miRNAs in Serum Exosomes for Differential Diagnosis of Brain Metastases

Extracellular vesicle-derived non-coding RNAs in remodeling melanoma

Melanoma is one of the most lethal cutaneous malignancies. Despite great advances in radiotherapy, chemotherapy, and immunotherapy, the survival rate and prognosis of patients with melanoma remain poor. The abundant and sophisticated reciprocal communication network between melanoma cells and non-tumor cells contributes to the high heterogeneity of the melanoma microenvironment and is intimately related to varying treatment responses and clinical courses. Extracellular vesicles (EVs) are membrane structures generated by nearly all cell types. EVs contain biologically active molecules, mainly comprising proteins, lipids, and RNAs, and undoubtedly play multifaceted roles in numerous diseases, represented by melanoma. Non-coding RNAs (ncRNAs) mainly encompass long non-coding RNAs, microRNAs, and circular RNAs and constitute the majority of the human transcriptome. Multiple ncRNAs encapsulated in EVs coordinate various pathophysiological processes in melanoma. This review summarizes the mechanisms by which EV-ncRNAs modulate biological behaviors and immunity, and their potential diagnostic and therapeutic applications in melanoma. Undoubtedly, further insight into EV-ncRNAs and their functions in melanoma will contribute to the clinical treatment of melanoma and the implementation of precision medicine.

MicroRNA as a potential diagnostic and prognostic biomarker in brain gliomas: a systematic review and meta-analysis

Introduction

Brain neoplasms and central nervous system (CNS) disorders, particularly gliomas, have shown a notable increase in incidence over the last three decades, posing significant diagnostic and therapeutic challenges. MicroRNAs (miRNAs) have emerged as promising biomarkers due to their regulatory role in gene expression, offering potential enhancements in glioma diagnosis and prognosis.

Methods

This systematic review and meta-analysis, adhering to PRISMA guidelines, included 25 studies for diagnostic accuracy and 99 for prognostic analysis, published until August 27th, 2023. Studies were identified through comprehensive searches of PubMed, Web of Science, and Scopus databases. Inclusion criteria encompassed peer-reviewed original research providing sensitivity, specificity, and area under the curve (AUC) for miRNAs in glioma diagnosis, as well as survival outcomes with hazard ratios (HRs) or mean survival.

Results and discussion

Meta-analysis demonstrated miRNAs' high diagnostic accuracy, with a pooled sensitivity of 0.821 (95% CI: 0.781-0.855) and specificity of 0.831 (95% CI: 0.792-0.865), yielding an AUC of 0.893. Subgroup analysis by specimen type revealed consistent accuracy across blood, cerebrospinal fluid (CSF), and tissue samples. Our results also showed miRNAs can be potential prognostic biomarkers. miRNAs showed significant associations with overall survival (OS) (pooled HR: 2.0221; 95% CI: 1.8497-2.2105), progression-free survival (PFS) (pooled HR: 2.4248; 95% CI: 1.8888-3.1128), and disease-free survival (DFS) (pooled HR: 1.8973; 95% CI: 1.1637-3.0933) in tissue specimens. These findings underscore miRNAs' potential as valuable biomarkers for improving glioma diagnosis and prognosis, offering insights for enhancing clinical decision-making and patient outcomes.

Hybridization chain reaction circuit controller: CRISPR/Cas12a conversion amplifier for miRNA-21 sensitive detection

MicroRNA (miRNA) is crucial to the diagnose of various diseases. However, the accurate detection of miRNA has been challenging due to its short length and low abundance. Here, we designed a hybridization chain reaction (HCR) circuit controller to initiate the CRISPR/Cas12a conversion amplifier (HCR-Cas12a controller) for sensitive detection of miRNA-21 (miR-21). In the HCR, pre-crRNA was encapsulated in a hairpin structure until the miR-21 was present. Afterward, Cas12a fully exerted its RNase activity to self-mature pre-crRNA. Then, the trans-cleavage activity of Cas12a was initiated by activator. This results in the conversion of biological signals to fluorescent signal. During HCR-Cas12a controller, the circuit formed quickly, while the Cas12a system worked in a short time. The miR-21 was ultra-sensitively detected with the wide detection range of 1 fM - 100 nM, and the calculated limit of detection was 75.4 aM. The sensitivity was an order of magnitude lower than the standard method. The formation of HCR at room temperature does not require a thermal cycler. Additionally, Cas12a can work without the need for precise or expensive instruments. Therefore, our proposed method was suitable for low-resource settings, and provided a technical basis for sensitive detection of miRNA in low concentration range.

Immunotherapy in patients with brain metastasis: advances and challenges for the treatment and the application of circulating biomarkers

The central nervous system (CNS) is one of the most frequent metastatic sites of various cancers, including lung cancer, breast cancer and melanoma. The development of brain metastases requires a specific therapeutic approach and is associated with high mortality and morbidity in cancer patients. Advances in precision medicine and the introduction in recent years of new drugs, such as immunotherapy, have made it possible to improve the prognosis of these patients by improving survival and quality of life. New diagnostic techniques such as liquid biopsy allow real-time monitoring of tumor evolution, providing molecular information on prognostic and predictive biomarkers of response to treatment in blood or other fluids. In this review, we perform an exhaustive update of the clinical trials that demonstrate the utility of immunotherapy in patients with brain metastases and the potential of circulating biomarkers to improving the results of efficacy and toxicity in this subgroup of patients.

The Dual Effects of Exosomes on Glioma: A Comprehensive Review

Glioma is a frequently occurring type of cancer that affects the central nervous system. Despite the availability of standardized treatment options including surgical resection, concurrent radiotherapy, and adjuvant temozolomide (TMZ) therapy, the prognosis for glioma patients is often unfavorable. Exosomes act as vehicles for intercellular communication, contributing to tissue repair, immune modulation, and the transfer of metabolic cargo to recipient cells. However, the transmission of abnormal substances can also contribute to pathologic states such as cancer, metabolic diseases, and neurodegenerative disorders. The field of exosome research in oncology has seen significant advancements, with exosomes identified as dynamic modulators of tumor cell proliferation, migration, and invasion, as well as angiogenesis and drug resistance. Exosomes have negligible cytotoxicity, low immunogenicity, and small size, rendering them an ideal therapeutic candidate for glioma. This comprehensive review discusses the dual effects of exosomes in glioma, with an emphasis on their role in facilitating drug resistance. Furthermore, the clinical applications and current limitations of exosomes in glioma therapy are also discussed in detail.

The impact of survivorship bias in glioblastoma research

Despite advances in the therapy of Central Nervous System (CNS) malignancies, treatment of glioblastoma (GB) poses significant challenges due to GB resistance and high recurrence rates following post-operative radio-chemotherapy. The majority of prognostic and predictive GB biomarkers are currently developed using tumour samples obtained through surgical interventions. However, the selection criteria adopted by different neurosurgeons to determine which cases are suitable for surgery make operated patients not representative of all GB cases. Particularly, geriatric and frail individuals are excluded from surgical consideration in some cancer centers. Such selection generates a survival (or selection) bias that introduces limitations, rendering the patients or data chosen for downstream analyses not representative of the entire community. In this review, we discuss the implication of survivorship bias on current and novel biomarkers for patient selection, stratification, therapy, and outcome analyses.

Therapeutic and Diagnostic Potential of Exosomes as Drug Delivery Systems in Brain Cancer

Cancer is designated as one of the principal causes of mortality universally. Among different types of cancer, brain cancer remains the most challenging one due to its aggressiveness, the ineffective permeation ability of drugs through the blood-brain barrier (BBB), and drug resistance. To overcome the aforementioned issues in fighting brain cancer, there is an imperative need for designing novel therapeutic approaches. Exosomes have been proposed as prospective "Trojan horse" nanocarriers of anticancer theranostics owing to their biocompatibility, increased stability, permeability, negligible immunogenicity, prolonged circulation time, and high loading capacity. This review provides a comprehensive discussion on the biological properties, physicochemical characteristics, isolation methods, biogenesis and internalization of exosomes, while it emphasizes their therapeutic and diagnostic potential as drug vehicle systems in brain cancer, highlighting recent advances in the research field. A comparison of the biological activity and therapeutic effectiveness of several exosome-encapsulated cargo including drugs and biomacromolecules underlines their great supremacy over the non-exosomal encapsulated cargo in the delivery, accumulation, and biological potency. Various studies on cell lines and animals give prominence to exosome-based nanoparticles (NPs) as a promising and alternative approach in the management of brain cancer.

Highly Effective Detection of Exosomal miRNAs in Plasma Using Liposome-Mediated Transfection CRISPR/Cas13a

Exosomal miRNAs play a critical role in cancer biology and could be potential biomarkers for cancer diagnosis. However, due to the low abundance of miRNAs in the exosomes, recognizing and detecting disease-associated exosomal miRNAs in an easy-to-operate way remain a challenge. Herein, we used a liposome-mediated membrane fusion strategy (MFS) to transfect CRISPR/Cas13a into exosomes, termed MFS-CRISPR, directly measuring exosomal miRNAs in plasma. Using the MFS-CRISPR platform for detection of the exosomal miR-21, we achieve a linear range spanning four orders of magnitude (10⁴-10⁸ particles/mL) and the method is able to detect the exosomal miR-21 in as low as 1.2 × 10³ particles/mL. The liposome-mediated MFS could confine fluorescent signals in fused vesicles, which can be used for exosome heterogeneity analysis. Moreover, MFS-CRISPR assay was evaluated by measuring clinical samples, and the difference of miR-21 expression of breast cancer patients and healthy donors was significant. Because of high sensitivity and simplicity, the proposed method could have promising clinical potential for cancer diagnosis and treatment monitoring.

Tumor microenvironment and exosomes in brain metastasis: Molecular mechanisms and clinical application

Metastasis is one of the important biological features of malignant tumors and one of the main factors responsible for poor prognosis. Although the widespread application of newer clinical technologies and their continuous development have significantly improved survival in patients with brain metastases, there is no uniform standard of care. More effective therapeutic measures are therefore needed to improve prognosis. Understanding the mechanisms of tumor cell colonization, growth, and invasion in the central nervous system is of particular importance for the prevention and treatment of brain metastases. This process can be plausibly explained by the “seed and soil” hypothesis, which essentially states that tumor cells can interact with various components of the central nervous system microenvironment to produce adaptive changes; it is this interaction that determines the development of brain metastases. As a novel form of intercellular communication, exosomes play a key role in the brain metastasis microenvironment and carry various bioactive molecules that regulate receptor cell activity. In this paper, we review the roles and prospects of brain metastatic tumor cells, the brain metastatic tumor microenvironment, and exosomes in the development and clinical management of brain metastases.