To discuss the potential role of the regulated genes in the proliferation increase we observed in both endometrial cancer cell lines, first, in HEC-1A cells, after knockdown of ERβ, expression of cyclin L1 (CCNL1) was found to be induced 2-fold, which is tempting to speculate as one mechanism underlying the observed proliferation increase. This evidence concerns the gene ESR2 and endometrial cancer.