A Novel NO Donor 3A72 Activates Mitochondrial-Associated Endoplasmic Reticulum Membrane Structures to Induce Ferroptosis in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) remains a major clinical challenge due to a lack of effective interventions and severe drug resistance. Disrupting tumor metabolism using nitric oxide (NO) donors to drive ferroptosis represents a promising therapeutic strategy. Here, we developed 3A72, a novel furan-coumarin-based NO donor with potent anti-TNBC efficacy. In vitro and in vivo studies demonstrated that 3A72 significantly suppresses TNBC cell proliferation and restricts xenograft tumor growth. Notably, its efficacy matches the first-line drug paclitaxel but with enhanced safety and reduced systemic toxicity. Mechanistically, 3A72 induces ferroptosis in triple negative breast cancer (TNBC) cells via a synergistic dual-pathway mechanism. Initially, 3A72 releases intracellular NO to trigger cytoplasmic calcium overload, followed by high-affinity binding to both inositol 1,4,5-trisphosphate receptor (IPR) and acyl-CoA synthetase long-chain family member 4 (ACSL4). Binding to IP3R provokes mitochondrial calcium overload and a massive burst of reactive oxygen species (ROS), while concurrent ACSL4 activation drives essential membrane phospholipid remodeling. Crucially, our transcriptomic and structural predictions reveal that while ACSL4 exhibits a broader distribution across organelle membranes, its functional association with IP3R spatially converges at the endoplasmic reticulum membranes associated with mitochondria (MAMs). This subcellular niche closely couples IPR-mediated ROS generation with ACSL4-driven lipid remodeling, accelerating lethal malondialdehyde (MDA) accumulation and triggering irreversible ferroptosis. Overall, these findings highlight the MAMs calcium-lipid metabolic hub as a promising structural scaffold for antitumor drug development.