Tumor-Associated Fibroblasts and Microvessels Contribute to the Expression of Immunosuppressive Factor Indoleamine 2, 3-Dioxygenase in Human Esophageal Cancers.

Recent studies have provided considerable evidence to support the hypothesis that tumor stroma plays a crucial role in the induction of immune tolerance to human cancers. Here, we investigated the contribution of reactive stromal tumor-associated fibroblasts (TAFs) and microvessels to the immunosuppressive factor indoleamine 2,3-dioxygenase (IDO) expression in the ESCC microenvironment. The immunohistochemical (IHC) analyses demonstrated a significant increased densities of TAFs and microvessels in the ESCC stroma, double IHCs showed that these increased TAFs and microvessels were with a high proliferation activity. Further IHC examinations revealed that increased expression of IDO were frequently observed in the stromal cells with TAF morphology and microvessels. Double immunofluorescence examinations confirmed the colocalization of IDO positive cells with SMA-alpha positive TAFs and CD34 positive endothelial cells in the ESCC stroma. Our current findings strongly suggest that the activated stromal TAFs and endothelial cells of microvessels contribute to the expression of IDO and then the orchestration of immunosuppressive microenvironment.