To identify histone demethylases which are required for the growth of ERα‐positive breast cancer cells, we transfected MCF7 cells, an ERα‐positive breast cancer cell line, with control siRNA or siRNA specifically against each individual member of the histone demethylase protein family except those that are specifically expressed on Y chromosome, then treated cells with or without estrogen followed by cell viability measurement. The gene discussed is ESR1; the disease is breast carcinoma.