metallothionein and Carcinoma--Papillary

Metallothioneins (MTs) are involved in numerous cell processes such as binding and transport of zinc and copper ions, differentiation, proliferation and apoptosis, therefore contributing to carcinogenesis. Scarce data exist on their expression in benign and malignant lesions of the thyroid.. mRNA expression of functional isoforms of MT genes (MT1A, MT1B, MT1E, MT1F, MT1G, MT1H, MT1X, MT2A, MT4) was studied in 17 nodular goiters (NG), 12 follicular adenomas (FA) and 26 papillary thyroid carcinomas (PTC).. One-way ANOVA revealed significant differences in mRNA expression levels of MT1A (p<0.05), MT1E (p<0.005), MT1F (p<0.0001), MT1G (p<0.005), MT1X (p<0.0005) and MT2A (p<0.005) in the analyzed samples. Post hoc analysis confirmed a significantly lower expression of MT1A mRNA in PTC compared to NG (p<0.05). Significant down-regulation was also noted for other MT isoforms in PTC in comparison to NG: MT1E (p<0.05), MT1F (p<0.0001), MT1G (p<0.005), MT1X (p<0.0005) and MT2A (p<0.05). In addition, significant down-regulation of MT1F and MT1G in FA compared to NG was observed (p<0.005 and p<0.05, respectively).. Expression of functional MT isoforms may contribute to thyroid carcinogenesis and potentially serve as a diagnostic marker in distinguishing benign and malignant lesions.

Topics: Adenoma; Adult; Aged; Aged, 80 and over; Carcinoma; Carcinoma, Papillary; Female; Gene Expression Regulation, Neoplastic; Goiter, Nodular; Humans; Male; Metallothionein; Middle Aged; Protein Isoforms; RNA, Messenger; Thyroid Cancer, Papillary; Thyroid Neoplasms; Young Adult

Hypoxia inducible factor-1α (HIF-1α) is upregulated by hypoxia, and involved in tumor growth and metastasis in many malignant tumors including papillary thyroid carcinoma (PTC). Metallothionein (MT) is a group of small molecular weight cysteine-rich proteins with a broad variety of functions. SLUG is a member of SNAIL superfamily of zinc finger transcriptional factors implicated in epithelial-mesenchymal transition (EMT). The purpose of this study was to examine HIF-1α, MT and SLUG expression in PTC and assess association of their expression with clinicopathological indicators. HIF-1α, MT and SLUG protein expression in 129 PTCs, 61 nodular hyperplasia and 118 normal thyroid tissue specimens were analyzed using immunohistochemistry. The protein expression levels of these three molecules were up-regulated in PTCs. High protein expression of HIF-1α, MT and SLUG was significantly correlated with high TNM stage (P=0.003, 0.002, 0.024, respectively) and lymph node metastasis (LNM) (P<0.001 for all three molecules). Furthermore, HIF-1α, MT and SLUG protein expression were correlated with one another. Concomitant high expression of any two of these three molecules had stronger correlation with high TNM stage (P≤0.001 for HIF-1α/MT, MT/SLUG and HIF-1α/SLUG) and LNM (P=0.008, 0.002, 0.019 for HIF-1α/MT, MT/SLUG and HIF-1α/SLUG, respectively) than did each alone, and concomitant high expression of all these three molecules is significantly associated with high TNM stage and LNM as compared with cases not showing such expression (P<0.001). These results demonstrated that the evaluation of HIF-1α, MT and SLUG expression in PTC may be useful in predicting the risk of LNM and high TNM stage.

Topics: Biomarkers, Tumor; Carcinoma; Carcinoma, Papillary; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Lymphatic Metastasis; Male; Metallothionein; Middle Aged; Neoplasm Staging; Snail Family Transcription Factors; Thyroid Cancer, Papillary; Thyroid Neoplasms; Tissue Array Analysis; Transcription Factors; Up-Regulation

Metallothionein (MT) isoforms have not been studied in papillary thyroid cancer. We examined how the functional MT1 and MT2 isoforms were expressed in papillary thyroid cancer (KAT5) cells. We demonstrated that KAT5 cells expressed eight functional MT1 and MT2 isoforms induced by cadmium. Elevated calcium and activated ERK1/2 predated MT expression. The inhibition of either calcium or ERK1/2 significantly blocked the isoform expression. The induction of these isoforms accompanied an increased progression of cell cycle from G0/G1 to G2-M. The alternation in cell cycle disappeared when the expression of MT isoforms was blocked by calcium inhibitor or ERK1/2 inhibitor. Collectively, KAT5 cells express eight functional MT1 and MT2 isoforms in a pathway controlled by calcium and ERK1/2. The elevation of the MT isoforms contributes to the decreased G0/G1 but increased G2-M phase. These results reveal a novel pathway for the expression of the functional MT in papillary thyroid cancer.

Topics: Blotting, Western; Carcinoma, Papillary; Cell Cycle; Cell Line, Tumor; Gene Expression Regulation, Neoplastic; Humans; Metallothionein; Protein Isoforms; Receptor, Melatonin, MT1; Receptor, Melatonin, MT2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thyroid Neoplasms

The molecular pathogenesis of tumors arising from the thyroid follicular epithelial cells, including papillary (PTC) and follicular thyroid carcinoma (FTC), is only partially understood, and the role of tumor suppressor genes has not yet been assessed. The metallothionein (MT) gene family encodes a class of metal-binding proteins involved in several cellular processes, and their expression is often deregulated in human tumors. Recently, downregulation of MT gene expression in PTC has been reported, suggesting a possible oncosuppressor role of this gene family in the pathogenesis of thyroid tumors. To further explore this possibility, we performed expression and functional studies. Analysis of microarray data of thyroid tumors of different histologic types showed that several MT genes were downregulated with respect to normal tissue. The microarray data were corroborated by quantitative PCR experiments, showing downregulation of MTs in PTC and FTC, but to a greater extent in papillary carcinoma. The expression of MTs was also investigated at the protein level by immunohistochemistry; the results were consistent with the microarray data, showing general downregulation in tumor samples, which was more evident in PTC. The functional consequence of MT downregulation was addressed employing an experimental model made of the PTC-derived K1 cell line in which MT1G expression is repressed by promoter methylation. Restoration of MT1G expression by cDNA transfection affected growth rate and in vivo tumorigenicity of K1 cells, indicating an oncosuppressor role for MT1G in thyroid papillary tumorigenesis.

Topics: Carcinoma; Carcinoma, Papillary; Cell Line, Tumor; DNA Methylation; DNA, Complementary; Down-Regulation; Gene Expression; Humans; Immunohistochemistry; Metallothionein; Microarray Analysis; Promoter Regions, Genetic; Thyroid Neoplasms; Transfection; Tumor Suppressor Proteins