Osteosarcoma-Derived Small Extracellular Vesicles Enhance Tumor Metastasis and Suppress Osteoclastogenesis by miR-146a-5p

Review of pre-metastatic niches induced by osteosarcoma-derived extracellular vesicles in lung metastasis: A potential opportunity for diagnosis and intervention

Osteosarcoma (OS) has a high propensity for lung metastasis, which is the leading cause of OS-related death and treatment failure. Intercellular communication between OS cells and distant lung host cells is required for the successful lung metastasis of OS cells to the lung. Before OS cells infiltrate the lung, in situ OS cells secrete extracellular vesicles (EVs) that act as mediators of cell-to-cell communication. In recent years, EVs have been confirmed to act as bridges and key drivers between in situ tumors and metastatic lesions by regulating the formation of a pre-metastatic niche (PMN), defined as a microenvironment suitable for disseminated tumor cell engraftment and colonization, in distant target organs. This review summarizes the current knowledge about the underlying mechanisms of PMN formation induced by OS-derived EVs and the potential roles of EVs as targets or drug carriers in regulating PMN formation in the lung. We also provide an overview of their potential EV-based therapeutic strategies for hindering PMN formation in the context of OS lung metastasis.

Extracellular vesicles promote silica nanoparticle aggregation that inhibits silica-induced cytotoxicity

Amorphous silica has been approved as a food and pharmaceutical additive. However, its potential to enhance the carcinogenicity of epithelial cells is incontrovertible. With their expanded surface area per unit mass and distinctive cellular incorporation, nano-sized silica particles (nSPs) exhibit heightened cytotoxicity compared to micrometer-sized counterparts. The precise effect of nSPs on the generation of small extracellular vesicles (sEVs) within endosomes after cellular uptake remains unclear. In the present study, we explored the secretion of sEVs from cells and their functional implications following exposure to nSPs. Our findings demonstrate that nSP50 exposure not only induced epithelial-mesenchymal transition (EMT) but also promoted the maturation of multivesicular endosomes (MVEs) along with the secretion of sEVs in A549 cells. Inhibition of sEV secretion using GW4869 and apoptosis activator 2 exacerbated nSP50-induced EMT, indicating that sEV secretion may suppress EMT. Analysis of the function of sEV in a cell-free system revealed that co-incubation of sEVs with nSP50 led to the formation of micrometer-sized aggregates, which exhibited limited uptake efficiency within A549 cells. These results strongly suggest that the secretion of sEVs plays a protective role against the cytotoxicity attributed to nSP50 exposure.

Extracellular Vesicles for Childhood Cancer Liquid Biopsy

Liquid biopsy involves the utilization of minimally invasive or noninvasive techniques to detect biomarkers in biofluids for disease diagnosis, monitoring, or guiding treatments. This approach is promising for the early diagnosis of childhood cancer, especially for brain tumors, where tissue biopsies are more challenging and cause late detection. Extracellular vesicles offer several characteristics that make them ideal resources for childhood cancer liquid biopsy. Extracellular vesicles are nanosized particles, primarily secreted by all cell types into body fluids such as blood and urine, and contain molecular cargos, i.e., lipids, proteins, and nucleic acids of original cells. Notably, the lipid bilayer-enclosed structure of extracellular vesicles protects their cargos from enzymatic degradation in the extracellular milieu. Proteins and nucleic acids of extracellular vesicles represent genetic alterations and molecular profiles of childhood cancer, thus serving as promising resources for precision medicine in cancer diagnosis, treatment monitoring, and prognosis prediction. This review evaluates the recent progress of extracellular vesicles as a liquid biopsy platform for various types of childhood cancer, discusses the mechanistic roles of molecular cargos in carcinogenesis and metastasis, and provides perspectives on extracellular vesicle-guided therapeutic intervention. Extracellular vesicle-based liquid biopsy for childhood cancer may ultimately contribute to improving patient outcomes.

miR-1246 promotes osteosarcoma cell migration via NamiRNA-enhancer network dependent on Argonaute 2

High metastatic propensity of osteosarcoma leads to its therapeutic failure and poor prognosis. Although nuclear activation miRNAs (NamiRNAs) are reported to activate gene transcription via targeting enhancer and further promote tumor metastasis, it remains uncertain whether NamiRNAs regulate osteosarcoma metastasis and their exact mechanism. Here, we found that extracellular vesicles of the malignant osteosarcoma cells (143B) remarkably increased the migratory abilities of MNNG cells representing the benign osteosarcoma cells by two folds, which attributed to their high miR-1246 levels. Specially, miR-1246 located in nucleus could activate the migration gene expression (such as MMP1) to accelerate MNNG cell migration through elevating the enhancer activities via increasing H3K27ac enrichment. Instead, MMP1 expression was dramatically inhibited after Argonaute 2 (AGO2) knockdown. Notably, in vitro assays demonstrated that AGO2 recognized the hybrids of miR-1246 and its enhancer DNA via PAZ domains to prevent their degradation from RNase H and these protective roles of AGO2 may favor the gene activation by miR-1246 in vivo. Collectively, our findings suggest that miR-1246 could facilitate osteosarcoma metastasis through interacting with enhancer to activate gene expression dependent on AGO2, highlighting the nuclear AGO2 as a guardian for NamiRNA-targeted gene activation and the potential of miR-1246 for osteosarcoma metastasis therapy.

Precise analysis of single small extracellular vesicles using flow cytometry

Methods that enable specific and sensitive quantification of small extracellular vesicles (sEVs) using flow cytometry are still under development. Aggregation or adsorption of antibodies causes sub-nano sized particles or non-specific binding and largely affects the results of flow cytometric analysis of single sEVs. Comparison of control IgG and target-specific IgG is inappropriate because they have different characters. Here, we evaluate four preparation methods for flow cytometry, including ultracentrifugation, density gradient centrifugation, size exclusion chromatography (SEC), and the TIM4-affinity method by using tetraspanin-deficient sEVs. The ultracentrifugation or density gradient centrifugation preparation method has large false-positive rates for tetraspanin staining. Conversely, preparation methods using SEC or the TIM4-affinity method show specific detection of single sEVs, which elucidate the roles of sEV biogenesis regulators in the generation of sEV subpopulations. The methods are also useful for the detection of rare disease-related markers, such as PD-L1. Flow cytometric analysis using SEC or the TIM4-affinity method could accelerate research into sEV biogenesis and the development of sEV-based diagnostics and therapies.

Acquisition of drug resistance in endothelial cells by tumor-derived extracellular vesicles and cancer progression

Angiogenesis by endothelial cells (ECs) is essential for tumor growth. Angiogenesis inhibitors are used in combination with anticancer drugs in many tumor types, but tumors eventually become resistant. Previously, the underlying mechanism for developing drug resistance was considered to be a change in the characteristics of tumor cells whereas ECs were thought to be genetically stable and do not contribute to drug resistance. However, tumor endothelial cells (TECs) have been shown to differ from normal endothelial cells (NECs) in that they exhibit chromosomal abnormalities, angiogenic potential, and drug resistance. Extracellular vesicles (EVs) secreted by tumor cells have recently attracted attention as a factor involved in the acquisition of such abnormalities. Various cells communicate with each other through EVs, and it has been reported that tumor-derived EVs act on other tumor cells or stromal cells to develop drug resistance. Drug-resistant tumor cells confer drug resistance to recipient cells by transporting mRNAs encoding ATP-binding cassette subfamily B member 1 (ABCB1) and ATP-binding cassette subfamily C member 1 (ABCC1) as well as miRNAs involved in signaling such as Akt, drug efflux transporters, and P-glycoprotein modulators via EVs. However, there are limited reports on the acquisition of drug resistance in ECs by tumor-derived EVs. Since drug resistance of ECs may induce tumor metastasis and support tumor cell proliferation, the mechanism underlying the development of resistance should be elucidated to find therapeutic application. This review provides insight into the acquisition of drug resistance in ECs via tumor EVs in the tumor microenvironment.

Extracellular vesicles in tumorigenesis, metastasis, chemotherapy resistance and intercellular communication in osteosarcoma

HIGHLIGHTS

Extracellular vehicles play crucial function in osteosarcoma tumorigenesis.Extracellular vehicles mediated the intercellular communication of osteosarcoma cells with other types cells in tumor microenvironment.Extracellular vehicles have potential utility in osteosarcoma diagnosis and treatment.

EV-miRNA-Mediated Intercellular Communication in the Breast Tumor Microenvironment

Cancer research has prioritized the study of the tumor microenvironment (TME) as a crucial area of investigation. Understanding the communication between tumor cells and the various cell types within the TME has become a focal point. Bidirectional communication processes between these cells support cellular transformation, as well as the survival, invasion, and metastatic dissemination of tumor cells. Extracellular vesicles are lipid bilayer structures secreted by cells that emerge as important mediators of this cell-to-cell communication. EVs transfer their molecular cargo, including proteins and nucleic acids, and particularly microRNAs, which play critical roles in intercellular communication. Tumor-derived EVs, for example, can promote angiogenesis and enhance endothelial permeability by delivering specific miRNAs. Moreover, adipocytes, a significant component of the breast stroma, exhibit high EV secretory activity, which can then modulate metabolic processes, promoting the growth, proliferation, and migration of tumor cells. Comprehensive studies investigating the involvement of EVs and their miRNA cargo in the TME, as well as their underlying mechanisms driving tumoral capacities, are necessary for a deeper understanding of these complex interactions. Such knowledge holds promise for the development of novel diagnostic and therapeutic strategies in cancer treatment.

A validation study for the utility of serum microRNA as a diagnostic and prognostic marker in patients with osteosarcoma

In our previous study, osteosarcoma advanced locally, and metastasis was promoted through the secretion of large number of small extracellular vesicles, followed by suppressing osteoclastogenesis via the upregulation of microRNA (miR)-146a-5p. An additional 12 miRNAs in small extracellular vesicles were also detected ≥6× as frequently in high-grade malignancy with the capacity to metastasize as in those with a low metastatic potential. However, the utility of these 13 miRNAs for determining the prognosis or diagnosis of osteosarcoma has not been validated in the clinical setting. In the present study, the utility of these miRNAs as prognostic and diagnostic markers was therefore assessed. In total, 30 patients with osteosarcoma were retrospectively reviewed, and the survival rate was compared according to the serum miRNA levels in 27 patients treated with chemotherapy and surgery. In addition, to confirm diagnostic competency for osteosarcoma, the serum miRNA levels were compared with those in patients with other bone tumors (n=112) and healthy controls (n=275). The patients with osteosarcoma with high serum levels of several miRNAs (miR-146a-5p, miR-1260a, miR-487b-3p, miR-1260b and miR-4758-3p) exhibited an improved survival rate compared with those with low levels. In particular, patients with high serum levels of miR-1260a exhibited a significantly improved overall survival rate, metastasis-free survival rate and disease-free survival rate compared with those with low levels. Thus, serum miR-1260a may potentially be a prognostic marker for patients with osteosarcoma. Moreover, patients with osteosarcoma had higher serum miR-1261 levels than those with benign or intermediate-grade bone tumors and thus may be a potential therapeutic target, in addition to being useful for differentiating whether or not a bone tumor is high-grade. A larger investigation is required to clarify the actual utility of these miRNAs in the clinical setting.

Exosomes in sarcoma: Prospects for clinical applications

Sarcoma is a group of rare and heterogeneous mesenchymal tumors, prone to late diagnosis and poor prognosis. Exosomes are cell-derived small extracellular vesicles found in most body fluids and contain nucleic acids, proteins, lipids, and other molecules. Qualitative and quantitative changes of exosomes and the contents are associated with sarcoma progression, exhibiting their potential as biomarkers. Exosomes possess the capacity of evading immune responses, bioactivity for trafficking, tumor tropism, and lesion residence. Thus, exosomes could be engineered as tumor-specific vehicles in drugs and RNA delivery systems. Exosomes might also serve as therapeutic targets in targeted therapy and immunotherapy and be involved in chemotherapy resistance. Here, we provide a comprehensive summary of exosome applications in liquid biopsy-based diagnosis and explore their implications in the delivery system, targeted therapy, and chemotherapy resistance of sarcoma. Moreover, challenges in exosome clinical applications are raised and some future research directions are proposed.

Exosomes in the tumor microenvironment of sarcoma: from biological functions to clinical applications

The current diagnosis and treatment of sarcoma continue to show limited timeliness and efficacy. In order to enable the early detection and management of sarcoma, increasing attentions have been given to the tumor microenvironment (TME). TME is a dynamic network composed of multiple cells, extracellular matrix, vasculature, and exosomes. Exosomes are nano-sized extracellular vesicles derived from various cells in the TME. The major function of exosomes is to promote cancer progress and metastasis through mediating bidirectional cellular communications between sarcoma cells and TME cells. Due to the content specificity, cell tropism, and bioavailability, exosomes have been regarded as promising diagnostic and prognostic biomarkers, and therapeutic vehicles for sarcoma. This review summarizes recent studies on the roles of exosomes in TME of sarcoma, and explores the emerging clinical applications.

Immunomodulatory Properties of Human Breast Milk: MicroRNA Contents and Potential Epigenetic Effects

Infants who are exclusively breastfed in the first six months of age receive adequate nutrients, achieving optimal immune protection and growth. In addition to the known nutritional components of human breast milk (HBM), i.e., water, carbohydrates, fats and proteins, it is also a rich source of microRNAs, which impact epigenetic mechanisms. This comprehensive work presents an up-to-date overview of the immunomodulatory constituents of HBM, highlighting its content of circulating microRNAs. The epigenetic effects of HBM are discussed, especially those regulated by miRNAs. HBM contains more than 1400 microRNAs. The majority of these microRNAs originate from the lactating gland and are based on the remodeling of cells in the gland during breastfeeding. These miRNAs can affect epigenetic patterns by several mechanisms, including DNA methylation, histone modifications and RNA regulation, which could ultimately result in alterations in gene expressions. Therefore, the unique microRNA profile of HBM, including exosomal microRNAs, is implicated in the regulation of the genes responsible for a variety of immunological and physiological functions, such as FTO, INS, IGF1, NRF2, GLUT1 and FOXP3 genes. Hence, studying the HBM miRNA composition is important for improving the nutritional approaches for pregnancy and infant's early life and preventing diseases that could occur in the future. Interestingly, the composition of miRNAs in HBM is affected by multiple factors, including diet, environmental and genetic factors.

Osteosarcoma and Metastasis

Osteosarcoma is the most common primary bone malignancy in adolescents. Its high propensity to metastasize is the leading cause for treatment failure and poor prognosis. Although the research of osteosarcoma has greatly expanded in the past decades, the knowledge and new therapy strategies targeting metastatic progression remain sparse. The prognosis of patients with metastasis is still unsatisfactory. There is resonating urgency for a thorough and deeper understanding of molecular mechanisms underlying osteosarcoma to develop innovative therapies targeting metastasis. Toward the goal of elaborating the characteristics and biological behavior of metastatic osteosarcoma, it is essential to combine the diverse investigations that are performed at molecular, cellular, and animal levels from basic research to clinical translation spanning chemical, physical sciences, and biology. This review focuses on the metastatic process, regulatory networks involving key molecules and signaling pathways, the role of microenvironment, osteoclast, angiogenesis, metabolism, immunity, and noncoding RNAs in osteosarcoma metastasis. The aim of this review is to provide an overview of current research advances, with the hope to discovery druggable targets and promising therapy strategies for osteosarcoma metastasis and thus to overcome this clinical impasse.

MiR-6924-5p-rich exosomes derived from genetically modified Scleraxis-overexpressing PDGFRα(+) BMMSCs as novel nanotherapeutics for treating osteolysis during tendon-bone healing and improving healing strength

Osteolysis at the tendon-bone interface can impair pullout strength during tendon-bone healing and lead to surgery failure, but the effects of clinical treatments are not satisfactory. Mesenchymal stem cell (MSC)-derived exosomes have been used as potent and feasible natural nanocarriers for drug delivery and have been proven to enhance tendon-bone healing strength, indicating that MSC-derived exosomes could be a promising therapeutic strategy. In this study, we explored Scleraxis (Scx) dynamically expressed in PDGFRα(+) bone marrow-derived mesenchymal stem cells (BMMSCs) during natural tendon-bone healing. Then, we investigated the role of PDGFRα(+) BMMSCs in tendon-bone healing after Scx overexpression as well as the underlying mechanisms. Our data demonstrated that Scx-overexpressing PDGFRα(+) BMMSCs (BMMSC^Scx) could efficiently inhibit peritunnel osteolysis and enhance tendon-bone healing strength by preventing osteoclastogenesis in an exosomes-dependent manner. Exosomal RNA-seq revealed that the abundance of a novel miRNA, miR-6924-5p, was highest among miRNAs. miR-6924-5p could directly inhibit osteoclast formation by binding to the 3'-untranslated regions (3'UTRs) of OCSTAMP and CXCL12. Inhibition of miR-6924-5p expression reversed the prevention of osteoclastogenic differentiation by BMMSC^Scx derived exosomes (BMMSC^Scx-exos). Local injection of BMMSC^Scx-exos or miR-6924-5p dramatically reduced osteoclast formation and improved tendon-bone healing strength. Furthermore, delivery of miR-6924-5p efficiently inhibited the osteoclastogenesis of human monocytes. In brief, our study demonstrates that BMMSC^Scx-exos or miR-6924-5p could serve as a potential therapy for the treatment of osteolysis during tendon-bone healing and improve the outcome.

A novel small-molecule antagonist enhances the sensitivity of osteosarcoma to cabozantinib in vitro and in vivo by targeting DNMT-1 correlated with disease severity in human patients

Advanced osteosarcoma (OSA) is highly aggressive and can lead to distant metastasis or recurrence. Here, a novel small-molecule inhibitor/antagonist of DNA methyltransferase 1 (DNMT-1) named DI-1 (inhibitor of DNMT-1) was explored to enhance the antitumor effect of a molecular-targeted agent, cabozantinib, on OSA cell lines. In patients with OSA, expression of DNMT-1 was negatively related with that of microRNA (miR)-34a and associated with a poor prognosis. In OSA cell lines (OSA cell line U2OS and an OSA cell line U2OSR resistance to cabozantinib), DI-1 treatment enhanced miR-34a expression by inhibiting hypermethylation of the promoter region of miR-34a mediated by DNMT-1. DI-1 enhanced the sensitivity of OSA cells (U2OS, 143B and MG63) to cabozantinib and other molecular-targeted agents by enhancing miR-34a expression and repressing activation of the Notch pathway. Mechanistically, DI-1 repressed recruitment of DNMT-1 to the promoter region of miR-34a and, in turn, decreased the methylation rate in the promoter region of miR-34a in OSA cells. These results suggest that repressing DNMT-1 activation by DI-1 enhances miR-34a expression in OSA cells and could be a promising therapeutic strategy for OSA.