Autocrine semaphorin 3A signaling promotes glioblastoma dispersal

Abstract

Glioblastoma multiforme (GBM) is the most malignant glioma type with diffuse borders due to extensive tumor cell infiltration. Therefore, understanding the mechanism of GBM cell dispersal is critical for developing effective therapies to limit infiltration. We identified neuropilin-1 as a mediator of cancer cell invasion by a functional proteomic screen and showed its role in GBM cells. Neuropilin-1 is a receptor for semaphorin3A (Sema3A), a secreted chemorepellent that facilitates axon guidance during neural development. Although neuropilin-1 expression in GBMs was previously shown, its role as a Sema3A receptor remained elusive. Using fluorophore-assisted light inactivation and RNA interference , we showed that neuropilin-1 is required for GBM cell migration. We also showed that GBM cells secrete Sema3A endogenously, and RNA interferencemediated downregulation of Sema3A inhibits migration and alters cell morphology that is dependent on Rac1 activity. Sema3A depletion also reduces dispersal, which is recovered by supplying Sema3A exogenously. Extracellular application of Sema3A decreases cell-substrate adhesion in a neuropilin-1-dependent manner. Using immunohistochemistry, we showed that Sema3A is overexpressed in a subset of human GBMs compared with the non-neoplastic brain. Together, these findings implicate Sema3A as an autocrine signal for neuropilin-1 to promote GBM dispersal by modulating substrate adhesion and suggest that targeting Sema3A-neuropilin-1 signaling may limit GBM infiltration.

Peptide-based interference of the transmembrane domain of neuropilin-1 inhibits glioma growth in vivo

“…Long-term analysis of pTM-NRP1 membrane incorporation using confocal microscopy revealed cell-surface clearance of peptide after 96 h (data not shown). Consistent with our previous description of the action mechanism of the peptide (Roth et al, 2008), we found in C6 cells that pTM-NRP1 altered oligomerization of NRP1 on addition of Sema3A (Figure 5a), a semaphorin involved in glioma migration (Nasarre et al, 2009) and shown to promote glioma dispersal through an autocrine mechanism (Bagci et al, 2009). Moreover, although not inducing acute toxicity in C6 cells (see Figure 5b), the addition of pTM-NPR1 induced a significant reduction of cell proliferation (À32%, Po0.05, Figure 5c).…”

“…This is reflected by a strong reduction of the tumour bulk and lack of tumour cell dissemination. A recent study shows that Sema3A stimulates glioma cells dispersal by an autocrine mechanism (Bagci et al, 2009). Thus, it is tempting to speculate that the observed reduction of tumour growth and dissemination in the presence of pTM-NRP1 is the consequence of the inhibition of this mechanism.…”

Semaphorin 5A and plexin-B3 regulate human glioma cell motility and morphology through Rac1 and the actin cytoskeleton

“…Although accumulating evidence has demonstrated a correlation between semaphorin expression and glioma progression (Correa et al, 2001;Rieger et al, 2003;Rich et al, 2005), studies of the expression of plexins and the role of semaphorin-plexin interactions in gliomas remain scanty (Rieger et al, 2003;Bagci et al, 2009;Nasarre et al, 2009;Coma et al, 2010). Here, we show that plexin-B3 is expressed in human glioma cells, which upon activation by its ligand Sema5A inhibits cell motility, triggers cell collapse and promotes ramification of processes.…”

Semaphorin 3A elevates endothelial cell permeability through PP2A inactivation

“…Likewise, S3A silencing allows revascularization in ischemic tissues (Joyal et al, 2011). S3A also influences tumour cell migration and spreading in glioma (Bagci et al, 2009), therefore suggesting both autocrine and paracrine actions of S3A in brain tumours. Thus, these studies converge on the idea that restoring S3A expression might be of therapeutic interest to slow down tumour progression and aggressiveness.…”