PLK2 and B-cell non-Hodgkin lymphoma: As in B-cell lymphoma, abnormal methylation occurs in the CpG island of the PLK2 gene; The PLK2 expression of DG75 (EBV-) and Rael (EBV+) cell lines increase after demethylation with 5-AZA and is further upregulated by combined administration of histone deacetylase inhibitor TSA.