Abstract 3972: Investigation of tumor intrinsic PD1/PD-L1 in canine urothelial carcinomas as a spontaneous translational model for human invasive bladder cancer

Abstract

Abstract Urothelial carcinoma (UC) is the fourth most common malignancy in human and the most common form of urinary bladder cancer in dogs. This neoplasia tends to be invasive at advanced stages hence novel therapeutic approaches are urgently needed. As urothelial carcinomas share many similarities between the dog and human in the immunological responses, dogs are a perfect model for studying immunotherapeutic approaches. Recently immuno-checkpoint blockade using anti-PD1/PD-L1 antibodies have shown a promising effect and durable responses in the treatment of UC. Although until recently the PD1/PD-L1 axis was considered to be mostly affecting immune cells, recent reports identified, that PD-1/PD-L1 interaction is also capable of pro-tumorigenic signaling in melanoma and other cancers. Yet, little is known regarding this phenomenon in UC. In our study, we aim at identification of the expression level of PD-1 in canine UC and subsequently characterize the effect of overexpression and CRISPR-based knock-out of PD-1 and PD-L1. Using flow cytometry and immunocytochemistry, we identified that PD-1 is expressed on the surface of canine UC cell line. Interestingly, incubation with high concentration of PD-1 antibody decreased the proliferation rate of the tumor. After transfection with a PD-1 overexpression vector, we notice a significant morphological change and decrease in proliferation and colony formation. Our result provides the first report on PD-1 intrinsic signaling play as an important role in tumor growth of canine UC and thus may also be responsive to immune checkpoint blockade. The effect identified further strengthens the dog as a potential translational model for UC immunotherapy. Citation Format: Yu Jia Wang, Katarzyna Pietrzak, Mikolaj Kocikowski, David Argyle, Ted Hupp, Maciej Parys. Investigation of tumor intrinsic PD1/PD-L1 in canine urothelial carcinomas as a spontaneous translational model for human invasive bladder cancer [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 3972.