In the present study, TLS-B cell density correlated negatively with CD4+ T cells expressing dipeptidyl peptidase-4 (DPP4), which inhibits the proliferative capacity of tumor-infiltrating effector T cells when expressed by cancer-associated fibroblast-subset 1 (CAF-S1) conditioned-Treg in triple-negative breast cancer (35). Here, DPP4 is linked to cancer.