The proliferation of T47D (ER + /PR +) cells was significantly decreased by 62.9% when cells transfected with si-control were treated with 20 μM tamoxifen (p = 0.003), but only a 31.1% decrease in proliferation was observed in cancer cells transfected with si-TMEM240 (Fig. 4E). This evidence concerns the gene ESR1 and cancer.