With intensive studies on the extraction, component analysis, and effects on tissue behavior, exosomes have attracted great interest as a new tool in tumor diagnosis and treatment. Designing exosomes to carry specific ligands and specific proteins allows the investigation of exosome-mediated drug transport and its effects on tumor lesions. With a deep comprehension of exosome modification and production, Creative Biolabs offers clients exosome modification services for targeting tumors.

Exosome Distribution in Tumors

The involvement of exosomes in intercellular communication and their role in tumor therapy has been widely recognized. It has been demonstrated that exosomes with natural lipid membrane structure and 100 nm size exhibit enhanced EPR effects in tumors. Not only are exosomes exposed to organ-selective ligands capable of recognizing tumor integrins, but are also covered with glycans that affect tissue distribution. For example, glioblastoma-derived exosomes carrying glycosaminoglycans are directed to CCR8-positive glioblasts by bridging CCL8. In addition, high levels of sphingomyelin and gangliosides attributed to the membrane turned positively charged in the acidic tumor microenvironment (TME), enhancing exosome uptake by tumors compared to physiological conditions. However, the higher inter-tissue osmolarity, inadequate blood perfusion, and the risk of metastasis in solid tumors still pose challenges to the exosome delivery of therapeutic agents. Benefiting from exosomes' high modifiability for targeted delivery is a blessing for the future of medical oncology, especially for tumors that are only diagnosed at advanced stages and have a poor prognosis.

Fig.1 The internal and surface protein modification of exosomes. (Wang, 2022)

Passive-targeted Exosome Modification Strategies for Tumor Cells at Creative Biolabs

Effective passive targeting facilitates the enrichment of systemically administered exosomes in tumor tissue, a prerequisite for subsequent exosome targeting to tumor-specific cells. Two measures for enhancing exosome passive targeting are prolonging circulation time and increasing tumor infiltration. On the one hand, overexpression of the surface anti-phagocytic cytokine CD47 protects exosomes from phagocytosis and clearance, thus significantly increasing the circulation time. Surface PEG conjugation results in long-circulating exosomes and improves their stability. On the other hand, exosome surface modification with ligands targeting surface receptors highly expressed on tumor vascular endothelial cells can enhance exosome tumor penetration. For example, membrane-modified RGD interacts with the vascular target integrin αvβ3, a cell-penetrating peptide applied to tumor targeting in a cytosolic-independent penetration manner. In addition, the dual function of exosomes for tumor homing and membrane penetration is achieved with surface modification of tLyp-1-mediated interaction with NRP-1, which is widely present in endothelial cells and TME. For the display and high expression of these ligands on the exosome surface, Creative Biolabs offers two types of exosome modification services, pre-isolation, and post-isolation, based on the modification time. Donor cells are transfected with plasmids containing ligand sequences prior to exosome isolation from the cells resulting in the exosome being produced with the corresponding ligands displayed on its surface. In post-isolation, the ligands are allowed to be directly modified on the exosome surface by conjugation reactions or click chemistry.

Active-targeted Exosome Modification Strategies for Tumor Cells at Creative Biolabs

Several modifiable proteins are available for exosome active targeting applications, including antibodies, peptides, protein-based ligands, nucleic acid-based ligands, and small molecules. Since TME limits intra-tumor infiltration of exosomes under pathological conditions, modifying exosomes to restore TME normalization is critical. Immune responses disrupted in TME by T-cell depletion can be relieved by constructing dual-targeted exosomes with anti-EGFR and anti-CD3. Exosomes with Lewis antigen modified by rocket algae glycosylated glycans show enhanced dendritic cell uptake and mediated immune activation. Methotrexate was demonstrated on the exosome surface to act as a ligand binding to tumor-associated macrophages with high folic acid receptor-2 expression.

Exosomes are modified with ligands that are selectively taken up by cancer cells. For example, the GE11 peptide targets EGFR overexpressing tumors, while the R8 peptide stimulates the exosome uptake by tumor cells. To avoid adverse effects on the particle size and physicochemical properties of exosomes after modifying large volumes of antibodies, antibody variable regions to greatly reduce antibody molecular weight and immunoreactivity are considered. Non-peptide ligands have also been used to modify exosome surfaces, such as AS1411 targeting tumor cells overexpressing nucleophosmin and Sgc8 targeting protein tyrosine kinase 7 positive tumors. In addition, cell-penetrating peptides to enhance the exosome intracellularization and external stimulation to address exosome crossing of biological barriers should also be taken into account in exosome modification strategies targeting specific tumor cells.

Fig.2 Graphical illustration of tumor targeting strategies of exosome-based delivery. (Shao, 2020)

As an advanced professional organization in the exosome research and application field, Creative Biolabs has accumulated extensive insight into various types of tumors and research projects applying exosome-targeted delivery. The exosome modification strategy for tumor targeting comprehensively takes into account factors including passive enrichment in tumor foci and selective internalization in specific pathological cells to optimize exosome targeting. Our experts specialize in providing customized exosome modification services for targeting tumors to meet the client's particular needs. Please contact us to discuss your project.

References

1. Wang, X.; et al. The updated role of exosomal proteins in the diagnosis, prognosis, and treatment of cancer. Exp Mol Med. 2022, 54(9): 1390-1400.
2. Shao, J.; et al. Advances in exosome-based drug delivery and tumor targeting: from tissue distribution to intracellular fate. Int J Nanomedicine. 2020, 15: 9355-9371.

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