Preclinical investigation of combined gene-mediated cytotoxic immunotherapy and immune checkpoint blockade in glioblastoma

MC Speranza, C Passaro, F Ricklefs, K Kasai… - Neuro …, 2018 - academic.oup.com
MC Speranza, C Passaro, F Ricklefs, K Kasai, SR Klein, H Nakashima, JK Kaufmann…
Neuro-oncology, 2018academic.oup.com
Background Combined immunotherapy approaches are promising cancer treatments. We
evaluated anti–programmed cell death protein 1 (PD-1) treatment combined with gene-
mediated cytotoxic immunotherapy (GMCI) performed by intratumoral injection of a prodrug
metabolizing nonreplicating adenovirus (AdV-tk), providing in situ chemotherapy and
immune stimulation. Methods The effects of GMCI on PD ligand 1 (PD-L1) expression in
glioblastoma were investigated in vitro and in vivo. The efficacy of the combination was …
Background
Combined immunotherapy approaches are promising cancer treatments. We evaluated anti–programmed cell death protein 1 (PD-1) treatment combined with gene-mediated cytotoxic immunotherapy (GMCI) performed by intratumoral injection of a prodrug metabolizing nonreplicating adenovirus (AdV-tk), providing in situ chemotherapy and immune stimulation.
Methods
The effects of GMCI on PD ligand 1 (PD-L1) expression in glioblastoma were investigated in vitro and in vivo. The efficacy of the combination was investigated in 2 syngeneic mouse glioblastoma models (GL261 and CT-2A). Immune infiltrates were analyzed by flow cytometry.
Results
GMCI upregulated PD-L1 expression in vitro and in vivo. Both GMCI and anti–PD-1 increased intratumoral T-cell infiltration. A higher percentage of long-term survivors was observed in mice treated with combined GMCI/anti–PD-1 relative to single treatments. Long-term survivors were protected from tumor rechallenge, demonstrating durable memory antitumor immunity. GMCI led to elevated interferon gamma positive T cells and a lower proportion of exhausted double positive PD1+TIM+CD8+ T cells. GMCI also increased PD-L1 levels on tumor cells and infiltrating macrophages/microglia. Our data suggest that anti–PD-1 treatment improves the effectiveness of GMCI by overcoming interferon-induced PD-L1–mediated inhibitory signals, and GMCI improves anti–PD-1 efficacy by increasing tumor-infiltrating T-cell activation.
Conclusions
Our data show that the GMCI/anti–PD-1 combination is well tolerated and effective in glioblastoma mouse models. These results support evaluation of this combination in glioblastoma patients.
Oxford University Press