HK Inhibits Angiogenesis/Peritoneal Dissemination Figure 1. Schematic representation of peritoneal metastasis mouse model with or without honokiol treatment. (A) Four groups of mice were investigated and listed. (B) The metastatic conditions in cancer cell inoculation by PET/CT surveillance and further then for honokiol treatment. The human gastric cancer cells (4,56106 cells) MKN45 (a) and SCM-1 (b) were inoculated to mice at day 7. doi:10.1371/journal.pone.0043711.g001 endothelial cell tube formation by reducing the tube-like structure in length and width (Figs. 5B and 5D). Honokiol Abolished STAT-3 Signaling in Human Gastric Cancer Cells, HUVECs, and Tumors Previous studies have shown a strong correlation between activated STAT-3 and angiogenic phenotype [11]. We further elucidated the effect of honokiol on the phosphorylation of STAT- 3 in human gastric cancer cells (MKN45 and AGS) and HUVECs. As shown in Figure 6, honokiol reduced the tyrosine (Tyr705) phosphorylation of STAT-3 in a time-dependent manner with about a two-fold decrease at 1–2 h in AGS cells (Fig. 6A) and a 3 to 10-fold decrease at 0.5–24 h in MKN45 cells (Fig. 6B). Surprisingly, honokiol induced STAT-3 dephosphorylation of Tyr705, but not Ser727, residues in these human gastric cancer cells. However, honokiol simultaneously inhibited both Tyr705 and Ser727 phosphorylation of STAT-3 in HUVECs (Fig. 6C). Quantitative analysis of protein bands in the Western blot using PLOS ONE | www.plosone.org 3 August 2012 | Volume 7 | Issue 8 | e43711