CD274 and diabetes mellitus: In previous studies, approximately 70% of EBV-positive NPC patients expressed programmed death-ligand 1 (PD-L1), and patients with DM with malignancy had higher levels of soluble PD-L1 in serum than nonmalignancy patients, which might provide evidence that EBV facilitates NPC cell production of PD-L1 and decreases local and systemic immune reactions43,44.