, 2007b, Pfuhler et al., 2011 and Dearfield et al., 2011). The current mammalian in vitro genotoxicity assays have a high rate of positive results that do not translate into positive rodent carcinogenicity results. This raises the concern that these in vitro assays are overly sensitive and therefore generate false positives ( Dearfield et al., 2011 and Kirkland et al., 2007b). Some companies use non-regulatory assays as early screening tools ( Jacobson-Kram and Contrera, 2007). Recently, Lynch et al. have reviewed

the status of new and emerging technologies, comparing them R428 manufacturer with the current battery of genotoxicity tests (Lynch et al., 2011). These tests do not yet have an accompanying OECD guideline, or not enough data has been collected to fully establish them (trials, validations). This group of assays includes, for example, the comet assay, GreenScreen assay and the γH2AX detection assay. These assays are classified as replacements or improvements of the traditional genotoxicity assays, forming a new approach to replace traditional assays or providing mechanistic understanding complementary to the traditional assays. Subcategories to classify these assays have been defined by experts in the field and are described as mature, maturing and emerging

(Lynch et al., 2011). Mature refers to methods or technologies that have been in the Olaparib purchase field for a relatively long time and are amongst those tests that are likely to become accepted in the foreseeable future. However, these are still not yet fully accepted by regulatory bodies. One reason for this lack of acceptance is the need for generating more data by comprehensive validation exercises. This 3-mercaptopyruvate sulfurtransferase category includes, for example, the comet assay, and in silico technologies for genotoxicity prediction based on chemical structure–activity relationships

(SARs) etc. Maturing refers to those methods or technologies that have proved to add value to the existing methods but have not yet gone through an extensive validation exercise. Maturing assays are the novel GreenScreen assay and yeast DEL assay. Additionally, this category also encompasses the automation of existing methods such as, for example, the development of flow cytometry to score in vitro micronucleus samples. Emerging refers to new technologies that are currently in development, i.e. they show interesting capabilities but require further testing/development. While the standard battery of genotoxicity assays looks at gene mutation or chromosomal damage and variation in chromosome numbers (aneugenicity), there are a number of promising new genotoxicity endpoints of interest related to DNA repair-related protein modification as a response to DNA damage, such as the histone phosphorylation to form γH2AX, subject of this paper.