Significant CircRNAs in liver cancer stem cell exosomes: mediator of malignant propagation in liver cancer?

CircPRMT5, a Potential Salivary Biomarker, Facilitates the Progression of Head and Neck Squamous Cell Carcinoma via the IGF2BP3-SERPINE1 Pathway

Purpose

Circular RNAs (circRNAs) are associated with the progression of tumors and hold promise as potential biomarkers for liquid biopsy. Among these, the role of circPRMT5 in head and neck squamous cell carcinoma (HNSCC) remains to be elucidated. This study aims to examine the role and underlying mechanisms of circPRMT5 in the progression of HNSCC and to assess its potential diagnostic value in saliva exosomes.

Methods

The expression of circPRMT5 and its clinical significance in HNSCC were investigated. Both in vitro and in vivo studies were performed to elucidate the biological role of circPRMT5 in HNSCC. RNA sequencing was utilized to identify downstream mechanisms. To evaluate and validate these mechanisms, Western blotting, RNA-FISH, immunofluorescence, immunohistochemistry, RIP, and rescue experiments were employed. Finally, salivary exosomes were isolated, and the expression levels of circPRMT5 were assessed using qRT-PCR.

Results

The upregulation of circPRMT5 in HNSCC tissues was identified to be correlated with cervical lymph node metastasis and advanced clinical T stage. Both in vitro and in vivo experiments manifested that circPRMT5 promoted the proliferation and metastasis of HNSCC. Mechanistically, circPRMT5 was demonstrated to directly bind to and stabilize the insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3), which, subsequently, binds to and stabilizes the serpin family E member 1 (SERPINE1) mRNA, thereby enhancing SERPINE1 expression. Furthermore, rescue experiments indicated that the proliferative, invasive, and migratory effects of circPRMT5 in HNSCC were dependent on the involvement of IGF2BP3 and SERPINE1. Notably, circPRMT5 levels were significantly elevated in the saliva exosomes of HNSCC patients, exhibiting substantial diagnostic value.

Conclusion

CircPRMT5 exhibits significant diagnostic utility through salivary exosomes and plays a crucial role in promoting the progression of HNSCC via the IGF2BP3-SERPINE1 pathway. These findings highlight the potential of circPRMT5 as a noninvasive diagnostic biomarker and a therapeutic target for patients with HNSCC.

circICMT upregulates and suppresses the malignant behavior of bladder cancer

BACKGROUND

Circular RNA (circRNA) is a new type of endogenous single-stranded RNA with a covalently closed circular structure. Increasing evidence shows that circRNA plays an important role in regulating gene expression in tumors. circICMT is a circular RNA produced by the ICMT gene. Currently, the molecular function of circICMT in bladder cancer remains unclear.

METHOD

Differentially expressed circRNAs were identified from RNA sequencing data and circICMT was identified as a new candidate circRNA. qRT-PCR and sanger sequencing were used to detect the expression of circICMT in bladder cancer tissue specimens. Stable cell lines overexpressing and knocking down circICMT were constructed to explore the effect of circICMT on bladder cancer cells. Its biological effects were detected through wound healing experiments, colony formation experiments, CCK-8 experiments and xenogeneic tumorigenesis experiments.

RESULT

This study found that circICMT was significantly upregulated in bladder cancer tissue specimens. Overexpression of circICMT can inhibit cell migration, proliferation and colony formation ability, while knockdown of circICMT promotes the malignant phenotype of bladder cancer cells. Bioinformatics predictions have found that circICMT can bind to a variety of miRNAs and RBPs and may form a complex regulatory network to regulate the progression of bladder cancer.

CONCLUSION

circICMT is significantly highly expressed in bladder cancer, and intervening circICMT expression affects the malignant phenotype of bladder cancer cells in vivo and in vitro, which may provide potential biomarkers and therapeutic targets for the management of bladder cancer.

Exosomal circRNAs: Deciphering the novel drug resistance roles in cancer therapy

Exosomal circular RNA (circRNAs) are pivotal in cancer biology, and tumor pathophysiology. These stable, non-coding RNAs encapsulated in exosomes participated in cancer progression, tumor growth, metastasis, drug sensitivity and the tumor microenvironment (TME). Their presence in bodily fluids positions them as potential non-invasive biomarkers, revealing the molecular dynamics of cancers. Research in exosomal circRNAs is reshaping our understanding of neoplastic intercellular communication. Exploiting the natural properties of exosomes for targeted drug delivery and disrupting circRNA-mediated pro-tumorigenic signaling can develop new treatment modalities. Therefore, ongoing exploration of exosomal circRNAs in cancer research is poised to revolutionize clinical management of cancer. This emerging field offers hope for significant breakthroughs in cancer care. This review underscores the critical role of exosomal circRNAs in cancer biology and drug resistance, highlighting their potential as non-invasive biomarkers and therapeutic targets that could transform the clinical management of cancer.

Exosomes in the Chemoresistance of Glioma: Key Point in Chemoresistance

Gliomas are the most ordinary primary virulent brain tumours and commonly used clinical treatments include tumour resection, radiation therapy and chemotherapy. Although significant progress has been made in recent years in progression-free survival (PFS) and overall survival (OS) for patients with high-grade gliomas, the prognosis for patients remains poor. Chemoresistance refers to the phenomenon of decreased sensitivity of tumour cells to drugs, resulting in reduced or ineffective drug efficacy, and is an important cause of failure of tumour chemotherapy. Exosomes, a type of extracellular vesicle, are secreted by cancer cells and various stromal cells in the tumour microenvironment (TME) and transfer their inclusions to cancer cells, increasing chemoresistance. Furthermore, depletion of exosomes reverses certain detrimental effects on tumour metabolism and restores sensitivity to chemotherapeutic agents. Here, we summarised the correlation between exosomes and resistance to chemotherapeutic agents in glioma patients, the mechanisms of action of exosomes involved in resistance and their clinical value. We aimed to afford new thoughts for research, clinical diagnosis and intervention in the mechanisms of chemoresistance in glioma patients.

Detection of Cancer Stem Cells from Patient Samples

The existence of cancer stem cells (CSCs) in various tumors has become increasingly clear in addition to their prominent role in therapy resistance, metastasis, and recurrence. For early diagnosis, disease progression monitoring, and targeting, there is a high demand for clinical-grade methods for quantitative measurement of CSCs from patient samples. Despite years of active research, standard measurement of CSCs has not yet reached clinical settings, especially in the case of solid tumors. This is because detecting this plastic heterogeneous population of cells is not straightforward. This review summarizes various techniques, highlighting their benefits and limitations in detecting CSCs from patient samples. In addition, methods designed to detect CSCs based on secreted and niche-associated signaling factors are reviewed. Spatial and single-cell methods for analyzing patient tumor tissues and noninvasive techniques such as liquid biopsy and in vivo imaging are discussed. Additionally, methods recently established in laboratories, preclinical studies, and clinical assays are covered. Finally, we discuss the characteristics of an ideal method as we look toward the future.

PCBP2-dependent secretion of miRNAs via extracellular vesicles contributes to the EGFR-driven angiogenesis

Rationale: The EGFR-driven angiogenesis is crucial in solid tumors, particularly through the delivery of biomolecules via extracellular vesicles (EVs), but the mechanism by which EGFR regulates EV cargo is still unclear. Methods: First, cell co-culture and murine tumor models were employed to examine the impact of EGFR overexpression on the pro-angiogenic properties of small EVs (sEVs) derived from oral squamous cell carcinoma (OSCC). Small RNA sequencing was then used to compare the miRNA profiles of OSCC-sEVs with and without EGFR overexpression, followed by functional enrichment and motif analyses of the differentially expressed miRNAs. Next, miRNA pull-down assays were conducted to identify potential molecules involved in sorting these miRNAs. Finally, the role of the candidate sorting protein was validated using existing public database, tissue samples, cell lines, and murine tumor models. Results: EGFR overexpression significantly enhances the pro-angiogenic effects of OSCC-sEVs, accompanied by a marked increase in the content of nucleic acid cargo carried in these sEVs. Small-RNA sequencing identified a group of miRNAs that were significantly enriched in OSCC-sEVs due to EGFR overexpression, which primarily functioned in angiogenesis and shared a characteristic "GGGU" motif. EGFR overexpression also strengthened the binding of PCBP2 with miRNAs containing this "GGGU" motif, thereby promoting their secretion through sEVs to support tumor angiogenesis. Mechanismly, EGFR overexpression upregulates PCBP2 protein content by activating its transcription rather than regulating the mRNA stability in OSCC cells. Additionally, depletion of PCBP2 impaired the EGFR-driven tumor angiogenesis by inhibiting the secretion of pro-angiogenic miRNAs through sEVs. Conclusions: EGFR boosts PCBP2 expression via transcriptional regulation, which then promotes the loading of specific miRNAs into sEVs by binding to the "GGGU" motif, thereby driving tumor angiogenesis.

Mesenchymal stem/stromal cells: dedicator to maintain tumor homeostasis

Mesenchymal stem/stromal cells （MSCs） act as a factor in tumor recurrence after drug treatment with their involvement observed in various cancer types. As a constituent of the tumor microenvironment (TME), MSCs not only provide support to tumor growth but also establish connections with diverse cell populations within the TME, serving as mediators linking different tumor-associated components. MSCs play an important role in maintaining tumor progression due to their stem cell properties and remarkable differentiation capacity. Given the intensification of tumor research and the encouraging results achieved in recent years，the aim of this article is to investigate the supportive role of MSCs in tumor cells as well as in various cellular and non-cellular components of the tumor microenvironment. Furthermore, the article shows that MSCs do not have a specific anatomical ecological niche and describes the contribution of MSCs to the maintenance of tumor homeostasis on the basis of homing, plasticity and tumor-forming properties. By elucidating the critical roles of different components of TME, this study provides a comprehensive understanding of tumor therapy and may offer new insights into defeating cancer.

Exosome crosstalk between cancer stem cells and tumor microenvironment: cancer progression and therapeutic strategies

Cancer stem cells (CSCs) represent a small yet pivotal subset of tumor cells endowed with self-renewal capabilities. These cells are intricately linked to tumor progression and are central to drug resistance, metastasis, and recurrence. The tumor microenvironment (TME) encompasses the cancer cells and their surrounding milieu, including immune and inflammatory cells, cancer-associated fibroblasts, adjacent stromal tissues, tumor vasculature, and a variety of cytokines and chemokines. Within the TME, cells such as immune and inflammatory cells, endothelial cells, adipocytes, and fibroblasts release growth factors, cytokines, chemokines, and exosomes, which can either sustain or disrupt CSCs, thereby influencing tumor progression. Conversely, CSCs can also secrete cytokines, chemokines, and exosomes, affecting various components of the TME. Exosomes, a subset of extracellular vesicles (EVs), carry a complex cargo of nucleic acids, proteins, and lipids, playing a crucial role in the communication between CSCs and the TME. This review primarily focuses on the impact of exosomes secreted by CSCs (CSC-exo) on tumor progression, including their roles in maintaining stemness, promoting angiogenesis, facilitating metastasis, inducing immune suppression, and contributing to drug resistance. Additionally, we discuss how exosomes secreted by different cells within the TME affect CSCs. Finally, we explore the potential of utilizing exosomes to mitigate the detrimental effects of CSCs or to target and eliminate them. A thorough understanding of the exosome-mediated crosstalk between CSCs and the TME could provide valuable insights for developing targeted therapies against CSCs.

FUS/circZEB1/miR-128-3p/LBH feedback loop contributes to the malignant phenotype of GSCs via TNF-α-mediated NF-κB signaling pathway

Glioblastoma (GBM) is the most lethal and common primary tumor of central nervous system with a poor prognosis. Glioma stem cells (GSCs) are particularly significant in GBM proliferation, invasion, self-renewal and recurrence. Circular RNAs (circRNAs) play important roles in various physiological and pathological processes, including regulating the biological behavior of GBM. Therefore, discovering novel circRNAs related to GSCs may contribute to a promising approach for treatment of GBM. Herein, we find out a novel circRNA termed circZEB1 with a high expression in glioma. Limb-bud and heart (LBH) is a transcription cofactor and promotes glioma stem cell tumorigenicity in our study. Mechanistically, circZEB1 can upregulate the expression of transcription cofactor LBH via sponging miR-128-3p in GSCs. LBH can facilitate the expression of tumor necrosis factor-α (TNF-α), thus activating the NF-κB signaling pathway to promote the glioma progression. Meanwhile, LBH can also upregulate the RNA binding protein Fused in Sarcoma (FUS) expression, which can bind to and maintain the stability of circZEB1. A positive feedback loop is formed among FUS, circZEB1, miR-128-3p and LBH in GSCs. Our study uncovers a critical role of circZEB1 and provides a novel biomarker for treating GBM.

The role of exosomes in liver cancer: comprehensive insights from biological function to therapeutic applications

In recent years, cancer, especially primary liver cancer (including hepatocellular carcinoma and intrahepatic cholangiocarcinoma), has posed a serious threat to human health. In the field of liver cancer, exosomes play an important role in liver cancer initiation, metastasis and interaction with the tumor microenvironment. Exosomes are a class of nanoscale extracellular vesicles (EVs)secreted by most cells and rich in bioactive molecules, including RNA, proteins and lipids, that mediate intercellular communication during physiological and pathological processes. This review reviews the multiple roles of exosomes in liver cancer, including the initiation, progression, and metastasis of liver cancer, as well as their effects on angiogenesis, epithelial-mesenchymal transformation (EMT), immune evasion, and drug resistance. Exosomes have great potential as biomarkers for liver cancer diagnosis and prognosis because they carry specific molecular markers that facilitate early detection and evaluation of treatment outcomes. In addition, exosomes, as a new type of drug delivery vector, have unique advantages in the targeted therapy of liver cancer and provide a new strategy for the treatment of liver cancer. The challenges and prospects of exosome-based immunotherapy in the treatment of liver cancer were also discussed. However, challenges such as the standardization of isolation techniques and the scalability of therapeutic applications remain significant hurdles.

A quartet of cancer stem cell niches in hepatocellular carcinoma

Hepatocellular Carcinoma (HCC), the most prevalent type of primary liver cancer, is known for its aggressive behavior and poor prognosis. The Cancer Stem Cell theory, which postulates the presence of a small population of self-renewing cells called Cancer Stem Cells (CSCs), provides insights into various clinical and molecular features of HCC such as tumor heterogeneity, metabolic adaptability, therapy resistance, and recurrence. These CSCs are nurtured in the tumor microenvironment (TME), where a mix of internal and external factors creates a tumor-supportive niche that is continuously evolving both spatially and temporally, thus enhancing the tumor's complexity. This review details the origins of hepatic CSCs (HCSCs) and the factors influencing their stem-like qualities. It highlights the reciprocal crosstalk between HCSCs and the TME (hypoxic, vascular, invasive, and immune niches), exploring the signaling pathways involved and how these interactions control the malignant traits of CSCs. Additionally, it discusses potential therapeutic approaches targeting the HCSC niche and their possible uses in clinical practice.

Cancer therapy resistance mediated by cancer-associated fibroblast-derived extracellular vesicles: biological mechanisms to clinical significance and implications

Cancer-associated fibroblasts (CAFs) are a diverse stromal cell population within the tumour microenvironment, where they play fundamental roles in cancer progression and patient prognosis. Multiple lines of evidence have identified that CAFs are critically involved in shaping the structure and function of the tumour microenvironment with numerous functions in regulating tumour behaviours, such as metastasis, invasion, and epithelial-mesenchymal transition (EMT). CAFs can interact extensively with cancer cells by producing extracellular vesicles (EVs), multiple secreted factors, and metabolites. Notably, CAF-derived EVs have been identified as critical mediators of cancer therapy resistance, and constitute novel therapy targets and biomarkers in cancer management. This review aimed to summarize the biological roles and detailed molecular mechanisms of CAF-derived EVs in mediating cancer resistance to chemotherapy, targeted therapy agents, radiotherapy, and immunotherapy. We also discussed the therapeutic potential of CAF-derived EVs as novel targets and clinical biomarkers in cancer clinical management, thereby providing a novel therapeutic strategy for enhancing cancer therapy efficacy and improving patient prognosis.

Unveiling the Dynamic Interplay between Cancer Stem Cells and the Tumor Microenvironment in Melanoma: Implications for Novel Therapeutic Strategies

Cutaneous melanoma still represents a significant health burden worldwide, being responsible for the majority of skin cancer deaths. Key advances in therapeutic strategies have significantly improved patient outcomes; however, most patients experience drug resistance and tumor relapse. Cancer stem cells (CSCs) are a small subpopulation of cells in different tumors, including melanoma, endowed with distinctive capacities of self-renewal and differentiation into bulk tumor cells. Melanoma CSCs are characterized by the expression of specific biomarkers and intracellular pathways; moreover, they play a pivotal role in tumor onset, progression and drug resistance. In recent years, great efforts have been made to dissect the molecular mechanisms underlying the protumor activities of melanoma CSCs to provide the basis for novel CSC-targeted therapies. Herein, we highlight the intricate crosstalk between melanoma CSCs and bystander cells in the tumor microenvironment (TME), including immune cells, endothelial cells and cancer-associated fibroblasts (CAFs), and its role in melanoma progression. Specifically, we discuss the peculiar capacities of melanoma CSCs to escape the host immune surveillance, to recruit immunosuppressive cells and to educate immune cells toward an immunosuppressive and protumor phenotype. We also address currently investigated CSC-targeted strategies that could pave the way for new promising therapeutic approaches for melanoma care.

ncStem: a comprehensive resource of curated and predicted ncRNAs in cancer stemness

Cancer stemness plays an important role in cancer initiation and progression, and is the major cause of tumor invasion, metastasis, recurrence, and poor prognosis. Non-coding RNAs (ncRNAs) are a class of RNA transcripts that generally cannot encode proteins and have been demonstrated to play a critical role in regulating cancer stemness. Here, we developed the ncStem database to record manually curated and predicted ncRNAs associated with cancer stemness. In total, ncStem contains 645 experimentally verified entries, including 159 long non-coding RNAs (lncRNAs), 254 microRNAs (miRNAs), 39 circular RNAs (circRNAs), and 5 other ncRNAs. The detailed information of each entry includes the ncRNA name, ncRNA identifier, disease, reference, expression direction, tissue, species, and so on. In addition, ncStem also provides computationally predicted cancer stemness-associated ncRNAs for 33 TCGA cancers, which were prioritized using the random walk with restart (RWR) algorithm based on regulatory and co-expression networks. The total predicted cancer stemness-associated ncRNAs included 11 132 lncRNAs and 972 miRNAs. Moreover, ncStem provides tools for functional enrichment analysis, survival analysis, and cell location interrogation for cancer stemness-associated ncRNAs. In summary, ncStem provides a platform to retrieve cancer stemness-associated ncRNAs, which may facilitate research on cancer stemness and offer potential targets for cancer treatment. Database URL: http://www.nidmarker-db.cn/ncStem/index.html.

A GalNAc-modified CaCO3 nano-immunomodulator for targeted and responsive immunotherapy against orthotopic liver cancer

A nano-immunomodulator modified with N-acetylgalactosamine (GalNAc) on calcium carbonate (CaCO3) was prepared for targeted and responsive immunotherapy. And the immunologic adjuvant (CpG ODNs) and doxorubicin (DOX) were released to synergistically improve immune response for treating orthotopic liver cancer.

Roles and mechanisms of circular RNA in respiratory system cancers

Circular RNAs (circRNAs) constitute a class of endogenous non-coding RNAs (ncRNAs) that lack a 5'-ended cap and 3'-ended poly (A) tail and form a closed ring structure with covalent bonds. Due to its special structure, circRNA is resistant to Exonuclease R (RNaseR), making its distribution in the cytoplasm quite rich. Advanced high-throughput sequencing and bioinformatics methods have revealed that circRNA is highly conserved, stable, and disease- and tissue-specific. Furthermore, increasing research has confirmed that circRNA, as a driver or suppressor, regulates cancer onset and progression by modulating a series of pathophysiological mechanisms. As a result, circRNA has emerged as a clinical biomarker and therapeutic intervention target. This article reviews the biological functions and regulatory mechanisms of circRNA in the context of respiratory cancer onset and progression.

The roles of cancer stem cell-derived secretory factors in shaping the immunosuppressive tumor microenvironment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide and has a poor prognosis. Although immune checkpoint inhibitors have entered a new era of HCC treatment, their response rates are modest, which can be attributed to the immunosuppressive tumor microenvironment within HCC tumors. Accumulating evidence has shown that tumor growth is fueled by cancer stem cells (CSCs), which contribute to therapeutic resistance to the above treatments. Given that CSCs can regulate cellular and physical factors within the tumor niche by secreting various soluble factors in a paracrine manner, there have been increasing efforts toward understanding the roles of CSC-derived secretory factors in creating an immunosuppressive tumor microenvironment. In this review, we provide an update on how these secretory factors, including growth factors, cytokines, chemokines, and exosomes, contribute to the immunosuppressive TME, which leads to immune resistance. In addition, we present current therapeutic strategies targeting CSC-derived secretory factors and describe future perspectives. In summary, a better understanding of CSC biology in the TME provides a rational therapeutic basis for combination therapy with ICIs for effective HCC treatment.

Extracellular vesicles and cancer stemness in hepatocellular carcinoma - is there a link?

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy, with high recurrence rates and notorious resistance to conventional chemotherapy. Cancer stemness refers to the stem-cell-like phenotype of cancer cells and has been recognized to play important roles in different aspects of hepatocarcinogenesis. Small extracellular vesicles (sEVs) are small membranous particles secreted by cells that can transfer bioactive molecules, such as nucleic acids, proteins, lipids, and metabolites, to neighboring or distant cells. Recent studies have highlighted the role of sEVs in modulating different aspects of the cancer stemness properties of HCC. Furthermore, sEVs derived from diverse cellular sources, such as cancer cells, stromal cells, and immune cells, contribute to the maintenance of the cancer stemness phenotype in HCC. Through cargo transfer, specific signaling pathways are activated within the recipient cells, thus promoting the stemness properties. Additionally, sEVs can govern the secretion of growth factors from non-cancer cells to further maintain their stemness features. Clinically, plasma sEVs may hold promise as potential biomarkers for HCC diagnosis and treatment prediction. Understanding the underlying mechanisms by which sEVs promote cancer stemness in HCC is crucial, as targeting sEV-mediated communication may offer novel strategies in treatment and improve patient outcome.