Tumour growth inhibition and anti-metastatic activity of a mutated furin-resistant Semaphorin 3E isoform.
Bottom Line: Here, we show that a mutated, uncleavable variant of Sema3E (Uncl-Sema3E) binds to PlexinD1 like p61-Sema3E, but does not promote the association of PlexinD1 with ErbB2 nor activates the ensuing signalling cascade leading to metastatic spreading.It activates a PlexinD1-mediated signalling cascade in endothelial cells that leads to the inhibition of adhesion to extracellular matrix, directional migration and cell survival.In summary, we conclude that Uncl-Sema3E is a novel inhibitor of tumour angiogenesis and growth that concomitantly hampers metastatic spreading.
Affiliation: Institute for Cancer Research and Treatment (IRCC), University of Torino Medical School, Candiolo, Italy.Show MeSH
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Mentions: A potential regulatory function of full-length uncleaved Sema3E in primary tumour development had never been investigated. We therefore assessed the activity of Uncl-Sema3E in multiple experimental models of tumour progression in mice. Initially, we exploited tumorigenic and weakly metastatic human MDA-MB-435 cancer cells that express PlexinD1 receptor but contain relatively low endogenous levels of Sema3E (see expression analysis in Supporting Information Fig 1). Notably, the over-expression of Uncl-Sema3E did not induce significant changes in the tumour cell proliferation rate in culture, even upon serum deprivation (Fig 5A and Supporting Information Fig 3A and B), consistent with our previous findings concerning p61-Sema3E isoform (Casazza et al, 2010). On the other hand, both Uncl-Sema3E and p61-Sema3E caused a striking inhibition of tumour growth upon subcutaneous transplantation of the overexpressing cells in immunodeficient mice (Fig 5B and C), putatively consistent with a paracrine effect in the tumour microenvironment. The histological analysis of explanted tumours actually revealed that Uncl-Sema3E had strongly reduced vessel density (Fig 5D). This was also confirmed in tumour samples explanted at an earlier stage when the size of control and Uncl-Sema3E-expressing xenografts was almost comparable (Supporting Information Fig 6A), consistent with the idea that the paracrine anti-angiogenic activity of this molecule was primarily responsible for tumour suppression. Moreover, we found that Uncl-Sema3E (and p61) impaired pericyte coverage of blood vessels (Fig 5E and Supporting Information Fig 6B), leading to reduced vessel functionality and perfusion (Fig 5F) as well as increased vessel permeability (Supporting Information Fig 6C). These data prompted us to investigate a potential regulatory activity of Uncl-Sema3E on vascular pericyte recruitment. In fact, we found that endothelial cells exposed to Uncl-Sema3E down-regulated the expression of PDGF-B, a major factor recruiting mural cells to vessels (Supporting Information Fig 7A). Moreover, the migration of primary microvascular pericytes in vitro was significantly inhibited by Uncl-Sema3E in a PlexinD1-dependent manner (Supporting Information Fig 7B). Thus, in addition to a direct inhibitory effect on endothelial cell adhesion, migration and survival, Uncl-Sema3E destabilized tumour vessels by interfering with pericyte recruitment.
Affiliation: Institute for Cancer Research and Treatment (IRCC), University of Torino Medical School, Candiolo, Italy.