Ferrocenyl-thymine-3,6-dihydro-2H-thiopyranes have been reported to show in vitro antiproliferative activity against human colon carcinoma HT-29, estrogen receptor-responsive human breast adenocarcinoma MCF-7, estrogen-negative human breast adenocarcinoma MDA-MB-231, human promyelocytic leukemia HL-60, and human monocytic MonoMac6 cancer cells [59]. Here, ESR1 is linked to breast adenocarcinoma.