In all cases a significant linear trend was also observed, indicating a concentration response relationship. These results were therefore considered to be clear evidence for the genotoxicity of all samples in this assay system when using 3 h treatments with and without S9, and 24 h treatments without S9. When the responses of PMs were compared as colonies/μg NFDPM, M4A was more mutagenic than 3R4F in both 20 h without S9 experiments (Fig. 3, Table 7). The increases were statistically significant and consistent with historical

data. W863 was less mutagenic than W861 in both experiments of all three treatment conditions, though a statistically OSI-906 research buy significant difference was achieved in only one experiment. W862 was less mutagenic than W861 in both 3 h with S9 experiments. Neither difference was statistically significant. W862 was less mutagenic than W862 in one 3 h with S9 experiment and more

mutagenic in the other. Neither difference was statistically significant. W862 was more mutagenic than W861 in both 3 h without S9 experiments. The difference was statistically significant in one experiment. The results are summarised qualitatively in Table 8. These results show that changing the tobacco type in the cigarettes used did not alter the spectrum of activity detected in the in vitro toxicity assays used ( Table 8). PMs from W860–W864 induced comparable dose-related cytotoxicities in the NRU. The inclusion of BT tobacco had no effect on NRU cytotoxicity. W860–W864 PMs were genotoxic in the IVMNT and MLA. W862 and W863 (both with 80%BT) were less genotoxic than W861 (control), in some, but not all, experiments. The data obtained with PRKD3 both GSK1210151A cell line of these assays were insufficiently consistent to show any definitive quantitative differences in genotoxicity between the different types of cigarettes. In SAL, unlike the

IVMNT or the MLA, no mutagenicity was detected in the absence of S9. No mutagenicity was detected in tester strains TA1535 or TA102 with S9 with all PM samples, both test and reference, compared with their mutagenicities in TA98, TA100 and TA1537. These data broadly agree with observations made by previous authors using PMs from a variety of tobaccos, ever since the original observations of Kier et al. (1974). Thus, PM was genotoxic in a variety of assays (Baker et al., 2004, Clive et al., 1997, Cobb et al., 1989, DeMarini, 2004, DeMarini et al., 2008, Guo et al., 2011, McAdam et al., 2011, Mitchell et al., 1981, Richter et al., 2010, Rickert et al., 2011, Rickert et al., 2007, Roemer et al., 2004, Roemer et al., 2002 and Sato et al., 1977). However, Putnam et al. (2002) did not find a clear concentration-related increase in cytotoxicity induced by PM in the NRU assay, and Roemer et al. (2002) observed mutagenicity in Ames strains TA98 and TA100 without S9. Of note are the results of testing the PMs with S9 in strain TA98, which showed a consistently lower mutagenic potency for W862 compared with W861.