Applying the MTT assay, the in vitro cytostatic effect was studied on ER(+) MCF-7 [24] and ER(−) MDA-MB-231 [25] human breast adenocarcinoma cells, A2058 human melanoma [26] and HT-29 human colorectal carcinoma [27] cell lines. The gene discussed is ESR1; the disease is colorectal carcinoma.