FUT1 and cholangiocarcinoma: However, we did not exclude the possibility of gemcitabine on regulating other immune checkpoint, especially those which had the evidence to highly express in CCA, i.e., human endogenous retrovirus-H long terminal repeat-associating protein 2 (HHLA2)26 and cytotoxic T lymphocyte antigen 4 (CTLA4)27.