Evens Andrew M, Prachand Sheila, Shi Bo, Paniaqua Mary, Gordon Leo I, Gartenhaus Ronald B
Departments of Medicine and Pathology, Feinberg School of Medicine and the Robert H Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, USA.
Clin Cancer Res. 2004 Feb 15;10(4):1481-91. doi: 10.1158/1078-0432.ccr-1058-03.
Imexon is a 2-cyanoaziridine agent that has been shown to inhibit growth of chemotherapy-sensitive myeloma cells through apoptosis with decreased cellular stores of glutathione and increased reactive oxygen species (ROS). We examined the mechanism of imexon cytotoxicity in a diverse panel of dexamethasone and chemotherapy-sensitive and -resistant myeloma cell lines.
We examined cellular cytotoxicity, apoptosis, and changes in redox state in dexamethasone-sensitive (C2E3), dexamethasone-resistant (1-310 and 1-414), chemotherapy-sensitive (RPMI-8226), and chemotherapy-resistant (DOX-1V and DOX-10V) myeloma cell lines.
We found significant cytotoxicity after 48-h incubation with imexon (80-160 microM) in dexamethasone and chemotherapy-sensitive and -resistant myeloma cell lines in a time- and dose-dependent manner. The mechanism of imexon cytotoxicity in all cell lines was related to induction of apoptosis with the presence of cleaved caspase-3. Moreover, after imexon exposure in C2E3 and 1-414 cell lines, we demonstrated caspase-8-dependent apoptosis. Bcl-2:bax was proapoptotic with imexon in C2E3, whereas bcl-2:bax was independent of steroid resistance, chemotherapy sensitivity, and chemotherapy resistance. Depletion of intracellular glutathione was documented in RPMI-8226 at high imexon concentrations (>or=225 microM) but not in other cell lines. Furthermore, ROS were found in C2E3, RPMI-8226, and 1-310 only at high imexon concentrations, whereas a sensitive marker of oxidative DNA damage, 8-hydroxydeoxyguanosine, was not increased in any cell line.
Our results demonstrate that imexon has significant broad antimyeloma activity that is mediated through apoptotic mechanisms that is not dependent on production of ROS. Moreover, we have identified a mechanism of cytotoxicity in dexamethasone-sensitive and -resistant myeloma cells induced by imexon that is caspase-8 dependent.
Imexon是一种2-氰基氮丙啶制剂，已显示其可通过凋亡抑制化疗敏感的骨髓瘤细胞生长，同时细胞内谷胱甘肽储备减少，活性氧（ROS）增加。我们研究了Imexon在多种地塞米松及化疗敏感和耐药的骨髓瘤细胞系中的细胞毒性机制。
我们检测了地塞米松敏感（C2E3）、地塞米松耐药（1-310和1-414）、化疗敏感（RPMI-8226）和化疗耐药（DOX-1V和DOX-10V）骨髓瘤细胞系中的细胞毒性、凋亡及氧化还原状态变化。
我们发现，在与Imexon（80-160 microM）孵育48小时后，地塞米松及化疗敏感和耐药的骨髓瘤细胞系均出现显著的细胞毒性，且呈时间和剂量依赖性。Imexon在所有细胞系中的细胞毒性机制均与凋亡诱导有关，伴有裂解的半胱天冬酶-3。此外，在C2E3和1-414细胞系中，Imexon处理后，我们证实了半胱天冬酶-8依赖性凋亡。在C2E3中，Imexon可使Bcl-2:bax促凋亡，而Bcl-2:bax与类固醇耐药、化疗敏感性和化疗耐药无关。在高浓度Imexon（≥225 microM）下，RPMI-8226细胞系中细胞内谷胱甘肽耗竭，但其他细胞系未出现。此外，仅在高浓度Imexon下，C2E3、RPMI-8226和1-310细胞系中发现了ROS，而氧化DNA损伤的敏感标志物8-羟基脱氧鸟苷在任何细胞系中均未增加。
我们的结果表明，Imexon具有显著的广泛抗骨髓瘤活性，其通过凋亡机制介导，不依赖于ROS的产生。此外，我们确定了Imexon诱导的地塞米松敏感和耐药骨髓瘤细胞中的细胞毒性机制，该机制是半胱天冬酶-8依赖性的。
