Kleiner-Hancock et al. BMC Cancer 2010, 10:394 http://www.biomedcentral.com/1471-2407/10/394 Page 6 of 10 30 ppm ± ACA demonstrated relatively similar levels of significance, suggesting the effect on tumor volume was dependent on dose of ATRA [Additional file 1: Supple- mental Table S4]. A linear trend analysis supported this observation [Additional file 1: Supplemental Table S6]. Live animal imaging (FLT) of representative mice from the 30 ppm ATRA combination study are shown in Fig- ure 4. Sagittal sections through the tumor indicated that the size of tumors visualized in live mice corresponded with the values obtained from caliper measurements. AUR and ATRA suppression of skin SCC tumor growth: Another potentially beneficial combination We next tested the AUR + ATRA combination in the skin SCC xenograft model. As shown in Figure 3D and [Additional file 1: Supplemental Table S7], treatment with AUR (1000 ppm in the diet) alone did not reduce tumor volume to a statistically significant level. 10 ppm ATRA, as observed in the first set of studies, signifi- cantly inhibited tumor volume by 49-87% starting at day 7 and continuing throughout the study (Figure 3D) and Figure 4 Representative FLT-PET live animal imaging from the ACA 500 ± ATRA 30 study. Solid arrows marked with “T” point to the tumors, and dashed arrows marked with “B” point to the urinary bladder, where the isotope is eliminated.