Targeting the androgen receptor to enhance NK cell killing efficacy in bladder cancer by modulating ADAR2/circ_0001005/PD-L1 signaling

Androgen receptor signalling in non-prostatic malignancies: challenges and opportunities

The androgen receptor (AR) signalling pathway has been intensively studied in the context of prostate cancer, where androgen deprivation therapy is part of the standard of care for metastatic disease. By contrast, fewer studies have investigated the impact and translational potential of targeting AR in other cancer types where it is also expressed and functional. In this Review, we discuss the current understanding of AR in non-prostatic cancer types and summarize ongoing AR-directed clinical trials. While different androgen levels contribute to sexual dimorphism in cancer, targeting the AR system could benefit both sexes and help overcome resistance to targeted therapies. However, a bimodal function of AR signalling, which suppresses stromal changes associated with the early stages of cancer development, also needs to be considered. Future research is necessary to scrutinize cellular and molecular mechanisms of action of AR in cancer cells and the tumour microenvironment, to develop selective modulators of AR activity, and to identify patients with non-prostatic cancer who might benefit from targeting this pathway. AR-directed manipulation of host immune cells may offer a promising therapeutic approach for many types of cancers.

MicroRNA-200c in Cancer Generation, Invasion, and Metastasis

MicroRNA-200c (miR-200c) is increasingly recognized as a crucial small RNA molecule that plays a significant and multifaceted role in the complex processes of tumor development, invasion, and metastasis across various types of cancers. Recent studies have compellingly demonstrated that miR-200c exerts its influence on tumor biology by meticulously regulating a range of critical processes, including cell proliferation, apoptosis, epithelial-mesenchymal transition (EMT), and cell migration, all of which are essential for the progression and aggressiveness of tumors. This comprehensive review aims to summarize the expression characteristics and functional implications of miR-200c across a diverse array of tumor types, delving into its potential utility as both a biomarker for early detection and a therapeutic target in the realm of cancer treatment. By synthesizing current research findings and insights, we aspire to provide valuable information that could significantly enhance early diagnostic capabilities and inform the strategic development of targeted therapy approaches in oncology.

Circular RNAs: key players in tumor immune evasion

Immune responses against tumor antigens play a role in confining tumor growth. In response, cancer cells developed several mechanisms to bypass or defeat these anti-tumor immune responses-collectively referred to as "tumor immune evasion". Recent studies have shown that a group of non-coding RNAs, namely circRNAs affect several aspects of tumor immune evasion through regulation of activity of CD8 + T cells, regulatory T cells, natural killer cells, cytokine-induced killer cells or other immune cells. Understanding the role of circRNAs in this process facilitate design of novel therapies for enhancing the anti-tumor capacity of immune system. This review provides an outline of different roles of circRNAs in the tumor immune evasion.

Are androgen receptor agonists a treatment option in bladder cancer?

Sex-related differences in bladder cancer incidence and progression infer a role for sex hormones and their cognate receptors in this disease. In part due to the oncogenic role of androgen receptor signaling in prostate cancer, the focus of most preclinical and clinical research to-date has been on the potential pro-tumorigenic action of androgens in urothelial cancers. However, clinical studies of androgen receptor antagonism have yielded minimal success. In this review, we explore the tumor suppressor role of androgen receptor in bladder cancer and discuss how it might be harnessed therapeutically.

Programmed death receptor (PD-)1/PD-ligand (L)1 in urological cancers : the "all-around warrior" in immunotherapy

Programmed death receptor-1 (PD-1) and its ligand, programmed death ligand-1 (PD-L1) are essential molecules that are key in modulating immune responses. PD-L1 is constitutively expressed on various immune cells, epithelial cells, and cancer cells, where it functions as a co-stimulatory molecule capable of impairing T-cell mediated immune responses. Upon binding to PD-1 on activated T-cells, the PD-1/PD-L1 interaction triggers signaling pathways that can induce T-cell apoptosis or anergy, thereby facilitating the immune escape of tumors. In urological cancers, including bladder cancer (BCa), renal cell carcinoma (RCC), and prostate cancer (PCa), the upregulation of PD-L1 has been demonstrated. It is linked to poor prognosis and enhanced tumor immune evasion. Recent studies have highlighted the significant role of the PD-1/PD-L1 axis in the immune escape mechanisms of urological cancers. The interaction between PD-L1 and PD-1 on T-cells further contributes to immunosuppression by inhibiting T-cell activation and proliferation. Clinical applications of PD-1/PD-L1 checkpoint inhibitors have shown promising efficacy in treating advanced urological cancers, significantly improving patient outcomes. However, resistance to these therapies, either intrinsic or acquired, remains a significant challenge. This review aims to provide a comprehensive overview of the role of the PD-1/PD-L1 signaling pathway in urological cancers. We summarize the regulatory mechanism underlying PD-1 and PD-L1 expression and activity, including genetic, epigenetic, post-transcriptional, and post-translational modifications. Additionally, we discuss current clinical research on PD-1/PD-L1 inhibitors, their therapeutic potential, and the challenges associated with resistance. Understanding these mechanisms is crucial for developing new strategies to overcome therapeutic limitations and enhance the efficacy of cancer immunotherapy.

Therapeutic importance and diagnostic function of circRNAs in urological cancers: from metastasis to drug resistance

Circular RNAs (circRNAs) are a member of non-coding RNAs with no ability in encoding proteins and their aberrant dysregulation is observed in cancers. Their closed-loop structure has increased their stability, and they are reliable biomarkers for cancer diagnosis. Urological cancers have been responsible for high mortality and morbidity worldwide, and developing new strategies in their treatment, especially based on gene therapy, is of importance since these malignant diseases do not respond to conventional therapies. In the current review, three important aims are followed. At the first step, the role of circRNAs in increasing or decreasing the progression of urological cancers is discussed, and the double-edged sword function of them is also highlighted. At the second step, the interaction of circRNAs with molecular targets responsible for urological cancer progression is discussed, and their impact on molecular processes such as apoptosis, autophagy, EMT, and MMPs is highlighted. Finally, the use of circRNAs as biomarkers in the diagnosis and prognosis of urological cancer patients is discussed to translate current findings in the clinic for better treatment of patients. Furthermore, since circRNAs can be transferred to tumor via exosomes and the interactions in tumor microenvironment provided by exosomes such as between macrophages and cancer cells is of importance in cancer progression, a separate section has been devoted to the role of exosomal circRNAs in urological tumors.

The role of circular RNA during the urological cancer metastasis: exploring regulatory mechanisms and potential therapeutic targets

Metastasis is a major contributor to treatment failure and death in urological cancers, representing an important biomedical challenge at present. Metastases form as a result of cancer cells leaving the primary site, entering the vasculature and lymphatic vessels, and colonizing clones elsewhere in the body. However, the specific regulatory mechanisms of action underlying the metastatic process of urological cancers remain incompletely elucidated. With the deepening of research, circular RNAs (circRNAs) have been found to not only play a significant role in tumor progression and prognosis but also show aberrant expression in various tumor metastases, consequently impacting tumor metastasis through multiple pathways. Therefore, circRNAs are emerging as potential tumor markers and treatment targets. This review summarizes the research progress on elucidating how circRNAs regulate the urological cancer invasion-metastasis cascade response and related processes, as well as their role in immune microenvironment remodeling and circRNA vaccines. This body of work highlights circRNA regulation as an emerging therapeutic target for urological cancers, which should motivate further specific research in this regard.

Circular RNAs in tumor immunity and immunotherapy

Circular RNAs (circRNAs) are unique noncoding RNAs that have a closed and stable loop structure generated through backsplicing. Due to their conservation, stability and tissue specificity, circRNAs can potentially be used as diagnostic indicators and therapeutic targets for certain tumors. Many studies have shown that circRNAs can act as microRNA (miRNA) sponges, and engage in interactions with proteins and translation templates to regulate gene expression and signal transduction, thereby participating in the occurrence and development of a variety of malignant tumors. Immunotherapy has revolutionized the treatment of cancer. Early researches have indicated that circRNAs are involved in regulating tumor immune microenvironment and antitumor immunity. CircRNAs may have the potential to be important targets for increasing sensitivity to immunotherapy and expanding the population of patients who benefit from cancer immunotherapy. However, few studies have investigated the correlation between circRNAs and tumor immunity. In this review, we summarize the current researches on circRNAs involved in antitumor immune regulation through different mechanisms and their potential value in increasing immunotherapy efficacy with the goal of providing new targets for cancer immunotherapy.

Sex differences in cancer and immunotherapy outcomes: the role of androgen receptor

Across the wide range of clinical conditions, there exists a sex imbalance where biological females are more prone to autoimmune diseases and males to some cancers. These discrepancies are the combinatory consequence of lifestyle and environmental factors such as smoking, alcohol consumption, obesity, and oncogenic viruses, as well as other intrinsic biological traits including sex chromosomes and sex hormones. While the emergence of immuno-oncology (I/O) has revolutionised cancer care, the efficacy across multiple cancers may be limited because of a complex, dynamic interplay between the tumour and its microenvironment (TME). Indeed, sex and gender can also influence the varying effectiveness of I/O. Androgen receptor (AR) plays an important role in tumorigenesis and in shaping the TME. Here, we lay out the epidemiological context of sex disparity in cancer and then review the current literature on how AR signalling contributes to such observation via altered tumour development and immunology. We offer insights into AR-mediated immunosuppressive mechanisms, with the hope of translating preclinical and clinical evidence in gender oncology into improved outcomes in personalised, I/O-based cancer care.

Synergistic Immunoregulation: harnessing CircRNAs and PiRNAs to Amplify PD-1/PD-L1 Inhibition Therapy

The utilization of PD-1/PD-L1 inhibitors marks a significant advancement in cancer therapy. However, the efficacy of monotherapy is still disappointing in a substantial subset of patients, necessitating the exploration of combinational strategies. Emerging from the promising results of the KEYNOTE-942 trial, RNA-based therapies, particularly circRNAs and piRNAs, have distinguished themselves as innovative sensitizers to immune checkpoint inhibitors (ICIs). These non-coding RNAs, notable for their stability and specificity, were once underrecognized but are now known for their crucial roles in regulating PD-L1 expression and bolstering anti-cancer immunity. Our manuscript offers a comprehensive analysis of selected circRNAs and piRNAs, elucidating their immunomodulatory effects and mechanisms, thus underscoring their potential as ICIs enhancers. In conjunction with the recent Nobel Prize-awarded advancements in mRNA vaccine technology, our review highlights the transformative implications of these findings for cancer treatment. We also discuss the prospects of circRNAs and piRNAs in future therapeutic applications and research. This study pioneers the synergistic application of circRNAs and piRNAs as novel sensitizers to augment PD-1/PD-L1 inhibition therapy, demonstrating their unique roles in regulating PD-L1 expression and modulating immune responses. Our findings offer a groundbreaking approach for enhancing the efficacy of cancer immunotherapy, opening new avenues for treatment strategies. This abstract aims to encapsulate the essence of our research and the burgeoning role of these non-coding RNAs in enhancing PD-1/PD-L1 inhibition therapy, encouraging further investigation into this promising field.

Hallmarks of sex bias in immuno-oncology: mechanisms and therapeutic implications

Sex differences are present across multiple non-reproductive organ cancers, with male individuals generally experiencing higher incidence of cancer with poorer outcomes. Although some mechanisms underlying these differences are emerging, the immunological basis is not well understood. Observations from clinical trials also suggest a sex bias in conventional immunotherapies with male individuals experiencing a more favourable response and female individuals experiencing more severe adverse events to immune checkpoint blockade. In this Perspective article, we summarize the major biological hallmarks underlying sex bias in immuno-oncology. We focus on signalling from sex hormones and chromosome-encoded gene products, along with sex hormone-independent and chromosome-independent epigenetic mechanisms in tumour and immune cells such as myeloid cells and T cells. Finally, we highlight opportunities for future studies on sex differences that integrate sex hormones and chromosomes and other emerging cancer hallmarks such as ageing and the microbiome to provide a more comprehensive view of how sex differences underlie the response in cancer that can be leveraged for more effective immuno-oncology approaches.

JAM3: A prognostic biomarker for bladder cancer via epithelial-mesenchymal transition regulation

Understanding the intricate relationship between prognosis, immune function, and molecular markers in bladder cancer (BC) demands sophisticated analytical methods. To identify novel biomarkers for predicting prognosis and immune function in BC patients, we combined weighted gene co-expression network analysis (WGCNA) and least absolute shrinkage and selection operator (LASSO) regression analysis. This was conducted using data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Ultimately, we screened the junctional adhesion molecule 3 (JAM3) as an independent risk factor in BC. High levels of JAM3 were linked to adverse clinical parameters, such as higher T and N stages. Additionally, a JAM3-based nomogram model accurately predicted 1-, 3- and 5-year survival rates of BC patients, indicating potential clinical utility. Functional enrichment analysis revealed that high JAM3 expression activated the calcium signaling pathway, the extracellular matrix (ECM)-receptor interaction, and the PI3K-Akt signaling pathway, and was positively correlated with genes associated with epithelial-mesenchymal transition (EMT). Subsequently, we found that overexpression of JAM3 promoted the migration and invasion abilities in BC cells, regulating the expression levels of N-cadherin, matrix metallopeptidase 2 (MMP2), and Claudin-1 thereby promoting EMT levels. Additionally, we showed that JAM3 was negatively correlated with anti-tumor immune cells such as CD8+ T cells, while positively correlated with pro-tumor immune cells such as M2 macrophages, suggesting its involvement in immune cell infiltration. The immune checkpoint CD200 also showed a positive correlation with JAM3. Our findings revealed that elevated JAM3 levels are predictive of poor prognosis and immune cell infiltration in BC patients by regulating the EMT process.

Innate Lymphoid Cells in Bladder Cancer: From Mechanisms of Action to Immune Therapies

Bladder tumors have a high mutational burden and tend to be responsive to immune therapies; however, response rates remain modest. To date, immunotherapy in bladder cancer has largely focused on enhancing T-cell immune responses in the bladder tumor microenvironment. It is anticipated that other immune cells, including innate lymphoid cells (ILC), which play an important role in bladder oncogenesis and tumor suppression, could be targeted to improve response to existing therapies. ILCs are classified into five groups: natural killer cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer cells. ILCs are pleiotropic and play dual and sometimes paradoxical roles in cancer development and progression. Here, a comprehensive discussion of the current knowledge and recent advancements in understanding the role of ILCs in bladder cancer is provided. We discuss the multifaceted roles that ILCs play in bladder immune surveillance, tumor protection, and immunopathology of bladder cancer. This review provides a rationale for targeting ILCs in bladder cancer, which is relevant for other solid tumors.

Identification of an inflammation-related risk signature for prognosis and immunotherapeutic response prediction in bladder cancer

Tumor inflammation is one of the hallmarks of tumors and is closely related to tumor occurrence and development, providing individualized prognostic prediction. However, few studies have evaluated the relationship between inflammation and the prognosis of bladder urothelial carcinoma (BLCA) patients. Therefore, we constructed a novel inflammation-related prognostic model that included six inflammation-related genes (IRGs) that can precisely predict the survival outcomes of BLCA patients. RNA-seq expression and corresponding clinical data from BLCA patients were downloaded from The Cancer Genome Atlas database. Enrichment analysis was subsequently performed to determine the enrichment of GO terms and KEGG pathways. K‒M analysis was used to compare overall survival (OS). Cox regression and LASSO regression were used to identify prognostic factors and construct the model. Finally, this prognostic model was used to evaluate cell infiltration in the BLCA tumor microenvironment and analyze the effect of immunotherapy in high- and low-risk patients. We established an IRG signature-based prognostic model with 6 IRGs (TNFRSF12A, NR1H3, ITIH4, IL1R1, ELN and CYP26B1), among which TNFRSF12A, IL1R1, ELN and CYP26B1 were unfavorable prognostic factors and NR1H3 and ITIH4 were protective indicators. High-risk score patients in the prognostic model had significantly poorer OS. Additionally, high-risk score patients were associated with an inhibitory immune tumor microenvironment and poor immunotherapy response. We also found a correlation between IRS-related genes and bladder cancer chemotherapy drugs in the drug sensitivity data. The IRG signature-based prognostic model we constructed can predict the prognosis of BLCA patients, providing additional information for individualized prognostic judgment and treatment selection.

Mechanisms of immune checkpoint inhibitors: insights into the regulation of circular RNAS involved in cancer hallmarks

Current treatment strategies for cancer, especially advanced cancer, are limited and unsatisfactory. One of the most substantial advances in cancer therapy, in the last decades, was the discovery of a new layer of immunotherapy approach, immune checkpoint inhibitors (ICIs), which can specifically activate immune cells by targeting immune checkpoints. Immune checkpoints are a type of immunosuppressive molecules expressed on immune cells, which can regulate the degree of immune activation and avoid autoimmune responses. ICIs, such as anti-PD-1/PD-L1 drugs, has shown inspiring efficacy and broad applicability across various cancers. Unfortunately, not all cancer patients benefit remarkably from ICIs, and the overall response rates to ICIs remain relatively low for most cancer types. Moreover, the primary and acquired resistance to ICIs pose serious challenges to the clinical application of cancer immunotherapy. Thus, a deeper understanding of the molecular biological properties and regulatory mechanisms of immune checkpoints is urgently needed to improve clinical options for current therapies. Recently, circular RNAs (circRNAs) have attracted increasing attention, not only due to their involvement in various aspects of cancer hallmarks, but also for their impact on immune checkpoints in shaping the tumor immune microenvironment. In this review, we systematically summarize the current status of immune checkpoints in cancer and the existing regulatory roles of circRNAs on immune checkpoints. Meanwhile, we also aim to settle the issue in an evidence-oriented manner that circRNAs involved in cancer hallmarks regulate the effects and resistance of ICIs by targeting immune checkpoints.

Targeting tumor and bone microenvironment: Novel therapeutic opportunities for castration-resistant prostate cancer patients with bone metastasis

Despite standard hormonal therapy that targets the androgen receptor (AR) attenuates prostate cancer (PCa) effectively in the initial stage, the tumor ultimately converts to castration-resistant prostate cancer (CRPC), and the acquired resistance is still a great challenge for the management of advanced prostate cancer patients. The tumor microenvironment (TME) consists of multiple cellular and noncellular agents is well known as a vital role during the development and progression of CRPC by establishing communication between TME and tumor cells. Additionally, as primary prostate cancer progresses towards metastasis, and CRPC always experiences bone metastasis, the TME is conducive to the spread of tumors to the distant sits, particularly in bone. In addition, the bone microenvironment (BME) is also closely related to the survival, growth and colonization of metastatic tumor cells. The present review summarized the recent studies which mainly focused on the role of TME or BME in the CRPC patients with bone metastasis, and discussed the underlying mechanisms, as well as the potential therapeutic values of targeting TME and BME in the management of metastatic CRPC patients.

BLCA prognostic model creation and validation based on immune gene-metabolic gene combination

BACKGROUND

Bladder cancer (BLCA) is a prevalent urinary system malignancy. Understanding the interplay of immunological and metabolic genes in BLCA is crucial for prognosis and treatment.

METHODS

Immune/metabolism genes were extracted, their expression profiles analyzed. NMF clustering found prognostic genes. Immunocyte infiltration and tumor microenvironment were examined. Risk prognostic signature using Cox/LASSO methods was developed. Immunological Microenvironment and functional enrichment analysis explored. Immunotherapy response and somatic mutations evaluated. RT-qPCR validated gene expression.

RESULTS

We investigated these genes in 614 BLCA samples, identifying relevant prognostic genes. We developed a predictive feature and signature comprising 7 genes (POLE2, AHNAK, SHMT2, NR2F1, TFRC, OAS1, CHKB). This immune and metabolism-related gene (IMRG) signature showed superior predictive performance across multiple datasets and was independent of clinical indicators. Immunotherapy response and immune cell infiltration correlated with the risk score. Functional enrichment analysis revealed distinct biological pathways between low- and high-risk groups. The signature demonstrated higher prediction accuracy than other signatures. qRT-PCR confirmed differential gene expression and immunotherapy response.

CONCLUSIONS

The model in our work is a novel assessment tool to measure immunotherapy's effectiveness and anticipate BLCA patients' prognosis, offering new avenues for immunological biomarkers and targeted treatments.

Sex hormone signaling and regulation of immune function

Immune responses to antigens, including innocuous, self, tumor, microbial, and vaccine antigens, differ between males and females. The quest to uncover the mechanisms for biological sex differences in the immune system has intensified, with considerable literature pointing toward sex hormonal influences on immune cell function. Sex steroids, including estrogens, androgens, and progestins, have profound effects on immune function. As such, drastic changes in sex steroid concentrations that occur with aging (e.g., after puberty or during the menopause transition) or pregnancy impact immune responses and the pathogenesis of immune-related diseases. The effect of sex steroids on immunity involves both the concentration of the ligand and the density and distribution of genomic and nongenomic receptors that serve as transcriptional regulators of immune cellular responses to affect autoimmunity, allergy, infectious diseases, cancers, and responses to vaccines. The next frontier will be harnessing these effects of sex steroids to improve therapeutic outcomes.

Role of sex and sex hormones in PD-L1 expression in NSCLC: clinical and therapeutic implications

Currently, immunotherapy based on PD-1/PD-L1 pathway blockade has improved survival of non-small cell lung cancer (NSCLC) patients. However, differential responses have been observed by sex, where men appear to respond better than women. Additionally, adverse effects of immunotherapy are mainly observed in women. Studies in some types of hormone-dependent cancer have revealed a role of sex hormones in anti-tumor response, tumor microenvironment and immune evasion. Estrogens mainly promote immune tolerance regulating T-cell function and modifying tumor microenvironment, while androgens attenuate anti-tumor immune responses. The precise mechanism by which sex and sex hormones may modulate immune response to tumor, modify PD-L1 expression in cancer cells and promote immune escape in NSCLC is still unclear, but current data show how sexual differences affect immune therapy response and prognosis. This review provides update information regarding anti-PD-1/PD-L immunotherapeutic efficacy in NSCLC by sex, analyzing potential roles for sex hormones on PD-L1 expression, and discussing a plausible of sex and sex hormones as predictive response factors to immunotherapy.

The androgen receptor in bladder cancer

Bladder cancer is the ninth most common cancer worldwide with a striking sex-based difference in incidence. Emerging evidence indicates that the androgen receptor (AR) might promote the development, progression and recurrence of bladder cancer, contributing to the observed sex differences. Targeting androgen-AR signalling has promise as potential therapy for bladder cancer and helps to suppress progression of this disease. In addition, the identification of a new membrane AR and AR-regulated non-coding RNAs has important implications for bladder cancer treatment. The success of human clinical trials of targeted-AR therapies will help in the development of improved treatments for patients with bladder cancer.

Circulating circRNA: a social butterfly in tumors

Circular RNAs (circRNAs) are a class of single-stranded non-coding RNAs that form circular structures through irregular splicing or post-splicing events. CircRNAs are abnormally expressed in many cancers and regulate the occurrence and development of tumors. Circulating circRNAs are cell-free circRNAs present in peripheral blood, they are considered promising biomarkers due to their high stability. In recent years, more and more studies have revealed that circulating circRNAs participate in various cellular communication and regulate the occurrence and development of tumors, which involve many pathological processes such as tumorigenesis, tumor-related immunity, tumor angiogenesis, and tumor metastasis. Understanding the role of cell communication mediated by circulating circRNAs in tumor will further reveal the value and significance behind their use as biomarkers and potential therapeutic targets. In this review, we summarize the recent findings and provide an overview of the cell-cell communication mediated by circulating circRNAs, aiming to explore the role and application value of circulating circRNAs in tumors.

Regulation of PD-L1 Expression by Nuclear Receptors

The suppression of excessive immune responses is necessary to prevent injury to the body, but it also allows cancer cells to escape immune responses and proliferate. Programmed cell death 1 (PD-1) is a co-inhibitory molecule that is present on T cells and is the receptor for programmed cell death ligand 1 (PD-L1). The binding of PD-1 to PD-L1 leads to the inhibition of the T cell receptor signaling cascade. PD-L1 has been found to be expressed in many types of cancers, such as lung, ovarian, and breast cancer, as well as glioblastoma. Furthermore, PD-L1 mRNA is widely expressed in normal peripheral tissues including the heart, skeletal muscle, placenta, lungs, thymus, spleen, kidney, and liver. The expression of PD-L1 is upregulated by proinflammatory cytokines and growth factors via a number of transcription factors. In addition, various nuclear receptors, such as androgen receptor, estrogen receptor, peroxisome-proliferator-activated receptor γ, and retinoic-acid-related orphan receptor γ, also regulate the expression of PD-L1. This review will focus on the current knowledge of the regulation of PD-L1 expression by nuclear receptors.

Regulation of the tumor immune microenvironment by cancer-derived circular RNAs

Circular RNA (circRNAs) is a covalently closed circular non-coding RNA formed by reverse back-splicing from precursor messenger RNA. It is found widely in eukaryotic cells and can be released to the surrounding environment and captured by other cell types. This, circRNAs serve as connections between different cell types for the mediation of multiple signaling pathways. CircRNAs reshape the tumor microenvironment (TME), a key factor involved in all stages of cancer development, by regulating epithelial-stromal transformation, tumor vascularization, immune cell function, and inflammatory responses. Immune cells are the most abundant cellular TME components, and they have profound toxicity to cancer cells. This review summarizes circRNA regulation of immune cells, including T cells, natural killer cells, and macrophages; highlights the impact of circRNAs on tumor progression, treatment, and prognosis; and indicates new targets for tumor immunotherapy.