AGT介导的氯乙基亚硝基脲耐药作用机理的密度泛函理论研究

AGT-mediated Drug Resistance Mechanism of Chloroethylnitrosoureas:A DFT Investigation

氯乙基亚硝基脲(CENUs)是一类重要的抗癌烷化剂,通过导致DNA互补鸟嘌呤-胞嘧啶之间的共价交联(GC交联)发挥抗肿瘤作用。然而,O^6-烷基鸟嘌呤-DNA烷基转移酶(AGT)对DNA烷化损伤的修复作用能够导致肿瘤细胞对CENUs产生耐药性。使用密度泛函理论(DFT)方法结合分子对接对AGT介导的CENUs耐药机制进行研究。结果表明,AGT能够与CENUs导致GC交联的两个前体物——O^6-氯乙基鸟嘌呤(O^6-ClEtG)和N1,O^6-桥亚乙基鸟嘌呤(N1,O^6-EtG)结合形成复合物,然后通过氢迁移和烷基转移两步反应,对这两个前体物进行修复,从而阻断GC交联的形成。在AGT对两个前体物的修复过程中,N1,O^6-EtG的修复在动力学和热力学上比O^6-ClEtG的修复均具有优势,但O^6-ClEtG更有利于与AGT形成复合物。阐明了AGT介导的CENUs耐药机制,这将为开发AGT抑制剂用于与CENUs联合用药以消除耐药性提供重要的理论依据。

Chloroethylnitrosoureas(CENUs)are important anticancer alkylating agents,which play an anti-tumor role by causing covalent crosslink between complementary DNA base pair guanine-cytosine(GC crosslink).However,the repair of DNA alkylation damage by O^6-alkylguanine-DNA alkyltransferase(AGT)can lead to the resistance of tumor cells to CENUs.Density functional theory(DFT)and molecular docking were used to investigate the mechanism of CENUs resistance mediated by AGT.The results showed that AGT combined with two precursors(O^6-ClEtG and N1,O^6-EtG)of GC crosslink to form a complex,and then repaired these two precursors through a two-step mechanism including proton transfer and alkyl transfer,thereby blocked the formation of GC crosslinking.In the process of AGT repairing the two precursors,N1,O^6-EtG is more readily to be repaired than O^6-ClEtG in kinetics and thermodynamics,while O^6-ClEtG is more favorable to form complex with AGT.The mechanism of drug resistance of CENUs mediated by AGT was elucidated,which will provide an important theoretical basis for the development of AGT inhibitors used in combination with CENUs to eliminate drug resistance.