Kizaki H, Ohnishi Y, Azuma Y, Mizuno Y, Ohsaka F
Department of Biochemistry, Tokyo Dental College, Chiba, Japan.
Immunopharmacology. 1992 Nov-Dec;24(3):219-27. doi: 10.1016/0162-3109(92)90077-p.
Incubation of mouse thymocytes with arabinosylcytosine or 5-azacytidine induced dose-dependent internucleosomal DNA cleavage followed by cell death. This process was RNA and protein synthesis-dependent, since DNA fragmentation and cell death was inhibited by actinomycin D and cycloheximide. The results suggest that the cytidine analogs induce apoptosis, a programmed cell death, in thymocytes. The DNA cleavage induced by arabinosylcytosine and 5-azacytidine was inhibited by deoxycytidine and cytidine, respectively, suggesting that phosphorylation of these antimetabolites is required to induce DNA cleavage. DNA fragmentation was unaffected by the addition of aphidicolin or 3-aminobenzamide, indicating that DNA cleavage is not due to the inhibition of DNA synthesis or repair. Other antimetabolites including methotrexate, fluoropyrimidines and thiopurines failed to induce DNA fragmentation. Arabinosylguanine induced DNA fragmentation similar to that produced by the cytidine analogs, suggesting similarity to the selective sensitivity of T lymphocytes to deoxyguanosine toxicity. The precise mechanism by which DNA cleavage is induced remains unclear, but the present study shows that certain antimetabolites act on cells not only by inhibiting proliferation, but by inducing apoptosis with internucleosomal DNA fragmentation.
用阿糖胞苷或5-氮杂胞苷孵育小鼠胸腺细胞会诱导剂量依赖性的核小体间DNA裂解，随后导致细胞死亡。这一过程依赖于RNA和蛋白质合成，因为放线菌素D和环己酰亚胺可抑制DNA片段化和细胞死亡。结果表明，胞苷类似物在胸腺细胞中诱导细胞凋亡，即程序性细胞死亡。阿糖胞苷和5-氮杂胞苷诱导的DNA裂解分别被脱氧胞苷和胞苷抑制，这表明这些抗代谢物的磷酸化是诱导DNA裂解所必需的。添加阿非科林或3-氨基苯甲酰胺不影响DNA片段化，这表明DNA裂解并非由于DNA合成或修复受到抑制。包括甲氨蝶呤、氟嘧啶和硫嘌呤在内的其他抗代谢物未能诱导DNA片段化。阿糖鸟嘌呤诱导的DNA片段化与胞苷类似物产生的片段化相似，这表明其与T淋巴细胞对脱氧鸟苷毒性的选择性敏感性相似。诱导DNA裂解的确切机制尚不清楚，但本研究表明，某些抗代谢物作用于细胞不仅是通过抑制增殖，还通过诱导核小体间DNA片段化的细胞凋亡。
