Splicing factor derived circular RNA circCAMSAP1 accelerates nasopharyngeal carcinoma tumorigenesis via a SERPINH1/c-Myc positive feedback loop

Exploring the oncogenic potential of circSOD2 in clear cell renal cell carcinoma: a novel positive feedback loop

BACKGROUND

Existing studies have found that circular RNAs (circRNAs) act as sponges for micro RNAs (miRNAs) to control downstream genes. However, the specific functionalities and mechanisms of circRNAs in human clear cell renal cell carcinoma (ccRCC) have yet to be thoroughly investigated.

METHODS

Patient cohorts from online databases were used to screen candidate circRNAs, while another cohort from our hospital was obtained for validation. CircSOD2 was identified as a potential oncogenic target, and its relevant characteristics were investigated during ccRCC progression through various assays. A positive feedback loop containing downstream miRNA and its target gene were identified using bioinformatics and validated by luciferase reporter assays, RNA pull-down, and high-throughput sequencing.

RESULTS

CircSOD2 expression was elevated in tumor samples and significantly correlated with overall survival (OS) and the tumor stage of ccRCC patients, which appeared in the enhanced proliferation, invasion, and migration of tumor cells. Through competitive binding to circSOD2, miR-532-3p can promote the expression of PAX5 and the progression of ccRCC, and such regulation can be salvaged by miR-532-3p inhibitor.

CONCLUSION

A novel positive feedback loop, PAX5/circSOD2/miR-532-3p/PAX5 was identified in the study, indicating that the loop may play an important role in the diagnosis and prognostic prediction in ccRCC patients.

Prospects for the clinical application of exosomal circular RNA in squamous cell carcinoma

Squamous cell carcinoma (SCC) is a prevalent malignancy affecting multiple organs in the human body, including the oral cavity, esophagus, cervix, and skin. Given its significant incidence and mortality rates, researchers are actively seeking effective diagnostic and therapeutic strategies. In recent years, exosomes and their molecular cargo, particularly circular RNA (circRNA), have emerged as promising areas of investigation in SCC research. Exosomes are small vesicles released into the extracellular environment by cells that contain biomolecules that reflect the physiological state of the cell of origin. CircRNAs, known for their unique covalently closed loop structure and stability, have garnered special attention in oncology and are closely associated with tumorigenesis, progression, metastasis, and drug resistance. Interestingly, exosomal circRNAs have been identified as ideal biomarkers for noninvasive cancer diagnosis and prognosis assessment. This article reviews the progress in research on exosomal circRNAs, focusing on their expression patterns, functions, and potential applications as biomarkers in SCC, aiming to provide new insights and strategies for the diagnosis and treatment of SCC.

Anti-pancreatic cancer activity of cassane diterpenoids isolated from the seeds of Caesalpinia sappan mediated by autophagy activation via ROS/AMPK/mTORC1 pathway

Three undescribed cassane diterpenoids, caesalpanins D-F (1-3), and seven known ones were isolated from the seeds of Caesalpinia sappan. Structures and absolute configurations of 1-3 were elucidated based on the extensive spectroscopic analysis, single-crystal X-ray diffraction analysis, and ECD calculations. Structurally, compound 1 was the first example of 18-norcassane diterpenoid and 2 was a rare 20-norcassane diterpenoid having an unusual five-membered oxygen bridge between C-10/C-18. The anti-proliferative activity of 1, 3, and 4-10 against PANC-1 cells (pancreatic ductal adenocarcinoma cell line) was evaluated, and phanginin H (4) was found to exhibit anti-cancer activity with IC50 value of 18.13 ± 0.63 μM. Compound 4 inhibited PANC-1 cell growth by arresting the cell cycle at G2/M phase via regulation of cyclin-dependent kinases, and the self-renewal and metastasis of PANC-1 cells by suppressing cancer cell stemness. Furthermore, compound 4 induced ROS generation and subsequently activated autophagy, which was demonstrated by the formation of autophagic vacuoles and dynamic change of autophagic flux. The induced ROS accumulation resulted in AMPK activation and subsequently regulation of mTORC1 activity and ULK phosphorylation, indicating that 4 triggered autophagy through ROS/AMPK/mTORC1 pathway. These findings suggested that 4 might potentially be an autophagy inducer for the therapy of pancreatic cancer.

Circular RNAs in Cell Cycle Regulation of Cancers

Cancer has been one of the most problematic health issues globally. Typically, all cancers share a common characteristic or cancer hallmark, such as sustaining cell proliferation, evading growth suppressors, and enabling replicative immortality. Indeed, cell cycle regulation in cancer is often found to be dysregulated, leading to an increase in aggressiveness. These dysregulations are partly due to the aberrant cellular signaling pathway. In recent years, circular RNAs (circRNAs) have been widely studied and classified as one of the regulators in various cancers. Numerous studies have reported that circRNAs antagonize or promote cancer progression through the modulation of cell cycle regulators or their associated signaling pathways, directly or indirectly. Mostly, circRNAs are known to act as microRNA (miRNA) sponges. However, they also hold additional mechanisms for regulating cellular activity, including protein binding, RNA-binding protein (RBP) recruitment, and protein translation. This review will discuss the current knowledge of how circRNAs regulate cell cycle-related proteins through the abovementioned mechanisms in different cancers.

SERPINH1 promoted the proliferation and metastasis of colorectal cancer by activating PI3K/Akt/mTOR signaling pathway

BACKGROUND

Serpin peptidase inhibitor clade H member 1 (SERPINH1) was initially recognized as an oncogene implicated in various human malignancies. Nevertheless, the clinical relevance and functional implications of SERPINH1 in colorectal cancer (CRC) remain largely elusive.

AIM

To investigate the effects of SERPINH1 on CRC cells and its specific mechanism.

METHODS

Quantitative real-time polymerase chain reaction, western blotting analysis, The Cancer Genome Atlas data mining and immunohistochemistry were employed to examine SERPINH1 expression in CRC cell lines and tissues. A series of in-vitro assays were performed to demonstrate the function of SERPINH1 and its possible mechanisms in CRC.

RESULTS

SERPINH1 demonstrated elevated expression levels in both CRC cells and tissues, manifested at both mRNA and protein tiers. Elevated SERPINH1 levels correlated closely with advanced T stage, lymph node involvement, and distant metastasis, exhibiting a significant association with poorer overall survival among CRC patients. Subsequent investigations unveiled that SERPINH1 overexpression notably bolstered CRC cell proliferation, invasion, and migration in vitro, while conversely, SERPINH1 knockdown elicited the opposite effects. Gene set enrichment analysis underscored a correlation between SERPINH1 upregulation and genes associated with cell cycle regulation. Our findings underscored the capacity of heightened SERPINH1 levels to expedite G1/S phase cell cycle progression via phosphatidylinositol 3-kinase/AKT/mechanistic target of rapamycin pathway activation, thereby facilitating CRC cell invasion and migration.

CONCLUSION

These findings imply a crucial involvement of SERPINH1 in the advancement and escalation of CRC, potentially positioning it as a novel candidate for prognostic assessment and therapeutic intervention in CRC management.

Emerging roles of circular RNAs in nasopharyngeal carcinoma: functions and implications

Nasopharyngeal carcinoma (NPC) is a distinct malignancy primarily prevalent in Southern China and Southeast Asia. Circular RNAs (circRNAs), a class of non-coding RNAs, are evolutionarily conserved and exhibit remarkable stability. Their dysregulation has been observed in various cancers, including NPC. In this review, we investigate the pivotal role of circRNAs in NPC, focusing specifically on their involvement in tumor proliferation, apoptosis, metastasis, angiogenesis, stemness, metabolism, and the tumor microenvironment. We highlight the diagnostic and prognostic potential of circRNAs in NPC, emphasizing their utility as biomarkers for early detection, disease monitoring, and prediction of treatment outcomes. Additionally, we explore the therapeutic implications of circRNAs in NPC, highlighting their potential for targeted therapies.

CircCDYL2 bolsters radiotherapy resistance in nasopharyngeal carcinoma by promoting RAD51 translation initiation for enhanced homologous recombination repair

BACKGROUND

Radiation therapy stands to be one of the primary approaches in the clinical treatment of malignant tumors. Nasopharyngeal Carcinoma, a malignancy predominantly treated with radiation therapy, provides an invaluable model for investigating the mechanisms underlying radiation therapy resistance in cancer. While some reports have suggested the involvement of circRNAs in modulating resistance to radiation therapy, the underpinning mechanisms remain unclear.

METHODS

RT-qPCR and in situ hybridization were used to detect the expression level of circCDYL2 in nasopharyngeal carcinoma tissue samples. The effect of circCDYL2 on radiotherapy resistance in nasopharyngeal carcinoma was demonstrated by in vitro and in vivo functional experiments. The HR-GFP reporter assay determined that circCDYL2 affected homologous recombination repair. RNA pull down, RIP, western blotting, IF, and polysome profiling assays were used to verify that circCDYL2 promoted the translation of RAD51 by binding to EIF3D protein.

RESULTS

We have identified circCDYL2 as highly expressed in nasopharyngeal carcinoma tissues, and it was closely associated with poor prognosis. In vitro and in vivo experiments demonstrate that circCDYL2 plays a pivotal role in promoting radiotherapy resistance in nasopharyngeal carcinoma. Our investigation unveils a specific mechanism by which circCDYL2, acting as a scaffold molecule, recruits eukaryotic translation initiation factor 3 subunit D protein (EIF3D) to the 5'-UTR of RAD51 mRNA, a crucial component of the DNA damage repair pathway to facilitate the initiation of RAD51 translation and enhance homologous recombination repair capability, and ultimately leads to radiotherapy resistance in nasopharyngeal carcinoma.

CONCLUSIONS

These findings establish a novel role of the circCDYL2/EIF3D/RAD51 axis in nasopharyngeal carcinoma radiotherapy resistance. Our work not only sheds light on the underlying molecular mechanism but also highlights the potential of circCDYL2 as a therapeutic sensitization target and a promising prognostic molecular marker for nasopharyngeal carcinoma.

CircBRD7 attenuates tumor growth and metastasis in nasopharyngeal carcinoma via epigenetic activation of its host gene

BRD7 was identified as a tumor suppressor in nasopharyngeal carcinoma (NPC). Circular RNAs (CircRNAs) are involved in the occurrence and development of NPC as oncogenes or tumor suppressors. However, the function and mechanism of the circular RNA forms derived from BRD7 in NPC are not well understood. In this study, we first identified that circBRD7 was a novel circRNA derived from BRD7 that inhibited cell proliferation, migration, invasion of NPC cells, as well as the xenograft tumor growth and metastasis in vivo. Mechanistically, circBRD7 promoted the transcriptional activation and expression of BRD7 by enhancing the enrichment of histone 3 lysine 27 acetylation (H3K27ac) in the promoter region of its host gene BRD7, and BRD7 promoted the formation of circBRD7. Therefore, circBRD7 formed a positive feedback loop with BRD7 to inhibit NPC development and progression. Moreover, restoration of BRD7 expression rescued the inhibitory effect of circBRD7 on the malignant progression of NPC. In addition, circBRD7 demonstrated low expression in NPC tissues, which was positively correlated with BRD7 expression and negatively correlated with the clinical stage of NPC patients. Taken together, circBRD7 attenuates the tumor growth and metastasis of NPC by forming a positive feedback loop with its host gene BRD7, and targeting the circBRD7/BRD7 axis is a promising strategy for the clinical diagnosis and treatment of NPC.

Hsa_circ_0001479 accelerates tumorigenesis of gastric cancer and mediates immune escape

Gastric cancer (GC) is a common fatal malignant tumor of the digestive tract, particularly in Asia. Circular RNA (circRNA) has been proved to regulate malignancy progression and immunotherapeutic efficacy in multiple tumors, including GC. Notably, the function of circRNAs in GC has not been completely revealed. Therefore, exploration of more GC related circRNAs may provide potential strategies for GC treatment. In the study, it was observed that hsa_circ_0001479 exhibited a high level of expression in GC and was subsequently found to be associated with the depth of invasion, lymph node metastasis, and TNM stage. Functionally, the overexpression of hsa_circ_0001479 was found to enhance the proliferation and migration of GC cells, as evidenced by various experiments such as CCK-8, EdU, colony forming and transwell. Dual-luciferase reporter assay verified that hsa_circ_0001479 upregulated DEK expression by sponge targeting miR-133a-5p. Further investigations indicated DEK affected the entry of β-catenin into the nucleus by activating Wnt/β-catenin signaling pathway to promote accumulation of downstream c-Myc. As a transcription factor, c-Myc combined with the promoter of hsa_circ_0001479 parent gene to stimulate hsa_circ_0001479 generation. Besides, hsa_circ_0001479 inhibited theinfiltration with CD8+T cells in GC and associated with immune checkpoints. In summary, hsa_circ_0001479 accelerated the development and metastasis of GC and mediates immune escape of CD8+T cells. Targeting it may provide a novel immunotherapy to better locally treat GC and reduce the incidence of metastases.

Spatial Profiling of Circular RNAs in Cancer Reveals High Expression in Muscle and Stromal Cells

Circular RNAs (circRNA) are covalently closed molecules that can play important roles in cancer development and progression. Hundreds of differentially expressed circRNAs between tumors and adjacent normal tissues have been identified in studies using RNA sequencing or microarrays, emphasizing a strong translational potential. Most previous studies have been performed using RNA from bulk tissues and lack information on the spatial expression patterns of circRNAs. Here, we showed that the majority of differentially expressed circRNAs from bulk tissue analyses of colon tumors relative to adjacent normal tissues were surprisingly not differentially expressed when comparing cancer cells directly with normal epithelial cells. Manipulating the proliferation rates of cells grown in culture revealed that these discrepancies were explained by circRNAs accumulating to high levels in quiescent muscle cells due to their high stability; on the contrary, circRNAs were diluted to low levels in the fast-proliferating cancer cells due to their slow biogenesis rates. Thus, different subcompartments of colon tumors and adjacent normal tissues exhibited striking differences in circRNA expression patterns. Likewise, the high circRNA content in muscle cells was also a strong confounding factor in bulk analyses of circRNAs in bladder and prostate cancers. Together, these findings emphasize the limitations of using bulk tissues for studying differential circRNA expression in cancer and highlight a particular need for spatial analysis in this field of research.

SIGNIFICANCE

The abundance of circRNAs varies systematically between subcompartments of solid tumors and adjacent tissues, implying that differentially expressed circRNAs discovered in bulk tissue analyses may reflect differences in cell type composition between samples.

RNA modifications in cancer

Currently, more than 170 modifications have been identified on RNA. Among these RNA modifications, various methylations account for two-thirds of total cases and exist on almost all RNAs. Roles of RNA modifications in cancer are garnering increasing interest. The research on m6A RNA methylation in cancer is in full swing at present. However, there are still many other popular RNA modifications involved in the regulation of gene expression post-transcriptionally besides m6A RNA methylation. In this review, we focus on several important RNA modifications including m1A, m5C, m7G, 2'-O-Me, Ψ and A-to-I editing in cancer, which will provide a new perspective on tumourigenesis by peeking into the complex regulatory network of epigenetic RNA modifications, transcript processing, and protein translation.

METTL3-Modulated circUHRF2 Promotes Colorectal Cancer Stemness and Metastasis through Increasing DDX27 mRNA Stability by Recruiting IGF2BP1

Increasing evidence has implicated that circular RNAs (circRNAs) exert important roles in colorectal cancer (CRC) occurrence and progression. However, the role of a novel circRNA, circUHRF2, remains unknown in CRC. Our work aimed at identifying the functional roles of circUHRF2 in CRC and illustrating the potential mechanisms. As assessed by quantitative real-time PCR (qRT-PCR), circUHRF2 and methyltransferase-like 3 (METTL3) were highly expressed in CRC specimens and cells. Sanger sequencing and RNase R assays were performed to verify the ring structure of circUHRF2. Notably, aberrantly increased expression of circUHRF2 was positively correlated with poor prognosis of CRC patients. Functional experiments indicated that CRC stemness, migration, and epithelial-mesenchymal transition (EMT) were suppressed by the knockdown of circUHRF2 or METTL3. Mechanistically, METTL3 enhanced circUHRF2 expression through N6-methyladenine (m⁶A) modification. Rescue experiments showed that overexpression of circUHRF2 reversed the repressive effect of METTL3 silencing on CRC progression. Moreover, circUHRF2 inhibited the loss of DEAD-box helicase 27 (DDX27) protein via promoting the interaction between insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) and DDX27 mRNA. DDX27 knockdown repressed CRC malignant properties, which was counteracted by circUHRF2 overexpression. The in vivo assays in nude mice demonstrated that circUHRF2 or METTL3 silencing exerted a suppressive effect on CRC growth and liver metastasis via repressing DDX27 protein expression. Taken together, METTL3-mediated m⁶A modification upregulated circUHRF2 and subsequently inhibited loss of DDX27 protein via recruitment of IGF2BP1, which conferred CRC stemness and metastasis. These findings shed light on CRC pathogenesis and suggest circUHRF2 as a novel target for CRC treatment.

Over-expression of hsa_circ_0088214 suppresses tumor progression by inhibiting Akt signaling pathway in osteosarcoma

BACKGROUND

To explore the effect of has_circ_0088214 in osteosarcoma cells and corresponding mechanisms.

METHODS

Osteosarcoma cell line MG63 and U2OS were selected in this study. Wound-healing and matrigel transwell assays were performed to detect migration and invasion capacities. CCK-8 assay was used to measure cell growth and cisplatin resistance. Cell apoptosis was observed by Hoechst 33342 staining after H₂O₂ induce. Western Blot was used to detect protein expression level. The rescue experiments were also performed using an Akt activator SC79.

RESULTS

Hsa_circ_0088214 was down-regulated in osteosarcoma cells compared to normal osteoblast cells. Over-expression of has_circ_0088214 significantly reduced osteosarcoma cells invasion, migration and resistance to cisplatin, but the apoptotic ratio was increased. The phosphorylation level of Akt could be regulated by hsa_circ_0088214, and rescue experiments proved Akt signaling pathway took part in above biological processes.

CONCLUSION

Up-regulation of hsa_circ_0088214 suppresses invasion, migration, cisplatin resistance but promoting apoptosis induced by H₂O₂ by inhibiting Akt signaling pathway in osteosarcoma.

Heat shock factor 5 establishes the male germ-line meiotic sex chromosome inactivation through regulation of Smarca4

Meiotic sex chromosome inactivation is an essential event in male germ cell development, which is directed by DNA damage response signaling independent of Xist RNA to silence the transcription activity of the sex chromosomes. However, the specific mechanism of establishment and maintenance of meiotic chromosome silencing is still unclear. Here we identify the HSF5 as a testicular specific protein and the expression of which was at the onset of meiosis pachytene stage to round sperm. When the function of the HSF5 was lost, meiosis sex chromosome remodeling and silencing fail, followed by activation of CHK2 checkpoint leads to germ cell apoptosis. Furthermore, we found that SMARCA4 in the linking the HSF5 to MSCI and uncover additional factors with meiotic sex chromosome remodeling. Together, our results demonstrate a requirement for HSF5 activity in spermatogenesis and suggest a role for the mammalian HSF5-SMARCA4 in programmed meiotic sex chromosome remodeling and silencing events that take place during meiosis.

Application prospect of circular RNA-based neoantigen vaccine in tumor immunotherapy

Neoantigen is a protein produced by mutant gene, which is only expressed in tumor cells. It is an ideal target for therapeutic tumor vaccines. Although synthetic long peptide (SLP)-based neoantigen vaccine, DNA-based neoantigen vaccine, and mRNA-based neoantigen vaccine are all in the development stage, they have some inherent shortcomings. Therefore, researchers turned their attention to a new type of "non-coding RNA (ncRNA)", circular RNA (circRNA), for potential better choice. Because of its unique high stability and protein-coding capacity, circRNA is a promising target in the field of neoantigen vaccine. In this paper, we reviewed the feasibility of circRNA encoding neoantigens, summarized the construction process, explained the mechanism of circRNA vaccine in vitro, and discussed the advantages and disadvantages of circRNA vaccine and possible combination with other immunotherapies.

Genome-wide analysis of circular RNA-mediated ceRNA regulation in porcine skeletal muscle development

BACKGROUND

As a diverse and abundant class of endogenous RNAs, circular RNAs (circRNAs) participate in various biological processes including cell proliferation and apoptosis. Nevertheless, few researchers have investigated the role of circRNAs in muscle development in cultivated pigs.

RESULTS

In this study, we used RNA-seq to construct circRNA expression profiles in skeletal muscle of Jinfen White pigs at the age of 1, 90, and 180 days. Among the 16,990 identified circRNAs, 584 circRNAs were differentially expressed. Moreover, the enrichment analysis of DE circRNA host genes showed that they were mainly involved in muscle contraction, muscle organ development and muscle system processes, as well as AMPK and cAMP-related signal pathways. We also constructed a circRNA-miRNA-mRNA co-expression network to find key circRNAs which many involved in the regulation of porcine skeletal muscle development through the competitive endogenous RNA (ceRNA) mechanism. It is noteworthy that circ_0018595/miR-1343/PGM1 axis may play a regulatory role in the development of porcine skeletal muscle.

CONCLUSIONS

This study identified the circRNAs and present the circRNA expression profile in the development of pigs, revealed that DE circRNA host genes participate in different cell fates and enriched the porcine ceRNA network. Thus, this work will become a valuable resource for further in-depth study of the regulatory mechanism of circRNA in the development of porcine skeletal muscle.

By using machine learning and in vitro testing, SERPINH1 functions as a novel tumorigenic and immunogenic gene and predicts immunotherapy response in osteosarcoma

Introduction

The most prevalent bone tumor with a relatively high level of aggressiveness and malignancy is osteosarcoma. The characteristics of the serpin family in osteosarcoma have not been defined.

Methods

In this study, the predictive significance of the serpin superfamily was investigated in the osteosarcoma and Gene Expression Omnibus (GEO) databases from The Cancer Genome Atlas (TCGA).

Results

It was discovered that SERPINH1 is a significant biological marker in osteosarcoma. According to the CCK-8, EdU, and Transwell assays as well as the IHC assay, SERPINH1 may promote osteosarcoma proliferation and migration. It is also more expressed in tumor samples than in healthy samples. SERPINH1 might forecast the effects of immunotherapy. Additionally, immune cells are interacted with through checkpoint, cytokine, and growth factor pathways in osteosarcomas with high SERPINH1 levels. The biological function, immunological characteristics, and treatment response (immunotherapy and chemotherapy responses) of patients with osteosarcoma were successfully predicted using a model related to SERPINH1. SERPINH1 and the SERPINH1-related score predict ferroptosis/pyroptosis/apoptosis/necroptosis in osteosarcoma.

Discussion

The SERPINH1-related score was an effective method for identifying osteosarcoma patients who would respond to immunotherapy and chemotherapy, as well as for predicting the survival outcomes of such patients.

hsa_circ_0136839 regulates the malignant phenotypes of nasopharyngeal carcinoma via the Wnt/β-catenin signaling pathway

With the development of RNA sequencing (RNA-seq) technology, circular RNA (circRNA), a new class of RNA, has received much attention in cancer research. However, information available on the biogenesis and functional value of circRNAs in nasopharyngeal carcinoma (NPC) is scarce. In the present study, we screened the circRNA profile of the NPC cell line C666-1 compared with that of the normal control NP69 by RNA-seq and identified a novel and relatively higher expressed circRNA, hsa_circ_0136839. Hsa_circ_0136839 was markedly downregulated in NPC tissues, as confirmed by quantitative reverse transcription polymerase chain reaction. Functional in vitro studies revealed that hsa_circ_0136839 knockdown in C666-1 cell notably promoted cell proliferation, migration, and invasion abilities, as well as affected cell cycle distribution with an S-phase arrest. However, hsa_circ_0136839 overexpression in CNE2 cells resulted in an opposite response. Mechanistically, we demonstrated that aberrant hsa_circ_0136839 expression might affect the malignant phenotypes of NPC cells by activating the wnt/β-catenin signaling pathway. Thus, our findings contribute to further the understanding of NPC pathogenesis and provide new ideas for NPC clinical diagnosis and treatment.

Research on liquid biopsy for cancer: A bibliometric analysis

BACKGROUND

In recent years, liquid biopsy has shown great potential for improving cancer diagnosis and treatment. This study aimed to explore the trends and prospects in liquid biopsy for cancer from a bibliometric perspective.

METHODS

Reviews and articles on liquid biopsy and cancer were collected from the Web of Science Core Collection (WoSCC). Key bibliometric characteristics were analyzed using CiteSpace. Co-occurrence analysis of keywords and co-citation analysis of references was performed.

RESULTS

A total of 6331 publications from 11 years of scientific research were retrieved. Ninety-five countries and 7004 institutions in liquid biopsy and cancer contributed. The United States (US) and China published the most articles. The institution with the most published articles was the University of Texas MD Anderson Cancer Center. The most published journals were Cancer and Frontiers in Oncology. "Bettegowda (2014)" was the most cited reference with the highest burst strength in the last decade. Cluster analysis revealed that the recent hot topics were "circulating tumor cells," "cancer," and "exosomes."

CONCLUSIONS

This bibliometric analysis maps the basic knowledge structure of the field of liquid biopsy for cancer. The field is entering a phase of rapid development. The hot spots identified in this study deserve further investigation.

CircOMA1 modulates cabergoline resistance by downregulating ferroptosis in prolactinoma

PURPOSE

Prolactinomas are one of the most common pituitary neuroendocrine tumors (PitNETs), accounting for approximately 50% of all pituitary tumors. Dopamine agonists are the main treatment for prolactinoma, but a small number of patients are still resistant to pharmacotherapy. Recent discoveries have revealed that ferroptosis is involved in regulating tumor drug resistance. However, the role of ferroptosis in prolactinoma has not been reported. In this study, we aimed to explore the mechanism of a circRNA in ferroptosis in prolactinoma.

METHODS

The expression of circOMA1 in prolactinoma tissues was examined by quantitative reverse transcription PCR (qRT-PCR). The biological function of circOMA1 was evaluated in vitro and in vivo. To explore the role of ferroptosis in prolactinoma, we used qRT-PCR and western blotting. Glutamate-cysteine ligase, modifier subunit (GCLM) was predicted to be a direct target gene of miR-145-5p by bioinformatics analysis, which was confirmed by luciferase reporter assays.

RESULTS

circOMA1 was overexpressed in drug-resistant prolactinoma tissues compared with sensitive prolactinoma samples. We further found that circOMA1 promoted MMQ cells growth in vivo and in vitro. In addition, GCLM was directly targeted by miR-145-5p and indirectly regulated by circOMA1. Importantly, circOMA1 induced ferroptosis resistance through the increased expression of Nrf2, GPX4, and xCT, and circOMA1 attenuated CAB-induced ferroptosis in MMQ cells in vivo and in vitro.

CONCLUSION

The present study demonstrates that circOMA1 attenuates CAB efficacy through ferroptosis resistance and may be a new therapeutic target for the individualized treatment of DA-resistant prolactinoma patients.

The regulatory role of alternative splicing in inflammatory bowel disease

Inflammatory bowel disease (IBD) mainly includes Crohn's disease and ulcerative colitis. These diseases have a progressive course of chronic relapse and remission and affect a large number of children and adults worldwide. The burden of IBD is rising worldwide, with levels and trends varying greatly in countries and regions. Like most chronic diseases, the costs associated with IBD are high, including hospitalizations, outpatient and emergency visits, surgeries, and pharmacotherapies. However, there is no radical cure for it yet, and its therapeutic targets still need further study. Currently, the pathogenesis of IBD remains unclear. It is generally assumed that the occurrence and development of IBD are related to the environmental factors, gut microbiota, immune imbalance, and genetic susceptibility. Alternative splicing contributes to a various diseases, such as spinal muscular atrophy, liver diseases, and cancers. In the past, it has been reported that alternative splicing events, splicing factors, and splicing mutations were associated with IBD, but there were no reports on the practical application for clinical diagnosis and treatment of IBD using splicing-related methods. Therefore, this article reviews research progress on alternative splicing events, splicing factors, and splicing mutations associated with IBD.

Circular RNAs: Emerging regulators of glucose metabolism in cancer

Aberrant glucose metabolism is one of the most striking characteristics of metabolic reprogramming in cancer. Thus, clarifying the regulatory mechanism of glucose metabolism is crucial to understanding tumor progression and developing novel therapeutic strategies for cancer patients. Recent developments in circular RNAs have explained the regulatory mechanism of glucose metabolism from a new dimension. In this review, we briefly summarize the recent advances in circRNA research on cancer glucose metabolism and emphasize the different regulatory mechanisms, including acting as miRNA sponges, interacting with proteins and being translated into proteins. Additionally, we discuss the future research directions of circular RNAs in the field of glucose metabolism.

SRSF10 stabilizes CDC25A by triggering exon 6 skipping to promote hepatocarcinogenesis

BACKGROUND

Alternative splicing (AS) events are extensively involved in the progression of diverse tumors, but how serine/arginine-rich splicing Factor 10 (SRSF10) behaves in hepatocellular carcinoma (HCC) has not been sufficiently studied. We aimed to determine SRSF10 associated AS mechanisms and their effects on HCC progression.

METHODS

The expression of SRSF10 in HCC tissues was examined, and the in vitro and in vivo functions of SRSF10 were investigated. The downstream AS targets were screened using RNA sequencing. The interaction between SRSF10 protein and exclusion of cell division cycle 25 A (CDC25A) mRNA was identified using RNA immunoprecipitation and crosslinking immunoprecipitation q-PCR. The effects of SRSF10 on CDC25A posttranslational modification, subcellular distribution, and protein stability were verified through coimmunoprecipitation, immunofluorescence, and western blotting.

RESULTS

SRSF10 was enriched in HCC tissues and facilitated HCC proliferation, cell cycle, and invasion. RNA sequencing showed that SRSF10 promotes exon 6 exclusion of CDC25A pre-mRNA splicing. As a crucial cell cycle mediator, the exon-skipped isoform CDC25A(△E6) was identified to be stabilized and retained in the nucleus due to the deletion of two ubiquitination (Lys150, Lys169) sites in exon 6. The stabilized isoform CDC25A(△E6) derived from AS had stronger cell cycle effects on HCC tumorigenesis, and playing a more significant role than the commonly expressed longer variant CDC25A(L). Interestingly, SRSF10 activated the carcinogenesis role of CDC25A through Ser178 dephosphorylation to cause nuclear retention. Moreover, CDC25A(△E6) was verified to be indispensable for SRSF10 to promote HCC development in vitro and in vivo.

CONCLUSIONS

We reveal a regulatory pattern whereby SRSF10 contributes to a large proportion of stabilized CDC25A(△E6) production, which is indispensable for SRSF10 to promote HCC development. Our findings uncover AS mechanisms such as CDC25A that might serve as potential therapeutic targets to treat HCC.

Functions and clinical significance of circular RNAs in acute myeloid leukemia

Circular RNAs (circRNAs) are a class of covalently closed single-stranded RNA molecules. Four types of circRNAs have been reported in animal cells, and they have typical characteristics in their biogenesis, nuclear export and degradation. Advances in our understanding of the molecular functions of circRNAs in sponging microRNAs, modulating transcription, regulating RNA-binding proteins, as well as encoding proteins have been made very recently. Dysregulated circRNAs are associated with human diseases such as acute myeloid leukemia (AML). In this review, we focus on the recently described mechanisms, role and clinical significance of circRNAs in AML. Although great progress of circRNAs in AML has been achieved, substantial efforts are still required to explore whether circRNAs exert their biological function by other mechanisms such as regulation of gene transcription or serving as translation template in AML. It is also urgent that researchers study the machineries regulating circRNAs fate, the downstream effectors of circRNAs modulatory networks, and the clinical application of circRNAs in AML.

Myc-mediated circular RNA circMcph1/miR-370-3p/Irak2 axis is a progressive regulator in hepatic fibrosis

AIMS

Treating hepatic fibrosis (HF) is a major challenge worldwide. However, the biological functions and regulatory mechanisms of circular RNAs (circRNAs) remain unclear in HF. The present study aimed to elucidate the novel role of circMcph1 in HF.

MAIN METHODS

HF mouse model was established by injecting CCl₄ intraperitoneally and validated using hematoxylin and eosin staining, immunohistochemistry, and serological tests in vivo. RAW264.7 cells were treated with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) in vitro inflammatory damage model. Gel electrophoresis, DNA sequencing, RNase R and actinomycin D treatment, random 6 primers and oligo dT primers assay, nuclear and cytoplasmic fractionation assay, and fluorescence in situ hybridization were performed to identify the characteristics of circMcph1. Functional assays such as ELISA, flow cytometry, and adeno-associated virus administration in vivo and liposome delivery gene therapy in vitro were used to determine the functional effects of circMcph1/miR-370-3p/interleukin-1 receptor-associated kinase 2 (Irak2) axis. Mechanistic assays such as luciferase reporter analysis, and chromatin immunoprecipitation revealed the molecular mechanism of the Myc/circMcph1/miR-370-3p/Irak2 axis in HF.

KEY FINDINGS

CircMcph1 expression was upregulated in liver tissues and primary Kupffer cells of CCl₄-induced HF mice, as well as in LPS and IFN-γ-treated RAW264.7 cells. Knockdown of circMcph1 ameliorated liver fibrogenesis and inflammatory damage in HF mice and reduced the inflammatory response in LPS and IFN-γ-treated RAW264.7 cells. Mechanically, circMcph1 mediated by Myc regulated the expression of Irak2 by sponging miR-370-3p in HF.

SIGNIFICANCE

The study findings suggested that the Myc/circMcph1/miR-370-3p/Irak2 axis might be a novel identifier and therapeutic target for HF.

CircRNAs: Roles in regulating head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC), the most common head and neck malignant tumor, with only monotherapy, is characterized by poor prognosis, and low 5-year survival rate. Due to the lack of therapeutic targets, the targeted drugs for HNSCC are rare. Therefore, exploring the regulation mechanism of HNSCC and identifying effective therapeutic targets will be beneficial to its treatment of. Circular RNA (CircRNA) is a class of RNA molecules with a circular structure, which is widely expressed in human body. CircRNAs regulate gene expression by exerting the function as a miRNA sponge, thereby mediating the occurrence and development of HNSCC cell proliferation, apoptosis, migration, invasion, and other processes. In addition, circRNAs are also involved in the regulation of tumor sensitivity to chemical drugs and other biological functions. In this review, we systematically listed the functions of circRNAs and explored the regulatory mechanisms of circRNAs in HNSCC from the aspects of tumor growth, cell death, angiogenesis, tumor invasion and metastasis, tumor stem cell regulation, tumor drug resistance, immune escape, and tumor microenvironment. It will assist us in discovering new diagnostic markers and therapeutic targets, while encourage new ideas for the diagnosis and treatment of HNSCC.

circRAB3IP modulates cell proliferation by reorganizing gene expression and mRNA processing in a paracrine manner

Circular RNAs are an endogenous long-lived and abundant noncoding species. Despite their prevalence, only a few circRNAs have been dissected mechanistically to date. Here, we cataloged nascent RNA-enriched circRNAs from primary human cells and functionally assigned a role to circRAB3IP in sustaining cellular homeostasis. We combined "omics" and functional experiments to show how circRAB3IP depletion deregulates hundreds of genes, suppresses cell cycle progression, and induces senescence-associated gene expression changes. Conversely, excess circRAB3IP delivered to endothelial cells via extracellular vesicles suffices for accelerating their division. We attribute these effects to an interplay between circRAB3IP and the general splicing factor SF3B1, which can affect transcript variant expression levels of cell cycle-related genes. Together, our findings link the maintenance of cell homeostasis to the presence of a single circRNA.

Circular RNA circPVT1 promotes nasopharyngeal carcinoma metastasis via the β-TrCP/c-Myc/SRSF1 positive feedback loop

Background

Circular RNAs (circRNAs) act as gene expression regulators and are involved in cancer progression. However, their functions have not been sufficiently investigated in nasopharyngeal carcinoma (NPC).

Methods

The expression profiles of circRNAs in NPC cells within different metastatic potential were reanalyzed. Quantitative reverse transcription PCR and in situ hybridization were used to detect the expression level of circPVT1 in NPC cells and tissue samples. The association of expression level of circPVT1 with clinical properties of NPC patients was evaluated. Then, the effects of circPVT1 expression on NPC metastasis were investigated by in vitro and in vivo functional experiments. RNA immunoprecipitation, pull-down assay and western blotting were performed to confirm the interaction between circPVT1 and β-TrCP in NPC cells. Co-immunoprecipitation and western blotting were performed to confirm the interaction between β-TrCP and c-Myc in NPC cells.

Results

We find that circPVT1, a circular RNA, is significantly upregulated in NPC cells and tissue specimens. In vitro and in vivo experiments showed that circPVT1 promotes the invasion and metastasis of NPC cells. Mechanistically, circPVT1 inhibits proteasomal degradation of c-Myc by binding to β-TrCP, an E3 ubiquiting ligase. Stablization of c-Myc by circPVT1 alters the cytoskeleton remodeling and cell adhesion in NPC, which ultimately promotes the invasion and metastasis of NPC cells. Furthermore, c-Myc transcriptionally upregulates the expression of SRSF1, an RNA splicing factor, and recruits SRSF1 to enhance the biosynthesis of circPVT1 through coupling transcription with splicing, which forms a positive feedback for circPVT1 production.

Conclusions

Our results revealed the important role of circPVT1 in the progression of NPC through the β-TrCP/c-Myc/SRSF1 positive feedback loop, and circPVT1 may serve as a prognostic biomarker or therapeutic target in patients with NPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01659-w.

Prognostic and immunological role of SERPINH1 in pan-cancer

Background: The SERPINH1 gene plays a vital part in tumorigenesis and development, whereas its potential as an immunotherapy target is still unknown. Hence, this research aimed to probe the roles of SERPINH1 in human tumors.

Method: Using The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx) database, Oncomine, and SangerBox software, the pan-cancer expression of SERPINH1 and its correlation were systematically analyzed. SERPINH1 protein information was detected by the Human Protein Atlas (HPA) database and STRING database. The genomic alterations of SERPINH1 were studied using the c-BioPortal database. The influence of SERPINH1 on prognosis was analyzed using Kaplan–Meier plotter. The R package “clusterProfiler” was used for enrichment analysis to detect the role of SERPINH1. The TIMER2 database was used to further analyze the correlation between the immune cell infiltration score of TCGA samples and the expression of SERPINH1.

Results: SERPINH1 overexpression was related to worse survival status in pan-cancer. In addition, high expression of SERPINH1 was positively associated with tumor stage and poor prognosis. Moreover, SERPINH1 played an important role in tumor microenvironment and immune regulation. Our study revealed that SERPINH1 expression has a strong correlation with immune cell filtration, immune regulation, chemokines, and immune checkpoints.

Conclusion: Our research found that SERPINH1 was a risk factor and predictor of poor prognosis in various tumors. High expression of SERPINH1 may contribute to tumor immune-suppressive status. Also, SERPINH1 may become a potential immunotherapy target in pan-cancer.

Circular RNA circCCNB1 inhibits the migration and invasion of nasopharyngeal carcinoma through binding and stabilizing TJP1 mRNA

Nasopharyngeal carcinoma (NPC) is a malignant tumor that usually occurs in people from Southeast Asia and Southern China. NPC is prone to migration and invasion, leading to poor prognosis. A large number of circular RNAs (circRNAs) exacerbate the process of metastasis in NPC; however, their underlying mechanisms remain unclear. We found that the circular RNA circCCNB1, encoded by the oncogene CCNB1, was downregulated in NPC biopsies and cell lines. In vitro assays show that circCCNB1 inhibits NPC cell migration and invasion. Moreover, circCCNB1 induces a protein, nuclear factor 90 (NF90), to bind and prolong the half-life of tight junction protein 1 (TJP1) mRNA. Upregulation of TJP1 enhances tight junctions between cancer cells and inhibits NPC cell migration and invasion. This study reveals a novel biological function of circCCNB1 in the migration and invasion of NPC by enhancing the tight junctions of cancer cells by binding to NF90 proteins and TJP1 mRNA, and may provide a potential therapeutic target for NPC.