The Emerging Roles of circFOXO3 in Cancer

CircRNAs: Pivotal modulators of TGF-β signalling in cancer pathogenesis

The intricate molecular landscape of cancer pathogenesis continues to captivate researchers worldwide, with Circular RNAs (circRNAs) emerging as pivotal players in the dynamic regulation of biological functions. The study investigates the elusive link between circRNAs and the Transforming Growth Factor-β (TGF-β) signalling pathway, exploring their collective influence on cancer progression and metastasis. Our comprehensive investigation begins by profiling circRNA expression patterns in diverse cancer types, revealing a repertoire of circRNAs intricately linked to the TGF-β pathway. Through integrated bioinformatics analyses and functional experiments, we elucidate the specific circRNA-mRNA interactions that modulate TGF-β signalling, unveiling the regulatory controls governing this crucial pathway. Furthermore, we provide compelling evidence of the impact of circRNA-mediated TGF-β modulation on key cellular processes, including epithelial-mesenchymal transition (EMT), migration, and cell proliferation. In addition to their mechanistic roles, circRNAs have shown promise as diagnostic and prognostic biomarkers, as well as potential molecular targets for cancer therapy. Their ability to modulate critical pathways, such as the TGF-β signalling axis, underscores their significance in cancer biology and clinical applications. The intricate interplay between circRNAs and TGF-β is dissected, uncovering novel regulatory circuits that contribute to the complexity of cancer biology. This review unravels a previously unexplored dimension of carcinogenesis, emphasizing the crucial role of circRNAs in shaping the TGF-β signalling landscape.

Noncoding RNAs and programmed cell death in hepatocellular carcinoma: Significant role of epigenetic modifications in prognosis, chemoresistance, and tumor recurrence rate

Hepatocellular carcinoma (HCC) is the most common type of liver cancer with a high death rate in the world. The molecular mechanisms related to the pathogenesis of HCC have not been precisely defined so far. Hence, this review aimed to address the potential cross-talk between noncoding RNAs (ncRNAs) and programmed cell death in HCC. All related papers in the English language up to June 2023 were collected and screened. The searched keywords in scientific databases, including Scopus, PubMed, and Google Scholar, were HCC, ncRNAs, Epigenetic, Programmed cell death, Autophagy, Apoptosis, Ferroptosis, Chemoresistance, Tumor recurrence, Prognosis, and Prediction. According to the reports, ncRNAs, comprising long ncRNAs, microRNAs, circular RNAs, and small nucleolar RNAs can affect cell proliferation, migration, invasion, and metastasis, as well as cell death-related processes, such as autophagy, ferroptosis, necroptosis, and apoptosis in HCC by regulating cancer-associated genes and signaling pathways, for example, phosphoinositide 3-kinase/Akt, extracellular signal-regulated kinase/MAPK, and Wnt/β-catenin signaling pathways. It seems that ncRNAs, as epigenetic regulators, can be utilized as biomarkers in diagnosis, prognosis, survival and recurrence rates prediction, chemoresistance, and evaluation of therapeutic response in HCC patients. However, more scientific evidence is suggested to be accomplished to confirm these results.

Circ-FOXO3 inhibits triple-negative breast cancer growth and metastasis via regulating WHSC1-H3K36me2-Zeb2 axis

Circular RNAs (circRNAs), a subclass of non-coding RNAs characterized by covalently closed continuous loops, play a key role in tumorigenesis and aggressiveness. However, the potential molecular mechanism of circRNAs in triple-negative breast cancer (TNBC) remains largely unknown. Exploring their roles and mechanisms in TNBC progression may help identify new diagnostic markers and therapeutic targets. In this study, we found that circ-FOXO3 was dramatically downregulated in TNBC tissues and blood samples from patients with TNBC. Notably, low circ-FOXO3 expression in TNBC tissues and bloods was associated with lymph node metastasis and unfavorable outcomes in patients with TNBC. Overexpression of circ-FOXO3 significantly inhibited the growth, invasion, and metastasis of TNBC cells both in vitro and in vivo. Moreover, we demonstrated that circ-FOXO3 was predominantly expressed in the cytoplasm and directly interacted with Wolf-Hirschhorn syndrome candidate 1 (WHSC1), thereby inhibiting WHSC1 nuclear localization and activity, resulting in the inhibition of H3K36me2 modifications at the Zeb2 promoter, ultimately inhibiting Zeb2 expression and halting TNBC growth and metastasis. Taken together, these results reveal the tumor-suppressive functions of circ-FOXO3 in inhibiting WHSC1-mediated H3K36me2 modification of Zeb2, suggesting that circ-FOXO3 could serve as a potential novel predictive prognostic biomarker and therapeutic target for TNBC.

CircFOXO3 mediates hypoxia-induced autophagy of endometrial stromal cells in endometriosis

Endometriosis is a benign gynecological disease that shares some common features of malignancy. Autophagy plays vital roles in endometriosis and influences endometrial cell metastasis, and hypoxia was identified as the initiator of this pathological process through hypoxia inducible factor 1 alpha (HIF-1α). A newly discovered circular RNA FOXO3 (circFOXO3) is critical in cell autophagy, migration, and invasion of various diseases and is reported to be related to hypoxia, although its role in endometriosis remains to be elucidated up to now. In this study, a lower circFOXO3 expression in ectopic endometrium was investigated. Furthermore, we verified that circFOXO3 could regulate autophagy by downregulating the level of p53 protein to mediate the migration and invasion of human endometrial stromal cells (T HESCs). Additionally, the effects of HIF-1α on circFOXO3 and autophagy were examined in T HESCs. Notably, overexpression of HIF-1α could induce autophagy and inhibit circFOXO3 expression, whereas overexpressing of circFOXO3 under hypoxia significantly inhibited hypoxia-induced autophagy. Mechanistically, the direct combination between HIF-1α and HIF-1α-binding site on adenosine deaminase 1 acting on RNA (ADAR1) promoter increased the level of ADAR1 protein, which bind directly with circFOXO3 pre-mRNA to block the cyclization of circFOXO3. All these results support that hypoxia-mediated ADAR1 elevation inhibited the expression of circFOXO3, and then autophagy was induced upon loss of circFOXO3 via inhibition of p53 degradation, participating in the development of endometriosis.

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.

SEL1L3 as a link molecular between renal cell carcinoma and atherosclerosis based on bioinformatics analysis and experimental verification

BACKGROUND

Renal cancer, the most common type of kidney cancer, develops in the renal tubular epithelium. Atherosclerosis of the aorta is the primary cause of atherosclerosis. However, the underlying mechanisms remain unclear.

METHODS

The renal clear cell carcinoma RNA sequence profile was obtained from The Cancer Genome Atlas (TCGA) database, and the atherosclerosis datasets GSE28829 and GSE43292 based on GPL570 and GPL6244 was obtained from the Gene Expression Omnibus (GEO) database. The difference and hub genes were identified by the Limma protein-protein interaction (PPI) network in R software. Functional enrichment, survival, and immunoinfiltration analyses were performed. The role of SEL1L3 in the ErbB/PI3K/mTOR signaling pathway, apoptosis, invasion, cell cycle, and inflammation was analyzed using western blotting.

RESULTS

764 DEGs were identified from TCGA Kidney Renal Clear Cell Carcinoma (KIRC) dataset. A total of 344 and 117 DEGs were screened from the GSE14762 and GSE53757 datasets, respectively. Functional enrichment analysis results primarily indicated enrichment in the transporter complex, DNA-binding transcription activator activity, morphogenesis of the embryonic epithelium, stem cell proliferation, adrenal overactivity and so on. Fifteen common DEGs overlapped among the three datasets. The PPI network revealed that SEL1L3 was the core gene. Survival analysis showed that lower SEL1L3 expression levels led to a worse prognosis. Immune cell infiltration analysis showed that SEL1L3 expression was significantly correlated with antibody-drug conjugates (aDC), B cells, eosinophils, interstitial dendritic cells (iDC), macrophages, and more.

CONCLUSIONS

SEL1L3 plays an important role in renal clear cell carcinoma and atherosclerosis and may be a potential link between them.

Circular RNA CCT3 is a unique molecular marker in bladder cancer

This study surveyed circular RNA CCT3 in bladder cancer (BCa). We recruited 85 BCa patients and 40 normal controls (Normal) and collected clinical specimens for analysis. circRNA CCT3 expression was analyzed by RT-qPCR, diagnostic accuracy was calculated by ROC curves, and survival outcomes were evaluated by survival curves. CircRNA CCT3 was overexpressed or knocked down in cells, thereafter to observe the changes in cell malignant phenotypes. The downstream molecules of circRNA CCT3 were detected. Our data suggest that circRNA CCT3 was upregulated in human BCa and was associated with poor survival outcomes of BCa patients. In cell experiments, overexpressing circRNA CCT3 promoted BCa cell malignancy, whereas silencing circRNA CCT3 did the opposite. In addition, circRNA CCT3 modulated PP2A expression by miR-135a-5p. This study demonstrates that circRNA CCT3 is a diagnostic and prognostic biomarker in BCa patients and is a tumor promoter in BCa.

Role of circ-FOXO3 and miR-23a in radiosensitivity of breast cancer

Identifying the radiosensitivity of cells before radiotherapy (RT) in breast cancer (BC) patients allows appropriate switching between routinely used treatment regimens and reduces adverse side effects in exposed patients. In this study, blood was collected from 60 women diagnosed with Invasive Ductal Carcinoma (IDC) BC and 20 healthy women. To predict cellular radiosensitivity, a standard G2-chromosomal assay was performed. From these 60 samples, 20 BC patients were found to be radiosensitive based on the G2 assay. Therefore, molecular studies were finally performed on two equal groups (20 samples each) of patients with and without cellular radiosensitivity. QPCR was performed to examine the expression levels of circ-FOXO3 and miR-23a in peripheral blood mononuclear cells (PBMCs) and RNA sensitivity and specificity were determined by plotting Receiver Operating Characteristic (ROC) curves. Binary logistic regression was performed to identify RNA involvement in BC and cellular radiosensitivity (CR) in BC patients. Meanwhile, qPCR was used to compare differential RNA expression in the radiosensitive MCF-7 and radioresistant MDA-MB-231 cell lines. An annexin -V FITC/PI binding assay was used to measure cell apoptosis 24 and 48 h after 2 Gy, 4 Gy, and 8 Gy gamma-irradiation. Results indicated that circ-FOXO3 was downregulated and miR-23a was upregulated in BC patients. RNA expression levels were directly associated with CR. Cell line results showed that circ-FOXO3 overexpression induced apoptosis in the MCF-7 cell line and miR-23a overexpression inhibited apoptosis in the MDA-MB-231 cell line. Evaluation of the ROC curves revealed that both RNAs had acceptable specificity and sensitivity in predicting CR in BC patients. Binary logistic regression showed that both RNAs were also successful in predicting breast cancer. Although only circ-FOXO3 has been shown to predict CR in BC patients, circ-FOXO3 may function as a tumor suppressor and miR-23a may function as oncomiR in BC. Circ-FOXO3 and miR-23a may be promising potential biomarkers for BC prediction. Furthermore, Circ-FOXO3 could be a potential biomarker for predicting CR in BC patients.

CircFOXP1 alleviates brain injury after acute ischemic stroke by regulating STAT3/apoptotic signaling

According to previous studies, circular RNAs (circRNAs) are involved in multiple pathological processes of acute ischemic stroke (AIS). However, the relationship between circFOXP1 and IS has not yet been reported. Here, we found that circFOXP1 expression was significantly decreased in the peripheral blood of AIS patients compared to controls and was associated with the severity and prognosis of AIS. Functionally, knockdown and overexpression of circFOXP1 promoted and inhibited apoptotic signaling, respectively, following oxygen-glucose deprivation/reperfusion (OGD/R) treatment in vitro. Adeno-associated virus (AAV)-mediated circFOXP1 overexpression attenuated neurological deficits and improved functional recovery after transient middle cerebral artery occlusion (tMCAO) treatment in vivo. Mechanistically, decreased QKI expression inhibited circFOXP1 biogenesis under hypoxic conditions. Decreased circFOXP1 expression accelerated signal transducer and activator of transcription 3 (STAT3) protein degradation by binding to and increasing STAT3 protein ubiquitination, ultimately aggravating brain injury after cerebral ischemia by activating apoptotic signaling. In summary, our study is the first to reveal that circFOXP1 alleviates brain injury after cerebral ischemia by regulating STAT3/apoptotic signaling, which provides a potentially novel therapeutic target for AIS.

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

CircRNA circ_0006156 inhibits the metastasis of prostate cancer by blocking the ubiquitination of S100A9

Circular RNAs (circRNAs) have been demonstrated to play vital roles in cancer development and progression. However, studies on the association between circRNAs and prostate cancer (PCa) are still lacking. CircRNA sequencing of two pairs of PCa tissues and adjacent normal tissues was conducted in the present study, and qRT-PCR was performed to verify the results. Functional experiments were performed to investigate cellular functions after specific changes. Mass spectrometry analysis after RNA pull-down experiments and Co-IP assays were further conducted. Downstream target proteins were predicted via online databases and detected in vitro by Western blot analysis and in vivo by immunohistochemistry. Hsa_circ_0006156 (subsequently named circ_0006156) expresses at low levels in both PCa tissues and cells, and it significantly inhibits the migration and invasion of PCa cells. Circ_0006156 binds to and blocks the ubiquitination of S100A9. Moreover, functional assays revealed that circ_0006156 represses the malignant progression of PCa by binding to S100A9. Finally, in vivo experiments showed that circ_0006156 suppresses PCa migration and invasion by increasing S100A9, revealing circ_0006156 as a potential novel effective target for PCa treatment.

Direct Interaction of miRNA and circRNA with the Oncosuppressor p53: An Intriguing Perspective in Cancer Research

Simple Summary

MicroRNAs and circular RNAs, which are single-stranded non-coding RNAs, play a key role as regulators at post-transcriptional level. Abnormal levels or dysregulation of miRNA or circRNA are linked to several cancerous pathologies. Starting from the evidence that some miRNAs and circRNAs are involved in the regulatory networks of the tumor suppressor protein p53, the possibility that a functional inhibition of p53 could arise from a direct interaction between p53 and oncogenic miRNAs or circRNAs was explored. Along this direction, the experimental evidence of the interaction between p53 and miRNAs and/or circRNAs is reviewed and discussed in connection with the development of new anticancer strategies.

Abstract

MicroRNAs (miRNAs) are linear single-stranded non-coding RNAs oligonucleotides, widely distributed in cells, playing a key role as regulators of gene expression at post-transcriptional level. Circular RNAs (circRNAs) are single-stranded RNA oligonucleotides forming a covalently closed continuous loop, which confers them a high structural stability and which may code for proteins or act as gene regulators. Abnormal levels or dysregulation of miRNA or circRNA are linked to several cancerous pathologies, so that they are receiving a large attention as diagnostic and prognostic tools. Some miRNAs and circRNAs are strongly involved in the regulatory networks of the transcription factor p53, which plays a pivotal role as tumor suppressor. Overexpression of miRNAs and/or circRNAs, as registered in a number of cancers, is associated to a concomitant inhibition of the p53 onco-suppressive function. Among other mechanisms, it was recently suggested that a functional inhibition of p53 could arise from a direct interaction between p53 and oncogenic miRNAs or circRNAs; a mechanism that might be reminiscent of the p53 inhibition by some E3 ubiquitin ligase such as MDM2 and COP1. Such evidence might deserve important implications for restoring the p53 anticancer functionality, and pave the way to intriguing perspectives for novel therapeutic strategies. In the present paper, the experimental evidence of the interaction between p53 and miRNAs and/or circRNAs is reviewed and discussed in connection with the development of new anticancer approaches.