Suppression of Calcium Entry Modulates the Expression of TRβ1 and Runx2 in Thyroid Cancer Cells, Two Transcription Factors That Regulate Invasion, Proliferation and Thyroid-Specific Protein Levels

Abstract

The thyroid hormone receptor beta 1 (TRβ1) is downregulated in several human cancer cell types, which has been associated with development of an aggressive tumor phenotype and the upregulation of Runt-related transcription factor 2 (Runx2). In this study, we show that the expression of TRβ1 protein is downregulated in human thyroid cancer tissues and cell lines compared with the normal thyroid tissues and primary cell line, whilst Runx2 is upregulated under the same conditions. In contrast, the expression of TRβ1 is upregulated, whereas Runx2 is downregulated, in STIM1, Orai1 and TRPC1 knockdown cells, compared to mock transfected cells. To study the functional significance of Runx2 in follicular thyroid cancer ML-1 cells, we downregulated it by siRNA. This increased store-operated calcium entry (SOCE), but decreased cell proliferation and invasion. Moreover, restoring TRβ1 expression in ML-1 cells decreased SOCE, basal and sphingosine 1-phosphate (S1P)-evoked invasion, the expression of the promigratory S1P3 receptor and pERK1/2, and at the same time increased the expression of the thyroid specific proteins thyroglobulin, thyroperoxidase, and thyroid transcription factor-1. In conclusion, we show that TRβ1 is downregulated in thyroid cancer cells and that restoration of its expression can reverse the cancer cell phenotype towards a normal thyroid cell phenotype.

RUNX2 and Cancer

“…In thyroid cancer, the biological significance of RUNX2 in follicular thyroid cancer ML-1 cells was investigated. Knockdown of RUNX2 by siRNA revealed a decrease in cancer cell proliferation accompanied by an increase in store-operated calcium entry (SOCE) [ 10 ]. In ccRCC, RUNX2 triggered cancer cell proliferation via SCD1-dependent Wnt/β-catenin pathway activation.…”

“…RUNX2 overexpression induced COL1A1 expression and promoted cancer cell migration and invasion in vitro and in an animal model of metastasis via COL1A1 [ 33 ]. In thyroid cancer, a reduction in invasion activity was detected after silencing RUNX2 by siRNA in ML-1 cells [ 10 ]. Stable knockdown of RUNX2 in a triple-negative breast cancer cell line (MDA-MB-231) resistant to epirubicin abolished the cell invasion and migration activity, determined by Transwell assay.…”

“…RUNX2 protein was detected in cervical cancer tissues, and RUNX2 expression declined upon overexpression of miR-218-5p in C-33A and CaSki cells [ 58 ]. RUNX2 protein was elevated in human thyroid cancer cell lines and cancer tissues compared with primary cell lines and normal thyroid tissues [ 10 ]. RUNX2 was overexpressed in lung adenocarcinoma in a large study that included 2418 tumor and 1574 nontumor lung samples [ 59 ].…”