Loss of heterozygosity of the VHL gene identifies malignancy and predicts death in follicular thyroid tumors

Expression of VHL tumor suppressor mRNA and miR-92a in papillary thyroid carcinoma and their correlation with clinical and pathological parameters

A growing body of evidence suggests a role of the von Hippel-Lindau (VHL) tumor suppressor gene in the progression of papillary thyroid carcinoma (PTC). Our previous study of VHL in PTCs showed that lower VHL expression was associated with aggressive tumor features, but we found no evidence for VHL downregulation through common genetic or epigenetic modifications. Several studies pointed to a role of microRNA-92a (miR-92a) in the regulation of VHL expression in different cancers. In the present study, we examined the expression levels of VHL mRNA and miR-92a in 42 pairs of PTCs and matched non-tumor thyroid tissues by means of quantitative RT-PCR. We explored the correlation between them and their association with clinicopathological parameters. The results revealed that both VHL and miR-92a were either up- or downregulated in PTCs compared to corresponding non-tumor tissues. On univariate analysis, lower VHL levels were significantly associated with extrathyroid spread (P = 0.022) and capsular invasion (P = 0.032). Multivariate analysis confirmed the association of low VHL with extrathyroid spread (OR 0.246, 95% CI 0.069-0.872, P = 0.038). Higher miR-92a among PTC tissues associated with the presence of nodal metastases (univariate analysis: P = 0.012; multivariate: OR 4.703, 95% CI 1.109-19.938, P = 0.036). A negative correlation between VHL and miR-92a was observed in a subgroup of PTCs having vascular invasion (P = 0.033, r = - 0.673). The data here reported demonstrate that the expression of both VHL and miR-92a is deregulated in PTC tissues and that in some PTCs they may have opposite roles. These roles, as well as their diagnostic and/or prognostic utility, remain to be clarified.

Deregulated expression of VHL mRNA variants in papillary thyroid cancer

Recent findings demonstrated that a subset of papillary thyroid cancers (PTCs) is characterized by reduced expression of the von Hippel-Lindau (VHL) tumor suppressor gene, and that lowest levels associated with more aggressive PTCs. In the present study, the levels of the two VHL mRNA splicing variants, VHL-213 (V1) and VHL-172 (V2), were measured in a series of 96 PTC and corresponding normal matched tissues by means of quantitative RT-PCR. Variations in the mRNA levels were correlated with patients' clinicopathological parameters and disease-free interval (DFI). The analysis of VHL mRNA in tumor tissues, compared to normal matched tissues, revealed that its expression was either up- or down-regulated in the majority of PTC. In particular, V1 and V2 mRNA levels were altered, respectively, in 78 (81.3%) and 65 (67.7%) out of the 96 PTCs analyzed. A significant positive correlation between the two mRNA variants was observed (p < 0.001). Univariate analysis documented the lack of association between each variant and clinicopathological parameters such as age, tumor size, histology, TNM stage, lymph node metastases, and BRAF mutational status. However, a strong correlation was found between altered V1 or V2 mRNA levels and DFI. Multivariate regression analysis indicated higher V1 mRNA values, along with lymph node metastases at diagnosis, as independent prognostic factors predicting DFI. In conclusion, the data reported demonstrate that VHL gene expression is deregulated in the majority of PTC tissues. Of particular interest is the apparent protective role exerted by VHL transcripts against PTC recurrences.

Incidence of malignancy in solitary thyroid nodules

Objectives:

This study aimed to investigate the prevalence and clinical significance of solitary thyroid nodules in patients who underwent thyroid surgery.

Methods:

A retrospective review was performed of the case notes of all adult patients who underwent thyroid surgery from January 2003 to December 2009. All patients with solitary thyroid nodules identified by ultrasonography were included.

Results:

In total, 225 patients underwent thyroid surgery. The prevalence of solitary thyroid nodules was 27.1 per cent (61 out of 225 patients). Seventy-two per cent of patients were women and the mean age at presentation was 52 ± 16 years. In all, 75.4 per cent of solitary nodules had neoplastic pathology and the malignancy rate was 34.4 per cent. The sensitivity and specificity of fine needle aspiration cytology for neoplasm detection were 73.9 per cent and 80.0 per cent, respectively. There was no association between the various ultrasonography parameters and malignancy risk (p > 0.05).

Conclusion:

Solitary thyroid nodules should be investigated thoroughly with a high index of suspicion because there is a high probability (34.0 per cent) of malignancy.

Molecular alterations in partially-encapsulated or well-circumscribed follicular variant of papillary thyroid carcinoma

BACKGROUND

Studies have described an encapsulated and an infiltrative form of the follicular variant of papillary thyroid carcinoma (FVPTC). Encapsulated FVPTCs have been reported to have virtually no recurrence risk or metastatic potential and to harbor RAS mutations but not BRAF mutations. In contrast, infiltrative tumors have significant metastatic potential, a risk of recurrence, and a BRAF mutation frequency of approximately 25%. In our experience, a substantial number of FVPTCs are neither fully encapsulated nor infiltrative, but instead are partially encapsulated (PE) or well circumscribed (WC). We have previously reported that PE/WC FVPTCs behave in an indolent fashion similar to encapsulated tumors. The purpose of the current study was to evaluate the molecular alterations in PE/WC FVPTC.

METHODS

We identified 28 PE/WC FVPTCs resected consecutively at our institution. Targeted mutation analysis of 41 genes including members of the RAS and RAF families was performed on DNA extracted from formalin-fixed, paraffin-embedded blocks using single-base extension chemistry and mass spectrometry.

RESULTS

Lymph node metastases were absent in all cases with sampled lymph nodes, and no patients developed tumor recurrences (median follow-up time, 72.8 months). Overall, 13 cases (46%) harbored RAS mutations, including seven (25%) with NRAS mutations (p.Gln61Arg) and six (21%) with HRAS mutations (five had p.Gln61Arg and one had a p.Gln61Lys substitution). No PE/WC FVPTCs had BRAF mutations.

CONCLUSIONS

The results of this study confirm our previous finding that PE/WC FVPTCs pursue an indolent clinical course. Additionally, we found that PE/WC tumors have a similar molecular profile to that of encapsulated FVPTCs with frequent RAS mutations (46%) and no BRAF mutations. These molecular results provide further evidence that PE/WC and encapsulated FVPTCs are biologically similar and should be distinguished from more aggressive infiltrative FVPTCs.

Predicting malignancy in thyroid nodules: molecular advances

Over the last several years, a clearer understanding has developed of the genetic alterations underlying thyroid carcinogenesis. This knowledge can be used to tackle 1 of the challenges facing thyroidologists: management of the indeterminate thyroid nodule. Despite the accuracy of fine-needle aspiration cytology, many patients undergo surgery to diagnose malignancy and better diagnostic tools are required. A number of biomarkers have recently been studied and show promise in this setting. In particular, BRAF, RAS, PAX8-PPARγ, microRNAs, and loss of heterozygosity have each been demonstrated as useful molecular tools for predicting malignancy and can potentially guide decisions regarding surgical management of nodular thyroid disease. This review summarizes the current literature surrounding each of these markers, highlights our institution's prospective analysis of these markers, and describes the subsequent incorporation of molecular markers into a management algorithm for thyroid nodules.

Thyroid cancer: current molecular perspectives

The thyroid cancer is a rare oncological entity, representing no more than 1% of all human malignant neoplasms. Recently, it has been demonstrated a sharp increase in incidence of differentiated thyroid carcinoma, equally occurring in both sexes. So far, multiple genetic alterations have been identified in differentiated thyroid carcinoma, leading to investigate the clinical utility of genetic studies. In particular, molecular genetic approaches searching for gene mutations in the material collected by fine needle ago-biopsy may have a particular utility in small nodules and in those specimens with an indeterminate cytology. The expansion of knowledge about genetic mutations occurring in different thyroid tumors has characterized recent years, allowing the identification of a correlation between specific mutations and phenotypic characteristics of thyroid cancers, essential for their prognosis. This review will briefly report on the histological features and the new entity represented by thyroid microcarcinoma and will focus on both environmental and genetic aspects associated with the occurrence of thyroid cancer.

Recent developments in predicting thyroid malignancy

PURPOSE OF REVIEW

To provide an update on potential predictors of thyroid malignancy and how their use may alter clinical management.

RECENT FINDINGS

As thyroid nodules become more prevalent clinicians are increasingly impelled to identify the optimal predictor(s) of thyroid malignancy, with the goal of guiding management based on assessed risk. The gold standard evaluation for thyroid nodules is ultrasound-guided fine-needle aspiration biopsy. Fine-needle aspiration biopsy is not perfect and adjuncts which complement its predictive value are being investigated from several innovative perspectives. These include large tumor size (> or =4 cm), which appears to be an independent predictor of thyroid malignancy; 18F-fluorodeoxyglucose positron emission tomography, which appears to facilitate exclusion of malignancy in cytologically indeterminate thyroid nodules; and peripheral blood and fine-needle aspiration biopsy analysis of molecular markers, which may help to identify malignant thyroid nodules with greater specificity.

SUMMARY

Fine-needle aspiration biopsy of large thyroid nodules has a high false-negative rate and should be considered for diagnostic lobectomy. Nodule size appears to be an independent factor predicting malignancy and indeterminate lesions at least 4 cm should be considered for initial total thyroidectomy. Nuclear imaging may aid exclusion of malignancy in thyroid nodules and molecular markers have great promise in predicting thyroid malignancy with higher specificity.

Molecular genetics of thyroid cancer: implications for diagnosis, treatment and prognosis

Thyroid cancer is the most common malignant tumor of the endocrine system and accounts for approximately 1% of all newly diagnosed cancer cases. The most frequent type of thyroid malignancy is papillary carcinoma, which constitutes approximately 80% of all cases. Papillary carcinomas frequently have genetic alterations leading to the activation of the MAPK signal pathway. Those include RET/PTC rearrangement and point mutations of the BRAF and RAS genes. Mutations in these genes are found in over 70% of papillary carcinomas and they rarely overlap in the same tumor. Frequent genetic alterations in follicular carcinomas, the second most common type of thyroid malignancy, include RAS mutations and PAX8-PPAR gamma rearrangement. RET point mutations are crucial for the development of medullary thyroid carcinomas. Many of these mutations, particularly those leading to the activation of the MAPK pathway, are being actively explored as therapeutic targets for thyroid cancer. Detection of these genetic alterations using molecular techniques is important for preoperative fine-needle aspiration diagnosis, prognosis and treatment of thyroid cancer.

Expression of hypoxia-inducible factor 1alpha, hypoxia-inducible factor 2alpha, and von Hippel-Lindau protein in epithelial ovarian neoplasms and allelic loss of von Hippel-Lindau gene: nuclear expression of hypoxia-inducible factor 1alpha is an independent prognostic factor in ovarian carcinoma

The hypoxia-inducible factor (HIF) is a transcriptional factor with important roles in tumor biology. To clarify the possible involvement of the HIF-alpha subunit and von Hippel-Lindau (VHL) protein in the development and progression of ovarian carcinoma, we analyzed the immunohistochemical expressions of HIF-1alpha, HIF-2alpha, and VHL in 107 cases of epithelial ovarian tumors. In addition, we examined loss of heterozygosity (LOH) at VHL gene loci. The frequency of the cytoplasmic expression of HIF-2alpha in carcinomas was higher than that in benign and borderline tumors (P < .0001). Furthermore, the nuclear expression of HIF-1alpha and the cytoplasmic expression of HIF-2alpha were significantly higher in tumors of FIGO (International Federation of Gynecology and Obstetrics) stages III and IV than in those of stages I and II. On the other hand, the cytoplasmic expression of HIF-1alpha did not show differences among histological malignancies. There was a positive correlation between nuclear HIF-1alpha expression and vascular endothelial growth factor (rho = 0.320, P < .001). Although LOH at the VHL gene locus was frequent in ovarian carcinomas (24%), there is no significant correlation between LOH and loss of VHL expression. In 22 clear cell carcinomas, VHL expression showed a significantly negative correlation with the nuclear expression of HIF-1alpha (rho = -0.529, P = .0153). The log-rank test showed that nuclear positive immunostaining for HIF-1alpha (P = .002) and cytoplasmic positive immunostaining for HIF-2alpha (P = .0112) in tumor cells are associated with poor prognosis of patients with ovarian carcinoma. Multivariate analysis also showed that the nuclear expression of HIF-1alpha is an independent prognostic factor. These results show that the HIF-alpha subunit represents an important biomarker in the evaluation of the prognosis of patients with ovarian carcinoma.

Current status of fine needle aspiration for thyroid nodules

When not to perform fine needle aspiration of a thyroid nodule In summary, FNA of thyroid nodules has become one of the most useful, safe, and accurate tools in the diagnosis of thyroid pathology. Thyroid nodules that should be considered for FNA include any firm, palpable, solitary nodule or nodule associated with worrisome clinical features (rapid growth, attachment to adjacent tissues, new hoarseness, or palpable lymphadenopathy). FNA should also be performed on nodules with suspicious ultrasonographic features (microcalcifications, rounded shape, predominantly solid composition); dominant or atypical nodules in multinodular goiter; complex or recurrent cystic nodules; or any nodule associated with palpable or ultrasonographically abnormal cervical lymph nodes. Finally, FNA should be performed on any abnormal-appearing or palpable cervical lymph nodes. The management of thyroid nodules based on FNA findings is summarized in Table 2. It can be argued that in certain circumstances the results of thyroid FNA do not change the surgical management of a thyroid nodule, and thus preoperative FNA may be unnecessary. These cases include solitary nodules in patients who have a strong family history of thyroid cancer, multiple endocrine neoplasia type II, or radiation to the head and neck. These patients when they have thyroid nodules have at least a 40% risk for thyroid cancer and frequent multifocal or bilateral disease and should undergo total thyroidectomy with or without central neck lymph node dissection. Patients who have multinodular goiter and compressive symptoms, patients who have Graves disease and a thyroid nodule, or patients who have large (greater than 4 cm) or symptomatic unilateral thyroid nodules could also be considered for total thyroidectomy or lobectomy as indicated without preoperative FNA. Finally, patients who have a solitary hyperfunctioning nodule on radioiodine scan and a suppressed TSH have an extremely low incidence of malignancy and may be considered for therapeutic thyroid lobectomy or radioiodine ablation as indicated without undergoing FNA biopsy.

A multinodular goiter as the initial presentation of a renal cell carcinoma harbouring a novel VHL mutation

BACKGROUND

Secondary involvement of the thyroid gland is rare. Often the origin of the tumor is difficult to identify from the material obtained by fine-needle aspiration cytology. Renal cell carcinoma of the clear-cell type is one of the more common carcinomas to metastasize to the thyroid gland. Somatic mutations of the von Hippel-Lindau tumor suppressor gene are associated with the sporadic form of this tumor. We aimed to illustrate the potential utility of DNA based technologies to search for specific molecular markers in order to establish the anatomic site of origin.

CASE PRESENTATION

A 54-yr-old Caucasian male complaining of a rapidly increasing neck tumor was diagnosed as having a clear-cell tumor by fine-needle aspiration cytology. A positive staining for cytokeratin as well as for vimentin and CD10 in the absence of staining for thyroglobulin, calcitonin and TTF1 suggested a renal origin confirmed by computed tomography. Using frozen RNA, obtained from cells left inside the needle used for fine needle aspiration cytology, it was possible to identify a somatic mutation (680 delA) in the VHL gene.

CONCLUSION

In the presence of a clear-cell tumor of the thyroid gland, screening for somatic mutations in the VHL gene in material derived from thyroid aspirates might provide additional information to immunocytochemical studies and therefore plays a contributory role to establish the final diagnosis. Moreover, in a near future, this piece of information might be useful to define a targeted therapy.

Capillary electrophoresis and the clinical laboratory

Over the past 15 years, CE as an analytical tool has shown great promise in replacing many conventional clinical laboratory methods, such as electrophoresis and HPLC. CE's appeal was that it was fast, used very small amounts of sample and reagents, was extremely versatile, and was able to separate large and small analytes, whether neutral or charged. Because of this versatility, numerous methods have been developed for analytes that are of clinical interest. Other than molecular diagnostic and forensic laboratories CE has not been able to make a major impact in the United States. In contrast, in Europe and Japan an increasing number of clinical laboratories are using CE. Now that automated multicapillary instruments are commercially available along with cost-effective test kits, CE may yet be accepted as an instrument that will be routinely used in the clinical laboratories. This review will focus on areas where CE has the potential to have the greatest impact on the clinical laboratory. These include analyses of proteins found in serum and urine, hemoglobin (A1c and variants), carbohydrate-deficient transferrin, forensic and therapeutic drug screening, and molecular diagnostics.

Promising molecular techniques for discriminating among follicular thyroid neoplasms

To guide the extent of thyroidectomy for indeterminate follicular neoplasm (FN), clinicians have long sought ways to differentiate follicular adenoma from carcinoma pre- or intraoperatively. Several promising molecular techniques have recently appeared including loss of heterozygosity analysis and molecular profiling microarray analysis. These new tools may also prove useful in determining prognosis, thus and allow a paradigm change in current management of the thyroid nodule.

New prognostic scales LAST-1 and LAST-2: supporting prediction and staging of thyroid cancer

INTRODUCTION

Epidemiologically, thyroid gland tumors are lesions of the highest importance among endocrine tumors in humans. Although the results of surgical treatment of the highly differentiated (follicular and papillary) tumors seem to be satisfactory, treatment of the poorly differentiated (medullary and anaplastic) tumor still demands clinical and basic investigations. In this study the authors sought to evaluate clinical and molecular factors that could contribute to preoperative detection of more advanced thyroid cancers (i.e., those that exhibit extrathyroid spread and lymph node invasion).

METHODS

A total of 27 patients operated on for thyroid cancer were evaluated according to age, sex, time from the onset of the disease, cytogenetic changes, and loss of heterozygosity (LOH) in 14 microsatellite markers. The output variables were defined according to postoperative findings and the TNM 2002 score. The T1-2 N0 M0 cases were defined as local malignancy (LM); and T3-4 any N any M, any T N1 any M, or any T any N M1 were considered advanced malignancy (AM). The control groups consisted of 25 patients with multinodular goiter (MNG) and 32 patients with follicular adenoma (FA). In all cases, clinical and molecular data similar to those listed above were collected, excluding staging and follow-up information.

RESULTS

There was no predominant specific type of chromosomal aberration observed and no marker lost in more than five patients (18%). The logistic regression identified three input variables as contributing significantly to the dichotomized outcome measure (LM vs. AM): LOH in any of the examined loci, age of the patient at the presentation, and the sex of the patient. Furthermore, discriminant analysis revealed four input variables differentiating among TC, FA, and MNG patients. Based on the multivariate analysis results, two numeric prognostic scales were fashioned: LAST-1, a scale applicable to differentiation of thyroid cancers at different degrees of clinical advancement; and LAST-2, a scale applicable to differentiation of any thyroid lumps.

CONCLUSIONS

It was concluded that LOH and the age and sex of the patients can provide sufficient data to predict thyroid cancer with a high degree of clinical advancement. LAST-1 scale is a reliable tool for identifying these patients. The LAST-2 scale gives supportive information about the character of thyroid lumps, distinguishing TC from MNG and FA.

Molecular events in follicular thyroid tumors

Knowledge of the molecular events that govern human thyroid tumorigenesis has grown considerably in the past ten years. Key genetic alterations and new oncogenic pathways have been identified. Molecular genetic aberrations in thyroid carcinomas bear noteworthy resemblance to those in acute myelogenous leukemias. Thyroid carcinomas and myeloid leukemias both possess transcription factor gene rearrangements-PPARgamma-related translocations in thyroid carcinoma and RARalpha-related and CBF-related translocations (amongst others) in myeloid leukemia. PPARgamma and RARalpha are closely related members ofthe same nuclear receptor subfamily, and the PML-RARalpha and PAX8-PPARgamma fusion proteins both function as dominant negative inhibitors of their wild-type parent proteins. Thyroid carcinomas and myeloid leukemias also both harbor NRAS mutations (15-25% of both cancers) and receptor tyrosine kinase mutations--RET mutations in thyroid carcinomas and FLT3 mutations in myeloid leukemias. The NRAS and tyrosine receptor kinase mutations are not observed in the same thyroid carcinoma or leukemia patients, suggesting that multiple initiating pathways exist in both. Lastly, thyroid carcinomas and myeloid leukemias possess p53 mutations at relatively low frequency (10-15%) in patients who tend to be older and have more aggressive, therapy resistant disease. Such parallels are unlikely to occur by chance alone and argue that common mechanisms underlie these diverse epithelial and hematologic cancers. The comparison of thyroid carcinomas and myeloid leukemias may highlight areas of thyroid cancer investigation worthy of further focus. For example, few collaborating mutations have been defined in thyroid carcinomas even though they play a clear role in myeloid leukemias, as exemplified by RARalpha rearrangements and FLT3 mutations that together dictate the promyleocytic leukemia phenotype. Functional interactions between collaborating mutations are possible at multiple levels, and it is tempting to speculate that some thyroid carcinomas might develop through an unique combination or co-activation of RET and RAS and/or RET and PPARgamma (and/or other) signaling systems. In fact, the ELE1-RET (PTC3) fusion protein contains the ELE1 nuclear receptor co-activator domain and it appears to physically associate with and inhibit wild-type PPARgamma in some papillary carcinomas. The similarities of the fusion proteins in thyroid carcinoma and myeloid leukemia suggest that a more directed search for fusion genes in non-thyroid carcinomas is warranted. In fact, novel fusion genes have been identified recently in aggressive midline, secretory breast, and renal cell carcinomas, although the epithelial nature of the latter is not well-documented. Interestingly, these cancers all tend to present more frequently in adolescence and young adulthood in a manner similar to thyroid and myeloid malignancies that have fusion genes. The analyses of cancers that present earlier in life may enhance fusion gene recognition in other carcinoma types. Definition and biologic characterization of the precursor cells that give rise to thyroid carcinoma will also be important. Myeloid leukemias are thought to arise from stem/progenitor cells that acquire disturbed self-renewal and differentiation capacities but retain characteristics of the myeloid lineages. Although the presence of comparable stem/progenitor cells in the thyroid are not defined, distinct thyroid cancer lineages and patterns of differentiation exist and candidate stem/progenitor cells such as the p63-immunoreactive solid cell nests are apparent. A last important area is development of molecular-based therapies for thyroid carcinoma patients resistant to standard radio-iodine treatment. Treatments for such cancers are limited and pathways defined by thyroid cancer mutations are prime targets for pharmacologic interventions with molecular inhibitors. Tyrosine kinase inhibitors and nuclear receptor ligands have proven dramatically effective in some myeloid leukemia patients. Various molecular inhibitors are being investigated now in thyroid cancer models. Such developments predict that the thyroid cancer model will continue to provide biologic insights into human carcinoma biology and that improved pathologic diagnosis and treatment for thyroid cancer patients sit on the not too distant horizon.