CD40LG and neoplasm: In contrast, while CD137 was also elevated in tumor-infiltrating CD8+ T cells (0.278 vs. 0.055, P < 0.05, Figure 3H), CD40L—a key effector molecule facilitating T cell–APC interactions—was significantly reduced in this subset (0.072 vs. 0.129, P < 0.05, Figure 3G).