TNFSF9 and neoplasm: 57 differentially expressed costimulatory molecules with p < 0.001 were identified, among which the expression of six costimulatory molecules including HHLA2, TNFRSF14, TNFRSF18, TNFRSF25, TNFRSF6B, and TNFSF9 were decreased in tumor samples (Figure 2A), whereas other costimulatory molecules were increased in tumor samples (Figures 2B–E).