Dual Inhibition of HDAC and Tyrosine Kinase Signaling Pathways with CUDC-907 Inhibits Thyroid Cancer Growth and Metastases.

Abstract

<b>Purpose:</b> There is currently no standard therapy for anaplastic thyroid cancer (ATC) and poorly differentiated thyroid cancer (PDTC), which account for two-thirds of thyroid cancer-related deaths. Driver mutations in the <i>PI3K/AKT</i> and <i>RAF/RAS/MEK/ERK</i> pathways are common in ATC and PDTC. Histone deacetylases (HDAC) regulate cancer initiation and progression. Our aim was to determine the therapeutic efficacy of simultaneously targeting these pathways in thyroid cancer with a single agent and to evaluate biomarkers of treatment response.<b>Experimental Design:</b> CUDC-907 is a first-in-class compound, functioning as a dual inhibitor of HDACs and the PI3K/AKT pathway. We investigated its antiproliferative effect <i>in vitro</i> and <i>in vivo</i><b>Results:</b> CUDC-907 significantly inhibited cellular proliferation in thyroid cancer cell lines, induced G₂-M arrest with decreased levels of the checkpoint regulators cyclin B1, AURKA, AURKB, PLK1, and increased p21 and p27. Treatment induced apoptosis with increased caspase-3/7 activity and decreased survivin levels and decreased cellular migration and invasion. CUDC-907 treatment caused H3 hyperacetylation and decreased HDAC2 expression. HDAC2 was upregulated in ATC and other thyroid cancer histologic subtypes. CUDC-907 treatment reduced both p-AKT and p-ERK1/2 levels. Finally, CUDC-907 treatment, in a metastatic mouse model of thyroid cancer, showed significant inhibition of growth and metastases, and tumors from treated mice had decreased HDAC2 expression, suggesting that this may be a useful biomarker of response.<b>Conclusions:</b> Dual inhibition of HDAC and the tyrosine kinase signaling pathways with CUDC-907 is a promising treatment strategy for advanced, metastatic thyroid cancer. <i>Clin Cancer Res; 23(17); 5044-54. ©2017 AACR</i>.