P53-armed Oncolytic Adenovirus Enhances the Efficacy of PD-1 Blockade in Neuroblastoma by Inducing Immunogenic Cell Death

Background/Aim: Neuroblastoma (NB) is a primary malignant tumor of the peripheral sympathetic nervous system. Although immunotherapy with immune checkpoint inhibitors (ICIs) targeting programmed cell death 1 (PD-1)/PD ligand 1 (PD-L1) has emerged as novel antitumor therapy, high-risk NB tumors are refractory to ICI therapy. Oncolytic virotherapy is expected to potentiate the antitumor immune response by inducing immunogenic cell death (ICD). In the present study, we assessed the therapeutic potential of OBP-301 and OBP-702, telomerase-specific oncolytic adenoviruses, for the induction of ICD and combined effect with PD-1 blockade against NB cells.
Materials and Methods: The cytopathic activity of OBP-301 and OBP-702 was assessed using three human MYCN-amplified NB cell lines (IMR-32, LA-N-5, and NB-1) and a murine non-MYCN-amplified NB cell line (Neuro-2a). Virus-mediated antitumor effect was assessed by analyzing cell viability, secretion of extracellular adenosine triphosphate (ATP) and high-mobility group box protein B1 (HMGB1), apoptosis, autophagy, and PD-L1 levels. A subcutaneous Neuro-2a tumor model was used to evaluate the in vivo antitumor effect of combination therapy with OBP-702 and anti-PD-1 antibody.
Results: OBP-702 exhibited stronger cytopathic activity, inducing ICD with secretion of ATP and HMGB1, compared to OBP-301 in human and murine NB cells. OBP-301 and OBP-702 increased apoptosis, autophagy, and PD-L1 expression in murine NB cells. Moreover, OBP-702 significantly prolonged the survival of tumor-bearing mice compared to monotherapy with PD-1 blockade.
Conclusion: OBP-702 is a promising antitumor strategy to promote the antitumor effect of ICIs by inducing ICD against NB tumors.