Nishio K, Ishida T, Arioka H, Kurokawa H, Fukuoka K, Nomoto T, Fukumoto H, Yokote H, Saijo N
Pharmacology Division, National Cancer Center Research Institute, Tokyo, Japan.
Anticancer Res. 1996 Nov-Dec;16(6B):3387-95.
Butyrolactone I, which is a naturally occurring specific inhibitor of the cdc2 kinase family, showed antitumor effects on several non-small- and small-cell-lung cancer cell lines with IC50 values the order of 50 micrograms/ml on the former. No cross-resistance of several drug-resistant cell lines, including those with the multidrug-resistant phenotype and five cisplatin-resistant cell lines to butyrolactone I was observed. The cdc2 kinase activity of PC-14 cells was inhibited by treatment with 20 micrograms/ml butyrolactone I, a concentration comparable to the IC50 value, for 2 hours. Longer exposure to butyrolactone I (> 24 hours) reduced the cdc2 kinase protein level. Butyrolactone I arrested the cells at the G2/M phase in a concentration dependent manner. These results suggest that butyrolactone I actually acts on cdc2 kinase, rather than other cdk kinases, in PC-14 cells. Inhibition of DNA synthesis, determined by measuring thymidine uptake, occurred earlier (2 hours) after initiating exposure than the decrease in the cdc2 protein level and was concentration dependent, suggesting that butyrolactone I inhibited DN4 synthesis. Cell permeabilization by digitonin enhanced DN4 synthesis inhibition by butyrolactone I, suggesting that the permeability of the membrane to this agent was the limiting factor for its growth inhibitory effect. Many anticancer agents, such as alkylating agents and cisplatin, cause cells to accumulate at the G2/M phase of the cell cycle. We investigated whether butyrolactone I had any modulatory effect on the antitumor effects of several anticancer drugs in vitro. Butyrolactone I showed no modulatory effects on vindesine, paclitaxel, or etoposide, but exposure of PC-9 and PC-14 cells to butyrolactone I together with or prior to treatment with cisplatin reduced the cytotoxicity of the latter. Thin-layer chromatographic analysis revealed that butyrolactone I bound to cisplatin, which was a possible cause of the reduced cisplatin cytotoxicity in the presence of bytyrolactone I.
丁内酯 I 是一种天然存在的细胞周期蛋白依赖性激酶 2（cdc2）激酶家族的特异性抑制剂，对几种非小细胞肺癌和小细胞肺癌细胞系显示出抗肿瘤作用，对前者的半数抑制浓度（IC50）值约为 50 微克/毫升。未观察到几种耐药细胞系，包括具有多药耐药表型的细胞系和五种顺铂耐药细胞系对丁内酯 I 产生交叉耐药。用 20 微克/毫升丁内酯 I（与 IC50 值相当的浓度）处理 PC - 14 细胞 2 小时，可抑制其 cdc2 激酶活性。长时间暴露于丁内酯 I（> 24 小时）会降低 cdc2 激酶蛋白水平。丁内酯 I 以浓度依赖性方式使细胞停滞在 G2/M 期。这些结果表明，在 PC - 14 细胞中，丁内酯 I 实际上作用于 cdc2 激酶，而非其他细胞周期蛋白依赖性激酶（cdk）激酶。通过测量胸苷摄取来确定的 DNA 合成抑制在开始暴露后更早（2 小时）出现，且早于 cdc2 蛋白水平的降低，并且具有浓度依赖性，这表明丁内酯 I 抑制了 DNA 合成。洋地黄皂苷使细胞透化增强了丁内酯 I 对 DNA 合成的抑制作用，这表明细胞膜对该药物的通透性是其生长抑制作用的限制因素。许多抗癌药物，如烷化剂和顺铂，会使细胞在细胞周期的 G2/M 期积累。我们研究了丁内酯 I 在体外对几种抗癌药物的抗肿瘤作用是否有任何调节作用。丁内酯 I 对长春地辛、紫杉醇或依托泊苷没有调节作用，但在 PC - 9 和 PC - 14 细胞中，在顺铂处理之前或同时暴露于丁内酯 I 会降低顺铂的细胞毒性。薄层色谱分析表明，丁内酯 I 与顺铂结合，这可能是在丁内酯 I 存在下顺铂细胞毒性降低的原因。
