New mechanism of action of the cancer chemotherapeutic agent 5-fluorouracil in human cells.
New mechanism of action of the cancer chemotherapeutic agent 5-fluorouracil in human cells.
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发表时间：
1994-04
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通讯作者：
J. Wurzer;R. Tallarida;M. Sirover
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作者：
J. Wurzer;R. Tallarida;M. Sirover
5-氟尿嘧啶(5-Florouracil，5-Florouracil)是一种用于治疗结肠癌、乳腺癌、卵巢癌和前列腺癌的癌症化疗药物，由于在DNA合成过程中作为5-FldUTP的使用，它被结合到DNA中。这种致突变的DNA损伤是由碱基切除修复酶尿嘧啶DNA糖基酶(UDG)切除的。在这份报告中，我们首次描述了5-FlUra作为游离碱在体内与非周期人类细胞中的UDG特异性结合的机制，从而抑制其活性。在未引起明显细胞毒性的5-FlUra浓度下，UDG活性呈剂量依赖性下降，接近对照细胞的30%。相反，细胞暴露于相同浓度的尿嘧啶、5-氟脱氧尿苷或5-溴-脱氧尿嘧啶对UDG活性没有影响。随后的研究证实了5-FlUra与糖基酶的可逆结合。采用非线性回归分析的动力学分析表明，5-FlUra与UDG在体内以竞争抑制模式结合，尽管5-FlUra-UDG在体外很容易解离。这些发现描述了5-FlUra在非增殖性人类细胞群中潜在的新的作用机制。这些发现与5-FlUra作为癌症化疗药物的用途的潜在相关性被考虑。
5-Fluorouracil (5-FlUra), a cancer chemotherapeutic agent used in the treatment of colon, breast, ovarian and prostate cancer, is incorporated into DNA as a result of its utilization as 5-FldUTP during DNA synthesis. This promutagenic DNA lesion is excised by the base excision repair enzyme uracil DNA glycosylase (UDG). In this report we describe for the first time a mechanism by which 5-FlUra as the free base specifically binds in vivo to the UDG in noncycling human cells, thereby inhibiting its activity. By using 5-FlUra concentrations which did not elicit demonstrable cell toxicity, a dose-dependent decrease in UDG activity was detected which approached 30% of that observed in control cells. In contrast, exposure of cells to equivalent concentrations of uracil, 5-fluorodeoxyuridine or 5-bromouracil had no effect on UDG activity. Subsequent studies demonstrated a reversible binding of 5-FlUra to the glycosylase. Kinetic analysis using nonlinear regression analysis demonstrated a competitive mode of inhibition and indicated a tight binding of 5-FlUra to UDG in vivo, although the 5-FlUra-UDG complex was easily dissociated in vitro. These findings describe a potentially new and novel mechanism of action of 5-FlUra in a nonproliferating human cell population. The potential relevance of these findings to the utility of 5-FlUra as a cancer chemotherapeutic agent is considered.