Detection of circulating thyroid cells in peripheral blood

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.

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.

Circulating thyroid cancer biomarkers: Current limitations and future prospects

Differentiated thyroid cancer (DTC) is the most common malignancy of the endocrine system. There has been a significant increase in its incidence over the past two decades attributable mainly to the use of more sensitive diagnostic modalities. Ultrasound-guided fine needle aspiration cytology is the mainstay of diagnosis of benign disorders and malignancy. However, approximately 20% of lesions cannot be adequately categorized as benign or malignant. In the postoperative setting, monitoring of thyroglobulin (Tg) levels has been employed for the detection of disease recurrence. Unfortunately, Tg antibodies are common and interfere with Tg measurement in this subset of patients. Despite this limitation, Tg remains the sole widely used thyroid cancer biomarker in the clinical setting. In an attempt to bypass antibody interference, research has focused mainly on mRNA targets thought to be exclusively expressed in thyroid cells. Tg and thyroid stimulating hormone receptor (TSHR) mRNA have been extensively studied both for discerning between benign disease and malignancy and in postoperative disease surveillance. However, results among reports have been inconsistent probably reflecting considerable differences in methodology. Recently, microRNA (miRNA) targets are being investigated as potential biomarkers in DTC. MiRNAs are more stable molecules and theoretically are not as vulnerable as mRNA during manipulation. Initial results have been encouraging but large-scale studies are warranted to verify and elucidate their potential application in diagnosis and postoperative surveillance of thyroid cancer. Several other novel targets, primarily mutations and circulating cells, are currently emerging as promising thyroid cancer circulating biomarkers. Although interesting and intriguing, data are limited and derive from small-scale studies in specific patient cohorts. Further research findings demonstrating their value are awaited with anticipation.

Circulating tumor cells in thyroid carcinoma - the prognostic role of this biomarker. Review of the literature

Thyroid cancer is a disease with a good prognosis and high survival rates, but having a marked growth of incidence all over the world in the last years. This fact requires special attention of researchers for understanding the behavior of this disease and to establish a correct therapy. Analysis of circulating tumor cells in patients with different malignancies is nowadays a new and exciting research tool, which can improve the diagnosis and prevent the metastatic disease. In the case of thyroid carcinoma there are few studies which explore these biomarkers and investigate the prognostic significance of circulating tumor cells. With this review we seek to emphasize the role of these cells to better understand the mechanisms of invasion or metastasis and to establish a new research base to treat aggressive forms of this type of cancer. Most of the included studies demonstrate the efficacy of these markers for diagnosis and follow up.

Circulating thyrotropin receptor messenger ribonucleic acid is not an effective marker in the follow-up of differentiated thyroid carcinoma

Background

Circulating thyrotropin receptor messenger ribonucleic acid (TSHR mRNA) assay has been validated in the follow-up of differentiated thyroid carcinoma (DTC) because of its high sensitivity during thyroid hormone therapy and no interference with endogenous anti-thyroglobulin antibodies (TgAb) compared to serum thyroglobulin (Tg). We investigated the efficacy of TSHR mRNA assay in 160 DTC patients using quantitative PCR (qPCR).

Findings

Only TSHR mRNA level of structural persistent disease with TgAb-positive (3.47 (2.97–9.53) pg equivalents/μg total RNA; p = 0.013) and its subgroup of distant metastasis patients with TgAb-positive (5.55 (3.28–12.52) pg equivalents/μg total RNA; p = 0.009) were significantly different from patients with no evidence of disease (2.32 (1.44–3.94) pg equivalents/μg total RNA). Applying cutoff at 2.00 pg equivalents/μg total RNA enabled us to predict structural persistent disease patients with a sensitivity of 62.3 % and a specificity of 42.9 %. Although, the sensitivity of TSHR mRNA assay in TgAb-postive patients (88.2 %) was superior than serum Tg (47.1 %) (p = 0.00002), the accuracy of the test is only 54.5 %.

Conclusions

This study demonstrated that TSHR mRNA assay has good sensitivity in TgAb-positive patients but it is neither specific enough as a first-line of testing nor a surrogate marker in the follow-up of our DTC patients.

Well-differentiated thyroid carcinomas: management of the central lymph node compartment and emerging biochemical markers

Well-differentiated thyroid cancers (WDTCs) are generally indolent cancers that are associated with a low mortality. Although the incidence of these tumors is increasing, there has not been an associated increase in the mortality rates. As we gain a greater understanding and more experience with these good prognosis cancers, the way in which we treat these tumors is evolving. The definition of persistent or recurrent disease has seen a shift from being a clinical and/or radiological diagnosis to now one based on a biochemical blood marker, thyroglobulin. Central lymph node metastases are a very common problem in WDTC, being present in up to 90% of patients. The optimal surgical management of the central lymph node compartment remains a hotly debated topic. This paper identifies these controversies and presents available data surrounding these issues. Biochemical tumor markers are gaining wider use in practice and in time hopefully provide more specific information with which surgical decision-making can be based. A summary of the clinically available markers is presented.

Recurrence of papillary thyroid cancer suspected by high anti-thyroglobulin antibody levels and detection of peripheral blood thyroglobulin mRNA

The amplification of thyroglobulin (TG) mRNA in peripheral blood of patients with thyroid cancer has been studied for almost one decade, but its real contribution for diagnosis of cancer relapse has not yet been established. In the present paper we report the case of a patient with papillary thyroid cancer with undetectable stimulated serum thyrogobulin levels after thyroid ablation. Follow-up showed the presence of high titers of anti-thyroglobulin antibodies and the presence of TG mRNA in a peripheral blood sample, while cervical ultrasound and thorax and cervical computerized tomography were negative. Reinvestigation confirmed lymph node metastases. Anti-TG antibodies progressively decreased after surgery for metastatic lymph nodes resection followed by radioiodine therapy. Although our recent findings show that patients with positive TG mRNA do not have increased risk of cancer recurrence after 24 months of follow-up, the presence of TG mRNA along with high anti-TG antibodies were important indicators that determined further extensive investigation of tumour relapse in this patient, since positron emission tomography scan was not available at our Institution. A methodological standardization that can distinguish specific from non-specific TG mRNA amplification might be of great interest for the follow-up of differentiated thyroid cancer, especially in patients with high levels of anti-TG antibodies.

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.

Circulating thyroglobulin mRNA does not predict early and midterm recurrences in patients undergoing thyroidectomy for cancer

BACKGROUND

The aim of the present study was to evaluate if serum Tg mRNA assay predicts recurrence in patients undergoing thyroidectomy for cancer.

METHODS

Sixty-four consecutive patients undergoing surgery between April 1997 and July 1999 were studied. One year after surgery, blood samples were taken for serum thyroglobulin (Tg) immunoassay and for Tg mRNA assay by reverse transcription-polymerase chain reaction (RT-PCR). All patients underwent periodical clinical examination, including laboratory tests for serum Tg immunoassay, neck ultrasound, radioiodine scans, and treatment if indicated. Kaplan-Meier estimates of survival were calculated according to the presence or absence of circulating Tg mRNA and according to baseline Tg levels.

RESULTS

Tg mRNA was detected in 14 (21.8%) of 64 patients with thyroid carcinoma. After a median follow-up of 110 months, 8 patients (12.5%) relapsed. Among patients with detectable Tg mRNA (n. 14), only 1 distant metastasis occurred (7%), whereas lymph node metastases (n = 3) or distant metastases (n = 4) were detected in 7 of 50 patients (14%) with undetectable Tg mRNA. Tumor relapse occurred in all 7 patients with increased serum Tg and only in 1 out of 57 patients (1.7%) with normal or undetectable serum Tg. The disease-free interval of patients positive at baseline for Tg mRNA was similar to that of patients with undetectable Tg mRNA at baseline. Similar results were obtained when we limited the analysis to only patients who received postsurgical radioiodine ablation.

CONCLUSIONS

The results of present study suggest that detection of circulating Tg mRNA 1 year after thyroidectomy for cancer might be of no utility in predicting early and midterm local and distant recurrences.

Thyroglobulin mRNA expression in peripheral blood lymphocytes of healthy subjects and patients with thyroid disease

BACKGROUND

Thyroglobulin (Tg) mRNA is expressed focally in thyroid tissue. In recent years, the Tg gene has been detected in other tissues, including lymphocytes, although the significance of its presence has not been elucidated yet. We measured Tg mRNA expression in the lymphocytes of healthy subjects and those with thyroid disease.

METHODS

Analysis of the quantification of Tg mRNA from 20 healthy subjects and 47 subjects with thyroid disease was carried out by real-time PCR. Furthermore, in cultured lymphocytes we compared changes in Tg mRNA expression following stimulation with TSH.

RESULTS

Tg mRNA was detected in the lymphocytes of all subjects. Tg mRNA in the lymphocyte sequence matched that derived from thyroid tissue, and mRNA levels were higher in subjects with thyroid disease than in healthy subjects. Following lymphocyte stimulation, Tg mRNA levels were observed to be increased 2.7-fold in Graves' disease and 1.6-fold in chronic thyroiditis compared to healthy subjects.

CONCLUSIONS

Tg mRNA in the lymphocytes was quantified by real-time PCR. The levels of Tg mRNA in the TSH-stimulated lymphocytes were noticeably increased in subjects with thyroid disease. These results suggest an interesting relationship between production of Tg antigen in peripheral blood and autoimmunity in thyroid disease.

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.

Molecular Profiling of Matched Samples Identifies Biomarkers of Papillary Thyroid Carcinoma Lymph Node Metastasis

Biomarkers of papillary thyroid carcinoma (PTC) metastasis can accurately identify metastatic cells and aggressive tumor behavior. To find new markers, serial analysis of gene expression (SAGE) was done on three samples from the same patient: normal thyroid tissue, primary PTC, and a PTC lymph node metastasis. This genomewide expression analysis identified 31 genes expressed in lymph node metastasis, but not in the primary tumor. Eleven genes were evaluated by quantitative real-time reverse transcription-PCR (qPCR) on independent sets of matched samples to find genes that were consistently different between the tumor and metastatic samples. LIMD2 and PTPRC (CD45) showed a statistically significant difference in expression between tumor and metastatic samples (P < 0.0045), and an additional gene (LTB) had borderline significance. PTPRC and LTB were tested by immunohistochemistry in an independent set of paired samples, with both markers showing a difference in protein expression. All 20 metastases from 6 patients showed expression in both markers, with little or no expression in primary tumor. Some of these markers could provide an improved means to detect metastatic PTC cells during initial staging of a newly diagnosed carcinoma and/or to rule out recurrence. The functional role of these genes may also provide insight into mechanisms of thyroid cancer metastasis.

Peripheral blood levels of thyroglobulin mRNA and serum thyroglobulin concentrations after radioiodine ablation of multinodular goiter with or without pre-treatment with recombinant human thyrotropin

We investigated the effect of therapeutic doses of radioiodine (RAI) on peripheral serum messenger thyroglobulin RNA (Tg mRNA) and serum thyroglobulin (sTg) in patients with multinodular goiter (MNG) preceded or not by treatment with recombinant human TSH (rhTSH). Fourteen patients with large MNG (91-542 ml) received RAI (550-2960 MBq). Half of the patients received 0.45 mg of rhTSH prior to the treatment (RAI+rhTSH group) and half did not (RAI group). Patients' blood samples were collected before and 24, 48, and 72 h; 7 and 30 days; and 6, 9, and 12 months after RAI treatment. Serum Tg was measured by immunoradiometric assay, serum anti-Tg by radioimmunoassay, and quantification of circulating Tg mRNA was performed by real-time PCR. The shrinkage of MNG volume was documented by serial computed tomography (CT) scans before, 6 and 12 months after RAI. Peak Tg mRNA and sTg were reached earlier in the RAI+rhTSH group (24 h and 48 h) than in the RAI group (7 days). Both declined after the peak and the lowest levels were observed at 12 months. The mean reduction of the thyroid volume was 19.8% (RAI group) and 30.3% (RAI+rhTSH group) at 6 months (ns) and 32.8% RAI and 52.5% (RAI+rhTSH group) at 12 months (p<0.05). After RAI treatment there was a significant and positive correlation between goiter volume and sTg only in the RAI group (r=0.7; p=0.032). Serum anti-Tg had a transitory and relatively small elevation in 3 and 2 patients, respectively, in the RAI and RAI+rhTSH groups. We concluded that after RAI ablation of MNG there is a rapid release of Tg into the serum possibly from the colloid, which is followed by an elevation of serum Tg mRNA that may be due to an increased release of follicular cells into the blood stream. Both phenomena are enhanced by the use of rhTSH before RAI treatment as a consequence of a more effective and prolonged radiation exposure of the thyroid follicles.

Galectin-3 and CD44v6 positivity by RT-PCR method in fine needle aspirates of benign thyroid lesions

OBJECTIVE

To investigate whether the presence of macrophages and Hürthle cells (HC) in benign thyroid lesions could explain the false-positive expression of galectin-3 and CD44v6 detected by reverse transcriptase-polymerase chain reaction (RT-PCR).

METHODS

For galectin-3 and CD44v6, RT-PCR was performed on RNA isolated from aspirates obtained by ultrasound guided fine needle aspiration cytology (FNAC) from 123 patients with benign thyroid lesions. The results of RT-PCR analysis were evaluated against the definitive FNAC diagnosis.

RESULTS

Galectin-3 expression was found in 29% follicular adenoma (FA), 26% Hashimoto thyroiditis (HT), and in 24% nodular goitre (NG). We found a statistically significant relationship between the presence of macrophages and galectin-3 positivity in NG and HT samples (P < 0.0001 and P = 0.0087 respectively). We found a statistically significant (P = 0.0219) relationship between the presence of HC and galectin-3 positivity in HT and a tendency of such a relationship (P = 0.0838) in NG. CD44v6 expression was found in 29% FA, 33% HT and in 18% NG. We found a statistically significant relationship between the presence of HC and positive expression of CD44v6 in NG (P = 0.0003) and a strong tendency of such a relationship in HT (P = 0.0571). We did not find a statistically significant relationship between the presence of macrophages and CD44v6 positivity. In FA, we did not find a statistically significant relationship between the presence of macrophages or HC and galectin-3 or CD44v6 positivity.

CONCLUSION

Our results suggest that the presence of macrophages and/or HC may explain the positive expression of galectin-3 and CD44v6 detected by RT-PCR in HT and NG cytological samples.

The utility of peripheral thyrotropin mRNA in the diagnosis of follicular neoplasms and surveillance of thyroid cancers

BACKGROUND

Thyroid cells in peripheral circulation express uniquely thyrotropin receptor (TSHR) mRNA, and their detection may aid thyroid cancer management.

METHODS

Since 2002, 258 patients had prospective TSHR mRNA measurement by quantitative RT-PCR from peripheral blood before and/or after thyroidectomy. Thyroid cancer detection was assessed from known clinical diagnostic criteria and mRNA for patients with follicular neoplasms (n = 64) and long-term cancer follow-up (n = 13).

RESULTS

Adding TSHR mRNA to fine-needle aspiration biopsy (FNAB) maintained high sensitivity (90%) but improved specificity (73%) for thyroid cancer diagnosis. When FNAB specimens indicated follicular neoplasm, a decision algorithm combining TSHR mRNA and abnormal thyroid ultrasound features correctly diagnosed all cancer patients (100% sensitivity) and would have spared operation for benign disease in 38%. Elevated TSHR mRNA on postoperative day 1 predicted persistent/recurrent cancer. During long-term thyroid cancer surveillance, TSHR mRNA had a 91% concordance with radioactive iodine whole body scan (WBS)-detectable disease, agreed with thyroglobulin (Tg) levels in 64% of patents, missed disease in 5%, but was more sensitive to detecting disease than Tg levels in 31% of patients, including all patients with Tg antibodies.

CONCLUSIONS

Detecting circulating thyroid cancer cells is useful for initial thyroid cancer diagnosis and postoperatively predicts recurrent cancer. This novel test promises to enhance thyroid cancer patient care by management algorithms that combine histologic, genomic, and clinical criteria.

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.

[Thyroglobulin mRNA amplification in peripheral blood of patients with differentiated thyroid carcinoma: what does it really mean?]

Despite the excellent prognosis, differentiated thyroid carcinoma (DTC) may recur in 20-40%, and prognosis is particularly related to early detection of recurrent disease. Therefore, long-term follow-up with sensitive tests is need. Serum thyroglobulin (Tg) has an established role as a tumor marker of relapse. However, there are technical limitations of Tg immunoassays, in special, the interference of anti-Tg antibodies and the method sensitivity is dependent on TSH stimulation. Detection of circulating malignant cells by amplification of tumor-specific mRNA showed initial promising results. However, almost one decade of studies of Tg mRNA detection in peripheral blood, its real contribution for DTC follow-up had not yet been established. After a critical analysis of published data, it is clear that there are many protocol differences and conflicting results. Therefore, it seems that amplification of thyroid-specific mRNAs is not superior to sensitive Tg assays and illegitimate transcription and alternative splicing of Tg are factors that may influence mRNA test specificity.

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.

BJ-TSA-9, a novel human tumor-specific gene, has potential as a biomarker of lung cancer

Using bioinformatics, we have identified a novel tumor-specific gene BJ-TSA-9, which has been validated by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). BJ-TSA-9 mRNA was expressed in 52.5% (21 of 40) of human lung cancer tissues and was especially higher in lung adenocarcinoma (68.8%). To explore the potential application of BJ-TSA-9 for the detection of circulating cancer cells in lung cancer patients, nested RT-PCR was performed. The overall positive detection rate was 34.3% (24 of 70) in peripheral blood mononuclear cells (PBMCs) of patients with various types of lung cancers and was 53.6% (15 of 28) in PBMCs of lung adenocarcinoma patients. In combination with the detection of two known marker genes SCC and LUNX, the detection rate was increased to 81.4%. A follow-up study was performed in 37 patients after surgical removal of tumor mass. Among nine patients with persistent detection of two to three tumor marker transcripts in PBMCs, six patients had recurrence/metastasis. In contrast, 28 patients with transient detection of one tumor marker or without detection of any tumor marker were all in remission. Thus, BJ-TSA-9 may serve as a marker for lung cancer diagnosis and as a marker, in combination with two other tumor markers, for the prediction of the recurrence and prognosis of lung cancer patients.

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.

Gene expression profiling identifies platelet-derived growth factor as a diagnostic molecular marker for papillary thyroid carcinoma

PURPOSE

Cancer diagnostics and therapeutics are often based on clinically relevant markers that are expressed specifically in a malignant tissue at levels higher than in normal tissue. We examined potential markers for papillary thyroid carcinoma (PTC) by monitoring PTC-specific gene expression using cDNA microarray.

EXPERIMENTAL DESIGN

Gene expression profiles for PTC tissue, normal thyroid tissue, and healthy peripheral blood cells were compared by use of a human 4000-gene cDNA microarray. Protein expressions of the up-regulated genes in PTC were examined in thyroid tissues by immunohistochemistry.

RESULTS

Sixty-four genes were overexpressed in PTC tissue relative to normal thyroid tissue and healthy peripheral blood cells. The genes that were up-regulated in PTC were involved in cell cycle regulation, DNA damage response, angiogenesis, and oncogenesis. Among these genes, basic fibroblast growth factor and platelet-derived growth factor were identified by immunochemical methods as proteins that are specifically expressed at high levels in thyroid neoplasms. Basic fibroblast growth factor, which has been identified as a biomarker for PTC, was overexpressed in 54% of PTC cases, 67% of follicular thyroid carcinomas, and 36% of benign thyroid neoplasms. Platelet-derived growth factor was overexpressed in 81% of PTC cases and 100% of follicular carcinomas, but was immunonegative in normal thyroid tissues and benign thyroid neoplasms.

CONCLUSIONS

Platelet-derived growth factor may be a potential biomarker for PTC and follicular carcinoma. Expression profile analysis using a microarray followed by immunohistochemical study can be used to facilitate the development of molecular biomarkers for cancer.

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.

Postoperative management of differentiated thyroid cancer

The large numbers of studies on the postoperative management of differentiated thyroid carcinoma allows us to use adjuvant treatment and follow-up studies more selectively based on patient risk for recurrence and mortality. Recurrent differentiated thyroid carcinoma is more easily and more effectively treated with early diagnosis. With this in mind, patients who are at high risk for life-threatening recurrent disease should be treated aggressively and followed up expectantly. In these patients, adjuvant treatment with 131I ablation and thyroid hormone suppression is appropriate. External irradiation may be considered, especially for patients with postoperative residual disease. Close follow-up with stimulated thyroglobulin and 131I whole body scans should be performed to facilitate early detection of recurrent disease. Low-risk patients may be effectively treated with more conservative management. 131I ablation has not resulted in improved survival in these patients. Follow-up with serum thyroglobulin after initial negative 131I whole body scan may be appropriate in these patients. Management of patients at intermediate risk remains controversial. Recombinant human thyrotropin allows us to obtain stimulated serum thyroglobulin and promises the ability to perform 131I ablation and whole body scan without the need for thyroid hormone withdrawal. Functional radionuclide imaging, such as FDG PET, now allows us to localize recurrent disease in patients with elevated serum thyroglobulin but negative 131I scan.

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.

Application of differential display to identify genes for lung cancer detection in peripheral blood

A blood assay for detection of lung cancer biomarkers could significantly improve cancer patient prognosis and survival rates. Amplified fragment length polymorphism-differential display (AFLP-DD) was used to identify gene transcripts found in lung cancer tissue and the peripheral blood of lung cancer patients. The clones were evaluated for gene expression in lung cancer tissue, peripheral blood of lung cancer patients and healthy volunteers' blood. The isolated gene transcript clones were found to be from the syndecan 1 gene, collagen 1 gene and 2 novel genes. All 4 transcripts were expressed in normal lung tissue, 4 cultured primary lung cells and 6 lung cancer cell lines. RNA was isolated from peripheral blood samples of 69 lung cancer patients. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to test for the presence of cytokeratin 19 and the 4 gene mRNA transcripts in blood RNA. The positive detection rate of at least 1 of the 5 transcripts was 79% for lung adenocarcinoma and 62% for squamous carcinoma. Using RT-PCR, at least 1 of the markers was found in 53% of stage I patients, 100% of stage II, 71% of stage III and 81% of stage IV lung cancer patients. Blood samples from 20 healthy volunteers were also tested, but only 1 of the 5 transcripts was found in 1 patient. These new molecular markers may aid early detection, staging and follow-up of lung cancer patients by RNA isolated from blood.

Validity of thyroglobulin mRNA assay in peripheral blood of postoperative thyroid carcinoma patients in predicting tumor recurrences varies according to the histologic type: results of a prospective study

BACKGROUND

The objective of the current study was to evaluate the ability of serum thyroglobulin mRNA assay in detecting local and distant recurrences in patients who underwent surgery for thyroid carcinoma.

METHODS

Sixty-six consecutive patients were studied. One year after surgery, all patients underwent clinical examination and radioiodine scan, and a blood sample was taken for serum thyroglobulin (Tg) immunoassay and for Tg mRNA assay by reverse transcription-polymerase chain reaction (RT-PCR). RNA was extracted from cells pellet and analyzed by RT-PCR using specific primers for Tg.

RESULTS

Thyroglobulin mRNA was detected in 14 (21.2%) patients. Seven of 16 patients with elevated serum thyroglobulin had detectable Tg mRNA. Six of 30 (20%) patients with absent or minimal thyroid bed radioiodine uptake and 7 of 36 (19.4%) patients with significant thyroid bed uptake had detectable Tg mRNA. Among 5 patients with metastases, only 1 (20%) showed circulating Tg mRNA. Overall, the sensitivity, specificity, and accuracy of Tg mRNA assay in predicting the results of the (131)I whole-body scans was 25%, 80%, 25%, respectively. Fourteen of 53 (26.4%) patients with papillary thyroid carcinoma had detectable thyroglobulin mRNA whereas none of the patients with other histologic types did. The sensitivity, specificity, and accuracy of Tg mRNA assay in predicting the results of the (131)I whole-body scans in patients with papillary thyroid carcinoma was 100%, 75%, and 100%, respectively. Of note, the percentage of cases with detectable Tg mRNA was similar among patients who did not receive postoperative (131)I and those who had postoperative radioiodine treatment.

CONCLUSIONS

The current study suggests that the validity of the Tg mRNA assay varies according to the histologic type of thyroid carcinoma and that this assay may play a role in the identification of metastatic disease in the subgroup of patients affected by papillary thyroid carcinoma but does not appear to be sensitive or active enough to direct clinical management.

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.

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.

Serum thyroglobulin measurement. Utility in clinical practice

Serum thyroglobulin measurement has greatly facilitated the clinical management of patients with differentiated thyroid cancer and a variety of other thyroid disorders. Thyroglobulin autoantibodies remain a significant obstacle to the clinical use of thyroglobulin measurement. The interpretation of any given thyroglobulin value requires the careful synthesis of all pertinent clinical and laboratory data available to the clinician. The diagnostic use of rhTSH-stimulated thyroglobulin levels has greatly facilitated the follow-up of low-risk patients with thyroid cancer. Although the measurement of thyroglobulin mRNA from peripheral blood is likely to affect the future management of these patients, it is expected that serum thyroglobulin measurement will continue to have a principal role in the care of patients with differentiated thyroid cancer.

Biological implications of tumor cells in blood and bone marrow of pancreatic cancer patients

BACKGROUND

Patients with pancreatic cancer often have tumor recurrence despite curative resection. Cancer cells detected in blood or bone marrow at the time of diagnosis may relate to tumor stage and to prognosis. Recent research emphasis has centered on tumor cells in bone marrow aspirates, but whether these represent early micrometastases or blood-borne cells in transit is unknown.

PATIENTS AND METHODS

We developed a specific immunocytochemical assay that evaluated more than 5.3 x 10(6) extracted mononuclear cells per sample of blood and bone marrow and that could identify a single tumor cell in that population. The assay was applied to samples of blood and bone marrow from 105 patients with pancreatic cancer and 66 controls. The prevalence of isolated tumor cells was compared with Union Internationale Contre le Cancer (UICC) stage. A multivariate Cox regression analysis for survival was performed.

RESULTS

Pancreatic cancer cells were detected in 26% of blood samples and in 24% of bone marrow specimens. Specificity for cancer was 96%. The prevalence of isolated tumor cells in patients with proven resectable cancer was 9% in blood and 13% in bone marrow. The prevalence increased with UICC tumor stage in blood (P =.04) but not in bone marrow (P =.52) and correlated in blood with resectability (P =.02), progression of disease (P=.08), and peritoneal dissemination (P =.003). While survival correlated significantly with tumor stage (P <.001) and isolated tumor cells in blood correlated with tumor stage, the finding of cancer cells in blood or bone marrow, or both, was not independently associated with survival in patients with pancreatic cancer.

CONCLUSIONS

Isolated tumor cells in blood but not bone marrow reflect the stage of growth and spread of pancreatic cancer, particularly in the peritoneal cavity. The findings are consistent with cells in bone marrow aspirates being in transit, not implanted. These disseminated cancer cells may be the consequence, rather than the cause, of progression.

Thyroglobulin messenger ribonucleic acid levels in the peripheral blood of children with benign and malignant thyroid disease

Reverse transcriptase-PCR has identified thyroglobulin mRNA (Tg mRNA) in peripheral blood of normal adults and adults with thyroid cancer. However, no children were studied. The primary objective of this study was to determine whether whole blood Tg mRNA levels differ between benign and malignant thyroid disease in children. The secondary goals were to determine whether whole blood Tg mRNA levels vary with age or pubertal development among children with thyroid disease. Whole blood Tg mRNA levels were determined in 38 children (29 girls, nine boys; median age, 14.5 y; range, 4.8-20.4 y) with benign and malignant thyroid disease and correlated with diagnosis, age, pubertal status, thyroid size, and serum levels of free thyroxine, TSH, and Tg protein. Tg mRNA levels ranged from 3.3 to 104 pg Eq/microg total thyroid RNA (mean, 28 +/- 20.2 pg Eq/microg total thyroid RNA) and were similar in benign and malignant disorders (p = 0.67). However, in children with previously treated papillary thyroid cancer, Tg mRNA levels directly correlated with total body (131)I uptake (p = 0.026) and serum Tg protein (p = 0.037). There was no difference between boys and girls, and no change with pubertal maturation. In children with benign thyroid disease, Tg mRNA levels correlated with serum TSH (p = 0.031), but not with diagnosis, age, Tanner stage, or thyroid size. We conclude that Tg mRNA levels are similar in children with benign and malignant thyroid disease and unchanged by age or pubertal status, but correlated with tumor burden in previously treated papillary thyroid cancer.

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

The sensitive detection of circulating tumour cells in patients with differentiated thyroid cancer may precede the detection of relapse by other diagnostic studies--such as serum thyroglobulin-and thus may have important therapeutic and prognostic implications. We performed reverse transcription-polymerase chain reaction (RT-PCR) on blood samples from patients diagnosed with thyroid disease using two different RT-PCR sensitivities. Additionally, tissue specificity of TG mRNA-expression was determined using RNA extracts from 27 different human tissues. The lower limit of detection was 50-100 TG mRNA producing cells/ml blood using a 'normal' RT-PCR sensitivity and 10-20 cells/ml blood using a 'high' sensitivity. With the normal sensitivity TG mRNA was detected in 9/13 patients with thyroid cancer and metastasis, 63/137 patients with a history of thyroid cancer and no metastasis, 21/85 with non-malignant thyroid disease and 9/50 controls. With the high sensitivity TG mRNA was detected in 11/13 patients with thyroid cancer and metastasis, 111/137 patients with a history of thyroid cancer and no metastasis, 61/85 with non-malignant thyroid disease and 41/50 controls. Interestingly, using the normal RT-PCR sensitivity TG mRNA transcripts are specific for thyroid tissue and detectable in the peripheral blood of controls and patients with thyroid disease, which correlates with a diagnosis of metastasized thyroid cancer. However, with a high RT-PCR sensitivity, TG mRNA expression was found not to be specific for thyroid tissue and was not correlated with a diagnosis of thyroid cancer in patients. As a consequence, to date TG mRNA detected by RT-PCR in the peripheral blood cannot be recommended as a tumour marker superior to TG serum-level.

Molecular diagnostic tests in the diagnosis and management of thyroid carcinoma

The application of molecular analysis of gene expression to clinical tissue samples represents one of the most exciting new areas in "translational" thyroid cancer research. Current data suggest that molecular diagnostic assays may 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. It is likely that at least some of these tests will become useful adjuncts in the diagnostic armamentarium of clinical endocrinologists in the future.

Review: polymerase chain reaction detection of micrometastases and circulating tumor cells: application to melanoma, prostate, and thyroid carcinomas

The main strategy used for the detection of circulating tumor cells (CTC) and micrometastases in solid tumors is the polymerase chain reaction (PCR) amplification of tissue specific messenger RNA present in the tumor cells. PCR was more sensitive than conventional techniques, allowing the identification of one tumor cell diluted into 1 mL of blood. PCR was shown to be specific in most studies related to the detection of CTC and marrow micrometastases in melanoma and prostate carcinoma (PC). PCR positivity for thyroid markers was reported in the blood of control subjects. Large variations in the PCR positivity rates and the prognostic value of these assays have been encountered in PC and melanoma. There was a correlation between PCR and stage in some but not all the studies. Despite these discrepancies, many investigators have shown PCR to be predictive of outcome in PC and especially in melanoma. PCR in blood and bone marrow was an independent predictor of overall and disease-free survival in melanoma patients rendered surgically free of disease. These tests may help better stratify patients for radical surgeries and adjuvant therapy. Large prospective and interlaboratory studies are needed to confirm the accuracy and prognostic value of these assays.

Quantitative Reverse Transcription-PCR Measurement of Thyroglobulin mRNA in Peripheral Blood of Healthy Subjects

Background: Thyroglobulin mRNA can be detected qualitatively in the peripheral blood of patients with metastatic thyroid cancer, thyroid cancer patients with residual thyroid bed uptake, and individuals with no known thyroid disease with intact thyroid glands by use of a lengthy, highly sensitive extraction technique. To improve and broaden the clinical usefulness of this assay, we developed a quantitative reverse transcription (RT)-PCR assay for thyroglobulin mRNA, using RNA recovered from whole blood with a simplified extraction technique.

Methods: Whole blood was drawn from 32 healthy subjects in standard EDTA blood collection tubes. Total RNA was extracted from whole blood, using the PUREscript RNA Isolation Kit. RT-PCR using intron-spanning primers was used to quantitatively amplify thyroglobulin mRNA, using the ABI PRISM 7700 Sequence Detection System with a fluorescent-labeled, thyroglobulin-specific oligonucleotide probe. Thyroid RNA calibration curves were created using total RNA recovered from a single nondiseased thyroid gland.

Results: Qualitative RT-PCR demonstrated the presence of thyroglobulin mRNA in the whole blood sample of each healthy subject. The mean concentration of thyroglobulin mRNA detected in these subjects was 433 ± 69 ng of total thyroid RNA per liter of whole blood (range, 26–1502 ng/L). Overall assay imprecision (CV) was 24% for five samples analyzed 10 times each in separate analytical runs on different days.

Conclusions: Thyroglobulin mRNA can be accurately detected and quantified in peripheral blood from healthy subjects. This new quantitative technique may improve the clinical utility of circulating thyroglobulin mRNA detection in patients with thyroid disease.

Utilization of polymerase chain reaction technology in the detection of solid tumors

BACKGROUND

Most cancer detection tests currently performed are based on either antibody assays to a marker protein with altered expression in cancer patients or on imaging studies to identify characteristic lesions. Generally, for a positive result, these detection assays require that a tumor have a significant volume of cancer cells. Advances in diagnostic techniques and technology may allow for cancer detection at earlier stages, when the tumor burden is smaller and potentially more curable. The molecular techniques of polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR) are highly sensitive methods for detecting a small number of cancer cells. Over the past few years, numerous clinical studies have used PCR techniques to detect physical alterations of genes, such as mutations, deletions, translocations and amplification, the presence of oncogenic viruses, and the expression of genes specific to tissue, cancer, and metastasis. The current status of PCR as a method for detecting marker genes in the management of solid tumors is reviewed.

METHODS

A review of the literature on the clinical utility of PCR and RT-PCR in the detection of solid tumor micrometastasis was conducted.

RESULTS

Amplification by PCR is a highly sensitive method to determine gene expression. A single cell expressing a tumor marker among 10-100 million lymphocytes can be detected by the PCR assay. This approach has been used to detect tumor cells in approximately 18 different solid tumor types, with melanoma and carcinoma of the breast and prostate the most widely investigated to date. PCR-based assays have been used to detect cancer cells in biopsies of solid tissue, lymph nodes, bone marrow, peripheral blood, and other body fluids. Several studies have reported a high specificity and sensitivity of tumor marker detection and a high correlation between PCR results and the presence of metastatic disease. However, in a few studies, PCR assays have not consistently demonstrated a higher sensitivity and specificity of detection than traditional modalities for many types of cancer. There has been a wide range in sensitivity and specificity among the studies, which may be partly attributed to the lack of uniformity among the PCR protocols used in different studies.

CONCLUSIONS

PCR can detect tumor marker-expressing cells that are otherwise undetectable by other means in patients with localized or metastatic cancer. Reports from various study groups have lacked uniformity in their protocols, and this has prevented adequate comparison. The clinical utility of this assay as a tool for the prognosis and management of cancer patients remains and area of active investigation. PCR is a powerful tool in the study of the biology of cancer metastasis and will likely serve as a useful adjunct to clinical decision-making in the future.

Utilization of polymerase chain reaction technology in the detection of solid tumors

BACKGROUND

Most cancer detection tests currently performed are based on either antibody assays to a marker protein with altered expression in cancer patients or on imaging studies to identify characteristic lesions. Generally, for a positive result, these detection assays require that a tumor have a significant volume of cancer cells. Advances in diagnostic techniques and technology may allow for cancer detection at earlier stages, when the tumor burden is smaller and potentially more curable. The molecular techniques of polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR) are highly sensitive methods for detecting a small number of cancer cells. Over the past few years, numerous clinical studies have used PCR techniques to detect physical alterations of genes, such as mutations, deletions, translocations and amplification, the presence of oncogenic viruses, and the expression of genes specific to tissue, cancer, and metastasis. The current status of PCR as a method for detecting marker genes in the management of solid tumors is reviewed.

METHODS

A review of the literature on the clinical utility of PCR and RT-PCR in the detection of solid tumor micrometastasis was conducted.

RESULTS

Amplification by PCR is a highly sensitive method to determine gene expression. A single cell expressing a tumor marker among 10-100 million lymphocytes can be detected by the PCR assay. This approach has been used to detect tumor cells in approximately 18 different solid tumor types, with melanoma and carcinoma of the breast and prostate the most widely investigated to date. PCR-based assays have been used to detect cancer cells in biopsies of solid tissue, lymph nodes, bone marrow, peripheral blood, and other body fluids. Several studies have reported a high specificity and sensitivity of tumor marker detection and a high correlation between PCR results and the presence of metastatic disease. However, in a few studies, PCR assays have not consistently demonstrated a higher sensitivity and specificity of detection than traditional modalities for many types of cancer. There has been a wide range in sensitivity and specificity among the studies, which may be partly attributed to the lack of uniformity among the PCR protocols used in different studies.

CONCLUSIONS

PCR can detect tumor marker-expressing cells that are otherwise undetectable by other means in patients with localized or metastatic cancer. Reports from various study groups have lacked uniformity in their protocols, and this has prevented adequate comparison. The clinical utility of this assay as a tool for the prognosis and management of cancer patients remains and area of active investigation. PCR is a powerful tool in the study of the biology of cancer metastasis and will likely serve as a useful adjunct to clinical decision-making in the future.