Expression of galectins in cancer: A critical review

Galectin-9 in tumor biology: a jack of multiple trades

Galectin family members have been shown to exert multiple roles in the context of tumor biology. Several recent findings support a similar multi-faceted role for galectin-9. Galectin-9 expression is frequently altered in cancer as compared to normal tissues. In addition, an increasing amount of evidence suggests that galectin-9 is involved in several aspects of tumor progression, including tumor cell adhesion and survival, immune escape and angiogenesis. Also, galectin-9 shows potential as a prognostic marker and a therapeutic target for several malignancies. In this review we summarize both the established and the emerging roles of galectin-9 in tumor biology and discuss the potential application of galectin-9 in anti-cancer therapy.

Overexpressed galectin-3 in pancreatic cancer induces cell proliferation and invasion by binding Ras and activating Ras signaling

Pancreatic cancer (PDAC) is a lethal disease with a five-year survival of 3–5%. Mutations in K-Ras are found in nearly all cases, but K-Ras mutations alone are not sufficient for the development of PDAC. Additional factors contribute to activation of Ras signaling and lead to tumor formation. Galectin-3 (Gal-3), a multifunctional β-galactoside-binding protein, is highly expressed in PDAC. We therefore investigated the functional role of Gal-3 in pancreatic cancer progression and its relationship to Ras signaling. Expression of Gal-3 was determined by immunohistochemistry, Q-PCR and immunoblot. Functional studies were performed using pancreatic cell lines genetically engineered to express high or low levels of Gal-3. Ras activity was examined by Raf pull-down assays. Co-immunoprecipitation and immunofluorescence were used to assess protein-protein interactions. In this study, we demonstrate that Gal-3 was highly up-regulated in human tumors and in a mutant K-Ras mouse model of PDAC. Down-regulation of Gal-3 by lentivirus shRNA decreased PDAC cell proliferation and invasion in vitro and reduced tumor volume and size in an orthotopic mouse model. Gal-3 bound Ras and maintained Ras activity; down-regulation of Gal-3 decreased Ras activity as well as Ras down-stream signaling including phosphorylation of ERK and AKT and Ral A activity. Transfection of Gal-3 cDNA into PDAC cells with low-level Gal-3 augmented Ras activity and its down-stream signaling. These results suggest that Gal-3 contributes to pancreatic cancer progression, in part, by binding Ras and activating Ras signaling. Gal-3 may therefore be a potential novel target for this deadly disease.

Downregulation of galectin-3 by EGF mediates the apoptosis of HepG2 cells

Epidermal growth factor (EGF) in high concentrations induces apoptosis of the tumor cells which express high levels of epidermal growth factor receptor. However, the precise mechanism for this induction is not clear. Galectin-3 is the most probable candidate for mediating this effect, as it is known to induce anti-apoptotic activity in a variety of tumor cells exposed to diverse apoptotic stimuli. In this study, we determined whether galectin-3 plays a role in high concentrations of EGF-induced apoptosis of HepG2 cells. We found that EGF in high concentrations led to the growth inhibition of HepG2 cells, which were associated with promotion of cell death. High concentrations of EGF suppressed cytoplasmic expression of galectin-3. Moreover, we demonstrated overexpression of galectin-3 could reduce EGF-induced apoptosis in HepG2 cells. Our study demonstrated for the first time that downregulation of cytoplasmic galectin-3 was essential for high concentrations of EGF-induced apoptosis in HepG2 cells.

Galectins and their ligands: negative regulators of anti-tumor immunity

Cytotoxic CD8(+) T cells are major players of anti-tumor immune responses, as their functional activity can limit tumor growth and progression. Data show that cytotoxic T cells efficiently control the proliferation of tumor cells through major histocompatibility complex class I-mediated mechanisms; nevertheless, the presence of tumor-infiltrating CD8(+) T cells in lesional tissue does not always correlate with better prognosis and increased survival of cancer patients. Similarly, adoptive transfer of tumor-specific cytotoxic T cells has only shown marginal improvement in life spans of patients with metastatic disease. In this report, we discuss experimental evidence showing that expression of tumor-derived galectins, galectin (Gal)-1, Gal-3 and Gal-9, and concomitant presence of their ligands on the surface of anti-tumor immunocytes directly compromise anti-tumor CD8(+) T cell immune responses and, perhaps, undermine the promise of adoptive CD8(+) T cell immunotherapy. Furthermore, we describe novel strategies designed to counteract Gal-1-, Gal-3- and Gal-9-mediated effects and highlight their targeting potential for creating more effective anti-tumor immune responses. We believe that Gal and their ligands represent an efficacious targeted molecular paradigm that warrants clinical evaluation.

Serum Levels of Galectin-3: Possible Association with Fibrosis, Aberrant Angiogenesis, and Immune Activation in Patients with Systemic Sclerosis

Objective.

Galectin-3 is a multifunctional protein implicated in a variety of biological processes including fibrosis, angiogenesis, and immune activation, all of which are associated with the development of systemic sclerosis (SSc). We investigated the clinical significance of serum galectin-3 levels in SSc.

Methods.

Serum galectin-3 levels were determined by a specific ELISA in 58 patients with SSc and 19 healthy controls.

Results.

Serum galectin-3 levels were significantly lower in patients with diffuse cutaneous SSc (dcSSc) than in controls (3.29 ± 3.27 ng/ml vs 4.91 ± 2.67 ng/ml, respectively; p < 0.05), while being comparable between limited cutaneous SSc (3.70 ± 2.39 ng/ml) and healthy controls. In dcSSc, serum galectin-3 levels significantly correlated with total skin score (r = 0.45, p < 0.05). Serum galectin-3 levels were significantly decreased in early dcSSc (disease duration < 1 year; 1.64 ± 1.74 ng/ml; p < 0.05), but not in mid-stage dcSSc (1 to 6 years; 3.22 ± 3.16 ng/ml) or late-stage dcSSc (> 6 years; 4.86 ± 4.10 ng/ml), compared with controls. Serum galectin-3 levels were higher in SSc patients with both digital ulcers (DU) and elevated right ventricular systolic pressure (RVSP) than in those without each symptom (DU: 5.44 ± 3.74 ng/ml vs 2.99 ± 2.36 ng/ml, p < 0.05; elevated RVSP: 4.44 ± 3.14 ng/ml vs 2.82 ± 2.64 ng/ml, p < 0.05).

Conclusion.

Galectin-3 may be related to the developmental process of skin sclerosis in dcSSc and of DU and pulmonary vascular involvements in total SSc.

Immune suppression in tumors as a surmountable obstacle to clinical efficacy of cancer vaccines

Human tumors are usually not spontaneously eliminated by the immune system and therapeutic vaccination of cancer patients with defined antigens is followed by tumor regressions only in a small minority of the patients. The poor vaccination effectiveness could be explained by an immunosuppressive tumor microenvironment. Because T cells that infiltrate tumor metastases have an impaired ability to lyse target cells or to secrete cytokine, many researchers are trying to decipher the underlying immunosuppressive mechanisms. We will review these here, in particular those considered as potential therapeutic targets. A special attention will be given to galectins, a family of carbohydrate binding proteins. These lectins have often been implicated in inflammation and cancer and may be useful targets for the development of new anti-cancer therapies.

Decreased galectin-8 is a strong marker for recurrence in urothelial carcinoma of the bladder

OBJECTIVE

To investigate galectin-8 expression patterns in normal urothelium and bladder cancer specimens and to elucidate its prognostic value.

MATERIALS AND METHODS

162 samples of non-muscle-invasive transitional cell carcinoma, 25 samples of muscle-invasive transitional cell carcinoma and 10 samples of normal urothelium were investigated by immunohistochemistry using tissue microarrays. Complete patient and tumor characteristics were compared with galectin-8 staining patterns. The likelihood of tumor recurrence and progression was analyzed based on a 3-year follow-up.

RESULTS

Loss of galectin-8 was associated with the likelihood of tumor recurrence in univariate (p < 0.05) and multivariate analyses (p < 0.01). No significance was observed for tumor progression. Patients whose specimens showed weak galectin-8 expression had a shorter recurrence-free interval (42 vs. 12 months; p < 0.01, log-rank test). All of the 10 normal urothelium samples showed high galectin-8 expression. Decreased staining was found to be associated with higher tumor stages and grades (p < 0.0001, one-way ANOVA). A significant difference was found comparing normal urothelium with any tumor stage (p < 0.01), pTa vs. pT1 tumors (p < 0.05) and non-muscle-invasive vs. muscle-invasive tumors (p < 0.0001).

CONCLUSIONS

Loss of galectin-8 might be an early step in the development of malignant lesions of the bladder and is a significant independent predictor of recurrence.

Evidence of heavy methylation in the galectin 3 promoter in early stages of prostate adenocarcinoma: development and validation of a methylated marker for early diagnosis of prostate cancer

Galectins, soluble intracellular and extracellular beta-galactoside-binding proteins, are known to be involved in the progression and metastasis of various cancers, including prostate adenocarcinoma, but the detailed mechanism of their biological roles remains elusive. In the prostate cancer cell lines PC-3 and DU-145, galectin 3 (gal3) is present at normal levels, whereas in LNCaP, its expression is silenced. In LNCaP, the gal3 promoter was heavily methylated, whereas PC-3 or DU-145 cells showed negligible or no methylation in the gal3 promoter indicating a negative correlation between gal3 promoter methylation and its expression. On immunohistochemical analysis of normal and tumor prostate tissues, gal3 was found expressed both in nucleus and cytoplasm of benign prostatic hyperplasia, high-grade prostatic intraepithelial neoplasia, and stage I. The expression of the gal3 was found drastically downregulated in advanced stages and, interestingly, mostly in the cytoplasm. On methylation analysis, the gal3 promoter in stage II prostate adenocarcinoma (PCa) was found heavily methylated, whereas in stages III and IV, it was only lightly methylated. However, in stage I PCa, both heavy and light methylations were observed in the gal3 promoter. In normal and benign prostatic hyperplasia tissues, the gal3 promoter was almost unmethylated. The differential cytosine methylation in the gal3 promoter in stages I to IV PCa enabled us to develop and validate a methylation-specific polymerase chain reaction-based sensitive assay specific for stages I and II PCa. These stages are considered the critical stages for successful intervention, thus underscoring the significance of this diagnostic assay.

Myenteric denervation downregulates galectin-1 and -3 expression in gastric carcinogenesis

BACKGROUND

This study evaluated the galectin-1 and -3 expression during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in denervated rat stomachs using benzalkonium chloride.

METHOD

Four experimental situations were evaluated: nondenervated and denervated stomachs without lesions and nondenervated and denervated stomachs with lesions. Sections of the pyloric region were stained with toluidine blue and incubated with mouse monoclonal anti-Gal-1 and rabbit polyclonal anti-Gal-3 for histopathological and immunohistochemical analysis, respectively.

RESULT

MNNG caused the development of benign and malignant epithelial lesions, which were more pronounced in nondenervated stomachs with lesions and accompanied by inflammatory cell-enriched stroma. By immunostaining, the epithelial cells, blood vessels, muscle layer, and myenteric plexus were Gal-1 and -3 positive. Gal-3 was also detected in the gastric crypts, mucus secretion, and fibroblasts of pyloric fragments. Development of lesions in denervated stomachs was associated with a significant decrease in Gal-1 and -3 expression in epithelial cells, mast cells, and neutrophil cytoplasm, compared with that of nondenervated stomach lesions (P < 0.01; P < 0.001; P < 0.001, respectively).

CONCLUSION

These results demonstrate that myenteric denervation downregulates endogenous Gal-1 and -3 expression, which might inhibit tumor development in this experimental model.

Galectin-3 secretion and tyrosine phosphorylation is dependent on the calpain small subunit, Calpain 4

Cell adhesion and migration are important events that occur during embryonic development, immune surveillance, wound healing and in tumor metastasis. It is a multi-step process that involves both mechanical and biochemical signaling that results in cell protrusion, adhesion, contraction and retraction. Each of these events generates mechanical forces into the environment measured as traction forces. We have previously found that the calpain small subunit, Calpain 4, is required for normal traction forces, and that this mechanism is independent of the catalytic activities of the holoenzymes that are formed between Calpain 4 and each of the proteolytic heavy chains of Calpain 1 and 2. To define a potential mechanism for the Calpain 4 regulation of traction force, we have evaluated the levels of tyrosine phosphorylation, a hallmark of force dependent signaling within focal adhesions. Using 2D gel electrophoresis we compared tyrosine phosphorylation profiles of Calpain 4 deficient mouse embryonic fibroblasts (MEFs) to the levels in wildtype MEFs and MEF's deficient in the large catalytic subunits, Capn1 and Capn2. Of particular interest, was the identification of Galectin-3, a galactose binding protein known to interact with integrins. Galectin-3 has previously been shown to regulate cell adhesion and migration in both normal and tumor cells; however its full mechanism remains elusive. We have found that Calpain 4 is essential for the tyrosine phosphorylation of galectin-3, and its ultimate secretion from the cell, and speculate that its secretion interferes with the production of traction forces.

Overexpression of Galectin-3 and its clinical significance in ovarian carcinoma

BACKGROUND

Galectin-3 (Gal-3) is a β-galactoside-binding lectin involved in regulating cell growth, angiogenesis, and tumor progression. We investigated the clinical significance of Gal-3 expression including its possible use as a prognostic marker or therapeutic target in epithelial ovarian carcinoma (EOC).

METHODS

Gal-3 expression was evaluated by immunohistochemistry in 71 patients with 54 serous, 13 endometrioid, and 4 mucinous ovarian carcinomas. We assessed the correlation of Gal-3 expression with clinical characteristics including histology, optimal debulking, chemosensitivity, and survival. In vitro, Gal-3 was inhibited using siRNA to evaluate its role in cell growth and sensitivity to chemotherapeutic agents in ovarian carcinoma cell lines.

RESULTS

Gal-3 protein, which was mainly cytoplasmic in location, was observed in a majority (63/71, 88.7%) of the EOCs but not in normal ovarian tissues (P < 0.001). High Gal-3 expression in EOCs correlated with shorter progression-free survival (PFS) of patients (P = 0.039; 43.1 and 49.5 months, respectively). Moreover, cotreatment with Gal-3 siRNA and paclitaxel showed an enhanced cytotoxic effect compared with control siRNA in SKOV3 cells.

CONCLUSION

These findings suggest that Gal-3 expression can be a prognostic factor for PFS and may be involved in regulating the response to paclitaxel-based chemotherapy in the treatment of EOC.

Absence of galectin-3 does not affect the development of experimental tongue carcinomas in mice

BACKGROUND

Galectin-3 is a lectin that presents pivotal roles in tumor biology and there are no studies evaluating their expression in dysplasias and carcinomas developed from tongue carcinogenesis models.

AIMS

To investigate the role of galectin-3 in the development of tongue carcinomas using a mouse model of oral carcinogenesis.

METHODS

Galectin-3-deficient (gal3(-/-)) and wild-type (gal3(+/+)) mice were challenged with 4-nitroquinoline-1-oxide in drinking water for 16weeks and killed at different times. Tongues were removed and the number of dysplasias and carcinomas was counted. An immunohistochemical study for galectin-3 was performed only in the tongue from gal3(+/+) mice.

RESULTS

In both groups, a reduction of dysplasias and an increase of carcinomas from week 16 to week 32 (p>0.05) were observed. A predominance of high cytoplasmic and nuclear galectin-3 expression was observed in carcinomas (64.7%) and dysplasias (55.5%), respectively (p>0.05). The perilesional areas always presented a statistical cytoplasmic and nuclear galectin-3 overexpression.

CONCLUSIONS

Absence of galectin-3 did not directly affect the process of carcinogenesis and a cytoplasm shift of galectin-3 seems to be associated with development of tongue carcinomas.

Investigation of galectin-3 and heparanase in endometrioid and serous carcinomas of the endometrium and correlation with known predictors of survival

INTRODUCTION

Inhibitors of tumor angiogenesis and metastasis are emerging as important new drug candidates for cancer therapy. Galectin-3 and heparanase have been shown to function in tumor progression and metastatic spread. Both of them exert pleiotropic effects; proliferation, cell migration, differentiation and tissue remodeling. The aim of this study was to investigate heparanase and galectin-3 expression in endometrioid and serous carcinomas of the endometrium and their relation with well-known prognostic factors, in addition to estrogen, progesterone, C-erbB-2, Ki-67 and p53.

MATERIALS AND METHODS

Sixty-four endometrial cancers, which include 24 serous types, were obtained from previously untreated patients. Immunohistochemical analysis of 64 carcinomas, 20 endometrial hyperplasia (ten of simple hyperplasia and ten of complex atypic hyperplasia) and 20 normal endometrium (ten of proliferative and ten of secretory) was performed.

CONCLUSION

This investigation suggests that the decreased expression of galectin-3 may be involved in the pathogenesis of endometrial carcinomas from normal endometrium to carcinoma. Also down-regulated stromal expression of galectin-3 in endometrial carcinoma may be involved in lymph node metastasis. Further studies on a larger advanced stage (FIGO stage 3-4) endometrial carcinoma group may determine the value of heparanase in the endometrial carcinoma.

Crystallization and preliminary X-ray crystallographic analysis of zebrafish prototype galectin Drgal1-L2

Zebrafish (Danio rerio) are an important developmental and embryological model given the optical clarity of the embryos and larvae, which permits real-time viewing of developing pathologies. More recently, a broader scope for these vertebrates to model a range of human diseases, including some cancers, has been indicated. Zebrafish Drgal1-L2 has been identified as an orthologue of mammalian galectin-1, which is is a carbohydrate-binding protein that exhibits β-galactoside-binding specificity and which is overexpressed by many aggressive human cancers. This study describes the cloning, expression in Escherichia coli, purification and crystallization of recombinant Drgal1-L2 protein in the presence of lactose (ligand). X-ray diffraction data from these novel crystals of zebrafish Drgal1-L2 were collected to a resolution of 1.5 Å using a synchrotron-radiation source, enabling their characterization.

Tumor cells secrete galectin-1 to enhance endothelial cell activity

Tumor angiogenesis is a key event in cancer progression. Here, we report that tumors can stimulate tumor angiogenesis by secretion of galectin-1. Tumor growth and tumor angiogenesis of different tumor models are hampered in galectin-1-null (gal-1(-/-)) mice. However, tumor angiogenesis is less affected when tumor cells express and secrete high levels of galectin-1. Furthermore, tumor endothelial cells in gal-1(-/-) mice take up galectin-1 that is secreted by tumor cells. Uptake of galectin-1 by cultured endothelial cells specifically promotes H-Ras signaling to the Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (Erk) kinase (Mek)/Erk cascade and stimulates endothelial cell proliferation and migration. Moreover, the activation can be blocked by galectin-1 inhibition as evidenced by hampered membrane translocation of H-Ras.GTP and impaired Raf/Mek/Erk phosphorylation after treatment with the galectin-1-targeting angiogenesis inhibitor anginex. Altogether, these data identify galectin-1 as a proangiogenic factor. These findings have direct implications for current efforts on galectin-1-targeted cancer therapies.

Diagnostic utility of galectin-3 in thyroid cancer

Galectin-3 (Gal-3), which has received significant recent attention for its utility as a diagnostic marker for thyroid cancer, represents the most well-studied molecular candidate for thyroid cancer diagnosis. Gal-3 is a protein that binds to beta-galactosidase residues on cell surface glycoproteins and has also been identified in the cytoplasmic and nuclear compartment. This marker has been implicated in regulation of normal cellular proliferation and apoptosis, as well as malignant transformation and the metastasis of cancer cells. We here present a mechanistic review of Gal-3 and its role in cancer development and progression. Gal-3 expression studies in thyroid tissue and cytologic tumor specimens and their methodological considerations are also discussed in this article. Despite great variance in their methodology, the majority of immunohistochemical studies found that Gal-3 was differentially expressed in thyroid carcinoma compared with benign and normal thyroid specimens, suggesting that Gal-3 is a good diagnostic marker for thyroid cancer. Recent studies have also demonstrated improved methodological reliability. On the other hand, Gal-3 genomic expression studies have shown inconsistent results for diagnostic utility and are not recommended. Overall, the development of Gal-3 as a diagnostic marker for thyroid cancer represents a promising avenue for future study, and its clinical application could significantly reduce the number of diagnostic thyroid operations performed for cases of indeterminant fine needle aspiration biopsy cytology, and thus positively impact the current management of thyroid nodular disease.

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.

A novel clinically relevant animal model for studying galectin-3 and its ligands during colon carcinogenesis

Galectin-3 (Gal-3) is a multifunctional protein that plays different roles in cancer biology. To better understand the role of Gal-3 and its ligands during colon carcinogenesis, we studied its expression in tumors induced in rats treated with 1,2-dimethylhydrazine (DMH) and in human tissues. Normal colon from untreated rats showed no staining using two specific monoclonal antibodies. In contrast, morphologically normal colon from DMH-treated rats and dysplastic aberrant crypt foci were strongly stained, indicating that increased Gal-3 expression is an early event during the neoplastic transformation in colon cells. Gal-3 was weakly expressed in adenocarcinomas. Overall, the Gal-3 expression pattern observed in the DMH rat model closely resembles that displayed by human colon stained with the same antibodies. We also found that Gal-3 phosphorylation diminishes in serines while increasing in tyrosines during rat colon carcinogenesis. Finally, we showed that Gal-3-ligands expression is strikingly similar in rat and human malignant colon and in non-malignant tissues. In conclusion, the DMH-induced rat colon cancer model displays expression patterns of Gal-3 and its ligands very similar to those observed in human samples. This animal model should contribute to clarifying the role of Gal-3 in colon carcinogenesis and also to finding effective preventive cancer agents based on Gal-3 targeting.

CD24 and galectin-1 expressions in gastric adenocarcinoma and clinicopathologic significance

CD24 and galectin-1 expression in gastric adenocarcinoma and their clinicopathologic significance remained largely unknown. We aimed to evaluate expressions and staining intensities of CD24 and galectin-1 in gastric adenocarcinoma and to investigate the interrelation with clinicopathologic parameters including survival. 93 cases with gastric adenocarcinoma were reevaluated histopathologically and immunohistochemistry was performed with antibodies against CD24 and galectin-1. Staining intensities of both markers in tumor cells and staining intensity of galectin-1 in tumor-associated stromal cells were scored semiquantitatively. The relationship between expression and staining intensity of CD24 and galectin-1 and clinicopathologic variables were assessed. CD24 staining intensity was associated with lymphovascular invasion (p = 0.007), serosal invasion (p = 0.001), stage (p = 0.001) and lymph node metastasis (p = 0.005). Galectin-1 staining intensity in tumor-associated stromal cells was associated with tumor location (p = 0.031), lymphovascular invasion (p = 0.001), perineural invasion (p = 0.001), serosal invasion (p = 0.001), differentiation (p = 0.003), stage (p = 0.001) and lymph node metastasis (p = 0.001). Staining intensity of CD24 (p = 0.019) and gal-1 (p = 0.018) were associated with patient survival. Staining intensity of CD24 in tumor cells and galectin-1 in tumor-associated stromal cells were related with certain clinicopathologic variables. Our findings suggest that these markers are independent prognostic indicators of poor survival and may serve as useful targets for novel therapies.

NMR and MD investigations of human galectin-1/oligosaccharide complexes

The specific recognition of carbohydrates by lectins plays a major role in many cellular processes. Galectin-1 belongs to a family of 15 structurally related beta-galactoside binding proteins that are able to control a variety of cellular events, including cell cycle regulation, adhesion, proliferation, and apoptosis. The three-dimensional structure of galectin-1 has been solved by x-ray crystallography in the free form and in complex with various carbohydrate ligands. In this work, we used a combination of two-dimensional NMR titration experiments and molecular-dynamics simulations with explicit solvent to study the mode of interaction between human galectin-1 and five galactose-containing ligands. Isothermal titration calorimetry measurements were performed to determine their affinities for galectin-1. The contribution of the different hexopyranose units in the protein-carbohydrate interaction was given particular consideration. Although the galactose moiety of each oligosaccharide is necessary for binding, it is not sufficient by itself. The nature of both the reducing sugar in the disaccharide and the interglycosidic linkage play essential roles in the binding to human galectin-1.

Dynamics of galectin-3 in the nucleus and cytoplasm

This review summarizes selected studies on galectin-3 (Gal3) as an example of the dynamic behavior of a carbohydrate-binding protein in the cytoplasm and nucleus of cells. Within the 15-member galectin family of proteins, Gal3 (M(r) approximately 30,000) is the sole representative of the chimera subclass in which a proline- and glycine-rich NH(2)-terminal domain is fused onto a COOH-terminal carbohydrate recognition domain responsible for binding galactose-containing glycoconjugates. The protein shuttles between the cytoplasm and nucleus on the basis of targeting signals that are recognized by importin(s) for nuclear localization and exportin-1 (CRM1) for nuclear export. Depending on the cell type, specific experimental conditions in vitro, or tissue location, Gal3 has been reported to be exclusively cytoplasmic, predominantly nuclear, or distributed between the two compartments. The nuclear versus cytoplasmic distribution of the protein must reflect, then, some balance between nuclear import and export, as well as mechanisms of cytoplasmic anchorage or binding to a nuclear component. Indeed, a number of ligands have been reported for Gal3 in the cytoplasm and in the nucleus. Most of the ligands appear to bind Gal3, however, through protein-protein interactions rather than through protein-carbohydrate recognition. In the cytoplasm, for example, Gal3 interacts with the apoptosis repressor Bcl-2 and this interaction may be involved in Gal3's anti-apoptotic activity. In the nucleus, Gal3 is a required pre-mRNA splicing factor; the protein is incorporated into spliceosomes via its association with the U1 small nuclear ribonucleoprotein (snRNP) complex. Although the majority of these interactions occur via the carbohydrate recognition domain of Gal3 and saccharide ligands such as lactose can perturb some of these interactions, the significance of the protein's carbohydrate-binding activity, per se, remains a challenge for future investigations.

KSHV downregulation of galectin-3 in Kaposi's sarcoma

Galectins are a family of proteins that share an affinity for beta-galactoside containing glycoconjugates. In prostate, ovarian and breast cancer, downregulation of galectin-3 is associated with malignancy and tumor progression. Kaposi's sarcoma (KS) is characterized as an angioproliferative tumor of vascular endothelial cells and produces rare B cell lymphoproliferative diseases in the form of primary effusion lymphomas and some forms of multicentric Castleman's disease. Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of KS. We found reduced levels of galectin-3 expression in a significant fraction of latency-associated nuclear antigen (LANA)-positive spindle cell regions in human archival KS tissue and as measured in KS tissue microarrays. Here we demonstrate that galectin-3 protein expression is downregulated 10-fold in 10-day KSHV-infected dermal microvascular endothelial cells (DMVEC) accompanied by downregulation of message. There is loss of galectin-3 staining in KSHV-infected DMVEC by dual labeled immunohistochemistry in LANA-positive spindle cells. We observed a consistent downregulation of galectin-3 by time-course transcriptional analysis. Of the galectins assayed, only galectin-1 was also downregulated in KSHV-infected DMVEC. We examined 86 KS tumors; 19 were LANA positive (22%) and 67 LANA negative (78%). All 86 tumors were found to be galectin-3 positive; 11 of 19 showed reduced expression of galectin-3 in LANA-positive spindle cell regions. Our data suggest that KSHV vFLIP and LANA are the viral genes targeting galectin-3 downregulation. The contribution of host factors to the pathogenesis of KS is essential for early detection and development of innovative therapies for treatment.

Gene expression profiling in sinonasal adenocarcinoma

BACKGROUND

Sinonasal adenocarcinomas are uncommon tumors which develop in the ethmoid sinus after exposure to wood dust. Although the etiology of these tumors is well defined, very little is known about their molecular basis and no diagnostic tool exists for their early detection in high-risk workers.

METHODS

To identify genes involved in this disease, we performed gene expression profiling using cancer-dedicated microarrays, on nine matched samples of sinonasal adenocarcinomas and non-tumor sinusal tissue. Microarray results were validated by quantitative RT-PCR and immunohistochemistry on two additional sets of tumors.

RESULTS

Among the genes with significant differential expression we selected LGALS4, ACS5, CLU, SRI and CCT5 for further exploration. The overexpression of LGALS4, ACS5, SRI, CCT5 and the downregulation of CLU were confirmed by quantitative RT-PCR. Immunohistochemistry was performed for LGALS4 (Galectin 4), ACS5 (Acyl-CoA synthetase) and CLU (Clusterin) proteins: LGALS4 was highly up-regulated, particularly in the most differentiated tumors, while CLU was lost in all tumors. The expression of ACS5, was more heterogeneous and no correlation was observed with the tumor type.

CONCLUSION

Within our microarray study in sinonasal adenocarcinoma we identified two proteins, LGALS4 and CLU, that were significantly differentially expressed in tumors compared to normal tissue. A further evaluation on a new set of tissues, including precancerous stages and low grade tumors, is necessary to evaluate the possibility of using them as diagnostic markers.

Computational studies of human galectin-1: role of conserved tryptophan residue in stacking interaction with carbohydrate ligands

Galectins belong to the family of glycan-binding proteins, defined by at least one conserved carbohydrate-recognition domain with a highly conserved amino acid sequence and affinity for beta galactosides. They all possess a tryptophan residue in the carbohydrate binding site that forms hydrophobic contacts with the carbohydrate ligands. Site directed mutagenesis experiments have shown that this conserved aromatic residue plays a key role in the interaction. We have studied the interaction between the corresponding human Galectin-1 in silico mutants and different carbohydrate ligands using molecular dynamics in explicit solvent. The results confirm the importance of the conserved tryptophan residue in the affinity of the ligand and gives further insights into the mode of interaction between lactose derivatives and human Galectin-1.

Expression of galectins-1, -3 and -4 varies with strain and type of experimental colitis in mice

Galectins are increasingly the focus of biomedical research. Although they are involved at different stages in inflammation, data on galectins in colitis remain scarce. The aim of this study was to determine and compare the expression of galectins in acute and chronic experimental colitis in mice. Immunohistochemistry for galectins-1, -3 and -4 was performed on colon tissue from C57BL/6 and BALB/c mice with acute dextran sodium sulphate colitis and from 129 Sv/Ev IL-10 knock-out (IL-10(-/-)) mice. From these three mouse strains, we first detected major differences in galectin expression related to the genetic background in the control animals. With regard to inflammation, chronic colitis in IL-10(-/-) mice was associated with increased galectin-4 expression; in contrast with the two other models, no galectin-1 and -3 alterations were observed in IL-10(-/-) mice. Acute colitis in C57BL/6 and BALB/c mice showed increased galectin-3 expression in the lamina propria and the crypt epithelium, together with a decreased nuclear expression. These results suggest an involvement of galectins in the development and perpetuation of colonic inflammation and illustrate that the choice of the mouse strain for studying galectins might influence the outcome of the experiments.

Renal expression of galectin-3 in systemic lupus erythematosus patients with nephritis

The aim of the study is to characterize the expression pattern of galectin-3 (Gal-3) in renal tissues of patients with systemic lupus erythematosus (SLE) nephritis and to determine whether tissue and serum Gal-3 are associated with SLE nephritis. Gal-3 expressions were examined with immunohistochemistry in renal biopsy specimens of 88 patients with SLE nephritis and in five normal specimens. Activity and chronicity indexes and glomerular Gal-3 expressions were analysed in each specimen. Serum Gal-3 levels were measured using enzyme-linked immunosorbent assays in 20 patients with SLE, including 11 with nephritis, and in 50 healthy controls. Glomerular Gal-3 expression was observed in 81.8% (72/88) of patients with SLE nephritis but not in 5 controls. Gal-3 staining was attributed mainly to its cellular expression rather than its deposition, and Gal-3 expression levels were correlated with histologic activity indexes, anti-dsDNA titers, and complement 3 and 4 levels. Serum Gal-3 levels were higher in patients with SLE, particularly in those with nephritis, than in healthy controls, and correlated with anti-dsDNA titers. In conclusion, glomerular Gal-3 expression in renal tissue and serum Gal-3 levels were elevated in patients with SLE nephritis versus healthy controls; moreover, they reflected disease activity. These findings suggest that Gal-3 might contribute to the inflammatory process in SLE.

Evaluation of galectin-8 expression in thyroid tumors

The expression of galectin-8 (gal-8) has been shown to be altered during neoplastic transformation of certain cell types. This is the first study aimed to analyze the expression of this protein in normal and pathological human thyroid tissue. A total of 41 archival thyroid tissue samples (5 follicular adenomas, 31 papillary carcinomas, 5 follicular carcinomas) together with 36 adjacent hyperplastic or normal thyroid tissues were analyzed by immunohistochemistry. Galectin-8 was expressed in the majority of papillary carcinomas (27/31; 87%). Positive but weaker staining was also found in some of the follicular thyroid carcinomas (2/5; 40%) and adenomas (2/5; 40%). This protein was not detectable in five normal thyroid tissue samples, whereas hyperplastic areas adjacent to tumor were weakly positive in 9 out of 31 cases (29%). High gal-8 immunostaining in papillary thyroid carcinoma indicates that gal-8 may potentially serve as a marker of papillary thyroid carcinoma. However, it does not seem to be helpful in the differential diagnostics of follicular carcinoma and adenoma. Further studies are required to determine biological functions and molecular mechanisms underlying the increased expression of gal-8 protein in thyroid lesions, particularly, in papillary thyroid carcinoma.

Expression profiling of Galectin-3-depleted melanoma cells reveals its major role in melanoma cell plasticity and vasculogenic mimicry

Galectin-3 (Gal-3) is a beta-galactoside-binding protein that is involved in cancer progression and metastasis. Using a progressive human melanoma tissue microarray, we previously demonstrated that melanocytes accumulate Gal-3 during the progression from benign to dysplastic nevi to melanoma and further to metastatic melanoma. Herein, we show that silencing of Gal-3 expression with small hairpin RNA results in a loss of tumorigenic and metastatic potential of melanoma cells. In vitro, Gal-3 silencing resulted in loss of tumor cell invasiveness and capacity to form tube-like structures on collagen ("vasculogenic mimicry"). cDNA microarray analysis after Gal-3 silencing revealed that Gal-3 regulates the expression of multiple genes, including endothelial cell markers that appear to be aberrantly expressed in highly aggressive melanoma cells, causing melanoma cell plasticity. These genes included vascular endothelial-cadherin, which plays a pivotal role in vasculogenic mimicry, as well as interleukin-8, fibronectin-1, endothelial differentiation sphingolipid G-protein receptor-1, and matrix metalloproteinase-2. Chromatin immunoprecipitation assays and promoter analyses revealed that Gal-3 silencing resulted in a decrease of vascular endothelial-cadherin and interleukin-8 promoter activities due to enhanced recruitment of transcription factor early growth response-1. Moreover, transient overexpression of early growth response-1 in C8161-c9 cells resulted in a loss of vascular endothelial-cadherin and interleukin-8 promoter activities and protein expression. Thus, Gal-3 plays an essential role during the acquisition of vasculogenic mimicry and angiogenic properties associated with melanoma progression.

Genetic assessment of the importance of galectin-3 in cancer initiation, progression, and dissemination in mice

The galectin family of beta-galactoside binding lectins is involved in normal and pathological processes. Altered expression of galectin-3 has been described in many cancers, and studies of cancer cell lines have implicated this lectin in various aspects of the tumorigenic cascade. The goal of this report was to directly assess the importance of galectin-3 in tumor biology by introducing the galectin-3 null mutation (galectin-3(-/-)) into mouse lines genetically programmed to develop cancers. We used two mouse models of human intestinal cancer, the Apc(Min) and Apc(1638N) lines, to study tumor initiation and tumor progression. We also crossed the galectin-3(-/-) mice with PyMT transgenic animals, a model in which primary mammary gland tumors give rise to lung metastases at high frequency. Unexpectedly, we show that the absence of galectin-3 does not affect the evolution of the disease in any of these three situations.

Expression of galectin-3 involved in prognosis of patients with hepatocellular carcinoma

AIMS

Galectins are multifunctional lectins binding to the beta-galactoside of glycoproteins that affect diverse physiological and pathophysiological processes such as development, inflammation and tumor growth. In hepatocellular carcinoma (HCC), the over-expression of galectin-1, 3, and 4 has been reported, although their function and correlation with tumor progression remain unknown. Thus, we aimed to assess the role of galectin-3 during HCC progression.

METHODS

Specimens were obtained during curative operations and used for immunohistochemical analysis of galectin-3 (n = 52), and statistically assessed for correlations with the clinical profiles and the prognoses of the patients. The serum galectin-3 levels from the patients with liver diseases including HCC were assessed by ELISA.

RESULTS

In total, galectin-3 expression was found in 34 of 52 tumors (65%) and was statistically correlated with histological differentiation and vascular invasion. Kaplan-Meier's analysis showed that patients with galectin-3 expression tended to relapse in the earlier phase and had worse overall survival. In particular, a higher expression rate of nuclear galectin-3 showed a markedly worse prognosis, and it was independent in the multivariate analysis for overall survival. Serum galectin-3 levels were significantly increased in HCC compared with chronic liver disease. The sensitivity and specificity of galectin-3 were equivalent to alpha-fetoprotein and Vitamin K absence or antagonist II, and the combination of HCC biomarkers with galectin-3 improved the diagnostic performance.

CONCLUSIONS

Galectin-3 expression was involved in the tumor progression and related to the prognosis of HCC. Our observations suggested that galectin-3 could be a novel tumor marker and therapeutic target.

Galectin-1 signaling in leukocytes requires expression of complex-type N-glycans

Dimeric galectin-1 (dGal-1) is a homodimeric lectin with multiple proposed functions. Although dGal-1 binds to diverse glycans, it is unclear whether dGal-1 preferentially binds to specific subsets of glycans on cell surfaces to transmit signals. To explore this question, we selectively inhibited major glycan biosynthetic pathways in human HL60, Molt-4, and Jurkat cells. Inhibition of N-glycan processing blocked surface binding of dGal-1 and prevented dGal-1-induced Ca(2+) mobilization and phosphatidylserine exposure. By contrast, inhibition of O-glycan or glycosphingolipid biosynthesis did not affect dGal-1 binding or dGal-1-induced Ca(2+) mobilization and phosphatidylserine exposure. These results demonstrate that dGal-1 preferentially binds to and signals through glycoproteins containing complex-type N-glycans in at least some leukocyte subsets.

Ovarian tumor growth regression using a combination of vascular targeting agents anginex or topomimetic 0118 and the chemotherapeutic irofulven

Combination of chemotherapeutic agents and angiogenesis inhibitors is now commonly employed in the clinic to treat cancer. Here, we used angiostatic agents anginex and 0118, in combination with the chemotherapeutic irofulven, to treat human ovarian tumor xenografts in mice. General linear mixed models were used to statistically analyze tumor growth curves. Overall, combination of a low, non-toxic dose of irofulven with either angiogenesis inhibitor was more effective at inhibiting tumor growth than any of the single agent therapies. For example, the anginex/irofulven and 0118/irofulven combinations inhibited tumor growth relative to controls by 92% (p<0.0001) and 96% (p<0.0001), respectively, with the 0118/irofulven combinations yielding 100% complete responses. This study suggests that combination therapy of 0118 or anginex and irofulven may be highly effective in the clinical setting.

The galectin profile of the endothelium: altered expression and localization in activated and tumor endothelial cells

We previously identified overexpression of galectin-1 in activated tumor endothelium. Currently, the tumor vasculature is a target for therapeutic approaches. Little is known about galectin expression and regulation in the tumor vasculature. Here, we report the expression of galectin-1/-3/-8/-9 in the endothelium as determined by quantitative PCR, Western blot, flow cytometry, and immunohistochemistry. Galectin-2/-4/-12 were detectable at the mRNA level, albeit very low. Galectin-8 and -9 displayed alternative splicing. Immunohistochemistry of normal tissues revealed a broad but low expression of galectin-1 in the vasculature, whereas the expression levels and localization of the other galectins varied. Endothelial cell activation in vitro significantly increased the expression of galectin-1 (5.32 +/- 1.97; P = 0.04) and decreased the expression of both galectin-8 (0.59 +/- 0.12; P < 0.04) and galectin-9 (0.32 +/- 0.06; P < 0.002). Galectin-3 expression was unaltered. Although a portion of these proteins is expressed intracellularly, the membrane protein level of galectin-1/-8/-9 was significantly increased on cell activation in vitro, 6-fold (P = 0.005), 3-fold (P = 0.002), and 1.4-fold (P = 0.04), respectively. Altered expression levels and cellular localization was also observed in vivo in the endothelium of human tumor tissue compared with normal tissue. These data show that endothelial cells express several members of the galectin family and that their expression and distribution changes on cell activation, resulting in a different profile in the tumor vasculature. This offers opportunities to develop therapeutic strategies that are independent of tumor type.

Involvement of decreased Galectin-3 expression in the pathogenesis and progression of prostate cancer

BACKGROUND

Altered expression or loss of function of Galectin-3 (Gal-3) was suggested to be involved in the pathogenesis and progression of various human cancer entities. The aim of the present study is to determine the expression of Gal-3 in prostate tissue emerging from a benign to a malignant, in the beginning hormone-sensitive and finally hormone-refractory status to further elucidate the role of this carbohydrate-binding protein for the pathogenesis and/or progression of malignant prostatic disease.

MATERIALS AND METHODS

Five hundred and eighty three tissue samples from malignant, tumor adjacent benign, and histologically benign intra-prostatic areas, retrieved out of 25 whole mounted prostate cancer (CaP) specimens and additional 95 samples of hormone-refractory CaP, were processed to tissue microarrays. Immunohistochemical Gal-3 expression was correlated with clinicopathological parameters among the different tissue entities.

RESULTS

Gal-3 expression was significantly decreased in the hormone-sensitive CaP specimens when compared with the respective benign tissue either localized far distant from the malignant lesion (P < 0.0001, Wilcoxon test) or directly neighboring the primary tumor (P < 0.0001). The staining reaction in the benign tissue areas directly neighboring the primary cancerous lesions differed significantly from the benign glands localized distant from the primary tumors (P < 0.001). A statistically highly significant, almost complete loss of Gal-3 was observed in the hormone-refractory when compared with the hormone-sensitive tumors (P < 0.0001; mean staining score: 27.7% vs. 8.5%).

CONCLUSIONS

The present investigation clearly indicates decreased expression of Gal-3 to be substantially involved in the pathogenesis and further progression of CaP from benign prostate glands to a finally hormone-refractory malignant disease.

Prostate cancer epigenetics: a review on gene regulation

Prostate cancer is the most common cancer in men in western countries, and its incidence is increasing steadily worldwide. Molecular changes including both genetic and epigenetic events underlying the development and progression of this disease are still not well understood. Epigenetic events are involved in gene regulation and occur through different mechanisms such as DNA methylation and histone modifications. Both DNA methylation and histone modifications affect gene regulation and play important roles either independently or by interaction in tumor initiation and progression. This review will discuss the genes associated with epigenetic alterations in prostate cancer progression: their regulation and importance as possible markers for the disease.

Inhibition of Wnt-2 and galectin-3 synergistically destabilizes beta-catenin and induces apoptosis in human colorectal cancer cells

Constitutive activation of the Wnt pathway as a result of APC, AXIN1 or CTNNB1 mutations has been found in most colorectal cancers. For a long time, this aberrant Wnt activation has been thought to be independent of upstream signals. However, recent studies indicate that upstream signals retain their ability to regulate the Wnt pathway even in the presence of downstream mutations. Wnt-2 is well known for its overexpression in colorectal cancer. Galectin-3 (Gal-3), a multifunctional carbohydrate binding protein implicated in a variety of biological functions, has recently been reported to interact with beta-catenin. In this study, we investigated roles of Wnt-2 and Gal-3 in the regulation of canonical Wnt/beta-catenin signaling. We found that siRNA silencing of either Wnt-2 or Gal-3 expression inhibited TCF-reporter activity, decreased cytosolic beta-catenin level and induced apoptosis in human colorectal cancer cells containing downstream mutations. More interestingly, we showed that inhibition of both Wnt-2 and Gal-3 had synergistic effects on suppressing canonical Wnt signaling and inducing apoptosis, suggesting that aberrant canonical Wnt/beta-catenin signaling in colorectal cancer can be regulated at multiple levels. The combined inhibition of Wnt-2 and Gal-3 may be of superior therapeutic advantage to inhibition by either one of them, giving rise to a potential development of novel drugs for the targeted treatment of colorectal cancer.

The MUC1 and galectin-3 oncoproteins function in a microRNA-dependent regulatory loop

The MUC1 heterodimeric transmembrane glycoprotein is aberrantly overexpressed by diverse human carcinomas. Galectin-3 is a beta-galactoside binding protein that has also been associated with the development of human cancers. The present results demonstrate that MUC1 induces galectin-3 expression by a posttranscriptional mechanism. We show that the MUC1 C-terminal subunit is glycosylated on Asn-36 and that this modification is necessary for upregulation of galectin-3. N-glycosylated MUC1-C increases galectin-3 mRNA levels by suppressing expression of the microRNA miR-322 and thereby stabilizing galectin-3 transcripts. The results show that, in turn, galectin-3 binds to MUC1-C at the glycosylated Asn-36 site. The significance of the MUC1-C-galectin-3 interaction is supported by the demonstration that galectin-3 forms a bridge between MUC1 and the epidermal growth factor receptor (EGFR) and that galectin-3 is essential for EGF-mediated interactions between MUC1 and EGFR. These findings indicate that MUC1 and galectin-3 function as part of a miR-322-dependent regulatory loop.

Crystallization and preliminary crystallographic analysis of recombinant human galectin-1

Galectin-1 is considered to be a regulator protein as it is ubiquitously expressed throughout the adult body and is responsible for a broad range of cellular regulatory functions. Interest in galectin-1 from a drug-design perspective is founded on evidence of its overexpression by many cancers and its immunomodulatory properties. The development of galectin-1-specific inhibitors is a rational approach to the fight against cancer because although galectin-1 induces a plethora of effects, null mice appear normal. X-ray crystallographic structure determination will aid the structure-based design of galectin-1 inhibitors. Here, the crystallization and preliminary diffraction analysis of human galectin-1 crystals generated under six different conditions is reported. X-ray diffraction data enabled the assignment of unit-cell parameters for crystals grown under two conditions, one belongs to a tetragonal crystal system and the other was determined as monoclinic P2(1), representing two new crystal forms of human galectin-1.

Galectins in the tumor endothelium: opportunities for combined cancer therapy

Galectins are emerging as a family of proteins that play an important role in several steps of tumorigenesis. Evidence is accumulating that galectins are expressed by the tumor endothelium, where they contribute to different steps of tumor progression such as immune escape and metastasis. Recent studies have identified an important role for galectins in tumor angiogenesis. Moreover, it has been shown that galectins in the endothelium can be targeted for therapeutic applications. This opens a window of opportunity for the development of tumor-type independent treatment strategies. This review focuses on the expression of galectins in the tumor endothelium, their contribution to tumor progression, and their application in tumor-type independent cancer therapy.

Galectin-1 expression in cancer-associated stromal cells correlates tumor invasiveness and tumor progression in breast cancer

Understanding the molecular background of breast cancer biology is critical in developing new biomarkers for earlier diagnosis and more optimized treatment. We performed a proteomic analysis of human breast carcinoma tissues to investigate the tumor-specific protein expression in breast carcinoma. Using 2-dimensional electorphoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), we were able to identify a list of proteins which are upregulated in cancerous tissue. There was significant increase of galectin-1 expression in all cancerous tissues compared to noncancerous tissues, and its increased expression was further confirmed by western blot immunostaining. Subsequent immunohistochemical staining against galectin-1 in 105 breast cancer specimens showed significant correlation between galectin-1 expression in cancer-associated stromal cells and tumor invasiveness, T stage, TNM stage, and axillary lymph node metastasis. Galectin-1 expressionin cancer cells showed no correlation to above-mentioned pathologic variables. Hormonal receptor status and galectin-1 expression showed no correlation. This study demonstrates the upregulation of galectin-1 in breast carcinoma tissues and the clinical significance of galectin-1 in breast cancer patients. Our data supports the recently highlighted roles of galectin-1 in cancer-associated stroma and in tumor immune privilege.

Effect of extended conjugation with a phenylethynyl group on the fluorescent properties of water-soluble arylboronic acids

Boronic acids that change fluorescent properties upon sugar binding are very important reporter units for the development of small molecule lectin mimics (boronolectins). Aimed at developing long wavelength fluorescent boronic acid reporter compounds, we have designed and synthesized a series of boronic acid analogs 2a-d with an extended π conjugation. Such designs are based on earlier fluorescent boronic acids that change fluorescent properties upon sugar binding. Compared with the corresponding parent chromophores, these new compounds with extended conjugations show longer excitation and emission wavelengths as designed. The patterns of fluorescent changes for the new compounds are also different from that of the corresponding parent compounds.

Differential expression of galectins in normal, benign and malignant prostate epithelial cells: silencing of galectin-3 expression in prostate cancer by its promoter methylation

Galectins (gal), a family of soluble beta-galactoside-binding proteins present at the cell surface, are involved in cancer progression and metastasis. Here we investigated the expression of several galectins in normal (PrEC), benign (BPH-1), and malignant (LNCaP) prostate epithelial cells and found that all galectins, except gal1 are differentially expressed. The gal3, 7, and 9 are highly expressed in PrEC, but not in LNCaP cells. Out of seven isoforms of gal8, the proto isoform gal8e and our newly discovered proto isoform gal8g were upregulated in LNCaP cells compared to PrEC, whereas the two tandem-repeat isoforms gal8a and gal8b were equally expressed in these cells. To determine if the silencing of gal3 in LNCaP cells was due to promoter methylation, LNCaP cells were treated with azacytidine. Azacytidine treatment induced the expression of gal3 in LNCaP cells, indicating that the gal3 gene was silenced by methylation of its promoter. To examine further, we evaluated cytosine methylation in gal3 promoter in LNCaP, normal prostate and placenta DNA and observed that it is highly methylated in LNCaP but not in normal cells and azacytidine completely abolished this methylation in LNCaP cells. Similar to prostate cancer cells, gal3 promoter was highly methylated in human prostate cancer tissue but not in normal tissue. To our knowledge, this is the first report indicating that gal3 expression is regulated by promoter methylation in LNCaP cells and prostate tumors. The methylation of gal3 promoter may constitute a powerful tool for early diagnosis of prostate cancer.

The oncofetal Thomsen-Friedenreich carbohydrate antigen in cancer progression

The oncofetal Thomsen-Friedenreich carbohydrate antigen (Galbeta1-3GalNAcalpha1-Ser/Thr TF or T antigen) is a pan-carcinoma antigen highly expressed by about 90% of all human carcinomas. Its broad expression and high specificity in cancer have attracted many investigations into its potential use in cancer diagnosis and immunotherapy. Over the past few years increasing evidence suggests that the increased TF occurrence in cancer cells may be functionally important in cancer progression by allowing increased interaction/communication of the cells with endogenous carbohydrate-binding proteins (lectins), particularly the members of the galactoside-binding galectin family. This review focuses on the recent progress in understanding of the regulation and functional significance of increased TF occurrence in cancer progression and metastasis.

A target cell-specific activatable fluorescence probe for in vivo molecular imaging of cancer based on a self-quenched avidin-rhodamine conjugate

A target cell-specific activation strategy for improved molecular imaging of peritoneal implants has been proposed, in which fluorophores are activated only in living targeted cells. A current example of an activatable fluorophore is one that is normally self-quenched by attachment to a peptide backbone but which can be activated by specific proteases that degrade the peptide resulting in "dequenching." In this study, an alternate fluorescence activation strategy is proposed whereby self-quenching avidin-rhodamine X, which has affinity for lectin on cancer cells, is activated after endocytosis and degradation within the lysosome. Using this approach in a mouse model of peritoneal ovarian metastases, we document target-specific molecular imaging of submillimeter cancer nodules with minimal contamination by background signal. Cellular internalization of receptor-ligand pairs with subsequent activation of fluorescence via dequenching provides a generalizable and highly sensitive method of detecting cancer microfoci in vivo and has practical implications for assisting surgical and endoscopic procedures.