Schisler Melissa R, Moore Martha M, Gollapudi B Bhaskar
Environmental, Health & Safety, The Dow Chemical Company, Midland, MI, USA.
Ramboll, Little Rock, AR, USA.
Methods Mol Biol. 2019;2031:3-28. doi: 10.1007/978-1-4939-9646-9_1.
The in vitro mouse lymphoma cell assay (MLA) is one of the most widely practiced assays in genetic toxicology. MLA detects forward mutations at the thymidine kinase (Tk) locus of the L5178Y (Tk -3.7.2C) cell line derived from a mouse thymic lymphoma. This assay is capable of detecting a wide range of genetic events including point mutations, deletions and multilocus, chromosomal rearrangements, mitotic recombination and nondisjunction. There are two equally accepted versions of the assay, one using soft agar cloning and the second method using liquid media cloning in 96-microwell plates. There are two morphologically distinct types of mutant colonies recovered in the MLA; small and large colony mutants. The induction of small colony mutants is associated with chemicals inducing gross chromosomal aberrations, whereas the induction of large mutant colonies is generally associated with chemicals inducing point mutations. The source and karyotype of the cell line as well as the culture conditions are important variables that could influence the assay performance. The assay when performed according to the standards recommended by the International Workshops on Genotoxicity Testing (IWGT) and the Organization of Economic Cooperation and Development Test Guideline 490 is capable of providing valuable genotoxicity hazard information as part of the overall safety assessment process of various classes of test substances.
体外小鼠淋巴瘤细胞试验（MLA）是遗传毒理学中应用最广泛的试验之一。MLA可检测源自小鼠胸腺淋巴瘤的L5178Y（Tk -3.7.2C）细胞系胸苷激酶（Tk）位点的正向突变。该试验能够检测多种遗传事件，包括点突变、缺失以及多位点、染色体重排、有丝分裂重组和不分离。该试验有两个同样被认可的版本，一个使用软琼脂克隆，第二种方法是在96孔板中使用液体培养基克隆。在MLA中可回收两种形态上不同类型的突变菌落；小菌落突变体和大菌落突变体。小菌落突变体的诱导与诱导染色体畸变的化学物质有关，而大菌落突变体的诱导通常与诱导点突变的化学物质有关。细胞系的来源和核型以及培养条件是可能影响试验性能的重要变量。按照遗传毒性测试国际研讨会（IWGT）和经济合作与发展组织测试指南490推荐的标准进行该试验，能够作为各类受试物质总体安全性评估过程的一部分，提供有价值的遗传毒性危害信息。
