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.


METHODS
BeWo choriocarcinoma cells were incubated for 24h in the absence (controls) and presence of 60microg/ml galectin-1. With the RayBio 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 RET(Y905). 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.


CONCLUSIONS
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.
Fischer
I
I
Ludwig Maximilians University of Munich, Department of Obstetrics and Gynecology, Munich, Germany.
Schulze
S
S
Kuhn
C
C
Friese
K
K
Walzel
H
H
Markert
U R
UR
Jeschke
U
U
D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D005260:Female; D037483:Galectin 1 / Q000494:pharmacology*; D006801:Humans; D007150:Immunohistochemistry; D053614:Janus Kinase 2 / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D040081:Protein Array Analysis; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014328:Trophoblastic Neoplasms / Q000378:metabolism / Q000473:pathology*; D014327:Trophoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D040321:Vascular Endothelial Growth Factor Receptor-3 / Q000378:metabolism*
D037483:Galectin 1; C445499:LGALS1 protein, human; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D020794:Receptor Protein-Tyrosine Kinases; D040321:Vascular Endothelial Growth Factor Receptor-3; C507924:JAK2 protein, human; D053614:Janus Kinase 2