Functions and mechanisms of circular RNAs in cancer radiotherapy and chemotherapy resistance

Dysregulated circular RNA and long non-coding RNA-Mediated regulatory competing endogenous RNA networks (ceRNETs) in ovarian and cervical cancers: A non-coding RNA-Mediated mechanism of chemotherapeutic resistance with new emerging clinical capacities

Cervical cancer (CC) and ovarian cancer (OC) are among the most common gynecological cancers with significant mortality in women, and their incidence is increasing. In addition to the prominent role of the malignant aspect of these cancers in cancer-related women deaths, chemotherapy drug resistance is a major factor that contributes to their mortality and presents a clinical obstacle. Although the exact mechanisms behind the chemoresistance in these cancers has not been revealed, accumulating evidence points to the dysregulation of non-coding RNAs (ncRNAs), particularly long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), as key contributors. These ncRNAs perform the roles of regulators of signaling pathways linked to tumor formation and chemoresistance. Strong data from various recent studies have uncovered that the main mechanism of these ncRNAs in the induction of chemoresistance of CC and OC is done through a dysregulated miRNA sponge activity as competing endogenous RNA (ceRNA) in the competing endogenous RNA networks (ceRNETs), where a miRNA regulating a messenger RNA (mRNA) is trapped, thereby removing its inhibitory effect on the desired mRNA. Understanding these mechanisms is essential to enhancing treatment outcomes and managing the problem of drug resistance. This review provides a comprehensive overview of lncRNA- and circRNA-mediated ceRNETs as the core process of chemoresistance against the commonly used chemotherapeutics, including cisplatin, paclitaxel, oxaliplatin, carboplatin, and docetaxel in CC and OC. Furthermore, we highlight the clinical potential of these ncRNAs serving as diagnostic indicators of chemotherapy responses and therapeutic targets.

Unveiling Pharmacogenomics Insights into Circular RNAs: Toward Precision Medicine in Cancer Therapy

Pharmacogenomics is revolutionizing precision medicine by enabling tailored therapeutic strategies based on an individual genetic and molecular profile. Circular RNAs (circRNAs), a distinct subclass of endogenous non-coding RNAs, have recently emerged as key regulators of drug resistance, tumor progression, and therapeutic responses. Their covalently closed circular structure provides exceptional stability and resistance to exonuclease degradation, positioning them as reliable biomarkers and novel therapeutic targets in cancer management. This review provides a comprehensive analysis of the interplay between circRNAs and pharmacogenomics, focusing on their role in modulating drug metabolism, therapeutic efficacy, and toxicity profiles. We examine how circRNA-mediated regulatory networks influence chemotherapy resistance, alter targeted therapy responses, and impact immunotherapy outcomes. Additionally, we discuss emerging experimental tools and bioinformatics techniques for studying circRNAs, including multi-omics integration, machine learning-driven biomarker discovery, and high-throughput sequencing technologies. Beyond their diagnostic potential, circRNAs are being actively explored as therapeutic agents and drug delivery vehicles. Recent advancements in circRNA-based vaccines, engineered CAR-T cells, and synthetic circRNA therapeutics highlight their transformative potential in oncology. Furthermore, we address the challenges of standardization, reproducibility, and clinical translation, emphasizing the need for rigorous biomarker validation and regulatory frameworks to facilitate their integration into clinical practice. By incorporating circRNA profiling into pharmacogenomic strategies, this review underscores a paradigm shift toward highly personalized cancer therapies. circRNAs hold immense potential to overcome drug resistance, enhance treatment efficacy, and optimize patient outcomes, marking a significant advancement in precision oncology.

Circular RNAs in cancer

Circular RNA (circRNA), a subtype of noncoding RNA, has emerged as a significant focus in RNA research due to its distinctive covalently closed loop structure. CircRNAs play pivotal roles in diverse physiological and pathological processes, functioning through mechanisms such as miRNAs or proteins sponging, regulation of splicing and gene expression, and serving as translation templates, particularly in the context of various cancers. The hallmarks of cancer comprise functional capabilities acquired during carcinogenesis and tumor progression, providing a conceptual framework that elucidates the nature of the malignant transformation. Although numerous studies have elucidated the role of circRNAs in the hallmarks of cancers, their functions in the development of chemoradiotherapy resistance remain unexplored and the clinical applications of circRNA-based translational therapeutics are still in their infancy. This review provides a comprehensive overview of circRNAs, covering their biogenesis, unique characteristics, functions, and turnover mechanisms. We also summarize the involvement of circRNAs in cancer hallmarks and their clinical relevance as biomarkers and therapeutic targets, especially in thyroid cancer (TC). Considering the potential of circRNAs as biomarkers and the fascination of circRNA-based therapeutics, the "Ying-Yang" dynamic regulations of circRNAs in TC warrant vastly dedicated investigations.

Emerging roles of CircRNA-miRNA networks in cancer development and therapeutic response

The complex interplay of epigenetic factors is essential in regulating the hallmarks of cancer and orchestrating intricate molecular interactions during tumor progression. Circular RNAs (circRNAs), known for their covalently closed loop structures, are non-coding RNA molecules exceptionally resistant to enzymatic degradation, which enhances their stability and regulatory functions in cancer. Similarly, microRNAs (miRNAs) are endogenous non-coding RNAs with linear structures that regulate cellular biological processes akin to circRNAs. Both miRNAs and circRNAs exhibit aberrant expressions in various cancers. Notably, circRNAs can function as sponges for miRNAs, influencing their activity. The circRNA/miRNA interaction plays a pivotal role in the regulation of cancer progression, including in brain, gastrointestinal, gynecological, and urological cancers, influencing key processes such as proliferation, apoptosis, invasion, autophagy, epithelial-mesenchymal transition (EMT), and more. Additionally, this interaction impacts the response of tumor cells to radiotherapy and chemotherapy and contributes to immune evasion, a significant challenge in cancer therapy. Both circRNAs and miRNAs hold potential as biomarkers for cancer prognosis and diagnosis. In this review, we delve into the circRNA-miRNA circuit within human cancers, emphasizing their role in regulating cancer hallmarks and treatment responses. This discussion aims to provide insights for future research to better understand their functions and potentially guide targeted treatments for cancer patients using circRNA/miRNA-based strategies.

Novel insights into the circ_0003489/let-7b-5p/GLUT1 axis and its possible role in multiple myeloma

BACKGROUND

Circular RNAs (circRNAs) act as vital players in multiple myeloma (MM). Herein, we focused on the function of hsa_circ_0003489 (circ_0003489) in MM development and bortezomib (BTZ) resistance.

METHODS

Relative RNA levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Relative protein levels were evaluated by Western blotting or immunohistochemistry (IHC). The 5'-ethynyl-2'-deoxyuridine (EdU) and cell colony formation (CF) assays were conducted for cell proliferation. Cell counting kit-8 assay was used to evaluate the BTZ resistance. Flow cytometry analysis was performed for cell apoptosis analysis. Glycolysis was determined by detecting the levels of ECAR, glucose consumption, and lactate production. Dual-luciferase reporter and RNA pull-down assays were carried out to analyze the relationships of circ_0003489 with let-7b-5p microRNA and glucose transporter 1 (GLUT1) glucose transporter protein. Xenograft models were conducted to assess the function of circ_0003489 in vivo.

RESULTS

Indeed, as shown by qRT-PCR, bone marrow samples of MM patients showed an upregulation of circ_0003489 RNA in comparison to normal controls (P < 0.0001). In in vitro experiments in MM cells, silencing of circ_0003489 repressed cell proliferation, BTZ resistance, and glycolysis. Furthermore, blocking circ_0003489 facilitated in vitro the apoptosis of MM cells. In vivo experiments showed that silencing circ_0003489 decreased tumor formation. Signaling experiments demonstrated that circ_0003489 sponged let-7b-5p microRNA and negatively regulated let-7b-5p microRNA expression. Loss of let-7b-5p microRNA ameliorated circ_0003489 silencing-mediated effects on MM cell malignant behaviors and BTZ resistance. Moreover, we showed that GLUT1 glucose transporter was targeted by let-7b-5p mircoRNA. GLUT1 enhancement reversed the repressive impacts of let-7b-5p upregulation on MM cell malignant behaviors and BTZ resistance.

CONCLUSION

We suggest that circ_0003489 RNA knockdown inhibited MM progression and reversed BTZ-induced resistance of MM growth by let-7b-5p microRNA regulated function of GLUT1 glucose transporter.

The role of CD95 in modulating CAR T-cell therapy: Challenges and therapeutic opportunities in oncology

CAR T cell therapy has revolutionized how we deliver cancer treatment, most notably for hematologic cancers, by compelling T cells to recognize and kill tumor cells. Nevertheless, current obstacles to utilizing this therapy in solid tumors and overcoming cancer resistance include radicalization. This review discusses how CD95 modulation can boost CAR T cell efficacy. Traditionally, CD95 was known to execute apoptosis induction, but it plays a dual role in induced cell death or in supporting cancer cell survival. Recent data have demonstrated that cancer cells escape CD95-mediated apoptosis via the downregulation of CD95, caspase 8 mutation, or the expression of the inhibition protein cFLIP. Additionally, the immunosuppressive tumor microenvironment, containing CD95L expressing immune cells, explains CAR T cell therapy resistance. Furthermore, we characterize the therapeutic potential of CD95 targeted approaches, including CD95L inhibition (APG101) and alterations in CAR T cell manufacturing (tyrosine kinase inhibitors to mitigate fratricide). In this review, we highlight the importance of multi-path way strategies combining CD95 modulation with CAR T cell engineering to overcome resistance, specifically to target tumor cells better and sustain CAR T cell persistence to enhance treatment efficacy in solid tumors.

Circ_0006174 Upregulates IGF1R to Enhance Radioresistance and Tumorigenesis in Colorectal Cancer via miR-940 Suppression

Colorectal cancer (CRC) is one of the most common malignancies all over the world. Increasing evidence has revealed that circular RNAs (circRNAs) are involved in the progression of CRC. In this study, we aimed to investigate the role and underlying mechanism of circ_0006174 in the development and radiosensitivity of CRC. Circ_0006174, microRNA-940 (miR-940), and insulin-like growth factor 1 receptor (IGF1R) expression levels were evaluated by real-time quantitative polymerase chain reaction (RT-qPCR). The radiosensitivity of cells also was assessed using colony formation assay. Besides, cell proliferation, apoptosis, migration, and invasion were detected by cell counting kit-8 (CCK-8), flow cytometry, and transwell assays. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to verify the relationship between miR-940 and circ_0006174 or IGF1R. IGF1R protein level was examined using western blot. A xenograft tumor model was used to verify the function of circ_0006174 in CRC tumor growth in vivo. Circ_0006174 and IGF1R levels were elevated and miR-940 expression was decreased in CRC tissues and cells. Circ_0006174 knockdown enhanced the radiosensitivity of CRC cells by regulating cell proliferation, apoptosis, migration, and invasion in vitro. In mechanism, circ_0006174 served as a sponge for miR-940 to upregulate IGF1R expression. Moreover, circ_0006174 silencing suppressed CRC growth in vivo. Circ_0006174 boosts radioresistance of CRC cells at least partly through upregulating IGF1R expression by sponging miR-940, providing a novel theoretical basis for CRC therapy.

cDTL contributes to breast cancer progression through regulating redox homeostasis via affecting the function of system xc. Biochem Biophys Res Commun 2025;744:151196. [PMID: 39706052 DOI: 10.1016/j.bbrc.2024.151196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Ferroptosis is a new type of cell death caused by redox imbalance mediated by iron-dependent lipid peroxidation, which is intimately linked to human disease. Circular RNA, characterized by covalently closed loop structure, has attracted much attention due to its involvement in various biological functions. However, little is known about the role of circRNA in ferroptosis. In this study, we identified cDTL (a circular RNA derived from DTL gene) as a ferroptosis-related circRNA. cDTL expression was remarkably elevated by ferroptotic stress. Knockdown of cDTL significantly inhibited breast cancer cell growth both in vitro and in vivo through promoting ferroptosis. Mechanistically, cDTL directly bound to NRF2 and BCLAF1 in the nucleus and cytoplasm, respectively, resulting in transcriptional activation and mRNA stability of SLC7A11 (the core subunit of system Xc-), thereby repressing ferroptosis via activating GSH/GPX4 axis. Moreover, cDTL was identified as a direct transcriptional target of Myc, a well-known protooncogene that is highly activated in breast cancer. More importantly, cDTL was overexpressed in human breast cancer tissues, which was associated with dismal progression-free survival and poor differentiation. In conclusion, our data suggest that cDTL is a novel regulator of ferroptosis, targeting cDTL may be a potential therapeutic strategy for breast cancer.

Dihydroartemisinin enhances the radiosensitivity of breast cancer by targeting ferroptosis signaling pathway through hsa_circ_0001610

OBJECTIVE

This study aimed to elucidate how DHA enhances the radiosensitivity of BC and to explain its potential mechanisms of action.

METHODS

The circular structure of hsa_circ_0001610 was confirmed by Sanger sequencing, RNase R treatment, RT-PCR analysis using gDNA or cDNA. Cellular localization of hsa_circ_0001610 and microRNA-139-5p (miR-139-5p) was detected by fluorescence in situ hybridization. Cell counting kit-8 assay, wound healing and colony formation tests for assessing cell proliferation, while flow cytometry was utilized to estimate cell cycle progression and apoptosis. Reactive oxygen species and malondialdehyde experiments were conducted to validate ferroptosis of BC cells. The expression of ncRNAs and mRNAs was quantified via qRT-PCR, and protein expression was analyzed using Western blot. The effects of hsa_circ_0001610 and DHA on radiosensitivity of BC in vivo were studied by establishing BC mice model.

RESULTS

In vivo and in vitro experimental results indicate that DHA promotes ferroptosis of BC cells at least partly by inhibiting hsa_circ_0001610/miR-139-5p/SLC7A11 pathway, thereby enhancing the radiosensitivity of BC cells.

CONCLUSIONS

Our findings showed that DHA can induce ferroptosis of BC cells by down-regulation of hsa_circ_0001610, thus enhancing radiosensitivity, suggesting a promising therapeutic strategy for enhancing BC radiosensitivity that is worthy of further exploration.

High expression of ADAR mediated by OGT promotes chemoresistance in colorectal cancer through the A-to-I editing pathway

Colorectal cancer (CRC) is a malignant tumor with poor prognosis and adverse therapeutic effect. The study aims to elucidate the contribution of OGT-mediated glycosylation of ADAR to chemoresistance in CRC through its role and regulatory mechanisms. Variations in OGT expression levels and their impact on CRC cell chemoresistance were investigated using gain-of-function and loss-of-function assays. Through a series of molecular biology experiments, we confirmed that ADAR is the downstream target of OGT regulation, emphasizing the role of OGT-mediated glycosylation in stabilizing ADAR. Furthermore, RNA immunoprecipitation (RIP) assays were conducted to examine the effects of ADAR-mediated A-to-I editing on the mRNA stability and translation of genes associated with DNA damage repair. Elevated OGT expression was found to enhance CRC's malignancy and resistance to chemotherapy. OGT's influence leads to the glycosylation of ADAR, thereby increasing its protein levels. ADAR, through its role in A-to-I editing, modulates the mRNA editing of genes implicated in DNA damage repair. This regulation enhances the expression of these genes, improves DNA repair capabilities, and ultimately, fosters chemoresistance in CRC cells. In conclusion, ADAR promotes PARP1 expression under the positive regulation of OGT-mediated O-glycosylation modification to enhance drug resistance in COAD cells. It provides the research basis for overcoming the drug resistance of CRC.

SAGCN: Using Graph Convolutional Network With Subgraph-Aware for circRNA-Drug Sensitivity Identification

Circular RNAs (circRNAs) play a significant role in cancer development and therapy resistance. There is substantial evidence indicating that the expression of circRNAs affects the sensitivity of cells to drugs. Identifying circRNAs-drug sensitivity association (CDA) is helpful for disease treatment and drug discovery. However, the identification of CDA through conventional biological experiments is both time-consuming and costly. Therefore, it is urgent to develop computational methods to predict CDA. In this study, we propose a new computational method, the subgraph-aware graph convolutional network (SAGCN), for predicting CDA. SAGCN first constructs a heterogeneous network composed of circRNA similarity network, drug similarity network, and circRNA-drug bipartite network. Then, a subgraph extractor is proposed to learn the latent subgraph structure of the heterogeneous network using a graph convolutional network. The extractor can capture 1-hop and 2-hop information and then a fusing attention mechanism is designed to integrate them adaptively. Simultaneously, a novel subgraph-aware attention mechanism is proposed to detect intrinsic subgraph structure. The final node feature representation is obtained to make the CDA prediction. Experimental results demonstrate that SAGCN obtained an average AUC of 0.9120 and AUPR of 0.8693, exceeding the performance of the most advanced models under 10-fold cross-validation. Case studies have demonstrated the potential of SAGCN in identifying associations between circRNA and drug sensitivity.

CircROBO1 knockdown improves the radiosensitivity of hepatocellular carcinoma by regulating RAD21

INTRODUCTION AND OBJECTIVES

Radioresistance is a common problem in the treatment of many cancers, including hepatocellular carcinoma (HCC). Previous studies have shown that circROBO1 is highly expressed in HCC tissues and acts as a cancer promoter to accelerate the malignant progression of HCC. However, the role and mechanism of circROBO1 in HCC radioresistance remain unclear.

MATERIALS AND METHODS

CircROBO1, microRNA (miR)-136-5p and RAD21 expression levels were analyzed by quantitative real-time PCR. Cell function and radioresistance were evaluated by colony formation assay, cell counting kit 8 assay, EdU assay and flow cytometry. Protein expression was determined using western blot analysis. RNA interaction was analyzed by dual-luciferase reporter assay and RNA pull-down assay. In vivo experiments were performed by constructing mice xenograft models.

RESULTS

CircROBO1 was highly expressed in HCC, and its knockdown inhibited HCC cell proliferation and promoted apoptosis to enhance cell radiosensitivity. On the mechanism, circROBO1 could serve as miR-136-5p sponge to positively regulate RAD21. MiR-136-5p inhibitor or RAD21 overexpression reversed the regulation of circROBO1 knockdown on the radiosensitivity of HCC cells. Also, circROBO1 interference improved the radiosensitivity of HCC tumors in vivo.

CONCLUSIONS

CircROBO1 might be a promising target for treating HCC radioresistance.

CircGSK3β mediates PD-L1 transcription through miR-338-3p/PRMT5/H3K4me3 to promote breast cancer cell immune evasion and tumor progression

Circular RNA (circRNA) plays a pivotal role in breast cancer onset and progression. Understanding the biological functions and underlying molecular mechanisms of dysregulated circRNAs in breast cancer is crucial for elucidating its pathogenesis and identifying potential therapeutic targets. In this study, we investigated the role and molecular mechanism of circGSK3β in breast cancer. We found that circGSK3β is highly expressed in breast cancer cell lines, where it promotes cell proliferation, migration, and invasion, thereby driving breast cancer progression. Furthermore, we observed a close association between circGSK3β expression levels and immune evasion in breast cancer cells. Mechanistically, circGSK3β acts as a competing endogenous RNA (ceRNA) by interacting with miR-338-3p, thereby promoting breast cancer cell proliferation, migration, and invasion. Additionally, circGSK3β positively regulates the expression of the target gene PRMT5 through its interaction with miR-338-3p. This, in turn, enhances H3K4me3 recruitment to the promoter region of PD-L1, resulting in upregulation of PD-L1 expression and consequent immune evasion in breast cancer. In summary, our findings underscore the significance of the circGSK3β-miR-338-3p-PRMT5-H3K4me3 axis in promoting breast cancer progression and immune evasion. CircGSK3β emerges as a critical player in breast cancer pathogenesis, potentially serving as a diagnostic and prognostic marker, and offering novel insights into the role of circRNAs in breast cancer progression.

CircNSD1 promotes cardiac fibrosis through targeting the miR-429-3p/SULF1/Wnt/β-catenin signaling pathway

Cardiac fibrosis is a detrimental pathological process, which constitutes the key factor for adverse cardiac structural remodeling leading to heart failure and other critical conditions. Circular RNAs (circRNAs) have emerged as important regulators of various cardiovascular diseases. It is known that several circRNAs regulate gene expression and pathological processes by binding miRNAs. In this study we investigated whether a novel circRNA, named circNSD1, and miR-429-3p formed an axis that controls cardiac fibrosis. We established a mouse model of myocardial infarction (MI) for in vivo studies and a cellular model of cardiac fibrogenesis in primary cultured mouse cardiac fibroblasts treated with TGF-β1. We showed that miR-429-3p was markedly downregulated in the cardiac fibrosis models. Through gain- and loss-of-function studies we confirmed miR-429-3p as a negative regulator of cardiac fibrosis. In searching for the upstream regulator of miR-429-3p, we identified circNSD1 that we subsequently demonstrated as an endogenous sponge of miR-429-3p. In MI mice, knockdown of circNSD1 alleviated cardiac fibrosis. Moreover, silence of human circNSD1 suppressed the proliferation and collagen production in human cardiac fibroblasts in vitro. We revealed that circNSD1 directly bound miR-429-3p, thereby upregulating SULF1 expression and activating the Wnt/β-catenin pathway. Collectively, circNSD1 may be a novel target for the treatment of cardiac fibrosis and associated cardiac disease.

Hallmarks of cancer resistance

This review explores the hallmarks of cancer resistance, including drug efflux mediated by ATP-binding cassette (ABC) transporters, metabolic reprogramming characterized by the Warburg effect, and the dynamic interplay between cancer cells and mitochondria. The role of cancer stem cells (CSCs) in treatment resistance and the regulatory influence of non-coding RNAs, such as long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), are studied. The chapter emphasizes future directions, encompassing advancements in immunotherapy, strategies to counter adaptive resistance, integration of artificial intelligence for predictive modeling, and the identification of biomarkers for personalized treatment. The comprehensive exploration of these hallmarks provides a foundation for innovative therapeutic approaches, aiming to navigate the complex landscape of cancer resistance and enhance patient outcomes.

Exploring the evolving roles and clinical significance of circRNAs in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) represents the predominant malignancies in the head and neck region, and has limited therapeutic alternatives. Circular RNAs (circRNAs), a substantial category of non-coding RNA molecules, exert influential roles in human disease development and progression, employing various mechanisms such as microRNA sponging, interaction with RNA-binding proteins, and translational capabilities. Accumulating evidence highlights the differential expression of numerous circRNAs in HNSCC, and numerous dysregulated circRNAs underscore their crucial involvement in malignant advancement and resistance to treatment. This review aims to comprehensively outline the characteristics, biogenesis, and mechanisms of circRNAs, elucidating their functional significance in HNSCC. In addition, we delve into the clinical implications of circRNAs, considering their potential as biomarkers or targets for diagnosis, prognosis, and therapeutic applications in HNSCC. The discussion extends to exploring future challenges in the clinical translation of circRNAs, emphasizing the need for further research.

Exploring non-coding RNA mechanisms in hepatocellular carcinoma: implications for therapy and prognosis

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths in the world. The development and progression of HCC are closely correlated with the abnormal regulation of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Important biological pathways in cancer biology, such as cell proliferation, death, and metastasis, are impacted by these ncRNAs, which modulate gene expression. The abnormal expression of non-coding RNAs in HCC raises the possibility that they could be applied as new biomarkers for diagnosis, prognosis, and treatment targets. Furthermore, by controlling the expression of cancer-related genes, miRNAs can function as either tumor suppressors or oncogenes. On the other hand, lncRNAs play a role in the advancement of cancer by interacting with other molecules within the cell, which, in turn, affects processes such as chromatin remodeling, transcription, and post-transcriptional processes. The importance of ncRNA-driven regulatory systems in HCC is being highlighted by current research, which sheds light on tumor behavior and therapy response. This research highlights the great potential of ncRNAs to improve patient outcomes in this difficult disease landscape by augmenting the present methods of HCC care through the use of precision medicine approaches.

The role of circular RNAs in regulating resistance to cancer immunotherapy: mechanisms and implications

Cancer immunotherapy has rapidly transformed cancer treatment, yet resistance remains a significant hurdle, limiting its efficacy in many patients. Circular RNAs (circRNAs), a novel class of non-coding RNAs, have emerged as pivotal regulators of gene expression and cellular processes. Increasing evidence indicates their involvement in modulating resistance to cancer immunotherapy. Notably, certain circRNAs function as miRNA sponges or interact with proteins, influencing the expression of immune-related genes, including crucial immune checkpoint molecules. This, in turn, shapes the tumor microenvironment and significantly impacts the response to immunotherapy. In this comprehensive review, we explore the evolving role of circRNAs in orchestrating resistance to cancer immunotherapy, with a specific focus on their mechanisms in influencing immune checkpoint gene expression. Additionally, we underscore the potential of circRNAs as promising therapeutic targets to augment the effectiveness of cancer immunotherapy. Understanding the role of circRNAs in cancer immunotherapy resistance could contribute to the development of new therapeutic strategies to overcome resistance and improve patient outcomes.

Riddle of the Sphinx: Emerging role of circular RNAs in cervical cancer

Cervical cancer is a prominent cause of cancer-related mortality among women, with recent attention directed toward exploring the involvement of circular RNAs (circRNAs) in this particular cancer. CircRNAs, characterized by a covalently closed loop structure, belong to a class of single-stranded non-coding RNA (ncRNA) molecules that play crucial roles in cancer development and progression through diverse mechanisms. The abnormal expression of circRNAs in vivo is significantly associated with the development of cervical cancer. Notably, circRNAs actively interact with miRNAs in cervical cancer, leading to the regulation of diverse signaling pathways, and they can contribute to cancer hallmarks such as self-sufficiency in growth signals, insensitivity to antigrowth signals, limitless proliferation, evading apoptosis, tissue invasion and metastasis, and sustained angiogenesis. Moreover, the distinctive biomedical attributes exhibited by circRNAs, including their abundance, conservation, and stability in body fluids, position them as promising biomarkers for various cancers. In this review, we elucidate the tremendous potential of circRNAs as diagnostic markers or therapeutic targets in cervical cancer by expounding upon their biogenesis, characteristics, functions, and databases, highlighting the novel advances in the signaling pathways associated with circRNAs in cervical cancer.

Circ-POSTN promotes the progression and reduces radiosensitivity in esophageal cancer by regulating the miR-876-5p/FYN axis

BACKGROUND

Circular RNAs (circRNAs) play critical roles in the tumorigenesis and radiosensitivity of multiple cancers. Nevertheless, the biological functions of circRNA periostin (circ-POSTN) in esophageal cancer (EC) progression and radiosensitivity have not been well elucidated.

METHODS

The expression of circ-POSTN, microRNA-876-5p (miR-876-5p), and proto-oncogene tyrosine-protein kinase (FYN) was analyzed by quantitative reverse transcription PCR (RT-qPCR). Cell proliferation was assessed by MTT, colony formation, and 5-ethynyl-2'-deoxyuridine (EDU) assays. All protein levels were detected by western blot assay. Cell apoptosis and invasion were assessed by flow cytometry analysis and transwell assay, respectively. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were used to validate the interaction between miR-876-5p and circ-POSTN or FYN. The role of circ-POSTN in vivo was explored by establishing mice xenograft model.

RESULTS

Circ-POSTN was overexpressed in EC tissues and cells. Knockdown of circ-POSTN inhibited cell proliferation and invasion and elevated apoptosis and radiosensitivity in EC cells. MiR-876-5p was a direct target of circ-POSTN, and its knockdown reversed the role of sh-circ-POSTN in EC cells. FYN was a direct target of miR-876-5p, and FYN elevation weakened the effects of miR-876-5p overexpression on the progression and radiosensitivity of EC cells. Moreover, circ-POSTN acted as a miR-876-5p sponge to regulate FYN expression. Circ-POSTN interference also suppressed tumor growth and enhanced radiosensitivity in vivo.

CONCLUSION

Circ-POSTN knockdown inhibited proliferation and invasion, but increased apoptosis and enhanced radiosensitivity in EC cells via modulating miR-876-5p/FYN axis, which might be a potential diagnostic and therapeutic target for EC.

Hypoxia-Inducible Factor-Dependent and Independent Mechanisms Underlying Chemoresistance of Hypoxic Cancer Cells

In hypoxic regions of malignant solid tumors, cancer cells acquire resistance to conventional therapies, such as chemotherapy and radiotherapy, causing poor prognosis in patients with cancer. It is widely recognized that some of the key genes behind this are hypoxia-inducible transcription factors, e.g., hypoxia-inducible factor 1 (HIF-1). Since HIF-1 activity is suppressed by two representative 2-oxoglutarate-dependent dioxygenases (2-OGDDs), PHDs (prolyl-4-hydroxylases), and FIH-1 (factor inhibiting hypoxia-inducible factor 1), the inactivation of 2-OGDD has been associated with cancer therapy resistance by the activation of HIF-1. Recent studies have also revealed the importance of hypoxia-responsive mechanisms independent of HIF-1 and its isoforms (collectively, HIFs). In this article, we collate the accumulated knowledge of HIF-1-dependent and independent mechanisms responsible for resistance of hypoxic cancer cells to anticancer drugs and briefly discuss the interplay between hypoxia responses, like EMT and UPR, and chemoresistance. In addition, we introduce a novel HIF-independent mechanism, which is epigenetically mediated by an acetylated histone reader protein, ATAD2, which we recently clarified.

Deciphering the impact of circRNA-mediated autophagy on tumor therapeutic resistance: a novel perspective

Cancer therapeutic resistance remains a significant challenge in the pursuit of effective treatment strategies. Circular RNAs (circRNAs), a class of non-coding RNAs, have recently emerged as key regulators of various biological processes, including cancer progression and drug resistance. This review highlights the emerging role of circRNAs-mediated autophagy in cancer therapeutic resistance, a cellular process that plays a dual role in cancer by promoting both cell survival and death. Increasing evidence suggests that circRNAs can modulate autophagy pathways, thereby influencing the response of cancer cells to therapeutic agents. In this context, the intricate interplay between circRNAs, autophagy, and therapeutic resistance is explored. Various mechanisms are discussed through which circRNAs can impact autophagy, including direct interactions with autophagy-related genes, modulation of signaling pathways, and cross-talk with other non-coding RNAs. Furthermore, the review delves into specific examples of how circRNA-mediated autophagy regulation can contribute to resistance against chemotherapy and radiotherapy. Understanding these intricate molecular interactions provides valuable insights into potential strategies for overcoming therapeutic resistance in cancer. Exploiting circRNAs as therapeutic targets or utilizing them as diagnostic and predictive biomarkers opens new avenues for developing personalized treatment approaches. In summary, this review underscores the importance of circRNA-mediated autophagy in cancer therapeutic resistance and proposes future directions for research in this exciting and rapidly evolving field.

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.

hsa_circ_0007919 promotes pancreatic cancer metastasis by modulating Sp1-mediated THBS1 transcription

CircRNAs are abnormally expressed in various cancers and play an important role in the occurrence and development of cancers. However, their biological functions and the underlying molecular mechanisms in pancreatic cancer (PC) metastasis are incompletely understood. Differentially expressed circRNAs were identified by second-generation transcriptome sequencing in three pairs of PC tissues and adjacent tissues. The expression and prognostic significance of hsa_circ_0007919 were evaluated by qRT-PCR and Kaplan-Meier survival curves. Gain- and loss-of-function assays were conducted to detect the role of hsa_circ_0007919 in PC metastasis in vitro. A lung metastasis model and IHC experiments were conducted to confirm the effects of hsa_circ_0007919 on tumor metastasis in vivo. Mechanistically, RNA immunoprecipitation and chromatin immunoprecipitation assays were conducted to explore the interplay among hsa_circ_0007919, Sp1, and the THBS1 promoter. hsa_circ_0007919 was significantly upregulated in PC tissues and cells and was correlated with lymph node metastasis, TNM stage, and poor prognosis. Knockdown of hsa_circ_0007919 significantly suppressed the migration and invasion of PC cells in vitro and inhibited tumor metastasis in vivo. However, overexpression of hsa_circ_0007919 exerted the opposite effects. Mechanistically, hsa_circ_0007919 could recruit the transcription factor Sp1 to inhibit THBS1 transcription, thereby facilitating PC metastasis. hsa_circ_0007919 can promote the metastasis of PC by inhibiting THBS1 expression. hsa_circ_0007919 may be a potential therapeutic target in PC.

Impact of Resistance on Therapeutic Design: A Moran Model of Cancer Growth

Resistance of cancers to treatments, such as chemotherapy, largely arise due to cell mutations. These mutations allow cells to resist apoptosis and inevitably lead to recurrence and often progression to more aggressive cancer forms. Sustained-low dose therapies are being considered as an alternative over maximum tolerated dose treatments, whereby a smaller drug dosage is given over a longer period of time. However, understanding the impact that the presence of treatment-resistant clones may have on these new treatment modalities is crucial to validating them as a therapeutic avenue. In this study, a Moran process is used to capture stochastic mutations arising in cancer cells, inferring treatment resistance. The model is used to predict the probability of cancer recurrence given varying treatment modalities. The simulations predict that sustained-low dose therapies would be virtually ineffective for a cancer with a non-negligible probability of developing a sub-clone with resistance tendencies. Furthermore, calibrating the model to in vivo measurements for breast cancer treatment with Herceptin, the model suggests that standard treatment regimens are ineffective in this mouse model. Using a simple Moran model, it is possible to explore the likelihood of treatment success given a non-negligible probability of treatment resistant mutations and suggest more robust therapeutic schedules.

Non-coding RNA and Drug resistance in cholangiocarcinoma

Cholangiocarcinoma is a highly aggressive cancer with a dismal prognosis and limited resectability. Chemotherapy has demonstrated tremendous benefits for patients with advanced and inoperable cancer, but drug resistance poses a significant obstacle. Despite recent progress in cancer therapy, the mechanisms driving drug resistance are multifaceted and not completely comprehended. Non-coding RNA refers to RNA molecules that are endogenous and do not code for proteins. Particularly microRNAs, long non-coding RNAs, circular RNAs, are widely acknowledged to be involved in cancer initiation, proliferation, and metastasis. Recently, evidences suggests that abnormal expression of non-coding RNAs contributes to resistance to different type of cancer therapies in cholangiocarcinoma. This occurs via the rewiring of signaling pathways including the reduction of anticancer drugs, apoptosis, interaction between cholangiocarcinoma and tumor-infiltrating immune cells, and cancer stemness. Thus, our review aims to demonstrate the potential of targeting non-coding RNA to override drug resistance and summarize the molecular mechanisms of how non-coding RNA contributes to drug resistance in cholangiocarcinoma.

dbCRAF: a curated knowledgebase for regulation of radiation response in human cancer

Radiation therapy (RT) is one of the primary treatment modalities of cancer, with 40-60% of cancer patients benefiting from RT during their treatment course. The intrinsic radiosensitivity or acquired radioresistance of tumor cells would affect the response to RT and clinical outcomes in patients. Thus, mining the regulatory mechanisms in tumor radiosensitivity or radioresistance that have been verified by biological experiments and computational analysis methods will enhance the overall understanding of RT. Here, we describe a comprehensive database dbCRAF (http://dbCRAF.xialab.info/) to document and annotate the factors (1,677 genes, 49 proteins and 612 radiosensitizers) linked with radiation response, including radiosensitivity, radioresistance in cancer cells and prognosis in cancer patients receiving RT. On the one hand, dbCRAF enables researchers to directly access knowledge for regulation of radiation response in human cancer buried in the vast literature. On the other hand, dbCRAF provides four flexible modules to analyze and visualize the functional relationship between these factors and clinical outcome, KEGG pathway and target genes. In conclusion, dbCRAF serves as a valuable resource for elucidating the regulatory mechanisms of radiation response in human cancers as well as for the improvement of RT options.

Autophagy-modulating biomembrane nanostructures: A robust anticancer weapon by modulating the inner and outer cancer environment

Recently, biomembrane nanostructures, such as liposomes, cell membrane-coated nanostructures, and exosomes, have demonstrated promising anticancer therapeutic effects. These nanostructures possess remarkable biocompatibility, multifunctionality, and low toxicity. However, their therapeutic efficacy is impeded by chemoresistance and radiotherapy resistance, which are closely associated with autophagy. Modulating autophagy could enhance the therapeutic sensitivity and effectiveness of these biomembrane nanostructures by influencing the immune system and the cancer microenvironment. For instance, autophagy can regulate the immunogenic cell death of cancer cells, antigen presentation of dendritic cells, and macrophage polarization, thereby activating the inflammatory response in the cancer microenvironment. Furthermore, combining autophagy-regulating drugs or genes with biomembrane nanostructures can exploit the targeting and long-term circulation properties of these nanostructures, leading to increased drug accumulation in cancer cells. This review explores the role of autophagy in carcinogenesis, cancer progression, metastasis, cancer immune responses, and resistance to treatment. Additionally, it highlights recent research advancements in the synergistic anticancer effects achieved through autophagy regulation by biomembrane nanostructures. The review also discusses the prospects and challenges associated with the future clinical translation of these innovative treatment strategies. In summary, these findings provide valuable insights into autophagy, autophagy-modulating biomembrane-based nanostructures, and the underlying molecular mechanisms, thereby facilitating the development of promising cancer therapeutics.

Exosome-transported of circ_0081069 induces SPIN1 production by binding to miR-195-5p to inhibit radiosensitivity in esophageal squamous cell carcinoma

Circ_0081069 plays a key role in tumor growth; however, its effect on radiosensitivity in esophageal squamous cell carcinoma (ESCC) remains unknown. The study is performed to reveal the association of circ_0081069 expression and radiosensitivity in ESCC and the underlying mechanism. Circ_0081069, miR-195-5p, and spindlin 1 (SPIN1) RNA expression were detected by quantitative real-time polymerase chain reaction. Protein expression was checked by Western blot analysis or immunohistochemistry assay. Cell viability, proliferation, cell apoptosis, migration, and invasion were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine, flow cytometry analysis, scratch test, and transwell assays, respectively. The sensitivity of ESCC cells to radiation was investigated by cell colony formation assay. The interactions among circ_0081069, miR-195-5p, and SPIN1 were identified by dual-luciferase reporter assay and RNA Immunoprecipitation assay. Xenograft mouse model assay was performed to determine the effect of circ_0007841 on radiosensitivity in vivo. Circ_0081069 and SPIN1 expression were upregulated, whereas miR-195-5p was downregulated in ESCC tissues, ESCC cells, and radiation-stimulated ESCC cells. Circ_0081069 silencing inhibited ESCC cell proliferation, invasion, and migration but improved cell apoptosis. In addition, circ_0081069 knockdown enhanced ESCC cell radiosensitivity in vitro and in vivo. Circ_0081069 bound to miR-195-5p and regulated radiosensitivity by binding to miR-195-5p in ESCC cells. Moreover, SPIN1, a target of miR-195-5p, rescued miR-195-5p-mediated effects in ESCC cells. Circ_0081069 was secreted from ESCC cells by being packaged into exosomes. Further, circ_0081069-Exo inhibited radiosensitivity in ESCC cells. Exosome-mediated transfer of circ_0081069 induced SPIN1 production by binding to miR-195-5p, further inhibiting radiosensitivity in ESCC.

Macrophage Membrane-Camouflaged Aggregation-Induced Emission Nanoparticles Enhance Photodynamic-Immunotherapy to Delay Postoperative Tumor Recurrence

Surgery is a traditional tumor treatment, and immunotherapy can reduce the postoperative recurrence of tumors. However, the intrinsic limits of low responsive rate and non-tumor specificity of immunotherapy agents are still insufficient to address therapeutic demands. Herein, the macrophages membrane camouflaged nanoparticles (NPs), named M@PFC, consisting of the aggregation-induced emission photosensitizer (PF3-PPh3 ) and immune adjuvant (CpG), are reported. As the protein on the membrane interacts with the vascular cell adhesion molecule 1 (VCAM-1) of cancer cells, M@PFC efficiently transports CpG to the tumor. Meanwhile, M@PFC can evade clearance by the immune system and prolong the circulation time in vivo; thus, enhancing their accumulation in tumors. PF3-PPh3 promotes high production of reactive oxygen species (ROS) and triggers immune cell death (ICD) in tumor cells under light exposure. Importantly, CpG enrichment in tumors can stimulate tumor cells to produce immune factors to assist in enhancing ICD effects. The synergistic effect combining the PDT properties of the aggregation-induced emission (AIE)-active photosensitizer and immunotherapy properties of CpG significantly delays tumor recurrence after surgery. In conclusion, this strategy achieves the synergistic activation of the immune system for anti-tumor activity, providing a novel paradigm for the development of therapeutic nanodrugs to delay postoperative tumor recurrence.

Has_circ_0071803 promotes colorectal cancer progression by regulating miR-330-5p/MAPK signaling pathway

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide. A lack of effective targeted therapies against CRC makes the treatment challenging. Here, we report a circular RNA (circRNA), has_circ_0071803, functioning as an oncogene in CRC. Circ_0071803 was upregulated in CRC tissues and cell lines, and its expression levels were inversely correlated with the prognosis and survival rate of patients with CRC. Circ_0071803 knockdown suppressed cell proliferation, migration, and invasion in CRC. Moreover, we found that circ_0071803 sponged miR-330-5p, thereby upregulating mitogen-activated protein kinase 1 (MAPK1) in CRC cells. The suppression of cell activities by circ_0071803 knockdown were rescued by miR-330-5p inhibition or MAPK1 overexpression. Collectively, our findings elucidate that circ_0071803 promotes CRC progression by regulating the miR-330-5p/MAPK1 pathway, providing potential therapeutic targets for designing effective targeted treatments.

Circular RNA from Tyrosylprotein Sulfotransferase 2 Gene Inhibits Cisplatin Sensitivity in Head and Neck Squamous Cell Carcinoma by Sponging miR-770-5p and Interacting with Nucleolin

Chemoresistance poses a significant challenge in the treatment of advanced head and neck squamous cell cancer (HNSCC). The role and mechanism of circular RNAs (circRNAs) in HNSCC chemoresistance remain understudied. We conducted circRNA microarray analysis to identify differentially expressed circRNAs in HNSCC. The expression of circRNAs from the tyrosylprotein sulfotransferase 2 (TPST2) gene and miRNAs was evaluated through qPCR, while the circular structure of circTPST2 was verified using Sanger sequencing and RNase R. Through Western blotting, biotin-labeled RNA pulldown, RNA immunoprecipitation, mass spectrometry, and rescue experiments, we discovered miR-770-5p and nucleolin as downstream targets of circTPST2. Functional tests, including CCK8 assays and flow cytometry, assessed the chemoresistance ability of circTPST2, miR-770-5p, and Nucleolin. Additionally, FISH assays determined the subcellular localization of circTPST2, miR-770-5p, and Nucleolin. IHC staining was employed to detect circTPST2 and Nucleolin expression in HNSCC patients. circTPST2 expression was inversely correlated with cisplatin sensitivity in HNSCC cell lines. Remarkably, high circTPST2 expression correlated with lower overall survival rates in chemotherapeutic HNSCC patients. Mechanistically, circTPST2 reduced chemosensitivity through sponge-like adsorption of miR-770-5p and upregulation of the downstream protein Nucleolin in HNSCC cells. The TCGA database revealed improved prognosis for patients with low circTPST2 expression after chemotherapy. Moreover, analysis of HNSCC cohorts demonstrated better prognosis for patients with low Nucleolin protein expression after chemotherapy. We unveil circTPST2 as a circRNA associated with chemoresistance in HNSCC, suggesting its potential as a marker for selecting chemotherapy regimens in HNSCC patients. Further exploration of the downstream targets of circTPST2 advanced our understanding and improved treatment strategies for HNSCC.

Circ_MACF1 targets miR-421 to upregulate FMO2 to suppress paclitaxel resistance and malignant cellular behaviors in lung adenocarcinoma

BACKGROUND

Chemoresistance remains an enormous challenge in the treatment of lung adenocarcinoma (LADC). Circular RNAs (circRNAs) exhibit important regulation in tumor progression and chemoresistance. This research focused on exploring the regulatory function and mechanism of circ_MACF1 (has_circ_0011780) in paclitaxel (PTX) resistance in LADC.

METHODS

Circ_MACF1, miR-421 and flavin-containing monooxygenase 2 (FMO2) were determined by RT-qPCR. MTT was applied to detect IC50 of PTX. The proliferation analysis was performed using EdU and colony formation assay. Cell apoptosis and motility were examined using flow cytometry and transwell assay, respectively. Western blot was administered for protein detection. A dual-luciferase reporter assay was performed for confirming target interaction. PTX sensitivity in vivo was researched via xenograft tumor assay.

RESULTS

Expression of circ_MACF1 was decreased in PTX-resistant LADC tissues and cells. Circ_MACF1 overexpression reduced chemoresistance, proliferation, motility and accelerated apoptosis in PTX-resistant LADC cells. Circ_MACF1 targeted miR-421 and miR-421 upregulation reverted circ_MACF1-evoked effects. FMO2 served as a downstream target of miR-421 and circ_MACF1 sponged miR-421 to elevate the expression of FMO2. MiR-421 enhanced PTX resistance and LADC progression via targeting FMO2. FMO2 knockdown enhanced IC50 of PTX and cell proliferation. In vivo, circ_MACF1 elevated PTX sensitivity of LADC by mediating miR-421/FMO2 axis.

CONCLUSION

These findings elucidated that circ_MACF1 inhibited PTX resistance by absorbing miR-421 to upregulate FMO2 in LADC.

Investigation of LGALS2 expression in the TCGA database reveals its clinical relevance in breast cancer immunotherapy and drug resistance

Breast cancer (BRCA) is known as the leading cause of death in women worldwide and has a poor prognosis. Traditional therapeutic strategies such as surgical resection, radiotherapy and chemotherapy can cause adverse reactions such as drug resistance. Immunotherapy, a new treatment approach with fewer side effects and stronger universality, can prolong the survival of BRCA patients and even achieve clinical cure. However, due to population heterogeneity and other reasons, there are still certain factors that limit the efficacy of immunotherapy. Therefore, the importance of finding new tumor immune biomarker cannot be emphasized enough. Studies have reported that LGALS2 was closely related to immunotherapy efficacy, however, it is unclear whether it can act as an immune checkpoint for BRCA immunotherapy. In the current study, changes in LGALS2 expression were analyzed in public datasets such as TCGA-BRCA. We found that LGALS2 expression was associated with immune infiltration, drug resistance and other characteristics of BRCA. Moreover, high LGALS2 expression was closely related to immunotherapy response, and was associated with methylation modifications and clinical resistance for the first time. These findings may help to elucidate the role of LGALS2 in BRCA for the development and clinical application of future immunotherapy strategies against BRCA.

SHF confers radioresistance in colorectal cancer by the regulation of mitochondrial DNA copy number

Altered mitochondrial function contributes greatly to pathogenesis and progression of colorectal cancer. In this study, we report a functional pool of Src homology 2 domain-containing F (SHF) in mitochondria controlling the response of colorectal cancer cells to radiation therapy. We found that elevated expression of SHF in cancer cells is essential for promoting mitochondrial function by increasing mitochondrial DNA copy number, thus reducing the sensitivity of colorectal cancer cells to radiation. Mechanistically, SHF binds to mitochondrial DNA and promotes POLG/SSBP1-mediated mitochondrial DNA synthesis. Importantly, SHF loss-mediated radiosensitization was phenocopied by depletion of mitochondrial DNA. Thus, our data demonstrate that mitochondrial SHF is an important regulator of radioresistance in colorectal cancer cells, identifying SHF as a promising therapeutic target to enhance radiotherapy efficacy in colorectal cancer.

Exosome-delivered circRNA circSYT15 contributes to cisplatin resistance in cervical cancer cells through the miR-503-5p/RSF1 axis

The development of chemotherapy resistance is a major obstacle for cervical cancer (CC) patients. Exosome-mediated transfer of circular RNAs (circRNAs) was found to have relevance to the CC. This study is designed to explore the role and mechanism of exosomal circRNA synaptotagmin 15 (circSYT15) on cisplatin (DDP) resistance in CC. Cell proliferation ability and apoptosis rate were detected by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), colony formation, and flow cytometry assays. CircSYT15, microRNA-503-5p (miR-503-5p), Remodeling spacing factor 1 (RSF1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Exosomes were analyzed by a transmission electron microscope and nanoparticle tracking analysis. CD63, CD81, TSC101, Bcl-2, Bax, C-caspase 3, and RSF1 protein levels were examined by western blot assay. The binding between miR-503-5p and circSYT15 or RSF1 was predicted by circBank or Starbase and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP). The biological role of exosomal circSYT15 in DDP resistance of CC in vivo. CircSYT15 was upregulated in the DDP-resistant CC cells and exosomes isolated from DDP-resistant CC cells. CircSYT15 knockdown repressed the proliferation and drug resistance of CC and induced apoptosis in CC cells. Exosomes shuttled circSYT15 act as a sponge to affect RSF1 expression, thereby promoting proliferation and drug resistance and repressing apoptosis of sensitive CC cells. Exosomal circSYT15 boost DDP resistance of cervical cancer in vivo. Exosome-mediated transfer of circSYT15 enhanced DDP resistance in CC partly by targeting the miR-503-5p/RSF1 axis, providing a foundation for future clinical applications of CC drug resistance.

Circular RNA EIF3I promotes papillary thyroid cancer progression by interacting with AUF1 to increase Cyclin D1 production

Circular RNAs (circRNAs) play an important role in regulating the development of human cancers through diverse biological functions. However, the exact molecular mechanisms underlying the role of circRNAs in papillary thyroid cancer (PTC) remain largely unknown. Here, we found that hsa_circ_0011385, designated as circular eukaryotic translation initiation factor 3 subunit I (circEIF3I), preferentially localized in the cytoplasm of PTC cells and was more stable than its linear counterpart, EIF3I. Gain- and loss-of-function studies indicated that circEIF3I promoted PTC progression by facilitating cell proliferation, cell cycle, cell migration, and invasion in vitro, as well as PTC cell proliferation in vivo. Mechanistically, circEIF3I interacted with AU-rich element (ARE) RNA-binding factor 1 (AUF1) in the cytoplasm of PTC cells, thus reducing the degradation of Cyclin D1 mRNA and increasing Cyclin D1 protein production, ultimately resulting in PTC progression. Collectively, our results demonstrate the vital role of circEIF3I in PTC progression, supporting its significance as a potential therapeutic target.

Injectable microenvironment-responsive hydrogels with redox-activatable supramolecular prodrugs mediate ferroptosis-immunotherapy for postoperative tumor treatment

Immunotherapy is an emerging antitumor modality with high specificity and persistence, but its application for resected tumor treatment is impeded by the low availability of tumor-specific antigens and strong immunosuppression in the wound margin. Here a nanoengineered hydrogel is developed for eliciting robust cooperative ferroptosis-immunotherapeutic effect on resected tumors. Specifically, β-cyclodextrin (β-CD) is first grafted onto oxidized sodium alginate (OSA) through Schiff base ligation, which could trap cRGD-modified redox-responsive Withaferin prodrugs (WA-cRGD) to obtain the hydrogel building blocks (Gel@WA-cRGD). Under Ca2+-mediated crosslinking, Gel@WA-cRGD rapidly forms physiologically stable hydrogels, of which the porous network is used to deliver programmed cell death ligand 1 antibodies (aPD-L1). After injection into the post-surgical wound cavity, the β-CD-entrapped WA-cRGD is detached by the local acidity and specifically internalized by residual tumor cells to trigger ferroptosis, thus releasing abundant damage-associated molecular patterns (DAMPs) and tumor-derived antigens for activating the antigen-presenting cell-mediated cross-presentation and downstream cytotoxic T cell (CTL)-mediated antitumor responses. Furthermore, aPD-L1 could block PD-1/PD-L1 interaction and enhance the effector function of CTLs to overcome tumor cell-mediated immunosuppression. This cooperative hydrogel-based antitumor strategy for ferroptosis-immunotherapy may serve as a generally-applicable approach for postoperative tumor management. STATEMENT OF SIGNIFICANCE: To overcome the immunosuppressive microenvironment in resected solid tumors for enhanced patient survival, here we report a nanoengineered hydrogel incorporated supramolecular redox-activatable Withaferin prodrug and PD-L1 antibody, which could elicit robust cooperative ferroptosis-immunotherapeutic effect against residual tumor cells in the surgical bed to prevent tumor relapse, thus offering a generally-applicable approach for postoperative tumor management.

Comparing Singlet Oxygen Generation of Schiff Base Substituted Novel Silicon Phthalocyanines by Sonophotochemical and Photochemical Applications

Although the sonophotodynamic method has an effective therapeutic outcome for anticancer treatment compared with the photodynamic method, there are not enough related studies in the literature and this study aims to contribute to the development of sonophotodynamic studies. For this purpose, the Schiff base substituted silicon phthalocyanines were designed and synthesized as effective sensitizer candidates and the photophysicochemical and sonophotochemical features of the phthalocyanines were examined to increase singlet oxygen efficiency. The calculated ΦΔ values indicate that the contribution of substituent groups improved the production of singlet oxygen compared with silicon (IV) phthalocyanine dichloride (SiPcCI2 ) and also the sonophotochemical applications increased the singlet oxygen yields. The ΦΔ values (ΦΔ  = 0.76 for axially bis-{4-[(E)-(pyridin-3-ylimino)methyl]phenol} substituted silicon (IV) phthalocyanine (2a), 0.68 for axially bis-4-[(E)-{[(pyridin-3-yl)methyl]imino}methyl]phenol substituted silicon (IV) phthalocyanine (2b) in photochemical study) reached to ΦΔ  = 0.98 for 2a, 0.94 for 2b in sonophotochemical study. This article will enrich the literature on increasing singlet oxygen yield.

CircRNA: a rising star in leukemia

Non-coding RNA are a class of RNA that lack the potential to encode proteins. CircRNAs, generated by a post-splicing mechanism, are a newly discovered type of non-coding RNA with multi-functional covalent loop structures. CircRNAs may play an important role in the occurrence and progression of tumors. Research has shown that circRNAs are aberrantly expressed in various types of human cancers, including leukemia. In this review, we summarize the expression and function of circRNAs and their impact on different types of leukemia. We also illustrate the function of circRNAs on immune modulation and chemoresistance in leukemia and their impact on its diagnosis and prognosis. Herein, we provide an understanding of recent advances in research that highlight the importance of circRNAs in proliferation, apoptosis, migration, and autophagy in different types of leukemia. Furthermore, circRNAs make an indispensable difference in the modulation of the immunity and chemoresistance of leukemia. Increasing evidence suggests that circRNAs may play a vital role in the diagnostic and prognostic markers of leukemia because of their prominent properties. More detailed preclinical studies on circRNAs are needed to explore effective ways in which they can serve as biomarkers for the diagnosis and prognosis of leukemia in vivo.

ALKBH5/YTHDF2-mediated m6A modification of circAFF2 enhances radiosensitivity of colorectal cancer by inhibiting Cullin neddylation

BACKGROUND

Circular RNA (circRNA) and N6-methyladenosine (m6A) play a critical role in tumour occurrence and development, including colorectal cancer (CRC). However, little is known about the interaction between circRNA and m6A in the radiosensitivity of CRC. Here, we investigated the role of a novel m6A-regulated circRNA in CRC.

METHODS

Differentially expressed circRNAs from radiosensitive and radioresistant CRC tissues were screened. Modifications of the selected circRNAs were examined by methylated RNA immunoprecipitation assay. Finally, the selected circRNAs were subjected to radiosensitivity assay.

RESULTS

We identified that circAFF2 is closely related to both radiosensitivity and m6A in CRC. CircAFF2 was highly expressed in patients with radiosensitive rectal cancer, and patients with high expression of circAFF2 had a better prognosis. In addition, circAFF2 can enhance the radiosensitivity of CRC cells both in vitro and in vivo. The regulation of circAFF2 involves ALKBH5-mediated demethylation, followed by its recognition and degradation via YTHDF2. Rescue experiments revealed that circAFF2 could reverse the radiosensitivity induced by ALKBH5 or YTHDF2. Mechanistically, circAFF2 binds with CAND1, promotes the binding of CAND1 to Cullin1 and inhibits its neddylation, subsequently impacting the radiosensitivity of CRC.

CONCLUSION

We identified and characterised circAFF2 as a novel m6A-modified circRNA and validated the ALKBH5/YTHDF2/circAFF2/Cullin-NEDD8 axis as a potential radiotherapy target for CRC.

CircEGFR reduces the sensitivity of pirarubicin and regulates the malignant progression of triple-negative breast cancer via the miR-1299/EGFR axis

Circular RNAs (circRNAs) have been found to be involved in cancer progression and chemotherapy sensitivity. However, the biological function of circRNAs in triple-negative breast cancer (TNBC) and its effect on the sensitivity to pirarubicin (THP) chemotherapy are still unclear. CircEGFR (hsa_circ_0080220) was screened and verified by bioinformatics analysis, proving it was highly expressed in TNBC cell lines, patient tissues, and plasma exosomes, and was associated with poor prognosis of patients. The expression level of circEGFR in patient tissue has potential diagnostic value to distinguish TNBC tissue from normal breast tissue. In vitro studies confirmed that overexpression of circEGFR promoted the proliferation, migration, invasion, and EMT of TNBC cells and decreased the sensitivity of THP treatment while silencing circEGFR showed the opposite effect. The circEGFR/miR-1299/EGFR pathway was cascaded and verified. CircEGFR regulated malignant progression of TNBC by regulating EGFR via sponging miR-1299. THP can inhibit the malignant phenotype of MDA-MB-231 cells by downregulating the expression of circEGFR. In vivo studies confirmed that overexpression of circEGFR can promote tumor growth and EMT and reduce tumor sensitivity to THP treatment. Silencing circEGFR inhibited the malignant progression of the tumor. These results revealed circEGFR is a promising biomarker for TNBC diagnosis, therapeutic and prognosis.

Paclitaxel inhibits hepatocellular carcinoma tumorigenesis by regulating the circ_0005785/miR-640/GSK3β

Paclitaxel (PTX) is an effective chemotherapeutic agent for cancer patients. It has been reported that circular RNA (circRNA) circ_0005785is involved in the progression of hepatocellular carcinoma (HCC). The purpose of this study is to explore the role and mechanism of circ_0005785 in the PTX resistance of HCC. Cell viability, proliferation, invasion, migration, apoptosis, and angiogenesis were detected using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation, transwell, wound-healing, flow cytometry, and tube formation assay. Circ_0005785, microRNA-640 (miR-640), and Glycogen synthase kinase-3 beta (GSK3β) levels were detected using real-time quantitative polymerase chain reaction. Protein levels of Proliferating cell nuclear antigen (PCNA), Bcl-2, and GSK3β were measured using western blot assay. After being predicted using Circular RNA interactome or TargetScan, binding between miR-640 and circ_0005785 or GSK3β was verified using dual-luciferase reporter and RNA Immunoprecipitation assay. PTX treatment could repress HCC cell viability, decrease circ_0005785 and GSK3β expression, and increase the miR-640 level in HCC cell lines. Furthermore, circ_0005785 and GSK3β were increased, and miR-640 was decreased in HCC tissues and cell lines. Moreover, circ_0005785 knockdown hindered proliferation, migration, invasion, angiogenesis, and boosted apoptosis in PTX-treated HCC cells in vitro. In addition, circ_0005785 silencing improved the PTX sensitivity of HCC in vivo. Mechanistically, circ_0005785 acted as a sponge of miR-640 to regulate GSK3β expression. PTX restrained HCC tumorigenesis partly via regulating the circ_0005785/miR-640/GSK3β axis, hinting at a promising therapeutic target for the HCC treatment.

Circular RNA circLRCH3 promotes oxaliplatin resistance in gastric cancer through the modulation of the miR-383-5p/FGF7 axis

BACKGROUND

Gastric cancer (GC) is a common malignant tumor of the digestive system. Circular RNAs (circRNAs) play a vital role in tumorigenesis and chemoresistance. The current study aimed to explore the possible role and mechanism of circRNA leucine rich repeats and calponin homology domain containing 3 (circLRCH3) in GC chemoresistance.

METHODS

The levels of circLRCH3, microRNA-383-5p (miR-383-5p) and fibroblast growth factor 7 (FGF7) were determined by quantitative real-time PCR or Western blot. Cell Counting Kit-8 (CCK-8) assay was utilized to evaluate cell survival rate and proliferation ability. Colony formation, transwell and flow cytometry assays were used to assess cell proliferation, migration, invasion and apoptosis. The expression of multidrug resistance proteins was detected by Western blot. The binding relationship between miR-383-5p and circLRCH3/FGF7 was verified by dual-luciferase reporter assay or RNA immunoprecipitation assay. Xenograft assay was conducted to analyze the role of circLRCH3 in OXA resistance in vivo.

RESULTS

CircLRCH3 and FGF7 levels were up-regulated, while miR-383-5p level was reduced in OXA-resistant GC tissues and cells. Depletion of circLRCH3 attenuated the resistance of OXA-resistant cells to OXA. CircLRCH3 silence reduced OXA resistance by regulating miR-383-5p. Besides, miR-383-5p elevated OXA sensitivity of GC cells by repressing FGF7. Moreover, the deletion of circLRCH3 increased OXA sensitivity in vivo.

CONCLUSIONS

Knockdown of circLRCH3 alleviated OXA resistance of GC by modulating the miR-383-5p/FGF7 axis, which provided a promising therapeutic target for GC chemoresistance.

Non-coding RNA-based therapeutics in cancer therapy: An emphasis on Wnt/β-catenin control

Non-coding RNA transcripts are RNA molecules that have mainly regulatory functions and they do not encode proteins. microRNAs (miRNAs), lncRNAs and circRNAs are major types of this family and these epigenetic factors participate in disease pathogenesis, especially cancer that their abnormal expression may lead to cancer progression. miRNAs and lncRNAs possess a linear structure, whereas circRNAs possess ring structures and high stability. Wnt/β-catenin is an important factor in cancer with oncogenic function and it can increase growth, invasion and therapy resistance in tumors. Wnt upregulation occurs upon transfer of β-catenin to nucleus. Interaction of ncRNAs with Wnt/β-catenin signaling can determine tumorigenesis. Wnt upregulation is observed in cancers and miRNAs are able to bind to 3'-UTR of Wnt to reduce its level. LncRNAs can directly/indirectly regulate Wnt and in indirect manner, lncRNAs sponge miRNAs. CircRNAs are new emerging regulators of Wnt and by its stimulation, they increase tumor progression. CircRNA/miRNA axis can affect Wnt and carcinogenesis. Overall, interaction of ncRNAs with Wnt can determine proliferation rate, migration ability and therapy response of cancers. Furthermore, ncRNA/Wnt/β-catenin axis can be utilized as biomarker in cancer and for prognostic applications in patients.

Knockdown of circ_0005615 enhances the radiosensitivity of colorectal cancer by regulating the miR-665/NOTCH1 axis

Radiotherapy resistance is a challenge for colorectal cancer (CRC) treatment. Circular RNAs (circRNAs) play vital roles in the occurrence and development of CRC. This study aimed to investigate the role of circ_0005615 in regulating the radiosensitivity of CRC. The levels of circ_0005615, microRNA-665 (miR-665), and notch receptor 1 (NOTCH1) were detected by quantitative real-time PCR or western blot. The radiosensitivity of CRC cells was assessed by colony formation assay. Cell viability, apoptosis, and colony formation were assessed by Cell Counting Kit-8 assay, flow cytometry, and colony formation assay. Cell migration and invasion were confirmed by transwell assay and scratch assay. The binding relationship between miR-665 and circ_0005615 or NOTCH1 was verified by dual-luciferase reporter assay. Xenograft assay was used to test the effect of circ_0005615 on radiosensitivity in vivo. circ_0005615 and NOTCH1 were up-regulated, and miR-665 was down-regulated in CRC tissues and cells. Radiation decreased circ_0005615 and NOTCH1 levels and increased miR-665 level. Knockdown of circ_0005615 enhanced radiosensitivity of CRC cells. Moreover, circ_0005615 sponged miR-665 to regulate the radioresistance of CRC cells. Besides, miR-665 targeted NOTCH1 to mediate the radiosensitivity of CRC cells. Furthermore, circ_0005615 depletion increased CRC radiosensitivity in vivo. circ_0005615 silencing elevated radiosensitivity of CRC by regulating miR-665/NOTCH1 axis.

In Vitro Biological Activity and Lymphoma Cell Growth Inhibition by Selected Mexican Medicinal Plants

Cancer is a major health problem with significant morbidity and mortality. In addition, plants are a source of metabolites with diverse biological properties, including antitumor potential. In this study, we investigated the in vitro murine lymphoma L5178Y-R cell growth inhibition, human peripheral blood mononuclear cells (PBMC) toxicity and proliferation, and antioxidant, hemolytic, and anti-hemolytic activities of methanol extracts from 15 plants of traditional use in Mexico. Justicia spicigera caused the highest tumor cell growth inhibition with a half maximal inhibitory concentration (IC50) of 29.10 µg/mL and a selectivity index >34.36 compared with those of PBMC, whereas Mimosa tenuiflora showed the highest lymphoproliferative activity from 200 µg/mL compared with that induced by concanavalin A. In addition, M. tenuiflora showed an antioxidant effect (IC50 = 2.86 µg/mL) higher than that of ascorbic acid. Regarding the hemolytic and anti-hemolytic activity, all extracts presented significant anti-hemolytic activity. The extract of J. spicigera is emerging as a possible source of effective antineoplastic compounds.

CTRR-ncRNA: A Knowledgebase for Cancer Therapy Resistance and Recurrence Associated Non-coding RNAs

Cancer therapy resistance and recurrence (CTRR) are the dominant causes of death in cancer patients. Recent studies have indicated that non-coding RNAs (ncRNAs) can not only reverse the resistance to cancer therapy but also are crucial biomarkers for the evaluation and prediction of CTRR. Herein, we developed CTRR-ncRNA, a knowledgebase of CTRR-associated ncRNAs, aiming to provide an accurate and comprehensive resource for research involving the association between CTRR and ncRNAs. Compared to most of the existing cancer databases, CTRR-ncRNA is focused on the clinical characterization of cancers, including cancer subtypes, as well as survival outcomes and responses to personalized therapy of cancer patients. Information pertaining to biomarker ncRNAs has also been documented for the development of personalized CTRR prediction. A user-friendly interface and several functional modules have been incorporated into the database. Based on the preliminary analysis of genotype-phenotype relationships, universal ncRNAs have been found to be potential biomarkers for CTRR. The CTRR-ncRNA is a translation-oriented knowledgebase and it provides a valuable resource for mechanistic investigations and explainable artificial intelligence-based modeling. CTRR-ncRNA is freely available to the public at http://ctrr.bioinf.org.cn/.

The critical role of circular RNAs in drug resistance in gastrointestinal cancers

Nowadays, drug resistance (DR) in gastrointestinal (GI) cancers, as the main reason for cancer-related mortality worldwide, has become a serious problem in the management of patients. Several mechanisms have been proposed for resistance to anticancer drugs, including altered transport and metabolism of drugs, mutation of drug targets, altered DNA repair system, inhibited apoptosis and autophagy, cancer stem cells, tumor heterogeneity, and epithelial-mesenchymal transition. Compelling evidence has revealed that genetic and epigenetic factors are strongly linked to DR. Non-coding RNA (ncRNA) interferences are the most crucial epigenetic alterations explored so far, and among these ncRNAs, circular RNAs (circRNAs) are the most emerging members known to have unique properties. Due to the absence of 5' and 3' ends in these novel RNAs, the two ends are covalently bonded together and are generated from pre-mRNA in a process known as back-splicing, which makes them more stable than other RNAs. As far as the unique structure and function of circRNAs is concerned, they are implicated in proliferation, migration, invasion, angiogenesis, metastasis, and DR. A clear understanding of the molecular mechanisms responsible for circRNAs-mediated DR in the GI cancers will open a new window to the management of GI cancers. Hence, in the present review, we will describe briefly the biogenesis, multiple features, and different biological functions of circRNAs. Then, we will summarize current mechanisms of DR, and finally, discuss molecular mechanisms through which circRNAs regulate DR development in esophageal cancer, pancreatic cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma.

Cancer stem cells (CSCs): key player of radiotherapy resistance and its clinical significance

Cancer stem cells (CSCs) are self-renewing and slow-multiplying micro subpopulations in tumour microenvironments. CSCs contribute to cancer's resistance to radiation (including radiation) and other treatments. CSCs control the heterogeneity of the tumour. It alters the tumour's microenvironment cellular singling and promotes epithelial-to-mesenchymal transition (EMT). Current research decodes the role of extracellular vesicles (EVs) and CSCs interlink in radiation resistance. Exosome is a subpopulation of EVs and originated from plasma membrane. It is secreted by several active cells. It involed in cellular communication and messenger of healthly and multiple pathological complications. Exosomal biological active cargos (DNA, RNA, protein, lipid and glycan), are capable to transform recipient cells' nature. The molecular signatures of CSCs and CSC-derived exosomes are potential source of cancer theranostics development. This review discusse cancer stem cells, radiation-mediated CSCs development, EMT associated with CSCs, the role of exosomes in radioresistance development, the current state of radiation therapy and the use of CSCs and CSCs-derived exosomes biomolecules as a clinical screening biomarker for cancer. This review gives new researchers a reason to keep an eye on the next phase of scientific research into cancer theranostics that will help mankind.