|Ph.D Student||Mumblat Yelena|
|Subject||The role of Semaphorin-3C in Tumor Progression|
|Department||Department of Medicine||Supervisor||Professor Emeritus Gera Neufeld|
|Full Thesis text|
Tumor metastasis to lymph nodes represents the first step of dissemination in head and neck tumors and in breast cancer tumors, and is a major prognostic indicator for disease progression. From there tumor cells can then enter the vascular circulation via the thoracic lymphatic duct. The metastatic spread of tumor cells to lymph nodes is enhanced following the induction of tumor lymphangiogenesis, which is driven by lymphangiogenic factors such as VEGF-C. Semaphorins play important regulatory roles in diverse processes such as axon guidance, angiogenesis and immune responses. We find that Semaphorin-3C (Sema3C) induces the collapse of the cytoskeleton of lymphatic endothelial cells (LEC) in a neuropilin-2, plexin-D1 and plexin-A1 dependent manner, while most other semaphorins, including anti-angiogenic semaphorins such as sema3A do not. Sema3C is cleaved, like other class-3 semaphorins, by furin like pro-protein convertases (FPPC). Cleaved sema3C (p65-Sema3C) was unable to induce the collapse of the cytoskeleton of LEC. FPPC are strongly up-regulated in tumor cells. In order to examine the effects of full length sema3C on tumor progression we therefore generated an active point mutated furin cleavage resistant sema3C (FR-sema3C). FR-sema3C inhibited potently proliferation of LEC and to a lesser extent proliferation of umbilical vein derived endothelial cells (HUVEC). FR-sema3C also inhibited VEGF-C induced phosphorylation of VEGFR-3, ERK1/2 and AKT. Expression of recombinant FR-sema3C in metastatic, triple negative LM2-4 breast cancer cells did not affect their migration or proliferation in-vitro. However, tumors derived from FR-sema3C expressing LM2-4 cells implanted in mammary fat pads developed at a slower rate, contained a lower concentration of blood vessels and lymph vessels, and metastasized much less effectively to lymph nodes. Interestingly, p65-Sema3C, but not FR-sema3C, rendered A549 lung cancer cells resistant to serum deprivation suggesting that previously reported pro-tumorigenic activities of sema3C may be due to p65-Sema3C produced by tumor cells. Our observations suggest that FR-sema3C may be further developed into a novel anti-tumorigenic drug.