Tenascin C in medullary thyroid microcarcinoma and C-cell hyperplasia

Histopathology of C Cells and Medullary Thyroid Carcinoma

C cells are the neuroendocrine cell component of the thyroid gland that embryologically arise from the pharyngeal endoderm. Normal C cells are concentrated in the upper two-thirds of both lateral lobes, appear singly or in small groups dispersed in, among or peripherally to the follicles, and are involved in the production of calcitonin. Reactive C-cell hyperplasia should be differentiated from proliferation of atypical C cells (neoplastic C-cell hyperplasia) which is considered an intraepithelial neoplasia of C cells/medullary carcinoma in situ, a precursor lesion associated to familial medullary thyroid carcinoma (MTC). MTC typically exhibits a lobular and/or trabecular growth pattern with amyloid deposits; however, due to its great histological variability, immunohistochemical positivity for calcitonin, carcinoembryonic antigen, calcitonin-gene-related peptide, insulinoma-associated protein 1, and/or other markers is necessary to confirm diagnosis. Investigation of germline RET proto-oncogene mutation is mandatory to identify familial MTC. Somatic RET mutations or fusions as well as RAS mutations in cytological and/or biopsy samples may represent therapeutic targets. Mixed medullary and follicular-derived cell carcinoma is a heterogeneous group of tumors which needs to be distinguished from collision tumors.

Immunohistochemical Comparative Study of Aggressive and Non-aggressive Central Giant Cell Lesions of the Jaws Based on the Tenascin-C Expression Profile

The purpose of this study was to compare the immunohistochemical expression of tenascin-C (Tn-C) regarding clinicopathological variables and its association with the clinical behavior of central giant cell lesions (CGCLs). Forty-eight paraffin-embedded samples of CGCLs were selected. Based on clinical and radiographic features, the lesions were classified as aggressive (A-CGCLs) and non-aggressive (NA-CGCLs) subtypes. Histological assessment included the microvessel count (MVC), multinucleated giant cell (MGC) count, and the proportion of tissue area involved by mononuclear stromal cells/interstitial fibrosis. Immunoreactivity, immunolocalization, and distribution patterns of Tn-C were studied immunohistochemically. The association between Tn-C expression and clinicopathological characteristics was analyzed separately and adjusted for confounders using logistic regression models. A significantly greater proportion of cases with moderate-to-intense, intracellular, and diffuse staining of Tn-C was observed in A-CGCLs. CGCLs with a size ≥3.3 cm, fast growth, cortical disruption, high MVC/MGC counts, and low interstitial fibrosis showed a significantly greater frequency of moderate-to-intense, intracellular, and diffuse staining. Logistic regression analysis indicated a strong/independent association of these three immunohistochemical parameters with the aggressiveness of lesions. These data appear to suggest a possible role for Tn-C in the etiopathogenesis of CGCLs of the jaws, where its upregulation might favor the destructive behavior of A-CGCLs.

TNRC6C Functions as a Tumor Suppressor and Is Frequently Downregulated in Papillary Thyroid Cancer

Our previous study found that trinucleotide repeat containing adaptor 6C (TNRC6C) may act as a tumor suppressor in papillary thyroid cancer (PTC). In this study, we aimed to confirm the effect of TNRC6C on PTC and investigate the underlying molecular mechanism. The difference of mRNA level of TNRC6C between PTC tissue and noncancerous thyroid tissue and the association of expression level of TNRC6C with clinicopathological features of PTC were analyzed using TCGA data. Immunohistochemical assay was performed to detect the protein expression of TNRC6C in PTC and its adjacent noncancerous tissue. Cell proliferation, migration, invasion, and apoptosis were analyzed after knockdown or overexpression of TNRC6C in BCPAP cells. RNA-sequencing was performed to find the target genes of TNRC6C, and potential targets were validated in BCPAP and TPC1 cells. Our results showed that TNRC6C was downregulated in PTC, and lower expression level of TNRC6C was associated with worse clinicopathological features. Overexpression of TNRC6C significantly inhibited proliferation, migration, and invasion of BCPAP cells and promoted its apoptosis, while knockdown of TNRC6C acted the opposite role. By analyzing RNA-sequencing data and TCGA data, 12 genes (SCD, CRLF1, APCDD1L, CTHRC1, PTPRU, ALDH1A3, VCAN, TNC, ECE1, COL1A1, CAMK2N2, and MMP14) were considered as potential target genes of TNRC6C, and most of them were associated with clinicopathological features of PTC in TCGA. All of them except CAMK2N2 were significantly downregulated after overexpressing TNRC6C. Our study demonstrated that TNRC6C functions as a tumor suppressor in PTC and may serve as a useful therapeutic target and prognostic marker for PTC patients.

RET-mediated modulation of tumor microenvironment and immune response in multiple endocrine neoplasia type 2 (MEN2)

Medullary thyroid carcinomas (MTC) arise from thyroid parafollicular, calcitonin-producing C-cells and can occur either as sporadic or as hereditary diseases in the context of familial syndromes, including multiple endocrine neoplasia 2A (MEN2A), multiple endocrine neoplasia 2B (MEN2B) and familial MTC (FMTC). In a large fraction of sporadic cases, and virtually in all inherited cases of MTC, activating point mutations of the RET proto-oncogene are found. RET encodes for a receptor tyrosine kinase protein endowed with transforming potential on thyroid parafollicular cells. As in other cancer types, microenvironmental factors play a critical role in MTC. Tumor-associated extracellular matrix, stromal cells and immune cells interact and influence the behavior of cancer cells both in a tumor-promoting and in a tumor-suppressing manner. Several studies have shown that, besides the neoplastic transformation of thyroid C-cells, a profound modification of tumor microenvironment has been associated to the RET FMTC/MEN2-associated oncoproteins. They influence the surrounding stroma, activating cancer-associated fibroblasts (CAFs), promoting cancer-associated inflammation and suppressing anti-cancer immune response. These mechanisms might be exploited to develop innovative anti-cancer therapies and novel prognostic tools in the context of familial, RET-associated MTC.

Expression of Tenascin C, EGFR, E-Cadherin, and TTF-1 in Medullary Thyroid Carcinoma and the Correlation with RET Mutation Status

Tenascin C expression correlates with tumor grade and indicates worse prognosis in several tumors. Epidermal growth factor receptor (EGFR) plays an important role in driving proliferation in many tumors. Loss of E-cadherin function is associated with tumor invasion and metastasis. Thyroid transcription factor-1 (TTF-1) is involved in rearranged during transfection (RET) transcription in Hirschsprung’s disease. Tenascin C, EGFR, E-cadherin, TTF-1-expression, and their correlations with RET mutation status were investigated in 30 patients with medullary thyroid carcinoma (MTC) (n = 26) or C-cell hyperplasia (n = 4). Tenascin C was found in all, EGFR in 4/26, E-cadherin in 23/26, and TTF-1 in 25/26 MTC. Tenascin C correlated significantly with tumor proliferation (overall, r = 0.61, p < 0.005; RET-mutated, r = 0.81, p < 0.01). E-cadherin showed weak correlation, whereas EGFR and TTF-1 showed no significant correlation with tumor proliferation. EGFR, E-cadherin, and TTF-1 showed weak correlation with proliferation of RET-mutated tumors. Correlation between TTF-1 and tenascin C, E-cadherin, and EGFR was r = −0.10, 0.37, and 0.21, respectively. In conclusion, MTC express tenascin C, E-cadherin, and TTF-1. Tenascin C correlates significantly with tumor proliferation, especially in RET-mutated tumors. EGFR is low, and tumors expressing EGFR do not exhibit higher proliferation. TTF-1 does not correlate with RET mutation status and has a weak correlation with tenascin C, E-cadherin, and EGFR expression.

[Thyroid C cells and their pathology: Part 2: Medullary thyroid carcinoma]

All tumours with C cell differentiation are designated as medullary carcinomas (MTC). MTC occur sporadically (75-80%) or hereditary (20-25%), the latter being part of the multiple endocrine neoplasia type 2. Familial MTC, which is commonly preceded by "neoplastic" C cell hyperplasia, is caused by autosomal-dominant inherited germ line mutation of the RET-protooncogene; dependent on the codon affected by the mutation, patients show substantially different clinical courses. Due to its morphological heterogeneity, the immunohistochemical demonstration of calcitonin is mandatory for the diagnosis of MTC. For early diagnosis of MTC calcitonin screening has been introduced in Germany and Austria approx. 10 years ago in patients with thyroid nodules; however, an increased calcitonin serum level may also be caused by "non-MEN2-associated" C cell, which is not regarded as a precursor of sporadic MTC. Very rarely tumours may show a mixed C cell-follicular cell differentiation.

Elevated expression of nuclear protein kinase CK2α as a poor prognosis indicator in lymph node cancerous metastases of human thyroid cancers

AIM

To investigate the expression of protein kinase CK2α (CK2α) in human thyroid disease and its relationship with thyroid cancer metastasis.

MATERIALS AND METHODS

Using immunohistochemistry we measured the expression of CK2α in 76 benign and malignant human thyroid cancer tissues, including 10 pairs of papillary carcinoma tissues with or without lymph node cancerous metastasis and similarly 10 pairs of lymph nodes.

RESULTS

The expression of CK2α was found to be higher in thyroid carcinoma cases (papillary carcinoma, follicular carcinoma, anaplastic carcinoma and medullary carcinoma) than in ones such as chronic lymphocytic thyroiditis, nodular goiter and adenoma. These findings were also confirmed by RT-PCR and Western blotting. More strikingly, elevated expression of CK2α in thyroid papillary carcinoma tissues was not only significantly associated with lymph node cancerous metastasis and clinical stage of thyroid cancers; but also correlated with epithelial-mesenchymal transition (EMT) and high tenascin C (TNC) expression. In addition, EMT and high TNC expression in thyroid carcinoma tissues was significantly associated with lymph node cancerous metastasis.

CONCLUSIONS

Elevated expression of nuclear CK2α is a poor prognosis indicator in lymph node cancerous metastasis of human thyroid cancers.

Histopathology of C Cells and Medullary Thyroid Carcinoma

The human thyroid gland contains less than 0.01-0.1% calcitonin producing and secreting C cells, which in men are almost exclusively situated in an intrafollicular location; the vast majority of C cells are embryologically derived of remnants of the ultimobranchial body and ultimately of the neural crest, a small subset, however, is presumed to originate from endodermal stem cells. Thyroid tumours with C cell differentiation have been named medullary thyroid carcinoma (MTC); calcitonin is also produced and secreted by MTC which makes this peptide hormone a very useful serum marker both for early detection and clinical follow-up of patients with MTC. About 70-80% of MTC are sporadic tumours, whereas 20-30% are familial MTC which are autosomal-dominant inherited and caused by germline mutations of the RET proto-oncogene located on chromosome 10. This article summarizes the histological, immunhistochemical and molecular genetic features of C cells, C-cell hyperplasia (CCH) and MTC, emphasizing the role of diagnostic pathology.

Identification of soluble candidate biomarkers of therapeutic response to sunitinib in medullary thyroid carcinoma in preclinical models

PURPOSE

Medullary thyroid carcinoma (MTC), an aggressive rare tumor due to activating mutations in the proto-oncogene RET, requires new therapeutic strategies. Sunitinib, a potent inhibitor of RET, VEGF receptor (VEGFR)-1, VEGFR-2, VEGFR-3, and platelet-derived growth factor receptor (PDGFR)α/β, has been reported as clinically effective in some patients with advanced MTC. In this study, we examine molecular mechanisms of action of sunitinib and identify candidate soluble biomarkers of response.

EXPERIMENTAL DESIGN

Both in vitro and in vivo assays, using the human TT RET(C634W) MTC cell line, were done to assess the activity of sunitinib. Kinetic microarray studies were used to analyze molecular pathways modified by sunitinib and to identify candidate biomarkers that were subsequently investigated in the serum of patients.

RESULTS

Sunitinib displayed antiproliferative and antiangiogenic activities and inhibited RET autophosphorylation and activation of downstream signaling pathways. We showed that sunitinib treatment induced major changes in the expression of genes involved in tissue invasion and metastasis including vimentin (VIM), urokinase plasminogen (PLAU), tenascin-C (TN-C), SPARC, and CD44. Analyzing downregulated genes, we identified those encoding secreted proteins and, among them, interleukin (IL)-8 was found to be modulated in the serum of xenografted mice under sunitinib treatment. Furthermore, we demonstrated that metastatic MTC patients presented increased serum levels of IL-8 and TGF-β2.

CONCLUSIONS

Experimental models confirm the clinical efficacy of sunitinib observed in a few studies. Molecular pathways revealed by genomic signatures underline the impact of sunitinib on tissue invasion. Selected soluble candidate biomarkers could be of value for monitoring sunitinib response in metastatic MTC patients.