Cancer Research Institute, Southern Medical University, Guangzhou, Guangdong, China.
Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA.
Stem Cells. 2017 May;35(5):1154-1161. doi: 10.1002/stem.2568. Epub 2017 Feb 23.
Human embryonic stem cells (hESCs) hold great promise in the regenerative therapy of many currently untreatable human diseases. One of the key bottlenecks is the immune rejection of hESC-derived allografts by the recipient. To overcome this challenge, we have established new approaches to induce immune protection of hESC-derived allografts through the coexpression of immune suppressive molecules CTLA4-Ig and PD-L1. However, this in turn raises a safety concern of cancer risk because these hESC-derived cells can evade immune surveillance. To address this safety concern, we developed a safety checkpoint so that the immune evasive hESC-derived cells in the graft can be effectively eliminated if any cellular transformation is detected. In this context, we knock-in the suicidal gene herpes simplex virus thymidine kinase (HSVTK) into the constitutive HPRT locus of CP hESCs (knock-in hESCs expressing CTLA4-Ig and PD-L1), denoted CPTK hESCs. Employing humanized mice (Hu-mice) reconstituted with human immune system, we demonstrated that the CPTK hESC-derived cells are protected from immune rejection. In addition, CPTK hESC-derived cells can be efficiently eliminated in vitro and in vivo with FDA approved TK-targeting drug ganciclovir. Therefore, this new safety checkpoint improves the feasibility to use the immune evasive hESC-derived cells for regenerative medicine. Stem Cells 2017;35:1154-1161.
人类胚胎干细胞（hESCs）在许多目前无法治疗的人类疾病的再生治疗中具有巨大的应用前景。其中一个关键的瓶颈是受体对 hESC 衍生同种异体移植物的免疫排斥。为了克服这一挑战，我们通过共表达免疫抑制分子 CTLA4-Ig 和 PD-L1，建立了诱导 hESC 衍生同种异体移植物免疫保护的新方法。然而，这反过来又引发了癌症风险的安全担忧，因为这些 hESC 衍生细胞可以逃避免疫监视。为了解决这个安全问题，我们开发了一个安全检查点，如果检测到任何细胞转化，就可以有效地消除移植物中逃避免疫的 hESC 衍生细胞。在这种情况下，我们将自杀基因单纯疱疹病毒胸苷激酶（HSVTK）敲入 CP hESC 的组成型 HPRT 基因座（表达 CTLA4-Ig 和 PD-L1 的敲入 hESC），命名为 CPTK hESC。利用重建有人免疫系统的人源化小鼠（Hu-mice），我们证明了 CPTK hESC 衍生细胞可以免受免疫排斥。此外，CPTK hESC 衍生细胞可以用 FDA 批准的 TK 靶向药物更昔洛韦在体外和体内有效地消除。因此，这个新的安全检查点提高了使用逃避免疫的 hESC 衍生细胞进行再生医学的可行性。《干细胞》2017；35:1154-1161。
