Abstract A031: CD8+T cells fail to form an effector memory in glioblastoma patients treated with dendritic cell immunotherapy in combination with chemotherapy

Abstract

Abstract A critical requirement of an efficient cancer immunotherapy is the generation of long-lasting, specific memory. In a clinical trial active at Istituto Besta, first diagnosis glioblastoma (GBM) patients, with post-surgery volume ≤10 cc, underwent leukapheresis before radiotherapy and chemotherapy with the alkylating agent temozolomide (TMZ). Three intradermal injections of mature dendritic cells (DCs) loaded by autologous tumor lysates were done before adjuvant chemotherapy. Subsequent 4 injections were performed in association with six cycles of adjuvant TMZ. Peripheral blood lymphocytes (PBLs) were analyzed by flow cytometry to characterize immune response before and after DC vaccines. The ratio of vaccination/baseline frequencies and counts (V/B ratio) of all of the immunological parameters for each patient was calculated, and the median of all of the observations used as the cut off value to separate patients. V/B ratio was correlated with the progression free survival (PFS) of each patient. Preliminary results from the interim analysis on 24 patients showed that an increased NK, but not CD8+ T cell response was significantly associated with prolonged survival (p<0.005). In a group of responder patients (PFS>12), during the first three vaccines, CD8+ T cells underwent a rapid expansion and produced higher levels of IFN-γ compared to the baseline (p<0.02). After the third vaccine and TMZ administration, primed CD8+ T cells failed to form an effector memory phenotype (CCR7negCD45RAnegCD62Llow/neg). Our results support a possible interference of adjuvant chemotherapy on effector memory formation. Further investigations are required to understand how memory T cells behave in response to repeated exposure to TMZ. Citation Format: Serena Pellegatta, Marica Eoli, Elena Anghileri, Sara Pessina, Carlo Antozzi, Simona Frigerio, Gabriele Cantini, Maria Grazia Bruzzone, Bianca Pollo, Eugenio A. Parati, Gaetano Finocchiaro. CD8+T cells fail to form an effector memory in glioblastoma patients treated with dendritic cell immunotherapy in combination with chemotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A031.