Nanoadjuvant-based membrane poration boosts antitumor immunity via modulating mitochondrial metabolism to downregulate PD-L1 and upregulate STING.

Abstract

Activation of the stimulator of interferon genes (STING) pathway represents a promising strategy for cancer immunotherapy. However, clinical translation of STING agonists has been hampered by inefficient intracellular delivery and compensatory upregulation of the negative feedback immune checkpoint molecule of programmed death-ligand 1 (PD-L1). In addition, nuclear PD-L1 induces resistance by transcriptionally repressing STING, but clinically approved anti-PD-L1 antibodies cannot target nuclear PD-L1, limiting their efficacy. Here, we developed a nanoadjuvant (cGAMP + Halicin@PFDBA) to potentiate STING-mediated antitumor immunity by strongly downregulating PD-L1 through the inhibition of mitochondrial metabolism. The nanoadjuvant targets sialic acid overexpressed on tumor cell surfaces to enable delivery via membrane perforation of the STING agonist 2'3'-cGAMP to activate innate immunity and halicin to inhibit mitochondrial oxidative phosphorylation, thereby activating AMPK signaling, which downregulates PD-L1 and increases STING protein levels. In tumors with intrinsically low STING expression, upregulation of STING is crucial for effective pathway activation. This dual modulation of metabolic and immune pathways elicits robust antitumor immunity. The administration of the nanoadjuvant to mice results in the complete regression of more than 60% of both subcutaneous and orthotopic tumors and abrogates deep tissue metastases. These results demonstrate that the modulation of mitochondrial metabolism is a promising strategy to overcome the current limitations of STING pathway immunotherapy.