ESR1 and breast cancer: Both studies showed that CCN5 is apositive regulator of ER-α in BC cells, as knocking down CCN5 drasticallyreduces the ER-α expression in MCF-7 cells and ZR-75-1 cells (Figures 4a and b), while transfection of expression vectorscontaining DDK-tagged-CCN5 induces ER-α expression in MDA-MB-231 cells(Figures 4c and d).