Endothelial deficiency of L1 reduces tumor angiogenesis and promotes vessel normalization
Elena Magrini, … , Massimiliano Mazzone, Ugo Cavallaro
Elena Magrini, … , Massimiliano Mazzone, Ugo Cavallaro
Published August 26, 2014
Citation Information: J Clin Invest. 2014;124(10):4335-4350. https://doi.org/10.1172/JCI70683.
View: Text | PDF | Corrigendum
Research Article

Endothelial deficiency of L1 reduces tumor angiogenesis and promotes vessel normalization

Abstract

While tumor blood vessels share many characteristics with normal vasculature, they also exhibit morphological and functional aberrancies. For example, the neural adhesion molecule L1, which mediates neurite outgrowth, fasciculation, and pathfinding, is expressed on tumor vasculature. Here, using an orthotopic mouse model of pancreatic carcinoma, we evaluated L1 functionality in cancer vessels. Tumor-bearing mice specifically lacking L1 in endothelial cells or treated with anti-L1 antibodies exhibited decreased angiogenesis and improved vascular stabilization, leading to reduced tumor growth and metastasis. In line with these dramatic effects of L1 on tumor vasculature, the ectopic expression of L1 in cultured endothelial cells (ECs) promoted phenotypical and functional alterations, including proliferation, migration, tubulogenesis, enhanced vascular permeability, and endothelial-to-mesenchymal transition. L1 induced global changes in the EC transcriptome, altering several regulatory networks that underlie endothelial pathophysiology, including JAK/STAT-mediated pathways. In particular, L1 induced IL-6–mediated STAT3 phosphorylation, and inhibition of the IL-6/JAK/STAT signaling axis prevented L1-induced EC proliferation and migration. Evaluation of patient samples revealed that, compared with that in noncancerous tissue, L1 expression is specifically enhanced in blood vessels of human pancreatic carcinomas and in vessels of other tumor types. Together, these data indicate that endothelial L1 orchestrates multiple cancer vessel functions and represents a potential target for tumor vascular-specific therapies.

Authors

Elena Magrini, Alessandra Villa, Francesca Angiolini, Andrea Doni, Giovanni Mazzarol, Noemi Rudini, Luigi Maddaluno, Mina Komuta, Baki Topal, Hans Prenen, Melitta Schachner, Stefano Confalonieri, Elisabetta Dejana, Fabrizio Bianchi, Massimiliano Mazzone, Ugo Cavallaro

×

Figure 7

L1 regulates EC function via the IL-6/JAK/STAT3 pathway.

Options: View larger image (or click on image) Download as PowerPoint
L1 regulates EC function via the IL-6/JAK/STAT3 pathway. (A) Gene networ...
(A) Gene network of L1-regulated genes. In bold, IPA-predicted upstream modulators. Lines connect modulators to direct targets, and colors indicate the consistency with the predicted activity with the expression change observed in L1-overexpressing luECs (i.e., target expression). Orange, consistent predicted activation of TFs; blue, consistent predicted inhibition of TFs; yellow, inconsistent predicted activation of TFs; grey, not defined activity. (B) qRT-PCR analysis of the indicated genes in mock- and L1-transfected luECs. Transcript levels were normalized as described in Methods and are shown as fold changes in L1-transfected cells relative to mock-transfected cells (n = 3). (C) The amount of IL-6 released in the culture medium by mock- and L1-transfected luECs was quantified by ELISA. (D) Immunoblotting analysis of mock- and L1-transfected luECs for IL-6Rα, phosphorylated STAT3, and total STAT3. (E) Immunoblotting analysis for phosphorylated and total STAT3 in mock- and L1-transfected luECs, treated either with anti–IL-6Rα antibody or with control IgG. (F) Immunoblotting analysis for phosphorylated and total STAT3 in mock- and L1-transfected luECs, treated either with vehicle (DMSO) or with 20 μM JAKi. Actin in D–F served as loading control. (G) Proliferation curves of mock- and L1-transfected luECs treated either with vehicle (DMSO) or with the indicated concentration of JAKi. (H) Mock- and L1-transfected luECs treated either with vehicle (DMSO) or with 20 μM JAKi were subjected to 24-hour migration assays. Data in G and H represent the mean ± SD from a representative experiment performed in triplicate. **P < 0.01; ***P < 0.001.