Department of Genetic and Molecular Toxicology, Kirkland Consulting, PO Box 79, Tadcaster LS24 0AS, UK.
Mutagenesis. 2010 Nov;25(6):539-53. doi: 10.1093/mutage/geq041. Epub 2010 Aug 18.
In the analysis by Parry et al. [Parry, J. M., Parry, E., Phrakonkham, P. and Corvi, R. (2010) Analysis of published data for top concentration considerations in mammalian cell genotoxicity testing. Mutagenesis, 25, 531-538], 24 rodent carcinogens that were negative in the Ames test were identified that were only positive in mammalian cell tests at concentrations between 1 and 10 mM. These carcinogens can be subdivided into four groups as follows: (1) probable non-genotoxic (non-mutagenic) carcinogens, tumour promoters or negative for genotoxicity in vivo (n=10); (2) questionable carcinogens (n=4); (3) carcinogens with a probable genotoxic mode of action (n=5); (4) compounds where carcinogenicity or in vivo genotoxicity is unknown or unclear (n=5). It is not expected that in vitro mammalian cell tests should give positive results with Group 1 chemicals. Within Groups 2-4, five chemicals were considered a low priority because they could be detected using modified conditions because genotoxicity was associated with precipitate or pH shifts or because non-standard metabolism was required. The remaining nine chemicals were therefore considered most critical in terms of detection of genotoxic activity in mammalian cells. Daminozide was also included because it may have given positive responses between 1 and 10 mM. Many of the reported studies could have given positive results only at >1 mM because 'old' protocols were followed. These 10 chemicals have therefore been retested using modern protocols. Some were negative even up to 10 mM. Others were positive at concentrations <1 mM. Only methylolacrylamide was positive at a concentration >1 mM (2 mM = 202 μg/ml). Low-molecular weight substances may therefore require concentrations >1 mM, but further work is needed. Based on this analysis, it is concluded that the 10 mM upper limit in mammalian cell tests can be lowered without any loss of sensitivity in detecting genotoxic rodent carcinogens. A new limit of 1 mM or 500 μg/ml, whichever is the higher, is proposed.
在 Parry 等人的分析中[Parry, J. M., Parry, E., Phrakonkham, P. and Corvi, R. (2010) 对哺乳动物细胞遗传毒性测试中最高浓度考虑因素的已发表数据的分析。诱变，25，531-538]，确定了 24 种在 Ames 试验中为阴性的啮齿动物致癌物，这些致癌物仅在哺乳动物细胞试验中在 1 至 10mM 浓度下为阳性。这些致癌物可以分为以下四组：(1) 可能非遗传毒性（非诱变）致癌物、肿瘤促进剂或体内遗传毒性阴性（n=10）；(2) 可疑致癌物（n=4）；(3) 可能具有遗传毒性作用模式的致癌物（n=5）；(4) 致癌性或体内遗传毒性未知或不清楚的化合物（n=5）。预计第 1 组化学物质不应在体外哺乳动物细胞试验中产生阳性结果。在第 2-4 组中，有 5 种化学物质被认为是低优先级的，因为它们可以使用改良条件来检测，因为遗传毒性与沉淀或 pH 变化有关，或者因为需要非标准代谢。因此，其余 9 种化学物质被认为是在检测哺乳动物细胞中遗传毒性活性方面最为关键的。达米诺泽德也被包括在内，因为它可能在 1 至 10mM 之间产生阳性反应。由于遵循了“旧”方案，许多报道的研究可能仅在>1mM 时才产生阳性结果。因此，这些 10 种化学物质已使用现代方案进行重新测试。有些甚至在 10mM 时仍为阴性。其他在浓度<1mM 时为阳性。只有甲基丙烯酰胺在浓度>1mM 时为阳性（2mM=202μg/ml）。因此，低分子量物质可能需要>1mM 的浓度，但还需要进一步的工作。基于此分析，可以得出结论，哺乳动物细胞试验中的 10mM 上限可以降低，而不会降低检测遗传毒性啮齿动物致癌物的敏感性。建议提出一个新的限值，即 1mM 或 500μg/ml，以较高者为准。
