17-DMAG-Loaded HER2-Targeted Extracellular Vesicles Induce PARP/Caspase3-Mediated Apoptosis in Gastric Carcinoma

Gastric cancer remains a major clinical challenge, underscoring the need for more effective drug delivery strategies. Approximately 10-20% of gastric cancers overexpress HER2, conferring aggressive tumor characteristics and poor survival, yet resistance to trastuzumab-based targeted therapy and limited intratumoral antibody penetration continue to restrict clinical outcomes. This study evaluated HER2-targeted exosomes as a delivery platform. Exosomes were engineered to express the p51 peptide, a high-affinity HER2-binding ligand, and loaded with 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), a potent HSP90 inhibitor. The cellular uptake and antitumor efficacy of p51-Exo^17-DMAG were assessed in vitro using NCI-N87 and AGS cells and in vivo using a mouse xenograft model. p51-modified exosomes exhibited superior HER2 specific uptake. Treatment with p51-Exo^17-DMAG significantly increased apoptosis, as demonstrated by elevated PARP and caspase3 cleavage, and downregulated oncogenic signaling molecules, including p-AKT, CDK2, VEGF, and c-Myc. Furthermore, p51-Exo^17-DMAG increased the number of TUNEL-positive cells. In the NCI-N87 xenograft model, systemic administration of p51-Exo^17-DMAG significantly inhibited tumor growth without toxicity or histological damage to major organs. Tumor analysis confirmed increased apoptosis and reduced proliferation in vivo. These findings demonstrate that p51-engineered exosomes provide an efficient, selective, and safe platform for HER2-targeted delivery of 17-DMAG, offering a promising precision medicine strategy for HER2-positive gastric cancer.