ProCure Program, IDIBELL-Institut Català d'Oncologia, l'Hospitalet de Llobregat, El Prat de Llobregat, Spain.
VCN Biosciences S.L., Grifols Corporate Offices, Sant Cugat del Vallès, Spain.
J Immunother Cancer. 2019 Jan 25;7(1):19. doi: 10.1186/s40425-019-0505-4.
Oncolytic 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-α (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.
The 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.
FBiTE 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.
Combination 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.
溶瘤病毒（OV）疗法在治疗实体瘤方面具有重要作用，包括直接细胞溶解和免疫原性细胞死亡。然而，肿瘤相关基质通过形成阻止有效病毒渗透和扩散的屏障，限制了溶瘤病毒的疗效。基质还在癌症的进展、免疫抑制和侵袭中起着关键作用。成纤维细胞激活蛋白-α（FAP）在癌相关成纤维细胞（CAFs）中高度过表达，CAFs 是肿瘤基质的主要细胞成分。在这项研究中，我们评估了用靶向 FAP 的双特异性 T 细胞衔接器（FBiTE）武装溶瘤腺病毒（OAd）是否可以将浸润的淋巴细胞重新靶向 CAFs，从而增强病毒的传播和 T 细胞介导的对肿瘤基质的细胞毒性，以提高治疗活性。
使用抗人 CD3 单链可变片段（scFv）连接抗鼠和人 FAP scFv 构建了 FBiTE。该 FBiTE 插入到在主要晚期启动子控制下的溶瘤腺病毒 ICOVIR15K 中，生成 ICO15K-FBiTE。在 HT1080 和 A549 肿瘤细胞系中评估了 ICO15K-FBiTE 的复制和效力。通过流式细胞术在体外评估了 FBiTE 的表达以及与 T 细胞介导的 CAFs 细胞毒性一起诱导的 T 细胞的激活和增殖。在体内，在 NOD/scid/IL2rg/（NSG）小鼠中进行了 T 细胞生物分布和抗肿瘤疗效研究。
FBiTE 的表达并未降低武装病毒的感染力和复制效力。FBiTE 介导的 CD3 效应 T 细胞和 FAP 靶细胞的结合导致 T 细胞在体外激活、增殖和杀伤 FAP 阳性细胞。在体内，FBiTE 的表达增加了肿瘤内 T 细胞的积累，并降低了肿瘤中 CAFs 的标志物 FAP 的水平。FBiTE 武装腺病毒的抗肿瘤活性优于亲本病毒。
病毒溶瘤作用与 FBiTE 介导的表达 FAP 的 CAFs 的细胞毒性相结合，可能是克服溶瘤病毒治疗的一个关键限制的有效策略，鼓励其进一步的临床发展。
