Molecular genetic alterations of FHIT and p53 genes in benign and malignant thyroid gland lesions

Minor role of TP53 and TERT promoter mutations in medullary thyroid carcinoma: report of new cases and revision of the literature

PURPOSE

Aims of this study were to investigate the prevalence of TP53 and TERT mutations in Medullary Thyroid carcinoma (MTC) and their role in inducing aggressiveness in positive cases.

METHODS

We performed a literature search in PubMed to identify studies investigating the prevalence of TERT and TP53 mutations in MTC. We also included data on MTC cases (n = 193) obtained at our center and unpublished. The in-silico pathogenicity of the TP53 mutations has been evaluated by predictor tools.

RESULTS

We identified a total of 25 and 11 published papers: all together 1280 cases have been investigated for the presence of TP53 mutations and 974 for TERT promoter mutation. Twenty-five out of 1280 (2%) cases had a TP53 mutation while only 3/974 MTC cases (0.3%) have been found to be positive for TERT promoter mutations. Among all, we identified 19 different TP53 mutations that in 12 cases were demonstrated to have an in silico predicted high pathogenic role and a high impact on protein function. Three non-sense and 4 probably not damaging mutations were also reported. The pathogenic role of the TERT promoter mutations has been previously in vitro determined. No correlation between TP53 and/or TERT mutations and aggressiveness of MTC has been demonstrated.

CONCLUSION

The prevalence of TP53 and TERT promoter mutations is very low in MTC. The reported mutations are pathogenic in the majority of cases. Because of their rarity it is not possible to clarify if they play or not a role in the pathogenesis and/or aggressiveness of this specific thyroid tumor.

A genome-wide DNA methylation analysis in peripheral blood from patients identifies risk loci associated with Graves' orbitopathy

OBJECTIVE

Graves' orbitopathy (GO) is an inflammatory orbital disease of autoimmune origin with the potential to cause severe functional and psychosocial effects. The pathogenesis has not been fully elucidated. We investigated whether DNA methylation was associated with GO incidence in Chinese patients.

MATERIALS AND METHODS

Six GO patients and six age-matched controls were recruited, and genome-wide DNA methylation patterns were analyzed in their peripheral blood. t tests were performed to determine differential methylated sites in genomic regions and the univariable logistic regression analyses was performed to evaluate their risk with GO incidence. Cluster analysis and principal component analysis (PCA) were performed to determine the effects of the extracted differentially methylated sites.

RESULTS

One hundred and forty-eight differentially methylated sites were identified, including CD14 (fold change = 4.31, p = 0.005), IL17RE (fold change = 2.128, p = 0.005), and DRD4 (fold change = 0.25, p = 0.004), and were supported by cluster and PCA analyses. Univariable logistic regression analyses showed that the methylation patterns at 12 loci were associated with GO incidence. The relative risk per 1% decrease in methylation at ZCCHC6 and GLI3 was 0.15 (95% CI 0.03-0.91; p = 0.039) and 0.65 (95% CI 0.42-0.98; p = 0.042), respectively. Pearson correlation analyses demonstrated that methylation levels at IL17RE were positively associated with Clinical Activity Score (CAS) (r = 0.967, p < 0.05).

CONCLUSIONS

Our results demonstrate that differential methylation levels at analyzed sites (genes) may be risk markers of GO. DNA methylation analysis could provide new insights into understanding the disease and provide new treatment strategies for GO in Chinese patients.

Animal models of medullary thyroid cancer: state of the art and view to the future

Medullary thyroid carcinoma is a neuroendocrine tumour originating from parafollicular C cells accounting for 5-10% of thyroid cancers. Increased understanding of disease-specific molecular targets of therapy has led to the regulatory approval of two drugs (vandetanib and cabozantinib) for the treatment of medullary thyroid carcinoma. These drugs increase progression-free survival; however, they are often poorly tolerated and most treatment responses are transient. Animal models are indispensable tools for investigating the pathogenesis, mechanisms for tumour invasion and metastasis and new therapeutic approaches for cancer. Unfortunately, only few models are available for medullary thyroid carcinoma. This review provides an overview of the state of the art of animal models in medullary thyroid carcinoma and highlights future developments in this field, with the aim of addressing salient features and clinical relevance.

p53 suppresses carcinoma progression by inhibiting mTOR pathway activation

Genetic alterations in human cancers and murine models indicate that Rb and p53 have critical tumor suppressive functions in retinoblastoma, a tumor of neural origin, and neuroendocrine tumors including small cell lung cancer and medullary thyroid cancer (MTC). Rb inactivation is the initiating lesion in retinoblastoma and current models propose that induction of apoptosis is a key p53 tumor suppressive function. Genetic studies in mice, however, indicate that other undefined p53 tumor suppressive functions are operative in vivo. How p53 loss cooperates with Rb inactivation to promote carcinogenesis is also not fully understood. In the current study, genetically engineered mice were generated to determine the role of Rb and p53 in MTC pathogenesis and test the hypothesis that p53 suppresses carcinogenesis by inhibiting mTOR signaling. Conditional Rb ablation resulted in thyroid tumors mimicking human MTC, and additional p53 loss led to rapid tumor progression. p53 suppressed tumorigenesis by inhibiting cell cycle progression, but did not induce apoptosis. On the contrary, p53 loss led to increased apoptosis that had to be overcome for tumor progression. mTOR activity was markedly increased in p53 deficient tumors and rapamycin treatment suppressed tumor cell growth identifying mTOR inhibition as a critical p53 tumor suppressive function. Rapamycin treatment did not result in AKT/MAPK activation providing evidence that this feedback mechanism operative in other cancers is not a general response to mTORC1 inhibition. Together, these studies provide mechanistic links between genetic alterations and aberrant signaling pathways critical in carcinogenesis, and identify essential Rb and p53 tumor suppressive functions in vivo.

A 95-year-old woman with leucocytosis and eosinophilia: anaplastic carcinoma in an ectopic thyroid

A 95-year-old woman had been treated over the past 8 years for progressive dysphagia. When her condition worsened, blood tests revealed the presence of leucocytosis and eosinophilia in the absence of anaemia or thrombocytopenia. Within 11 days of diagnosis, the patient died of respiratory failure. Necropsy showed normal thyroid tissue and an absence of infectious disease. However, an upper mediastinal tumour was found and was histopathologically diagnosed as a neoplastic transformation of the ectopic thyroid. Only 1% of endothoracic goitres present as ectopic or autonomous goitre with no parenchymal or vascular connection to the thyroid gland. This case represents a very rare situation in which a leukemoid reaction and peripheral hypereosinophilia were observed as a manifestation of an anaplastic thyroid carcinoma in an ectopic mass.

Comparative analysis of protein expression in differentiated thyroid tumours: a multicentre study

This study compared clinical features and protein expression profiles in differentiated thyroid tumours to identify protein markers with the potential for indicating malignancy status. Tissue microarrays were constructed using 119 thyroid tumour samples (45 papillary carcinomas, 26 follicular carcinomas, 48 adenomas). Generally, there was overexpression of proliferating cell nuclear antigen (PCNA), p53, matrix metalloproteinase (MMP)-7, Hector Battifora mesothelial-1 (HBME-1), MMP-2, pituitary tumour-transforming gene (PTTG) and human telomerase reverse transcriptase (hTERT) in malignant thyroid carcinomas, and overexpression of fragile histidine triad (FHIT), p16 and E-cadherin in thyroid adenomas. Multiple factor binary logistic regression analysis indicated that MMP-2, HBME-1, p16 and FHIT were independently related to differentiated thyroid tumours. Receiver-operating characteristics for these four factors showed HBME-1 as best for diagnostic accuracy. Sensitivity and specificity were enhanced using an HBME-1 and p16 cluster. HBME-1 expression was not significantly different for papillary and follicular carcinomas, whereas p16 expression was significantly specific.

Biological role and potential therapeutic targeting of the chemokine receptor CXCR4 in undifferentiated thyroid cancer

Anaplastic thyroid carcinoma (ATC) is a rare thyroid cancer type with an extremely poor prognosis. Despite appropriate treatment, which includes surgery, radiotherapy, and chemotherapy, this cancer is invariably fatal. CXCR4 is the receptor for the stromal cell-derived factor-1 (SDF-1)/CXCL12 chemokine and it is expressed in a variety of solid tumors, including papillary thyroid carcinoma. Here, we show that ATC cell lines overexpress CXCR4, both at the level of mRNA and protein. Furthermore, we found that CXCR4 was overexpressed in ATC clinical samples, with respect to normal thyroid tissues by real-time PCR and immunohistochemistry. Treatment of ATC cells with SDF-1 induced proliferation and increase in phosphorylation of extracellular signal-regulated kinases and protein kinase B/AKT. These effects were blocked by the specific CXCR4 antagonist AMD3100 and by CXCR4 RNA interference. Moreover, AMD3100 effectively reduced tumor growth in nude mice inoculated with different ATC cells. Thus, we suggest that CXCR4 targeting is a novel potential strategy in the treatment of human ATC.

Association between decreased WWOX protein expression and thyroid cancer development

CONTEXT

Chromosomal fragile sites are often related to cancer development. The WW domain-containing oxidoreductase gene (WWOX) spans the second most common chromosomal fragile site (FRA16D) and encodes an important proapoptotic protein.

OBJECTIVE

To verify our hypothesis that underexpression of WWOX could contribute to malignant transformation of the thyroid cells.

METHOD

We compared WWOX expression among follicular adenomas (FAs) and differentiated thyroid carcinomas [follicular thyroid carcinomas (FTCs) and papillary thyroid carcinomas (PTCs)] in 53 thyroid tumors resected from patients submitted to total thyroidectomy.

DESIGN

Multiple fields of tumor areas of FAs, FTCs, and PTCs as well as normal thyroid tissue were stained with WWOX antiserum, and classified by the extent of staining (percentage of cells staining) and staining intensity.

MAIN OUTCOME

PTCs showed a significantly decreased expression of WWOX when compared to FAs and FTCs. Further, using a unique model of comparison in patients in whom FAs and PTCs were concomitantly present, we detected the same result (i.e., no expression in PTCs).

CONCLUSION

We conclude that WWOX underexpression is an important step that might increase the vulnerability to the carcinogenesis process in PTCs.

New drugs in thyroid cancer

This review is focused on "new drugs" that might be developed for thyroid cancer treatment. Thyroid cancer is frequently associated to the activation of specific protein (RET, BRAF) and lipid [PI(3)K] kinases. There is good evidence that these genetic lesions are causative events in thyroid cancer initiation or progression. Therefore, novel compounds able to target these kinases might be useful for thyroid cancer treatment. The power of this approach is witnessed by the examples of BCR-ABL, c-KIT and EGFR inhibitors in the treatment of chronic myelogenous leukemia (CML), gastro-intestinal stromal tumors (GIST) and non-small cell lung carcinoma (NSCLC).