Role of tumor cell-secreted TGF-b on macrophage phenotype in HNSCC

Objectives: Macrophages are the most abundant immune cell type in the tumor microenvironment (TME) of head and neck squamous cell carcinomas (HNSCC), representing up to 50% of the tumor mass. In the TME, macrophages are called tumor-associated macrophages (TAM) and their phenotype is determined by external cues, including neoplastic cell-secreted products. In HNSCC, increased M2-like macrophage infiltration is associated with worse prognosis and poor survival. The goal of this study is to determine, in vitro, the relative contribution of HNSCC cell-secreted transforming growth factor beta (TGF-β) on macrophage phenotype.
Methods: We used macrophages derived from a human monocytic cell line (THP-1), which were exposed to the secreted products (conditioned medium, CM) from two HNSCC cell lines for 24 h: H314 (SCC floor of mouth, high TGF-β) and SCC9 (SCC tongue, low TGF-β). Phenotype of macrophages were studied by expression of TGF-β, IL-12, IL-10, TNF, M-CSF, MMP-2 and MMP-9 by RT-qPCR. One-way ANOVA and Kruskal-Wallis tests were used for data analysis. The significance level adopted was 95% (p ≤ 0.05) and 'GraphPad Prism 6' software were used for the statistical analyses.
Results: In comparison to unstimulated control (mock CM), expression of M-CSF, TGF-β and IL10 was increased in macrophages exposed to CM from H314 cells (p <0.05). On the other hand, macrophages exposed to CM from SCC9 cells had increased expression of MMP-2 expression, but no significant differences were observed for M-CSF, TNF, TGF-β and IL-10 in comparison to negative control.
Conclusions: In conclusion, high expression of TGF-β in cell-secreted products from HNSCC induces an M2-like phenotype in macrophages.