VEGFR1 and VEGFR2 Involvement in Extracellular Galectin-1- and Galectin-3-Induced Angiogenesis

Abstract

AimAccumulating evidence suggests that extracellular galectin-1 and galectin-3 promote angiogenesis. Increased expression of galectin-1 and/or galectin-3 has been reported to be associated with tumour progression. Thus, it is critical to identify their influence on angiogenesis.MethodsWe examined the individual and combined effects of galectin-1 and galectin-3 on endothelial cell (EC) growth and tube formation using two EC lines, EA.hy926 and HUVEC. The activation of vascular endothelial growth factor receptors (VEGFR1 and VEGFR2) was determined by ELISA and Western blots. We evaluated the VEGFR1 and VEGFR2 levels in endosomes by proximity ligation assay.ResultsWe observed different responses to exogenous galectins depending on the EC line. An enhanced effect on EA.hy926 cell growth and tube formation was observed when both galectins were added together. Focusing on this enhanced effect, we observed that together galectins induced the phosphorylation of both VEGFR1 and VEGFR2, whereas galectin-1 and −3 alone induced VEGFR2 phosphorylation only. In the same way, the addition of a blocking VEGFR1 antibody completely abolished the increase in tube formation induced by the combined addition of both galectins. In contrast, the addition of a blocking VEGFR2 antibody only partially inhibited this effect. Finally, the addition of both galectins induced a decrease in the VEGFR1 and VEGFR2 endocytic pools, with a significantly enhanced effect on the VEGFR1 endocytic pool. These results suggest that the combined action of galectin-1 and galectin-3 has an enhanced effect on angiogenesis via VEGFR1 activation, which could be related to a decrease in receptor endocytosis.

Canonical and Noncanonical Vascular Endothelial Growth Factor Pathways

“…Combined treatment of Gal1 and Gal3 enhances angiogenic tube formation at the cellular level, which is not observed upon addition of either single galectin 67 . While the addition of single (or combined) galectins induced equivalent phospho-VEGFR2 levels, only combined Gal1 and Gal3 treatment uniquely induces VEGFR1 phosphorylation 67 .…”

“…While the addition of single (or combined) galectins induced equivalent phospho-VEGFR2 levels, only combined Gal1 and Gal3 treatment uniquely induces VEGFR1 phosphorylation 67 . Similar to the effects of Gal3 on VEGFR2 trafficking, combined treatment decreased endocytosis of VEGF1, trapping it at the plasma membrane.…”

“…Similar to the effects of Gal3 on VEGFR2 trafficking, combined treatment decreased endocytosis of VEGF1, trapping it at the plasma membrane. The downstream effects of this were the induction of Hsp27, and amplification of ERK phosphorylation 67 .…”

The Great Escape; the Hallmarks of Resistance to Antiangiogenic Therapy

“…Moreover, other members of the galectin protein family are expressed by EC (Thijssen et al, 2008) and have been associated with angiogenesis, including galectin-3 (Nangia- Makker et al, 2000Makker et al, , 2010Markowska et al, 2010), galectin-8 (Delgado et al, 2011), and galectin-9 (Heusschen et al, 2014;Thijssen and Griffioen, 2014). Similarly, as described by Croci et al (2014), their angioregulatory activity appears to involve glycandependent homo-and heterotypic receptor clustering as well as increasing the surface retention of receptors (Hsieh et al, 2008;Markowska et al, 2011;D'Haene et al, 2013). Although this has identified galectins as promising targets for antiangiogenic therapy (Thijssen et al, 2007, the exact role of galectins and altered receptor glycosylation in resistance to antiangiogenic therapy still requires further investigation.…”

A novel PI3K inhibitor iMDK suppresses non-small cell lung Cancer cooperatively with A MEK inhibitor

“…Tube formation was quantified by measuring the total length of the tube network and the number of branching points using Image J software (NIH, Bethesda) [20,21]. …”