Abstract 3073: Action of thyroid hormones in sorafenib treatment of thyroid cancer

Background: Thyroid carcinoma (TC) is the most common endocrine neoplasia. Its incidence has increased in the last 40 years worldwide. Sorafenib (Sor), a tyrosine kinase inhibitor (TKI), was approved for the treatment of TC, being hypothyroidism the most frequent consequence of Sor-induced endocrine dysfunction. We have described that thyroid hormones (TH) increase cell proliferation in TC cell lines. Thus, hormone replacement therapy to treat Sor-induced hypothyroidism could negatively affect its antitumor action. We have also shown that the selective inhibition of the TH membrane receptor, integrin αVβ3, diminishes proliferation. Objective: To study integrin αVβ3 inhibition to enhance Sor antineoplastic activity in TC and the molecular mechanisms involved. Experimental Procedures: 8505C human anaplastic TC cell viability was evaluated by MTS assay. Sor was the TKI used, and Cilengitide (Cile) was used to inhibit integrin αVβ3. Protein modulation was measured by Western blot. Apoptosis induction was determined by APC-Annexin V Propidium iodide staining, followed by flow cytometry. In silico analysis on several databases were performed using CBioPortal (https://cbioportal.org/; TCGA, Cell 2014, n=504) and R2 (http://r2.amc.nl; GSE126729, n=28). Results: We first performed a bioinformatic analysis by cBioPortal on the PanCancer Atlas data and found that thyroid tumors are those with the highest integrin αVβ3 subunits expression. We then studied the role of integrin αVβ3 in Sor inhibition of TH-induced proliferation in TC cells. Treatment of 8505C cells with integrin αVβ3 antagonist Cile inhibits TH-induced proliferation (p&lt0.0001), confirming the participation of the integrin. As expected, Sor treatment decreases proliferation (p&lt0.05) while Cile addition did not change the inhibition level. Also, we found that Sor and Cile treatment diminished PCNA and Cyclin D1 expression levels. Cells were preincubated with Sor and Cile and then treated or not with TH for 48h to analyze apoptosis. Sor treatment increases the number of apoptotic cells relative to untreated control (p&lt0.0001) and the presence of TH reduces the rate of apoptosis (p&lt0.01). We then studied Sor target genes expression by R2 on an anaplastic TC patients’ database. FGFR is highly expressed among Sor targets, and it is correlated with integrin αVβ3 expression. Thus, FGFR expression modulation was studied by Western blot on cells treated as previously described. Finally, we found that TH t