circRNA_100859 functions as an oncogene in colon cancer by sponging the miR-217-HIF-1α pathway

Hsa_circ_0101050 accelerates the progression of Colon cancer by targeting the miR-140-3 p/MELK axis

BACKGROUND

Circular RNAs (circRNAs) are involved in the progression of colon cancer (CC). This study aimed to examine the role of a new circRNA circ_0101050 in CC.

METHODS

Dual-luciferase reporter and RNA immunoprecipitation analyses were performed to validate the target relationships among maternal embryonic leucine zipper kinase (MELK), microRNA (miR)-140-3 p, and circ_0101050. Expression levels were calculated using western blotting and/or quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Western blotting was performed to evaluate the relative expression of Bcl-2 and Bax proteins to determine cell death. Cell Counting Kit-8 (CCK-8) and colony formation assays were performed to determine the proliferative potential of CC cells. The migration rate of CC cells was evaluated using wound healing assays. Tumor formation tests were performed to determine the effect of circ_0101050 on tumor development in vivo.

RESULTS

Elevated levels of circ_0101050 and MELK were observed in CC. By inhibiting circ 0,101,050 or MELK, CC cell proliferation and migration were inhibited, but CC cell apoptosis was promoted. Silencing circ_0101050 also inhibited CC growth in vivo. We also found that miR-140-3 p was downregulated, which alleviated the repressive effects of circ_0101050 knockdown on proliferating and migrating CC cells, as well as the stimulating effect on apoptosis. In addition, the absence of MELK alleviated the effects of miR-140-3 p downregulation, which enhanced CC cell malignancy.

CONCLUSIONS

Circ_0101050 exacerbates malignant phenotypes in CC by targeting the miR-140-3 p/MELK axis. These findings suggested that the circ_0101050/miR-140-3 p/MELK network may be a prospective target for CC treatment.

Diagnostic value of urine cyclic RNA-0071196 for bladder urothelial carcinoma

OBJECTIVE

To investigate the diagnostic value of urine cyclic RNA-0071196 (circRNA-0071196) in the patients with bladder urothelial carcinoma (BUC).

METHOD

The expression of circRNA-0071196 was detected in the urine samples using qRT-PCR from 40 BUC patients and 30 non-UBC patients at our department from December 2018 to September 2021. The expression difference of circRNA-0071196 was compared between the two groups, and the relationship between the expression of circRNA-0071196 in the urine of UBC patients and the clinical pathological characteristics was analyzed.

RESULTS

(1) The expression of circRNA-0071196 in the urine of BUC group was significantly higher than that in the non-BUC group (P < 0.05). (2) The expression of circRNA-0071196 in the urine of BUC group was not related to age, sex, or lymph node metastasis (P > 0.05). (3) The expression of circRNA-0071196 in the urine of BUC group was related to tumor T stage, tumor grade and muscle invasion. (4) The urine circRNA-0071196 expression effectively distinguished BUC patients from non-BUC patients.

CONCLUSION

The elevated expression of urine circRNA-0071196 in BUC patients indicates that circRNA-0071196 has promising potential as a non-invasive urinary biomarker for detecting BUC.

The strict regulation of HIF-1α by non-coding RNAs: new insight towards proliferation, metastasis, and therapeutic resistance strategies

The hypoxic environment is prominently witnessed in most solid tumors and is associated with the promotion of cell proliferation, epithelial-mesenchymal transition (EMT), angiogenesis, metabolic reprogramming, therapeutic resistance, and metastasis of tumor cells. All the effects are mediated by the expression of a transcription factor hypoxia-inducible factor-1α (HIF-1α). HIF-1α transcriptionally modulates the expression of genes responsible for all the aforementioned functions. The stability of HIF-1α is regulated by many proteins and non-coding RNAs (ncRNAs). In this article, we have critically discussed the crucial role of ncRNAs [such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), Piwi-interacting RNAs (piRNAs), and transfer RNA (tRNA)-derived small RNAs (tsRNAs)] in the regulation of stability and expression of HIF-1α. We have comprehensively discussed the molecular mechanisms and relationship of HIF-1α with each type of ncRNA in either promotion or repression of human cancers and therapeutic resistance. We have also elaborated on ncRNAs that are in clinical examination for the treatment of cancers. Overall, the majority of aspects concerning the relationship between HIF-1α and ncRNAs have been discussed in this article.

Hsa_circ_0092856 Promoted the Proliferation, Migration, and Invasion of NSCLC Cells by Up-Regulating the Expression of eIF3a

Circular RNA (circRNA) plays a very important regulatory role in a variety of human malignancies such as non-small-cell lung cancer (NSCLC). In the current study, we explored the role of hsa_circ_0092856 in the progression of NSCLC. We screened CircRNA from the eIF3a gene in the Circbase database. The biological functions of hsa_circ_0092856 in NSCLC were analyzed via qRT-PCR, a CCK-8 assay, a plate cloning experiment, scratch testing, a transwell chamber experiment, an RNA nuclear mass separation experiment, an RIP experiment, and a Western blot test. The results showed that hsa_circ_0092856 was highly expressed in NSCLC cells, and the knockdown of hsa_circ_0092856 could inhibit the proliferation, migration, and invasion of NSCLC cells. The overexpression of hsa_circ_0092856 has the opposite effect. The expression of eIF3a also changed with the change in hsa_circ_0092856. These results suggest that hsa_circ_0092856 may play a key role in the progression of NSCLC by regulating the expression of eIF3a.

Regulation of the HIF switch in human endothelial and cancer cells

Hypoxia-inducible factors (HIFs) are transcription factors that reprogram the transcriptome for cells to survive hypoxic insults and oxidative stress. They are important during embryonic development and reprogram the cells to utilize glycolysis when the oxygen levels are extremely low. This metabolic change facilitates normal cell survival as well as cancer cell survival. The key feature in survival is the transition between acute hypoxia and chronic hypoxia, and this is regulated by the transition between HIF-1 expression and HIF-2/HIF-3 expression. This transition is observed in many human cancers and endothelial cells and referred to as the HIF Switch. Here we discuss the mechanisms involved in the HIF Switch in human endothelial and cancer cells which include mRNA and protein levels of the alpha chains of the HIFs. A major continuing effort in this field is directed towards determining the differences between normal and tumor cell utilization of this important pathway, and how this could lead to potential therapeutic approaches.

Noncoding RNAs as regulators of STAT3 pathway in gastrointestinal cancers: Roles in cancer progression and therapeutic response

Gastrointestinal (GI) tumors (cancers of the esophagus, gastric, liver, pancreas, colon, and rectum) contribute to a large number of deaths worldwide. STAT3 is an oncogenic transcription factor that promotes the transcription of genes associated with proliferation, antiapoptosis, survival, and metastasis. STAT3 is overactivated in many human malignancies including GI tumors which accelerates tumor progression, metastasis, and drug resistance. Research in recent years demonstrated that noncoding RNAs (ncRNAs) play a major role in the regulation of many signaling pathways including the STAT3 pathway. The major types of endogenous ncRNAs that are being extensively studied in oncology are microRNAs, long noncoding RNAs, and circular RNAs. These ncRNAs can either be tumor-promoters or tumor-suppressors and each one of them imparts their activity via different mechanisms. The STAT3 pathway is also tightly modulated by ncRNAs. In this article, we have elaborated on the tumor-promoting role of STAT3 signaling in GI tumors. Subsequently, we have comprehensively discussed the oncogenic as well as tumor suppressor functions and mechanism of action of ncRNAs that are known to modulate STAT3 signaling in GI cancers.

Highlighting functions of apoptosis and circular RNAs in colorectal cancer

Colorectal cancer (CRC) is known as one of the global problems that endangers the lives of thousands of people every year. Various treatments have been used to deal with this disease, but in some cases, they are not effective. Circular RNAs, as a novel class of noncoding RNAs, have different expression levels and various functions in cancer cells, such as gene regulation through microRNA sponging. They play an important role in various cellular processes, including differentiation, proliferation, invasion, and apoptosis. Changes in the process of apoptosis are closely related to the progression or inhibition of various malignancies. Induction of apoptosis in cancer cells is a promising target for tumor therapy. In this study, circRNAs were investigated as being central to the induction or inhibition of apoptosis in CRC. It is hoped that through targeted changes in the function of these biomolecules, better outcomes will be achieved in cancer treatment. Perhaps better outcomes for cancer treatment can be achieved by using new methods and modifying the expression of these nucleic acids. However, using this method may come with challenges and limitations.

CircSHKBP1 regulates colon cancer cell proliferation and apoptosis by targeting miR-125a-5p

BACKGROUND

Colon cancer is a common malignant tumor in clinical practice. It has been reported that circular RNAs (circRNAs) are involved in the occurrence and development of cancer. Among them, circSHKBP1 acts as an oncogene to promote cancer progression. Thus, we hypothesized that circSHKBP1 might be also implicated in the development of colon cancer.

AIM

To explore the role of circSHKBP1 in colon cancer cell proliferation and apoptosis and the possible mechanism involved.

METHODS

Sixty-nine cancer tissues and matched adjacent normal tissues were selected from March 2020 to July 2020 at our hospital. The expression of circSHKBP1 and miR-125a-5p was detected by qRT-PCR. Human colon cancer cells (HT29) cultured in vitro were randomly divided into sh-NC group, sh-circSHKBP1 group, miR-NC group, miR-125a-5p group, sh-circSHKBP1 + anti-miR-NC group, and sh-circSHKBP1 + anti-miR-125a-5p group. MTT assay, colony formation experiment, and flow cytometry were used to detect cell proliferation, colony formation, and apoptosis, respectively. The dual luciferase reporter experiment was used to detect the impact of miR-125a-5p overexpression on the luciferase activity of the wild-type vector wt-circSHKBP1. Western blot was used to detect the protein expression of Bax and Bcl-2.

RESULTS

Compared with adjacent tissues, the expression of circSHKBP1 in colon cancer tissues was increased (P < 0.05), while the expression of miR-125a-5p was decreased (P < 0.05). Cell proliferation inhibition rate, apoptosis rate, and Bax protein level in the sh-circSHKBP1 group were increased (P < 0.05), while the number of cell colonies (P < 0.05) and Bcl-2 protein level were decreased (P < 0.05). Overexpression of miR-125a-5p could reduce the luciferase activity of wt-circSHKBP1 (P < 0.05). Relative to the miR-NC group, miR-125a-5p reduced cell proliferation, increased apoptosis rate and Bax protein level (P < 0.05), decreased the number of cell colonies (P < 0.05), and reduced Bcl-2 protein level (P < 0.05). Compared with the sh-circSHKBP1 + anti-miR-NC group, cell proliferation inhibition rate, apoptosis, and the protein level of Bax in the sh-circSHKBP1 + anti-miR-125a-5p group were decreased (P < 0.05), while the number of cell colonies and Bcl-2 protein level were increased (P < 0.05).

CONCLUSION

Knockdown of circSHKBP1 could inhibit colon cancer cell proliferation and promote apoptosis via up-regulating miR-125a-5p expression.

CircRNA RNA hsa_circ_0008234 Promotes Colon Cancer Progression by Regulating the miR-338-3p/ETS1 Axis and PI3K/AKT/mTOR Signaling

Circular RNAs (circRNAs) have been shown to play a crucial role in cancer occurrence and progression. This present work investigated the link between hsa_circ_0008234 and colon cancer. Data retrieved from GSE172229 was used to compare the circRNA profiles of colon cancer and surrounding non-tumorous tissues. The amount of RNA and protein in the molecules was determined using quantitative real-time PCR (qRT-PCR) and Western blot analysis, respectively. The cell proliferation ability was assessed using CCK8, EdU, colon formation, and nude mice tumorigenesis tests. Cell invasion and migration abilities were evaluated using transwell wound healing and mice lung metastasis model. Hsa_circ_0008234 piqued our interest because bioinformatics and qRT-PCR analyses revealed that it is upregulated in colon cancer tissue. Cell phenotypic studies suggest that hsa_circ_0008234 may significantly increase colon cancer cell aggressiveness. Mice experiments revealed that inhibiting hsa_circ_0008234 significantly reduced tumor growth and metastasis. Moreover, the fluorescence in situ hybridization experiment demonstrated that hsa_circ_0008234 is primarily found in the cytoplasm, implying that it potentially functions via a competitive endogenous RNA pathway. These findings indicated that hsa_circ_0008234 may act as a “molecular sponge” for miR-338-3p, increasing the expression of miR-338-target 3p’s ETS1. In addition, the traditional oncogenic pathway PI3K/AKT/mTOR signaling was found to be the potential downstream pathway of the hsa_circ_0008234/miR-338-3p/ETS1 axis. In conclusion, hsa_circ_0008234 increases colon cancer proliferation, infiltration, and migration via the miR-338-3p/ETS1/PI3K/AKT axis; therefore, it could serve as a target and a focus for colon cancer therapy.

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.

Long Noncoding RNAs and Circular RNAs Regulate AKT and Its Effectors to Control Cell Functions of Cancer Cells

AKT serine-threonine kinase (AKT) and its effectors are essential for maintaining cell proliferation, apoptosis, autophagy, endoplasmic reticulum (ER) stress, mitochondrial morphogenesis (fission/fusion), ferroptosis, necroptosis, DNA damage response (damage and repair), senescence, and migration of cancer cells. Several lncRNAs and circRNAs also regulate the expression of these functions by numerous pathways. However, the impact on cell functions by lncRNAs and circRNAs regulating AKT and its effectors is poorly understood. This review provides comprehensive information about the relationship of lncRNAs and circRNAs with AKT on the cell functions of cancer cells. the roles of several lncRNAs and circRNAs acting on AKT effectors, such as FOXO, mTORC1/2, S6K1/2, 4EBP1, SREBP, and HIF are explored. To further validate the relationship between AKT, AKT effectors, lncRNAs, and circRNAs, more predicted AKT- and AKT effector-targeting lncRNAs and circRNAs were retrieved from the LncTarD and circBase databases. Consistently, using an in-depth literature survey, these AKT- and AKT effector-targeting database lncRNAs and circRNAs were related to cell functions. Therefore, some lncRNAs and circRNAs can regulate several cell functions through modulating AKT and AKT effectors. This review provides insights into a comprehensive network of AKT and AKT effectors connecting to lncRNAs and circRNAs in the regulation of cancer cell functions.

Circular RNAs play roles in regulatory networks of cell signaling pathways in human cancers

AIMS

Circular RNAs (circRNAs) are endogenous covalently closed non-coding RNAs produced by reverse splicing of linear RNA. These molecules are highly expressed in mammalian cells and show cell/tissue-specific expression patterns. They are also significantly dysregulated in various cancers and function as oncogenes or tumor suppressors. Emerging evidence reveals that circRNAs contribute to cancer progression via modulating different cell signaling pathways. Nevertheless, the functional significance of circRNAs in cell signaling pathways regulation is still largely elusive. Considering this, shedding light on the multi-pathway effects of circRNAs may improve our understanding of targeted cancer therapy. Here, we discuss how circRNAs regulate the major cell signaling pathways in human cancers.

MATERIALS AND METHODS

We adopted a systematic search in PubMed using the following MeSH terms: circRNAs, non-coding RNAs, lncRNAs, exosomal circRNAs, cancer, and cell signaling.

KEY FINDINGS

We discussed different roles of circRNAs during tumorigenesis in which circRNAs affect tumor development through activating or inactivating certain cell signaling pathways via molecular interactions using various signaling pathways. We also discussed how crosstalk between circRNAs and lncRNAs modulate tumorigenesis and provides a resource for the identification of cancer therapeutic targets.

SIGNIFICANCE

We here elucidated how circRNAs can modulate different cell signaling pathways and play roles in cancer. This can broaden our horizons toward introducing promising prognostic, diagnostic, and therapeutic targets.

Emerging role of circRNAs in cancer under hypoxia (Review)

Circular RNA (circRNA), a recently identified type of non-coding RNAs (ncRNAs), forms a covalently closed loop with neither a 5′ cap structure nor a 3′ polyadenylated tail. Due to their lack of free ends, circRNAs are not easily cleaved by RNase R, thus avoiding degradation and being more stable than linear RNAs. Recent studies have suggested that circRNAs play a crucial role in regulating gene expression by acting as microRNAs sponges, RNA binding protein sponges and translational regulators. Currently, circRNAs are hot research topics due to their close association with the development of cancer and other diseases. Hypoxia is the most common microenvironment during tumor growth, and hypoxia-inducible factors have different effects on tumor growth and influence important cancer characteristics, including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune response, invasion and metastasis. The present review aimed to study the biogenesis and mechanisms of gene regulation of circRNAs in hypoxia, to summarize the latest studies on circRNAs as potential diagnostic and prognostic biomarkers in hypoxia, and to understand the role of circRNAs in the process of tumor drug resistance under hypoxia.

Hypoxia-responsive circRNAs: A novel but important participant in non-coding RNAs ushered toward tumor hypoxia

Given the rapid developments in RNA-seq technologies and bioinformatic analyses, circular RNAs (circRNAs) have gradually become recognized as a novel class of endogenous RNAs, characterized by covalent loop structures lacking free terminals, which perform multiple biological functions in cancer genesis, progression and metastasis. Hypoxia, a common feature of the tumor microenvironments, profoundly affects several fundamental adaptive responses of tumor cells by regulating the coding and non-coding transcriptomes and renders cancer's phenotypes more aggressive. Recently, hypoxia-responsive circRNAs have been recognized as a novel player in hypoxia-induced non-coding RNA transcriptomics to modulate the hypoxic responses and promote the progression and metastasis of hypoxic tumors. Moreover, via extracellular vesicles-exosomes, these hypoxia-responsive circRNAs could transmit hypoxia responses from cancer cells to the cells of surrounding matrices, even more distant cells of other organs. Here, we have summarized what is known about hypoxia-responsive circRNAs, with a focus on their interaction with hypoxia-inducible factors (HIFs), regulation of hypoxic responses and relevance with malignant carcinoma's clinical features, which will offer novel insights on the non-coding RNAs' regulation of cancer cells under hypoxic stress and might aid the identification of new theranostic targets and define new therapeutic strategies for those cancer patients with resistance to radiochemotherapy, because of the ubiquity of tumoral hypoxia.

Negative regulation of miR-1288-3p/KRT4 axis through a circular RNA in oral cancer

Circular RNA (circRNA) has been widely reported to be involved in oral squamous cell carcinoma (OSCC), while the way in which hsa_circ_0096042 affects OSCC remains unclear. The hsa_circ_0096042, miR-1288-3p, and KRT4 expression in OSCC tissues and cell lines were detected by quantitative reverse-transcription polymerase chain reaction. Based on the overexpression of hsa_circ_0096042, miR-1288-3p, or KRT4, the viability and proliferation of OSCC cells were analyzed by cell counting kit-8 and colony formation assay, and the protein levels of Bax and Bcl-2 were detected by western blot, and the growth of cancer cells in vivo was analyzed by xenograft experiment. In addition, the database was used to predict the binding of hsa_circ_0096042, miR-1288-3p, and KRT4, and the interaction was confirmed by luciferase, RIP, and RNA pull-down assay. Hsa_circ_0096042 and KRT4 were abnormally downregulated and miR-1288-3p was upregulated in OSCC. Hsa_circ_0096042 overexpression restrained the proliferation and viability of OSCC cells, facilitated apoptosis, and inhibited the growth of cancer cells in vivo. Hsa_circ_0096042 bound to miR-1288-3p, whose upregulation promoted OSCC progression and eliminated the effects of overexpression of hsa_circ_0096042 on OSCC cells. KRT4 was the target gene for miR-1288-3p. Hsa_circ_0096042 plays an antitumor role in OSCC via miR-1288-3p/KRT4 axis.

Circular RNA MTCL1 promotes advanced laryngeal squamous cell carcinoma progression by inhibiting C1QBP ubiquitin degradation and mediating beta-catenin activation

Background

Circular RNAs (circRNAs) are involved in regulatory processes of ubiquitination and deubiquitination in various tumors at post-transcriptional epigenetic modification level. However, the underlying mechanism and its biological functions of circRNAs in the advanced laryngeal squamous cell carcinoma (LSCC) remain obscure.

Methods

RNA sequencing and quantitative real-time PCR (qRT-PCR) assays were applied to screen for circRNAs differentially expressed in LSCC tissues and cell lines. The candidate RNA-binding proteins and target signalling pathway were detected by RNA pull-down and mass spectrometry, in situ hybridization (ISH), immunohistochemistry (IHC), qRT-PCR assays, and bioinformatics analysis. The functional roles of these molecules were investigated using in vitro and in vivo experiments including EdU, transwell, wound healing, western blot assays, and the xenograft mice models. The molecular mechanisms were identified using RNA pull-down assays, RNA immunoprecipitation (RIP), Co-IP, ISH, Ubiquitination assay, bioinformatics analysis, and the rescue experiments.

Results

Here, we unveil that microtubule cross-linking factor 1 circRNA (circMTCL1, circ0000825) exerts its critical oncogenic functions by promoting complement C1q-binding protein (C1QBP)-dependent ubiquitin degradation and subsequently activating Wnt/β-catenin signalling in laryngeal carcinoma initiation and development. Specifically, circMTCL1 was remarkably up-regulated in the paired tissues of patients with LSCC (n = 67), which predicted a worse clinical outcome. Functionally, circMTCL1 exerted oncogenic biological charactersistics by promoting cell proliferative capability and invasive and migrative abilities. Ectopic circMTCL1 augumented cell proliferation, migration, and invasion of LSCC cells, and this effect could be reversed by C1QBP knocking down in vitro and in vivo. Mechanistically, circMTCL1 directly recruited C1QBP protein by harboring the specific recognized sequence (+ 159 − + 210), thereby accelerating the translation of C1QBP expression by inhibiting its ubiquitin–proteasome-mediated degradation. Importantly, the direct interaction of C1QBP with β-catenin protein was enhanced via suppressing the β-catenin phosphorylation and accelerating its accumulation in cytoplasm and nucleus.

Conclusion

Our findings manifested a novel circMTCL1-C1QBP-β-catenin signaling axis involving in LSCC tumorigenesis and progression, which shed new light on circRNAs-ubiquitous acidic glycoprotein mediated ubiquitin degradation and provided strategies and targets in the therapeutic intervention of LSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01570-4.

Circular RNA hsa_circ_0119412 contributes to tumorigenesis of gastric cancer via the regulation of the miR-1298-5p/zinc finger BED-type containing 3 (ZBED3) axis

Circular RNAs (circRNAs) are associated with the progression of gastric cancer (GC). This study investigates the regulation of the circular RNA, hsa_circ_0119412 in GC and its effects on GC cells. The expression of hsa_circ_0119412, microRNA (miR)-1298-5p, and zinc finger BED-type containing 3 (ZBED3) were measured by quantitative reverse transcription-PCR (qRT-PCR) and Western blotting. The cell counting kit-8 (CCK-8) assay, flow cytometry, transwell, and animal assays were performed to identify the roles of hsa_circ_0119412, miR-1298-5p, and ZBED3 in the viability, apoptosis, invasion, and growth of GC cells. The relationship between hsa_circ_0119412, miR-1298-5p, and ZBED3 was confirmed by luciferase, RNA immunoprecipitation (RIP), and RNA pull-down assays. Our data revealed that hsa_circ_0119412 and ZBED3 expression was upregulated in GC, while miR-1298-5p expression was downregulated. Both the knockdown of hsa_circ_0119412/ZBED3 and miR-1298-5p overexpression inhibited GC cell growth and invasion, and enhanced cell apoptosis, while miR-1298-5p interference or ZBED3 overexpression showed the opposite trend. Mechanistically, hsa_circ_0119412 sponges miR-1298-5p, which regulates ZBED3 expression. Silencing hsa_circ_0119412 inhibits the progression of GC, at least in part, by targeting the miR-1298-5p/ZBED3 axis.

circPTEN1, a circular RNA generated from PTEN, suppresses cancer progression through inhibition of TGF-β/Smad signaling

Background

PTEN is one of the most frequently mutated genes in human cancer. Although the roles of canonical PTEN protein and PTEN isoforms have been extensively explored, the current understanding of PTEN family members cannot fully illustrate the diversity of their roles in biological processes and tumor development. Notably, the function of noncoding RNAs arising from PTEN has been less elucidated.

Methods

We searched circBase and circInteractome to analyze the potential of PTEN for generating circRNAs. Then, Sanger sequencing, RNase R and Actinomycin D assays were used to verify the ring structure of circPTEN1. In situ hybridization and qRT-PCR were used to determine the level of circPTEN1 in peritumor and tumor tissues of colorectal cancer (CRC). Furthermore, functional experiments, including Transwell assay, 3D multicellular tumor spheroid invasion assay and metastasis models, were performed using circPTEN1 knockdown and overexpression cell lines in vitro and in vivo to investigate the effects of circPTEN1 on tumor metastasis in CRC. Mechanistically, luciferase reporter assay, fluorescence in situ hybridization, electrophoretic mobility shift assay, RNA immunoprecipitation, RNA pull-down and mass spectrometry were executed.

Results

We identified a circular RNA generated from the PTEN gene, designated circPTEN1, that is frequently downregulated in colorectal cancer, and decreased expression of circPTEN1 predicts poor survival. Low expression of circPTEN1 promotes metastasis in PDX models in vivo and accelerates cancer cell invasion in vitro, whereas overexpression of circPTEN1 reveals opposite roles. Mechanically, we found that circPTEN1 is capable of binding the MH2 domain of Smad4 to disrupt its physical interaction with Smad2/3, which reduces the formation and subsequent nucleus translocation of Smad complexes and consequently suppresses the expression of its downstream genes associated with epithelial-mesenchymal transition upon TGF-β stimulation. Furthermore, we found that eIF4A3 suppresses the cyclization of circPTEN1 by directly binding to the circPTEN1 flanking region.

Conclusions

Our study uncovered a novel PTEN gene-generated circRNA with a tumor suppression function, and further revealed the mechanism of circPTEN1 in CRC metastasis mediated by TGF-β. The identification of circPTEN1 provides a new direction for PTEN investigation, and elucidation of circPTEN1/TGF-β/Smad signaling may pave the way for the development of a potential therapeutic strategy for the suppression of cancer progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01495-y.

Circular RNA circCSPP1 promotes the occurrence and development of colon cancer by sponging miR-431 and regulating ROCK1 and ZEB1

Background

Colon cancer is a common malignant tumor of the digestive tract, and its incidence is ranked third among gastrointestinal tumors. The present study aims to investigate the role of a novel circular RNA (circCSPP1) in colon cancer and its underlying molecular mechanisms.

Methods

Bioinformatics analysis and reverse transcription-quantitative PCR were used to detect the expression levels of circCSPP1 in colon cancer tissues and cell lines. The effects of circCSPP1 on the behavior of colon cancer cells were investigated using CCK-8, transwell and clonogenic assays. Bioinformatics analysis along with luciferase, fluorescence in situ hybridization and RNA pull-down assays were used to reveal the interaction between circCSPP1, microRNA (miR)-431, Rho associated coiled-coil containing protein kinase 1 (ROCK1) and zinc finger E-box binding homeobox 1 (ZEB1).

Results

It was found that circCSPP1 expression was significantly upregulated in colon cancer tissues and cell lines. Overexpression of circCSPP1 significantly promoted the proliferation, migration and invasion of colon cancer cells, whereas silencing of circCSPP1 exerted opposite effects. Mechanistically, circCSPP1 was found to bind with miR-431. In addition, ROCK1 and ZEB1 were identified as the target genes of miR-431. Rescue experiments further confirmed the interaction between circCSPP1, miR-431, ROCK1 and ZEB1. Moreover, circCSPP1 promoted the expression level of ROCK1, cyclin D1, cyclin-dependent kinase 4, ZEB1 and Snail, and lowered the E-cadherin expression level.

Conclusion

Taken together, the findings of the present study indicated that circCSPP1 may function as a competing endogenous RNA in the progression of colon cancer by regulating the miR-431/ROCK1 and miR-431/ZEB1 signaling axes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03240-x.

Has_Circ_0002490 Circular RNA: A Potential Novel Biomarker for Lung Cancer

Background: Lung cancer (LC) is ranked as a leading cause of cancer-related death worldwide. However, there are still few reliable screening biomarkers for daily clinical practice in LC. Circular RNAs (circRNAs) have been suggested as valuable diagnostic biomarkers in various cancers. In this study, the expression and diagnostic potential of several circRNAs for LC were explored. Methods: Seventy-two pairs of LC tissues and adjacent normal lung tissues were collected to measure the relative expression level of circRNAs using quantitative reverse transcription-polymerase chain reaction. In addition, the relationships between circRNAs and the clinicopathological features of LC patients were analyzed. Furthermore, the sensitivities and specificities of the circRNAs were evaluated by receiver operating characteristic (ROC) analysis. Results: The expression levels of has_circ_0002490, has_circ_0087357, has_circ_0004891, has_circ_0074368, and has_circ_0000896 were downregulated in LC tissues compared with adjacent normal lung tissues. The lower levels of has_circ_0002490, has_circ_0087357, has_circ_0004891, and has_circ_0000896 were significantly correlated with advanced disease stages. The area under the ROC curves of has_circ_0002490, has_circ_0087357, has_circ_0074368, has_circ_0004891, and has_circ_0000896 were 0.833, 0.793, 0.773, 0.730, and 0.645, respectively. Conclusions: Has_circ_0002490, has_circ_0087357, has_circ_0074368, has_circ_0004891, and has_circ_0000896 are capable of distinguishing LC tissues from normal lung tissues. Besides, the biggest area under the ROC curve value of has_circ_000249 suggests it appears to be a better diagnosis marker for LC patients.

circ_ZFR Is Linked to Paclitaxel Resistance in Cervical Cancer via miR-944 Sponging and IL-10 Upregulation

Objective

Cervical cancer (CC) has an elevated rate of invasion and death despite surgical treatment, radiotherapy, and chemotherapy. Several studies revealed that circRNAs have a key contribution to the resistance of drugs against different types of carcinomas. The goal of the existing study was to figure out what role circ_ZFR plays in paclitaxel (PTX) resistance in cervical cancer (CC) patients.

Materials and Methods

Herein, two types of CC cells (SiHa/PTX and Hela/PTX) were utilized. The levels of IL-10 mRNA, miR-944, and circ_ZFR were measured using qRT-PCR analyses. The CCK-8 assay was used to determine PTX resistance. The IL-10 expression was measured via the ELISA technique. The combination of miR-944 and circ_ZFR or IL-10 was validated using a dual-luciferase reporter (DLR) assay.

Results

The amount of circ_ZFR was increased in PTX-resistant CC cells and tissues. In PTX-resistant CC cells, knocking down circ_ZFR expression decreased PTX resistance. circ_ZFR knockdown significantly reduced IL-10 expression via sponging miR-944, increasing PTX sensitivity in PTX-resistant CC cells.

Conclusion

circ_ZFR knockdown has a considerable role in overwhelming CC-associated PTX resistance by modifying the axis of miR-944/IL-10 axis, suggesting that developing a circRNA target-based treatment could be considered prevent CC progression.

Accentuating CircRNA-miRNA-Transcription Factors Axis: A Conundrum in Cancer Research

Circular RNAs (circRNAs) are the newly uncovered class of non-coding RNAs being cognized as profound regulators of gene expression in developmental and disease biology. These are the covalently closed RNAs synthesized when the pre-mRNA transcripts undergo a back-splicing event. In recent years, circRNAs are gaining special attention in the scientific world and are no longer considered as "splicing noise" but rather structurally stable molecules having multiple biological functions including acting as miRNA sponges, protein decoys/scaffolds, and regulators of transcription and translation. Further, emerging evidence suggests that circRNAs are also differentially expressed in multiple cancers where they play oncogenic roles. In addition, circRNAs in association with miRNAs change the expression patterns of multiple transcription factors (TFs), which play important roles in cancer. Thus, the circRNA-miRNA-TFs axis is implicated in the progression or suppression of various cancer types and plays a role in cell proliferation, invasion, and metastasis. In this review article, we provide an outline of the biogenesis, localization, and functions of circRNAs specifically in cancer. Also, we highlight the regulatory function of the circRNA-miRNA-TFs axis in the progression or suppression of cancer and the targeting of this axis as a potential therapeutic approach for cancer management. We anticipate that our review will contribute to expanding the knowledge of the research community about this recent and rapidly growing field of circRNAs for further thorough investigation which will surely help in the management of deadly disease cancer.

MicroRNA-217: a therapeutic and diagnostic tumor marker

INTRODUCTION

Cancer as one of the most common causes of death has always been one of the major health challenges globally. Since, the identification of tumors in the early tumor stages can significantly reduce mortality rates; it is required to introduce novel early detection tumor markers. MicroRNAs (miRNAs) have pivotal roles in regulation of cell proliferation, migration, apoptosis, and tumor progression. Moreover, due to the higher stability of miRNAs than mRNAs in body fluids, they can be considered as non-invasive diagnostic or prognostic markers in cancer patients.

AREAS COVERED

In the present review we have summarized the role of miR-217 during tumor progressions. The miR-217 functions were categorized based on its target molecular mechanisms and signaling pathways.

EXPERT OPINION

It was observed that miR-217 mainly exerts its function by regulation of the transcription factors during tumor progressions. The WNT, MAPK, and PI3K/AKT signaling pathways were also important molecular targets of miR-217 in different cancers. The present review clarifies the molecular biology of miR-217 and paves the way of introducing miR-217 as a non-invasive diagnostic marker and therapeutic target in cancer therapy.

Tumor Suppressive Circular RNA-102450: Development of a Novel Diagnostic Procedure for Lymph Node Metastasis from Oral Cancer

Circular RNAs (circRNAs), which form as covalently closed loop structures, have several biological functions such as regulation of cellular behavior by adsorbing microRNAs. However, there is limited information of circRNAs in oral squamous cell carcinoma (OSCC). Here, we aimed to elucidate the roles of aberrantly expressed circRNAs in OSCC. CircRNA microarray showed that circRNA-102450 was down-regulated in OSCC cells. Clinical validation of circRNA-102450 was performed using highly sensitive droplet digital PCR in preoperative liquid biopsy samples from 30 OSCC patients. Interestingly, none of 16 studied patients with high circRNA-102450 had regional lymph node metastasis (RLNM), whereas 4 of 14 studied patients (28.5%) with low expression had pathologically proven RLNM. Overexpressed circRNA-102450 significantly inhibited the tumor metastatic properties of cell proliferation, migration, and invasion. Furthermore, circRNA-102450 directly bound to, and consequently down-regulated, miR-1178 in OSCC cells. Taken together, circRNA-102450 has a tumor suppressive effect via the circRNA-102450/miR-1178 axis and may be a novel potential marker of RLNM in OSCC patients.

The Dual Role of Circular RNAs as miRNA Sponges in Breast Cancer and Colon Cancer

Breast cancer (BC) and colon cancer (CRC) are the two most deadly cancers in the world. These cancers partly share the same genetic background and are partially regulated by the same genes. The outcomes of traditional chemoradiotherapy and surgery remain suboptimal, with high postoperative recurrence and a low survival rate. It is, therefore, urgent to innovate and improve the existing treatment measures. Many studies primarily reported that the microRNA (miRNA) sponge functions of circular RNA (circRNA) in BC and CRC have an indirect relationship between the circRNA–miRNA axis and malignant behaviors. With a covalent ring structure, circRNAs can regulate the expression of target genes in multiple ways, especially by acting as miRNA sponges. Therefore, this review mainly focuses on the roles of circRNAs as miRNA sponges in BC and CRC based on studies over the last three years, thus providing a theoretical reference for finding new therapeutic targets in the future.

The emerging roles of circular RNAs in vessel co-option and vasculogenic mimicry: clinical insights for anti-angiogenic therapy in cancers

Unexpected resistance to anti-angiogenic treatment prompted the investigation of non-angiogenic tumor processes. Vessel co-option (VC) and vasculogenic mimicry (VM) are recognized as primary non-angiogenic mechanisms. In VC, cancer cells utilize pre-existing blood vessels for support, whereas in VM, cancer cells channel and provide blood flow to rapidly growing tumors. Both processes have been implicated in the development of tumor and resistance to anti-angiogenic drugs in many tumor types. The morphology, but rare molecular alterations have been investigated in VC and VM. There is a pressing need to better understand the underlying cellular and molecular mechanisms. Here, we review the emerging circular RNA (circRNA)-mediated regulation of non-angiogenic processes, VC and VM.

Oncogenic Functions and Clinical Significance of Circular RNAs in Colorectal Cancer

Colorectal cancer (CRC) is ranked as the second most commonly diagnosed disease in females and the third in males worldwide. Therefore, the finding of new more reliable biomarkers for early diagnosis, for prediction of metastasis, and resistance to conventional therapies is an important challenge in overcoming the disease. The current review presents circular RNAs (circRNAs) with their unique features as potential prognostic and diagnostic biomarkers in CRC. The review highlights the mechanism of action and the role of circRNAs with oncogenic functions in the CRC as well as the association between their expression and clinicopathological characteristics of CRC patients. The comprehension of the role of oncogenic circRNAs in CRC pathogenesis is growing rapidly and the next step is using them as suitable new drug targets in the personalized treatment of CRC patients.

Circular RNAs regulate cancer-related signaling pathways and serve as potential diagnostic biomarkers for human cancers

Circular RNAs (circRNAs) are RNAs that have an important role in various pathological processes, including cancer. After the usage of high-throughput RNA sequencing, many circRNAs were found to be differentially expressed in various cancer cell lines and regulate cell signaling pathways by modulating particular gene expressions. Understanding their role in these pathways and what cancers they are found in can set the stage for identifying diagnostic and prognostic biomarkers and therapeutic targets of cancer. This paper will discuss which circRNAs are found in different cancers and what mechanisms they use to upregulate or downregulate certain cellular components.

miR-217-5p Inhibits Invasion and Metastasis of Prostate Cancer by Targeting Clusterin

Prostate cancer is not easy to metastasize because it is difficult to diagnose at an early stage, and there is no effective treatment currently. miRNA-217-5p has been reported to be a regulator in the process of prostate cancer. This study aimed to investigate how miRNA-217-5p affects the invasion and migration of prostate cancer. Luciferase assay was used to clarify whether the target gene Clusterin (CLU) was interacted directly with miR-217-5p. miR-217-5p and CLU were knocked down by transfecting respective siRNA into DU145 cells. The expression level of epithelial-mesenchymal transition (EMT)-related proteins was detected by Western blotting. Invasion and migration of DU145 cell were examined by wound healing assay. The results showed that miR-217-5p directly interacted with its target gene CLU, and the transfection of si-CLU and si-miR-217-5p had similar ability to regulate the expression level of EMT-related proteins, which in turn affected the migration and invasion of prostate cancer cell line DU145. In addition, miR-217-5p inhibited the expression of EMT-related proteins by regulating the expression of the target gene CLU, and further inhibited the invasion and migration of prostate cancer cells. Our findings provide a theoretical target basis for the treatment of prostate cancer.

LINC02257, an Enhancer RNA of Prognostic Value in Colon Adenocarcinoma, Correlates With Multi-Omics Immunotherapy-Related Analysis in 33 Cancers

Accumulated evidence supports that long non-coding RNAs (lncRNAs) are involved significantly in the development of human cancers. Enhancer RNAs (eRNAs), a subtype of lncRNAs, have recently attracted much attention about their roles in carcinogenesis. Colon adenocarcinoma is one of the most commonly diagnosed tumors with unfavorable prognosis. It highlights the great significance of screening and identifying novel biomarkers. More importantly, it remains to be elucidated with respect to the function of eRNAs in colon adenocarcinoma, as is in pan-cancers. The expression of LINC02257 was determined based on the data obtained from The Cancer Genome Atlas (TCGA). Further evaluation was performed on the basis of the following analyses: clinicopathology and survival analysis, gene ontology (GO) terms, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, as well as multi-omics immunotherapy-related analysis and co-expression analysis. The statistical analysis was conducted in R software, and immune cell infiltration of LINC02257 expression in cancers was investigated by using the CIBERSORT algorithm. By large-scale data mining, our study highlighted that a total of 39 eRNA genes were associated with colon adenocarcinoma prognosis, among which 25 eRNAs showed significant associations with their predicted target genes. LINC02257 was identified as the most significant survival-associated eRNA, with DUSP10 as its target gene. Besides, the high expression of LINC02257 in colon adenocarcinoma was more vulnerable to unfavorable prognosis and correlated with various clinical characteristics. GO and KEGG analyses revealed that LINC02257 was closely correlated with extracellular matrix organization via the PI3K-Akt signaling pathway. Besides, LINC02257 expression correlated with a multi-omics analysis of 33 cancer types, such as survival analysis [overall survival (OS), disease-specific survival (DSS), disease-free interval (DFI), and progression-free interval (PFI)] and immunotherapy-related analysis [tumor microenvironment (TME), tumor mutational burden (TMB), and microsatellite instability (MSI)]. Finally, we investigated the co-expression genes of LINC02257 and its potential signaling pathways across different cancer types. LINC02257 is screened and can function as an independent prognostic biomarker through the PI3K-Akt signaling pathway for colon adenocarcinoma. Simultaneously, LINC02257 may be a multifaceted and significant immunotherapy-related eRNA in different cancers.

Role of circular RNAs in colorectal tumor microenvironment

Circular RNAs (circRNAs) are a class of endogenous noncoding RNA, which were previously considered as a byproduct of RNA splicing error. Numerous studies have demonstrated the altered expression of circRNAs in organ tissues during pathological conditions and their involvements in disease pathogenesis and progression, including cancers. In colorectal cancer (CRC), multiple circRNAs have been identified and characterized as "oncogenic", given their involvements in the downregulation of tumor suppressor genes and induction of tumor initiation, progression, invasion, and metastasis. Additionally, other circRNAs have been identified in CRC and characterized as "tumor suppressive" based on their ability of inhibiting the expression of oncogenic genes and suppressing tumor growth and proliferation. circRNAs could serve as potential diagnostic and prognostic biomarkers, and therapeutic targets or vectors to be utilized in cancer therapies. This review briefly describes the dynamic changes of the tumor microenvironment inducing immunosuppression and tumorigenesis, and outlines the biogenesis and characteristics of circRNAs and recent findings indicating their roles and functions in the CRC tumor microenvironment. It also discusses strategies and technologies, which could be employed in the future to overcome current cancer therapy challenges associated with circRNAs.

Clinical Significance of has_circ_0055625 in Colon Cancer Patients Undergoing FOLFOX Chemotherapy Treatment

Objective

Colon cancer is a leading global cancer-related cause of morbidity and mortality. The oxaliplatin, 5-fluorouracil (5-FU), and leucovorin (FOLFOX) regimen is a standard chemotherapeutic approach used to treat colon cancer. However, chemoresistant tumor cells typically lead to the emergence of recurrent FOLFOX-resistant tumors after initial treatment. As such, it is vital that novel approaches to identifying and eliminating such chemoresistant tumors be developed in an effort to improve patient chemotherapy outcomes.

Materials and Methods

In total, 100 samples of serum were obtained between April 2014 and April 2019 from patients who had been pathologically diagnosed with colon cancer from the Xiamen Haicang Hospital, and after these patients received FOLFOX chemotherapy treatment, serum samples were collected again. The expression of has_circ_0055625 in these serum samples was assessed via qPCR. Additionally, 5-FU IC50 values were detected via CCK-8 assay.

Results

We found has_circ_0055625 to be significantly upregulated in colon cancer patient serum. After FOLFOX treatment, chemotherapy-resistance was associated with the upregulation of has_circ_0055625.

Conclusion

In summary, these data may provide a foundation for future studies of chemotherapeutic resistance in patients undergoing FOLFOX treatment, potentially guiding treatment adjustment strategies. However, further work will be necessary to expand upon these findings.

The Biomarker and Therapeutic Potential of Circular Rnas in Schizophrenia

Circular RNAs (circRNAs) are endogenous, single-stranded, most frequently non-coding RNA (ncRNA) molecules that play a significant role in gene expression regulation. Circular RNAs can affect microRNA functionality, interact with RNA-binding proteins (RBPs), translate proteins by themselves, and directly or indirectly modulate gene expression during different cellular processes. The affected expression of circRNAs, as well as their targets, can trigger a cascade of events in the genetic regulatory network causing pathological conditions. Recent studies have shown that altered circular RNA expression patterns could be used as biomarkers in psychiatric diseases, including schizophrenia (SZ); moreover, circular RNAs together with other cell molecules could provide new insight into mechanisms of this disorder. In this review, we focus on the role of circular RNAs in the pathogenesis of SZ and analyze their biomarker and therapeutic potential in this disorder.