Takeda Kenichi, Suyama Hisashi, Igishi Tadashi, Shigeoka Yasushi, Matsumoto Shingo, Yamasaki Akira, Hashimoto Kiyoshi, Sumikawa Takashi, Morita Masato, Ueda Yasuto, Shimizu Eiji
Division of Medical Oncology and Molecular Respirology, Faculty of Medicine, Tottori University, Yonago 683-8504, Japan.
Oncol Rep. 2008 Apr;19(4):945-51.
Despite the high response rates of small cell lung cancer (SCLC) to first-line cisplatin-based chemotherapies, most patients with SCLC will eventually experience disease progression. Accordingly, novel chemotherapeutic regimens are desired. This in vitro study was carried out in order to develop novel chemotherapeutic regimens containing 5-fluorouracil (5-FU) or oral fluoropyrimidine for SCLC. 5-FU was combined with other standard drugs for SCLC (cisplatin, etoposide, an active metabolite of irinotecan and amrubicin) in different schedules. The combination effects were analyzed by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and an isobologram method using H69 SCLC cells. Among the examined combinations, synergistic growth inhibition was observed only when H69 cells were treated with 7-ethyl-10-hydroxycamptothecin (SN-38; an active metabolite of irinotecan) followed by 5-FU. The findings of a flow cytometric analysis were consistent with the enhancement of apoptotic cell death by this sequential treatment. This synergism was observed in 4 out of 5 SCLC cell lines tested. The effects of 5-FU and SN-38 on thymidylate synthase (TS) protein expression, an important determinant of 5-FU sensitivity, were assessed by Western blot analysis in H69 cells. Treatment with SN-38 for 24 h suppressed TS protein expression and this low level of TS was maintained for at least 72 h. Pretreatment with SN-38 inhibited the 5-FU-induced increase of TS protein. The synergistic effect induced by the combination of SN-38 and 5-FU may be attributable to the SN-38-induced suppression of TS protein. Furthermore, uracil and 5-chloro-2,4-hydroxypyridine, which are clinically available dihydropyrimidine dehydrogenase inhibitors, enhanced 5-FU-induced growth inhibition. These observations provide evidence supporting the clinical applications of the combination chemotherapy using irinotecan and 5-FU or oral fluoropyrimidines against SCLC.
尽管小细胞肺癌（SCLC）对一线铂类化疗药物的反应率较高，但大多数SCLC患者最终仍会出现疾病进展。因此，需要新的化疗方案。进行这项体外研究是为了开发含5-氟尿嘧啶（5-FU）或口服氟嘧啶的SCLC新化疗方案。5-FU与其他SCLC标准药物（顺铂、依托泊苷、伊立替康的活性代谢产物和氨柔比星）按不同方案联合使用。采用3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四氮唑溴盐（MTT）法和等效线图法，利用H69 SCLC细胞分析联合效应。在所检测的联合用药中，仅当H69细胞先用7-乙基-10-羟基喜树碱（SN-38；伊立替康的活性代谢产物）处理后再用5-FU处理时，才观察到协同生长抑制作用。流式细胞术分析结果与这种序贯治疗导致凋亡性细胞死亡增加一致。在所测试的5种SCLC细胞系中，有4种观察到了这种协同作用。通过蛋白质免疫印迹分析评估了5-FU和SN-38对胸苷酸合成酶（TS）蛋白表达的影响，TS是5-FU敏感性的一个重要决定因素。用SN-38处理24小时可抑制TS蛋白表达，且这种低水平的TS至少维持72小时。用SN-38预处理可抑制5-FU诱导的TS蛋白增加。SN-38与5-FU联合诱导的协同效应可能归因于SN-38诱导的TS蛋白抑制。此外，临床上可用的二氢嘧啶脱氢酶抑制剂尿嘧啶和5-氯-2,4-羟基吡啶增强了5-FU诱导的生长抑制作用。这些观察结果为伊立替康与5-FU或口服氟嘧啶联合化疗用于SCLC的临床应用提供了证据支持。
