Combined Vorinostat and Chloroquine Inhibit Sodium-Iodide Symporter Endocytosis and Enhance Radionuclide Uptake In Vivo

PURPOSE

Patients with aggressive thyroid cancer are frequently failed by the central therapy of ablative radioiodide (RAI) uptake, due to reduced plasma membrane (PM) localization of the sodium/iodide symporter (NIS). We aimed to understand how NIS is endocytosed away from the PM of human thyroid cancer cells, and whether this was druggable in vivo.

EXPERIMENTAL DESIGN

Informed by analysis of endocytic gene expression in patients with aggressive thyroid cancer, we used mutagenesis, NanoBiT interaction assays, cell surface biotinylation assays, RAI uptake, and NanoBRET to understand the mechanisms of NIS endocytosis in transformed cell lines and patient-derived human primary thyroid cells. Systemic drug responses were monitored via 99mTc pertechnetate gamma counting and gene expression in BALB/c mice.

RESULTS

We identified an acidic dipeptide within the NIS C-terminus that mediates binding to the σ2 subunit of the Adaptor Protein 2 (AP2) heterotetramer. We discovered that the FDA-approved drug chloroquine (CQ) modulates NIS accumulation at the PM in a functional manner that is AP2 dependent. In vivo, CQ treatment of BALB/c mice significantly enhanced thyroidal uptake of 99mTc pertechnetate in combination with the histone deacetylase (HDAC) inhibitor vorinostat/SAHA, accompanied by increased thyroidal NIS mRNA. Bioinformatic analyses validated the clinical relevance of AP2 genes with disease-free survival in RAI-treated DTC, enabling construction of an AP2 gene-related risk score classifier for predicting recurrence.

CONCLUSIONS

NIS internalization is specifically druggable in vivo. Our data, therefore, provide new translatable potential for improving RAI therapy using FDA-approved drugs in patients with aggressive thyroid cancer. See related commentary by Lechner and Brent, p. 1220.

MON-717 Novel GLI2 Mutations Identified in Pediatric Patients with Combined Pituitary Hormone Deficiency: One Gene, Various Genotypes

Combined pituitary hormone deficiency (CPHD) is an important clinical problem caused by mutations in more than 30 different genes. Six genes in the Sonic Hedgehog (SHH) signalling pathway are reported to cause CPHD. SHH signaling is essential to induce pituitary cell identity in cells of Rathke’s pouch by stimulating expression of the transcription factors Lhx3 and Lhx4. In the absence of SHH signaling, a repressive isoform of the transcription factor GLI2 (Gli-Kruppel family member 2) suppresses gene expression. In the presence of SHH signaling, the activating form of GLI2 gains access to the nucleus and induces expression of downstream target genes. Heterozygous GLI2 loss of function mutations are found in patients with holoprosencephaly (HPE), HPE-like phenotypes associated with pituitary anomalies, and combined pituitary hormone deficiency with or without other extra-pituitary findings. We sought to identify the cause of CPHD in 171 unrelated patients diagnosed with or without extra-pituitary manifestations that were recruited from several Argentinean medical centers. We conducted panel sequencing, and identified GLI2 heterozygous variants that were rare and predicted to be deleterious in two unrelated patients, (p.L761P and p.1404Lfs) and a single, heterozygous, rare, likely deleterious GLI2 variant identified by exome sequencing (p.A203T). p.L761P and p.A203T variants were previously reported as candidates for HPE/CPHD, no functional studies were carried out to determine the effect of the variants on the gene function. We performed functional analysis of these variants using a mammalian cell line (NIH/3T3-CG) previously engineered to be a sensor for SHH signaling. It was stably transfected with a reporter gene that expresses GFP in response to GLI2 activation by a SHH agonist. We modified this cell line to assay GLI2 variants. We created a homozygous knock out of both endogenous Gli2 genes using CRISPR-Cas9 editing, and individual cell clones were selected for loss of GFP expression in response to SHH agonist treatment by FACS. We verified that transfecting the knockout cells with wild type Gli2 restored SHH responsive GFP expression. We assayed the ability of three patient GLI2 variants to rescue GFP expression and SHH agonist responsiveness and found that all three failed to fully rescue to wild type levels. This supports the hypothesis that the GLI2 variants in three CPHD patients are likely pathogenic. Thus, we identified three likely pathogenic GLI2 mutations in CPHD patients from Argentina. The variable phenotype of patients with GLI2 mutations worldwide could be caused by variation in other genes, environmental exposures, maternal effects, and/or epigenetic factors.

The ERα membrane pool modulates the proliferation of pituitary tumours

The molecular mechanisms underlying the ERα nuclear/cytoplasmic pool that modulates pituitary cell proliferation have been widely described, but it is still not clear how ERα is targeted to the plasma membrane. The aim of this study was to analyse ERα palmitoylation and the plasma membrane ERα (mERα) pool, and their participation in E2-triggered membrane-initiated signalling in normal and pituitary tumour cell growth. Cell cultures were prepared from anterior pituitaries of female Wistar rats and tumour GH3 cells, and treated with 10 nM of oestradiol (E2). The basal expression of ERα was higher in tumour GH3 than in normal pituitary cells. Full-length palmitoylated ERα was observed in normal and pituitary tumour cells, demonstrating that E2 stimulation increased both, ERα in plasma membrane and ERα and caveolin-1 interaction after short-term treatment. In addition, the Dhhc7 and Dhhc21 palmitoylases were negatively regulated after sustained stimulation of E2 for 3 h. Although the uptake of BrdU into the nucleus in normal pituitary cells was not modified by E2, a significant increase in the GH3 tumoural cell, as well as ERK1/2 activation, with this effect being mimicked by PPT, a selective antagonist of ERα. These proliferative effects were blocked by ICI 182780 and the global inhibitor of palmitoylation. These findings indicate that ERα palmitoylation modulated the mERα pool and consequently the ERK1/2 pathway, thereby contributing to pituitary tumour cell proliferation. These results suggest that the plasma membrane ERα pool might be related to the proliferative behaviour of prolactinoma and may be a marker of pituitary tumour growth.

Inefficient N2-Like Neutrophils Are Promoted by Androgens During Infection

Neutrophils are major effectors of acute inflammation against infection and tissue damage, with ability to adapt their phenotype according to the microenvironment. Although sex hormones regulate adaptive immune cells, which explains sex differences in immunity and infection, little information is available about the effects of androgens on neutrophils. We therefore aimed to examine neutrophil recruitment and plasticity in androgen–dependent and –independent sites under androgen manipulation. By using a bacterial model of prostate inflammation, we showed that neutrophil recruitment was higher in testosterone-treated rats, with neutrophil accumulation being positively correlated to serum levels of testosterone and associated to stronger inflammatory signs and tissue damage. Testosterone also promoted LPS-induced neutrophil recruitment to the prostate, peritoneum, and liver sinusoids, as revealed by histopathology, flow cytometry, and intravital microscopy. Strikingly, neutrophils in presence of testosterone exhibited an impaired bactericidal ability and a reduced myeloperoxidase activity. This inefficient cellular profile was accompanied by high expression of the anti-inflammatory cytokines IL10 and TGFβ1, which is compatible with the “N2-like” neutrophil phenotype previously reported in the tumor microenvironment. These data reveal an intriguing role for testosterone promoting inefficient, anti-inflammatory neutrophils that prolong bacterial inflammation, generating a pathogenic environment for several conditions. However, these immunomodulatory properties might be beneficially exploited in autoimmune and other non-bacterial diseases.

Testosterone Rescues the De-Differentiation of Smooth Muscle Cells Through Serum Response Factor/Myocardin

Prostatic smooth muscle cells (pSMCs) differentiation is a key factor for prostatic homeostasis, with androgens exerting multiple effects on these cells. Here, we demonstrated that the myodifferentiator complex Srf/Myocd is up-regulated by testosterone in a dose-dependent manner in primary cultures of rat pSMCs, which was associated to the increase in Acta2, Cnn1, and Lmod1 expressions. Blocking Srf or Myocd by siRNAs inhibited the myodifferentiator effect of testosterone. While LPS led to a dedifferentiated phenotype in pSMCs, characterized by down-regulation of Srf/Myocd and smooth muscle cell (SMC)-restricted genes, endotoxin treatment on Myocd-overexpressing cells did not result in phenotypic alterations. Testosterone at a physiological dose was able to restore the muscular phenotype by normalizing Srf/Myocd expression in inflammation-induced dedifferentiated pSMCs. Moreover, the androgen reestablished the proliferation rate and IL-6 secretion increased by LPS. These results provide novel evidence regarding the myodifferentiating role of testosterone on SMCs by modulating Srf/Myocd. Thus, androgens preserve prostatic SMC phenotype, which is essential to maintain the normal structure and function of the prostate. J. Cell. Physiol. 232: 2806-2817, 2017. © 2016 Wiley Periodicals, Inc.

Effects of 2-iodohexadecanal in the physiology of thyroid cells

Iodide has direct effects on thyroid function. Several iodinated lipids are biosynthesized by the thyroid and they were postulated as intermediaries in the action of iodide. Among them, 2-iodohexadecanal (2-IHDA) has been identified and proposed to play a role in thyroid autoregulation. The aim of this study was to compare the effect of iodide and 2-IHDA on thyroid cell physiology. For this purpose, FRTL-5 thyroid cells were incubated with the two compounds during 24 or 48 h and several thyroid parameters were evaluated such as: iodide uptake, intracellular calcium and H₂O₂ levels. To further explore the molecular mechanism involved in 2-IHDA action, transcript and protein levels of genes involved in thyroid hormone biosynthesis, as well as the transcriptional expression of these genes were evaluated in the presence of iodide and 2-IHDA. The results obtained indicate that 2-IHDA reproduces the action of excess iodide on the "Wolff-Chaikoff" effect as well as on thyroid specific genes transcription supporting its role in thyroid autoregulation.

Beyond non-integer Hill coefficients: A novel approach to analyzing binding data, applied to Na+-driven transporters

A novel approach to analyzing binding data from proteins with two binding sites for the same substrate provides information beyond that accessible with traditional Hill equation analysis.

Prokaryotic and eukaryotic Na⁺-driven transporters couple the movement of one or more Na⁺ ions down their electrochemical gradient to the active transport of a variety of solutes. When more than one Na⁺ is involved, Na⁺-binding data are usually analyzed using the Hill equation with a non-integer exponent n. The results of this analysis are an overall K_d-like constant equal to the concentration of ligand that produces half saturation and n, a measure of cooperativity. This information is usually insufficient to provide the basis for mechanistic models. In the case of transport using two Na⁺ ions, an n < 2 indicates that molecules with only one of the two sites occupied are present at low saturation. Here, we propose a new way of analyzing Na⁺-binding data for the case of two Na⁺ ions that, by taking into account binding to individual sites, provides far more information than can be obtained by using the Hill equation with a non-integer coefficient: it yields pairs of possible values for the Na⁺ affinities of the individual sites that can only vary within narrowly bounded ranges. To illustrate the advantages of the method, we present experimental scintillation proximity assay (SPA) data on binding of Na⁺ to the Na⁺/I⁻ symporter (NIS). SPA is a method widely used to study the binding of Na⁺ to Na⁺-driven transporters. NIS is the key plasma membrane protein that mediates active I⁻ transport in the thyroid gland, the first step in the biosynthesis of the thyroid hormones, of which iodine is an essential constituent. NIS activity is electrogenic, with a 2:1 Na⁺/I⁻ transport stoichiometry. The formalism proposed here is general and can be used to analyze data on other proteins with two binding sites for the same substrate.

The iodide-transport-defect-causing mutation R124H: a δ-amino group at position 124 is critical for maturation and trafficking of the Na+/I- symporter

Na(+)/I(-) symporter (NIS)-mediated active accumulation of I(-) in thyrocytes is a key step in the biosynthesis of the iodine-containing thyroid hormones T3 and T4. Several NIS mutants have been identified as a cause of congenital I(-) transport defect (ITD), and their investigation has yielded valuable mechanistic information on NIS. Here we report novel findings derived from the thorough characterization of the ITD-causing mutation R124H, located in the second intracellular loop (IL-2). R124H NIS is incompletely glycosylated and colocalizes with endoplasmic reticulum (ER)-resident protein markers. As a result, R124H NIS is not targeted to the plasma membrane and therefore does not mediate any I(-) transport in transfected COS-7 cells. Strikingly, however, the mutant is intrinsically active, as revealed by its ability to mediate I(-) transport in membrane vesicles. Of all the amino acid substitutions we carried out at position 124 (K, D, E, A, W, N and Q), only Gln restored targeting of NIS to the plasma membrane and NIS activity, suggesting a key structural role for the δ-amino group of R124 in the transporter's maturation and cell surface targeting. Using our NIS homology model based on the structure of the Vibrio parahaemolyticus Na(+)/galactose symporter, we propose an interaction between the δ-amino group of either R or Q124 and the thiol group of C440, located in IL-6. We conclude that the interaction between IL-2 and IL-6 is critical for the local folding required for NIS maturation and plasma membrane trafficking.

The KCNQ1-KCNE2 K⁺ channel is required for adequate thyroid I⁻ uptake

The KCNQ1 α subunit and the KCNE2 β subunit form a potassium channel in thyroid epithelial cells. Genetic disruption of KCNQ1-KCNE2 causes hypothyroidism in mice, resulting in cardiac hypertrophy, dwarfism, alopecia, and prenatal mortality. Here, we investigated the mechanistic requirement for KCNQ1-KCNE2 in thyroid hormone biosynthesis, utilizing whole-animal dynamic positron emission tomography. The KCNQ1-specific antagonist (-)-[3R,4S]-chromanol 293B (C293B) significantly impaired thyroid cell I(-) uptake, which is mediated by the Na(+)/I(-) symporter (NIS), in vivo (dSUV/dt: vehicle, 0.028 ± 0.004 min(-1); 10 mg/kg C293B, 0.009 ± 0.006 min(-1)) and in vitro (EC(50): 99 ± 10 μM C293B). Na(+)-dependent nicotinate uptake by SMCT, however, was unaffected. Kcne2 deletion did not alter the balance of free vs. thyroglobulin-bound I(-) in the thyroid (distinguished using ClO(4)(-), a competitive inhibitor of NIS), indicating that KCNQ1-KCNE2 is not required for Duox/TPO-mediated I(-) organification. However, Kcne2 deletion doubled the rate of free I(-) efflux from the thyroid following ClO(4)(-) injection, a NIS-independent process. Thus, KCNQ1-KCNE2 is necessary for adequate thyroid cell I(-) uptake, the most likely explanation being that it is prerequisite for adequate NIS activity.

Nuclear factor (NF)-kappaB-dependent thyroid hormone receptor beta1 expression controls dendritic cell function via Akt signaling

Despite considerable progress in our understanding of the interplay between immune and endocrine systems, the role of thyroid hormones and their receptors in the control of adaptive immunity is still uncertain. Here, we investigated the role of thyroid hormone receptor (TR) beta(1) signaling in modulating dendritic cell (DC) physiology and the intracellular mechanisms underlying these immunoregulatory effects. Exposure of DCs to triiodothyronine (T(3)) resulted in a rapid and sustained increase in Akt phosphorylation independently of phosphatidylinositol 3-kinase activation, which was essential for supporting T(3)-induced DC maturation and interleukin (IL)-12 production. This effect was dependent on intact TR beta(1) signaling as small interfering RNA-mediated silencing of TR beta(1) expression prevented T(3)-induced DC maturation and IL-12 secretion as well as Akt activation and I kappaB-epsilon degradation. In turn, T(3) up-regulated TR beta(1) expression through mechanisms involving NF-kappaB, suggesting an autocrine regulatory loop to control hormone-dependent TR beta(1) signaling. These findings were confirmed by chromatin immunoprecipitation analysis, which disclosed a new functional NF-kappaB consensus site in the promoter region of the TRB1 gene. Thus, a T(3)-induced NF-kappaB-dependent mechanism controls TR beta(1) expression, which in turn signals DCs to promote maturation and function via an Akt-dependent but PI3K-independent pathway. These results underscore a novel unrecognized target that regulates DC maturation and function with critical implications in immunopathology at the cross-roads of the immune-endocrine circuits.

Expression of Toll-like receptor 4 in the prostate gland and its association with the severity of prostate cancer

BACKGROUND

Chronic inflammation has been postulated to be an important driving force to prostate carcinoma. Toll-like receptors (TLRs) compose a family of receptors mainly expressed on immune cells. Recently, functional TLRs have been shown to be also expressed in numerous cancer cells, but their significance has only recently begun to be explored. The purpose of this study was to investigate the putative role of TLR4 expression in prostate carcinoma.

METHODS

To determine if there is an association between TLR4 expression and the malignancy of the tumor, 35 prostate carcinoma samples showing different Gleason grades were analyzed by immunohistochemistry. Also, to explore the functionality of the receptors expressed on the epithelium, we analyzed the type of cytokine response elicited and the signaling pathways involved after TLR4 triggering in the human prostate adenocarcinoma cell line, DU-145.

RESULTS

TLR4 is expressed in the normal prostate gland in both stroma and epithelium. TLR4 expression significantly drops to negative values as the Gleason grade augments in both, stroma and epithelium. Moreover, DU-145 cells also exhibit TLR4 expression and respond to TLR4 agonists, activating the transcription factor NF-kappaB and increasing the expression of pro-inflammatory mediators. Inhibition of the molecular adaptors MyD88 and MAL by overexpression of dominant-negative mutants diminished LPS-induced activation of NF-kappaB, showing that DU-145 cells activate the NF-kappaB through MyD88-dependent signaling pathways.

CONCLUSIONS

We hypothesize that TLR4 in prostate cells could synergize with innate immune cells contributing to an eventual inflammatory process, which in genetically prone individuals could promote carcinogenesis. Prostate 69: 1387-1397, 2009. (c) 2009 Wiley-Liss, Inc.

Endogenous thyrocyte-produced nitric oxide inhibits iodide uptake and thyroid-specific gene expression in FRTL-5 thyroid cells

Nitric oxide (NO) is a free radical that mediates a wide array of cell functions. It is generated from l-arginine by NO-synthase (NOS). Expression of NOS isoforms has been demonstrated in thyroid cells. Previous reports indicated that NO donors induce dedifferentiation in thyrocytes. However, the functional significance of endogenous thyrocyte-produced NO has not been explored. This work aimed to study the influence of endogenous NO on parameters of thyroid cell function and differentiation in FRTL-5 cells. We observed that treatment with the NOS inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME), increased the TSH-stimulated iodide uptake. The TSH-induced sodium iodide symporter (NIS) and thyroglobulin (TG) mRNA expressions were increased after incubation with L-NAME. In transient transfection assays, TSH-stimulated transcriptional activities of NIS and TG promoters were increased by L-NAME. An increment of the TSH-stimulated cell proliferation was observed after NOS inhibition. Similar results were obtained when the action of another NOS inhibitor, N(g)-monomethyl-L-arginine, was analysed for most of these studies. The production of NO, which was not detectable in basal conditions, was increased by TSH. Our data provide strong evidence that endogenous NO could act as a negative signal for TSH-stimulated iodide uptake and thyroid-specific gene expression as well as proliferation in thyrocytes. These findings reveal a possible new inhibitory pathway in the regulation of thyroid cell function.