We recently identified a novel role for the L1 transmembrane glycoprotein (also known as L1CAM or CD171) in the regulation of tumor angiogenesis and vessels stabilization. L1 overexpression in cultured endothelial cells of the lung (luECs) exerted a pleiotropic effect in that it regulated proliferation, migration, tubulogenesis, vascular permeability, and endothelial-to-mesenchymal transition (EndMT). In addition, we provided strong evidence that antibody-mediated targeting of L1 may be an effective strategy for vessel normalization with the potential to increase efficacy of chemotherapeutic agents. High-throughput microarray expression profile revealed that L1 modulates the expression of hundreds of genes mainly involved in cell cycle regulation, DNA replication, cellular assembly, migration, development and organization. By using a 'pathway-oriented' analysis strategy we were able to identify a network of 105 genes modulated by L1 through the predicted activation of five transcription factors: STAT1, STAT2, STAT3, IRF7, and ATF4. Indeed, L1 overexpression resulted in the strong induction of STAT3 phosphorylation which was abolished by antibody-mediated neutralization of IL-6Rα. These results indicated that L1 promoted STAT3 activation via the IL-6/IL-6Rα axis.
Keywords: Endothelial cells; L1CAM; Microarray; STAT3; Tumor angiogenesis.