Quan T, Reiners J J, Culp S J, Richter P, States J C
Center for Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan 48201, USA.
Mol Carcinog. 1995 Feb;12(2):91-102. doi: 10.1002/mc.2940120206.
DNA repair-deficient (xeroderma pigmentosum group A (XPA)) and DNA repair-proficient (normal) human skin fibroblasts were genetically engineered by transformation with a controllable human cytochrome P450 (CYP)1A1 expression vector. Induction of CYP1A1 enabled these cells to metabolize (+/-)-benzo[a]pyrene-trans-7,8-dihydrodiol (BPD) into a potent cytotoxicant and mutagen. The XPA cells were more susceptible than the normal cells to the cytotoxic effects of both CYP1A1-metabolized BPD and exogenously supplied (+/-)-anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10- epoxide (BPDE). Furthermore, the differential cytotoxicity between XPA and normal cells induced by CYP1A1-metabolized BPD was 8.4-fold greater than that induced by exogenously supplied BPDE. The two cell lines had similar CYP1A1 activities, suggesting that a difference in metabolic potential was not the cause of the differential response to BPD. At comparable cytotoxicity in both XPA and normal cells, BPD treatment induced more mutants and more DNA adducts than BPDE treatment did. At similar levels of DNA adducts in XPA cells, the levels of cytotoxicity induced by CYP1A1-metabolized BPD and exogenously supplied BPDE were similar, but CYP1A1-metabolized BPD induced a threefold higher hypoxanthine phosphoribosyltransferase mutation frequency. In contrast, at similar levels of adducts in CYP1A1-expressing normal cells, BPD induced less cytotoxicity and a lower mutation frequency. DNA adducts were identified and quantified by 32P-postlabeling analyses. The principal adduct formed by both CYP1A1-metabolized BPD and exogenously supplied BPDE was 10-beta-(deoxyguanosin-N2-yl)-7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10- tetrahydrobenzo[a]pyrene, indicating that the differential effects of BPD- and BPDE-induced adducts were not due to a difference in the types of adducts formed. The results of these studies suggest that CYP1A1-metabolized BPD may form adducts preferentially in transcriptionally active genes or that the intracellular concentration of BPDE may influence the balance between cytotoxicity and mutagenicity (or both).
通过用可控的人细胞色素P450（CYP）1A1表达载体进行转化，对DNA修复缺陷型（A型着色性干皮病（XPA））和DNA修复 proficient 型（正常）人皮肤成纤维细胞进行基因工程改造。CYP1A1的诱导使这些细胞能够将（±）-苯并[a]芘-反式-7,8-二氢二醇（BPD）代谢为一种强效细胞毒性剂和诱变剂。XPA细胞比正常细胞对CYP1A1代谢的BPD和外源供应的（±）-反式-苯并[a]芘-反式-7,8-二氢二醇-9,10-环氧化物（BPDE）的细胞毒性作用更敏感。此外，CYP1A1代谢的BPD诱导的XPA细胞和正常细胞之间的差异细胞毒性比外源供应的BPDE诱导的高8.4倍。这两种细胞系具有相似的CYP1A1活性，表明代谢潜能的差异不是对BPD差异反应的原因。在XPA细胞和正常细胞中具有相当的细胞毒性时，BPD处理比BPDE处理诱导更多的突变体和更多的DNA加合物。在XPA细胞中DNA加合物水平相似时，CYP1A1代谢的BPD和外源供应的BPDE诱导的细胞毒性水平相似，但CYP1A1代谢的BPD诱导的次黄嘌呤磷酸核糖基转移酶突变频率高3倍。相反，在表达CYP1A1的正常细胞中加合物水平相似时，BPD诱导的细胞毒性较小且突变频率较低。通过32P后标记分析鉴定和定量DNA加合物。CYP1A1代谢的BPD和外源供应的BPDE形成的主要加合物是10-β-（脱氧鸟苷-N2-基）-7β，8α，9α-三羟基-7,8,9,10-四氢苯并[a]芘，表明BPD和BPDE诱导的加合物的差异效应不是由于形成的加合物类型的差异。这些研究结果表明，CYP1A1代谢的BPD可能优先在转录活性基因中形成加合物，或者BPDE的细胞内浓度可能影响细胞毒性和诱变性（或两者）之间的平衡。
