Ye et al. BMC Cancer 2010, 10:611 http://www.biomedcentral.com/1471-2407/10/611 Page 6 of 11 Figure 1 Expression of Plexin-B1 in benign, borderline, and malignant ovarian tissues and in ovarian cancer cell lines. Immunohistochemical staining showed the presence of Plexin-B1 in human ovarian tissues with different pathological changes. In normal ovaries (A) and benign serous ovarian cystadenomas (B), Plexin-B1 protein expression was virtually negative, whereas in serous borderline ovarian tumors, Plexin-B1 expression was higher and stained membranes; the insert shows the dashed line region at a higher magnification to demonstrate the membrane reaction product (C). In serous ovarian cystadenocarcinomas, Plexin-B1 expression was further up-regulated and showed strong cytoplasmic staining (D). Representative images are shown. Magnification, ×200. Expression of Plexin-B1 in four human ovarian cancer cell lines at both the mRNA and protein levels was detected with RT-PCR and western blotting. (E) RT-PCR showed the relative level of mRNA for Plexin-B1 in SKOV3, A2780, C13* and OV2008 cells. GAPDH was used for normalization. Product sizes: Plexin-B1, 150 bp; GAPDH, 240 bp. (F) Western blot showing Plexin-B1 protein expression in SKOV3, A2780, C13* and OV2008 cells. b-actin was used as a loading control. Product sizes: Plexin-B1, about 200 KD; b-actin, 43 KD. determine whether repression of Plexin-B1 expression inhibits SKOV3 cell migration and invasion, a wound- healing assay and a cell invasion assay were performed on SKOV3 cells either untransfected or transfected with Plexin-B1 siRNA2, Plexin-B1 siRNA3 or negative control siRNA for 24 h. As shown in Figure 3A-B, at 24 h and 48 h (respectively), Plexin-B1 siRNA2-treated cells showed 40% and 70% wound closure, Plexin-B1 siRNA3-treated cells showed 40% and 60% wound clo- sure, and negative control siRNA-treated cells showed