HK Inhibits Angiogenesis/Peritoneal Dissemination Figure 5. Effects of honokiol on endothelial cell sprouting and endothelial cell tube formation. (A) Honokiol inhibited endothelial cell sprouting in an aortic ring assay. Aortas were harvested from 6-week-old Sprague-Dawley rats and cut into 1-mm slices, which were then placed in 12-well plates containing matrigel. The rings were photographed and analyzed. The endothelial cell sprouting was abundant in the control aortic rings (left panels), but not in the rings treated with honokiol (HK; middle panels, 40 mM; right panels, 60 mM). (B) Honokiol suppressed the endothelial cell tube formation. HUVECs were seeded into matrigel-coated 96-well plates. Cells were treated with honokiol (40 and 60 mM) for 12–18 h. The tube formation images were captured in an inverted photomicroscope, and tube formations were scored. (C) The degree of microvessel sprouting from aortic rings was scored from 0 (least positive) to 4 (most positive). (D) Quantification of HUVEC tube formation is shown. All data are presented as mean 6 SEM (n = 8–10). *p,0.05 as compared with control. doi:10.1371/journal.pone.0043711.g005 honokiol are shown in Figure 10B-b. We next examined whether endogenous SHP-1 is modulated by honokiol. Honokiol was capable of evoking the SHP-1 activity in gastric cancer cells, HUVECs and SVECs in a time-dependent manner (Fig. 11A). Honokiol also enhanced the SHP-1 protein expression in peritoneal metastatic tumors isolated from MKN45-inoculated mice as revealed by immunohistochemical analysis (Fig. 11B). We further investigated the interaction between SHP-1 and STAT-3 PLOS ONE | www.plosone.org 7 August 2012 | Volume 7 | Issue 8 | e43711