1 Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, California.
2 Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California.
Hum Gene Ther. 2019 Apr;30(4):413-428. doi: 10.1089/hum.2018.180.
Using gene modification of hematopoietic stem cells (HSC) to create persistent generation of multilineage immune effectors to target cancer cells directly is proposed. Gene-modified human HSC have been used to introduce genes to correct, prevent, or treat diseases. Concerns regarding malignant transformation, abnormal hematopoiesis, and autoimmunity exist, making the co-delivery of a suicide gene a necessary safety measure. Truncated epidermal growth factor receptor (EGFRt) was tested as a suicide gene system co-delivered with anti-CD19 chimeric antigen receptor (CAR) to human HSC. Third-generation self-inactivating lentiviral vectors were used to co-deliver an anti-CD19 CAR and EGFRt. In vitro, gene-modified HSC were differentiated into myeloid cells to allow transgene expression. An antibody-dependent cell-mediated cytotoxicity (ADCC) assay was used, incubating target cells with leukocytes and monoclonal antibody cetuximab to determine the percentage of surviving cells. In vivo, gene-modified HSC were engrafted into NSG mice with subsequent treatment with intraperitoneal cetuximab. Persistence of gene-modified cells was assessed by flow cytometry, droplet digital polymerase chain reaction (ddPCR), and positron emission tomography (PET) imaging using Zr-Cetuximab. Cytotoxicity was significantly increased (p = 0.01) in target cells expressing EGFRt after incubation with leukocytes and cetuximab 1 μg/mL compared to EGFRt+ cells without cetuximab and non-transduced cells with or without cetuximab, at all effector:target ratios. Mice humanized with gene-modified HSC presented significant ablation of gene-modified cells after treatment (p = 0.002). Remaining gene-modified cells were close to background on flow cytometry and within two logs of decrease of vector copy numbers by ddPCR in mouse tissues. PET imaging confirmed ablation with a decrease of an average of 82.5% after cetuximab treatment. These results give proof of principle for CAR-modified HSC regulated by a suicide gene. Further studies are needed to enable clinical translation. Cetuximab ADCC of EGFRt-modified cells caused effective killing. Different ablation approaches, such as inducible caspase 9 or co-delivery of other inert cell markers, should also be evaluated.
利用造血干细胞(HSC)的基因修饰来直接产生多谱系免疫效应物,以靶向癌细胞,这是一种被提出的方法。基因修饰的人类 HSC 已被用于引入基因以纠正、预防或治疗疾病。人们对恶性转化、异常造血和自身免疫存在担忧,因此必须共同递送自杀基因作为安全措施。截短的表皮生长因子受体(EGFRt)被测试为与嵌合抗原受体(CAR)共递送的自杀基因系统,以靶向人类 HSC。第三代自失活慢病毒载体被用于共同递送抗 CD19 CAR 和 EGFRt。在体外,基因修饰的 HSC 分化为髓样细胞以允许转基因表达。抗体依赖性细胞介导的细胞毒性(ADCC)测定用于孵育靶细胞与白细胞和单克隆抗体西妥昔单抗,以确定存活细胞的百分比。在体内,基因修饰的 HSC 被植入 NSG 小鼠中,随后用腹腔内西妥昔单抗进行治疗。通过流式细胞术、液滴数字聚合酶链反应(ddPCR)和使用 Zr-西妥昔单抗的正电子发射断层扫描(PET)成像来评估基因修饰细胞的持久性。与未经西妥昔单抗处理的 EGFRt+细胞和未经转导的细胞相比,在用白细胞和 1μg/mL 西妥昔单抗孵育后,表达 EGFRt 的靶细胞的细胞毒性显著增加(p=0.01),在所有效应物:靶标比值下均如此。用基因修饰的 HSC 人源化的小鼠在治疗后基因修饰细胞的明显消融(p=0.002)。在用西妥昔单抗治疗后,通过 ddPCR 在小鼠组织中检测到基因修饰细胞的拷贝数减少了两个对数级,接近背景水平。PET 成像证实了消融,在接受西妥昔单抗治疗后平均减少了 82.5%。这些结果为受自杀基因调节的 CAR 修饰的 HSC 提供了原理证明。需要进一步的研究来实现临床转化。西妥昔单抗对 EGFRt 修饰细胞的 ADCC 引起了有效的杀伤。还应评估其他消融方法,如诱导型半胱天冬酶 9 或共同递送其他惰性细胞标记物。