Tonkinson J L, Worzalla J F, Teng C H, Mendelsohn L G
Cancer Research Division, Lilly Research Laboratories, Eli Lilly and Co., Indianapolis, Indiana 46285, USA.
Cancer Res. 1999 Aug 1;59(15):3671-6.
The proliferation rate of HT29 colon carcinoma cells was decreased by the multitargeted antifolate (MTA), LY231514. This effect correlated with a buildup of cells near the G1-S interface after 24 h of incubation, and a synchronized progression of the population through S phase during the next 24 h. MTA treatment (0.03-3 microM) was minimally cytotoxic (20-30%) to HT29 cells after a 24-h exposure, and no dose response was observed. In contrast, the nucleoside analogue gemcitabine (GEM) was cytotoxic (IC50, 0.071 +/- 0.011 microM; IC90, 0.648 +/- 0.229 microM) after a 24-h exposure. We hypothesized that pretreatment of these cells with MTA would increase the potency of GEM by synchronizing the population for DNA synthesis. The cytotoxicity of GEM increased 2-7-fold when MTA was administered 24 h before GEM (IC50, 0.032 +/- 0.009 microM; IC90, 0.094 +/- 0.019 microM). In addition, an increase in cell kill for the combination compared with GEM alone (IC99, 12 microM for GEM alone; IC99, 0.331 microM for combination) was observed. No increase in potency or cell kill was observed when the two compounds were added simultaneously. MTA pretreatment also potentiated the cytotoxicity of a 1-h exposure to GEM. These cell-based observations were extended to evaluate the schedule-dependent interaction of these two agents in vivo using a nude mouse HT29 xenograft tumor model. At the doses tested, MTA alone (100 mg/kg) had a marginal effect on tumor growth delay, whereas GEM (80 mg/kg) produced a statistically significant tumor growth delay. In combination, the increase in tumor growth delay was greatest when MTA was administered before GEM, compared with simultaneous drug administration or the reverse sequence, e.g., GEM followed by MTA. The effect of sequential administration of MTA followed by GEM was greater than additive, indicating synergistic interaction of these agents. Thus, in vitro, MTA induced cell cycle effects on HT29 cells that resulted in potentiation of the cytotoxicity of GEM. In vivo, combination of these two drugs also demonstrated a schedule-dependent synergy that was optimal when MTA treatment preceded GEM.
多靶点抗叶酸剂（MTA）LY231514可降低HT29结肠癌细胞的增殖速率。这种效应与孵育24小时后G1-S界面附近细胞的积累相关，并且在接下来的24小时内群体同步进入S期。24小时暴露后，MTA处理（0.03 - 3 microM）对HT29细胞的细胞毒性极小（20 - 30%），且未观察到剂量反应。相比之下，核苷类似物吉西他滨（GEM）在24小时暴露后具有细胞毒性（IC50，0.071±0.011 microM；IC90，0.648±0.229 microM）。我们假设用MTA预处理这些细胞会通过使群体同步进行DNA合成来增加GEM的效力。当在GEM给药前24小时给予MTA时，GEM的细胞毒性增加了2 - 7倍（IC50，0.032±0.009 microM；IC90，0.094±0.019 microM）。此外，观察到与单独使用GEM相比（单独使用GEM时IC99为12 microM；联合使用时IC99为0.331 microM），联合用药时细胞杀伤增加。当同时添加这两种化合物时，未观察到效力或细胞杀伤增加。MTA预处理还增强了1小时暴露于GEM的细胞毒性。这些基于细胞的观察结果被扩展到使用裸鼠HT29异种移植肿瘤模型在体内评估这两种药物的时间依赖性相互作用。在测试剂量下，单独使用MTA（100 mg/kg）对肿瘤生长延迟的影响很小，而GEM（80 mg/kg）产生了统计学上显著的肿瘤生长延迟。联合使用时，与同时给药或相反顺序（例如，GEM后接MTA）相比，当在GEM之前给予MTA时，肿瘤生长延迟的增加最大。MTA后接GEM的序贯给药效果大于相加作用，表明这些药物具有协同相互作用。因此，在体外，MTA对HT29细胞诱导细胞周期效应，导致GEM细胞毒性增强。在体内，这两种药物的联合使用也表现出时间依赖性协同作用，当MTA治疗先于GEM时最为理想。
