SUO 2018: Qualitative and Quantitative Evidence of Sipuleucel-T Induced PAP and PA2024 Specific CD8+ Cytolytic Response and its Association with Overall Survival

Phoenix, Arizona ( In this oral abstract presentation, Dr. Kibel presented a multi-institutional analysis assessing sipuleucel-T induced peripheral cellular and humoral immune response to prostatic acid phosphatase and/or PA2024. Previous studies have demonstrated that CD4 and CD8 T cells at the prostate tumor rim after neoadjuvant sipuleucel-T leads to an immune response that may mediate clinical survival benefits. To evaluate this, Kibel’s group evaluated T cell-induced cytolysis and assessed the relationship of PAP and PA2024 specific cytolytic response with survival. Flow cytometry was utilized to assess cytolytic activity with CD8 positive cells measured at baseline, 6 weeks, and 26 weeks. Real time imaging of cytolytic activity was also performed.

Dr. Kibel summarized his groups findings that cytolytic activity showed statistically significant increases at weeks 6 and 26, with the degree of cytolytic activity correlated with overall survival rates. Video evidence was provided at these time points where CD8+ T cells migrated toward PAP target cells, resulting in cell death. Additionally, cell destruction was not observed in cells which did not express PAP.

This study is thought-provoking as it provides evidence and the potential mechanism of action of sipuleucel-T induced PAP specific CT8 T cell mediated responses. Moreover, the degree of OS and magnitude of cytolytic activity has been correlated.

Presented By: Adam S. Kibel, MD

Written by: David B. Cahn, DO, MBS, Fox Chase Cancer Center, Philadelphia, PA, @dbcahn, at the 19th Annual Meeting of the Society of Urologic Oncology (SUO), November
28-30, 2018 – Phoenix, Arizona