Parker W B, Allan P W, Shaddix S C, Rose L M, Speegle H F, Gillespie G Y, Bennett L L
Southern Research Institute, Birmingham, AL 35205, USA.
Biochem Pharmacol. 1998 May 15;55(10):1673-81. doi: 10.1016/s0006-2952(98)00034-3.
Activation of purine nucleoside analogs by Escherichia coli purine nucleoside phosphorylase (PNP) is being evaluated as a suicide gene therapy strategy for the treatment of cancer. Because the mechanisms of action of two toxic purine bases, 6-methylpurine (MeP) and 2-fluoroadenine (F-Ade), that are generated by this approach are poorly understood, mechanistic studies were initiated to learn how these compounds differ from agents that are being used currently. The concentration of F-Ade, MeP, or 5-fluorouracil required to inhibit CEM cell growth by 50% after a 4-hr incubation was 0.15, 9, or 120 microM, respectively. F-Ade and MeP were also toxic to quiescent MRC-5, CEM, and Balb 3T3 cells. Treatment of CEM, MRC-5, or Balb 3T3 cells with either F-Ade or MeP resulted in the inhibition of protein, RNA, and DNA syntheses. CEM cells converted F-Ade and MeP to F-ATP and MeP-ribonucleoside triphosphate (MeP-R-TP), respectively. The half-life for disappearance of HeP-ribonucleoside triphosphate from CEM cells was approximately 48 hr, whereas the half-lives of F-ATP and ATP were approximately 5 hr. Both MeP and F-Ade were incorporated into the RNA and DNA of CEM cells. These studies indicated that the mechanisms of action of F-Ade and MeP were quite different from those of other anticancer agents, and suggested that the generation of these agents in tumor cells by E. coli PNP could result in significant advantages over those generated by either herpes simplex virus thymidine kinase or E. coli cytosine deaminase. These advantages include a novel mechanism of action resulting in toxicity to nonproliferating and proliferating tumor cells and the high potency of these agents during short-term treatment.
大肠杆菌嘌呤核苷磷酸化酶（PNP）激活嘌呤核苷类似物作为一种癌症治疗的自杀基因治疗策略正在进行评估。由于通过这种方法产生的两种有毒嘌呤碱基6-甲基嘌呤（MeP）和2-氟腺嘌呤（F-Ade）的作用机制尚不清楚，因此开展了机制研究以了解这些化合物与目前使用的药物有何不同。在4小时孵育后抑制CEM细胞生长50%所需的F-Ade、MeP或5-氟尿嘧啶的浓度分别为0.15、9或120微摩尔。F-Ade和MeP对静止的MRC-5、CEM和Balb 3T3细胞也有毒性。用F-Ade或MeP处理CEM、MRC-5或Balb 3T3细胞会导致蛋白质、RNA和DNA合成受到抑制。CEM细胞分别将F-Ade和MeP转化为F-ATP和MeP-核糖核苷三磷酸（MeP-R-TP）。MeP-核糖核苷三磷酸从CEM细胞中消失的半衰期约为48小时，而F-ATP和ATP的半衰期约为5小时。MeP和F-Ade都被掺入到CEM细胞的RNA和DNA中。这些研究表明，F-Ade和MeP的作用机制与其他抗癌药物有很大不同，并表明大肠杆菌PNP在肿瘤细胞中产生这些药物可能比单纯疱疹病毒胸苷激酶或大肠杆菌胞嘧啶脱氨酶产生的药物具有显著优势。这些优势包括一种新的作用机制，导致对非增殖和增殖肿瘤细胞有毒性，以及这些药物在短期治疗期间的高效性。
