Here we showed that expression of NPM1 in primary human endometrial adenocarcinoma cells was up-regulated by estrogen in a dose-dependent manner and estrogen increased NPM1 expression via ERα-mediated signaling not ERβ, which are consistent with others’ study with endometrial cancer cell lines Ishikawa and ARK1 [26]. The gene discussed is ESR1; the disease is endometrial cancer.