Abstract A16: Expression of PD-L1 and BCG immunotherapy in non-muscle invasive bladder cancer

Abstract

Abstract Background: Immunotherapy based on BCG has been a standard therapy to prevent recurrence and progression in bladder cancer. Activation of immune checkpoints by binding PD-1 to its ligands, PD-L1, is vital for physiologic regulation of immune system. Tumor cells can co-opt the PD-1 pathway to escape from immunosurveillance mechanism. We investigated expression of immune checkpoints and their effects on T cells in bladder cancer. Methods: A panel of transitional cell carcinoma cell lines (UC-3,T24,KU1919 and 253J) and normal human bladder urothelial cells (SVHUC1) were used to evaluate expression of immune checkpoints. Western blot analysis was used for protein expressions from cell lines and qPCR for RNA expression from human bladder tissues. Human bladder cancer/normal paired tissues were obtained at two time points; surgical resection and then after BCG immunotherapy. Immunohistochemical staining was performed to assess infiltration and distribution of CD4+ and CD8+ T cells in bladder tumor tissues and normal bladder tissues. Immune cells were isolated and T cells were isolated by FACS sorting after immune cell isolation from tumor/normal tissues. Results: PD-L1 proteins were highly expressed in bladder cancer cell lines compared to normal bladder epithelial cell line (SVHUC1). In paired human samples (cancer and normal tissues), PD-L1 were also highly expressed in bladder cancer tissues compared with paired normal tissues. Real time RT-PCR confirmed the high expression of PD-L1 in bladder cancer tissues. Interestingly, normal epithelial tissues regenerated after surgical resection of the tumor and BCG immunotherapy had low PD- after surgical resection and BCG immunotherapy while recurred tumor showed high expression of PD-L1. Isolation of TIL and immunohistochemical staining with CD4/CD8 showed that T cells were more infiltrated in bladder cancer tissues compared to paired normal tissues. Mouse bladder tumor model expressing PD-L1 showed increased CD3+CD4+ T cells and Treg cells. Conclusion: PD-L1 are highly expressed in bladder cancer. CD3+CD4+ T cells and Treg cells are highly infiltrated in human and mouse bladder cancer tissues. Our data suggest that PD-L1 might be involved in tumor recurrence after BCG immunotherapy and might be a novel targets in bladder cancer. Citation Format: Jun Hyeok Heo, Hyun A. Jin, You Hyun Kang, Ki Hong Kim, Sung Joon Hong, Kyung Seok Han. Expression of PD-L1 and BCG immunotherapy in non-muscle invasive bladder cancer. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A16.