Abstract
The improved survival rate of ovarian cancer (OC) is related to the action of infiltrating cytotoxic T lymphocytes (CTLs). Recently, oncolytic adenoviruses (OAds) have emerged as a key player in treating solid tumors; however, the immunosuppressive tumor microenvironment (TME) and the body-mediated antiviral immune response limit their therapeutic effect. In this study, we tested the hypothesis that bispecific T-cell engagers (BiTEs) could activate and redirect CTLs to increase the anti-tumor effect of OAds. We modified the parental OAd to express a MUC16-targeting BiTE antibody (OAd-MUC16-BiTE), which retained its oncolytic properties and replication ability in vitro. This BiTE secreted from infected tumor cells into the microenvironment binds to MUC16 on target cells and cross-links them to CD3 on T cells, leading to activation, proliferation, and toxicity of T cells against MUC16+ tumor cells. In cell coculture assays, OAd-MUC16-BiTE-mediated oncolysis enhanced T-cell-mediated tumor cell killing and bystander effect. In ex vivo tumor cultures freshly derived from OC patients, OAd-MUC16-BiTE overcame the suppressed immune TME, achieving stronger toxicity than the parental virus. Moreover, in the cell-derived xenograft and patient-derived xenograft model, OAd-MUC16-BiTE showed stronger antitumor activity and increased the number of CTLs, compared with the parental virus. Further, we demonstrated that the OAd-MUC16-BiTE-mediated anti-tumor activity is related to the reversal of the TME and improved MHC I antigen presentation. Overall, our results show how arming OAds with BiTE can overcome limitations in oncolytic virotherapy, yielding a potent therapy that is ready for clinical assessment.