Tsukamoto N, Chen J, Yoshida A
Gunma University School of Medicine, Maebashi, Japan.
Blood Cells Mol Dis. 1998 Jun;24(2):231-8. doi: 10.1006/bcmd.1998.0188.
Elevation of activity and mRNA level of a cytosolic aldehyde dehydrogenase-1 (ALDH1), which oxidizes aldophosphamide, was previously observed in a cyclophosphamide-resistant murine leukemia cell line. However, changes in other enzyme(s) which may detoxify the drug or produce anti-alkylating agent(s), have not been examined. The human leukemia cell line, K562, was made 30-fold resistant against 4-hydroperoxycyclophosphamide (4HC) by exposing the cells to increasing concentrations of the drug. Resistance against cisplatin was also increased by about 3-fold. Activities of glucose-6-phosphate dehydrogenase (G6PD) and ALDH1 were elevated more than 7-fold in the resistant cells. The mRNA level of the two enzymes was also proportionally elevated. The concentration of reduced glutathione (GSH) was higher in the resistant cells (i.e., 21.1 versus 4.68 nmole per 10(6) cells), while activities of gamma-glutamylcysteine synthetase and glutathione synthetase, and the expressions of other human ALDH genes were not increased in the resistant cells. These findings suggest that the acquired resistance against 4HC is a consequence of transcriptional activation of two genes, i.e., one encoding the G6PD, a major enzyme regenerating anti-alkylating GSH, and the other encoding ALDH1, which has a high activity for oxidation of aldophosphamide derived from 4HC.
先前在一种对环磷酰胺耐药的小鼠白血病细胞系中观察到，胞质醛脱氢酶-1（ALDH1）（可氧化醛磷酰胺）的活性和mRNA水平升高。然而，尚未检测其他可能使该药物解毒或产生抗烷化剂的酶的变化。通过将人白血病细胞系K562暴露于浓度不断增加的4-氢过氧环磷酰胺（4HC）中，使其对4HC产生了30倍的耐药性。对顺铂的耐药性也增加了约3倍。耐药细胞中葡萄糖-6-磷酸脱氢酶（G6PD）和ALDH1的活性升高了7倍以上。这两种酶的mRNA水平也相应升高。耐药细胞中还原型谷胱甘肽（GSH）的浓度更高（即每10^6个细胞中分别为21.1和4.68纳摩尔），而耐药细胞中γ-谷氨酰半胱氨酸合成酶和谷胱甘肽合成酶的活性以及其他人ALDH基因的表达并未增加。这些发现表明，对4HC获得性耐药是两个基因转录激活的结果，即一个编码G6PD（一种再生抗烷化剂GSH的主要酶），另一个编码ALDH1（对源自4HC的醛磷酰胺具有高氧化活性）。
