Aklillu Eleni, Øvrebø Steinar, Botnen Ingrid V, Otter Charlotta, Ingelman-Sundberg Magnus
Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska University Hospital-Huddinge, Stockholm, Sweden.
Cancer Res. 2005 Jun 15;65(12):5105-11. doi: 10.1158/0008-5472.CAN-05-0113.
Cytochrome P450 1B1 (CYP1B1), an extrahepatic enzyme inducible by smoking, is overexpressed in many tumors and catalyzes the metabolic activation of procarcinogens such as polycyclic aromatic hydrocarbons. In human, CYP1B1 is genetically polymorphic and five common missense mutations causing amino acid substitution have been identified. In this study, we have investigated CYP1B1 haplotypes present in a Spanish population and carried out functional analyses of the corresponding enzymes in yeast using benzo[a]pyrene as a substrate. CYP1B11, CYP1B12, CYP1B13, CYP1B14, CYP1B16, and CYP1B17, encoding combinations of the Arg48Gly, Ala119Ser, Leu432Val, Asn453Ser, and Ala443Gly amino acid substitutions, were present at frequencies of 14.3%, 25.5%, 38.8%, 18.1%, 0.4%, and 2.6%, respectively. The variant CYP1B1 forms were heterologously expressed with human reductase in Saccharomyces cerevisiae and kinetic analyses of benzo[a]pyrene metabolism were carried out. CYP1B1.7, having the amino acid substitutions Arg48Gly, Ala119Ser, Leu432Val, and Ala443Gly, exhibited a significantly decreased capacity (P < 0.001) for the formation of (+/-)-benzo[a]pyrene-trans-7,8-dihydrodiol from benzo[a]pyrene as indicated by lower intrinsic clearance (Vmax/Km). A somewhat decreased clearance was observed for CYP1B1.4, whereas no significant differences in kinetic properties among the remaining variant enzymes were observed as compared with CYP1B1.1. Thus, genetic polymorphism in the CYP1B1 gene, as defined by the haplotypes investigated, might cause interindividual differences in susceptibility (e.g., to lung cancer induced by smoking). The results indicate the necessity to make molecular epidemiologic investigations regarding the association of the specific CYP1B1 haplotypes and cancer risk.
细胞色素P450 1B1（CYP1B1）是一种可被吸烟诱导的肝外酶，在许多肿瘤中过度表达，并催化多环芳烃等前致癌物的代谢活化。在人类中，CYP1B1具有遗传多态性，已鉴定出五个导致氨基酸替换的常见错义突变。在本研究中，我们调查了西班牙人群中存在的CYP1B1单倍型，并以苯并[a]芘为底物，在酵母中对相应酶进行了功能分析。编码精氨酸48甘氨酸、丙氨酸119丝氨酸、亮氨酸432缬氨酸、天冬酰胺453丝氨酸和丙氨酸443甘氨酸氨基酸替换组合的CYP1B11、CYP1B12、CYP1B13、CYP1B14、CYP1B16和CYP1B17的出现频率分别为14.3%、25.5%、38.8%、18.1%、0.4%和2.6%。将变异的CYP1B1形式与人还原酶在酿酒酵母中进行异源表达，并对苯并[a]芘代谢进行动力学分析。具有精氨酸48甘氨酸、丙氨酸119丝氨酸、亮氨酸432缬氨酸和丙氨酸443甘氨酸氨基酸替换的CYP1B1.7，从苯并[a]芘形成（+/-）-苯并[a]芘-反式-7,8-二氢二醇的能力显著降低（P<0.001），内在清除率（Vmax/Km）较低表明了这一点。观察到CYP1B1.4的清除率有所降低，而与CYP1B1.1相比，其余变异酶的动力学性质未观察到显著差异。因此，由所研究的单倍型定义的CYP1B1基因中的遗传多态性可能导致个体间易感性差异（例如，对吸烟诱导的肺癌的易感性）。结果表明有必要对特定CYP1B1单倍型与癌症风险的关联进行分子流行病学调查。
