Papillary thyroid câncer driving oncogene BRAFV600E promotes aberrant Toll-like receptor 4 overexpression

PEYRET V; NAZAR, M; MARTIN, M; FUZIWARA CS; FERNANDEZ, EA; GEYSELS, R; MONTESINOS, MM; MALDONADO CA; QUINTAR, AA; SANTISTEBAN P; KIMURA ET; PELLIZAS, CG; NICOLA JP; MASINI-REPISO AM

Rìo de Janeiro

Congreso; XVI Congreso Latinoamericano de Tiroides (LATS); 2017

Sociedad Latinoamericana de Tiroides

Introduction: Emerging evidence suggests that hyperactivity of Toll like receptors (TLRs) signaling promotes tumor survival signals, thus favoring tumor progression. Recently, aberrant TLR4 overexpression was evidenced in papillary thyroid carcinomas (PTC). Objective: To study the mechanisms underlying TLR4 overexpression in PTC harboring the BRAFV600E mutation. Methods: TLR4 expression was studied in thyroid tissue derived from human PTCs and transgenic mice expressing BRAFV600E in thyrocytes (Tg-BRAFV600E mice) (IHC, RT/qPCR). BRAFV600E-positive PTC cell line BCPAP and PCCl3 cells expressing BRAFV600E in response to doxycycline (PC/BRAFV600E) were used to study BRAFV600E-driven TLR4 expression (western blot, RT/qPCR, siRNA silencing, luciferase assay). The Cancer Genome Atlas (TCGA) database was used to perform combined analysis. Results: We evidenced TLR4 overexpression in PTCs compared to normal thyroid tissues. Moreover, match-samples of primary PTCs and its lymph node metastasis showed a significant upregulation of TLR4 levels in the metastatic tissues. In agreement, TLR4 expression was increased in the thyroid tissue of Tg-BRAFV600E mice compared to littermate controls. Furthermore, we demonstrated functional TLR4 expression in PTC cells models which evidenced an increased NF-κB transcriptional activity in response to the exogenous TLR4-agonist lipopolysaccharide. TCGA data analysis revealed that patients with BRAFV600E-positive tumors and high TLR4 expression have shorter disease-free survival. Consistently with transcriptomic data showing correlation between TLR4 expression and ERK activation score, conditional BRAFV600E expression in PC/BRAFV600E cells upregulates TLR4 protein levels. Moreover, chemical blockage of MAPK/ ERK signaling abrogated BRAFV600E-induced TLR4 expression. Deletion analysis of TLR4 promoter revealed a critical MAPK/ERK-sensitive ETS binding-site involved in BRAFV600E responsiveness. Furthermore, we evidenced that the ETS binding factor ETS1 is critical for BRAFV600E-driven MAPK/ERK signaling-mediated TLR4 gene expression in PTCs.Conclusions: Increased TLR4 expression in PTCs would be a functional consequence of deregulated MAPK/ERK/ETS1 signaling as a result of thyroid tumors-drivers oncogenes such as BRAFV600E. Considering the oncogenic ability of aberrant NF-κB signaling activation in the promotion of thyroid tumor growth, our results suggest a pro-oncogenic potential of TLR4 downstream signaling in thyroid tumorigenesis.