CCND1 and nasopharyngeal carcinoma: According to the linear regression equation, y = 11.11×-36.93 (where x and y represent the log of EBV DNA load and CNV ratio of [CCND1/CDKN2A], respectively; Fig. 5b), in cases where EBV DNA load in plasma is 5000 copies/ml, the CNV ratio is ~ 4, supporting amplification of CCND1 and/or deletion of CDKN2A. Thus, high EBV DNA load in the plasma is simultaneously associated with CNV gain in CCND1 (a cell cycle accelerator), loss in CDKN2A (a cell cycle brake), and uncontrollable cell growth in EBV-positive NPC tumors.