Antioxidant Defense Capacity Is Reduced in Thyroid Stem/Precursor Cells Compared to Differentiated Thyrocytes.

There is much evidence linking oxidative stress to thyroid cancer, and stem cells are thought to play a key role in the tumor-initiating mechanism. Their vulnerability to oxidative stress is unexplored. This study aimed to comparatively evaluate the antioxidant capacity of stem/precursor thyroid cells and mature thyrocytes. Human stem/precursor cells and mature thyrocytes were exposed to increasing concentrations of menadione, an oxidative-stress-producing agent, and reactive oxygen species (ROS) production and cell viability were measured. The expression of antioxidant and detoxification genes was measured via qPCR as well as the total antioxidant capacity and the content of glutathione. Menadione elevated ROS generation in stem/precursor thyroid cells more than in mature thyrocytes. The ROS increase was inversely correlated (p = 0.005) with cell viability, an effect that was partially prevented by the antioxidant curcumin. Most thyroid antioxidant defense genes, notably those encoding for the glutathione-generating system and phase I detoxification enzymes, were significantly less expressed in stem/precursor thyroid cells. As a result, the glutathione level and the total antioxidant capacity in stem/precursor thyroid cells were significantly decreased. This reduced antioxidant defense may have clinical implications, making stem/precursor thyroid cells critical targets for environmental conditions that are not detrimental for differentiated thyrocytes.

Pim-1 kinase is a positive feedback regulator of the senescent lung fibroblast inflammatory secretome.

Cellular senescence is emerging as a driver of idiopathic pulmonary fibrosis (IPF), a progressive and fatal disease with limited effective therapies. The senescence-associated secretory phenotype (SASP), involving the release of inflammatory cytokines and profibrotic growth factors by senescent cells, is thought to be a product of multiple cell types in IPF, including lung fibroblasts. NF-κB is a master regulator of the SASP, and its activity depends on the phosphorylation of p65/RelA. The purpose of this study was to assess the role of Pim-1 kinase as a driver of NF-κB-induced production of inflammatory cytokines from low-passage IPF fibroblast cultures displaying markers of senescence. Our results demonstrate that Pim-1 kinase phosphorylates p65/RelA, activating NF-κB activity and enhancing IL-6 production, which in turn amplifies the expression of PIM1, generating a positive feedback loop. In addition, targeting Pim-1 kinase with a small molecule inhibitor dramatically inhibited the expression of a broad array of cytokines and chemokines in IPF-derived fibroblasts. Furthermore, we provide evidence that Pim-1 overexpression in low-passage human lung fibroblasts is sufficient to drive premature senescence, in vitro. These findings highlight the therapeutic potential of targeting Pim-1 kinase to reprogram the secretome of senescent fibroblasts and halt IPF progression.

Heavy Metals in the Environment and Thyroid Cancer.

In recent decades, the incidence of thyroid cancer has increased more than most other cancers, paralleling the generalized worldwide increase in metal pollution. This review provides an overview of the evidence supporting a possible causative link between the increase in heavy metals in the environment and thyroid cancer. The major novelty is that human thyroid stem/progenitor cells (thyrospheres) chronically exposed to different metals at slightly increased environmentally relevant concentrations show a biphasic increase in proliferation typical of hormesis. The molecular mechanisms include, for all metals investigated, the activation of the extracellular signal-regulated kinase (ERK1/2) pathway. A metal mixture, at the same concentration of individual metals, was more effective. Under the same conditions, mature thyrocytes were unaffected. Preliminary data with tungsten indicate that, after chronic exposure, additional abnormalities may occur and persist in thyrocytes derived from exposed thyrospheres, leading to a progeny population of transformation-prone thyroid cells. In a rat model predisposed to develop thyroid cancer, long-term exposure to low levels of metals accelerated and worsened histological signs of malignancy in the thyroid. These studies provide new insight on metal toxicity and carcinogenicity occurring in thyroid cells at a low stage of differentiation when chronically exposed to metal concentrations that are slightly increased, albeit still in the "normal" range.

Thyroid Stem Cells But Not Differentiated Thyrocytes Are Sensitive to Slightly Increased Concentrations of Heavy Metals.

Thyroid cancer incidence is markedly increased in volcanic areas where residents are biocontaminated by chronic lifelong exposure to slightly increased metals in the environment. Metals can influence the biology of living cells by a variety of mechanisms, depending not only on the dose and length of exposure but also on the type and stage of differentiation of target cells. We explored the effect of five heavy metals (Cu, Hg, Pd, W and Zn) at nanomolar concentrations (the biocontamination level in residents of the volcanic area in Sicily where thyroid cancer is increased) on stimulating the proliferation of undifferentiated (thyrospheres) and differentiated human thyroid cells. Thyrosphere proliferation was significantly increased after exposure to each individual metal and a greater stimulating effect was observed when a mixture of the examined metals was used. No effect was seen in differentiated thyrocytes. For all metals, the dose-response curve followed a biphasic pattern that is typical of hormesis. Thyrosphere growth concerned the size rather than number, except with the metal mixture. An altered morphology was also observed in metal-treated thyrospheres. Metal-induced proliferation was due to activation of the ERK1/2 pathway, as confirmed by growth inhibition when ERK1/2 signaling was blocked. These studies show that stem/precursor thyroid cells are sensitive to small increases in environmental metal concentrations that are harmless for differentiated thyrocytes.

The Possible Role of Cancer Stem Cells in the Resistance to Kinase Inhibitors of Advanced Thyroid Cancer.

Target therapy with various kinase inhibitors (KIs) has been extended to patients with advanced thyroid cancer, but only a subset of these compounds has displayed efficacy in clinical use. However, after an initial response to KIs, dramatic disease progression occurs in most cases. With the discovery of cancer stem cells (CSCs), it is possible to postulate that thyroid cancer resistance to KI therapies, both intrinsic and acquired, may be sustained by this cell subtype. Indeed, CSCs have been considered as the main drivers of metastatic activity and therapeutic resistance, because of their ability to generate heterogeneous secondary cell populations and survive treatment by remaining in a quiescent state. Hence, despite the impressive progress in understanding of the molecular basis of thyroid tumorigenesis, drug resistance is still the major challenge in advanced thyroid cancer management. In this view, definition of the role of CSCs in thyroid cancer resistance may be crucial to identifying new therapeutic targets and preventing resistance to anti-cancer treatments and tumor relapse. The aim of this review is to elucidate the possible role of CSCs in the development of resistance of advanced thyroid cancer to current anti-cancer therapies and their potential implications in the management of these patients.

Increased Thyroid Cancer Incidence in Volcanic Areas: A Role of Increased Heavy Metals in the Environment?

Thyroid cancer incidence is significantly increased in volcanic areas, where relevant non-anthropogenic pollution with heavy metals is present in the environment. This review will discuss whether chronic lifelong exposure to slightly increased levels of metals can contribute to the increase in thyroid cancer in the residents of a volcanic area. The influence of metals on living cells depends on the physicochemical properties of the metals and their interaction with the target cell metallostasis network, which includes transporters, intracellular binding proteins, and metal-responsive elements. Very little is known about the carcinogenic potential of slightly increased metal levels on the thyroid, which might be more sensitive to mutagenic damage because of its unique biology related to iodine, which is a very reactive and strongly oxidizing agent. Different mechanisms could explain the specific carcinogenic effect of borderline/high environmental levels of metals on the thyroid, including (a) hormesis, the nonlinear response to chemicals causing important biological effects at low concentrations; (b) metal accumulation in the thyroid relative to other tissues; and (c) the specific effects of a mixture of different metals. Recent evidence related to all of these mechanisms is now available, and the data are compatible with a cause-effect relationship between increased metal levels in the environment and an increase in thyroid cancer incidence.

Selenium exerts protective effects against oxidative stress and cell damage in human thyrocytes and fibroblasts.

PURPOSE: Selenium, incorporated into specific seleno-enzymes, is essential to proper thyroid function and protect cells from oxidative damage induced by H2O2 during thyroid hormone synthesis. Several studies indicated that low selenium levels are associated with thyroid autoimmunity and related disorders, but real effectiveness of selenium supplementation in such diseases is still controversial. We evaluated the effect of selenium on oxidative damage in human thyrocytes and thyroid fibroblasts in vitro. METHODS: To induce oxidative stress, primary cultures were exposed to H2O2, in the presence or the absence of selenium, as either selenomethionine or selenite. We performed the following assays: cell viability, caspase-3 activity, BCL-2/BAX gene expression, DNA fragmentation, malondialdehyde levels, and glutathione peroxidase (GPx) activity measurements. RESULTS: Thyrocytes and thyroid fibroblasts exposed to H2O2 and preincubated with both selenocompounds displayed a significant dose-dependent increase in cell viability compared to cells incubated with H2O2 alone. Pretreatment with selenomethionine and selenite significantly reduced caspase-3 activity and BAX mRNA levels and increased BCL-2 mRNA levels in a dose-dependent manner. Accordingly, H2O2 induced a diffuse pattern of DNA degradation and an increase in malondialdehyde levels, which was prevented by the pretreatment with both selenomethionine and selenite. Both selenocompounds induced an increase in GPx activity, suggesting that these protective effects may be, almost in part, mediated by these selenoproteins. CONCLUSION: In human thyrocytes and fibroblasts in vitro, selenium exerts protective effects against H2O2 in a dose-dependent manner, being selenite effective at lower doses than selenomethionine.

Concentration of Metals and Trace Elements in the Normal Human and Rat Thyroid: Comparison with Muscle and Adipose Tissue and Volcanic Versus Control Areas.

Background: The concentration of trace elements and metals in the thyroid is the result of exposure, uptake, retention, and clearance. The specificity and selectivity of thyroid capacity to concentrate these elements relative to other tissues are not known. To obtain this information, we measured the tissue concentration of 26 elements in the thyroid, muscle, and fat of euthyroid human subjects and also in normal rats. Methods: At programmed surgery, small (<1 g) tissue fragments were collected in 77 euthyroid subjects. Macroscopically normal thyroid tissue, sternothyroid muscle, and neck subcutaneous fat samples were excised, and thyroid tissue was confirmed to be morphologically normal through microscopy. Tissue specimens (thyroid, hindlimb muscle, and abdominal fat) were also obtained from normal rats. Measurements of trace elements were performed on tissues using inductively coupled plasma mass spectrometry (DRC-ICP-MS). Results: Only 19 of the 26 investigated elements were measurable as 7 elements were below the limit of detection. The ranking concentration in human thyroid tissue, not considering iodide, indicated that Zn, Br, Cu, Cr, Se, and Mn represented over 95% of the measured elements. A similar ranking was observed in the rat thyroid. A comparison with other tissues indicated that in addition to I, also Br, Mn, Se, and Sn were significantly more concentrated in the thyroid, and this was also the case for the recognized carcinogens As, Cd, and Hg. As and Hg, but not Cd (which was not detectable in any of the rat tissues), were also more concentrated in the rat thyroid. Since human thyroid specimens were also obtained from residents of a volcanic area, where environmental pollution may cause human biocontamination, we compared the trace element concentration in specimens from the volcanic area with controls. Many trace elements were slightly, but not significantly, increased in the volcanic area specimens. Conclusions: In the normal human thyroid, many trace elements, including Br, Mn, Se, and Sn, and the recognized carcinogens, As, Cd, and Hg, are significantly more concentrated than in muscle and fat of the same individual. Similar data were observed in rats. The reason for the differential element accumulation in the thyroid is unclear; a better understanding may be useful to further clarify thyroid biology.

Molecular Alterations in Thyroid Cancer: From Bench to Clinical Practice.

Thyroid cancer comprises different clinical and histological entities. Whereas differentiated (DTCs) malignancies are sensitive to radioiodine therapy, anaplastic (ATCs) and medullary (MTCs) tumors do not uptake radioactive iodine and display aggressive features associated with a poor prognosis. Moreover, in a majority of DTCs, disease evolution leads to the progressive loss of iodine sensitivity. Hence, iodine-refractory DTCs, along with ATCs and MTCs, require alternative treatments reflective of their different tumor biology. In the last decade, the molecular mechanisms promoting thyroid cancer development and progression have been extensively studied. This has led to a better understanding of the genomic landscape, displayed by thyroid malignancies, and to the identification of novel therapeutic targets. Indeed, several pharmacological compounds have been developed for iodine-refractory tumors, with four multi-target tyrosine kinase inhibitors already available for DTCs (sorafenib and lenvatinib) and MTCs (cabozantib and vandetanib), and a plethora of drugs currently being evaluated in clinical trials. In this review, we will describe the genomic alterations and biological processes intertwined with thyroid cancer development, also providing a thorough overview of targeted drugs already tested or under investigation for these tumors. Furthermore, given the existing preclinical evidence, we will briefly discuss the potential role of immunotherapy as an additional therapeutic strategy for the treatment of thyroid cancer.

Effect of low-dose tungsten on human thyroid stem/precursor cells and their progeny.

Thyroid cancer incidence is increased in volcanic areas where environment pollution biocontaminates residents. Tungsten (W) is the most increased heavy metal in drinking water of Mount Etna volcanic area where it exceeds the normal range in the urine of 27% inhabitants. The possible connection between increased tungsten and thyroid cancer has never been studied. We investigated in vitro the effect tungsten on both human thyrocytes in primary culture, thyrospheres (aggregates of stem/precursor thyroid cells) and thyrocytes differentiated from tungsten-exposed thyrospheres. Chronic exposure to low-dose (nanomolar range, as in the urines of volcanic area residents) soluble tungsten had major biological effects on thyroid stem/precursor cells, promoting growth with a biphasic (hormetic) dose-response and reducing apoptosis. No such effects were observed in mature thyrocytes. In addition, tungsten-exposed thyrospheres had abnormal expression of genes commonly altered also in thyroid cancer and increased activation of the DNA-repair proteins H2AX and 53BP1. Moreover, exposure to tungsten decreased thyrosphere differentiation, as indicated by the reduced expression of thyroid-specific genes in derived thyrocytes that also showed preneoplastic changes such as increased anchorage-independent growth, clonogenic growth and migration capacity. The mechanism of action of tungsten on thyroid stem/precursor cells is unclear but involves membrane G-proteins and activation of the ERK signaling pathway. These data indicate that chronic exposure to slightly increased tungsten, harmless for mature thyrocytes, importantly affects the biology of stem/precursor thyroid cells and of their progeny, inducing characteristics of preneoplastic transformation.

The Copper(II)-Assisted Connection between NGF and BDNF by Means of Nerve Growth Factor-Mimicking Short Peptides.

Nerve growth factor (NGF) is a protein necessary for development and maintenance of the sympathetic and sensory nervous systems. We have previously shown that the NGF N-terminus peptide NGF(1-14) is sufficient to activate TrkA signaling pathways essential for neuronal survival and to induce an increase in brain-derived neurotrophic factor (BDNF) expression. Cu2+ ions played a critical role in the modulation of the biological activity of NGF(1-14). Using computational, spectroscopic, and biochemical techniques, here we report on the ability of a newly synthesized peptide named d-NGF(1-15), which is the dimeric form of NGF(1-14), to interact with TrkA. We found that d-NGF(1-15) interacts with the TrkA-D5 domain and induces the activation of its signaling pathways. Copper binding to d-NGF(1-15) stabilizes the secondary structure of the peptides, suggesting a strengthening of the noncovalent interactions that allow for the molecular recognition of D5 domain of TrkA and the activation of the signaling pathways. Intriguingly, the signaling cascade induced by the NGF peptides ultimately involves cAMP response element-binding protein (CREB) activation and an increase in BDNF protein level, in keeping with our previous result showing an increase of BDNF mRNA. All these promising connections can pave the way for developing interesting novel drugs for neurodegenerative diseases.

Short-term adverse effects of anticancer drugs in patients with type 2 diabetes.

The short-term adverse effects of anticancer drugs (AD) in patients with type 2 diabetes (T2D) are poorly studied and their management still represents an important challenge for clinicians. We carried out a retrospective single-center study in 168 patients with T2D and cancer, evaluating both the short-term effects of first-line AD on glycemic control and chronic diabetes complications. Average glycated hemoglobin significantly increased after AD compared to values before treatment (7.5 vs. 7.1%, p < 0.005). In 46.4% of patients, diabetes therapy had to be potentiated, in most cases (82.1%) by shifting to insulin. The use of alkylating agents and high-dose glucocorticoids predicted the need to potentiate diabetes therapy. After AD transaminase values significantly increased, whereas the estimated glomerular filtration rate decreased (in 12.5% <60 mL/min). Kinase inhibitors significantly increased the risk of microalbuminuria onset or progression. The present study provides a real-life information on the effects of different AD on the management of patients with T2D affected by several types of cancer.

Computational modeling reveals MAP3K8 as mediator of resistance to vemurafenib in thyroid cancer stem cells.

MOTIVATION: Val600Glu (V600E) mutation is the most common BRAF mutation detected in thyroid cancer. Hence, recent research efforts have been performed trying to explore several inhibitors of the V600E mutation-containing BRAF kinase as potential therapeutic options in thyroid cancer refractory to standard interventions. Among them, vemurafenib is a selective BRAF inhibitor approved by Food and Drug Administration for clinical practice. Unfortunately, vemurafenib often displays limited efficacy in poorly differentiated and anaplastic thyroid carcinomas probably because of intrinsic and/or acquired resistance mechanisms. In this view, cancer stem cells (CSCs) may represent a possible mechanism of resistance to vemurafenib, due to their self-renewal and chemo resistance properties. RESULTS: We present a computational framework to suggest new potential targets to overcome drug resistance. It has been validated with an in vitro model based upon a spheroid-forming method able to isolate thyroid CSCs that may mimic resistance to vemurafenib. Indeed, vemurafenib did not inhibit cell proliferation of BRAF V600E thyroid CSCs, but rather stimulated cell proliferation along with a paradoxical over-activation of ERK and AKT pathways. The computational model identified a fundamental role of mitogen-activated protein kinase 8 (MAP3K8), a serine/threonine kinase expressed in thyroid CSCs, in mediating this drug resistance. To confirm model prediction, we set a suitable in vitro experiment revealing that the treatment with MAP3K8 inhibitor restored the effect of vemurafenib in terms of both DNA fragmentation and poly (ADP-ribose) polymerase cleavage (apoptosis) in thyroid CSCs. Moreover, MAP3K8 expression levels may be a useful marker to predict the response to vemurafenib. AVAILABILITY AND IMPLEMENTATION: The model is available in GitHub repository visiting the following URL: https://github.com/francescopappalardo/MAP3K8-Thyroid-Spheres-V-3.0. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Amyloid Beta monomers regulate cyclic adenosine monophosphate response element binding protein functions by activating type-1 insulin-like growth factor receptors in neuronal cells.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with synaptic dysfunction, pathological accumulation of ß-amyloid (Aß), and neuronal loss. The self-association of Aß monomers into soluble oligomers seems to be crucial for the development of neurotoxicity (J. Neurochem., 00, 2007 and 1172). Aß oligomers have been suggested to compromise neuronal functions in AD by reducing the expression levels of the CREB target gene and brain-derived neurotrophic factor (BDNF) (J. Neurosci., 27, 2007 and 2628; Neurobiol. Aging, 36, 2015 and 20406 Mol. Neurodegener., 6, 2011 and 60). We previously reported a broad neuroprotective activity of physiological Aß monomers, involving the activation of type-1 insulin-like growth factor receptors (IGF-IRs) (J. Neurosci., 29, 2009 and 10582, Front Cell Neurosci., 9, 2015 and 297). We now provide evidence that Aß monomers, by activating the IGF-IR-stimulated PI3-K/AKT pathway, induce the activation of CREB in neurons and sustain BDNF transcription and release.

Thyroid Cancer in the Pediatric Age in Sicily: Influence of the Volcanic Environment.

BACKGROUND/AIM: Pediatric thyroid cancer (TC) is rare but its incidence is increasing. We analyzed incidence and characteristics of pediatric TC in Sicily and comparatively evaluated data from the volcanic and non-volcanic areas. MATERIALS AND METHODS: All incident pediatric (0-19 years) TCs in Sicily between 2002-2009 were analyzed for the area of residence and compared to data for adults. RESULTS: A total of 54 differentiated TCs (DTC) and nine medullary TCs were diagnosed in Sicily in children between 2002-2009. DTC age standardized rate for the world population (ASRw) was 0.8/105 in females and 0.2/105 in males, with a higher incidence in the volcanic area (ASRw=1.4/105 in females, 0.5/105 in males) vs. the rest of Sicily (ASRw=0.6/105 in females, 0.1/105 in males). Pediatric TCs were larger in size and more frequently with extrathyroid extension and lymph-node involvement in comparison to TCs in adults. CONCLUSION: In the volcanic environment of Sicily, TC incidence is markedly increased in children, suggesting a short-term effect of unidentified carcinogens of volcanic origin.

The Inorganic Side of NGF: Copper(II) and Zinc(II) Affect the NGF Mimicking Signaling of the N-Terminus Peptides Encompassing the Recognition Domain of TrkA Receptor.

The nerve growth factor (NGF) N-terminus peptide, NGF(1-14), and its acetylated form, Ac-NGF(1-14), were investigated to scrutinize the ability of this neurotrophin domain to mimic the whole protein. Theoretical calculations demonstrated that non-covalent forces assist the molecular recognition of TrkA receptor by both peptides. Combined parallel tempering/docking simulations discriminated the effect of the N-terminal acetylation on the recognition of NGF(1-14) by the domain 5 of TrkA (TrkA-D5). Experimental findings demonstrated that both NGF(1-14) and Ac-NGF(1-14) activate TrkA signaling pathways essential for neuronal survival. The NGF-induced TrkA internalization was slightly inhibited in the presence of Cu2+ and Zn2+ ions, whereas the metal ions elicited the NGF(1-14)-induced internalization of TrkA and no significant differences were found in the weak Ac-NGF(1-14)-induced receptor internalization. The crucial role of the metals was confirmed by experiments with the metal-chelator bathocuproine disulfonic acid, which showed different inhibitory effects in the signaling cascade, due to different metal affinity of NGF, NGF(1-14) and Ac-NGF(1-14). The NGF signaling cascade, activated by the two peptides, induced CREB phosphorylation, but the copper addition further stimulated the Akt, ERK and CREB phosphorylation in the presence of NGF and NGF(1-14) only. A dynamic and quick influx of both peptides into PC12 cells was tracked by live cell imaging with confocal microscopy. A significant role of copper ions was found in the modulation of peptide sub-cellular localization, especially at the nuclear level. Furthermore, a strong copper ionophoric ability of NGF(1-14) was measured. The Ac-NGF(1-14) peptide, which binds copper ions with a lower stability constant than NGF(1-14), exhibited a lower nuclear localization with respect to the total cellular uptake. These findings were correlated to the metal-induced increase of CREB and BDNF expression caused by NGF(1-14) stimulation. In summary, we here validated NGF(1-14) and Ac-NGF(1-14) as first examples of monomer and linear peptides able to activate the NGF-TrkA signaling cascade. Metal ions modulated the activity of both NGF protein and the NGF-mimicking peptides. Such findings demonstrated that NGF(1-14) sequence can reproduce the signal transduction of whole protein, therefore representing a very promising drug candidate for further pre-clinical studies.

Thyrospheres From Normal or Malignant Thyroid Tissue Have Different Biological, Functional, and Genetic Features.

CONTEXT: Cancer stem cells from several human malignancies, including poorly differentiated thyroid carcinoma and thyroid cancer cell lines, have been cultured in vitro as sphere-forming cells. These thyroid cancer stem cells were proven to be able to reproduce the original tumor in a xenograft orthotopic model. OBJECTIVES: The objective of the study was to characterize papillary thyroid carcinoma (PTC) spheres from well-differentiated thyroid cancer and normal thyroid (NT) spheres obtained from the contralateral thyroid tissue of the same patient. DESIGN: Thyrospheres from PTCs and NTs were isolated. MAIN OUTCOME MEASURES: Gene expression analysis by real-time PCR, immunofluorescence studies, and fluorescence-activated cell sorter analysis in thyrospheres from PTCs and NTs have been evaluated. CONCLUSIONS: Compared with NT spheres, PTC spheres are larger, more irregular, and more clonogenic and have a higher rate of symmetric division. Moreover, PTC spheres express higher levels of stem cell markers and lower levels of thyroid-specific genes compared with NT spheres. Under appropriate conditions, NT spheres differentiated into thyrocytes, whereas PTC spheres did not, displaying a defect in the differentiation potential. Immunofluorescence experiments indicated that, in NT spheres, progenitor cells are mainly present in the sphere core, and the sphere periphery contains thyroid precursor cells already committed to differentiation. PTC spheres are not polarized like NT spheres. Unlike cells differentiated from NT spheres, TSH did not significantly stimulate cAMP production in cells differentiated from PTC spheres. A microarray analysis performed in paired samples (NT and PTC spheres from the same patient) indicated that NT and PTC spheres display a gene expression pattern typical of stem/progenitor cells; however, compared with NT spheres, PTC spheres display a unique gene expression pattern that might be involved in PTC progression.

Thyroid cancer cell resistance to gefitinib depends on the constitutive oncogenic activation of the ERK pathway.

CONTEXT: Poorly differentiated thyroid carcinomas are refractory to common anticancer therapies, and novel inhibitors are being tested in these deadly malignancies. The epidermal growth factor receptor (EGFR) tyrosine kinase represents an attractive target for treatment because it is up-regulated in thyroid cancer and plays a role in cancer progression. However, EGFR inhibitors have provided poor results in thyroid carcinomas. OBJECTIVE: We evaluated the possible mechanism underlying the resistance of thyroid cancer cells to EGFR inhibitors. DESIGN: We tested the effect of the EGFR tyrosine kinase inhibitor gefitinib in a panel of thyroid cancer cell lines. RESULTS: We found that in most of the cell lines, although gefitinib inhibited EGFR phosphorylation, it was poorly effective in reducing cell viability. gefitinib, however, was able to inhibit epidermal growth factor-induced cell migration and matrix invasion. In most thyroid cancer cell lines, gefitinib significantly inhibited Akt phosphorylation by inhibiting EGFR activation, but it had limited or no effect on ERK phosphorylation. The poor cell response to gefitinib was associated with genetic alterations, leading to constitutive activation of the ERK pathway, including BRAF(V600E) and HRAS(G12A/Q61R) mutations and RET/PTC1 rearrangement. When BRAF(V600E)-positive thyroid cancer cells were incubated with the specific BRAF inhibitor PLX4032, sensitivity to gefitinib was restored. Similar results were obtained with rat sarcoma and RET/papillary thyroid cancer inhibitors. CONCLUSIONS: These results indicate that thyroid cancer resistance to gefitinib is due to the constitutive activation of the mitogenic pathway by either signals downstream of EGFR or other tyrosine kinase receptors. This resistance can be overcome by the combined use of selective inhibitors.

Reactivation of p53 mutants by prima-1 [corrected] in thyroid cancer cells.

Most undifferentiated thyroid carcinomas express p53 mutants and thereafter, are very resistant to chemotherapy. p53 reactivation and induction of massive apoptosis (Prima-1) is a compound restoring the tumor-suppressor activity of p53 mutants. We tested the effect of Prima-1 in thyroid cancer cells harboring p53 mutations. Increasing doses of Prima-1 reduced viability of thyroid cancer cells at a variable extent (range 20-80%). Prima-1 up-regulated p53 target genes (p21(WAF1) , BCL2-associated X protein (Bax), and murine double minute 2 (MDM2)), in BC-PAP and Hth-74 cells (expressing D259Y/K286E and K286E p53 mutants) but had no effect in SW1736 (p53 null) and TPC-1 (expressing wild-type p53) thyroid cancer cells. Prima-1 also increased the cytotoxic effects of either doxorubicin or cisplatin in thyroid cancer cells, including the chemo-resistant 8305C, Hth-74 and BC-PAP cells. Moreover, real-time PCR and Western blot indicated that Prima-1 increases the mRNA of thyroid-specific differentiation markers in thyroid cancer cells. Fluorescence-activated cell sorting analysis revealed that Prima-1 effect on thyroid cancer cells occurs via the enhancement of both cell cycle arrest and apoptosis. Small interfering RNA experiments indicated that Prima-1 effect is mediated by p53 mutants but not by the p53 paralog p73. Moreover, in C-643 thyroid cancer cells, forced to ectopically express wild-type p53, Prima-1 prevented the dominant negative effect of double K248Q/K286E p53 mutant. Finally, co-IP experiments indicated that in Hth-74 cells Prima-1 prevents the ability of p53 mutants to sequestrate the p53 paralog TAp73. These in vitro studies imply that p53 mutant reactivation by small compounds may become a novel anticancer therapy in undifferentiated thyroid carcinomas.

Insulin receptor isoforms and insulin-like growth factor receptor in human follicular cell precursors from papillary thyroid cancer and normal thyroid.

CONTEXT: Factors involved in the biology of normal and cancer stem/precursor cells from the thyroid are unknown. Thyroid cancer cells are responsive to insulin and IGF-I and IGF-II and often overexpress the insulin receptor (IR) and the IGF-I receptor (IGF-IR). OBJECTIVE: We investigated the role of IR isoforms (IR-A and IR-B), IGF-IR, and their ligands in thyroid follicular cell precursors both normal and malignant. DESIGN: We established cultures of follicular cell precursors as thyrospheres from three papillary thyroid cancers and the corresponding nonaffected tissues. The expression of IR, IGF-IR, and their ligands was evaluated by quantitative RT-PCR and, in one case, also by Western blot. The effects of insulin and IGFs on thyrosphere growth and self-renewal were evaluated. RESULTS: Thyrospheres were characterized by the expression of stem cell markers and low/absent thyroid specific markers. Thyrospheres from normal tissue, but not from cancer tissue, could be induced to differentiate. Both IR isoforms, IGF-IR, IGF-I and IGF-II, were expressed at high levels in thyrospheres and markedly decreased in differentiating cells. IR-A was the predominant isoform in thyrospheres, especially from cancer, while IR-B was predominant in differentiating cells. Cancer thyrosphere growth was stimulated by insulin and IGFs. CONCLUSIONS: Our data suggest that IR isoforms and IGF-IR play a role in the biology of follicular thyroid precursors. Cell differentiation is associated with marked changes in the expression of these receptors and cognate ligands. These data may provide insight for future differentiation therapies in thyroid cancer.