Bramson J, McQuillan A, Aubin R, Alaoui-Jamali M, Batist G, Christodoulopoulos G, Panasci L C
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Que., Canada.
Mutat Res. 1995 May;336(3):269-78. doi: 10.1016/0921-8777(94)00063-c.
Acquired resistance is a limiting factor in chemotherapy. We have employed nitrogen mustard resistant B-cell chronic lymphocytic leukemia (B-CLL) as a clinically relevant model to study this phenomenon. Resistance in B-CLL is associated with enhanced repair of nitrogen mustard crosslinks. In order to identify the repair pathway responsible for nitrogen mustard resistance, lymphocytes were screened for cross-resistance to a variety of DNA damaging agents. The MTT assay was used to measure the resistance of B-CLL lymphocytes to various DNA damaging agents, including nitrogen mustards, UV light, methyl methanesulfonate, and mitomycin C. We have shown that B lymphocytes from patients with nitrogen mustard resistant chronic lymphocytic leukemia reflect their clinical status. This assay allows us to classify lymphocytes as nitrogen mustard sensitive or resistant, based on in vitro observations. The resistant population was 5.6 and 4.1 fold more resistant to the nitrogen mustard analogs, chlorambucil and melphalan, respectively. Resistant lymphocytes displayed no increased resistance to either methyl methanesulfonate or UV light, indicating that neither classical base nor nucleotide excision repair is rate-limiting in resistance. Resistant lymphocytes were 6.0 and 2.2 fold more resistant to mitomycin C and cis-diamminedichloroplatinum (II), respectively, suggesting enhanced crosslink repair. Neither glutathione nor glutathione S-transferase levels correlated with resistance. The development of nitrogen mustard drug resistance in B-CLL appears to be associated with cross-resistance to other bifunctional alkylating agents which produce interstrand crosslinks. Our results indicate that resistance to nitrogen mustards in chronic lymphocytic leukemia is associated with enhanced repair of DNA crosslinks which may involve a recombination dependent system. This model should prove very useful in the elucidation of the molecular mechanisms of crosslink repair.
获得性耐药是化疗中的一个限制因素。我们采用氮芥耐药的B细胞慢性淋巴细胞白血病（B-CLL）作为临床相关模型来研究这一现象。B-CLL中的耐药与氮芥交联修复增强有关。为了确定负责氮芥耐药的修复途径，对淋巴细胞进行了对多种DNA损伤剂的交叉耐药性筛选。MTT法用于测量B-CLL淋巴细胞对各种DNA损伤剂的耐药性，包括氮芥、紫外线、甲基磺酸甲酯和丝裂霉素C。我们已经表明，来自氮芥耐药慢性淋巴细胞白血病患者的B淋巴细胞反映了他们的临床状态。该检测方法使我们能够根据体外观察结果将淋巴细胞分类为对氮芥敏感或耐药。耐药群体对氮芥类似物苯丁酸氮芥和美法仑的耐药性分别高5.6倍和4.1倍。耐药淋巴细胞对甲基磺酸甲酯或紫外线均未表现出耐药性增加，这表明经典碱基修复和核苷酸切除修复在耐药性方面均不是限速因素。耐药淋巴细胞对丝裂霉素C和顺二氯二氨铂（II）的耐药性分别高6.0倍和2.2倍，提示交联修复增强。谷胱甘肽和谷胱甘肽S-转移酶水平均与耐药性无关。B-CLL中氮芥耐药的发生似乎与对其他产生链间交联的双功能烷化剂的交叉耐药有关。我们的结果表明，慢性淋巴细胞白血病中对氮芥的耐药与DNA交联修复增强有关，这可能涉及一个依赖重组的系统。该模型在阐明交联修复的分子机制方面应该非常有用。
