Cancer-associated fibroblasts promote an immunosuppressive microenvironment through the induction and accumulation of protumoral macrophages

Abstract

// Hideyuki Takahashi 1 , Koichi Sakakura 1 , Takeshi Kudo 1 , Minoru Toyoda 1 , Kyoichi Kaira 2 , Tetsunari Oyama 3 , Kazuaki Chikamatsu 1 1 Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Gunma, Japan 2 Department of Oncology Clinical Development, Gunma University Graduate School of Medicine, Gunma, Japan 3 Department of Pathology, Gunma University Graduate School of Medicine, Gunma, Japan Correspondence to: Kazuaki Chikamatsu, email: tikamatu@gunma-u.ac.jp Keywords: cancer-associated fibroblast (CAF), tumor-associated macrophage (TAM), tumor microenvironment (TME), immunomodulation, immunosuppression Received: August 01, 2016     Accepted: December 07, 2016     Published: December 30, 2016 ABSTRACT Stromal cells in the tumor microenvironment (TME) closely interact with tumor cells and affect tumor cell behavior in diverse manners. We herein investigated the mechanisms by which cancer-associated fibroblasts (CAFs) affect the functional polarization of tumor-associated macrophages (TAMs) in oral squamous cell carcinoma (OSCC) in vitro and in human cancer samples. The expression of CD68, CD14, CD163, CD200R, CD206, HLA-G, CD80, and CD86 was higher in CD14-positive cells co-cultured with the culture supernatants of CAFs established from OSCC specimens (CAF-educated cells) than in control cells. The gene expression level of ARG1 , IL10 , and TGFB1 was increased in CAF-educated cells. CAF-educated cells suppressed T cell proliferation more strongly than control cells, and the neutralization of TGF-β IL-10, or arginase I significantly restored T cell proliferation. We then investigated the relationship between the infiltration of CAFs and TAMs using tissue samples obtained from patients with OSCC. The infiltration of CAFs was associated with the numbers of CD68-positive and CD163-positive macrophages. It also correlated with lymphatic invasion, vascular invasion, lymph node involvement, and the TNM stage. The infiltration of CAFs was identified as an independent prognostic factor in OSCC. Our results indicate that CAFs play important roles in shaping the tumor immunosuppressive microenvironment in OSCC by inducing the protumoral phenotype of TAMs. Therapeutic strategies to reverse CAF-mediated immunosuppression need to be considered.