Background: The cisplatin resistance of non-small cell lung cancer (NSCLC) patients results in low response rate and overall survival rate. Exosomes contribute to pathological processes of multiple cancers.

Objective: In this study, we explored the function and mechanisms of exosomal miR-103a-3p derived from cancer-associated fibroblast (CAF) in cisplatin resistance in NSCLC.

Results: MiR-103a-3p was highly expressed in CAFs and CAF exosomes, and exosomal miR-103a-3p derived from CAFs in NSCLC. CAFs exosomes co-cultured with NSCLC cells promoted miR-103a-3p expression both in NSCLC cells and its exosomes. Functional experiments showed that exo-miR-103a-3p derived from CAFs promoted cisplatin resistance and inhibited apoptosis in NSCLC cells. Pumilio2 (Pum2) bound with miR-103a-3p in cytoplasm and nucleus, and facilitated packaging into CAF-derived exosomes in NSCLC cells. Further analysis showed Bak1 was a direct target of miR-103a-3p, and miR-103a-3p accelerated cisplatin resistance in NSCLC cells via Bak1 downregulation. In vivo tumorigenesis assay showed CAF-derived exosomal miR-103a-3p enhanced cisplatin resistance and inhibited cell apoptosis in NSCLC.

Conclusion: Our study revealed that CAFs-derived exosomal miR-103a-3p promoted cisplatin resistance by suppressing apoptosis via targeting Bak1, which provided a potential therapeutic target for cisplatin resistance in NSCLC.