N-cadherin-mediated adhesion and aberrant catenin expression in anaplastic thyroid-carcinoma cell lines

FAM83B is involved in thyroid cancer cell differentiation and migration

FAM83B has been recently identified as an oncogene, but its role in thyroid cancers (TC) is still unclear. We examined the expression of FAM83B and its possible involvement in cell migration and differentiation, in neoplastic/normal thyroid tissues and in TC human cell lines. FAM83B expression in TC varies according to the tumor histotype, being significantly downregulated in more aggressive and metastatic tissues. FAM83B levels in cell lines recapitulate patients’ samples variations, and its total and cytoplasmic levels decrease upon the induction of migration, together with an increase in its nuclear localization. Similar variations were detected in the primary tumor and in the metastatic tissues from a follicular TC. FAM83B knock down experiments confirmed its role in thyroid differentiation and cell migration, as demonstrated by the reduction of markers of thyroid differentiation and the increase of the mesenchymal marker vimentin. Moreover, the silencing of FAM83B significantly increased cells migration abilities, while not affecting the oncogenic RAS/MAPK/PI3K pathways. Our data indicate for the first time a role for FAM83B in TC cell differentiation and migration. Its expression is reduced in dedifferentiated tumors and its nuclear re-localization could favour distant migration, suggesting that FAM83B should be considered a possible diagnostic and prognostic biomarker.

Identification of key genes and miRNAs markers of papillary thyroid cancer

OBJECTIVE

In this study, crucial genes and microRNAs (miRNAs) associated with the progression, staging, and prognosis of papillary thyroid cancer (PTC) were identified.

METHODS

Four PTC datasets, including our own mRNA-sequencing (mRNA-seq) dataset and three public datasets downloaded from Gene Expression Omnibus and The Cancer Genome Atlas, were used to analyze differentially expressed genes (DEGs) and miRNAs (DEMs) between PTC tumor tissues and paired normal tissues (control). Gene ontology (GO) terms and pathways associated with these DEGs were identified, and protein-protein interactions (PPIs) were analyzed. Additionally, an miRNA-mRNA regulatory network was constructed and the functions of DEMs were explored. Finally, miRNAs/mRNAs associated with tumor staging and prognosis were identified. The expression levels of several key genes and miRNAs were validated by qRT-PCR.

RESULTS

Numerous DEGs and DEMs were identified between tumor and control groups in four datasets. The DEGs were significantly enriched in cell adhesion and cancer-related GO terms and pathways. In the constructed PPI network, ITGA2, FN1, ICAM1, TIMP1 and CDH2 were hub proteins. In the miRNA-mRNA negative regulatory networks, miR-204-5p regulated the largest number of target genes, such as TNFRSF12A. miR-146b, miR-204, miR-7-2, and FN1 were associated with tumor stage in PTC, and TNFRSF12A and CLDN1 were related to prognosis.

CONCLUSIONS

Our results suggested the important roles of ITGA2, FN1, ICAM1, TIMP1 and CDH2 in the progression of PTC. miR-204-5p, miR-7-2, and miR-146b are potential biomarkers for PTC staging and FN1, CLDN1, and TNFRSF12A may serve as markers of prognosis in PTC.

15-Deoxy-Δ12,14-prostaglandin J2 inhibits migration of human thyroid carcinoma cells by disrupting focal adhesion complex and adherens junction

Metastasis is frequently observed in human follicular thyroid carcinoma. The present study investigated the peroxisome proliferator-activated receptor γ agonist, 15-deoxy-Δ^12,14-prostaglandin J² (15d-PGJ₂), and its effect on the migration of CGTH W-2 human thyroid carcinoma cells. 15d-PGJ₂ decreased the survival rate of CGTH W-2 cells in a dose-dependent manner. The Transwell migration assay demonstrated that 15d-PGJ₂ reduced the migration rate of CGTH W-2 cells by 35% following treatment with 30 µM 15d-PGJ₂ compared with control cells. The cell adhesion assay indicated that, following 15d-PGJ₂ treatment for 24 h, cell adhesion decreased by 26% compared with the control group. The expression levels of focal adhesion proteins, including integrin β1, phospho-focal adhesion kinase and p-paxillin, were downregulated following treatment with 15d-PGJ₂. Immunostaining revealed that the puncta of vinculin were reduced and the actin stress fiber was disassembled following 15d-PGJ₂ treatment. By contrast, p120-catenin (p120-ctn) and β-catenin levels staining accumulated in the region of the lamellipodium following 15d-PGJ₂ treatment. Membrane fractionation revealed that p120-ctn and N-cadherin were decreased in the cell membrane, but increased in the cytoplasm of 15d-PGJ₂-treated cells. Therefore, 15d-PGJ₂ inhibited human thyroid carcinoma cell migration and this may be due to the impairment of focal adhesion complexes and the accumulation of p120-ctn in the cytoplasm in the region of the lamellipodium.

Differential effects of MAPK pathway inhibitors on migration and invasiveness of BRAF(V600E) mutant thyroid cancer cells in 2D and 3D culture

Tumor microenvironment influences targeted drug therapy. In this study we compared drug responses to RAF and MEK inhibitors on tumor cell migration in 2D and 3D culture of BRAF(V600E) mutant cell lines derived from human papillary (BCPAP) and anaplastic (SW1736) thyroid carcinomas. Scratch wounding was compared to a double-layered collagen gel model developed for analysis of directed tumor cell invasion during prolonged culture. In BCPAP both PLX4720 and U0126 inhibited growth and migration in 2D and decreased tumor cell survival in 3D. In SW1736 drugs had no effect on migration in 2D but decreased invasion in 3D, however this related to reduced growth. Dual inhibition of BRAF(V600E) and MEK reduced but did not prevent SW1736 invasion although rebound phosphorylation of ERK in response to PLX4720 was blocked by U0126. These findings indicate that anti-tumor drug effects in vitro differ depending on culture conditions (2D vs. 3D) and that the invasive features of anaplastic thyroid cancer depend on non-MEK mechanism(s).

Assessment Of Plasma B-Catenin Concentration As Biomarker Of Thyroid Cancer

New diagnostic methods for thyroid diseases are still being searched for. Immunohistochemical diagnosis is expanded by the introduction of new biomarkers including ß-catenin (B-Cat). Associations are indicated between the cellular expression of this biomarker and tumor stage, nodal metastases and the degree of tumor cell differentiation. Reports are scarce regarding the plasma level of this biomarker in malignant neoplastic diseases. The aim of the study was to analyze the plasma B-Cat concentration and the possibility of it use in the diagnostics of patients with nodular goiter and papillary thyroid carcinoma.

MATERIAL AND METHODS

Plasma B-Cat concentration was determined in 64 patients with goiter and 15 healthy volunteers. The final histopathological examination revealed 41 cases of papillary thyroid carcinoma (PTC) and 13 cases of nodular goiter (NG).

RESULTS

A significant increase in B-Cat (p <0.05) in both groups compared to the control group. No differences in the concentrations of biomarker was demonstrated between the PTC and NG groups. After determining the AUC for the tested biomarker, the B-Cat ratio of the area value 0.721 was the strong diagnostic test.

CONCLUSIONS

Changes in the plasma B-Cat concentration can be the biomarker of thyroid cancer but it cannot be used for the detection of papillary thyroid carcinoma because of concomitant tumor-like lesions in the thyroid gland.

p120catenin alteration in cancer and its role in tumour invasion

Since its discovery in 1989 as a substrate of the Src oncogene, p120catenin has been revealed as an important player in cancer initiation and tumour dissemination. p120catenin regulates a wide range of cellular processes such as cell-cell adhesion, cell polarity and cell proliferation and plays a pivotal role in morphogenesis, inflammation and innate immunity. The pleiotropic effects of p120catenin rely on its interactions with numerous partners such as classical cadherins at the plasma membrane, Rho-GTPases and microtubules in the cytosol and transcriptional modulators in the nucleus. Alterations of p120catenin in cancer not only concern its expression level but also its intracellular localization and can lead to both pro-invasive and anti-invasive effects. This review focuses on the p120catenin-mediated pathways involved in cell migration and invasion and discusses the potential consequences of major cancer-related p120catenin alterations with respect to tumour spread.

RhoA is down-regulated at cell-cell contacts via p190RhoGAP-B in response to tensional homeostasis

p190RhoGAP-B mediates Rho activity and ductal morphogenesis in response to 3D collagen stiffness. p190B associates with p120-catenin at cell–cell contacts, where RhoA activity is decreased compared to cell–ECM adhesions. This suggests that Rho is in an inactive pool at cell–cell contacts and is recruited to cell–ECM contacts in stiff matrices.

Breast epithelial cells cultured in three-dimensional (3D) collagen gels undergo ductal morphogenesis when the gel is compliant and they can achieve tensional homeostasis. We previously showed that this process requires down-regulation of Rho in compliant collagen gels, but the mechanism remains undefined. In this study, we find that p190RhoGAP-B, but not p190RhoGAP-A, mediates down-regulation of RhoA activity and ductal morphogenesis in T47D cells cultured in compliant 3D collagen gels. In addition, both RhoA and p190RhoGAP-B colocalize with p120-catenin at sites of cell–cell contact. The association between p190RhoGAP-B and p120-catenin is regulated by matrix compliance such that it increases in compliant vs. rigid collagen gels. Furthermore, knockdown of p120-catenin disrupts ductal morphogenesis, disregulates RhoA activity, and results in loss of p190B at cell–cell contacts. Consistent with these findings, using a RhoA-specific FRET biosensor (RhoA-FLARE.sc), we determined spatial RhoA activity to be significantly decreased at cell–cell contacts versus cell–ECM adhesions, and, of importance, spatial RhoA activity is regulated by p190B. This finding suggests that RhoA exists as an inactive pool at cell–cell contacts and is recruited to cell–ECM contacts within stiff matrices. Overall, these results demonstrate that RhoA is down-regulated at cell–cell contacts through p190RhoGAP-B, which is localized to cell–cell contacts by association with p120-catenin that is regulated by tensional homeostasis.

Glycolytic inhibition alters anaplastic thyroid carcinoma tumor metabolism and improves response to conventional chemotherapy and radiation

Anaplastic thyroid carcinoma (ATC) accounts for more than 50% of thyroid cancer mortality and is generally refractory to conventional treatment. On the basis of recent studies, we hypothesized that ATC metabolism can be targeted to improve response to chemoradiotherapy. Eight established and authenticated ATC cell lines were sequenced at 140 sites contained within 26 commonly mutated genes to identify novel potential therapeutic targets. Cellular proliferation, energy, and reducing potential stores were measured under conditions of specific nutrient deprivation. Tumor metabolism was evaluated using hyperpolarized (13)C MRI in a murine orthotopic xenograft model of ATC. Sensitivity to chemotherapeutic agents and radiation (XRT) was assayed using cytotoxicity assays. We identified mutations in BRAF, NRAS, and KIT but failed to identify generalized novel targets for therapeutic intervention. ATC cell lines exhibited a mesenchymal phenotype and generalized dependence on glucose for energy, reducing potential and survival. Glycolytic inhibition using 2-deoxyglucose (2-DG) sensitized ATC cells to conventional chemotherapy and external beam radiation. In vivo, 2-DG induced a transient, but significant reduction in ATC metabolic activity. Generalized dependence of ATC cells on glucose catabolism makes them susceptible to the sensitizing effects of 2-DG for radiation therapy and chemotherapy. Under in vivo conditions, 2-DG can inhibit ATC metabolism. However, the modest magnitude and transient nature of this effect suggest the need for antimetabolic agents with more favorable pharmacodynamics to achieve therapeutic effects.

Plakoglobin: role in tumorigenesis and metastasis

Plakoglobin (γ-catenin) is a member of the Armadillo family of proteins and a homolog of β-catenin. As a component of both the adherens junctions and desmosomes, plakoglobin plays a pivotal role in the regulation of cell-cell adhesion. Furthermore, similar to β-catenin, plakoglobin is capable of participating in cell signaling. However, unlike β-catenin that has well-documented oncogenic potential through its involvement in the Wnt signaling pathway, plakoglobin generally acts as a tumor/metastasis suppressor. The exact roles that plakoglobin plays during tumorigenesis and metastasis are not clear; however, recent evidence suggests that it may regulate gene expression, cell proliferation, apoptosis, invasion, and migration. In this paper, we describe plakoglobin, its discovery and characterization, its role in regulating cell-cell adhesion, and its signaling capabilities in regulation of tumorigenesis and metastasis.

Sunitinib exerts only limited effects on the proliferation and differentiation of anaplastic thyroid cancer cells

BACKGROUND

Novel molecularly targeted drugs are undergoing preclinical and clinical testing to assess their efficacy against refractory thyroid carcinomas. The multikinase inhibitor Sunitinib has been shown to inhibit the kinase activity of the RET oncogene and reduce proliferation in differentiated thyroid cancer cells harboring the RET/PTC rearrangement. In this study, we evaluated its effects in human cell lines derived from differentiated (TPC-1) and anaplastic (8505C, CAL-62, and C643) thyroid cancers.

METHODS

The cells exposed to various concentrations of Sunitinib were examined for: (1) cell viability and presence of apoptosis, analyzed by cell counts, MTT assay, trypan blue exclusion assay, western blotting, and immunofluorescence; (2) expression of cyclin D1 and phosphorylated and nonphosphorylated extracellular signal-regulated kinase (ERK) and Akt proteins, analyzed by western blotting; and (3) transcription of genes encoding thyrocyte differentiation markers (thyroid-stimulating hormone receptor, sodium/iodide symporter, thyroglobulin, and thyroperoxidase) and proangiogenic factors (vascular endothelial growth factor A, platelet-derived growth factors A and B), measured by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Exposure to nanomolar concentrations of Sunitinib significantly reduced cell viability in only TPC-1 cells, and this effect was paralleled by reduction of cyclin D1 levels. Western blotting revealed reduced phosphorylation of ERK and Akt after 3 and 6 hours of drug exposure. In contrast, the growth of 8505C, CAL-62, and C-643 cells was significantly reduced only by micromolar concentrations of Sunitinib, mainly due to induced necrotic rather than apoptotic death. In these cells, Sunitinib exerted a few significant effects on the transcription of angiogenic factors or thyrocyte differentiation markers.

CONCLUSIONS

Sunitinib has little or no effect on the growth or differentiation of anaplastic thyroid cancer cells, thus suggesting that it is unlikely to be effective in the treatment of anaplastic thyroid cancer.

N-cadherin mediates angiogenesis by regulating monocyte chemoattractant protein-1 expression via PI3K/Akt signaling in prostate cancer cells

Over the past decade, evidence continues to mount showing that N-cadherin is a critical protein in cancer progression and metastasis. In the present study, we evaluated the expression of N-cadherin in human prostate cancer tissue specimens and cell lines. Enhanced expression of N-cadherin was observed in both the malignant and bone-metastasized prostate tissue specimens compared to the healthy prostate tissues. Consistent with the tissue array data, N-cadherin was highly expressed in PC3, but not in Du145 and LNCaP human prostate cell lines. Based on cell to cell binding assay, we found that N-cadherin expression facilitates homotypic interaction between human prostate cancer cells and human microvascular endothelial cells (HMEC). Human angiogenesis antibody array and in vitro angiogenesis assay showed that siRNA-mediated knockdown of N-cadherin reduced the secretion of monocyte chemoattractant protein-1 (MCP-1), which played a potential role in stimulating capillary network formation of HMEC. Additionally, culture supernatant of Du145 cells transfected with full-length N-cadherin expressing plasmid showed increased MCP-1 expression and chemoattractant ability compared to normal Du145 cells. Further, we noticed that blocking PI3K activity inhibited N-cadherin mediated MCP-1 expression. Our data demonstrated that N-cadherin in prostate cancer cell mediates cell-cell adhesion and regulates MCP-1 expression via the PI3K/Akt signaling pathway.

Aberrant methylation accounts for cell adhesion-related gene silencing during 3-methylcholanthrene and diethylnitrosamine induced multistep rat lung carcinogenesis associated with overexpression of DNA methyltransferases 1 and 3a

To evaluate the significance of alterations in cell adhesion-related genes methylation during lung multistep carcinogenesis induced by the genotoxic carcinogens 3-methylcholanthrene (MCA) and diethylnitrosamine (DEN), tissue samples microdissected from MCA/DEN-induced rat lung carcinogenesis model were subjected to methylation-specific PCR to evaluate the DNA methylation status of CADM1, TIMP3, E-cadherin and N-cadherin. Immunohistochemistry was used to determine protein expression of CADM1, TIMP3, N-cadherin and the DNA methyltransferases (DNMTs) 1, 3a and 3b. E-cadherin hypermethylation was not detected in any tissue. CADM1, TIMP3 and N-cadherin hypermethylation was correlated with the loss of their protein expression during the progression of pathologic lesions. The prevalence of DNA methylation of at least one gene and the average number of methylated genes increased with the histological progression. DNMT1 and DNMT3a protein expression increased progressively during the stages of lung carcinogenesis, whereas DNMT3b overexpression was only found in several samples. Furthermore, DNMT1 protein expression levels were correlated with CADM1 methylation, and DNMT3a protein expression levels were correlated with CADM1, TIMP3 and N-cadherin methylation. The average number of methylated genes during carcinogenesis was significantly correlated with DNMT1 and DNMT3a protein expression levels. Moreover, mRNA expression of CADM1 significantly increased after treatment with DNMT inhibitor 5-aza-2'-deoxycytidine in CADM1-methylated primary tumor cell lines. Our findings suggest that an accumulation of hypermethylation accounts for cell adhesion-related gene silencing is associated with dynamic changes in the progression of MCA/DEN-induced rat lung carcinogenesis. We suggest that DNMT1 and DNMT3a protein overexpression may be responsible for this aberrant DNA methylation.

Altered expression of p120catenin predicts poor outcome in invasive breast cancer

PURPOSE

The study focuses on p120catenin, a regulator of cell adhesion, which has previously been described in many malignancies and suggested with a role in invasion and metastatic behaviour. In this study, we investigate the role of altered immunoexpression of p120catenin isoforms in the prognosis of invasive breast cancer (n = 351).

METHODS

We used cDNA microarrays to screen differences in gene expression in invasive breast cancer in general, and between local and metastasized disease particularly. On this basis, we performed p120catenin immunohistochemistry in order to confirm the prognostic value of p120catenin isoforms on tissue microarrays comprising 341 patients from the era of mammographic screening, directed to modern surgical and oncological treatments, and followed-up for maximum of 20 years.

RESULTS

In cDNA microarray analysis, p120catenin was discovered down-regulated along with E-cadherin and alpha-catenin. In addition, p120catenin distinguished metastasized breast cancer from local disease. Immunohistochemistry confirmed the value of p120catenin as an independent prognosticator of breast cancer survival. In our results, p120catenin was associated with 3.7-fold risk of breast cancer death in multivariate Cox's regression analyses adjusted for the established prognosticators of breast cancer (p = 0.039). Particularly, the long isoform of p120catenin predicted metastatic disease (p = 0.029).

CONCLUSION

The present paper is the first report on p120catenin in invasive breast cancer based on a well-characterized patient material with long-term follow-up. We observed altered expression of p120catenin isoforms in invasive breast cancer and, in our material, the decrease in p120 immunoexpression was significantly associated with poor outcome of disease.

Anaplastic thyroid cancer: molecular pathogenesis and emerging therapies

Anaplastic thyroid cancer (ATC) is a rare malignancy. While external beam radiation therapy has improved locoregional control, the median survival of approximately 4 months has not changed in more than half a century due to uncontrolled systemic metastases. The objective of this study was to review the literature in order to identify potential new strategies for treating this highly lethal cancer. PubMed searches were the principal source of articles reviewed. The molecular pathogenesis of ATC includes mutations in BRAF, RAS, catenin (cadherin-associated protein), beta 1, PIK3CA, TP53, AXIN1, PTEN, and APC genes, and chromosomal abnormalities are common. Several microarray studies have identified genes and pathways preferentially affected, and dysregulated microRNA profiles differ from differentiated thyroid cancers. Numerous proteins involving transcription factors, signaling pathways, mitosis, proliferation, cell cycle, apoptosis, adhesion, migration, epigenetics, and protein degradation are affected. A variety of agents have been successful in controlling ATC cell growth both in vitro and in nude mice xenografts. While many of these new compounds are in cancer clinical trials, there are few studies being conducted in ATC. With the recent increased knowledge of the many critical genes and proteins affected in ATC, and the extensive array of targeted therapies being developed for cancer patients, there are new opportunities to design clinical trials based upon tumor molecular profiling and preclinical studies of potentially synergistic combinatorial novel therapies.

Bioimaging TOF-SIMS: High resolution 3D imaging of single cells

The distribution of phosphocholine ions (m/z 184, m/z 86), sodium ions, and potassium ions in thyroid tumor cells was analyzed by imaging TOF-SIMS. Repeated sputtering with a C(60) (+) source and subsequent analysis with a Bi(3) (+) gun produced a series of 138 images that were stacked to make a 3D display of the chemistry of cells. Phosphocholine was seen in the plasma membrane (m/z 184) and intracellular membranes (m/z 86). The different fragmentation of the phospholipid probably reflects the chemical composition of membranes at these sites. High intensity of secondary ion signals of potassium was seen in membrane-encompassed cellular compartments. The data indicate that potassium ions are compartmentalized in thyroid tumor cells.

Promoter methylation is associated with the age-dependent loss of N-cadherin in the rat kidney

The cadherins are cell adhesion molecules required for cellular homeostasis, and N-cadherin is the predominant cadherin expressed in proximal tubular epithelial cells in humans and rats. Our laboratory previously reported an age-dependent decrease in renal N-cadherin expression; the levels of N-cadherin mRNA and protein expression decreased in parallel, implicating a transcriptional mechanism in the age-dependent loss of expression (19). In this study, we examined the hypothesis that promoter hypermethylation underlies the loss of N-cadherin expression in aging rat kidney. We cloned the 5' flanking region of the rat N-cadherin gene and observed basic promoter activity in a 3,992-bp region localized immediately upstream of the ATG start site. Nucleotide analysis revealed 87% identity with the human N-cadherin minimal promoter region. Consistent with a role for regulation by DNA methylation, we found that a dense CpG island, which spans 1,104 bp (-1,158 to -55), flanks the rat N-cadherin gene; a similar CpG profile was found in the human N-cadherin 5' flanking region. Methylation-specific PCR analysis demonstrated that the promoter region of N-cadherin is heavily methylated in aged, but not young, rat kidney. Interestingly, the promoter is not methylated in age-matched, calorically restricted animals. In contrast, the promoter region is not methylated in either young or aged rat liver; this corresponds to the finding that aging is not associated with decreased N-cadherin expression in the liver. In addition, N-cadherin expression is markedly induced in NRK-52E cells treated with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine, further suggesting that methylation at CpG in the promoter region may underlie the age-dependent decrease in renal N-cadherin expression.

Molecular classification and biomarker discovery in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy, with an incidence of approximately 22,000 cases in 2004 in the USA. Incidence is increasing, with a global estimate of half a million new cases this year. PTC is found in a variety of morphologic variants, usually grows slowly and is clinically indolent, although rare, aggressive forms with local invasion or distant metastases can occur. In recent years, thyroid cancer has been at the forefront of molecular pathology as a result of the consequences of the Chernobyl disaster and the recognition of the role of Ret/PTC rearrangements in PTC. Nonetheless, the molecular pathogenesis of this disease remains poorly characterized. In the clinical setting, benign thyroid nodules are far more frequent, and distinguishing between them and malignant nodules is a common diagnostic problem. It is estimated that 5-10% of people will develop a clinically significant thyroid nodule during their lifetime. Although the introduction of fine-needle aspiration has made PTC identification more reliable, clinicians often have to make decisions regarding patient care on the basis of equivocal information. Thus, the existing diagnostic tools available to distinguish benign from malignant neoplasms are not always reliable. This article will critically evaluate recently described putative biomarkers and their potential future role for diagnostic purposes in fine-needle aspiration cytology samples. It will highlight the evolution of our understanding of the molecular biology of PTC, from a narrow focus on specific molecular lesions such as Ret/PTC rearrangements to a pan-genomic approach.

Diverse functions of p120ctn in tumors

p120ctn is a member of the Armadillo protein family. It stabilizes the cadherin-catenin adhesion complex at the plasma membrane, but also has additional roles in the cytoplasm and nucleus. Extensive alternative mRNA splicing and multiple phosphorylation sites generate additional complexity. Evidence is emerging that complete loss, downregulation or mislocalization of p120ctn correlates with progression of different types of human tumors. It remains to be determined whether a causal relationship exists between specific isoform expression, subcellular localization or selective phosphorylation of p120ctn on the one hand and tumor prognosis on the other.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

Gene expression in thyroid autonomous adenomas provides insight into their physiopathology

The purpose of this study was to use the microarray technology to define expression profiles characteristic of thyroid autonomous adenomas and relate these findings to physiological mechanisms. Experiments were performed on a series of separated adenomas and their normal counterparts on Micromax cDNA microarrays covering 2400 genes (analysis I), and on a pool of adenomatous tissues and their corresponding normal counterparts using microarrays of 18,000 spots (analysis II). Results for genes present on the two arrays corroborated and several gene regulations previously determined by Northern blotting or microarrays in similar lesions were confirmed. Five overexpressed and 24 underexpressed genes were also confirmed by real-time RT-PCR in some of the samples used for microarray analysis, and in additional tumor specimens. Our results show: (1) a change in the cell populations of the tumor, with a marked decrease in lymphocytes and blood cells and an increase in endothelial cells. The latter increase would correspond to the establishment of a close relation between thyrocytes and endothelial cells and is related to increased N-cadherin expression. It explains the increased blood flow in the tumor; (2) a homogeneity of tumor samples correlating with their common physiopathological mechanism: the constitutive activation of the thyrotropin (TSH)/cAMP cascade; (3) a low proportion of regulated genes consistent with the concept of a minimal deviation tumor; (4) a higher expression of genes coding for specific functional proteins, consistent with the functional hyperactivity of the tumors; (5) an increase of phosphodiesterase gene expression which explains the relatively low cyclic AMP levels measured in these tumors; (6) an overexpression of antiapoptotic genes and underexpression of proapoptotic genes compatible with their low apoptosis rate; (7) an overexpression of N-cadherin and downregulation of caveolins, which casts doubt about the use of these expressions as markers for malignancy.

Reduced E-cadherin expression contributes to the loss of p27kip1-mediated mechanism of contact inhibition in thyroid anaplastic carcinomas

In the present study, we have characterized several human thyroid cancer cell lines of different histotypes for their responsiveness to contact inhibition. We found that cells derived from differentiated carcinoma (TPC-1, WRO) arrest in G(1) phase at confluence, whereas cells derived from anaplastic carcinoma (ARO, FRO and FB1) continue to grow after reaching confluence. Furthermore, we provide experimental evidence that the axis, E-cadherin/beta-catenin/p27(Kip1), represents an integral part of the regulatory mechanism that controls proliferation at a high cell density, whose disruption may play a key role in determining the clinical behaviour of thyroid cancer. This conclusion derives from the finding that: (i) the expression of p27(Kip1) is enhanced at high cell density only in cells responsive to contact inhibition (TPC-1, WRO), but not in contact-inhibition resistant cells (ARO, FRO or FB1 cells); (ii) the increase in p27(Kip1) also resulted in increased levels of p27(Kip1) bound to cyclin E-Cdk2 complex, a reduction in cyclin E-Cdk2 activity and dephosphorylation of the retinoblastoma protein; (iii) antisense inhibition of p27(Kip1) upregulation at high cell density in confluent-sensitive cells completely prevents the confluence-induced growth arrest; (iv) proper expression and/or membrane localization of E-cadherin is observed only in cells responsive to contact inhibition (TPC-1, NPA, WRO) but not in unresponsive cells (ARO, FRO or FB1); (v) disruption of E-cadherin-mediated cell-cell contacts at high cell density induced by an anti-E-cadherin neutralizing antibody, inhibits the induction of p27(kip1) and restores proliferation in contact-inhibited cells; (vi) re-expression of E-cadherin into cells unresponsive to contact inhibition (ARO, FB1) induces a p27(kip1) expression and growth arrest. In summary, our data indicate that the altered response to contact inhibition exhibited by thyroid anaplastic cancer cells is due to the failure to upregulate p27(Kip1) in response to cell-cell interactions.

Mutated E-cadherin: genomic and functional characterization in thyroid cells from the KAT family

Members of a family of thyroid cell lines (KAT) were analyzed because they expressed a higher molecular weight (135 kd) form of E-cadherin at their surface. We found that this aberrant E-cadherin is the result of a point mutation in the exon 9 donor splice site causing a skipping of exon 9 with consequent deletion of the corresponding aminoacids on E-cadherin protein. As a spin-off, we report that the various members of the KAT family share this mutation as well as the genetic background. Furthermore we found that this mutated protein leads to disturbed cell-cell adhesion although E-cadherin is still able to mediate the formation of the cadherin/ catenin complex. We also demonstrate the presence of another cell-cell adhesion complex, formed by Pcadherin and the catenins. The latter is also not able to mediate cell-cell adhesion. Although these cells lack cell-cell adhesion they are not invasive without exogenous stimulus.

Cytoplasmic localization of p120ctn and E-cadherin loss characterize lobular breast carcinoma from preinvasive to metastatic lesions

Accumulating evidences indicate that p120 catenin, a member of the E-cadherin (E-CD)/catenin adhesion complex, plays a role in tumor invasion. To establish the expression pattern of p120 in breast cancer, we analysed 326 breast tissue biopsies by tissue microarray. Most of the lobular tumors (88%) showed exclusive cytoplasmic localization, and 6% of them also had p120 nuclear staining. Cytoplasmic p120 strongly associated with complete loss of E-CD and beta-catenin not only in lobular carcinoma and its metastases but also in atypical lobular hyperplasias. In the latter, loss of heterozygosity of E-CD gene was also observed. Complete loss of E-CD and cytoplasmic and nuclear p120 staining was also observed in primary lobular cancer cell cultures generated by us. In ductal tumors, by contrast, reduction of p120 and E-CD in membrane was very common (57 and 53%, respectively), whereas cytoplasmic p120 staining was rarely seen. This simultaneous reduction of membranous E-CD and p120 was not associated with increased Src kinase activity. To demonstrate that cytoplasmic p120 localization was a consequence of the absence of E-CD, the endogenous E-CD was re-expressed in MDA-231 cells by 5-Aza-2'-deoxycytidine (5Aza) treatment. After treatment, p120 shifted from the cytoplasm to the membrane, where it colocalized with endogenous E-CD. Additionally, suppressing E-CD expression in Madin-Darby canine kidney cells by stable transfection of the transcriptional repressors Snail, E47 or Slug, provokes p120 cytoplasmic localization and p120 isoform switching. In conclusion, abnormal cytoplasmic and nuclear localization of p120, which are mediated by the absence of E-CD, characteristically occur in the early stages of lobular breast cancer and are maintained during tumor progression to metastasis. Consequently, p120 may be an important mediator of the oncogenic effects derived from E-CD inactivation, including enhanced motility and invasion, in lobular breast cancer.

Role of tissue stroma in cancer cell invasion

Maintenance of epithelial tissues needs the stroma. When the epithelium changes, the stroma inevitably follows. In cancer, changes in the stroma drive invasion and metastasis, the hallmarks of malignancy. Stromal changes at the invasion front include the appearance of myofibroblasts, cells sharing characteristics with fibroblasts and smooth muscle cells. The main precursors of myofibroblasts are fibroblasts. The transdifferentiation of fibroblasts into myofibroblasts is modulated by cancer cell-derived cytokines, such as transforming growth factor-beta (TGF-beta). TGF-beta causes cancer progression through paracrine and autocrine effects. Paracrine effects of TGF-beta implicate stimulation of angiogenesis, escape from immunosurveillance and recruitment of myofibroblasts. Autocrine effects of TGF-beta in cancer cells with a functional TGF-beta receptor complex may be caused by a convergence between TGF-beta signalling and beta-catenin or activating Ras mutations. Experimental and clinical observations indicate that myofibroblasts produce pro-invasive signals. Such signals may also be implicated in cancer pain. N-Cadherin and its soluble form act as invasion-promoters. N-Cadherin is expressed in invasive cancer cells and in host cells such as myofibroblasts, neurons, smooth muscle cells, and endothelial cells. N-Cadherin-dependent heterotypic contacts may promote matrix invasion, perineural invasion, muscular invasion, and transendothelial migration; the extracellular, the juxtamembrane and the beta-catenin binding domain of N-cadherin are implicated in positive invasion signalling pathways. A better understanding of stromal contributions to cancer progression will likely increase our awareness of the importance of the combinatorial signals that support and promote growth, dedifferentiation, invasion, and ectopic survival and eventually result in the identification of new therapeutics targeting the stroma.

E-cadherin loss rather than beta-catenin alterations is a common feature of poorly differentiated thyroid carcinomas

AIMS

To investigate the immunohistochemical and molecular genetic features of the cadherins/catenins complex in thyroid carcinoma based on the hypothesis that poorly differentiated carcinoma of the thyroid represents an intermediate step between well-differentiated and undifferentiated carcinomas.

METHODS AND RESULTS

Immunohistochemistry for E-, P- and N-cadherins and alpha-, beta- and gamma-catenins was performed in a series of 17 cases of poorly differentiated carcinoma of the thyroid. All cases showed absence of membranous expression of E-cadherin with no aberrant expression of P- or N-cadherins; regarding catenins there was heterogeneous loss of expression with membranous immunolocalization of the three catenins in most cases. Molecular analysis of the E-cadherin gene and exon 3 of the beta-catenin gene was also performed by polymerase chain reaction/single-strand conformation polymorphism and sequencing. No mutations in either gene were detected in any case.

CONCLUSIONS

In contrast to previous reports, our results suggest that loss of E-cadherin rather than beta-catenin mutation is the crucial event in determining the differentiation 'level' of thyroid carcinomas.

Function and regulation of melanoma-stromal fibroblast interactions: when seeds meet soil

Melanoma development and progression not only involve genetic and epigenetic changes that take place within the melanocytic cells, but also involve processes that are determined collectively by contextual factors including intercellular adhesions and communications. In this review, we focus on melanoma-stromal fibroblast crosstalk by direct cell-cell contact and by growth factors/cytokines/chemokines interacting with their respective receptors. The interactions between melanoma cells and stromal fibroblasts create a context that promotes tumor growth, migration/invasion, and angiogenesis. An understanding of this process and developing new experimental and screening models are of great importance for the development of effective therapeutical strategies to treat melanoma.

Real-time analysis of beta- and gamma-catenin mRNA expression in ret/PTC-1 activated and nonactivated thyroid tissues

Our group has previously demonstrated an association between ret/PTC-1 activation and decreased E-cadherin mRNA levels in papillary thyroid carcinoma. We also observed similarities in the E-cadherin expression profiles of Hashimoto thyroiditis and ret/PTC-1-positive papillary thyroid carcinomas and have hypothesized that ret/PTC-1 activation might cause not only the structural and nuclear peculiarities of PTC but also an immune reaction to thyroid epithelium. The objective of this study was to examine the expression of E-cadherin's ligands, beta- and gamma-catenin, in various thyroid tissue types in the context of ret/PTC-1 positivity using laser capture microdissection and TaqMan (Applied Biosystems, Foster City, CA). One-Step RT-PCR. Beta-catenin mRNA levels were found to be consistently decreased in both papillary and anaplastic carcinomas when compared with a normal/follicular adenoma group. A significant difference in expression levels was observed between papillary and follicular thyroid carcinomas with the latter having elevated mRNA levels of beta-catenin. Gamma-catenin mRNA was decreased in anaplastic carcinomas compared with normal/follicular adenoma groups. A similar expression profile of gamma-catenin as beta-catenin was observed in papillary and follicular carcinomas with the latter once again having higher mRNA levels. These results therefore suggest that although beta- and gamma-catenin may play a role in the progression of thyroid cancer in general, they do not appear to be associated with ret/PTC-1-modulated pathways.

TCDD-dependent downregulation of gamma-catenin in rat liver epithelial cells (WB-F344)

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is the most potent tumor promoter ever tested in rodents. Although it is known that most of the effects of TCDD are mediated by binding to the aryl hydrocarbon receptor (AHR), the mechanisms leading to tumor promotion still remain to be elucidated. Loss of contact-inhibition is a characteristic hallmark in tumorigenesis. In WB-F344 cells, TCDD induces a release from contact-inhibition manifested by a 2- to 3-fold increase in DNA-synthesis and the emergence of foci when TCDD (1 nM) is given to confluent cells. We focussed our interest on potential cell membrane proteins mediating contact-inhibition in WB-F344 cells, namely E-cadherin, alpha,- beta,- and gamma-catenin (plakoglobin). Using indirect immunofluorescence, E-cadherin, alpha-, beta- and gamma-catenin were detected at cell adhesion sites in untreated, confluent cells. After TCDD-exposure, gamma-catenin was exclusively localized in the cytoplasm whereas localization of E-cadherin, alpha- and beta-catenin remained unaffected. Cytoplasmic gamma-catenin could be extracted by Triton X-100 treatment, demonstrating that gamma-catenin was no longer bound to the actin cytoskeleton. Western blot analysis showed downregulation of gamma-catenin protein levels. This effect was not blocked by pre-incubation with the selective proteasome inhibitor MG-132, indicating that proteolytical degradation of gamma-catenin by the proteasome system was not increased by TCDD. Because mRNA-levels of gamma-catenin were markedly diminished after TCDD-exposure, we conclude that transcriptional downregulation or destabilization of the mRNA contributes to the decrease in gamma-catenin protein levels in response to TCDD. Because gamma-catenin is considered to be a tumor suppressor, our findings might give more insight into the tumor promoting actions of TCDD.

Follicular growth of a thyroid carcinoma cell line (KAT-4) with abnormal E-cadherin and impaired epithelial barrier

Loss of the epithelial phenotype is a well-established phenomenon during progression of carcinomas to a more malignant state. In the present study, we describe a human thyroid tumor cell line (KAT-4), established from a poorly differentiated carcinoma, which displays exceptional features. In culture, the KAT-4 cells had a fast proliferation rate that was not restricted by high cell density, resulting in multilayered growth. Unexpectedly, the cells expressed normal levels of epithelial markers, e.g., cytokeratin, occludin, and E-cadherin, showed apical-basolateral polarization of the plasma membrane including microvilli and junction complexes, and formed intercellular lumens resembling thyroid follicles. Yet, when grown on filter, the cells were unable to establish a tight paracellular barrier. Moreover, E-cadherin expressed at the cell surface consisted of two peptides with abnormal size (135 and 95 kd, respectively) as compared to mature E-cadherin (120 kd) in nonneoplastic thyrocytes. Northern blot analysis and examination of immunoreactivity, glycosylation, and catenin binding suggested that E-cadherin was aberrant because of altered posttranscriptional processing. Thus, the KAT-4 thyroid carcinoma cell line has a unique phenotype, with maintained epithelial morphology despite dysfunctioning tight junctions, abnormal E-cadherin, and loss of contact-inhibited growth, that is not previously identified in other wild-type tumor cell lines.

Identification of an invasive, N-cadherin-expressing epithelial cell type in endometriosis using a new cell culture model

Studies of molecular, cellular, and pathophysiological parameters in endometriosis are primarily hampered by a lack of in vitro model systems, such as endometriotic cell lines. To overcome this we successfully established cell lines from peritoneal endometriotic biopsies and characterized them at the molecular and cellular level. Two types of cells could be transformed: one exhibiting stromal cell features (cytokeratin/E-cadherin-negative), the other epithelial-like (cytokeratin-positive/E-cadherin-negative, invasive in vitro). Using a Matrigel assay the epithelial-like cell lines proved as invasive as metastatic carcinoma cells, possibly through the influence of N-cadherin implicated as a path-finding cadherin allowing cellular invasion and migration in both normal and pathophysiological processes. Our results support the idea that endometriosis, although not neoplastic, shares features with malignant cells and that metastasis in endometriosis may include mechanisms proposed for micrometastasis in cancer. Thus our cell lines will not only be useful tools for analyzing molecular and cellular events relating to endometriosis, but may also represent a paradigm for invasion and metastasis in general.

Absence of mutations in the beta-catenin and adenomatous polyposis coli genes in papillary and follicular thyroid carcinomas

beta-Catenin has multiple functions both in intercellular adhesion and in signal transduction. As a signaling molecule, mutations in exon 3 of the beta-catenin gene stabilize this protein in the cytoplasm. Subsequently, accumulated beta-catenin protein translocates to nuclei with T-cell factor-4, and upregulates transcriptional activity of the target genes involved in carcinogenesis. Mutations in exon 3 of the beta-catenin gene have been detected in various carcinomas. We examined immunolocalization of beta-catenin protein and mutations in the beta-catenin and adenomatous polyposis coli (APC) genes in papillary carcinoma (25 cases), follicular carcinoma (two cases), and benign thyroid tumor (29 cases). We detected no mutation in exon 3 of the beta-catenin gene in both malignant and benign thyroid tumors by polymerase chain reaction (PCR) and direct sequencing. No mutations in the mutation cluster region of APC were found in any tumor samples analyzed. Immunohistochemically, beta-catenin showed membranous localization in most specimens. These results suggest that mutations of the beta-catenin and APC genes are rare and that activation of the Wnt signaling pathway may not contribute to pathogenesis in human papillary and follicular thyroid carcinomas.

Expression and prognostic value of alpha-, beta-, and gamma-catenins indifferentiated thyroid carcinoma

Catenins (alpha, ss, and gamma) are a group of intracellular cell adhesion molecules that unite cytoskeleton with extracellular adhesion system. Abnormal expression of these molecules may have prognostic relevance in various carcinomas, including differentiated thyroid carcinoma (DTC). We have, therefore, evaluated the prognostic value of alpha-, ss-, and gamma-catenins along with traditional risk factors in 206 consecutive DTC patients by immunohistochemistry. Papillary carcinomas showed normal staining pattern for alpha-, ss-, and gamma-catenins in 124 (60%), 136 (67%), and 94 (46%) cases, respectively. Follicular carcinomas expressed alpha-, ss-, and gamma-catenins normally in 16 (48%), 18 (55%), and 8 (32%) cases, respectively. Follicular type of tumor showed more often reduced staining for all catenins than papillary carcinoma (P: = 0.009, P: = 0.004, and P: = 0.002, respectively). Age (>60 yr) and pTNM-stage were related to reduced alpha- and ss-catenin expression levels (P: = 0.027 and P: = 0.026, respectively) and larger size of the tumor to reduced ss- and gamma-catenin expressions (P: = 0.039 and P: = 0.007, respectively). Nodal metastases at the time of primary treatment related to reduced alpha-catenin expression and distal metastases to reduced ss- and gamma-catenin staining signals (P: = 0.022, P: = 0.014, and P: = 0.039, respectively). Reduced alpha-catenin associated with tumor recurrence (P: = 0.002) and reduced ss-catenin with cancer-related mortality (P: = 0.005). The multivariate analysis for recurrence-free survival showed that alpha-catenin and serum thyroglobulin level 1 yr after primary treatment were prognostic of recurrent disease (hazards ratio, 3.42, P: = 0.022; and hazards ratio, 10.03, P: = 0.0001). In addition, alpha-catenin retained its prognostic significance in low-stage patients (P: = 0.0151). We propose that the evaluation of alpha-catenin expression by immunohistochemistry in DTC patients has prognostic value in addition to that obtained by traditional prognostic factors.

Management of undifferentiated thyroid cancer

Management of thyroid carcinoma relies upon the tumour cells maintaining the differentiated functions that are typical of normal thyroid follicular cells, such as: dependence upon thyrotropin for growth, production of thyroglobulin and effective transport of iodine. Likewise, differentiated thyroid carcinomas often exhibit an auspicious clinical behaviour with a slow rate of growth and low potential for invasion and distant metastasis. These features permit therapy of disseminated tumour, effective follow-up surveillance and the assumption of a good prognosis. As each of these features are lost, the opportunities for both disease status assessment and therapeutic intervention diminish accordingly. A major obstacle is our failure to define effective systemic treatments to replace radioiodine therapy, whose loss is consonant with the loss of iodine transport and retention. The extreme of undifferentiated clinical behaviour is epitomized by anaplastic thyroid carcinoma, a rare, terminally dedifferentiated malignancy that is rapidly and invariably fatal. It is important to be attuned to clinical clues suggesting the presence of dedifferentiated tumour and related prognostic signs. This allows the application of currently limited therapeutic options and defines the need for research to develop new systemic treatments.

Fibrosis in undifferentiated (anaplastic) thyroid carcinomas: evidence for a dual action of tumour cells in collagen type I synthesis

The mechanisms involved in stromal reactions and fibrosis in solid malignant tumours are incompletely understood. In the present study, collagen type I production was investigated in tissues and cell lines derived from human undifferentiated (anaplastic) thyroid carcinomas, a highly aggressive, often fibrotic malignancy with mesenchymal phenotype. In situ hybridization showed the expression of pro-alpha1(I) collagen mRNA throughout the stromal part of the tumours. However, immunofluorescence staining using an anti-pro-collagen type I antibody revealed the synthesis of pro-collagen type I protein mainly in stromal cells juxtaposed to nests of tumour cells. In one out of five tissue samples from human undifferentiated thyroid carcinomas, pro-alpha1(I) collagen mRNA expression was also found in a small number of tumour cells. Several well-characterized cell lines established from undifferentiated thyroid carcinomas, two from tumours included in the present study, expressed both pro-alpha1(I) collagen and prolyl 4-hydroxylase mRNA, and three of these cell lines also synthesized native triple-helical collagen type I. Taken together, these data suggest that stromal fibroblasts are the main producers of collagen type I in anaplastic thyroid tumours. The carcinoma cells seem to play a regulatory role, stimulating the synthesis of collagen type I protein in the surrounding stroma by increasing pro-alpha1(I) collagen mRNA translation. However, collagen type I production by the carcinoma cells might also contribute to the marked desmoplasia commonly seen in these tumours.

Dynamics of intercellular communication during melanoma development

Melanoma development involves processes determined collectively by various microenvironmental factors, among which intercellular communication has drawn increased attention. Cell-cell crosstalk mediated by cadherins and connexins results in coordinated regulation of cell growth, differentiation, apoptosis and migration. Abnormal expression of adhesion receptors and dysregulated intercellular communication appears to drive tumor development and progression.