Investigating the anti-metastatic activity of semaphorin-3F

Abstract

Metastasis is the leading cause of cancer-related deaths. Although there are many factors that promote and facilitate invasive tumors—angiogenesis and lymphangiogenesis provide a means by which invasive tumor cells can spread to distant organs. Semaphorins (SEMAs) were originally discovered for their role in axon guidance during development, however, SEMAs are now known for their anti-metastatic potential. SEMA3F is a 95-kDA protein that induces both anti-angiogenic and anti-lymphangiogenic effects by binding its receptor, Neuropilin 2 (NRP2). SEMA3F-induced signaling via NRP2/plexinA1 complexes inhibits RhoA and results in f-actin depolymerization. SEMA3F may also inhibit angiogenic and lymphangiogenic signaling by competitive inhibition of VEGF-C and VEGF-A binding to NRP2. In this study we have purified SEMA3F protein for use in several in vitro and in vivo studies. Endothelial cell spheroids were unable to produce sprouts during an in vitro spheroid sprouting assay when treated with SEMA3F. In addition, treatment with SEMA3F induced f-actin depolymerization and cell collapse during in vitro endothelial cell collapse assays. A375SM human melanoma cells were injected in nude mice and treated with SEMA3F purified protein. The resultant tumors showed decreased intra- and peri-tumoral lymphatic and vascular densities. Tumors in SEMA3F treated mice were also found to be more necrotic than those of the control. In a second study, slow release osmotic pumps containing SEMA3F protein were implanted in Nrp2+/LacZ heterozygous mice prior to the injection of B16F10 mouse melanoma cells. These mice exhibited decreased tumor volumes indicating SEMA3F may inhibit tumorigenesis. These results indicate the potential of SEMA3F as an anti-metastatic/anti-tumorigenic therapeutic.