Vaccination with Irradiated Autologous Tumor Cells Mixed with Irradiated GM-K562 Cells Provokes Lymphocyte Activation and Specific Antitumor Immunity in Patients with Recurrent Glioblastoma

Abstract

We have previously reported the safety and feasibility of vaccinating recurrent malignant glioma patients with irradiated autologous cells mixed with irradiated GM-K562 cells. Here, we report the impact of vaccination on the expression of T-lymphocyte co-stimulatory and co-inbhibitory molecules as well as on regulatory T-lymphocytes. Furthermore, we explored the impact of vaccination on patient humoral immune responses with particular attention to antibody titers against molecules associated with tumor angiogenesis. Blood was collected from 9 of 10 treated patients at regular intervals and submitted for immune analysis. 5-color flow cytometry was employed after staining of whole blood by an immunophenotyping antibody panel. Antibody titers to tumor-associated antigens were measured by ELISA of patient plasma - all assays were performed in duplicate. Treatment-associated change in percent expression of various markers was analyzed via the non-parametric sign-rank test. p < 0.05 was considered statistically significant. In patients undergoing craniotomy for recurrent malignant glioma, vaccination with irradiated autologous tumor cells and irradiated GM-K562 cells was associated with statistically significant increases in CD4+ T-lymphocyte expression of costimulatory molecules OX40 and 4-1BB (CD137). CD8+ T-lymphocytes saw increased expression of 4-1BB as well. Likewise, there were increases in CD4+ T-lymphocyte expression of CTLA-4, PD1, and FOXP3 - each of which is associated with negative immune regulation and are targetable with existing monoclonal antibodies. 7 of 9 patients had marked treatment-driven increases in antibody titers to Angiopoietin 2, which may represent a novel glioma vasculature-associated antigen. Vaccination with irradiated autologous tumor cells mixed with irradiated GM-K562 cells in patients with recurrent malignant glioma is biologically active and activates both T-lymphoctes and humoral antitumor immunity. Vaccine-induced expression of costimulatory molecules may provide the rationale for combination therapies with either co-stimulatory receptor agonist or co-inhibitory receptor antagonist molecules.