridine, flow cytometry with Annexin V-FITC/PI staining, caspase-3 activity assay Kit, enzyme linked immunosorbent assay (ELISA), RT-qPCR and western blotting were used to evaluate the effect of hsa_circ_0001162 / miR-149-5p / MMP9 axis on high glucose-induced podocyte injury. Mechanistically, dual luciferase reporter was used to confirm the relationship of miR-149-5p and hsa_circ_0001162 or MMP9. Furthermore, RNA-pull down and immunoprecipitation assay were implemented to verify the potential regulatory effects of EIF4A3 on biogenesis of hsa_circ_0001162. Our results showed that hsa_circ_0001162 was highly expressed in peripheral blood of DN patients and high glucose-induced podocytes injury model, and the knockdown of hsa_circ_0001162 increased the proliferation, inhibited the apoptosis, and suppressed inflammatory response in high glucose-induced podocytes injury. Mechanism studies demonstrated that EIF4A3 bound with flanking sequences of hsa_circ_0001162 to promote hsa_circ_0001162 expression, upregulated hsa_circ_0001162 increased the MMP9 expression via sponging miR-149-5p, thus aggravating the high glucose-induced podocytes injury. Overall, our data demonstrated that knockdown of hsa_circ_0001162 inhibited high glucose-induced podocytes injury by regulating miR-149-5p/MMP9 axis, and intervention of hsa_circ_0001162/miR-149-5p/MMP9 axis may be a potentially promising therapeutic strategy for podocyte injury in DN patients.

RBMS3-induced circHECTD1 encoded a novel protein to suppress the vasculogenic mimicry formation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a highly vascularized malignant cancer of the central nervous system, and the presence of vasculogenic mimicry (VM) severely limits the effectiveness of anti-vascular therapy. In this study, we identified downregulated circHECTD1, which acted as a key VM-suppressed factor in GBM. circHECTD1 elevation significantly inhibited cell proliferation, migration, invasion and tube-like structure formation in GBM. RIP assay was used to demonstrate that the flanking intron sequence of circHECTD1 can be specifically bound by RBMS3, thereby inducing circHECTD1 formation to regulate VM formation in GBM. circHECTD1 was confirmed to possess a strong protein-encoding capacity and the encoded functional peptide 463aa was identified by LC-MS/MS. Both circHECTD1 and 463aa significantly inhibited GBM VM formation in vivo and in vitro. Analysis of the 463aa protein sequence revealed that it contained a ubiquitination-related domain and promoted NR2F1 degradation by regulating the ubiquitination of the NR2F1 at K396. ChIP assay verified that NR2F1 could directly bind to the promoter region of MMP2, MMP9 and VE-cadherin, transcriptionally promoting the expression of VM-related proteins, which in turn enhanced VM formation in GBM. In summary, we clarified a novel pathway for RBMS3-induced circHECTD1 encoding functional peptide 463aa to mediate the ubiquitination of NR2F1, which inhibited VM formation in GBM. This study aimed to reveal new mechanisms of GBM progression in order to provide novel approaches and strategies for the anti-vascular therapy of GBM. The schematic illustration showed the inhibitory effect of circHECTD1-463aa in the VM formation in GBM.

EGCG-LYS Fibrils-Mediated CircMAP2K2 Silencing Decreases the Proliferation and Metastasis Ability of Gastric Cancer Cells in Vitro and in Vivo

Aberrant expression of circular RNAs (circRNAs) has been reported to play an important biological regulatory role in gastric cancer (GC). For the purpose of silencing cancer-related genes, a new approach for cancer treatment using nanocarriers to deliver siRNA has been proposed. In this study, abundantly expressed circMAP2K2 (hsa_circRNA_102415) is identified in GC cells. CircMAP2K2 regulates the PCBP1/GPX1 axis through proteasome-mediated degradation, which further mediates the activation of the AKT/GSK3β/epithelial-to-mesenchymal transition (EMT) signaling pathway and enhances the proliferation and metastatic ability of GC cells. To establish novel GC treatment, epigallocatechin-3-gallate-lysozyme (EGCG-LYS) fibrils are synthesized, and in vitro experiments demonstrate that EGCG-LYS has a higher siRNA delivery efficiency than Lipofectamine 2000 (lipo2000), which effectively silences the expression of circMAP2K2. Further studies show that EGCG-LYS carrying siRNA can successfully achieve lysosome escape, which allows it to be located in the cytoplasm to achieve post-transcriptional gene silencing. In addition, EGCG-LYS carrying si-circMAP2K2 has good circulating stability, excellent biosafety and antitumor ability in vivo. The EGCG-LYS fibrils delivery system provides a new tool and approach for the treatment of GC.

circPSD3 is a promising inhibitor of uPA system to inhibit vascular invasion and metastasis in hepatocellular carcinoma

BACKGROUND

Vascular invasion is a major route for intrahepatic and distant metastasis in hepatocellular carcinoma (HCC) and is a strong negative prognostic factor. Circular RNAs (circRNAs) play important roles in tumorigenesis and metastasis. However, the regulatory functions and underlying mechanisms of circRNAs in the development of vascular invasion in HCC are largely unknown.

METHODS

High throughput sequencing was used to screen dysregulated circRNAs in portal vein tumor thrombosis (PVTT) tissues. The biological functions of candidate circRNAs in the migration, vascular invasion, and metastasis of HCC cells were examined in vitro and in vivo. To explore the underlying mechanisms, RNA sequencing, MS2-tagged RNA affinity purification, mass spectrometry, and RNA immunoprecipitation assays were performed.

RESULTS

circRNA sequencing followed by quantitative real-time PCR (qRT-PCR) revealed that circRNA pleckstrin and Sect. 7 domain containing 3 (circPSD3) was significantly downregulated in PVTT tissues. Decreased circPSD3 expression in HCC tissues was associated with unfavourable characteristics and predicted poor prognosis in HCC. TAR DNA-binding protein 43 (TDP43) inhibited the biogenesis of circPSD3 by interacting with the downstream intron of pre-PSD3. circPSD3 inhibited the intrahepatic vascular invasion and metastasis of HCC cells in vitro and in vivo. Serpin family B member 2 (SERPINB2), an endogenous bona fide inhibitor of the urokinase-type plasminogen activator (uPA) system, is the downstream target of circPSD3. Mechanistically, circPSD3 interacts with histone deacetylase 1 (HDAC1) to sequester it in the cytoplasm, attenuating the inhibitory effect of HDAC1 on the transcription of SERPINB2. In vitro and in vivo studies demonstrated that circPSD3 is a promising inhibitor of the uPA system.

CONCLUSIONS

circPSD3 is an essential regulator of vascular invasion and metastasis in HCC and may serve as a prognostic biomarker and therapeutic target.

Silencing circSERPINE2 restrains mesenchymal stem cell senescence via the YBX3/PCNA/p21 axis

Increasing evidence indicates that circular RNAs (circRNAs) accumulate in aging tissues and nonproliferating cells due to their high stability. However, whether upregulation of circRNA expression mediates stem cell senescence and whether circRNAs can be targeted to alleviate aging-related disorders remain unclear. Here, RNA sequencing analysis of differentially expressed circRNAs in long-term-cultured mesenchymal stem cells (MSCs) revealed that circSERPINE2 expression was significantly increased in late passages. CircSERPINE2 small interfering RNA delayed MSC senescence and rejuvenated MSCs, while circSERPINE2 overexpression had the opposite effect. RNA pulldown followed by mass spectrometry revealed an interaction between circSERPINE2 and YBX3. CircSERPINE2 increased the affinity of YBX3 for ZO-1 through the CCAUC motif, resulting in the sequestration of YBX3 in the cytoplasm, inhibiting the association of YBX3 with the PCNA promoter and eventually affecting p21 ubiquitin-mediated degradation. In addition, our results demonstrated that senescence-related downregulation of EIF4A3 gave rise to circSERPINE2. In vivo, intra-articular injection of si-circSerpine2 restrained native joint-resident MSC senescence and cartilage degeneration in mice with aging-related osteoarthritis. Taken together, our findings provide strong evidence for a regulatory role for the circSERPINE2/YBX3/PCNA/p21 axis in MSC senescence and the therapeutic potential of si-circSERPINE2 in alleviating aging-associated syndromes, such as osteoarthritis.

Identification of m6A suppressor EIF4A3 as a novel cancer prognostic and immunotherapy biomarker through bladder cancer clinical data validation and pan-cancer analysis

EIF4A3 represents a novel m6A suppressor that exerts control over the global m6A mRNA modification level, therefore influencing gene destiny. Despite increasing evidence that highlights a pivotal role of EIF4A3 in tumor progression and immunity, a comprehensive pan-cancer analysis of EIF4A3 has yet to be conducted, in order to ascertain whether EIF4A3 could be a viable biomarker for cancer screening, prediction of prognosis, and to facilitate accurate therapy design in various human malignancies. We analyzed the expression levels of EIF4A3 in bladder cancer compared to para-cancer tissue. Subsequently survival analysis was conducted to ascertain the potential association between EIF4A3 expression and patient prognosis. To further corroborate this evidence, we conducted an extensive data mining process of several publicly available databases, including UCSC Xena database, TCGA, and GTEx. Raw data from the UCSC Xena database was processed using online tools to obtain results that could be subjected to further analysis. Our study unveiled a considerable increase in the expression levels of EIF4A3 in bladder cancer compared to para-cancer tissue. Subsequent validation experiments confirmed that bladder cancer patients exhibiting higher levels of EIF4A3 expression have significantly worse prognostic outcomes. Next, our pan-cancer analysis found that the expression level of EIF4A3 is significantly higher in most cancers. Notably, high expression levels of EIF4A3 were negatively associated with patient prognosis across various cancer types. Furthermore, as a novel m6A suppressor, EIF4A3 was found to be correlated with numerous RNA modification genes in multiple cancer types. Meanwhile, analysis of publicly available databases revealed that EIF4A3 expression was significantly related to immune score and immune cell levels in most cancer types. Interestingly, EIF4A3 was also identified as a superior immunotherapy biomarker when compared to several traditional immunotherapy biomarkers. Lastly, genetic alterations analysis revealed that amplification was the most frequently occurring abnormality in the EIF4A3 gene. EIF4A3 emerges as a promising biomarker with the potential to significantly enhance tumor screening, prognostic evaluation, and the design of individualized treatment strategies across a diverse array of malignancies.

EIF4A3-mediated circ_0042881 activates the RAS pathway via miR-217/SOS1 axis to facilitate breast cancer progression

Breast cancer (BC) is one of the most frequent cancer-related deaths in women worldwide. Studies have shown the potential impact of circRNAs in multiple human tumorigeneses. Research on the vital signaling pathways and therapeutic targets of circRNAs is indispensable. Here, we aimed to investigate the clinical implications and underlying mechanisms of circ_0042881 in BC. RT-qPCR validated circ_0042881 was notably elevated in BC tissues and plasma, and closely associated with BC clinicopathological features. Functionally, circ_0042881 significantly accelerated the proliferation, migration, and invasion of BC cells in vitro and tumor growth and metastasis in vivo. Mechanistically, circ_0042881 promoted BC progression by sponging miR-217 to relieve its inhibition effect in son of sevenless 1 (SOS1), which further activated RAS protein and initiated downstream signaling cascades, including MEK/ERK pathway and PI3K/AKT pathway. We also demonstrated that treatment of BAY-293, an inhibitor of SOS1 and RAS interaction, attenuated BC progression induced by circ_0042881 overexpression. Furthermore, Eukaryotic initiation factor 4A-III (EIF4A3) could facilitate circ_0042881 circularization. Altogether, we proposed a novel signaling network in which circ_0042881, induced by EIF4A3, influences the process of BC tumorigenesis and metastasis by miR-217/SOS1 axis.

Molecular interplay between EIF4 family and circular RNAs in cancer: Mechanisms and therapeutics

The eukaryotic translation initiation factor 4 (EIF4) family is a major contributor to the recruitment of mRNAs to ribosomes during the initial translation stage in eukaryotes, whose dysregulation either allows for cancer transformation or prevents disordered cancerous cell growth. Circular RNAs (circRNAs), which exhibit distinctive structures and are widely expressed in eukaryotes, are anticipated to be a clinical diagnostic biomarker for cancer therapy. There is considerable evidence that EIF4s can influence the biogenesis, transport, and function of circRNAs and, in turn, circRNAs can control the expressions of EIF4s through certain molecular pathways. Herein, we primarily review the emerging studies of the EIF4 family and pinpoint the roles of dysregulated EIF4s in cancer. We also evaluate the patterns of intricate interactions between circRNAs and EIF4s and discuss the potential utility of circRNA-based therapeutics targeting EIF4s in clinical cancer research.

NSD2 promotes pressure overload-induced cardiac hypertrophy via activating circCmiss1/TfR1/ferroptosis signaling

Heart failure typically occurs early in the clinical course of sustained cardiac hypertrophy that is accompanied by maladaptive remodeling of the heart. It is critical to discover new mechanisms and effective therapeutic targets to prevent and cure pathological cardiac hypertrophy. The objective of the study was to evaluate the effects of circRNAs on NSD2-induced ventricular remodeling. We screened the dysregulated circRNAs in normal or NSD2^-/- C57BL/6 mice with or without transverse aortic constriction (TAC), and found that circCmss1 significantly increased in normal TAC mice, but decreased in NSD2^-/- TAC mice. Angiotensin II(Ang II)induced neonatal cardiomyocyte hypertrophy in vitro and the pressure overload-induced cardiac hypertrophy in vivo can be reduced by Knocking down circCmss1. We further investigated the downstream signaling of circCmss1 in the progression of NSD2-promoted ventricular remodeling and discovered that circCmss1 could interact with a transcription factor EIF4A3 and induce the expression of transferrin receptor 1 (TfR1), thus activating the ferroptosis in cardiomyocytes. This study highlights the significance of NSD2 activation of circCmss1/EIF4A3/TfR1 as therapeutic targets for treating pathological myocardial hypertrophy.

EIF4A3-induced Circ_0001187 facilitates AML suppression through promoting ubiquitin-proteasomal degradation of METTL3 and decreasing m6A modification level mediated by miR-499a-5p/RNF113A pathway

Aberrant expression of circRNAs has been proven to play a crucial role in the progression of acute myeloid leukemia (AML); however, its regulatory mechanism remains unclear. Herein, we identified a novel circRNA, Circ_0001187, which is downregulated in AML patients, and its low level contributes to a poor prognosis. We further validated their expression in large-scale samples and found that only the expression of Circ_0001187 was significantly decreased in newly diagnosed (ND) AML patients and increased in patients with hematological complete remission (HCR) compared with controls. Knockdown of Circ_0001187 significantly promoted proliferation and inhibited apoptosis of AML cells in vitro and in vivo, whereas overexpression of Circ _0001187 exerted the opposite effects. Interestingly, we found that Circ_0001187 decreases mRNA m⁶A modification in AML cells by enhancing METTL3 protein degradation. Mechanistically, Circ_0001187 sponges miR-499a-5p to enhance the expression of E3 ubiquitin ligase RNF113A, which mediates METTL3 ubiquitin/proteasome-dependent degradation via K48-linked polyubiquitin chains. Moreover, we found that the low expression of Circ _0001187 is regulated by promoter DNA methylation and histone acetylation. Collectively, our findings highlight the potential clinical implications of Circ _0001187 as a key tumor suppressor in AML via the miR-499a-5p/RNF113A/METTL3 pathway.

EIF4a3-regulated circRABL2B regulates cell stemness and drug sensitivity of lung cancer via YBX1-dependent downregulation of MUC5AC expression

Identification of mucin modulators is of remarkable significance to facilitate mucin-based antineoplastic therapy. However, little is known about circular RNAs (circRNAs) on regulating mucins. Dysregulated mucins and circRNAs were identified via high-throughput sequencing and their relationships with lung cancer survival were analyzed in tumor samples of 141 patients. The biological functions of circRABL2B were determined via gain- and loss-of-function experiments and exosome-packaged circRABL2B treatment in cells, patient-derived lung cancer organoids and nude mice. We identified that circRABL2B was negatively correlated with MUC5AC. Patients with low circRABL2B and high MUC5AC displayed the poorest survival (HR=2.00; 95% CI=1.12-3.57). Overexpressed circRABL2B significantly inhibited cell malignant phenotypes, while it knock-down exerted opposite effects. CircRABL2B interacted with YBX1 to inhibit MUC5AC, and subsequently suppressed integrin β4/pSrc/p53 signaling and impoverished cell stemness, and promoted erlotinib sensitivity. Exosome-packaged circRABL2B exerted significant anti-cancer actions in cells, patient-derived lung cancer organoids and nude mice. Meanwhile, circRABL2B in plasma exosomes could distinguish early-stage lung cancer patients from healthy controls. Finally, we found circRABL2B was downregulated at the transcriptional level, and EIF4a3 involved the formation of circRABL2B. In conclusion, our data suggest that circRABL2B counteracts lung cancer progression via MUC5AC/integrin β4/pSrc/p53 axis, which provides a rationale to enhance the efficacy of anti-MUCs treatment in lung cancer.

Nucleic acid immunotherapeutics and vaccines: A promising approach to glioblastoma multiforme treatment

Glioblastoma multiforme (GBM) is a deadly and difficult to treat primary brain tumor for which satisfactory therapeutics have yet to be discovered. While cancer immunotherapeutics, such as immune checkpoint inhibitors, have successfully improved the treatment of some other types of cancer, the poorly immunogenic GBM tumor cells and the immunosuppressive GBM tumor microenvironment have made it difficult to develop GBM immunotherapeutics. Nucleic acids therapeutics and vaccines, particularly those of mRNA, have become a popular field of research in recent years. This review presents the progress of nucleic acid therapeutics and vaccines for GBM and briefly covers some representative delivery methods of nucleic acids to the central nervous system (CNS) for GBM therapy.

EIF4A3-induced circZFAND6 promotes breast cancer proliferation and metastasis through the miR-647/FASN axis

AIMS

Circular RNAs (circRNAs) are important regulators in breast cancer progression. However, the underlying mechanism of circRNAs functions in breast cancer remain largely unclear.

MAIN METHODS

To investigate the circRNAs expression pattern in breast cancer, high-throughput circRNA microarray assay was used. The top up-regulated circRNA, circZFAND6, was submitted to further experiments, including cell counting kit-8 (CCK-8) assay, colony formation assay, transwell assay and mouse xenograft assay. To investigate the underlying mechanism of circZFAND6 function in breast cancer progression, luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted.

KEY FINDINGS

We found a novel circRNA, circZFAND6, was up-regulated in breast cancer tissues and cell lines. Inhibition of circZFAND6 reduced proliferation and metastasis of breast cancer. Mechanically, circZFAND6 acted as a competing endogenous RNA (ceRNA) to sponge miR-647 and increase fatty acid synthase (FASN) expression. And eukaryotic translation initiation factor 4A3 (EIF4A3) was found to bind to circZFAND6 pre-mRNA transcript upstream region, leading to the high expression of circZFAND6 in breast cancer. Inhibition of EIF4A3 also suppressed proliferation and metastasis of breast cancer.

SIGNIFICANCE

EIF4A3-induced circZFAND6 up-regulation promoted proliferation and metastasis of breast cancer through the miR-647/FASN axis. Our results uncovered a possible mechanism underlying breast cancer progression and might provide a breast cancer treatment target.

EIF4A3-induced circular RNA SCAP facilitates tumorigenesis and progression of non-small-cell lung cancer via miR-7/SMAD2 signaling

The eukaryotic translation initiation factor 4A (eIF4A) family determines transcription efficiency by directly binding to precursor RNAs. One member, EIF4A3, modulates the expression of circRNAs. Circular RNA SCAP (circSCAP), a newly found circRNA, has been implicated in atherosclerosis. Yet, how circSCAP regulates cancer development and progression remains understudied. Here, we investigated the function of circSCAP and the molecular mechanism in the tumorigenesis and progression of non-small-cell lung cancer (NSCLC). CircSCAP was upregulated in both NSCLC tissues and cell lines and was mainly located in the cytoplasm. CircSCAP expression was promoted by EIF4A3, which was associated with poor prognosis in patients with NSCLC. CircSCAP sponged miR-7 to upregulate small mothers against decapentaplegic 2 (SMAD2). CircSCAP knockdown undermined cell proliferation, migration, and invasion abilities in NSCLC cell lines (SPCA1 and A549), which was rescued by either inhibiting miR-7 or overexpressing SMAD2. Moreover, circSCAP knockdown upregulated E-cadherin, while downregulating N-cadherin, Vimentin, and MMP9 in SPCA1 and A549 cells, which were abolished by either inhibiting miR-7 or overexpressing SMAD2. Additionally, miR-7 was markedly downregulated, whereas SMAD2 was significantly upregulated in NSCLC tissues. MiR-7 expression was inversely correlated with circSCAP and SMAD2 expression in NSCLC tissues. In conclusion, this study demonstrates that circSCAP is significantly upregulated in NSCLC cell lines and tissues and elucidates that circSCAP facilitates NSCLC progression by sponging miR-7 and upregulating SMAD2. The study provides a novel molecular target for early diagnosis and treatment of NSCLC.

FXR1 promotes glioma progression by downregulating microRNA-124-3p through long noncoding RNA FGD5-AS1 upregulation

OBJECTIVE

As reported, glioma progression is affected by altered FXR1, long non-coding RNA FGD5-AS1, and microRNA (miR)-124-3p. However, relationships among these genes remain unclear. Accordingly, this paper ascertains whether FXR1 manipulates glioma progression via the FGD5-AS1/miR-124-3p axis.

METHODS

Glioma tissues were harvested, in which FGD5-AS1 and miR-124-3p levels were examined with qRT-PCR and FXR1 level was assessed with qRT-PCR and western blot. The interaction of miR-124-3p with FGD5-AS1 was analyzed by dual-luciferase reporter, RIP, and Pearson correlation coefficient assays, and that of FXR1 with FGD5-AS1 was assessed by RIP and Pearson correlation coefficient assays. Glioma cells were obtained, followed by qRT-PCR detection of miR-124-3p expression. After gain- or loss-of-function assays, EdU, Transwell, and tubule formation assays were performed to determine cell proliferation, invasion and migration, and angiogenesis. Next, the intracranial in situ graft tumor model was established for in vivo verification.

RESULTS

FGD5-AS1 and FXR1 levels were high, but miR-124-3p level was low in glioma tissues. Likewise, glioma cells had downregulated miR-124-3p expression. Mechanistically, FGD5-AS1 negatively bound to miR-124-3p, and FXR1 was positively correlated and interacted with FGD5-AS1. miR-124-3p overexpression or FGD5-AS1 or FXR1 knockdown restricted cell invasion, proliferation, migration, and angiogenesis in gliomas. miR-124-3p inhibition abrogated the repressive impacts of FXR1 knockdown on the malignant progression of gliomas. Also, FXR1 constrained tumor growth and angiogenesis in mice, which was counterweighed by inhibiting miR-124-3p.

CONCLUSION

FXR1 might act as an oncogene in gliomas by declining miR-124-3p through FGD5-AS1.

Insight on Non-Coding RNAs from Biofluids in Ovarian Tumors

Ovarian tumors are the most frequent adnexal mass, raising diagnostic and therapeutic issues linked to a large spectrum of tumors, with a continuum from benign to malignant. Thus far, none of the available diagnostic tools have proven efficient in deciding strategy, and no consensus exists on the best strategy between "single test", "dual testing", "sequential testing", "multiple testing options" and "no testing". In addition, there is a need for prognostic tools such as biological markers of recurrence and theragnostic tools to detect women not responding to chemotherapy in order to adapt therapies. Non-coding RNAs are classified as small or long based on their nucleotide count. Non-coding RNAs have multiple biological functions such as a role in tumorigenesis, gene regulation and genome protection. These ncRNAs emerge as new potential tools to differentiate benign from malignant tumors and to evaluate prognostic and theragnostic factors. In the specific setting of ovarian tumors, the goal of the present work is to offer an insight into the contribution of biofluid non-coding RNAs (ncRNA) expression.

ALKBH5-induced circular RNA NRIP1 promotes glycolysis in thyroid cancer cells by targeting PKM2

Although circular RNAs (circRNAs) are involved in cell proliferation, differentiation, apoptosis, and invasion, the underlying regulatory mechanisms of circRNAs in thyroid cancer have not been fully elucidated. This article aimed to study the role of circRNA regulated by N6-methyladenosine modification in papillary thyroid cancer (PTC). Quantitative real-time PCR, western blotting, and immunohistochemistry were used to investigate the expressions of circRNA nuclear receptor-interacting protein 1 (circNRIP1) in PTC tissues and adjacent noncancerous thyroid tissues. In vitro and in vivo assays were carried out to assess the effects of circNRIP1 on PTC glycolysis and growth. The N6-methyladenosine mechanisms of circNRIP1 were evaluated by methylated RNA immunoprecipitation sequencing, luciferase reporter gene, and RNA stability assays. Results showed that circNRIP1 levels were significantly upregulated in PTC tissues. Furthermore, elevated circNRIP1 levels in PTC patients were correlated with high tumor lymph node metastasis stage and larger tumor sizes. Functionally, circNRIP1 significantly promoted glycolysis, PTC cell proliferation in vitro, and tumorigenesis in vivo. Mechanistically, circNRIP1 acted as a sponge for microRNA (miR)-541-5p and miR-3064-5p and jointly upregulated pyruvate kinase M2 (PKM2) expression. Knockdown of m⁶ A demethylase α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5) significantly enhanced circNRIP1 m⁶ A modification and upregulated its expression. These results show that ALKBH5 knockdown upregulates circNRIP1, thus promoting glycolysis in PTC cells. Therefore, circNRIP1 can be a prognostic biomarker and therapeutic target for PTC by acting as a sponge for oncogenic miR-541-5p and miR-3064-5p to upregulate PKM2 expression.

CircRNA circ_POSTN promotes the malignancy of glioma by regulating the miR-433-3p/SPARC axis

Glioma is a common tumor in the brain. CircRNA hsa_circ_0030018, also termed as hsa_circPOSTN_001 (circ_POSTN), is reported to exert a promoting influence on the development of glioma. Our study intends to deeply explore its regulation mechanism of circ_POSTN. Expression of circ_POSTN, microRNA-433-3p (miR-433-3p) and Secreted protein acidic and rich in cysteine (SPARC) was detected by qRT-PCR or western blot assay. The function of circ_POSTN was analyzed by loss-of-function experiments. The targeting relationship between miR-433-3p and circ_POSTN or SPARC was predicted by bioinformatics analysis and validated by dual-luciferase reporter assay. Xenograft modeling was employed to validate the function of circ_POSTN in glioma in vivo. circ_POSTN and SPARC were upregulated while miR-433-3p was downregulated in glioma tissues and cells. Both circ_POSTN and SPARC knockdown inhibited clonogenicity, migration, and promoted apoptosis of glioma cells. Circ_POSTN sponged miR-433-3p to regulate SPARC expression. Gain of SPARC largely attenuated circ_POSTN knockdown or miR-433-3p overexpression-mediated effects on glioma cell clonogenicity, migration, and apoptosis. Furthermore, silencing of circ_POSTN decreased xenograft tumor growth in vivo. Inhibition of circ_POSTN repressed glioma development, at least in part, via regulating the miR-433-3p/SPARC axis, providing evidence for circ_POSTN as a potential therapeutic target for glioma.

Tumor-Derived Biomarkers in Liquid Biopsy of Glioblastoma

There is a pressing clinical need for minimally invasive liquid biopsies to supplement imaging in the treatment of glioblastoma. Diagnostic imaging is often difficult to interpret and the medical community is divided on distinguishing among complete response, partial response, stable disease, and progressive disease. A minimally invasive liquid biopsy would supplement imaging and clinical findings and has the capacity to be helpful in several ways: 1) diagnosis, 2) selection of patients for specific treatments, 3) tracking of treatment response, and 4) prognostic value. The liquid biome is the combination of biological fluids including blood, urine, and cerebrospinal fluid that contain small amounts of tumor cells, DNA/RNA coding material, peptides, and metabolites. Within the liquid biome, 2 broad categories of biomarkers can exist: tumor-derived, which can be directly traced to the tumor, and tumor-associated, which can be traced back to the response of the body to disease. Although tumor-associated biomarkers are promising liquid biopsy candidates, recent advances in biomarker enrichment and detection have allowed concentration on a new class of biomarker: tumor-derived biomarkers. This review focuses on making the distinction between the 2 biomarker categories and highlights promising new direction.

EIF4A3-Induced Upregulation of hsa_circ_0040039 is a Biomarker and Aggravates IL-1β-Stimulated Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is characterised by nucleus pulposus (NP) loss and extracellular matrix (ECM) degeneration. Circular RNAs (circRNAs) have been reported to be dysregulated during IDD progression. Recently, reports showed that hsa_circ_0040039 was increased in degenerated lumbar disc samples. The aim of this study was to explore the specific role and underlying mechanisms of hsa_circ_0040039 in IDD. The expression of hsa_circ_0040039 was investigated in NP tissues of IDD patients. IL-1β was used to treat NP cells to construct an IDD in vitro model. Overexpression and loss-of-function assays and bioinformatic analysis were performed to evaluate the role and potential mechanism of hsa_circ_0040039 during IDD progression. Hsa_circ_0040039 expression was increased about 2 folds in NP tissues compared with normal tissues and IL-1β-stimulated NP cells also presented hsa_circ_0040039 upregulation, and its overexpression promoted cell proliferation and ECM degeneration. The depletion of hsa_circ_0040039 had the opposite effects. Based on bioinformatics prediction, Luciferase assay, PCR and Western blot, our study verified that hsa_circ_0040039 directly bond to miR-146b-3p, then mediated its targeted MMP2 and PCNA. Moreover, the overexpression of miR-146b-3p and the silence of MMP2 or PCNA, partially abolished the effect of hsa_circ_0040039 on IL-1β-stimulated NPs. Hsa_circ_0040039 may participate in IDD development by mediating the repair and regeneration of NPs through upregulation MMP2 and PCNA mediated by miR-146b-3p.

Recent Advances of Circular RNAs as Biomarkers for Osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor in young adult, which is prone to early metastasis and poor prognosis. The current treatment methods need to be improved. Circular RNA is a covalently blocked circular, non-coding RNA that plays an essential role in the occurrence, development, clinical diagnosis, and treatment of various diseases. Recently, an increasing number of circRNAs have been identified in osteosarcoma. Understanding its role in osteosarcoma is conducive to the early detection, diagnosis, and treatment of osteosarcoma. In this paper, we reviewed the mechanism of action of circular RNA in the occurrence and development of osteosarcoma and its clinical application in recent years.

Recent insights into the roles of circular RNAs in human brain development and neurologic diseases

Circular RNAs (circRNAs) are a novel class of non-coding RNAs. They are single-stranded RNA transcripts characterized with a closed loop structure making them resistant to degrading enzymes. Recently, circRNAs have been suggested with regulatory roles in gene expression involved in controlling various biological processes. Notably, they have demonstrated abundance, dynamic expression, back-splicing events, and spatiotemporally regulation in the human brain. Accordingly, they are expected to be involved in brain functions and related diseases. Studies in animals and human brain have revealed differential expression of circRNAs in brain compartments. Interestingly, contributing roles of circRNAs in the regulation of central nervous system (CNS) development have been demonstrated in a number of studies. It has been proposed that circRNAs play role in substantial neurological functions like neurotransmitter-associated tasks, neural cells maturation, and functions of synapses. Furthermore, 3 main pathways have been identified in association with circRNAs's host genes including axon guidance, Wnt signaling, and transforming growth factor beta (TGF-β) signaling pathways, which are known to be involved in substantial functions like migration and differentiation of neurons and specification of axons, and thus play role in brain development. In this review, we have an overview to the biogenesis, biological functions of circRNAs, and particularly their roles in human brain development and the pathogenesis of neurodegenerative diseases including Alzheimer's diseases, multiple sclerosis, Parkinson's disease and brain tumors.

The U2AF65/circNCAPG/RREB1 feedback loop promotes malignant phenotypes of glioma stem cells through activating the TGF-β pathway

Glioma is the most aggressive and common malignant neoplasms in human brain tumors. Numerous studies have showed that glioma stem cells (GSCs)drive the malignant progression of gliomas. Recent studies have revealed that circRNAs can maintain stemness and promote malignant progression of glioma stem cells. We used bioinformatics analysis to identify circRNAs and potential RNA-binding proteins (RBPs) in glioma. qRT-PCR, western blotting, RNA FISH, RNA pull-down, RNA immunoprecipitation assay, ChIP, immunohistochemistry, and immunofluorescence methods were used to quantified the expression of circNCAPG, U2AF65, RREB1 and TGF-β1, and the underlying mechanisms between them. MTS, EDU, neurosphere formation, limiting dilution neurosphere formation and transwell assays examined the proliferation and invasive capability of GSCs, respectively. We identified a novel circRNA named circNCAPG was overexpressed and indicated the poor prognosis in glioma patients. Upregulating circNCAPG promoted the malignant progression of GSCs. RNA binding protein U2AF65 could stabilize circNCAPG by direct binding. Mechanically, circNCAPG interacted with and stabilized RREB1, as well as stimulated RREB1 nuclear translocation to activate TGF-β1 signaling pathway. Furthermore, RREB1 transcriptionally upregulated U2AF65 expression to improve the stability of circNCAPG in GSCs, which established a feedback loop involving U2AF65, circNCAPG and RREB1. Since circRNA is more stable than mRNA and can execute its function continuously, targeting circNCAPG in glioma may be a novel promising therapeutic.

Exosome-Delivered circSTAU2 Inhibits the Progression of Gastric Cancer by Targeting the miR-589/CAPZA1 Axis

Background

Circular RNAs (circRNAs) are endogenous noncoding RNAs that play vital roles in many biological processes, particularly in human cancer. Recent studies indicate that circRNAs play an important role in tumor progression through exosomes. However, the specific functions of gastric cancer-derived exosomes and the role of circSTAU2 in gastric cancer (GC) remain largely unknown.

Methods

Differentially expressed circRNAs in GC were identified by circRNA microarrays analysis and quantitative real-time polymerase chain reaction (qRT-PCR). The role of circSTAU2 in GC was verified by circSTAU2 knockdown and overexpression with functional assays both in vitro and in vivo. Fluorescence in situ hybridization (FISH), immunofluorescence, RNA immunoprecipitation (RIP), dual-luciferase reporter assay, qRT-PCR and Western blot were adopted to evaluate the expression and regulatory mechanism of MBNL1, circSTAU2, miR-589 and CAPZA1. Furthermore, the role of exosomes was demonstrated by transmission electron microscopy and nano-sight particle tracking analysis.

Results

CircSTAU2, mainly localized in the cytoplasm, was significantly downregulated in GC. CircSTAU2 overexpression inhibited GC cell proliferation, invasion and migration both in vitro and in vivo, while circSTAU2 knockdown had the inverse effect. CircSTAU2 could be wrapped in exosomes and delivered to recipient cells, and functioned as a sponge for miR-589 to relieve its inhibitory effect on CAPZA1, thus inhibiting GC progression. Furthermore, MBNL1 acted as the upstream RNA-binding protein of circSTAU2 and significantly influenced the circularization and expression of circSTAU2.

Conclusion

Exosome-delivered circSTAU2 may act as a tumor suppressor that restrains GC progression via miR-589/CAPZA1 axis, which demonstrates a potential therapeutic target for GC.

Leucine-rich repeats containing 4 protein (LRRC4) in memory, psychoneurosis, and glioblastoma

ABSTRACT

Leucine-rich repeats containing 4 ( LRRC4 , also named netrin-G ligand 2 [NGL-2]) is a member of the NetrinGs ligands (NGLs) family. As a gene with relatively high and specific expression in brain, it is a member of the leucine-rich repeat superfamily and has been proven to be a suppressor gene for gliomas, thus being involved in gliomagenesis. LRRC4 is the core of microRNA-dependent multi-phase regulatory loops that inhibit the proliferation and invasion of glioblastoma (GB) cells, including LRRC4/NGL2-activator protein 2 (AP2)-microRNA (miR) 182-LRRC4 and LRRC4-miR185-DNA methyltransferase 1 (DNMT1)-LRRC4/specific protein 1 (SP1)-DNMT1-LRRC4. In this review, we demonstrated LRRC4 as a new member of the partitioning-defective protein (PAR) polarity complex that promotes axon differentiation, mediates the formation and plasticity of synapses, and assists information input to the hippocampus and storage of memory. As an important synapse regulator, aberrant expression of LRRC4 has been detected in autism, spinal injury and GBs. LRRC4 is a candidate susceptibility gene for autism and a neuro-protective factor in spinal nerve damage. In GBs, LRRC4 is a novel inhibitor of autophagy, and an inhibitor of protein-protein interactions involving in temozolomide resistance, tumor immune microenvironment, and formation of circular RNA.

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.

Diagnostic and therapeutic potential of circular RNA in brain tumors

Circular RNAs (circRNAs) are a class of RNA with a stable cyclic structure. They are expressed in various tissues and cells with conserved, specific characteristics. CircRNAs have been found to play critical roles in a wide range of cellular processes by regulating gene expression at the epigenetic, transcriptional, and posttranscriptional levels. There is an accumulation of evidence on newly discovered circRNAs, their molecular interactions, and their roles in the development and progression of human brain tumors, including cell proliferation, cell apoptosis, invasion, and chemoresistance. Here we summarize the current state of knowledge of the circRNAs that have been implicated in brain tumor pathogenesis, particularly in gliomas and medulloblastomas. In providing a comprehensive overview of circRNA studies, we highlight how different circRNAs have oncogenic or tumor-suppressive roles in brain tumors, making them attractive therapeutic targets and biomarkers for personalized therapy and precision diagnostics. This review article discusses circRNAs' functional roles and the prospect of using them as diagnostic biomarkers and therapeutic targets in patients with brain tumors.

EIF4A3-induced circBRWD3 promotes tumorigenesis of breast cancer through miR-142-3p_miR-142-5p/RAC1/PAK1 signaling

CircBRWD3 is a newly discovered circRNA, and its potential function has not been probed. Here, we aimed to molecularly dissect the role of circBRWD3 in the tumorigenesis and progression of breast cancer (BC). qRT-PCR analysis revealed that circBRWD3 expression was dramatically upregulated in BC tissues, a feature that was positively correlated with the poor prognosis of patients with BC. CircBRWD3 knockdown repressed cell proliferation and metastasis, while promoting cell apoptosis in vitro. Consistently, an in vivo circBRWD3 deficiency model exhibited suppressed tumor metastasis and oncogenesis. On the other hand, circBRWD3 overexpression promoted cancer cell activity and tumorigenesis. Further, mechanistic studies elucidated that circBRWD3 sponged both miR-142-3p and miR-142-5p to modulate RAC1 expression, which subsequently activated the RAC1/PAK1 signaling to facilitate the tumorigenesis and progression of BC. Moreover, we discovered that EIF4A3 facilitated circBRWD3 expression by targeting the upstream of BRWD3 pre-mRNA. In conclusion, our study reveals that circBRWD3 facilitates BC tumorigenesis by regulating the circBRWD3/miR-142-3p_miR-142-5p /RAC1/PAK1 axis. In addition, circBRWD3 expression is positively regulated by an RNA-binding protein, EIFA3. Our results provide valuable scientific data for early diagnosis and therapy for breast cancer patients.

eIF3j inhibits translation of a subset of circular RNAs in eukaryotic cells

Increasing studies have revealed that a subset of circular RNAs (circRNAs) harbor an open reading frame and can act as protein-coding templates to generate functional proteins that are closely associated with multiple physiological and disease-relevant processes, and thus proper regulation of synthesis of these circRNA-derived proteins is a fundamental cellular process required for homeostasis maintenance. However, how circRNA translation initiation is coordinated by different trans-acting factors remains poorly understood. In particular, the impact of different eukaryotic translation initiation factors (eIFs) on circRNA translation and the physiological relevance of this distinct regulation have not yet been characterized. In this study, we screened all 43 Drosophila eIFs and revealed the conflicting functions of eIF3 subunits in the translational control of the translatable circRNA circSfl: eIF3 is indispensable for circSfl translation, while the eIF3-associated factor eIF3j is the most potent inhibitor. Mechanistically, the binding of eIF3j to circSfl promotes the disassociation of eIF3. The C-terminus of eIF3j and an RNA regulon within the circSfl untranslated region (UTR) are essential for the inhibitory effect of eIF3j. Moreover, we revealed the physiological relevance of eIF3j-mediated circSfl translation repression in response to heat shock. Finally, additional translatable circRNAs were identified to be similarly regulated in an eIF3j-dependent manner. Altogether, our study provides a significant insight into the field of cap-independent translational regulation and undiscovered functions of eIF3.

Spliceosomal profiling identifies EIF4A3 as a novel oncogene in hepatocellular carcinoma acting through the modulation of FGFR4 splicing

INTRODUCTION

Altered splicing landscape is an emerging cancer hallmark; however, the dysregulation and implication of the cellular machinery controlling this process (spliceosome components and splicing factors) in hepatocellular carcinoma (HCC) is poorly known. This study aimed to comprehensively characterize the spliceosomal profile and explore its role in HCC.

METHODS

Expression levels of 70 selected spliceosome components and splicing factors and clinical implications were evaluated in two retrospective and six in silico HCC cohorts. Functional, molecular and mechanistic studies were implemented in three cell lines (HepG2, Hep3B and SNU-387) and preclinical Hep3B-induced xenograft tumours.

RESULTS

Spliceosomal dysregulations were consistently found in retrospective and in silico cohorts. EIF4A3, RBM3, ESRP2 and SRPK1 were the most dysregulated spliceosome elements in HCC. EIF4A3 expression was associated with decreased survival and greater recurrence. Plasma EIF4A3 levels were significantly elevated in HCC patients. In vitro EIF4A3-silencing (or pharmacological inhibition) resulted in reduced aggressiveness, and hindered xenograft-tumours growth in vivo, whereas EIF4A3 overexpression increased tumour aggressiveness. EIF4A3-silencing altered the expression and splicing of key HCC-related genes, specially FGFR4. EIF4A3-silencing blocked the cellular response to the natural ligand of FGFR4, FGF19. Functional consequences of EIF4A3-silencing were mediated by FGFR4 splicing as the restoration of non-spliced FGFR4 full-length version blunted these effects, and FGFR4 inhibition did not exert further effects in EIF4A3-silenced cells.

CONCLUSIONS

Splicing machinery is strongly dysregulated in HCC, providing a source of new diagnostic, prognostic and therapeutic options in HCC. EIF4A3 is consistently elevated in HCC patients and associated with tumour aggressiveness and mortality, through the modulation of FGFR4 splicing.

A review on the role of cyclin dependent kinases in cancers

The Cyclin-dependent kinase (CDK) class of serine/threonine kinases has crucial roles in the regulation of cell cycle transition and is mainly involved in the pathogenesis of cancers. The expression of CDKs is controlled by a complex regulatory network comprised of genetic and epigenetic mechanisms, which are dysregulated during the progression of cancer. The abnormal activation of CDKs results in uncontrolled cancer cell proliferation and the induction of cancer stem cell characteristics. The levels of CDKs can be utilized to predict the prognosis and treatment response of cancer patients, and further understanding of the function and underlying mechanisms of CDKs in human tumors would pave the way for future cancer therapies that effectively target CDKs. Defects in the regulation of cell cycle and mutations in the genes coding cell-cycle regulatory proteins lead to unrestrained proliferation of cells leading to formation of tumors. A number of treatment modalities have been designed to combat dysregulation of cell cycle through affecting expression or activity of CDKs. However, effective application of these methods in the clinical settings requires recognition of the role of CDKs in the progression of each type of cancer, their partners, their interactions with signaling pathways and the effects of suppression of these kinases on malignant features. Thus, we designed this literature search to summarize these findings at cellular level, as well as in vivo and clinical levels.