Tumor-derived exosomal circRNA_102481 contributes to EGFR-TKIs resistance via the miR-30a-5p/ROR1 axis in non-small cell lung cancer

CircHIF1A induces cetuximab resistance in colorectal cancer by promoting HIF1α-mediated glycometabolism alteration

Epidermal growth factor receptor (EGFR)-targeted therapy is an important treatment for RAS wild-type metastatic colorectal cancer (mCRC), but the resistance mechanism remains unclear. Here, the differential expression of circRNAs between Cetuximab sensitive and resistant cell lines was analyzed using whole-transcriptome sequencing. We identified that the expression of circHIF1A was significantly higher in LIM1215-R than in LIM1215. When treated with Cetuximab, downregulation of circHIF1A level weakened the proliferation and clonal formation ability of LIM1215-R, caused more cells to enter G0-G1 phase, and significantly reduced the basal respiration, ATP production, and maximal respiration, as well as the glycolytic capacity and glycolytic reserve. The response rate and prognosis of circHIF1A-positive patients were inferior to those of negative patients. Mechanistically, circHIF1A can upregulate the level of hypoxia-inducible factor 1 A (HIF1A) by competitively binding to miR-361-5p, inducing the overexpression of enzymes such as glucose transporter 1 (GLUT1) and lactate dehydrogenase A (LDHA). In a xenograft model, inhibition of circHIF1A expression increased the sensitivity to Cetuximab treatment. In conclusion, circHIF1A can promote HIF1α-mediated glycometabolism alteration to induce Cetuximab resistance in CRC. It has the potential to become a screening indicator for the Cetuximab beneficial population in mCRC and a new therapeutic target for enhancing treatment efficacy.

circ_PPAPDC1A promotes Osimertinib resistance by sponging the miR-30a-3p/ IGF1R pathway in non-small cell lung cancer (NSCLC)

BACKGROUND

Recent evidence has demonstrated that abnormal expression and regulation of circular RNA (circRNAs) are involved in the occurrence and development of a variety of tumors. The aim of this study was to investigate the effects of circ_PPAPDC1A in Osimertinib resistance in NSCLC.

METHODS

Human circRNAs microarray analysis was conducted to identify differentially expressed (DE) circRNAs in Osimertinib-acquired resistance tissues of NSCLC. The effect of circ_PPAPDC1A on cell proliferation, invasion, migration, and apoptosis was assessed in both in vitro and in vivo. Dual-luciferase reporter assay, RT-qPCR, Western-blot, and rescue assay were employed to confirm the interaction between circ_PPAPDC1A/miR-30a-3p/IGF1R axis.

RESULTS

The results revealed that circ_PPAPDC1A was significantly upregulated in Osimertinib acquired resistance tissues of NSCLC. circ_PPAPDC1A reduced the sensitivity of PC9 and HCC827 cells to Osimertinib and promoted cell proliferation, invasion, migration, while inhibiting apoptosis in Osimertinib-resistant PC9/OR and HCC829/OR cells, both in vitro and in vivo. Silencing circ_PPAPDC1A partially reversed Osimertinib resistance. Additionally, circ_PPAPDC1A acted as a competing endogenous RNA (ceRNA) by targeting miR-30a-3p, and Insulin-like Growth Factor 1 Receptor (IGF1R) was identified as a functional gene for miR-30a-3p in NSCLC. Furthermore, the results confirmed that circ_PPAPDC1A/miR-30a-3p/IGF1R axis plays a role in activating the PI3K/AKT/mTOR signaling pathway in NSCLC with Osimertinib resistance.

CONCLUSIONS

Therefore, for the first time we identified that circ_PPAPDC1A was significantly upregulated and exerts an oncogenic role in NSCLC with Osimertinib resistance by sponging miR-30a-3p to active IGF1R/PI3K/AKT/mTOR pathway. circ_PPAPDC1A may serve as a novel diagnostic biomarker and therapeutic target for NSCLC patients with Osimertinib resistance.

Tanreqing suppresses the proliferation and migration of non-small cell lung cancer cells by mediating the inactivation of the HIF1α signaling pathway via exosomal circ-WDR78

Circular RNAs (circRNAs) have emerged as regulators of cancer progression, including non-small cell lung cancer (NSCLC). Tanreqing (TRQ), a traditional Chinese medicine, is used clinically for respiratory diseases. RT-qPCR quantified circ-WDR78 expression in NSCLC cells. Cell growth, apoptosis, invasion, and migration were assessed by functional assays. RNA-binding protein immunoprecipitation (RIP), luciferase reporter, and RNA pull-down assays determined the competing endogenous RNA (ceRNA) network of circ-WDR78. The interaction between HIF1α and CD274 (PD-L1) promoter was analyzed by chromatin immunoprecipitation (ChIP). Circ-WDR78 expression was up-regulated in TRQ-treated NSCLC cells. Functionally, circ-WDR78 exhibited anti-tumor effects in these cells. Additionally, circ-WDR78 could also induce reactive oxygen species (ROS) accumulation by down-regulating HIF1α expression, promoting autophagy. Mechanistically, circ-WDR78 destabilizes HIF1α via the miR-1265/FBXW8 axis. TRQ-induced exosome secretion from NSCLC cells inhibits PD-L1 expression, preventing immune escape. We found that TRQ-treated NSCLC cells secrete exosomes to transmit circ-WDR78 to untreated NSCLC cells, inhibiting the malignancy of recipient tumor cells. In conclusion, TRQ inhibits NSCLC cell proliferation, invasion, and migration through exosomal circ-WDR78-mediated inactivation of the HIF1α signaling pathway, providing potential insight into TRQ injection for NSCLC treatment.Communicated by Ramaswamy H. Sarma.

Non-coding RNAs as potential therapeutic targets for receptor tyrosine kinase signaling in solid tumors: current status and future directions

This review article presents an in-depth analysis of the current state of research on receptor tyrosine kinase regulatory non-coding RNAs (RTK-RNAs) in solid tumors. RTK-RNAs belong to a class of non-coding RNAs (nc-RNAs) responsible for regulating the expression and activity of receptor tyrosine kinases (RTKs), which play a critical role in cancer development and progression. The article explores the molecular mechanisms through which RTK-RNAs modulate RTK signaling pathways and highlights recent advancements in the field. This include the identification of potential new RTK-RNAs and development of therapeutic strategies targeting RTK-RNAs. While the review discusses promising results from a variety of studies, encompassing in vitro, in vivo, and clinical investigations, it is important to acknowledge the challenges and limitations associated with targeting RTK-RNAs for therapeutic applications. Further studies involving various cancer cell lines, animal models, and ultimately, patients are necessary to validate the efficacy of targeting RTK-RNAs. The specificity of ncRNAs in targeting cellular pathways grants them tremendous potential, but careful consideration is required to minimize off-target effects, the article additionally discusses the potential clinical applications of RTK-RNAs as biomarkers for cancer diagnosis, prognosis, and treatment. In essence, by providing a comprehensive overview of the current understanding of RTK-RNAs in solid tumors, this review emphasizes their potential as therapeutic targets for cancer while acknowledging the associated challenges and limitations.

The emerging role of noncoding RNAs in the EGFR signaling pathway in lung cancer

Noncoding ribonucleic acids (ncRNAs) have surfaced as essential orchestrators within the intricate system of neoplastic biology. Specifically, the epidermal growth factor receptor (EGFR) signalling cascade shows a central role in the etiological underpinnings of pulmonary carcinoma. Pulmonary malignancy persists as a preeminent contributor to worldwide mortality attributable to malignant neoplasms, with non-small cell lung carcinoma (NSCLC) emerging as the most predominant histopathological subcategory. EGFR is a key driver of NSCLC, and its dysregulation is frequently associated with tumorigenesis, metastasis, and resistance to therapy. Over the past decade, researchers have unveiled a complex network of ncRNAs, encompassing microRNAs, long noncoding RNAs, and circular RNAs, which intricately regulate EGFR signalling. MicroRNAs, as versatile post-transcriptional regulators, have been shown to target various components of the EGFR pathway, influencing cancer cell proliferation, migration, and apoptosis. Additionally, ncRNAs have emerged as critical modulators of EGFR signalling, with their potential to act as scaffolds, decoys, or guides for EGFR-related proteins. Circular RNAs, a relatively recent addition to the ncRNA family, have also been implicated in EGFR signalling regulation. The clinical implications of ncRNAs in EGFR-driven lung cancer are substantial. These molecules exhibit diagnostic potential as robust biomarkers for early cancer detection and personalized treatment. Furthermore, their predictive value extends to predicting disease progression and therapeutic outcomes. Targeting ncRNAs in the EGFR pathway represents a novel therapeutic approach with promising results in preclinical and early clinical studies. This review explores the increasing evidence supporting the significant role of ncRNAs in modulating EGFR signalling in lung cancer, shedding light on their potential diagnostic, prognostic, and therapeutic implications.

Hsa_circ_0041150 serves as a novel biomarker for monitoring chemotherapy resistance in small cell lung cancer patients treated with a first-line chemotherapy regimen

PURPOSE

To explore the potential of circRNAs as biomarkers in non-invasive body fluids for monitoring chemotherapy resistance in SCLC patients.

METHODS

CircRNAs were screened and characterized using transcriptome sequencing, Sanger sequencing, actinomycin D treatment, and Ribonuclease R assay. Our study involved 174 participants, and serum samples were collected from all chemotherapy-resistant patients (n = 54) at two time points: stable disease and progressive disease. We isolated and identified serum extracellular vesicles (EVs) from the patients using ultracentrifugation, transmission electron microscopy, nanoflow cytometry, and western blotting analysis. The expression levels of serum and serum EVs circRNAs were determined by quantitative real-time polymerase chain reaction (qRT-PCR). The impact of circRNA on the function of SCLC cells was assessed through various assays, including proliferation assay, scratch assay, transwell assay, and cisplatin resistance assay.

RESULTS

Hsa_circ_0041150 was found to be upregulated in chemoresistant SCLC cells and played a role in promoting proliferation, invasion, migration, and cisplatin resistance. Furthermore, the expression levels of hsa_circ_0041150 in serum and serum EVs increased when SCLC patients developed resistance after a first-line chemotherapy regimen. When combined with NSE, the monitoring sensitivity (70.37%) and specificity (81.48%) for chemotherapy resistance significantly improved. Moreover, the expression level of hsa_circ_0041150 showed significant associations with time to progression from SD to PD, and high hsa_circ_0041150 levels after drug resistance were more likely to cause chemotherapy resistance. Additionally, hsa_circ_0041150 demonstrated valuable potential in monitoring the progression from initial diagnosis to chemotherapy resistance in SCLC patients.

CONCLUSION

Thus, EVs hsa_circ_0041150 holds promise as a biomarker for monitoring chemotherapy resistance in SCLC patients.

CircRNAs and lung cancer: Insight into their roles in metastasis

Lung cancer is the leading cause of cancer-related mortality worldwide. A major contributing factor to the poor survival rates in lung cancer is the high prevalence of metastasis at the time of diagnosis. To address this critical issue, it is imperative to investigate the mechanisms underlying lung cancer metastasis. Circular RNAs (circRNAs), a distinct type of ribonucleic acid characterized by their unique circular structure, have been implicated in the progression of various diseases. Recent studies have highlighted the close association between circRNAs and the occurrence and development of lung cancer, particularly in relation to metastasis. In this review, we provide a concise overview of the expression patterns and prognostic significance of circRNAs in lung cancer. Additionally, we summarized the current understanding of the clinical relevance of circRNAs in lung cancer metastasis. Furthermore, we systematically focused on the roles of circRNAs in each step of lung cancer metastasis, reflecting the sequential progression of this process. Notably, circRNAs exhibit dual functionality in lung cancer metastasis, acting both as facilitators and inhibitors of metastatic processes. Given their potential, circRNAs hold promise as novel biomarkers and therapeutic targets for lung cancer metastasis, warranting further investigation.

The therapeutic potential of exosomes in lung cancer

BACKGROUND

Lung cancer (LC) is one of the most common malignancies globally. Besides early detection and surgical resection, there is currently no effective curative treatment for metastatic advanced LC. Exosomes are endogenous nano-extracellular vesicles produced by somatic cells that play an important role in the development and maintenance of normal physiology. Exosomes can carry proteins, peptides, lipids, nucleic acids, and various small molecules for intra- and intercellular material transport or signal transduction. LC cells can maintain their survival, proliferation, migration, invasion, and metastasis, by producing or interacting with exosomes. Basic and clinical data also show that exosomes can be used to suppress LC cell proliferation and viability, induce apoptosis, and enhance treatment sensitivity. Due to the high stability and target specificity, good biocompatibility, and low immunogenicity of exosomes, they show promise as vehicles of LC therapy.

CONCLUSION

We have written this comprehensive review to communicate the LC treatment potential of exosomes and their underlying molecular mechanisms. We found that overall, LC cells can exchange substances or crosstalk with themselves or various other cells in the surrounding TME or distant organs through exosomes. Through this, they can modulate their survival, proliferation, stemness, migration, and invasion, EMT, metastasis, and apoptotic resistance.

Recent advances of exosomal circRNAs in cancer and their potential clinical applications

Circular RNA (circRNA) is a type of non-coding RNA that forms a covalently closed, uninterrupted loop. The expression of circRNA differs among cell types and tissues, and various circRNAs are aberrantly expressed in a variety of diseases, including cancer. Aberrantly expressed circRNAs contribute to disease progression by acting as microRNA sponges, functional protein sponges, or novel templates for protein translation. Recent studies have shown that circRNAs are enriched in exosomes. Exosomes are spherical bilayer vesicles released by cells into extracellular spaces that mediate intercellular communication by delivering cargoes. These cargoes include metabolites, proteins, lipids, and RNA molecules. Exosome-mediated cell-cell or cell-microenvironment communications influence the progression of carcinogenesis by regulating cell proliferation, angiogenesis, metastasis as well as immune escape. In this review, we summarize the current knowledge about exosomal circRNAs in cancers and discuss their specific functions in tumorigenesis. Additionally, we discuss the potential value of exosomal circRNAs as diagnostic biomarkers and the potential applications of exosomal circRNA-based cancer therapy.

Exosomal non-coding RNAs-mediated EGFR-TKIs resistance in NSCLC with EGFR mutation

Lung cancer is the leading cause of cancer-related mortality worldwide. The advent of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) has significantly improved survival rates of patients with EGFR-mutant non-small cell lung cancer (NSCLC). However, as with other antitumor drugs, resistance to EGFR-TKIs is inevitably develops over time. Exosomes, extracellular vesicles with a 30-150 nm diameter, have emerged as vital mediators of intercellular communication. Recent studies revealed that exosomes carry non-coding RNAs (ncRNAs), including circular RNA (circRNA), microRNA (miRNA), and long noncoding RNA (lncRNA), which contribute to the development of EGFR-TKIs resistance. This review provides a comprehensive overview of the current research on exosomal ncRNAs mediating EGFR-TKIs resistance in EGFR-mutated NSCLC. In the future, detecting exosome ncRNAs can be used to monitor targeted therapy for NSCLC. Meanwhile, developing therapeutic regimens targeting these resistance mechanisms may provide additional clinical benefits to patients with EGFR-mutated NSCLC.

Exosomal circRNAs in cancer: Implications for therapy resistance and biomarkers

Despite the advances in cancer treatment in recent years, the development of resistance to cancer therapy remains the biggest hurdle towards curative cancer treatments. Therefore, investigating the molecular mechanisms underlying cancer therapy resistance is of paramount clinical importance. Circular RNAs (circRNAs), novel members of the noncoding RNA family, are endogenous biomolecules in eukaryotes characterized by a covalently closed loop structure with multiple biological functions. Significantly, circRNAs are abundant and stable in exosomes and can be packaged, secreted and transferred to targeted tumour cells, thereby modulating diverse hallmarks of cancer behaviours, such as proliferation, migration, and immune escape. Notably, a great number of exosomal circRNAs are abnormally expressed during cancer treatment and can mediate cancer therapy resistance through complex mechanisms; therefore, targeting exosomal circRNAs is a promising therapeutic method to reverse therapy resistance. This review aimed to elucidate the mechanisms underlying exosomal circRNAs controlling the resistance of cancer to common therapies, such as chemotherapy, targeted therapy, immunotherapy and radiotherapy, and we also discussed the therapeutic potential of exosomal circRNAs as clinical biomarkers and novel targets in cancer clinical management. We also discussed the prospects and challenges of targeting exosomal circRNAs as a novel therapeutic strategy for reversing cancer therapy resistance.

Long non-coding RNAs in non-small cell lung cancer: implications for EGFR-TKI resistance

Non-small cell lung cancer (NSCLC) is one of the most common types of malignant tumors as well as the leading cause of cancer-related deaths in the world. The application of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) has dramatically improved the prognosis of NSCLC patients who harbor EGFR mutations. However, despite an excellent initial response, NSCLC inevitably becomes resistant to EGFR-TKIs, leading to irreversible disease progression. Hence, it is of great significance to shed light on the molecular mechanisms underlying the EGFR-TKI resistance in NSCLC. Long non-coding RNAs (lncRNAs) are critical gene modulators that are able to act as oncogenes or tumor suppressors that modulate tumorigenesis, invasion, and metastasis. Recently, extensive evidence demonstrates that lncRNAs also have a significant function in modulating EGFR-TKI resistance in NSCLC. In this review, we present a comprehensive summary of the lncRNAs involved in EGFR-TKI resistance in NSCLC and focus on their detailed mechanisms of action, including activation of alternative bypass signaling pathways, phenotypic transformation, intercellular communication in the tumor microenvironment, competing endogenous RNAs (ceRNAs) networks, and epigenetic modifications. In addition, we briefly discuss the limitations and the clinical implications of current lncRNAs research in this field.

Regulatory mechanisms and clinical applications of tumor-driven exosomal circRNAs in cancers

Malignant tumors seriously affect people's survival and prognosis. Exosomes, as vesicle structures widely existing in human tissues and body fluids, are involved in cell-to-cell transmission. Tumor-derived exosomes were secreted from tumors and involved in the development of carcinogenesis. Circular RNA (circRNA), a novel member of endogenous noncoding RNAs, is widespread in human and play a vital role in many physiological or pathological processes. Tumor-driven exosomal circRNAs are often involved in tumorigenesis and development including the proliferation, invasion, migration and chemo-or-radiotherapy sensitivity of tumor cell by multiple regulatory mechanisms. In this review, we will elaborate the roles and functions of tumor-driven exosomal circRNAs in cancers which may be used as potential cancer biomarkers and novel therapeutic targets.

Cardioprotective effects of circ_0002612 in myocardial ischemia/reperfusion injury correlate with disruption of miR-30a-5p-dependent Ppargc1a inhibition

INTRODUCTION

Novel mechanistic insights into the effects of circular RNAs (circRNAs) on the physiology and pathology of cardiovascular diseases are under increasingly active investigation. This study defined the cardioprotective role and mechanistic actions of circ_0002612 in myocardial ischemia/reperfusion injury (MI/RI).

METHODS

MI/RI was induced in mice by ligation of the left anterior descending (LAD) artery followed by reperfusion, and the in vitro model was established in cultured cardiomyocytes under hypoxia/reoxygenation (H/R) conditions. Interaction among circ_0002612, miR-30a-5p, Ppargc1a, and NLRP3 was predicted by bioinformatics analysis and further experimentally identified. Gain- and loss-of-function experiments were performed to evaluate the effect of the circ_0002612/miR-30a-5p/Ppargc1a/NLRP3 axis on the cardiac function and myocardial infarction of I/R-injured mice, as well as viability and apoptosis of H/R-challenged cardiomyocytes.

RESULTS

In the myocardial tissues of MI/RI mice, miR-30a-5p was negatively correlated with circ_0002612 or Ppargc1a, but circ_0002612 was positively correlated with the expression of Ppargc1a. circ_0002612 competitively bound to miR-30a-5p to release expression of its target gene Ppargc1a. circ_0002612 promoted cardiomyocyte viability while suppressing the apoptosis by impairing the miR-30a-5p-mediated inhibition of Ppargc1a. Additionally, Ppargc1a inhibited the expression of NLRP3 and consequently facilitated cardiomyocyte proliferation while suppressing cell apoptosis. By inhibiting the expression of NLRP3, circ_0002612 protected mice from MI/RI.

CONCLUSION

Overall, this study demonstrates the cardioprotective role of circ_0002612 against MI/RI, which may be a viable target for MI/RI.

Evaluation and Application of Drug Resistance by Biomarkers in the Clinical Treatment of Liver Cancer

Liver cancer is one of the most lethal cancers in the world, mainly owing to the lack of effective means for early monitoring and treatment. Accordingly, there is considerable research interest in various clinically applicable methods for addressing these unmet needs. At present, the most commonly used biomarker for the early diagnosis of liver cancer is alpha-fetoprotein (AFP), but AFP is sensitive to interference from other factors and cannot really be used as the basis for determining liver cancer. Treatment options in addition to liver surgery (resection, transplantation) include radiation therapy, chemotherapy, and targeted therapy. However, even more expensive targeted drug therapies have a limited impact on the clinical outcome of liver cancer. One of the big reasons is the rapid emergence of drug resistance. Therefore, in addition to finding effective biomarkers for early diagnosis, an important focus of current discussions is on how to effectively adjust and select drug strategies and guidelines for the treatment of liver cancer patients. In this review, we bring this thought process to the drug resistance problem faced by different treatment strategies, approaching it from the perspective of gene expression and molecular biology and the possibility of finding effective solutions.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

Circular RNAs in chemotherapy resistance of lung cancer and their potential therapeutic application

Lung cancer is one of the high malignancy-related incidence and mortality worldwide, accounting for about 13% of total cancer diagnoses. Currently, the use of anti-cancer agents is still the main therapeutic method for lung cancer. However, cancer cells will gradually show resistance to these drugs with the progress of treatment. And the molecular mechanisms underlying chemotherapy agents resistance remain unclear. circRNAs are newly identified noncoding RNAs molecules with covalently closed circular structures. Previous studies have shown that circRNAs are associated with tumorigenesis and progression of various cancers, including lung cancer. Recently, growing reports have suggested that circRNAs could contribute to drug resistance of lung cancer cell through different mechanisms. Therefore, in this review, we summarized the functions and underlying mechanisms of circRNAs in regulating chemoresistance of lung cancer and discussed their potential applications for diagnosis, prognosis, and treatment of lung cancer.

Circ-N4BP2L2 enhances mitochondrial function in non-small cell lung cancer cells through regulating the miR-135a-5p/ARL5B axis

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer with a high incidence and mortality. Circular RNAs (circRNAs) exert vital functions in various cancers by acting as a sponge of miRNAs to abolish their inhibitory effect on target genes. This study aims to explore the biological function of circRNA NEDD4 binding protein 2 like 2 (circ-N4BP2L2) in NSCLC. We found that circ-N4BP2L2 was upregulated in NSCLC tissues and cells by using RT-qPCR. A549 cells were transfected with pcDNA-circN4BP2L2 or sh-circN4BP2L2 to obtain circN4BP2L2-overexpressed or -silenced cells, and then cell proliferation, invasion and apoptosis were determined. The results showed that knockdown of circ-N4BP2L2 repressed cell proliferation, invasion as well as mitochondrial function, and promoted cell apoptosis; while overexpression of circ-N4BP2L2 resulted in the opposite results. Mechanistically, the targeting correlations between miR-135a-5p and circ-N4BP2L2 or ADP-ribosylation factorlike 5B (ARL5B) were confirmed by using dual luciferase reporter, RNA pull-down and RNA immunoprecipitation assays. In addition, we found that circ-N4BP2L2 could promote the expression of ARL5B by serving as a sponge of miR-135a-5p. Moreover, rescue assays revealed that silencing miR-135a-5p or overexpressing ARL5B was able to abate the effects of circ-N4BP2L2 knockdown on malignant phenotypes and mitochondrial function of A549 cells. Finally, tumorigenicity assay demonstrated that circ-N4BP2L2 facilitated NSCLC tumor growth in vivo. Taken together, circ-N4BP2L2 enhanced NSCLC progression via the miR-135a-5p/ARL5B axis, which may provide a novel therapeutic target of NSCLC.

Exosomal ncRNAs facilitate interactive 'dialogue' between tumor cells and tumor-associated macrophages

As a biological carrier, exosomes participate in the communication between various kinds of cells, and can mediate the interactive 'dialogue' between tumor cells and tumor-associated macrophages (TAMs). TAMs are the most abundant cell population in the tumor stroma and are an important part of the tumor immune microenvironment. Various stimulating factors in the tumor microenvironment influence the polarization of TAMs into multiple phenotypes, such as M1 and M2. It plays a dual role in tumor immunity by both promoting and inhibiting tumor growth. Exosome-encapsulated non-coding RNAs (ncRNAs) participate in the interactive 'dialogue' between exosome-mediated TAMs and tumor cells. Tumor-derived exosomal ncRNAs can promote macrophage polarization, whereas exosomal ncRNAs derived from TAMs can affect tumor proliferation, metastasis, angiogenesis, and chemotherapy resistance. The present review summarizes the dual effects of exosomal ncRNAs on tumor cells and TAMs, and discusses the application of exosomal ncRNAs as a potential diagnostic or prognostic marker and drug delivery system, to provide a new perspective and potential therapeutic drugs on targeting exosomes and macrophages in the treatment of tumors.

Unraveling the significance of exosomal circRNAs in cancer therapeutic resistance

Exosomes are nanoscale extracellular vesicles secreted by a variety of cells, affecting the physiological and pathological homeostasis. They carry various cargoes including proteins, lipids, DNA, and RNA and have emerged as critical mediators of intercellular communication. During cell-cell communication, they can internalize either by autologous or heterologous recipient cells, which activate different signaling pathways, facilitating malignant progression of cancer. Among different types of cargoes in exosomes, the endogenous non-coding RNAs, such as circular RNAs (or circRNAs), have gained tremendous attention for their high stability and concentration, playing promising functional roles in cancer chemotherapeutic response by regulating the targeted gene expression. In this review, we primarily described the emerging evidence demonstrating the important roles of circular RNAs derived from exosomes in the regulation of cancer-associated signaling pathways that were involved in cancer research and therapeutic interventions. Additionally, the relevant profiles of exosomal circRNAs and their biological implications have been discussed, which is under investigation for their potential effect on the control of cancer therapeutic resistance.

Circ-PGAM1 Enhances Matrine Resistance of Non-Small Cell Lung Cancer via the miR-326/CXCR5 Axis

Background: Circular RNAs (circ-RNAs) have been demonstrated to influence initiation, drug resistance, and metastasis of tumors. However, the effects of circular-phosphoglycerate mutase 1 (circ-PGAM1) on matrine resistance in nonsmall cell lung cancer (NSCLC) remain unknown. Materials and Methods: The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to determine gene expression. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and cell colony formation assays were used to evaluate NSCLC apoptosis and cell proliferation after indicated treatments, respectively. Results: circ-PGAM1 was upregulated in human NSCLC cell lines (H1299 and A549) compared with the human normal lung epithelial (BEAS-2B) cells. circ-PGAM1 overexpression reversed the matrine treatment-induced inhibition on proliferation of NSCLC cells (A549 and H1299) and rescued the matrine treatment-stimulated apoptosis of these cells. miR-326 was demonstrated to interact with circ-PGAM1. circ-PGAM1 knockdown enhanced the antitumor effect of matrine on NSCLC cell proliferation and apoptosis, which was reversed by miR-326 inhibition. The authors also identified CXCR5 as a key downstream target of miR-326 in A549 cells. Conclusions: circ-PGAM1 enhances matrine resistance of NSCLC cells through the miR-326/CXCR5 axis. The authors' findings provide new insights into NSCLC-targeted therapy.

Landscape of circular RNAs in different types of lung cancer and an emerging role in therapeutic resistance (Review)

Lung cancer is one of the most common malignant tumor types and the leading cause of cancer‑associated death worldwide. Different types of lung cancer exhibit differences in terms of pathophysiology and pathogenesis, and also treatment and prognosis. Accumulating evidence has indicated that circular RNAs (circRNAs) are abnormally expressed among different types of lung cancer and confer important biological functions in progression and prognosis. However, studies comparing different circRNAs in lung cancer subtypes are scarce. Furthermore, circRNAs have an important role in drug resistance and are related to clinicopathological features in lung cancer. Summaries of the association of circRNAs with drug resistance are also scarce in the literature. The present study outlined the biological functions of circRNAs and focused on discriminating differential circRNA patterns and mechanisms in three different types of lung cancer. The emerging roles of circRNAs in the resistance to chemotherapy, targeted therapy, radiotherapy and immunotherapy were also highlighted. Understanding these aspects of circRNAs sheds light on novel physiological and pathophysiological processes of lung cancer and suggests the application of circRNAs as biomarkers for diagnosis and prognosis, as well as therapeutic resistance.

Exosomal circular RNA: a signature for lung cancer progression

Membrane vesicles having a diameter of 30-150 nm are known as exosomes. Several cancer types secrete exosomes, which may contain proteins, circular RNAs (circRNAs), microRNAs, or DNA. CircRNAs are endogenous RNAs that do not code for proteins and can create continuous and covalently closed loops. In cancer pathogenesis, especially metastasis, exosomal circRNAs (exo-circRNAs) have a crucial role mainly due to the frequently aberrant expression levels within tumors. However, neither the activities nor the regulatory mechanisms of exo-circRNAs in advancing lung cancer (LC) are obvious. A better understanding of the regulation and network connections of exo-circRNAs will lead to better treatment for LCs. The main objective of the current review is to highlight the functions and mechanisms of exo-circRNAs in LC and assess the relationships between exo-circRNA dysregulation and LC progression. In addition, underline the possible therapeutic targets based on exo-circRNA modulating.

Exosomal circ-1199 derived from EPCs exposed to oscillating shear stress acts as a sponge of let-7g-5p to promote endothelial-mesenchymal transition of EPCs by increasing HMGA2 expression

AIMS

Our previous study showed that oscillatory shear stress (OSS) induces endothelial progenitor cells (EPCs) to undergo endothelial to mesenchymal transition (EndoMT), which may contribute to the onset and progression of atherosclerosis (AS). However, the underlying mechanisms have not been elucidated. A recent study showed that exosomes (Exos) released from EPCs played a key role in various cardiovascular diseases. The purpose of this study was to identify the role and mechanism of Exos released by EPCs exposed to OSS in EPC EndoMT.

MAIN METHODS

EPCs derived from the human umbilical cord blood were cultured and characterized. The Flexcell flow STR-4000 parallel plate flow chamber system was employed to apply OSS (±3.5 dyne/cm², 1 Hz) to EPCs for 12 h. Then, Exos were extracted from the cellular supernatant (Static-Exos) or perfusate (OSS-Exos) by exoEasy Maxi Kit. Afterward, cellular intervention, angiogenesis assays, high-throughput sequencing and online database predictions were used to identify the role and mechanism of OSS-Exos in EPC EndoMT.

KEY FINDINGS

OSS-Exos inhibited angiogenesis, promoted the proliferation of EPCs both in vivo and in vitro, and induced EPC EndoMT. In addition, the expression of circ-1199 in OSS-Exos was higher than that in Static-Exos. Moreover, circ-1199 induced EPC EndoMT. The dual-luciferase reporter gene assay showed that let-7g-5p was the direct target of circ-1199. Furthermore, OSS-Exos upregulated the expression of circ-1199 and then downregulated let-7g-5p, upregulating HMGA2, which activated p-Smad3/Smad3 and Snail.

SIGNIFICANCE

OSS-Exos played an important role in the EndoMT of EPCs, which was mediated by the circ-1199/let-7g-5p/HMGA2 signaling pathway. These studies would have a high probability of revealing the mechanism of EPC EndoMT.

The emerging role of circular RNAs in drug resistance of non-small cell lung cancer

Due to the characteristics of aggressiveness and high risk of postoperative recurrence, non-small cell lung cancer (NSCLC) is a serious hazard to human health, accounting for 85% of all lung cancer cases. Drug therapies, including chemotherapy, targeted therapy and immunotherapy, are effective treatments for NSCLC in clinics. However, most patients ultimately develop drug resistance, which is also the leading cause of treatment failure in cancer. To date, the mechanisms of drug resistance have yet to be fully elucidated, thus original strategies are developed to overcome this issue. Emerging studies have illustrated that circular RNAs (circRNAs) participate in the generation of therapeutic resistance in NSCLC. CircRNAs mediate the modulations of immune cells, cytokines, autophagy, ferroptosis and metabolism in the tumor microenvironment (TME), which play essential roles in the generation of drug resistance of NSCLC. More importantly, circRNAs function as miRNAs sponges to affect specific signaling pathways, directly leading to the generation of drug resistance. Consequently, this review highlights the mechanisms underlying the relationship between circRNAs and drug resistance in NSCLC. Additionally, several therapeutic drugs associated with circRNAs are summarized, aiming to provide references for circRNAs serving as potential therapeutic targets in overcoming drug resistance in NSCLC.

Extracellular vesicles and particles impact the systemic landscape of cancer

Intercellular cross talk between cancer cells and stromal and immune cells is essential for tumor progression and metastasis. Extracellular vesicles and particles (EVPs) are a heterogeneous class of secreted messengers that carry bioactive molecules and that have been shown to be crucial for this cell-cell communication. Here, we highlight the multifaceted roles of EVPs in cancer. Functionally, transfer of EVP cargo between cells influences tumor cell growth and invasion, alters immune cell composition and function, and contributes to stromal cell activation. These EVP-mediated changes impact local tumor progression, foster cultivation of pre-metastatic niches at distant organ-specific sites, and mediate systemic effects of cancer. Furthermore, we discuss how exploiting the highly selective enrichment of molecules within EVPs has profound implications for advancing diagnostic and prognostic biomarker development and for improving therapy delivery in cancer patients. Altogether, these investigations into the role of EVPs in cancer have led to discoveries that hold great promise for improving cancer patient care and outcome.

Engaging innate immunity for targeting the epidermal growth factor receptor: Therapeutic options leveraging innate immunity versus adaptive immunity versus inhibition of signaling

The epidermal growth factor receptor (EGFR) is a key player in the normal tissue physiology and the pathology of cancer. Therapeutic approaches have now been developed to target oncogenic genetic aberrations of EGFR, found in a subset of tumors, and to take advantage of overexpression of EGFR in tumors. The development of small-molecule inhibitors and anti-EGFR antibodies targeting EGFR activation have resulted in effective but limited treatment options for patients with mutated or wild-type EGFR-expressing cancers, while therapeutic approaches that deploy effectors of the adaptive or innate immune system are still undergoing development. This review discusses EGFR-targeting therapies acting through distinct molecular mechanisms to destroy EGFR-expressing cancer cells. The focus is on the successes and limitations of therapies targeting the activation of EGFR versus those that exploit the cytotoxic T cells and innate immune cells to target EGFR-expressing cancer cells. Moreover, we discuss alternative approaches that may have the potential to overcome limitations of current therapies; in particular the innate cell engagers are discussed. Furthermore, this review highlights the potential to combine innate cell engagers with immunotherapies, to maximize their effectiveness, or with unspecific cell therapies, to convert them into tumor-specific agents.

Emerging Role of Noncoding RNAs in EGFR TKI-Resistant Lung Cancer

Lung cancer accounts for the majority of malignancy-related mortalities worldwide. The introduction of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) has revolutionized the treatment and significantly improved the overall survival (OS) of lung cancer. Nevertheless, almost all EGFR-mutant patients invariably acquire TKI resistance. Accumulating evidence has indicated that noncoding RNAs (ncRNAs), such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), have a central role in the tumorigenesis and progression of lung cancer by regulating crucial signaling pathways, providing a new approach for exploring the underlying mechanisms of EGFR-TKI resistance. Therefore, this review comprehensively describes the dysregulation of ncRNAs in EGFR TKI-resistant lung cancer and its underlying mechanisms. We also underscore the clinical application of ncRNAs as prognostic, predictive and therapeutic biomarkers for EGFR TKI-resistant lung cancer. Furthermore, the barriers that need to be overcome to translate the basic findings of ncRNAs into clinical practice are discussed.

CircKIF4A promotes non-small cell lung cancer proliferation and metastasis through MiR-1238/CLDN14 axis

As the leading cause of cancer-related death worldwide, non-small-cell lung cancer (NSCLC) is still in need of improved therapeutic strategies. CircKIF4A has been found to be involved in the progression of multiple cancers while its role in NSCLC remains unclear. To investigate the functions of circKIF4A, we assessed the expression of circKIF4A in NSCLC cells and tissues and performed experiments to determine the detailed functions of circKIF4A in NSCLC, including migration and proliferation. We found CircKIF4A expressed more heavily in the cells and tissues of NSCLC patients, and functional studies showed that inhibition of circKIF4A reduced NSCLC cells metastasis and proliferation. Furthermore, we seek to identify the underlying regulatory effect of circKIF4A in NSCLC. Studies revealed that circKIF4A sponged miR-1238 to promote NSCLC progression by up-regulating claudin14 (CLDN14) expression. In conclusion, circKIF4A is a potential diagnostic and therapeutic target in the circKIF4A/miR-1238/CLDN14 axis that plays an important role in NSCLC progression.

Role of circular RNAs in the diagnosis, regulation of drug resistance and prognosis of lung cancer (Review)

Lung cancer is one of the most common malignant tumors in China and is the highest cause of mortality among male and female patients, both in urban and rural areas. A subset of patients with lung cancer only display chest tightness without any other obvious symptoms. This is because most symptoms do not manifest during the early stages of disease development. Consequently, most patients with lung cancer are diagnosed when the disease is in the advanced stages, when they are already unfit for surgical treatment. Furthermore, the prognosis of patients with lung cancer is poor. The 5-year survival rate of patients with stage IA lung cancer is 85%, compared with 6% in those with stage IV. This requires the development of strategies for early diagnosis, treatment and prognosis to improve the management of lung cancer. Circular RNAs (circRNAs) belong to a class of closed circular non-coding RNAs formed by reverse splicing of a precursor mRNA. These RNAs are highly stable, ubiquitously expressed, conserved, and show high specificity. CircRNAs regulate biological processes, such as the proliferation, differentiation and invasion of lung cancer cells. Therefore, they can be used as biomarkers for the early diagnosis and prognosis prediction of lung cancer, as well as novel targets for therapy design. In the present review, the biological characteristics and functions of circRNAs, as well as their application in the diagnosis, control of drug resistance and effect on the prognosis of patients with lung cancer, will be discussed.

Exosomal hsa_circ_0017252 attenuates the development of gastric cancer via inhibiting macrophage M2 polarization

Gastric cancer (GC) is an aggressive malignant tumor of the digestive system, with high morbidity rates. We previously demonstrated that miR-17-5p can modify tumorigenesis in GC. In addition, other studies have shown that circRNAs can regulate GC progression by sponging various miRNAs. However, the association between circRNAs and miR-17-5p in GC has not yet been explored. Hence, this study aimed to explore the possible interactions between various circRNAs and miR-17-5p using a dual-luciferase assay. CCK-8 was used to determine cell viability, and a Transwell assay was used to measure cell invasion and migration. Gene expression was assessed using quantitative reverse transcription PCR (RT-qPCR), and exosomes were identified using transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Annexin V/PI staining was also used to detect cell apoptosis. These investigations collectively revealed that miR-17-5p is a target of the circRNA hsa_circ_0017252 and hsa_circ_0017252 is significantly downregulated in GC tissues. In addition, the overexpression of hsa_circ_0017252 inhibited GC cell migration by sponging of miR-17-5p, and GC cell-secreted exosomal hsa_circ_0017252 effectively inhibited macrophage M2-like polarization, which in turn suppressed GC cell invasion. Notably, exosomes containing hsa_circ_0017252 also suppressed GC tumor growth in vivo. Thus, our data suggest that the overexpression of hsa_circ_0017252 suppresses GC malignancy by sponging miR-17-5p. In addition, exosomal hsa_circ_0017252 excreted from GC cells attenuated GC progression by suppressing macrophage M2-like polarization. These findings improve our basic understanding of GC and open a novel avenue for developing more effective GC treatments.

Circular RNAs and Their Role in Exosomes

As a novel class of endogenous non-coding RNAs discovered in recent years, circular RNAs (circRNAs) are highly conserved and stable covalently closed ring structures with no 5'-end cap or 3'-end poly(A) tail. CircRNAs are formed by reverse splicing, mainly by means of a noose structure or intron complementary pairing. Exosomes are tiny discoid vesicles with a diameter of 40-100 nm that are secreted by cells under physiological and pathological conditions. Exosomes play an important role in cell-cell communication by carrying DNA, microRNAs, mRNAs, proteins and circRNAs. In this review, we summarize the biological functions of circRNAs and exosomes, and further reveal the potential roles of exosomal circRNAs in different diseases, providing a scientific basis for the diagnosis, treatment, and prognosis of a wide variety of diseases.

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 Ror-Family Receptors in Development, Tissue Regeneration and Age-Related Disease

The Ror-family proteins, Ror1 and Ror2, act as receptors or co-receptors for Wnt5a and its related Wnt proteins to activate non-canonical Wnt signaling. Ror1 and/or Ror2-mediated signaling plays essential roles in regulating cell polarity, migration, proliferation and differentiation during developmental morphogenesis, tissue-/organo-genesis and regeneration of adult tissues following injury. Ror1 and Ror2 are expressed abundantly in developing tissues in an overlapping, yet distinct manner, and their expression in adult tissues is restricted to specific cell types such as tissue stem/progenitor cells. Expression levels of Ror1 and/or Ror2 in the adult tissues are increased following injury, thereby promoting regeneration or repair of these injured tissues. On the other hand, disruption of Wnt5a-Ror2 signaling is implicated in senescence of tissue stem/progenitor cells that is related to the impaired regeneration capacity of aged tissues. In fact, Ror1 and Ror2 are implicated in age-related diseases, including tissue fibrosis, atherosclerosis (or arteriosclerosis), neurodegenerative diseases, and cancers. In these diseases, enhanced and/or sustained (chronic) expression of Ror1 and/or Ror2 is observed, and they might contribute to the progression of these diseases through Wnt5a-dependent and -independent manners. In this article, we overview recent advances in our understanding of the roles of Ror1 and Ror2-mediated signaling in the development, tissue regeneration and age-related diseases, and discuss their potential to be therapeutic targets for chronic inflammatory diseases and cancers.

Roles and clinical application of exosomal circRNAs in the diagnosis and treatment of malignant tumors

Exosomes are microvesicles secreted by cells. They contain a variety of bioactive substances with important roles in intercellular communication. Circular RNA (circRNA), a type of nucleic acid molecule found in exosomes, forms a covalently bonded closed loop without 5′ caps or 3′ poly(A) tails. It is structurally stable, widely distributed, and tissue specific. CircRNAs mainly act as microRNA sponges and have important regulatory roles in gene expression; they are superior to other non-coding RNAs as molecular diagnostic markers and drug treatment targets. Exosomal-derived circRNAs in the body fluids of tumor patients can modulate tumor proliferation, invasion, metastasis, and drug resistance. They can be used as effective biomarkers for early non-invasive diagnosis and prognostic evaluation of tumors, and also represent ideal targets for early precision therapeutic intervention. This review provides a theoretical basis for exploring the applications of exosomal circRNAs in malignant tumor diagnosis and treatment. We describe the biological functions of exosomal circRNAs in the occurrence and development of malignant tumors, their potential utility in diagnosis and treatment, and possible mechanisms.

Regulation of apoptosis, autophagy and ferroptosis by non‑coding RNAs in metastatic non‑small cell lung cancer (Review)

Non-small cell lung cancer (NSCLC), a common type of cancer worldwide, is normally associated with a poor prognosis. It is difficult to treat successfully as it often metastasizes into brain or bone. Methods to facilitate the induction of effective programmed cell death (PCD) in NSCLC cells to reverse drug resistance, or to inhibit the invasion and migration of NSCLC cells, are currently under investigation. The present study summarized the regulatory functions of PCD, including apoptosis, autophagy and ferroptosis, in the context of NSCLC metastasis. It further summarized how regulatory agents, including long non-coding RNAs, circular RNAs and microRNAs, regulate PCD during the metastasis of NSCLC and characterized new potential diagnostic biomarkers of NSCLC metastasis.

Emerging function and clinical significance of extracellular vesicle noncoding RNAs in lung cancer

Lung cancer (LC) is a commonly diagnosed cancer with an unsatisfactory prognosis. Extracellular vesicles (EVs) are lipid bilayer-delimited particles that mediate cell-cell communication by transporting various biomacromolecules, such as nucleic acids, proteins, and lipids. Noncoding RNAs (ncRNAs), including microRNAs, circular RNAs, and long noncoding RNAs, are important noncoding transcripts that play critical roles in a variety of physiological and pathological processes, especially in cancer. ncRNAs have been verified to be packaged into EVs and transported between LC cells and stromal cells, regulating multiple LC malignant phenotypes, such as proliferation, migration, invasion, epithelial-mesenchymal transition, metastasis, and treatment resistance. Additionally, EVs can be detected in various body fluids and are associated with the stage, grade, and metastasis of LC. Herein, we summarize the biological characteristics and functions of EV ncRNAs in the biological processes of LC, focusing on their potential to serve as diagnostic and prognostic biomarkers of LC as well as their probable role in the clinical treatment of LC. EV ncRNAs provide a new perspective for understanding the mechanism underlying LC pathogenesis and development, which might benefit numerous LC patients in the future.

CircRNA SOD2 motivates non-small cell lungs cancer advancement with EMT via acting as microRNA-2355-5p’s competing endogenous RNA to mediate calmodulin regulated spectrin associated proteins-2

Circular RNAs (circRNAs) are closely linked with human cancer development such as non-small-cell lung cancer (NSCLC). However, the characteristics and specific functions of most circRNAs in NSCLC remained unknown. Previous studies have suggested that circRNA SOD2 (CircSOD2) expression was upregulated in a number of cancers. This study aimed to explore the functions of circSOD2 in NSCLC advancement with epithelial-mesenchymal transition (EMT). Expression profile analysis of circSOD2, miR-2355-5p, and calmodulin-regulated spectrin-associated protein 2 (CAMSAP2) was detected by real-time quantitative PCR (RT-qPCR). Transwell assay, cell migration assay, CCK8, ELISA, RIP assay, RNA pull-down assay, and Western blot analysis were performed to evaluate the functions of circSOD2, miR-2355-5p, and CAMSAP2. We found elevated expression of circSOD2 and CAMSAP2 while reduced expression of miR-2355-5p in NSCLC tumor tissues. Silencing or overexpression of CircSOD2 resulted in increased or decreased expression of miR-2355-5p, respectively. Mechanically, we showed that silencing of CircSOD2 and overexpression of miR-2355-5p resulted in the reduced rate of NSCLC cell proliferation. Inhibition of miR-2355-5p reversed the changes induced via silencing of CircSOD2. MiR-2355-5p binds to the CircSOD2 promoter and triggered its stimulation, which further activated circSOD2 expression. CircSOD2 suppression impaired lung cancer cell growth, cell migration, prohibited cell cycle progression, and in vivo tumor growth by targeting miR-2355-5p expression in NSCLC tissues. Meanwhile, increased expression of CAMSAP2 reversed the changes stimulated by the elevated level of miR-2355-5p in NSCLC progression. This innovative signaling axis CircSOD2/miR-2355-5p/CAMSAP2 illustrated the new horizon to investigate NSCLC tumorigenesis and provided new prognosis and treatment of NSCLC.

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

Simple Summary

Drug resistance to systematic treatment in genitourinary tumors severely aggravated the burden on patients and society. Multiple mechanisms were involved in drug resistance. As typical non-coding RNAs, circRNAs play a critical role in the onset and development of cancers and several studies implied their function in the regulation of drug resistance. Here, we reviewed the investigations of circRNAs’ behavior in drug resistance of genitourinary cancers and summarized the underlying mechanisms. This review emphasized the essential role of circRNAs in drug resistance development and also pointed out the potential topics that need further investigations in the future.

Abstract

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.

The Role of Circular RNAs in the Drug Resistance of Cancers

Cancer is a major threat to human health and longevity. Chemotherapy is an effective approach to inhibit cancer cell proliferation, but a growing number of cancer patients are prone to develop resistance to various chemotherapeutics, including platinum, paclitaxel, adriamycin, and 5-fluorouracil, among others. Significant progress has been made in the research and development of chemotherapeutic drugs over the last few decades, including targeted therapy drugs and immune checkpoint inhibitors; however, drug resistance still severely limits the application and efficacy of these drugs in cancer treatment. Recently, emerging studies have emphasized the role of circular RNAs (circRNAs) in the proliferation, migration, invasion, and especially chemoresistance of cancer cells by regulating the expression of related miRNAs and targeted genes. In this review, we comprehensively summarized the potential roles and mechanisms of circRNAs in cancer drug resistance including the efflux of drugs, apoptosis, intervention with the TME (tumor microenvironment), autophagy, and dysfunction of DNA damage repair, among others. Furthermore, we highlighted the potential value of circRNAs as new therapeutic targets and prognostic biomarkers for cancer.

Exosomes in cancer immunoediting and immunotherapy

As an important means of communication among cells, exosomes are being studied more and more widely, especially in the context of cancer immunotherapy. In the phase of tumor immunoediting, exosomes derived from tumor cells and different immune cells have complex and changeable physiological functions, because they carry different proteins and nucleic acid from the source cells. Based on the role of exosomes in the communication between different cells, cancer treatment methods are also under continuous research. This review briefly introduces the molecular composition of exosomes, which is closely related to their secretion mechanism. Subsequently, the role of exosomes encapsulating different information molecules is summarized. The role of exosomes in the three phases of tumor immunoediting is introduced in detail, and the relevant literature of exosomes in the tumor immune microenvironment is summarized by using a novel framework for extracting relevant documents. Finally, it summarizes the various exosome-based immunotherapies currently proposed, as well as the challenges and future prospects of exosomes in tumor immunotherapy.

Emerging noncoding RNAs contained in extracellular vesicles: rising stars as biomarkers in lung cancer liquid biopsy

Lung cancer has a high morbidity and mortality rate, and affected patients have a poor prognosis and low survival. The therapeutic approaches for lung cancer treatment, including surgery, radiotherapy, and chemotherapy, are not completely effective, due to late diagnosis. Although the identification of genetic drivers has contributed to the improvement of lung cancer clinical management, the discovery of new diagnostic and prognostic tools remains a critical issue. Liquid biopsy (LB) represents a minimally invasive approach and practical alternative source to investigate tumor-derived alterations and to facilitate the selection of targeted therapies. LB allows for the testing of different analytes such as circulating tumor cells, extracellular vesicles (EVs), tumor-educated platelets, and cell-free nucleic acids including DNAs, RNAs, and noncoding RNAs (ncRNAs). Several regulatory factors control the key cellular oncogenic pathways involved in cancers. ncRNAs have a wide range of regulatory effects in lung cancers. This review focuses on emerging regulatory ncRNAs, freely circulating in body fluids or shuttled by EVs, such as circular-RNAs, small nucleolar-RNAs, small nuclear-RNAs, and piwi-RNAs, as new biomarkers for early detection, prognosis, and monitoring of therapeutic strategy of lung cancer treatment.

Potential Clinical Applications of Exosomal Circular RNAs: More than Diagnosis

Exosomes are small vesicles derived from cells used as cell-to-cell communication goods in numerous diseases including tumorigenesis, neurological diseases, cardiovascular diseases and other diseases. Circular RNAs (circRNAs) are an innovative constituent of non-coding endogenous RNAs generated through backsplicing, catalyzed by RNA polymerase Ⅱ. These non-coding RNAs have been suggested to control gene expression through miRNA sponging, RNA-binding protein regulation and translational capabilities. Genome-wide RNA sequence analyses observed that circRNAs were stably improved in exosomes in association to parental cells. Little attention has been dedicated to exosomal circRNAs (exo-circRNAs). However, research has demonstrated that exo-circRNAs may have important regulatory functions because of their stability in cells and within exosomes. If well understood, the precise roles and mechanisms of exo-circRNAs might surge the impending clinical applications of these molecules as markers in the identification, prediction and treatment of various diseases. In this review, we outline recent findings regarding exo-circRNAs which includes their functions and highlights their potential applications and therapeutic targets in human diseases.

Exosomal circRNAs: Emerging Players in Tumor Metastasis

Metastasis is an important feature of malignant tumors, and is the primary cause of poor prognosis and treatment failure, in addition to representing a potentially fatal challenge for cancer patients. Exosomes are small extracellular vesicles 30–150 nm in diameter that transmit cargo, such as DNA, RNA, and proteins, as a means of intercellular communication. Exosomes play crucial roles in a range of human diseases, especially malignant tumors. A growing number of studies have verified that circRNAs can be enveloped in exosomes and transferred from secretory cells to recipient cells, thereby regulating tumor progression, especially tumor metastasis. Exosomal circRNAs regulate tumor cell metastasis not only by regulating the signaling pathways, but also by affecting the tumor microenvironment. Moreover, exosomal circRNAs have the potential to serve as valuable diagnostic biomarkers and novel therapeutic targets in cancer patients. In this review, we summarize the mechanism by which exosomal circRNAs modulate metastatic phenomena in various types of tumors, and put forward the prospects of clinical applications of exosomal circRNAs in tumor therapy.

Roles and mechanisms of exosomal non-coding RNAs in human health and diseases

Exosomes play a role as mediators of cell-to-cell communication, thus exhibiting pleiotropic activities to homeostasis regulation. Exosomal non-coding RNAs (ncRNAs), mainly microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are closely related to a variety of biological and functional aspects of human health. When the exosomal ncRNAs undergo tissue-specific changes due to diverse internal or external disorders, they can cause tissue dysfunction, aging, and diseases. In this review, we comprehensively discuss the underlying regulatory mechanisms of exosomes in human diseases. In addition, we explore the current knowledge on the roles of exosomal miRNAs, lncRNAs, and circRNAs in human health and diseases, including cancers, metabolic diseases, neurodegenerative diseases, cardiovascular diseases, autoimmune diseases, and infectious diseases, to determine their potential implication in biomarker identification and therapeutic exploration.

Formation, contents, functions of exosomes and their potential in lung cancer diagnostics and therapeutics

Lung cancer is the leading cause of cancer-related death worldwide due to diagnosis in the advanced stage and drug resistance in the subsequent treatments. Development of novel diagnostic and therapeutic methods is urged to improve the disease outcome. Exosomes are nano-sized vehicles which transport different types of biomolecules intercellularly, including DNA, RNA and proteins, and are implicated in cross-talk between cells and their surrounding microenvironment. Tumor-derived exosomes (TEXs) have been revealed to strongly influence the tumor microenvironment, antitumor immunoregulatory activities, tumor progression and metastasis. Potential of TEXs as biomarkers for lung cancer diagnosis, prognosis and treatment prediction is supported by numerous studies. Moreover, exosomes have been proposed to be promising drug carriers. Here, we review the mechanisms of exosomal formation and uptake, the functions of exosomes in carcinogenesis, and potential clinical utility of exosomes as biomarkers, tumor vaccine and drug delivery vehicles in the diagnosis and therapeutics of lung cancer.

Exosome-Mediated Crosstalk Between Tumor and Tumor-Associated Macrophages

Exosomes are nanosized vesicles, derived from the endolysosomal compartment of cells and can shuttle diverse biomolecules such as nucleic acids, proteins, lipids, amino acids, and metabolites, which can reflect their origin cells. Delivery of these cargoes to recipient cells enables exosomes to influence diverse cellular functions. As one of the most abundant immune cells in the tumor microenvironment, tumor-associated macrophages (TAMs) are educated by the tumor milieu, which is rich in cancer cells and stroma components, to exert functions such as the promotion of tumor growth, immunosuppression, angiogenesis, and cancer cell dissemination. Herein, we focus on exosomes-mediated intercellular communication between tumor cells and TAM in the tumor microenvironment, which may provide new targets for anti-tumor treatment. In this review, we highlight the most recent studies on the effect of tumor/macrophage-derived exosomes on macrophage/tumor function in different cancer types.

Exosome to Promote Cancer Progression via Its Bioactive Cargoes

Exosomes are nanosized, organelle-like membranous vesicles secreted from various cell types, including normal cells and cancer cells. Exosomes contain abundant bioactive molecules, including nucleic acids, lipids, and proteins and dynamically participate in intercellular communications. By shuttling the functional molecules into the recipient cells, exosomes secreted by cancerous cells can alter the cellular environment to favor tumor growth and metastasis. In this review, we focus on exosomes to promote cancer progression via their various bioactive cargoes through different mechanisms/pathways. By recognizing these pathways, we can design efficient therapeutic strategies to control cancer progression.