Full-Length Semaphorin-3C Is an Inhibitor of Tumor Lymphangiogenesis and Metastasis

Abstract

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 antiangiogenic 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 upregulated 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 human umbilical vein-derived endothelial cells. 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 protumorigenic 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 antitumorigenic drug. Cancer Res; 75(11); 2177-86. Ó2015 AACR.

Tumor-associated Lymphatic Endothelial Cells Promote Lymphatic Metastasis By Highly Expressing and Secreting SEMA4C

“…For instance, soluble TNFa (sTNFa) induces necrocytosis, whereas membrane TNFa induces apoptosis and shows cytotoxicity, even in sTNFa-resistant tumor cells (40,41). It was recently reported that cleaved SEMA3C (p65-SEMA3C) is a protumorigenic factor but that full-length SEMA3C functions as an inhibitor of tumor angiogenesis, lymphangiogenesis, and lymphatic metastasis (17). Nevertheless, sSEMA4C promotes lymphangiogenesis, and our results also show that the inhibitory effect of blocking SEMA4C cleavage (by GM6001) on LECs was weaker than the effect of using SEMA4C siRNAs or a function-blocking antibody, suggesting that the effect of mSEMA4C on lymphangiogenesis is also promotional.…”

“…Plexins A1-A4 have been described as transducers of antiangiogenic signals conveyed by class-3 semaphorins such as sema3F, while the SEMA4D-PlexinB1 has been known as a potent inducer of angiogenesis and is associated with poor prognosis in various solid tumors (15,16). Angiogenesis and lymphangiogenesis intersect in the regulation of tumor microenvironment, and several recent studies also suggested that semaphorins may affect lymphangiogenesis (17,18). Nevertheless, the knowledge about the role of the semaphorin-mediated regulation of tumor lymphangiogenesis is still limited.…”

Gambogic acid inhibits the growth of ovarian cancer tumors by regulating p65 activity

“…Stimulated of the cells by various internal and external factors activated NF-κB, promoting the expression of a series of anti-apoptotic genes. Previous studies have demonstrated that the NF-κB signaling pathway plays a crucial role in the development of various tumors (23)(24)(25). However, it remains unknown whether GA acts on ovarian cancer tumor cells by stimulating the NF-κB signaling pathway, to induce apoptosis.…”

The role of the semaphorins in cancer

“…The VEGF-A binding domain of neuropilin-1 seems to be distinct from its semaphorin binding domain 59 and it was indeed observed that sema3A and sema3F inhibit VEGF induced activation of ERK1/2 without inhibition of VEGF induced auto-phosphorylation of the VEGFR2 receptor which associates with neuropilin-1 52,60 lending support to the structural observations. However, there is also evidence suggesting that some class-3 semaphorins may compete with VEGF family members for binding to neuropilins 61 and that post-translational modifications of semaphorins such as cleavage by furin like pro-protein convertases 62 may modulate their neuropilin binding ability and their ability to complete with VEGFs for binding to neuropilins. 63 Interestingly, it is not clear if the binding of VFGF to neuropilins is required for the enhancement of VEGF induced signal transduction.…”

“…Interestingly, some semaphorins such as sema3C, sema6A and sema3E display dual activities and have been characterized in some publications as inducers of tumor progression 108,[111][112][113][114] and in other publications as inhibitors of tumor progression. 61,92,115,116 The mechanisms responsible for this duality are not yet completely clear and are likely the result of post translational processing and the formation of complex associations between semaphorin receptors and other types of membrane bound receptors such as various tyrosinekinase receptors and adhesion receptors.…”