Stopper H, Körber C, Schiffmann D, Caspary W J
Institute of Pharmacology and Toxicology, University of Würzburg, Germany.
Mutat Res. 1993 Aug;300(3-4):165-77. doi: 10.1016/0165-1218(93)90048-i.
5-Azacytidine was originally developed to treat human myelogenous leukemia. However, interest in this compound has expanded because of reports of its ability to affect cell differentiation and to alter eukaryotic gene expression. In an ongoing attempt to understand the biochemical effects of this compound, we examined the effects of 5-azacytidine on mitosis and on micronucleus formation in mammalian cells. In L5178Y mouse cells, 5-azacytidine induced micronuclei at concentrations at which we and others have already reported its mutagenicity at the tk locus. Using CREST staining and C-banding studies, we showed that the induced micronuclei contained mostly chromosomal fragments although some may have contained whole chromosomes. By incorporating BrdU into the DNA of SHE cells, we determined that micronuclei were induced only when the compound was added while the cells were in S phase. Microscopically visible effects due to 5-azacytidine treatment were not observed until anaphase of the mitosis following treatment or thereafter. 5-Azacytidine did not induce micronuclei via interference with formation of the metaphase chromosome arrangement in mitosis, a common mechanism leading to aneuploidy. Supravital UV microscopy revealed that chromatid bridges were observed in anaphase and, in some cases, were sustained into interphase. In the first mitosis after 5-azacytidine treatment we observed that many cells were unable to perform anaphase separation. All of these observations indicate that 5-azacytidine is predominantly a clastogen through its incorporation into DNA.
5-氮杂胞苷最初是为治疗人类骨髓性白血病而研发的。然而，由于有报道称其能够影响细胞分化并改变真核基因表达，人们对这种化合物的兴趣有所扩大。为了持续深入了解该化合物的生化效应，我们研究了5-氮杂胞苷对哺乳动物细胞有丝分裂和微核形成的影响。在L5178Y小鼠细胞中，5-氮杂胞苷在我们及其他研究已报道其在tk位点具有致突变性的浓度下诱导产生了微核。通过着丝粒蛋白C（CREST）染色和C带研究，我们发现诱导产生的微核大多包含染色体片段，不过有些可能包含整条染色体。通过将5-溴脱氧尿嘧啶核苷（BrdU）掺入SHE细胞的DNA中，我们确定只有在细胞处于S期时添加该化合物才会诱导产生微核。直到处理后的有丝分裂后期或之后，才观察到5-氮杂胞苷处理所导致的显微镜下可见的效应。5-氮杂胞苷并非通过干扰有丝分裂中期染色体排列的形成来诱导微核，而这是导致非整倍体的常见机制。超活细胞紫外线显微镜检查显示，在后期观察到了染色单体桥，在某些情况下，这些染色单体桥会持续到间期。在5-氮杂胞苷处理后的首次有丝分裂中，我们观察到许多细胞无法进行后期分离。所有这些观察结果表明，5-氮杂胞苷主要通过掺入DNA而成为一种断裂剂。
