Alpha-smooth muscle actin-positive fibroblasts promote biliary cell proliferation and correlate with poor survival in cholangiocarcinoma

Cancer-associated fibroblasts have been proposed to play a role in promoting carcinogenesis and tumor progression. To our knowledge, no direct evidence concerning fibroblasts in the genesis of cholangiocarcinoma (CCA) has previously been presented. This study aims to assess the value of activated fibroblasts with high alpha-smooth muscle actin (alpha-SMA) expression as an indicator for survival in CCA patients. The immunohistochemistry results indicated a high expression of alpha-SMA in CCA fibroblasts which had a statistically significant correlation with larger tumor size (P=0.009) and shorter survival time (P=0.013). The effect of CCA-associated fibroblasts (Cfs) on non-tumorigenic biliary epithelial cells (H-69) and CCA cell lines was investigated in vitro and compared to the effect of non-tumorigenic liver fibroblasts (Lfs). The increased proliferation effect of Cfs having high alpha-SMA on H-69 and 4 CCA cell lines compared to Lfs that expressed low alpha-SMA was observed. Cell cycle analysis indicated that Cf-derived conditioned-medium and direct Cf-epithelial cell contaction could drive epithelial cells into S+G2/M phases. These results indicate that fibroblasts in CCA stroma express high alpha-SMA and can be a prognostic indicator for poor patient survival. CCA fibroblasts have proliferative effects which may directly effect tumor promotion and progression of biliary epithelial cells. This warrants further investigation of fibroblasts as alternative therapeutic targets in CCA patients.