Endothelial LGALS9 splice variant expression in endothelial cell biology and angiogenesis

Abstract

Galectins are carbohydrate binding proteins with versatile functions in tumor progression. Galectin-9, encoded by LGALS9, has been associated with metastasis and immunosuppression. We previously reported on regulation of LGALS9 expression during endothelial cell activation. Here, we show increased galectin-9 protein levels in the endothelium of different tumors, including carcinomas of the lung, liver, breast and kidney. Endothelial cells were found to express five LGALS9 splice variants, two of which have not been reported before. Splicing was found to be confined to exons 5, 6 and 10. Transfection of human microvascular endothelial cells (HMEC) with galectin-9∆5, a specific LGALS9 splice variant, induced a small but significant increase of proliferation, while migration was not affected by any LGALS9 splice variant. Application of recombinant galectin-9∆5 protein dose-dependently reduced proliferation and migration of HMEC as well as human umbilical vein endothelial cells in vitro. Enhanced sprouting and migration of human umbilical vein endothelial cell (HUVEC) towards a galectin-9∆5 gradient were observed. Interestingly, galectin-9∆5 was found to induce a small inhibitory effect on angiogenesis in vivo. Collectively, these data show that endothelial cells regulate the expression and splicing of LGALS9 during angiogenesis. The function of the dominant splice variant, i.e. galectin-9∆5, in endothelial cell biology depends on the concentration and environmental context in which it is presented to the cells.

Galectin Expression Profiling Identifies Galectin-1 and Galectin-9Δ5 as Prognostic Factors in Stage I/II Non-Small Cell Lung Cancer

“…Whether and how all these parameters influence lung cancer progression requires further studies. Possibly, galectin-9 can act as a chemoattractant for lung cancer cells, similar as described for eosinophils [46], [47] or endothelial cells [26]. Together with our observation that stromal galectin-9Δ5 expression remains elevated in lung tumors this chemoattracting activity indicates that galectin-9Δ5 might act as a guidance cue for metastatic tumor cells to migrate towards the site of intravasation, i.e.…”

“…galectin-1, -3, -4, -7, -8, and -9, mRNA expression could be detected (Figure 1A). Because extensive splicing has been reported for galectin-9 [23], [25], [26], we also determined the mRNA expression of the most common galectin-9 splice variants, i.e. galectin-9 full length (FL), galectin-9 with a deletion of exon 5 (Δ5), and galectin-9 with a deletion of exons 5 and 6 (Δ5/6).…”

The Great Escape; the Hallmarks of Resistance to Antiangiogenic Therapy

“…This corroborates previous findings by us and others showing that galectin-1 promotes tumor angiogenesis and is a target for antiangiogenic cancer therapy (Rabinovich et al, 2006;Thijssen et al, 2006Thijssen et al, , 2010Ito et al, 2011;Croci et al, 2012). 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).…”

Galectin-1, -3 and -9 Expression and Clinical Significance in Squamous Cervical Cancer

“…The protein acts as an eosinophil chemoattractant while intracellular expression has been reported to induce apoptosis in activated T cells, potentially via T cell immunoglobulin mucin-3 (TIM-3), leading to inhibition of T helper 1 (Th1) and Th17 cells and stimulation of regulatory T cells (Tregs) [14,15]. Galectin-9 expression has also been reported in endothelial cells but the role of this protein in angiogenesis appears to be limited [16]. …”