Gene expression and functional evidence of epithelial-to-mesenchymal transition in papillary thyroid carcinoma invasion

EGF and TGF-β1 Effects on Thyroid Function

Normal epithelial thyroid cells in culture are inhibited by TGF-β1. Instead, transformed thyroid cell lines are frequently resistant to its growth inhibitory effect. Loss of TGF-β responsiveness could be due to a reduced expression of TGF-β receptors, as shown in transformed rat thyroid cell lines and in human thyroid tumors, or to alterations of other genes controlling TGF-β signal transduction pathway. However, in thyroid neoplasia, a complex pattern of alterations occurring during transformation and progression has been identified. Functionally, TGF-β1 acts as a tumor suppressor in the early stage of transformation or as a tumor promoter in advanced cancer. This peculiar pleiotropic behaviour of TGF-β may result from cross-talk with signalling pathways mediated by other growth factors, among which EGF-like ligands play an important role. This paper reports evidences on TGF-β1 and EGF systems in thyroid tumors and on the cross-talk between these growth factors in thyroid cancer.

Identification of proteins secreted by head and neck cancer cell lines using LC-MS/MS: Strategy for discovery of candidate serological biomarkers

In search of blood-based biomarkers that would enhance the ability to diagnose head and neck/oral squamous cell carcinoma (HNOSCC) in early stages or predict its prognosis, we analyzed the HNOSCC secretome (ensemble of proteins secreted and/or shed from the tumor cells) for potential biomarkers using proteomic technologies. LC-MS/MS was used to identify proteins in the conditioned media of four HNOSCC cell lines (SCC4, HSC2, SCC38, and AMOSIII); 140 unique proteins were identified on the basis of 5% global false discovery rate, 122 of which were secretory proteins, with 29 being previously reported to be overexpressed in HNOSCC in comparison to normal head and neck tissues. Of these, five proteins including α-enolase, peptidyl prolyl isomerase A/cyclophilin A, 14-3-3 ζ, heterogeneous ribonucleoprotein K, and 14-3-3 σ were detected in the sera of HNOSCC patients by Western blot analysis. Our study provides the evidence that analysis of head and neck cancer cells' secretome is a viable strategy for identifying candidate serological biomarkers for HNOSCC. In future, these biomarkers may be useful in predicting the likelihood of transformation of oral pre-malignant lesions, prognosis of HNOSCC patients and evaluate response to therapy using minimally invasive tests.

Metastatic dormancy and progression in thyroid cancer: targeting cells in the metastatic frontier

BACKGROUND

Metastatic dormancy, or the ability of cancer cells to survive but not progress in metastatic environments, is now recognized to be a common occurrence in cancer.

SUMMARY

From a clinical perspective, this phenomenon is common in metastatic well-differentiated thyroid cancer, whereby patients often present with distant metastases that remain stable for years after removal of the primary tumor and subsequent treatment. Experimental data suggest that metastases can develop throughout the life of a cancer and that progression in the distant environment depends on the biology of the cancer cells that metastasize as well as that of the various microenvironments they encounter. A firm understanding of how thyroid cancer cell progression is regulated in different metastatic environments is necessary to devise effective therapies targeting progressive metastatic thyroid cancer.

CONCLUSION

In this review, current models of metastatic progression and factors that regulate late-stage metastatic progression that are particularly relevant for thyroid cancer are discussed.

Molecular analyses of thyroid tumors for diagnosis of malignancy on fine-needle aspiration biopsies and for prognosis of invasiveness on surgical specimens

High throughput genetic and genomic analyses have allowed the identification of series of genes exhibiting either distinct expression profiles or a particular mutational status in the different types or subtypes of thyroid tumors. The use of molecular data to improve the preoperative diagnosis of thyroid cancer on materiel from fine-needle aspiration biopsy (FNAB) is in the course of validation by numerous teams throughout the world. We have proposed a molecular test based on the expression level of a series of 19 genes, capable of discriminating malignant from benign tumors [15]. A prospective study aiming at the clinical validation of the molecular test has been performed on a cohort of 730 patients with a thyroid nodule. In patients subjected to tumor resection (≈ 220), the preoperative molecular diagnosis (generated on FNAB material from analyses of the expression level of the 19 genes) was compared to the postoperative diagnosis given by the pathologist (used as reference). Treatment and follow-up of the serious forms of thyroid cancer should benefit by the early identification of tumors with a metastatic potential using molecular characteristics differentiating invasive and non-invasive thyroid carcinomas. We have performed genetic and genomic analyses on a series of 200 papillary thyroid carcinomas (non-invasive or NI-PTC, 50%; invasive or I-PTC, 50%). BRAF(V600E) mutation or/and RET/PTC gene rearrangement have been detected in less than 25% of NI-PTC but in more than 75% of I-PTC. Pan-genomic analyses (Agilent microarray) revealed that 1373 genes are differentially expressed (fold change greater than 2) in NI-PTC as compared to I-PTC samples. The majority of genes (≈ 1200) are overexpressed in I-PTC. Data related to the two domains: diagnosis and prognosis of thyroid cancer will be presented at 2011 International H.P. KLOTZ conference on Clinical Endocrinology.

TIMP3 regulates migration, invasion and in vivo tumorigenicity of thyroid tumor cells

Papillary thyroid carcinoma (PTC) arises from the thyroid follicular epithelium and represents the most frequent thyroid malignancy. PTC is associated with gene rearrangements generating RET/PTC and TRK oncogenes, and to the BRAFV600E activating point mutation. A role of tumor-suppressor genes in the pathogenesis of PTC has not been assessed yet. The tissue inhibitor of metalloproteinase-3 (TIMP3) gene, encoding a metalloproteinases inhibitor and capable of inhibiting growth, angiogenesis, invasion and metastasis of several cancers, was found to be silenced by promoter methylation in a consistent fraction of PTCs, in association with tumor aggressiveness and BRAFV600E mutation, thus suggesting an oncosuppressor role. To explore this possibility, in this study we performed gene expression and functional studies. Analysis of gene expression data produced in our laboratory as well as meta-analysis of publicly available data sets confirmed the downregulation of TIMP3 gene expression in PTC with respect to normal thyroid. The functional consequences of TIMP3 downregulation were investigated in the PTC-derived NIM1 cell line, in which the expression of TIMP3 is silenced. Restoration of TIMP3 expression by exposure to soluble TIMP3 protein or by complementary DNA transfection had no effect on the growth rate of NIM1 cells. Instead, it affected the adhesive, migratory and invasive capabilities of NIM1 cells by modulating several proteins involved in these processes. A striking effect was observed in vivo, as TIMP3 reduced the tumorigenicity of NIM1 cells by repressing angiogenesis and macrophage infiltration. Our data indicate that the loss of TIMP3 expression exerts a functional role in the pathogenesis of PTC.

Identification of soluble candidate biomarkers of therapeutic response to sunitinib in medullary thyroid carcinoma in preclinical models

PURPOSE

Medullary thyroid carcinoma (MTC), an aggressive rare tumor due to activating mutations in the proto-oncogene RET, requires new therapeutic strategies. Sunitinib, a potent inhibitor of RET, VEGF receptor (VEGFR)-1, VEGFR-2, VEGFR-3, and platelet-derived growth factor receptor (PDGFR)α/β, has been reported as clinically effective in some patients with advanced MTC. In this study, we examine molecular mechanisms of action of sunitinib and identify candidate soluble biomarkers of response.

EXPERIMENTAL DESIGN

Both in vitro and in vivo assays, using the human TT RET(C634W) MTC cell line, were done to assess the activity of sunitinib. Kinetic microarray studies were used to analyze molecular pathways modified by sunitinib and to identify candidate biomarkers that were subsequently investigated in the serum of patients.

RESULTS

Sunitinib displayed antiproliferative and antiangiogenic activities and inhibited RET autophosphorylation and activation of downstream signaling pathways. We showed that sunitinib treatment induced major changes in the expression of genes involved in tissue invasion and metastasis including vimentin (VIM), urokinase plasminogen (PLAU), tenascin-C (TN-C), SPARC, and CD44. Analyzing downregulated genes, we identified those encoding secreted proteins and, among them, interleukin (IL)-8 was found to be modulated in the serum of xenografted mice under sunitinib treatment. Furthermore, we demonstrated that metastatic MTC patients presented increased serum levels of IL-8 and TGF-β2.

CONCLUSIONS

Experimental models confirm the clinical efficacy of sunitinib observed in a few studies. Molecular pathways revealed by genomic signatures underline the impact of sunitinib on tissue invasion. Selected soluble candidate biomarkers could be of value for monitoring sunitinib response in metastatic MTC patients.

Loss of cellular polarity/cohesiveness in the invasive front of papillary thyroid carcinoma, a novel predictor for lymph node metastasis; possible morphological indicator of epithelial mesenchymal transition

BACKGROUND

Loss of cellular polarity/cohesiveness (LOP/C) in the invasive front of papillary thyroid carcinoma (PTC) results in a high recurrence risk of PTC.

AIMS

To investigate the immunohistochemical features of LOP/C in PTC and to show that this feature is linked to a high association of lymph node metastasis (LNM) at surgery and tumour recurrence.

METHODS

The degree of LOP/C of the PTCs was evaluated histologically using a cut-off value of 20% and the immunohistochemical features of LOP/C were analysed using immunohistochemical staining for E-cadherin, β-catenin and vimentin. The relationship between the LOP/C and the other clinicopathological parameters was analysed.

RESULTS

43 cases of PTC with LOP/C (≥20%) were selected and 27 cases with LOP/C (<20%) were included as control tumours. 11/44 cases (25%) were observed to develop recurrence, LNM or distant metastasis at an average follow-up of 31 months. Less expression of E-cadherin and aberrant localisation of β-catenin and vimentin were observed in PTC tumour cells with LOP/C. LOP/C (≥20%) was significantly correlated with extrathyroid invasion (r=0.336, p=0.003), advanced tumour stage (r=0.275, p=0.017), LNM (r=0.389, p<0.001) and recurrence after surgery (r=0.302, p=0.036). Both extrathyroid invasion and LOP/C were independent significant predictors of LNM.

CONCLUSIONS

LOP/C may be a useful morphological feature of epithelial mesenchymal transition under H&E observation, and it is an important indicator of lymph node metastasis and aggressive clinical behaviour of PTC.

Cancer stem cells: repair gone awry?

Because cell turnover occurs in all adult organs, stem/progenitor cells within the stem-cell niche of each tissue must be appropriately mobilized and differentiated to maintain normal organ structure and function. Tissue injury increases the demands on this process, and thus may unmask defective regulation of pathways, such as Hedgehog (Hh), that modulate progenitor cell fate. Hh pathway dysregulation has been demonstrated in many types of cancer, including pancreatic and liver cancers, in which defective Hh signaling has been linked to outgrowth of Hh-responsive cancer stem-initiating cells and stromal elements. Hence, the Hh pathway might be a therapeutic target in such tumors.

TAZ/WWTR1 is overexpressed in papillary thyroid carcinoma

In this study, we analysed the expression of the transcriptional coactivator TAZ (transcriptional co-activator with PDZ-binding motif), also named WWTR1, in a panel of papillary thyroid carcinoma samples and we observed a significant deregulation of its expression in such tumours. Specifically, by quantitative real-time PCR (qRT-PCR) we evaluated TAZ mRNA levels in tissue specimens (n=61) of papillary thyroid carcinoma (PTC) and herein we show that the PTC samples express much higher TAZ mRNA levels with respect to the normal thyroid tissue (p<0.001). TAZ expression was also evaluated in normal (n=10) and pathological human thyroids (n=17) by immunohistochemical analysis and the increase of TAZ protein levels in PTC was confirmed. To further analyse the molecular mechanisms underlying TAZ overexpression in PTC, we used an inducible system consisting of FRTL-5 rat thyroid cells expressing a conditional RAS oncoprotein and we show that the activation of the RAS signalling pathway is involved in TAZ deregulation. These observations suggest that the activated effectors of the RAS/RAF/MEK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) signalling pathway are involved in the increased expression of TAZ, supporting the idea that this may also occur in thyroid papillary carcinoma. Moreover, we demonstrated that the overexpression of TAZ is able to confer growth advantage to thyroid cells in culture and to induce epithelial-mesenchymal transition. In conclusion, these findings support a potential role for TAZ in the pathogenesis of papillary thyroid carcinomas.

Group I p21-activated kinases regulate thyroid cancer cell migration and are overexpressed and activated in thyroid cancer invasion

p21-activated kinases (PAKs) are a family of serine/threonine kinases that regulate cytoskeletal dynamics and cell motility. PAKs are subdivided into group I (PAKs 1-3) and group II (PAKs 4-6) on the basis of structural and functional characteristics. Based on prior gene expression data that predicted enhanced PAK signaling in the invasive fronts of aggressive papillary thyroid cancers (PTCs), we hypothesized that PAKs functionally regulate thyroid cancer cell motility and are activated in PTC invasive fronts. We examined PAK isoform expression in six human thyroid cancer cell lines (BCPAP, KTC1, TPC1, FTC133, C643, and SW1746) by quantitative reverse transcription-PCR and western blot. All cell lines expressed PAKs 1-4 and PAK6 mRNA and PAKs 1-4 protein; PAK6 protein was variably expressed. Samples from normal and malignant thyroid tissues also expressed PAKs 1-4 and PAK6 mRNA; transfection with the group I (PAKs 1-3) PAK-specific p21 inhibitory domain molecular inhibitor reduced transwell filter migration by ∼50% without altering viability in all cell lines (P<0.05). BCPAP and FTC133 cells were transfected with PAK1, PAK2, or PAK3-specific small interfering RNA (siRNA); only PAK1 siRNA reduced migration significantly for both cell lines. Immunohistochemical analysis of seven invasive PTCs demonstrated an increase in PAK1 and pPAK immunoactivity in the invasive fronts versus the tumor center. In conclusion, PAK isoforms are expressed in human thyroid tissues and cell lines. PAK1 regulates thyroid cancer cell motility, and PAK1 and pPAK levels are increased in PTC invasive fronts. These data implicate PAKs as regulators of thyroid cancer invasion.

Integrated ligand-receptor bioinformatic and in vitro functional analysis identifies active TGFA/EGFR signaling loop in papillary thyroid carcinomas

Background

Papillary thyroid carcinoma (PTCs), the most frequent thyroid cancer, is usually not life threatening, but may recur or progress to aggressive forms resistant to conventional therapies. A more detailed understanding of the signaling pathways activated in PTCs may help to identify novel therapeutic approaches against these tumors. The aim of this study is to identify signaling pathways activated in PTCs.

Methodology/Principal Findings

We examined coordinated gene expression patterns of ligand/receptor (L/R) pairs using the L/R database DRLP-rev1 and five publicly available thyroid cancer datasets of gene expression on a total of 41 paired PTC/normal thyroid tissues. We identified 26 (up) and 13 (down) L/R pairs coordinately and differentially expressed. The relevance of these L/R pairs was confirmed by performing the same analysis on REarranged during Transfection (RET)/PTC1-infected thyrocytes with respect to normal thyrocytes. TGFA/EGFR emerged as one of the most tightly regulated L/R pair. Furthermore, PTC clinical samples analyzed by real-time RT-PCR expressed EGFR transcript levels similar to those of 5 normal thyroid tissues from patients with pathologies other than thyroid cancer, whereas significantly elevated levels of TGFA transcripts were only present in PTCs. Biochemical analysis of PTC cell lines demonstrated the presence of EGFR on the cell membrane and TGFA in conditioned media. Moreover, conditioned medium of the PTC cell line NIM-1 activated EGFR expressed on HeLa cells, culminating in both ERK and AKT phosphorylation. In NIM-1 cells harboring BRAF mutation, TGFA stimulated proliferation, contributing to PI3K/AKT activation independent of MEK/ERK signaling.

Conclusions/Significance

We compiled a reliable list of L/R pairs associated with PTC and validated the biological role of one of the emerged L/R pair, the TGFA/EGFR, in this cancer, in vitro. These data provide a better understanding of the factors involved in the biology of PTCs and would be useful in developing combination therapeutic approaches against these cancers.

Influence of RET/PTC1 and RET/PTC3 oncoproteins in radiation-induced papillary thyroid carcinomas on amounts of cytoskeletal protein species

Radiation-induced human papillary thyroid carcinomas (PTCs) show a high prevalence of fusions of the RET proto-oncogene to heterologous genes H4 (RET/PTC1) and ELE1 (RET/PTC3), respectively. In contrast to the normal membrane-bound RET protein, aberrant RET fusion proteins are constitutively active oncogenic cytosolic proteins that can lead to malignant transformation of thyroid epithelia. To detect specific tumor-associated protein changes that reflect the effect of RET/PTC fusion proteins, we analyzed normal thyroid tissues, thyroid tumors of the RET/PTC1 and RET/PTC3 type and their respective lymph node metastases by a combination of high-resolution two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-mass spectrometry. PTCs without RET rearrangements served as controls. Several cytoskeletal protein species showed quantitative changes in tumors and lymph node metastases harboring RET/PTC1 or RET/PTC3. We observed prominent C-terminal actin fragments assumedly generated by protease cleavages induced due to enhanced amounts of the active actin-binding protein cofilin-1. In addition, three truncated vimentin species, one of which was proven to be headless, were shown to be highly abundant in tumors and metastases of both RET/PTC types. The observed protein changes are closely connected with the constitutive activation of RET-rearranged oncoproteins and reflect the importance to elucidate disease-related typical signatures on the protein species level.

CRABP1-reduced expression is associated with poorer prognosis in serous and clear cell ovarian adenocarcinoma

PURPOSE

CRABP1 is a modulator of retinoic acid function. The aim of the present study was to investigate CRABP1 expression and its clinical significance in ovarian carcinoma.

METHODS

Expression of CRABP1 protein was investigated by immunohistochemical analysis in 100 ovarian carcinomas of various histological sub-types, including serous and clear cell adenocarcinomas. Relationship of CRABP1 expression to clinical features, including prognosis, was analyzed.

RESULTS

Reduced expression of CRABP1 protein was detected especially frequently in the serous and clear cell adenocarcinomas sub-types, 50% (20 of 40) and 38% (10 of 26) of cases, respectively. We found that in both serous and clear cell adenocarcinomas overall survival was significantly poorer in the cases with reduced CRABP1 expression compared to similar cases where expression was maintained, irrespective of the disease stage (P = 0.0073 and 0.049, respectively). Disease-free survival of the serous and clear cell adenocarcinoma cases with reduced CRABP1 expression was significantly poorer, compared to the cases whose CRABP1 expression was maintained (P = 0.024). Multivariate analysis showed that reduced expression of CRABP1 was a significantly important prognostic factor (adjusted hazard ratio: 8.189 (95% CI, 2.186-30.672, P = 0.0019)).

CONCLUSIONS

The present study is the first to demonstrate that the reduced expression of CRABP1 has a potential as a prognostic marker for serous adenocarcinoma which is the most frequent histological ovarian tumor type and also for clear cell carcinoma that often exhibits chemo-resistance. Further study is necessary to clarify how CRABP1 protein expression was altered and how CRABP1 affects ovarian carcinoma cells.

Integrative and comparative genomics analysis of early hepatocellular carcinoma differentiated from liver regeneration in young and old

BACKGROUND

Hepatocellular carcinoma (HCC) is the third-leading cause of cancer-related deaths worldwide. It is often diagnosed at an advanced stage, and hence typically has a poor prognosis. To identify distinct molecular mechanisms for early HCC we developed a rat model of liver regeneration post-hepatectomy, as well as liver cells undergoing malignant transformation and compared them to normal liver using a microarray approach. Subsequently, we performed cross-species comparative analysis coupled with copy number alterations (CNA) of independent early human HCC microarray studies to facilitate the identification of critical regulatory modules conserved across species.

RESULTS

We identified 35 signature genes conserved across species, and shared among different types of early human HCCs. Over 70% of signature genes were cancer-related, and more than 50% of the conserved genes were mapped to human genomic CNA regions. Functional annotation revealed genes already implicated in HCC, as well as novel genes which were not previously reported in liver tumors. A subset of differentially expressed genes was validated using quantitative RT-PCR. Concordance was also confirmed for a significant number of genes and pathways in five independent validation microarray datasets. Our results indicated alterations in a number of cancer related pathways, including p53, p38 MAPK, ERK/MAPK, PI3K/AKT, and TGF-beta signaling pathways, and potential critical regulatory role of MYC, ERBB2, HNF4A, and SMAD3 for early HCC transformation.

CONCLUSIONS

The integrative analysis of transcriptional deregulation, genomic CNA and comparative cross species analysis brings new insights into the molecular profile of early hepatoma formation. This approach may lead to robust biomarkers for the detection of early human HCC.

The PI3K-Akt-mTOR pathway in initiation and progression of thyroid tumors

The phosphoinositide-3 (OH) kinase (PI3K) signaling cascade is involved in regulating glucose uptake and metabolism, growth, motility, and other essential functions for cell survival. Unregulated activation of this pathway commonly occurs in cancer through a variety of mechanisms, including genetic mutations of kinases and regulatory proteins, epigenetic alterations that alter gene expression and translation, and posttranslational modifications. In thyroid cancer, constitutive activation of PI3K signaling has been shown to play a role in the genetic predisposition for thyroid neoplasia in Cowden's syndrome, and is recognized to be frequently overactivated in sporadic forms of thyroid cancer including those with aggressive clinical behaviors. In this review, the key signaling molecules in the PI3K signaling cascade, the abnormalities known to occur in thyroid cancer, and the potential for therapeutic targeting of PI3K pathway members will be discussed.

Downregulation of microRNAs directs the EMT and invasive potential of anaplastic thyroid carcinomas

Anaplastic thyroid carcinomas (ATCs) arise from epithelial thyroid cells by mesenchymal de-/transdifferentiation and rapidly invade the adjacent tissue. Specific microRNA signatures were suggested to distinguish ATCs from normal thyroid tissue and other thyroid carcinomas of follicular origin. Whether distinct microRNA patterns correlate with de-/transdifferentiation and invasion of ATCs remained elusive. We identified two significantly decreased microRNA families that unambiguously distinguish ATCs from papillary and follicular thyroid carcinomas: miR-200 and miR-30. Expression of these microRNAs in mesenchymal ATC-derived cells reduced their invasive potential and induced mesenchymal-epithelial transition (MET) by regulating the expression of MET marker proteins. Supporting the role of transforming growth factor (TGF)beta signaling in modulating MET/epithelial-mesenchymal transition (EMT), expression of SMAD2 and TGFBR1, upregulated in most primary ATCs, was controlled by members of the miR-30 and/or miR-200 families in ATC-derived cells. Inhibition of TGFbeta receptor 1 (TGFBR1) in these cells induced MET and reduction of prometastatic miR-21, but caused an increase of the miR-200 family. These findings identify altered microRNA signatures as potent markers for ATCs that promote de-/transdifferentiation (EMT) and invasion of these neoplasias. Hence, TGFBR1 inhibition could have a significant potential for the treatment of ATCs and possibly other invasive tumors.

The evolution of biomarkers in thyroid cancer-from mass screening to a personalized biosignature

Thyroid cancer is the most common malignancy of the endocrine system. The diagnosis of thyroid nodules, made by neck examination and ultrasonography, is a common event occurring in over 50% of the patient population over the age of 50. Yet, only 5% of these patients will be diagnosed with cancer. Fine needle aspiration biopsy is the gold standard for diagnosing thyroid nodules. However, 10–15% of these biopsies are inconclusive, ultimately requiring a diagnostic thyroid lobectomy. Consequently, research in thyroid biomarkers has become an area of active interest. In the 40 years since calcitonin was first described as the biomarker for medullary thyroid cancer, new biomarkers in thyroid cancer have been discovered. Advances in genomic and proteomic technologies have defined many of these novel thyroid biomarkers. The purpose of this article is to provide a comprehensive literature review of how these biomarkers have evolved from simple screening tests into a complex array of multiple markers to help predict the malignant potential and genetic signature of thyroid neoplasms.

IGFBP7: an oncosuppressor gene in thyroid carcinogenesis

Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein involved in several cellular processes, including proliferation, senescence and apoptosis. Loss of IGFBP7 expression is a critical step in the development of human tumors, including melanoma and colon cancer. By microarray gene expression studies, we have detected downregulation of IGFBP7 gene expression in follicular and papillary thyroid tumors in comparison with normal thyroid tissue. Evaluation of publicly available PTC microarray gene expression data sets confirmed, in a consistent fraction of tumors, the downregulation of IGFBP7 transcript levels. The functional consequence of IGFBP7 downregulation was addressed in the PTC-derived NIM1 cell line in which IGFBP7 expression is repressed by promoter hypermethylation. Exposure to soluble IGFBP7 protein or restoration of IGFBP7 expression by complementary DNA transfection reduced growth rate, migration, anchorage-independent growth and tumorigenicity of NIM1 cells. We show that the effects of IGFBP7 are related to apoptosis. Our data suggest that loss of IGFBP7 expression has a functional role in thyroid carcinogenesis, and it may represent a possible basis for therapeutic strategies.

Dynamic changes in E-cadherin gene promoter methylation during metastatic progression in papillary thyroid cancer

Thyroid cancer cells undergo epithelial to mesenchymal transition (EMT) in the invasive front of tumor. To determine whether the mesenchymal feature of invasive cancer cells is maintained in metastatic sites, we examined E-cadherin methylation and E-cadherin expression in 66 papillary thyroid cancer (PTC) samples and in 34 corresponding lymph node metastases (LNM). Relationships between E-cadherin and cell motility were evaluated using thyroid cancer cell lines. Hypermethylation of the E-cadherin gene promoter was detected in 39.3% of the PTCs, and loss of E-cadherin expression correlated with lymphocytic infiltration, extrathyroidal invasion and the presence of metastases. Comparing primary PTCs to the corresponding LNM, E-cadherin methylation status was identical in 60% of the cases. The switch in E-cadherin promoter status from unmethylated in PTCs to hypermethylated in LNM was detected in 5%; and from hypermethylatated in PTCs to unmethylated in LNM in 35%. Loss of epigenetic silencing in LNM was associated with a gain of E-cadherin expression. Hypermethylation of the E-cadherin gene promoter was detected in thyroid cancer cell lines with mesenchymal-like morphology. Loss of E-cadherin expression in these cells correlated with high migratory ability. Inhibition of RAS/ERK or PI3K/AKT signaling decreased the migratory ability of these cells but did not induce E-cadherin expression. In the cells with epithelial-like morphology, treatments with phorbol-ester or tumor necrosis factor (TNF)-α resulted in translocation of membranous E-cadherin to the cytoplasm and induction of migration. E-cadherin promoter methylation status and E-cadherin expression were not affected by TNF. Demethylating agents induced apoptosis in the mesenchymal-like cells but had no effect on E-cadherin expression or on migratory ability. Together, dynamic changes in E-cadherin methylation occur during metastatic progression in thyroid cancer. Epigenetic mechanisms and TNF-inducible signaling independently contribute to the regulation of E-cadherin expression and localization. These mechanisms may play a role in the induction of EMT in primary tumors and in the conversion from the mesenchymal to the epithelial phenotype in metastases.

Tumor-associated lymphocytes and increased FoxP3+ regulatory T cell frequency correlate with more aggressive papillary thyroid cancer

CONTEXT

Ten to 30% of patients with papillary thyroid cancer (PTC) develop recurrent disease and may benefit from innovative adjuvant therapies. Immune-based therapies are under investigation to treat many types of cancer. The role of the immune system in PTC is poorly understood.

OBJECTIVE

We investigated whether tumor-associated lymphocytes (TAL), in the absence of background thyroiditis (LT), contribute to disease severity. We hypothesized that the type of lymphocytes associated with PTC would correlate with parameters of disease.

DESIGN

This retrospective study analyzed archived PTC samples for the presence of TAL and/or LT. A group of patients with TAL was evaluated for lymphocyte subsets by immunohistofluorescence.

PATIENTS AND SETTING

One hundred PTC patients were analyzed for LT and TAL, and 10 PTC patients with TAL were assessed for lymphocyte subsets at University of Colorado Hospital.

MAIN OUTCOME

We assessed correlations between disease and the presence of TAL, LT, and lymphocyte subset frequency.

RESULTS

Patients with TAL exhibited higher disease stage and increased incidence of invasion and lymph node metastasis compared with patients without lymphocytes or with LT. CD4(+) T cell frequency correlated with tumor size (r = 0.742; P = 0.017). FoxP3(+) regulatory T cell (Treg) frequency correlated with lymph node metastases (r = 0.858; P = 0.002), and CD8 to Treg ratio correlated inversely with tumor size (r = -0.804; P = 0.007).

CONCLUSIONS

TAL and high Treg frequency in primary thyroid tumors correlates with more aggressive disease. Future prospective studies may identify Treg frequency as a predictive factor in PTC, and the suppressive effects of Treg should be considered in the design of immune-based therapies.

Epithelial-mesenchymal transition in development and cancer

The epithelial-mesenchymal transition (EMT) is a critical developmental process from the earliest events of embryogenesis to later morphogenesis and organ formation. EMT contributes to the complex architecture of the embryo by permitting the progression of embryogenesis from a simple single-cell layer epithelium to a complex three-dimensional organism composed of both epithelial and mesenchymal cells. However, in most tissues EMT is a developmentally restricted process and fully differentiated epithelia typically maintain their epithelial phenotype. Recently, elements of EMT, specifically the loss of epithelial markers and the gain of mesenchymal markers, have been observed in pathological states, including epithelial cancers. Analysis of the molecular mechanisms of this oncogenic epithelial plasticity have implicated the inappropriate expression and activation of developmental EMT programs, suggesting that cancer cells may reinstitute properties of developmental EMT including enhanced migration and invasion. Thus, in the context of cancer, an EMT-like process may permit dissemination of tumor cells from the primary tumor into the surrounding stroma, setting the stage for metastatic spread. Consistent with this hypothesis, activation of these developmental EMT programs in human cancer correlates with advanced disease and poor prognosis. This review will focus on the current knowledge regarding developmental EMT pathways that have been implicated in cancer progression.

Tumor expression of integrin-linked kinase (ILK) correlates with the expression of the E-cadherin repressor snail: an immunohistochemical study in ductal pancreatic adenocarcinoma

Integrin-linked kinase (ILK) is a key molecule involved in mediating several biological functions including cell-matrix interactions, angiogenesis, and invasion, as well as playing a role in epithelial to mesenchymal transition (EMT) in cancer cells. In ductal pancreatic adenocarcinoma, increased expression of ILK has been linked to tumor prognosis and correlated with increased chemoresistance to drugs, such as gemcitabine. However, the precise relationship between ILK, Snail, E-cadherin, and N-cadherin expression on the stepwise development of pancreatic cancer is unknown. Hence, the purpose of this work was to investigate levels of expression of ILK, Snail, and the cadherins in pancreatic intraepithelial neoplasia (PanIN), and cancer. Resection specimens of 25 randomly selected patients, who underwent a pyloric preserving pancreatoduodenectomy for ductal pancreatic adenocarcinoma, were utilized for this study. Formalin-fixed paraffin embedded pancreatic tissue was immunostained for ILK, E-cadherin, N-cadherin, and Snail by standard techniques. The extent of staining positivity was scored and the results correlated with clinicopathological parameters. In 23 of 25 cases, ILK expression showed extensive positivity (>50%), while two cases did not demonstrate any ILK staining. PanIN grades 1 (n = 16), 2 (n = 11), and 3 (n = 19) lesions demonstrated only focal positivity (<10%) for ILK. E-cadherin showed a reciprocal staining pattern to ILK in 21 of 25 cases, with only focal expression of the marker in pancreatic adenocarcinoma. Interestingly, 15 of 19 PanIN-3 lesions expressed extensive E-cadherin staining. N-cadherin, however, was moderately expressed in the majority of cases (n = 18). Snail expression (n = 22) correlated with ILK expression in ductal pancreatic adenocarcinoma (rho = 0.8168, p = 0.02), but only minimal Snail staining activity was detected in PanIN lesions. The increase in expression of the E-cadherin repressor Snail, as well as the related increase in the ILK expression, may point towards an ILK-mediated induction, opening possible avenues for targeted drug therapy.

The BRAFV600E oncogene induces transforming growth factor beta secretion leading to sodium iodide symporter repression and increased malignancy in thyroid cancer

The activating mutation BRAF(V600E) is a frequent genetic event in papillary thyroid carcinomas (PTC) that predicts a poor prognosis, leading to loss of sodium/iodide symporter (NIS) expression and subsequent radioiodide-refractory metastatic disease. The molecular basis of such an aggressive behavior induced by BRAF remains unclear. Here, we show a mechanism through which BRAF induces NIS repression and promotes epithelial to mesenchimal transition and invasion based on the operation of an autocrine transforming growth factor (TGF)beta loop. BRAF induces secretion of functional TGFbeta and blocking TGFbeta/Smad signaling at multiple levels rescues BRAF-induced NIS repression. Although this mechanism is MAP/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK independent, secreted TGFbeta cooperates with MEK-ERK signaling in BRAF-induced cell migration, Matrigel invasion, and EMT. Consistent with this process, TGFbeta and other key components of TGFbeta signaling, such as TbetaRII and pSmad2, are overexpressed in human PTC, suggesting a widespread activation of this pathway by locally released TGFbeta. Moreover, this high TGFbeta/Smad activity is associated with PTC invasion, nodal metastasis, and BRAF status. Interestingly, TGFbeta is overexpressed in the invasive front, whereas NIS is preferentially expressed in the central regions of the tumors, suggesting that this negative correlation between TGFbeta and NIS occurs locally inside the tumor. Our study describes a novel mechanism of NIS repression in thyroid cancer and provides evidence that TGFbeta may play a key role in promoting radioiodide resistance and tumor invasion during PTC progression.

Molecular markers of aggressiveness of thyroid cancer

PURPOSE OF REVIEW

To review recent progress at defining molecular markers that predict the biological behavior of thyroid cancer.

RECENT FINDINGS

Thyroid cancer behavior is defined by the effects of the initiating oncogene as well as secondary events in tumor cells and the tumor microenvironment that are both genetic and epigenetic. Over the past several years, there has been intense focus on identifying molecular markers to better predict the aggressiveness of thyroid cancers and also to define therapeutic targets. The results of recent articles in this area of work are summarized with a focus of differentiated follicular-cell-derived forms of thyroid cancer.

SUMMARY

Clinical staging predicts tumor behavior in many cases, but does not allow true 'personalization' of initial therapy or identify potential therapeutic targets for patients with progressive disease that does not respond to standard therapies. Recent data point to several new opportunities to refine thyroid cancer treatment based on molecular information. Several highlighted articles have begun to apply this information with clinical intent.

Novel non-genomic signaling of thyroid hormone receptors in thyroid carcinogenesis

The thyroid hormone receptors (TRs) are transcription factors that mediate the pleiotropic activities of the thyroid hormone, T3. Four T3-binding isoforms, TRalpha1, TRbeta1, TRbeta2, and TRbeta3, are encoded by two genes, THRA and THRB. Mutations and altered expression of TRs have been reported in human cancers. A targeted germ-line mutation of the Thrbeta gene in the mouse leads to spontaneous development of follicular thyroid carcinoma (TRbeta(PV/PV) mouse). The TRbetaPV mutant has lost T3-binding activity and displays potent dominant negative activity. The striking phenotype of thyroid cancer exhibited by TRbeta(PV/PV) mice has recently led to the discovery of novel non-genomic actions of TRbetaPV that contribute to thyroid carcinogenesis. These actions involve direct physical interaction of TRbetaPV with cellular proteins, namely the regulatory subunit of the phosphatidylinositol 3-kinase (p85alpha), the pituitary tumor transforming gene (PTTG) and beta-catenin, that are critically involved in cell proliferation, motility, migration, and metastasis. Thus, a TRbeta mutant (TRbetaPV), via a novel mode of non-genomic action, acts as an oncogene in thyroid carcinogenesis.

Classification of follicular cell tumors of the thyroid gland: analysis involving Japanese patients from one institute

Prognostic analyses of thyroid carcinomas of follicular cell origin were carried out on patients treated at Kuma Hospital, Kobe, Japan. A new histopathological classification based on the prognostic evidence is proposed in this study, and it is applicable to the patients treated curatively. Major histological types of papillary carcinoma, follicular carcinoma and poorly differentiated carcinoma were combined into one single entity of follicular cell adenocarcinoma because (i) they have the same cell origin (follicular cell); (ii) clear-cut separation of papillary and follicular carcinoma is not always possible, and 10 year cause-specific survival was essentially similar when the patients were treated curatively; and (iii) poorly differentiated carcinoma usually has a background of either papillary or follicular carcinoma. This adenocarcinoma together with undifferentiated carcinoma was stratified into four prognostic groups using pure morphological criteria of the degree of cellular differentiation and histological grade. They are termed well-differentiated adenocarcinoma, moderately differentiated adenocarcinoma, poorly differentiated carcinoma and undifferentiated carcinoma of the thyroid. The 10 year disease-free survival rates were 86.3-93.1%, 65.4-78.7%, and 43.0-53.8%, and 0%, respectively. The 10 year cause-specific survival rates were 97.2-100%, 91.5-97.4%, and 71.2-80.0%, and 0%, respectively.

Role of transforming growth factor beta in the regulation of thyroid function and growth

Transforming growth factor beta (TGF-beta) exists in nature as three isoforms. They exert their effects by binding to a type II receptor located at the cell membrane. The TGF-beta-type II receptor complex then recruits type I receptor, and this new complex stimulates the phosphorylation of Smads 2 and 3, which are subsequently transferred to the nucleus, where they regulate gene transcription. The thyroid gland expresses the TGF-beta1 gene mRNA and synthesizes the protein, which under physiologic conditions regulates thyroid growth and function. Different studies have demonstrated that TGF-beta1 inhibits cell proliferation and a number of functional parameters. These include cyclic adenosine monophosphate (AMP) formation, iodine uptake and organification, hormone secretion, and the expression of thyroglobulin, thyroid peroxidase, and Na(+)/I(-) symporter. The expression of the TGF-beta1 gene and protein may be stimulated by iodine under normal conditions. Since TGF-beta1 mimics some of the inhibitory actions of iodine, its participation in thyroid autoregulation has been proposed; however, this concept is still debated. In thyroid tumors, the inhibitory action of TGF-beta1 on cell proliferation is progressively lost as the tumor becomes more undifferentiated. The alterations in the signaling pathway of TGF-beta1 are not the same in tumors from different species. Even within the same species, such as the pig thyroid, the results may be different depending on whether monolayers or follicular suspensions are employed. The data suggest that it is not entirely possible to apply the results obtained in animal studies to normal or pathological human thyroid tissue. More studies are required to provide the information needed to develop treatments, based on targeting the signaling pathway of TGF-beta1, for undifferentiated thyroid cancer and other thyroid diseases.

Transcript level modulates the inherent oncogenicity of RET/PTC oncoproteins

Mutations to the RET proto-oncogene occur in as many as one in three cases of thyroid cancer and have been detected in both the medullary (MTC) and the papillary (PTC) forms of the disease. Of the nearly 400 chromosomal rearrangements resulting in oncogenic fusion proteins that have been identified to date, the rearrangements that give rise to RET fusion oncogenes in PTC remain the paradigm for chimeric oncoprotein involvement in solid tumors. RET-associated PTC tumors are phenotypically indolent and relatively less aggressive than RET-related MTCs. The mechanism(s) contributing to the differences in oncogenicity of RET-related MTC and PTC remains unexplained. Here, through cellular and molecular characterization of the two most common RET/PTC rearrangements (PTC1 and PTC3), we show that RET/PTC oncoproteins are highly oncogenic when overexpressed, with the ability to increase cell proliferation and transformation. Further, RET/PTCs activate similar downstream signaling cascades to wild-type RET, although at different levels, and are relatively more stable as they avoid lysosomal degradation. Absolute quantitation of transcript levels of RET, CCDC6, and NCOA4 (the 5' fusion genes involved in PTC1 and PTC3, respectively) suggest that these rearrangements result in lower RET expression in PTCs relative to MTCs. Together, our findings suggest PTC1 and PTC3 are highly oncogenic proteins when overexpressed, but result in indolent disease compared with RET-related MTCs due to their relatively low expression from the NCOA4 and CCDC6 promoters in vivo.

Size-dependent regulation of Snail2 by hyaluronan: its role in cellular invasion

Hyaluronan (HA) induces changes in cellular behavior that are crucial during both embryonic development and cancer progression. However, the biological effects of varying sizes of HA and the signal transduction mechanisms that these polymers may activate remain unclear. In this study, we demonstrate that pulse stimulation of mouse embryonic fibroblasts with high-molecular-weight (HMW) HA, but not HA of lower molecular sizes, leads to increases in Snail2 protein which are dependent on NFkappaB activity. Involvement of CD44, the main HA receptor, in these responses was determined by use of a CD44 blocking antibody and CD44 siRNA. Both the blockade and silencing of CD44 significantly abrogate the increases in nuclear factor kappaB (NFkappaB) activity and Snail2 protein following HMW-HA stimulation. Furthermore, we show that HMW-HA induces cellular invasion and that inhibition of CD44, Snail2, or NFkappaB significantly decreases this response. These studies elucidate a novel HA/Snail2 functional connection through CD44 and NFkappaB that is important for the induction of cellular invasion and is dependent on HA size.

GABA receptor expression in benign and malignant thyroid tumors

Neurotransmitter systems have recently been shown to be involved in multiple malignancies including breast, colon and prostate cancers. The role of neurotransmitters and neurotrophic factors has not yet been examined in thyroid cancer. To determine the possible involvement of neurotransmitter systems in thyroid carcinogenesis we characterized the patterns of gamma-aminobutyric acid (GABA) receptor expression in normal thyroid and thyroid tumors. We examined the expression patterns of the GABAergic system in 70 human thyroid tumor samples (13 follicular adenomas, 14 follicular carcinomas, 43 papillary carcinomas) and adjacent normal thyroid by immunohistochemistry. GABAergic system mRNA expression in thyroid cancer cell lines derived from primary (FTC133) and metastatic tumors (FTC236 and FTC238) was examined by real time PCR. Overall, GABA receptor expression is increased in tumors compared to normal thyroid tissue. Expression of GABAA receptor beta2 was detected in the vasculature of normal thyroid and thyroid tumors but not in thyroid cancer cells. GABAA alpha2 was detected in metastatic-derived but not in primary-tumor derived cell lines. Expression levels of GABAB R2 and GABA receptor associated protein (GABARAP) are increased in adenomas and thyroid cancer suggesting their role in early stages of thyroid tumorigenesis. This study represents the first demonstration of GABA receptor expression in human thyroid tissue and suggests that the GABAergic system is involved in thyroid carcinogenesis.

Loss of cellular polarity/cohesiveness in the invasive front of papillary thyroid carcinoma and periostin expression

Loss of cellular polarity/cohesiveness and periostin expression are involved in the epithelial-mesenchymal transition in the epithelial malignancies. Their roles in papillary thyroid carcinoma were studied. There was a significant correlation between the loss of cellular polarity/cohesiveness in the invasive front and the up-regulation of periostin in tumors. Both of them were significantly correlated with extrathyroid invasion, pT and lymph node metastasis. Our results suggest that the loss of cellular polarity/cohesiveness is a useful parameter for predicting prognosis of patients with papillary thyroid carcinoma, and periostin could be a candidate gene for therapeutic targeting for the blockage of tumor invasion.

Prognostic significance of epithelial-mesenchymal and mesenchymal-epithelial transition protein expression in non-small cell lung cancer

PURPOSE

In carcinomas, invasive tumor growth is accompanied by desmoplastic stroma reaction and facilitated by epithelial-mesenchymal transition (EMT) of cancer cells. We investigated the prognostic significance of the EMT indicator proteins periostin and vimentin in comparison with versican, a putative indicator of the opposite mechanism mesenchymal-epithelial transition (MET), and to the desmoplasia proteins collagen and elastin in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Tumor of 533 patients with surgically resected NSCLC was used for analysis of stromal and epithelial protein expression by immunohistochemistry (EMT-MET proteins) and Elastica van Gieson histochemical staining (collagen and elastin). A semiquantitative sum scoring system was done on three tissue microarrays.

RESULTS

Of the 533 patients, 48% had squamous cell carcinoma, 47% adenocarcinoma, and 5% adenosquamous carcinoma. High expression of periostin in either stroma or tumor epithelia, independently scored by two pathologists, correlated with male gender, higher stage, higher pT category, and larger tumor size, and in only stroma with tumor relapse. High expression of versican in either stroma or epithelia as well as of stromal collagen had fewer but concordant associations with advanced tumor and periostin, respectively. High expression of elastin was oppositely associated with less advanced disease. Associations of high vimentin were inconsistent (all P values < 0.05). High stromal periostin was found to be a prognostic factor for decreased progression-free survival on univariate analysis (P = 0.007).

CONCLUSIONS

Because up-regulation is frequently observed in the stromal and epithelial tumor compartment, EMT-MET indicator proteins may be integrated in progression models of NSCLC.

Possible involvement of BRAFV600E in altered gene expression in papillary thyroid cancer

Somatic mutations in BRAF, especially BRAFV600E, are frequently identified in papillary thyroid cancer (PTC) tumors. It has been established that expression levels of numbers of genes are characteristically altered in PTC, however, the link between BRAF mutation and gene expression patterns are still elusive. In the present study, we analyzed relative expression levels of the wild type BRAF and BRAFV600E mRNA by using quantitative PCR (qPCR) and cDNAPCR- RFLP in 19 PTC specimens and adjacent normal thyroid tissues. BRAFV600E mRNA was detected in 17 out of 19 PTC specimens, and the expression levels were valuable among the specimens, suggesting alternative expression of BRAFV600E in each cell and/or alternative population of BRAFV600E-positive clones in the tumor. We then analyzed expression levels of 20 genes by qPCR, and analyzed for possible correlation with expression levels of BRAFV600E mRNA. Expression levels of fibronectin, vimentin and CITED1 (Cbp/p300 interacting protein with glutamic acid and aspartic acid rich carboxyl terminal domain) were positively correlated with those of BRAFV600E, suggesting pathophysiological links between activated BRAF and overexpression of these genes. Among these genes expression of vimentin was decreased by inhibiting BRAF expression in NPA cells that express BRAFV600E by means of siRNA, suggesting activated BRAF positively regulate expression of vimentin. Collectively, our analyses illustrated the possibilities that variable expression of BRAFV600E may modify characters of PTC through its effects on gene expression.

Molecular and pathological signatures of epithelial-mesenchymal transitions at the cancer invasion front

Reduction of epithelial cell-cell adhesion via the transcriptional repression of cadherins in combination with the acquisition of mesenchymal properties are key determinants of epithelial-mesenchymal transition (EMT). EMT is associated with early stages of carcinogenesis, cancer invasion and recurrence. Furthermore, the tumor stroma dictates EMT through intensive bidirectional communication. The pathological analysis of EMT signatures is critically, especially to determine the presence of cancer cells at the resection margins of a tumor. When diffusion barriers disappear, EMT markers may be detected in sera from cancer patients. The detection of EMT signatures is not only important for diagnosis but can also be exploited to enhance classical chemotherapy treatments. In conclusion, further detailed understanding of the contextual cues and molecular mediators that control EMT will be required in order to develop diagnostic tools and small molecule inhibitors with potential clinical implications.

Vimentin filaments support extension of tubulin-based microtentacles in detached breast tumor cells

Solid tumor metastasis often involves detachment of epithelial carcinoma cells into the vasculature or lymphatics. However, most studies of cytoskeletal rearrangement in solid tumors focus on attached cells. In this study, we report for the first time that human breast tumor cells produce unique tubulin-based protrusions when detached from extracellular matrix. Tumor cell lines of high metastatic potential show significantly increased extension and frequency of microtubule protrusions, which we have termed tubulin microtentacles. Our previous studies in nontumorigenic mammary epithelial cells showed that such detachment-induced microtentacles are enriched in detyrosinated alpha-tubulin. However, amounts of detyrosinated tubulin were similar in breast tumor cell lines despite varying microtentacle levels. Because detyrosinated alpha-tubulin associates strongly with intermediate filament proteins, we examined the contribution of cytokeratin and vimentin filaments to tumor cell microtentacles. Increased microtentacle frequency and extension correlated strongly with loss of cytokeratin expression and up-regulation of vimentin, as is often observed during tumor progression. Moreover, vimentin filaments coaligned with microtentacles, whereas cytokeratin did not. Disruption of vimentin with PP1/PP2A-specific inhibitors significantly reduced microtentacles and inhibited cell reattachment to extracellular matrix. Furthermore, expression of a dominant-negative vimentin mutant disrupted endogenous vimentin filaments and significantly reduced microtentacles, providing specific genetic evidence that vimentin supports microtentacles. Our results define a novel model in which coordination of vimentin and detyrosinated microtubules provides structural support for the extensive microtentacles observed in detached tumor cells and a possible mechanism to promote successful metastatic spread.

Targeted deletion of Prkar1a reveals a role for protein kinase A in mesenchymal-to-epithelial transition

Dysregulation of protein kinase A (PKA) activity, caused by loss of function mutations in PRKAR1A, is known to induce tumor formation in the inherited tumor syndrome Carney complex (CNC) and is also associated with sporadic tumors of the thyroid and adrenal. We have previously shown that Prkar1a(+/-) mice develop schwannomas reminiscent of those seen in CNC and that similar tumors are observed in tissue-specific knockouts (KO) of Prkar1a targeted to the neural crest. Within these tumors, we have previously described the presence of epithelial islands, although the nature of these structures was unclear. In this article, we report that these epithelial structures are derived from KO cells originating in the neural crest. Analysis of the mesenchymal marker vimentin revealed that this protein was markedly down-regulated not only from the epithelial islands, but also from the tumor as a whole, consistent with mesenchymal-to-epithelial transition (MET). In vitro, Prkar1a null primary mouse embryonic fibroblasts, which display constitutive PKA signaling, also showed evidence for MET, with a loss of vimentin and up-regulation of the epithelial marker E-cadherin. Reduction of vimentin protein occurred at the posttranslational level and was rescued by proteasomal inhibition. Finally, this down-regulation of vimentin was recapitulated in the adrenal nodules of CNC patients, confirming an unexpected and previously unrecognized role for PKA in MET.

Genome-wide studies in thyroid neoplasia

There is much interest in the application of genome biology to the field of thyroid neoplasia, despite the relatively low mortality rate associated with thyroid cancer in general. The principal reason for this interest is that the field of thyroid neoplasia stands to benefit from the application of genomic information to address a variety of pathologic and clinical issues. In addition to practical patient care issues, there is an excellent opportunity of expand the basic understanding of thyroid carcinogenesis. In this article, the most relevant genomic work on thyroid tumors performed to date is reviewed along with some general comments about the potential impact of genomic biology on thyroid pathology and the management of patients with thyroid nodules and cancer.

Epithelial mesenchymal transition traits in human breast cancer cell lines

Epithelial mesenchymal transition (EMT) has long been associated with breast cancer cell invasiveness and evidence of EMT processes in clinical samples is growing rapidly. Genome-wide transcriptional profiling of increasingly larger numbers of human breast cancer (HBC) cell lines have confirmed the existence of a subgroup of cell lines (termed Basal B/Mesenchymal) with enhanced invasive properties and a predominantly mesenchymal gene expression signature, distinct from subgroups with predominantly luminal (termed Luminal) or mixed basal/luminal (termed Basal A) features (Neve et al Cancer Cell 2006). Studies providing molecular and cellular analyses of EMT features in these cell lines are summarised, and the expression levels of EMT-associated factors in these cell lines are analysed. Recent clinical studies supporting the presence of EMT-like changes in vivo are summarised. Human breast cancer cell lines with mesenchymal properties continue to hold out the promise of directing us towards key mechanisms at play in the metastatic dissemination of breast cancer.

Idiopathic pulmonary fibrosis: aberrant recapitulation of developmental programs?

The authors discuss evidence suggesting that embryonic signaling pathways involved in epithelium/mesenchymal communication and epithelial cell plasticity may be aberrantly switched on in idiopathic pulmonary fibrosis.

Modulation of NFkappaB activity and E-cadherin by the type III transforming growth factor beta receptor regulates cell growth and motility

Transforming growth factor beta is growth-inhibitory in non-transformed epithelial cells but becomes growth-promoting during tumorigenesis. The role of the type I and II receptors in tumorigenesis has been extensively studied, but the role of the ubiquitously expressed type III receptor (TbetaRIII) remains elusive. We developed short hairpin RNAs directed against TbetaRIII to investigate the role of this receptor in breast cancer tumorigenesis. Nontumorigenic NMuMG mouse cells stably expressing short hairpin RNA specific to mouse TbetaRIII (NM-kd) demonstrated increased cell growth, motility, and invasion as compared with control cells expressing shRNA to human TbetaRIII (NM-con). Reconstitution of TbetaRIII expression with rat TbetaRIII abrogated the increased growth and motility seen in the NM-kd cells. In addition, the NM-kd cells exhibited marked reduction in the expression of the adherens junction protein, E-cadherin. This loss of E-cadherin was due to increased NFkappaB activity that, in turn, resulted in increased expression of the transcriptional repressors of E-cadherin such as Snail, Slug, Twist, and Sip1. Finally, NMuMG cells in which TbetaRIII had been knocked down formed invasive tumors in athymic nude mice, whereas the control cells did not. These data indicate that TbetaRIII acts as a tumor suppressor in nontumorigenic mammary epithelial cells at least in part by inhibiting NFkappaB-mediated repression of E-cadherin.

An immune escape screen reveals Cdc42 as regulator of cancer susceptibility to lymphocyte-mediated tumor suppression

Adoptive cellular immunotherapy inducing a graft-versus-tumor (GVT) effect is the therapeutic mainstay of allogeneic hematopoietic stem cell transplantation (ASCT) for high-risk leukemias. Autologous immunotherapies using vaccines or adoptive transfer of ex vivo-manipulated lymphocytes are clinically explored in patients with various cancer entities. Main reason for failure of ASCT and cancer immunotherapy is progression of the underlying malignancy, which is more prevalent in patients with advanced disease. Elucidating the molecular mechanisms contributing to immune escape will help to develop strategies for the improvement of immunologic cancer treatment. To this end, we have undertaken functional screening and expression cloning of factors mediating resistance to antigen-specific cytotoxic T lymphocytes (CTLs). We have identified Cdc42, a GTPase regulating actin dynamics and growth factor signaling that is highly expressed in invasive cancers, as determinator of cancer cell susceptibility to antigen-specific CTLs in vitro and adoptively transferred immune effectors in vivo. Cdc42 prevents CTL-induced apoptosis via mitogen-activated protein kinase (MAPK) signaling and posttranscriptional stabilization of Bcl-2. Pharmacologic inhibition of MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) overcomes Cdc42-mediated immunoresistance and activation of Bcl-2 in vivo. In conclusion, Cdc42 signaling contributes to immune escape of cancer. Targeting Cdc42 may improve the efficacy of cancer immunotherapies.

Epithelial-mesenchymal transition (EMT) and activated extracellular signal-regulated kinase (p-Erk) in surgically resected pancreatic cancer

BACKGROUND

EMT or transformation to the mesenchymal phenotype plays an important role in tumor invasion and metastasis. In vitro data suggest that mesenchymal transformation may correlate with the activation of PI3 kinase and Ras/Erk pathways. We investigated the expression of EMT markers (low E-cadherin, high fibronectin, and vimentin) and their association with p-Erk in resected pancreatic cancer.

METHODS

Clinical data/surgical specimens from 34 consecutive pancreatic cancer patients (pts) who underwent pancreatectomy were included. Immunohistochemical staining was performed on formalin-fixed paraffin-embedded tissues using monoclonal antibodies against vimentin, fibronectin, E-cadherin, and p-Erk. The results were correlated with clinicopathological parameters and survival. Survival analysis (log-rank test, Cox proportional hazard model), categorical data analysis (Pearson's chi-square, Fisher's exact test) and Kendall's tau were performed at a significance level of 0.05.

RESULTS

The patient population was formed from 13 males and 21 females, with a median age of 66 years (range 38-84 years); American Joint Committee on Cancer (AJCC) stage 1 (n = 2), 2 (n = 27), 3 (n = 5); histological grade 1 (n = 4), 2 (n = 13), 3 (n = 16), 4 (n = 1). Median survival was 15 months (95% CI: 11-24 months). Fibronectin overexpression correlated with the presence of vimentin (p = 0.0048) and activated Erk (p = 0.0264). There was a borderline association of fibronectin with worsening grade (p = 0.06). A negative association between vimentin and E-cadherin was noted (p = 0.0024). Increased fibronectin or vimentin and decreased E-cadherin correlated with poor survival.

CONCLUSION

EMT is associated with poor survival in surgically resected pancreatic adenocarcinoma. A correlation between activated Erk and fibronectin was identified that may open avenues for targeted therapy for this subgroup.

Molecular profiling related to poor prognosis in thyroid carcinoma. Combining gene expression data and biological information

Undifferentiated and poorly differentiated thyroid tumors are responsible for more than half of thyroid cancer patient deaths in spite of their low incidence. Conventional treatments do not obtain substantial benefits, and the lack of alternative approaches limits patient survival. Additionally, the absence of prognostic markers for well-differentiated tumors complicates patient-specific treatments and favors the progression of recurrent forms. In order to recognize the molecular basis involved in tumor dedifferentiation and identify potential markers for thyroid cancer prognosis prediction, we analysed the expression profile of 44 thyroid primary tumors with different degrees of dedifferentiation and aggressiveness using cDNA microarrays. Transcriptome comparison of dedifferentiated and well-differentiated thyroid tumors identified 1031 genes with >2-fold difference in absolute values and false discovery rate of <0.15. According to known molecular interaction and reaction networks, the products of these genes were mainly clustered in the MAPkinase signaling pathway, the TGF-beta signaling pathway, focal adhesion and cell motility, activation of actin polymerization and cell cycle. An exhaustive search in several databases allowed us to identify various members of the matrix metalloproteinase, melanoma antigen A and collagen gene families within the upregulated gene set. We also identified a prognosis classifier comprising just 30 transcripts with an overall accuracy of 95%. These findings may clarify the molecular mechanisms involved in thyroid tumor dedifferentiation and provide a potential prognosis predictor as well as targets for new therapies.

Poly(ADP-ribose) polymerase-1 regulates vimentin expression in lung cancer cells

Vimentin is one of the mammalian intermediate filament proteins. It is expressed in cells of mesenchymal origin and is characteristic of proliferating cells at the fetal stage. During malignancy, vimentin expression is activated in certain lung epithelial cells. Examination of a group of lung cancer cells showed a marked difference in their vimentin expression. The difference in vimentin expression among lung cancer cells is due to differential regulation at the transcriptional level. Analysis of the vimentin promoter revealed a 102-bp promoter sequence that is important for promoter activity in a lung cancer cell line in which vimentin is strongly expressed. This promoter region interacts with poly(ADP-ribose) polymerase-1 (PARP-1), which is also a transcription regulator. Exogenous expression of PARP-1 increased vimentin promoter activity. A shortened PARP-1 without the COOH-terminal catalytic domain showed the same promoter activation effect. Treatment of cells with H(2)O(2) reduced PARP-1 and vimentin expression at the protein level. H(2)O(2) also dose dependently suppressed vimentin promoter activity in cells overexpressing PARP-1. These results demonstrate that vimentin expression in lung cancer cells is regulated at the transcriptional level and that PARP-1 binds and activates the vimentin promoter independent of its catalytic domain and may play a role in H(2)O(2)-induced inhibition of vimentin expression.