TNFSF4 and neoplasm: OX40 and OX40L can be expressed on various types of cells, including TCs, ICs, and tumor-associated endothelial cells and tumor-associated microvessels (39), and the functions of OX40 or OX40L expressed on endothelial cells are independent of the costimulatory function of OX40/OX40L, which may not be associated with OX40/OX40L-mediated immunoactivities in PDAC.