Chu E, Zinn S, Boarman D, Allegra C J
Division of Cancer Treatment, National Cancer Institute, Bethesda, Maryland 20892.
Cancer Res. 1990 Sep 15;50(18):5834-40.
The antiproliferative effects and pharmacological interactions of 5-fluorouracil (5-FU) in combination with gamma interferon (IFN-gamma) were determined against the human colon carcinoma H630 cell line in vitro. H630 was 9-fold more resistant to 5-FU, as compared to a relatively sensitive human colon line (C1). IFN-gamma showed modest antiproliferative activity against the H630 line, with a 50% inhibitory concentration of 440 units/ml. Simultaneous treatment of H630 with subinhibitory concentrations of IFN-gamma and 5-FU produced a significant enhancement of the 5-FU-associated growth inhibition. The growth-inhibitory activity of the combination against H630 was prevented by the addition of 20 microM thymidine. Thymidylate synthase (TS) activity was measured by both the 5-fluoro-2'-deoxyuridine-5'-monophosphate binding and catalytic assays, using cytosolic extracts. A 24-h exposure to 1 microM 5-FU in the H630 line resulted in a 3.1-fold increase in the total amount of TS, while in the 5-FU/IFN-gamma-treated cells TS remained unchanged from non-drug-treated control levels. Moreover, we found that free thymidylate synthase in the 5-FU/IFN-gamma-treated cells was significantly decreased, as compared to the cells treated with 5-FU alone. Incorporation of 5-FU into both the RNA and DNA fractions did not change with the addition of IFN-gamma. Accumulation of the fluoropyrimidine metabolites 5-fluoro-2'-deoxyuridine-5'-monophosphate and 5-fluorouridine-5'-triphosphate remained the same for 5-FU alone and the combination treatment. These findings suggest that acute TS induction by 5-FU may provide an important mechanism by which human colon carcinoma cells express decreased sensitivity to 5-FU and that IFN-gamma can reverse the development of resistance to 5-FU in the H630 line by inhibiting the overexpression of TS that results from 5-FU exposure. These studies contribute to a growing understanding of the complex interaction between 5-FU and IFN-gamma.
在体外对人结肠癌H630细胞系测定了5-氟尿嘧啶（5-FU）与γ干扰素（IFN-γ）联合使用时的抗增殖作用及药理相互作用。与相对敏感的人结肠细胞系（C1）相比，H630对5-FU的耐药性高9倍。IFN-γ对H630细胞系显示出适度的抗增殖活性，其50%抑制浓度为440单位/毫升。用亚抑制浓度的IFN-γ和5-FU同时处理H630细胞，可显著增强5-FU相关的生长抑制作用。添加20微摩尔胸苷可阻止该联合用药对H630的生长抑制活性。使用细胞溶质提取物，通过5-氟-2'-脱氧尿苷-5'-单磷酸结合试验和催化试验测定胸苷酸合成酶（TS）活性。H630细胞系暴露于1微摩尔5-FU 24小时后，TS总量增加3.1倍，而在5-FU/IFN-γ处理的细胞中，TS与未用药物处理的对照水平相比无变化。此外，我们发现与单独用5-FU处理的细胞相比，5-FU/IFN-γ处理的细胞中游离胸苷酸合成酶显著减少。添加IFN-γ后，5-FU掺入RNA和DNA组分的情况没有变化。单独使用5-FU和联合处理时，氟嘧啶代谢产物5-氟-2'-脱氧尿苷-5'-单磷酸和5-氟尿苷-5'-三磷酸的积累情况相同。这些发现表明，5-FU急性诱导TS可能是人类结肠癌细胞对5-FU敏感性降低的重要机制，并且IFN-γ可通过抑制5-FU暴露导致的TS过表达来逆转H630细胞系对5-FU的耐药性发展。这些研究有助于加深对5-FU与IFN-γ之间复杂相互作用的理解。
