Human telomerase reverse transcriptase expression in Diff-Quik-stained FNA samples from thyroid nodules

MicroRNA signature in thyroid fine needle aspiration cytology applied to "atypia of undetermined significance" cases

BACKGROUND

MicroRNA (miR) expression signatures are proposed to be able to differentiate thyroid cancer from benign thyroid lesions. We selected eight miRs (miR-146b, -221, -187, -197, -346, -30d, -138, and -302c) to examine the potential use of miRs to supplement diagnostic cytology in cases designated as "atypia of undetermined significance."

METHODS

miR expression was measured in thyroid fine needle aspiration (FNA) specimens by quantitative polymerase chain reaction. Gene expression analyses and linear discriminant analysis (LDA) were performed in a training sample set (n=60) to obtain a classification rule to predict FNA cases as benign or malignant. The predictions were cross-validated by comparing with the corresponding histological diagnoses. A validation sample set (n=68) was further tested with the established four-miR LDA classification rule.

RESULTS

A set of four miRs (miR-146b, -221, -187, and -30d) was identified that could differentiate malignant from benign lesions. A four-miR LDA classification rule was obtained and used to predict FNA cases as benign or malignant. For the training sample set, we obtained a diagnostic accuracy of 93.3%, sensitivity of 93.2%, specificity of 93.8%, positive predictive value (PPV) of 0.98, and negative predictive value (NPV) of 0.83. For the validation sample set, we obtained a diagnostic accuracy of 85.3%, sensitivity of 88.9%, specificity of 78.3%, PPV of 0.89, and NPV of 0.78. For the 30 atypia cases in the validation sample set, we obtained a diagnostic accuracy of 73.3%, sensitivity of 63.6%, specificity of 78.9%, PPV of 0.64, and NPV of 0.79. Based on the miR predictions, we classified the atypia cases predicted as "malignant" into "high risk" and those predicted as "benign" into "low risk" categories. While thyroid carcinomas, particularly papillary thyroid carcinomas (PTCs), were relatively enriched in the high-risk category, this particular miR panel is subject to inaccurate results in follicular neoplasias in atypia cases.

CONCLUSIONS

We demonstrate that miR amplification from FNA samples is feasible and that the particular four miR profile in this study can identify PTCs. However, further refinement is required for application to FNA cytology of "atypia of undetermined significance" cases due to low accuracy in classifying follicular neoplasias.

Importance of Hormones and Proteins Determination in the Material Obtained by Fine-Needle Aspiration

More than a half century of experience with aspiration punch of nodal changes in the thyroid gland has confirmed this procedure as a golden standard in the examination of thyroid nodal disease. Although sensitivity, specificity, reliability and reproducibility are incontestably high, this procedure cannot give a simple answer on whether the change examined is benign or malignant. Numerous attempts to improve the procedure resulted in considerably advanced findings. Besides refining the cytopathologic examination techniques, confirmation or determination of hormones, proteins and other substances in the material obtained by fine-needle aspiration are actually the greatest contribution to improvement the of procedure's diagnostic value. These markers are actually followed, in most medical centers, in aspirates of thyroid nodal changes but also surrounding lymph nodes in order to evaluate with greater certainty the type, volume and spread; this is important to establish treatment procedures and to evaluate the residual disease after accomplishing the treatment.

Telomeres and thyroid cancer

Telomeres are specialized structures at the ends of chromosomes, consisting of hundreds of repeated hexanucleotides (TTAGGG)n. Genetic integrity is partly maintained by the architecture of telomeres and it is gradually lost as telomeres progressively shorten with each cell replication, due to incomplete lagging DNA strand synthesis and oxidative damage. Telomerase is a reverse transcriptase enzyme that counteracts telomere shortening by adding telomeric repeats to the G-rich strand. It is composed of a telomerase RNA component and a protein component, telomerase reverse transcriptase. In the absence of telomerase or when the activity of the enzyme is low compared to the replicative erosion, apoptosis is triggered. Patients who have inherited genetic defects in telomere maintenance seem to have an increased risk of developing familial benign diseases or malignant diseases. At the somatic level, telomerase is reactivated in the majority of human carcinomas, suggesting that telomerase reactivation is a critical step for cancerogenesis.In sporadic thyroid carcinoma telomerase activity is detectable in nearly 50% of thyroid cancer tissues and some authors proposed that the detection of telomerase activity may be used for differentiating between benign and malignant thyroid tumours. Recently a germline alteration of telomere-telomerase complex has been identified in patients with familial papillary thyroid cancer, characterized by short telomeres and increased expression and activity of telomerase compared to patients with sporadic papillary thyroid cancer.In this report, we will review the role of telomere-telomerase complex in sporadic and familial thyroid cancer.

Thyroglobulin may affect telomerase activity in thyroid follicular cells

Telomerase (TA) activity is known to be present in malignant tumor cells, but not in most somatic differentiated cells. TA shows relatively high activity in thyroid cancer cells, but reports vary. This fact prompted us to elucidate whether cell component inhibitors of TA in the thyroid follicles can modulate its activity. The activity of TA extracted from Hela cells was inhibited by mixing with the supernatant fraction of human thyroid tissue extract. To examine the effect of iodine, thyroid hormones (l-T3 and l-T4) and human thyroglobulin (hTg) contained in the thyroid follicles, l-T3, l-T4 and hTg were added to the TRAP assay system in vitro, using TA from Hela cells. Iodine, l-T3 and l-T4 did not affect TA activity, but hTg inhibited the TA activity in a dose-dependent manner (IC(50) of hTg: ca 0.45 microM: inhibiting concentration of hTg was from 0.15 microM to 3.0 microM). The hTg inhibition was not evident in the RT-PCR system, suggesting no effect of hTg on Taq DNA polymerase activity. The hTg inhibition of TA activity was attenuated by dNTP but not significantly by TS primer. These data suggest that hTg contained in thyroid follicular cells of various thyroid diseases may affect the TA activity measured in biopsied thyroid specimens, and that the reduction of the TA activity by hTg may induce slow progression and growth, and low grade malignancy of thyroid cancer, particularly differentiated carcinoma.

Thyroid fine-needle aspiration samples inadequate for reverse transcriptase-polymerase chain reaction analysis

BACKGROUND

Analysis of different tumor markers by reverse transcriptase-polymerase chain reaction (RT-PCR) in fine-needle aspiration samples of thyroid nodules has been studied with the objective of improving the accuracy of the preoperative diagnosis of thyroid lesions. The aim of the current study was to investigate thyroid fine-needle aspiration samples inadequate for RT-PCR analysis and to determine whether there is a correlation between their proportion and the method of sampling used or the greatest dimension of the nodules.

METHODS

A total of 350 fine-needle aspiration samples from patients with thyroid nodules were analyzed. After the aspirate was smeared for conventional cytology, the leftover material in the needle was used for RT-PCR analysis in 1 group of 175 patients. In another group of 175 patients, a separate puncture was performed to obtain material for RT-PCR analysis only. Samples were considered adequate for RT-PCR analysis if the expression of both glyceraldehyde-3-phosphate dehydrogenase and thyroglobulin was found by RT-PCR.

RESULTS

In total, 61 (17.4%) samples inadequate for RT-PCR were detected. All 12 samples that were inadequate for cytologic diagnosis were also found to be inadequate for RT-PCR analysis. The proportion of inadequate samples for RT-PCR was found to be significantly higher in samples taken from leftover material in the needle (21.7%) then in samples from a separate puncture (13.1%) (P = .049). No statistically significant correlation between the adequacy of samples for RT-PCR and the largest dimension of the nodule was found.

CONCLUSIONS

The proportion of samples inadequate for RT-PCR was found to be higher in samples taken from leftover material in the needle than in samples obtained from a separate puncture.

Applications of molecular techniques to fine-needle aspiration biopsy

The effectiveness of fine-needle aspiration biopsy (FNAB) for rendering a specific diagnosis can be improved by applying several ancillary modalities. This review details several applications of molecular techniques using FNAB specimens with an emphasis on those used for patient care. A detailed search of the literature was conducted to collect all reports that used FNAB for different types of molecular tests. Several types of molecular tests, including in-situ hybridization, polymerase chain reaction, Southern blotting, and gene microarrays using FNAB specimens have been reported. These tests have been used with different organ systems and different objectives, including the detection of cancer cells, diagnosis, distinction of benign and malignant disease, prediction of response to chemotherapy, risk assessment, and selection of patients for targeted therapy. Except for a few tests such as assessment of HER2/neu for gene amplification in breast cancer, detection of clonality in hematopoietic neoplasms, and specific chromosomal translocations in the former and in the diagnosis of soft tissue sarcoma, most of the molecular tests using FNAB specimens are currently investigational. The reported literature indicates the excellent potential of using material procured from FNAB for almost any type of molecular test. Whereas few of these tests alone are used for patient care, some of them have the potential for clinical use in the near future.

Diagnostic molecular markers in thyroid cancer

The use of molecular assays to analyze clinical tissues in the diagnosis and management of thyroid cancer, similar to other tumors, will likely allow for more accurate characterization of the aggressiveness of individual tumors and may allow for the early diagnosis of recurrence. The application of these methods to thyroid nodules and nodal metastases is less encumbered by difficulties arising from amplification of transcripts in non-thyroid cells. For these tissues, these assays are likely to be used clinically in the near-future. New data arising from cDNA arrays identifying novel markers of malignancy or tumor aggressiveness make this a growing area of interest. The use of molecular assays in diagnosing distant metastases is more problematic due to issues with ectopic expression of either full length or splice variants of genes thought to be thyroid-specific. Assay quantitation is a complex problem owing to variability in the level of expression of "housekeeping" genes and the variety of phlebotomy and RT-PCR methods reported. Additional research in this area is clearly required before a recommendation can be given regarding clinically applicability of these tests.

Telomerase activity in “suspicious” thyroid cytology

BACKGROUND

Telomerase activity (TA) has been detected in most malignant neoplasms, including thyroid carcinomas. The authors studied the utility of TA detection as an ancillary tool to thyroid fine-needle aspiration (FNA) for patients with nonconclusive cytologic diagnoses.

METHODS

Material obtained by FNA from palpable thyroid nodules in 167 consecutive patients was processed for conventional cytologic studies and simultaneously for TA study. Another 8 patients were excluded from TA because of the presence of lymphocytes. All patients with negative results cases were followed for > 1 year, and those who had tumors that were suspicious or positive by FNA or TA underwent resection for pathologic study of nodules. TA was analyzed by telomere repeat amplification protocol-polymerase chain reaction analysis.

RESULTS

After excluding 20 patients because of insufficient material for cytologic study, 120 patients had negative results for malignant cells in cytology material, and the remaining 27 patients had results that were either suspicious (n = 21 patients) or positive (n = 6 patients). Histopathologic confirmation was obtained in 23 patients, including 18 with suspicious cytology (1 with scanty material) and 5 with positive FNA. The histopathologic diagnoses were nodular hyperplasia in 5 patients, follicular adenoma in 3 patients, papillary carcinoma in 11 patients, follicular carcinoma in 1 patient, medullary carcinoma in 2 patients, and lymphoma in 1 patient. TA was detected in 6 of 18 histologically confirmed thyroid neoplasms (1 of 3 follicular adenomas, 3 of 11 papillary carcinomas, 0 of 1 follicular carcinoma, 1 of 2 medullary carcinomas, and 1 of 1 lymphoma), including 1 neoplasm with scanty atypical cells.

CONCLUSIONS

The detection of TA helped to confirm neoplasia in 6 of 23 suspicious thyroid nodules. Although it was less sensitive than FNA, TA specificity was 100% for neoplasia and 87.5% for malignancy. The sensitivity of thyroid FNA increased with the use of TA detection when cytology was nonconclusive for malignancy.

Human telomerase reverse transcriptase gene expression and the surgical management of suspicious thyroid tumors

PURPOSE

Patients with a preoperative cytologic diagnosis of a suspicious thyroid nodule present a therapeutic dilemma because surgery differs for benign and malignant lesions. To address this issue, several molecular markers, including human telomerase reverse transcriptase (TERT), have been tested as markers of thyroid cancer. Because most studies select cases falling into well-defined categories to test new markers, they may overestimate their discriminatory power when applied to samples that are difficult to classify. Fine-needle aspirates (FNAs) of the thyroid with indeterminate cytology are an example of such cases.

EXPERIMENTAL DESIGN

We examined whether assessing TERT mRNA by reverse transcription-PCR could have improved the surgical management in a cohort of 100 patients undergoing thyroidectomy for indeterminate FNA results.

RESULTS

Ninety percent of 48 cancers were TERT positive, as were 35% of 52 benign lesions. When 10 cases with concomitant lymphocytic thyroiditis were excluded, the overall sensitivity of TERT was 91% (95% confidence interval, 80-98%) and specificity was 79% (64-90%). No clinical or tumor variable contributed to the predictive ability of TERT except for tumor size, which added only marginally. Basing the surgical approach on the TERT assay alone would have reduced lobectomies performed for malignant disease from 11 to 4 cases and reduced total thyroidectomies for benign lesions from to 15 to 9, an overall 50% reduction in suboptimal treatment.

CONCLUSIONS

The overall performance of preoperative differential diagnosis for thyroid tumors with indeterminate FNA results can be substantially improved by the inclusion of molecular markers such as TERT.

Assay of Free Thyroxine and Free Triiodothyronine in Fine-Needle Aspiration of Thyroid Nodules: a Useful and Low-Cost Assessment

OBJECTIVE

To evaluate whether analysis of thyroid hormones in fine-needle aspiration (FNA) of thyroid nodules can provide information about the functional status and the nature of the nodules.

METHODS

We studied 4 groups of patients: group 1, 17 patients with autonomous hyperfunctioning thyroid nodules; group 2, 52 patients with cold nonfunctioning thyroid nodules; group 3, 12 patients with malignant thyroid nodules; and group 4 (control group), 10 patients with nonthyroid nodular lesions (enlarged parathyroid glands or lymph nodes). The assay of thyroid hormones was performed in FNA after the washing of needles and, with patient consent, also in normal thyroid parenchyma.

RESULTS

The free thyroxine (FT(4)) and free triiodothyronine (FT(3)) values were remarkably high in group 1 (mean, 5.5 +/- 0.53 ng/dL and 27.6 +/- 3.1 pg/mL, respectively; P<0.05 versus group 2 and group 4, the control group). The levels of FT(4) and FT(3) were very low in group 3 (<0.2 ng/dL and <1.0 pg/mL, respectively; P<0.05 versus group 2). Thyroglobulin values in FNA specimens were much higher than the normal range in human serum, but no significant differences were found between the various groups. The control group had low levels of FT(4) and FT(3) (<0.2 ng/dL and <1.0 pg/mL, respectively) in conjunction with low levels of thyroglobulin, whereas parathyroid hormone levels were high in parathyroid nodules.

CONCLUSION

These results show that assay of FT(4) and FT(3) in FNA can yield information about the functional status of thyroid nodules and, indirectly, about the nature of nodules. In this era of sophisticated new molecular markers in FNA cytology, this low-cost diagnostic method can be readily performed in every laboratory.

[Current opinion on the etiology of differentiated thyroid carcinoma]

It is apparent that in the last decade carcinoma of the thyroid is becoming increasingly prevalent. The multistage complex theory of thyroid carcinogenesis is based on observations made on cohort patients studies and during animal experiments over a period of last fifty years. The process of thyroid oncogenesis is conceived to be a series of events induced by genetic and environmental factors which alter follicular cells division and growth control. These factors can be considered as initiators (chemical agents and ionising radiation) and promoters (some goitrogenes and drugs). The first class of factors induce incipient tumorigenesis while the second augments TSH secretion and radically increases tumour growth. Normally silent, intracellular proto-oncogenes (of which Ret/PTC series are the most conceived ones) can become activated by chromosomal translocations, deletions or mutations and can transform normal follicular cell into a condition of uncontrolled division and growth. The most significant known cause of thyroid carcinomas in men is exposure to external or internal ionising radiation. Beside that, long-term iodine deficiency, effects of certain chemical carcinogens, drugs and goitrogenes must be considered as significant risk factors. Possible role of sodium/iodide symporter is becoming an objective of the most recent investigations.

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

BACKGROUND

Follicular thyroid tumors (FTT) usually require resection to distinguish adenoma from carcinoma. Better markers that predict histologic subtype and prognosis are needed for FTT.

METHODS

Seventeen benign and malignant FTT with follow-up were selected. Pathologic diagnosis was confirmed, tumor and normal tissue were microdissected, and DNA was extracted. Polymerase chain reaction (PCR) products for a microsatellite marker at the von Hippel Lindau gene (VHL) gene locus (3p26) were analyzed with semiquantitative capillary gel electrophoresis to detect loss of heterozygosity (LOH). Data were assessed for statistical significance with chi(2).

RESULTS

Mean follow-up was 77 months (range 29 to 120 months). Four cases were uninformative (homozygous microsatellite). Among 13 evaluable patients (6 adenomas, 7 follicular cancers) LOH of VHL was present only in carcinomas (P=.013). LOH was present in 4/4 patients with recurrence and 0/3 patients without recurrence (P=.017). Death from disease has occurred in 3 patients. LOH of VHL was strongly associated with death from disease (P=.034).

CONCLUSIONS

FTT can be analyzed for LOH at the VHL gene locus. In this initial study, LOH of VHL was highly specific for malignancy and predicted death from disease. The analysis of VHL may provide for preoperative detection in cytologic samples with potential impact on clinical management of FTT.

Antisense hTERT inhibits thyroid cancer cell growth

Activation of telomerase represents an early step in carcinogenesis. Increased telomerase expression in malignant thyroid tumors suggests that inactivation of telomerase may represent a potential chemotherapeutic target. The purpose of this study was to inhibit the protein component of telomerase, hTERT, in a human thyroid cancer cell line in vitro and in vivo using an antisense strategy. A 235-bp fragment of hTERT cDNA was subcloned, and sense and antisense hTERT expression vectors were constructed. These vectors were transfected into a human thyroid carcinoma cell line (FRO). Tumorigenic potential was determined by cellular growth assay, rate of apoptosis, anchorage-independent growth, and tumor growth in a nude mouse model. Significant down-regulation of hTERT expression was seen in the antisense transfected cells, compared with control and those transfected with the sense vector. A decrease in telomerase activity by TRAP assay was observed in the antisense hTERT cells but not in cells transfected with the sense hTERT construct. Inhibition of cell growth was observed after approximately 20 population doublings in the antisense-hTERT clones and was associated with an increase in the rate of apoptosis and a change in cellular morphology. Moreover, anchorage-independent growth was reduced in vitro, and tumor growth rate was diminished in vivo in the antisense hTERT clones. Inhibition of telomerase activity with antisense hTERT in human thyroid cancer cells is achievable and may represent a novel target to inhibit tumor growth.

Management of simple nodular goiter: current status and future perspectives

The simple nodular goiter, the etiology of which is multifactorial, encompasses the spectrum from the incidental asymptomatic small solitary nodule to the large intrathoracic goiter, causing pressure symptoms as well as cosmetic complaints. Its management is still the cause of considerable controversy. The mainstay in the diagnostic evaluation is related to functional and morphological characterization with serum TSH and (some kind of) imaging. Because malignancy is just as common in patients with a multinodular goiter as patients with a solitary nodule, we support the increasing use of fine-needle aspiration biopsy (cytology). Most patients need no treatment after malignancy is ruled out. In case of cosmetic or pressure symptoms, the choice in multinodular goiter stands between surgery, which is still the first choice, and radioiodine if uptake is adequate. In addition to surgery, the solitary nodule, whether hot or cold, can be treated with percutaneous ethanol injection therapy. If hot, radioiodine is the therapy of choice. Randomized studies are scarce, and the side effects of nonsurgical therapy are coming into focus. Therefore, the use of the optimum option in the individual patient cannot at present be based on evidence. However, we are of the view that levothyroxine, although widely used, should no longer be recommended routinely for this condition. Within a few years, the introduction of recombinant human TSH and laser therapy may profoundly alter the nonsurgical treatment of simple nodular goiter.