Establishment and biological characterization of an in vitro human cytomegalovirus latency model

DLK1-DIO3 region as a source of tumor suppressor miRNAs in papillary thyroid carcinoma

BACKGROUND

In previous studies, we demonstrated the downregulation of several miRNAs from the DLK1-DIO3 genomic region in papillary thyroid carcinoma (PTC). Due to the large number of miRNAs within this region, the individual contribution of these molecules to PTC development and progression remains unclear.

OBJECTIVE

In this study, we aimed to clarify the contribution of DLK1-DIO3-derived miRNAs to PTC.

METHODS

We used different computational approaches and in vitro resources to assess the biological processes and signaling pathways potentially modulated by these miRNAs.

RESULTS

Our analysis suggests that, out of more than 100 mature miRNAs originated from the DLK1-DIO3 region, a set of 12 miRNAs accounts for most of the impact on PTC development and progression, cooperating to modulate distinct cancer-relevant biological processes, such as cell migration, extracellular matrix remodeling, and signal transduction. The restoration of the expression of one of these miRNAs (miR-485-5p) in a BRAFT199A-positive PTC cell line impaired proliferation and migration, suppressing the expression of GAB2 and RAC1, validated miR-485-5p targets.

CONCLUSIONS

Overall, our results shed light on the role of the DLK1-DIO3 region, which harbors promising tumor suppressor miRNAs in thyroid cancer, and open prospects for the functional exploration of these miRNAs as therapeutic targets for PTC.

Relaxin-2 is a novel biomarker for differentiated thyroid carcinoma in humans

Relaxin's role in differentiated thyroid cancer (DTC) has been suggested but its characterization in a large clinical sample remains limited. We performed immunohistochemistry for relaxin-2 (RLN2), CD68 (total macrophages), CD163 (M2 macrophages) on tissue microarrays from 181 subjects with non-distant metastatic DTC, and 185 subjects with benign thyroid tissue. Mean pixels/area for each marker was compared between tumor and adjacent tissue via paired-t test and between DTC and benign subjects via t-test assuming unequal variances. RNA qPCR was performed for expression of RLN2, RLN1, and RXFP1 in cell lines. Amongst 181 cases, the mean age was 46 years, 75 % were females. Tumoral tissue amongst the DTC cases demonstrated higher mean expression of RLN2 (53.04 vs. 9.79; p < 0.0001) compared to tumor-adjacent tissue. DTC tissue also demonstrated higher mean expression of CD68 (14.46 vs. 4.79; p < 0.0001), and CD163 (23.13 vs. -0.73; p < 0.0001) than benign thyroid. These markers did not differ between tumor-adjacent and benign thyroid tissue groups; and amongst cases, did not differ by demographic or clinicopathologic features. RLN1 and RXFP1 expression was detected in a minority of the cell lines, while RLN2 was expressed by 6/7 cell lines. In conclusion, widespread RLN2 expression in DTC tissue and most cell lines demonstrates that RLN2 acts in a paracrine manner, and that RLN1 and RXFP1 are probably not involved in thyroid cancer cell signaling. RLN2 is a biomarker for thyroid carcinogenesis, being associated with but not secreted by immunosuppressive macrophages. These findings will guide further investigations for therapeutic avenues against thyroid cancer.

miR-210 Expression Is Strongly Hypoxia-Induced in Anaplastic Thyroid Cancer Cell Lines and Is Associated with Extracellular Vesicles and Argonaute-2

Hypoxia, or low oxygen tension, is frequently found in highly proliferative solid tumors such as anaplastic thyroid carcinoma (ATC) and is believed to promote resistance to chemotherapy and radiation. Identifying hypoxic cells for targeted therapy may thus be an effective approach to treating aggressive cancers. Here, we explore the potential of the well-known hypoxia-responsive microRNA (miRNA) miR-210-3p as a cellular and extracellular biological marker of hypoxia. We compare miRNA expression across several ATC and papillary thyroid cancer (PTC) cell lines. In the ATC cell line SW1736, miR-210-3p expression levels indicate hypoxia during exposure to low oxygen conditions (2% O2). Furthermore, when released by SW1736 cells into the extracellular space, miR-210-3p is associated with RNA carriers such as extracellular vesicles (EVs) and Argonaute-2 (AGO2), making it a potential extracellular marker for hypoxia.

Characterization of Allele-Specific Regulation of Telomerase Reverse Transcriptase in Promoter Mutant Thyroid Cancer Cell Lines

Background: Telomerase reverse transcriptase (TERT) promoter mutations play a role in carcinogenesis and are found in both tumors and cancer cell lines. TERT promoter methylation, transcription factor binding, chromatin remodeling, and alternative splicing are also known to play an integral role in TERT regulation. Methods: Using nanopore Cas9 targeted sequencing, we characterized allele-specific methylation in thyroid cancer cell lines heterozygous for the TERT promoter mutation. Furthermore, using chromatin immunoprecipitation followed by Sanger sequencing, we probed allele-specific binding of the transcription factors GABPA (GA binding protein transcription factor subunit alpha) and MYC, as well as the chromatin marks H3K4me3 and H3K27me3. Finally, using coding single nucleotide polymorphisms and the long-read sequencing, we examined complementary DNA for monoallelic expression (MAE). Results: We found the mutant TERT promoter allele to be significantly less methylated than wild type, while more methylated in the gene body in heterozygous TERT mutant cell lines. We demonstrated that the transcriptional activators GABPA and MYC bind only to the mutant TERT allele. In addition, the activating and repressive chromatin marks H3K4me3 and H3K27me3, respectively, bind mutant and wild-type alleles exclusively. Finally, in heterozygous mutant cell lines, TERT exhibits MAE from the mutant allele only. Conclusions: In summary, by employing new long-read sequencing methods, we were able to definitively demonstrate allele-specific DNA methylation, histone modifications, transcription factor binding, and the resulting monoallelic transcription in cell lines with heterozygous TERT mutations.

VEGFA and NFE2L2 Gene Expression and Regulation by MicroRNAs in Thyroid Papillary Cancer and Colloid Goiter

Deregulation of VEGFA (Vascular Endothelial Growth Factor A) and NFE2L2 (Nuclear Factor (Erythroid-derived 2)-Like 2), involved in angiogenesis and oxidative stress, can lead to thyroid cancer progression. MiR-17-5p and miR-612 are possible regulators of these genes and may promote thyroid disorders. In order to evaluate the involvement of VEGFA, NFE2L2, hsa-miR-17-5p, and hsa-miR-612 in thyroid pathology, we examined tissue samples from colloid goiter, papillary thyroid cancer (PTC), and a normal thyroid. We found higher levels of VEGFA and NFE2L2 transcripts and the VEGFA protein in goiter and PTC samples than in normal tissue. In the goiter, miR-612 and miR-17-5p levels were lower than those in PTC. Tumors, despite showing lower VEGFA mRNA expression, presented higher VEGFA protein levels compared to goiter tissue. In addition, NRF2 (Nuclear Related Transcription Factor 2) protein levels in tumors were higher than those in goiter and normal tissues. Inhibition of miR-17-5p resulted in reduced NFE2L2 expression. Overall, both transcript and protein levels of NFE2L2 and VEGFA were elevated in PTC and colloid goiter. Hsa-miR-612 showed differential expression in PTC and colloid goiter, while hsa-miR-17-5p showed differential expression only in colloid goiter, suggesting that hsa-miR-17-5p may be a positive regulator of NFE2L2 expression in PTC.

The Aryl Hydrocarbon Receptor Is Expressed in Thyroid Carcinoma and Appears to Mediate Epithelial-Mesenchymal-Transition

Aryl hydrocarbon receptor (AhR) is expected to promote initiation, progression and invasion of cancer cells regulating proliferation, differentiation, gene expression, inflammation, cell motility and migration. Furthermore, an immunosuppressant function of AhR has been recognized. This study evaluated AhR expression and its role in thyroid cancer progression. AhR expression was assessed by qPCR in 107 thyroid cancer samples (90 PTCs, 11 MTCs, 6 ATCs), and by immunohistochemistry in 41 PTCs. To estimate receptor activation, the expression of target genes CYP1A1 and CYP1B1 was measured. AhR functional effects were evaluated in kynurenine-stimulated FTC-133 and BcPap cell lines by analyzing the expression of genes involved in EMT and cell motility. AhR mRNA expression resulted significantly higher in all the analyzed thyroid cancer samples compared to normal thyroid and a statistically significant correlation with CYP1B1 was detected. Kynurenine-stimulated FTC-133 and BcPap showed the activation of a specific AhR-driven EMT program characterized by E-cadherin decrease and SLUG, N-cadherin and fibronectin increase, resulting in boost of cell motility and invasion. This study confirmed the importance of the IDO1-Kyn-AhR pathway in thyroid cancer tumorigenesis, suggesting an AhR pivotal role in mediating an immunosuppressive microenvironment and favoring the acquisition of a mesenchymal phenotype that could promote invasiveness and metastasis.

MAPK- and AKT-activated thyroid cancers are sensitive to group I PAK inhibition

The number of individuals who succumb to thyroid cancer has been increasing and those who are refractory to standard care have limited therapeutic options, highlighting the importance of developing new treatments for patients with aggressive forms of the disease. Mutational activation of MAPK signaling, through BRAF and RAS mutations and/or gene rearrangements, and activation of PI3K signaling, through mutational activation of PIK3CA or loss of PTEN, are well described in aggressive thyroid cancer. We previously reported overactivation and overexpression of p21-activated kinases (PAKs) in aggressive human thyroid cancer invasive fronts and determined that PAK1 functionally regulated thyroid cancer cell migration. We reported mechanistic crosstalk between the MAPK and PAK pathways that are BRAF-dependent but MEK independent, suggesting that PAK and MEK inhibition might be synergistic. In the present study, we tested this hypothesis. Pharmacologic inhibition of group I PAKs using two PAK kinase inhibitors, G-5555 or FRAX1036, reduced thyroid cancer cell viability, cell cycle progression and migration and invasion, with greater potency for G-5555. Combination of G-5555 with vemurafenib was synergistic in BRAFV600E-mutated thyroid cancer cell lines. Finally, G-5555 restrained thyroid size of BRAFV600E-driven murine papillary thyroid cancer by >50% (P < 0.0001) and reduced carcinoma formation (P = 0.0167), despite maintenance of MAPK activity. Taken together, these findings suggest both that group I PAKs may be a new therapeutic target for thyroid cancer and that PAK activation is functionally important for BRAFV600E-mediated thyroid cancer development.

Characterization of human telomerase reverse transcriptase promoter methylation and transcription factor binding in differentiated thyroid cancer cell lines

Telomerase reverse transcriptase (TERT) activation plays an important role in cancer development by enabling the immortalization of cells. TERT regulation is multifaceted, and its promoter methylation has been implicated in controlling expression through alteration in transcription factor binding. We have characterized TERT promoter methylation, transcription factor binding, and TERT expression levels in five differentiated thyroid cancer (DTC) cell lines and six normal thyroid tissue samples by targeted bisulfite sequencing, ChIP-qPCR, and qRT-PCR. DTC cell lines express varying levels of TERT and exhibit TERT promoter methylation patterns similar to patterns seen in other telomerase positive cancer cell lines. The minimal promoter immediately surrounding the transcription start site is hypomethylated, while further upstream portions show dense methylation. In contrast, the TERT promoter in normal thyroid tissue is largely unmethylated throughout and expresses TERT minimally. Transcription factor binding is also affected by TERT mutation status. The E-twenty-six (ETS) factor GABPA exhibits TERT binding in the TERT mutant DTC cells only, and allele-specific methylation patterns at the minimal promoter were observed as well, which may indicate allele-specific factor recruitment at the minimal promoter. Furthermore, we identified binding sites for activators MYC and GSC in the hypermethylated upstream region, pointing to its possible importance in TERT regulation. Overall, TERT expression and telomerase activity depend on the interplay of multiple regulatory mechanisms including TERT promoter methylation, mutation status, and recruitment of transcription factors. This work explores of the interplay between these regulatory mechanisms and offers insight into cellular control of active telomerase in human cancer.

Podoplanin (PDPN) affects the invasiveness of thyroid carcinoma cells by inducing ezrin, radixin and moesin (E/R/M) phosphorylation in association with matrix metalloproteinases

Background

Podoplanin (PDPN) is a mucin-type transmembrane glycoprotein specific to the lymphatic system. PDPN expression has been found in various human tumors and is considered to be a marker of cancer. We had previously shown that PDPN expression contributes to carcinogenesis in the TPC1 papillary thyroid cancer-derived cell line by enhancing cell migration and invasiveness. The aim of this study was to determine the effect of PDPN down-regulation in another thyroid cancer-derived cell line: BcPAP.

Methods

In order to determine the effects of PDPN on malignant features of BcPAP cells (harboring the BRAFV600E mutated allele) and TPC1 cells (carrying the RET/PTC1 rearrangement), we silenced PDPN in these cells using small interfering RNA (siRNA). The efficacy of PDPN silencing was confirmed by qRT-PCR and Western blotting. Then, we tested the motility and invasiveness of these cells (using scratch test and Transwell assay), their growth capacities F(cell cycle analysis, viability, clonogenic activity) and apoptosis assays), adhesion-independent colony-formation capacities, as well as the effect of PDPN silencing on MMPs expression and activity (zymography).

Results

We found that PDPN-induced cell phenotype depended on the genetic background of thyroid tumor cells. PDPN down-regulation in BcPAP cells was negatively correlated with the migration and invasion, in contrast to TPC1 cells in which PDPN depletion resulted in enhanced migration and invasiveness. Moreover, our results suggest that in BcPAP cells, PDPN may be involved in the epithelial-mesenchymal transition (EMT) through regulating the expression of the ezrin, radixin and moesin (E/R/M) proteins, MMPs 9 and MMP2, remodeling of actin cytoskeleton and cellular protrusions. We also demonstrated that PDPN expression is associated with the MAPK signaling pathway. The inhibition of the MAPK pathway resulted in a decreased PDPN expression, increased E/R/M phosphorylation and reduced cell migration. Additionally, PDPN depleted BcPAP cells treated with inhibitors of MEK1/2 kinases (U0126) or of the BRAF V600E protein (PLX4720) had reduced motility, similar to that previously observed in TPC1 cells after PDPN knock-down.

Conclusions

Altogether, our data suggest that PDPN may play an important role in the control of invasion and migration of papillary thyroid carcinoma cells in association with the E/R/M, MMPs and MAPK kinases.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5239-z) contains supplementary material, which is available to authorized users.

Methodology, Criteria, and Characterization of Patient-Matched Thyroid Cell Lines and Patient-Derived Tumor Xenografts

OBJECTIVE

To investigate the molecular underpinnings of thyroid cancer, preclinical cell line models are crucial; however, ∼40% of these have been proven to be either duplicates of existing thyroid lines or even nonthyroid-derived lines or are not derived from humans at all. Therefore, we set out to establish procedures and guidelines that should proactively avoid these problems, which facilitated the creation of criteria to make valid preclinical models for thyroid cancer research.

DESIGN

Based on our recommendations, we systematically characterized all new cell lines that we generated by a standardized approach that included (1) determination of human origin, (2) exclusion of lymphoma, (3) DNA fingerprinting and histological comparisons to establish linkage to presumed tissue of origin, (4) examining thyroid differentiation by screening two to three thyroid markers, (5) examination of biological behavior (growth rate, tumorigenicity), and (6) presence of common thyroid cancer genetic changes (TP53, BRAF, PTEN, PIK3CA, RAS, TERT promoter, RET/PTC, PAX8/PPARγ, NF1, and EIF1AX).

RESULTS

We established seven new thyroid cell lines (LAM136, EAM306, SDAR1, SDAR2, JEM493, THJ529, and THJ560) out of 294 primary culture attempts, and 10 patient-derived tumor xenografts (PDTXs; MC-Th-95, MC-Th-374, MC-Th-467, MC-Th-491, MC-Th-493, MC-Th-504, MC-Th-524, MC-Th-529, MC-Th-560, and MC-Th-562) out of 67 attempts. All were successfully validated by our protocols.

CONCLUSIONS

This standardized approach for cell line and PDTX characterization should prevent (or detect) future cross-contamination and ensure that only valid preclinical models are used for thyroid cancer research.

Extracellular ATP is Differentially Metabolized on Papillary Thyroid Carcinoma Cells Surface in Comparison to Normal Cells

The incidence of differentiated thyroid cancer has been increasing. Nevertheless, its molecular mechanisms are not well understood. In recent years, extracellular nucleotides and nucleosides have emerged as important modulators of tumor microenvironment. Extracellular ATP is mainly hydrolyzed by NTPDase1/CD39 and NTPDase2/CD39L1, generating AMP, which is hydrolyzed by ecto-5'-nucleotidase (CD73) to adenosine, a possible promoter of tumor growth and metastasis. There are no studies evaluating the expression and functionality of these ectonucleotidases on normal or tumor-derived thyroid cells. Thus, we investigated the ability of thyroid cancer cells to hydrolyze extracellular ATP generating adenosine, and the expression of ecto-enzymes, as compared to normal cells. We found that normal thyroid derived cells presented a higher ability to hydrolyze ATP and higher mRNA levels for ENTDP1-2, when compared to papillary thyroid carcinoma (PTC) derived cells, which had a higher ability to hydrolyze AMP and expressed CD73 mRNA and protein at higher levels. In addition, adenosine induced an increase in proliferation and migration in PTC derived cells, whose effect was blocked by APCP, a non-hydrolysable ADP analogue, which is an inhibitor of CD73. Taken together, these results showed that thyroid follicular cells have a functional purinergic signaling. The higher expression of CD73 in PTC derived cells might favor the accumulation of extracellular adenosine in the tumor microenvironment, which could promote tumor progression. Therefore, as already shown for other tumors, the purinergic signaling should be considered a potential target for thyroid cancer management and treatment.

RUNX2 expression in thyroid and breast cancer requires the cooperation of three non-redundant enhancers under the control of BRD4 and c-JUN

Aberrant reactivation of embryonic pathways is a common feature of cancer. RUNX2 is a transcription factor crucial during embryogenesis that is aberrantly reactivated in many tumors, including thyroid and breast cancer, where it promotes aggressiveness and metastatic spreading. Currently, the mechanisms driving RUNX2 expression in cancer are still largely unknown. Here we showed that RUNX2 transcription in thyroid and breast cancer requires the cooperation of three distantly located enhancers (ENHs) brought together by chromatin three-dimensional looping. We showed that BRD4 controls RUNX2 by binding to the newly identified ENHs and we demonstrated that the anti-proliferative effects of bromodomain inhibitors (BETi) is associated with RUNX2 transcriptional repression. We demonstrated that each RUNX2 ENH is potentially controlled by a distinct set of TFs and we identified c-JUN as the principal pivot of this regulatory platform. We also observed that accumulation of genetic mutations within these elements correlates with metastatic behavior in human thyroid tumors. Finally, we identified RAINs, a novel family of ENH-associated long non-coding RNAs, transcribed from the identified RUNX2 regulatory unit. Our data provide a new model to explain how RUNX2 expression is reactivated in thyroid and breast cancer and how cancer-driving signaling pathways converge on the regulation of this gene.

RDM1 gene overexpression represents a therapeutic target in papillary thyroid carcinoma

RAD52 motif containing 1 (RDM1) encodes the RAD52 protein involved in DNA double-strand break repair and recombination events. However, the importance of RDM1 in papillary thyroid carcinoma (PTC) is largely unknown. In the present study, we examined the role of RDM1 in thyroid cancer. The RDM1 expression in PTC patients was examined using immunohistochemistry. The expression levels of RDM1 mRNA in thyroid cancer cells were measured by quantitative real-time PCR (qRT-PCR). Lentivirus-mediated small interfering RNAs (siRNAs) were used to knock down the RDM1 expression in the K1 and TPC1 cells. Then, changes in the RDM1 target gene expression were determined by qRT-PCR and Western blot. Cell proliferation was examined by a high content screening assay. Cell cycle distribution and apoptosis were detected by flow cytometric analysis and MTT analysis. We showed that the RDM1 expression was higher in PTC tissue compared to pericarcinous tissue. RDM1 mRNA was found to be expressed by qRT-PCR. Using a lentivirus-based RNA interference (RNAi) approach, the RDM1 expression was significantly inhibited. The inhibition of RDM1 expression by RNAi significantly impaired cell proliferation, increased apoptosis and arrested cells in the G2/M phase. These data showed that RDM1 was highly expressed in PTC tissue and thyroid cancer cell lines. Moreover, RDM1 may play an important role in cell proliferation, cell cycle distribution and apoptosis of human PTC cells.

DUSP5 and DUSP6, two ERK specific phosphatases, are markers of a higher MAPK signaling activation in BRAF mutated thyroid cancers

Background

Molecular alterations of the MAPK pathway are frequently observed in papillary thyroid carcinomas (PTCs). It leads to a constitutive activation of the signalling pathway through an increase in MEK and ERK phosphorylation. ERK is negatively feedback-regulated by Dual Specificity Phosphatases (DUSPs), especially two ERK-specific DUSPs, DUSP5 (nuclear) and DUSP6 (cytosolic). These negative MAPK regulators may play a role in thyroid carcinogenesis.

Methods

MAPK pathway activation was analyzed in 11 human thyroid cancer cell lines. Both phosphatases were studied in three PCCL3 rat thyroid cell lines that express doxycycline inducible PTC oncogenes (RET/PTC3, H-RAS^V12 or BRAF^V600E). Expression levels of DUSP5 and DUSP6 were quantified in 39 human PTCs. The functional role of DUSP5 and DUSP6 was investigated through their silencing in two human BRAF^V600E carcinoma cell lines.

Results

BRAF^V600E human thyroid cancer cell lines expressed higher phospho-MEK levels but not higher phospho-ERK levels. DUSP5 and DUSP6 are specifically induced by the MEK-ERK pathway in the three PTC oncogenes inducible thyroid cell lines. This negative feedback loop explains the tight regulation of p-ERK levels. DUSP5 and DUSP6 mRNA are overexpressed in human PTCs, especially in BRAF^V600E mutated PTCs. DUSP5 and/or DUSP6 siRNA inactivation did not affect proliferation in two BRAF^V600E mutated cell lines, which may be explained by a compensatory increase in other phosphatases. In the light of this, we observed a marked DUSP6 upregulation upon DUSP5 inactivation. Despite this, DUSP5 and DUSP6 positively control cell migration and invasion.

Conclusions

Our results are in favor of a stronger activation of the MAPK pathway in BRAF^V600E PTCs. DUSP5 and DUSP6 have pro-tumorigenic properties in two BRAF^V600E PTC cell line models.

In vitro and in vivo anti-tumor activity of alectinib in tumor cells with NCOA4-RET

Rearranged during transfection (RET) fusion-positive non-small cell lung cancer (NSCLC) accounts for approximately 1–2% of all NSCLCs. To date, RET fusions that involve at least six fusion partners in NSCLC, such as KIF5B, CCDC6, NCOA4, TRIM33, CLIP1, and ERC1, have been identified. Recent clinical trials for RET fusion-positive NSCLC using vandetanib or cabozantinib demonstrated positive clinical response and considerable differential activities for RET inhibitors among fusion partners. Alectinib, an approved ALK inhibitor, is reported to inhibit KIF5B-RET and CCDC6-RET. However, the activity of alectinib with respect to RET with other fusion partners is unknown. In the present study, we investigated the effects of alectinib on NCOA4-RET fusion-positive tumor cells in vitro and in vivo. Alectinib inhibited the viability of NCOA4-RET-positive EHMES-10 cells, as well as CCDC6-RET-positive LC-2/ad and TPC-1 cells. This was achieved via inhibition of the phosphorylation of RET and induction of apoptosis. Moreover, alectinib suppressed the production of thoracic tumors and pleural effusions in an orthotopic intrathoracic inoculation model of EHMES-10 cells. In vivo imaging of an orthotopically inoculated EHMES-10 cell model also revealed that alectinib could rescue pleural carcinomatosis. These results suggest that alectinib may be a promising RET inhibitor against tumors positive for not only KIF5B-RET and CCDC6-RET, but also NCOA4-RET.

FUCA1 is induced by wild-type p53 and expressed at different levels in thyroid cancers depending on p53 status

Fucose residues of cell surface glycans, which play important roles in growth, invasion and metastasis, are added by fucosyltransferases (FUTs) and removed by α-L-fucosidases (FUCAs). By the differential display method, we isolated a 3' non-coding region of α-L-fucosidase-1 (FUCA1) (a gene coding for the lysosomal fucosidase-1 enzyme) as a wild-type p53-inducible gene: 18S and 20S FUCA1 mRNA species were induced in Saos-2 cells transfected with a temperature-sensitive p53 mutant at the permissive temperature. By microarray analyses of thyroid cancer biopsy samples, FUCA1 RNA expression levels were found to be lower in anaplastic thyroid cancer samples (ATCs), while they were higher in papillary thyroid cancer samples (PTCs) and in normal thyroid tissues. Since most ATCs were reported to carry the mutated form of p53, while PTCs carry mostly the wild-type form of p53, it is likely that FUCA1 expression levels are regulated, at least in part, by the p53 status in thyroid cancers. In order to better understand the role played by FUCA genes in thyroid tumorigenesis, we examined the clonogenic potential in vitro of thyroid cell lines transfected with either FUCA1 or FUCA2 (the latter gene coding for a secreted, non-lysosomal enzyme). We found that α-L-fucosidases did not suppress grossly cell growth. Contrary to what we observed with the expression of FUCA1, the FUT8 expression levels were found high in ATCs but lower in PTCs and normal thyroid tissues. Taken together, these results suggest the possibility that the higher fucose levels on cell surface glycans of aggressive ATCs, compared to those of less aggressive PTCs, may be at least in part responsible for the more aggressive and metastatic phenotype of ATCs compared to PTCs, as the expression levels of FUCA1 and FUT8 were inversely related in these two types of cancers.

Robust Thyroid Gene Expression and Radioiodine Uptake Induced by Simultaneous Suppression of BRAF V600E and Histone Deacetylase in Thyroid Cancer Cells

CONTEXT

Use of BRAF V600E inhibitors to restore thyroid iodide-handling gene expression and radioactive iodine (RAI) avidity is an attractive therapeutic strategy for RAI-refractory thyroid cancer, but recent initial clinical responses were modest. Given histone deacetylation at the sodium/iodide symporter promoter by histone deacetylase (HDAC) as a mechanism, simultaneously targeting BRAF V600E and HDAC could be a more effective strategy.

OBJECTIVES

The objective of the study was to test whether suppressing both BRAF V600E and HDAC could more effectively induce thyroid gene expression and RAI uptake in thyroid cancer cells.

RESEARCH DESIGN

We tested the BRAF V600E inhibitor PLX4032 (vemurafenib) and the HDAC inhibitor SAHA (vorinostat), two major anticancer drugs currently approved for clinical use, in inducing thyroid gene expression and RAI uptake in thyroid cancer cells.

RESULTS

PLX4032 alone induced a modest expression of thyroid genes and RAI uptake preferentially in thyroid cancer cells harboring BRAF V600E. SAHA showed an effect in a genetic-independent manner in all the cells. A robust synergistic effect on thyroid gene expression and RAI uptake was observed in BRAF V600E-positive thyroid cancer cells when the two inhibitors were simultaneously used. This was dramatically enhanced further by TSH; triple combination of PLX4032, SAHA, and TSH showed the most robust effect on thyroid gene expression and RAI uptake in cells harboring BRAF V600E. Abundant sodium/iodide symporter protein expression in thyroid cancer cells under these conditions was confirmed by immunofluorescent microscopy.

CONCLUSIONS

Simultaneously suppressing BRAF V600E and HDAC, particularly when cotreated with TSH, induced a far more robust expression of thyroid genes and RAI uptake in thyroid cancer cells than suppressing BRAF V600E alone. Triple combination of PLX4032, SAHA, and TSH is a specific robust regimen to restore RAI avidity in RAI-refractory BRAF V600E-positive thyroid cancer, which warrants clinical trials to confirm.

Induction of atypical cell death in thyroid carcinoma cells by the indirubin derivative 7-bromoindirubin-3'-oxime (7BIO)

BACKGROUND

The indirubin derivative 7-bromoindirubin-3'-oxime (7BIO) has already shown anticancer properties by causing cell death in some tumour cell lines and may be a new therapeutic option for treatment-resistant tumour cells. Since dedifferentiated and anaplastic thyroid carcinomas do not take up radioiodine and are insensitive to chemotherapeutic treatment and external radiation, direct cell death induction in these tumour cells may be a promising approach. We thus investigated the effect of 7BIO on thyroid carcinoma cell lines of different histological origins and characterized the type of cell death induction by 7BIO.

METHODS

Cell viability was measured with MTT assay. Cell death was analysed by caspase 3/7 activity, lactate dehydrogenase liberation, caspase cleavage products, DNA fragmentation, cell cycle phase distribution and LC3B analysis.

RESULTS

After 7BIO treatment, cell viability was reduced in all 14 thyroid carcinoma cell lines investigated. Treated cells showed DNA fragmentation, cell cycle arrest and lactate dehydrogenase liberation but no LC3B cleavage. Caspase activation following 7BIO treatment was found in five of six cell lines investigated. Interestingly, inhibition of caspases had no effect on viability of the cells after 7BIO incubation.

CONCLUSIONS

Our results indicate that 7BIO efficiently killed dedifferentiated thyroid carcinoma cells. It induced a non-classical kind of cell death that was caspase-independent and includes DNA fragmentation. 7BIO and related indirubin components thus may have value as a new therapeutic option for dedifferentiated thyroid cancer irrespective of the exact target molecules and the kind of cell death they induce.

A novel dual AMPK activator/mTOR inhibitor inhibits thyroid cancer cell growth

CONTEXT

Activated AMP protein kinase (AMPK) is a key regulator of intracellular energy homeostasis and may also function as a tumor suppressor by inhibiting cell growth through suppression of mammalian target of rapamycin (mTOR)/p70S6K signaling. AMPK activating agents, such as metformin and 5-aminoimidazole-4-carboxamide-ribonucleoside, have been demonstrated to inhibit thyroid cancer cell growth in in vitro and in vivo models. OSU-53, a recently developed AMPK activator, was previously shown to exhibit both in vitro and in vivo antitumor activity against aggressive breast cancer cell lines and their xenografts in nude mice.

OBJECTIVE

The objective of the study was to assess the in vitro effects of OSU-53 treatment in a panel of thyroid cancer cells.

DESIGN

Experiments were performed to determine the effects of OSU-53 on cell growth, oncogenic signaling, apoptosis, autophagy, and cell rescue after selective knockdown of AMPK.

RESULTS

OSU-53 inhibited in vitro cell growth of all seven thyroid cancer cells tested and induced activation of AMPK. Cell lines with activating mutations in RAS or BRAF, compared with cells with phosphatase and tensin homolog deleted from chromosome 10 null and RET/papillary thyroid carcinoma mutations, were more sensitive to drug treatment and demonstrated a more robust AMPK activation, inhibition of mTOR signaling, and autophagy stimulation. After selective knockdown of AMPK, cell rescue from OSU-53 treatment was not observed. We demonstrated an off-target effect of direct mTOR inhibition by OSU-53. Increased autophagy was observed in cells with activation RAS or BRAF mutations.

CONCLUSIONS

OSU-53, a novel dual-AMPK activator/mTOR inhibitor, effectively inhibits growth in a variety of thyroid cancer cell lines and is most potent in cells with activating mutations in RAS or BRAF.

Sorafenib inhibits intracellular signaling pathways and induces cell cycle arrest and cell death in thyroid carcinoma cells irrespective of histological origin or BRAF mutational status

BACKGROUND

Patients with dedifferentiated or anaplastic thyroid carcinomas currently lack appropriate treatment options. Kinase inhibitors are among the most promising new agents as alternative strategies. The BRAF- and multi-kinase inhibitor, sorafenib, has already shown antitumor effects in thyroid carcinoma patients in a phase III clinical trial. In this study we aim to better characterize molecular effects and efficacy of sorafenib against thyroid carcinoma cells with various histological origins and different BRAF mutational status. Analysis of different signaling pathways affected by sorafenib may contribute to assist a more specific therapy choice with fewer side effects. Twelve thyroid carcinoma cell lines derived from anaplastic, follicular and papillary thyroid carcinomas with wildtype or mutationally activated BRAF were treated with sorafenib. Growth inhibition, cell cycle arrest, cell death induction and inhibition of intracellular signaling pathways were then comprehensively analyzed.

METHODS

Cell viability was analyzed by MTT assay, and the cell cycle was assessed by flow cytometry after propidium iodide staining. Cell death was assessed by lactate dehydrogenase liberation assays, caspase activity assays and subG1 peak determinations. Inhibition of intracellular pathways was analyzed in dot blot and western blot analyses.

RESULTS

Sorafenib inhibited proliferation of all thyroid carcinoma cell lines tested with IC50 values ranging between 1.85 and 4.2 μM. Cells derived from papillary carcinoma harboring the mutant BRAF (V600E) allele were slightly more sensitive to sorafenib than those harboring wildtype BRAF. Cell cycle analyses and caspase assays showed a sorafenib-dependent induction of apoptosis in all cell lines, whereas increased lactate dehydrogenase release suggested cell membrane disruption. Sorafenib treatment caused a rapid inhibition of various MAP kinases in addition to inhibiting AKT and receptor tyrosine kinases.

CONCLUSIONS

Sorafenib inhibited multiple intracellular signaling pathways in thyroid carcinoma cells, which resulted in cell cycle arrest and the initiation of apoptosis. Sorafenib was effective against all thyroid carcinoma cell lines regardless of their tumor subtype origin or BRAF status, confirming that sorafenib is therapeutically beneficial for patients with any subtype of dedifferentiated thyroid cancer. Inhibition of single intracellular targets of sorafenib in thyroid carcinoma cells may allow the development of more specific therapeutic intervention with less side effects.

Nuclear factor κB-dependent regulation of angiogenesis, and metastasis in an in vivo model of thyroid cancer is associated with secreted interleukin-8

CONTEXT

Development of novel strategies in the treatment of advanced thyroid cancer are needed. Our laboratory has previously identified a role for nuclear factor κB (NF-κB) signaling in human thyroid cancer cell growth, survival, and invasion.

OBJECTIVE

Our goal was to establish the role of NF-κB signaling on thyroid cancer growth and metastases in vivo and to begin to dissect mechanisms regulating this effect.

SETTING AND DESIGN

We examined tumor formation of five thyroid cancer cell lines in an in vivo model of thyroid cancer and observed tumor establishment in two of the cell lines (8505C and BCPAP).

RESULTS

Inhibition of NF-κB signaling by overexpression of a dominant-negative IκBα (mIκBα) significantly inhibited thyroid tumor growth in tumors derived from both cell lines. Further studies in an experimental metastasis model demonstrated that NF-κB inhibition impaired growth of tumor metastasis and prolonged mouse survival. Proliferation (mitotic index) was decreased in 8505C tumors, but not in BCPAP tumors, while in vitro angiogenesis and in vivo tumor vascularity were significantly inhibited by mIkBα only in the BCPAP cells. Cytokine antibody array analysis demonstrated that IL-8 secretion was blocked by mIκBα expression. Interestingly, basal NF-κB activity and IL-8 levels were significantly higher in the two tumorigenic cell lines compared with the nontumorigenic lines. Furthermore, IL-8 transcript levels were elevated in high-risk human tumors, suggesting that NF-κB and IL-8 are associated with more aggressive tumor behavior.

CONCLUSIONS

These studies suggest that NF-κB signaling is a key regulator of angiogenesis and growth of primary and metastatic thyroid cancer, and that IL-8 may be an important downstream mediator of NF-κB signaling in advanced thyroid cancer growth and progression.

The role of podoplanin in the biology of differentiated thyroid cancers

Podoplanin (PDPN), a mucin-type transmembrane glycoprotein specific to the lymphatic system is expressed in a variety of human cancers, and is regarded as a factor promoting tumor progression. The purpose of this study was to elucidate the molecular role of PDPN in the biology of thyroid cancer cells. PDPN expression was evaluated in primary thyroid carcinomas and thyroid carcinoma cell lines by RT-qPCR, Western blotting, IF and IHC. To examine the role of podoplanin in determining a cell's malignant potential (cellular migration, invasion, proliferation, adhesion, motility, apoptosis), a thyroid cancer cell line with silenced PDPN expression was used. We observed that PDPN was solely expressed in the cancer cells of 40% of papillary thyroid carcinoma (PTC) tissues. Moreover, PDPN mRNA and protein were highly expressed in PTC-derived TPC1 and BcPAP cell lines but were not detected in follicular thyroid cancer derived cell lines. PDPN knock-down significantly decreased cellular invasion, and modestly reduced cell migration, while proliferation and adhesion were not affected. Our results demonstrate that PDPN mediates the invasive properties of cells derived from papillary thyroid carcinomas, suggesting that podoplanin might promote PTC progression.

Indoleamine 2,3-dioxygenase 1 (IDO1) is up-regulated in thyroid carcinoma and drives the development of an immunosuppressant tumor microenvironment

CONTEXT

Indoleamine 2,3-dioxygenase 1 (IDO1) is a single chain oxidoreductase that catalyzes tryptophan degradation to kynurenine. In cancer, it appears to exert an immunosuppressive function as part of an acquired mechanism of immune escape mediated by the inhibition of lymphocyte proliferation and survival and by the induction of FoxP3+ T regulatory cells.

OBJECTIVE

The objective of the study was to evaluate IDO1 expression in thyroid carcinoma and demonstrate its immunosuppressive function in the context of thyroid tumors.

SETTING

IDO1 expression was evaluated by quantitative PCR in 105 papillary thyroid carcinomas (PTCs), 11 medullary thyroid carcinomas, six anaplastic thyroid carcinomas, and five thyroid carcinoma cell lines (TCCLs), by immunohistochemistry in 55 PTCs and by Western blotting in five TCCLs. FoxP3+ Treg lymphocyte density was evaluated by immunohistochemistry in 29 PTCs. IDO1 inhibitory effect on lymphocyte proliferation was tested in coculture experiments of TCCLs and activated lymphocytes.

RESULTS

IDO1 mRNA expression resulted significantly higher in all the analyzed thyroid carcinoma histotypes compared with normal thyroid. Interestingly, an increase of IDO1 mRNA expression magnitude could be observed with gain of aggressiveness (PTCs and medullary thyroid carcinomas ≪ anaplastic thyroid carcinomas). In PTCs, IDO1 mRNA expression magnitude correlated with IDO1 immunostaining intensity in cancer cells and with FoxP3+ Treg lymphocyte density in the tumor microenvironment. IDO1 was expressed in human thyroid cancer cell lines in vitro, and FTC-133 cells showed high kynurenine concentration in the conditioned medium and a strong suppressive action on the proliferation of activated lymphocytes in coculture experiments.

CONCLUSIONS

For the first time, this study demonstrates a pivotal role of IDO1 in the suppression of lymphocyte function in thyroid carcinoma microenvironment.

Brief report: Mesenchymal stromal cell atrophy in coculture increases aggressiveness of transformed cells

Mesenchymal stromal cells (MSCs) are able to influence the growth abilities of transformed cells. Here, we show that papillary thyroid cancer TPC1 and HEK 293T cells interact physically with human primary bone marrow-derived MSCs followed by evanescence of MSC cytoplasm. Interestingly, transformed cells were able to connect only to apoptotic MSCs that had lost their migration ability, whereas naïve MSCs avoided the direct contact. The interaction stimulated the proliferation of the cocultured transformed cells, activated mitogen and stress signaling, and increased resistance to cytotoxins. Consistent with in vitro data, the MSC interaction stimulated transformed cells had enhanced ability to grow and metastasize in vivo. The parental control cells showed mild tumorigenicity as compared to MSC interaction stimulated cells yielding measurable tumors in 31 days and 7 days, respectively. Our coculture model system describes how adjacent transformed cells absorb stromal cells thereby leading to the stroma-driven evolution of moderately carcinogenic cells to highly aggressive metastatic cells.

Cadherin 6 is a new RUNX2 target in TGF-β signalling pathway

Modifications in adhesion molecules profile may change the way tumor cells interact with the surrounding microenvironment. The Cadherin family is a large group of transmembrane proteins that dictate the specificity of the cellular interactions. The Cadherin switch that takes place during epithelial-mesenchymal transition (EMT) contributes to loosening the rigid organization of epithelial tissues and to enhancing motility and invasiveness of tumor cells. Recently, we found Cadherin-6 (CDH6, also known as K-CAD) highly expressed in thyroid tumor cells that display mesenchymal features and aggressive phenotype, following the overexpression of the transcriptional regulator Id1. In this work, we explored the possibility that CDH6 is part of the EMT program in thyroid tumors. We demonstrate that CDH6 is a new transforming growth factor-β (TGF-β) target and that its expression is modulated similarly to other EMT mesenchymal markers, both in vitro and in thyroid tumor patients. We show for the first time that CDH6 is expressed in human thyroid carcinomas and that its expression is enhanced at the invasive front of the tumor. Finally, we show that CDH6 is under the control of the transcription factor RUNX2, which we previously described as a crucial mediator of the Id1 pro-invasive function in thyroid tumor cells. Overall, these observations provide novel information on the mechanism of the EMT program in tumor progression and indicate CDH6 as a potential regulator of invasiveness in thyroid tumors.

Development of p21 activated kinase-targeted multikinase inhibitors that inhibit thyroid cancer cell migration

CONTEXT

The p21 activated kinases (PAKs) are a family of serine/threonine kinases that are downstream effectors of small GTPase Cdc42 and Rac. PAKs regulate cell motility, proliferation, and cytoskeletal rearrangement. PAK isoform expression and activity have been shown to be enhanced in cancer and to function as an oncogene in vivo. PAKs also have been implicated in cancer progression.

OBJECTIVE

In thyroid cancer, we have previously determined that PAK overactivation is common in the invasive fronts of aggressive tumors and that it is functionally involved in thyroid cancer cell motility using molecular inhibitors. We report the development of two new PAK-inhibiting compounds that were modified from the structure OSU-03012, a previously identified multikinase inhibitor that competitively blocks ATP binding of both phosphoinositide-dependent kinase 1 (PDK1) and PAK1.

RESULTS

Seventeen compounds were created by combinatorial chemistry predicted to inhibit PAK activity with reduced anti-PDK1 effect. Two lead compounds were identified based on the ability to inhibit PAK1 activity in an ATP-competitive manner without discernible in vivo PDK1 inhibitory activity in thyroid cancer cell lines. Both compounds reduced thyroid cancer cell viability. Although they are not PAK-specific on a multikinase screening assay, the antimigration activity effect of the compounds in thyroid cancer cells was rescued by overexpression of a constitutively active PAK1, suggesting this activity is involved in this biological effect.

CONCLUSIONS

We have developed 2 new multikinase inhibitors with anti-PAK activity that may serve as scaffolds for further compound development targeting this progression-related thyroid cancer target.

Homologous chromosomes make contact at the sites of double-strand breaks in genes in somatic G0/G1-phase human cells

Double-strand DNA breaks (DSBs) are continuously induced in cells by endogenously generated free radicals and exogenous genotoxic agents such as ionizing radiation. DSBs activate the kinase activity in sensor proteins such as ATM and DNA-PK, initiating a complex DNA damage response that coordinates various DNA repair pathways to restore genomic integrity. In this study, we report the unexpected finding that homologous chromosomes contact each other at the sites of DSBs induced by either radiation or the endonuclease I-PpoI in human somatic cells. Contact involves short segments of homologous chromosomes and is centered on a DSB in active genes but does not occur at I-PpoI sites in intergenic DNA. I-PpoI-induced contact between homologous genes is abrogated by the transcriptional inhibitors actinomycin D and α-amanitin and requires the kinase activity of ATM but not DNA-PK. Our findings provide documentation of a common transcription-related and ATM kinase-dependent mechanism that induces contact between allelic regions of homologous chromosomes at sites of DSBs in human somatic cells.

Thyroid cancer cell lines: an overview

Human thyroid cancer cell lines are the most used models for thyroid cancer studies. They must be used with detailed knowledge of their characteristics. These in vitro cell lines originate from differentiated and dedifferentiated in vivo human thyroid tumors. However, it has been shown that mRNA expression profiles of these cell lines were closer to dedifferentiated in vivo thyroid tumors (anaplastic thyroid carcinoma, ATC) than to differentiated ones. Here an overview of the knowledge of these models was made. The mutational status of six human thyroid cancer cell lines (WRO, FTC133, BCPAP, TPC1, K1, and 8505C) was in line with previously reported findings for 10 genes frequently mutated in thyroid cancer. However, the presence of a BRAF mutation (T1799A: V600E) in WRO questions the use of this cell line as a model for follicular thyroid carcinoma (FTC). Next, to investigate the biological meaning of the modulated mRNAs in these cells, a pathway analysis on previously obtained mRNA profiles was performed on five cell lines. In five cell lines, the MHC class II pathway was down-regulated and in four of them, ribosome biosynthesis and translation pathways were up-regulated. mRNA expression profiles of the cell lines were also compared to those of the different types of thyroid cancers. Three datasets originating from different microarray platforms and derived from distinct laboratories were used. This meta-analysis showed a significant higher correlation between the profiles of the thyroid cancer cell lines and ATC, than to differentiated thyroid tumors (i.e., PTC or FTC) specifically for DNA replication. This already observed higher correlation was obtained here with an increased number of in vivo tumors and using different platforms. In summary, this would suggest that some papillary thyroid carcinoma or follicular thyroid carcinoma (PTC or FTC) cell lines (i.e., TPC-1) might have partially lost their original DNA synthesis/replication regulation mechanisms during their in vitro cell adaptation/evolution.

Chromatin immunoprecipitation to analyze DNA binding sites of HMGA2

Background

HMGA2 is an architectonic transcription factor abundantly expressed during embryonic and fetal development and it is associated with the progression of malignant tumors. The protein harbours three basically charged DNA binding domains and an acidic protein binding C-terminal domain. DNA binding induces changes of DNA conformation and hence results in global overall change of gene expression patterns. Recently, using a PCR-based SELEX (Systematic Evolution of Ligands by Exponential Enrichment) procedure two consensus sequences for HMGA2 binding have been identified.

Methodology/Principal Findings

In this investigation chromatin immunoprecipitation (ChIP) experiments and bioinformatic methods were used to analyze if these binding sequences can be verified on chromatin of living cells as well.

Conclusion

After quantification of HMGA2 protein in different cell lines the colon cancer derived cell line HCT116 was chosen for further ChIP experiments because of its 3.4-fold higher HMGA2 protein level. 49 DNA fragments were obtained by ChIP. These fragments containing HMGA2 binding sites have been analyzed for their AT-content, location in the human genome and similarities to sequences generated by a SELEX study. The sequences show a significantly higher AT-content than the average of the human genome. The artificially generated SELEX sequences and short BLAST alignments (11 and 12 bp) of the ChIP fragments from living cells show similarities in their organization. The flanking regions are AT-rich, whereas a lower conservation is present in the center of the sequences.

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.

Secretome-based identification and characterization of potential biomarkers in thyroid cancer

In search of thyroid cancer biomarkers, proteins secreted by thyroid cancer cell lines, papillary-derived TPC-1 and anaplastic-derived CAL62, were analyzed using liquid chromatography-tandem mass spectrometry. Of 46 high-confidence identifications, 6 proteins were considered for verification in thyroid cancer patients' tissue and blood. The localization of two proteins, nucleolin and prothymosin-α (PTMA), was confirmed in TPC-1 and CAL62 cells by confocal microscopy and immunohistochemically in xenografts of TPC-1 cells in NOD/SCID/γ mice and human thyroid cancers (48 tissues). Increased nuclear and cytoplasmic expression of PTMA was observed in anaplastic compared to papillary and poorly differentiated carcinomas. Nuclear expression of nucleolin was observed in all subtypes of thyroid carcinomas, along with faint cytoplasmic expression in anaplastic cancers. Importantly, PTMA, nucleolin, clusterin, cysteine-rich angiogenic inducer 61, enolase 1, and biotinidase were detected in thyroid cancer patients' sera, warranting future analysis to confirm their potential as blood-based thyroid cancer markers. In conclusion, we demonstrated the potential of secretome analysis of thyroid cancer cell lines to identify novel proteins that can be independently verified in cell lines, xenografts, tumor tissues, and blood samples of thyroid cancer patients. These observations support their potential utility as minimally invasive biomarkers for thyroid carcinomas and their application in management of these diseases upon future validation.

'Chromosomal Rainbows' Detect Oncogenic Rearrangements of Signaling Molecules in Thyroid Tumors

Altered signal transduction can be considered a hallmark of many solid tumors. In thyroid cancers the receptor tyrosine kinase (rtk) genes NTRK1 (Online Mendelian Inheritance in Man = OMIM *191315, also known as 'TRKA'), RET ('Rearranged during Transfection protooncogene', OMIM *164761) and MET (OMIM *164860) have been reported as activated, rearranged or overexpressed. In many cases, a combination of cytogenetic and molecular techniques allows elucidation of cellular changes that initiate tumor development and progression. While the mechanisms leading to overexpression of the rtk MET gene remain largely unknown, a variety of chromosomal rearrangements of the RET or NTKR1 gene could be demonstrated in thyroid cancer. Abnormal expressions in these tumors seem to follow a similar pattern: the rearrangement translocates the 3'- end of the rtk gene including the entire catalytic domain to an expressed gene leading to a chimeric RNA and protein with kinase activity. Our research was prompted by an increasing number of reports describing translocations involving ret and previously unknown translocation partners.We developed a high resolution technique based on fluorescence in situ hybridization (FISH) to allow rapid screening for cytogenetic rearrangements which complements conventional chromosome banding analysis. Our technique applies simultaneous hybridization of numerous probes labeled with different reporter molecules which are distributed along the target chromosome allowing the detection of cytogenetic changes at near megabasepair (Mbp) resolution. Here, we report our results using a probe set specific for human chromosome 10, which is altered in a significant portion of human thyroid cancers (TC's). While rendering accurate information about the cytogenetic location of rearranged elements, our multi-locus, multi-color analysis was developed primarily to overcome limitations of whole chromosome painting (WCP) and chromosome banding techniques for fine mapping of breakpoints in papillary thyroid cancer (PTC).

MEK inhibitor PD0325901 significantly reduces the growth of papillary thyroid carcinoma cells in vitro and in vivo

Papillary thyroid carcinomas (PTC) are the most common type of thyroid malignancy. Most PTC carry one of the two mutations, RET/PTC rearrangement or BRAF mutation. Both mutations are able to activate the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) signaling transduction pathway leading to cellular proliferation, differentiation, and apoptosis. PD0325901 is a specific MEK1/2 inhibitor and therefore is a promising drug to treat thyroid cancers with either RET/PTC or BRAF mutation. In this study we tested the effects of PD0325901 on PTC cells harboring either mutation in vitro by growth curves and Western blots and in vivo using a murine orthotopic xenograft model. We found that 50% growth inhibition (GI(50)) by PD0325901 was 11 nmol/L for the PTC cells with the RET/PTC1 rearrangement and 6.3 nmol/L for PTC cells with a BRAF mutation, with both concentrations readily achievable in serum. After 1 week of oral administration of PD0325901 (20-25 mg/kg/day) in mice, no tumor growth was detected in mice inoculated with PTC cells bearing a BRAF mutation. For PTC with the RET/PTC1 rearrangement, the average tumor volume of the orthotopic tumor was reduced by 58% as compared with controls. In conclusion, our data suggested that PTC cells carrying a BRAF mutation were more sensitive to PD0325901 than were PTC cells carrying the RET/PTC1 rearrangement. Our findings support the clinical evaluation of PD0325901 for patients with PTC and potentially other carcinomas with BRAF mutations.

Transcriptional Profile of Ki-Ras-Induced Transformation of Thyroid Cells

In the last years, an increasing number of experiments has provided compelling evidence for a casual role of Ras protein mutations, resulting in their constitutive activation, in thyroid carcinogenesis. However, despite the clear involvement of Ras proteins in thyroid carcinogenesis, the nature of most of the target genes, whose expression is modulated by the Ras-induced signaling pathways and that are ultimately responsible for Ras-induced cellular transformation, remains largely unknown. To analyze Ras-dependent modulation of gene expression in thyroid cells we took advantage of a differentiated rat thyroid cell line, FRTL-5. As a model for Ras-dependent thyroid transformation, we used FRTL-5 cells infected with the Kirsten murine sarcoma virus, carrying the v-Ki-Ras oncogene. The infected cells (FRTL-5 v-Ki-Ras) have lost expression of the thyroid differentiation markers and also are completely transformed. We hybridized two different Affimetrix chips containing probe sets interrogating both known rat genes and ESTs for a total of more than 17,000 sequences using mRNA extracted from FRTL-5 and FRTL-5 v-Ki-Ras cell lines. We identified about 50 genes whose expression was induced and about 40 genes whose expression was downregulated more than 10-fold by Ras. We confirmed the differential expression of many of these genes in FRTL-5 v-Ki-Ras as compared to parental cells by using alternative techniques. Remarkably, we investigated the expression of some of the Ras-regulated genes in human thyroid carcinoma cell lines and tumor samples, our results, therefore, providing a new molecular profile of the genes involved in thyroid neoplastic transformation.

Conventional and molecular cytogenetics of human non-medullary thyroid carcinoma: characterization of eight cell line models and review of the literature on clinical samples

Background

Cell lines are often poorly characterized from a genetic point of view, reducing their usefulness as tumor models. Our purpose was to assess the genetic background of eight commonly used human thyroid carcinoma models and to compare the findings with those reported for primary tumors of the gland.

Methods

We used chromosome banding analysis and comparative genomic hybridization to profile eight non-medullary thyroid carcinoma cell lines of papillary (TPC-1, FB2, K1 and B-CPAP), follicular (XTC-1) or anaplastic origin (8505C, C643 and HTH74). To assess the representativeness of the findings, we additionally performed a thorough review of cytogenetic (n = 125) and DNA copy number information (n = 270) available in the literature on clinical samples of thyroid carcinoma.

Results

The detailed characterization of chromosomal markers specific for each cell line revealed two cases of mistaken identities: FB2 was shown to derive from TPC-1 cells, whereas K1 cells have their origin in cell line GLAG-66. All cellular models displayed genomic aberrations of varying complexity, and recurrent gains at 5p, 5q, 8q, and 20q (6/7 cell lines) and losses at 8p, 13q, 18q, and Xp (4/7 cell lines) were seen. Importantly, the genomic profiles were compatible with those of the respective primary tumors, as seen in the meta-analysis of the existing literature data.

Conclusion

We provide the genomic background of seven independent thyroid carcinoma models representative of the clinical tumors of the corresponding histotypes, and highlight regions of recurrent aberrations that may guide future studies aimed at identifying target genes. Our findings further support the importance of routinely performing cytogenetic studies on cell lines, to detect cross-contamination mishaps such as those identified here.

Deoxyribonucleic acid profiling analysis of 40 human thyroid cancer cell lines reveals cross-contamination resulting in cell line redundancy and misidentification

CONTEXT

Cell lines derived from human cancers provide critical tools to study disease mechanisms and develop novel therapies. Recent reports indicate that up to 36% of cell lines are cross- contaminated.

OBJECTIVE

We evaluated 40 reported thyroid cancer-derived cell lines using short tandem repeat and single nucleotide polymorphism array analysis.

RESULTS

Only 23 of 40 cell lines tested have unique genetic profiles. The following groups of cell lines are likely derivatives of the same cell line: BHP5-16, BHP17-10, BHP14-9, and NPA87; BHP2-7, BHP10-3, BHP7-13, and TPC1; KAT5, KAT10, KAT4, KAT7, KAT50, KAK1, ARO81-1, and MRO87-1; and K1 and K2. The unique cell lines include BCPAP, KTC1, TT2609-C02, FTC133, ML1, WRO82-1, 8505C, SW1736, Cal-62, T235, T238, Uhth-104, ACT-1, HTh74, KAT18, TTA1, FRO81-2, HTh7, C643, BHT101, and KTC-2. The misidentified cell lines included the DRO90-1, which matched the melanoma-derived cell line, A-375. The ARO81-1 and its derivatives matched the HT-29 colon cancer cell line, and the NPA87 and its derivatives matched the M14/MDA-MB-435S melanoma cell line. TTF-1 and Pax-8 mRNA levels were determined in the unique cell lines.

CONCLUSIONS

Many of these human cell lines have been widely used in the thyroid cancer field for the past 20 yr and are not only redundant, but not of thyroid origin. These results emphasize the importance of cell line integrity, and provide the short tandem repeat profiles for a panel of thyroid cancer cell lines that can be used as a reference for comparison of cell lines from other laboratories.

Oncogenic role of miR-17-92 cluster in anaplastic thyroid cancer cells

Micro RNAs (miRNAs) are non-coding small RNAs and constitute a novel class of negative gene regulators that are found in both plants and animals. Several miRNAs play crucial roles in cancer cell growth. To identify miRNAs specifically deregulated in anaplastic thyroid cancer (ATC) cells, we performed a comprehensive analysis of miRNA expressions in ARO cells and primary thyrocytes using miRNA microarrays. MiRNAs in a miR-17-92 cluster were overexpressed in ARO cells. We confirmed the overexpression of those miRNAs by Northern blot analysis in ARO and FRO cells. In 3 of 6 clinical ATC samples, miR-17-3p and miR-17-5p were robustly overexpressed in cancer lesions compared to adjacent normal tissue. To investigate the functional role of these miRNAs in ATC cells, ARO and FRO cells were transfected with miRNA inhibitors, antisense oligonucleotides containing locked nucleic acids. Suppression of miR-17-3p caused complete growth arrest, presumably due to caspase activation resulting in apoptosis. MiR-17-5p or miR-19a inhibitor also induced strong growth reduction, but only miR-17-5p inhibitor led to cellular senescence. On the other hand, miR-18a inhibitor only moderately attenuated the cell growth. Thus, we have clarified functional differences among the members of the cluster in ATC cells. In conclusion, these findings suggest that the miR-17-92 cluster plays an important role in certain types of ATCs and could be a novel target for ATC treatment.

Human thyroid tumor cell lines derived from different tumor types present a common dedifferentiated phenotype

Cell lines are crucial to elucidate mechanisms of tumorigenesis and serve as tools for cancer treatment screenings. Therefore, careful validation of whether these models have conserved properties of in vivo tumors is highly important. Thyrocyte-derived tumors are very interesting for cancer biology studies because from one cell type, at least five histologically characterized different benign and malignant tumor types can arise. To investigate whether thyroid tumor-derived cell lines are representative in vitro models, characteristics of eight of those cell lines were investigated with microarrays, differentiation markers, and karyotyping. Our results indicate that these cell lines derived from differentiated and undifferentiated tumor types have evolved in vitro into similar phenotypes with gene expression profiles the closest to in vivo undifferentiated tumors. Accordingly, the absence of expression of most thyrocyte-specific genes, the nonresponsiveness to thyrotropin, as well as their large number of chromosomal abnormalities, suggest that these cell lines have acquired characteristics of fully dedifferentiated cells. They represent the outcome of an adaptation and evolution in vitro, which questions the reliability of these cell lines as models for differentiated tumors. However, they may represent useful models for undifferentiated cancers, and by their comparison with differentiated cells, can help to define the genes involved in the differentiation/dedifferentiation process. The use of any cell line as a model for a cancer therefore requires prior careful and thorough validation for the investigated property.

UbcH10 overexpression may represent a marker of anaplastic thyroid carcinomas

The hybridisation of an Affymetrix HG_U95Av2 oligonucleotide array with RNAs extracted from six human thyroid carcinoma cell lines and a normal human thyroid primary cell culture led us to the identification of the UbcH10 gene that was upregulated by 150-fold in all of the carcinoma cell lines in comparison to the primary culture cells of human normal thyroid origin. Immunohistochemical studies performed on paraffin-embedded tissue sections showed abundant UbcH10 levels in thyroid anaplastic carcinoma samples, whereas no detectable UbcH10 expression was observed in normal thyroid tissues, in adenomas and goiters. Papillary and follicular carcinomas were only weakly positive. These results were further confirmed by RT-PCR and Western blot analyses. The block of UbcH10 protein synthesis induced by RNA interference significantly reduced the growth rate of thyroid carcinoma cell lines. Taken together, these results would indicate that UbcH10 overexpression is involved in thyroid cell proliferation, and may represent a marker of thyroid anaplastic carcinomas.

Inhibitory effect of hexamethylene bisacetamide on replication of human cytomegalovirus

The effect of hexamethylane bisacetamide (HMBA), a hybrid polar compound, on gene expression and replication of human cytomegalovirus (HCMV) was studied. When HCMV-infected human thyroid papillary carcinoma (TPC-1) and human embryonic lung (HEL) fibroblast cells were maintained with medium containing 2.5 and 5 mM HMBA for 10 days, there was a greater than 2- to 3-log reduction in virus yield compared to that in untreated cells. Infection of TPC-1 cells with HCMV resulted in an establishment of persistent infection and the cells continuously produced virus with titer of over 10(5) PFU/ml, whereas HMBA prevented the infected cells from entering into the persistent infection. Moreover, treatment of the persistently infected cultures with HMBA reduced production of infectious HCMV more efficiently than did ganciclovir, and eventually ceased HCMV production. Western blotting analysis revealed that HMBA blocks accumulation of the immediate early 2 (IE2) protein in TPC-1 cells and delays synthesis of this protein in HEL cells, but has little effect on the level of the IE1 protein during the early times after infection. Synthesis of the viral early and late proteins in both cells was also substantially blocked by HMBA. The results indicate that the inhibition or the delay of the critical IE2 protein synthesis in the presence of HMBA would actually be a process that fails to proceed beyond the IE stages in HCMV replication cycle.

Glucose transporters in the thyroid

Glucose transport, mediated by proteins expressed from the glucose transporter genes, plays an essential role in cellular metabolism. Increased uptake of glucose compared to cells in normal tissue is a defining characteristic of malignant cells. This has been the basis for positron emission tomography imaging of thyroid tumor metastases using fluorodeoxyglucose uptake. Despite this key difference between tumor and normal cells, the mechanism which mediates increased glucose uptake is poorly understood. Several research studies have assessed the expression of different glucose transporter (GLUT) proteins and expression of the genes which code for them in thyroid tissues. While no consensus exists on the specifics of which GLUT genes or proteins are expressed, a picture has emerged that a single specific transporter, GLUT1, is expressed at higher levels in thyroid carcinomas compared to a variety of normal and nonmalignant forms of thyroid disease. Greater levels of GLUT1 expression may be associated with poorer prognosis. Experiments in established thyroid carcinoma cells lines may provide useful insights into glucose transport in the thyroid. Thyroid cells show increased glucose uptake in response to thyroid-stimulating hormone (TSH), but expression of GLUT genes does not appear to be significantly affected by TSH suggesting TSH affects glucose uptake by affecting GLUT localization/ translocation rather than through increased GLUT gene expression. Improving technologies are providing a stronger foundation for detailed analyses of glucose transporters in thyroid to better elucidate the mechanisms by which these genes and proteins are regulated in normal and pathogenic tissue.

Proteomic analysis of human thyroid cell lines reveals reduced nuclear localization of Mn-SOD in poorly differentiated thyroid cancer cells

Differential protein arrays between nuclear extracts of human thyroid cell lines obtained from tumors with different degree of differentiation were exploited to define molecular alterations occurring during thyroid tumor progression. Nuclear extracts from the well differentiated TPC-1 (from papillary carcinoma) and the poorly differentiated ARO (from anaplastic carcinoma) cells showed an overall similar pattern of protein expression as revealed by two-dimensional gel electrophoresis analysis. However, manganese-superoxide dismutase (Mn-SOD) was clearly identified by mass spectrometry procedures as significantly less expressed in ARO compared to TPC-1 cells. A reduced expression of Mn-SOD in the nuclear compartment was confirmed by Western blot and immunofluorescence analysis. A similar expression pattern of nuclear Mn-SOD was detected by immunohistochemistry in human thyroid tumors, with the lowest or absent detection in anaplastic carcinomas. Moreover, the levels of nuclear Mn-SOD in tumor cells were lower than in the normal thyrocytes. These data indicate that an altered nuclear expression of Mn-SOD parallels, together with changes in other elements of the antioxidant protective system, the loss of differentiation occurring during the progression of thyroid tumors.

Cloning and molecular characterization of a novel gene strongly induced by the adenovirus E1A gene in rat thyroid cells

Expression of the adenovirus E1A gene in the rat thyroid differentiated cell line PC Cl 3 induces thyrotropin-independent cell growth and impairs differentiation. However, the malignant phenotype is achieved only when the PC E1A cells are infected with other murine retroviruses carrying the v-abl, v-raf or polyoma middle-T genes. To determine through which genes E1A affects thyroid cells, we differentially screened PC Cl 3 and PC E1A cells. Here we report a new gene, named CL2, that is upregulated in PC E1A cells. The CL2 transcript is 4.4 kb long and encodes a 949 amino-acid protein. Conceptual translation of the open reading frame showed one product with a signal peptide, multiple nuclear localization signals and three newly described domains. Furthermore, in vivo, this protein was located juxtanuclear, which is suggestive of Golgian localization, and also in cytoplasm and nucleus/nucleolus. Finally, CL2 gene expression was drastically downregulated in human thyroid neoplastic cell lines and tissues.

Establishment of a non-tumorigenic papillary thyroid cell line (FB-2) carrying the RET/PTC1 rearrangement

A novel human thyroid papillary carcinoma cell line (FB-2) has been established and characterized. FB-2 cells harbor the RET/PTC1 chimeric oncogene in which the RET kinase domain is fused to the H4 gene. FB-2 cells neither formed colonies in semisolid media nor induced tumors after heterotransplant into severe combined immunodeficient mice. However, HMGI(Y), HMGI-C and c-myc genes, which are associated to thyroid cell transformation, were abundantly expressed in FB-2 cells but not in normal thyroid cells. FB-2 cells only partially retained the differentiated thyroid phenotype. In fact, the PAX-8 gene, which codes for a transcriptional factor required for thyroid cell differentiation, was expressed, while thyroglobulin, TSH-receptor and thyroperoxidase genes were not. Moreover, FB-2 cells produced high levels of interleukin (IL)-6 and IL-8.

A dimeric mutant of human pancreatic ribonuclease with selective cytotoxicity toward malignant cells

Monomeric human pancreatic RNase, devoid of any biological activity other than its RNA degrading ability, was engineered into a dimeric protein with a cytotoxic action on mouse and human tumor cells, but lacking any appreciable toxicity on mouse and human normal cells. This dimeric variant of human pancreas RNase selectively sensitizes to apoptotic death cells derived from a human thyroid tumor. Because of its selectivity for tumor cells, and because of its human origin, this protein represents a potentially very attractive, novel tool for anticancer therapy.

The immunology of thyroid cancer

This article reviews the immunologic aspects of thyroid cancer, including thyroid-specific effector elements on thyroid cancer, and discusses the potential antigens, unique molecular markers, and transcription factors that could serve as targets for immunotherapy. The potential role of this type of treatment for thyroid cancer is examined also.

Cell types involved in replication and distribution of human cytomegalovirus

As the number of patients suffering from severe HCMV infections has steadily increased, there is a growing need to understand the molecular mechanisms by which the virus causes disease. The factors that control infection at one time and the events leading to virus multiplication at another time are only beginning to be understood. The interaction of HCMV with different host cells is one key for elucidating these processes. Through modern techniques, much has been learned about the biology of HCMV infections in culture systems. In addition to endothelial cells, epithelial cells, and smooth muscle cells, fibroblasts are one cell population preferentially infected in solid tissues in vivo. From these sites of multiplication, the virus may be carried by peripheral monocytes and circulating endothelial cells to reach distant sites of the body. This would explain the multiorgan involvement in acute HCMV infection and the modes of viral transmission. From what has been learned mainly from human fibroblast culture systems, future studies will focus on how HCMV regulates the expression of its putative 200 genes in different host cells at different stages of cell differentiation and activation to result in viral latency and pathogenesis.

Sodium butyrate-inducible replication of human cytomegalovirus in a human epithelial cell line

Replication of human cytomegalovirus (HCMV) in a human epithelial thyroid papillary carcinoma cell line (TPC-1) was restricted. However, pretreatment of these cells with 5 mM sodium butyrate (NaB) for 24 hr before infection enhanced both HCMV yield and infectious center titer to a similar level of that seen in human embryonic lung fibroblast cells. Immunofluorescence staining, gel electrophoresis, and Northern blot analysis revealed that TPC-1 cells are nonpermissive for expression of HCMV major immediate early (IE1) functions, but many of the cells become permissive after being treated with NaB. The presence of cycloheximide during NaB pretreatment of the cells efficiently diminished the stimulatory effect of NaB on expression of the IE1 gene. Therefore, it appeared that NaB induces the synthesis of a cellular protein(s) which apparently plays an important role in the conversion of nonpermissive cells to a permissive state for expression of this critical viral gene. Transient chloramphenicol acetyltransferase (CAT) assay experiments indicated that in TPC-1 cells the HCMV-CAT construct which contains the complete IE1 promoter regulatory region was expressed poorly, whereas a high level of CAT activity was detectable in the NaB-treated cells. Therefore, these results suggest that the enhancing effect of NaB on HCMV replication is expressed through some host cellular factor(s), and the HCMV IE1 promoter regulatory region is most likely to be the primary target of NaB action.

cDNA cloning and characterization of ret activated in a human papillary thyroid carcinoma cell line

We obtained activated ret cDNAs (retTPC) from a human papillary thyroid carcinoma cell line, TPC-1, and characterized its structure. The nucleotide sequence indicated that the recombination had occurred just upstream of the kinase domain of ret proto-oncogene and that the position, where the conserved sequence of ret proto-oncogene starts in retTPC transcripts, was exactly the same as that of ret-II which we have previously analyzed. Furthermore, a unique 13-glycine stretch, which is also present in a small subunit of the calcium dependent protease, calpain, was detected in the replaced sequence of retTPC. The aberrant tyrosine kinase activity induced by the rearrangement of ret proto-oncogene could be involved in the development of papillary thyroid carcinoma.