Inhibiton of RET and JAK2 Signals and Upregulation of VEGFR3 Phosphorylation in Vitro by Galectin-1 in Trophoblast Tumor Cells BeWo

Background: Galectin-1 (gal-1), a member of the mammalian beta-galactoside-binding proteins, binds to cell surface glycoproteins (Mucin-1) on trophoblast cells. Although it has been demonstrated that gal-1 induces cell differentiation processes in these cells, no information on its signal transduction processes is available so far. As tyrosine phosphorylation is a major mechanism that controls multiple biological processes including cell differentiation, survival and proliferation, the aim of this study was to examine which human receptor tyrosine kinases (RTKs) were phosphorylated in trophoblast cells by gal-1. Materials and Methods: BeWo choriocarcinoma cells were incubated for 24 h in the absence (controls) and presence of 60 mu g/ml galectin-1. With the RayBio (R) Human RTK Phosphorylation Antibody Array 1, the relative levels of phosphorylation of different human RTKs could be detected simultaneously. The signal intensities were compared and quantified with the Quantity One Version 4.5.2 program. Gal-1-treated and non-treated cells were incubated with antibodies against REarranged during Transfection (RET) and phosphorylated RETY905. Staining reaction was performed with the avidin-biotinylated peroxidase complex (ABC) reagent. Results: We demonstrated that gal-1 inhibited RET and Janus Kinase 2 (JAK2) signals and upregulated Vascular endothelial growth factor receptor 3 (VEGFR3) signal in BeWo cells. We also showed the downregulation of phosphorylation on RET phosphotyrosine residue 905 in BeWo cells with phosphorylation specific antibodies and immunocytochemistry. Conclusion: Out of a number of 71 different RTKs, the stimulation of BeWo cells with gal-1 showed a significant alteration of signal intensity in only 3 RTKs: JAK2, RET and VEGFR3. Our data suggest that phosphorylation of these RTKs could be involved in cell differentiation processes that could be responsible for the already known effect of gal-1 on BeWo cells, the inhibition of proliferation. (C) 2009 Elsevier Ltd. All rights reserved.