Additionally, checkpoint molecules belonging to the tumor necrosis factor receptor superfamily (TNFR-SF), such as glucocorticoid-induced TNFR-related gene (GITR/TNFRSF18/CD357), TNFRSF4 (OX40/CD134), TNFRSF5 (CD40), TNFRSF7 (CD27), and TNFRSF9 (CD137/4-1BB), have also been defined as stimulatory immune checkpoints and under evaluation as potential targets for intervention in the field of cancer immunotherapy [124]. This evidence concerns the gene TNFRSF9 and cancer.