EZH2 and neoplasm: Furthermore, xenograft assay using stable EZH2-overexpressing HeLa cells showed that the tumors formed by HeLa-EZH2 cells appeared earlier (a palpable tumor formed at 9 days for HaLa-EZH2 cells and at 12 days for HeLa-GFP cells), progressed much faster and were heavier than those formed by HeLa-GFP cells (Figure 2C2 and 2C3, P<0.05).