We then identified genes whose expression was strongly associated with the expression of Epi-differ 2 signature (Supplementary information, Table S6).23 Intriguingly, genes related to viral entry into host cell (i.e., TMPRSS2, PVRL4, CTSB, and SLC20A2) were revealed to be highly associated with the Epi-differ 2 signature, suggesting their potential roles in promoting epithelial differentiation by regulating EBV infection in NPC. The gene discussed is CTSB; the disease is Epstein-Barr virus infection.