An immune-activated co-culture model of patient-derived gastric cancer organoids and peripheral blood mononuclear...

Selecting effective chemotherapy after immunotherapy remains a major clinical challenge in advanced gastric cancer because patient responses are highly heterogeneous. A major obstacle is the lack of personalized preclinical models that faithfully recapitulate the immune-activated tumor microenvironment (TME) following immunotherapy and enable evaluation of subsequent chemotherapy responses while preserving immune-tumor interactions. Here, we developed an immune-activated co-culture model comprising patient-derived gastric cancer organoids and autologous peripheral blood mononuclear cells (PBMCs). Immune activation was achieved using anti-PD-1-loaded gold nanocages (aPD-1@Au NCs), which integrate near-infrared-triggered photothermal tumor ablation with sustained anti-PD-1-mediated immune modulation. The resulting model recapitulates key features of the post-immunotherapy TME, including enhanced immune-cell infiltration, increased tumor-cell apoptosis, and CD8⁺ T-cell activation. We then applied this model to evaluate five clinically relevant chemotherapeutic agents, including oxaliplatin, irinotecan, fluorouracil, doxorubicin, and docetaxel, for personalized chemotherapy screening after immunotherapy. Compared with monoculture organoids or non-activated co-cultures, the immune-activated model revealed drug-specific differences in tumor-killing efficacy, immune-mediated chemosensitization, and PBMC toxicity. Among the tested agents, oxaliplatin showed the strongest immune-mediated chemosensitization, whereas docetaxel achieved favorable tumor cell killing with relatively low immunotoxicity. These findings demonstrate that chemotherapy responses after immune activation are highly drug-specific, underscoring the importance of personalized chemotherapy selection following immunotherapy. As a proof-of-concept study, this work establishes an immune-activated patient-derived gastric cancer organoid-PBMC co-culture model that partially recapitulates the post-immunotherapy TME. This model provides a promising framework for developing personalized chemotherapy screening strategies after immunotherapy. STATEMENT OF SIGNIFICANCE: Selecting effective chemotherapy after immunotherapy remains a major challenge in advanced gastric cancer because of substantial interpatient heterogeneity. Progress in personalized treatment is limited by the lack of preclinical models that faithfully recapitulate the post-immunotherapy tumor microenvironment (TME). Here, we developed an immune-activated co-culture model integrating patient-derived gastric cancer organoids with autologous peripheral blood mononuclear cells (PBMCs). Immune activation was achieved using anti-PD-1-loaded gold nanocages (aPD-1@Au NCs), which combine near-infrared-triggered photothermal tumor ablation with sustained aPD-1-mediated immune modulation. This platform preserves patient-specific tumor characteristics while capturing key immune-tumor interactions following immunotherapy. Using this model, we evaluated five clinically relevant chemotherapeutic agents and identified distinct drug-specific differences in tumor-killing efficacy, immune-mediated chemosensitization, and immunotoxicity. As a proof-of-concept study, this work establishes a promising framework for personalized chemotherapy screening after immunotherapy and supports the development of precision treatment strategies for gastric cancer.