Association of increased survival in glioblastoma patients treated with dendritic cell vaccinations and temozolomide with increased activity of NK cells and ABCC3 expression.
ABSTRACT
Background: In the two stage phase I-II study DENDR-I, 24 patients with first diagnosis of glioblastoma (GBM) were treated with DC immunotherapy associated to standard radio-chemotherapy. To go to stage II progression-free survival (PFS) 12 months after surgery (PFS-12) was expected in at least 8 cases. Evidence of immune response was investigated.
Methods: Patients with post-surgery volume ≤ 10 cc underwent leukapheresis before radiotherapy and chemotherapy with temozolomide (TMZ). Three intradermal injections of mature DC loaded with whole tumor lysate were done before and four after adjuvant TMZ.
Results: The treatment was well tolerated. After a median follow up of 18.8 months 10 patients reached PFS12 (responders). Median overall survival (OS) was 19.4 mo comparing favorably with OS expected using the EORTC nomogram model 3 of 13.0 mo (p = 0.01). The immune activation of effector cells was assessed by intracellular staining of interferon-gamma (IFN-γ) in PBLs of 5 responders and 6 non-responders. In responders DC vaccination induced a significant expansion of NK cells producing IFN- γ after the second vaccine (p = 0.02 vs 1st vaccine). NK cells continued to produce high levels of IFN-g in response to and at the end of treatment (P = 0.004, responders vs non-responders). CD8+ T cells underwent a rapid expansion and produced higher levels of IFN-γ compared to baseline (p < 0.02), but after the first administration of adjuvant TMZ primed CD8+ T cells failed to form an effector memory phenotype (CCR7negCD45RAnegCD62Llow/neg).We also studied in human PBL the expression of the multidrug-resistance protein Abcc3, conferring chemotherapy resistance to murine NK cells. Using Real Time-PCR, Abcc3 expression was found higher in responders vs non-responders before and after radiochemotherapy (p = 0.0005 and p = 0.02, respectively) and during vaccination and adjuvant TMZ (p < 0.01).
Conclusions: These findings demonstrate that in DENDR-I patients with longer PFS DC vaccinations increase the number of active NK cells and the expression of Abcc3 and suggest that adjuvant chemotherapy interferes with effector memory formation.