GADD45a mediates the adaptive response to genotoxic stress. The patented GFP fluorescence reporter includes complex regulatory elements, and gives positive results for direct acting mutagens, clastogens, as well as aneugens, and topoisomerase and polymerase inhibitors. Importantly the assay gives correct negative results for non-genotoxins, many of which give misleading positive results in other in vitro tests.
Without metabolic activation (-S9)
Nine, 2-fold dilutions of each compound together with positive controls are set out in the 96-well microplate and growing cells are added to each well. 2 strains (test and control) are used. After incubation for 48 hours and measurement in a microplate reader, simple software gives automated decisions and a clear graphical output.
With metabolic activation (+S9)
Cells are incubated in 96-well microplates for 3 hours in the presence of the test compound and 1% S9 mix. After plate washing to remove S9, the cells are re-suspended in fresh recovery medium and incubated for a further 45 hours. Following flow cytometry data collection, a data processing template generates positive / negative genotoxicity outcomes alongside a clear graphical output.
A unique combination of both high specificity and high sensitivity genotoxicity assessment in a human cell line has been demonstrated in a wide range of validation exercises with diverse sets of compounds. See the related articles section for details of specific publications.