Galectin-3 expression in various thyroid neoplasms and its possible role in metastasis formation

Human galectin-3 immunoexpression in thyroid follicular adenomas with cell atypia

Human galectin-3 (hgal-3) is a beta-galactoside binding protein involved in a number of physiological and pathological processes. Increasing hgal-3 immunoexpression has been reported in several human tumors, including thyroid carcinomas, but not in benign thyroid lesions. We analyzed the immunolocalization of hgal-3 in cell compartments of benign and malignant thyroid lesions. Hgal-3 immunoperoxidase reaction was carried out on 133 thyroid tissue samples obtained from 113 patients; 20 of these were normal (NT), 85 were benign thyroid lesions [20 colloid nodules (CN), 21 nodular hyperplasias (NH), 7 focal lymphocytic thyroiditis (FLT), 15 Hashimoto's thyroiditis (HT), 22 follicular adenomas (FA)], 25 differentiated carcinomas [15 papillary carcinomas (PC), 6 follicular carcinomas (FC) and 4 Hürthle cell carcinomas (HC)] and 3 anaplastic carcinomas (AC). Among the malignant thyroid lesions, hgal-3 was detected in 12/15 (80%) PC, 3/4 (75%) HC and in 4/6 (66.6%) FC, but in none of the 3 AC. Conversely, hgal-3 immunoexpression was absent in NT and in all benign thyroid lesions, but 1/15 HT and 10/22 (45.4%) FA. In the latter, hgal-3 was mostly expressed in microfollicular areas and in five of the six atypical FA. Hgal-3 cytoplasmic-perinuclear immunolocalization was observed in the majority of thyroid carcinomas and in more than half of the FA, theoretically suggesting an involvement of this protein in thyroid tumorigenesis throughout an antiapoptotic activity. Moreover, hgal-3 expression in FA might anticipate the likelihood of evolution of these benign lesions towards malignancy.

Galectin-3, fibronectin-1, CITED-1, HBME1 and cytokeratin-19 immunohistochemistry is useful for the differential diagnosis of thyroid tumors

The diagnosis of thyroid tumors is critical for clinical management; however, tumors with follicular architecture often present problems. We evaluated the diagnostic use of the protein expression of four genes that were found to be upregulated in papillary thyroid carcinoma compared to normal thyroid (LGALS3, FN1, CITED1 and KRT19), and of the mesothelial cell surface protein recognized by monoclonal antibody HBME1 in thyroid tumors. Tissues from 85 carcinomas (67 papillary, six follicular, eight Hürthle cell and four anaplastic) and 21 adenomas were evaluated by immunohistochemistry for the expression of these gene protein products, for example, galectin-3 (GAL3), fibronectin-1 (FN1), CITED1, cytokeratin-19 (CK19) and HBME1. Non-neoplastic thyroids (29 adenomatous and 14 thyrotoxic hyperplasia, and 59 normal) were also studied. The expression of all five proteins was significantly associated with malignancy, and highly specific (> or = 90%) for carcinoma compared to adenoma. GAL3, FN1 and/or HBME1 expression was seen in 100% of carcinomas (85/85) and in 24% of adenomas (5/21). Coexpression of multiple proteins was seen in 95% of carcinomas and only 5% of adenomas (P<0.0001). Coexpression of FN1 and GAL3 (FN1+ GAL3+, 70/85) or FN1 and HBME1 (FN1+ HBME1+, 53/85) was restricted to carcinomas, while their concurrent absence (FN1- GAL3- or FN1- HBME1-, 18/21 adenoma) was highly specific (96%) for benign lesions. Among non-neoplastic thyroids, adenomatous hyperplasia frequently expressed GAL3 (n=16), CK19 (n=9) and CITED1 (n=7), but the expression was predominantly focal in contrast to the diffuse expression in carcinomas. An immunohistochemical panel consisting of GAL3, FN1 and HBME1 may be useful in the diagnosis of follicular cell-derived thyroid tumors.

Differential expression of galectin-3 in papillary projections of malignant and non-malignant hyperplastic thyroid lesions

Galectin-3 is a a beta-galactoside binding protein recently proposed to be a promising presurgical molecular marker for distinguishing benign from malignant thyroid neoplasms. We analyzed galectin-3 expression immunohistochemically in papillary areas of hyperplastic lesions of benign thyroid tissue in comparison with malignant papillary projections of papillary thyroid carcinoma (PTC). A monoclonal antibody to galectin-3 and ABC immunohistochemical technique were used to evaluate galectin-3 expression in 26 cases of benign papillary hyperplasia (8 cases of hyperplastic adenoma, 8 cases of hyperplastic colloid goiter, 10 cases of Graves disease) in comparison with 25 cases of PTC. Immunohistochemical results showed no reactivity for galectin-3 in papillary areas of benign hyperplastic lesions. Strong cytoplasmic galectin-3 immunoreactivity was found in all 25 cases of PTC. These results show that galectin-3 expression is a feature of malignant papillary projections but not of benign papillary hyperplasia. Thus, the immunohistochemical evaluation of galectin-3 might contribute to differential diagnosis between malignant and benign thyroid lesions with papillary projections.

Differential expression of S100C in thyroid lesions

Identification of new potential markers that may help in the diagnosis of benign and malignant thyroid lesions is needed. By comparative 2-dimensional gel electrophoresis of microdissected cells from tumors and normal thyroid tissue, we identified a new protein, S100C, which is highly expressed in papillary carcinomas. In order to validate this finding, we investigated the immunohistochemical expression and the potential role in diagnosis of these markers in 94 specimens representing the spectrum of malignant and benign thyroid lesions. Normal thyroid tissue was evaluated in 57 specimens. Galectin-3, a marker reported as specific for malignant lesions, was also evaluated in the same lesions. S100C protein was expressed in the nuclei of normal tissue, hyperplastic nodules, and follicular adenomas and carcinomas. Papillary carcinomas showed a strong, but cytoplasmic, pattern of staining. Galectin-3 immunostaining was strongly positive in papillary carcinomas, and negative in benign lesions, confirming its value in differential diagnosis. These findings suggest that immunohistochemical staining of S100C could be helpful in the pathological study of thyroid lesions, especially in cases in which follicular variants of papillary carcinoma and follicular carcinoma are considered in the differential diagnosis.

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.

Galectin-3 expression in non-small cell lung carcinoma

Galectins are a family of animal beta-galactoside-binding lectins involved in malignant transformation and progression. The present study evaluated the immunohistochemical expression of galectin-3 in a consecutive series of 81 radically resected non-small cell lung carcinomas (NSCLCs). The main pattern of galectin-3 expression was cytoplasmic (median percentage of cells with cytoplasmic positivity: 80.0%). The median percentage of tumor cells with nuclear and cytoplasmic co-expression of galectin-3 was 3.5%. No cases with exclusive nuclear immunostaining were observed. Functional interaction between galectin-3 and the thyroid transcription factor-1 (TTF-1) was previously demonstrated by cotransfection experiments. In the present study, concomitant expression of nuclear galectin-3 and TTF-1 was independently associated with a worse clinical outcome (HR 2.0; P = 0.01).

Practical markers used in the diagnosis of endocrine tumors

Endocrine tumors constitute a large group of neoplasms that are widely dispersed throughout the body. They are made up mostly of neuroendocrine tumors (NE), which are characterized by the presence of secretory granules and production of peptide hormones, and non-NE tumors such as those derived from thyroid follicular cells and adrenal cortical cells. Immunohistochemical markers have been used to characterize these lesions and distinguish them from other histologically similar tumors. Chromogranin and synaptophysin are the most widely used broad-spectrum neuroendocrine tumor markers. The use of antibodies to transcription factors, keratins, and specific peptides is quite valuable in the diagnosis of endocrine tumors. This article reviews the common markers used to characterize endocrine tumors and to recognize tumors involved in the differential diagnosis of specific lesions.

[Cytologic evaluation of solitary thyroid nodules]

Fine-needle aspiration is a low-cost diagnostic tool with principal value in determining which patients with thyroid nodules should undergo surgery. Team work and close cooperation among endocrinologists, surgeons, and pathologists are essential for success. Cytologic criteria for diagnosis of the most frequent conditions (benign cystic lesions), Hashimoto thyroiditis and malignancies found in thyroid aspirates have been provided. The unsolved problem of the so-called "follicular" or oxyphilic lesion or neoplasia will be investigated by immunocytochemistry.

Macrofollicular Variant of Papillary Carcinoma of the Thyroid

Context.—The macrofollicular variant of papillary carcinoma of the thyroid is a rare entity described by J. Albores-Saavedra and colleagues in 1991. It is characterized histologically by a predominance of macrofollicles and clinically by a low incidence of metastasis. This entity may represent a source of diagnostic error, since it can be easily misinterpreted as a macrofollicular adenoma or nodular goiter.

Design.—In this study, we describe 3 cases of papillary carcinoma of the thyroid with a macrofollicular growth pattern and review the literature.

Results.—The fine-needle aspiration biopsies in 2 cases showed large cells with optically clear nuclei and nuclear grooves, suggestive of papillary carcinoma of the thyroid. In one case, the cytology showed no signs of malignancy. In all cases, the tumors showed a combination of the conventional follicular variant of papillary carcinoma of the thyroid and macrofollicles (diameter, &gt;250 μm) occupying more than 50% of the cross-sectional area. Cytologic features were large, cuboidal cells with optically clear, ground-glass nuclei with smooth outlines, a fine chromatin pattern, nuclear grooves, and pseudoinclusions. The colloid was dense and more eosinophilic than in adjacent normal follicles. In 2 cases, there was capsular or blood vessel infiltration, and one tumor had metastasized to a cervical lymph node. One tumor recurred 1 year later as an anaplastic carcinoma. Immunohistochemical staining showed a positivity of the tumor cells for cytokeratins 7, 17, and 19, thyroid transcription factor-1, and galectin-3 and a negativity for cytokeratin 20 and p53.

Conclusions.—Although it has been suggested that this tumor is a highly differentiated variant with a favorable prognosis, our study shows that its biologic behavior is not conclusive because metastases and recurrences with dedifferentiation may occur.

Galectin-3 and oncofetal-fibronectin expression in thyroid neoplasia as assessed by reverse transcription-polymerase chain reaction and immunochemistry in cytologic and pathologic specimens

Oncofetal fibronectin (onfFN) and galectin-3 (Gale-3) have been proposed as possible tools for the preoperative diagnosis of thyroid carcinomas, based on the finding that the expression of both onfFN and Gale-3 are significantly increased in papillary and anaplastic carcinomas, compared to normal thyroid tissues and follicular adenomas. In this study we analyzed the expression of these markers by immunochemical and molecular analysis of benign and malignant thyroid tumors. Sixty-five thyroid nodules, consisting of 20 follicular adenomas (FAs) and 45 papillary thyroid carcinomas (PTCs) at final histology were examined. At the molecular level, among the 45 PTCs, 44 (97.8%) showed a variable level of onfFN mRNA, while 8 of the 20 (40%) adenomas expressed the same marker. Similar results have been found analyzing Gale-3 expression: 97.8% of PTC and 55% of FAs were positive for this marker. Immunohistochemistry (IHC) for Gale-3 was positive in 42 of 45 (93.3%) PTC tissues. Staining was invariably confined to the cytoplasm, with a homogeneous distribution in the large majority of the neoplastic cells. The 3 negative cases (6.7%) were represented by 2 classic variants of PTC and 1 follicular variant of PTC. Eighteen of the 20 (90.0%) adenomas stained negative for Gale-3. A significant association was found between positive staining and malignant phenotype (p < 0.0001). Gale-3 protein expression was also performed on samples obtained by ex vivo fine-needle aspiration (FNA) in 35 PTCs by immunocytochemistry (ICC). Immunoreactivity was present in 32 (91.0%) and negative in 3 (8.8%) cases. With the exception of 1 case (negative by ICC and positive by IHC), ICC and IHC were fully concordant. In conclusion, our results indicate that a search for Gale-3 protein overexpression by IIC or ICC, but not by reverse transcription-polymerase chain reaction (RT-PCR), may yield an additional marker of malignant potential of thyroid nodular lesions, and may be a useful adjunct to the currently available diagnostic tools for the preoperative diagnosis of malignant thyroid tumors.

Differences in glycosylation of intracellular proteins between benign and malignant thyroid neoplasms

Differences in glycosylation of nuclear and cytosolic proteins isolated from benign and malignant human thyroid neoplasms were analyzed by lectin blotting and enzyme linked lectino-solid-phase assay using Erythrina cristagalli and Ricinus communis agglutinins. The results reported in this study have not shown any significant differences in lectin binding by nuclear proteins of benign and malignant tumors, however, quantitative and qualitative differences were observed in the patterns of cytosolic glycoproteins. In the majority of carcinomas samples lectin binding to cytosolic proteins was definitely weaker in comparison with adenomas and non-neoplastic specimens, which suggested alterations in glycosylation of cytosolic proteins in malignant tumors.

Expression of galectin-1 and galectin-3 in human fetal thyroid gland

High levels of expression of galectin-1 and galectin-3, the beta-galactoside-binding proteins, have been recently described in malignant thyroid tumors but not in adenomas nor in normal thyroid tissue. However, there are no data about the expression of these galectins during fetal thyroid development. In this study we analyzed immunohistochemically the presence of galectin-1 and galectin-3 in human fetal thyroid glands (16-37 weeks of gestation). Weak to moderate cytoplasmic staining for galectin-1 was observed in follicular cells of all fetal thyroids. Galectin-3 could not be detected in thyroid follicular cells of any fetal thyroid investigated. Both galectins were detected in stromal tissue, but staining for galectin-1 was more intense. The absence of galectin-3 in thyroid cells during fetal development suggests that galectin-3 is expressed de novo during malignant transformation of thyroid epithelium, and that galectin-1 could be considered an oncofetal antigen. The results obtained indicated potential roles for galectin-1 and galectin-3 during the investigated period of human fetal thyroid gland development. Both galectins might participate in developmental processes regarding stromal fetal thyroid tissue organization, whereas galectin-1 might have a function in thyroid epithelium maturation.

Distinction between papillary thyroid hyperplasia and papillary thyroid carcinoma by immunohistochemical staining for cytokeratin 19, galectin-3, and HBME-1

The histopathology of papillary thyroid hyperplasia and papillary thyroid carcinoma is similar enough to cause a diagnostic dilemma in a few cases. Both lesions may have papillary fronds with fibrovascular cores, nuclear crowding, and nuclear anisocytosis. Formalin- fixed paraffin-embedded tissues from 30 randomly selected patients with papillary thyroid hyperplasia and an equal number from patients with papillary thyroid carcinoma were analyzed for expression of cytokeratin 19 (CK19), galectin-3, and HBME-1. Cases of papillary thyroid carcinoma had moderate to strong CK19, galectin-3, and HBME-1 reactivity although both CK19 and galectin-3 showed positive staining in a significant number of nonneoplastic thyroid cases. HBME-1 was uncommon in the nonneoplastic cases. These results indicate that HBME-1 may be useful in helping to distinguish papillary thyroid carcinoma from hyperplasia in diagnostically difficult cases.

Galectin-3 expression in medullary thyroid carcinoma in relation to tumor progression

BACKGROUND: Galectin-3, a lectin with specificity for beta galactosides, is believed to be implicated in multiple biological processes through interactions with complementary glycoconjugates. Alterations in galectin-3 expression are observed in a variety of human tumors. In thyroid, this lectin has been found to be highly expressed in malignancies of epithelial origin. We analyzed galectin-3 expression in medullary thyroid carcinoma (MTC). MATERIALS AND METHODS: An immunohistochemical study using monoclonal antibody was performed on paraffin sections of twenty cases of sporadic MTC comprising ten cases without and ten cases with lymph node metastases at the time of surgery. RESULTS: Positive cytoplasmic staining for galectin-3 was found in 16/20 cases, but varied in intensity and distribution from weak/focal (7/16) to moderate (7/16) or strong (2/16). Advanced stage of MTC (with lymph node metastases at the time of surgery) showed moderate to strong galectin-3 expression more frequently (8/10) than cases without lymph node metastases (1/10). CONCLUSION: These findings suggest that galectin-3 expression is associated with the advanced stage of disease and that this lection might play a role in the pathobiology of MTC.

Differential expression of galectin-3 in medullary thyroid carcinoma and C-cell hyperplasia

OBJECTIVE AND DESIGN

Galectin-3 is a beta-galactoside-binding protein that plays a role in cell adhesion and tumour progression. It was shown recently to diagnose malignant follicular thyroid lesions accurately. The reliability of this marker in the differential diagnosis between medullary thyroid carcinoma and C-cell hyperplasia was studied by immunohistochemistry.

PATIENTS

Tissue specimens were obtained from 34 patients belonging to families with medullary thyroid carcinoma who underwent prophylactic thyroidectomy for RET gene mutation and/or abnormally increased plasma calcitonin levels.

RESULTS

Galectin-3 was expressed in 23 of 25 cases of medullary thyroid carcinoma and in none of the nine cases of C-cell hyperplasia only, giving a sensitivity of 92% and a specificity of 100% for the diagnosis of carcinoma. A significant association was found between higher galectin-3 expression and occurrence of lymph node metastases (P < 0.05).

CONCLUSIONS

Galectin-3 is a reliable diagnostic marker of medullary thyroid carcinoma, and its use may provide relevant information for prognosis and therapy.

Lack of expression of galectin-3 is associated with a poor outcome in node-negative patients with laryngeal squamous-cell carcinoma

PURPOSE

Galectin-3 is a pleiotropic carbohydrate-binding protein participating in a variety of normal and pathologic processes, including cancer progression. This study was aimed at evaluating the prognostic value of galectin-3 expression in node-negative laryngeal squamous-cell carcinoma (SCC).

PATIENTS AND METHODS

Galectin-3 expression was analyzed by immunohistochemistry using M3/38 monoclonal antibody, in a single-institution series of 73 node-negative laryngeal SCC patients (median follow-up, 52 months; range, 2 to 90 months).

RESULTS

Forty-two (57.5%) of 73 patients expressed galectin-3. Galectin-3 expression was positively associated with tumor keratinization and histologic grade. A significant correlation was found between galectin-3 tumor positivity and longer relapse-free and overall survival. In univariate analysis, high-grade (grade 3 or 4) tumors, nonkeratinizing tumors, and galectin-3-negative tumors showed a significantly increased risk of relapse and death. In multivariate analysis, only galectin-3 expression retained an independent prognostic significance for both relapse-free and overall survival.

CONCLUSION

We conclude that the absence of galectin-3 expression is an independent negative prognostic marker in laryngeal SCC patients. Thus, histochemical detection of galectin-3 in these tumors could be useful for the selection of node-negative patients with potentially unfavorable outcomes, to establish adjuvant therapy protocols.

Cytokeratin 19 and galectin-3 immunohistochemistry in the differential diagnosis of solitary thyroid nodules

AIMS

The immunohistochemical expression of cytokeratin 19 (CK 19) and galectin-3 was evaluated in 69 thyroid lesions to assess their potential as markers in the diagnosis and classification of thyroid malignancy. The following were studied: 26 cases of papillary carcinoma, 12 of follicular carcinoma, 20 follicular adenomas, two medullary carcinomas, one anaplastic carcinoma and eight multinodular goitres.

METHODS AND RESULTS

Formalin-fixed paraffin-embedded thyroid tissues were stained immunohistochemically for both CK 19 and galectin-3. CK 19 expression was found in all 26 papillary carcinomas, five of 12 follicular carcinomas, two of two medullary carcinomas and one case of anaplastic carcinoma. Only five of 20 follicular adenomas were positive for CK 19, and this was in a focal distribution. Two of eight multinodular goitres stained focally positive. Galectin-3 expression was found in 22 of 26 papillary carcinomas, 12 of 12 follicular carcinomas and one of two cases of medullary carcinoma. Only two of 20 follicular adenomas were positive. Three of eight multinodular goitres showed focal galectin-3 expression.

CONCLUSIONS

Our findings suggest that the immunohistochemical localization of CK 19 and of galectin-3 is a useful adjunct to the histopathological diagnosis of a solitary thyroid lesion. The expression of CK 19 favours a diagnosis of papillary carcinoma in all its variant patterns. Galectin-3 may serve as a marker for the recognition of follicular carcinoma, particularly the minimally invasive form.

Possible role of galectin-9 in cell aggregation and apoptosis of human melanoma cell lines and its clinical significance

Galectin-9 expression was examined in 6 human melanoma cell lines. Among them, MM-BP proliferated with colony formation, but MM-RU failed. RT-PCR analysis revealed evident expression of galectin-9 mRNA in MM-BP but not in MM-RU. MM-BP expressed galectin-9 protein both on the surface and in the cytoplasm, whereas MM-RU expressed it only weakly in the cytoplasm. Exogenous galectin-9 induced in vitro both cell aggregation and apoptosis of MM-RU proliferating without colony formation. Association of galectin-9 expression in melanoma cells with prognosis of the patients bearing melanocytic tumors was further examined. Galectin-9 protein was strongly and homogeneously expressed in melanocytic nevi, but down-regulated in melanoma cells especially in metastatic lesions. High galectin-9 expression was inversely correlated with the progression of this disease, suggesting that high galectin-9 expression in primary melanoma lesions links to a better prognosis.

Immunohistochemical expression of galectin-3 in benign and malignant thyroid lesions

CONTEXT

The expression of galectin-3, a human lectin, has been shown to be highly associated with malignant behavior of thyroid lesions.

DESIGN

We studied the immunohistochemical expression pattern of galectin-3 in a variety of follicular-derived thyroid lesions (13 benign and 62 malignant), including Hürthle cell and follicular carcinoma, papillary carcinomas and variants, and anaplastic and poorly differentiated carcinomas.

RESULTS

Immunoreactivity was strongest in papillary thyroid carcinomas, whereas staining was less intense in Hürthle cell and anaplastic carcinomas, and even weaker in the follicular variant of papillary thyroid carcinoma. Staining was absent or weak in the 3 follicular thyroid carcinomas and was negative in both insular carcinomas. In several tumors, staining was stronger at the advancing invasive edge of the lesion than in the central portion of the tumor. Galectin-3 was also expressed focally and weakly in reactive follicular epithelium and entrapped follicles in chronic lymphocytic thyroiditis. A variety of thyroid lesions showed prominent endogenous, biotin-like activity, which could cause flaws in interpretation if a biotin-detection system were used.

CONCLUSION

We conclude that galectin-3 immunostaining, when used in biotin-free detection systems, may be useful as an adjunct to distinguish benign from malignant thyroid lesions.

The constitutive expression of galectin-3 is downregulated in the intestinal epithelia of Crohn's disease patients, and tumour necrosis factor alpha decreases the level of galectin-3-specific mRNA in HCT-8 cells

OBJECTIVE

Galectin-3, a lectin with specificity for beta galactoside, is expressed by a variety of cells, including intestinal epithelial cells. Among other functions, galectin-3 mediates cell adhesion and is involved in inflammatory processes. In this study, we assessed the expression of galectin-3 in intestinal epithelial cells from Crohn's disease patients (n = 10), ileum adjacent to resected colon carcinoma (n = 9), unspecific bowel inflammation (n = 1), diverticulosis (n = 1), ulcerative colitis (n = 3) and healthy jejunum used for interposition in larynx carcinoma (n = 1). The role of cytokines on galectin-3 expression was a further aim of our study.

METHODS

The galectin-3 distribution in intestinal epithelia was analysed by immunohistochemistry, immunoblotting, immunofluorescence and reverse transcriptase polymerase chain reaction (RT-PCR). Human intestinal epithelial cell line (HCT-8) and primary cultured intestinal epithelial cells were treated with cytokines, and the effects on galectin-3 expression were determined by RT-PCR.

RESULTS

Galectin-3 showed a homogeneous distribution in epithelia from control patients. In contrast, in epithelial cells from Crohn's disease lesions, galectin-3 staining was strongly spotted and heterogeneous. In inflamed and reorganized tissue, galectin-3 expression was markedly reduced, and was associated with disintegration of epithelia. Primary cultured epithelial cells as well as HCT-8 cells expressed galectin-3 protein and mRNA. Incubation of HCT-8 cells with tumour necrosis factor alpha (TNF-alpha), but not with other cytokines, substantially reduced galectin-3 expression as shown by semiquantitative RT-PCR.

CONCLUSIONS

Downregulation of galectin-3 in the intestinal epithelium of Crohn's disease patients may be a consequence of enhanced TNF-alpha production by inflammatory cells, thereby contributing to the pathophysiology of the disease.

Galectin-3, a marker of well-differentiated thyroid carcinoma, is expressed in thyroid nodules with cytological atypia

AIMS

The distribution of galectin-3, a widely recognized marker of well-differentiated thyroid carcinoma, was investigated in 95 thyroid lesions including nodules with foci of cytoarchitectural atypia.

METHODS AND RESULTS

Twenty-eight papillary carcinomas, five follicular carcinomas, one Hurthle cell carcinoma, three poorly differentiated carcinomas, one anaplastic carcinoma, 25 nodular hyperplasias and 27 follicular adenomas, including nodules with atypical features, three neoplasms of undetermined malignant potential and two thyroiditis cases were examined. By immunohistochemistry, galectin-3 was consistently found in carcinomas; otherwise benign nodules exhibited galectin-3-positive clusters of cells with poorly developed features of differentiated carcinoma (mainly of papillary type) such as nuclear chromatin clearing, nuclear clefting, pseudoinclusions, which, in each case, were not histologically sufficient to warrant a definitive diagnosis of malignancy. In other nodules galectin-3 staining was negative. The latter were either clearly benign or showed constantly a minor degree of chromatin clearing and of other atypical features when compared with galectin-3-positive cases.

CONCLUSIONS

Galectin-3, a reliable marker of differentiated thyroid carcinoma as confirmed in our series of malignant neoplasms, appears expressed in nodules with an overall benign appearance but with focal areas suspicious for malignancy. The significance of such findings needs to be further investigated.

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.

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.