Preclinical study using circular RNA 17 and micro RNA 181c-5p to suppress the enzalutamide-resistant prostate cancer progression

Research progress on circular RNA in the regulation of drug resistance in genitourinary cancers

In recent years, significant progress has been made in the management of genitourinary cancers, primarily due to advancements in surgical techniques, the emergence of targeted therapy and immunotherapy, and the refinement of chemotherapy agents. However, despite the expanding arsenal of treatment modalities, some patients still face challenges associated with drug resistance, which hinders efforts to improve survival rates. Circular RNAs (circRNAs) are covalently closed RNA molecules with a stable structure and a unique ability to form reverse splicing loops. Increasing evidence suggests that abnormal expression of circRNAs is significantly correlated with the occurrence of genitourinay cancers, indicating their potentials as diagnostic and prognostic biomarkers, as well as new targets for treatment. Although research on circRNAs in genitourinary cancers has progressed, it is still in the preliminary stage. This review summarizes the properties and functions of circRNAs, focusing on their molecular and cellular mechanisms involved in mediating cancer-related drug resistance in the genitourinary system, including autophagy, epithelial-mesenchymal transition, and glycolysis, etc. The clinical potential of circRNAs in regulating drug resistance is also carefully discussed.

VAV2 exists in extrachromosomal circular DNA and contributes Enzalutamide resistance of prostate cancer via stabilization of AR/ARv7

Extrachromosomal circular DNAs (eccDNAs) are circular, double-stranded DNA molecules ubiquitously present across various organisms, playing a critical role in tumorigenesis and tumor progression. However, their precise contribution to prostate cancer (PCa) remains incompletely understood. To elucidate the function of eccDNAs in PCa, eccDNA sequencing and annotation were performed in PCa tissues and cell lines using Circle-seq. Amplified genes on eccDNAs were identified by cross-referencing annotated eccDNA-associated genes with those overexpressed in PCa based on TCGA data. Furthermore, eccDNA profiles were compared between Enzalutamide-sensitive and -resistant cell lines to investigate their role in resistance mechanisms. Notably, VAV2 was detected on both linear and circular DNA, as confirmed by PCR and Sanger sequencing. Functional analyses demonstrated that VAV2 overexpression promotes PCa proliferation and metastasis by activating the PAK1/AKT signaling pathway through PAK1 phosphorylation. Additionally, VAV2 contributes to Enzalutamide resistance by enhancing AR/ARv7 protein stability via reduced ubiquitination, mediated through the recruitment of the deubiquitinating enzyme USP48. These findings establish VAV2, identified through eccDNA sequencing, as a potential oncogene and a promising biomarker for PCa diagnosis and prognosis.

Prostate Cancer: De-regulated Circular RNAs With Efficacy in Preclinical In Vivo Models

Therapy resistance, including castration-resistance and metastasis, remains a major hurdle in the treatment of prostate cancer. In order to identify novel therapeutic targets and treatment modalities for prostate cancer, we conducted a comprehensive literature search on PubMed to identify de-regulated circular RNAs that influence treatment efficacy in preclinical prostate cancer-related in vivo models. Our analysis identified 49 circular RNAs associated with various processes, including treatment resistance, transmembrane and secreted proteins, transcription factors, signaling cascades, human antigen R, nuclear receptor binding, ubiquitination, metabolism, epigenetics and other target categories. The identified targets and circular RNAs can be further scrutinized through target validation approaches. Down-regulated circular RNAs are candidates for reconstitution therapy, while up-regulated RNAs can be inhibited using small interfering RNA (siRNA), antisense oligonucleotides (ASO) or clustered regularly interspaced short palindromic repeats/CRISPR associated (CRISPR-CAS)-related approaches.

Multiple roles of circular RNAs in prostate cancer: from the biological basis to potential clinical applications

Prostate cancer is an important health concern affecting men. Circular RNAs (circRNAs) play an important molecular biological role in regulating gene expression due to their unique structure. Studies have revealed the involvement of circRNAs in many human diseases. In prostate cancer, circRNAs can act as oncogenes or tumour suppressor genes and affect cancer cell proliferation, invasion, resistance to chemotherapy and, consequently, disease progression. Accordingly, prostate cancer-related circRNAs are expected to serve as new targets in early clinical diagnosis and targeted therapy, but the various roles of circRNAs in prostate cancer have not been fully elucidated. This article reviews the molecular pathological roles of circRNA in prostate cancer and explores its prospects as a translational medicine in clinical treatment and prognostic evaluation.

Role of circular RNAs in cancer therapy resistance

Over the past decade, circular RNAs (circRNAs) have gained recognition as a novel class of genetic molecules, many of which are implicated in cancer pathogenesis via different mechanisms, including drug resistance, immune escape, and radio-resistance. ExosomalcircRNAs, in particular, facilitatecommunication between tumour cells and micro-environmental cells, including immune cells, fibroblasts, and other components. Notably, micro-environmental cells can reportedly influence tumour progression and treatment resistance by releasing exosomalcircRNAs. circRNAs often exhibit tissue- and cancer-specific expression patterns, and growing evidence highlights their potential clinical relevance and utility. These molecules show strong promise as potential biomarkers and therapeutic targets for cancer diagnosis and treatment. Therefore, this review aimed to briefly discuss the latest findings on the roles and resistance mechanisms of key circRNAs in the treatment of various malignancies, including lung, breast, liver, colorectal, and gastric cancers, as well as haematological malignancies and neuroblastoma.This review will contribute to the identification of new circRNA biomarkers for the early diagnosis as well as therapeutic targets for the treatment of cancer.

CircPTK2 as a Valuable Biomarker and Treatment Target in Cancer

Circular RNA (CircRNA)s, a newly discovered type of noncoding RNAs, have been found to play a role in controlling the development and aggressiveness of tumors. Abnormal control of circRNA has been observed in various types of human cancers, including bladder cancer, hepatocellular carcinoma (HCC), breast cancer, and gastric cancer (GC). CircRNAs possess binding sites for microRNAs (miRNAs) and function as miRNA sponges in posttranscriptional regulation. This mechanism has been documented to influence the course of cancer. Significantly, among these putative circRNAs, circular RNA protein tyrosine kinase 2 (circPTK2) exhibited increased expression and displayed a substantial association with adverse clinical characteristics and a negative prognosis. The production of these transcripts occurs via a back-splicing mechanism. The enclosed conformation of circRNAs shields them from destruction and enhances their potential as biomarkers. Gaining insight into the molecular mechanisms involved in these processes would aid in the development of treatment approaches and the discovery of new tumor markers. This article provides a comprehensive assessment of the latest research on the biosynthesis and features of circRNAs. It examines the role of circPTK2 in the diagnosis, treatment, and prognosis evaluation of cancer.

A novel peptide encoded by circSRCAP confers resistance to enzalutamide by inhibiting the ubiquitin-dependent degradation of AR-V7 in castration-resistant prostate cancer

BACKGROUND

The sustained activation of androgen receptor splice variant-7 (AR-V7) is a key factor in the resistance of castration-resistant prostate cancer (CRPC) to second-generation anti-androgens such as enzalutamide (ENZ). The AR/AR-V7 protein is regulated by the E3 ubiquitin ligase STUB1 and a complex involving HSP70, but the precise mechanism remains unclear.

METHODS

High-throughput RNA sequencing was used to identify differentially expressed circular RNAs (circRNAs) in ENZ-resistant and control CRPC cells. The coding potential of circSRCAP was confirmed by polysome profiling and LC-MS. The function of circSRCAP was validated in vitro and in vivo using gain- and loss-of-function assays. Mechanistic insights were obtained through immunoprecipitation analyses.

RESULTS

A novel ENZ-resistant circRNA, circSRCAP, was identified and shown to be upregulated in ENZ-resistant C4-2B (ENZR-C4-2B) cells, correlating with increased AR-V7 protein levels. circSRCAP is generated via splicing by eIF4A3, forming a loop structure and is exported from the nucleus by the RNA helicase DDX39A. Mechanistically, circSRCAP encodes a 75-amino acid peptide (circSRCAP-75aa) that inhibits the ubiquitination of AR/AR-V7's co-chaperone protein HSP70 by disrupting the interaction with the E3 ligase STUB1. This process results in the upregulation of AR-V7 expression and promotes ENZ resistance in CRPC cells. Xenograft tumor models further confirmed the role of circSRCAP in CRPC progression and its potential as a therapeutic target for ENZ-resistant CRPC.

CONCLUSIONS

circSRCAP provides an epigenetic mechanism influencing AR-V7 stability and offers a promising therapeutic target for treating ENZ-resistant CRPC.

Prostate cancer and the cell cycle: Focusing on the role of microRNAs

Prostate cancer is the most frequent solid tumor in terms of incidence and ranks second only to lung cancer in terms of cancer mortality among men. It has a considerably high mortality rate; around 375,000 deaths occurred worldwide in 2020. In 2024, the American Cancer Society estimated that the number of new prostate cancer cases will be around 299,010 cases, and the estimated deaths will be around 32,250 deaths only in the USA. Cell cycle dysregulation is inevitable in cancer etiology and is targeted by various therapies in cancer treatment. MicroRNAs (miRNAs) are small, endogenous, non-coding regulatory molecules involved in both normal and abnormal cellular events. One of the cellular processes regulated by miRNAs is the cell cycle. Although there are some exceptions, tumor suppressor miRNAs could potentially arrest the cell cycle by downregulating several molecular machineries involved in catalyzing the cell cycle progression. In contrast, oncogenic miRNAs (oncomirs) help the cell cycle to progress by targeting various regulatory proteins such as retinoblastoma (Rb) or cell cycle inhibitors such as p21 or p27, and hence may contribute to prostate cancer progression; however, this is not always the case. In this review, we emphasize how a dysregulated miRNA expression profile is linked to an abnormal cell cycle progression in prostate cancer, which subsequently paves the way to a new therapeutic option for prostate cancer.

The role of circRNAs in resistance to doxorubicin

Doxorubicin is an anthracyline recognized as an antitumor antibiotic agent. It is widely used in the chemotherapeutic regimens in different types of cancers. Resistance to doxorubicin is a major clinical obstacle and main cause of failure in cancer chemotherapy. Among different mechanisms involved in this process, the role of epigenetic factors has been highlighted. Circular RNAs (circRNAs) have a prominent role in this process. Here, we summarize the recent findings on the role of circRNAs in doxorubicin resistance, particularly in breast cancer and osteosarcoma and underscore their clinical application as potential biomarkers and therapeutic targets in this field. Recognition of the underlying mechanism of circRNAs involvement in doxorubicin resistance will expand our understanding of chemoresistance establishment and may provide a prospect to develop circRNA-based predictive biomarkers of chemotherapy or therapeutic strategies for cancer patients.

Circular RNAs: Novel Players in Cancer Mechanisms and Therapeutic Strategies

Circular RNAs (circRNAs) are a novel class of noncoding RNAs that have emerged as pivotal players in gene regulation. Our understanding of circRNAs has greatly expanded over the last decade, with studies elucidating their biology and exploring their therapeutic applications. In this review, we provide an overview of the current understanding of circRNA biogenesis, outline their mechanisms of action in cancer, and assess their clinical potential as biomarkers. Furthermore, we discuss circRNAs as a potential therapeutic strategy, including recent advances in circRNA production and translation, along with proof-of-concept preclinical studies of cancer vaccines.

The function and mechanism of circRNAs in 5-fluorouracil resistance in tumors: Biological mechanisms and future potential

5-Fluorouracil (5-FU) is a well-known chemotherapy drug extensively used in the treatment of breast cancer. It works by inhibiting cancer cell proliferation and inducing cell death through direct incorporation into DNA and RNA via thymidylate synthase (TS). Circular RNAs (circRNAs), a novel family of endogenous non-coding RNAs (ncRNAs) with limited protein-coding potential, contribute to 5-FU resistance. Their identification and targeting are crucial for enhancing chemosensitivity. CircRNAs can regulate tumor formation and invasion by adhering to microRNAs (miRNAs) and interacting with RNA-binding proteins, regulating transcription and translation. MiRNAs can influence enzymes responsible for 5-FU metabolism in cancer cells, affecting their sensitivity or resistance to the drug. In the context of 5-FU resistance, circRNAs can target miRNAs and regulate biological processes such as cell proliferation, cell death, glucose metabolism, hypoxia, epithelial-to-mesenchymal transition (EMT), and drug efflux. This review focuses on the function of circRNAs in 5-FU resistance, discussing the underlying molecular pathways and biological mechanisms. It also presents recent circRNA/miRNA-targeted cancer therapeutic strategies for future clinical application.

Epigenetic regulation of androgen dependent and independent prostate cancer

Prostate cancer is one of the most common malignancies among men worldwide. Besides genetic alterations, epigenetic modulations including DNA methylation, histone modifications and miRNA mediated alteration of gene expression are the key driving forces for the prostate tumor development and cancer progression. Aberrant expression and/or the activity of the epigenetic modifiers/enzymes, results in aberrant expression of genes involved in DNA repair, cell cycle regulation, cell adhesion, apoptosis, autophagy, tumor suppression and hormone response and thereby disease progression. Altered epigenome is associated with prostate cancer recurrence, progression, aggressiveness and transition from androgen-dependent to androgen-independent phenotype. These epigenetic modifications are reversible and various compounds/drugs targeting the epigenetic enzymes have been developed that are effective in cancer treatment. This chapter focuses on the epigenetic alterations in prostate cancer initiation and progression, listing different epigenetic biomarkers for diagnosis and prognosis of the disease and their potential as therapeutic targets. This chapter also summarizes different epigenetic drugs approved for prostate cancer therapy and the drugs available for clinical trials.

BJLD-CMI: a predictive circRNA-miRNA interactions model combining multi-angle feature information

Increasing research findings suggest that circular RNA (circRNA) exerts a crucial function in the pathogenesis of complex human diseases by binding to miRNA. Identifying their potential interactions is of paramount importance for the diagnosis and treatment of diseases. However, long cycles, small scales, and time-consuming processes characterize previous biological wet experiments. Consequently, the use of an efficient computational model to forecast the interactions between circRNA and miRNA is gradually becoming mainstream. In this study, we present a new prediction model named BJLD-CMI. The model extracts circRNA sequence features and miRNA sequence features by applying Jaccard and Bert's method and organically integrates them to obtain CMI attribute features, and then uses the graph embedding method Line to extract CMI behavioral features based on the known circRNA-miRNA correlation graph information. And then we predict the potential circRNA-miRNA interactions by fusing the multi-angle feature information such as attribute and behavior through Autoencoder in Autoencoder Networks. BJLD-CMI attained 94.95% and 90.69% of the area under the ROC curve on the CMI-9589 and CMI-9905 datasets. When compared with existing models, the results indicate that BJLD-CMI exhibits the best overall competence. During the case study experiment, we conducted a PubMed literature search to confirm that out of the top 10 predicted CMIs, seven pairs did indeed exist. These results suggest that BJLD-CMI is an effective method for predicting interactions between circRNAs and miRNAs. It provides a valuable candidate for biological wet experiments and can reduce the burden of researchers.

Circular RNAs in the KRAS pathway: Emerging players in cancer progression

Circular RNAs (circRNAs) have been recognized as key components in the intricate regulatory network of the KRAS pathway across various cancers. The KRAS pathway, a central signalling cascade crucial in tumorigenesis, has gained substantial emphasis as a possible therapeutic target. CircRNAs, a subgroup of non-coding RNAs known for their closed circular arrangement, play diverse roles in gene regulation, contributing to the intricate landscape of cancer biology. This review consolidates existing knowledge on circRNAs within the framework of the KRAS pathway, emphasizing their multifaceted functions in cancer progression. Notable circRNAs, such as Circ_GLG1 and circITGA7, have been identified as pivotal regulators in colorectal cancer (CRC), influencing KRAS expression and the Ras signaling pathway. Aside from their significance in gene regulation, circRNAs contribute to immune evasion, apoptosis, and drug tolerance within KRAS-driven cancers, adding complexity to the intricate interplay. While our comprehension of circRNAs in the KRAS pathway is evolving, challenges such as the diverse landscape of KRAS mutant tumors and the necessity for synergistic combination therapies persist. Integrating cutting-edge technologies, including deep learning-based prediction methods, holds the potential for unveiling disease-associated circRNAs and identifying novel therapeutic targets. Sustained research efforts are crucial to comprehensively unravel the molecular mechanisms governing the intricate interplay between circRNAs and the KRAS pathway, offering insights that could potentially revolutionize cancer diagnostics and treatment strategies.

Glycolysis related lncRNA SNHG3 / miR-139-5p / PKM2 axis promotes castration-resistant prostate cancer (CRPC) development and enzalutamide resistance

Although androgen deprivation therapy (ADT) by the anti-androgen drug enzalutamide (Enz) may improve the survival level of patients with castration-resistant prostate cancer (CRPC), most patients may eventually fail due to the acquired resistance. The reprogramming of glucose metabolism is one type of the paramount hallmarks of cancers. PKM2 (Pyruvate kinase isozyme typeM2) is a speed-limiting enzyme in the glycolytic mechanism, and has high expression in a variety of cancers. Emerging evidence has unveiled that microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) have impact on tumor development and therapeutic efficacy by regulating PKM2 expression. Herein, we found that lncRNA SNHG3, a highly expressed lncRNA in CRPC via bioinformatics analysis, promoted the invasive ability and the Enz resistance of the PCa cells. KEGG pathway enrichment analysis indicated that glucose metabolic process was tightly correlated with lncRNA SNHG3 level, suggesting lncRNA SNHG3 may affect glucose metabolism. Indeed, glucose uptake and lactate content determinations confirmed that lncRNA SNHG3 promoted the process of glycolysis. Mechanistic dissection demonstrated that lncRNA SNHG3 facilitated the advance of CRPC by adjusting the expression of PKM2. Further explorations unraveled the role of lncRNA SNHG3 as a 'sponge' of miR-139-5p and released its binding with PKM2 mRNA, leading to PKM2 up-regulation. Together, Our studies suggest that lncRNA SNHG3 / miR-139-5p / PKM2 pathway promotes the development of CRPC via regulating glycolysis process and provides valuable insight into a novel therapeutic approach for the disordered disease.

Overcoming chemoresistance and radio resistance in prostate cancer: The emergent role of non-coding RNAs

Prostate cancer (PCa) continues to be a major health concern worldwide, with its resistance to chemotherapy and radiation therapy presenting major hurdles in successful treatment. While patients with localized prostate cancer generally have a good survival rate, those with metastatic prostate cancer often face a grim prognosis, even with aggressive treatments using various methods. The high mortality rate in severe cases is largely due to the lack of treatment options that can offer lasting results, especially considering the significant genetic diversity found in tumors at the genomic level. This comprehensive review examines the intricate molecular mechanisms governing resistance in PCa, emphasising the pivotal contributions of non-coding RNAs (ncRNAs). We delve into the diverse roles of microRNAs, long ncRNAs, and other non-coding elements as critical regulators of key cellular processes involved in CR & RR. The review emphasizes the diagnostic potential of ncRNAs as predictive biomarkers for treatment response, offering insights into patient stratification and personalized therapeutic approaches. Additionally, we explore the therapeutic implications of targeting ncRNAs to overcome CR & RR, highlighting innovative strategies to restore treatment sensitivity. By synthesizing current knowledge, this review not only provides a comprehension of the chemical basis of resistance in PCa but also identifies gaps in knowledge, paving the way for future research directions. Ultimately, this exploration of ncRNA perspectives offers a roadmap for advancing precision medicine in PCa, potentially transforming therapeutic paradigms and improving outcomes for patients facing the challenges of treatment resistance.

Deregulated miRNAs in enzalutamide resistant prostate cancer: A comprehensive review of key molecular alterations and clinical outcomes

Prostate cancer (PC) is the second most frequently diagnosed cancer and the fifth leading cause of cancer-related deaths in male population worldwide. Since the growth and progression of PC highly depend on the androgen pathway, androgen deprivation therapy (ADT) is the mainstay of systemic treatment. Enzalutamide is a second-generation antiandrogen, which is widely used for the treatment of advanced and metastatic PC. However, treatment failure and disease progression, caused by the emergence of enzalutamide resistant phenotypes, remains an important clinical challenge. MicroRNAs (miRNAs) are key regulators of gene expression and have recently emerged as potential biomarkers for being stable and easily analysed in several biological fluids. Several miRNAs that exhibit dysregulated expression patterns in enzalutamide-resistant PC have recently been identified, including miRNAs that modulate critical signalling pathways and genes involved in PC growth, survival and in the acquisition of enzalutamide phenotype. The understanding of molecular mechanisms by which miRNAs promote the development of enzalutamide resistance can provide valuable insights into the complex interplay between miRNAs, gene regulation, and treatment response in PC. Moreover, these miRNAs could serve as valuable tools for monitoring treatment response and disease progression during enzalutamide administration. This review summarises the miRNAs associated with enzalutamide resistance in PC already described in the literature, focusing on their biological roles and on their potential as biomarkers.

A Crosstalk Between Castration-Resistant Prostate Cancer Cells, M2 Macrophages, and NK Cells: Role of the ATM-PI3K/AKT-PD-L1 Pathway

Castration-resistant prostate cancer (CRPC) in males is associated with a poor prognosis and a higher risk of treatment-related adverse effects, with high mortality among cancers globally. It is thus imperative to explore novel potential molecules with dual therapeutic and biomarker functions. Based on the recent research findings, the expression levels of ataxia telangiectasia mutant kinase (ATM) in prostate cancer (PC) tissues collected from CRPC patients were higher than hormone-dependent PC patients. Using CRPC cell lines (C4-2 and CWR22Rv1), the transwell chamber experiments revealed ATM promoted macrophage recruitment in CRPC cells in vitro via C-X-C motif chemokine ligand 12 (CXCL12). Further in vitro investigations demonstrated that polarized macrophages prevented NK cell recruitment and reduced the immunocidal activity of NK cells against CRPC cell lines. Moreover, ATM boosted programmed death receptor ligand 1 (PD-L1) expression while inhibiting NK group 2D (NKG2D) ligand expression in selected cell lines via PI3K/AKT signaling pathway. The in vivo investigations revealed ATM induced proliferation of CRPC and macrophage recruitment, while the NK cell recruitment was found to suppress ATM expression and CRPC proliferation. In conclusion, it could be demonstrated that inhibiting ATM increased the susceptibility of CRPC to NK cell inhibitors by dampening the CXCL12 and PI3K/AKT-PD-L1 pathways, thereby offering a novel and individualized treatment protocol for treating CRPC.

Circ_0005276 Promotes Prostate Cancer Progression Through the Crosstalk of miR-128-3p/DEPDC1B Axis

This study aimed to investigate more detailed functions of circ_0005276 in prostate cancer (PCa) and provide a novel mechanism for circ_0005276 action. The expression of circ_0005276, microRNA-128-3p (miR-128-3p) and DEP domain containing 1B (DEPDC1B) was detected by quantitative real-time PCR. In functional assays, cell proliferation was determined by CCK-8 assay and EdU assay. Cell migration and invasion were determined by transwell assay. The ability of angiogenesis was determined by tube formation assay. Cell apoptosis was determined by flow cytometry assay. The potential binding relationship between miR-128-3p and circ_0005276 or DEPDC1B was ascertained by dual-luciferase reporter assay and RIP assay. Mouse models were used to verify the role of circ_0005276 in vivo. The upregulation of circ_0005276 was determined in PCa tissues and cells. Circ_0005276 knockdown inhibited proliferation, migration, invasion and angiogenesis in PCa cells, and circ_0005276 knockdown also blocks tumor growth in vivo. Mechanism analysis discovered that miR-128-3p was a target of circ_0005276, and miR-128-3p inhibition recovered circ_0005276 knockdown-inhibited proliferation, migration, invasion and angiogenesis. In addition, DEPDC1B was a target of miR-128-3p, and miR-128-3p restoration-inhibited proliferation, migration, invasion and angiogenesis were rescued by DEPDC1B overexpression. Circ_0005276 might promote the development of PCa by activating the expression of DEPDC1B via targeting miR-128-3p.

Going circular: history, present, and future of circRNAs in cancer

To date, thousands of highly abundant and conserved single-stranded RNA molecules shaped into ring structures (circRNAs) have been identified. CircRNAs are multifunctional molecules that have been shown to regulate gene expression transcriptionally and post-transcriptionally and exhibit distinct tissue- and development-specific expression patterns associated with a variety of normal and disease conditions, including cancer pathogenesis. Over the past years, due to their intrinsic stability and resistance to ribonucleases, particular attention has been drawn to their use as reliable diagnostic and prognostic biomarkers in cancer diagnosis, treatment, and prevention. However, there are some critical caveats to their utility in the clinic. Their circular shape limits their annotation and a complete functional elucidation is lacking. This makes their detection and biomedical application still challenging. Herein, we review the current knowledge of circRNA biogenesis and function, and of their involvement in tumorigenesis and potential utility in cancer-targeted therapy.

Non-coding RNAs in enzalutamide resistance of castration-resistant prostate cancer

Enzalutamide (Enz) is a next-generation androgen receptor (AR) antagonist used to treat castration-resistant prostate cancer (CRPC). Unfortunately, the relapsing nature of CRPC results in the development of Enz resistance in many patients. Non-coding RNAs (ncRNAs) are RNA molecules that do not encode proteins, which include microRNAs (miRNA), long ncRNAs (lncRNAs), circular RNAs (circRNAs), and other ncRNAs with known and unknown functions. Recently, dysregulation of ncRNAs in CRPC, particularly their regulatory function in drug resistance, has attracted more and more attention. Herein, we introduce the roles of dysregulation of different ncRNAs subclasses in the development of CRPC progression and Enz resistance. Recently determined mechanisms of Enz resistance are discussed, focusing mainly on the role of AR-splice variant-7 (AR-V7), mutations, circRNAs and lncRNAs that act as miRNA sponges. Also, the contributions of epithelial-mesenchymal transition and glucose metabolism to Enz resistance are discussed. We summarize the different mechanisms of miRNAs, lncRNAs, and circRNAs in the progression of CRPC and Enz resistance, and highlight the prospect of future therapeutic strategies against Enz resistance.

Circular RNA EPHA3 suppresses progression and metastasis in prostate cancer through the miR-513a-3p/BMP2 axis

BACKGROUND

Circular RNAs (circRNAs) may regulate the onset and progression of human malignancies by competitively binding to microRNA (miRNA) sponges, thus regulating the downstream genes. However, aberrant circRNA expression patterns and their biological functions in prostate cancer (PCa) warrant further studies. Our research sought to shed further light on the possible role and molecular mechanism of circEPHA3 action in controlling the growth and metastasis of PCa cells.

MATERIALS AND METHODS

circEPHA3 (has_circ_0066596) was initially screened from a previous circRNA microarray and identified following Actinomycin D and RNase R assays. Fluorescence in situ hybridization, biotin-coupled probe RNA pulldown, and dual-luciferase reporter gene assays were performed to examine the relationship between circEPHA3 and miR-513a-3p. The biological role of circEPHA3 in PCa was assessed by CCK8, wound healing, Transwell assays, and animal experiments.

RESULTS

We identified a novel circular RNA, circEPHA3 (has_circ_0066596), which was down-regulated in high-grade PCa tissues and cell lines. The outcomes of CCK8, wound healing, Transwell assays, and animal experiments revealed that circEPHA3 prohibited the progression and metastasis of PCa in vivo and in vitro. Mechanistically, circEPHA3 was directly bound to miR-513a-3p and regulated the downstream gene, BMP2, thereby serving as a tumor suppressor in PCa.

CONCLUSIONS

As a tumor suppressor, circEPHA3 inhibited the proliferation and metastasis of PCa cells through the miR-513a-3p/BMP2 axis, suggesting that circEPHA3 might be a potential therapeutic target for PCa.

The function and mechanisms of action of circular RNAs in Urologic Cancer

Kidney, bladder, and prostate cancer are the three major tumor types of the urologic system that seriously threaten human health. Circular RNAs (CircRNAs), special non-coding RNAs with a stabile structure and a unique back-splicing loop-forming ability, have received recent scientific attention. CircRNAs are widely distributed within the body, with important biologic functions such as sponges for microRNAs, as RNA binding proteins, and as templates for regulation of transcription and protein translation. The abnormal expression of circRNAs in vivo is significantly associated with the development of urologic tumors. CircRNAs have now emerged as potential biomarkers for the diagnosis and prognosis of urologic tumors, as well as targets for the development of new therapies. Although we have gained a better understanding of circRNA, there are still many questions to be answered. In this review, we summarize the properties of circRNAs and detail their function, focusing on the effects of circRNA on proliferation, metastasis, apoptosis, metabolism, and drug resistance in kidney, bladder, and prostate cancers.

Molecular predictors of metastasis in patients with prostate cancer

INTRODUCTION

Prostate cancer is a serious threat to the health of older adults worldwide. The quality of life and survival time of patients sharply decline once metastasis occurs. Thus, early screening for prostate cancer is very advanced in developed countries. The detection methods used include Prostate-specific antigen (PSA) detection and digital rectal examination. However, the lack of universal access to early screening in some developing countries has resulted in an increased number of patients presenting with metastatic prostate cancer. In addition, the treatment methods for metastatic and localized prostate cancer are considerably different. In many patients, early-stage prostate cancer cells often metastasize due to delayed observation, negative PSA results, and delay in treatment time. Therefore, the identification of patients who are prone to metastasis is important for future clinical studies.

AREAS COVERED

this review introduced a large number of predictive molecules related to prostate cancer metastasis. These molecules involve the mutation and regulation of tumor cell genes, changes in the tumor microenvironment, and the liquid biopsy.

EXPERT OPINION

In next decade, PSMA PET/CT and liquid biopsy will be the excellent predicting tools, while ¹⁷⁷ Lu- PSMA-RLT will be showed excellent anti-tumor efficacy in mPCa patients.

Plasma extracellular vesicle circRNA signature and resistance to abiraterone in metastatic castration-resistant prostate cancer

BACKGROUND

We aimed to develop and validate a plasma extracellular vesicle circular RNA (circRNA)-based signature that can predict overall survival (OS) in first-line abiraterone therapy for metastatic castration-resistant prostate cancer (mCRPC) patients.

METHODS

In total, 582 mCRPC patients undergoing first-line abiraterone therapy from four institutions were sorted by three phases. In the discovery phase, 30 plasma samples from 30 case-matched patients with or without early progression were obtained to generate circRNA expression profiles using RNA sequencing. In the training phase, differentially expressed circRNAs were examined using digital droplet PCR in a training cohort (n = 203). The circRNA signature was constructed using a least absolute shrinkage and selection operator Cox regression to predict OS. In the validation phase, the prognostic ability of this signature was prospectively validated in two external cohorts (Cohort I, n = 183; Cohort II, n = 166).

RESULTS

We developed a five-circRNA signature, based on circCEP112, circFAM13A, circBRWD1, circVPS13C and circMACROD2, which successfully stratified patients into high-risk and low-risk groups. The prognostic ability of this signature was prospectively validated in two external cohorts (P < 0.0001, P < 0.0001). Patients with high-risk scores had shorter OS than patients with low-risk scores.

CONCLUSION

This five-circRNA signature is a reliable predictor of OS for mCRPC patients undergoing abiraterone.

Exosomes derived from myeloid-derived suppressor cells facilitate castration-resistant prostate cancer progression via S100A9/circMID1/miR-506-3p/MID1

Background

Castration-resistant prostate cancer (CRPC) is a major cause of recurrence and mortality among prostate cancer (PCa) patients. Myeloid-derived suppressor cells (MDSCs) regulate castration resistance in PCa. Previously, it was shown that intercellular communication was efficiently mediated by exosomes (Exos), but the role and the mechanism of MDSC-derived Exos in CRPC progression was unclear.

Methods

In this study, the circRNA expression profiles in PC3 cells treated with MDSC-Exo and control cells were investigated using a circRNA microarray.

Results

The data showed that circMID1 (hsa_circ_0007718) expression was elevated in PC3 cells treated with MDSC-Exo. Moreover, high circMID1 expression was found in PCa compared with benign prostatic hyperplasia (BPH) tissues and in CRPC patients compared with hormone sensitive prostate cancer (HSPC) patients. Further studies showed that MDSC-Exo accelerated PCa cell proliferation, migration, and invasion, while circMID1 deficiency inhibited MDSC-Exo-regulated CRPC progression in vitro and in vivo. Mechanistically, MDSC-derived exosomal S100A9 increased circMID1 expression to sponge miR-506-3p, leading to increased MID1 expression and accelerated tumor progression.

Conclusion

Together, our results showed that a S100A9/circMID1/miR-506-3p/MID1 axis existed in MDSC-Exo-regulated CRPC progression, which provided novel insights into MDSC-Exo regulatory mechanisms in CRPC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03494-5.

Advances in the Study of CircRNAs in Tumor Drug Resistance

Recent studies have revealed that circRNAs can affect tumor DNA damage and repair, apoptosis, proliferation, and invasion and influence the transport of intratumor substances by acting as miRNA sponges and transcriptional regulators and binding to proteins in a variety of ways. However, research on the role of circRNAs in cancer radiotherapy and chemoresistance is still in its early stages. Chemotherapy is a common approach to oncology treatment, but the development of tumor resistance limits the overall clinical efficacy of chemotherapy for cancer patients. The current study suggests that circRNAs have a facilitative or inhibitory effect on the development of resistance to conventional chemotherapy in a variety of tumors, suggesting that circRNAs may serve as a new direction for the study of antitumor drug resistance. In this review, we will briefly discuss the biological features of circRNAs and summarize the recent progression of the involvement of circRNAs in the development and pathogenesis of cancer chemoresistance.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

Breast Cancer; Discovery of Novel Diagnostic Biomarkers, Drug Resistance, and Therapeutic Implications

Breast cancer is the second most reported cancer in women with high mortality causing millions of cancer-related deaths annually. Early detection of breast cancer intensifies the struggle towards discovering, developing, and optimizing diagnostic biomarkers that can improve its prognosis and therapeutic outcomes. Breast cancer-associated biomarkers comprise macromolecules, such as nucleic acid (DNA/RNA), proteins, and intact cells. Advancements in molecular technologies have identified all types of biomarkers that are exclusively studied for diagnostic, prognostic, drug resistance, and therapeutic implications. Identifying biomarkers may solve the problem of drug resistance which is a challenging obstacle in breast cancer treatment. Dysregulation of non-coding RNAs including circular RNAs (circRNAs) and microRNAs (miRNAs) initiates and progresses breast cancer. The circulating multiple miRNA profiles promise better diagnostic and prognostic performance and sensitivity than individual miRNAs. The high stability and existence of circRNAs in body fluids make them a promising new diagnostic biomarker. Many therapeutic-based novels targeting agents have been identified, including ESR1 mutation (DNA mutations), Oligonucleotide analogs and antagonists (miRNA), poly (ADP-ribose) polymerase (PARP) in BRCA mutations, CDK4/6 (cell cycle regulating factor initiates tumor progression), Androgen receptor (a steroid hormone receptor), that have entered clinical validation procedure. In this review, we summarize the role of novel breast cancer diagnostic biomarkers, drug resistance, and therapeutic implications for breast cancer.

Circular RNAs and Drug Resistance in Genitourinary Cancers: A Literature Review

In recent years, systematic treatment has made great progress in genitourinary tumors. However, some patients develop resistance to the treatments, resulting in an increase in mortality. Circular RNAs (circRNAs) form a class of non-coding RNAs with high stability and significant clinical relevance. Accumulating evidence indicates that circRNAs play a vital role in cancer development and tumor chemotherapy resistance. This review summarizes the molecular and cellular mechanisms of drug resistance mediated by circRNAs to common drugs used in the treatment of genitourinary tumors. Several circRNAs were identified to regulate the responsiveness to systemic treatments in genitourinary tumors, including chemotherapies such as cisplatin and targeted therapies such as enzalutamide. Canonically, cicrRNAs participate in the competing endogenous RNA (ceRNA) network, or in some cases directly interact with proteins, regulate downstream pathways, and even some circRNAs have the potential to produce proteins or polypeptides. Several cellular mechanisms were involved in circRNA-dependent drug resistance, including autophagy, cancer stem cells, epithelial-mesenchymal transition, and exosomes. The potential clinical prospect of circRNAs in regulating tumor drug resistance was also discussed.

Estrogen receptor beta increases clear cell renal cell carcinoma stem cell phenotype via altering the circPHACTR4/miR-34b-5p/c-Myc signaling

Early clinical studies indicated that estrogen receptor beta (ERβ) might play key roles to impact the progression of clear cell renal cell carcinoma (ccRCC). The detailed molecular mechanisms, however, remain unclear. Here, we found ERβ could increase the cancer stem cell (CSC) population via altering the circPHACTR4/miR-34b-5p/c-Myc signaling. Mechanism dissection revealed that ERβ could suppress circular RNA PHACTR4 (circPHACTR4) expression via direct binding to the estrogen response elements (EREs) on the 5' promoter region of its host gene, phosphatase and actin regulator 4 (PHACTR4) to decrease miR-34b-5p expression. The decreased miRNA-34b-5p could then increase c-Myc mRNA translation via targeting its 3' untranslated region (3' UTR). The in vivo mouse model with subcutaneous xenografts of ccRCC cells also validated the in vitro data. Importantly, analysis results from ccRCC TCGA database and our clinical data further confirmed the above in vitro/in vivo data. Together, these results suggest that ERβ may increase CSC population in ccRCC via altering ERβ/circPHACTR4/miR-34b-5p/c-Myc signaling and that targeting this newly identified signal pathway may help physicians to better suppress ccRCC progression.

hsa_circ_0001275 Is One of a Number of circRNAs Dysregulated in Enzalutamide Resistant Prostate Cancer and Confers Enzalutamide Resistance In Vitro

Simple Summary

Although newer generations of androgen deprivation therapy such as enzalutamide are providing hope, it is clinically challenging to deliver effective therapy to individuals with metastatic castrate-resistant prostate cancer. Between 20–40% of patients have intrinsic resistance to therapy and all patients will ultimately experience disease progression due to acquired resistance, which is a significant clinical dilemma. The aim of our study was to evaluate the role of circular RNAs (circRNAs) in enzalutamide-resistant prostate cancer as part of the effort to identify useful biomarkers for patient selection and potential new therapeutic targets. We confirmed that hsa_circ_0001275 was highly upregulated in an enzalutamide resistant cell line and demonstrated that its overexpression resulted in increased enzalutamide resistance. Our data showed that hsa_circ_0001275 was not expressed abundantly in patient plasma samples, however, a trend of expression was evident which paralleled disease activity indicating a possible association with enzalutamide resistance. Overall, we have provided evidence that hsa_circ_0001275 promotes enzalutamide resistance and thus may serve as a potential therapeutic target.

Abstract

Background: Enzalutamide is part of the treatment regimen for metastatic castration-resistant prostate cancer (MCRPC). However, both intrinsic and acquired resistance to the drug remain substantial clinical quandaries. circRNAs, a novel type of non-coding RNA, have been identified in a number of cancers including prostate cancer and have been associated with cancer development and progression. circRNAs have shown great potential as clinically useful blood-based ‘liquid biopsies’ and as therapeutic targets in prostate cancer. The aim of this study was to examine the role of circRNA transcripts in enzalutamide-resistant prostate cancer cells and assess their utility as biomarkers. Methods: An isogenic cell line model of enzalutamide resistance was subjected to circRNA microarray profiling. Several differentially expressed circRNAs, along with their putative parental genes were validated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). circRNAs of interest were stably overexpressed in the control cell line and drug sensitivity was assessed using an ELISA-based proliferation assay. The candidate circRNA, hsa_circ_0001275, was measured in patient plasma samples using RT-droplet digital PCR (RT-ddPCR). Results: hsa_circ_0001275 and its parental gene, PLCL2, were significantly up-regulated in strongly resistant clones vs. control (p < 0.05). Overexpression of hsa_circ_0001275 in the control cell line resulted in increased resistance to enzalutamide (p < 0.05). While RT-ddPCR analysis of hsa_circ_0001275 expression in plasma samples of 44 clinical trial participants showed a trend that mirrored the stages of disease activity (as defined by PSA level), the association did not reach statistical significance. Conclusions: Our data suggest that increased levels of hsa_circ_0001275 contribute to enzalutamide resistance. hsa_circ_0001275 plasma expression showed a trend that mirrors the PSA level at specific disease time points, indicating that circRNAs mirror disease recurrence and burden and may be associated with enzalutamide resistance.

The circRAB3IP Mediated by eIF4A3 and LEF1 Contributes to Enzalutamide Resistance in Prostate Cancer by Targeting miR-133a-3p/miR-133b/SGK1 Pathway

An increasing number of studies have shown that circRNAs are closely related to the carcinogenesis and development of prostate cancer (PCa). However, little is known about the effect of the biological functions of circRNAs on the enzalutamide resistance of PCa. Through bioinformatic analysis and experiments, we investigated the expression pattern of circRNAs in enzalutamide-resistant PCa cells. Quantitative real-time PCR was used to detect the expression of circRAB3IP, and plasmids that knock down or overexpress circRAB3IP were used to evaluate its effect on the enzalutamide sensitivity of PCa cells. Mechanistically, we explored the potential regulatory effects of eIF4A3 and LEF1 on the biogenesis of circRAB3IP. Our in vivo and in vitro data indicated that increased expression of circRAB3IP was found in enzalutamide-resistant PCa, and knockdown of circRAB3IP significantly enhanced enzalutamide sensitivity in PCa cells. However, upregulation of circRAB3IP resulted in the opposite effects. Further mechanistic research demonstrated that circRAB3IP could regulate the expression of serum and glucocorticoid-regulated kinase 1 (SGK1) by serving as a sponge that directly targets miR-133a-3p/miR-133b. Then, we showed that circRAB3IP partially exerted its biological functions via SGK1 signaling. Furthermore, we discovered that eIF4A3 and LEF1 might increase circRAB3IP expression in PCa.

Diverse Roles and Therapeutic Potentials of Circular RNAs in Urological Cancers

Circular RNAs (circRNAs) are a novel class of noncoding RNAs, which are mainly formed as a loop structure at the exons caused by noncanonical splicing; they are much more stable than linear transcripts; recent reports have suggested that the dysregulation of circRNAs is associated with the occurrence and development of diseases, especially various human malignancies. Emerging evidence demonstrated that a large number of circRNAs play a vital role in a series of biological processes such as tumor cell proliferation, migration, drug resistance, and immune escape. Additionally, circRNAs were also reported to be potential prognostic and diagnostic biomarkers in cancers. In this work, we systematically summarize the biogenesis and characteristics of circRNAs, paying special attention to potential mechanisms and clinical applications of circRNAs in urological cancers, which may help develop potential therapy targets for urological cancers in the future.

Circular RNAs in prostate cancer: Biogenesis,biological functions, and clinical significance

Circular RNAs (circRNAs) are covalently closed RNA molecules that play important regulatory roles in various tumors. Prostate cancer (PCa) is one of the most common malignant tumors in the world, with high morbidity and mortality. In recent years, more and more circRNAs have been found to be abnormally expressed and involved in the occurrence and development of PCa, including cell proliferation, apoptosis, invasion, migration, metastasis, chemotherapy resistance, and radiotherapy resistance. Most of the circRNAs regulate biological behaviors of cancer through a competitive endogenous RNA (ceRNA) regulatory mechanism, and some can exert their functions by binding to proteins. circRNAs are also associated with many clinicopathological features of PCa, including tumor grade, lymph node metastasis, and distant metastasis. In addition, circRNAs are potential diagnostic and prognostic biomarkers for PCa. Considering their critical regulatory roles in the progression of PCa, circRNAs would be the potential therapeutic targets. In this paper, the current research status of circRNAs in PCa is briefly reviewed.

The Role and Clinical Potentials of Circular RNAs in Prostate Cancer

Globally, prostate cancer (PCa) is the second most commonly diagnosed cancer in men globally. Early diagnosis may help in promoting survival in the affected patients. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) which have been found to show extensive dysregulation in a handful of human diseases including cancers. Progressions in RNA identification techniques have provided a vast number of circRNAs exhibiting either up-regulation or down-regulation in PCa tissues compared to normal adjacent tissues. The mechanism of action is not clear for most of dysregulated circRNAs. Among them, function of a number of newly identified dysregulated circRNAs have been assessed in PCa cells. Increase in cell proliferation, migration, invasion, and metastasis have been reported for up-regulated circRNAs which suggest their role as oncogenes. On the other hand, down-regulated circRNAs have shown tumor suppressing actions in experimental studies. Furthermore, in a majority of studies, circRNAs have been found to sponge microRNAs (miRNAs), negatively regulating expression or activity of the downstream miRNAs. Additionally, they have been identified in interaction with regulatory proteins. This axis consequently regulates a signaling pathway, a tumor suppressor, or an oncogene. Easy, quick, and reliable detection of circRNAs in human body fluids also suggests their potentials as biomarker candidates for diagnosis and prediction of prognosis in PCa patients. In this review, we have discussed the role and potentials of a number of dysregulated circRNAs in PCa.

Interaction between Non-Coding RNAs and Androgen Receptor with an Especial Focus on Prostate Cancer

The androgen receptor (AR) is a member of the nuclear receptor superfamily and has three functional domains, namely the N-terminal, DNA binding, and C-terminal domain. The N-terminal domain harbors potent transactivation functions, whereas the C-terminal domain binds to androgens and antiandrogens used to treat prostate cancer. AR has genomic activity being DNA binding-dependent or through interaction with other DNA-bound transcription factors, as well as a number of non-genomic, non-canonical functions, such as the activation of the ERK, AKT, and MAPK pathways. A bulk of evidence indicates that non-coding RNAs have functional interactions with AR. This type of interaction is implicated in the pathogenesis of human malignancies, particularly prostate cancer. In the current review, we summarize the available data on the role of microRNAs, long non-coding RNAs, and circular RNAs on the expression of AR and modulation of AR signaling, as well as the effects of AR on their expression. Recognition of the complicated interaction between non-coding RNAs and AR has practical importance in the design of novel treatment options, as well as modulation of response to conventional therapeutics.

miRNAs and androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) is mainly used for the treatment of advanced, metastatic or recurrent prostate cancer (PCa). However, patients progress to ADT resistance and castration-resistant prostate cancer (CRPC) with a poor prognosis. Reliable validated markers of ADT resistance with proven clinical utility are necessary for timely correction of the therapy as well as for improvement of patient quality of life. MiRNAs involved in the ADT response and CRPC development via multiple mechanisms may act as biomarkers for patient outcomes. Available data on miRNAs associated with the ADT response (resistance and sensitivity) are summarized and analyzed in the manuscript, including analyses using bioinformatics resources. Molecular targets of miRNAs, as well as reciprocal relations between miRNAs and their targets, were studied using different databases. Special attention was dedicated to the mechanisms of ADT resistance and CRPC development, including testosterone, PI3K-AKT, VEGF pathways and associated genes. Several different approaches can be used to search for miRNAs associated with the ADT response, each of which focuses on the associated set of miRNAs - potential markers of ADT. The intersection of these approaches and combined analysis allowed us to select the most promising miRNA markers of the ADT response. Meta-analysis of the current data indicated that the selected 5 miRNAs (miRNAs - 125b, miR-21, miR-23b, miR-27b and miR-221) and 14 genes are involved in the regulation of key processes of CRPC development and represent the most promising predictors of the ADT response, further demonstrating their potential in combination therapy for advanced PCa.

Roles of circRNAs in cancer chemoresistance (Review)

Circular RNA (circRNA) is a type of endogenous, high‑stability, noncoding RNA. circRNAs exhibit various biological functions, and are involved in physiological and pathological processes occurring in various diseases, including cancers. They can not only act as microRNA and protein sponges, but also interact with proteins, translated peptides, and transcriptional and translational regulators, and compete with pre‑mRNA splicing. Chemotherapy is one of the most important types of cancer treatment. However, the resistance of cancer cells to chemotherapy is a leading reason for the failure of chemotherapy. It has been reported that circRNAs play important roles in cancer resistance via a number of mechanisms. The functions of the circRNAs provide insight into their roles in chemoresistance pathways. In addition, some circRNAs may serve as novel biomarkers for the diagnosis and prognosis of cancer resistance. Obtaining improved understanding of the molecular regulatory networks featuring circRNAs in tumors and searching for markers for the diagnosis and treatment of cancer resistance are leading issues in circRNA research. The present review introduced the functions of circRNAs, illustrated the mechanisms underlying drug resistance in cancer, described the contributions of circRNAs to this resistance and discussed the potential application of circRNAs in the treatment of drug‑resistant cancer. In particular, the review aimed to reveal the main mechanisms of circRNAs in cancer drug resistance, including mechanisms involving drug transport and metabolism, alterations of drug targets, DNA damage repair, downstream resistance mechanisms, adaptive responses and the tumor microenvironment. The findings may provide novel therapeutic targets for clinical treatment of cancer chemoresistance.

The Emerging Role of Circular RNAs in Prostate Cancer: A Systematic Review

Prostate cancer is one of the most common malignant tumors that threaten the health of men. It is urgent to explore new molecular targets and develop new drugs for the treatment of prostate cancer. Circular RNAs (circRNAs) are aberrantly expressed in various malignant tumors. The dysregulated circRNAs are involved in the metastasis, tumor growth, drug resistance, and immunosuppression of malignant tumors. The present review systematically summarized publications concerning the biological implications of circRNAs in prostate cancer. The PubMed and Web of Science databases were used to retrieve publications concerning circRNAs and prostate cancer until June 16, 2021. The following keywords were used in the literature search: (circRNA OR circular RNA) AND prostate cancer. 73 publications were enrolled in the present systematic review to summarize the role of circRNAs in prostate cancer. The dysregulated and functional circRNAs were involved in the cell cycle, proliferation, migration, invasion, metastasis, drug resistance and radiosensitivity of prostate cancer. In addition, circRNAs could function through EVs and serve as prognostic and diagnostic biomarkers. Certain circRNAs were correlated with clinicopathological features of prostate cancer. A comprehensive review of the molecular mechanism of the tumorigenesis and progression of prostate cancer may contribute to the development of new therapies of prostate cancer in the future.

Downregulation of LINC00665 suppresses the progression of lung adenocarcinoma via regulating miR-181c-5p/ZIC2 axis

Long non-coding RNA (lncRNA) LINC00665 was demonstrated to be upregulated in lung adenocarcinoma (LUAD) and target miR-181c-5p. ZIC2, which is upregulated in LUAD, serves as a putative target of miR-181c-5p. In this study, we aimed to reveal whether LINC00665 regulates miR-181c-5p/ZIC2 axis to promote LUAD progression. The results showed that LINC00665, HOXA1, ZIC2, and HOXA11 levels were increased in LUAD tissues, while miR-181c-5p level was decreased when compared to the adjacent normal tissues. High expression levels of LINC00665, ZIC2, HOXA1 and HOXA11, and low expression of miR-181c-5p were closely linked to poor prognosis of LUAD patients. Knockdown of LINC00665 induced obvious inhibitions in cell viability, clone formation, invasion and tumorigenesis in LUAD cells, whereas miR-181c-5p downregulation significantly neutralized these effects. In addition, downregulation of ZIC2 obviously reversed the enhancements of cell viability, clone formation, invasion and tumorigenesis induced by miR-181c-5p knockdown. In summary, the present study reveals that silencing of LINC00665 suppresses LUAD progression through targeting miR-181c-5p/ZIC2 axis.

hsa_circ_0062019 promotes the proliferation, migration, and invasion of prostate cancer cells via the miR-195-5p/HMGA2 axis

Circular RNA (circRNA) is a new class of non-coding RNA. It was reported that circRNA involves in the metastasis of cancer. The aim of this study is to explore the role and mechanism of circRNA hsa_circ_0062019 in the development of prostate cancer (PCa). Our results showed that hsa_circ_0062019 was highly expressed in PCa cell lines. Cell Counting Kit-8 assay revealed that upregulation of hsa_circ_0062019 boosted PCa cell proliferation, and silencing of hsa_circ_0062019 inhibited cell proliferation. Meanwhile, transwell assay proved that upregulation of hsa_circ_0062019 facilitated PCa cell invasion and migration, while downregulation of hsa_circ_0062019 inhibited these malignant phenotypes. Furthermore, luciferase reporter assay proved the binding of hsa_circ_0062019 with miR-195-5p and the binding between miR-195-5p and high mobility group AT-hook 2 (HMGA2), suggesting that hsa_circ_0062019 promoted the expression of HMGA2 by sponging miR-195-5p. In addition, our results revealed that the hsa_circ_0062019-induced PCa cell malignant phenotypes were notably reversed by the downregulation of HMGA2. Overall, our study demonstrated that hsa_circ_0062019 promoted PCa cell proliferation, migration, and invasion via upregulation of HMGA2 expression by sponging miR-195-5p. Our study proved a novel molecular mechanism of PCa development and provided a potential target for the treatment of PCa.

SMARCC1 Suppresses Tumor Progression by Inhibiting the PI3K/AKT Signaling Pathway in Prostate Cancer

Background

SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin subfamily C member 1 (SMARCC1) protein is a potential tumor suppressor in various cancers. However, its role in prostate cancer (PCa) remains controversial. The aim of this study was to determine the biological function of SMARCC1 in PCa and explore the underlying regulatory mechanisms.

Methods

The expression of SMARCC1 was validated in PCa tissues by immunohistochemistry. Meanwhile, function experiments were used to evaluate the regulatory role on cell proliferation and metastasis in PCa cells with SMARCC1 depletion both in vitro and in vivo. The expression levels of relevant proteins were detected by Western blotting.

Results

Our finding showed that SMARCC1 was significantly downregulated in prostate adenocarcinoma, with a higher Gleason score (GS) than that in low GS. The decreased expression of SMARCC1 was significantly correlated with a higher GS and poor prognosis. Additionally, we found that silencing of SMARCC1 dramatically accelerated cell proliferation by promoting cell cycle progression and enhancing cell migration by inducing epithelial mesenchymal transition (EMT). Furthermore, depletion of SMARCC1 facilitated PCa xenograft growth and lung metastasis in murine models. Mechanistically, the loss of SMARCC1 activated the PI3K/AKT pathway in PCa cells.

Conclusion

SMARCC1 suppresses PCa cell proliferation and metastasis via the PI3K/AKT signaling pathway and is a novel therapeutic target.

Identification of Enzalutamide Resistance-Related circRNA-miRNA-mRNA Regulatory Networks in Patients with Prostate Cancer

Purpose

This study aimed to identify enzalutamide resistant-related (EnzR-related) circRNAs and to characterize and validate circRNA-miRNA-mRNA ceRNA regulatory network and corresponding prognostic signature of prostate cancer patients.

Methods

We obtained circRNA expression microarray from the Gene Expression Omnibus (GEO) database and performed differential expression analysis to identify EnzR-related circRNAs using the limma package. The miRNA and mRNA expression profiling were downloaded and performed differential expression analysis, then overlapped with predicted candidates. Next, we established circRNA-miRNA-mRNA ceRNA network and PPI network utilized Cytoscape software and STRING database, respectively. In addition, univariate and Lasso Cox regression analyses were applied to generate a prognostic signature. Receiver operating characteristic (ROC) curves and Kaplan–Meier analysis were used to evaluate the reliability and sensitivity of the signature. Ultimately, we chose hsa_circ_0047641 to validate the feasibility of the EnzR-related ceRNA regulatory pathway using qRT-PCR, CCK8 and Transwell assays.

Results

We identified 13 EnzR-related circRNAs and constructed a ceRNA regulatory network that contained two downregulated circRNAs (has-circ-00000919 and has-circ-0000036) and two upregulated circRNAs (has-circ-0047641 and has-circ-0068697), and their sponged 6 miRNAs and 167 targeted mRNAs. Subsequently, these targeted mRNAs were performed to implement PPI analysis and to identify 10 Hub genes. Functional enrichment analysis provided new ways to seek potential biological functions. Besides, we established a prognostic signature of PCa patients based on 8 prognostic-associated mRNAs. We confirmed that the survival rates of PCa patients with high-risk subgroup were slightly lower than those with low-risk subgroup in the TCGA dataset (p<0.001), and ROC curves revealed that the AUC value for prognostic signature was 0.816. Finally, the functional analysis suggested that knockdown of hsa_circ_0047641 could inhibit the progression of PCa and could reverse Enz-resistance in vitro.

Conclusion

We identified 13 EnzR-related circRNAs, and constructed and confirmed that EnzR-related circRNA-miRNA-mRNA ceRNA network and corresponding prognostic signature could be a useful prognostic biomarker and therapeutic target.

Role of noncoding RNA in drug resistance of prostate cancer

Prostate cancer is one of the most prevalent forms of cancer around the world. Androgen-deprivation treatment and chemotherapy are the curative approaches used to suppress prostate cancer progression. However, drug resistance is extensively and hard to overcome even though remarkable progress has been made in recent decades. Noncoding RNAs, such as miRNAs, lncRNAs, and circRNAs, are a group of cellular RNAs which participate in various cellular processes and diseases. Recently, accumulating evidence has highlighted the vital role of non-coding RNA in the development of drug resistance in prostate cancer. In this review, we summarize the important roles of these three classes of noncoding RNA in drug resistance and the potential therapeutic applications in this disease.

Gene Expression Profiles of Circular RNAs and MicroRNAs in Chronic Rhinosinusitis With Nasal Polyps

Introduction: Chronic rhinosinusitis (CRS) is often classified primarily on the basis of the absence or presence of nasal polyps (NPs), that is, as CRS with nasal polyps (CRSwNP) or CRS without nasal polyps (CRSsNP). Additionally, according to the percentage of eosinophils, CRSwNP can be further divided into eosinophilic CRSwNP (ECRSwNP) and non-ECRSwNP. CRSwNP is a significant public health problem with a considerable socioeconomic burden. Previous research reported that the pathophysiology of CRSwNP is a complex, multifactorial disease. There have been many studies on its etiology, but its pathogenesis remains unclear. Dysregulated expression of microRNAs (miRNAs) has been shown in psoriasis, rheumatoid arthritis, pulmonary fibrosis, and allergic asthma. Circular RNAs (circRNAs) are also involved in inflammatory diseases such as rheumatoid arthritis, septic acute kidney injury, myocardial ischemia/reperfusion injury, and sepsis-induced liver damage. The function of miRNAs in various diseases, including CRSwNP, is a research hotspot. In contrast, there have been no studies on circRNAs in CRSwNP. Overall, little is known about the functions of circRNAs and miRNAs in CRSwNP. This study aimed to investigate the expression of circRNAs and miRNAs in a CRSwNP group and a control group to determine whether these molecules are related to the occurrence and development of CRSwNP. Methods: Nine nasal mucosa samples were collected, namely, three ECRSwNP samples, three non-ECRSwNP samples, and three control samples, for genomic microarray analysis of circRNA and microRNA expression. All of the tissue samples were from patients who were undergoing functional endoscopic sinus surgery in our department. Then we selected some differentially expressed miRNAs and circRNAs for qPCR verification. Meanwhile, GO enrichment analysis and KEGG pathway analysis were applied to predict the biological functions of aberrantly expressed circRNAs and miRNAs based on the GO and KEGG databases. Receiver operating characteristic (ROC) curve analysis and principal component analysis (PCA) were performed to confirm these molecules are involved in the occurrence and development of CRSwNP. Results: In total, 2,875 circRNAs showed significant differential expression in the CRSwNP group. Specifically, 1794 circRNAs were downregulated and 1,081 circRNAs were upregulated. In the CRSwNP group, the expression of 192 miRNAs was significantly downregulated, and none of the miRNAs were significantly upregulated. GO and KEGG analysis showed differential circRNAs and miRNAs were enriched in "amoebiasis," "salivary secretion," "pathways in cancer," and "endocytosis." Through qRT-PCR verification, the expression profiles of hsa-circ-0031593, hsa-circ-0031594, hsa-miR-132-3p, hsa-miR-145-5p, hsa-miR-146a-5p, and hsa-miR-27b-3p were shown to have statistical differences. In addition, ROC curve analysis showed that the molecules with the two highest AUCs were hsa-circ-0031593 with AUC 0.8353 and hsa-miR-145-5p with AUC 0.8690. Through PCA with the six ncRNAs, the first principal component explained variance ratio was 98.87%. The AUC of the six ncRNAs was 0.8657. Conclusion: In our study, the expression profiles of ECRSwNP and non-ECRSwNP had no statistical differences. The differentially expressed circRNAs and miRNAs between CRSwNP and control may play important roles in the pathogenesis of CRSwNP. Altered expression of hsa-circ-0031593 and hsa-miR-145-5p have the strongest evidence for involvement in the occurrence and development of CRSwNP because their AUCs are higher than the other molecules tested in this study.

Increased transcription and high translation efficiency lead to accumulation of androgen receptor splice variant after androgen deprivation therapy

Upregulation of androgen receptor splice variants (AR-Vs), especially AR-V7, is associated with castration resistance of prostate cancer. At the RNA level, AR-V7 upregulation is generally coupled with increased full-length AR (AR-FL); consequently, AR-V7 and AR-Vs collectively constitute a minority of the AR population. However, Western blotting showed that the relative abundance of AR-V proteins is much higher in many castration-resistant prostate cancers (CRPCs). To address the mechanism underlying this discrepancy, we analyzed RNA-seq data from ~350 CRPC samples and found a positive correlation between all canonical and alternative AR splicing. This indicates that increased alternative splicing is not at the expense of canonical splicing. Instead, androgen deprivation releases AR-FL from repressing the transcription of the AR gene to induce coordinated increase of AR-FL and AR-V mRNAs. At the protein level, however, androgen deprivation induces AR-FL, but not AR-V, degradation. Moreover, AR-V7 is translated much faster than AR-FL. Thus, androgen-deprivation-induced AR-gene transcription and AR-FL protein decay, together with efficient AR-V7 translation, explain the discrepancy between the relative AR-V mRNA and protein abundances in many CRPCs, highlighting the inevitability of AR-V induction after endocrine therapy.

Androgen Receptor-Related Non-coding RNAs in Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death among men in the United States. Androgen receptor (AR) signaling is the dominant oncogenic pathway in PCa and the main strategy of PCa treatment is to control the AR activity. A large number of patients acquire resistance to Androgen deprivation therapy (ADT) due to AR aberrant activation, resulting in castration-resistant prostate cancer (CRPC). Understanding the molecular mechanisms underlying AR signaling in the PCa is critical to identify new therapeutic targets for PCa patients. The recent advances in high-throughput RNA sequencing (RNA-seq) techniques identified an increasing number of non-coding RNAs (ncRNAs) that play critical roles through various mechanisms in different diseases. Some ncRNAs have shown great potentials as biomarkers and therapeutic targets. Many ncRNAs have been investigated to regulate PCa through direct association with AR. In this review, we aim to comprehensively summarize recent findings of the functional roles and molecular mechanisms of AR-related ncRNAs as AR regulators or targets in the progression of PCa.

Circular RNAs: new biomarkers of chemoresistance in cancer

Chemotherapeutics are validated conventional treatments for patients with advanced cancer. However, with continual application of chemotherapeutics, chemoresistance, which is often predictive of poor prognosis, has gradually become a concern in recent years. Circular RNAs (circRNAs), a class of endogenous noncoding RNAs (ncRNAs) with a closed-loop structure, have been reported to be notable targets and markers for the prognosis, diagnosis, and treatment of many diseases, particularly cancer. Although dozens of studies have shown that circRNAs play major roles in drug-resistance activity in tumors, the mechanisms by which circRNAs affect chemoresistance have yet to be explored. In this review, we describe the detailed mechanisms of circRNAs and chemotherapeutics in various cancers and summarize potential therapeutic targets for drug-resistant tumors.

Roles of circRNAs in prostate cancer: Expression, mechanism, application and potential

Circular RNA (circRNA) is a member of the non-coding RNA family that is formed by trans-splicing. Because of its unique structure and characteristics, it has extraordinary value for the diagnosis, treatment, and prognosis of diseases, particularly for tumors. Study of the role of circRNAs in the occurrence and development of prostate cancer has made considerable progress, but many areas remain that require further exploration and improvement. This article describes research into sequencing expression profiles, expression regulation, potential value as biomarkers, mechanism in the occurrence and development, therapy resistance, relationship with clinicopathological features, and prognostic value of circRNAs in prostate cancer from the past few years.