Potentiation of nitrosourea cytotoxicity in human leukemic cells by inactivation of O6-alkylguanine-DNA alkyltransferase.
Potentiation of nitrosourea cytotoxicity in human leukemic cells by inactivation of O6-alkylguanine-DNA alkyltransferase.
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发表时间：
1988-03
期刊：
影响因子：
11.2
通讯作者：
S. Gerson;J. Trey;K. Miller
中科院分区：
文献类型：
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作者：
S. Gerson;J. Trey;K. Miller
HL-60早幼粒细胞白血病细胞系对亚硝基脲具有抗性，并含有高水平的DNA修复蛋白O 6-烷基鸟嘌呤-DNA烷基转移酶（烷基转移酶）。我们研究了在该髓性白血病细胞系中观察到的亚硝基脲抗性中烷基转移酶的保护作用，以确定用修饰的碱基O 6-甲基鸟嘌呤（O 6 mGua）灭活烷基转移酶是否可以使这些细胞对亚硝基脲敏感。在0.5 mM O 6 mGua中预孵育24小时后，当烷基转移酶失活88%时，HL-60细胞对五种不同的亚硝基脲致敏约3.0倍。O 6 mGua预孵育在K562慢性髓性白血病细胞系中没有观察到任何影响，该细胞系对亚硝基脲敏感并且具有低水平的烷基转移酶活性。当再生的HL-60烷基转移酶活性暴露于亚硝基脲后，通过保持细胞在O 6 mGua，HL-60变得更加敏感（3.7至8.5倍），亚硝基脲，但仍然略高于耐药K562。接下来，我们比较了在HL-60中具有细胞毒性的甲基亚硝基脲和氯乙基亚硝基脲的剂量与引起烷基转移酶修复诱导失活的剂量。甲基和氯乙基亚硝基脲引起的烷基转移酶的剂量依赖性失活，并与两者，细胞毒性增加与O 6 mGua曝光。然而，氯乙基亚硝基脲，形成各种O 6烷基化加合物，其中一些修复不良，表现出7-12倍的细胞毒性相对于修复诱导的烷基转移酶失活，而甲基亚硝基脲成为细胞毒性只有当烷基转移酶已被灭活。这些数据表明，白血病细胞敏感的甲基和氯乙基亚硝基脲时，O 6 mGua是用来持久地抑制烷基转移酶。然而，烷基转移酶比氯乙基亚硝基脲提供更有效的保护，最有可能是因为后者形成加合物，该加合物被蛋白质修复不良，并且如果未修复可能成为细胞毒性交联。
The HL-60 promyelocytic leukemia cell line is resistant to nitrosoureas and contains high levels of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (alkyltransferase). We examined the protective role of the alkyltransferase in the nitrosourea resistance observed in this myeloid leukemia cell line to determine whether inactivation of the alkyltransferase with the modified base, O6-methylguanine (O6mGua), could sensitize these cells to nitrosoureas. The HL-60 cells were sensitized approximately 3.0-fold to five different nitrosoureas when the alkyltransferase was inactivated by 88% following a 24-h preincubation in 0.5 mM O6mGua. No effect of O6mGua preincubation was observed in the K562 chronic myelogenous leukemia cell line which is sensitive to nitrosoureas and has low levels of alkyltransferase activity. When regeneration of HL-60 alkyltransferase activity after exposure to nitrosoureas was prevented by maintaining cells in O6mGua, HL-60 became even more sensitive (3.7- to 8.5-fold) to nitrosoureas but remained slightly more resistant than K562. Next, we compared the dose of methyl- and chloroethylnitrosoureas which were cytotoxic in HL-60 with the dose which caused repair-induced inactivation of the alkyltransferase. Both methyl- and chloroethyl-nitrosoureas caused the dose-dependent inactivation of the alkyltransferase and with both, cytotoxicity was increased with O6mGua exposure. However, chloroethylnitrosoureas, which form a variety of O6 alkylation adducts, some of which are poorly repaired, exhibited 7-12 times more cytotoxicity relative to repair-induced inactivation of the alkyltransferase whereas methylnitrosoureas became cytotoxic only when the alkyltransferase had been inactivated. These data suggest that leukemic cells are sensitized to both methyl- and chloroethylnitrosoureas when O6mGua is used to persistently inactivate the alkyltransferase. However, the alkyltransferase provides more efficient protection from methylnitrosoureas than chloroethylnitrosoureas most likely because the latter form adducts which are poorly repaired by the protein and which if unrepaired may become cytotoxic cross-links.