Exosomes as Biomarkers for Precision Diagnosis of Lung Cancer

Academic Background

Lung cancer is one of the leading causes of cancer-related deaths worldwide, with early diagnosis and precision treatment of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) remaining significant challenges. Although traditional tissue biopsy is considered the “gold standard” for lung cancer diagnosis, its invasiveness, time-consuming nature, and high cost limit its application in early diagnosis. In recent years, liquid biopsy has emerged as a non-invasive diagnostic method, gaining significant attention. Liquid biopsy analyzes biomarkers such as circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and extracellular vesicles (EVs) in body fluids, offering new possibilities for early diagnosis and precision treatment of lung cancer.

Exosomes are nanoscale membrane-enclosed vesicles secreted by cells, carrying various bioactive molecules such as proteins, lipids, DNA, and RNA. They regulate the biological behavior of recipient cells through intercellular communication. The widespread presence of exosomes in body fluids and their disease-related molecular cargo make them potential tumor biomarkers. However, the isolation, detection, and analysis of exosomes still face numerous challenges, including the standardization of isolation methods and the improvement of detection sensitivity and specificity. Therefore, the development of efficient exosome isolation and detection technologies, particularly innovative methods based on nanotechnology, has become a key research focus.

Source of the Paper

The review paper titled “Circulating Extracellular Vesicles as Promising Biomarkers for Precision Diagnostics: A Perspective on Lung Cancer” was co-authored by Sunil Vasu, Vinith Johnson, Archana M, K. Anki Reddy, and Uday Kumar Sukumar*. It was published in December 2024 in ACS Biomaterials Science & Engineering (Volume 11, Pages 95-134). The paper was published by the American Chemical Society, with the DOI 10.1021/acsbiomaterials.4c01323.

Main Content of the Paper

1. The Importance of Exosomes in Lung Cancer

Exosomes play a crucial role in the initiation, progression, and metastasis of lung cancer. They regulate processes such as cell proliferation, angiogenesis, epithelial-mesenchymal transition (EMT), and metastasis within the tumor microenvironment (TME) by carrying specific molecules such as miRNAs, lncRNAs, circRNAs, and proteins. For example, exosomal miRNAs (e.g., miR-21, miR-96) promote the proliferation and migration of lung cancer cells by downregulating tumor suppressor genes or activating signaling pathways (e.g., the mTOR pathway). Additionally, exosomal proteins (e.g., EGFR, PD-L1) play a key role in immune evasion and tumor progression in lung cancer.

2. Applications of Exosomes in Liquid Biopsy

Liquid biopsy, through the analysis of exosomes in body fluids, provides new avenues for early diagnosis, tumor heterogeneity assessment, prognosis monitoring, and drug resistance analysis in lung cancer. Compared to traditional tissue biopsy, liquid biopsy offers advantages such as non-invasiveness, real-time monitoring, and high sensitivity. Exosomes are present in high concentrations in body fluids (approximately 10^9/ml), and their lipid bilayer membrane structure protects internal molecules from degradation, making them an ideal source of biomarkers.

2.1 Applications of Exosomal Nucleic Acids

Exosomal non-coding RNAs, such as miRNAs, lncRNAs, and circRNAs, show great potential in lung cancer diagnosis. For example, miR-21 and miR-155 are significantly upregulated in exosomes from NSCLC patients and can distinguish lung cancer patients from healthy controls. Additionally, lncRNA MALAT-1 and circRNA hsa_circ_0023179 have demonstrated high sensitivity and specificity in early lung cancer diagnosis.

2.2 Applications of Exosomal Proteins

Exosomal proteins (e.g., EGFR, PD-L1, CD63) regulate the tumor microenvironment and immune evasion mechanisms, making them important targets for lung cancer diagnosis and treatment. For instance, exosomal PD-L1 promotes tumor immune evasion by inhibiting T-cell activity, while exosomal EGFR promotes angiogenesis by activating the MAPK and AKT signaling pathways.

3. Advances in Exosome Isolation Technologies

Exosome isolation is a critical step in liquid biopsy, directly affecting the sensitivity and specificity of subsequent detection. The paper provides a detailed overview of traditional and emerging exosome isolation methods:

3.1 Traditional Isolation Methods

• Ultracentrifugation: Separates exosomes through high-speed centrifugation and is considered the gold standard, but it suffers from protein contamination and sample loss.
• Ultrafiltration: Uses porous membranes to separate exosomes based on size; it is simple to operate but prone to clogging.
• Size-Exclusion Chromatography (SEC): Separates exosomes using porous beads, preserving exosome structure but with low separation efficiency.
• Immunoaffinity-based Isolation: Utilizes antibodies for specific exosome capture, offering high purity but at a higher cost.

3.2 Emerging Isolation Methods

• Magnetic Nanowires: Efficiently isolate exosomes through the binding of magnetic nanowires with antibodies, offering high purity and recovery rates.
• Microfluidics: Uses microfluidic chips to separate exosomes based on their physical and biochemical properties, providing high throughput and low sample consumption.

4. Innovations in Exosome Detection Technologies

Exosome detection is another critical aspect of liquid biopsy. The paper highlights several innovative detection methods:

4.1 Surface Plasmon Resonance (SPR)

SPR detects changes in refractive index caused by the binding of exosomes to a metal surface, enabling highly sensitive exosome detection. For example, Liu et al. developed an SPR biosensor capable of detecting exosomal EGFR and PD-L1 expression levels in lung cancer patient serum.

4.2 Surface-Enhanced Raman Spectroscopy (SERS)

SERS enhances Raman signals through metal nanostructures, enabling the detection of exosomal molecular composition. For instance, Shin et al. combined SERS with deep learning algorithms to successfully distinguish exosomes from lung cancer patients and healthy controls.

4.3 Electrochemical Biosensors

Electrochemical biosensors convert biological interactions into electrical signals, enabling highly sensitive exosome detection. For example, Irani et al. developed a gold nanoisland-based electrochemical biosensor capable of detecting exosome concentrations as low as 20 exosomes/ml.

5. Challenges and Future Directions in Exosome-Based Lung Cancer Diagnosis

Despite the significant potential of exosomes in lung cancer diagnosis, their clinical application faces several challenges, including the standardization of isolation and detection methods, addressing exosome heterogeneity, and the lack of large-scale clinical validation. Future research directions include developing more efficient exosome isolation technologies, integrating multiple biomarkers to improve diagnostic accuracy, and advancing the clinical translation of exosome detection technologies.

Significance and Value of the Paper

This review paper systematically summarizes the current applications and technological advancements of exosomes in precision diagnosis of lung cancer, providing a comprehensive reference for researchers. The paper not only details the biological functions of exosomes and their mechanisms in lung cancer but also explores the latest developments in exosome isolation and detection technologies, offering new insights for early diagnosis and precision treatment of lung cancer. Additionally, the paper highlights current research challenges and future directions, laying the groundwork for the clinical application of exosomes.

Highlights

1. Potential of Exosomes as Lung Cancer Biomarkers: The paper elaborates on the applications of exosomal miRNAs, lncRNAs, circRNAs, and proteins in lung cancer diagnosis and treatment.
2. Innovative Isolation and Detection Technologies: The paper introduces emerging technologies such as magnetic nanowires, microfluidics, SPR, and SERS in exosome isolation and detection.
3. Clinical Translation Prospects: The paper identifies challenges in exosome-based lung cancer diagnosis and proposes future research directions, providing valuable insights for clinical applications.

This paper not only offers a new perspective on lung cancer research but also serves as a reference for the application of exosomes in the diagnosis of other diseases.