Stimulation of syncytium formation in vitro in human trophoblast cells by galectin-1

BACKGROUND

Galectin-1 (gal-1), a member of the mammalian beta-galactoside-binding proteins, exerts biological effects by recognition of glycan ligands, including those involved in cell adhesion and growth regulation. In trophoblast cells, gal-1 binds to cell surface glycoproteins (e.g., Mucin1). It has been demonstrated that gal-1 recognizes appropriate glycotopes on the syncytiotrophoblast and extravillous trophoblast from second trimester human placenta and choriocarcinoma cells BeWo, which reveal two coexisting phenotypes, the cytotrophoblast-like and the syncytiotrophoblast-like phenotype. So the aim of this study was to investigate the effect of gal-1 on syncytium formation in BeWo and human villous trophoblasts (HVT) cells.

MATERIALS AND METHODS

The effect of gal-1 on syncytium formation was investigated with immunocytochemical and double immunofluorescence stainings, cell-labelling and Real-time RT-PCR. BeWo choriocarcinoma and HVT cells were incubated in vitro for 24 and 48 h in the absence (controls) and presence of gal-1 and forskolin and stained with antibodies against Ki67, beta-catenin, E-cadherin and syncytin. BeWo and HVT cells were incubated with 60 microg/ml gal-1 for 48 h (BeWo) or 96 h (HVT) and cell fusion was detected by fluorescent cell-labelling solution. Finally, BeWo cells were incubated for 1 h or 48 h in the absence and presence of 60 microg/ml gal-1 and Real-time RT-PCR was performed.

RESULTS

We showed with immunocytochemical staining a downregulation of beta-catenin expression in the 24 h BeWo cell culture and with double immunofluorescence staining an inhibition of the beta-catenin and E-cadherin expression in the 48 h BeWo cell culture stimulated with gal-1 or forskolin. The inhibition of E-cadherin was demonstrated on mRNA level in the 1 h BeWo cell culture too. Increased cell fusion was also showed with DiO and DiI fluorescent cell-labelling solution in the 48 h BeWo cell culture. In addition, we demonstrated the downregulation of Ki67 protein expression in the 24 h BeWo cell culture and on mRNA level in the 1 h BeWo cell culture. We also showed the upregulation of syncytin protein and mRNA expression after incubation of the 48 h BeWo cell culture with gal-1 or forskolin. Similar results were obtained with HVT cells: the amount of cell fusion was significantly increased in the gal-1 treated 48 h HVT cell culture in vitro compared to untreated cells as demonstrated with beta-catenin and E-cadherin double immunofluorescence staining. This increase was also shown by fluorescent cell-labelling with DiO and DiI in the 96 h HVT cell culture compared to untreated cells.

CONCLUSION

Our data suggest that gal-1 stimulates the syncytium formation in choriocarcinoma cells BeWo and HVT cells in vitro and inhibits the expression of beta-catenin, E-cadherin and in addition Ki67 in BeWo cells. Therefore gal-1 may be a major trigger for the process of trophoblast cell fusion.

Effects of phytoestrogen extracts isolated from flax on estradiol production and ER/PR expression in MCF7 breast cancer cells

BACKGROUND

In this study, we tested the effects of crude extracts from flax (Linum usitatissimum) on the production of estradiol and expression of estrogen receptor (ER) and progesterone receptor (PR) in human breast cancer MCF7 cells.

MATERIALS AND METHODS

Isoflavone and lignan extracts from flax plant Linum usitatissimum were obtained, using different extraction methods. Breast carcinoma cells (MCF7) were incubated with various concentrations of the isolated extracts. Untreated MCF7 cells were used as controls. Supernatants were removed at designated times and tested for estradiol with an ELISA method. Furthermore, the effect of phytoestrogen extracts on the production of ERa and ERbeta as well as on PR was examined.

RESULTS AND CONCLUSION

Production of estradiol is elevated in MCF7 cells in a concentration-dependent manner after stimulation with isoflavone and lignan extracts from Linum usitatissimum. Expression of ERalpha is up-regulated after stimulation with lower concentrations of lignan extracts from flax plants, unchanged at median concentrations and down-regulated at high concentrations. Expression of ERbeta is down-regulated in a concentration-dependent manner.

Glycoprotein and carbohydrate binding protein expression in the placenta in early pregnancy loss

Glycoproteins expressed at the fetal-maternal interface have been shown to exert immunomodulating effects. Glycodelin, hCG and transferrin have been used in in vitro experiments as ligands to block E-selectin-mediated cell adhesion. We found that glycodelin is a strong inhibitor of the E-selectin-mediated cell adhesion with a 10(3)-fold increase in potency compared to the monovalent tetrasaccharide sialyl Lewis X. HCG with distinct carbohydrate expression is also an effective selectin antagonist, whereas the potency of transferrin is low. This could indicate a possible role of glycodelin, hCG and transferrin in preventing leukocyte adhesion to the fetal trophoblast. In decidual tissue of abortion patients, glycodelin expression was significantly reduced compared to normal gestation. These results were confirmed by in situ hybridization. Moreover, glycodelin expression in endometrial cells in vitro could be stimulated by addition of hCG. Because hCG is down-regulated in women with abortion, we speculate that hCG could be one of the factors regulating glycodelin expression. Galectins are structurally related proteins with the ability to bind beta-galactosides through a conserved carbohydrate recognition domain. Galectin-1 (gal-1) expression in the syncytiotrophoblast is down-regulated in early pregnancy loss. Gal-1 recognizes the Thomsen-Friedenreich disaccharide (Galbeta1-3GalNAc-) on the syncytiotrophoblast and extravillous trophoblast. Gal-1 also inhibited trophoblast cell proliferation but did not induce apoptosis in BeWo cells. Ligation of Gal-1 on trophoblast cells may have regulatory effects on trophoblast cell differentiation. Decreased expression of Gal-1 may partly explain disturbed trophoblast differentiation during early placentation leading to early pregnancy loss.

Topoisomerase IIalpha expression rather than gene amplification predicts responsiveness of adjuvant anthracycline-based chemotherapy in women with primary breast cancer

INTRODUCTION

Adjuvant anthracycline-based chemotherapy (AbCTX) is a standard treatment for patients with primary breast cancer. Its main target is topoisomerase IIalpha (TopIIa), a nuclear protein which is important for DNA replication and mitosis. We propose that the overexpression of the TopIIa protein or amplification of the TopIIa gene may be useful in predicting increased responsiveness towards AbCTX.

METHODS

Tumor tissues of 118 patients who received adjuvant AbCTX were examined by immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH) for TopIIa and HER2. For IHC, the primary antibodies 485 (Dako) and NCL-TOPOIIA (Novocastra) were used. FISH analysis was performed with the SPEC HER2/CEP 17 Dual Color Probe (Zytovision) and LSI TOP 2A Spectrum Orange/CEP 17 Spectrum Green probe (Abbott). TopIIa IHC was evaluated by the immunoreactive score (IRS). FISH amplification was stated at an HER2-TopIIa/CEP 17 ratio > or = 2, deletion of TopIIa at a ratio <0.8.

RESULTS

The median age of the patient population was 50 years (range 23-77), 76 (64%) had tumors >2 cm in size, 98 (85%) were nodal positive, and 72 (66%) estrogen-receptor positive. Chemotherapy regimes consisted of epirubicin-cyclophosphamide (EC 40 pts), EC-CMF (18 pts), FAC/FEC (33 pts), anthracycline-taxane combinations (23 pts) and others (4 pts). After IHC, it was found that 19% of the tumors were positive for HER2 (3+) and the median IRS for TopIIa staining was 2 (49% positive); 28 (24%) tumors showed HER2 amplification, therefrom 20/22 (91%) within the HER2 3+ group. TopIIa gene was amplified in 17 cases (16%) and deletion was seen in 6 (5%) tumors. Of all cases with HER2 gene amplification, 14 (50%) cases of TopIIa co-amplification and one case of deletion were seen. Looking at histological parameters, TopIIa IHC correlated with nodal status (P = 0.018) and high grading (G3) (P = 0.047). After a median follow-up of 42 months (range 1-242), a significant prognostic factor for local recurrence was HER2 positivity (IHC P = 0.013 and FISH P = 0.023). Thirty-two patients developed metastasis (27%), which was correlated with HER2 FISH positivity (P = 0.024) and, as a trend, Top IIa IHC negativity (P = 0.094); 25 (21%) patients died from the disease. Negative prognostic parameters were the lack of estrogen-receptor expression (P = 0.008), lymphangiosis (P = 0.02), and TopIIa IHC negativity (P = 0.03).

CONCLUSION

In this cohort of patients, HER2 positivity indicated higher rates of local and distant recurrence. In contrast, TopIIa IHC positivity predicted lower risk of metastases and death, thus being a positive-predictive factor for the responsiveness to AbCTX. TopIIa gene amplification did not add predictive information. Therefore, we conclude that TopIIa protein expression might rather be the target of anthracyclines independent from gene copy number.

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 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.

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.