Specificity of mutations induced by methyl methanesulfonate in mismatch repair-deficient human cancer cell lines
Specificity of mutations induced by methyl methanesulfonate in mismatch repair-deficient human cancer cell lines
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DOI：
10.1016/s0027-5107(99)00091-3
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发表时间：
1999-06-30
影响因子：
2.3
通讯作者：
Skopek, TR
中科院分区：
文献类型：
--
作者：
Glaab, WE;Tindall, KR;Skopek, TR
最近，我们发现，在人类细胞中的细胞毒性和致突变反应的模型S（N）2烷化剂甲基甲磺酸酯（MMS）可以通过错配修复（MMR）途径进行调制。也就是说，MMR缺陷的人癌细胞系对MMS暴露的细胞毒性作用更具抗性，并且在HPRT基因座处遭受比MMR熟练的细胞系更多的诱导突变。由于MMS几乎不产生O-6-甲基鸟嘌呤（O-6-meG），因此在MMR缺陷细胞中观察到的超变性和对细胞毒性的抗性可能是由O-6-meG以外的病变引起的。MMS产生高产量的N7-甲基鸟嘌呤（N7-meG）和N3-甲基腺嘌呤（N3-meA），这可能导致形成前致突变脱碱基位点，这些病变可能是观察到的MMS细胞毒性和/或致突变作用的原因。为了进一步研究MMS诱变的机制，用MMS处理两种MMR缺陷的人癌细胞系，并测定在HPRT基因座产生的突变的频率和类型。MMS处理（1.5 mM）分别使HCT 116和DLD-1细胞系中的突变增加1.6倍和2.2倍。观察到颠换突变平均增加3.7倍，占两种细胞系中所有诱导突变的三分之一以上。相比之下，在过渡突变（预期来自O-烷基化产物的类别）中观察到平均1.6倍的增加。由于颠换突变不产生O-6-meG，这些研究结果表明，脱碱基位点可能是负责大比例的MMS致突变性在MMR缺陷细胞的病变。此外，这些数据表明MMS诱导的损伤，无碱基位点诱导的碱基改变（即，N7-meG和N3-meA）或所得脱碱基位点本身可以是MMR蛋白识别和/或修复的底物。(C)1999 Elsevier Science B. V.保留所有权利。
Recently, we showed that the cytotoxic and mutagenic response in human cells to the model S(N)2 alkylating agent methyl methanesulfonate (MMS) can be modulated by the mismatch repair (MMR) pathway. That is, human cancer cell lines defective in MMR are more resistant to the cytotoxic effects of MMS exposure and suffer more induced mutations at the HPRT locus than MMR-proficient cell lines. Since MMS produces little O-6-methylguanine (O-6-meG), the observed hypermutability and resistance to cytotoxicity in MMR-defective cells likely results from lesions other than O-6-meG. MMS produces a high yield of N7-methylguanine (N7-meG) and N3-methyladenine (N3-meA), which can lead to the formation of promutagenic abasic sites, and these lesions may be responsible for the observed cytotoxic and/or mutagenic effects of MMS. To further investigate the mechanism of MMS mutagenesis, two MMR-defective human cancer cell lines were treated with MMS and the frequency and the types of mutations produced at the HPRT locus were determined. MMS treatment (1.5 mM) produced a 1.6- and a 2.2-fold increase in mutations above spontaneous levels in HCT116 and DLD-1 cell lines, respectively. An average 3.7-fold increase in transversion mutations was observed, which accounted for greater than one-third of all induced mutations in both cell lines. In contrast, an average 1.6-fold increase was seen among transition mutations (the class expected from O-alkylation products). Since transversion mutations are not produced by O-6-meG, these findings suggest that abasic sites may be the lesion responsible for a large proportion of MMS mutagenicity in MMR-defective cells. Furthermore, these data suggest the MMS-induced damage, either abasic site-inducing base alterations (i.e., N7-meG and N3-meA) or the resulting abasic sites themselves, may be substrates for recognition and/or repair by MMR proteins. (C) 1999 Elsevier Science B.V. All rights reserved.