Loss of inhibitory semaphorin 3A (SEMA3A) autocrine loops in bone marrow endothelial cells of patients with multiple myeloma

Abstract

IntroductionMultiple myeloma (MM) remains an incurable disease, despite conventional and high-dose chemotherapies. 1 Molecules targeting not only plasma cells, but also the bone marrow (BM) microenvironment are needed to overcome drug resistance.Pathologic angiogenesis is a constant component of the MM microenvironment. 2 The vascular endothelial growth factor (VEGF)/ VEGF receptor-2 (VEGFR-2) pathway greatly contributes to MM angiogenesis and growth, 3 and mediates proliferation and capillarogenesis in MM endothelial cells (MMECs) through an autocrine loop. 4 VEGF 165 is the most abundant and effective isoform. 5 It binds simultaneously to its cognate receptors VEGFR-1 and VEGFR-2 and to the coreceptor neuropilin-1 (NRP1), a cellsurface glycoprotein expressed on axons in the developing nervous system as well. 6 NRP1 is the ligand-binding subunit of the receptor complex for class 3 semaphorins, a family of secreted proteins that mediate neuronal guidance. 7 Binding of secreted semaphorin 3A (SEMA3A) to NRP1 induces the collapse of neuronal growth cones 8 by activating the signal-transducing subunit(s) of the receptor complex, that is, class A plexins, a family of transmembrane proteins whose cytoplasmic domain is endowed with an R-Ras GAP activity that inhibits integrin function. 9 NRP1 is also expressed on ECs, 10 where it acts as an isoform-specific receptor for VEGF 165 , and enhances by 4-to 6-fold its affinity for VEGFR-2, as well as VEGF 165 -induced cell chemotaxis and proliferation. 11 By competing with VEGF 165 for binding to NRP1 12 and by activating class A plexins, 13 SEMA3A inhibits integrinbased EC adhesion and migration and capillary sprouting. Autocrine loops of endothelial SEMA3A play a self-limiting role in angiogenesis and regulate EC behavior during its physiologic development. 13 Here we analyze the expression levels of VEGF 165 , SEMA3A, and their receptors NRP1 and plexin-A1 in BM ECs isolated from patients with MM and MGUS (MMECs and MGECs), and from the human umbilical vein (HUVECs). We show that overangiogenic MMECs display a high VEGF 165 /SEMA3A ratio and behave like MGECs and HUVECs upon exposure to exogenous SEMA3A, which seems as effective as an anti-VEGFR-2 antibody. Our observations point to SEMA3A as a potential antiangiogenic Patients, materials, and methods PatientsThirty-two patients fulfilling the International Myeloma Working Group diagnostic criteria 14 for MM (n ϭ 18) and MGUS (n ϭ 14) were studied at diagnosis. The MM patients (12 male, 6 female) were aged 44 to 81 years (median 68.5 years) and staged 15 as IIA (n ϭ 4), IIB (n ϭ 2), IIIA (n ϭ 10), and IIIB (n ϭ 2); the M-component was IgG (n ϭ 12), IgA (n ϭ 4), and or (n ϭ 2). The MGUS patients (8 male, 6 female) were aged 42 to 79 years (median 70.6 years) and were IgG (n ϭ 10) or IgA (n ϭ 4). The study was approved by the local ethics committee of the University of Bari Medical School, Italy, and all patients gave their informed consent in accordance with the Declaration of Helsinki. Separation and culture of ECs and...

Semaphorin, neuropilin and VEGF expression in glial tumours: SEMA3G, a prognostic marker?

“…For this last point, several studies reported VEGF expression inhibition by semaphorins. For example, when VEGF 165 -stimulated multiple myeloma ECs were exposed to SEMA3A, a time-dependent decrease of endogenous VEGF 165 mRNA was observed (Vacca et al, 2006). Similarly, VEGF in addition to NRP1 was downregulated in SEMA3B-transfected ovarian adenocarcinoma cells (Naylor, AACR Meeting 2003, Poster no.…”

Zoledronic acid affects over-angiogenic phenotype of endothelial cells in patients with multiple myeloma

“…Stromal cells and endothelial cells [multiple myeloma patient-derived endothelial cells (MMECs)] behave as secondary inducers following recruitment and activation by plasma cells (4,5), being a huge source of these growth factors too (6). The VEGF/VEGF receptor-2 (VEGFR2) pathway greatly contributes to multiple myeloma angiogenesis and growth (7) and mediates proliferation and capillarogenesis in MMECs through an autocrine loop (8), supporting the view that effective antiangiogenesis could be achieved via VEGF-VEGFR2 inhibition (9). Zoledronic acid is a bisphosphonate used for multiple myeloma bone disease and hypercalcemia.…”

“…The human endothelial cell -like immortalized cell line EA.hy926, derived from the fusion of human umbilical vascular endothelial cells with the lung carcinoma cell line A549 (16), was used as control because its over-angiogenic phenotype, in terms of enhanced proliferative, chemotactic, and capillarogenic activities, overlaps that of MMECs (6,9). It was maintained in DMEM containing 10% FCS and 1% glutamine.…”

The Neuroimmune Semaphorin-3A Reduces Inflammation and Progression of Experimental Autoimmune Arthritis

“…An increasing amount of data show that this family also exerts its action outside the nervous system, because it plays a critical role in cardiac and skeletal development (3), epithelial morphogenesis (4), angiogenesis (5-10) and tumor progression (11)(12)(13)(14)(15)(16). Moreover, studies suggest that these molecules are important players during immune response, because they regulate interactions between T cells and APCs during primary immune response (17).…”