ICAM1 and cholangiocarcinoma: To determine whether the membrane protein ICAM1 in CCA could effectively internalize its antibody into the cytoplasm through antigen-mediated endocytosis, we first observed the endocytosis phenomenon of ICAM1 protein on the surface of two CCA cell lines by immunofluorescent confocal microscopy using phycoerythrin (PE) labeled ICAM1 antibodies (Fig. 2a).