PDCD1 and cholangiocarcinoma: To overcome this challenge and take advantage of PD-L1 upregulation after gemcitabine treatment, investigators produced a recombinant PD-L1xCD3 bispecific T-cell attractor that specifically binds to CD3 on T-lymphocytes as well as PD-L1 overexpressed on CCA cells after gemcitabine treatment, thereby simultaneously blocking PD-1/PD-L1 signaling and recruiting T-lymphocytes to eliminate CCA cells.