Abstract 689: Immune checkpoint targeting to improve immunotherapy in neuroblastoma

Abstract

Abstract Neuroblastoma (NB) is the most common extracranial solid tumor in children. Current treatments accounts only for at the most 40% of survival rate in high-risk NB patients. Hence, there is a need to develop new strategies that disrupt immunosuppressive signals in the tumor microenvironment in order to achieve robust anti-tumor immune responses. Co-inhibitory signals through receptors such as PD-1 can lead to the inactivation of T cells. On the other hand, co-stimulatory signals through receptors such as 41BB can enhance T cell activity against tumors. These receptors can serve as tools to develop strategies to optimize and enhance T cell anti-tumor functions. In this study, we used 9464D NB tumor mouse model to evaluate antibody treatment as a possible immunotherapy strategy. We further examine the infiltration and function of T cells after targeting checkpoints in 9464D NB tumor bearing mice. Blockade of various receptors in mice bearing 9464D tumor showed that anti-PD1 and anti-41BB delayed tumor growth. Combination therapy with anti-PD1 and anti-41BB antibodies significantly delayed tumor growth compared to single antibody treatment. This combination therapy led to a higher infiltration of CD8+ cells within the tumor. Splenocytes from 9464D tumor bearing mice treated with anti-PD1 and anti-41BB are tumor specific. In conclusion, our findings intend to design the best complement therapy to improve survival of patients with advanced NB. Our data demonstrates that tumor reactive T cells in NB tumors may express different checkpoint receptors including PD1 and 41BB. 9464D tumor bearing mice that received a combination of anti-PD1 and anti-41BB antibodies have smaller tumor size compared to single antibody therapy. Future direction includes examine T cells activation after combination therapy of BMT and immunecheckpoint targeting. Also we want to test adoptive transfer of T cells in tumor bearing mice after BMT. Further we want to measure the infiltration of other immune cells, such as myeloid cells and Tregs, in the tumor environment and possible target immune suppressive populations to see the effects in tumor growth. Citation Format: Myrna L. Ortiz-Ruiz. Immune checkpoint targeting to improve immunotherapy in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 689. doi:10.1158/1538-7445.AM2017-689