HK Inhibits Angiogenesis/Peritoneal Dissemination Figure 3. Quantification of honokiol-inhibited peritoneal metastasis of gastric tumor cells. Mice were inoculated with human gastric cancer cells (MKN45 and SCM-1). [18F]-FDG-PET/CT imaging was performed and analyzed. (A) Quantifications of estimated radioactivity (Bq/ml, a) and specific uptake values (SUV, b) were calculated. SUV is used as an index to determine if a hotspot is significant. (B) Photomacrographs of metastatic peritoneal nodules are shown. All data are presented as mean 6 SEM (n = 6–8). *p,0.05 as compared with control. doi:10.1371/journal.pone.0043711.g003 STAT-3 overexpression and accumulation in the tumor region, including nuclei and cytoplasm, was significantly reversed by honokiol treatment (Fig. 8B). In Western blotting analysis, honokiol markedly decreased the accumulation of p-STAT3 in tumors as compared with vehicle control (Fig. 9A). The expression of constitutive STAT3 was not affected. Moreover, the DNA binding activity of STAT-3 was further confirmed using EMSA. As shown in Figure 9B, honokiol markedly inhibited the increased DNA binding activity of STAT-3 in human gastric cancer cells. Honokiol also inhibited the VEGF- increased STAT-3 DNA binding activity in HUVECs (Fig. 9B). Honokiol Induced SHP-1-regulated STAT-3 Dephosphorylation in Gastric Cancer Cells, Endothelial Cells, and Tumors SHP-1 is a non-transmembrane PTP [12]. We next examined whether honokiol can regulate the expression and activity of SHP- 1. As shown in Figure 10A, honokiol enhanced the protein expression of SHP-1, but not SHP-2, in HUVECs and AGS cells in a time-dependent manner. Pharmacological PTP inhibitor and SHP-1 siRNA transfection effectively abolished the honokiol- induced STAT-3 dephosphorylation in HUVECs and AGS cells (Fig. 10B-a). Similar results in SCM-1 cells and SV-40 immortal- ized mouse microvascular endothelial cells (SVECs) treated with PLOS ONE | www.plosone.org 5 August 2012 | Volume 7 | Issue 8 | e43711