A Multifunctional Exosome with Dual Homeostasis Disruption Augments cGAS-STING-Mediated Tumor Immunotherapy by Boosting Ferroptosis.

Ferroptosis has shown great potential in activating antitumor immunity. However, the cunning tumor cells can evade ferroptosis by increasing the efflux of iron and promoting the production of the reductant glutathione to mitigate oxidative stress. Herein, a multifunctional exosome loaded with manganese-doped iron oxide nanoparticles (MnIO), GW4869, and l-buthionine sulfoximine (BSO) is developed to disrupt the iron metabolism homeostasis and redox homeostasis to enhance tumor immunotherapy. The efficient transport of MnIO by exosomes and the inhibition of iron exocytosis by GW4869 led to a high retention of up to 29.57% ID/g for iron in the tumors. Such a high retention of iron, in combination with the BSO-induced disruption of the redox homeostasis, effectively promotes the ferroptosis of tumor cells. Consequently, the multifunctional exosomes that noticeably enhance ferroptosis by dual homeostasis disruption provoke the cGAS-STING-based antitumor immune response and effectively suppress tumor growth and lung metastasis in orthotopic breast cancer.