Iodine mediated mechanisms and thyroid carcinoma

Association between Consumption of Iodine-Rich Foods and Thyroid Cancer Prevalence: Findings from a Large Population-Based Study

The influence of iodine-rich foods on thyroid cancer (TC) risk remains inadequately understood. Therefore, we aimed to comprehensively investigate the relationship between three iodine-rich food groups and TC prevalence using extensive data from a large Korean population. We assessed the dietary intake of 169,057 participants in the Korean Genome and Epidemiology Study (2004-2013) using a food frequency questionnaire. The top-three iodine-rich food groups (including egg, seaweed, and dairy) were selected based on Korean dietary reference intakes and categorized by weekly consumption frequency. We conducted multiple logistic regression models to examine the relationship between food consumption and TC prevalence. After adjusting for confounding factors, higher seaweed consumption (>5 times/week) was significantly associated with lower TC prevalence (odds ratio [OR], 95% confidence interval [CI] = 0.42, 0.32-0.56, p-value < 0.001). In contrast, compared with moderate dairy consumption (3-4 times/week), lower dairy product intake (<1 time/week) was associated with higher TC prevalence (OR, 95% CI = 1.32, 1.05-1.67, p-value = 0.017). Our findings suggest that sufficient seaweed consumption may offer protection against TC, and incorporating dairy products into the diet may lower TC incidence in the Korean population. The most significant limitations of our study are the absence of 24 h urine samples for iodine status assessment and the lack of clinical data on the diagnosis of thyroid cancer.

Biological regulation on iodine using nano-starch for preventing thyroid dysfunction

The growing incidence of thyroid disease triggered by excess iodine uptake poses a severe health threat throughout the world. Extracellular interference therapies impede iodine transport across the sodium-iodide symporter (NIS) membrane protein and thus prevent excessive iodine uptake by thyroid cells, which may lessen the occurrence of disease. Herein, we for the first time utilized nano-starch particles (St NPs) to regulate iodine transport across the NIS protein of thyroid cells by using extracellular interference therapy. By precisely encapsulating iodine within the cavity of a glucan α-helix via hydrogen bonding, extracellular St NPs prevented excess iodine uptake by thyroid cells in vitro and in vivo; this down-regulated the expression of NIS protein (0.06-fold) and autophagy protein LC3B-II (0.35-fold). We also found that St NPs regulated the metabolic pathway of iodine in zebrafish. We believe this proposed strategy offers a novel insight into controlling iodine uptake by the thyroid and indicates a new direction for preventing iodine-induced thyroid disease.

Association between exposure to radioactive iodine after the Chernobyl accident and thyroid volume in Belarus 10-15 years later

BACKGROUND

While there is a robust literature on environmental exposure to iodine-131 (131I) in childhood and adolescence and the risk of thyroid cancer and benign nodules, little is known about its effects on thyroid volume.

METHODS

To assess the effect of 131I dose to the thyroid on the volume of the thyroid gland, we examined the data from the baseline screening of the Belarusian-American Cohort Study of residents of Belarus who were exposed to the Chernobyl fallout at ages ≤18 years. Thyroid dose estimates were based on individual thyroid activity measurements made shortly after the accident and dosimetric data from questionnaires obtained 10-15 years later at baseline screening. During baseline screening, thyroid gland volume was assessed from thyroid ultrasound measurements. The association between radiation dose and thyroid volume was modeled using linear regression where radiation dose was expressed with power terms to address non-linearity. The model was adjusted for attained age, sex, and place of residence, and their modifying effects were examined.

RESULTS

The analysis was based on 10,703 subjects. We found a statistically significant positive association between radiation dose and thyroid volume (P < 0.001). Heterogeneity of association was observed by attained age (P < 0.001) with statistically significant association remaining only in the subgroup of ≥18 years at screening (P < 0.001). For this group, increase in dose from 0.0005 to 0.15 Gy was associated with a 1.27 ml (95% CI: 0.46, 2.07) increase in thyroid volume. The estimated effect did not change with increasing doses above 0.15 Gy.

CONCLUSIONS

This is the first study to examine the association between 131I dose to the thyroid gland and thyroid volume in a population of individuals exposed during childhood and systematically screened 10-15 years later. It provides evidence for a moderate statistically significant increase in thyroid volume among those who were ≥ 18 years at screening. Given that this effect was observed at very low doses and was restricted to a narrow dose range, further studies are necessary to better understand the effect.

Trace elements and the thyroid

Trace elements, such as iodine and selenium (Se), are vital to human health and play an essential role in metabolism. They are also important to thyroid metabolism and function, and correlate with thyroid autoimmunity and tumors. Other minerals such as iron (Ir), lithium (Li), copper (Co), zinc (Zn), manganese (Mn), magnesium (Mg), cadmium (Cd), and molybdenum (Mo), may related to thyroid function and disease. Normal thyroid function depends on a variety of trace elements for thyroid hormone synthesis and metabolism. These trace elements interact with each other and are in a dynamic balance. However, this balance may be disturbed by the excess or deficiency of one or more elements, leading to abnormal thyroid function and the promotion of autoimmune thyroid diseases and thyroid tumors.The relationship between trace elements and thyroid disorders is still unclear, and further research is needed to clarify this issue and improve our understanding of how trace elements mediate thyroid function and metabolism. This paper systematically reviewed recently published literature on the relationship between various trace elements and thyroid function to provide a preliminary theoretical basis for future research.

High Iodine Nutrition May Be a Risk Factor for Cervical Lymph Node Metastasis in Papillary Thyroid Cancer Patients

PURPOSE

The aim of this study was to retrospectively identify the effect of iodine on the papillary thyroid cancer (PTC) process and investigate the risk clinicopathologic characteristics of cervical lymph node metastasis (CLNM) for achieving a better preventive strategy of PTC.

METHODS

Totally 187 patients with CLNM and 279 without CLNM (NCLNM) were enrolled, and their urinary iodine concentration (UIC) and serum iodine concentration (SIC) were measured. Logistic regressions were used to reveal the effects of iodine nutrition on the CLNM status of PTC.

RESULTS

The levels of thyroid-stimulating hormone (TSH) and thyroglobulin (TG) were higher in the CLNM group than in the NCLNM group. UIC and SIC were positively correlated, and both of them were correlated with TSH, free thyroxine, and TG. The proportions of UIC >300 μg/L and of SIC >90 μg/L were higher in the CLNM than in the NCLNM. Logistic analysis showed that SIC >90 μg/L was an independent predictor for CLNM in PTC. Additionally, age ≥45, female, TG, multifocality, and diameter of cancer invasion >1 cm also affected CLNM status in PTC, and their logistic regression model showed a certain diagnostic accuracy (area under the receiver-operating characteristic curve = 0.72).

CONCLUSIONS

Relatively high iodine nutrition seemed to be a significant risk factor for the occurrence of CLNM in PTC and may promote lymphatic metastasis in PTC.

Expression of lncRNA-HOTAIR in the serum of patients with lymph node metastasis of papillary thyroid carcinoma and its impact

The present study aimed to investigate the expression of long non-coding HOX transcript antisense RNA (lncRNA-HOTAIR) in the serum of patients with lymph node metastasis of papillary thyroid carcinoma (PTC) and the underlying mechanism. A total of 89 patients with PTC at Beijing Geriatric Hospital were recruited in this study. Based on the results of color Doppler ultrasound examination, the patients were evaluated for cervical lymph node metastases, and were thereby divided into a metastasis-negative group and a metastasis-positive group. Quantitative fluorescent PCR was used to assess the expression of HOTAIR in serum samples. The PTC cell line TPC-1 was randomly divided into a control and siRNA group. The control group was transfected with a nonsense sequence, while the siRNA group was transfected with si-HOTAIR. After transfection, cell proliferation was evaluated using the MTT assay, and cell migration and invasion were assessed using the cell scratch assay and Transwell assay. Expression levels of vimentin, E-cadherin and proteins associated with the Wnt/β-catenin signaling pathway were assessed using western blot analysis. Based on the results of the ultrasound examination, 53 patients were allocated to the metastasis-negative group, and 36 to the metastasis-positive group. The expression level of lncRNA-HOTAIR was higher in the metastasis-positive group than that in the metastasis-negative group (P<0.05). Compared with the control group, cell proliferation was reduced while cell migration rate and the number of migrating cells were increased in the siRNA group. Compared with the control group, the expression levels of WIF1 and E-cadherin were significantly increased, while the levels of β-catenin and vimentin were significantly decreased. In conclusion, lncRNA-HOTAIR is overexpressed in the serum of patients with lymph node metastasis of PTC. In vitro experiments showed that HOTAIR promoted the proliferation and metastasis of PTC cells by regulating epithelial-mesenchymal transition (EMT) mediated by the Wnt/catenin pathway. Thus, lncRNA-HOTAIR is proposed as a molecular target for the treatment of lymph node metastasis of PTC.

Does relatively low iodine intake contribute to thyroid cancer? An ecological comparison of epidemiology

Research on the relationship between iodine intake and thyroid cancer (TC) risk is limited, and the findings are inconclusive. The objective of this study was to provide emerging evidence for the association between iodine intake and TC risk in a Chinese population.An ecological study of epidemiology is used to compare the iodine intake among populations with different TC incidence in Zhoushan, China. Incidence rates of TC were investigated and compared among four counties of the Zhoushan Islands from 2014 to 2018. Iodized salt consumption rate and the level of urinary iodine concentration (UIC) were analyzed for pupils and pregnant women from four counties.During 2014 to 2018, a total of 2495 new cases of TC were diagnosed in Zhoushan Islands. The mean crude incidence rate of TC was 51.29 per 100,000 inhabitants, and the standardized (world population) incidence rate (SIR) was 31.34 per 100,000 population. Incidence rates (SIR and crude incidence rates) were significantly higher in women than in men (χ test, P < .05). Both male and female, the incidence of TC in Daishan County is higher than the other three counties of Zhoushan. Iodized salt consumption rate and median UIC in pupils and pregnant women in Daishan County was significantly lower than the other three counties (χ test and Kruskal-Wallis test, all P < .05). The population with high TC incidence has a lower iodized salt consumption and a lower level of UIC compare with the relative low TC incidence populations.The low consumption of iodized salt with mild iodine deficiency may contribute to explain the exceptionally high incidence of TC in Daishan County. Further subtle designed studies are needed to provide additional insights into the epidemiology and etiology of TC and help identify the safe limit of iodine intake for prevention.

Iodine promotes thyroid cancer development via SPANXA1 through the PI3K/AKT signalling pathway

The aim of this study was to examine the impact of iodine on the development of thyroid cancer cells and to detect the underlying mechanisms. It was observed that proliferation was promoted and apoptosis was inhibited in cells treated with iodine at a specific concentration. This treatment group was then selected for further analysis, to investigate how iodine affects the development of thyroid cancer cells. It was reported that sperm protein associated with the nucleus, X-linked, family member A1 (SPANXA1) expression in iodine-treated cells was significantly upregulated. Furthermore, downregulation of SPANXA1 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis. These results suggested that SPANXA1 played an important role in iodine-treated thyroid cancer cells. Novel associations between SPANXA1 and thyroid cancer were described in the current study. In addition, SPANXA1 gene silencing resulted in the downregulation of PI3K and phosphorylated (p)AKT expression in iodine-treated thyroid cancer cells, whereas iodine treatment alone resulted in upregulated PI3K and p-AKT expression. Inhibiting PI3K further suppressed cell proliferation and contributed to apoptosis, even in the presence of SPANXA1 at high levels. As a consequence, PI3K/AKT may be one of the key signalling pathways by which iodine promotes thyroid cancer development in association with SPANXA1. In addition, our results further suggested that patients with thyroid cancer may need to avoid high-iodine intake.

Functional analysis and clinical significance of sodium iodide symporter expression in gastric cancer

BACKGROUND

Recent studies have described important roles for the sodium iodide symporter (NIS) in tumor behavior. The objectives of the present study were to investigate the role of NIS in the regulation of genes involved in tumor progression and the clinicopathological significance of its expression in gastric cancer (GC).

METHODS

In human GC cell lines, knockdown experiments were conducted using NIS siRNA, and the effects on proliferation, survival, and cellular movement were analyzed. The gene expression profiles of cells were examined using a microarray analysis. An immunohistochemical analysis was performed on 145 primary tumor samples obtained from GC patients.

RESULTS

NIS was strongly expressed in MKN45 and MKN74 cells. The depletion of NIS inhibited cell proliferation, migration, and invasion and induced apoptosis. The results of the microarray analysis revealed that various interferon (IFN) signaling-related genes, such as STAT1, STAT2, IRF1, and IFIT1, were up-regulated in NIS-depleted MKN45 cells. Furthermore, the down-regulation of NIS affected the phosphorylation of MAPKs and NF-kB. Immunohistochemical staining showed that NIS was primarily located in the cytoplasm or cell membranes of carcinoma cells, and its expression was related to the histological type or venous invasion. Prognostic analyses revealed that the strong expression of NIS was associated with shorter postoperative survival.

CONCLUSIONS

These results suggest that NIS regulates tumor progression by affecting IFN signaling, and that its strong expression is related to a worse prognosis in patients with GC. These results provide an insight into the role of NIS as a mediator and/or a biomarker for GC.

Iodine intake as a risk factor for BRAF mutations in papillary thyroid cancer patients from an iodine-replete area

PURPOSE

Both deficient and excessive iodine intake leads to thyroid disease, which shows U-shaped curves. Our previous study showed that a relatively low [urinary iodine concentration (UIC) <300 μg/L] and extremely excessive (UIC ≥ 2500 μg/L) iodine intake were associated with thyroid cancer in Korea, an iodine-replete area. Papillary thyroid cancer (PTC) accounts for more than 97 % of thyroid cancer and 80% or more PTC cases harbor the BRAF mutation in Korea. We aimed to investigate the relationship between iodine intake and the prevalence of the BRAF mutation in PTC in Korea.

METHODS

UIC was measured by inductively coupled plasma mass spectrometry. The BRAF mutation was detected using both allele-specific polymerase chain reaction and mutant enrichment with 3'-modified oligonucleotide sequencing. Risk factors for the occurrence of BRAF mutations in PTC were evaluated using multivariate logistic regression models.

RESULTS

The median UIC in all patients with PTC was 287 μg/L (range from 7 to 7, 426 μg/L). Nearly half of the patients (102/215, 47%) belonged to the excessive iodine intake category (UIC ≥ 300 μg/L) according to the WHO iodine recommendations. The frequency of BRAF mutations was lowest in the 300-499 μg/L UIC group; it was significantly different compared to the relatively low (UIC < 300 μg/L) and more than excessive (UIC ≥ 500 μg/L) iodine intake groups. UIC was an independent predictor for BRAF mutations in PTC. The multivariate-adjusted odds ratios (95% confidence intervals) in the relatively low and more than excessive iodine intake groups for the BRAF mutation were 4.761 (1.764-12.850) and 6.240 (2.080-18.726), respectively, compared to the 300-499 μg/L UIC group.

CONCLUSION

Relatively low iodine intake and more than excessive iodine intake seem to be significant risk factors for the occurrence of BRAF mutations in the thyroid and, therefore, may be risk factors for the development of PTC in an iodine-replete area.

Diversity of mutations in the RET proto-oncogene and its oncogenic mechanism in medullary thyroid cancer

Thyroid cancer is the most common endocrine malignancy and accounts for nearly 1% of all of human cancer. Thyroid cancer has four main histological types: papillary, follicular, medullary, and anaplastic. Papillary, follicular, and anaplastic thyroid carcinomas are derived from follicular thyroid cells, whereas medullary thyroid carcinoma (MTC) originates from the neural crest parafollicular cells or C-cells of the thyroid gland. MTC represents a neuroendocrine tumor and differs considerably from differentiated thyroid carcinoma. MTC is one of the aggressive types of thyroid cancer, which represents 3-10% of all thyroid cancers. It occurs in hereditary (25%) and sporadic (75%) forms. The hereditary form of MTC has an autosomal dominant mode of inheritance. According to the present classification, hereditary MTC is classified as a multiple endocrine neoplasi type 2 A & B (MEN2A & MEN2B) and familial MTC (FMTC). The RET proto-oncogene is located on chromosome 10q11.21. It is composed of 21 exons and encodes a transmembrane receptor tyrosine kinase. RET regulates a complex network of signal transduction pathways during development, survival, proliferation, differentiation, and migration of the enteric nervous system progenitor cells. Gain of function mutations in RET have been well demonstrated in MTC development. Variants of MTC result from different RET mutations, and they have a good genotype-phenotype correlation. Various MTC related mutations have been reported in different exons of the RET gene. We proposed that RET genetic mutations may be different in distinct populations. Therefore, the aim of this study was to find a geographical pattern of RET mutations in different populations.

Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies

Thyroid cancer (TC) is the most common endocrine malignancy and in most countries, incidence rates are increasing. Although differences in population iodine intake are a determinant of benign thyroid disorders, the role of iodine intake in TC remains uncertain. We review the evidence linking iodine intake and TC from animal studies, ecological studies of iodine intake and differentiated and undifferentiated TC, iodine intake and mortality from TC and occult TC at autopsy, as well as the case–control and cohort studies of TC and intake of seafood and milk products. We perform a new meta-analysis of pooled measures of effect from case–control studies of total iodine intake and TC. Finally, we examine the post-Chernobyl studies linking iodine status and risk of TC after radiation exposure. The available evidence suggests iodine deficiency is a risk factor for TC, particularly for follicular TC and possibly, for anaplastic TC. This conclusion is based on: a) consistent data showing an increase in TC (mainly follicular) in iodine deficient animals; b) a plausible mechanism (chronic TSH stimulation induced by iodine deficiency); c) consistent data from before and after studies of iodine prophylaxis showing a decrease in follicular TC and anaplastic TC; d) the indirect association between changes in iodine intake and TC mortality in the decade from 2000 to 2010; e) the autopsy studies of occult TC showing higher microcarcinoma rates with lower iodine intakes; and f) the case control studies suggesting lower risk of TC with higher total iodine intakes.

[Rising incidence of papillary thyroid carcinoma in Germany]

BACKGROUND

The incidence of thyroid cancer (TC), a rare malignancy, has strongly risen in recent decades. Possible causes of this rise include increasing diagnostic activity, nuclear tests after World War II, and the Chernobyl disaster.

AIM

This article presents the time trends of TC incidence between 2003 and 2008 in Germany according to histological tumor type and sex, and provides a description of TC incidence according to districts (Kreise) and sex in Germany.

METHODS

Data on persons newly diagnosed with thyroid cancer (ICD-10 code, C73) between 2003 and 2008 were obtained from the Center of Cancer Registry Data at the Robert Koch Institute. Official population and mortality data were used. Age-specific and age-standardized incidence rates (ASIR) were calculated according to sex and tumor histology.

RESULTS

Between 2003 and 2008, the ASIR of TC rose from 2.7 to 3.4 (men) and from 6.5 to 8.9 (women) per 100,000 per year. This rise can be almost completely attributed to the rising incidence of papillary TC. The steepest rise in frequency was observed in TNM-T1 tumors. A positive north-south gradient of TC incidence was found.

DISCUSSION

The cause of the marked rise of TC incidence in recent decades is unknown. The positive north-south gradient of the TC incidence may possibly be attributed in part to long-standing differences of iodine intake between different German regions.

CONCLUSION

An epidemiological study of the possible causes of the rising TC incidence and of the regional differences of TC incidence in Germany is recommended.

Rising incidence, no change in survival and decreasing mortality from thyroid cancer in The Netherlands since 1989

The incidence of thyroid cancer (TC) is increasing worldwide, partly due to increased detection. We therefore assessed combined trends in incidence, survival and mortality of the various types of TC in The Netherlands between 1989 and 2009. We included all patients ≥15 years with TC, diagnosed in the period 1989-2009 and recorded in The Netherlands Cancer Registry (n=8021). Information on age, gender, date of diagnosis, histological type of tumour and tumour-node-metastasis classification was recorded. Mortality data (up to 1st January 2010) were derived from Statistics Netherlands. Annual percentages of change in incidence, mortality and relative survival were calculated. Since 1989 the incidence of TC increased significantly in The Netherlands (estimated annual percentage change (EAPC)=+1.7%). The incidence rates increased for all age groups (except for females >60 years), papillary tumours (EAPC=+3.5%), T1 and T3 TC (EAPC=+7.9 and +5.8% respectively). Incidence rates decreased for T4 TC (-2.3%) and remained stable for follicular, medullary anaplastic and T2 TC. Five-year relative survival rates remained stable for papillary (88%) and follicular (77%) TC, all age groups and T1-T3 TC (96, 94 and 80% respectively) and somewhat lower for T4 (53%), medullary (65%) and anaplastic TC (5%) in the 2004-2009 period compared with earlier periods. Mortality due to TC decreased (EAPC=-1.9%). TC detection and incidence has been rising in The Netherlands, while mortality rates are decreasing and survival rates remained stable or slightly decreasing.

TRPM7 is regulated by halides through its kinase domain

Transient receptor potential melastatin 7 (TRPM7) is a divalent-selective cation channel fused to an atypical α-kinase. TRPM7 is a key regulator of cell growth and proliferation, processes accompanied by mandatory cell volume changes. Osmolarity-induced cell volume alterations regulate TRPM7 through molecular crowding of solutes that affect channel activity, including magnesium (Mg(2+)), Mg-nucleotides and a further unidentified factor. Here, we assess whether chloride and related halides can act as negative feedback regulators of TRPM7. We find that chloride and bromide inhibit heterologously expressed TRPM7 in synergy with intracellular Mg(2+) ([Mg(2+)]i) and this is facilitated through the ATP-binding site of the channel's kinase domain. The synergistic block of TRPM7 by chloride and Mg(2+) is not reversed during divalent-free or acidic conditions, indicating a change in protein conformation that leads to channel inactivation. Iodide has the strongest inhibitory effect on TRPM7 at physiological [Mg(2+)]i. Iodide also inhibits endogenous TRPM7-like currents as assessed in MCF-7 breast cancer cells, where upregulation of SLC5A5 sodium-iodide symporter enhances iodide uptake and inhibits cell proliferation. These results indicate that chloride could be an important factor in modulating TRPM7 during osmotic stress and implicate TRPM7 as a possible molecular mechanism contributing to the anti-proliferative characteristics of intracellular iodide accumulation in cancer cells.

The changing incidence of thyroid carcinoma in Shenyang, China before and after universal salt iodization

BACKGROUND

An increase in the prevalence of thyroid disease has been found with increasing iodine intake, since universal salt iodization (USI) was instituted throughout China in 1996. The aim of this study was to analyze the incidence of thyroid carcinoma (TC) before and after USI in Shenyang, a city of northeastern China.

MATERIAL/METHODS

The pathology reports were collected from patients with thyroid diseases who underwent surgery in the First Hospital of China Medical University from January 1, 1992 to December 31, 2009. The detection rate, the constituent ratio, the changes of sex, age, and concomitant thyroid diseases of each histological type of TC were analyzed.

RESULTS

The detection rate of TC, papillary thyroid carcinoma (PTC), and medullary thyroid carcinoma (MTC) increased; that of follicular thyroid carcinoma (FTC) decreased; and that of undifferentiated thyroid carcinoma (UTC) showed no change after USI. The constituent ratio of PTC increased, that of FTC and UTC decreased, and that of MTC showed no change after USI. The mean age of female patients with TC decreased after USI. The incidences of PTC complicated with either nodular goiter or chronic lymphocytic thyroiditis increased after USI.

CONCLUSIONS

The detection rate of TC increased significantly, PTC predominated in the histological types of TC, and the mean age of female patients with TC decreased after USI. The patients with either nodular goiter or chronic lymphocytic thyroiditis under high iodine intake should be followed up.

Uptake and antitumoral effects of iodine and 6-iodolactone in differentiated and undifferentiated human prostate cancer cell lines

BACKGROUND

Evidence indicates that iodine per se could be implicated in the physiology of several organs that can internalize it. In thyroid and breast cancer, iodine treatments inhibit cell proliferation and induce apoptosis through a direct (mitochondria) and/or indirect effect (iodolipid generation). Here, we determined the uptake of iodide (I(-) ) and iodine (I(2) ), as well as the antiproliferative and apoptotic effects of 6-iodolactone (6-IL) and both forms of iodine in human prostate cells lines.

METHODS

Non-cancerous (RWPE-1) and cancerous (LNCaP, DU-145) cells, as well as nude mice xenotransplanted with DU-145 cells were used as cancer models. Iodine uptake was analyzed with radioactive tracers, transporter expression by qRT-PCR, cell proliferation by blue trypan, apoptosis by enzyme immunoassay or fluorescence, BAX and BCL-2 by western-blot, and caspsase 3 by enzymatic assay.

RESULTS

All three cell lines take up both forms of iodine. In RWPE-1 cells, I(-) uptake depends on the Na(+) /I(-) symporter (NIS), whereas it was independent of NIS in LNCaP and DU-145 cells. Antiproliferative effects of iodine and 6-IL were dose and time dependent; RWPE-1 was most sensitive to I(-) and 6-IL, whereas LNCaP was more sensitive to I(2) . In the three cell lines both forms of iodine activated the intrinsic apoptotic pathway (increasing the BAX/BCL-2 index and caspases). Iodine supplementation impaired growth of the DU-145 tumor in nude mice.

CONCLUSION

Normal and cancerous prostate cells can take up iodine, and depending on the chemical form, it exerts antiproliferative and apoptotic effects both in vitro and in vivo.

Membrane lipids and nuclear DNA are differently susceptive to Fenton reaction substrates in porcine thyroid

Fenton reaction (Fe(2+)+H(2)O(2) → Fe(3+)+()OH+OH(-)) is of special significance in the thyroid, as both substrates are indispensable for thyroid hormone synthesis, therefore being available presumably at high concentrations under physiological conditions. The study aimed at evaluation if both Fenton reaction substrates are required to induce oxidative damage to membrane lipids and nuclear DNA in porcine thyroid homogenates, and if these macromolecules are vulnerable to the same extent. Thyroid homogenates and nuclear DNA were incubated in the presence of H(2)O(2) and/or Fe(2+). Malondialdehyde+4-hydroxyalkenals (MDA+4-HDA) concentration (lipid peroxidation index) was measured spectrophotometrically, and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) concentration (DNA damage index) by HPLC. Whereas Fenton reaction substrates, used separately, did not affect lipid peroxidation, they increased 8-oxodG level for the highest H(2)O(2) concentration (100mM) and in Fe(2+) concentration-dependent manner (300, 150, 30 and 15 μM). If Fe(2+) and H(2)O(2) were applied together, lipid peroxidation increased significantly, however without H(2)O(2) concentration- but with clear Fe(2+) concentration-dependent effect. Concerning DNA damage, Fe(2+) enhanced H(2)O(2) effect, whereas Fe(2+) concentration-dependent effect was not changed by H(2)O(2). Excess of exclusively one of Fenton reaction substrates is sufficient to induce oxidative DNA damage, but not lipid peroxidation, in porcine thyroid. Comparing to H(2)O(2), Fe(2+) seems to be a stronger damaging substrate.

Iodide transporter NIS regulates cancer cell motility and invasiveness by interacting with the Rho guanine nucleotide exchange factor LARG

A number of solute carrier (SLC) proteins are subject to changes in expression and activity during carcinogenesis. Whether these changes play a role in carcinogenesis is unclear, except for some nutrients and ion carriers whose deregulation ensures the necessary reprogramming of energy metabolism in cancer cells. In this study, we investigated the functional role in tumor progression of the sodium/iodide symporter (NIS; aka SLC5A5), which is upregulated and mislocalized in many human carcinomas. Notably, we found that NIS enhanced cell migration and invasion without ion transport being involved. These functions were mediated by NIS binding to leukemia-associated RhoA guanine exchange factor, a Rho guanine exchange factor that activates the small GTPase RhoA. Sequestering NIS in intracellular organelles or impairing its targeting to the cell surface (as observed in many cancers) led to a further increase in cell motility and invasiveness. In sum, our results established NIS as a carrier protein that interacts with a major cell signaling hub to facilitate tumor cell locomotion and invasion.

Subcellular distribution of the sodium iodide symporter in benign and malignant thyroid tissues

BACKGROUND

Membranous expression of the sodium iodide symporter (NIS) is a prerequisite for iodide uptake in thyrocytes. Previous studies reported heterogeneous results on the relative frequency of staining in various pathological conditions of the thyroid. The present study aimed at determining membranous staining by using confocal laser microscopy in benign and malignant thyroid diseases, complemented in a subgroup of patients with recurrent or metastatic disease with functional findings of radioiodine uptake (RIU).

METHODS

There were 380 malignant thyroid tumors (145 papillary, 51 follicular, 87 Hurthle cell, and 97 undifferentiated thyroid carcinomas [UTC]), 115 benign adenomas, 62 diffuse goiters, 89 inflammatory conditions (Graves', Hashimoto, Thyroiditis deQuervain, and lymphocytic thyroiditis), and 179 normal tissues (NT, fetal, and adult). These were subjected to NIS (two different antibodies) and thyroglobulin (TG) staining and evaluated by confocal microscopy.

RESULTS

In a subgroup of 50 samples from patients with recurrent or metastatic disease, NIS staining was correlated with the RIU. As compared with NT, Graves' patients had significantly higher positive NIS membrane staining (>97% vs. 69%) whereas patients with Hashimoto, lymphocytic thyroiditis but also benign adenomas scored lower than NT (56.7% and 55.8% vs. 69%). Depending on their differentiation NIS staining was significantly lower in thyroid carcinomas in parallel with TG staining with only 1/97 UTCs being positive. RIU was more frequently detectable than NIS staining.

CONCLUSION

Confocal staining strictly evaluating only membranous expression of NIS has not used on a large scale before this study. We confirm the loss of membranous NIS in benign but more prominently in malignant thyroid tumors. NIS staining of diagnostic tissues cannot be used to predict RIU.

Thyroid cancer incidence by histological type and related variants in a mildly iodine-deficient area of Northern Italy, 1998 to 2009

BACKGROUND

The incidence of thyroid cancer is increasing in several countries. However, the issue of whether this applies to all different histological types and related variants is poorly addressed.

METHODS

All incident thyroid cancers diagnosed between 1998 and 2009 in a mildly iodine-deficient area in northern Italy were derived from a population-based tumor registry. Stage of disease, size of the tumor, focality, and histological variants were recorded from a review of pathology reports and slides. The mean annual increase (MAI) of the standardized incidence rate was calculated over the entire 12-year period of observation and a standardized rate ratio was evaluated to compare the mean standardized incidence between 2 periods of 6 years each (1998-2003 vs 2004-2009).

RESULTS

In total, 980 cases were considered. An increase in the incidence trend for all thyroid tumors was demonstrated; the increase was found to be continuous from 1998 to 2002 but not afterward. The cancer incidence increased in both male and female subjects. Papillary thyroid carcinoma (PTC), the follicular variant of PTC, the tall cell variant of PTC (TCV-PTC), and Hurthle cell carcinoma (HC) showed the most relevant changes in incidence whereas follicular carcinoma was not found to be significantly affected. TCV-PTC was the only histological type to demonstrated a significant (P < .01) proportional increase in the second 6-year period of observation. Only TCV-PTC and HC were found to display a significant MAI after 2002.

CONCLUSIONS

The incidence of thyroid cancer has increased within the last decade, an increase that is accounted for mostly by differentiated tumors. The most significant increases were documented for aggressive variants of basic histotypes.

The Chernobyl accident--an epidemiological perspective

Twenty-five years have passed since radioactive releases from the Chernobyl nuclear accident led to the exposure of millions of people in Europe. Studies of affected populations have provided important new data on the links between radiation and cancer-particularly the risk of thyroid tumours from exposure to iodine isotopes-that are important not only for a fuller scientific understanding of radiation effects, but also for radiation protection. It is now well documented that children and adolescents exposed to radioiodines from Chernobyl fallout have a sizeable dose-related increase in thyroid cancer, with the risk greatest in those youngest at exposure and with a suggestion that deficiency in stable iodine may increase the risk. Data on thyroid cancer risks to other age groups are somewhat less definitive. In addition, there have been reported increases in incidence and mortality from non-thyroid cancers and non-cancer end points. Although some studies are difficult to interpret because of methodological limitations, recent investigations of Chernobyl clean-up workers ('liquidators') have provided evidence of increased risks of leukaemia and other haematological malignancies and of cataracts, and suggestions of an increase in the risk of cardiovascular diseases, following low doses and low dose rates of radiation. Further careful follow-up of these populations, including the establishment and long-term support of life-span study cohorts, could provide additional important information for the quantification of radiation risks and the protection of persons exposed to low doses of radiation.

Urinary Iodine and Goiter Prevalence in Belarus: experience of the Belarus-American cohort study of thyroid cancer and other thyroid diseases following the Chornobyl nuclear accident

BACKGROUND

Because iodine deficiency can influence background rates of thyroid disease or modify radiation dose-response relationships, we compiled descriptive data on iodine status among participants in a Belarusian-American screening study who were exposed in childhood to radioiodine fallout from the Chornobyl nuclear accident. We have used the data from two consecutive screening cycles to examine whether indicators of iodine status changed before and after documented government initiatives to improve iodine intake.

METHODS

Urinary iodine concentrations in spot samples and prevalence of diffuse goiter by palpation were assessed in 11,676 exposed subjects who were 18 years or younger at the time of the accident on April 26, 1986, and were screened beginning 11 years later in connection with the Belarus-American Thyroid Study. Data for the first ( January 1997-March 2001) and second (April 2001-December 2004) screening cycles, which largely correspond to time periods before and after official iodination efforts in 2000/2001, were compared for the cohort overall as well as by oblast of residence (i.e., state) and type of residency (urban/rural).

RESULTS

Median urine iodine levels among cohort members increased significantly in the later period (111.5 mg/L) compared to the earlier (65.3 mg/L), with the cycle 2 level in the range defined as adequate iodine intake by the World Health Organization. During the same period, a significant decline in diffuse goiter prevalence was also observed. In both cycles, urinary iodine levels were lower in rural than in urban residents. Urinary iodine levels, but not rates of goiter, varied by oblast of residence. In both periods, adjusted median urine iodine concentrations were similar in Gomel and Minsk oblasts, where *89% of cohort members resided, and were lowest in Mogilev oblast. Yet Mogilev oblast and rural areas showed the most marked increases over time.

CONCLUSIONS

Trends in urinary iodine concentrations and prevalence of diffuse goiter by palpation suggest that iodination efforts in Belarus were successful, with benefits extending to the most iodine-deficient populations. Iodine status should be considered when evaluating thyroid disease risk in radioiodine-exposed populations since it can change over time and may influence rates of disease and, possibly, dose-response relationships

Clinical and pathological implications of concurrent autoimmune thyroid disorders and papillary thyroid cancer

Cooccurrences of chronic lymphocytic thyroiditis (CLT) and thyroid cancer (DTC) have been repeatedly reported. Both CLT and DTC, mainly papillary thyroid carcinoma (PTC), share some epidemiological and molecular features. In fact, thyroid lymphocytic inflammatory reaction has been observed in association with PTC at variable frequency, although the precise relationship between the two diseases is still debated. It also remains a matter of debate whether the association with a CLT or even an autoimmune disorder could influence the prognosis of PTC. A better understanding about clinical implications of autoimmunity in concurrent thyroid cancer could raise new insights of thyroid cancer immunotherapy. In addition, elucidating the molecular mechanisms involved in autoimmune disease and concurrent cancer allowed us to identify new therapeutic strategies against thyroid cancer. The objective of this article was to review recent literature on the association of these disorders and its potential significance.

Role of iodine in thyroid physiology

Adequate levels of iodine, a trace element variably distributed on the earth, are required for the synthesis of the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃). The iodide cycle consists of a series of transport, oxidation and coupling steps in thyroid follicular cells to produce thyroid hormone. The sodium/iodide symporter (NIS) transports iodide into the thyrocyte. Competitive inhibitors of NIS, such as perchlorate and thiocyanate, can decrease the entrance of iodide into the follicular cell. Pendrin is the primary protein that is responsible for iodide efflux out of the thyrocyte and into the follicular lumen. T₄ is deiodinated in target tissues to produce the active form of thyroid hormone, T₃, and other metabolites. Exposure to excessive iodine or chronic iodine deficiency may result in various clinical disorders. The Wolff-Chaikoff effect and Jöd-Basedow phenomenon describe mechanisms of thyroid autoregulation and dysregulation, respectively, during iodine excess. Population studies have determined that iodine deficiency exists in approximately 38% of the world's population, is the leading cause of preventable mental retardation, and is of particular concern to women and their infants. Finally, the unique role of iodine utilization in thyroid physiology has applications in many important clinical areas.