This paper deals with specific targeting of the prodrug/enzyme regimen, CNOB/HChrR6, to treat a serious disease, namely HER2+ human breast cancer with minimal off-target toxicity. HChrR6 is an improved bacterial enzyme that converts CNOB into the cytotoxic drug MCHB. Extracellular vesicles (EV) were used for mRNA-based HchrR6 gene delivery: EVs may cause minimal immune rejection, and mRNA may be superior to DNA for gene delivery. To confine HChrR6 generation and CNOB activation to the cancer, the EVHB chimeric protein was constructed. It contains high-affinity anti-HER2 scFv antibody (ML39) and is capable of latching on to EV surface. Cells transfected with EVHB-encoding plasmid generated EVs displaying this protein (“directed EVs”). Transfection of a separate batch of cells with the new plasmid, XPort/HChrR6, generated EVs containing HChrR6 mRNA; incubation with pure EVHB enabled these to target the HER2 receptor, generating “EXO-DEPT” EVs. EXO-DEPT treatment specifically enabled HER2-overexpressing BT474 cells to convert CNOB into MCHB in actinomycin D–independent manner, showing successful and specific delivery of HChrR6 mRNA. EXO-DEPTs—but not undirected EVs—plus CNOB caused near-complete growth arrest of orthotopic BT474 xenografts in vivo, demonstrating for the first time EV-mediated delivery of functional exogenous mRNA to tumors. EXO-DEPTs may be generated from patients' own dendritic cells to evade immune rejection, and without plasmids and their potentially harmful genetic material, raising the prospect of clinical use of this regimen. This approach can be used to treat any disease overexpressing a specific marker. Mol Cancer Ther; 17(5); 1133–42. ©2018 AACR.

中文翻译：

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抗 HER2 scFv 导向的细胞外囊泡介导的基于 mRNA 的基因递送通过前药激活抑制 HER2 阳性人乳腺肿瘤异种移植物的生长

本文讨论了前药/酶方案 CNOB/HChrR6 的特异性靶向，以治疗严重疾病，即具有最小脱靶毒性的 HER2+ 人类乳腺癌。HChrR6 是一种改良的细菌酶，可将 CNOB 转化为细胞毒性药物 MCHB。细胞外囊泡 (EV) 用于基于 mRNA 的 HchrR6 基因传递：EVs 可能导致最小的免疫排斥，而 mRNA 可能优于 DNA 的基因传递。为了将 HChrR6 生成和 CNOB 激活限制在癌症中，构建了 EVHB 嵌合蛋白。它包含高亲和力的抗 HER2 scFv 抗体 (ML39)，能够锁定在 EV 表面。用 EVHB 编码质粒转染的细胞产生展示这种蛋白质的 EV（“定向 EV”）。用新质粒 XPort/HChrR6 转染另一批细胞，产生含有 HChrR6 mRNA 的 EV；与纯 EVHB 孵育使它们能够靶向 HER2 受体，产生“EXO-DEPT”EV。EXO-DEPT 处理特别使 HER2 过表达的 BT474 细胞能够以不依赖放线菌素 D 的方式将 CNOB 转化为 MCHB，显示出 HChrR6 mRNA 的成功和特异性递送。EXO-DEPTs——但不是非定向 EVs——加上 CNOB 导致原位 BT474 异种移植物在体内几乎完全生长停滞，首次证明了 EV 介导的功能性外源 mRNA 向肿瘤的传递。EXO-DEPTs 可能由患者自身的树突状细胞产生，以逃避免疫排斥反应，并且不含质粒及其潜在有害的遗传物质，这为该方案的临床应用提供了前景。这种方法可用于治疗任何过度表达特定标记物的疾病。摩尔癌症治疗; 17(5); 1133-42。©2018 AACR。