Hu X, Herzog C, Zimniak P, Singh S V
Cancer Research Laboratory, Mercy Cancer Institute, Mercy Hospital of Pittsburgh, Pennsylvania 15219, USA.
Cancer Res. 1999 May 15;59(10):2358-62.
The pi class glutathione S-transferase (GSTP1-1), which is polymorphic in human populations, is believed to play an important role in detoxification of the ultimate carcinogen of widespread environmental pollutant benzo[a]pyrene [(+)-anti-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide [(+)-anti-BPDE]]. The allelic variants of human GSTP1-1 (hGSTP1-1) differ in their structures by the amino acids in positions 104 (isoleucine or valine) and/or 113 (valine or alanine). Here, we have determined the protective effect of overexpression of allelic variants of hGSTP1-1, through stable transfection in HepG2 cells, against (+)-anti-BPDE-induced DNA modification. Clonal transfectants of HepG2 cells corresponding to the three allelic variants of hGSTP1-1 [(I104,A113), (V104,A113), and (V104,V113), denoted hGSTP1(IA), hGSTP1(VA), and hGSTP1(VV), respectively] with similar levels of hGSTP1 protein were identified and characterized for their GST activity and (+)-anti-BPDE-induced DNA modification. The glutathione S-transferase activity toward (+)-anti-BPDE was significantly higher (approximately 3.0-3.6-fold) in cells transfected with hGSTP1(VA) [HepG2(VA)] and hGSTP1(VV) [HepG2(VV)] compared with hGSTP1(IA) transfectant [HepG2(IA)]. The formation of (+)-anti-BPDE-DNA adducts was significantly reduced in HepG2(VA) and HepG2(VV) cells compared with cells transfected with insert-free vector (HepG2-vect). Maximum protection against (+)-anti-BPDE-induced DNA damage was afforded by the hGSTP1(VV) isoform. The results of this study indicate that the allelic variants of hGSTP1-1 significantly differ in their ability to provide protection against (+)-anti-BPDE-induced DNA damage. Thus, hGSTP1-1 polymorphism may be an important factor in differential susceptibility of individuals to tumorigenesis induced by benzo[a]pyrene.
π类谷胱甘肽S-转移酶（GSTP1-1）在人群中具有多态性，被认为在广泛存在的环境污染物苯并[a]芘的最终致癌物（(+)-反式苯并[a]芘-7,8-二氢二醇-9,10-环氧化物[(+)-反式-BPDE]）的解毒过程中发挥重要作用。人类GSTP1-1（hGSTP1-1）的等位基因变体在其结构上因第104位氨基酸（异亮氨酸或缬氨酸）和/或第113位氨基酸（缬氨酸或丙氨酸）而有所不同。在此，我们通过在HepG2细胞中稳定转染，确定了hGSTP1-1等位基因变体过表达对(+)-反式-BPDE诱导的DNA修饰的保护作用。鉴定并表征了与hGSTP1-1的三种等位基因变体[(I104,A113)、(V104,A113)和(V104,V113)，分别记为hGSTP1(IA)、hGSTP1(VA)和hGSTP1(VV)]相对应的HepG2细胞克隆转染子，它们具有相似水平的hGSTP1蛋白，并检测了其GST活性和(+)-反式-BPDE诱导的DNA修饰情况。与hGSTP1(IA)转染子[HepG2(IA)]相比，用hGSTP1(VA)[HepG2(VA)]和hGSTP1(VV)[HepG2(VV)]转染的细胞对(+)-反式-BPDE的谷胱甘肽S-转移酶活性显著更高（约3.0 - 3.6倍）。与用无插入载体转染的细胞（HepG2-vect）相比，HepG2(VA)和HepG2(VV)细胞中(+)-反式-BPDE-DNA加合物的形成显著减少。hGSTP1(VV)同工型对(+)-反式-BPDE诱导的DNA损伤提供了最大程度的保护。本研究结果表明，hGSTP1-1的等位基因变体在提供针对(+)-反式-BPDE诱导的DNA损伤的保护能力上存在显著差异。因此，hGSTP1-1多态性可能是个体对苯并[a]芘诱导的肿瘤发生易感性差异的一个重要因素。
