Kleiner-Hancock et al. BMC Cancer 2010, 10:394 http://www.biomedcentral.com/1471-2407/10/394 [Additional file 1: Supplemental Table S7]. The combi- nation of AUR + 10 ppm ATRA also significantly inhib- ited tumor volume by 62-84% starting at day 7 and continuing until day 25. At day 28, the combination of ATRA + AUR suppressed tumor volume by 84%, although the results were not statistically significant at this date. Photos of tumors from representative mice illustrate this strong combination effect (Figure 5). Sta- tistical analysis of body weights showed a modest reduc- tion in body weights in the ATRA treated groups [Additional file 1: Supplemental Table S8]. Our laboratory and others have shown that one of the chemopreventive activities of AUR is induction of phase II detoxifying enzymes through activation of the Nrf-2/ antioxidant response element [35,36]. In the current study, we also assessed whether the combination of AUR and ATRA maintained this effect. As shown in Table 1, AUR significantly induced GST activities using DCNB as a substrate. No significant effects on NQO activities or on GST activities using CDNB as a sub- strate were observed. CDNB is a more general substrate for GST activities [37], hence may have diluted out any specific effects of AUR at the dietary exposure level in the current study. Also, we have previously observed that AUR is also not a very strong inducer of hepatic Page 7 of 10 Table 1 Effects of dietary combinations of AUR and ATRA on NQO1 and GST activities. Diet Control AUR ATRA AUR + ATRA NQO1 3.17 ± 0.27 4.09 ± 0.30 3.01 ± 0.50 4.27 ± 0.57 CDNB * 1000 DCNB * 1000 316 ± 36 371 ± 47 371 ± 34 386 ± 16 14.9 ± 2.0 27.5 ± 0.7** 18.3 ± 1.5 18.8 ± 1.6 ** Significantly different from control diet (p < 0.01, Tukey’s test) Figures represent mean activities (μmol/min/mg protein) ± SE (n = 4-5). NQO activity [35], so these results are not surprising. However, it appeared that ATRA itself might have mod- estly increased GST activity, and the combination of AUR and ATRA did not afford any increase in activity (using DCNB as a substrate) compared to ATRA alone, and no statistically significant increase compared to the vehicle control group. Thus ATRA may slightly inhibit the GST inducing effect of AUR. Discussion Taken together, the current studies have demonstrated that ACA and AUR suppressed LPS-induced activation of NF- B in NF- B-Re-luc mice, and modestly inhibited SRB12-p9 tumor growth in the xenograft model. Although ATRA was fairly effective at doses as low as Figure 5 Representative tumors from the Auraptene 1000 ± ATRA 10 study. Photographs were taken from duplicate mice in each group. Lines were drawn around the tumor margins for clarity.