To study the contribution of lncRNA UCA1 to tamoxifen resistance of breast cancer, we firstly established two tamoxifen-resistant breast cancer cell lines from the parental MCF-7 and T47D cells, and examined the expression of lncRNA UCA1 in these tamoxifen-resistant breast cancer cells (MCF-7-R and T47D-R, respectively). Here, UCA1 is linked to breast cancer.