G9a expression is positively correlated with cell proliferation and poor prognosis in HNSCC patients. (A) Correlation between Ki-67 and G9a expression. The expression of two proteins were analyzed by IHC staining of tissue microarray (TMA) containing 46 normal and 108 tumor sections from HNSCC patients. The expression level of both Ki-67 and G9a was measured by relative staining intensity multiplied by percentage. Scale bar, 50 μm. (*, p < 0.05; ***, p < 0.001). (B) Ki-67 and G9a IHC staining of serial section of tumors. Low or high Ki-67 and G9a expression were defined by a threshold of 80 and 143, which is the average of relative staining intensity multiplied by percentage of Ki-67 and G9a. Scale bar, 50 μm. (***, p < 0.001). (C) Kaplan-Meier plot of overall survival of 77 HNSCC patients from a National Taiwan University Hospital cohort stratified by G9a expression level.