Reciprocal Interaction of Cancer Stem Cells of Cholangiocarcinoma with Macrophage.

Cholangiocarcinoma is an aggressive type of liver cancer with few effective treatment options. Therefore, there is great need to better understand the biology of this malignancy to further development of novel treatment options. Cancer stem cells (CSCs) are thought to the underlying reason for cancer initiation, metastasis, and relapse. However, due to their elusive character and differences in identification among different types of cancer, it remains a challenge to study such cells. Additionally, characterization of the tumor microenvironment such as interactions with immune cells remain largely unknown. Here, we employ a fluorescent reporter system to track and isolate stem-like cancer cells of cholangiocarcinoma cell lines. Following verification of a stem-like signature (upregulated expression of stemness markers, resistance to chemotherapy, increased spheroid formation, and tumorigenesis capabilities despite inoculation of a small number of cells), we analyzed the interaction of these cells with macrophages via direct and indirect coculture assays. We noted direct coculturing increased stemness among CSC populations and induced both M1 (CD80 and HLA-DR) and M2 (CD163) tumor associated macrophage polarization. These studies suggest that there is a bi-directional crosstalk between macrophages and CSCs that promotes stemness renewal and tumor associated macrophage polarization.