The Emerging Role of Circ-SHPRH in Cancer

The Role of the Dysregulation of circRNAs Expression in Glioblastoma Multiforme

Primary brain tumors that were the most severe and aggressive were called glioblastoma multiforme (GBM). Cancers are caused in part by aberrant expression of circular RNA. Often referred to as competitive endogenous RNA (ceRNA), circRNA molecules act as "miRNA sponges" in cells by decreasing the inhibitory impact of miRNA on their target genes and hence raising the expression levels of those genes. circRNA molecules are rich in miRNA binding sites. The discovery of more structurally diverse and GBM-related circRNAs has great promise for the use of GMB prognostic biomarkers and therapeutic targets, as well as for comprehending the molecular regulatory mechanisms of GBM. In this work, we present an overview of the circRNA expression patterns associated with GBM and offer a potential integrated electrochemical strategy for detecting circRNA with extreme sensitivity in the diagnosis of glioblastoma.

Translation of circular RNAs

Circular RNAs (circRNAs) are covalently closed RNAs that are present in all eukaryotes tested. Recent RNA sequencing (RNA-seq) analyses indicate that although generally less abundant than messenger RNAs (mRNAs), over 1.8 million circRNA isoforms exist in humans, much more than the number of currently known mRNA isoforms. Most circRNAs are generated through backsplicing that depends on pre-mRNA structures, which are influenced by intronic elements, for example, primate-specific Alu elements, leading to species-specific circRNAs. CircRNAs are mostly cytosolic, stable and some were shown to influence cells by sequestering miRNAs and RNA-binding proteins. We review the increasing evidence that circRNAs are translated into proteins using several cap-independent translational mechanisms, that include internal ribosomal entry sites, N6-methyladenosine RNA modification, adenosine to inosine RNA editing and interaction with the eIF4A3 component of the exon junction complex. CircRNAs are translated under conditions that favor cap-independent translation, notably in cancer and generate proteins that are shorter than mRNA-encoded proteins, which can acquire new functions relevant in diseases.

circ-ZEB1 Enhances NSCLC Metastasis and Proliferation by Modulating the miR-491-5p/EIF5A Axis

Background: Circular RNAs (circRNAs), covalently closed single-stranded RNAs, have been implicated in cancer progression. A previous investigation revealed that circ-ZEB1 is expressed abnormally in liver cancer. However, the roles of circ-ZEB1 in non-small cell lung cancer (NSCLC) are unknown. Methods: In this study, we used fluorescence in situ hybridization (FISH) and RT-qPCR to study circ-ZEB1 expression in NSCLC cells and tissues. A luciferase reporter assay was performed to validate downstream targets of circ-ZEB1. Transwell migration, 5-ethynyl-20-deoxyuridine (EdU), and cell counting kit-8 (CCK8) assays were performed to assess proliferation and migration. In vivo metastasis and tumorigenesis assays were also performed to investigate circ-ZEB1 functions during NSCLC. Results: Our results showed that circ-ZEB1 expression was increased in NSCLC tissues and cells. circ-ZEB1 downregulation suppressed NSCLC cell proliferation as well as migration in vitro and in vivo. Luciferase data confirmed EIF5A and miR-491-5p as downstream targets of circ-ZEB1. EIF5A overexpression and miR-491-5p suppression reversed NSCLC cell migration post circ-ZEB1 silencing. Conclusion: Our collective findings advised that circ-ZEB1 takes part in the malignant progression through regulating the miR-491-5p/EIF5A axis, highlighting its potential as an effective NSCLC therapeutic target.

Circular RNAs in cancer: roles, mechanisms, and therapeutic potential across colorectal, gastric, liver, and lung carcinomas

The prominence of circular RNAs (circRNAs) has surged in cancer research due to their distinctive properties and impact on cancer development. This review delves into the role of circRNAs in four key cancer types: colorectal cancer (CRC), gastric cancer (GC), liver cancer (HCC), and lung cancer (LUAD). The focus lies on their potential as cancer biomarkers and drug targets. Our study analyses the reported circRNAs in the mentioned malignancies, examining their nature, functions, targets, origins, and contributions as tumor enhancers or suppressors. The approach involved assessing full-text reports on PMC, utilizing keywords such as "CircRNA" and "Cancer types," coupled with bioinformatics, experimental assays, or clinical investigations. Exclusions encompassed non-English publications, conference abstracts, letters, and expert opinions. The findings unveil 577 identified circRNAs across these cancer types: 124 in CRC, 177 in GC, 93 in HCC, and 183 in LUAD. Mechanistic insights into how circRNAs modulate gene expression in cancer are explored, particularly their interactions with microRNAs and RNA-binding proteins. Dysregulation of circRNAs across various cancers and their potential as diagnostic and prognostic indicators are synthesized. The exploration extends to the potential of targeting circRNAs as a novel cancer therapy strategy, either through inhibiting oncogenic circRNAs or reinstating tumor-suppressive ones. This article discusses the challenges and prospects in harnessing circRNAs for cancer diagnostics and therapies. These comprehensive analyses hold promise for advancing cancer research and fostering the development of innovative therapies and diagnostics.

Therapeutic SHPRH-146aa encoded by circ-SHPRH dynamically upregulates P21 to inhibit CDKs in neuroblastoma

Recent research has underscored the significance of circular RNAs (circRNAs) in various cancers, including neuroblastoma (NB). Specifically, circ-SHPRH, a unique circRNA, has been revealed to inhibit tumor growth by sequestering miRNAs or producing the SHPRH-146aa protein. To explore circ-SHPRH's involvement in NB and its potential application in gene therapy, this study examined circ-SHPRH expression in 94 NB tissues and cell lines (SK-N-BE(2), SH-SY5Y) using real-time PCR and fluorescence in situ hybridization (FISH). Functional assays encompassing both overexpression and knockdown experiments in NB cell lines, as well as in vivo investigations, were conducted. RNA-seq analysis revealed a correlation between circ-SHPRH and the pathway of P21 (CDKN1A), a pivotal cell cycle regulator. Validation through PCR and other techniques confirmed that circ-SHPRH upregulated P21 expression. Furthermore, the regulatory role of circ-SHPRH in the P21-CDK pathway was corroborated through SHPRH-146aa expression analysis. Notably, adenovirus-mediated circ-SHPRH overexpression effectively curbed NB tumor growth in NSG mice, while combining circ-SHPRH with everolimus exhibited potential for NB treatment. This study elucidates the remarkable significance of circ-SHPRH in NB and its prospective utility in gene therapy, thereby paving the way for innovative therapeutic approaches.

EIF4A3-induced hsa_circ_0078136 inhibits the tumorigenesis of retinoblastoma via IL-17 signaling pathway

PURPOSE

Retinoblastoma (RB) is one of the most common intraocular cancers, with the highest prevalence among infants and young children under the age five. Numerous findings across the literature illustrate the involvement and significance of circular RNAs (circRNAs) in human malignancies, including RB. The current investigation attempted to decipher the exact roles and underlying mechanisms of a novel circRNA, hsa_circ_0078136, in RB progression.

METHODS

The hsa_circ_0078136 expression was evaluated in RB tumors and cell lines via qRT-PCR. The significance of hsa_circ_0078136 in RB was examined by performing CCK8 assay, transwell assays, western blotting of apoptotic and IL-17 signaling ligand molecules, and a subcutaneous xenograft tumor model. In addition, the interaction of circRNA and eukaryotic translation initiation factor 4A3 (EIF4A3) was determined with bioinformatics, western blot, and RIP assay.

RESULTS

The hsa_circ_0078136 expression was reduced in RB tumor samples and cells. Additionally, its overexpression restricted the oncogenic properties of RB cells in vitro. Moreover, hsa_circ_0078136 overexpression lowered the protein levels of cytokine ligand molecules of IL-17 signaling pathway in RB cell lines. In vivo, hsa_circ_0078136 overexpression in subcutaneous tumor xenografts reduced tumor growth. We also observed that EIF4A3 binds to the downstream flanking sequence of hsa_circ_0078136 in the SHRPH pre-mRNA transcript, and EIF4A3 overexpression reduced hsa_circ_0078136 expression, suggesting that EIF4A3 inhibited hsa_circ_0078136 formation.

CONCLUSIONS

Our results demonstrate that hsa_circ_0078136 is regulated by EIF4A3 and functions as a tumor suppressor via the IL-17 signaling pathway in RB.

Integrative genomics identifies SHPRH as a tumor suppressor gene in lung adenocarcinoma that regulates DNA damage response

BACKGROUND

Identification of driver mutations and development of targeted therapies has considerably improved outcomes for lung cancer patients. However, significant limitations remain with the lack of identified drivers in a large subset of patients. Here, we aimed to assess the genomic landscape of lung adenocarcinomas (LUADs) from individuals without a history of tobacco use to reveal new genetic drivers of lung cancer.

METHODS

Integrative genomic analyses combining whole-exome sequencing, copy number, and mutational information for 83 LUAD tumors was performed and validated using external datasets to identify genetic variants with a predicted functional consequence and assess association with clinical outcomes. LUAD cell lines with alteration of identified candidates were used to functionally characterize tumor suppressive potential using a conditional expression system both in vitro and in vivo.

RESULTS

We identified 21 genes with evidence of positive selection, including 12 novel candidates that have yet to be characterized in LUAD. In particular, SNF2 Histone Linker PHD RING Helicase (SHPRH) was identified due to its frequency of biallelic disruption and location within the familial susceptibility locus on chromosome arm 6q. We found that low SHPRH mRNA expression is associated with poor survival outcomes in LUAD patients. Furthermore, we showed that re-expression of SHPRH in LUAD cell lines with inactivating alterations for SHPRH reduces their in vitro colony formation and tumor burden in vivo. Finally, we explored the biological pathways associated SHPRH inactivation and found an association with the tolerance of LUAD cells to DNA damage.

CONCLUSIONS

These data suggest that SHPRH is a tumor suppressor gene in LUAD, whereby its expression is associated with more favorable patient outcomes, reduced tumor and mutational burden, and may serve as a predictor of response to DNA damage. Thus, further exploration into the role of SHPRH in LUAD development may make it a valuable biomarker for predicting LUAD risk and prognosis.

Protein-coding circular RNAs - mechanism, detection, and their role in cancer and neurodegenerative diseases

Circular RNAs (circRNAs) are a unique class of non-coding RNAs and were originally thought to have no protein-coding potential due to their lack of a 5' cap and 3' poly(A) tail. However, recent studies have challenged this notion and revealed that some circRNAs have protein-coding potential. They have emerged as a key area of interest in cancer and neurodegeneration research as recent studies have identified several circRNAs that can produce functional proteins with important roles in cancer progression. The protein-coding potential of circRNAs is determined by the presence of an open reading frame (ORF) within the circular structure that can encode a protein. In some cases, the ORF can be translated into a functional protein despite the lack of traditional mRNA features. While the protein-coding potential of most circRNAs remains unclear, several studies have identified specific circRNAs that can produce functional proteins. Understanding the protein-coding potential of circRNAs is important for unravelling their biological functions and potential roles in disease. Our review provides comprehensive coverage of recent advances in the field of circRNA protein-coding capacity and its impact on cancer and neurodegenerative diseases pathogenesis and progression.