Breast cancer cells are characterized by heightened autophagy, which impairs tumor-associated antigen presentation and represents a significant barrier to the antitumor immunity. In this study, a PD-L1-targeting autophagy modulator (PFC@CQ) is fabricated to activate the photoimmunotherapy against breast cancer. Specifically, the hydrophobic photosensitizer protoporphyrin IX (PpIX) is covalently linked to the hydrophobic peptide FFVLK and a PD-L1-targeting peptide sequence CLQKTPKQC, resulting in the formation of an amphiphilic photosensitizer-peptide conjugate (PpIX-FFVLK-CLQKTPKQC, called PFC), which is capable of encapsulating the autophagy inhibitor chloroquine (CQ). PFC@CQ can not only facilitate the targeted drug codelivery to PD-L1-overexpressing breast cancer cells, but also effectively disrupt their immune evasion by blocking PD-1/PD-L1 pathway. Upon light irradiation, the photodynamic therapy (PDT) of PFC@CQ induces tumor cell destruction and immunogenic cell death (ICD), causing the release of damage-associated molecular patterns (DAMPs). Simultaneously, PFC@CQ can inhibit autophagy pathway to mediate the upregulation of MHC-I, thereby enhancing antigen presentation. This cascade immunomodulation promotes the dendritic cell maturation and CD8⁺ T cell activation, leading to a synergistic suppression of both primary and metastatic tumors. This work introduces an innovative autophagy modulation strategy with potent immunomodulatory capability, demonstrating a potential to trigger systemic antitumor immune responses through local treatment.

Keywords: MHC-I; autophagy regulation; drug delivery; immunogenic cell death; photoimmunotherapy.