Effect of armed oncolytic adenovirus on immunotherapy for primary and metastatic brain tumors.

Abstract

2048 Background: Oncolytic viruses have shown promise in clinical trials for solid tumors, including glioma and melanoma, but only a subset of patients benefits. We previously showed that arming the oncolytic adenovirus Delta-24-RGD with OX40L can enhance antitumor immunity. To further boost efficacy, we developed Delta-24-RGDOX-IL15, co-expressing OX40L and IL-15, and tested it in preclinical models of primary and metastatic brain tumors. Methods: To evaluate IL-15 and its receptor (IL15RA) expression in patients with glioma and melanoma, we conducted gene expression and survival analysis using the GEPIA web server, integrating RNA sequencing data from TCGA and GTEx. Transgene expression in Delta-24-RGDOX-IL15 was assessed via flow cytometry and ELISA, while viral potency was evaluated using replication and cell viability assays. Anti-tumor activity was tested in syngeneic intracranial models derived from mouse diffuse midline (DMG) glioma and melanoma cell lines in C57BL/6 mice, both of which expressed GD2 and luciferase. Tumor growth was monitored with bioluminescent imaging, survival with Kaplan-Meier analysis, and immune profiling of the tumor microenvironment using flow cytometry. Results: GEPIA analysis showed that melanoma had higher expression of IL-15 and IL-15RA compared to glioma. In melanoma patients, higher expression of IL-15RA or IL-15 was linked to better overall survival (P < 0.005), while no survival difference was found in patients with glioma. Delta-24-RGDOX-IL15 infected and co-expressed OX40L and IL-15 effectively in mouse glioma and melanoma cells, and induced potent oncolysis. Delta-24-RGDOX-IL15-infected tumor cells significantly enhanced the oncolysis activity of GD2 CAR T cells in culture. Intratumoral injection of the virus also resulted in better tumor reduction and improved survival in C57BL6 mice with gliomas derived from mouse DMG cells while no significant toxicity was observed. Additionally, locoregional therapy with Delta-24-RGDOX-IL15 induced a systemic inflammatory response in the tumor microenvironment, characterized by increased frequency of T cells and reduced that of myeloid cells. Conclusions: Higher expression of IL-15/IL-15RA is associated with better survival in patients with melanoma. Delta-24-RGDOX-IL15 demonstrates potent oncolytic activity in both glioma and melanoma cell lines. In the intracranial brain tumor mouse model, it exhibited promising anti-tumor effects with enhanced T cell stimulation and minimal toxicity. Delta-24-RGDOX-IL15 is a promising candidate for combination with cellular therapies in both primary and metastatic brain tumors.