Loss of function of Lin28 impaired breast cancer stem cell expansion through Wnt-β-catenin-pathway.Lin28 increased the population of cancer stem cells (CSCs) by activating HER2 expression or cell fate determination factor DACH1.Lin28 could be strongly inhibited by miR-200 and allowed CSCs to gain stemness. The gene discussed is ERBB2; the disease is breast carcinoma.