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

Abstract

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 þ cells and only weakly expressed in the CD8 þ group. CK 19 was notable in each leukocyte population except for resting CD14 þ , as well as for activated and resting CD19 þ 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) ¼ 25.9570.73 (FTC)/24.5575.43 (PTC) (P ¼ 0.2878); onfFN ¼ 25.4873.15 (FTC)/21.4473.44 (PTC) (*P ¼ 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 realtime 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.

Oncofetal Fibronectin mRNA Is Highly Abundant in the Blood of Patients with Papillary Thyroid Carcinoma and Correlates with High-Serum Thyroid-Stimulating Hormone Levels

“…Copy numbers were normalized to porphobilinogen desaminase, and results were expressed as arbitrary units. All procedures have been described previously in all details (12).…”

“…2,[9][10][11]. A recent report from our group has described a highly sensitive assay to quantify oncofetal fibronectin (onfFN) mRNA in the peripheral blood of patients with DTC metastatic disease (12). As discussed later, we consider that onfFN mRNA in peripheral blood is probably derived from circulating rather than tissue cells.…”

Serum Oncofetal Fibronectin (onfFN) mRNA in Differentiated Thyroid Carcinoma (DTC): Large Overlap between Disease-Free and Metastatic Patients

“…Also, there were only 4 FTC out of 21 patients (19.0%) in the disease groups and 7 out of 30 (23.3%) in the disease-free group, therefore, the inclusion proportion of patients with FTC should not account for this indifference. In fact, Hesse et al (Hesse et al, 2005) showed that detectable levels of onfFN were found in the majority of the tissue samples of FTC but only 11% having high expression. Also, a quarter of all PTC tumours only displayed intermediate and low (13%) onfFN signals.…”

“…Based on the use of OnfFN mRNA in identifying metastatic DTC by Hesse et al (Hesse et al, 2005), we applied to assess if the onfFN mRNA in the peripheral blood of the patients with metastatic DTC can be used to differentiate between the active and disease-free groups. Generally, the patients were considered disease-free after total thyroidectomy and radioiodine ablation.…”

“…In search of a more promising tumour marker, a number of potential tumour markers including the mRNA of Tg, thyroid-stimulating hormone receptor (TSH-R), cytokeratin 19 (CK19), human telomerase reverse transcriptase (hTERT), and oncofetal fibronectin (onfFN) transcripts in leukocytes, as well as in PTCs and FTCs have been studied (Hesse et al, 2005). Interestingly, onfFN transcripts were detected in peripheral blood samples of 6 out of 9 patients with known DTC metastases, suggesting the possible role of onfFN as a marker.…”