Al Oncology, University of Colorado Well being Sciences Center, Box B171, 4200 East Ninth Avenue, Denver, CO 80262, USAAbstract SEMA3F, isolated from a 3p21.3 deletion, has antitumor activity in transfected cells, and protein expression correlates with tumor stage and histology. In main tumors, SEMA3F and VEGF surface staining is inversely correlated. Coupled with SEMA3F in the leading edge of motile cells, we previously suggested that both proteins competitively regulate cell motility and adhesion. We have investigated this working with the breast cancer cell line, MCF7. SEMA3F inhibited cell attachment and spreading as evidenced by loss of lamellipodia extensions, membrane ruffling, and cell cell contacts, with cells sooner or later rounding – up and detaching. In contrast, VEGF had opposite effects. While SEMA3F binds NRP2 with ten – fold higher MMP-7 Proteins Synonyms affinity than NRP1, the Breast Tumor Kinase Proteins Purity & Documentation effects in MCF7 have been mediated by NRP1. This was determined by receptor expression and blocking of anti – NRP1 antibodies. Equivalent effects, but by means of NRP2, were observed within the C100 breast cancer cell line. Though we have been unable to demonstrate alterations in total GTP bound Rac1 or RhoA, we did observe alterations inside the localization of Rac1 – GFP utilizing time lapse microscopy. Following SEMA3F, Rac1 moved towards the base of lamellipodia and — with their collapse — towards the membrane. These results help the notion that SEMA3F and VEGF have antagonistic actions affecting motility in main tumor cell. Neoplasia ( 2003) five, 83 Keyword phrases: semaphorin SEMA3F, neuropilin, VEGF, cell spreading, small GTPases.Introduction Semaphorins are a large loved ones of secreted, transmembrane – and membrane – linked proteins containing a conserved, cystine – wealthy, 500 – amino – acid Sema domain [ 1 ]. SEMA3A ( Collapsin), also as SEMA3F and also other class 3 semaphorins ( SEMA3B, C, D and E), are secreted proteins containing an immunoglobulin – sort domain. Initially identified as repulsive molecules for nerve development cones [ two ], their widespread expression recommended that they had added functions outside the nervous program. This was confirmed bya SEMA3A knockout mouse that resulted in abnormal improvement of somite – derived and visceral tissues, as well as neural abnormalities [ 3,4 ]. SEMA3F was initially isolated from a recurrent 3p21.three homozygous deletion in tiny cell lung cancer cell lines, suggesting that it may be a tumor – suppressor gene [ 5 7 ]. Similarly, SEMA3B was also identified from the very same 3p21.3 deletion [ 6 ]. In main lung tumors, antibody staining against SEMA3F was shown to correlate with both tumor stage and histological subtype [ eight ]. Within a human lung cancer cell line NCI – H1299, expressing predominantly NRP1, transfection of SEMA3B and — to a lesser extent — SEMA3F inhibited in vitro colony formation [ 9 ]. SEMA3F also inhibited tumorigenesis of A9 cells inside a nude mouse model [ 10 ]. Likewise, the tumorigenicity of HEY ovarian adenocarcinoma cells was inhibited by SEMA3B [ 11 ]. Thus, SEMA3F and SEMA3B demonstrate clear antitumor effects as judged by correlations with staging and by their effects in in vitro and in vivo model systems. The receptors for class 3 semaphorins are two associated proteins, neuropilin – 1 ( NRP1) and neuropilin – two ( NRP2) [ 12,13 ]. Furthermore, NRP1 in endothelial cells is a coreceptor for vascular endothelial growth factor VEGF165 [ 14 ], and NRP2 binds VEGF165 and VEGF145 [ 15 ]. In endothelial cells, SEMA3A blocks VEGF165 – induced cel.