Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Environ Mol Mutagen. 2010 Mar;51(2):146-55. doi: 10.1002/em.20513.
K-Ras mutant fraction (MF) was measured to examine the default assumption of low-dose linearity in the benzo[a]pyrene (B[a]P) mutational response. Groups of 10 male A/J mice (7- to 9-weeks old) received a single i.p. injection of 0, 0.05, 0.5, 5, or 50 mg/kg B[a]P and were sacrificed 28 days after treatment. K-Ras codon 12 TGT and GAT MFs in lung DNAs were measured using Allele-specific Competitive Blocker-PCR (ACB-PCR). The K-Ras codon 12 TGT geometric mean MF was 3.88 x 10(-4) in controls, indicating an average of 1 mutation in every approximately 1,288 lung cells. The K-Ras codon 12 TGT geometric mean MFs were as follows: 3.56 x 10(-4); 6.19 x 10(-4); 2.02 x 10(-3), and 3.50 x 10(-3) for the 0.05, 0.5, 5, and 50 mg/kg B[a]P treatment groups, respectively. The 5 and 50 mg/kg dose groups had TGT MFs significantly higher than did controls. Although 10(-5) is considered as the limit of accurate ACB-PCR quantitation, K-Ras codon 12 GAT geometric mean MFs were as follows: 8.38 x 10(-7), 1.47 x 10(-6), 2.19 x 10(-6), 5.71 x 10(-6), and 8.99 x 10(-6) for the 0, 0.05, 0.5, 5, and 50 mg/kg B[a]P treatment groups, respectively. The K-Ras TGT and GAT MFs increased in a B[a]P-dose-dependent manner, with response approximately linear over the 0.05 to 5 mg/kg dose range. K-Ras MF increased with B[a]P adduct burden measured for identical doses in a separate study. Thus, ACB-PCR may be useful in characterizing the shape of a dose-response curve at low doses and establishing relationships between DNA adducts and tumor-associated mutations.
K-Ras 突变分数 (MF) 用于检测苯并[a]芘 (B[a]P) 突变反应中低剂量线性的默认假设。每组 10 只 7-9 周龄雄性 A/J 小鼠接受单次腹腔注射 0、0.05、0.5、5 或 50mg/kg B[a]P，并在治疗后 28 天处死。使用等位基因特异性竞争阻断 PCR (ACB-PCR) 测量肺 DNA 中的 K-Ras 密码子 12 TGT 和 GAT MF。对照组中 K-Ras 密码子 12 TGT 的几何平均 MF 为 3.88×10(-4)，表明每 1288 个肺细胞中约有 1 个突变。K-Ras 密码子 12 TGT 的几何平均 MF 如下：0.05、0.5、5 和 50mg/kg B[a]P 处理组分别为 3.56×10(-4)、6.19×10(-4)、2.02×10(-3)和 3.50×10(-3)。5 和 50mg/kg 剂量组的 TGT MF 明显高于对照组。尽管 10(-5) 被认为是 ACB-PCR 定量的准确极限，但 K-Ras 密码子 12 GAT 的几何平均 MF 如下：0、0.05、0.5、5 和 50mg/kg B[a]P 处理组分别为 8.38×10(-7)、1.47×10(-6)、2.19×10(-6)、5.71×10(-6)和 8.99×10(-6)。K-Ras TGT 和 GAT MF 随 B[a]P 剂量呈剂量依赖性增加，在 0.05 至 5mg/kg 剂量范围内反应呈近似线性。在另一项单独研究中，用相同剂量测量的 B[a]P 加合物负担增加了 K-Ras MF。因此，ACB-PCR 可能有助于在低剂量下描述剂量反应曲线的形状，并建立 DNA 加合物与肿瘤相关突变之间的关系。
