Novel treatment strategy targeting interleukin-6 induced by cancer associated fibroblasts for peritoneal metastasis of gastric cancer
Ema Mitsui, Satoru Kikuchi, Tomohiro Okura, Hiroshi Tazawa, Yuta Une, Noriyuki Nishiwaki, Shinji Kuroda, Kazuhiro Noma, Shunsuke Kagawa, Toshiaki Ohara, Junko Ohtsuka, Rieko Ohki, Toshiyoshi Fujiwara
Abstract
Cancer-associated fibroblasts (CAFs) are a crucial component in the tumor microenvironment (TME) of peritoneal metastasis (PM), where they contribute to tumor progression and metastasis via secretion of interleukin-6 (IL-6). Here, we investigated the role of IL-6 in PM of gastric cancer (GC) and assessed whether anti-IL-6 receptor antibody (anti-IL-6R Ab) could inhibit PM of GC. We conducted immunohistochemical analysis of IL-6 and α-smooth muscle (α-SMA) expressions in clinical samples of GC and PM, and investigated the interactions between CAFs and GC cells in vitro. Anti-tumor effects of anti-IL-6R Ab on PM of GC were investigated in an orthotopic murine PM model. IL-6 expression was significantly correlated with α-SMA expression in clinical samples of GC, and higher IL-6 expression in the primary tumor was associated with poor prognosis of GC. Higher IL-6 and α-SMA expressions were also observed in PM of GC. In vitro, differentiation of fibroblasts into CAFs and chemoresistance were observed in GC cells cocultured with fibroblasts. Anti-IL-6R Ab inhibited the progression of PM in GC cells cocultured with fibroblasts in the orthotopic mouse model but could not inhibit the progression of PM consisting of GC cells alone. IL-6 expression in the TME was associated with poor prognosis of GC, and CAFs were associated with establishment and progression of PM via IL-6. Anti-IL-6R Ab could inhibit PM of GC by the blockade of IL-6 secreted by CAFs, which suggests its therapeutic potential for PM of GC.