iRGD-modified 3D exosomes delivered miR-99b-5p induces ferroptosis to inhibit colorectal cancer progression by regulating FGFR3/PI3K/AKt pathway.

Abstract

Background: Mesenchymal stem cells (MSCs)-derived exosomes present great potential as nanocarriers for targeted drug delivery. Moreover, the therapeutic efficacy of exosomes can be substantially enhanced through functional modifications and the incorporation of bioactive molecules.

Methods: In this study, the MSCs were cultured under two-dimensional (2D) and three-dimensional (3D) cell culture conditions. The culture supernatants were collected for isolating exosomes. The characteristics and yields of exosomes from 2D and 3D cultures were detected by nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), western blot analysis, and bicinchoninic acid (BCA) assay. Subsequently, 3D exosomes were loaded with miR-99b-5p and modified with iRGD peptide were formed into a new engineered exosome, designated as iRGD-Exo-miR-99b-5p. The effects of these engineered exosomes on the progression of colorectal cancer (CRC) were assessed through a series of in vivo and in vitro experiments.

Results: The 3D-cultured MSCs exhibited a higher yield of exosomes and enhanced uptake by CRC cells. Further in vitro experiments demonstrated that 3D-exosomes loaded with miR-99b-5p effectively inhibit the proliferation, invasion, migration and epithelial-mesenchymal transition (EMT) of CRC cells. Results from a xenograft tumor model indicate that iRGD-modified exosomes were significantly enriched at tumor sites. Furthermore, exosomes modified with iRGD and loaded with miR-99b-5p were employed for CRC treatment, resulting in substantial tumor growth inhibition and enhanced the chemotherapy efficacy of 5-fluorouracil (5-FU) in vivo, without inducing notable toxicity or side effects. Mechanistically, exosome-mediated delivery of miR-99b-5p downregulated FGFR3 expression, thereby inhibiting the activation of the PI3K/AKt signaling pathway and promoting ferroptosis, ultimately attenuating CRC progression.

Conclusions: Collectively, iRGD-modified 3D exosomes loaded with miR-99b-5p were able to specifically target tumor sites, thereby significantly suppressing CRC growth through the induction of ferroptosis via regulating the FGFR3/PI3K/AKt signaling pathway. These findings suggest that functional engineering and bioactive loading of 3D-exosomes derived from MSCs represent a promising strategy for targeted cancer therapy.