Objective  To compare the expression of histone methylase G9a in diffuse large B-cell lymphoma (DLBCL) and inflammatory hyperplasia of lymph nodes, and to explore and analyze the correlation between the expression level of G9a and the clinical characteristics, pathological types, efficacy and prognosis of DLBCL patients.

  Methods  Seventy-five newly treated DLBCL patients with complete clinical and follow-up data and admitted to The Affiliated Cancer Hospital of Zhengzhou University were selected. Twenty-five lymph node inflammatory hyperplasia samples were selected as controls. Immunohistochemistry was used to detect the expression of G9a protein in all samples. The correlation between the expression of G9a protein and clinicopathological features, efficacy and prognosis of DLBCL patients was analyzed. Complete remission (CR), overall survival (OS), and progression-free survival (PFS) were determined to explore the effect of treatment on survival and prognosis of the patients.

  Results   The positive expression rate of G9a protein in DLBCL tissues (65.3%) was significantly higher than that in lymph node reactive hyperplasia tissues (20%)(P<0.001). There were no significant differences in gender, age, B symptoms, lactate dehydrogenase (LDH) level, or initial treatment remission rate between G9a positive and G9a negative patients (P>0.05). β2 microglobulin, Ann Arbor staging, and Ki-67 index in patients with positive G9a protein expression were significantly higher than those in patients with negative G9a protein expression (P=0.041、0.019和0.044, respectively). The expression rate of G9a in the non-GCB group was significantly higher than that in GCB group (P=0.023). Cox multivariate analysis showed that positive G9a protein expression was not an independent risk factor for OS and PFS in DLBCL patients. Univariate analysis showed that the 3-year OS of negative and positive G9a protein group was 89.5% and 74.4%, and the differences between the two groups was statistically significant (P=0.043). The 3-year PFS of the G9a negative and G9a positive group was 79.3% and 59.4% (P=0.038).

  Conclusions   Expression of G9a protein was significantly increased in DLBCL samples relative to those with inflammatory hyperplasia of lymph nodes. The higher values of β2 microglobulin value, Ann Arbor staging, and Ki-67 index in DLBCL patients with positive G9a protein expression than those of patients with negative G9a protein expression indicates that the overexpression of G9a may be related to the proliferation and invasion of DLBCL tumor cells. Positive G9a protein expression is a poor prognostic factor that affects 3-year OS and PFS in newly treated DLBCL patients, but it is not an independent prognostic factor.