PURPOSE: EZH2 is a member of the polycomb group of genes and important in cell 
cycle regulation. Increased expression of EZH2 has been associated previously 
with invasive growth and aggressive clinical behavior in prostate and breast 
cancer, but the relationship with tumor cell proliferation has not been examined 
in human tumors. The purpose of this study was to validate previous findings in 
a population-based setting, also including tumors that have not been studied 
previously.
PATIENTS AND METHODS: In our study of nearly 700 patients, we examined EZH2 
expression and its association with tumor cell proliferation and other tumor 
markers, clinical features, and prognosis in cutaneous melanoma and cancers of 
the endometrium, prostate, and breast.
RESULTS: Strong EZH2 expression was associated with increased tumor cell 
proliferation in all four cancer types. Associations were also found between 
EZH2 and important clinicopathologic variables. EZH2 expression showed 
significant prognostic impact in melanoma, prostate, and endometrial carcinoma 
in univariate survival analyses, and revealed independent prognostic importance 
in carcinoma of the endometrium and prostate. CONCLUSION Our findings point at 
EZH2 as a novel and independent prognostic marker in endometrial cancer, and 
validate previous findings on prostate and breast cancer. Further, EZH2 
expression was associated with features of aggressive cutaneous melanoma. The 
fact that EZH2 might identify increased tumor cell proliferation and aggressive 
subgroups in several cancers may be of practical interest because the polycomb 
group proteins have been suggested as candidates for targeted therapy. EZH2 
expression should, therefore, be further examined as a possible predictive 
factor.