Mutant cystathionine gamma-lyase was targeted to phosphatidylserine exposed on tumor vasculature through fusion with Annexin A1 or Annexin A5. Cystathionine gamma-lyase E58N, R118L, and E338N mutations impart nonnative methionine gamma-lyase activity, resulting in tumor-localized generation of highly toxic methylselenol upon systemic administration of nontoxic selenomethionine. The described therapeutic system circumvents systemic toxicity issues using a novel drug delivery/generation approach and avoids the administration of nonnative proteins and/or DNA required with other enzyme prodrug systems. The enzyme fusion exhibits strong and stable in vitro binding with dissociation constants in the nanomolar range for both human and mouse breast cancer cells and in a cell model of tumor vascular endothelium. Daily administration of the therapy suppressed growth of highly aggressive triple-negative murine 4T1 mammary tumors in immunocompetent BALB/cJ mice and MDA-MB-231 tumors in SCID mice. Treatment did not result in the occurrence of negative side effects or the elicitation of neutralizing antibodies. On the basis of the vasculature-targeted nature of the therapy, combinations with rapamycin and cyclophosphamide were evaluated. Rapamycin, an mTOR inhibitor, reduces the prosurvival signaling of cells in a hypoxic environment potentially exacerbated by a vasculature-targeted therapy. IHC revealed, unsurprisingly, a significant hypoxic response (increase in hypoxia-inducible factor 1 α subunit, HIF1A) in the enzyme prodrug–treated tumors and a dramatic reduction of HIF1A upon rapamycin treatment. Cyclophosphamide, an immunomodulator at low doses, was combined with the enzyme prodrug therapy and rapamycin; this combination synergistically reduced tumor volumes, inhibited metastatic progression, and enhanced survival. Mol Cancer Ther; 16(9); 1855–65. ©2017 AACR . This article is featured in Highlights of This Issue, [p. 1727][1] [1]: /lookup/volpage/16/1727?iss=9

中文翻译：

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肿瘤血管靶向酶前药系统，雷帕霉素和环磷酰胺的抗肿瘤协同作用和提高的生存率

通过与膜联蛋白A1或膜联蛋白A5融合，突变型胱硫醚γ-裂解酶靶向暴露于肿瘤血管上的磷脂酰丝氨酸。胱硫醚γ-裂合酶E58N，R118L和E338N突变赋予非天然蛋氨酸γ-裂合酶活性，导致在全身施用无毒硒代蛋氨酸后肿瘤局部生成高毒性甲基硒醇。所描述的治疗系统使用新颖的药物递送/产生方法来规避系统毒性问题，并且避免了其他酶前药系统所需的非天然蛋白质和/或DNA的管理。对于人类和小鼠乳腺癌细胞以及在肿瘤血管内皮细胞模型中，该酶融合物均表现出强而稳定的体外结合，其解离常数在纳摩尔范围内。每日给予该疗法可抑制具有免疫能力的BALB / cJ小鼠中高侵袭性三阴性鼠4T1乳腺肿瘤的生长，并抑制SCID小鼠的MDA-MB-231肿瘤的生长。治疗未导致不良副作用的发生或中和抗体的诱发。根据治疗的血管靶向性质，评估了雷帕霉素和环磷酰胺的联合用药。雷帕霉素是一种mTOR抑制剂，可降低在缺氧环境中以脉管系统为靶点的治疗方法可能加剧的细胞的生存信号。毫不奇怪，IHC揭示了在用前药酶治疗的肿瘤中有明显的低氧反应（缺氧诱导因子1α亚基，HIF1A增加），雷帕霉素治疗后HIF1A显着降低。环磷酰胺，低剂量的免疫调节剂，与酶前药疗法和雷帕霉素联合使用；这种组合可协同减少肿瘤体积，抑制转移进程并提高生存率。分子癌疗法；16（9）; 1855–65。©2017 AACR。本文在本期要点[p。1727] [1] [1]：/ lookup / volpage / 16/1727？iss = 9