FGF2-targeted Timosaponin AIII provokes ER stress and dampens PI3KAKT signaling pathway in breast cancer.

Timosaponin AIII (Tim-AIII), a steroidal saponin derived from Anemarrhena asphodeloides, has emerged as a promising antitumor agent, yet its precise molecular targets and mechanisms in breast cancer remain poorly defined. Here, we identify fibroblast growth factor 2 (FGF2) as a direct binding target of Tim-AIII using a combination of network pharmacology, CETSA, and surface plasmon resonance assays. Mechanistically, Tim-AIII exhibits a dual therapeutic mode of action. First, it induces reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, activating the eIF2α-ATF4-CHOP axis and initiating apoptosis. Second, it dampens the FGF2-FGFR1-PI3K/AKT signaling cascade, thereby inhibiting epithelial-mesenchymal transition (EMT) and suppressing cell migration and invasion. RNA sequencing and enrichment analyses confirm that Tim-AIII regulates critical oncogenic pathways, including ER stress, calcium signaling, and PI3K/AKT. In vivo evaluations demonstrate that Tim-AIII significantly reduces tumor growth without detectable systemic toxicity in breast cancer-bearing mice. This study not only elucidates the molecular basis of Tim-AIII's antitumor efficacy but also positions it as a potential targeted therapeutic for breast cancer, with dual action on ERS-induced apoptosis and EMT suppression.