Zhouting Zhu, Wenyan Han, Yufei Deng, Zhaoyang Jia, Gulshanbir Baidwan, Lujing Wu, Shweta Jakhmola, Tongyun Wang, Dhenugen Logeswaran, Jing Wen, Amanda Sun, Bill Bray, Na Li, Lingling Wang, Hui Hui, Jiaqian Wu, Sandip Pravin Patel, Tariq M. Rana
Immune checkpoint therapy (ICT) can induce durable tumor control but is limited by primary and acquired resistance. The mechanisms underlying immune-resistant tumor microenvironments (TMEs) remain incompletely understood. Here we show that deletion of microRNA-25 (miR-25) sensitizes tumors to ICT across multiple syngeneic mouse models. Single-cell transcriptomics reveals that miR-25 deficiency activates innate and humoral immunity by increasing major histocompatibility complex class II (MHC II) expression in tumor-associated macrophages (TAMs) and enhancing classical complement signaling in cancer-associated fibroblasts (CAFs). Complement activation shifts CAFs toward an inflammatory (iCAF) state, reduces suppressive crosstalk with TAMs, and promotes a pro-inflammatory TME. Mechanistically, miR-25 represses Syndecan-3 (SDC3) in response to interferon-γ (IFN-γ). Editing the miR-25 binding site in Sdc3 restores SDC3 expression and overcomes resistance. These findings identify miR-25-mediated SDC3 repression as a driver of immune resistance and suggest strategies to convert immune-cold tumors into ICT-responsive hot tumors, offering avenues to enhance ICT.