Abstract 57: Development of anin vitro3D model system for testing PD-1/ PDL-1 immune checkpoint inhibitors

Background Immune checkpoint inhibitors provide a new hope for cancer patients not responding to chemotherapy by removing the tumor protection against immune cell attacks. Nevertheless, only a subset of patients responds well to these therapies, and recent studies demonstrated that the mechanisms of action are more complex than expected, often involving multiple cell types of the immune system. Importantly, for a better understanding and assessment of immune cell eliciting cell tumor death, there is a need to have fully human, complex 3D in vitro models. We developed a 3D tumor-immune cell coculture model and show here acquired insights on the modulatory capacity of immune checkpoint inhibitors. Aim In the present study we have developed a 3D tumor - immune cell coculture model and evaluated its application to study the effect of immune checkpoint inhibitors on tumor viability, cytokine secretion, and immune cell infiltration. Material & Methods GFP-labelled A549 tumor cells were aggregated together with human dermal fibroblast to produce 3D tumor microtissues in Akura 96-well and 384-well format. Immune cells were pre-treated using different activation protocols to induce priming and pT-cell exhaustion. 3D tumor-immune cell cocultures were treated for 10 days with Nivolumab, its corresponding isotype and non-treated controls. Tumor viability was measured by GFP-fluorescence over time. Additionally, we have evaluated the effect of nivolumab by measuring the microtissue size by automatic stage fluorescence microscopy. Cytokine levels of IL-2, TNFα, IFNγ and GS-CSM were measured with a MAGPIXTM Luminex system and were monitored over time. The validation of immune cell infiltration and characterization of tumor and immune cell specific markers was based on histological analysis. Results Based on tumor fluorescence we have shown a superior effect of Nivolumab versus its isotype control antibody on tumor viability at the end of the treatment period. The cytokine analysis of supernatants has shown higher levels of IFNγ and GS-CSM in the wells treated with Nivolumab compared to the isotype control. CoCultures with PBMCs have shown stronger activation upon treatment compared to the T-cells alone. The histological analysis has demonstrated a higher number of T-cell infiltration and activation, as well as a stronger induction of apoptosis in the tumor microtissues treated with Nivolumab. Conclusion In summary, our novel in vitro immuno-oncology model system allows high throughput screening of immune check point inhibitors alone and in combination with other anti-cancer drugs for making it efficient for a broad range of tumor diseases. Citation Format: Nicole Buschmann, Silvan Strebel, Francesca Chiovaro, Patrick Guye, Irina Agarkova. Development of an in vitro 3D model system for testing PD-1/ PDL-1 immune checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 57.