Reduced expression of THRβ in papillary thyroid carcinomas: relationship with BRAF mutation, aggressiveness and miR expression

Purpose Down-regulation of thyroid hormone receptor beta (THRβ) gene has been described in several human malignancies, including thyroid cancer. In this study, we analyzed THRβ mRNA expression in surgical specimens from a series of human papillary thyroid carcinomas (PTCs), characterized by their genotypic and clinical–biological features. Methods Thirty-six PTCs were divided into two groups according to the 2009 American Thyroid Association risk classification (17 low, 19 intermediate), and each group was divided into subgroups based on the presence or absence of the BRAFV600E mutation (21 BRAF mutated, 15 BRAF wild type). Gene expression was analyzed using fluidic cards containing probes and primers specific for the THRβ gene, as well as for genes of thyroperoxidase (TPO), sodium/iodide symporter (NIS), thyroglobulin (Tg) and thyroid stimulating hormone receptor (TSH-R) and for some miRNAs involved in thyroid neoplasia and targeting THRβ. The mRNA levels of each tumor tissue were compared with their correspondent normal counterpart. Results THRβ transcript was down-regulated in all PTCs examined. No significant differences were found between intermediate- vs low-risk PTCs patients, and BRAF-mutated vs BRAF wild-type groups. THRβ expression was directly correlated with NIS, TPO, Tg and TSH-R, and inversely correlated to miR-21, -146a, -181a and -221 expression. Conclusions Our results demonstrate that down-regulation of THRβ is a common feature of PTCs. While it is not associated with a more aggressive phenotype of PTC, it correlates with the reduction of all the markers of differentiation and is associated with overexpression of some miRNAs supposed to play a role in thyroid tumorigenesis

Thyrocyte-specific inactivation of p53 and Pten results in anaplastic thyroid carcinomas faithfully recapitulating human tumors

Anaplastic thyroid carcinoma (ATC) is the most aggressive form of thyroid cancer, and often derives from pre-existing well-differentiated tumors. Despite a relatively low prevalence, it accounts for a disproportionate number of thyroid cancer-related deaths, due to its resistance to any therapeutic approach. Here we describe the first mouse model of ATC, obtained by combining in the mouse thyroid follicular cells two molecular hallmarks of human ATC: activation of PI3K (via Pten deletion) and inactivation of p53. By 9 months of age, over 75% of the compound mutant mice develop aggressive, undifferentiated thyroid tumors that evolve from pre-existing follicular hyperplasia and carcinoma. These tumors display all the features of their human counterpart, including pleomorphism, epithelial-mesenchymal transition, aneuploidy, local invasion, and distant metastases. Expression profiling of the murine ATCs reveals a significant overlap with genes found deregulated in human ATC, including genes involved in mitosis control. Furthermore, similar to the human tumors, [Pten, p53]thyr−/− tumors and cells are highly glycolytic and remarkably sensitive to glycolysis inhibitors, which synergize with standard chemotherapy. Taken together, our results show that combined PI3K activation and p53 loss faithfully reproduce the development of thyroid anaplastic carcinomas, and provide a compelling rationale for targeting glycolysis to increase chemotherapy response in ATC patients

Increased expression of pro-angiogenic factors and vascularization in thyroid hyperfunctioning adenomas with and without TSH receptor activating mutations

Autonomously functioning thyroid nodules (AFTN) are known to receive an increased blood influx necessary to sustain their high rate of growth and hormone production. Here, we investigated the expression of hematic and lymphatic vases in a series of 20 AFTN compared with the contralateral non-tumor tissues of the same patients, and the transcript levels of proteins involved in the control of vascular proliferation, including the vascular endothelial growth factor (VEGF) and platelet-derived growth factors (PDGF) and their receptors and the endothelial nitric oxide synthase (eNOS). In parallel, the expression of the differentiation markers sodium/iodide symporter (NIS), thyroperoxidase (TPO), thyroglobulin (Tg), and TSH receptor (TSHR) was also investigated. The data were further analyzed comparing subgroups of tumors with or without mutations in the TSHR gene. Analysis by means of CD31 and D2-40 immunostaining showed in AFTN an increased number of hematic, but not lymphatic, vessels in parallel with an enhanced proliferation rate shown by increased Ki67 staining. Quantitative RT-PCR analysis revealed an increase of VEGF, VEGFR1 and 2, PDGF-A, PDGF-B, and eNOS expression in tumor versus normal tissues. Also, higher transcript levels of NIS, TPO, and Tg were detected. Comparison of the two subgroups of samples revealed only few differences in the expression of the genes examined. In conclusion, these data demonstrate an increased expression of angiogenesis-related factors associated with an enhanced proliferation of hematic, but not lymphatic, vessels in AFTNs. In this context, the presence of TSHR mutations may only slightly influence the expression of pro-angiogenic growth factors

Establishment and characterization of cell lines from a novel mouse model of poorly differentiated thyroid carcinoma: powerful tools for basic and preclinical research.

Poorly differentiated and anaplastic thyroid carcinomas have a rather poor prognosis. The development of relevant model systems to unravel in vitro and in vivo the molecular mechanisms governing the resistance of these tumors to therapy, as well as to test novel drug combinations, is a clear priority for thyroid-focused research. Several novel cell lines were established from tumors developed by mice engineered to simultaneously express a loss-of-function Pten allele and an oncogenic Kras allele. Similar to most poorly differentiated thyroid tumors, these cell lines are characterized by simultaneous activation of the PI3K and MAPK pathways, by the presence of wild-type, functional p53, and by the severe downregulation of thyroid differentiation markers, including sodium-iodide symporter (NIS). Further, they display a highly glycolytic phenotype. They can be grafted to syngeneic, immunocompetent hosts, and easily metastasize to the lungs. These mouse cell lines are a novel and invaluable tool that can be used to develop innovative therapeutic approaches to poorly differentiated carcinomas in a more physiological context than using xenografts of human cell lines in immunocompromised mice

Cross-talk between PI3K and estrogen in the mouse thyroid predisposes to the development of follicular carcinomas with a higher incidence in females.

It is well known that thyroid disease is more frequent in women than in men; however, the molecular basis for this gender-based difference is still poorly understood. The activation of phosphoinositide 3-kinase (PI3K), through different mechanisms including loss of the PTEN tumor suppressor, is being increasingly recognized as a major player in the development of thyroid neoplastic lesions. Loss of Pten in the mouse thyroid results in a significant increase in the thyrocyte proliferative index, which is more prominent in the female mice. In this study, we show that 52% of the Pten(-/-) female mice, but only 12% of the males, develop follicular adenomas by 1 year of age. In addition, 50% of female mutants, but only 35% of males older than 1 year of age develop invasive, and often metastatic, follicular carcinomas. Mutant females have a significantly shorter overall survival compared with male mutants. Hormonal manipulation experiments established a direct role of estrogens in controlling the increased thyrocyte proliferation index in mutant females. Furthermore, while genetic ablation of one Cdkn1b allele accelerated the development of neoplastic lesions, it also abolished the gender differences in survival and reduced the difference in neoplastic lesion development rate, underlining a key role of p27 in mediating estrogen action in the thyroid follicular cells. These data, based on a clinically relevant model of thyroid follicular carcinoma, provide, to the best of our knowledge, for the first time in vivo evidence that circulating estrogens are directly responsible for the increased female susceptibility to thyroid disease, at least on activation of the PI3K pathway, and provide new insights into the gender-based differences characterizing thyroid neoplastic disorders

High periostin expression correlates with aggressiveness in papillary thyroid carcinomas

Periostin is a mesenchyme-specific gene product, which acts as an adhesion molecule during bone formation and supports osteoblastic cell line attachment and spreading. However, periostin expression is activated in a large variety of epithelial human tumors and correlates with their aggressiveness. Knowledge of expression of periostin in thyroid tumors is still scanty. The aim of the present work was to investigate periostin expression in differentiated neoplasms of the thyroid and to correlate it with several clinical and molecular features of these tumors. Periostin expression was evaluated by quantitative PCR and immunohistochemistry in normal thyroid tissues, papillary thyroid carcinomas (PTCs), follicular thyroid carcinomas (FTCs), and follicular adenomas (FAs). Periostin mRNA levels were also evaluated in several thyroid tumor cell lines. PTCs show mean periostin mRNA levels significantly higher than corresponding normal tissues. In five PTCs, periostin mRNA values were at least 30-fold higher than corresponding normal tissues. Conversely, mean periostin mRNA levels of FTCs and FAs were similar to those of normal tissues. Consistent with mRNA studies, periostin was detectable by immunohistochemistry in cancerous epithelial cells only in several cases of PTCs but not in normal tissue, FTCs, and FAs. III PTCs, periostin mRNA levels positively correlate with extrathyroidal invasion, distant metastasis, and higher grade staging. A negative correlation between periostin and expression of some markers of the thyroid-differentiated phenotype (thyroglobulin, thyrotropin receptor) was also present in the PTCs. These results indicate that an increase in periostin gene expression is present in several PTCs, in which it appears as a marker of aggressiveness. Experiments in thyroid tumor cell lines indicate that high levels of periostin mRNA are due, at least in part, to the increase in periostin promoter activity

TSH receptor extracellular region mutations in thyroid functioning nodules: further evidence for the functional role of this region in the receptor activation

[No abstract available

Thyrocyte-specific inactivation of p53 and Pten results in anaplastic thyroid carcinomas faithfully recapitulating human tumors.

Anaplastic thyroid carcinoma (ATC) is the most aggressive form of thyroid cancer, and often derives from pre-existing well-differentiated tumors. Despite a relatively low prevalence, it accounts for a disproportionate number of thyroid cancer-related deaths, due to its resistance to any therapeutic approach. Here we describe the first mouse model of ATC, obtained by combining in the mouse thyroid follicular cells two molecular hallmarks of human ATC: activation of PI3K (via Pten deletion) and inactivation of p53. By 9 months of age, over 75% of the compound mutant mice develop aggressive, undifferentiated thyroid tumors that evolve from pre-existing follicular hyperplasia and carcinoma. These tumors display all the features of their human counterpart, including pleomorphism, epithelial-mesenchymal transition, aneuploidy, local invasion, and distant metastases. Expression profiling of the murine ATCs reveals a significant overlap with genes found deregulated in human ATC, including genes involved in mitosis control. Furthermore, similar to the human tumors, [Pten, p53]thyr-/- tumors and cells are highly glycolytic and remarkably sensitive to glycolysis inhibitors, which synergize with standard chemotherapy. Taken together, our results show that combined PI3K activation and p53 loss faithfully reproduce the development of thyroid anaplastic carcinomas, and provide a compelling rationale for targeting glycolysis to increase chemotherapy response in ATC patients