The gene for polycomb group protein enhancer of zeste homolog 2 (EZH2) is amplified in late-stage prostate cancer

Overexpression of the polycomb group protein enhancer of zeste homologue 2 (EZH2) has been found in several malignancies, including prostate cancer, with an aggressive phenotype. Amplification of the gene has previously been demonstrated in several malignancies, but not in prostate cancer. Our goal was to evaluate the gene copy number and expression alterations of EZH2 in prostate cancer. The copy number of EZH2 in cell lines (LNCaP, DU145, PC‐3, 22Rv1), xenografts (n = 10), and clinical tumors (n = 191) was studied with fluorescence in situ hybridization. All cell lines had a gain of EZH2. Eight of the ten xenografts showed an increased copy number of the gene, including one case of high‐level amplification (≥5 copies of the gene and EZH2/centromere ratio ≥2). 34/125 (27%) of untreated prostate carcinomas showed increased copy number, but only one case of low‐level amplification (≥5 copies of the gene and EZH2/centromere ratio