Topf N, Worgall S, Hackett N R, Crystal R G
Division of Pulmonary and Critical Care Medicine, New York Hospital-Cornell Medical Center, NY 10021, USA.
Gene Ther. 1998 Apr;5(4):507-13. doi: 10.1038/sj.gt.3300611.
Direct administration of an adenoviral vector expressing the cytosine deaminase gene (AdCMV.CD) to tumors of colon carcinoma cells, with concomitant systemic administration of 5-fluorocytosine (5FC), results in local production of 5-fluorouracil (5FU) and suppression of tumor growth. Based on the demonstration that in vivo adenovirus-mediated gene transfer to intrahepatic tumors is relatively inefficient compared with in vivo gene transfer to hepatocytes, we developed a 'regional' prodrug strategy using in vivo Ad-mediated CD gene transfer to normal liver, permitting hepatocytes to convert 5FC into 5FU to treat local metastasis effectively in a 'trans' fashion. To show that hepatocytes can generate and export sufficient 5FU to achieve this goal, primary rat hepatocytes were exposed to AdCMV.CD and 5FC. Evaluation of the supernatants by spectrophotometry and by HPLC demonstrated significant conversion of 5FC into 5FU. When supernatants of hepatocytes exposed to AdCMV.CD and 5FC were transferred to cultures of CT26 mouse colon carcinoma cells, the CT26 viability was reduced by 80%. To show that this regional AdCMV.CD/5FC prodrug strategy can suppress tumor growth in vivo, a model of metastatic colon carcinoma was established by injecting CT26 cells into the left lobe of the liver of syngeneic Balb/c mice. The next day, AdCMV.CD was transferred to hepatocytes by intravenous administration, and 5FC treatment was started the following day. Evaluation of tumor growth after 15 days showed marked suppression of tumor growth in AdCMV.CD- and 5FC- treated animals compared to control groups (P < 0.007). We conclude that primary hepatocytes are capable of converting 5FC into 5FU and exporting sufficient amounts of 5FU to the local milieu to suppress the growth of liver metastases of colon carcinoma cells.
将表达胞嘧啶脱氨酶基因的腺病毒载体（AdCMV.CD）直接注射到结肠癌细胞肿瘤中，并同时全身给予5-氟胞嘧啶（5FC），可导致局部产生5-氟尿嘧啶（5FU）并抑制肿瘤生长。基于体内腺病毒介导的基因转移至肝内肿瘤相对低效这一现象（与体内基因转移至肝细胞相比），我们开发了一种“区域”前药策略，即利用体内腺病毒介导的CD基因转移至正常肝脏，使肝细胞将5FC转化为5FU，从而以“转”的方式有效治疗局部转移灶。为了证明肝细胞能够产生并输出足够的5FU以实现这一目标，将原代大鼠肝细胞暴露于AdCMV.CD和5FC中。通过分光光度法和高效液相色谱法对上清液进行评估，结果表明5FC已显著转化为5FU。当将暴露于AdCMV.CD和5FC的肝细胞上清液转移至CT26小鼠结肠癌细胞培养物中时，CT26细胞的活力降低了80%。为了证明这种区域AdCMV.CD/5FC前药策略能够在体内抑制肿瘤生长，通过将CT26细胞注射到同基因Balb/c小鼠的左肝叶中建立了转移性结肠癌模型。第二天，通过静脉给药将AdCMV.CD转移至肝细胞，随后第二天开始给予5FC治疗。15天后对肿瘤生长进行评估，结果显示与对照组相比，接受AdCMV.CD和5FC治疗的动物肿瘤生长受到显著抑制（P < 0.007）。我们得出结论，原代肝细胞能够将5FC转化为5FU，并向局部环境输出足够量的5FU以抑制结肠癌细胞肝转移灶的生长。
