MicroRNA core machinery maintains mitochondrial integrity to empower cancer escape from natural killer cell cytotoxicity

Natural killer (NK) cells offer a promising off-the-shelf platform for cancer immunotherapy, yet their clinical efficacy is often limited by tumor-intrinsic resistance. Here, we show that loss of core microRNA (miRNA) machinery components, Argonaute‑2 (AGO2) or Ankyrin Repeat Domain 52 (ANKRD52), renders tumor cells hypersensitive to NK cell-mediated killing in both co-culture and xenograft models. Mechanistically, genetic ablation of Ago2 or Ankrd52 impairs miRNA-mediated silencing of critical mitochondrial apoptotic regulators and NK-cell-associated ligands in tumor cells, exemplified by the disrupted repression of pro-apoptotic Bim transcripts by miR-24 and miR-29b, thereby unleashing rapid TNF-α-driven apoptosis. Additionally, metabolic and ultrastructural analyses demonstrate collapsed membrane potential, diminished ATP levels, and fragmented mitochondria in Ago2- or Ankrd52-mutant tumor cells, accompanied by a lower apoptotic threshold upon TNF-α or NK cell challenge. Genome‑wide CRISPR library screen further revealed a selective fitness dependency on mitochondrial electron‑transport and ATP‑synthase genes in mutant tumor cells. Collectively, these findings define defective miRNA machinery as a tumor‑intrinsic vulnerability that couples mitochondrial fragility with increased NK-mediated cytotoxicity, nominate miRNA‑pathway status as a predictive biomarker, and propose that co‑targeting mitochondrial metabolism or apoptosis may potentiate NK‑cell therapies.