[Targeted therapy for colorectal cancer through miR-204-5p delivered by nanobody-engineered exosomes: an experimental study].

Objective: To develop an EGFR-targeting nanobody engineered exosome drug delivery system and evaluate its antitumor efficacy for colorectal cancer. Methods: The HEK293T cell line stably expressing the pan-cancer inhibitor miR-204-5p, previously established by our group, was selected as a tool cell line to prepare miR-204-5p-enriched exosomes. Using metabolic glycoengineering combined with bioorthogonal reaction strategy, these exosomes were modified with the EGFR-specific nanobody 7D12. Western blot, electron microscopy, and dynamic light scattering were used to characterize the engineered exosomes. The tumor target potential of engineered exosomes was evaluated using immunofluorescence and RT-qPCR. The in vitro anti-tumor activities of engineered exosomes were evaluated using cell growth curves, colony formation, Transwell, and apoptosis analyses. The in vivo anti-tumor activity and safety of engineered exosomes were evaluated using a nude mouse xenograft tumor model. Results: The particle size of 7D12-hExo was (116.8±36.8) nm, with a potential of around -10 mV, and there was no significant change compared with the unmodified hExo. Immunofluorescence assay showed that the fluorescence intensity of the hExo group, 7D12-hExo group, and 7D12+7D12-hExo group were 48.4±3.9, 141.0±6.6, and 38.7±3.2 in EGFR⁺ HCT116 cells, respectively. Compared with the hExo group, the fluorescence intensity of HCT116 cells in the 7D12-hExo group was significantly enhanced (P＜0.05). Compared with the 7D12-hExo group, the fluorescence intensity in HCT116 cells in the 7D12+7D12-hExo group was significantly decreased (P＜0.05). However, there was no significant difference in the uptake of hExo and 7D12-hExo in EGFR^- SW620 colorectal cancer cells. The number of cell clones, invasion, and migration of HCT116 cells in the hExo (204) group was 215.0±14.0, 862.3±61.4, and 1 197.0 ± 36.7, respectively, with an apoptosis rate of (14.1±1.4)%. The number of cell clones, invasion, and migration of HCT116 cells in the 7D12-hExo (204) group was (65.0±15.1), (232.0±27.9), (725.7±32.7), respectively, with an apoptosis rate of (29.3±1.0)%. The 7D12-hExo (204) significantly inhibited the proliferation, invasion, and migration ability of HCT116 cells (P＜0.05), resulting in promoting the apoptosis of HCT116 cells (P＜0.05). Nude mouse experiments showed that 7D12-hExo (204) significantly inhibited the growth of tumors transplanted with HCT116 cells, with the inhibition rate being 82.8%. However, there was no significant change in mouse weight, and H&E staining of major organs such as heart, liver, spleen, lung, and kidney did not show any abnormalities. Conclusion: Naturally miR-204-5p-loaded exosomes were successfully modified with nanobody 7D12, which can efficiently deliver miR-204-5p into EGFR⁺ tumor cells, thereby exerting good anti-tumor therapeutic effects.