RESUMO
Anaplastic thyroid cancer (ATC) is a clinically aggressive form of undifferentiated thyroid cancer with limited treatment options. Tumor-associated macrophages (TAMs) constitute over 50% of ATC-infiltrating cells, and their presence is associated with a poor prognosis. We have previously shown that paracrine signals released by ATC cells induced pro-tumor M2-like polarization of human monocytes. However, which soluble factors derived from ATC cells drive monocyte activation, are largely unknown. In this study we investigated the participation of transforming growth factor ß1 (TGFß1) on the phenotype of macrophage activation induced by ATC cell-derived conditioned media (CM). THP-1 cells exposed to CM derived from ATC cells and recombinant human TGFß1 induced M2-like macrophage polarization, showing high CD163 and Dectin1 expression. Moreover, we showed that TGFß1 induced the messenger RNA (mRNA) and protein expression of the transcription factors SNAIL and SLUG. Accordingly, increased TGFß1 secretion from ATC cells was confirmed by enzyme-linked immunosorbent assay (ELISA). Addition of SB431542, a TGFß receptor inhibitor, significantly decreased the Dectin1, CD163, SNAIL and SLUG expression stimulated by ATC cell-derived CM. We validated the clinical significance of the expression of TGFß ligands, their receptors, as well as SNAIL and SLUG in human ATC by analyzing public microarray datasets. We found that the expression of the main TGFß ligands, TGFß1 and TGFß3, along with their receptors, TGFR1 and TGFR2, as well as SLUG, was significantly higher in human ATC tissue samples than in normal thyroid tissues. Our findings indicate that ATC cell-secreted TGFß1 may play a key role in M2-like macrophage polarization of human monocytes and in the up-regulation of SNAIL and SLUG transcription factors. Thus, ours results uncovered a novel mechanism involved in the activation of TAMs by soluble factors released by ATC cells, which suggest potential therapeutic targets for ATC.
RESUMO
Emerging evidence suggests that unregulated Toll-like receptor (TLR) signaling promotes tumor survival signals, thus favoring tumor progression. Here, the mechanism underlying TLR4 overexpression in papillary thyroid carcinomas (PTC) mainly harboring the BRAFV600E mutation was studied. TLR4 was overexpressed in PTC compared with nonneoplastic thyroid tissue. Moreover, paired clinical specimens of primary PTC and its lymph node metastasis showed a significant upregulation of TLR4 levels in the metastatic tissues. In agreement, conditional BRAFV600E expression in normal rat thyroid cells and mouse thyroid tissue upregulated TLR4 expression levels. Furthermore, functional TLR4 expression was demonstrated in PTC cells by increased NF-κB transcriptional activity in response to the exogenous TLR4-agonist lipopolysaccharide. Of note, The Cancer Genome Atlas data analysis revealed that BRAFV600E-positive tumors with high TLR4 expression were associated with shorter disease-free survival. Transcriptomic data analysis indicated a positive correlation between TLR4 expression levels and MAPK/ERK signaling activation. Consistently, chemical blockade of MAPK/ERK signaling abrogated BRAFV600E-induced TLR4 expression. A detailed study of the TLR4 promoter revealed a critical MAPK/ERK-sensitive Ets-binding site involved in BRAFV600E responsiveness. Subsequent investigation revealed that the Ets-binding factor ETS1 is critical for BRAFV600E-induced MAPK/ERK signaling-dependent TLR4 gene expression. Together, these data indicate that functional TLR4 overexpression in PTCs is a consequence of thyroid tumor-oncogenic driver dysregulation of MAPK/ERK/ETS1 signaling.Implications: Considering the participation of aberrant NF-κB signaling activation in the promotion of thyroid tumor growth and the association of high TLR4 expression with more aggressive tumors, this study suggests a prooncogenic potential of TLR4 downstream signaling in thyroid tumorigenesis. Mol Cancer Res; 16(5); 833-45. ©2018 AACR.