A unique galectin signature in human prostate cancer progression suggests galectin-1 as a key target for treatment of advanced disease.

Galectins, a family of glycan-binding proteins, influence tumor progression by modulating interactions between tumor, endothelial, stromal, and immune cells. Despite considerable progress in identifying the roles of individual galectins in tumor biology, an integrated portrait of the galectin network in different tumor microenvironments is still missing. We undertook this study to analyze the "galectin signature" of the human prostate cancer microenvironment with the overarching goal of selecting novel-molecular targets for prognostic and therapeutic purposes. In examining androgen-responsive and castration-resistant prostate cancer cells and primary tumors representing different stages of the disease, we found that galectin-1 (Gal-1) was the most abundantly expressed galectin in prostate cancer tissue and was markedly upregulated during disease progression. In contrast, all other galectins were expressed at lower levels: Gal-3, -4, -9, and -12 were downregulated during disease evolution, whereas expression of Gal-8 was unchanged. Given the prominent regulation of Gal-1 during prostate cancer progression and its predominant localization at the tumor-vascular interface, we analyzed the potential role of this endogenous lectin in prostate cancer angiogenesis. In human prostate cancer tissue arrays, Gal-1 expression correlated with the presence of blood vessels, particularly in advanced stages of the disease. Silencing Gal-1 in prostate cancer cells reduced tumor vascularization without altering expression of other angiogenesis-related genes. Collectively, our findings identify a dynamically regulated "galectin-specific signature" that accompanies disease evolution in prostate cancer, and they highlight a major role for Gal-1 as a tractable target for antiangiogenic therapy in advanced stages of the disease.

Galectin-1 confers immune privilege to human trophoblast: implications in recurrent fetal loss.

Mechanisms accounting for the protection of the fetal semi-allograft from maternal immune cells remain incompletely understood. In previous studies, we showed that galectin-1 (Gal1), an immunoregulatory glycan-binding protein, hierarchically triggers a cascade of tolerogenic events at the mouse fetomaternal interface. Here, we show that Gal1 confers immune privilege to human trophoblast cells through the modulation of a number of regulatory mechanisms. Gal1 was mainly expressed in invasive extravillous trophoblast cells of human first trimester and term placenta in direct contact with maternal tissue. Expression of Gal1 by the human trophoblast cell line JEG-3 was primarily controlled by progesterone and pro-inflammatory cytokines and impaired T-cell responses by limiting T cell viability, suppressing the secretion of Th1-type cytokines and favoring the expansion of CD4(+)CD25(+)FoxP3(+) regulatory T (T(reg)) cells. Targeted inhibition of Gal1 expression through antibody (Ab)-mediated blockade, addition of the specific disaccharide lactose or retroviral-mediated siRNA strategies prevented these immunoregulatory effects. Consistent with a homeostatic role of endogenous Gal1, patients with recurrent pregnancy loss showed considerably lower levels of circulating Gal1 and had higher frequency of anti-Gal1 auto-Abs in their sera compared with fertile women. Thus, endogenous Gal1 confers immune privilege to human trophoblast cells by triggering a broad tolerogenic program with potential implications in threatened pregnancies.

Hexachlorobenzene induces deregulation of cellular growth in rat liver.

Hexachlorobenzene (HCB) is an organochlorine pesticide widely distributed in the biosphere. The aim of the present study was to investigate the effect of HCB on the homeostasis of liver cell growth, analyzing parameters of cell proliferation and apoptosis, in HCB (0.1, 1, 10 and 100 mg/kg body weight)-treated rats, during 4 weeks. Cell proliferation and ERK1/2 phosphorylation, associated with survival mechanisms, were increased at HCB 100 mg/kg. The pesticide increased the number of apoptotic cells, and the activation of caspase-3, -9 and -8, in a dose-dependent manner, suggesting that HCB-induced apoptosis is mediated by caspases. Increased Fas and FasL protein levels indicate that the death receptor pathway is also involved. This process is associated with decreased Bid, and increased cytosolic cytochrome c protein levels. Transforming growth factor-beta1 (TGF-ß1) intervenes in apoptotic and/or proliferative processes in hepatocytes. TGF-ß1 cDNA and protein levels are dose-dependently increased, suggesting that this cytokine might be involved in HCB-induced dysregulation of cell proliferation and apoptosis. In conclusion, this study reports for the first time that HCB induces loss of the homeostatic balance between cell growth and cell death in rat liver. Induced apoptosis occurs by mechanisms involving signals emanating from death receptors, and the mitochondrial pathway.