TGFB1 and cholangiocarcinoma: The substances secreted from CCA cells were studied in vitro with human macrophages, and the results exhibited M2 polarization of macrophages as well as overproduction of cytokines and other bioactive molecules, including IL-10, VEGF-A, TGF-β, and matrix metalloproteinase- (MMP-) 2 [45].