Selective Therapy of Neuroblastoma

描述（申请人提供）：神经母细胞瘤（Neuroblastoma， NB）是儿科患者中最常见的颅外实体瘤。高危患者的治疗包括手术和自体干细胞抢救的大剂量化疗。然而，尽管进行了积极的治疗，高达80%的患者复发并死于播散性疾病。因此，需要新的治疗NB的方法。一种潜在的方法是病毒导向酶前药治疗（VDEPT），利用腺病毒递送编码羧酸酯酶（CEs）的cdna，有效激活前药CPT-11。该药物在NB患者中显示出令人鼓舞的活性，但在体内激活效率不高。之前的研究表明，兔肝CE/CPT-11 VDEPT可使原代NB细胞对CPT-11致敏，并可用于清除人造血“干细胞”中的NB细胞，而对祖细胞或CD34+ NOD/SCID再生细胞无毒性。在下一个资助周期，我们建议完成一项正在进行的非治疗性临床试验，用于清除含有bbbb1%肿瘤细胞的骨髓标本，并确定合适的CE，使CE/CPT-11 VDEPT可用于体内应用。具体目标包括：1)完成正在进行的临床试验；2)对人酶进行修饰，以产生具有最小免疫原性的高效CPT-11激活酶；3)利用肿瘤特异性启动子和复制选择性腺病毒载体传递CE cDNA，实现NB小鼠模型的肿瘤特异性毒性。总之，这些研究应该为高危神经母细胞瘤提供替代的治疗方式。

DESCRIPTION (provided by applicant): Neuroblastoma (NB) is the most common extracranial solid tumor in pediatric patients. Treatment for high-risk patients includes surgery and high dose chemotherapy with autologous stem cell rescue. However, in spite of aggressive therapy, up to 80% of patients relapse and die of disseminated disease. Therefore, novel approaches to the treatment of NB are necessary. One potential approach is viral-directed enzyme prodrug therapy (VDEPT), using adenoviruses to deliver cDNAs encoding carboxylesterases (CEs) that efficiently activate the prodrug CPT-11. This drug has shown encouraging activity in NB patients, but is activated inefficiently in vivo. Work during the previous funding cycle documented that rabbit liver CE/CPT-11 VDEPT sensitizes primary NB cells to CPT-11, and can be used to purge NB cells from human hematopoietic "stem" cells without toxicity to progenitor cells or CD34+ NOD/SCID repopulating cells. In the next funding cycle, we propose to complete an ongoing nontherapeutic clinical trial for purging bone marrow specimens containing >1% tumor cells, and to identify appropriate CEs to make CE/CPT-11 VDEPT useful for in vivo application. Specific Aims include: 1) completion of the ongoing clinical trial; 2) modification of a human enzyme to produce an efficient CPT-11 activating enzyme with minimal immunogenicity; and 3) to achieve tumor-specific toxicity in mouse models of NB by using tumor specific promoters and replication-selective adenoviral vectors to deliver CE cDNA. Overall, these studies should provide alternative treatment modalities for high-risk neuroblastoma.