Cancer-associated fibroblast-derived miR-486-3p suppresses bladder cancer by targeting the HER-2/MDK-NCL axis

Cancer-associated fibroblasts (CAFs) are key stromal components of the tumor microenvironment (TME), but their potential to deliver the tumor-suppressive signals remains unclear. Here, through integrative single-cell and transcriptomic analyses, we identify miR-486-3p, localized to CAFs and consistent with exosomal delivery, as a critical suppressor of bladder cancer (BLCA) progression. miR-486-3p was consistently downregulated in BLCA tissues and correlated with favorable overall survival, while its direct target HER-2 was upregulated and linked to poor prognosis. Mechanistically, miR-486-3p directly bound the 3′-UTR of HER-2 mRNA, and HER-2 reconstitution abrogated the tumor-suppressive effects of miR-486-3p on proliferation, migration, invasion, and apoptosis. Single-cell RNA-seq of 58,982 cells localized HER-2 and related targets exclusively to malignant populations, with a HER-2-high subpopulation exhibiting hyper-proliferative signatures. Computational screening identified zongertinib as a high-affinity HER-2 inhibitor with favorable pharmacokinetics. Clinically, low miR-486-3p or high HER-2 expression predicted immune-cold phenotypes and resistance to PD-1/PD-L1 blockade in immunotherapy cohorts. Collectively, this study uncovers a stromal-epithelial checkpoint in which miR-486-3p, with its expression localized to CAFs and likely delivered via exosomes, suppresses BLCA by targeting the HER-2/MDK-NCL axis, with implications for prognosis, immune evasion, and HER-2-directed therapy.