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Long-term estradiol deprivation in breast cancer cells up-regulates growth factor signaling and enhances estrogen sensitivity.

Deprivation of estrogen causes breast tumors in women to adapt and develop enhanced sensitivity to this steroid. Accordingly, women relapsing after treatment with oophorectomy, which substantially lowers estradiol for a prolonged period, respond secondarily to aromatase inhibitors with tumor regression. We have utilized in vitro and in vivo model systems to examine the biologic processes whereby long-term estradiol deprivation (LTED) causes cells to adapt and develop hypersensitivity to estradiol. Several mechanisms are associated with this response, including up-regulation of estrogen receptor-alpha (ERalpha) and the MAP kinase, phosphoinositol 3 kinase (PI3-K) and mammalian target of rapamycin (mTOR) growth factor pathways. ERalpha is four- to tenfold up-regulated and co-opts a classical growth factor pathway using Shc, Grb-2 and Sos. This induces rapid non-genomic effects which are enhanced in LTED cells. The molecules involved in the non-genomic signaling process have been identified. Estradiol binds to cell membrane-associated ERalpha, which physically associates with the adaptor protein Shc, and induces its phosphorylation. In turn, Shc binds Grb-2 and Sos, which result in the rapid activation of MAP kinase. These non-genomic effects of estradiol produce biologic effects as evidenced by Elk-1 activation and by morphologic changes in cell membranes. Additional effects include activation of the PI3-K and mTOR pathways through estradiol-induced binding of ERalpha to the IGF-I and epidermal growth factor receptors. A major question is how ERalpha locates in the plasma membrane since it does not contain an inherent membrane localization signal. We have provided evidence that the IGF-I receptor serves as an anchor for ERalpha in the plasma membrane. Estradiol causes phosphorylation of the adaptor protein, Shc and the IGF-I receptor itself. Shc, after binding to ERalpha, serves as the 'bus' which carries ERalpha to Shc-binding sites on the activated IGF-I receptors. Use of small inhibitor (si) RNA methodology to knockdown Shc allows the conclusion that Shc is needed for ERalpha to localize in the plasma membrane. In order to abrogate growth factor-induced hypersensitivity, we have utilized a drug, farnesylthiosalicylic acid, which blocks the binding of GTP-Ras to its membrane acceptor protein, galectin 1, and reduces the activation of MAP kinase. We have also shown that this drug is a potent inhibitor of mTOR as an additional mechanism of inhibition of cell proliferation. The concept of 'adaptive hypersensitivity' and the mechanisms responsible for this phenomenon have important clinical implications. The efficacy of aromatase inhibitors in patients relapsing on tamoxifen could be explained by this mechanism and inhibitors of growth factor pathways should reverse the hypersensitivity phenomenon and result in prolongation of the efficacy of hormonal therapy for breast cancer.

Adaptor Proteins, Signal Transducing↗

Galectin-3 expression correlates with apoptosis of tumor-associated lymphocytes in human melanoma biopsies.

The immune system recognizes diverse melanoma antigens. However, tumors can evade the immune response, therefore growing and progressing. It has been reported that galectin-3 and galectin-1 can induce apoptosis of activated lymphocytes. However, there is strong evidence indicating that the regulation of galectins function in the human tumor microenvironment is a complex process that is influenced by diverse biological circumstances. Here, we have investigated 33 biopsies (eight primary and 25 metastases) from 24 melanoma patients (15-72 years old) and describe the correlation between the expression of galectin-3 or galectin-1 and the level of apoptosis of tumor-associated lymphocytes using immunohistochemistry and an in situ nick translation assay. The range of galectin-3-positive tumor cells varied between 0% and 93% and that of galectin-1-positive tumor cells varied between 5% and 97%. In addition, 23 +/- 27% of tumor-associated lymphocytes were apoptotic. Although our results show a correlation between galectin-3 expression and apoptosis of tumor-associated lymphocytes, we could not find such correlation with galectin-1. Considering the complex process of cancer immunoediting, various interacting factors must be considered.

Adolescent↗

Endogenous lectins (galectins-1 and -3) as probes to detect differentiation-dependent alterations in human squamous cell carcinomas of the oropharynx and larynx.

Expression of glycan determinants for in situ binding is the prerequisite for a productive protein (lectin)-carbohydrate recognition. Labeled tissue lectins as tools are preferable to plant lectins to assess this parameter, because plant and animal lectins with identical saccharide specification can well differ in their profiles of oligosaccharide binding pattern. Due to their relevance in growth control and matrix adhesion the family of galectins (galactoside-binding metal ion independent animal lectins) is receiving increasing utilization in human biology. Employing biotinylated galectin-1 and galectin-3 we studied the expression of binding sites for these galectins in normal human squamous epithelium and human carcinomas from the oropharyngeal region and larynx in relation to the expression of LP-34+ cytokeratins by the procedure of double labeling. Tissue sites accessible for galectin-1 were located in all layers of normal epithelium and in tumor cells. In contrast, galectin-3 binding was suprabasal in the normal epithelium and in tumor cells exhibiting signs of keratinization. These results reveal differences in the localization of accessible sites for the two galectins. Relating to cell development galectin-3 appeared to display affinity to areas with increased extent of differentiation.

Antigens, Differentiation↗

Differential expression of galectin-1 and galectin-3 in benign and malignant salivary gland neoplasms.

Galectins are a family of non-integrin beta-galactosidase-binding lectins. Altered expression of galectins has been associated with neoplastic transformation and progression in several human tumors. In this study, we examined the distribution patterns of galectin-1 and galectin-3 in normal (n=45), benign (n=16), and malignant (n=49) salivary gland specimens using immunohistochemistry to determine their diagnostic and/or biological implications in salivary gland tumorigenesis. In normal salivary glands, galectin-3 expression was limited to ductal cells, and galectin-1 was usually faintly detected in ductal cells and strongly positive in myoepithelial cells. In benign tumors, galectin-3 maintained the ductal localization, but galectin-1 showed variable expression in ductal and myoepithelial cells. In malignant tumors, most of the polymorphous low-grade adenocarcinomas and carcinoma ex-pleomorphic adenomas expressed both galectins, whereas adenoid cystic and acinic cell carcinomas showed dramatically reduced galectin-3 expression and heterogeneous galactin-1 staining. Our data demonstrated altered localization and expression of galectin-3, and to lesser extent, galectin-1 in salivary gland carcinomas. These findings may assist in the differential diagnosis of some salivary gland malignancies, especially when using small and limited fine-needle aspiration materials.

Adenoma↗

Activation of the neutrophil nicotinamide adenine dinucleotide phosphate oxidase by galectin-1.

Galectins are a group of lactose-binding proteins widely distributed in nature. Twelve mammalian galectins have so far been identified, but their functions are to a large extent unknown. In this work we study galectin-1 in its interaction with human neutrophils, with regard to both cell surface binding and activation of the superoxide-producing NADPH-oxidase. We show that galectin-1 is able to activate the neutrophil NADPH-oxidase, provided that the cells have been primed by extravasation from the blood into the tissue, an activation pattern that is similar to that of galectin-3. Using in vitro priming protocols, the galectin-1 responsiveness was found to correlate to granule mobilization and galectin-1 binding to the cells, suggesting the presence of granule-localized receptors that are up-regulated to the cell surface upon priming. By galectin-1 overlay of fractionated neutrophils we identified potential galectin-1 receptor candidates localized in the membranes of the secretory vesicle and gelatinase granules. The binding of galectin-1 and galectin-3 to neutrophil proteins was compared, as were the dose dependencies for activation by the two lectins. The results suggest that, although similarities are found between the two galectins, they appear to activate the NADPH-oxidase using different receptors. In conclusion, galectin-1 appears to have proinflammatory functions, mediated through activation of the neutrophil respiratory burst.

Adjuvants, Immunologic↗

Human galectin-2: novel inducer of T cell apoptosis with distinct profile of caspase activation.

Galectin-2 is structurally closely related to galectin-1, but has a distinct expression profile primarily confined to the gastrointestinal tract. Prominent differences in the proximal promoter regions between galectins-2 and -1 concern Sp1-, hepatocyte NF-3, and T cell-specific factor-1 binding sites. Of note, these sequence elements are positioned equally in the respective regions for human and rat galectins-2. Labeled galectin-2 binds to T cells in a beta-galactoside-specific manner. In contrast to galectin-1, the glycoproteins CD3 and CD7 are not ligands, while the shared affinity to beta1 integrin (or a closely associated glycoprotein) accounts for a substantial extent of cell surface binding. The carbohydrate-dependent binding of galectin-2 induces apoptosis in activated T cells. Fluorogenic substrate and inhibitor assays reveal involvement of caspases-3 and -9, in accordance with cleavage of the DNA fragmentation factor. Enhanced cytochrome c release, disruption of the mitochondrial membrane potential, and an increase of the Bax/Bcl-2 ratio by opposite regulation of expression of both proteins add to the evidence that the intrinsic apoptotic pathway is triggered. Cell cycle distribution and expression of regulatory proteins remained unaffected. Notably, galectins-1 and -7 reduce cyclin B1 expression, defining functional differences between the structurally closely related galectins. Cytokine secretion of activated T cells was significantly shifted to the Th2 profile. Our study thus classifies galectin-2 as proapoptotic effector for activated T cells, raising a therapeutic perspective. Of importance for understanding the complex galectin network, it teaches the lesson that selection of cell surface ligands, route of signaling, and effects on regulators of cell cycle progression are markedly different between structurally closely related galectins.

Animals↗

Galectin-3 and galectin-1 bind distinct cell surface glycoprotein receptors to induce T cell death.

Galectins are a family of mammalian beta-galactoside-binding proteins that positively and negatively regulate T cell death. Extracellular galectin-1 directly induces death of T cells and thymocytes, while intracellular galectin-3 blocks T cell death. In contrast to the antiapoptotic function of intracellular galectin-3, we demonstrate that extracellular galectin-3 directly induces death of human thymocytes and T cells. However, events in galectin-3- and galectin-1-induced cell death differ in a number of ways. Thymocyte subsets demonstrate different susceptibility to the two galectins: whereas galectin-1 kills double-negative and double-positive human thymocytes with equal efficiency, galectin-3 preferentially kills double-negative thymocytes. Galectin-3 binds to a complement of T cell surface glycoprotein receptors distinct from that recognized by galectin-1. Of these glycoprotein receptors, CD45 and CD71, but not CD29 and CD43, appear to be involved in galectin-3-induced T cell death. In addition, CD7 that is required for galectin-1-induced death is not required for death triggered by galectin-3. Following galectin-3 binding, CD45 remains uniformly distributed on the cell surface, in contrast to the CD45 clustering induced by galectin-1. Thus, extracellular galectin-3 and galectin-1 induce death of T cells through distinct cell surface events. However, as galectin-3 and galectin-1 cell death are neither additive nor synergistic, the two death pathways may converge inside the cell.

Antigens, CD↗

[Galectins: a novel family of proteins involved in the regulation of the immune response. Implications in immunopathological processes].

Galectins have emerged as a new family of closely related carbohydrate-binding proteins, which exert their functions by virtue of their ability to decipher glycocodes on complex glycoconjugates. They have been implicated in different immunological processes, such as lymphocyte adhesion, cytokine production, cell growth regulation, apoptosis and central and peripheral immune tolerance. In the present article we analyze the implications of this protein family in different immune pathologies with up- or down-regulated immune responses, such as autoimmune disorders, acute and chronic inflammation, allergic diseases, infection and metastases. The use of recombinant galectins or their antagonists will have future implications in the diagnosis, prognosis and treatment of these diseases, widening the horizons of molecular immunopathology.

Antigens, Differentiation↗

Expression of endogenous lectins (galectins, receptors for ABH-epitopes) and the MIB-1 antigen in esophageal carcinomas and their syntactic structure analysis in relation to post-surgical tumor stage and lymph node involvement.

Squamous cell carcinomas of the esophagus, a disease with poor prognosis, are especially frequent in China and South Africa. To initiate the study of endogenous lectins in this tumor class we employed synthetic neoglycoconjugates and focused on galectins as markers. Histological sections of 43 cases of esophageal carcinomas were analyzed with labeled galectins-1 and -3 and their specific antibodies, neoglycoconjugates exposing chemically prepared histo-blood group A-, B- and H-trisaccharides and the antibody MIB-1 (Ki-67). Features of structural and numerical staining intensities determined quantitatively were correlated to clinical data sets of pTN stages, sex and age of patients. Low tumor stages (pT1/T2) were seen in 10/43 cases (23%) and 65% of the carcinomas surgically treated lacked notable lymph node involvement (pN0). The women were younger than the men (47 years versus 54 years). The proliferation activity of the tumor cells was high and amounted to 75% at average. The presence of galectin-1 and the structural entropy of distribution of staining with carrier-immobilized A-trisaccharide were associated with pN stages. These initial data indicate that distinct glycohistochemical features appear to have prognostic significance in this tumor class, adding to the emerging significance of this marker class in lung cancer.

ABO Blood-Group System↗

Expression of galectins-1 and -3 correlates with defective mononuclear cell apoptosis in patients with juvenile idiopathic arthritis.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) is characterized by hyperplasia of synovial cells and accumulation of mononuclear inflammatory infiltrates, which are locally maintained through a balance between cell proliferation and apoptosis. Although defective clearance of activated T cells in RA joints has been explained by alterations of the Fas-Fas ligand system, this has not been confirmed in synovial tissue of patients with JIA. We evaluated the relation between expression of galectin-1 (Gal-1) and galectin-3 (Gal-3) (beta-galactoside-binding proteins with pro- and anti-apoptotic properties, respectively) and the apoptosis and proliferation rates of infiltrative lymphocytes in synovial tissue of patients with JIA. METHODS: Using slide cytometry and in situ end labeling we observed dysregulated apoptosis of infiltrating mononuclear cells within the synovial tissue of patients with JIA. RESULTS: Patients with pauciarticular JIA showed minimal apoptosis, high Bcl-2 expression, and high or normal proliferation rates, while patients with polyarticular disease showed the lowest apoptotic indexes, accompanied by low Bcl-2 expression and low proliferation rates. We found that Gal-1 expression is downregulated and Gal-3 expression is upregulated in synovial tissue from patients with JIA. CONCLUSION: In patients with polyarticular JIA, accumulation of inflammatory cells is mainly due to downregulated apoptosis, whereas in patients with pauciarticular disease the process results from increased proliferation. Defective mononuclear apoptosis in synovial inflammatory infiltrates from patients with JIA could be explained in part by decreased Gal-1 and increased Gal-3 expression.

Antigens, Differentiation↗

Association of galectin-1- but not galectin-3-dependent parameters with proliferation activity in human neuroblastomas and small cell lung carcinomas.

BACKGROUND: Galectins, a family of animal lectins binding beta-galactosides, are involved in growth regulation of diverse cell types in vitro, even harboring the potential to act as biphasic modulators with cell type selectivity. Owing to this capacity they might affect tumor growth when expression is adapted adequately. MATERIALS AND METHODS: To determine galectin-1-/-3- related features in routinely-fixed sections of two tumor types with poor prognosis (neuroblastoma and small cell lung carcinoma), immuno- and lectin histochemistry with specific antibodies and labeled galectins was performed. RESULTS: In comparison to previously studied tissue culture models, galectin-3 was frequently present, documenting occurrence of discrepancies between tumor models and clinical material for this protein. Cytoplasmic staining with galectin-1 and its antibody coincides with the proliferative activity of positive tumor cells determined by the MIB-1 monoclonal antibody. No statistical correlation was seen for galectin-3. CONCLUSION: These results encourage further cell biological studies to assess a regulatory role of galectin-1 on cell growth in vitro as a model for interfering with tumor proliferation by modulating expression of this type of endogenous effector(s).

Antigens, Differentiation↗

Transient expression of keratin 19 is induced in originally negative interfollicular epidermal cells by adhesion of suspended cells.

Keratin 19 and nuclear reactivity to an endogenous lectin, galectin-1, represent a potential marker of epidermal stem cells. We detected expression of keratin 19 and nuclear binding sites for galectin-1 in adult cells migrating from the hair follicle, where cells expressing keratin 19 are located in the bulge region. The results were compared with the expression of both markers in cells adhering from suspension prepared from the interfollicular epidermis without keratin-19-positive cells and with nuclear binding sites for galectin-1. The results were compared with data from basal cell carcinomas. All cells were analyzed concerning size, as it is known that cell diameter influences the clonogenic potential of keratinocytes. The major result of this study is the observation of transient expression of keratin 19 and nuclear galectin-1 binding sites in originally negative interfollicular epidermal cells induced by adhesion. These cells were very small in size, similar to basal cells of the interfollicular epidermis or the bulge region of the hair follicle. The influence of the suspension regimen on beta1-integrin expression, cell diameter and growth was also monitored. A population of cells highly positive for beta1 integrin of the same diameter as keratin-19-positive cells insensitive to induction of terminal differentiation by lack of anchorage was characterized. Cells of the same size were also observed in the keratin-19-positive cells of basal cell carcinomas. In conclusion, the expression of poor levels of differentiation induced by cell adhesion is transient. Also, keratin 19 expression should not be exclusively regarded as a marker of stem cell activity.

Basal Cell Carcinoma↗

Differential expression of endogenous galectin-1 and galectin-3 in human prostate cancer cell lines and effects of overexpressing galectin-1 on cell phenotype.

We have analyzed the expression of galectin-1 and galectin-3 in four human prostate carcinoma cell lines. Northern analysis and immunoblotting experiments showed that three cell lines express both galectins. However, only galectin-1 was detected on the surface of these cells. The LNCaP line expressed neither galectin. LNCaP was transfected with galectin-1 and four clones were isolated, all of which expressed galectin-1 on the cell surface. Kinetics of binding to extracellular matrix proteins appeared to be accelerated in the transfected lines, but overall binding was not enhanced. When the same experiments were performed in the presence of EDTA to eliminate the effects of integrins, binding of a galectin-1 clone to laminin and fibronectin was increased relative to the control cell line. We propose that galectins may contribute to the adhesive properties of some prostate cancer cells.

Antigens, Differentiation↗

Spatiotemporal organization of Ras signaling: rasosomes and the galectin switch.

1. Ras signaling and oncogenesis depend on the dynamic interplay of Ras with distinctive plasma membrane (PM) microdomains and various intracellular compartments. Such interaction is dictated by individual elements in the carboxy-terminal domain of the Ras proteins, including a farnesyl isoprenoid group, sequences in the hypervariable region (hvr)-linker, and palmitoyl groups in H/N-Ras isoforms. 2. The farnesyl group acts as a specific recognition unit that interacts with prenyl-binding pockets in galectin-1 (Gal-1), galectin-3 (Gal-3), and cGMP phosphodiesterase delta. This interaction appears to contribute to the prolongation of Ras signals in the PM, the determination of Ras effector usage, and perhaps also the transport of cytoplasmic Ras. Gal-1 promotes H-Ras signaling to Raf at the expense of phosphoinositide 3-kinase (PI3-K) and Ral guanine nucleotide exchange factor (RalGEF), while galectin-3 promotes K-Ras signaling to both Raf and PI3-K. 3. The hvr-linker and the palmitates of H-Ras and N-Ras determine the micro- and macro-localizations of these proteins in the PM and in the Golgi, as well as in 'rasosomes', randomly moving nanoparticles that carry palmitoylated Ras proteins and their signal through the cytoplasm.4. The dynamic compartmentalization of Ras proteins contributes to the spatial organization of Ras signaling, promotes redistribution of Ras, and provides an additional level of selectivity to the signal output of this regulatory GTPase.

Amino Acid Sequence↗

Galectin-9 induces apoptosis through the calcium-calpain-caspase-1 pathway.

Galectin-9 (Gal-9) induced the apoptosis of not only T cell lines but also of other types of cell lines in a dose- and time-dependent manner. The apoptosis was suppressed by lactose, but not by sucrose, indicating that beta-galactoside binding is essential for Gal-9-induced apoptosis. Moreover, Gal-9 required at least 60 min of Gal-9 binding and possibly de novo protein synthesis to mediate the apoptosis. We also assessed the apoptosis of peripheral blood T cells by Gal-9. Apoptosis was induced in both activated CD4(+) and CD8(+) T cells, but the former were more susceptible than the latter. A pan-caspase inhibitor (Z-VAD-FMK) inhibited Gal-9-induced apoptosis. Furthermore, a caspase-1 inhibitor (Z-YVAD-FMK), but not others such as Z-IETD-FMK (caspase-8 inhibitor), Z-LEHD-FMK (caspase-9 inhibitor), and Z-AEVD-FMK (caspase-10 inhibitor), inhibited Gal-9-induced apoptosis. We also found that a calpain inhibitor (Z-LLY-FMK) suppresses Gal-9-induced apoptosis, that Gal-9 induces calcium (Ca(2+)) influx, and that either the intracellular Ca(2+) chelator BAPTA-AM or an inositol trisphosphate inhibitor 2-aminoethoxydiphenyl borate inhibits Gal-9-induced apoptosis. These results suggest that Gal-9 induces apoptosis via the Ca(2+)-calpain-caspase-1 pathway, and that Gal-9 plays a role in immunomodulation of T cell-mediated immune responses.

Adjuvants, Immunologic↗

Galectin-3 modulates rat mesangial cell proliferation and matrix synthesis during experimental glomerulonephritis induced by anti-Thy1.1 antibodies.

Galectin-3 is a beta-galactoside-binding protein synthesized by macrophages and other inflammatory cells and expressed in various branching epithelia, including the developing kidney. The expression of galectin-3 has been studied in a rat model of acute mesangial proliferative glomerulonephritis in which a single injection of anti-Thy1.1 antibodies leads to destruction of mesangial cells expressing a Thy1.1 epitope on their surface. The glomerular lesion is characterized by expansion of the mesangial matrix, especially laminin and collagen type IV, and mesangial hypercellularity. Galectin-3 expression, which is sparse in mature rat kidney and confined to the apical face of some distal tubules, is increased within 1-3 days following antibody administration, with the recruitment of glomerular macrophages and pronounced neo-expression in the cytoplasm and at the basal face of distal tubules. At later times, galectin-3 is detected immunohistochemically in the repopulating mesangial cell mass, preceding the extensive mesangial deposition of laminin and collagen type IV. Mesangial cells in culture do not produce appreciable amounts of galectin-3 but do bind and endocytose exogenously added lectin. Addition of galectin-3 to primary cultures of mesangial cells prepared from normal rats induces a 1.5-fold increase in the synthesis of collagen type IV and it also acts in synergy with a quantitatively similar stimulatory effect of transforming growth factor beta (TGF-beta) on matrix synthesis. Exogenous galectin-3 prolongs the survival of mesangial cells in serum-free cultures and also protects these cells against cytotoxic effects of TGF-beta. The data support the notion that the increased expression and secretion of galectin-3 in infiltrating macrophages and in distal tubular epithelia, together with up-regulation of IL-1beta and TGF-beta genes, play a role in mesangial hypercellularity in the progression of one model of inflammatory renal disease.

Animals↗

Galectin 7 (p53-induced gene 1): a new prognostic predictor of recurrence and survival in stage IV hypopharyngeal cancer.

BACKGROUND: Eighty percent of hypopharyngeal squamous cell carcinoma patients have advanced stages (III and IV) of the disease, and biological markers are required to predict high-risk head and neck squamous cell carcinoma patients in need of highly aggressive treatments after surgery to improve the survival rate. We analyzed the potential prognostic value of galectin 7 in a series of 81 stage IV hypopharyngeal SCCs because galectin 7 is an emerging marker involved in the epidermal development of pluristratified epithelia and in epidermal cell migration. METHODS: The immunohistochemical expression of galectin 7 was determined on a series of 81 stage IV hypopharyngeal SCCs and was compared with that of galectins 1 and 3. RESULTS: High levels of galectin 7 expression were associated with rapid recurrence rates and dismal prognoses in these 81 stage IV hypopharyngeal SCCs, a feature not observed with galectin 3 and one observed weakly, if at all, with galectin 1. CONCLUSIONS: These data suggest that the immunohistochemical determination of galectin 7 expression in the case of high-risk hypopharyngeal cancers is a meaningful tool to identify patients who should benefit from aggressive postsurgical adjuvant therapy after surgery, including not only radiotherapy, but also chemotherapy.

Adenocarcinoma↗