Exosomes derived from cancer-associated fibrolasts mediated ciplatin resistance.

Objective: Nasopharyngeal carcinoma (NPC), a highly invasive form of head and neck cancer, carries a significant risk of distant metastasis. NPC is particularly prevalent in Asia and has a high incidence in southern China. Cisplatin-diamminedichloroplatinum (DDP), a chemotherapy agent, is commonly employed in NPC treatment. Despite DDP's efficacy, many patients eventually develop resistance to it over the course of their therapy, which significantly hinders treatment outcomes. Cancer-associated fibroblasts (CAFs) are key components of the tumor micro-environment and contribute to tumor progression and chemotherapy resistance. Exosomes secreted by CAFs serve as crucial mediators of intercellular communication and participate in modulating diverse biological processes. This study aimed to explore how exosomes derived from CAFs contribute to DDP resistance in NPC.

Material and methods: An in vitro coculture system was used to simulate the interaction between CAFs and NPC cells, and exosomes secreted by CAFs were isolated and characterized. The expression of autophagy hallmark proteins was detected by Western blot and quantitative real-time polymerase chain reaction. Autophagy intensity was quantified using monodansylcadaverine staining, and cell proliferation was assessed by colony formation assays and methylthiazolyldiphenyl-tetrazolium assays. NPC cells were treated with autophagy inducers (rapamycin), and the expression of Ras homologue enriched in brain (Rheb), mammalian target of rapamycin complex (mTORC1), and UNC51-like kinase was detected. Immunofluorescence was used to determine the cellular localization and expression intensity of mTORC1, and the effect on DDP sensitivity was evaluated through cell proliferation rates. In addition, the exosome-mediated resistance mechanism was further validated using an in vivo xenograft tumor model.

Results: Coculture of CAFs with NPC cells significantly promoted the proliferation of NPC cells (P < 0.01), significantly elevated the IC50 value of DDP (P < 0.01), and elevated the resistance of NPC cells to DDP. CAF-derived exosomes elevated autophagy hallmark proteins light chain 3B-II, Beclin, and increased the autophagy intensity (P < 0.01). CAF-derived exosomes promoted autophagy by inhibiting mTORC1 (P < 0.01). In the in vitro model, exosomes promoted the growth of tumor tissues (P < 0.01), and the inhibition of exosome secretion reversed the promotion effect of autophagy (P < 0.01) and elevated the sensitivity of NPC cells to DDP.

Conclusion: CAF-derived exosomes promote protective autophagy in NPC cells through the Rheb/mTOR axis, and result in DDP resistance in NPC.