Aberrant Expression of the Runx Family Genes in Thyroid Carcinomas
Tetsuo Kondo, Dongfeng Niu, Tadao Nakazawa, Tomonori Kawasaki, Naoki Oishi, Kunio Mochizuki, Tetsu Yamane, Ryohei Katoh. University of Yamanashi, Yamanashi, Japan
Background: The mammalian runt-related transcription factor (Runx) genes, including RUNX1 (AML1/CBFA2), RUNX2 (AML2/CBFA1) and RUNX3 (AML3/CBFA3), encode transcription factors that are master regulators of proliferation and differentiation during embryonic development. Recently, aberrant expression of the Runx family genes and its oncogenic or anti-oncogenic functions have been identified in the progression of human cancers.
Design: In this study, we investigated the expression profile of Runx family genes in normal thyroid tissue, non-neoplastic but abnormal thyroid tissue, various types of thyroid tumors and representative human thyroid carcinoma cell lines.
Results: Using reverse transcriptase polymerase chain reaction and Western blotting, we found that Runx2 was consistently up-regulated in papillary thyroid carcinomas (PTCs) and thyroid carcinoma cell lines compared with normal thyroid tissue. With immunohistochemistry, we observed negative or focal immunoreactivity of Runx2 in the nuclei of normal thyroid follicular cells. None of the non-neoplastic thyroid tissues, including Graves' thyroid and adenomatous goiter, had diffuse positivity of Runx2. Expression of Runx2 in benign follicular adenomas varied from negative to diffusely positive. Meanwhile, all malignant thyroid tumors showed some Runx2 immunopositivity. It was diffuse and intense in 83% (19/23) of PTCs, 71% (5/7) of follicular thyroid carcinomas (FCTs) and 40% (4/10) of undifferentiated thyroid carcinomas (UTCs). In thyroid carcinoma cell lines, the MEK inhibitor U0126 suppressed Runx2 suggesting an association of the MAPK/ERK pathway with Runx2 regulation. Effective silencing of Runx2 by short interfering RNA (siRNA) demonstrated down-regulation of EMT-related molecules (SNAI2, SNAI3 and TWIST1), MMP2 and vasculogenic factors (VEGFA and VEGFC) in thyroid carcinoma cells. We also confirmed that Runx2 silencing suppresses thyroid carcinoma cell invasion in transwell assays.
Conclusions: The present study provides insight into the potential molecular mechanism of thyroid cancer invasion. Our data suggest that enhanced Runx2 is functionally linked to tumor invasion and metastasis of thyroid carcinoma by regulating EMT-related molecules, matrix metalloproteinases and angiogenic/lymphangiogenic factors.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 37, Tuesday Afternoon