SPDL1 and breast cancer: Although several functions of sPD-L1 in the TME of advanced pancreatic cancer, hepatocellular carcinoma, and breast cancer have been explored (16, 17), the involvement of sPD-L1 in B-cell differentiation has not been clarified, except for several previous studies showing that sPD-L1 is associated with prognostic prediction and responses to immunotherapies (15, 17).