Targeted molecular therapies in thyroid carcinoma

Overexpression of mir-129-1, miR-146b, mir-183, and mir-197 in follicular thyroid carcinoma and adenoma tissues

Follicular thyroid carcinoma (FTC) is responsible for approximately 10% of thyroid malignancies. Since this type of malignancy indicates no capsular and vascular invasions, adenoma and follicular carcinoma of thyroid are not distinguishable. It has been proved that microRNAs, which regulate approximately 30% of coding proteins, have an association with follicular thyroid adenoma (FTA) and carcinoma of the thyroid. Therefore, the aim of this study was to assess the expression of some miRNAs for detecting the most appropriate miRNA as potential biomarker in the diagnosis of FTA and FTC patients. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was applied to determine the expression levels of miR-129-1, miR-146b,-183 and miR-197 in 48 cases (16 FTC, 16 FTA and 16 hyperplasia/multinodular goiter (MNG) cases). The significance of miRNA differential expression levels among groups were assessed using Multivariate test by Statistical Package for Science Software (SPSS v.20) and Graph Pad Prism v.8. Results indicated that all of the miRNAs had significant overexpression in FTC and FTA versus MNG cases, and also increased expression level in FTC in comparison with FTA, however it was not significant. The results of ROC curve analysis determined the significant overexpression and prognostic value of miR-129-1 in FTA cases and miR-146b in both FTA and FTC cases compared to MNG group. Although all of the earlier mentioned microRNAs were overexpressed in FTC and FTA cases, the ROC curve results demonstrated that miR-129-1 had agreeable AUC for FTA cases. Therefore, it seems that it's cut-off point could be helpful in distinguishing between FTA and multinodular goiter cases. On the other hand, although miR-146b has excellent diagnostic value in both FTA and FTC groups, it seems that this microRNA is unable to act as a specific biomarker to discriminate between FTA and FTC cases. This data need to be confirmed in a large cohort study and other biological samples such as plasma.

Development of an athyroid mouse model using 131I ablation after preparation with a low-iodine diet

We optimized the protocol for thyroid ablation in living mice using radioactive iodine (RAI) and a low-iodine diet (LID). To examine the effect of LID on thyroid ablation, mice were randomly divided into 4 groups: Vehicle, ¹³¹I 2.775 MBq, ¹³¹I 5.55 MBq, and LID + ¹³¹I 2.775 MBq. The LID group was fed a LID for up to 7 days and then mice in the ¹³¹I 2.775, ¹³¹I 5.55, and LID + ¹³¹I 2.775 MBq groups were intravenously administrated with ¹³¹I, respectively. Scintigraphy imaging with ^99mTc pertechnetate was performed once in 2 weeks for 4 weeks. After establishment of athyroid mice, control or athyroid mice were injected with human anaplastic thyroid cancer cells co-expressing sodium iodine symporter and enhanced firefly luciferase (ARO/NF) to evaluate RAI uptake. Scintigraphy imaging with ^99mTc pertechnetate was performed with ARO/NF tumor-bearing mice. Scintigraphy imaging showed decreased thyroid uptake in the LID + ¹³¹I 2.775 MBq group compared to other groups. Scintigraphy images showed that tumor uptake was statically higher in athyroid mice than in control mice. These data suggest that these optimized conditions for thyroid ablation could be helpful to establish an in vivo mouse model.

Therapeutic effects of adenovirus-mediated CD and NIS expression combined with Na131I/5-FC on human thyroid cancer

Thyroid cancer is the most common type of malignant endocrine tumor diagnosed. Previous studies have indicated that gene therapy is the most promising and effective therapeutic method for thyroid cancer. Therefore, in the present study, Na¹³¹I/5-fluorocytosine (5-FC) treatment was combined with cytosine deaminase (CD, encoded by the CDA gene) and sodium iodide symporter (NIS, encoded by the SLC5A5 gene) to act together as a therapeutic tool for thyroid cancer. The present study explored the combined cytotoxic effects of adenovirus-mediated CD and NIS under the control of the progression elevated gene-3 (PEG-3) promoter (Ad-PEG-3-CD-NIS) with Na¹³¹I/5-FC against the human thyroid cancer TT cell line in vitro. The PEG-3 fragment was obtained by polymerase chain reaction (PCR) using rat genomic DNA as the template, and then Ad-PEG-3-CDA-SLC5A5 was constructed using XbaI. TT cells were transfected by recombinant adenovirus. The method of reverse transcription-quantitative PCR was performed to test the expression of CD and NIS at the level of transcription. The morphological change was assessed by fluorescence microscopy and investigated by western blot analysis. An MTT assay was used to determine the number of living cells inhibited by single or combination therapies on TT cells. The results indicated that the PEG-3 was successfully cloned, and was also positively regulated in 293 cells. CDA and SLC5A5 genes were highly expressed in TT cells. Na¹³¹I combined with 5-FC significantly decreased the human thyroid cancer cells. In conclusion, combination therapy of Ad-PEG3-CDA-SLC5A5 and Na¹³¹I/5-FC induces significantly more apoptotic characteristics than either single treatment with Ad-PEG-3-CDA-SLC5A5 or Na¹³¹I/5-FC, and low doses of Ad-PEG-3-CDA-SLC5A5 enhanced the cytotoxic effects.

Platelet-derived growth factor receptor-α promotes lymphatic metastases in papillary thyroid cancer

Lymph node metastases are common in papillary thyroid cancer (PTC) and can be resistant to surgical extirpation or radioiodine ablation. We examined the role of platelet-derived growth factor receptor (PDGFR) in mediating lymph node metastases in PTC. Clinical specimens of PTC (n = 137) were surveyed in a tissue array and by western blots to examine the relationship between expression of the α and β subunits of PDGFR and lymph node metastases. PDGFR-α was found at high levels in primary tumours with known lymphatic metastases but not in those tumours lacking nodal involvement (p < 0.0001). However, PDGFR-β expression was not linked to metastatic disease (p = 0.78) as it was found in virtually all PTC specimens. A matching analysis in fresh PTC specimens (n = 13) confirmed that PDGFR-α expression was strongly linked to metastatic spread (p = 0.0047). PDGFR-α and -β were not found in normal thyroid tissue (p < 0.0001). PTC cell lines selectively expressing PDGFR-α or -β were assessed for invasive potential and activation of downstream signal transduction pathways. PTC cell lines expressing PDGFR-α responded to PDGF-BB stimulation with increased invasive potential and this process can be blocked by the tyrosine kinase receptor inhibitor sunitinib (p < 0.009). Cell lines with only PDGFR-β, or no PDGFR, did not show significant changes in invasive potential. Activation of PDGFR-α led to downstream up-regulation of both the MAPK/ERK and PI3K/Akt pathways and disruption of either pathway is sufficient to block PDGFR-mediated increases in invasive potential. Thus, PDGFR-α is associated with lymph node metastases in papillary thyroid carcinoma and PDGFR-α promotes increased invasive potential in PTC cell lines. PDGFR-α is a strong candidate for a diagnostic biomarker to identify patients at risk of nodal metastases. Our results also strengthen the rationale for selection of tyrosine kinase receptor inhibitors that target PDGFR in the treatment of progressive, metastatic PTC.

Sunitinib exerts only limited effects on the proliferation and differentiation of anaplastic thyroid cancer cells

BACKGROUND

Novel molecularly targeted drugs are undergoing preclinical and clinical testing to assess their efficacy against refractory thyroid carcinomas. The multikinase inhibitor Sunitinib has been shown to inhibit the kinase activity of the RET oncogene and reduce proliferation in differentiated thyroid cancer cells harboring the RET/PTC rearrangement. In this study, we evaluated its effects in human cell lines derived from differentiated (TPC-1) and anaplastic (8505C, CAL-62, and C643) thyroid cancers.

METHODS

The cells exposed to various concentrations of Sunitinib were examined for: (1) cell viability and presence of apoptosis, analyzed by cell counts, MTT assay, trypan blue exclusion assay, western blotting, and immunofluorescence; (2) expression of cyclin D1 and phosphorylated and nonphosphorylated extracellular signal-regulated kinase (ERK) and Akt proteins, analyzed by western blotting; and (3) transcription of genes encoding thyrocyte differentiation markers (thyroid-stimulating hormone receptor, sodium/iodide symporter, thyroglobulin, and thyroperoxidase) and proangiogenic factors (vascular endothelial growth factor A, platelet-derived growth factors A and B), measured by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Exposure to nanomolar concentrations of Sunitinib significantly reduced cell viability in only TPC-1 cells, and this effect was paralleled by reduction of cyclin D1 levels. Western blotting revealed reduced phosphorylation of ERK and Akt after 3 and 6 hours of drug exposure. In contrast, the growth of 8505C, CAL-62, and C-643 cells was significantly reduced only by micromolar concentrations of Sunitinib, mainly due to induced necrotic rather than apoptotic death. In these cells, Sunitinib exerted a few significant effects on the transcription of angiogenic factors or thyrocyte differentiation markers.

CONCLUSIONS

Sunitinib has little or no effect on the growth or differentiation of anaplastic thyroid cancer cells, thus suggesting that it is unlikely to be effective in the treatment of anaplastic thyroid cancer.