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

Galectin-3 is a key hepatoprotective molecule against the deleterious effect of cisplatin

AIMS

Evaluate the role of galectin-3 in the liver using an acute model of cisplatin-induced toxicity.

MATERIAL AND METHODS

Modified citrus pectin (MCP) treatment was used to inhibit galectin-3. Rats were distributed into four groups: SHAM, CIS, MCP and MCP + CIS. On days 1-7, animals were treated by oral gavage with 100 mg/kg/day of MCP (MCP and MCP + CIS groups). On days 8, 9 and 10, animals received intraperitoneal injection of 10 mg/kg/day of cisplatin (CIS and MCP + CIS groups) or saline (SHAM and MCP groups).

KEY FINDINGS

Cisplatin administration caused a marked increase in hepatic leukocyte influx and liver degeneration, and promoted reactive oxygen species production and STAT3 activation in hepatocytes. Plasma levels of cytokines (IL-6, IL-10), and hepatic toxicity biomarkers (hepatic arginase 1, α-glutathione S-transferase, sorbitol dehydrogenase) were also elevated. Decreased galectin-3 levels in the livers of animals in the MCP + CIS group were also associated with increased hepatic levels of malondialdehyde and mitochondrial respiratory complex I. Animals in the MCP + CIS group also exhibited increased plasma levels of IL-1β, TNF-α, and aspartate transaminase 1. Furthermore, MCP therapy efficiently antagonized hepatic galectin-9 in liver, but not galectin-1, the latter of which was increased.

SIGNIFICANCE

Reduction of the endogenous levels of galectin-3 in hepatocytes favors the process of cell death and increases oxidative stress in the acute model of cisplatin-induced toxicity.

Mutation of the galectin-3 glycan-binding domain (Lgals3-R200S) enhances cortical bone expansion in male mice and trabecular bone mass in female mice

We previously observed that genomic loss of galectin-3 (Gal-3; encoded by Lgals3) in mice has a significant protective effect on age-related bone loss. Gal-3 has both intracellular and extracellular functionality, and we wanted to assess whether the affect we observed in the Lgals3 knockout (KO) mice could be attributed to the ability of Gal-3 to bind glycoproteins. Mutation of a highly conserved arginine to a serine in human Gal-3 (LGALS3-R186S) blocks glycan binding and secretion. We generated mice with the equivalent mutation (Lgals3-R200S) and observed a subsequent reduction in Gal-3 secretion from mouse embryonic fibroblasts and in circulating blood. When examining bone structure in aged mice, we noticed some similarities to the Lgals3-KO mice and some differences. First, we observed greater bone mass in Lgals3-R200S mutant mice, as was previously observed in Lgals3-KO mice. Like Lgals3-KO mice, significantly increased trabecular bone mass was only observed in female Lgals3-R200S mice. These results suggest that the greater bone mass observed is driven by the loss of extracellular Gal-3 functionality. However, the results from our cortical bone expansion data showed a sex-dependent difference, with only male Lgals3-KO mice having an increased response, contrasting with our earlier study. These notable sex differences suggest a potential role for sex hormones, most likely androgen signaling, being involved. In summary, our results suggest that targeting extracellular Gal-3 function may be a suitable treatment for age-related loss of bone mass.

Galectin-3 as a Novel Multifaceted and Not Only Cardiovascular Biomarker in Patients with Psoriasis with Regard to Systemic Treatment-Preliminary Data

Simple Summary

Galectin-3 (gal-3) regulates many different biological processes and diseases, which are common accompanying diseases of psoriasis. Psoriasis is one of the most common skin diseases. There is little information about potential diagnostic role of gal-3 in psoriasis. Serum gal-3 concentrations were measured before and after twelve weeks of antipsoriatic treatment in patients with psoriasis and compared to 11 persons without psoriasis (control group). Serum gal-3 level in patients with psoriasis was significantly higher compared to the control group. In obese patients and long-lasting psoriasis positive relations of gal-3 and index of psoriasis severity were noted. In psoriatics with low gal-3 levels, it was noted that the higher the gal-3, the higher the BMI and glucose level. In patients with long history of psoriasis it was observed that the higher gal-3, the lower the lipids levels. The Gal-3 level might be a factor affecting the course of psoriasis and useful in prediction of cardiometabolic comorbidities, especially in patients with a long history of the disease or obesity. Patients with low serum gal-3 and a short history of psoriasis may have greater risk of diabetes. In obese patients with long-lasting psoriasis, gal-3 may have a beneficial influence against abnormal lipid profiles or perhaps further cardiovascular disorder development.

Abstract

Galectin-3 (gal-3) is a multifunctional regulator of various biological processes and diseases, which are common comorbidities in psoriasis. Data regarding potential diagnostic role of gal-3 in psoriasis are insufficient. Serum gal-3 levels were evaluated before and after twelve weeks of treatment with acitretin or methotrexate in 31 patients with plaque-type psoriasis and compared to 11 healthy control group. The mean serum galectin-3 level in patients with psoriasis was significantly higher compared to the control group (p < 0.01). In patients with obesity and long-lasting psoriasis (>20 years) positive relations of gal-3 and PASI were noted. In psoriatics with low gal-3 levels, positive correlations between the gal-3 and BMI, glucose level, and with the latter in short-lasting psoriasis (<20 years) were noted. In the long history of psoriasis, gal-3 was negatively correlated with lipids levels. The Gal-3 level might be a multifaceted modulator of the course of psoriasis and predictive factor of cardiometabolic comorbidities’ development, especially in patients with a long history of the disease or obesity. Patients with low serum gal-3 and short history of psoriasis are presumably at greater risk of diabetes. In patients with long-lasting psoriasis and concomitant obesity, gal-3 may exert a protective role against dyslipidemia or perhaps further CMD development.

mRNA coexpression patterns of Wnt pathway components and their clinicopathological associations in breast and colorectal cancer

Aberrant Wnt signaling is implicated in carcinogenesis triggering efforts for the development of new therapeutic agents, many of which have entered clinical trials. We extend our previous analysis of WNT3, FZD7, LEF1 expression levels in breast and colorectal cancer including WNT2, FZD4 and β-catenin expression, in an effort to delineate their relative expression levels along with concurrent expression patterns and possible prognostic value. We analyzed 82 breast and 102 colorectal carcinomas for relative mRNA expression levels of the investigated genes by RT-PCR relative quantification with the ΔΔCt method. Statistical analysis was performed in order to determine associations of relative mRNA expression and linear correlations. β-catenin expression was determined by immunochemistry. Regarding breast carcinomas, decreased relative mRNA expression levels of WNT2, FZD4 were found frequently and WNT2 expression was correlated with ER/ PR status (p = 0.045/p = 0.028), whereas β-catenin with grade (p = 0.026). In colorectal carcinomas, increased relative mRNA expression levels of WNT2 and FZD4 were found in 59% and 32% of cases respectively, whereas β-catenin showed decreased mRNA expression levels in 57% of cases and a correlation with pN-category (p = 0.037). Linear correlations were observed between WNT2/FZD4 (R=0.542, p < 0.001), WNT2/β-catenin (R=0.254, p = 0.010), FZD4/β-catenin (R=0.406, p < 0.001) expression and a correlation between mRNA expression and membranous/cytoplasmic β-catenin emerged (p = 0.039/0.046). Our results suggest a possible clinical significance for Wnt pathway gene expression levels in both tumour types. The concurrent expression of the investigated genes as well as the different expression profiles, underlines the complexity of this pathway and the necessity of patient selection in order to maximize the efficacy of drugs targeting Wnt pathway.

Glycopolymers for Efficient Inhibition of Galectin-3: In Vitro Proof of Efficacy Using Suppression of T Lymphocyte Apoptosis and Tumor Cell Migration

The development of efficient galectin-3 (Gal-3) inhibitors draws attention in the field of anti-cancer therapy, especially due to the prominent role of extra- and intracellular Gal-3 in vital processes of cancerogenesis, such as immunosuppression, stimulation of tumor cells proliferation, survival, invasion, apoptotic resistance, and metastasis formation and progression. Here, by combining poly-LacNAc (Galβ4GlcNAc)-derived oligosaccharides with N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers, we synthesized multivalent glycopolymer inhibitors with a high potential to target extracellular and intracellular Gal-3. The inhibitory capabilities of the best conjugate in the studied series were in the nanomolar range proving the excellent Gal-3 inhibitory potential. Moreover, thorough investigation of the inhibitory effect in the biological conditions showed that the glycopolymers strongly inhibited Gal-3-induced apoptosis of T lymphocytes and suppressed migration and spreading of colorectal, breast, melanoma, and prostate cancer cells. In sum, the strong inhibitory activity toward Gal-3, combined with favorable pharmacokinetics of HPMA copolymers ensuring enhanced tumor accumulation via the enhanced permeability and retention effect, nominate the glycopolymers containing LacdiNAc-LacNAc (GalNAcβ4GlcNAcβ3Galβ4GlcNAc) tetrasaccharide as promising tools for preclinical in anti-cancer therapy evaluation.

Galectins and Ovarian Cancer

Ovarian cancer is known for its aggressive pathological features, including the capacity to undergo epithelial to mesenchymal transition, promoting angiogenesis, metastatic potential, chemoresistance, inhibiting apoptosis, immunosuppression and promoting stem-like features. Galectins, a family of glycan-binding proteins defined by a conserved carbohydrate recognition domain, can modulate many of these processes, enabling them to contribute to the pathology of ovarian cancer. Our goal herein was to review specific galectin members identified in the context of ovarian cancer, with emphasis on their association with clinical and pathological features, implied functions, diagnostic or prognostic potential and strategies being developed to disrupt their negative actions.

Emerging Roles of Wnt Ligands in Human Colorectal Cancer

Colorectal cancer (CRC) is the fourth leading cause of cancer death worldwide, and constitutive activation of the Wnt signaling pathway is universal in most CRC cases. Wnt ligands (Wnts) are secreted glycoproteins and fundamentally essential for the transduction of Wnt signaling pathway. However, the 19 members of Wnts in humans imply a daunting complexity of Wnt signaling and biological effects, and our understanding of their roles in CRC tumorigenesis is still quite rudimentary. This review will give an overview of the structural characteristics and maturation process of Wnts. The expression pattern of all human Wnts in CRC tissues, including Wnt1, Wnt2, Wnt2b, Wnt3, Wnt3a, Wnt4, Wnt5a, Wnt5b, Wnt6, Wnt7a, Wnt7b, Wnt8a, Wnt8b, Wnt9a, Wnt9b, Wnt10a, Wnt10b, Wnt11, and Wnt16, and their relationship with the tumorigenesis and the progression of CRC will be specifically summarized separately. Despite certain challenges, Wnt-based therapeutics for CRC emerge continuously and some are now in clinical trials. In conclusion, a deep understanding of Wnts is very helpful for a better management of this disease.

Beyond immunohistochemistry and immunocytochemistry: a current perspective on galectin-3 and thyroid cancer

Introduction: Thyroid nodules are very common in the general population, most are benign, and do not require any intervention. However, often a challenge exists in discriminating benign thyroid nodules from cancer, without performing a biopsy or operation. Galectin-3 is a beta-galactoside binding protein that is involved in diverse biological processes and has been found to have increased expression in many human cancer types including thyroid cancer. As a result, recent studies have investigated its utility as a serum biomarker for thyroid cancer, as well as a novel target for in vivo molecular imaging of cancer. Additionally, given its role in tumorigenesis and cancer progression, galectin-3 targeting is currently under investigation for its potential utility as treatment for thyroid cancer.Areas covered: Recent studies of galectin-3 as a serum marker for thyroid cancer diagnosis, and in the preclinical setting as a target for cancer imaging and therapy.Expert opinion: Even though current studies evaluating galectin-3 as a serum marker and target for cancer imaging and therapy are promising, further research is required before it can be adopted into routine clinical use.

Galectin 3: an extraordinary multifunctional protein in dermatology. Current knowledge and perspectives

Galectin 3 is a unique ~31 kDa protein that recognizes the N-acetyl-lactosamine structure of several glycoconjugates. It mainly occurs in epithelial and myeloid cells, but is also found in a variety of human cell types. In view of the crucial role played by galectin 3 in the regulation of cellular processes of essential importance and in the pathogenetic mechanisms of diverse disorders, it is not surprising that, particularly in the last three decades, the attention of the scientific community has been increasingly drawn to this extraordinary and multifunctional galectin. In this paper the authors summarize current knowledge on the expression of galectin 3 in normal and diseased human skin, its implications in the pathogenesis, diagnosis and prognosis of cutaneous disorders, and the perspectives of a novel approach to the treatment of the latter using galectin 3 or its inhibitors/antagonists.

Galectin-3 Deficiency Facilitates TNF-α-Dependent Hepatocyte Death and Liver Inflammation in MCMV Infection

Galectin-3 (Gal-3) has a role in multiple inflammatory pathways. Various, opposite roles of Gal-3 in liver diseases have been described but there are no data about the role of Gal-3 in development of hepatitis induced with cytomegalovirus infection. In this study we aimed to clarify the role of Gal-3 in murine cytomegalovirus (MCMV)-induced hepatitis by using Gal-3-deficient (Gal-3 KO) mice. Here we provide the evidence that Gal-3 has the protective role in MCMV-induced hepatitis. Enhanced hepatitis manifested by more inflammatory and necrotic foci and serum level of ALT, enhanced apoptosis and necroptosis of hepatocytes and enhanced viral replication were detected in MCMV-infected Gal-3 deficient mice. NK cells does not contribute to more severe liver damage in MCMV-infected Gal-3 KO mice. Enhanced expression of TNF-α in the hepatocytes of Gal-3 KO mice after MCMV infection, abrogated hepatocyte death, and attenuated inflammation in the livers of Gal-3 KO mice after TNF-α blockade suggest that TNF-α plays the role in enhanced disease in Gal-3 deficient animals. Treatment with recombinant Gal-3 reduces inflammation and especially necrosis of hepatocytes in the livers of MCMV-infected Gal-3 KO mice. Our data highlight the protective role of Gal-3 in MCMV-induced hepatitis by attenuation of TNF-α-mediated death of hepatocytes.

Galectin-3 and cancer stemness

Over the last few decades galectin-3, a carbohydrate binding protein, with affinity for N-acetyllactosamine residues, has been unique due to the regulatory roles it performs in processes associated with tumor progression and metastasis such as cell proliferation, homotypic/heterotypic aggregation, dynamic cellular transformation, migration and invasion, survival and apoptosis. Structure-function association of galectin-3 reveals that it consists of a short amino terminal motif, which regulates its nuclear-cytoplasmic shuttling; a collagen α-like domain, susceptible to cleavage by matrix metalloproteases and prostate specific antigen; accountable for its oligomerization and lattice formation, and a carbohydrate-recognition/binding domain containing the anti-death motif of the Bcl2 protein family. This structural complexity permits galectin-3 to associate with numerous molecules utilizing protein-protein and/or protein-carbohydrate interactions in the extra-cellular as well as intracellular milieu and regulate diverse signaling pathways, a number of which appear directed towards epithelial-mesenchymal transition and cancer stemness. Self-renewal, differentiation, long-term culturing and drug-resistance potential characterize cancer stem cells (CSCs), a small cell subpopulation within the tumor that is thought to be accountable for heterogeneity, recurrence and metastasis of tumors. Despite the fact that association of galectin-3 to the tumor stemness phenomenon is still in its infancy, there is sufficient direct evidence of its regulatory roles in CSC-associated phenotypes and signaling pathways. In this review, we have highlighted the available data on galectin-3 regulated functions pertinent to cancer stemness and explored the opportunities of its exploitation as a CSC marker and a therapeutic target.

Structural and dynamic characterization of human Wnt2-Fzd7 complex using computational approaches

Wnt and Frizzled (Fzd) family members play crucial roles in the self-renewal of tumor-initiating cells. Until now, only a few studies have addressed the distinct mechanism of Wnt-Fzd interactions. In this study, we suggest a possible interaction mode of Wnt2 with the Fzd7 cysteine-rich domain (CRD)-both of which are up-regulated in some types of cancer. A combination of homology modeling, molecular docking and molecular dynamics (MD) simulations was carried out to study this ligand-receptor complex in great detail. The results demonstrated the unique dynamic behavior of Wnt2 upon binding to Fzd7. Interestingly, the β-strand content of the C-terminal binding site of Wnt2 was obviously reduced when bound to Fzd7 CRD. Moreover, the N-terminal and C-terminal binding sites of Wnt2 appeared to interact with the C-terminal and N-terminal binding sites of Fzd7, respectively. Calculation of the binding energies uncovered the pivotal role of electrostatic and hydrophobic interactions in the binding of Wnt2 to Fzd7 CRD. In conclusion, this study provides valuable insights into the mechanism of the Wnt2-Fzd7 CRD interaction for application in colorectal cancer prevention programs. Graphical abstract Flowchart representation of different steps used in this study.

Posttranscriptional regulation of Galectin-3 by miR-128 contributes to colorectal cancer progression

Here we demonstrated that Galectin-3 protein level was frequently up-regulated in colorectal cancer (CRC) cells and tissues. Galectin-3 up-regulation correlated with CRC progression and predicted a shorter overall survival of CRC patients. Galectin-3 overexpression attenuated the chemo-sensitivity of cancer cells, but enhanced the potential invasiveness. To explore the mechanism for Galectin-3 dysregulation, we found that miR-128 level was frequently down-regulated in CRC and negatively correlated with Galectin-3 level. Using bioinformatics analysis and experimental validation, we showed that miR-128 could directly target Galectin-3 to repress its protein level. MiR-128 decrease associated with CRC progression and predicted a worse overall survival of CRC patients. Ectopic miR-128 expression enhanced the chemo-sensitivity of CRC cells in vitro and in vivo, and inhibited the potential invasiveness. Galectin-3 expression impaired the cancer suppressive effects of miR-128. These data highlighted the role of miR-128/Galectin-3 axis in colorectal cancer.

Galectin-3 Expression in Colorectal Cancer and its Correlation with Clinical Pathological Characteristics and Prognosis

Objective

To explore the expression levels of galectin-3 in colorectal cancer and the association between galectin-3 and its clinical pathological parameters, as well as the prognosis of colorectal cancer patients.

Methods

An immunohistochemistry assay was used to test the expression levels of galectin-3 in cancer tissues of 61 colorectal cancer cases and in normal intestinal tissues adjacent to the cancer tissues of 23 cases. The associations between protein expression levels of galectin-3 and the clinicopathological features, such as age, sex, pathology type, lymphatic metastasis, and prognosis were also analyzed.

Results

The positive rate of galectin-3 in cancer tissues was significantly higher than that of cancer-adjacent tissues: 62.5% (38/61) versus 13.0% (3/23) (P<0.05), respectively. Correlation was found between the protein expression of galectin-3 and the tumor size (P<0.05), as well as between the tumor differentiation (P<0.05) and Duke staging (P<0.05). The median progression-free survival times of patients with galectin-3 positive and negative expression were 19.2 and 35.1 months, respectively, with significant statistical difference (P<0.05).

Conclusion

Galectin-3 expression was correlated with the genesis and development of colorectal cancer and which could be used a biological marker for the prognosis of colorectal cancer patients.

Wnt2 complements Wnt/β-catenin signaling in colorectal cancer

Wnt2 is implicated in various human cancers. However, it remains unknown how Wnt2 is upregulated in human cancer and contributes to tumorigenesis. Here we found that Wnt2 is highly expressed in colorectal cancer (CRC) cells. In addition to co-expression of Wnt2 with Wnt/β-catenin target genes in CRC, knockdown or knockout of Wnt2 significantly downregulates Wnt/β-catenin target gene expression in CRC cells. Importantly, depletion or ablation of endogenous Wnt2 inhibits CRC cell proliferation. Similarly, neutralizing secreted Wnt2 reduces Wnt target gene expression and suppresses CRC cell proliferation. Conversely, Wnt2 increases cell proliferation of intestinal epithelial cells. Intriguingly, WNT2 expression is transcriptionally silenced by EZH2-mediated H3K27me3 histone modification in non-CRC cells, However, WNT2 expression is de-repressed by the loss of PRC2's promoter occupancy in CRC cells. Our results reveal the unexpected roles of Wnt2 in complementing Wnt/β-catenin signaling for CRC cell proliferation.

Deletion of Galectin-3 Enhances Xenobiotic Induced Murine Primary Biliary Cholangitis by Facilitating Apoptosis of BECs and Release of Autoantigens

Galectin-3 (Gal-3) is a carbohydrate binding lectin, with multiple roles in inflammatory diseases and autoimmunity including its antiapoptotic effect on epithelial cells. In particular, increased expression of Gal-3 in epithelial cells is protective from apoptosis. Based on the thesis that apoptosis of biliary epithelial cells (BECs) is critical to the pathogenesis of Primary Biliary Cholangitis (PBC), we have analyzed the role of Gal-3 in the murine model of autoimmune cholangitis. We took advantage of Gal-3 knockout mice and immunized them with a mimotope of the major mitochondrial autoantigen of PBC, 2-octynoic acid (2-OA) coupled to BSA (2OA-BSA) and evaluated the natural history of subsequent disease, compared to control wild-type mice, by measuring levels of antibodies to PDC-E2, immunohistology of liver, and expression of Gal-3. We report herein that deletion of Gal-3 significantly exacerbates autoimmune cholangitis in these mice. This is manifested by increased periportal infiltrations, bile duct damage, granulomas and fibrosis. Interestingly, the BECs of Gal-3 knockout mice had a higher response to apoptotic stimuli and there were more pro-inflammatory lymphocytes and dendritic cells (DCs) in the livers of Gal-3 knockout mice. In conclusion, Gal-3 plays a protective role in the pathways that lead to the inflammatory destruction of biliary epithelial cells.

Gene silencing of galectin-3 changes the biological behavior of Eca109 human esophageal cancer cells

Galectin-3 is a multifunctional β-galactoside-binding lectin that is involved in multiple biological functions which are upregulated in malignancies, including cell growth, adhesion, proliferation, progression and metastasis, as well as apoptosis. A previous study has confirmed the roles of galecin-3 overexpression in the biological behavior of Eca109 human esophageal cancer (EC) cells. In the present study, small interfering (si)RNA-mediated galectin-3 silencing was performed to analyze the effects of decreased galectin-3 expression on the biological behavior of EC cells. Western blot and quantitative polymerase chain reaction analyses were utilized to confirm galectin-3 knockdown at the protein and mRNA level (P<0.05 vs. siRNA-control and untransfected groups). Cell proliferation was assessed using the Cell Counting Kit-8 assay. At 72 and 96 h after transfection, the proliferation of Eca109 cells in the siRNA-Gal-3 group was decreased compared with that in the siRNA-Control and untransfected groups (P<0.001 and P=0.004, respectively). Furthermore, Transwell assays demonstrated that inhibition of galecin-3 significantly reduced the migration and invasion of Eca109 cells compared with that in the other groups (P<0.05). Finally, apoptosis of Eca109 cells was detected using Annexin V/7-amino-actinomycin double-staining and flow cytometric analysis. Galectin-3 knockdown significantly enhanced the apoptotic rate of Eca109 cells compared with that in the siRNA-control and untreated groups (P=0.031 and P=0.047, respectively). In conclusion, following successful knockdown of galecin-3 expression in Eca109 cells, the cell proliferation, migration and invasion were reduced, while the apoptosis was enhanced, which indicates that galectin silencing may represent a therapeutic strategy for EC.

Recent advances toward the development of inhibitors to attenuate tumor metastasis via the interruption of lectin-ligand interactions

Aberrant glycosylation is a well-recognized phenomenon that occurs on the surface of tumor cells, and the overexpression of a number of ligands (such as TF, sialyl Tn, and sialyl Lewis X) has been correlated to a worse prognosis for the patient. These unique carbohydrate structures play an integral role in cell-cell communication and have also been associated with more metastatic cancer phenotypes, which can result from binding to lectins present on cell surfaces. The most well studied metastasis-associated lectins are the galectins and selectins, which have been correlated to adhesion, neoangiogenesis, and immune-cell evasion processes. In order to slow the rate of metastatic lesion formation, a number of approaches have been successfully developed which involve interfering with the tumor lectin-substrate binding event. Through the generation of inhibitors, or by attenuating lectin and/or carbohydrate expression, promising results have been observed both in vitro and in vivo. This article briefly summarizes the involvement of lectins in the metastatic process and also describes different approaches used to prevent these undesirable carbohydrate-lectin binding events, which should ultimately lead to improvement in current cancer therapies.

Galectins in epithelial functions

Galectins are a family of animal lectins comprising 15 members in vertebrates. These proteins are involved in many biological processes including epithelial homeostasis and tumor progression by displaying intracellular and extracellular activities. Hence Galectins can be found either in the cytoplasm or the nucleus, associated with membranes or in the extracellular matrix. Current studies aim at understanding the roles of Galectins in cell-cell and cell-matrix adhesion, cellular polarity and motility. This review discusses recent progress in defining the specificities and mechanisms of action of Galectins as cell regulators in epithelial cells. Physiological, cellular and molecular aspects of Galectin specificities will be treated successively.

Nuclear transport of galectin-3 and its therapeutic implications

Galectin-3, a member of β-galactoside-binding gene family is a multi-functional protein, which regulates pleiotropic biological functions such as cell growth, cell adhesion, cell-cell interactions, apoptosis, angiogenesis and mRNA processing. Its unique structure enables it to interact with a plethora of ligands in a carbohydrate dependent or independent manner. Galectin-3 is mainly a cytosolic protein, but can easily traverse the intracellular and plasma membranes to translocate into the nucleus, mitochondria or get externalized. Depending on the cell type, specific experimental conditions in vitro, cancer type and stage, galectin-3 has been reported to be exclusively cytoplasmic, predominantly nuclear or distributed between the two compartments. In this review we have summarized the dynamics of galectin-3 shuttling between the nucleus and the cytoplasm, the nuclear transport mechanisms of galectin-3, how its specific interactions with the members of β-catenin signaling pathways affect tumor progression, and its implications as a therapeutic target.

Galectin-3 in cancer

Galectin-3 (Gal-3) plays important roles in cell proliferation, adhesion, differentiation, angiogenesis and apoptosis in normal and pathologic tissues. Accumulated evidences indicate that Gal-3 is closely involved in tumor cell transformation, migration, invasion and metastasis. In this review, the associations of the expression and localization of Gal-3 as well as its potential action mechanism in tumorigenesis in a variety of cancers were summarized and concluded. Gal-3 is gaining its attraction as a potential new biomarker for the diagnosis, treatment and prognosis of certain tumors.

Intracellular galectins in cancer cells: potential new targets for therapy (Review)

Dysregulation of galectin expression is frequently observed in cancer tissues. Such an abnormal expression pattern often correlates with aggressiveness and relapse in many types of cancer. Because galectins have the ability to modulate functions that are important for cell survival, migration and metastasis, they also represent attractive targets for cancer therapy. This has been well-exploited for extracellular galectins, which bind glycoconjugates expressed on the surface of cancer cells. Although the existence of intracellular functions of galectins has been known for many years, an increasing number of studies indicate that these proteins can also alter tumor progression through their interaction with intracellular ligands. In fact, in some instances, the interactions of galectins with their intracellular ligands seem to occur independently of their carbohydrate recognition domain. Such findings call for a change in the basic assumptions, or paradigms, concerning the activity of galectins in cancer and may force us to revisit our strategies to develop galectin antagonists for the treatment of cancer.

Galectin-3 silencing inhibits epirubicin-induced ATP binding cassette transporters and activates the mitochondrial apoptosis pathway via β-catenin/GSK-3β modulation in colorectal carcinoma

Multidrug resistance (MDR), an unfavorable factor compromising the treatment efficacy of anticancer drugs, involves the upregulation of ATP binding cassette (ABC) transporters and induction of galectin-3 signaling. Galectin-3 plays an anti-apoptotic role in many cancer cells and regulates various pathways to activate MDR. Thus, the inhibition of galectin-3 has the potential to enhance the efficacy of the anticancer drug epirubicin. In this study, we examined the effects and mechanisms of silencing galectin-3 via RNA interference (RNAi) on the β-catenin/GSK-3β pathway in human colon adenocarcinoma Caco-2 cells. Galectin-3 knockdown increased the intracellular accumulation of epirubicin in Caco-2 cells; suppressed the mRNA expression of galectin-3, β-catenin, cyclin D1, c-myc, P-glycoprotein (P-gp), MDR-associated protein (MRP) 1, and MRP2; and downregulated the protein expression of P-gp, cyclin D1, galectin-3, β-catenin, c-Myc, and Bcl-2. Moreover, galectin-3 RNAi treatment significantly increased the mRNA level of GSK-3β, Bax, caspase-3, and caspase-9; remarkably increased the Bax-to-Bcl-2 ratio; and upregulated the GSK-3β and Bax protein expressions. Apoptosis was induced by galectin-3 RNAi and/or epirubicin as demonstrated by chromatin condensation, a higher sub-G1 phase proportion, and increased caspase-3 and caspase-9 activity, indicating an intrinsic/mitochondrial apoptosis pathway. Epirubicin-mediated resistance was effectively inhibited via galectin-3 RNAi treatment. However, these phenomena could be rescued after galectin-3 overexpression. We show for the first time that the silencing of galectin-3 sensitizes MDR cells to epirubicin by inhibiting ABC transporters and activating the mitochondrial pathway of apoptosis through modulation of the β-catenin/GSK-3β pathway in human colon cancer cells.

Galectin-3 gene silencing inhibits migration and invasion of human tongue cancer cells in vitro via downregulating β-catenin

AIM

Galectin-3 (Gal-3) is a member of the carbohydrate-binding protein family that contributes to neoplastic transformation, tumor survival, angiogenesis, and metastasis. The aim of this study is to investigate the role of Gal-3 in human tongue cancer progression.

METHODS

Human tongue cancer cell lines (SCC-4 and CAL27) were transfected with a small-interfering RNA against Gal-3 (Gal-3-siRNA). The migration and invasion of the cells were examined using a scratch assay and BD BioCoat Matrigel Invasion Chamber, respectively. The mRNA and protein levels of β-catenin, Akt/pAkt, GSK-3β/pGSK-3β, MMP-9 in the cells were measured using RT-PCR and Western blotting, respectively.

RESULTS

Transient silencing of Gal-3 gene for 48 h significantly suppressed the migration and invasion of both SCC-4 and CAL27 cells. Silencing of Gal-3 gene significantly decreased the protein level of β-catenin, leaving the mRNA level of β-catenin unaffected. Furthermore, silencing Gal-3 gene significantly decreased the levels of phosphorylated Akt and GSK-3β, and suppressed the mRNA and protein levels of MMP-9 in the cells.

CONCLUSION

Our data suggest that Gal-3 mediates the migration and invasion of tongue cancer cells in vitro via regulating the Wnt/β-catenin signaling pathway and Akt phosphorylation.

Silibinin inhibits Wnt/β-catenin signaling by suppressing Wnt co-receptor LRP6 expression in human prostate and breast cancer cells

Silibinin is a natural compound isolated from milk thistle seed extracts, and has traditionally been used as a hepatoprotectant. A number of studies have also established the cancer therapeutic and chemopreventive role of silibinin in both in vitro and in vivo models. The low density lipoprotein receptor-related protein-6 (LRP6) is an essential Wnt co-receptor for the Wnt/β-catenin pathway and represents a promising target for cancer prevention and therapy. In the present study, we found that silibinin was able to repress endogenous LRP6 expression and block Wnt3A-induced LRP6 phosphorylation and Wnt/β-catenin signaling activation in HEK293 cells. Importantly, silibinin was also able to suppress endogenous LRP6 expression and phosphorylation and block Wnt/β-catenin signaling in prostate cancer PC-3 and DU-145 cells and breast cancer MDA-MB-231 and T-47D cells. Mechanistically, silibinin inhibited LRP6 promoter activity and decreased LRP6 mRNA levels in prostate and breast cancer cells. Finally, we demonstrated that silibinin displayed anticancer activity with IC(50) values comparable to those shown to suppress LRP6 expression and Wnt/β-catenin signaling activities in prostate and breast cancer cells. Our data indicate that silibinin is a novel small molecule Wnt/β-catenin signaling inhibitor by suppressing Wnt co-receptor LRP6 expression at the transcription level, and that the anti-cancer activity of silibinin is associated with its inhibitory effect on Wnt/LRP6 signaling.

Inhibition of Wnt signaling by cucurbitacin B in breast cancer cells: reduction of Wnt-associated proteins and reduced translocation of galectin-3-mediated β-catenin to the nucleus

The cucurbitacins are tetracyclic triterpenes found in plants of the family Cucurbitaceae. Cucurbitacins have been shown to have anti-cancer and anti-inflamatory activities. We investigated the anti-cancer activity of cucurbitacin B extracted from Thai medicinal plant Trichosanthes cucumerina Linn. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results indicated that cucurbitacin B from T. cucumerina Linn. has a cytotoxic effect on breast cancer cell lines SKBR-3 and MCF-7 with an IC50 of 4.60 and 88.75 µg/ml, respectively. Growth inhibition was attributed to G2/M phase arrest and apoptosis. Cyclin D1, c-Myc, and β-catenin expression levels were reduced. Western blot analysis showed increased PARP cleavage and decreased Wnt-associated signaling molecules β-catenin, galectin-3, cyclin D1 and c-Myc, and corresponding changes in phosphorylated GSK-3β levels. Cucurbitacin B treatment inhibited translocation to the nucleus of β-catenin and galectin-3. The depletion of β-catenin and galectin-3 in the nucleus was confirmed by cellular protein fractionation. T-cell factor (TCF)/lymphoid enhancer factor (LEF)-dependent transcriptional activity was disrupted in cucurbitacin B treated cells as tested by a TCF reporter assay. The relative luciferase activity was reduced when we treated cells with cucurbitacin B compound for 24 h. Our data suggest that cucurbitacin B may in part induce apoptosis and exert growth inhibitory effect via interruption the Wnt signaling.

Niclosamide suppresses cancer cell growth by inducing Wnt co-receptor LRP6 degradation and inhibiting the Wnt/β-catenin pathway

The Wnt/β-catenin signaling pathway is important for tumor initiation and progression. The low density lipoprotein receptor-related protein-6 (LRP6) is an essential Wnt co-receptor for Wnt/β-catenin signaling and represents a promising anticancer target. Recently, the antihelminthic drug, niclosamide was found to inhibit Wnt/β-catenin signaling, although the mechanism was not well defined. We found that niclosamide was able to suppress LRP6 expression and phosphorylation, block Wnt3A-induced β-catenin accumulation, and inhibit Wnt/β-catenin signaling in HEK293 cells. Furthermore, the inhibitory effects of niclosamide on LRP6 expression/phosphorylation and Wnt/β-catenin signaling were conformed in human prostate PC-3 and DU145 and breast MDA-MB-231 and T-47D cancer cells. Moreover, we showed that the mechanism by which niclosamide suppressed LRP6 resulted from increased degradation as evident by a shorter half-life. Finally, we demonstrated that niclosamide was able to induce cancer cell apoptosis, and displayed excellent anticancer activity with IC₅₀ values less than 1 µM for prostate PC-3 and DU145 and breast MDA-MB-231 and T-47D cancer cells. The IC₅₀ values are comparable to those shown to suppress the activities of Wnt/β-catenin signaling in prostate and breast cancer cells. Our data indicate that niclosamide is a unique small molecule Wnt/β-catenin signaling inhibitor targeting the Wnt co-receptor LRP6 on the cell surface, and that niclosamide has a potential to be developed a novel chemopreventive or therapeutic agent for human prostate and breast cancer.

Methylator phenotype of malignant germ cell tumours in children identifies strong candidates for chemotherapy resistance

BACKGROUND

Yolk sac tumours (YSTs) and germinomas are the two major pure histological subtypes of germ cell tumours. To date, the role of DNA methylation in the aetiology of this class of tumour has only been analysed in adult testicular forms and with respect to only a few genes.

METHODS

A bank of paediatric tumours was analysed for global methylation of LINE-1 repeat elements and global methylation of regulatory elements using GoldenGate methylation arrays.

RESULTS

Both germinomas and YSTs exhibited significant global hypomethylation of LINE-1 elements. However, in germinomas, methylation of gene regulatory regions differed little from control samples, whereas YSTs exhibited increased methylation at a large proportion of the loci tested, showing a 'methylator' phenotype, including silencing of genes associated with Caspase-8-dependent apoptosis. Furthermore, we found that the methylator phenotype of YSTs was coincident with higher levels of expression of the DNA methyltransferase, DNA (cytosine-5)-methyltransferase 3B, suggesting a mechanism underlying the phenotype.

CONCLUSION

Epigenetic silencing of a large number of potential tumour suppressor genes in YSTs might explain why they exhibit a more aggressive natural history than germinomas and silencing of genes associated with Caspase-8-dependent cell death might explain the relative resistance of YSTs to conventional therapy.

Comprehensive expressional analyses of antisense transcripts in colon cancer tissues using artificial antisense probes

Background

Recent studies have identified thousands of sense-antisense gene pairs across different genomes by computational mapping of cDNA sequences. These studies have shown that approximately 25% of all transcriptional units in the human and mouse genomes are involved in cis-sense-antisense pairs. However, the number of known sense-antisense pairs remains limited because currently available cDNA sequences represent only a fraction of the total number of transcripts comprising the transcriptome of each cell type.

Methods

To discover novel antisense transcripts encoded in the antisense strand of important genes, such as cancer-related genes, we conducted expression analyses of antisense transcripts using our custom microarray platform along with 2376 probes designed specifically to detect the potential antisense transcripts of 501 well-known genes suitable for cancer research.

Results

Using colon cancer tissue and normal tissue surrounding the cancer tissue obtained from 6 patients, we found that antisense transcripts without poly(A) tails are expressed from approximately 80% of these well-known genes. This observation is consistent with our previous finding that many antisense transcripts expressed in a cell are poly(A)-. We also identified 101 and 71 antisense probes displaying a high level of expression specifically in normal and cancer tissues respectively.

Conclusion

Our microarray analysis identified novel antisense transcripts with expression profiles specific to cancer tissue, some of which might play a role in the regulatory networks underlying oncogenesis and thus are potential targets for further experimental validation. Our microarray data are available at http://www.brc.riken.go.jp/ncrna2007/viewer-Saito-01/index.html.

Dishevelled-1 and dishevelled-3 affect cell invasion mainly through canonical and noncanonical Wnt pathway, respectively, and associate with poor prognosis in nonsmall cell lung cancer

Dishevelled (Dvl) family proteins are overexpressed in nonsmall cell lung cancer (NSCLC), but the correlation between Dvl overexpression and patient prognosis is not clear. The underlying mechanisms of Dvl-1 and Dvl-3 promoting lung cancer cell invasion require further research. We used immunohistochemistry to assess the presence of Dvl-1, Dvl-3, beta-catenin, and p120ctn, and compared their expression to the prognosis in 102 specimens from NSCLC patients. We also examined the effect of Dvl-1 and Dvl-3 on Tcf-dependent transcriptional activity, as well as on the invasiveness in A549 and LTEP-alpha-2 lung cancer cells. The results showed that Dvl-1 correlated to the abnormal expression of beta-catenin, while Dvl-3 correlated to p120ctn. Both Dvl-1 and Dvl-3 were related to the poor prognosis of patient. Dvl-1 overexpression enhanced the Tcf-dependent transcriptional activity and beta-catenin expression significantly. However, Dvl-3 had little effect on the Tcf-dependent transcriptional activity and beta-catenin expression, which was accompanied by p38 and JNK phosphorylation. Furthermore, the invasiveness of Dvl-3-enhanced cells was inhibited by p38 and JNK inhibitors. Exogenous expression of both Dvl-1 and Dvl-3 increased the p120ctn protein expression, while only Dvl-3 upregulated p120ctn mRNA. We conclude that both protein and mRNA of Dvl-1 and Dvl-3 are overexpressed in NSCLC in a manner related to poor prognosis. Dvl-1 may affect the biological behavior of lung cancer cells mainly through beta-catenin (canonical Wnt pathway), while Dvl-3 mainly through p38 and JNK pathway (noncanonical Wnt pathway).

Evidence for self-renewing lung cancer stem cells and their implications in tumor initiation, progression, and targeted therapy

The discovery of rare tumor cells with stem cell features first in leukemia and later in solid tumors has emerged as an important area in cancer research. It has been determined that these stem-like tumor cells, termed cancer stem cells, are the primary cellular component within a tumor that drives disease progression and metastasis. In addition to their stem-like ability to self-renew and differentiate, cancer stem cells are also enriched in cells resistant to conventional radiation therapy and to chemotherapy. The immediate implications of this new tumor growth paradigm not only require a re-evaluation of how tumors are initiated, but also on how tumors should be monitored and treated. However, despite the relatively rapid pace of cancer stem cell research in solid tumors such as breast, brain, and colon cancers, similar progress in lung cancer remains hampered in part due to an incomplete understanding of lung epithelial stem cell hierarchy and the complex heterogeneity of the disease. In this review, we provide a critical summary of what is known about the role of normal and malignant lung stem cells in tumor development, the progress in characterizing lung cancer stem cells and the potential for therapeutically targeting pathways of lung cancer stem cell self-renewal.

Single nucleotide polymorphisms in Wnt signaling and cell death pathway genes and susceptibility to colorectal cancer

It is well known that approximately 90% of colorectal cancer (CRC) cases originate from the constitutive activation of the canonical Wnt signaling pathway. There is increasing evidence that genetic variation both in Wnt and apoptotic pathway genes affects CRC susceptibility and progression. This population-based case-control study, including 1795 CRC cases and 1805 controls, investigates the association between common, putative functional polymorphisms in DNFA5, HIF1A, NDRG1, PYGO1, SFRP2, SFRP4, WISP1 and WISP3 genes and CRC risk. We found no evidence for an association between the selected allelic variants and risk of CRC. Subsite analyses, however, revealed a significant association of HIF1A c.*191T>C with rectal cancer risk [odds ratio (OR) = 1.25, 95% confidence interval (CI), 1.03-1.51, P = 0.03] comparing minor allele carriers with major allele homozygotes. In addition, homozygosity for the minor allele of SFRP4 P320T was significantly associated with rectal cancer risk (OR = 1.37, 95% CI, 1.06-1.79, P = 0.02) and early-stage CRC (OR = 1.33, 95% CI, 1.05-1.69, P = 0.02). This study does not support the hypothesis that Wnt signaling- and apoptosis-related polymorphisms contribute to CRC risk. However, our results provide evidence that CRC subsets may be affected. If confirmed, this knowledge may be used to assess individual susceptibility and to target potential measures of cancer prevention.

Dissecting the signal transduction pathways triggered by galectin-glycan interactions in physiological and pathological settings

Galectins are a family of evolutionarily conserved animal lectins with pleiotropic functions and widespread distribution. Fifteen members have been identified in a wide variety of cells and tissues. Through recognition of cell surface glycoproteins and glycolipids, these endogenous lectins can trigger a cascade of intracellular signaling pathways capable of modulating cell differentiation, proliferation, survival, and migration. These cellular events are critical in a variety of biological processes including embryogenesis, angiogenesis, neurogenesis, and immunity and are substantially altered during tumorigenesis, neurodegeneration, and inflammation. In addition, galectins can modulate intracellular functions and this effect involves direct interactions with distinct signaling pathways. In this review, we discuss current knowledge on the intracellular signaling pathways triggered by this multifunctional family of beta-galactoside-binding proteins in selected physiological and pathological settings. Understanding the "galectin signalosome" will be essential to delineate rational therapeutic strategies based on the specific control of galectin expression and function.

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.

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.

WNT2 regulates DNA synthesis in mouse granulosa cells through beta-catenin

WNTs are secreted extracellular signaling molecules that transduce their signals by binding to G protein-coupled receptors of the frizzled (FZD) family. They control diverse developmental processes, such as cell fate specification, cell proliferation, cell differentiation, and apoptosis. Although WNT signaling has been shown to be essential for development of the ovary, its mechanistic role in folliculogenesis within the adult ovary has not been studied extensively. Therefore, the objective of this study was to investigate the regulation and function of WNT2 signaling in mouse granulosa cells. Immunostaining identified WNT2 as being expressed in granulosa cells throughout folliculogenesis, but with varying signal strength: in sequential sections, WNT2 immunoreactivity was strongest in healthy antral follicles but weak in atretic follicles. Knockdown of WNT2 expression using transfected short interfering RNA decreased DNA synthesis in granulosa cells, whereas WNT2 overexpression using a recombinant viral vector enhanced it. WNT2 knockdown led to accumulation of glycogen synthase kinase-3beta (GSK3B) in the cytoplasm but reduced the expression of beta-catenin. Conversely, WNT2 overexpression reduced the expression of GSK3B in the cytoplasm and induced beta-catenin translocation from the membrane into the nucleus. Beta-catenin knockdown also inhibited DNA synthesis in granulosa cells and neutralized the effect of WNT2 overexpression. WNT2/beta-catenin signaling had a slight effect on the apoptosis of granulosa cells. Taken together, the data indicate that WNT2 regulates beta-catenin localization in granulosa cells, and WNT2/beta-catenin signaling contributes to regulating their proliferation.

The effect on cell growth by Wnt1 RNAi in human neuroblastoma SH-SY5Y cell line

PURPOSE

We tested the hypothesis that Wnt signaling pathways are critical to neuroblastoma development. Our objective was to explore the novel role that Wnt/beta-catenin plays in human neuroblastoma cell line SH-SY5Y, including detection of expression of wnt1 and beta-catenin in SH-SY5Y, and the morphological and proliferative changes after Wnt1 RNAi in SH-SY5Y.

METHODS

PCR, Western blot and immunofluorescence technology were used to detect the expression of Wnt1 in human neuroblastoma SH-SY5Y cell line. RNAi technology was used to knock down the expression of Wnt1in SH-SY5Y. SiRNA targeting Wnt1 was transfected into SH-SY5Y cells by Lipofectamine2000. The protein expression of Wnt1 and beta-catenin were detected by Western blotting 48 h after transfection. The quantity and the morphologic changes of the cells were recorded under light microscope. The growth curve of SH-SY5Y cells after RNAi transfection was drawn through MTT assay.

RESULTS

Wnt1 was expressed in human neuroblastoma SH-SY5Y cells. The SH-SY5Y cell was successfully transfected with siRNA targeting Wnt1 mediated by Lipofectamine in vitro. The proteins expression of Wnt1 and beta-catenin decreased after transfection with siRNA; the numbers of the cells were decreased, accompanying abundant floating and dead cells under the light microscope. SH-SY5Y cells transfected with siRNA targeting Wnt1 showed less viability.

CONCLUSION

Wnt1 and beta-catenin expressed in SH-SY5Y cells. Knockdown of endogenous wnt1 expression could result in cell death and inhibit cell growth. From our study, we suggest that the activated embryonal development-related wnt1/beta-catenin pathway might take part in the oncogenesis and growth of neural crest-derived neuroblastoma.

Suppression of galectin-3 expression enhances apoptosis and chemosensitivity in liver fluke-associated cholangiocarcinoma

Cholangiocarcinoma (CCA) is a fatal disease with high resistance to anticancer drugs. This is probably in part due to enhanced resistance to apoptosis. We have previously shown that galectin-3 (Gal-3), a beta-galactoside-binding lectin, is highly expressed in CCA tissues. In this study, we demonstrated further that Gal-3 plays a direct role in anti-apoptosis regardless of the apoptotic insults. The anti-apoptotic activity and chemoresistance of CCA cells were related to Gal-3 expression level. Suppression of Gal-3 expression with siRNA stimulated apoptosis. siGal-3-K626 transiently depleted Gal-3 expression to the baseline and dramatically induced apoptosis, while siGal-3-K402 suppressed Gal-3 expression by 50% and provoked cell apoptosis, but only under apoptotic insults (hypoxic conditions or short UV radiation). These actions were reversed in Gal-3 overexpressing CCA cells. The correlation between the degree of anti-apoptotic activity and the level of endogenous Gal-3 was demonstrated. Suppression of Gal-3 expression in CCA cells with siGal-3-K402 significantly enhanced apoptosis induced by cisplatin or 5-fluorouracil by approximately 10 times, whereas overexpression of Gal-3 led to an increased resistance to drugs. In summary, the present study showed that the cellular level of Gal-3 might contribute to the anti-apoptotic activity and chemoresistance of CCA cells. Hence, Gal-3 expression level in cancer cells or tissues may be a marker for predicting chemotherapeutic response, and Gal-3 may be a specific gene-targeting therapy option for treating CCA.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.

Galectin-3 mediates nuclear beta-catenin accumulation and Wnt signaling in human colon cancer cells by regulation of glycogen synthase kinase-3beta activity

Wnt/beta-catenin signaling plays an essential role in colon carcinogenesis. Galectin-3, a beta-galactoside-binding protein, has been implicated in Wnt signaling, but the precise mechanisms by which galectin-3 modulates the Wnt pathway are unknown. In the present study, we determined the effects of galectin-3 on the Wnt/beta-catenin pathway in colon cancer cells, as well as the mechanisms involved. Galectin-3 levels were manipulated in human colon cancer cells by stable transfection of galectin-3 antisense, short hairpin RNA, or full-length galectin-3 cDNA, and effects on beta-catenin levels, subcellular distribution, and Wnt signaling were determined. Galectin-3 levels correlated with beta-catenin levels in a variety of colon cancer cell lines. Down-regulation of galectin-3 resulted in decreased beta-catenin protein levels but no change in beta-catenin mRNA levels, suggesting that galectin-3 modulates beta-catenin by another mechanism. Reduction of galectin-3 led to reduced nuclear beta-catenin with a concomitant decrease in TCF4 transcriptional activity and expression of its target genes. Conversely, transfection of galectin-3 cDNA into colon cancer cells increased beta-catenin expression and TCF4 transcriptional activity. Down-regulation of galectin-3 resulted in AKT and glycogen synthase kinase-3beta (GSK-3beta) dephosphorylation and increased GSK activity, increasing beta-catenin phosphorylation and degradation. Ly294002, an inhibitor of phosphatidylinositol 3-kinase, and dominant-negative AKT, suppressed TCF4 transcriptional activity induced by galectin-3 whereas LiCl, a GSK-3beta inhibitor, increased TCF4 activity, mimicking the effects of galectin-3. These results suggest that galectin-3 mediates Wnt signaling, at least in part, by regulating GSK-3beta phosphorylation and activity via the phosphatidylinositol 3-kinase/AKT pathway, and, thus, the degradation of beta-catenin in colon cancer cells.

Galectin-3 regulates apoptosis and doxorubicin chemoresistance in papillary thyroid cancer cells

A subset of patients with papillary thyroid cancer (PTC) present with aggressive disease that is refractory to conventional treatment. Novel therapies are needed to treat this group of patients. Galectin-3 (Gal-3) is a beta-galactoside-binding protein with anti-apoptotic activity. Over 30 studies in the last 3 years have reported that Gal-3 is highly expressed in PTC relative to normal thyrocytes. In this study, we show that Gal-3 silencing with RNA interference stimulates apoptosis, while Gal-3 overexpression protects against both TRAIL- and doxorubicin-induced apoptosis in PTC cells. The anti-apoptotic activity and chemoresistance related to Gal-3 function can be partially reversed through the inhibition of the PI3K-Akt pathway, suggesting that Gal-3 acts, at least in part, on the PI3K-Akt axis. These observations support further evaluation of Gal-3 as a potential therapeutic target in patients with aggressive PTC.

Inhibitory effect of modified citrus pectin on liver metastases in a mouse colon cancer model

AIM: To discuss the expression of glactin-3 in liver metastasis of colon cancer and its inhibition by modified citrus pectin (MCP) in mice.

METHODS: Seventy-five Balb/c mice were randomly divided into negative control group (n = 15), positive control group (n = 15), low MCP concentration group (n = 15), middle MCP concentration group (n = 15) and high MCP concentration group (n = 15). CT26 colon cancer cells were injected into the subcapsule of mouse spleen in positive control group, low, middle and high MCP concentrations groups, except in negative control, to set up a colon cancer liver metastasis model. The concentration of MCP in drinking water was 0.0%, 0.0%, 1.0%, 2.5% and 5.0% (wt/vol), respectively. Liver metastasis of colon cancer was observed after 3 wk. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentration of galectin-3 in serum. Expression of galectin-3 in liver metastasis was detected by immunohistochemistry.

RESULTS: Except for the negative group, the percentage of liver metastasis in the other 4 groups was 100%, 80%, 73.3% and 60%, respectively. The number of liver metastases in high MCP concentration group was significantly less than that in positive control group (P = 0.008). Except for the negative group, the median volume of implanted spleen tumor in the other 4 groups was 1.51 cm³, 0.93 cm³, 0.77 cm³ and 0.70 cm³, respectively. The volume of implanted tumor in middle and high MCP concentration groups was significantly smaller than that in positive control group (P = 0.019; P = 0.003). The concentration of serum galectin-3 in positive control and MCP treatment groups was significantly higher than that in the negative control group. However, there was no significant difference between them. Except for the negative control group, the expression of galectin-3 in liver metastases of the other 4 groups showed no significant difference.

CONCLUSION: Expression of galectin-3 increases significantly in liver metastasis of colon cancer, which can be effectively inhibited by MCP.

Thyroid cancer imaging in vivo by targeting the anti-apoptotic molecule galectin-3

Background

The prevalence of thyroid nodules increases with age, average 4–7% for the U.S.A. adult population, but it is much higher (19–67%) when sub-clinical nodules are considered. About 90% of these lesions are benign and a reliable approach to their preoperative characterization is necessary. Unfortunately conventional thyroid scintigraphy does not allow the distinction among benign and malignant thyroid proliferations but it provides only functional information (cold or hot nodules).

The expression of the anti-apoptotic molecule galectin-3 is restricted to cancer cells and this feature has potential diagnostic and therapeutic implications. We show here the possibility to obtain thyroid cancer imaging in vivo by targeting galectin-3.

Methods

The galectin-3 based thyroid immuno-scintigraphy uses as radiotracer a specific ^99mTc-radiolabeled mAb. A position-sensitive high-resolution mini-gamma camera was used as imaging capture device. Human galectin-3 positive thyroid cancer xenografts (ARO) and galectin-3 knockout tumors were used as targets in different experiments in vivo. 38 mice with tumor mass of about 1 gm were injected in the tail vein with 100 µCi of ^99mTc-labeled mAb to galectin-3 (30 µg protein/in 100 µl saline solution). Tumor images were acquired at 1 hr, 3 hrs, 6 hrs, 9 hrs and 24 hrs post injection by using the mini-gamma camera.

Findings

Results from different consecutive experiments show an optimal visualization of thyroid cancer xenografts between 6 and 9 hours from injection of the radiotracer. Galectin-3 negative tumors were not detected at all. At 6 hrs post-injection galectin-3 expressing tumors were correctly visualized, while the whole-body activity had essentially cleared.

Conclusions

These results demonstrate the possibility to distinguish preoperatively benign from malignant thyroid nodules by using a specific galectin-3 radio-immunotargeting. In vivo imaging of thyroid cancer may allow a better selection of patients referred to surgery. The possibility to apply this method for imaging and treatment of other galectin-3 expressing tumors is also discussed.

The galectin family and digestive disease

The soluble-type lectins or galectins constitute a family of proteins defined by shared consensus amino acid sequence and affinity for beta-galactose-containing oligosaccharides. These molecules are widely distributed in the animal kingdom; to date, 15 mammalian galectins have been described but more are likely to be discovered. These proteins are involved in many biological processes including cell-cell and cell-matrix adhesion, growth regulation, signaling, and cytokine secretion. Over the last decade, a vast amount of reports has shown the importance of several galectins in the development and progression of malignancies in the digestive tract, mainly colorectal cancers. More recent data indicate that some of these molecules are also involved in inflammatory bowel diseases. This review focuses on the current knowledge of galectin expression and putative functions in the oesophagus, stomach, small intestine, and colon. It also highlights that the rapid accumulation of research data promises future scenarios in which individual members of the galectin family and/or their ligands will be used as diagnostic and therapeutic modalities for neoplastic as well as inflammatory disorders. However, the concretization of these potential modalities requires substantial improvements in terms of standardization of galectin expression evaluation together with prospective validation of the present data.

The upstream components of the Wnt signalling pathway in the dynamic EMT and MET associated with colorectal cancer progression

The constitutive activation of beta-catenin-dependent ('canonical') Wnt signalling is a necessary initiating event in the genesis of most colorectal cancers. As this constitutive activation occurs through genetic mutation of one of the down-stream components of the signalling pathway, it was presumed that additional regulation of beta-catenin-dependent Wnt signalling would be inconsequential. However, it is now recognised that additional modulation of beta-catenin-dependent Wnt signalling is involved in tumour progression, and many of the genes associated with tumour invasion and metastasis are beta-catenin/TCF transcriptional target genes that are dynamically regulated during cancer progression. Intriguingly, the demonstration that naturally occurring inhibitors of Wnt-Frizzled (FZD) interaction are bona fide tumour suppressors in this cancer suggests that additional modulation of Wnt signalling is via the upstream components of the pathway. This is corroborated by recent studies that demonstrate tumour-promoting roles for Wnt and FZD per se. Moreover, both beta-catenin-dependent and beta-catenin-independent Wnt/FZD-mediated signalling is implicated during the dynamic and reversible EMT and MET that underscore colorectal cancer progression. Importantly, therapeutic targeting of the Wnt signalling pathway at the plasma membrane is clearly indicated by the profound anti-tumour activity of small molecule inhibitors and dominant-negative receptor constructs that target the receptor complex. The potential to effectively target EMT and MET processes at the plasma membrane via the upstream components of the Wnt signalling pathway offers new hope for anti-cancer therapy.