Oncolytic adenovirus therapy is believed to be a promising way to treat cancer patients. To be able to target tumor cells with an oncolytic adenovirus, expression of the adenovirus receptor on the tumor cell is essential. Different adenovirus types bind to different receptors on the cell, of which the expression can vary between tumor types. Pre-existing neutralizing immunity to human adenovirus species C type 5 (HAdV-C5) has hampered its therapeutic efficacy in clinical trials, hence several adenoviral vectors from different species are currently being developed as a means to evade pre-existing immunity. Therefore, knowledge on the expression of appropriate adenovirus receptors on tumor cells is important. This could aid in determining which tumor types would benefit most from treatment with a certain oncolytic adenovirus type. This review provides an overview of the known receptors for human adenoviruses and how their expression on tumor cells might be differentially regulated compared to healthy tissue, before and after standardized anticancer treatments. Mechanisms behind the up- or downregulation of adenovirus receptor expression are discussed, which could be used to find new targets for combination therapy to enhance the efficacy of oncolytic adenovirus therapy. Additionally, the utility of the adenovirus receptors in oncolytic virotherapy is examined, including their role in viral spread, which might even surpass their function as primary entry receptors. Finally, future directions are offered regarding the selection of adenovirus types to be used in oncolytic adenovirus therapy in the fight against cancer.

Immunotherapy, including the use of immune checkpoint inhibitors, has emerged as an attractive strategy for treatment of various cancers. Unfortunately, less than half of the bladder cancer patients demonstrate clinical benefit from immune checkpoint inhibitors. Novel therapeutic approaches such as oncolytic virotherapy may unleash the full potential of immunotherapy. Oncolytic viruses display tumor-lysing properties, while leaving normal cells unharmed. Besides the direct oncolytic effects, oncolytic viruses are capable of inducing systemic anti-tumor immune responses, thereby representing a promising anti-cancer therapy. In our multi-center oncolytic viro-immunotherapy (OVIT) consortium we evaluate and compare the oncolytic and immunomodulatory properties of several oncolytic viruses (reoviruses, novel non-human primate Adenoviruses, Newcastle disease virus), develop tools to predict oncolytic virus efficacy and design strategies to personalize oncolytic virus therapy. In this study we evaluated and compared the direct oncolytic and indirect immunostimulatory effects of wildtype reovirus R124 and mutant reovirus jin-3 in human bladder cancer. Mutant reovirus jin-3 harbors mutations in the spike protein Sigma-1 and can infect cells independently of junction adhesion molecule A (JAM-A) expression on the tumor cell surface. For this, we exploited multiple preclinical bladder cancer models, including patient-derived tumor models (e.g. 3D cultures) and ex-vivo cultured tumor tissue slices. Both R124 and jin-3 reoviruses could infect, replicate and induce cell death in a panel of 2D and 3D cultured bladder cancer cells lines with a basal, luminal or mixed phenotype. Furthermore, the viruses were capable of infecting the tumor cells and induced cell death in ex-vivo cultured tumor tissue slices. Reovirus mutant jin-3, and to a lesser extent R124, strongly induced immunogenic cell death markers (HMGB1, cell surface expression of calreticulin, HSP90), interferon-stimulated genes, and inflammatory cytokines (IFNβ, CXCL10, TNFα) in human bladder cancer cells. Co-culture of reovirus-infected murine bladder cancer cells MB-49 with murine splenocytes resulted in increased activation markers of dendritic cells and NK cells. In conclusion, reoviruses display oncolytic properties in multiple preclinical models of human bladder cancer. Mutant reovirus jin-3 displays more potent immunomodulatory responses in preclinical bladder cancer models compared with wildtype reovirus R124. Therefore, jin-3 represents an attractive candidate for clinical translation. Citation Format: Arjanneke F. Van De Merbel, Maaike H. van der Mark, Thijs J. Janssen, Lobke C. Hensen, Diana J. van den Wollenberg, Rob C. Hoeben, Rob F. Bevers, Rob C. Pelger, Gabri van der Pluijm, Geertje van der Horst. Mammalian orthoreoviruses R124 and jin-3 demonstrate oncolytic and immune-stimulatory effects in human preclinical bladder cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1845.