Overexpression of G 9a and MCM 7 in oesophageal squamous cell carcinoma is associated with poor prognosis

Aims Histone methyltransferase G9a has been primarily understood as a co‐repressor of gene expression, but it has been shown that G9a also positively regulates nuclear receptor‐mediated transcription. MCM 7, a critical component of the DNA replication licensing complex, is amplified and overexpressed in a variety of human malignancies. The objectives of the present study were to study the relationship between the expression of G9a and MCM 7 and the pathological grade, clinical stage and prognosis of oesophageal squamous cell carcinoma ( OSCC ). Methods and results We collected 139 formalin‐fixed and paraffin‐embedded tissues from patients with OSCC and surveyed them by tissue microarray‐based immunohistochemical staining. Associations between the expression of MCM 7 and G9a and clinicopathological parameters and prognosis of OSCC were examined. From tissue microarray immunohistochemistry staining results, we found that nuclear staining intensity for MCM 7 and G9a was associated with histological grade (both P  <   0.001), tumour depth ( P  =   0.050, 0.034), lymph node metastasis ( P  =   0.001, 0.009) and tumour stage ( P  <   0.001, =0.003). G9a expression was correlated with that of MCM 7. G9a overexpression independently predicted poor cancer‐specific survival in OSCC (hazard ratio 0.05, 95% confidence interval 0.006–0.417, P  =   0.006) and MCM 7 (hazard ratio 0.05, 95% confidence interval 0.013–0.441, P  =   0.004). OSCC patients whose tumours showed double‐positive expression of G9a and MCM 7 (G9a + MCM 7 + ) had much shorter survival than those from either the G9a or MCM 7 low expression groups (G9a − MCM 7 − , G9a + MCM 7 − , G9a − MCM 7 + ). Conclusions MCM 7 and G9a may serve as effective prognostic factors and could also be used as biomarkers for predicting various clinical outcomes of OSCC s in the Chinese population.