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Targeting the tumor stroma with an oncolytic adenovirus secreting a fibroblast activation protein-targeted bispecific T-cell engager Sostoa, Jana de Fajardo Calderón, Carlos Alberto Moreno Olié, Rafael Ramos, Maria D. Farrera Sal, Martí Alemany Bonastre, Ramon Tumors Adenovirus Oncologia Adenoviruses Oncology BackgroundOncolytic virus (OV)-based therapies have an emerging role in the treatment of solid tumors, involving both direct cell lysis and immunogenic cell death. Nonetheless, tumor-associated stroma limits the efficacy of oncolytic viruses by forming a barrier that blocks efficient viral penetration and spread. The stroma also plays a critical role in progression, immunosuppression and invasiveness of cancer. Fibroblast activation protein- (FAP) is highly overexpressed in cancer-associated fibroblasts (CAFs), the main cellular component of tumor stroma, and in this study we assessed whether arming oncolytic adenovirus (OAd) with a FAP-targeting Bispecific T-cell Engager (FBiTE) could retarget infiltrated lymphocytes towards CAFs, enhancing viral spread and T cell-mediated cytotoxicity against the tumor stroma to improve therapeutic activity.MethodsThe bispecific T-cell Engager against FAP was constructed using an anti-human CD3 single-chain variable fragment (scFv) linked to an anti-murine and human FAP scFv. This FBiTE was inserted in the oncolytic adenovirus ICOVIR15K under the control of the major late promoter, generating the ICO15K-FBiTE. ICO15K-FBiTE replication and potency were assessed in HT1080 and A549 tumor cell lines. The expression of the FBiTE and the activation and proliferation of T cells that induced along with the T cell-mediated cytotoxicity of CAFs were evaluated by flow cytometry in vitro.In vivo, T-cell biodistribution and antitumor efficacy studies were conducted in NOD/scid/IL2rg(-)/(-) (NSG) mice.ResultsFBiTE expression did not decrease the infectivity and replication potency of the armed virus. FBiTE-mediated binding of CD3(+) effector T cells and FAP(+) target cells led to T-cell activation, proliferation, and cytotoxicity of FAP-positive cells in vitro. In vivo, FBiTE expression increased intratumoral accumulation of T cells and decreased the level of FAP, a marker of CAFs, in tumors. The antitumor activity of the FBiTE-armed adenovirus was superior to the parental virus.ConclusionsCombination of viral oncolysis of cancer cells and FBiTE-mediated cytotoxicity of FAP-expressing CAFs might be an effective strategy to overcome a key limitation of oncolytic virotherapy, encouraging its further clinical development. 2020-11-02T10:18:22Z 2020-11-02T10:18:22Z 2019-01-25 2020-10-26T09:26:53Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Reproducció del document publicat a: https://doi.org/10.1186/s40425-019-0505-4 Journal For Immunotherapy Of Cancer, 2019-01-25, Vol. 7, num. 19 https://doi.org/10.1186/s40425-019-0505-4 cc by (c) Sostoa, Jana de et al., 2019 http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Bmc Articles publicats en revistes (Institut d'lnvestigació Biomèdica de Bellvitge (IDIBELL))