DiMaio J M, Clary B M, Via D F, Coveney E, Pappas T N, Lyerly H K
Department of Surgery, Duke University Medical Center, Durham, NC 27710.
Surgery. 1994 Aug;116(2):205-13.
Directed enzyme pro-drug therapy incorporates the delivery of a gene to a cancer cell that will be specifically expressed and will confer sensitivity to a therapeutic agent. Tumor-specific gene expression can be achieved by coupling the promoter for the carcinoembryonic antigen (CEA) to a gene such as herpes simplex virus thymidine kinase (HSV-tk), which phosphorylates ganciclovir to a potent DNA synthesis inhibitor.
Retroviral vectors were constructed to contain the CEA promoter coupled to HSV-tk (LN-CEA-TK) and were used to transduce the CEA-expressing pancreatic carcinoma cell line BXPC3. Recombinant pancreatic carcinoma cell lines expressing HSV-tk (BXPC3CEA-TK) were then tested for sensitivity to the toxic effects on ganciclovir after engraftment into severe combined immunodeficient mice. Tumors were generated by subcutaneous inoculation of 20 x 10(6) tumor cells consisting of BXPC3 and/or BXPC3CEA-TK cells in ratios of 100:0, 90:10, 50:50, 10:90, and 0:100. After 3 days mice received daily ganciclovir (0.1 mg/kg) or phosphate-buffered saline solution by intraperitoneal injection and were monitored for tumor growth.
All severe combined immunodeficient mice inoculated with BXPC3 or BXPC3CEA-TK cells in any proportion developed large pancreatic tumors. As expected, a significant reduction in tumor size was seen in the BXPC3CEA-TK engrafted mice receiving ganciclovir compared with mice receiving phosphate-buffered saline solution or mice engrafted with only BXPC3. In addition, all animals with any fraction of cells expressing HSV-tk exhibited a significant reduction in tumor growth, including animals with only 10% of cells expressing HSV-tk.
These results suggest the potential utility of directed enzyme pro-drug therapy in patients with CEA-expressing pancreatic carcinoma.
导向酶前药疗法包括将一个基因导入癌细胞，该基因将在癌细胞中特异性表达，并使癌细胞对治疗剂敏感。通过将癌胚抗原（CEA）的启动子与单纯疱疹病毒胸苷激酶（HSV-tk）等基因偶联，可实现肿瘤特异性基因表达，HSV-tk能将更昔洛韦磷酸化为一种强效的DNA合成抑制剂。
构建逆转录病毒载体，使其包含与HSV-tk偶联的CEA启动子（LN-CEA-TK），并用于转导表达CEA的胰腺癌细胞系BXPC3。然后将表达HSV-tk的重组胰腺癌细胞系（BXPC3CEA-TK）植入严重联合免疫缺陷小鼠体内，检测其对更昔洛韦毒性作用的敏感性。通过皮下接种由BXPC3和/或BXPC3CEA-TK细胞组成的肿瘤细胞（比例为100:0、90:10、50:50、10:90和0:100），每只接种20×10⁶个肿瘤细胞，生成肿瘤。3天后，小鼠每天通过腹腔注射接受更昔洛韦（0.1mg/kg）或磷酸盐缓冲盐溶液，并监测肿瘤生长情况。
所有按任何比例接种BXPC3或BXPC3CEA-TK细胞的严重联合免疫缺陷小鼠均长出大的胰腺肿瘤。正如预期的那样，与接受磷酸盐缓冲盐溶液的小鼠或仅植入BXPC3的小鼠相比，接受更昔洛韦的植入BXPC3CEA-TK的小鼠肿瘤大小显著减小。此外，所有含有任何比例表达HSV-tk细胞的动物肿瘤生长均显著减缓，包括仅10%细胞表达HSV-tk的动物。
这些结果表明导向酶前药疗法在表达CEA的胰腺癌患者中具有潜在应用价值。
