Human Monoclonal Antibody against hIL18 Receptor Accessory Protein Chain Promotes Anti-Tumor Activity in Triple-Negative Breast Cancer.

[OBJECTIVE] Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks effective targeted therapies. The interleukin-18 (IL-18) signaling pathway contributes to cancer progression and poor survival outcomes in several tumor types, including TNBC. IL-18 receptor accessory protein chain (IL-18RAcP), binding to the IL18/IL18R complex, plays a critical role in initiating and transducing IL-18 signaling. Targeting IL-18RAcP with human antibodies may offer a promising therapeutic strategy for TNBC.

[METHODS] Human single-chain variable fragment (scFv) antibodies targeting IL-18RAcP were screened via phage display and characterized using ELISA, SPR, and crystallography. The functional assays that were used included qRT-PCR, MTT, Western blotting, flow cytometry, and xenograft models. Binding interactions were further validated through yeast two-hybrid assays and structural analysis.

[RESULTS] We found that elevated IL-18RAcP expression in TNBC is associated with poor recurrence-free survival (RFS), suggesting its potential as both a clinical marker and a therapeutic target. Using combinatorial scFv antibody phage display libraries, we identified a human monoclonal antibody, scFvAPC10, which binds IL-18RAcP with high affinity. scFvAPC10 significantly inhibits TNBC cell proliferation and reduces tumor growth by inducing apoptosis. Mechanistic studies reveal that scFvAPC10 impairs both NF-B and MAPK signaling pathways. Structural analysis shows that scFvAPC10 interacts with the D1-D2 domains of IL-18RAcP through three hydrogen bonds, confirming the specificity of the interaction.

[CONCLUSIONS] Our findings highlight the therapeutic potential of targeting IL-18RAcP in TNBC through modulation of IL-18/IL-18R-mediated signaling pathways. The development of scFvAPC10 offers a promising approach for novel antibody-based therapies in the treatment of TNBC.