GSH-responsive nanoparticles enhance ovarian cancer chemo-immunotherapy via DNA damage repair pathway inhibition and cGAS-STING pathway activation

Ovarian cancer, especially the drug-resistant subtype, has a treatment response rate of less than 30 %, primarily due to enhanced DNA damage repair mechanisms that reduce the efficacy of chemotherapy. Moreover, the low level of immune cell infiltration in ovarian tumors limits the therapeutic response to immune checkpoint inhibitors (ICIs). Addressing both chemoresistance and immune activation is essential to improve outcomes. DNA-dependent protein kinase catalytic subunit (DNA-PKcs), a critical component of the DNA damage repair pathway, plays a key role in the repair of DNA double-strand breaks (DSBs). Inhibition of DNA-PKcs not only sensitizes tumors to chemotherapy but also activates the cGAS-STING innate immunity pathway. Herein, we developed a glutathione (GSH)-responsive nanoparticle (NP2), self-assembled from a GSH-sensitive doxorubicin prodrug (PHHM-SS-DOX) and a DNA-PKcs inhibitor (AZD7648). NP2 responds to elevated GSH levels in cancer cells and releases DOX and AZD7648. AZD7648 inhibits DNA-PKcs phosphorylation, suppressing the non-homologous end joining (NHEJ) pathway and exacerbating doxorubicin-induced DSBs. Then sustained accumulation of dsDNA further activates the cGAS-STING pathway. In vivo, NP2 demonstrated significant tumor growth inhibition and modulation of antitumor immunity. It activated the cGAS-STING pathway and enhanced the release of inflammatory cytokines, maturation of dendritic cells, infiltration of CD8⁺ T cells, and polarization of tumor-associated macrophages toward the pro-inflammatory M1 phenotype. These effects reprogrammed the ovarian cancer microenvironment into an "immune-hot" tumor, significantly improving the response to ICIs. This strategy provides a novel therapeutic avenue to overcome chemoresistance and enhance the efficacy of immunotherapy in ovarian cancer.