Dorr Robert T, Raymond Mary Ann, Landowski Terry H, Roman Nicholas O, Fukushima Shoji
The University of Arizona, College of Medicine, Department of Pharmacology, 1515 N Campbell Avenue, Tucson, Arizona 85724, USA.
Int J Gastrointest Cancer. 2005;36(1):15-28. doi: 10.1385/IJGC:36:1:015.
Imexon is an aziridine-containing small molecule currently in Phase I clinical trials. This agent has been shown to bind to thiols and increase intracellular oxidants, inducing apoptosis in hematologic cancer cells. Pancreatic cancers are known to be sensitive to oxidation, suggesting this disease may be an appropriate target for this agent. The current report examines the activity of imexon in pancreatic cells. Imexon induced concentration-dependent and time-dependent apoptosis in a panel of six human pancreatic carcinoma cell (PCC) lines. The mean IC50 (SD) for growth inhibition by the SRB assay was 200 (101) microM for a 48 h exposure with a range of 64-358 microM. Cell killing was schedule-dependent, favoring exposure times > or =48 h. Imexon-treated MiaPaCa-2 cells underwent non-lethal growth arrest following exposure to concentrations < or =200 microM for 48 h. When concentrations were increased to 300 microM for > or =48 h, the MiaPaCa-2 cells arrested in G2 phase and activated caspases 3, 8, and 9 were detected. After a 72 h exposure to the IC80 concentration of imexon, cells exhibited a loss of mitochondrial membrane potential detected by CMXRos staining. However, there was no loss of reduced cellular thiols unless very high concentrations of > or =400 microM were used. In contrast, reactive oxygen species (ROS) were elevated in a dose-dependent fashion, starting at very low imexon concentrations. Imexon also significantly inhibited MiaPaCa-2 tumor growth in SCID mice at 100 mg/kg/d for 9 d. The tumor growth inhibition (% T/C) was 27% of control, and the tumor growth delay was 21 d, indicating an active agent by NCI standards. The levels of imexon that are cytotoxic in human PCC's are achievable based on the preliminary results of the ongoing Phase I trial. Imexon appears to be active against PCCs in vitro and has an entirely novel mechanism of action involving G2 arrest, accumulation of ROS, and the induction of apoptosis.
艾美克生是一种含氮丙啶的小分子，目前正处于I期临床试验阶段。该药物已被证明能与硫醇结合并增加细胞内氧化剂，从而诱导血液系统癌细胞凋亡。已知胰腺癌对氧化敏感，这表明该疾病可能是这种药物的合适靶点。本报告研究了艾美克生在胰腺细胞中的活性。艾美克生在一组六种人胰腺癌（PCC）细胞系中诱导了浓度依赖性和时间依赖性凋亡。通过SRB法检测，48小时暴露的生长抑制平均IC50（标准差）为200（101）微摩尔，范围为64 - 358微摩尔。细胞杀伤具有时间依赖性，暴露时间≥48小时更为有利。艾美克生处理的MiaPaCa - 2细胞在暴露于≤200微摩尔浓度48小时后经历非致死性生长停滞。当浓度增加到300微摩尔且暴露时间≥48小时时，MiaPaCa - 2细胞停滞在G2期，并检测到激活的半胱天冬酶3、8和9。在暴露于艾美克生的IC80浓度72小时后，通过CMXRos染色检测到细胞线粒体膜电位丧失。然而，除非使用非常高的浓度≥400微摩尔，否则细胞内还原型硫醇不会减少。相反，活性氧（ROS）以剂量依赖性方式升高，从非常低的艾美克生浓度开始。艾美克生在SCID小鼠中以100毫克/千克/天的剂量给药9天，也显著抑制了MiaPaCa - 2肿瘤生长。肿瘤生长抑制率（%T/C）为对照组的27%，肿瘤生长延迟为21天，根据美国国立癌症研究所（NCI）标准表明该药物具有活性。根据正在进行的I期试验的初步结果，在人PCC中具有细胞毒性的艾美克生水平是可以达到的。艾美克生在体外似乎对PCC有活性，并且具有一种全新的作用机制，涉及G2期停滞、ROS积累和凋亡诱导。
