The NET-DNA-CCDC25 inhibitor di-Pal-MTO suppresses tumor progression and promotes the innate immune response

The DNA component of neutrophil extracellular traps (NET-DNA) is associated with cancer metastasis and chemotherapy resistance. However, recent studies have suggested that NET-DNA contributes to the activation of dendritic cells (DCs) and promotes the innate immune response to anticancer immunity. Therefore, exploring therapeutic approaches to inhibit NET-mediated tumor progression while maintaining antitumor immunity is essential. Our groups recently identified CCDC25 as a specific NET-DNA sensor on the cytoplasmic membrane of cancer cells that promotes cancer metastasis. In this study, we performed small-molecule compound screening and revealed that mitoxantrone (MTO) could block the interaction between NET-DNA and CCDC25. Molecular docking results indicated that MTO competed with NET-DNA by binding with the amino acid residues Tyr²⁴ (Y24), Glu²⁵ (E25), and Asp²⁸ (D28) of the crystal structure of CCDC25. More importantly, we conjugated MTO with palmitoleic acids such as di-Pal-MTO to increase its residence time on the cytoplasmic membrane, which increased its inhibitory efficiency and decreased its cytotoxicity. In addition, di-Pal-MTO markedly inhibited the RAC1-CDC42 cascade to alleviate the NET-induced cytoskeleton arrangement and chemotactic migration of cancer cells. In multiple mouse models, di-Pal-MTO can suppress breast cancer metastasis and have synergistic effects with chemotherapeutics. Moreover, di-Pal-MTO promotes NET-DNA-dependent DC activation, leading to the subsequent expression of various chemokines that facilitate the infiltration of CD8⁺ T cells. Overall, we successfully identified a small molecule inhibitor, di-Pal-MTO, with dual effects on tumor repression and the antitumor immune response, which provides a novel therapeutic strategy against breast cancer.