A Pilot Study of 5-FC and Genetically-Modified Neural Stem Cells to Treat Gliomas

描述(由申请人提供)：高级别胶质瘤的弥漫性、浸润性是治疗这些肿瘤的主要障碍。为了对存活率产生重大影响，新的治疗策略必须特别针对这些极具侵袭性的肿瘤细胞。人类神经干细胞(NSCs)因其固有的靶向肿瘤细胞遍及整个大脑的能力，在脑胶质瘤的治疗方面有着巨大的希望。通过利用NSCs的肿瘤趋向性并对其进行基因修饰以表达治疗性转基因，NSCs可以作为靶向抗癌治疗的载体。神经干细胞介导的治疗方法可以潜在地增加肿瘤的选择性，降低毒性，并达到足以消除侵袭性和残留性肿瘤细胞的治疗指数。我们建议使用一个特性良好的克隆同种异体神经干细胞系(HB1.F3)来稳定表达胞嘧啶脱氨酶(CD)，该酶能将口服前药5-氟胞嘧啶(5-FC)转化为化疗药物5-氟尿嘧啶(5-FU)。在正常和原位胶质瘤小鼠模型中的初步数据表明，该细胞系是安全的、无致瘤作用、无免疫原性和治疗活性的。在本研究项目的具体目标1中，将对复发的高级别胶质瘤患者进行初步可行性研究，以确定脑内应用HB1.F3.CD神经干细胞与5-FC联合使用的安全性。将测试三种剂量水平的神经干细胞。具体目标2将通过评估表达CD的神经干细胞在肿瘤部位将5-FC转化为5-FU的程度来演示概念验证。用微透析法测定脑内5-FC和5-FU的浓度，并研究随NSC剂量水平增加脑内和全身5-FC和5-FU浓度的关系。在5-FC治疗期间，19F-MRS也将被用来非侵入性地记录5-FU在大脑中的存在。与公共卫生相关：人类胎儿神经干细胞(NSCs)具有天然的肿瘤亲和性。当神经干细胞被修饰以表达治疗性转基因时，它有可能被用作抗癌治疗的载体。我们提出了一种具有良好特性的克隆性同种异体神经干细胞系HB1.F3的临床应用，该株已被修饰为表达胞嘧啶脱氨酶(CD)。CD将失活的前体药物5-氟胞嘧啶(5-FC)转化为活性的化疗药物5-氟尿嘧啶(5-FU)。初步的生物分布研究表明，该细胞系是安全的，不会致癌，也不会产生免疫原性。HB1.F3.CD神经干细胞已在动物脑胶质瘤模型中显示出疗效。这项研究的具体目的1是确定脑内注射HB1.F3CD神经干细胞联合口服5-FC治疗复发的高级别胶质瘤患者的安全性。特异性目标2将评估HB1.F3.CD神经干细胞在肿瘤部位将5-FC转化为5-FU的程度。

DESCRIPTION (provided by applicant): The diffuse, infiltrative nature of high-grade gliomas is a major obstacle to curing these tumors. In order to make a significant impact on survival, new treatment strategies must specifically target these extremely invasive tumor cells. Human neural stem cells (NSCs) hold great promise for glioma therapy because of their inherent ability to target tumor cells throughout the brain. By harnessing their tumor-tropism and genetically modifying them to express a therapeutic transgene, NSCs can act as delivery vehicles for targeted anti-cancer therapies. NSC-mediated treatment approaches can potentially increase tumor-selectivity, decrease toxicities, and achieve therapeutic indices sufficient to eradicate invasive and residual tumor cells. We propose the use of a well-characterized, clonal, allogeneic NSC line (HB1.F3) that has been retrovirally-transduced to stably express the enzyme, cytosine deaminase (CD), which converts the oral prodrug 5- fluorocytosine (5-FC) to the chemotherapeutic agent 5-fluorouracil (5-FU). Preliminary data in normal and orthotopic glioma murine models indicate that this cell line is safe, non-tumorigenic, non-immunogenic, and therapeutically active. In Specific Aim 1 of this research project, a pilot feasibility study in recurrent high-grade glioma patients will be performed to determine the safety of intracerebral administration of HB1.F3.CD NSCs in combination with 5-FC. Three dose levels of NSCs will be tested. Specific Aim 2 will demonstrate proof-of-concept by assessing the extent to which the CD-expressing NSCs convert 5-FC to 5-FU at sites of tumor. Intracerebral levels of 5-FC and 5-FU will be measured by micro dialysis, and we will characterize the relationship between intracerebral and systemic concentrations of 5-FC and 5-FU with increasing NSC dose level. 19F MRS will also be used to non-invasively document the presence of 5-FU in the brain during 5-FC treatment. PUBLIC HEALTH RELEVANCE: Human fetal neural stem cells (NSCs) are inherently tumor-tropic. When modified to express a therapeutic transgene, NSCs have the potential to be used as delivery vehicles for anti-cancer therapies. We propose the clinical use of a well-characterized, clonal, allogeneic NSC line, HB1.F3, which has been modified to express cytosine deaminase (CD). CD converts the inactive prodrug 5-fluorocytosine (5-FC) to the active chemotherapeutic 5-fluorouracil (5-FU). Preliminary biodistribution studies indicate this cell line is safe, non-tumorigenic and non-immunogenic. HB1.F3.CD NSCs have demonstrated efficacy in animal glioma models. Specific Aim 1 of this research proposal is to determine the safety of intracerebral administration of HB1.F3.CD NSCs in combination with oral 5-FC, in patients with recurrent high-grade gliomas. Specific Aim 2 will assess the extent to which the HB1.F3.CD NSCs convert 5-FC to 5-FU at sites of tumor.