DNA DAMAGE BY ALKYLATING AGENTS AND THEIR REPAIR IN HUMAN TUMOR CELLS

D.Yarosh，R.S.日，三，和其他人已经表明，大约20%的 人肿瘤细胞系和病毒转化细胞系对 由于明显不存在06-甲基鸟嘌呤DNA， 甲基转移酶（06 MT）;这种表型已被指定为mer-。 这 酶去除鸟嘌呤0-6位的烷基化损伤，但不 DNA中的其他位点。 我们和其他人已经分离了06 MT cDNA克隆。 我们的克隆已被用作探针来测量mRNA水平， 已被用于合成用于抗体开发的重组蛋白。 我们 之前已经发现，06 MT mRNA在所有的聚体中都显著减少， 检查的肿瘤细胞系。 06 MT mRNA水平在正常对照组中变化10倍， mer+细胞系，并与已知的蛋白质水平相关， 特殊细胞 与D合作。Yarosh，06 MT mRNA水平和 现已在患者活检标本中测定了06 MT活性 患有肺癌和脑瘤 这种活性在肿瘤中变化很大， 不同的患者，但肿瘤和邻近正常组织相似 同一个病人。 总体而言，相对06 MT mRNA水平与 但在一些肺活检中，活性相当低 而mRNA水平则没有。 这表明，06 MT表达也可能 在翻译和/或翻译后水平进行控制。 我们 这些发现可能对癌症治疗有重要意义， 例如BCNU。

D.Yarosh, R.S. Day, III, and others have shown that approximately 20% of human tumor lines and viral transformed lines are hypersensitive to alkylating agents due to an apparent absence of 06-methylguanine DNA methyltransferase (06MT); this phenotype has been designated mer-. This enzyme removes alkylation damage at the 0-6 position of guanine but not at other sites in DNA. We and others have isolated 06MT cDNA clones. Our clone has been used as a probe to measure mRNA levels and has also been used to synthesize recombinant protein for antibody development. We have found previously that 06MT mRNA was markedly reduced in all the mer- tumor cells lines examined. The level of 06MT mRNA varied by 10-fold in mer+ cell lines and correlated with known levels of the protein in particular cells. In collaboration with D. Yarosh, 06MT mRNA levels and 06MT activity have now been determined in biopsy specimens of patients with lung and brain tumors. The activity varied widely in tumors from different patients, but was similar in tumor and adjacent normal tissue from the same patient. In general, relative 06MT mRNA levels correlated with activity, but in several lung biopsies the activity was quite low while mRNA levels were not. This indicates that 06MT expression may also be controlled at the translational and/or post-translational levels. Our findings may have important implications in cancer therapy where agents such as BCNU are used.