Molecular detection of thyroglobulin mRNA transcripts in peripheral blood of patients with thyroid disease by RT-PCR

New biomarkers: prospect for diagnosis and monitoring of thyroid disease

After the metabolic syndrome and its components, thyroid disorders represent the most common endocrine disorders, with increasing prevalence in the last two decades. Thyroid dysfunctions are distinguished by hyperthyroidism, hypothyroidism, or inflammation (thyroiditis) of the thyroid gland, in addition to the presence of thyroid nodules that can be benign or malignant. Thyroid cancer is typically detected via an ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) and cytological examination of the specimen. This approach has significant limitations due to the small sample size and inability to characterize follicular lesions adequately. Due to the rapid advancement of high-throughput molecular biology techniques, it is now possible to identify new biomarkers for thyroid neoplasms that can supplement traditional imaging modalities in postoperative surveillance and aid in the preoperative cytology examination of indeterminate or follicular lesions. Here, we review current knowledge regarding biomarkers that have been reliable in detecting thyroid neoplasms, making them valuable tools for assessing the efficacy of surgical procedures or adjunctive treatment after surgery. We are particularly interested in providing an up-to-date and systematic review of emerging biomarkers, such as mRNA and non-coding RNAs, that can potentially detect thyroid neoplasms in clinical settings. We discuss evidence for miRNA, lncRNA and circRNA dysregulation in several thyroid neoplasms and assess their potential for use as diagnostic and prognostic biomarkers.

An inflammatory bowel disease-associated SNP increases local thyroglobulin expression to develop inflammation in miniature dachshunds

Inflammatory colorectal polyp (ICRP) in miniature dachshunds (MDs) is a chronic inflammatory bowel disease (IBD) characterized by granulomatous inflammation that consists of neutrophil infiltration and goblet cell hyperplasia in the colon. Recently, we identified five MD-associated single-nucleotide polymorphisms (SNPs), namely PLG, TCOF1, TG, COL9A2, and COL4A4, by whole-exome sequencing. Here, we investigated whether TG c.4567C>T (p.R1523W) is associated with the ICRP pathology. We found that the frequency of the T/T SNP risk allele was significantly increased in MDs with ICRP. In vitro experiments showed that TG expression in non-immune cells was increased by inducing the IL-6 amplifier with IL-6 and TNF-α. On the other hand, a deficiency of TG suppressed the IL-6 amplifier. Moreover, recombinant TG treatment enhanced the activation of the IL-6 amplifier, suggesting that TG is both a positive regulator and a target of the IL-6 amplifier. We also found that TG expression together with two NF-κB targets, IL6 and CCL2, was increased in colon samples isolated from MDs with the T/T risk allele compared to those with the C/C non-risk allele, but serum TG was not increased. Cumulatively, these results suggest that the T/T SNP is an expression quantitative trait locus (eQTL) of TG mRNA in the colon, and local TG expression triggered by this SNP increases the risk of ICRP in MDs via the IL-6 amplifier. Therefore, TG c.4567C>T is a diagnostic target for ICRP in MDs, and TG-mediated IL-6 amplifier activation in the colon is a possible therapeutic target for ICRP.

Role of Advanced Glycation End-Products and Other Ligands for AGE Receptors in Thyroid Cancer Progression

To date, thyroid cancers (TCs) remain a clinical challenge owing to their heterogeneous nature. The etiopathology of TCs is associated not only with genetic mutations or chromosomal rearrangements, but also non-genetic factors, such as oxidative-, nitrosative-, and carbonyl stress-related alterations in tumor environment. These factors, through leading to the activation of intracellular signaling pathways, induce tumor tissue proliferation. Interestingly, the incidence of TCs is often coexistent with various simultaneous mutations. Advanced glycation end-products (AGEs), their precursors and receptors (RAGEs), and other ligands for RAGEs are reported to have significant influence on carcinogenesis and TCs progression, inducing gene mutations, disturbances in histone methylation, and disorders in important carcinogenesis-related pathways, such as PI₃K/AKT/NF-kB, p21/MEK/MPAK, or JAK/STAT, RAS/ERK/p53, which induce synthesis of interleukins, growth factors, and cytokines, thus influencing metastasis, angiogenesis, and cancer proliferation. Precursors of AGE (such as methylglyoxal (MG)) and selected ligands for RAGEs: AS1004, AS1008, and HMGB1 may, in the future, become potential targets for TCs treatment, as low MG concentration is associated with less aggressive anaplastic thyroid cancer, whereas the administration of anti-RAGE antibodies inhibits the progression of papillary thyroid cancer and anaplastic thyroid cancer. This review is aimed at collecting the information on the role of compounds, engaged in glycation process, in the pathogenesis of TCs. Moreover, the utility of these compounds in the diagnosis and treatment of TCs is thoroughly discussed. Understanding the mechanism of action of these compounds on TCs pathogenesis and progression may potentially be the grounds for the development of new treatment strategies, aiming at quality-of-life improvements.

Determining Specific Thyroid Transcripts in Peripheral Blood: A Single Center Study Experience

Thyroid carcinoma (TC) comprises a spectrum of different tumors with a wide range of biological behavior and prognosis. The techniques based on the latest trends in molecular biology may have application in diagnosis of metastatic TC. The aim of this study was to apply and analyze mRNA expression in peripheral blood of thyrotropin receptor [thyroid stimulating hormone receptor (TSHR-mRNA)] gene and thyroglobulin (Tg-mRNA) gene using 2^–ΔΔCt method in differentiated TC patients and healthy individuals. Fifty-seven subjects were included in the study, consisting of 40 patients with TC and 17 healthy volunteers as a control group. Total RNA was isolated from peripheral blood and used for two-step reverse transcriptase-polymerase chain reaction (PCR). Real-time PCR was performed with appropriate primers. Relative quantification using the 2^–ΔΔCt method was applied. Thyroid carcinoma patients with metastatic disease or loco-regional relapse expressed TSHR-mRNA by a 8.57-fold higher level than healthy controls. Thyroid carcinoma patients with biochemical relapse expressed TSHR-mRNA by a 14.17-fold higher level than healthy controls, while expression of Tg-mRNA was 6.6-fold higher in TC patients with metastatic disease and loco-regional relapse than healthy controls and 8.34-fold higher level compared with TC patients with excellent response to treatment. Our preliminary study showed that the TSHR gene expression might have more useful application as a biomarker compared to detection of Tg gene expression.

One-step nucleic acid amplification testing in medullary thyroid cancer lymph nodes: a case series

INTRODUCTION

Locoregional relapse in medullary thyroid cancer (MTC) may be caused by nodal micrometastases. Medullary thyroid cancer lymph nodes have not yet been evaluated by one-step nucleic acid amplification (OSNA). Therefore, the aim of this study was to detect MTC cells by OSNA in cervical lymph nodes and compare the obtained outcomes with conventional histopathology.

MATERIAL AND METHODS

Twenty-one randomized, unenlarged lymph nodes from 5 patients with MTC were examined by histopathology and OSNA. Lymph nodes were divided into four representative blocks by a sterile, single use, special cutting device in the same way as in the clinical protocol study performed by Tsujimoto et al. Two blocks were used for histopathology and immunohistochemistry, 2 for OSNA.

RESULTS

Positive results of histopathology and OSNA were revealed in 4 patients. The outcomes of OSNA and histopathology were corresponding in 3 patients. Positive histopathology results of 2 lymph nodes from 2 patients were confirmed by OSNA. In 1 patient there were only negative results of both examinations. One-step nucleic acid amplification failed to detect metastasis in 1 lymph node in 2 patients although it did not change the TNM status in these patients. There were no false positive results in the OSNA test.

CONCLUSIONS

One-step nucleic acid amplification may be an alternative method to histopathology in detecting nodal involvement in MTC. Further studies should evaluate the sensitivity and specificity of OSNA and the impact on staging in MTC.

Evaluation of proopiomelanocortin mRNA in the peripheral blood from patients with Cushing's syndrome of different origin

ACTH-dependent Cushing's syndrome is due to ACTH overproduction originating from a pituitary corticotroph adenoma (Cushing's disease) or from ectopic tumors (ectopic ACTH syndrome). Due to difficulties in the differential diagnosis between these two forms of hypercortisolism it would be important to have molecular tools able to discriminate the two conditions. It is known that proopiomelanocortin (POMC) gene transcription can originate messengers of different length. ACTHomas show the normal 1072 nucleotides (nt) transcript, whereas ectopic tumors seem to be associated with a longer mRNA form (1450 nt). In order to analyse the presence of different POMC transcripts, we extracted total RNA from peripheral lymphocytes of 10 patients with Cushing's disease, 10 with ectopic Cushing syndrome, and 20 controls as well as from pituitary tissues (2 ACTH-omas and a normal pituitary polyA+ sample). Northern blot analysis correctly revealed a 1072 nt mRNA molecule in pituitary ACTH-oma and in the normal pituitary polyA+ RNA samples, whereas neither this molecule nor other alternative transcripts were detected in blood samples from patients and controls. These data were confirmed by the more sensitive RT-PCR technique. This study further underlines the need for alternative approaches in the diagnosis of ACTH-dependent Cushing's syndrome.

Circulating thyroid cancer markers

PURPOSE OF REVIEW

To describe the progress in the field of circulating markers of thyroid cancer.

RECENT FINDINGS

Thyroid cancer cells in the circulation can be detected by measuring the mRNA of thyroid-specific genes. Among these, thyroglobulin, and more recently thyroid-stimulating hormone receptor mRNAs' provide high diagnostic sensitivity and specificity for thyroid cancer detection. These markers can be used in synergy with current diagnostic modalities, i.e. fine-needle aspiration and ultrasound, for preoperative diagnosis and serum thyroglobulin measurement for monitoring.

SUMMARY

For the detection of recurrent/residual thyroid cancer, serum thyroglobulin remains the sole circulating marker, but lacks sensitivity and is unreliable in the presence of antithyroglobulin antibodies. The measurement of thyroid-specific mRNA in blood may provide sensitive/specific markers, but significant variability exists among various studies for thyroglobulin mRNA in particular, questioning the validity of this marker. Recent studies have demonstrated the high sensitivity and specificity of thyroid-stimulating hormone receptor mRNA in detecting recurrent/residual disease even in the presence of thyroglobulin antibodies. Fine-needle aspiration biopsy is currently the sole method for evaluating thyroid nodules. Indeterminate fine-needle aspiration cytology is found in approximately 15-30% of specimens. Thyroid-stimulating hormone receptor mRNA measurement in patients with indeterminate fine-needle aspiration may enhance cancer detection and save unnecessary surgeries.

Molecular diagnostic methods in the diagnosis and follow-up of well-differentiated thyroid carcinoma

Thyroid cancers are the most common endocrine malignancies and are being diagnosed with increased frequency in modern clinical practice. Among other diagnostic modalities, fine-needle aspiration (FNA) biopsy of clinically suspicious thyroid nodules is becoming increasingly popular. Preliminary investigations have suggested that molecular diagnostic assays using tumor-specific markers may improve the sensitivity and accuracy of FNA and so may be expected to reduce the frequency of open surgical procedures by identifying those patients with demonstrably benign lesions who do not require definitive surgical excision of their lesions for diagnosis. At the same time, thyroid-specific mRNA assays (especially thyroglobulin mRNA testing) have been used by investigators in the postoperative follow-up of patients with thyroid cancer as a potential means of detecting tumor recurrence in the peripheral blood. Although these studies have not all reported unqualified successes--indeed, some problems based on both technical and biologic limitations have been identified-these assays still hold out the possibility that potentially important new advances in the management of patients with well-differentiated thyroid cancer may be offered by these and other molecular diagnostic methods.

Quantitation of thyroid peroxidase mRNA in peripheral blood for early detection of thyroid papillary carcinoma

We applied quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to detect tissue-specific mRNAs in circulating cancer cells for the diagnosis of early-stage cancer. By Northern blotting, the thyroid peroxidase gene (TPO) was strictly expressed in the thyroid. We also used RT-PCR to examine TPO and thyroid stimulating hormone receptor (TSHR) mRNAs in peripheral blood in 33 thyroid papillary carcinoma patients at stages I (23 cases), II (8 cases) and III (3 cases), 49 noncancer patients with benign thyroid diseases, and 20 healthy volunteers. TPO mRNA was detected in 14 of 23 (61%) cases of stage I carcinoma but only 2 of 49 cases with benign thyroid disease. TPO mRNA was not detected in 20 healthy volunteers. By real-time quantitative RT-PCR, the estimated number of thyrocytes in the circulation ranged from 0.24 and 2700 cells per milliliter of whole blood in 7 of 9 patients at stages I and II, and thyrocyte number did not correlate with tumor size or serum thyroglobulin level. Our results might suggest that detection and quantification of tissue-specific mRNAs (e.g., TPO) in peripheral blood could serve as a means to identify potential tumor markers at early stages of cancer.

Oncofoetal fibronectin--a tumour-specific marker in detecting minimal residual disease in differentiated thyroid carcinoma

Supposedly, thyrocyte-specific transcripts such as thyroglobulin (Tg) and thyroid-stimulating hormone receptor (TSH-R) were proposed to be useful for the diagnosis of circulating tumour cells in patients suffering from differentiated thyroid carcinoma (DTC). However, several research groups reported blood-borne Tg transcripts in healthy individuals. This study determines in particular the origin of Tg mRNA in nucleated blood cells and analyses whether other tumour-associated sequences are absent in leukocytes, but widely expressed in DTC. Therefore, expression analyses for Tg, TSH-R, cytokeratin 19 (CK 19), human telomerase reverse transcriptase (hTERT) and oncofoetal fibronectin (onfFN) were carried out using cDNAs derived from (1) leukocyte fractions, (2) 18 follicular thyroid carcinomas (FTCs) and 48 papillary thyroid carcinomas (PTCs), and (3) leukocytes of two thyrocyte-depleted individuals treated for C-cell carcinoma of the thyroid. Expression of onfFN was additionally analysed by semiquantitative RT–PCR and by quantitative fluorescence-based real-time PCR. Tg and TSH-R expression was demonstrated not only in both athyroid individuals, but in all leukocyte subgroups tested, while hTERT was absent in resting CD4⁺ cells and only weakly expressed in the CD8⁺ group. CK 19 was notable in each leukocyte population except for resting CD14⁺, as well as for activated and resting CD19⁺ cells. All blood cell fractions proved negative for onfFN mRNA, whereas its presence in thyroid carcinoma was 78/98% (FTC/PTC). Threshold cycle values were calculated at: porphobilinogen deaminase (PBGD) =25.95±0.73 (FTC)/24.55±5.43 (PTC) (P=0.2878); onfFN=25.48±3.15 (FTC)/21.44±3.44 (PTC) (^*P=0.0001). Finally, onfFN transcripts were detected in blood samples of six out of nine patients with known DTC metastases, demonstrating a reliable assay functionality. We propose that real-time RT–PCR of onfFN mRNA is superior to other markers in monitoring minimal residual disease in DTC with regard to both assay sensitivity and specificity.

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.

Detection of lymph node metastases of papillary thyroid cancer-comparison of the results of histopathology, immunohistochemistry and reverse transcription-polymerase chain reaction-a preliminary report

BACKGROUND

The range of lymphadenectomy in differentiated thyroid cancer remains still a matter of controversy because of the lack of reliable diagnostic methods for nodal metastases, other than histopathology.

AIM

To compare the results of detection of lymph node metastases of papillary thyroid cancer by conventional histopathology and immunohistochemistry with the results of reverse transcription-polymerase chain reaction for thyroglobulin mRNA.

PATIENTS AND METHODS

Each of 166 cervical lymph nodes obtained from 21 patients was divided into two halves: one was used for conventional histopathology and immunohistochemistry, the other part was investigated by molecular examination.

RESULTS

We obtained different results from examination of the lymph nodes in six (28.6%) patients. In four patients (19.1%) reverse transcription-polymerase chain reaction (RT-PCR) was more sensitive in detection of positive lymph nodes; in two patients (9.5%) it revealed fewer metastasised lymph nodes than did histopathology. The rest of the patients did not have any differences: 12 (57.1%) of them had negative lymph nodes and three (14.3%) had positive lymph nodes in all examinations.

CONCLUSIONS

(1) Thyroglobulin (Tg) RT-PCR is an appropriate method of detection for thyroid cancer cells. (2) In combination with histopathology, it might help to qualify patients' nodal status better.

Detection of circulating Tg-mRNA in the follow-up of papillary and follicular thyroid cancer: how useful is it?

To investigate the usefulness of thyroglobulin mRNA (Tg-mRNA) detection in peripheral blood in the follow-up of papillary and follicular (differentiated) thyroid cancer, a literature study was performed. Both evidence for and evidence against the usefulness of Tg-mRNA detection were found. Also, evidence for the expression of Tg-mRNA in cells other than normal or neoplastic thyroid follicular cells was found. It is concluded that currently Tg-mRNA detection is not a useful tool in the follow-up of differentiated thyroid carcinoma, but that the concept of using RT–PCR measurements during follow-up still warrants further research.

Evaluation of quantitative measurement of thyroglobulin mRNA in the follow-up of differentiated thyroid cancer

Detection of thyroid cancer by thyroglobulin (Tg) assay in peripheral blood is useful in the absence of residual thyroid tissue, but it requires thyrotropin stimulation for maximal sensitivity and is affected by circulating antithyroglobulin antibodies. To avoid these drawbacks, thyroglobulin mRNA (Tg mRNA) assay in circulating blood has been proposed. Initial studies showed that Tg mRNA assay was more positive in patients with metastasis than in cured patients. Further studies showed controversial data. We measured Tg mRNA in 26 patients undergoing levothyroxine (LT(4)) suppressive therapy after total thyroidectomy for thyroid cancer and in 11 controls. The stage of the cancer was defined according to the findings of the latest whole-body (131)I scan and serum Tg performed under LT(4) withdrawal. Patients were classified as cured (negative scan, negative stimulated Tg, 8 patients), with metastasis (positive scan in extrathyroid bed regions, positive Tg, 7 patients), with thyroid remnants (positive scan in thyroid bed, positive Tg, 8 patients), and discordant cases (negative scan, positive Tg, 3 patients). RNA was extracted from blood and analyzed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) using two sets of primers and internal probes specific for Tg mRNA. This method allowed the detection of Tg mRNA in thyroid biopsies. Tg mRNA was undetectable in all control subjects and in all patients with cured cancer, positive in 1 of 8 patients with thyroid remnants, and in only 1 of 7 patients with metastasis. In conclusion, our data do not support the usefulness of Tg mRNA measurements in blood for monitoring thyroid cancer.

Measurement of thyroglobulin mRNA in peripheral blood as an adjunctive test for monitoring thyroid cancer

AIMS

Monitoring treated patients with thyroid cancer for recurrent or metastatic disease is currently based upon the serial measurement of circulating plasma thyroglobulin (Tg) concentrations. However, the clinical usefulness of Tg immunoassays is limited by poor sensitivity and interference from anti-Tg antibodies. This study investigated whether the detection of Tg mRNA in peripheral blood, using reverse transcriptase polymerase chain reaction (RT-PCR), is of value in the biochemical surveillance of patients with thyroid cancer.

METHODS

RNA was extracted from peripheral blood of five normal controls, six patients with abnormal thyroid function tests, and 28 patients who had undergone thyroidectomy for well differentiated thyroid cancer. From each, an 87 bp product from base pair 262 to 348 in the cDNA sequence of the thyroglobulin gene was amplified by RT-PCR.

RESULTS

Tg mRNA was detected in normal individuals and patients with thyroid cancer. In the group of patients studied, identification of metastatic thyroid tissue by radioiodine scanning correlated better with Tg mRNA assay results than with serum Tg concentrations (accuracy 84% v 75%). No interference from circulating Tg antibodies was apparent. In patients studied prospectively over a 12 month period, there was a significant correlation between detectable Tg mRNA in peripheral blood and the presence or absence of metastatic disease, as demonstrated by radioiodine scanning.

CONCLUSIONS

These results suggest that detection of Tg mRNA in blood is a more sensitive marker for metastatic thyroid disease than Tg immunoassay, and appears to be unaffected by the presence of circulating anti-Tg antibodies.

Human kallikrein 2 (hK2) mRNA in peripheral blood of patients with thyroid cancer: a novel molecular marker?

PURPOSE

To elucidate whether hK2 mRNA can be detected in peripheral blood of patients with thyroid disease using reverse transcription polymerase chain reaction (RT-PCR).

METHODS

A nested RT-PCR protocol for the detection of hK2 mRNA was established, and blood samples of 72 patients with a history of thyroid cancer, 10 patients with current metastases of thyroid cancer, and 32 volunteers were tested.

RESULTS

hK2-transcripts were significantly more often detected in patients with thyroid cancer (20/72=28%) than in the control group (2/32=6%, P = 0.03, chi-square analysis).

CONCLUSIONS

This is the first study reporting on hK2 as a potential molecular marker for patients with thyroid cancer. We could demonstrate a correlation between diagnosis of thyroid cancer and the positive signal for hK2 in the RT-PCR assay. Future studies are necessary to prove the clinical value of hK2 as a molecular marker regarding recurrence and outcome.

Polymerase chain reaction in the detection of tumor cells: new approaches in diagnosis and follow-up of patients with thyroid cancer

Thyroid cancers are the most common endocrine malignancies and are being diagnosed with increasing frequency. In addition to other measures, diagnosis is based on fine-needle aspiration cytology examination. Recently, new assays using reverse transcription-polymerase chain reaction (PCR) are being tested to improve sensitivity and specificity of primary diagnosis and detection of recurrent thyroid cancer. In the preoperative diagnosis of thyroid cancer, several tissue- and/or tumor-specific mRNA have been described and in several cases, a higher sensitivity and specificity could be achieved using molecular techniques compared to conventional methods. In the postoperative follow-up of patients with thyroid cancer, conflicting data have been published and the use of PCR techniques revealed several problems of the molecular approach, which are based on some technical as well as biologic limitations. Despite these problems, which are discussed in detail in this review, molecular techniques may nevertheless improve the sensitivity and accuracy of fine-needle aspiration of thyroid nodules, fine-needle aspiration of metastases, and detection of recurrent disease in peripheral blood samples.

Recurrent and/or metastatic thyroid cancer: therapeutic options

Thyroid cancer is relatively rare, accounting for 0.5 - 10 cases per 100,000 individuals per year. Despite their generally favourable prognosis, patients with differentiated thyroid cancer are at risk of tumour recurrence for decades after diagnosis. The optimal management remains controversial even in the low-risk patients because of the high cure rates, long natural history and rarity of these tumours. Therapeutic interventions in recurrent and metastatic differentiated thyroid cancer depend on the type of initial treatment, the site and the extent of disease. Surgical excision of the amenable-to-surgery lesions and radioiodine administration remain the first approach. External radiotherapy may be given to patients with inoperable lesions or those not concentrating radioiodine. Chemotherapy has not provided consistently successful results. Various therapeutic approaches for anaplastic carcinoma give poor results, making the development of novel treatments necessary. Innovative strategies, including recombinant human thyroid stimulating hormone, retinoic acid redifferentiation therapy and gene therapy, may lead to further improvement in the management of thyroid cancer arising from follicular cells.

Cancer-specific mRNAs in thyroid carcinomas: detection, use, and their implication in thyroid carcinogenesis

Molecular-based diagnosis ofthyroid carcinomas can be more easily establishedby utilizing specific mRNAs that are expressed in a restricted manner in cancer tissues. Accordingly, several cancer-specific mRNAs in thyroid carcinomas have been identified by means of sequence specific-differential display (SS-DD), serial analysis of gene expression (SAGE) and other new techniques. By using these cancer-specific mRNAs, some new methods of preoperative diagnosis of thyroid carcinomas have been developed. In one such method, Aspiration Biopsy-Reverse Transcription-Polymerase Chain Reaction (ABRP), RNA is extracted from leftover cells within the needle used for fine needle aspiration biopsies (FNABs), thereby allowing cytological and molecular-based diagnoses to be performed simultaneously. ABRP provides both RNA information and a cytological diagnosis without further invasion to the patient. By ABRP detection of cancer-specific mRNAs, papillary, anaplastic and medullary carcinomas and a part of malignant lymphomas can be accurately diagnosed preoperatively. It remains to be clarified why cancer-specific mRNAs, especially those that are overexpressed in fetal tissues, can clearly distinguish benign tissues from carcinomas, while genomic alternations, such as mutations in the RAS or P53 gene cannot. Further, the widely accepted hypothesis of multi-step carcinogenesis cannot explain some of the clinical and experimental findings of thyroid carcinomas. Considering these facts, we propose a novel hypothesis of thyroid carcinogenesis, the "germ-cell carcinogenesis" hypothesis, in which cancer cells derive from the remnants of fetal thyroid germ cells (thyroblasts) instead of normal thyroid follicular cells.

Circulating calcitonin and carcinoembryonic antigen m-RNA detected by RT-PCR as tumour markers in medullary thyroid carcinoma

Detection of local relapse or metastasis in medullary thyroid carcinoma (MTC) continue to pose a major diagnostic challenge. Besides established diagnostic studies such as serum calcitonin (CT) and carcinoembryonic antigen (CEA), molecular detection of circulating tumour cells may be an additional diagnostic tool for the early detection of disease recurrence. We performed reverse transcription-polymerase chain reaction (RT-PCR) on blood samples from patients diagnosed with MTC disease using primers specific for CT and CEA, respectively. CT mRNA was not detectable in peripheral blood of all patients with MTC (n = 11) and all controls (n = 32). CEA mRNA was significantly more often detected patients with MTC (72.7%) than in controls (34.4%; p = 0.038; Fisher exact test). With an example of a patient with MTC and massive tumour mass in the neck we demonstrate the failure of detection of CT mRNA over a period of 6 months, whereas CEA mRNA could be detected in peripheral blood of this patient. As a consequence, CT mRNA detected by RT-PCR in the peripheral blood can not be recommended as a tumour marker in MTC. However, the use of carcinoembryonic mRNA may provide a significant improvement in diagnosis of recurrent disease in MTC.

Quantitative measurement of thyroglobulin mRNA in peripheral blood of patients after total thyroidectomy

Previous studies have reported the clinical usefulness of reverse transcription-polymerase chain reaction (RT-PCR) detection of thyroglobulin (TG) mRNA in the peripheral blood of patients with differentiated thyroid carcinoma. To evaluate this usefulness, we measured TG mRNA in the peripheral blood of patients diagnosed with thyroid carcinoma after total thyroidectomy by real-time quantitative RT-PCR using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA as an internal control. Surprisingly, we detected TG mRNA in all samples obtained after total thyroidectomy, including those from 4 medullary carcinomas. Further, there was no statistical difference in expression levels of TG mRNA in the patients with or without metastasis, and no significant correlation was found between serum TG concentrations and the expression levels of TG mRNA. These results give rise to a question regarding the clinical applications of not only RT-PCR detection but also quantitative measurement of TG mRNA in peripheral blood.

Minimal residual disease in thyroid carcinoma

The detection of disseminated tumor cells in differentiated (DTC) and medullary thyroid carcinomas (MTC) is one of the main topics in current thyroid cancer research. Immunocytochemistry and polymerase chain reaction (PCR) provide the tools for the identification of a small number of thyroid cancer cells in peripheral blood and cervical lymph nodes. Thyroid-specific markers, such as thyroglobulin (Tg) mRNA and thyroid peroxidase (TPO) mRNA, have been detected with RT-PCR in blood samples of tumor patients and healthy control subjects. To prevent false-positive results, quantitative PCR systems were established. Tumor-specific markers, such as telomerase activity and cytokeratin 20 (CK20), have been detected in various epithelial tumors. Amplification products of these markers were found in blood samples and in fine-needle aspiration (FNA) biopsies of patients with thyroid carcinomas. Using molecular detection of disseminated tumor cells in cervical lymph nodes with CK20 RT-PCR, a higher percentage of involved lymph nodes was detected compared to immunohistochemistry. The results of the presented studies may help researchers to develop more sensitive methods for early tumor cell dissemination, and refine risk groups that might benefit from more extensive surgical procedures or adjuvant therapy. However, the prognostic value of minimal residual disease (MRD) in thyroid carcinoma has to be confirmed in large or multicenter prospective studies.