Milsom Michael D, Williams David A
Cincinnati Children's Research Foundation, Cincinnati Children's Hospital Medical Center, Division of Experimental Hematology, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
DNA Repair (Amst). 2007 Aug 1;6(8):1210-21. doi: 10.1016/j.dnarep.2007.03.020. Epub 2007 May 7.
Gene transfer into hematopoietic stem cells (HSC) provides a potential means of correcting monogenic defects and altering drug sensitivity of normal bone marrow to cytotoxic agents. These applications have significant therapeutic potential but the translation of successful murine studies into human therapies has been hindered by low gene transfer in large animals (including humans), and recent serious side effects in a human immunodeficiency trial related to insertional mutagenesis. The latter trial, along with other subsequent trials, while bringing into focus the potential risks of integrating vector systems, also clearly demonstrate the potential usefulness of in vivo selection as it relates to inefficient stem cell transduction. Developing from initial studies by our group and other investigators in which drug resistance was utilized to demonstrate the feasibility of using gene transfer to effect protection from myelotoxicity of chemotherapeutic agents, expression of mutant forms of O(6)-methyguanine-DNA-methytransferase (MGMT) coupled with the simultaneous use of pharmacologic inhibitors and chemotherapeutic agents has been shown to provide a powerful method to select HSC in vivo. While stem and progenitor cell protection and resulting selection in vivo has potential applications for the treatment of selected cancers (allowing dose escalation) and for correction of monogenic disease (allowing an iatrogenic survival advantage of transduced cells in vivo), such an in vivo selection may have untoward effects on stem cell behavior. These deleterious effects may include stem cell exhaustion; lineage skewing; accumulation of genotoxic lesions; and clonal dominance driven towards a pro-leukemic phenotype. Knowledge of the likelihood of such deleterious events occurring as well as their potential implications will be critical to future clinical applications and may also enhance our understanding of both normal stem cell behavior and the evolution of hematopoietic malignancies.
将基因导入造血干细胞（HSC）为纠正单基因缺陷以及改变正常骨髓对细胞毒性药物的敏感性提供了一种潜在手段。这些应用具有重大的治疗潜力，但成功的小鼠研究向人类治疗的转化受到了大型动物（包括人类）中基因转移效率低下的阻碍，并且在一项与插入诱变相关的人类免疫缺陷试验中出现了近期严重的副作用。后一项试验以及其他后续试验，在聚焦整合载体系统潜在风险的同时，也清楚地证明了体内选择在低效干细胞转导方面的潜在有用性。从我们小组和其他研究人员的初步研究发展而来，在这些研究中利用耐药性来证明使用基因转移实现对化疗药物骨髓毒性的保护的可行性，O(6)-甲基鸟嘌呤-DNA-甲基转移酶（MGMT）突变形式的表达与同时使用药理抑制剂和化疗药物已被证明是一种在体内选择HSC的有力方法。虽然干细胞和祖细胞的保护以及由此产生的体内选择在治疗特定癌症（允许剂量递增）和纠正单基因疾病（允许转导细胞在体内具有医源性生存优势）方面具有潜在应用，但这种体内选择可能对干细胞行为产生不良影响。这些有害影响可能包括干细胞耗竭；谱系偏移；基因毒性损伤的积累；以及向促白血病表型驱动的克隆优势。了解此类有害事件发生的可能性及其潜在影响对于未来的临床应用至关重要，也可能增强我们对正常干细胞行为和造血恶性肿瘤演变的理解。
