Normal Thyroid Cells Research Articles

Abstract 3494: Microfluidic platform for a protein-based thyroid cancer diagnostics

Abstract a) The current gold-standard of care in the management of patients with thyroid nodules is ultrasound-guided fine needle aspiration biopsy (FNAB) followed by microscopic examination of cell morphology by a trained cytopathologist. Due to the lack of distinguishing morphology, 10-25% of FNAs are termed “indeterminate” and required surgery. However, only 35% of them are found to have cancer. There is a need for a more accurate and minimally invasive cancer diagnostic technology. Our objective is to develop an inexpensive, point-of-care molecular diagnostic platform to isolate and detect thyroid specific proteins to enable real-world use of biomarkers to inform patient care. b) In this study, we engineer a miniature ion exchange column within a plastic (cyclic olefin polymer), disposable lab-on-a-chip platform for sample preparation and protein purification using microfluidic channels with a specialized porous polymer monolith (PPM)-based resin bed. We capitalized on the finding that cancer cells exhibit differential protein expressional patterns compared to normal thyroid cells by targeting thyroid transcription factor (TTF-1), a thyroid specific enhancer binding protein, as a biomarker for the diagnosis of thyroid cancer. The ability to capture and release TTF-1 from the papillary thyroid cancer (PTC) cell line was evaluated via western blot. We also tested various types of thyroid samples obtained from malignant and benign human thyroid nodules. c) We compared the efficiency of a small-scale protein prep using a commercial gravity column versus our lab-on-a-chip column. Our method showed TTF-1 protein was detectable from the lysate of 5x104 cultured BCPAP cancer cell line. In contrast, it was not detectable when purified by gravity ion-exchange column. We next showed that one can maximize the concentration of protein eluted from as fewer cells as possible. We found that by titrating the elution volume per fraction down to 10 µl, the final concentration of eluted protein can be increased, and hence increase the downstream LOD to 104 cells. Next, we evaluated our extraction and purification system by using 10 mg patient thyroid tissue samples. We tested 11 human thyroid specimens for TTF-1 protein capture. They were all found to be positive which correlated with the official histopathological findings. All tissue extracts had measurable levels of TTF-1 protein and the levels of the TTF-1 were variable in the tissue specimens. We also tested one negative thyroid specimen. No TTF-1 protein was found. d) Our microfluidic protein extraction and purification system is a platform technology that may allow for optimal use of low-volume sample preparation such as we see in thyroid biopsies. This manner, when combined with an on-chip ELISA assay, would be a simple, cost effective test that gives the doctor all the needed information quickly in a single test. When mature, the device can be applied to other type of cancer based on tailored assays for specific biomarkers. Citation Format: Shichu Huang, Siddhartha Sharma, Lena Liu, Andy Fan, Catherine Klapperich, Jennifer Rosen. Microfluidic platform for a protein-based thyroid cancer diagnostics. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3494. doi:10.1158/1538-7445.AM2014-3494

Modulation of sodium iodide symporter in thyroid cancer.

Radioactive iodine (RAI) is a key therapeutic modality for thyroid cancer. Loss of RAI uptake in thyroid cancer inversely correlates with patient's survival. In this review, we focus on the challenges encountered in delivering sufficient doses of I-131 to eradicate metastatic lesions without increasing the risk of unwanted side effects. Sodium iodide symporter (NIS) mediates iodide influx, and NIS expression and function can be selectively enhanced in thyroid cells by thyroid-stimulating hormone. We summarize our current knowledge of NIS modulation in normal and cancer thyroid cells, and we propose that several reagents evaluated in clinical trials for other diseases can be used to restore or further increase RAI accumulation in thyroid cancer. Once validated in preclinical mouse models and clinical trials, these reagents, mostly small-molecule inhibitors, can be readily translated into clinical practice. We review available genetically engineered mouse models of thyroid cancer in terms of their tumor development and progression as well as their thyroid function. These mice will not only provide important insights into the mechanisms underlying the loss of RAI uptake in thyroid tumors but will also serve as preclinical animal models to evaluate the efficacy of candidate reagents to selectively increase RAI uptake in thyroid cancers. Taken together, we anticipate that the optimal use of RAI in the clinical management of thyroid cancer is yet to come in the near future.

MiR-618 inhibits anaplastic thyroid cancer by repressing XIAP in one ATC cell line

X-linked inhibitor of apoptosis protein (XIAP) is a major factor in cancer growth and progression. Reduction of XIAP induces apoptosis of anaplastic thyroid cancer (ATC), which accounts for more than 50% of thyroid cancer mortality. MicroRNAs (miRNAs) are short non-coding RNA molecules, which modulate gene expression via interaction with mRNA by binding to the 3′-untranslated region (3′-UTR), playing a critical role in cell proliferation, migration, and invasion. In this study, we recruited the ATC cell line 8305C and normal human thyroid cell Nthy-ori 3-1, aiming to find the miRNA which could regulate XIAP and therefore inhibit the growth and invasion of ATC. We first used quantitative real-time PCR (qPCR) to reveal that XIAP mRNA expression was 4.6±0.56 folds (P=0.029) up-regulated in 8305C cells, compared with Nthy-ori 3-1 cells. Then miR-618, predicted to target XIAP directly, was detected 0.24±0.06 folds (P=0.019) down-regulated in 8305C cells. Next we used Luciferase assay showing that XIAP was a target gene of miR-618, which could repress the XIAP expression at both mRNA and protein levels. After that, CCK-8 assay was performed to show that over-expression of miR-618 could inhibit the growth of 8305C cells. Finally, we employed transwell method to prove that miR-618 could prevent the invasion and migration of 8305C cells. In conclusion, our collective data showed that over-expression of miR-618 could inhibit ATC cells by targeting XIAP gene.

The Effect of Thyroid-Stimulating Hormone on Tumor Size in Differentiated Thyroid Carcinoma.

We evaluated the correlation between serum thyroid-stimulating hormone (TSH) levels and tumor size and other invasiveness parameters of tumor in patients with differentiated thyroid carcinoma (DTC). Several clinical studies have reported that TSH may also have a role as a regulator of the development and function of the thyroid gland. It is currently not clear whether TSH is involved in the existence of thyroid cancer or progression of thyroid cancer or both. Patients with DTC who underwent thyroid surgery between 2003 and 2008 were included this study. Preoperative serum T3, T4, and TSH levels were compared with the size and invasiveness of cancer, retrospectively. DTC was observed in 110 patients over the 5-year period. Seventy-seven (70%) of them were euthyroid and classified as the "normal-TSH group" (NTG), and 33 (30%) have an overt or subclinical hyperthyroidism, classified as the "low-TSH group" (LTG). The mean tumor diameter in the LTG was found to be 8.91 ± 8.03mm; however, it was found to be 18.19 ± 16.24mm in the NTG. There were significantly differences among the groups related to the diameter of tumor (p = 0.001). Microcarcinoma was determined in 36 patients (46.8%) in the NTG and 23 patients (69.7%) in the LTG (p = 0.027). Although there were no significant differences, tumor capsule invasion (33.8 vs. 18.2%, p = 0.099) and lymphovascular invasion (16.9 vs. 6.1%, p = 0.130) rates were higher in the NTG. These findings suggest that TSH has effects on growing and proliferation of not only normal thyroid cells but also cancer cells in DTC. This study revealed that serum TSH level can be explored as an important factor that affects the size and invasiveness of tumor in DTC.

MiR-145 suppresses thyroid cancer growth and metastasis and targets AKT3.

The expression and function of miR-145 in thyroid cancer is unknown. We evaluated the expression and function of miR-145 in thyroid cancer and its potential clinical application as a biomarker. We found that the expression of miR-145 is significantly downregulated in thyroid cancer as compared with normal. Overexpression of miR-145 in thyroid cancer cell lines resulted in: decreased cell proliferation, migration, invasion, VEGF secretion, and E-cadherin expression. miR-145 overexpression also inhibited the PI3K/Akt pathway and directly targeted AKT3. In vivo, miR-145 overexpression decreased tumor growth and metastasis in a xenograft mouse model, and VEGF secretion. miR-145 inhibition in normal primary follicular thyroid cells decreased the expression of thyroid cell differentiation markers. Analysis of indeterminate fine-needle aspiration samples showed miR-145 had a 92% negative predictive value for distinguishing benign from malignant thyroid nodules. Circulating miR-145 levels were significantly higher in patients with thyroid cancer and showed a venous gradient. Serum exosome extractions revealed that miR-145 is secreted. Our findings suggest that miR-145 is a master regulator of thyroid cancer growth, mediates its effect through the PI3K/Akt pathway, is secreted by the thyroid cancer cells, and may serve as an adjunct biomarker for thyroid cancer diagnosis.

Perspectives of the AMP-activated kinase (AMPK) signalling pathway in thyroid cancer.

Approximately 90% of non-medullary thyroid malignancies originate from the follicular cell and are classified as papillary or follicular (well-differentiated) thyroid carcinomas, showing an overall favourable prognosis. However, recurrence or persistence of the disease occurs in some cases associated with the presence of loco-regional or distant metastatic lesions that generally become resistant to radioiodine therapy, while glucose uptake and metabolism are increased. Recent advances in the field of tumor progression have shown that CTC (circulating tumour cells) are metabolic and genetically heterogeneous. There is now special interest in unravelling the mechanisms that allow the reminiscence of dormant tumour lesions that might be related to late disease progression and increased risk of recurrence. AMPK (AMP-activated protein kinase) is activated by the depletion in cellular energy levels and allows adaptive changes in cell metabolism that are fundamental for cell survival in a stressful environment; nevertheless, the activation of this kinase also decreases cell proliferation rate and induces tumour cell apoptosis. In the thyroid field, AMPK emerged as a novel important intracellular pathway, since it regulates both iodide and glucose uptakes in normal thyroid cells. Furthermore, it has recently been demonstrated that the AMPK pathway is highly activated in papillary thyroid carcinomas, although the clinical significance of these findings remains elusive. Herein we review the current knowledge about the role of AMPK activation in thyroid physiology and pathophysiology, with special focus on thyroid cancer.

High Iodine Blocks a Notch/miR-19 Loop Activated by the BRAFV600E Oncoprotein and Restores the Response to TGFβ in Thyroid Follicular Cells

Excess iodine inhibits thyroid follicular cell proliferation associated with TGFβ pathway activation, although thyroid cancers are frequently refractory to TGFβ signaling. The TGFβ pathway is predicted to be regulated by miR-17-92 cluster microRNAs. MicroRNAs are small noncoding RNAs that inhibit target mRNA translation and have emerged as potent modulators of tumorigenesis. Although the BRAF(V600E) mutation is the most prevalent alteration in thyroid cancer, the impact of iodine intake on BRAF-mediated oncogenesis remains unclear. Therefore, the aim of this study was to investigate the influence of high iodine on miR-17-92 transcriptional regulation and expression in thyroid cells expressing activated BRAF. Rat thyroid follicular cells that conditionally express BRAF(V600E) under doxycycline stimulation (PC-BRAF(V600E)-6) were derived from the PCCl3 line. These cells were treated with doxycycline for two days, in the absence or presence of 10 μM sodium iodide. The thyroid cancer cell lines BCPAP and KTC2 were also analyzed. Expression of the miR-17-92 cluster and Notch1 was analyzed by quantitative polymerase chain reaction, and expression of these genes was modulated by anti-miR or anti-Notch1 siRNAs transfection. Protein expression was assessed by Western blot. Luciferase assays were used to quantify Smad4 3'-UTR/miR-19 interaction and Notch signaling activation. TGFβ responsiveness was evaluated by cell cycle analysis of TGFβ-treated cells. High iodine blocked BRAF(V600E)-induced upregulation of miR-17-92, including miR-19a/b. miR-17-92 promoter region analysis revealed a putative binding site for Hes1, a transcription factor responsive to Notch signaling. Notch-1 overexpression resulted in miR-19 upregulation in normal thyroid cells, while Notch-1 knockdown blocked BRAF-induced miR-19 expression. Moreover, in anaplastic thyroid cancer cells, Notch-1 knockdown reduced miR-19. Expression of BRAF(V600E) decreased Smad4 protein in normal thyroid cells. Smad4 was validated as a miR-19 target by luciferase assays, which revealed reduced luminescence associated with miR-19 interaction in Smad4 3'-UTR. Iodine treatment restored Smad4 levels in BRAF-activated cells, resulting in enhanced G1-cell cycle arrest in response to TGFβ. Moreover, this effect was mimicked in papillary thyroid cancer cells treated with anti-miR-19. High iodine abrogates BRAF(V600E)-induced activation of miR-19, a newly identified Smad4 regulator, through Notch pathway inhibition and restores responsiveness to TGFβ signaling. Our results indicate that iodine exerts protective effects in thyroid cells, attenuating acute BRAF oncogene-mediated microRNA deregulation.

A case of psoriasis exacerbated by radioactive iodine therapy.

Dear Editor: Psoriasis is a chronic inflammatory skin disease that is characterized by erythematous, sharply demarcated papules and plaques covered by scales. Although the exact causes of psoriasis still remains obscure, it is known that genetic, immunological, and environmental factors contribute to its etiopathogenesis. Several factors such as trauma, stress, infections, and medications may exacerbate psoriasis. The most common medications known to trigger or worsen existing psoriasis include lithium, gold salts, beta blockers, and antimalarials. Exacerbation of psoriasis due to medications such as adrenergic antagonists, interferon, gemfibrozil, iodine, digoxin, and chlonidine has also been observed1. Radioactive iodine (RAI) therapy has been used for the remnant ablation and adjuvant therapy of thyroid cancer. The mechanism of RAI treatment is as follows: the thyroid gland needs iodine and absorbs it from the bloodstream, and then radiation destroys both cancerous and normal thyroid cells. Herein, we report the first case of psoriasis exacerbated by RAI therapy. A 32-year-old Korean woman presented with a 5-day history of erythroderma with papules and pustules on the whole body. On general inspection, generalized, scaly erythroderma with papules and pustules was observed (Fig. 1). She had a history of psoriasis for about 20 years and had undergone systemic narrow band ultraviolet (UV)-B phototherapy. Fig. 1 Generalized, scaly erythroderma with papules and pustules was observed on the arm (A) and abdomen (B) 5 days after radioactive iodine therapy. She received a diagnosis of papillary thyroid cancer and underwent total thyroidectomy 14 months previously. She was scheduled to have RAI therapy for thyroid cancer and was treated with phototherapy for psoriasis for up to 2 days before RAI therapy. Since then, she had applied topical steroid and calcipotriol ointment for the treatment of psoriasis. Five days after RAI therapy, erythroderma with papules and pustules developed over her whole body. Thus, this case was diagnosed as psoriasis exacerbated by RAI therapy. She applied topical desonide lotion and calcipotriol cream for 3 weeks, and clinical improvement was observed. She restarted to undergo systemic narrow band UV-B phototherapy for the treatment of psoriasis. Shelley2 reported two cases of generalized pustular psoriasis induced by potassium iodide. Kaufman3 observed that iodine/iodides specifically activate the enzyme dihydrofolic reductase. Methotrexate and aminopterin, as folic acid analogues, bind this enzyme, which blocks the metabolic steps in the synthesis of deoxyribronucleic acid and also blocks cell division4,5. Thus, activation of dihydrofolic reductase is associated with aggravation of the disease and inactivation associated with remission. This suggests that dihydrofolic reductase plays an important role in the pathogenesis of pustular psoriasis. We suspected that the mechanism in this case was related to the activation of dihydrofolic reductase through RAI. Further study about the folic acid pathway in psoriasis and the connection between RAI and psoriasis may be necessary.

Targeted Expression of Suicide Gene by Tissue-Specific Promoter and MicroRNA Regulation for Cancer Gene Therapy

In order to realise the full potential of cancer suicide gene therapy that allows the precise expression of suicide gene in cancer cells, we used a tissue specific Epithelial cell adhesion molecule (EpCAM) promoter (EGP-2) that directs transgene Herpes simplex virus–thymidine kinase (HSV-TK) expression preferentially in EpCAM over expressing cancer cells. EpCAM levels are considerably higher in retinoblastoma (RB), a childhood eye cancer with limited expression in normal cells. Use of miRNA regulation, adjacent to the use of the tissue-specific promoter, would provide the second layer of control to the transgene expression only in the tumor cells while sparing the normal cells. To test this hypothesis we cloned let-7b miRNA targets in the 3’UTR region of HSV-TK suicide gene driven by EpCAM promoter because let-7 family miRNAs, including let-7b, were found to be down regulated in the RB tumors and cell lines. We used EpCAM over expressing and let-7 down regulated RB cell lines Y79, WERI-Rb1 (EpCAM +ve/let-7bdown-regulated), EpCAM down regulated, let-7 over expressing normal retinal Müller glial cell line MIO-M1(EpCAM −ve/let-7bup-regulated), and EpCAM up regulated, let-7b up-regulated normal thyroid cell line N-Thy-Ori-3.1(EpCAM +ve/let-7bup-regulated) in the study. The cell proliferation was measured by MTT assay, apoptosis was measured by probing cleaved Caspase3, EpCAM and TK expression were quantified by Western blot. Our results showed that the EGP2-promoter HSV-TK (EGP2-TK) construct with 2 or 4 copies of let-7b miRNA targets expressed TK gene only in Y79, WERI-Rb-1, while the TK gene did not express in MIO-M1. In summary, we have developed a tissue-specific, miRNA-regulated dual control vector, which selectively expresses the suicide gene in EpCAM over expressing cells.

Expression of functional folate receptors by human parathyroid cells

Human pituitary adenomas express folate receptors (FR); therefore, we hypothesized that parathyroid (PT) tumors also might express FR, whereas normal human thyroids might not. The purpose of our study was to characterize the functionality of FRs on human PT tumors, with the goal of developing an imaging tool that would concentrate in PT more than in the thyroid. Human PTs and thyroids were evaluated for FR expression by immunohistochemistry. Expression of genes for FRα and FRβ was measured with the Illumina Human HT-12 Expression BeadChips and verified by quantitative reverse-transcription polymerase chain reaction. Folate incorporation by PT cells versus normal thyroid cells was determined by incubation with (99m)Technetium ((99m)Tc)(CO)3-folate and (99m)Tc-Etarfolatide, and uptake was determined by gamma counting. Specific targeting of FRs was demonstrated by blocking with cold folate. A549 cells and Jurkat cells served as FR-negative controls, and KB cells and HeLa cells were FR-positive controls. On immunohistochemistry and Western blotting, human PT cells expressed FRs, whereas human thyroid cells did not. The FRα gene was expressed in all PTs analyzed, and the FRβ gene was expressed by most. Uptake of (99m)Tc(CO)3-folate was increased in PT cells versus thyroid cells. There was dose-dependent uptake of (99m)Tc-etarfolatide, and uptake was inhibited by preincubation with cold folate, confirming FR-mediated binding. This is the first report of the expression and functionality of FRs on human PT cells. These findings suggest that (99m)Tc-folate holds potential for localization of PT tumors preoperatively and their treatment.

The Role of Epithelial Mesenchymal Transition Markers in Thyroid Carcinoma Progression

Understanding the molecular mechanisms involved in thyroid cancer progression may provide targets for more effective treatment of aggressive thyroid cancers. Epithelial mesenchymal transition (EMT) is a major pathologic mechanism in tumor progression and is linked to the acquisition of stem-like properties of cancer cells. We examined expression of ZEB1 which activates EMT by binding to the E-box elements in the E-cadherin promoter, and expression of E-cadherin in normal and neoplastic thyroid tissues in a tissue microarray which included 127 neoplasms and 10 normal thyroid specimens. Thyroid follicular adenomas (n = 32), follicular thyroid carcinomas (n = 28), and papillary thyroid carcinomas (n = 57) all expressed E-cadherin and were mostly negative for ZEB1 while most anaplastic thyroid carcinomas (ATC, n = 10) were negative for E-cadherin, but positive for ZEB1. A validation set of 10 whole sections of ATCs showed 90% of cases positive for ZEB1 and all cases were negative for E-cadherin. Analysis of three cell lines (normal thyroid, NTHY-OR13-1; PTC, TPC-1, and ATC, THJ-21T) showed that the ATC cell line expressed the highest levels of ZEB1 while the normal thyroid cell line expressed the highest levels of E-Cadherin. Quantitative RT-PCR analyses showed that Smad7 mRNA was significantly higher in ATC than in any other group (p < 0.05). These results indicate that ATCs show evidence of EMT including decreased expression of E-cadherin and increased expression of ZEB1 compared to well-differentiated thyroid carcinomas and that increased expression of Smad7 may be associated with thyroid tumor progression.

Switching from MAPK-dependent to MAPK-independent repression of the sodium-iodide symporter in 2D and 3D cultured normal thyroid cells

Loss of sodium-iodide symporter (NIS) expression in thyroid tumour cells primarily caused by constitutive MAPK pathway activation is often refractory to small molecule MAPK inhibitors. Suggested mechanisms are rebound MAPK signalling and activation of alternative signalling pathways. Here we provide evidence that failure to recover down-regulated NIS by MEK inhibition is not specific to tumour cells. NIS mRNA levels remained repressed in TSH-stimulated primary thyroid cells co-treated with epidermal growth factor (EGF) and pan-MEK inhibitor U0126 in the presence of 5% fetal bovine serum or, independently of serum, in 3D cultured thyroid follicles. This led to inhibited iodide transport and iodination. In contrast, U0126 restituted thyroglobulin synthesis in EGF-treated follicular cells. Serum potentiated TSH-stimulated NIS expression in 2D culture. U0126 blocked down-regulation of NIS only in serum-starved cells with a diminished TSH response. Together, this suggests that morphogenetic signals modify the expression of NIS and recovery response to MEK inhibition.

Patterns of FOXE1 Expression in Papillary Thyroid Carcinoma by Immunohistochemistry

FOXE1, a thyroid-specific transcription factor also known as TTF-2, was recently identified as a major genetic risk factor for papillary thyroid carcinoma (PTC). Its role in thyroid carcinogenesis, however, remains unknown. The purpose of the present study was to assess the relationship between the FOXE1 immunohistochemical features and the clinical and genetic characteristics of PTC. Immunohistochemical staining of FOXE1 was performed in 48 PTC cases. Two single nucleotide polymorphisms immediately inside (rs1867277) or in the vicinity (rs965513) of the FOXE1 gene were genotyped by direct sequencing. Histopathological, clinical, and genetic data were included in statistical analyses. FOXE1 exhibited cytoplasmic overexpression in tumor tissue compared to the normal counterpart (p<0.001). Both cancer and normal thyroid cells demonstrated the highest FOXE1 scores in the areas closest to the tumor border (<300 μm) compared with more distant areas (p<0.001). No differences in FOXE1 staining distributions were found between microcarcinomas and PTC of larger size, between different histopathological variants of PTC, and encapsulated and nonencapsulated tumors. Multivariate regression analysis revealed that nuclear FOXE1 expression in neoplastic cells in the vicinity of the tumor border independently associated with the genotype at rs1867277 (the dominant model of inheritance, p=0.037) and tumor multifocality (p=0.032), and with marginal significance with capsular invasion (p=0.051). FOXE1 overexpression and translocation to the cytoplasm are phenotypic hallmarks of tumor cells suggesting that FOXE1 is involved in the pathogenesis of PTC. Nuclear FOXE1 expression in tumor cells in the vicinity of the PTC border is associated with the presence of a risk allele of rs1867277 (c.-238G>A) in the 5' untranslated region of the FOXE1 gene, as well as with pathological characteristics of PTC, suggesting possible FOXE1 involvement in the facilitation of tumor development beginning at an early stage.

Cellular and molecular basis for thyroid cancer imaging in nuclear medicine

Papillary and follicular thyroid carcinomas (well-differentiated forms) are the most common follicular cell-derived thyroid malignancies, while poorly differentiated thyroid carcinomas and anaplastic thyroid carcinomas (also poorly differentiated) are the less common ones. Papillary carcinomas are morphologically and genetically different from follicular carcinomas: the former are associated, in up to 70 % of cases, with BRAF or RAS point mutations or RET/PTC rearrangements; the latter carry the RAS point mutation or the PAX8/PPARgamma rearrangement. The poorly differentiated forms have abnormalities in the TP53 and the CTNNB1 genes. The best way to image thyroid cancer cells is to exploit the capability of normal follicular thyroid cells to concentrate iodine 131I through the sodium–iodine symporter. Iodine is necessary for the production of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). Unfortunately, the cells of poorly differentiated carcinomas lose the capability to concentrate iodine; at the same time, their basal metabolism increases to satisfy the energy demands of highly proliferating cells. These cells require more glucose and a glucose analog, namely 18F-2-fluoro-2-deoxy-d-glucose (18FDG), is used in place of glucose to study their metabolism. The increased intake of glucose is mediated by a transmembrane transporter called glucose transporter-1 located on the cell membrane. The alternation of 131I and 18FDG uptake observed in thyroid tumors and their metastases is known as the “flip-flop” phenomenon. This review looks at the cellular and molecular mechanisms underlying thyroid cancer and thyroid cancer imaging.

Investigating an orally available small-molecule inhibitor (vemurafenib) of BRAFV600E in a novel preclinical model of human papillary thyroid cancer.

e17014 Background: Patients with BRAFV600E-positive human papillary thyroid cancer (PTC) have poorer prognosis, higher rates of metastases and mortality, and resistance to radioiodine treatment. The goal of this study was to assess the therapeutic efficacy of vemurafenib (a new orally available BRAFV600E selective inhibitor) in a translational therapeutic model of BRAFV600E human nonmetastatic or metastatic PTC. Methods: We have established in vitro cultures of human primary PTC cells with or without heterozygous BRAFWT/V600E, primary normal thyroid (NT) cells, and used previously established human PTC cell lines with BRAFV600E. Immunocytochemistry was used to characterize markers of differentiation. Genotyping (over 500 genes analyzed) by mass spectrometry was performed to determine genetic alterations. Cell viability assays were performed upon different concentrations of vemurafenib: 0.01, 0.1, 1, 5, and 10 µM. Phosphorylation (p) of ERK1/2 (downstream BRAFV600E) was used to measure BRAFV600E activity. Results: We have isolated 8 independent batches of primary human non-metastatic or metastatic PTC cells from total thyroidectomy patients with PTC &gt;1.1 cm, and 4 independent batches of primary NT cells from normal matched thyroid tissue specimens. 62.5% of the isolated batches of PTC cells were heterozygous BRAFWT/V600E and expressed epithelial markers and thyroid differentiation markers (e.g. PAX8, TSH-receptor). The NT cells showed no mutations. BRAFWT/V600E nonmetastatic PTC cells showed decreased viability (IC50: 5 µM) and pERK1/2 levels (IC90: 10 µM) when exposed to vemarufenib, with no toxic effects. PTC cells with BRAFWT, or NT cells showed no change in viability and pERK1/2 levels when exposed to vemarufenib. Importantly, BRAFWT/V600E metastatic PTC cells showed a partial suppression of viability and inhibition of pERK1/2 but only at a higher dose (10 µM) of vemurafenib. Conclusions: We have established the first translational therapeutic model of heterozygous BRAFWT/V600E-PTC. Testing of PTC samples for BRAFWT/V600E and testing in vitro will help predict therapeutic efficacy of Vemurafenib in patients with BRAFWT/V600E-PTC.

Abstract 3559: FKBP5 is an androgen-responsive gene in thyroid cancer cells.

Abstract There has been a steady increase in the incidence thyroid cancer in the United States, with over 56,000 cases predicted for 2012. The increased aggressiveness of the disease and poorer clinical outcome in men and postmenopausal women may be due to androgen/androgen receptor (AR) related functions. FK506 binding protein 51 (FKBP5) is a member of the immunophilin family and plays a role in steroid receptor function. Further, FKBP5 regulates the NFkB and AKT pathways and is thought to be relevant to the neoplastic process. Immunohistochemical analysis of 38 papillary thyroid cancer (PTC) specimens indicated that androgen receptor is expressed in both normal and cancerous epithelial cells, in both men and women. Analysis of AR expression in thyroid cell lines indicated that the normal thyroid cell line, Nthy-ori 3-1 and PTC cell lines BCPAP and TPC-1 expressed very low levels of AR, as measured by qRT-PCR and western blotting (&amp;gt;1000 fold less than the prostate cancer cell line, LNCaP). In contrast, PTC/anaplastic 8505C cells expressed higher levels of AR protein (approximately one third the level expressed in LNCaP cells). Upon addition of androgen, AR in 8505C translocated into the nucleus (as determined by immunocytochemistry) and upregulated transcription of both AR (∼1.7 fold) and FKBP5 (∼1.8 fold). To more fully understand the function of androgen/AR in thyroid cells, the AR cDNA from pSG5-AR was subcloned into the pcDNA3.1+ expression vector and stably transfected into thyroid cell lines. Primers for qRT-PCR of the endogenous or the transfected gene were designed. The 84E7 clone of transfected 8505C cells expressed 68 fold higher levels of AR mRNA than 8505C and 16 fold higher AR protein expression (∼5 fold higher AR protein expression than LNCaP). Upon addition of DHT to clone 84E7, AR translocated into the nucleus, and increased AR and FKBP5 mRNA expression (∼3 fold and ∼13 fold, respectively). The association between androgens/AR and upregulation of FKBP5 in thyroid cancer cells suggests that FKBP5 may play a role in thyroid cancer etiology and the different clinical presentation and outcomes between young women and men/postmenopausal women. Citation Format: Melanie E. MacEwan, Ken Wong, Ismatun Swati, Suqing Xie, Mohammad Rasul, Olena Ardacheva, Joseph Buchsbaum, Edward Shin, Augustine Moscatello, Stimson Schantz, Raj K. Tiwari, Jan Geliebter. FKBP5 is an androgen-responsive gene in thyroid cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3559. doi:10.1158/1538-7445.AM2013-3559

Notch Pathway Is Activated by MAPK Signaling and Influences Papillary Thyroid Cancer Proliferation

Mutually exclusive genetic alterations in the RET, RAS, or BRAF genes, which result in constitutively active mitogen-activated protein kinase (MAPK) signaling, are present in about 70% of papillary thyroid carcinomas (PTCs). However, the effect of MAPK activation on other signaling pathways involved in oncogenic transformation, such as Notch, remains unclear. In this study, we tested the hypothesis that the MAPK pathway regulates Notch signaling and that Notch signaling plays a role in PTC cell proliferation. Conditional induction of MAPK signaling oncogenes RET/PTC3 or BRAFT1799A in normal rat thyroid cell line mediated activation of Notch signaling, upregulating Notch1 receptor and Hes1, the downstream effector of Notch pathway. Conversely, pharmacological inhibition of MAPK reduced Notch signaling in PTC cell. Thyroid tumor samples from transgenic mice expressing BRAFT1799A and primary human PTC samples showed high levels of Notch1 expression. Down-regulation of Notch signaling by γ-secretase inhibitor (GSI) or NOTCH1 RNA interference reduces PTC cell proliferation. Moreover, the combination of GSI with a MAPK inhibitor enhanced the growth suppression in PTC cells. This study revealed that RET/PTC and BRAFT1799A activate Notch signaling and promote tumor growth in thyroid follicular cell. Taken together, these data suggest that Notch signaling may be explored as an adjuvant therapy for thyroid papillary cancer.

Humanized Medium (h7H) Allows Long-Term Primary Follicular Thyroid Cultures From Human Normal Thyroid, Benign Neoplasm, and Cancer

Mechanisms of thyroid physiology and cancer are principally studied in follicular cell lines. However, human thyroid cancer lines were found to be heavily contaminated by other sources, and only one supposedly normal-thyroid cell line, immortalized with SV40 antigen, is available. In primary culture, human follicular cultures lose their phenotype after passage. We hypothesized that the loss of the thyroid phenotype could be related to culture conditions in which human cells are grown in medium optimized for rodent culture, including hormones with marked differences in its affinity for the relevant rodent/human receptor. The objective of the study was to define conditions that allow the proliferation of primary human follicular thyrocytes for many passages without losing phenotype. Concentrations of hormones, transferrin, iodine, oligoelements, antioxidants, metabolites, and ethanol were adjusted within normal homeostatic human serum ranges. Single cultures were identified by short tandem repeats. Human-rodent interspecies contamination was assessed. We defined an humanized 7 homeostatic additives medium enabling growth of human thyroid cultures for more than 20 passages maintaining thyrocyte phenotype. Thyrocytes proliferated and were grouped as follicle-like structures; expressed Na+/I- symporter, pendrin, cytokeratins, thyroglobulin, and thyroperoxidase showed iodine-uptake and secreted thyroglobulin and free T3. Using these conditions, we generated a bank of thyroid tumors in culture from normal thyroids, Grave's hyperplasias, benign neoplasms (goiter, adenomas), and carcinomas. Using appropriate culture conditions is essential for phenotype maintenance in human thyrocytes. The bank of thyroid tumors in culture generated under humanized humanized 7 homeostatic additives culture conditions will provide a much-needed tool to compare similarly growing cells from normal vs pathological origins and thus to elucidate the molecular basis of thyroid disease.

RAC1b overexpression in papillary thyroid carcinoma: a role to unravel

The BRAF V600E mutation is the most frequent genetic alteration in papillary thyroid carcinoma (PTC). In colorectal cancer, BRAF V600E was described to functionally cooperate with RAC1b, a hyperactive splice variant of the small GTPase RAC1, to sustain cell survival. This interplay has never been investigated in PTCs. We aimed to analyze the expression of RAC1b in PTC and correlate its expression with BRAF V600E mutational status, histopathological features, and clinical outcome. Sixty-one patients and 87 samples (61 PTCs and 26 normal thyroid tissues) were included. Patients were divided into two groups based on longitudinal evolution and final outcome. RAC1b expression levels were determined by quantitative RT-PCR and western blotting. RAC1b was expressed in thyroid and overexpressed in 46% of PTCs. Neither RAC1b overexpression nor V600E mutation correlated with histopathological features classically associated with worse prognosis. RAC1b overexpression was significantly associated with both V600E mutation (P=0.0008) and poor clinical outcome (P=0.0029). Whereas BRAF V600E alone did not associate with patient outcome (P=0.2865), the association of RAC1b overexpression with BRAF V600E was overrepresented in the group with poorer clinical outcome (P=0.0044). Present results document, for the first time, expression of RAC1b in normal thyroid cells as well as overexpression in a subset of PTCs. Furthermore, they suggest a possible interplay between BRAF V600E and RAC1b contributing to poor clinical outcome. Future studies are needed to clarify the oncogenic potential of RAC1b in thyroid carcinogenesis.

Protection against Radiation-Induced Damage of 6-Propyl-2-thiouracil (PTU) in Thyroid Cells

Many epidemiologic studies have shown that the exposure to high external radiation doses increases thyroid neoplastic frequency, especially when given during childhood or adolescence. The use of radioprotective drugs may decrease the damage caused by radiation therapy and therefore could be useful to prevent the development of thyroid tumors. The aim of this study was to investigate the possible application of 6-propyl-2-thiouracil (PTU) as a radioprotector in the thyroid gland. Rat thyroid epithelial cells (FRTL-5) were exposed to different doses of γ irradiation with or without the addition of PTU, methimazole (MMI), reduced glutathione (GSH) and perchlorate (KClO4). Radiation response was analyzed by clonogenic survival assay. Cyclic AMP (cAMP) levels were measured by radioimmunoassay (RIA). Apoptosis was quantified by nuclear cell morphology and caspase 3 activity assays. Intracellular reactive oxygen species (ROS) levels were measured using the fluorescent dye 2',7'-dichlorofluorescein-diacetate. Catalase, superoxide dismutase and glutathione peroxidase activities were also determined. Pretreatment with PTU, MMI and GSH prior to irradiation significantly increased the surviving cell fraction (SF) at 2 Gy (P < 0.05), while no effect was observed with KClO4. An increase in extracellular levels of cAMP was found only in PTU treated cells in a dose and time-dependent manner. Cells incubated with agents that stimulate cAMP (forskolin and dibutyril cAMP) mimicked the effect of PTU on SF. Moreover, pretreatment with the inhibitor of protein kinase A, H-89, abolished the radioprotective effect of PTU. PTU treatment diminished radiation-induced apoptosis and protected cells against radiation-induced ROS elevation and suppression of the antioxidant enzyme's activity. PTU was found to radioprotect normal thyroid cells through cAMP elevation and reduction in both apoptosis and radiation-induced oxidative stress damage.