Homotypic and Heterotypic Activation of the Notch Pathway in Multiple Myeloma–Enhanced Angiogenesis: A Novel Therapeutic Target?

Abstract

Interactions of multiple myeloma (MM) cells with endothelial cells (ECs) enhance angiogenesis and MM progression. Here, we investigated the role of Notch signaling in the cross talk between ECs and MM cells enabling angiogenesis. MMECs showed higher expression of Jagged1/2 ligands, of activated Notch1/2 receptors, and of Hes1/Hey1 Notch target genes than ECs from monoclonal gammopathy of undetermined significance patients, suggesting that homotypic activation of Notch pathway occurs in MM. MM cells co-cultured with MMECs triggered Notch activation in these cells through a cell-to-cell contact-dependent way via Jagged1/2, resulting in Hes1/Hey1 overexpression. The angiogenic effect of Notch pathway was analyzed through Notch1/2·siRNAs and the γ-secretase inhibitor MK-0752 by in vitro (adhesion, migration, chemotaxis, angiogenesis) and in vivo (Vk12598/C57B/6 J mouse model) studies. Activated Notch1/2 pathway was associated with the overangiogenic MMEC phenotype: Notch1/2 knockdown or MK-0752 treatment reduced Hes1/Hey1 expression, impairing in vitro angiogenesis of both MMECs alone and co-cultured with MM cells. MM cells were unable to restore angiogenic abilities of treated MMECs, proving that MMEC angiogenic activities closely rely on Notch pathway. Furthermore, Notch1/2 knockdown affected VEGF/VEGFR2 axis, indicating that the Notch pathway interferes with VEGF-mediated control on angiogenesis. MK-0752 reduced secretion of proangiogenic/proinflammatory cytokines in conditioned media, thus inhibiting blood vessel formation in the CAM assay. In the Vk12598/C57B/6 J mouse, MK-0752 treatment restrained angiogenesis by reducing microvessel density. Overall, homotypic and heterotypic Jagged1/2-mediated Notch activation enhances MMECs angiogenesis. Notch axis inhibition blocked angiogenesis in vitro and in vivo, suggesting that the Notch pathway may represent a novel therapeutic target in MM.

Insights into the Regulation of Tumor Angiogenesis by Micro-RNAs

“…VEGF-A, -B, -C, and -D, the most important regulators of angiogenesis [17], bind to three VEGF tyrosine kinase receptors, VEGFR-1, VEGFR-2, and VEGFR-3. These receptors are specific for endothelial cells and their expression is strongly influenced by the Notch signaling pathway [18,19]. VEGF-A is the prototypic member of the VEGF superfamily, and along with its receptors, VEGFR-2 and VEGFR-1, forms the best-characterized signaling pathway involved in angiogenesis [20].…”

The immune landscape of primary central nervous system diffuse large B cell lymphoma

“…Immune-poor PCNSL harbored activated WNT/β-catenin, HIPPO, and NOTCH signaling. All the deregulated pathways in the immune-poor subtype were correlated with ECs and are known to play a role in angiogenesis [45,46]. No clear association was found with the immune-intermediate subtype, which is not surprising given its heterogeneous immune cell composition.…”

Mechanisms of Resistance to Anti-CD38 Daratumumab in Multiple Myeloma

“…MM cells home to and expand in the BM, establishing a relationship with BM stromal cells (SCs) (i.e., endothelial cells, fibroblasts, osteoblasts, osteoclasts, and immune cells) [5][6][7][8], thus creating a supportive niche. Inside the niche, the cellular/noncellular components favor MM cell survival through the activation of several biological processes, i.e., angiogenesis, hypoxia, autophagy, metabolism reprogramming, and apoptosis resistance, which gradually modify tumor microenvironment and BMSCs [9][10][11][12][13]. Accordingly, targeting both tumor and nontumor cells is the main goal of the new anti-MM therapeutic approaches.…”