Galectin-3 expression is induced in cirrhotic liver and hepatocellular carcinoma

Galectin-3 is critical for the development of the allergic inflammatory response in a mouse model of atopic dermatitis

Galectin-3 belongs to a family of beta-galactoside-binding animal lectins expressed in several cell types, including epithelial and immune cells. To establish the role of galectin-3 in the development of allergic skin inflammation, we compared inflammatory skin responses of galectin-3-deficient (gal3(-/-)) and wild-type (gal3(+/+)) mice to epicutaneous sensitization with ovalbumin (OVA). OVA-treated gal3(-/-) mice exhibited markedly reduced epidermal thickening, lower eosinophil infiltration, and lower serum IgE levels compared with gal3(+/+) mice. The former evoked lower interleukin-4, but higher interferon-gamma, mRNA expression at OVA-treated skin sites. Moreover, gal3(-/-) splenocytes from OVA-sensitized mice secreted more interleukin-12 compared with gal3(+/+) splenocytes. In addition, antigen presentation by gal3(-/-) dendritic cells to T cells in vitro were T helper cell (Th1)-polarized relative to presentation by gal3(+/+) dendritic cells. When exposed to OVA, recipients engrafted with T cells from gal3(-/-) OVA-specific T cell receptor transgenic mice developed significantly reduced dermatitis and a markedly lower Th2 response compared with recipients of comparable gal3(+/+) T cells. We conclude that galectin-3 is critical for the development of inflammatory Th2 responses to epicutaneously administered antigens; in its absence, mice develop a Th1-polarized response. This regulatory effect of galectin-3 on Th development is exerted at both the dendritic cell and T cell levels. Our studies suggest that galectin-3 may play an important role in the acute phase of human atopic dermatitis.

Nonalcoholic steatohepatitis and hepatocellular carcinoma in galectin-3 knockout mice

AIM

Nonalcoholic fatty liver disease (NAFLD) represents a growing health concern due to its rapidly increasing prevalence worldwide. Nonalcoholic steatohepatitis (NASH) is a progressing form of NAFLD, and recently many studies have reported that it could eventually develop into hepatocellular carcinoma (HCC). We previously reported that 6-month-old male galectin-3 knockout (gal3(-/-)) mice developed clinicopathological features similar to those of NAFLD in humans. Our aim was to investigate the changes in liver histology in gal3(-/-) mice by long-term observation.

METHODS

We initially investigated three 15-month-old gal3(-/-) mice, of which two developed multiple liver nodules with dysplastic changes. Then, we histopathologically examined the liver specimens of the 15-, 20- and 25-month-old gal3(-/-) mice and attempted to evaluate the liver morphology by contrast enhanced computed tomography (CT) before sacrifice.

RESULTS

At the age of 15 months or later, gal3(-/-) mice developed liver nodules with varying degrees of architectural and nuclear atypia based on mild to moderate delicate zone 3 fibrosis. In addition, we successfully confirmed the presence of some of the liver nodules by CT. We report herein that gal3(-/-) mice develop dysplastic liver nodules and HCC.

CONCLUSIONS

We believe that it would be interesting to use this murine model to investigate liver carcinogenesis based on a natural history of NAFLD. Furthermore, CT scanning might be a useful tool for longitudinal evaluation of morphological changes in vivo.

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.

The Molecular Diagnosis of Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) infection is the major cause of hepatocellular carcinoma (HCC) worldwide. The pathogenesis of HBV-associated HCC has been studied extensively, and molecular changes during malignant transformation have been identified. It has been proposed that the insertion of HBV DNA into the human genome results in chromosomal instability and inactivation of tumor suppressor genes. Transactivation of oncogenes, inactivation of tumor suppressor genes, and alteration of the cell cycle by HBV proteins are also involved in the progression of hepatocellular carcinogenesis. Traditional clinical examinations of HCC, such as biopsy, computer tomography, ultrasonic imaging, and detection of such biomarkers as a-fetoprotein, are currently the "gold standard" in diagnosis. These tests diagnose HCC only in the late stages of disease. This limitation has greatly reduced the chance of survival of HCC patients. To resolve this problem, new biomarkers that can diagnose HCC in earlier stages are necessary. Based on recent molecular studies of the effects of HBV on cellular transformation, differentially expressed biomarkers of HBV infection have been elucidated. With the analyses of the HBV replication profile, the viral load (HBV DNA levels) of patients, and the viral protein expression, the severity of hepatitis in the preneoplastic stages can be assessed. In the future, with the molecular profiles identified by genomic and proteomic approaches, stage-specific biomarkers should be identified to monitor the progression and prognosis of HCC.

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.

Li-cadherin is inversely correlated with galectin-3 expression in gastric cancer

The aims of this study were to examine the expressions of Li-cadherin and Galectin-3 in gastric cancer, and the correlation between Li-cadherin and Galectin-3 in gastric cancer was also analyzed. The present study investigated the expression level of Li-cadherin and Galectin-3 by immunohistochemistry and semiquantitative polymerase chain reaction (PCR), and correlated this with clinicopathologic parameters in 91 cases of gastric cancer. The correlation between expression levels of Li-cadherin and Galectin-3 was analyzed by Spearman correlation analysis. The expression level of Li-cadherin mRNA was correlated to differentiation and lymph node metastasis, and the expression level of Galectin-3 was related to TNM staging, differentiation and lymph node metastasis. On Spearman correlation analysis, a definitive negative correlation was found between the expression levels of Li-cadherin and Galectin-3 in gastric cancerous tissues. We postulate that interaction between Li-cadherin and Galectin-3 may play an important role in the development of gastric cancer.

Serum level of galectin-3 in human bladder cancer

We examine serum level of galectin-3 in patients with bladder cancer. We used serum samples of 67 patients with urological diseases and classified these patients into bladder cancer group (n=43) and control group (n=24). Galectin-3 concentration was measured by ELISA (Human Galectin-3 Assay Kit, IBL). And we selected the patient with high serum galectin-3 concentration (Urothelial Carcinoma, G3, pT3a pN0M0), we performed immunohistochemical staining with the VECTASTAIN ABC (Avidin Biotinylated enzyme Complex) system. Median value of serum galectin-3 concentration was 1068 pg/ml (range 551-2028) in the cancer group vs 584 pg/ml (range 259-1262) in controls. Serum galectin-3 concentration of the bladder cancer patients was statistically higher than that of controls (p<0.0005). There was no apparent correlation in serum galectin-3 concentration with the clinico-pathological features such as stage and grade. Higher expression of galectin-3 was observed in bladder cancer tissue than in normal bladder tissue. We suggest the measurement of serum galectin-3 is useful for diagnosis of bladder cancer.

Galectin-3: a useful biomarker for differential diagnosis of brain tumors

Galectin-3 (gal-3) is a 31 kDa beta-galactoside-binding lectin that is immunohistochemically expressed in macrophages, lymphocytes, and endothelial cells, and also in some neoplastic cells. Gal-3's expression in and significance to brain tumors has not been fully addressed. Here, we investigated its immunohistochemical expression in 409 cases of surgically resected primary brain tumors, including various glioneuronal tumors, pituitary adenomas, meningiomas and Schwannomas, among others. In normal brain tissues, gal-3 was robustly expressed in normal astrocytes, endothelial cells and macrophages. It showed consistent and diffuse positivity in 100% of the pilocytic astrocytomas, pleomorphic xanthoastrocytomas (PXA), Schwannomas, meningiomas, capillary hemangioblastomas, as well as in ependymomas, but it was completely negative in the diffuse astrocytomas, anaplastic astrocytomas, both low- and high-grades of the oligodendrogliomas, central neurocytomas, and medulloblastomas. Definitely positive but heterogeneous expression was found in various tumors including subependymal giant cell astrocytomas (SEGA), classic glioblastoma multiforme, anaplastic oligoastrocytomas, CNS primitive neuroectodermal tumors (CNS PNETs), and hemangiopericytomas. Eighty percent of small cell glioblstomas were completely negative, but 20% showed heterogeneous positivity for gal-3. Focal positivity for gal-3 was also found in dysembryoplastic neuroepithelial tumors (DNTs) and gangliogliomas, in which the positive cells were the astrocytic component. On the basis of our immunohistochemical data in conjunction with previous reports, we therefore conclude that gal-3 is differentially expressed in various brain tumors, and thereby, is a helpful biomarker in making differential diagnoses, especially in cases where a morphological diagnosis is controversial.

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.

Galectin-3 may contribute to Cisplatin resistance in clear cell carcinoma of the ovary

Our previous findings suggested that lower cell proliferation of clear cell carcinoma (CCC) of the ovary may contribute to its resistance to chemotherapy. We conducted the present study to find the gene that regulates cell proliferation of CCC and to elucidate whether it contributes to cisplatin (CDDP) resistance. Complementary DNA microarray analysis revealed that the gene expression level of galectin-3 of CCC cell lines (KK, RMG-I, HAC-2) was over threefold higher than that of ovarian serous adenocarcinoma (SAC) cell lines (HRA, KF). S-phase fraction increased after knocking down galectin-3 using small interfering RNA in RMG-I, KK, and HAC-2 cells. The protein expression of p27 decreased after knocking down galectin-3. CDDP-induced apoptosis was increased after knocking down galectin-3, and this cytotoxic effect was canceled by roscovitine. Immunohistochemical staining showed that galectin-3 expression in tumors of 20 CCC was significantly more frequent than that of 20 SAC (70.0% vs 15.0%, P = 0.0004). The present study showed that the expression of galectin-3 in CCC might contribute to its lower cell proliferation and lead to CDDP resistance.

Role of galectin-3 in human pulmonary fibrosis

BACKGROUND

Galectin-3 is a beta-galactoside-binding protein which is implicated in diverse physiological and pathological processes including human liver cirrhosis and a mouse lung fibrosis model. The aim of this study is to determine whether galectin-3 is involved in human lung fibrosis.

METHODS

We measured galectin-3 concentration in bronchoalveolar lavage fluid (BALF) and examined its expression in alveolar macrophages from patients with interstitial lung disorders using ELISA and immunohistochemical staining, respectively. Using monocyte/macrophage cell lines in vitro, we examined the effect of cytokines on galectin-3 expression, and the opposite similarly by RT-PCR and Western blotting. Finally, we performed Micro Boyden chamber assay and Sircoll assay to determine whether galectin-3 induces migration and collagen synthesis, respectively, in fibroblasts.

RESULTS

Galectin-3 was specifically increased in BALF from patients with idiopathic pulmonary fibrosis (IPF) and interstitial pneumonia associated with collagen vascular disease (CVD-IP). Galectin-3 levels in BALF seemed to be lower in IPF and CVD-IP patients receiving corticosteroid therapy. Alveolar macrophages from IPF patients expressed more galectin-3 compared with those from control. Galectin-3 expression was induced by tumor necrosis factor-alpha (TNF-alpha) and interferon (IFN)-gamma in a monocytic cell line U937. Galectin-3 also induced mRNA expression and protein production of TNF-alpha and interleukin (IL)-8 in a macrophage cell line THP-1. This lectin stimulated NIH-3T3 fibroblast to induce migration and collagen synthesis in vitro.

CONCLUSIONS

These results suggest that galectin-3 is involved in the pathogenesis of human IPF and CVD-IP by activating macrophages and fibroblasts.

Disrupted galectin-3 causes non-alcoholic fatty liver disease in male mice

Galectin-3, a beta-galactoside-binding animal lectin, is a multifunctional protein. Previous studies have suggested that galectin-3 may play an important role in inflammatory responses. Non-alcoholic fatty liver disease (NAFLD) is increasingly recognized as a liver condition that may progress to end-stage liver disease and based on the known functions of galectin-3, it was hypothesized that galectin-3 might play a role in the development of NAFLD. Thus, this study investigated the role of galectin-3 in NAFLD by comparing galectin-3 knockout (gal3(-/-)) mice and wild-type (gal3(+/+)) mice. The livers of gal3(-/-) male mice at 6 months of age histologically displayed mild to severe fatty change. The liver weight per body weight ratio, serum alanine aminotransferase levels, liver triglyceride levels, and liver lipid peroxide in gal3(-/-) mice were significantly increased compared with those in gal3(+/+) mice. Furthermore, the hepatic protein levels of advanced glycation end-products (AGE), receptor for AGE (RAGE), and peroxisome proliferator-activated receptor gamma (PPARgamma) were increased in gal3(-/-) mice relative to gal3(+/+) mice. In conclusion, this study suggests that the absence of gal3 can cause clinico-pathological features in male mice similar to those of NAFLD.

Differential gene expression in mouse primary hepatocytes exposed to the peroxisome proliferator-activated receptor alpha agonists

Background

Fibrates are a unique hypolipidemic drugs that lower plasma triglyceride and cholesterol levels through their action as peroxisome proliferator-activated receptor alpha (PPARα) agonists. The activation of PPARα leads to a cascade of events that result in the pharmacological (hypolipidemic) and adverse (carcinogenic) effects in rodent liver.

Results

To understand the molecular mechanisms responsible for the pleiotropic effects of PPARα agonists, we treated mouse primary hepatocytes with three PPARα agonists (bezafibrate, fenofibrate, and WY-14,643) at multiple concentrations (0, 10, 30, and 100 μM) for 24 hours. When primary hepatocytes were exposed to these agents, transactivation of PPARα was elevated as measured by luciferase assay. Global gene expression profiles in response to PPARα agonists were obtained by microarray analysis. Among differentially expressed genes (DEGs), there were 4, 8, and 21 genes commonly regulated by bezafibrate, fenofibrate, and WY-14,643 treatments across 3 doses, respectively, in a dose-dependent manner. Treatments with 100 μM of bezafibrate, fenofibrate, and WY-14,643 resulted in 151, 149, and 145 genes altered, respectively. Among them, 121 genes were commonly regulated by at least two drugs. Many genes are involved in fatty acid metabolism including oxidative reaction. Some of the gene changes were associated with production of reactive oxygen species, cell proliferation of peroxisomes, and hepatic disorders. In addition, 11 genes related to the development of liver cancer were observed.

Conclusion

Our results suggest that treatment of PPARα agonists results in the production of oxidative stress and increased peroxisome proliferation, thus providing a better understanding of mechanisms underlying PPARα agonist-induced hepatic disorders and hepatocarcinomas.

Hepatic expression of galectin-3 and receptor for advanced glycation end products in patients with liver disease

BACKGROUND

Advanced glycation end products (AGEs) are a heterogeneous group of glycosylated proteins (of which carboxymethyl-lysine (CML) is the most common) which accumulate during ageing processes and play an important role in the pathogenesis of a variety of chronic diseases. Impaired hepatic function might result in elevated levels of AGEs, as the liver represents the major site of AGE metabolism. The actions of AGEs are mediated by various receptors, among which the AGE-receptor complex (including galectin-3 as an essential part) is thought to have a cytoprotective effect, and receptor for advanced glycation end product (RAGE) a cytotoxic effect.

AIM

To assess the relationship between CML and expression of galectin-3 and RAGE in different histological structures in biopsy specimens from patients with varying degrees of liver impairment.

METHOD

Immunohistochemical staining of 164 biopsies from patients with varying degrees of liver impairment was performed to determine the levels of CML, galectin-3 and RAGE in hepatocytes, Kupffer cells and bile ducts by a semiquantative score.

RESULTS

Independent of diagnosis, CML and RAGEs were detected in hepatocytes, whereas galectin-3 was present only in hepatocytes of cirrhotics. By contrast, CML and galectin-3 were highly expressed in Kupffer cells (well correlating levels, highest scores in cholestasis) whereas expression of RAGEs was not significant. All three assessed biochemical markers showed their highest levels of expression/detection in bile ducts.

CONCLUSION

These findings indicate an increased susceptibility of hepatocytes to the detrimental effects of AGEs and underline the protective function of Kupffer cells. Furthermore, the biliary system seems to play an important role in the disposition of AGEs.

Galectin-3 regulates myofibroblast activation and hepatic fibrosis

Central to fibrogenesis and the scarring of organs is the activation of fibroblasts into matrix-secreting myofibroblasts. We demonstrate that Galectin-3 expression is up-regulated in established human fibrotic liver disease and is temporally and spatially related to the induction and resolution of experimental hepatic fibrosis. Disruption of the Galectin-3 gene blocks myofibroblast activation and procollagen (I) expression in vitro and in vivo, markedly attenuating liver fibrosis. Addition of exogenous recombinant Galectin-3 in vitro reversed this abnormality. The reduction in hepatic fibrosis observed in the Galectin-3(-/-) mouse occurred despite equivalent liver injury and inflammation, and similar tissue expression of TGF-beta. TGF-beta failed to transactivate Galectin-3(-/-) hepatic stellate cells, in contrast with WT hepatic stellate cells; however, TGF-beta-stimulated Smad-2 and -3 activation was equivalent. These data suggest that Galectin-3 is required for TGF-beta mediated myofibroblast activation and matrix production. Finally, in vivo siRNA knockdown of Galectin-3 inhibited myofibroblast activation after hepatic injury and may therefore provide an alternative therapeutic approach to the prevention and treatment of liver fibrosis.

Galectin-3 interacts with naive and primed neutrophils, inducing innate immune responses

The neutrophil is the first line of defense against infection. As a part of the innate immune response, neutrophils start to emigrate from blood to an affected site and their state is altered from passively circulating naïve to primed, and then to fully activated. The extent of neutrophil activation and their subsequent response varies depending on the stimuli and environment that neutrophils encounter. Because neutrophils can also induce deleterious effects on host tissues, tight regulation of recruitment and functions of neutrophils is required for efficient recovery. Galectin-3, a soluble beta-galactoside binding protein, of which expression is up-regulated during inflammation/infection, is suggested to be involved in various inflammatory responses. However, the precise roles of this lectin in innate immunity remain unknown, while it has been demonstrated that galectin-3 binds to naïve and primed neutrophils. Here we report that galectin-3 can induce L-selectin shedding and interleukin-8 production in naïve and primed neutrophils. These activities were shown to be dependent on the presence of the C-terminal lectin domain and the N-terminal nonlectin domain of galectin-3, which is involved in oligomerization of this lectin. We also found that, after galectin-3 binds to neutrophils, primed but not naïve neutrophils can cleave galectin-3, mainly through elastase, which results in the formation of truncated galectin-3 lacking the N-terminal domain. Together, these results suggest that galectin-3 activates naïve and primed neutrophils, and galectin-3-activated primed neutrophils have an ability to inactivate galectin-3.

Galectin-3: an open-ended story

Galectins, an ancient lectin family, are characterized by specific binding of beta-galactosides through evolutionary conserved sequence elements of carbohydrate-recognition domain (CRD). A structurally unique member of the family is galectin-3; in addition to the CRD it contains a proline- and glycine-rich N-terminal domain (ND) through which is able to form oligomers. Galectin-3 is widely spread among different types of cells and tissues, found intracellularly in nucleus and cytoplasm or secreted via non-classical pathway outside of cell, thus being found on the cell surface or in the extracellular space. Through specific interactions with a variety of intra- and extracellular proteins galectin-3 affects numerous biological processes and seems to be involved in different physiological and pathophysiological conditions, such as development, immune reactions, and neoplastic transformation and metastasis. The review attempts to summarize the existing information on structural, biochemical and intriguing functional properties of galectin-3.

Unraveling the Pathogenesis of Type 1 Diabetes with Proteomics: Present And Future Directions

Type 1 diabetes (T1D) is the result of selective destruction of the insulin-producing beta-cells in the pancreatic islets of Langerhans. T1D is due to a complex interplay between the beta-cell, the immune system, and the environment in genetically susceptible individuals. The initiating mechanism(s) behind the development of T1D are largely unknown, and no genes or proteins are specific for most T1D cases. Different pro-apoptotic cytokines, IL-1 beta in particular, are present in the islets during beta-cell destruction and are able to modulate beta-cell function and induce beta-cell death. In beta-cells exposed to IL-1 beta, a race between destructive and protective events are initiated and in susceptible individuals the deleterious events prevail. Proteins are involved in most cellular processes, and it is thus expected that their cumulative expression profile reflects the specific activity of cells. Proteomics may be useful in describing the protein expression profile and thus the diabetic phenotype. Relatively few studies using proteomics technologies to investigate the T1D pathogenesis have been published to date despite the defined target organ, the beta-cell. Proteomics has been applied in studies of differentiating beta-cells, cytokine exposed islets, dietary manipulated islets, and in transplanted islets. Although that the studies have revealed a complex and detailed picture of the protein expression profiles many functional implications remain to be answered. In conclusion, a rather detailed picture of protein expression in beta-cell lines, islets, and transplanted islets both in vitro and in vivo have been described. The data indicate that the beta-cell is an active participant in its own destruction during diabetes development. No single protein alone seems to be responsible for the development of diabetes. Rather the cumulative pattern of changes seems to be what favors a transition from dynamic stability in the unperturbed beta-cell to dynamic instability and eventually to beta-cell destruction.

Galectin-3 does not reliably distinguish benign from malignant thyroid neoplasms

AIMS

To determine whether galectin-3 is a sensitive indicator of thyroid malignancy. It has been suggested as a potential marker for differentiating thyroid carcinoma from benign or non-neoplastic lesions in preoperative fine-needle aspirates (FNAs).

METHODS

Galectin-3 protein expression was assessed by immunohistochemistry in formalin-fixed thyroid tissues from 124 patients with histological diagnoses of papillary carcinoma (n = 38), follicular carcinoma (n = 19), follicular adenoma (n = 32) and dominant nodules of multinodular goitre (n = 35). Expression of galectin-3 was also assessed by Western blotting in 24 fresh thyroid tissues.

RESULTS

Galectin-3 expression was observed in the majority of carcinomas (papillary 92%; follicular 74%). However, a large proportion of follicular adenomas (72%) and multinodular goitres (57%) also expressed galectin-3. In addition, galectin-3 expression was observed in epithelial cells of normal thyroid tissue and Hashimoto's thyroiditis. Galectin-3 immunopositivity was significantly greater in papillary carcinomas than in dominant nodules or follicular adenomas (P < 0.0001, P = 0.0005, respectively). However, galectin-3 expression was no greater in follicular carcinomas than in follicular adenomas (P = 0.8735). Western blotting analysis confirmed both the specificity of the antiserum and expression of galectin-3 in multinodular goitres, follicular adenomas/carcinomas and papillary carcinomas.

CONCLUSION

The data demonstrate that galectin-3 is not a reliable immunohistochemical marker to distinguish benign from malignant thyroid follicular lesions.

Impact of transforming viruses on cellular mutagenesis, genome stability, and cellular transformation

It is estimated that 15% of all cancers are etiologically linked to viral infection. Specific cancers including adult T-cell leukemia, hepatocellular carcinoma, and uterine cervical cancer are associated with infection by human T-cell leukemia virus type I, hepatitis B virus, and high-risk human papilloma virus, respectively. In these cancers, genomic instability, a hallmark of multistep cancers, has been explicitly linked to the expression of oncoproteins encoded by these viruses. This review discusses mechanisms utilized by these viral oncoproteins, Tax, HBx, and E6/E7, to mediate genomic instability and cellular transformation.

Purification and Characterization of Liver Lectins from a Lizard,Sceloporus spinosus

This study discusses the purification of soluble beta-galactose lectins obtained from the lizard liver of Sceloporus spinosus. The first lectin named lizard hepatic lectin-1 (LHL-1) presented a molecular weight of 31,750, with an isoelectric point of 4.25. The highest specific hemagglutinating activity was achieved using human blood type A1: N-acetylgalactosamine (GalNAc)-galactose (Gal)-fucose (Fuc). Carbohydrate inhibition assays indicated a higher lectin specificity for GalNAc. For LHL-2 the molecular weight obtained was 23,850 with an isoelectric point of 3.25. The highest carbohydrate specificity was observed for Gal. These lizard hepatic lectins are similar to the mammal hepatic lectins previously reported. However, it is different from the alligator hepatic lectin (AHL). The homology analyses of LHL-1 resulted in 100% identity with the Steroidogenic acute regulatory protein (StAR), while LHL-2 was similar to adenylate kinase (75% identity). We suggest that these liver lectins are related to the inherent functions of liver previously reported.

Toward functional glycomics by localization of tissue lectins: immunohistochemical galectin fingerprinting during diethylstilbestrol-induced kidney tumorigenesis in male Syrian hamster

The current study focused on galectins (-1, -3, -4, -7, and -8) and deliberately performed immunohistochemical fingerprinting to explore their complexity in a context of experimental renal carcinogenesis. The diethylstilbestrol (DES)-induced renal tumors in male Syrian hamster kidney (SHKT) represent a unique animal model for the study of estrogen-dependent renal malignancies. Kidney sections of DES-treated hamsters (3 days to 11 months of DES exposure) were analyzed by immunohistochemistry using a panel of non-crossreactive antibodies raised against galectins-1, -3, -4, -7, and -8. Levels of expression were quantitatively determined by using computer-assisted microscopy on immunostained tissue sections. Except for galectin-4, all above mentioned galectins were expressed in kidney tumors. Small clusters of galectin-1-positive, most likely preneoplastic cells at the corticomedullary junction were already evident 1 week after DES administration. Galectin-1 and -3 expression was apparently associated with the first steps of the neoplastic transformation, because small tumorous buds were found to be positive after 1 month of treatment. In contrast, galectins-7 and -8 were detected in large tumors and medium-sized tumors, respectively, thereby indicating an involvement in later stages of DES-induced SHKT. Galectins-1, -3, -7, and -8 were also detected by immunofluorescence staining in the HKT-1097 cell line established from SHKT, thus illustrating the stability of galectin expression in tumor cells. Our data document the presence and differential regulation of galectins in the course of renal tumorigenesis in the model of DES-induced SHKT.

Galectin-1: a bifunctional regulator of cellular proliferation

Galectin-1 has demonstrated a diverse range of activities in relation to cell survival and proliferation. In different circumstances, it acts as a mitogen, as an inhibitor of cell proliferation, and as a promoter of cellular apoptosis. Many of these activities, particularly the mitogenic and apoptotic responses, follow from the interaction of galectin-1 with cell-surface beta-galactoside ligands, but there is increasing evidence for protein-protein interactions involving galectin-1, and for a beta-galactoside-independent cytostatic mechanism. The bifunctional nature of galectin-1, in conjunction with other experimental variables, makes it difficult to assess the overall outcomes and significance of the growth-regulatory actions in many previous investigations. There is thus a need for well-defined experimental cross-correlation of observations, for which specific loss-of-function galectin-1 mutants will be invaluable. Unsurprisingly, in view of this background, the interpretation of the actions of galectin-1 in developmental situations, both normal and neoplastic, is often very complex.

90K (Mac-2 BP) and galectins in tumor progression and metastasis

Galectins and their ligands have been implicated in cell transformation and cancer metastasis, and found to have prognostic value. Mac-2 BP, also known as 90K, is a highly glycosylated, secreted protein extensively studied in human cancer, which binds galectin-1, galectin-3 and galectin-7. High expression levels of 90K are associated with a shorter survival, the occurrence of metastasis or a reduced response to chemotherapy in patients with different types of malignancy. The mechanisms underlying the prognostic significance of 90K and galectins in cancer are far from being understood, although they may be related to the ability of these proteins to interact and, to some extent, modulate cell-cell and cell-matrix adhesion and apoptosis. The resulting scenario is even more complex, as data have been presented that all these proteins might be associated with either a positive or a negative outcome of the patients. It is hypothesised that different galectins and galectin ligands with overlapping or opposite functions, expressed in different tumors during the different steps of the metastatic cascade might play a crucial role in tumor progression.

Expression of galectins in cancer: a critical review

A large body of literature has examined and described galectin expression in cancer. Discrepancies have been observed in the reported data, which hampered clear understanding of the expression profiles. This relates to the use of different types of methods that evaluate either global or specific gene expression in heterogeneous cancer tissue samples, type of antibodies used in immunohistochemistry and procedures of comparison of gene expression. In this manuscript, we review the main data concerning expression of galectins in human cancer. Only galectin-1 and galectin-3, the most abundant and examined galectins, will be examined here.

90K (Mac-2 BP) and galectins in tumor progression and metastasis

Galectins and their ligands have been implicated in cell transformation and cancer metastasis, and found to have prognostic value. Mac-2 BP, also known as 90K, is a highly glycosylated, secreted protein extensively studied in human cancer, which binds galectin-1, galectin-3 and galectin-7. High expression levels of 90K are associated with a shorter survival, the occurrence of metastasis or a reduced response to chemotherapy in patients with different types of malignancy. The mechanisms underlying the prognostic significance of 90K and galectins in cancer are far from being understood, although they may be related to the ability of these proteins to interact and, to some extent, modulate cell-cell and cell-matrix adhesion and apoptosis. The resulting scenario is even more complex, as data have been presented that all these proteins might be associated with either a positive or a negative outcome of the patients. It is hypothesised that different galectins and galectin ligands with overlapping or opposite functions, expressed in different tumors during the different steps of the metastatic cascade might play a crucial role in tumor progression.

A gene-expression signature can quantify the degree of hepatic fibrosis in the rat

BACKGROUNDS/AIMS

A more accurate and objective quantification of hepatic fibrosis would provide clinically useful information for the monitoring of chronic liver disease progression and therapy recommendation.

METHODS

Using a cDNA microarray of 14,814 clones, we analyzed the gene-expression profiles of fibrotic livers in a rat model.

RESULTS

We identified 750 up- and 345 down-regulated genes by combining a signal-to-noise score and a random permutation test (P<0.01). The functions of these genes provided insight into the underlying molecular mechanisms of both structural remodeling and functional deficits in cirrhosis. To quantify the extent of liver fibrosis, we have generated for the first time a 'genetic fibrosis index' based on gene-expression profiling of 95 genes by combining a Pearson correlation coefficient and a 'leave-one-out' cross-validation procedure. This technique based on a supervised learning analysis correctly quantified the various degrees of fibrosis in both 20 training samples (R(2)=0.829, P<0.001) and 6 test samples (R(2)=0.822, P<0.05).

CONCLUSIONS

Our method will assist researchers in identifying rational targets for intervention and might help clinicians to objectively monitor the severity of liver fibrosis.

Disease- and cell-specific expression of GP73 in human liver disease

OBJECTIVES

GP73, a Golgi membrane protein, is expressed at high levels in hepatocytes of patients with decompensated cirrhosis. Its expression in other forms of liver disease has not been investigated. Therefore, we studied GP73 expression in patients with noncirrhotic liver disease.

METHODS

GP73 expression was detected immunohistochemically and by immunofluorescence microscopy in patients with acute hepatitis of various etiologies, autoimmune hepatitis, chronic HCV infection, and alcoholic liver disease. In order to quantitate hepatocyte GP73 expression, an immunohistochemical scoring system was developed, and validated by a direct comparison with GP73 protein levels as determined by Western blotting.

RESULTS

GP73 immunostaining and Western blotting data were highly correlated, demonstrating the suitability of the immunohistochemical scoring system to quantitate hepatocyte GP73 expression. Hepatocyte GP73 expression was increased in patients with acute and autoimmune hepatitis. Treatment of autoimmune hepatitis was associated with a normalization of GP73 expression, indicating that the initial upregulation was reversible. Increased levels of GP73 expression were also noted in chronic HCV infection and alcoholic liver disease. Under these conditions, GP73 levels were correlated with disease stage but not grade. GP73 immunoreactivity was occasionally detected in alpha-SMA-positive, sinusoidal lining cells, suggesting activated stellate cells as a potential source of GP73.

CONCLUSIONS

Hepatocyte GP73 levels are upregulated in acute hepatitis and during the progression of liver disease to cirrhosis. This expression pattern suggests the presence of two regulatory mechanisms, the first triggered during acute hepatocellular injury, the second during the progression of chronic liver disease.

An anti-apoptotic role for galectin-3 in diffuse large B-cell lymphomas

Increased resistance to apoptosis promotes lymphomagenesis with aberrant expression of cell survival proteins such as BCL-2 and c-MYC occurring in distinct lymphoma subtypes. Galectin-3 is an anti-apoptotic protein that protects T cells, macrophages, and breast carcinoma cells from death triggered by a variety of agents. We have found high levels of galectin-3 protein expression in a subset of B-cell neoplasms including diffuse large B-cell lymphoma (DLBCL), primary effusion lymphoma (PEL), and multiple myeloma (MM), in both cell lines and patient samples. However, we failed to detect galectin-3 in Burkitt lymphoma (BL), follicular lymphoma (FL), marginal zone lymphoma (MZL), MALT lymphoma or B-small lymphocytic lymphoma (B-SLL) cell lines or patient samples. To determine whether galectin-3 expression protects B cells from apoptosis, galectin-3-negative BL cells were transfected with a galectin-3 expressing plasmid, which resulted in markedly increased resistance to anti-Fas-induced cell death. In contrast, galectin-3-positive PEL cells transfected with an amino-terminal truncated galectin-3 vector showed increased sensitivity to anti-Fas induced apoptosis. During normal B-cell development, galectin-3 expression was lowest in germinal center and plasma B cells, from which DLBCL, PEL, and MM derive, and highest in long-lived naïve and memory B cells. This pattern of expression suggests that aberrantly increased galectin-3 levels in specific B-cell populations may yield a protective advantage during transformation and/or progression of certain B-cell neoplasms.

Galectin-3 expression in normal, hyperplastic, and neoplastic endometrial tissues

This study evaluated the expression of galectin-3 in 101 curettage specimens from normal, hyperplastic, and neoplastic endometrial tissues using immunohistochemistry. The histologic diagnoses were as follows: normal proliferative (n = 8) and secretory (n = 4) phase, simple hyperplasia (SH, n = 16), complex hyperplasia without atypia (CH, n = 11), atypical hyperplasia (AH, n = 13), endometrioid adenocarcinoma (EC, n = 35), serous papillary carcinoma (SPC, n = 10), and clear cell carcinoma (CC, n = 4). Immunostaining was scored with regard to the approximate percentage of positive tumor cells and relative staining intensity. The scores of immunostaining increased significantly from NE, SH, CH, and AH to the adenocarcinomas (ANOVA, p < 0.0001). Subsequently, three significantly different levels of galectin-3 expression were found (Newman-Keuls multiple comparison test). These consisted of (a) NE, SH, and CH, (b) AH and EC, and (c) SPC and CC. Galectin-3 expression increased with tumor grade (ANOVA, p = 0.0026). The scores of FIGO stages I to III did not differ significantly (ANOVA, p = 0.1687). Enhanced nuclear galectin-3 expression was noted in carcinomas, immunostaining of stromal cells decreased in the latter. This study shows that galectin-3 expression increases from normal and hyperplastic to atypical hyperplastic and cancerous states of endometrial tissues, and provides further evidence of a relationship between AH and EC.

Analysis of gene expression in carbon tetrachloride-treated rat livers using a novel bioarray technology

The present study successfully utilizes a new ADME Rat Expression Bioarray, containing 1040 metabolism- and toxicology-linked genes, to monitor gene expression from the livers of rats treated with carbon tetrachloride (CCl(4)). Histopathological analysis, hierarchical clustering methods, and gene expression profiling are compared between the control and CCl(4)-treated animals. A total of 44 transcripts were found to be altered in response to the hepatotoxin, 19 of which were upregulated and 25 were downregulated. Some of these gene expression changes were expected and concurred with previously published data while others were novel findings.

Malignant transformation of thyroid follicular cells by galectin-3

Galectin-3, a beta-galactoside binding lectin, is highly expressed in thyroid carcinomas of follicular cell origin, whereas neither benign thyroid adenomas nor normal thyroid tissues express galectin-3. We previously showed that antisense inhibition of galectin-3 expression markedly reduced the malignant phenotype of thyroid papillary carcinoma cells. In the present study we transfected galectin-3 cDNA into TAD-2 normal thyroid follicular cells. Stable transfectants expressing galectin-3 acquired the phenotype of serum-independent growth, clonogenicity in soft agar, as well as loss of contact inhibition. We also compared the gene expression profile of the galectin-3 transfectants to that of the vehicle control, which revealed that a series of genes were differentially expressed between the two. They include proliferating cell nuclear antigen, replication factor C, and retinoblastoma genes that participate in G1-S transition. These results indicate the transformation of thyroid follicular cells by galectin-3 and possible involvement of galectin-3 in cell cycle.

Stimulation of proliferation of rat hepatic stellate cells by galectin-1 and galectin-3 through different intracellular signaling pathways

We found that the expression of galectin-1 and galectin-3 was significantly up-regulated in hepatic stellate cells (HSCs) both in the course of their transdifferentiation into myofibroblasts, a process of "self-activation," and in the fibrosis of liver tissues. Recombinant galectin-1 and galectin-3 stimulated the proliferation of cultured HSCs via the MEK1/2-ERK1/2 signaling pathway. However, galectin-3 utilized protein kinases C and A to induce this process, whereas galectin-1 did not. We also found that thiodigalactoside, a potent inhibitor of beta-galactoside binding, attenuated the effects of both galectins. In addition, galectin-1, but not galectin-3, promoted the migration of HSCs. Thus, it appears that galectin-1 and galectin-3, generated by activated HSCs, could participate in beta-galactoside binding and induce different intracellular signaling pathways leading to the proliferation of HSCs.

Galectins and urological cancer

Galectins are a family of proteins defined by their affinity for beta-galactoside and by their conserved sequence. Each galectins exhibits a specific expression pattern in various tissues and their expression is regulated during development. Their expression is altered in many types of cancers and non-cancerous disorders. They interact with glycoproteins in both extracellular and intracellular milieu and regulate various biological phenomenon including cell growth, cell differentiation, cell adhesion, and apoptosis. A series of experimental and clinical evidences have been reported to support correlation between galectin expressions and neoplastic transformation. The recent findings show that expressions of galectins are elevated with neoplastic progression in certain malignancies, and therefore, galectins are expected to serve as reliable tumor markers. In this review, we describe the expression and role of galectins in urological cancers and their clinical applications for diagnostic and therapeutic use.

Binding free energy calculations of galectin-3-ligand interactions

Galectins show remarkable binding specificity towards beta-galactosides. A recently developed method for calculating binding free energies between a protein and its substrates has been used to evaluate the binding specificity of galectin-3. Five disaccharides and a tetrasaccharide were used as the substrates. The calculated binding free energies agree quite well with the experimental data and the ranking of binding affinities is well reproduced. For all the six protein-ligand complexes it was observed that electrostatic interactions oppose binding whereas the non-polar contributions drive complex formation. The observed binding specificity of galectin-3 for galactosides rather than glucosides is discussed in light of our results.

'Spindle cell oncocytoma' of the adenohypophysis: a tumor of folliculostellate cells?

We describe five primary tumors of the adenohypophysis featuring mitochondrion-rich spindle cells. The patient ages ranged from 53 to 71 years (mean 61.6 years); two were female. All presented with panhypopituitarism. Two also had visual field defect. On neuroimaging all tumors showed suprasellar extension and were indistinguishable from pituitary adenoma. None showed imaging or operative evidence of dural involvement. All were gross totally removed: four by transsphenoidal surgery and one by frontal craniotomy. Follow-up ranged from 2 to 68 months (mean 35.4 months). No recurrences were noted. The clinical workup was noncontributory in all but two patients: one (case no. 4) with an oncocytic thyroid adenoma and another (case no. 5) with squamous carcinoma of both the uterine cervix and of vocal cord. Histologically, the five tumors were composed mainly of fascicles of spindle cells with eosinophilic, granular cytoplasm. Mitoses were rare and necrosis was absent. Neoplastic cells were immunoreactive for vimentin, epithelial membrane antigen, S-100 protein, and galectin-3. Stains for pituitary hormones, synaptophysin, chromogranin, glial fibrillary acidic protein, cytokeratin CAM5.2, smooth muscle actin, CD34, and CD68 were negative. No thyroglobulin immunoreactivity was noted in the tumor of case no. 4. Ultrastructurally, the neoplastic cells contained numerous mitochondria with lamellar cristae. The neoplastic cells were linked by intermediate junctions and desmosomes. No secretory granules were noted. The histologic, immunohistochemical, and fine structural features of these tumors were unlike those of pituitary adenoma or any other primary sellar tumor. A derivation from adenohypophyseal folliculostellate cells is suggested.

Identification of autoantibodies associated with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of antinuclear antibodies. We performed serological analysis of cDNA expression library (SEREX) to identify autoantibodies associated with SLE. The screening of three different cDNA expression libraries with pooled sera of patients with SLE yielded 11 independent clones that reacted with pooled sera of patients with SLE. In this screening, autoantibodies to poly(ADP-ribose) polymerase (PARP), U1snRNP, and galectin-3 were prevalent in the sera of patients with SLE (26/68, 25/68, 12/63, respectively). The frequency of autoantibody to PARP was significantly higher in SLE than that of healthy donors (0/76) (38.2% vs 0%, p<0.00001). The autoantibody to PARP was infrequently detected in the serum of patients with RA (1/50). However, autoantibody to PARP was not found in the sera of patients with other rheumatic diseases including Sjogren's syndrome (0/19), systemic sclerosis (0/18), and polymyositis/myositis (0/37). The frequency of autoantibody to human galectin-3 (12/63) was significantly higher in SLE than that of healthy donors (0/56) (19% vs 0%, p=0.0006). Autoantibody to galectin-3 was not found in the sera of patients with rheumatoid arthritis (0/50), Sjogren's syndrome (0/18), and systemic sclerosis (0/19). Interestingly, autoantibody to galectin-3 was also prevalent in the sera of patients with polymyositis/dermatomyositis (16/37, 43.2%). Further functional characterization of these autoantibodies would be necessary to determine their value as diagnostic markers or to define clinical subsets of patients with SLE. Statistical analysis revealed that the presence of autoantibody to PARP was inversely related with pleurisy, and the presence of autoantibody to galectin-3 related with renal disease.

Effects of galectin-3 expression on growth and tumorigenicity of the prostate cancer cell line LNCaP

BACKGROUND

Galectin-3 is a beta-galactoside-binding vertebrate lectin. In human prostate cancer, galectin-3 expression has been shown to decrease with progression of disease. In the present study, we further investigated the role of galectin-3 in this malignancy by examining the phenotype of galectin-3-transfected prostate cancer cells.

METHODS

Stably transfected galectin-3-expressing cell lines were developed from the prostate cancer cell line LNCaP, which does not constitutively express this molecule. Transfected cells lines were analyzed for alterations in morphology and growth rates, and for ability to form tumors in nude mice.

RESULTS

Morphologically, when compared to the parental LNCaP cells, the galectin-3 transfectants had broader, flatter cell bodies, shorter and less finely branched dendritic processes, and large nuclei with pronounced and often multiple nucleoli. The galectin-3 lines were found to proliferate at a slower rate in vitro than either the vector control-transfected lines or parental LNCaP. When injected subcutaneously in nude mice, four of six galectin-3 lines formed tumors at a slower rate than control lines. Twenty-four tumors that formed from the transfected cell lines were examined by immunohistochemistry for galectin-3 expression. Only one tumor was found to express galectin-3, suggesting that the transfected cells which formed tumors were those which successfully down-regulated galectin-3 expression.

CONCLUSIONS

In contrast to an apparent stimulatory role in some tumor types, galectin-3 is an inhibitory molecule for prostate cancer.

Influences of the lysosomal associated membrane proteins (Lamp-1, Lamp-2) and Mac-2 binding protein (Mac-2-BP) on the prognosis of pancreatic carcinoma

BACKGROUND

Lamps and Mac-2-BP are ligands of galectin-3, and they were suggested to influence tumor proliferation and metastasis formation. The authors studied the expression of Lamp-1, Lamp-2, and Mac-2-BP in pancreatic carcinoma and evaluated their influence on patient prognosis.

METHODS

Northern blot analysis, in situ hybridization, and immunohistochemistry were performed in 12 normal and 28 pancreatic carcinoma tissue samples and in pancreatic carcinoma cell lines. The molecular findings in the tumor samples were correlated with the prognosis and histopathologic tumor characteristics. In addition, in Lamp-1 transfected CAPAN-1 pancreatic carcinoma cells, cell proliferation was analyzed.

RESULTS

Lamp-1, Lamp-2, and Mac-2-BP were overexpressed in 61% (1.6-fold increase, not significant), 71% (3.0-fold increase, P < 0.01), and 93% (5.6-fold increase, P < 0.01) of the pancreatic carcinoma samples. Lamp-1 and Lamp-2 immunoreactivity was present at the luminal side of the ductal carcinoma cells whereas Mac-2-BP immunoreactivity was diffusely spread over the whole cytoplasm and the nucleolus of ductal carcinoma cells. Correlation of the molecular data with clinical patient parameters revealed that patients whose tumors exhibited high Lamp-1 mRNA expression lived significantly longer (median, 17 months) after tumor resection than patients whose tumors exhibited low to moderate Lamp-1 mRNA levels (median, 8 months; P < 0.02). No relation between Lamp-2 and Mac-2-BP mRNA expression and any of the histopathologic parameters was found. Lamp-1 transfected CAPAN-1 cells showed decreased cell growth compared with the nontransfected cells.

CONCLUSIONS

Lamp-1 might influence local tumor progression rather than the formation of tumor metastasis in pancreatic carcinoma, whereas Mac-2-BP and Lamp-2 seem to have little influence on these parameters in pancreatic carcinoma.

Expression of galectins in cancer: A critical review

A large body of literature has examined and described galectin expression in cancer. Discrepancies have been observed in the reported data, which hampered clear understanding of the expression profiles. This relates to the use of different types of methods that evaluate either global or specific gene expression in heterogeneous cancer tissue samples, type of antibodies used in immunohistochemistry and procedures of comparison of gene expression. In this manuscript, we review the main data concerning expression of galectins in human cancer. Only galectin-1 and galectin-3, the most abundant and examined galectins, will be examined here.

Identification of differentially expressed genes in hepatocellular carcinoma and metastatic liver tumors by oligonucleotide expression profiling

BACKGROUND

The characterization of differentially expressed genes between cancerous and normal tissues is an important step in the understanding of tumorigenesis. Global gene expression profiling with microarrays has now offered a powerful tool to measure the changes of thousands of genes in any carcinoma tissues in an effort to identify these key disease-related genes. To compare the gene expression of a primary liver carcinoma, metastatic carcinoma to the liver, and normal liver, the authors analyzed tissue from six primary hepatocellular carcinomas (HCCs), five colorectal adenocarcinoma metastases to the liver, and eight normal livers.

METHODS

Samples were processed from total RNA to fragmented cRNA and hybridized onto Affymetrix GeneChip(R) expression arrays. Analyses were performed to determine the consensus pattern of gene expression for primary liver carcinoma, metastatic liver carcinoma, and normal liver tissue and their changes in expression level.

RESULTS

In hepatocellular carcinoma, 842 genes were overexpressed, and 393 genes were underexpressed in comparison with genes of normal liver tissue. Of note, 7 of the 20 most increased identified known genes previously have been associated with liver carcinoma or other types of cancers. The 13 additional identified genes until now have not previously shown strong association with cancers. Furthermore, the authors identified 42 genes and 24 expressed sequence tags that are expressed at a significant level in both HCC and metastastic tumors, presenting a list of marker genes indicative of cancerous liver tissue.

CONCLUSIONS

In this study, genes that can be involved in the production of and maintenance of hepatic carcinomas were identified. These data offer new insight into genes that are potentially important in the pathogenesis of liver carcinoma, as well as additional targets for new strategies for cancer therapy and treatment.

Cell cycle regulation by galectin-12, a new member of the galectin superfamily

Galectins are a family of beta-galactoside-binding animal lectins with conserved carbohydrate recognition domains (CRDs). Here we report the identification and characterization of a new galectin, galectin-12, which contains two domains that are homologous to the galectin CRD. The N-terminal domain contains all of the sequence elements predicted to form the two beta-sheets found in other galectins, as well as conserved carbohydrate-interacting residues. The C-terminal domain shows considerable divergence from the consensus sequence, and many of these conserved residues are not present. Nevertheless, the protein has lactose binding activity, most likely due to the contribution of the N-terminal domain. The mRNA for galectin-12 contains features coding for proteins with growth-regulatory functions. These include start codons in a context that are suboptimal for translation initiation and AU-rich motifs in the 3'-untranslated region, which are known to confer instability to mRNA. Galectin-12 mRNA is sparingly expressed or undetectable in many tissues and cell lines tested, but it is up-regulated in cells synchronized at the G(1) phase or the G(1)/S boundary of the cell cycle. Ectopic expression of galectin-12 in cancer cells causes cell cycle arrest at the G(1) phase and cell growth suppression. We conclude that galectin-12 is a novel regulator of cellular homeostasis.

An antibody to p16INK4A recognizes a modified form of galectin-3

Galectin-3 is a carbohydrate binding protein involved in multiple processes including cell-cycle regulation and apoptosis. The ability of galectin-3 to protect cells from apoptosis is dependent upon a region of the protein known as a BH-1 domain for its homology to the anti-apoptotic protein Bcl-2. Here, we show that a monoclonal antibody (MAb) to the human tumor suppressor protein p16INK4A recognizes a post-translationally modified form of human galectin-3. The modified form is detectable in only a subset of cell types expressing galectin-3, indicating that the modification is cell-type-specific. Although there is little amino acid sequence homology between p16INK4a and galectin-3, we show by epitope mapping that the modification directly affects the structure of galectin-3's BH-1 domain. Elucidation of the nature of this modification might provide further insight into galectin-3 function.

Comparative analysis of galectins in primary tumors and tumor metastasis in human pancreatic cancer

Galectins are galactoside-binding proteins that exhibit an important function in tumor progression by promoting cancer cell invasion and metastasis formation. Using Northern blotting and Western blotting analysis, in situ hybridization (ISH), and immunohistochemistry (IHC), we studied galectin-1 and galectin-3 in tissue samples of 33 primary pancreatic cancers and in tumor metastases in comparison to 28 normal pancreases. Furthermore, the molecular findings were correlated with the clinical and histopathological parameters of the patients. Northern blotting and Western blotting analysis showed significantly higher galectin-1 and galectin-3 mRNA and protein levels in pancreatic cancer samples than in normal controls. For galectin-1, no ISH signals and immunoreactivity were observed in acinar or ductal cells in the normal pancreas and in pancreatic cancer cells, whereas fibroblasts and extracellular matrix cells around the cancer mass exhibited strong mRNA signals and immunoreactivity. Galectin-3 mRNA signals and immunoreactivity were strongly present in most pancreatic cancer cells, whereas in the normal controls only faint ISH and IHC signals were seen in some ductal cells. Metastatic pancreatic cancer cells exhibited moderate to strong galectin-3 immunoreactivity but were negative for galectin-1. No relationship between the galectin-1 and galectin-3 mRNA levels and the tumor stage or between the IHC staining score and the tumor stage was found. However, galectin-1 mRNA levels and the IHC staining score were significantly higher in poorly differentiated tumors compared with well/moderately differentiated tumors, whereas for galectin 3 no differences were found. The expression pattern of galectin-1 and galectin-3 in pancreatic cancer tissues indicates that galectin-1 plays a role in the desmoplastic reaction that occurrs around pancreatic cancer cells, whereas galectin-3 appears to be involved in cancer cell proliferation. High levels of galectin-3 in metastatic cancer cells suggest an impact on metastasis formation.