This explains why the mutation is always heterozygous, since the mutant enzyme needs the wildtype protein to monomethylate H3K27.21, 117 Conditional expression of Y641 mutant EZH2 in GC B cells leads to GC hyperplasia and lymphomagenesis.16 EZH2‐specific inhibitors or shRNA cause proliferation arrest and a partial plasma cell phenotype in DLBCL cells, and eventually some degree of apoptosis.16 These effects occur more rapidly in cell lines harboring EZH2 mutations, and justified the clinical translation of EZH2 inhibitors for patients with FL and DLBCL.16 The gene discussed is EZH2; the disease is diffuse large B-cell lymphoma.