At physiological concentrations, reactive oxygen species (ROS), including superoxide anions and H2O2, are considered as second messengers that play key roles in cellular functions, such as proliferation, gene expression, host defence and hormone synthesis. However, when they are at supraphysiological levels, ROS are considered potent DNA-damaging agents. Their increase induces oxidative stress, which can initiate and maintain genomic instability. The thyroid gland represents a good model for studying the impact of oxidative stress on genomic instability. Indeed, one particularity of this organ is that follicular thyroid cells synthesise thyroid hormones through a complex mechanism that requires H2O2. Because of their detection in thyroid adenomas and in early cell transformation, both oxidative stress and DNA damage are believed to be neoplasia-preceding events in thyroid cells. Oxidative DNA damage is, in addition, detected in the advanced stages of thyroid cancer, suggesting that oxidative lesions of DNA also contribute to the maintenance of genomic instability during the subsequent phases of tumourigenesis. Finally, ionizing radiation and the mutation of oncogenes, such as RAS and BRAF, play a key role in thyroid carcinogenesis through separate and unique mechanisms: they upregulate the expression of two distinct ‘professional’ ROS-generating systems, the NADPH oxidases DUOX1 and NOX4, which cause DNA damage that may promote chromosomal instability, tumourigenesis and dedifferentiation.
Rabii Ameziane El Hassani, Camille Buffet, Sophie Leboulleux, and Corinne Dupuy
Zhenying Guo, Heather Hardin, and Ricardo V Lloyd
Thyroid cancer is one of the most rapidly increasing malignancies. The reasons for this increase is not completely known, but increases in the diagnosis of papillary thyroid microcarcinomas and follicular variant of papillary thyroid carcinomas along with the enhanced detection of well-differentiated thyroid carcinomas are probably all contributing factors. Although most cases of well-differentiated thyroid carcinomas are associated with an excellent prognosis, a small percentage of patients with well-differentiated thyroid carcinomas as well as most patients with poorly differentiated and anaplastic thyroid carcinomas have recurrent and/or metastatic disease that is often fatal. The cancer stem-like cell (CSC) model suggests that a small number of cells within a cancer, known as CSCs, are responsible for resistance to chemotherapy and radiation therapy, as well as for recurrent and metastatic disease. This review discusses current studies about thyroid CSCs, the processes of epithelial-to-mesenchymal transition (EMT), and mesenchymal-to-epithelial transition that provide plasticity to CSC growth, in addition to the role of microRNAs in CSC development and regulation. Understanding the biology of CSCs, EMT and the metastatic cascade should lead to the design of more rational targeted therapies for highly aggressive and fatal thyroid cancers.
Brian Hung-Hin Lang, Chung-Yau Lo, Wai-Fan Chan, King-Yin Lam, and Koon-Yat Wan
A number of risk-group stratification or staging systems have been found useful at stratifying patients with differentiated thyroid carcinoma into risk groups. Those identified as high risk could be subjected to more aggressive treatment, while those at low risk could be spared of such treatment. However, the best stratification system in patients with follicular thyroid carcinoma (FTC) remains unclear. Through a comprehensive MEDLINE search from 1965 to 2005, a total of 18 different staging systems were identified in the literature and 14 of them were applicable to 171 patients, with FTC managed at our institution from 1961 to 2001. Cancer-specific survivals (CSS) were calculated by Kaplan–Meier method and were compared by log-rank test. Using Cox proportional hazards analysis, the relative importance of each staging system in determining CSS was calculated by the proportion of variation in survival time explained (PVE). CSS were predicted by 13 out of the 14 staging systems significantly (P < 0.001). The three highest ranked staging systems by PVE were the new American Joint Commitee on Cancer/Union Internationale Centre le Cancer 6th edition, tumour, node, metastases (TNM; 22.4), followed by the Clinical Class (21.2) and the metastases, age, completeness of resection, invasion, size (MACIS; 20.4). In conclusion, 13 out of the 14 presently available staging systems predicted CSS significantly in FTC. When predictability was measured by PVE, the TNM system was found to have the best predictability and thus, should be the stratification system of choice for FTC in the future.
David Viola, Laura Valerio, Eleonora Molinaro, Laura Agate, Valeria Bottici, Agnese Biagini, Loredana Lorusso, Virginia Cappagli, Letizia Pieruzzi, Carlotta Giani, Elena Sabini, Paolo Passannati, Luciana Puleo, Antonio Matrone, Benedetta Pontillo-Contillo, Valentina Battaglia, Salvatore Mazzeo, Paolo Vitti, and Rossella Elisei
Thyroid cancer is rare, but it is the most frequent endocrine malignancy. Its prognosis is generally favorable, especially in cases of well-differentiated thyroid cancers (DTCs), such as papillary and follicular cancers, which have survival rates of approximately 95% at 40 years. However, 15–20% of cases became radioiodine refractory (RAI-R), and until now, no other treatments have been effective. The same problems are found in cases of poorly differentiated (PDTC) and anaplastic (ATC) thyroid cancers and in at least 30% of medullary thyroid cancer (MTC) cases, which are very aggressive and not sensitive to radioiodine. Tyrosine kinase inhibitors (TKIs) represent a new approach to the treatment of advanced cases of RAI-R DTC, MTC, PDTC, and, possibly, ATC. In the past 10 years, several TKIs have been tested for the treatment of advanced, progressive, and RAI-R thyroid tumors, and some of them have been recently approved for use in clinical practice: sorafenib and lenvatinib for DTC and PDTC and vandetanib and cabozantinib for MTC. The objective of this review is to present the current status of the treatment of advanced thyroid cancer with the use of innovative targeted therapies by describing both the benefits and the limits of their use based on the experiences reported so far. A comprehensive analysis and description of the molecular basis of these therapies, as well as new therapeutic perspectives, are reported. Some practical suggestions are given for both the choice of patients to be treated and their management, with particular regard to the potential side effects.
Susanne Singer, Susan Jordan, Laura D Locati, Monica Pinto, Iwona M Tomaszewska, Cláudia Araújo, Eva Hammerlid, E Vidhubala, Olga Husson, Naomi Kiyota, Christine Brannan, Dina Salem, Eva M Gamper, Juan Ignacio Arraras, Georgios Ioannidis, Guy Andry, Johanna Inhestern, Vincent Grégoire, Lisa Licitra, and on behalf of the EORTC Quality of Life Group, the EORTC Head and Neck Cancer Group, and the EORTC Endocrine Task Force
The purpose of the study was to pilot-test a questionnaire measuring health-related quality of life (QoL) in thyroid cancer patients to be used with the European Organisation for Research and Treatment of Cancer (EORTC) core questionnaire EORTC QLQ-C30. A provisional questionnaire with 47 items was administered to patients treated for thyroid cancer within the last 2 years. Patients were interviewed about time and help needed to complete the questionnaire, and whether they found the items understandable, confusing or annoying. Items were kept in the questionnaire if they fulfilled pre-defined criteria: relevant to the patients, easy to understand, not confusing, few missing values, neither floor nor ceiling effects, and high variance. A total of 182 thyroid cancer patients in 15 countries participated (n = 115 with papillary, n = 31 with follicular, n = 22 with medullary, n = 6 with anaplastic, and n = 8 with other types of thyroid cancer). Sixty-six percent of the patients needed 15 min or less to complete the questionnaire. Of the 47 items, 31 fulfilled the predefined criteria and were kept unchanged, 14 were removed, and 2 were changed. Shoulder dysfunction was mentioned by 5 patients as missing and an item covering this issue was added. To conclude, the EORTC quality of life module for thyroid cancer (EORTC QLQ-THY34) is ready for the final validation phase IV.
G Riesco-Eizaguirre, P Gutiérrez-Martínez, M A García-Cabezas, M Nistal, and P Santisteban
The oncogene BRAFV600E is the most frequent genetic event in papillary thyroid carcinoma (PTC) but its prognostic impact still remains to be elucidated. We evaluated a representative series of 67 individuals with PTC who underwent total thyroidectomy. BRAF-positive tumours correlated with early recurrences (32% vs 7.6%; P=0.02) during a median postoperative follow-up period of 3 years. Interestingly, within the recurrences, a significant majority had negative radioiodine (131I) total body scans, predicting a poorer outcome as treatment with 131I is not effective. This last observation led us to investigate the role of BRAFV600E and the MEK-ERK pathway in thyroid dedifferentiation, particularly in Na+/I− symporter (NIS) impairment, as this thyroid-specific plasma membrane glycoprotein mediates active transport of I− into the thyroid follicular cells. A subset of 60 PTC samples was evaluated for NIS immunoreactivity and, accordingly, we confirmed a significant low NIS expression and impaired targeting to membranes in BRAF-positive samples (3.5% vs 30%; P=0.005). Furthermore, experiments with differentiated PCCl3 thyroid cells demonstrated that transient expression of BRAFV600E sharply impaired both NIS expression and targeting to membrane and, surprisingly, this impairment was not totally dependent on the MEK-ERK pathway. We have concluded that BRAFV600E is a new prognostic factor in PTC that correlates with a high risk of recurrences and less differentiated tumours due to the loss of NIS-mediated 131I uptake.
M M Muresan, P Olivier, J Leclère, F Sirveaux, L Brunaud, M Klein, R Zarnegar, and G Weryha
The presence of distant metastases from differentiated thyroid carcinoma decreases the 10-year survival of patients by 50%. Bone metastases represent a frequent complication especially of follicular thyroid cancer and severely reduce the quality of life causing pain, fractures, and spinal cord compression. Diagnosis is established by correlating clinical suspicion with imaging. Imaging is essential to detect, localize, and assess the extension of the lesions and should be used in conjunction with clinical evidence. Bone metastases are typically associated with elevated markers of bone turnover, but these markers have not been evaluated in differentiated thyroid cancer. Skeletal and whole-body magnetic resonance imaging and fusion 2-deoxy-2-[18F]fluoro-d-glucose whole-body positron emission tomography/computed tomography (PET/CT) are the best anatomic and functional imaging techniques available in specialized centers. For well-differentiated lesions, iodine-PET scan combined 124I-PET/CT is the newest imaging development and 131I is the first line of treatment. Bisphosphonates reduce the complications rate and pain, alone or in combination with radioiodine, radionuclides, or external beam radiotherapy and should be employed. Surgery and novel minimally invasive consolidation techniques demand an appropriate patient selection for best results on a multimodal approach. Basic research on interactions between tumor cells and bone microenvironment are identifying potential novel targets for future more effective therapeutic interventions for less differentiated tumors.
Xiaoyun Dong, Waixing Tang, Stephen Stopenski, Marcia S Brose, Christopher Korch, and Judy L Meinkoth
The functional significance of decreased RAP1GAP protein expression in human tumors is unclear. To identify targets of RAP1GAP downregulation in the thyroid gland, RAP1 and RAP2 protein expression in human thyroid cells and in primary thyroid tumors were analyzed. RAP1GAP and RAP2 were co-expressed in normal thyroid follicular cells. Intriguingly, RAP1 was not detected in normal thyroid cells, although it was detected in papillary thyroid carcinomas, which also expressed RAP2. Both RAP proteins were detected at the membrane in papillary thyroid tumors, suggesting that they are activated when RAP1GAP is downregulated. To explore the functional significance of RAP1GAP depletion, RAP1GAP was transiently expressed at the lowest level that is sufficient to block endogenous RAP2 activity in papillary and anaplastic thyroid carcinoma cell lines. RAP1GAP impaired the ability of cells to spread and migrate on collagen. Although RAP1GAP had no effect on protein tyrosine phosphorylation in growing cells, RAP1GAP impaired phosphorylation of focal adhesion kinase and paxillin at sites phosphorylated by SRC in cells acutely plated on collagen. SRC activity was increased in suspended cells, where it was inhibited by RAP1GAP. Inhibition of SRC kinase activity impaired cell spreading and motility. These findings identify SRC as a target of RAP1GAP depletion and suggest that the downregulation of RAP1GAP in thyroid tumors enhances SRC-dependent signals that regulate cellular architecture and motility.
Roberto Bellelli, Maria Domenica Castellone, Ginesa Garcia-Rostan, Clara Ugolini, Carmelo Nucera, Peter M Sadow, Tito Claudio Nappi, Paolo Salerno, Maria Carmela Cantisani, Fulvio Basolo, Tomas Alvarez Gago, Giuliana Salvatore, and Massimo Santoro
Anaplastic thyroid carcinoma (ATC) is a very aggressive thyroid cancer. forkhead box protein M1 (FOXM1) is a member of the forkhead box family of transcription factors involved in control of cell proliferation, chromosomal stability, angiogenesis, and invasion. Here, we show that FOXM1 is significantly increased in ATCs compared with normal thyroid, well-differentiated thyroid carcinomas (papillary and/or follicular), and poorly differentiated thyroid carcinomas (P=0.000002). Upregulation of FOXM1 levels in ATC cells was mechanistically linked to loss-of-function of p53 and to the hyperactivation of the phosphatidylinositol-3-kinase/AKT/FOXO3a pathway. Knockdown of FOXM1 by RNA interference inhibited cell proliferation by arresting cells in G2/M and reduced cell invasion and motility. This phenotype was associated with decreased expression of FOXM1 target genes, like cyclin B1 (CCNB1), polo-like kinase 1 (PLK1), Aurora B (AURKB), S-phase kinase-associated protein 2 (SKP2), and plasminogen activator, urokinase: uPA (PLAU). Pharmacological inhibition of FOXM1 in an orthotopic mouse model of ATC reduced tumor burden and metastasization. All together, these findings suggest that FOXM1 represents an important player in thyroid cancer progression to the anaplastic phenotype and a potential therapeutic target for this fatal cancer.
Xinying Li, Zhiming Wang, Jianming Liu, Cane Tang, Chaojun Duan, and Cui Li
The fusion gene encoding the thyroid-specific transcription factor PAX8 and peroxisome proliferator-activated receptor γ (PPARγ (PPARG)) (designated as the PPFP gene) is oncogenic and implicated in the development of follicular thyroid carcinoma (FTC). The effects of PPFP transfection on the biological characteristics of Nthy-ori 3-1 cells were studied by MTT assay, colony formation, soft-agar colony formation, and scratch wound-healing assays as well as by flow cytometry. Furthermore, the differentially expressed proteins were analyzed on 2-DE maps and identified by MALDI-TOF-MS. Validation of five identified proteins (prohibitin, galectin-1, cytokeratin 8 (CK8), CK19, and HSP27) was determined by western blot analysis. PPFP not only significantly increased the viability, proliferation, and mobility of the Nthy-ori 3-1 cells but also markedly inhibited cellular apoptosis. Twenty-eight differentially expressed proteins were identified, among which 19 proteins were upregulated and nine proteins were downregulated in Nthy-ori 3-1PPFP (Nthy-ori 3-1 cells transfected with PPFP). The western blot results, which were consistent with the proteome analysis results, showed that prohibitin was downregulated, whereas galectin-1, CK8, CK19, and HSP27 were upregulated in Nthy-ori 3-1PPFP. Our results suggest that PPFP plays an important role in malignant thyroid transformation. Proteomic analysis of the differentially expressed proteins in PPFP-transfected cells provides important information for further study of the carcinogenic mechanism of PPFP in FTCs.