Papillary thyroid cancer-driving oncogene BRAFV600E induces Toll-like receptor 4 overexpression

PEYRET VICTORIA; NAZAR MAGALÍ; NICOLA JUAN PABLO; PEYRET VICTORIA, NAZAR MAGALÍ, NICOLA JUAN PABLO, FUZIWARA CESAR SEIGI, KIMURA EDNA TERUKO, MONTESINOS MARÍA DEL MAR, PELLIZAS CLAUDIA GABRIELA, MASINI - REPISO ANA MARÍA.; KIMURA EDNA TERUKO; MONTESINOS MARÍA DEL MAR; PELLIZAS CLAUDIA G; MASINI - REPISO ANA M

Córdoba

Jornada; VII Jornadas Posgrado - I Jornada de Ciencia y Tecnología.; 2016

Facultad de Ciencias Químicas - Universidad Nacional de Córdoba

ABSTRACTIntroduction: Toll like receptors (TLRs) comprise a family of transmembrane proteins related to the Interleukin-1 receptor. Emerging evidence suggests that deregulated TLRs expression in tumor tissue promotes tumor survival signals, thus favoring tumor progression. Recently, aberrant TLR4 overexpression was demonstrated in papillary thyroid cancer (PTC).Aim: To study the mechanisms underlying TLR4 overexpression in PTC harboring the BRAF mutation.Methods / Case Presentation: TLR4 expression was evaluated in thyroid tissue derived from human PTCs and transgenic mice expressing BRAF in thyrocytes (TgBRAF mice) (immunohistochemistry and RT/qPCR). PCCl3 cells expressing BRAF in response to doxycycline (PCBRAF) and BRAF positive PTC cell line BCPAP were used to study BRAF driven TLR4 expression (western blot, RT/qPCR, and gene reporter assays).Results / Discussion: Immunohistochemistry analysis showed TLR4 overexpression in primary and metastatic human PTCs compared to normal thyroid tissue. Moreover, TLR4 expression was increased in thyroid tissue from TgBRAF mice compared to littermate controls.Stimulation of doxycycline treated PCBRAF and BCPAP cells with the TLR4 agonist lipopolysacharide induced the activation of the transcription factor NFκB(5X NFκBLuciferase reporter), suggesting functional TLR4 signaling.Doxycycline induced BRAF expression in PCBRAF cells upregulated TLR4 protein levels.BRAF increased TLR4 expression at transcriptional level by stimulating TLR4 promoter activity. Deletion analysis of the TLR4 promoter revealed a distal mitogenactivated protein kinase (MAPK)sensitive ETS bindingsite critical for BRAF induced TLR4 expression. Consistently, pharmacological inhibition of BRAF and MEK/ERK signaling reduced TLR4 mRNA expression in the BRAF positive PTC cell line BCPAP.Conclusions: Our findings revealed that the oncogene BRAF induces functional TLR4 overexpression in thyroid cancer involving a MEK/ERKdependent TLR4 gene transcriptional activation. Altogether, these data raise an intriguing question regarding the role of TLR4 signaling in the development and progression of PTC,opening new possibilities for the design of therapeutic approaches.