Background: Immunotherapy based on BCG has been a standard therapy to prevent tumor recurrence and progression in bladder cancer. Activation of immune checkpoint pathways by binding of PD-1 to its ligands, PD-L1 or PD-L2, is vital for the physiologic regulation of the immune system. Tumor cells can at times 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, K1919 and 253J) and normal human bladder urothelial cells (SVHUC1) were used to evaluate expression of immune checkpoints including PD-1, PDL1, PD-L2 and CTLA-4. 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 and PD-L2 proteins were highly expressed in bladder cancer cell lines compared to normal bladder epithelial cell line (SVHUC-1). In paired human samples (cancer and normal tissues), PD-L1 and 2 were also highly expressed in bladder cancer tissues compared with paired normal tissues. Real time RT-PCR comfirmed the high expression of PD-L1/2 in bladder cancer tissues. Interestingly, normal epithelial tissues regenerated after surgical resection of the tumor and BCG immunotherapy had low PD-L1/2 expression while recurred tissues after surgical resection of the tumor and BCG had high expression of PD-L1/2, which suggest that PD-L1/2 might be involved in tumor relapse after surgical resection and BCG immunotherapy. Immunohistochemical staining with CD4 and CD8 showed that the number of T cells was in bladder cancer tissues compared with paired normal tissues regardless of PD-L1/2 expression. T lymphocytes isolated from human bladder cancer tissues and paired normal tissues showed that infiltrating T cell function is significantly deteriorated in bladder cancer tissue compared with cells from paired normal tissues.
Conclusions: PD-L1 and PD-L2 are highly expressed in bladder cancer and though to be involved in relapse after BCG intravesical immunotherapy through suppressing infiltrating T cell function. Our data suggest that immunecheckpoint might be a novel targets in bladder cancer.
Citation Format: Jun Hyeok Heo, Hye Young Kim, Ki Chung Park, Sung Joon Hong, Kang Su Cho, Kyung Seok Han. Expression of programmed cell death ligand 1/2 and BCG immunotherapy in bladder cancer. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B41.
- ©2015 American Association for Cancer Research.